Home

QCM200 rev2.2

Contents

1. Figure 11 Retainer cover in place 10 Tighten the retainer cover the rest of the way finger tight is OK SRS QCM200 Quartz Crystal Microbalance 10 Getting Started Chapter 1 11 Connect the Crystal Holder to the QCM25 Crystal Oscillator as shown in Figure 12 Figure 12 The QCM Probe consisting of a Crystal Holder and QCM25 Crystal Oscillator QCM200 Quartz Crystal Microbalance SRS Chapter 1 Getting Started 11 Flow Cell The Flow Cell Adapter SRS Part O100FC attaches to the crystal holder to create a small volume Stagnation Point Flow Cell Figure 13 The Axial Flow Cell Adapter mounted on a crystal holder Use the Axial Flow Cell Adapter for adsorption desorption studies when 1 well defined flow conditions are needed 2 high sensitivity is required 3 small rinse volume is desirable and 4 flow induced surface shear forces need to be minimized In Flow Out Flow Guat 7 Stagnation Point Crystal me Figure 14 Schematic representation of the liquid flow pattern in the Axial Flow Cell A cross sectional view of the Axial Flow Cell including a schematic representation of the stagnation point flow is shown in Figure 14 In the axial flow cell the sample flows radially outward from the input port at the center of the cell to the exit channel at the edge of the cell in a volume of about 150 ul The sample solution is perpendicularly injected ASRS QCM200 Quartz Crystal Microbalance 12 Ge
2. RS 232 Interface The QCM200 comes standard with an RS 232 communications port and both Windows and Mac software The standard software provided with the QCM200 system can be downloaded from the SRS Website www thinksrs com Use the on line help provided with the software to learn about its powerful display and storage features For custom applications requiring specialized software any host computer interfaced to the QCM200 through its RS 232 port can easily configure diagnose and operate the quartz crystal microbalance using simple ASCII commands A complete listing of the RS 232 commands is in Appendix B of this manual The RS 232 interface connector is a standard 9 pin type D female connector configured as a DCE transmit on pin 3 receive on pin 2 The communication parameters are fixed at 9600 Baudrate 8 Data bits 1 Stop bit No Parity No Flow Control ASRS QCM200 Quartz Crystal Microbalance 6 Getting Started Chapter 1 Crystal Installation This section describes the procedure required to replace or install the QCM crystal in the Crystal Holder Figure 5 shows the basic components of the Crystal Holder including a standard 1 inch sensor crystal Crystal holder crystal cavity side arm and neag BNC connector head oring contact springs O sensor eae retainer cover cover eae side up retainer ring retainer ring Figure 5 Crystal Holder components The standard 1 inch diameter sensor
3. The QCM25 consists of transformer isolated and gain controlled RF amplifiers which maintain the 5 MHz oscillation of the crystal in the holder The QCM25 is powered from the QCM200 which also provides the varactor bias to the QCM25 to null the effect of the crystal s static and holder capacitance allowing the crystal to run at the series resonance frequency The 5 MHz signal from the QCM25 is sent differentially to the QCM200 via one twisted pair in the Cat 5 cable allowing measurement of the crystal s series resonant frequency An analog voltage which is proportional to the RF gain in dB required to sustain the crystal s oscillation is also passed to the QCM200 allowing measurement of the crystal s motional resistance QCM25 Crsytal Oscillator SRS The heart of the QCM25 is U1 an AD8367 RF amplifier with 500 MHz bandwidth and up to 45 dB of voltage controlled gain The integrated circuit also has a square law detector SLD and automatic gain control AGC amplifier which measures and controls the amplitude of its output The oscillation of the 5 MHz crystal is sustained by the gain provided by this integrated circuit The gain required to sustain the oscillation is a measure of the losses in the crystal The RF output of U1 is applied via the transformer T1 to the resistor network formed from the series combination of the 50 Q output resistance of U1 plus R12 49 9 Q plus the crystal s resistance 0 4 KQ and terminated into
4. If desired due to existing system integration or other issues an external frequency counter may be used to measure the frequency of the square wave provided at the front panel Frequency Output Consult Appendix A for recommendations on the selection of frequency counters for QCM measurements Error Analysis The QCM25 Crystal Oscillator will oscillate at the frequency such that the phase shift around the entire loop is 360 Referring to Figure 20 important sources of phase shift within the network include 1 180 from the inverting amplifier Aj 2 180 37 p Hz deviation from 5 MHz from the low pass filter 3 0 0 20 pF Rm 40 Q or 0 81 pF Rm 375 Q from uncompensated Cy 4 0 0 207Hz Rm 40 Q or 0 04 Hz Rm 375 Q deviation from series resonance from the crystal in the Rs Rm Ry network If an extraneous phase shift 2 or 3 is present the oscillator will operate away from series resonance allowing the crystal network 4 to cancel the extraneous phase shift QCM200 Quartz Crystal Microbalance ASRS Chapter 2 ASRS Theory Operation and Calibration 21 The small value of the extraneous phase shifts together with the large do df of the crystal network keeps these frequency errors small The QCM25 Crystal Oscillator is intended to operate only with 5 MHz crystals Typical accuracy of the crystal frequency is 100 ppm or 500 Hz The low pass filter will add an additional phase shift o
5. Overview vii Back Panel Overview is C POWER sin 75011 CHASSIS AS RURE Hese mang OA ut External 10 MHz GROUND MADE IN U S A A WARNING SRS QCM200 NO USER SERVICEABLE PARTS INSIDE EJ REFER SERVICE TO QUALIFIED TECHNICIAN A SEE OPERATION MANUAL FOR SAFETY NOTICE PA ka Raiko 90 132 or 175 264 VAC 47 63 Hz 20 VA TOTAL Figure 2 Back Panel of QCM200 Digital Controller A C POWER The Power Entry Module is used to connect the QCM200 Controller to a power source through the power cord provided with the instrument The center pin is connected to the QCM200 chassis so that the entire box is grounded The source voltage requirements are 90 132 or 175 264 VAC 47 63 Hz 20 VA total Connect the QCM200 to a properly grounded outlet Consult an electrician if necessary Chassis Ground Use this grounding lug to connect the QCM200 chassis directly to facility ground RS 232 The QCM200 comes standard with an RS 232 communications port The RS 232 interface connector is a standard 9 pin type D female connector configured as a DCE transmit on pin 3 receive on pin 2 The communication parameters are fixed at 9600 Baudrate 8 Data bits 1 Stop bit No Parity No Flow Control A host computer interfaced to the QCM200 can easily configure diagnose and operate the quartz crystal microbalance using simple ASCII commands see Appendix B Frequency Analog Output Connector The Frequency Ana
6. method The accuracy of the mass load and film thickness calculation is often limited by how well the Z Factor and density of the material are known Density and Z Factor values are typically very close to bulk values The bulk density and shear modulus values for common film materials can be found in many material reference handbooks The Lu and Lewis equation is generally considered to be a good match to the experimental results for frequency changes up to 40 relative to the unloaded crystal Keep also in mind that the Z match equation strictly applies to rigid deposits Films which behave viscoelastically such as some organic polymer films with large thickness or viscosity will exhibit significant deviations from both equations 1 and 5 Crystal failures are also often seen before a 40 shift in frequency is reached Common problems are 1 shorts in the crystal electrodes due to excessive buildup 2 mode hopping to other anharmonic resonant frequencies due to the buildup of composite resonant modes 3 deviations from theory due to fringing electrode fields developed between the electrodes and the film 4 unexpected shifts in fundamental frequency due to stress build up on the crystal surface 5 splitting of source material resulting in non uniform films etc QCM200 Quartz Crystal Microbalance SRS Chapter 2 Theory Operation and Calibration 29 Liquid Contact Measurements Until fairly recently it was believed tha
7. speed time base stability computer interfaces and software drivers Careful selection is required otherwise the frequency counter may degrade the quality of mass measurements The table below lists the typical characteristics of the frequency signal from the QCM200 Frequency Output port for a crystal in water Description Typical Value Frequency 5 0 01 MHz Waveform into 50 Q 2 4 V square wave Stability second to second 0 002 Hz Stability minute to minute 0 10 Hz Temperature Coefficient static 8 Hz C Frequency Mass coefficient 0 057 Hz ng cr SRS QCM200 Quartz Crystal Microbalance 100 Frequency Counter Selection Criteria Appendix A Many of a frequency counter s characteristics are determined by its time base If the time base changes frequency by 10 ppm the reported values will also change by 10 ppm While the accuracy of the counter s time base is not particularly important the stability of the time base is critically important as variations in the time base will be indistinguishable from changes in accumulated mass on the surface of the crystal Often manufacturers will specify accuracy and aging but do not specify short term stability In virtually all counters the short term stability will improve if they are allowed to warm up for an extended period of time To avoid degrading frequency measurements the time base should have a 1 second stability of better than 002 Hz 5 MHz or 4x10 The
8. 10ppm to achieve phase lock The front panel display can indicate how far the internal oscillator is being pulled as a percentage of its full range 100 This percentage provides a gross indication of the stability of the external 10 MHz input After warmup of both the external oscillator and the QCM200 a pull percentage that fluctuates by more than a couple of counts indicates a problem with either the internal or the external oscilator Contact SRS for assistance in this case QCM200 Quartz Crystal Microbalance SRS Overview ix QCM25 Crystal Oscillator Overview SRS QCM Controller Crystal Face Bias Power SRS QCM25 Crystal Oscillator 5 MHz Crystal Figure 3 QCM25 Crystal Controller top view QCM Controller Connector The QCM Controller connector is a RJ 45 connector Use this connector to connect the QCM25 Crystal Oscillator to the QCM200 Controller Crystal Probe connector A 3 foot long Cat 5 Straight Through cable is used to connect the two boxes A cable up to 25 feet in length may be used A green Power LED lights up to indicate the presence of electrical power in the QCM25 box Crystal Face Bias The Crystal Face Bias connector provides a direct electrical connection to the QCM crystal s liquid face electrode i e outer electrode in contact with the solution Use this connector to electrically connect the crystal s liquid face to the Work Electrode lead of a potentiostat while us
9. 1836 14 K Keiji Kanazawa and Joseph Gordon II Frequency of a Quartz Microbalance in Contact with Liquid Anal Chem 57 1985 1770 K Keiji Kanazawa and Joseph G Gordon II Analytica Chimica Acta 175 1985 99 105 SRS QCM200 Quartz Crystal Microbalance 44 Theory Operation and Calibration Chapter 2 a Stephen J Martin James J Spates Kurt O Wesendorf Thomas Schnneider and Robert J Huber Resonator Oscillator Response to Liquid Loading Anal Chem 69 1997 2050 16 Stephen Martin Victoria Edwards Granstaff and Gregory C Frye Characterization of a Quartz Crystal Microbalance with Simultaneous Mass and Liquid Loading Anal Chem 63 1991 2272 17 Operation in liquids requires that the crystal be mounted in a holder such that only the front surface of the crystal is in contact with the fluid while at the same time providing an electrical connection to both electrodes 1 For pure water at 20 C pL 0 9982 g cm and n 1 002107 g cm s H Muramatsu Eiichi Tamiya and Isao Karube Computation of Equivalent Circuit Parameters of Quartz Crystals in Contact with Liquids and Study of Liquid Properties Anal Chem 60 1988 2142 S J Geelhood C W Frank and K Kanazawa Transient Quartz Crystal Microbalance Behaviors Compared Journal of the Electrochemical Society 149 2002 H33 H38 Mengsu Yang and Michael Thompson Multiple Chemical Information from the Thickness Shear Mo
10. 60 Sensor Crystals and Holders Chapter 3 Sputtering or evaporation Thin films i e nm thickness of metals or metal oxides are commonly deposited by sputtering or evaporation To obtain reproducible results careful attention must be paid to cleanliness both in the vacuum chamber and in the preparation of the crystals prior to coating It is generally realized by individual researchers that unless highly specialized coatings are required it is a lot more convenient and cost effective to have a specialized commercial source deposit the electrodes on crystal blanks Spin coating Spin coating is a technique by which very thin polymeric films nm to um thickness are deposited onto a solid substrate To fabricate thin polymer films the polymer material is first dissolved in a volatile solvent If a drop of solution is placed on a substrate it can flow to form a metastable continuous film or form a droplet on the surface depending on the wettability of the substrate By spinning the substrate the droplet is forced to spread out while the solvent evaporates If deposition conditions such as choice of solvent solution concentration and spin speed are chosen carefully a thin film of uniform thickness is deposited on the substrate Polystyrene is a common material spin coated onto QCM sensor crystals Toluene is the solvent of choice UV Ozone treatment can be used to tailor the hydrophobicity of organic polymeric coatings Co
11. ID tubing with 0 040 ID thru hole Model P 663 from www upchurch com Recommended flow rate lt 0 2 mL min Maximum flow rate 5 mL min Materials Cell Kynar Inlet Outlet Tubes Tefzel O ring Viton QCM200 Quartz Crystal Microbalance SRS Theory Operation and Calibration 15 Chapter 2 Theory Operation and Calibration This chapter provides a brief introduction to the measurement techniques and calibration procedures available to QCM200 users and describes the most popular theoretical models used to interpret the results The procedure for capacitance compensation is also described in detail Background SRS Sauerbrey was the first to recognize the potential usefulness of the Quartz Crystal Microbalance QCM technology and demonstrate the extremely sensitive nature of these piezoelectric devices towards mass changes at the surface of QCM electrodes The results of his work are embodied in the Sauerbrey equation which relates the mass change per unit area at the QCM electrode surface to the observed change in oscillation frequency of the crystal Af C Am eqn 1 where Af the observed frequency change in Hz Am the change in mass per unit area in g cm C the sensitivity factor for the crystal 56 6 Hz ug cm for a 5 MHz AT cut quartz crystal at room temperature The Sauerbrey equation relies on a linear sensitivity factor C which is a fundamental property of the QCM crystal Thus
12. Pei 200 00 350 00 m 220 00 355 00 ea S eee eee eS aan eee 240 00 360 00 f f f f f i 1 I 1 1 1 1 1 17260 00 1 00 0 90 0 80 0 70 0 60 0 50 0 40 0 30 0 20 0 10 0 00 0 10 0 20 0 30 0 40 Potential vs Agl4gCl Figure 26 Voltammogram and massogram data for the oxidation of pyrrole to form a polypyrrole film on a gold coated QCM Sensor Crystal Seven cycles of voltammetry between 0 4 and 0 95 V were conducted in this experiment Pyrrole monomer can be oxidized to its radical at 0 65 V As this happens a thin polypyrrole film is formed on the crystal surface resulting in a decrease in the fundamental frequency of oscillation of the crystal The continuous growth of the film is evidenced by the irreversible decrease in frequency during the scans A straightforward way to detect changes in film viscoelastic properties of redox films is to simultaneously monitor the series resonance resistance R of the quartz oscillator during the electrochemical experiment Some theoretical models based on the simultaneous measurement of Af and AR have been discussed in the literature for the extension of EQCM gravimetric measurements to non rigid films The viscoelastic analysis of polymeric thin films in EQCM systems is complex because the shear wave exists simultaneously in the quartz crystal the viscoelastic film and the adjacent solution so reflection of the shear wave must be taken into account However solution of this problem wou
13. in mass from the foreign film is treated as though it were really an extension of the thickness of the underlying quartz The foreign film is considered rigid and so thin that it does not experience any shear forces during vibration As a result the sensitivity factor C is a fundamental property of the quartz crystal and does not consider any of the properties of the foreign film i e it is only dependent on the acousto elastic properties of quartz ants V2 Haq eqn 12 where n number of the harmonic at which the crystal is driven fo the resonant frequency of the fundamental mode of the crystal in Hz Pq density of quartz 2 648 g cm Ug shear modulus of quartz 2 947 x 10 gems The dependence of the frequency change on the mass coverage per unit area emphasizes the fact that within certain limits the sensitivity factor is independent of the electrode geometry Thus in theory the QCM mass sensor does not require calibration for this application This ability to calculate mass loading from first principles is obviously a very attractive feature of these devices Film thickness is often the parameter of interest in gas phase thin film depositions If the mass coverage is believed to be uniform the thickness of the film is easily calculated by dividing the mass per unit area provided by Sauerbrey s equation by the material s density _Am Tes Py eqn 13 where pi density of film materia
14. in situ and in real time the rate of adsorption of alkanethiols onto gold the change i e decrease in frequency resulting from the adsorption of alkanethiol molecules onto the gold electrode of a QCM crystal allows direct measurement of the rate of formation of SAMs Tip Silanes are another common material used in SAMs Silanization has also been studied with QCMs using crystals with electrodes custom coated with thin layers of Si 111 Several examples of direct measurement of adsorption kinetics of alkanethiolate SAMs on QCM crystals from both gas and liquid phase are included in the references list at the end of this chapter Figure 29 is a graphical representation of the chemical adsorption kinetics of 16 mercaptohexadecanoic acid on to bare gold measured in real time with a QCM200 quartz crystal microbalance In this simple experiment a polished Au Cr crystal mounted on a standard holder was immersed in 200 mL of ethanol housed inside a temperature stabilized 500 mL beaker The reaction was triggered by rapidly injecting 1 mL of 10 M solution of 16 mercaptohexadecanoic acid providing a diluted 5x10 M solution of alkanethiol to react with the bare gold A short transient in the frequency and resistance indicates the point of insertion of the thiol and is due to a slight temperature difference between the solvent and the sample solution The fast drop in frequency following the injection is due to the fast formation of thiol
15. 09K Thin Film 1 50 ppm MELF Resistor R19 4 01242 462 20 0K Thin Film 1 50 ppm MELF Resistor R 20 4 01088 462 499 Thin Film 1 50 ppm MELF Resistor R21 4 01088 462 499 Thin Film 1 50 ppm MELF Resistor R 22 4 01227 462 14 0K Thin Film 1 50 ppm MELF Resistor R 23 4 01213 462 10 0K Thin Film 1 50 ppm MELF Resistor R 24 4 01338 462 200K Thin Film 1 50 ppm MELF Resistor R25 4 01338 462 200K Thin Film 1 50 ppm MELF Resistor R 26 4 01213 462 10 0K Thin Film 1 50 ppm MELF Resistor R 27 4 01191 462 5 90K Thin Film 1 50 ppm MELF Resistor R 28 4 01455 461 100 Thick Film 5 200 ppm Chip Resistor R 29 4 01447 461 47 Thick Film 5 200 ppm Chip Resistor R 30 4 01447 461 47 Thick Film 5 200 ppm Chip Resistor R31 4 01117 462 1 00K Thin Film 1 50 ppm MELF Resistor R 32 4 01117 462 1 00K Thin Film 1 50 ppm MELF Resistor R 33 4 01146 462 2 00K Thin Film 1 50 ppm MELF Resistor R 34 4 01146 462 2 00K Thin Film 1 50 ppm MELF Resistor R 35 4 01527 461 100K Thick Film 5 200 ppm Chip Resistor R 36 4 01199 462 7 15K Thin Film 1 50 ppm MELF Resistor R 37 4 01479 461 1 0K Thick Film 5 200 ppm Chip Resistor R 38 4 01338 462 200K Thin Film 1 50 ppm MELF Resistor R 39 4 01338 462 200K Thin Film 1 50 ppm MELF Resistor R 40 4 01213 462 10 0K Thin Film 1 50 ppm MELF Resistor R41 4 01191 462 5 90K Thin Film 1 50 ppm MELF Resistor QCM200 Quartz Crystal Micro
16. 75 Resistance range 0 5000 Voltage level 0 10 625 VDC log scale Impedance 1k Connector BNC Capacitance Cancellation Range 10 40 pF 20 pF nominal Limit 0 01 pF Physical Interface RS 232 9600 baud no parity no flow control Dimensions 10 625 x 2 x 7 WHD Weight 2 Ibs Operating temperature 0 C 40 C ASRS Specifications xi Quartz Crystals polished Frequency 5 MHz AT cut plano plano Diameter 1 inch Electrodes Chromium gold titanitum gold titanium platinum and indium tin oxide transparent Crystal Holder Material Kynar O ring Viton Connector BNC QCM200 Quartz Crystal Microbalance xii Specifications QCM200 Quartz Crystal Microbalance SRS Getting Started 1 Chapter 1 Getting Started This chapter provides instructions for 1 unpacking 2 checking and 3 connecting the QCM200 Quartz Crystal Microbalance Controller to its accessories and to your experiment Quick Start instructions are also provided to perform QCM measurements QCM200 System Figure 4 Complete QCM setup consisting of QCM200 Digital Controller QCM25 Crystal Oscillator Crystal Holder and three 3 quartz crystal sensors The QCM200 System is a stand alone instrument with a built in frequency counter and resistance meter It includes controller crystal oscillator electronics crystal holder and three 3 quartz crystals Series resonance frequency and resistance are measured and disp
17. AT gt 2 C external thermal equilibration of the sample fluid is recommended A common trick is to add a temperature equalization loop immersed in the liquid bath between the sample container and the flow cell to provide complete equalization ASRS QCM200 Quartz Crystal Microbalance 70 Sensor Crystals and Holders Chapter 3 References 1 D S Ballantine et al Acoustic Wave Sensors Theory Design and Physico Chemical Applications Academic Press 1996 C Lu and O Lewis Investigation of film thickness determination by oscillating quartz resonators with large mass load J Appl Phys 43 1972 4385 S J Martin R J Huber et al Resonator Oscillator Response to Liquid Loading Anal Chem 69 1997 2050 1D Johannsmann Viscoelastic Analysis of Organic Thin Films on Quartz Resonators Macromol Chem Phys 200 1999 501 E J Calvo et al Quartz Crystal impedance studies at 10 MHz of viscoelastic liquids and films Faraday Discuss 107 1997 141 R W Cernosek et al Analysis of the radial dependence of mass sensitivity for modified electrode quartz crystal resonators Anal Chem 50 1998 237 H K Pulker and W Schadler Nuovo Cimento 57B 1968 19 T W Schneider and S J Martin Influence of compressional wave generation on a thickness shear mode resonator response in a fluid Anal Chem 67 1995 3324 H Bahadurand R Parshad Physical Acoustics Vol 16 W
18. Chip Resistor R70 4 01527 461 100K Thick Film 5 200 ppm Chip Resistor R71 4 01479 461 1 0K Thick Film 5 200 ppm Chip Resistor R72 4 01431 461 10 Thick Film 5 200 ppm Chip Resistor R 73 4 01431 461 10 Thick Film 5 200 ppm Chip Resistor R74 4 01479 461 1 0K Thick Film 5 200 ppm Chip Resistor R75 4 01527 461 100K Thick Film 5 200 ppm Chip Resistor R76 4 01479 461 1 0K Thick Film 5 200 ppm Chip Resistor R77 4 01479 461 1 0K Thick Film 5 200 ppm Chip Resistor R78 4 01479 461 1 0K Thick Film 5 200 ppm Chip Resistor R 121 4 01479 461 1 0K Thick Film 5 200 ppm Chip Resistor R122 4 01479 461 1 0K Thick Film 5 200 ppm Chip Resistor S11 2 00053 208 B3F 1052 Switch Momentary Push Button NO S12 2 00053 208 B3F 1052 Switch Momentary Push Button NO swi 2 00025 217 SPDT Switch On None On Toggle Right Angle TA 6 00622 610 ADT1 6T Transformer U1 3 00346 329 7812 Voltage Reg TO 220 TAB Package U2 3 00112 329 7805 Voltage Reg TO 220 TAB Package U3 3 00581 360 AD822 Integrated Circuit Surface Mount Pkg U4 3 00684 360 CD4060BCM Integrated Circuit Surface Mount Pkg U5 3 00375 360 DS8921AM Integrated Circuit Surface Mount Pkg U6 3 00749 360 74HC541 Integrated Circuit Surface Mount Pkg U7 3 01469 360 MAX6250BCSA Integrated Circuit Surface Mount Pkg U8 3 00581 360 AD822 Integrated Circuit Surface Mount Pkg U9 3 01445 360 LMC6082IM Integrated Circuit Surface Mount Pkg U 10 3 01445 360
19. DESCRIPTION 83 C1 5 00318 569 C2 5 00318 569 C3 5 00318 569 C4 5 00299 568 C5 5 00372 552 C6 5 00363 552 C7 5 00299 568 C8 5 00299 568 c9 5 00299 568 C10 5 00299 568 C11 5 00299 568 C12 5 00052 512 C13 5 00052 512 C14 5 00056 512 C15 5 00056 512 C16 5 00299 568 C17 5 00299 568 C18 5 00299 568 C19 5 00299 568 C 20 5 00052 512 C21 5 00052 512 C 22 5 00052 512 C 23 5 00052 512 C 24 5 00060 512 C25 5 00299 568 C 26 5 00375 552 C27 5 00299 568 C 28 5 00299 568 C1110 5 00299 568 C 1120 5 00299 568 C 1210 5 00299 568 C 1220 5 00299 568 C 1230 5 00299 568 D1 3 00010 303 D2 3 00010 303 D3 3 0001 1 303 D4 3 0001 1 303 D5 3 0001 1 303 D6 3 0001 1 303 D11 3 01163 303 D12 3 00544 360 D13 3 00544 360 D 121 3 00010 303 J1 1 00031 133 J1 1 00505 100 SRS 2 2U T35 2 2U T35 2 2U T35 AU 56P 10P AU AU AU AU AU 01U 01U AU AU AU AU AU AU 01U 01U 01U 01U 1 0U AU 100P AU AU AU AU AU AU AU GREEN GREEN RED RED RED RED XLUGR29M BAV70LT1 BAV70LT1 GREEN 16 PIN SRA RJ45 MODULAR Cap Tantalum SMT all case sizes Cap Tantalum SMT all case sizes Cap Tantalum SMT all case sizes Cap Ceramic 50V SMT 1206 10 X7R Capacitor Chip SMT1206 50V 5 NPO Capacitor Chip SMT1206 50V 5 NPO Cap Ceramic 50V SMT 1206 10 X7R Cap Ceramic 50V SMT 1206 10 X7R Cap Ceramic 50V SMT 1206 10 X7R Cap Cerami
20. R17 49 9 Q The attenuation of this network is the smallest at the series resonant frequency of the crystal The AGC amplifier QCM200 Quartz Crystal Microbalance 76 QCM Circuit Description Chapter 4 has sufficient gain to maintain the amplitude of the output of U1 at 1 Vpp provided that the crystal s series resistance is less than 4 kQ Dry crystals have about 10 Q of resistance at series resonance while crystals with one face in water have about 400 Q of resistance at series resonance At series resonance the crystal impedance is resistive In addition there is about 15 pF of capacitance in parallel with this resistance due to the crystal s electrodes and holder The current which passes through this capacitance is canceled by an equal and opposite current which passes through the varactor diode D2 The QCM200 provides a bias to the varactor diode so that the varactor capacitance is equal to the electrode plus holder capacitance The varactor is driven by the inverted version of the 5 MHz signal from the center tapped secondary of transformer T1 The output from the crystal network is amplified by U4 an AD8009 RF operational amplifier The gain of U4 can be adjusted between 3 5x 5 2x with the potentiometer P2 The pot is adjusted during factory calibration to calibrate the offset on the AGC voltage The slope and offset of the AGC voltage is adjusted to assure compliance to the Veong VS Rerystal characteristic The output of U4 dr
21. SMT 1206 10 X7R C 2510 5 00519 569 33U T35 Cap Tantalum SMT all case sizes C 2520 5 00299 568 AU Cap Ceramic 50V SMT 1206 10 X7R C 2610 5 00519 569 33U T35 Cap Tantalum SMT all case sizes C 2620 5 00299 568 AU Cap Ceramic 50V SMT 1206 10 X7R C 2710 5 00472 569 4 7U T35 Cap Tantalum SMT all case sizes C 2720 5 00593 569 33U 25V Cap Tantalum SMT all case sizes C 2730 5 00593 569 33U 25V Cap Tantalum SMT all case sizes C 2740 5 00593 569 33U 25V Cap Tantalum SMT all case sizes C 2750 5 00299 568 AU Cap Ceramic 50V SMT 1206 10 X7R C 2810 5 00519 569 33U T35 Cap Tantalum SMT all case sizes C 2820 5 00299 568 AU Cap Ceramic 50V SMT 1206 10 X7R CN12 1 00473 114 2 PIN WHITE Header Amp MTA 100 CN21 1 00251 130 10 PIN DIL Connector Male D13 3 00544 360 BAV7OLT1 Integrated Circuit Surface Mount Pkg D 2710 3 00926 360 MBRO540T1 Integrated Circuit Surface Mount Pkg J11 1 00289 130 6 PIN DI TSW 07 Connector Male J21 1 00473 114 2 PIN WHITE Header Amp MTA 100 J 23 1 00473 114 2 PIN WHITE Header Amp MTA 100 J 31 1 00473 114 2 PIN WHITE Header Amp MTA 100 J171 1 00473 114 2 PIN WHITE Header Amp MTA 100 L271 6 00273 600 33UH SMT Misc Components PC1 7 01511 701 QCM200 MAIN BD Printed Circuit Board Q 12 3 00601 360 MMBT3904LT1 Integrated Circuit Surface Mount Pkg R11 4 01455 461 100 Thick Film 5 200 ppm Chip Resistor R12 4 01455 461 100 Thi
22. This ability to calculate the mass sensitivity from first principles is obviously a very attractive feature of these devices However it is very important to notice that the Sauerbrey equation is only strictly applicable to uniform rigid thin film deposits originating from a low pressure i e vacuum gas environment Thick deposits and operation in liquid environments or in contact with viscoelastic films relies on the use of more complex equations relating the frequency shifts to mass loading and often requires calibration of the setup for accurate results Several articles have presented simple ways to calibrate the mass sensitivity of QCMs for electrochemical applications and for vacuum thin film deposition processes and some useful calibration guidelines were also included in Chapter 2 of this manual There is ample evidence supporting a Gaussian mass sensitivity distribution for AT cut crystals with the maximum sensitivity at the center of the electrode and zero sensitivity at the edges for harmonically driven plane crystals The mass sensitivity distribution has also been shown to become slightly more confined to the electrode region as the mass loading is increased In order to assure reproducibility of results it is very important to assure uniform coverage of the electrodes during measurements There are also situations in which the QCM does not act as a microbalance at all but responds instead to properties such as vis
23. as a two dimensional film one molecule thick covalently assembled at an interface The classical example of a SAM is the reaction of alkanethiols with a gold surface Since sulfur donor atoms strongly coordinate on metal substrates Au Ag Pt etc sulfur containing molecules such as disulfides R SS R sulfides R S R and thiols RSH can form various functionalized SAMs with highly organized and compact construction For example when a clean gold surface is immersed in an alkanethiol solution the following self assembly chemisorption reaction takes place Au RSH amp Au SR 1 2 Hj This reaction self terminates at one monolayer when all accessible gold sites are consumed The Langmuir adsorption model has been applied successfully to model the adsorption desorption kinetics of these processes The self assembly of alkanethiol monolayers onto gold has been studied extensively due to the potential application of these interfaces to 1 chemical and biological sensing 2 nano and micro device manufacturing and 3 surface modification A significant amount of work has been dedicated to understanding the steady state properties of SAMs once they have formed However more recently it has become clear that alkanethiol SAMs are highly dynamic structures and a lot of renewed effort has been dedicated to the understandin g of the mechanism of monolayer formation The QCM200 system provides a unique opportunity to monitor
24. chapter describes the basic features and functionality of the QCM Sensor Crystals and Holder including recommended practices for 1 cleaning 2 handling 3 surface modification 4 probe mounting 5 electrical connection and 6 general maintenance Introduction The standard sensor crystal used by the QCM200 System consists of a thin disk of 5 MHz AT cut o quartz with circular electrodes patterned on both sides Figure 30 Standard 1 inch QCM sensor crystal The crystal on the left shows the contact surface while the one on the right shows the liquid surface Standard sensor crystals are 1 inch in diameter and are available with a variety of electrode materials and either a polished or unpolished finish Stanford Research Systems also provides a rugged and easy to operate Crystal Holder compatible with both gas and liquid QCM experiments Crystal Holders must be electrically connected to the QCM25 Crystal Oscillator for operation with a QCM200 Controller ASRS QCM200 Quartz Crystal Microbalance 50 Sensor Crystals and Holders Chapter 3 Sensor Crystals QCM Sensor Crystals are available directly from Stanford Research Systems in a variety of electrode materials and surface finishes Standard 1 inch 5MHz QCM Sensor Crystals Qty 10 per pack SRS Part SRS Order Material Finish Maxtek Part 6 00613 O100RX1 Chrome Gold Polished 149211 1 6 00630 O100RX2 Indium Tin Oxide Transparent N A 6 00615 0100RX3 Tita
25. crystal has two sides that must be clearly identified before this procedure is started Contact Surface The contact surface has two separate circuits and the smaller electrode pad Figure 6 Contact Surface of QCM crystal QCM200 Quartz Crystal Microbalance SRS Chapter 1 Getting Started 7 Liquid Surface The liquid surface has the larger electrode pad which connects through a wrap around pad to one of the circuits on the Contact Surface This is the outside i e modified surface in direct contact with the gas or liquid during QCM experiments Figure 7 Liquid surface of QCM crystal In order to insert a new crystal into the holder the following steps must be followed 1 Bs Place the Crystal Holder s head on a flat surface with its crystal cavity pointing up The crystal cavity contains two spring loaded contacts POGO pins which connect the two Contact Surface circuits of the crystal to the BNC connector on the opposite end of the probe Inspect the head o ring to make sure it is free of defects clean and properly seated in its dovetail groove The o ring should be free of low spots and show sufficient height above the center ring when viewed from the side with the naked eye Make sure the crystal cavity is clean and dry Dry if necessary Test the travel of the POGO contacts Gently depress the POGO pins a thin wooden applicator does a good job Make sure that they travel freely i e their
26. from the analog board appears on connector CN12 goes to the CPLD through a protection resistor R142 After the MCU writes the current gate interval to the CPLD it initiates a new count cycle by asserting CNTR_EN high At the end of the gate interval the CPLD notifies the MCU that a new count value is ready by asserting CNT_DONE high When the MCU detects the count done condition it asserts CNTR_WR low Then the MCU clocks toggling SCLK the count and interpolation data SIG_COUNT_Q and SIG_COUNT_QB from the CPLD and de asserts CNTR _WR high The MCU calculates the frequency by dividing the total count by the actual gate interval to interpolate the unknown frequency to the nearest sixteenth of a cycle 12 5ns out of 200ns The MCU subtracts the frequency from the offset to arrive at the delta frequency and scales the result with a constant to calculate the delta mass The DAC value is calculated by multiplying the delta frequency by a constant determined by the Scale setting and adding an offset calibration constant The exact values of the DAC scaling factors and offset calibrations are determined at the factory and permanently written into the MCU program of each QCM200 The MCU asserts DAC1_CS low and clocks toggles SCLK 32 bits of configuration and data on SDATA to the DAC The OV to 5V output of the 20 bit Delta Sigma DAC U16 is buffered offset by 2 5V inverted and amplified by U12 R124 protects U12 from damage in the ev
27. gold bonds followed by a SRS QCM200 Quartz Crystal Microbalance 42 Theory Operation and Calibration Chapter 2 slower annealing process The absence of a sharp positive step in the resistance verifies that the fast frequency drop is not due to a change in the viscosity of the solution The results are in excellent agreement with the observations of Blanchard s group corresponding to the adsorption desorption kinetics of thiols from hexane and under very similar experimental conditions Self Assembled Monolayer eee Alkanethiol Adsorption to Gold Resistance 341 340 5 340 339 5 339 Frequency Shift Hz Resistance Ohms 338 5 338 337 5 150 170 190 210 230 250 270 290 310 Time seconds Figure 29 Raw QCM Af vs time and Resistance vs time data for adsorption of 5 10 M 16 mercaptohexadecanoic acid from ethanol to bare gold Besides good mechanical and chemical properties an additional advantage of SAMs is that they make it possible to tailor probe surfaces at the molecular level for the immobilization of specific biomolecules such as proteins or DNA Several studies have reported significant improvement in detection limits when SAM immobilization is used to design immunosensor QCM probes Dissipation Technique An alternative method for studying the properties of the loaded QCM Sensor called the Dissipation Technique has been used in gaseous as well as in liqui
28. may not be serviced by the user SRS QCM200 Quartz Crystal Microbalance ii Safety and Preparation For Use Operate Only With Covers In Place To avoid personal injury do not remove the product covers or panels Do not operate the product without all covers and panels in place Liquid Contact With the exception of the Crystal Holder this product is intended for use only in a clean dry laboratory environment Operation in other environments may cause damage to the product and reduce the effectiveness of the safety features To reduce the risk of fire or electrocution do not expose this product to rain or excessive moisture Be careful not to spill liquid of any kind onto or into the product Serviceable Parts The QCM200 Controller does not include any user serviceable parts inside Refer service to a qualified technician QCM200 Quartz Crystal Microbalance SRS Contents Contents iii Safety and Preparation for Use i Contents iii Front Panel Overview v Back Panel Overview vii QCM25 Crystal Oscillator Overview ix Specifications xi Chapter 1 Getting Started 1 QCM200 System 1 Unpacking 2 Quick Start Instructions 3 QCM200 User Interface 4 Crystal Installation 6 Flow Cell 11 Chapter 2 Theory Operation and Calibration 15 Background 15 The QCM Oscillator 16 Capacitance Cancellation 19 Frequency Measurement 20 Resistance Measurement 22 Gas Phase Measurements 27 Liquid Contact Measurements 29 Immersion Test
29. neglected The relative importance of the mass loading and viscoelastic contributions of the film to the observed QCM response is a subject that has yet to be resolved In no area have the QCM applications seen such dramatic increase in recent years as in the field of biochemical analysis QCM devices are routinely used as biochemical and immunological probes as well as for the investigation and or monitoring of biochemically significant processes BSA Adsorption to Gold 5 Mhz data Frequency Shift Hz D gt 10 T T T T T T T T 0 200 400 600 800 1000 1200 1400 1600 Time seconds Figure 27 A 10ug ml solution of BSA in 2mM NaCl is flowed over a polished Au Cr QCM crystal in an axial flow cell at a rate of 50uL min Due to the non specific adsorption of the protein the frequency of oscillation decreases by 9Hz over a period of 5 minutes The sensitivity of the QCM200 for the detection of microgram quantities of proteins is clearly demonstrated by this very straightforward experiment QCM200 Quartz Crystal Microbalance SRS Chapter 2 ASRS Frequency Shift Hz Theory Operation and Calibration 39 An example of a complex and dynamic biochemical process which has been successfully studied with quartz crystal microbalances is the adsorption of proteins to solid surfaces Figure 27 is the result of a QCM experiment following the adsorption kinetics of bovine serum albumin BSA from an aqueous saline so
30. signal transients are to be expected after sudden changes in flow rates and after liquid exchanges i e new sample injections Flow transients can last less several seconds and can seriously compromise your long term measurements if bubbles are introduced into the flow stream or large temperature differences between the liquid and the holder are established Use small and constant flow rates During liquid flow experiments flowrates should be kept small and constant to eliminate signal transients due to pressure and temperature fluctuations Recommended flow rates should be below 0 2 mL min to assure minimal transients and flow induced noise in the frequency measurements Rely on gravity the siphon principle or syringe pumps to flow liquids through a cell in Open Flow Systems whenever possible If necessary use Flow Injection Analysis FIA compatible pumps and high quality injection ports to flow sample and carriers over the QCM200 Quartz Crystal Microbalance 66 Sensor Crystals and Holders Chapter 3 crystal Syringe based injection analysis systems often produce cleaner baselines because of the absence of noise transients induced by peristaltic pumps Peristaltic pumps are suitable for flow measurements in closed systems but they always add noise to the signal A capillary tube located between the chamber outlet and the pump is often recommended to reduce noise caused by pressure fluctuations induced by the pump Pulse dampening modul
31. small eight character input buffer and processes commands in the order received If the input buffer overflows it is cleared and a communication error is flagged Since no handshaking is supported it is recommended 1 to send commands one at a time 2 to confirm all settings with query commands and 3 waiting for query responses to be fully transmitted before sending a new command to the QCM200 QCM200 Quartz Crystal Microbalance ASRS 102 QCM200 Remote Programming Appendix B A query is constructed by appending a question mark to the command Values returned by the QCM200 are transmitted as a string of ASCII characters terminated by a lt CR gt Examples of commands F lt CR gt Query the Absolute Frequency G lt CR gt Set the Frequency Offset to the current Absolute Frequency G lt CR gt Query the Frequency Offset DO lt CR gt Set the Measurement Display to Absolute Frequency readings D lt CR gt Query the current Measurement display setting l lt CR gt Query the ID string fro the instrument Command Syntax The one letter mnemonic shown in CAPS in each command sequence specifies the command The rest of the sequence consists of parameters Parameters shown in are not always required Generally parameters in are required to set a value in the QCM200 The present value of a parameter may be determined by sending a query command Commands that MAY be queried show a question mark in parenthesis aft
32. source injects a current via an adjustable capacitor Cy to cancel the current injected via C Exact cancellation is achieved when the adjustable capacitor is made equal to Co In the SRS QCM25 Crystal Oscillator C is a varactor which is made equal to C by finding the bias setting which minimizes the gain required to sustain oscillation QCM200 Quartz Crystal Microbalance 18 Theory Operation and Calibration Chapter 2 AGC Amp gt Figure 18 Oscillator Circuit with Varactor Nulling of Co With C canceled the circuit simplifies to that shown in Figure 19 For this circuit the zero phase condition is achieved at series resonance where the reactance of Cm and Ly cancel At series resonance Rm and R form a resistive attenuator requiring an AGC gain of Ay Rm R_ R_ to sustain oscillation By knowing the AGC gain Ay required to sustain oscillation we can determine Rm R1 Av 1 AGC Amp Lm Om Rm Ri Zim Zom 0 Figure 19 Oscillator Circuit Model with Co cancelled by C QCM200 Quartz Crystal Microbalance SRS Chapter 2 Theory Operation and Calibration 19 Capacitance Cancellation The QCM200 System incorporates a method of nulling C capacitance insuring that the frequency and resistance values measured correspond to the true series resonant parameters of the quartz oscillator The front panel of the QCM200 Controller includes 1 a ten turn dial to control the
33. the application of the electrochemical waveform to the working electrode and the simultaneous measurement of the current flowing through the electrochemical cell and the oscillation frequency and series resonance resistance of the crystal QCM200 Quartz Crystal Microbalance 34 Theory Operation and Calibration Chapter 2 Figure 24 is an example of a typical voltammogram massogram plot obtained from a 10 mM solution of CuSO in 0 1 M H SO using a 1 inch diameter Au coated quartz crystal mounted in a standard Crystal Holder as the working electrode Note cathodic current is treated as positive 4imM CuSO in 0 1MH SO Reduction 50 Yoltammogram 4750 7 0 00 200 100 00 Faia paw f S E 2750 R 5 30 00 pi 400 00 3254 sooo 00 537 507 600 00 rang 800 00 scl Cu s gt Cu 342 507 i i L p 1 i p oe t D 1 t 1 p 7900 00 055 O50 045 040 03 03 025 020 015 O10 006 000 005 010 215 00 025 063 O08 O40 Patents vs AgiAgCh Figure 24 Cyclic voltammogram and massogram data for Cu deposition on a Au electrode The frequency potential diagram shows a frequency decrease in perfect sync with the deposition of Cu metal reduction on the crystal s surface The mass sensing capabilities of the QCM200 are complemented by its ability to simultaneously detect subtle changes in the viscous loading of the QCM crystal during redox processes Figure 25 is a graphical representation of t
34. the circuit ground via the series combination of C10 1000 pF and R6 47 Q QCM200 Analog Board SRS The analog board contains all of the analog circuitry of the QCM200 power AGC amplifier filter etc The digital board and display board contain the microprocessor controlled frequency counter A D and D A converter RS 232 interface and display This section only describes the analog circuitry The analog board is used with the QCM25 Oscillator to provide power varactor bias and conversion of the differential 5 MHz and AGC signals from the QCM25 into single ended signals available to the user on the front panel BNCs The QCM200 is powered by a universal input 15VDC 1A power supply The line input should be between 90 and 264 VAC 47 to 63 Hz allowing worldwide operation from line power The 15 VDC from the switching power supply is re regulated to 12 VDC and 5 VDC by linear regulators The 12 VDC power supply is used for analog circuits and the 5 VDC supply is used to power the 5 MHz TTL output buffer and to power the QCM25 oscillator via the Cat 5 cable The differential RS 485 5 MHz signal from the QCM25 is terminated into R12 100 Q and converted to a single ended TTL signal by U5 a DS8921A RS 485 transceiver The 5 MHz TTL signal drives all eight inputs of U6 a 74HC541 octal buffer The outputs of the octal buffer are combined via R15 amp R16 each 100 Q which drive the output BNC via the balun T1 The output has a 5
35. the electrodes e Do not handle the sensor crystal using bare fingers Hold the sensor crystal with tweezers and only from its outer edge outside the electrode area to prevent scratches The tweezers should have smooth gripping surfaces and preferably be made out of soft plastic material e Before starting a surface cleaning confirm that the crystal material will not be damaged by the cleaning solutions Perform a test run on a discarded or practice crystal whenever possible Cleaning The surface properties of the sensor crystal determine the interaction of sample material with the surface Therefore the development of proper protocols for surface preparation and cleaning are required to obtain reproducible measurements This section provides the basic information you need to develop a cleaning protocol suitable for your sample surface system Figure 30 shows a standard 1 inch diameter gold coated sensor crystal When mounted on a Crystal Holder it is the Liquid Surface that will be in contact with the sample gas or liquid during the measurements The counter electrode and electrical contacts for the electrodes are on the Contact Surface of the crystal in the leak proof crystal chamber The most appropriate cleaning method depends on the sample system the interaction of the sample with the crystal surface and the properties of the sensor crystal itself QCM200 Quartz Crystal Microbalance ASRS Chapter 3 SRS Sensor Crysta
36. the liquid contact electrode is connected to the working electrode lead of the potentiostat through the Crystal Face Bias connector of the QCM25 Crystal Oscillator Notes The QCM25 Crystal Oscillator provides transformer isolation of the crystal s front face i e liquid surface electrode This allows direct electrical connection of the quartz crystal face to the working electrode pin of any standard potentiostat galvanostat The Frequency Analog Out voltage signal is proportional to the Relative Frequency readings and can be used to interface the QCM frequency signal to the data acquisition infrastructure of most commercially available potentiostats Temperature stabilization is essential in EQCM experiments for high accuracy measurements Reference Counter Potentiostat Work Crystal Face Bias QCM25 Aux A D Input Analog Frequency QCM200 Figure 23 Basic EQCM setups with a QCM200 For the QCM200 setup the Frequency Analog Out signal of the QCM controller is connected to the Ext A D Input of the potentiostat The Scale value is adjusted to best match the Relative Frequency changes expected during the electrochemical processes The potentiostat digitizes the voltage signal and its PC software displays the Relative Frequency changes in synchronicity with the electrochemical data With the setup of Figure 23 a typical cyclic voltammetric EQCM experiment would involve
37. to determine the resonance frequency of the crystal It determines the data acquisition rate and the frequency resolution of the QCM200 i Gate time 0 100 msec 1 1 sec 2 10 sec Example P1 lt CR gt Set the gate time to 1 second P lt CR gt Returns the Gate Time i SRS QCM200 Quartz Crystal Microbalance 104 QCM200 Remote Programming Appendix B G S Query Absolute Frequency Query the Absolute Frequency Example F lt CR gt Returns the Absolute Frequency in Hz Frequency Offset Set the Frequency Offset value or query the Relative Frequency Relative Frequency Absolute Frequency Frequency Offset Example G lt CR gt Set the Frequency Offset to the current Absolute Frequency G lt CR gt Returns the Relative Frequency in Hz Query Absolute Resistance Query the Absolute Resistance Example R lt CR gt The Absolute Resistance is returned in Ohms Resistance Offset Set the Resistance Offset or query the Relative Resistance Relative Resistance Absolute Resistance Resistance Offset Example S lt CR gt Set the Resistance Offset to the current Absolute Resistance S lt CR gt Returns the Resistance Offset in Ohms Identification String Query the Identification String Example I lt CR gt Returns a string similar to QCM200 rev 1 04 s n69001 Query Status Query the Status Byte The value is returned as a decimal number from 0 to 255 The conditions for each bit are listed below Bit S
38. unwanted effects due to changes in the properties of the carrier buffer liquid or solvent solutions should be prepared carefully Whenever possible use purified samples at high concentration and dilute them in the appropriate buffer or solvent just before measurement Use solvents or buffers from the same stock during each measurement series Avoid mechanical vibrations Keep the sensor away from mechanical equipment containing motors or similar vibrating parts Fasten all dangling cables that might transfer vibrations to the crystal holder flow cell Avoid transients Avoid sudden mechanical stresses such as knocking on the crystal holder pulling on cables sudden shifts in the experimental setup etc Avoid sudden temperature changes In AT cut quartz crystals frequency fluctuations depend not only on the T but also on the rate of change of T Avoid sudden pressure changes such as pressure transients in gas flow systems or flowrate changes in liquid flow injection systems Whenever possible replace peristaltic pumps with siphon setups or syringe pumps Relax mechanical stress It is often a good practice to tap on the holder flow cell before starting a new set of measurements Gentle tapping helps to dislodge trapped bubbles and relaxes mechanical stresses at the o ring seats resulting in reduced drift problems Wait for the signal to stabilize after liquid exchange In flowing setups it is important to keep in mind that detectable
39. 0 output impedance and the balun ensures that the shield current returns to the source which reduces the opportunity for the 5 MHz spreading everywhere The differential AGC signal is ac terminated by R29 R30 and C16 17 and is applied to the differential amplifier U9A creating a single ended voltage with a gain of 1x The gain of 1x is with respect to the AGC voltage in the QCM25 One needs to be aware that the QCM25 has a source resistance of 2X1 KQ for the differential AGC signal to compute the gain correctly U9B functions as a comparator which turns the OSC LED on when the AGC voltage exceeds about 0 8 VDC or Voong gt 2 0 which corresponds to crystal with a resistance of less than 4 kQ The single ended AGC voltage is further amplified and filtered by two low pass Butterworth filters Both filters have two poles The first U10B is set to 80 Hz and the second U10A is set to 8 Hz The Veong BNC output is driven by the second filter via a QCM200 Quartz Crystal Microbalance 78 QCM Circuit Description Chapter 4 1 kQ resistor Together these filters provide a gain of 2 5x for the AGC signal from the QCM25 The gain is adjusted at the factory by setting P1 Capacitive Nulling The rest of the circuits on the analog board schematic are used to determine and set the correct bias for the varactor in the QCM25 As previously discussed a varactor is used in the QCM25 circuit which cancels the current that flows though the cryst
40. 0299 568 5 00299 568 5 00299 568 5 00299 568 5 00299 568 5 00299 568 5 00299 568 5 00299 568 5 00299 568 5 00299 568 5 00470 569 5 00299 568 5 00470 569 VALUE 022UF X7R 022UF X7R 022UF X7R 022UF X7R 022UF X7R 022UF X7R 022UF X7R 022UF X7R 022UF X7R 120P AU AU AU 01U 2 2U T16 2 2U T16 1000P 3300P 01U 022UF X7R AU AU AU AU AU AU AU 01U AU AU AU AU AU AU AU AU AU AU AU AU AU AU AU AU AU 2 2U T16 AU 2 2U T16 QCM Circuit Description DESCRIPTION Capacitor Chip SMT0805 50V 10 NPO Capacitor Chip SMT0805 50V 10 NPO Capacitor Chip SMT0805 50V 10 NPO Capacitor Chip SMT0805 50V 10 NPO Capacitor Chip SMT0805 50V 10 NPO Capacitor Chip SMT0805 50V 10 NPO Capacitor Chip SMT0805 50V 10 NPO Capacitor Chip SMT0805 50V 10 NPO Capacitor Chip SMT0805 50V 10 NPO Capacitor Chip SMT1206 50V 5 NPO Cap Ceramic 50V SMT 1206 10 X7R Cap Ceramic 50V SMT 1206 10 X7R Cap Ceramic 50V SMT 1206 10 X7R Capacitor Chip SMT1206 50V 5 NPO Cap Tantalum SMT all case sizes Cap Tantalum SMT all case sizes Capacitor Chip SMT1206 50V 5 NPO Capacitor Chip SMT1206 50V 5 NPO Capacitor Chip SMT1206 50V 5 NPO Capacitor Chip SMT0805 50V 10 NPO Cap Ceramic 50V SMT 1206 10 X7R Cap Ceramic 50V SMT 1206 10 X7R Cap Ceramic 50V SMT 1206 10 X7
41. 0K Thick Film 5 200 ppm Chip Resistor R327 4 00485 441 1K Pot Multi Turn Trim 3 8 Square Top Ad R 1210 4 01431 461 10 Thick Film 5 200 ppm Chip Resistor R 1220 4 01431 461 10 Thick Film 5 200 ppm Chip Resistor R 1310 4 01431 461 10 Thick Film 5 200 ppm Chip Resistor R 1320 4 01431 461 10 Thick Film 5 200 ppm Chip Resistor R 1610 4 01455 461 100 Thick Film 5 200 ppm Chip Resistor R 1620 4 01431 461 10 Thick Film 5 200 ppm Chip Resistor R1710 4 01431 461 10 Thick Film 5 200 ppm Chip Resistor T11 6 00622 610 ADT1 6T Transformer U 12 3 00952 360 OPA2277UA Integrated Circuit Surface Mount Pkg U 13 3 00967 360 OPA177GS Integrated Circuit Surface Mount Pkg U 14 3 01145 360 XC95288XL Integrated Circuit Surface Mount Pkg U 16 3 00969 360 DAC1220E Integrated Circuit Surface Mount Pkg U 17 3 01397 360 LTC2410CGN Integrated Circuit Surface Mount Pkg U 18 3 00970 360 MAX6225BCSA Integrated Circuit Surface Mount Pkg U 21 3 01146 360 PIC16F873A I SO Integrated Circuit Surface Mount Pkg U 22 3 00936 360 MAX3232CSE Integrated Circuit Surface Mount Pkg U 23 3 01008 360 LT1521CST 3 3V Integrated Circuit Surface Mount Pkg U 24 3 00709 360 78L05 Integrated Circuit Surface Mount Pkg U 25 3 00602 360 78L12 Integrated Circuit Surface Mount Pkg U 27 3 01147 360 LM2674M Integrated Circuit Surface Mount Pkg U 28 3 00712 360 79L05 Integrated Circuit Surface Mount Pkg U 31 3 00781 360 NJM3
42. 1 QCM100 Printed Circuit Board PC1 7 01512 701 QCM200 DISPLAY Printed Circuit Board Q1 3 00580 360 MMBT3906LT1 Integrated Circuit Surface Mount Pkg Q 12 3 00601 360 MMBT3904LT1 Integrated Circuit Surface Mount Pkg R1 4 01213 462 10 0K Thin Film 1 50 ppm MELF Resistor R2 4 01280 462 49 9K Thin Film 1 50 ppm MELF Resistor R3 4 01471 461 470 Thick Film 5 200 ppm Chip Resistor R4 4 01503 461 10K Thick Film 5 200 ppm Chip Resistor R5 4 01503 461 10K Thick Film 5 200 ppm Chip Resistor R6 4 01503 461 10K Thick Film 5 200 ppm Chip Resistor R7 4 01503 461 10K Thick Film 5 200 ppm Chip Resistor R8 4 01503 461 10K Thick Film 5 200 ppm Chip Resistor R9 4 01503 461 10K Thick Film 5 200 ppm Chip Resistor R10 4 01575 461 10M Thick Film 5 200 ppm Chip Resistor R11 4 01338 462 200K Thin Film 1 50 ppm MELF Resistor R11 4 01466 461 300 Thick Film 5 200 ppm Chip Resistor R12 4 01455 461 100 Thick Film 5 200 ppm Chip Resistor R12 4 01466 461 300 Thick Film 5 200 ppm Chip Resistor R13 4 01447 461 47 Thick Film 5 200 ppm Chip Resistor R14 4 01447 461 47 Thick Film 5 200 ppm Chip Resistor R15 4 01455 461 100 Thick Film 5 200 ppm Chip Resistor R15 4 01479 461 1 0K Thick Film 5 200 ppm Chip Resistor R16 4 01455 461 100 Thick Film 5 200 ppm Chip Resistor R16 4 01479 461 1 0K Thick Film 5 200 ppm Chip Resistor R17 4 01146 462 2 00K Thin Film 1 50 ppm MELF Resistor R18 4 01209 462 9
43. 2 and ZERO LEDS A 12 character 5x7 alphanumeric LED display on the front panel of the QCM200 controller displays frequency mass and resistance measurements and also relevant instrument settings The RS 232 LED is an activity indicator that flashes whenever a character is received or transmitted over RS232 The ZERO LED flashes to indicate zeroing of the Relative Frequency or Relative Resistance readings after the VALUE key is held down for 2 seconds Menu System PARAMETER and VALUE buttons Two front panel keys labeled PARAMETER and VALUE navigate through the menus Use the PARAMETER key to display the next parameter The VALUE key walks through the circular list of possible values for the current parameter The displayed value becomes active immediately Pressing the PARAMETER key stores the new value into memory and displays the next parameter also in a circular list Parameter Value Symbol Display Absolute Frequency Hz Absolute q y Hz Frequency F series resonance frequency of the quartz crystal Relative Frequency Hz Frequency Relative f q y Hz Frequency Absolute Frequency Frequency Offset Mass Displacement ng Mass m l p ng Relative Frequency 0 0566 Absolute Resistance Ohm series resonance resistance of the quartz crystal Absolute Resistance Relative Resistance Ohm Absolute Resistance Resistance Offset 10 seconds Gate 10S Gate 1 second Gate 1 S Gate time fo
44. 32 Electrochemical Quartz Crystal Microbalance 32 Chemical and Biological Sensors 38 Self Assembled Monolayers 41 Dissipation Technique 42 References 43 Chapter 3 Sensor Crystals and Holders 49 SRS Introduction 49 Sensor Crystals 50 Principle of Operation 50 Crystal Handling 56 Surface Modifications 59 Crystal Holder 62 QCM200 Quartz Crystal Microbalance iv Contents Crystal Cleaning Basket 63 Tips for Operation in Liquids 64 Tips for Operation in Gases 67 Bubbles and Liquid Flow Cells 68 References 70 Chapter 4 QCM Circuit Description 75 Introduction 75 QCM25 Crsytal Oscillator 75 QCM200 Analog Board 77 QCM200 Digital Boards 80 Parts Lists 83 Appendix A Frequency Counter Selection Criteria 99 Appendix B QCM200 Remote Programming 101 Introduction 101 Command Syntax 102 Command List 103 QCM200 Quartz Crystal Microbalance SRS Overview v Front Panel Overview Jes SET DIAL TO NULL Co ADJUST HOLD ich e Nuu e 4 vow HOLD TO ZERO Figure 1 Front Panel of QCM200 Digital Controller Power Switch green PWR LED The QCM200 Controller is turned on by toggling the power switch The green PWR LED lights up to indicate that the unit is powered on Crystal Probe Connector green OSC LED The Crystal Probe connector is an RJ 45 receptacle used to connect the QCM200 Controller to the QCM25 Crystal Oscillator QCM Controller connector A 3 foot long Cat 5 straight th
45. 50 ppm MELF Resistor R125 4 01280 462 49 9K Thin Film 1 50 ppm MELF Resistor R126 4 01455 461 100 Thick Film 5 200 ppm Chip Resistor R127 4 01471 461 470 Thick Film 5 200 ppm Chip Resistor R131 4 01213 462 10 0K Thin Film 1 50 ppm MELF Resistor R132 4 01213 462 10 0K Thin Film 1 50 ppm MELF Resistor R141 4 01455 461 100 Thick Film 5 200 ppm Chip Resistor R142 4 01461 461 180 Thick Film 5 200 ppm Chip Resistor R171 4 01455 461 100 Thick Film 5 200 ppm Chip Resistor R172 4 01213 462 10 0K Thin Film 1 50 ppm MELF Resistor R173 4 01146 462 2 00K Thin Film 1 50 ppm MELF Resistor R211 4 01519 461 47K Thick Film 5 200 ppm Chip Resistor R213 4 01467 461 330 Thick Film 5 200 ppm Chip Resistor R214 4 01467 461 330 Thick Film 5 200 ppm Chip Resistor R215 4 01496 461 5 1K Thick Film 5 200 ppm Chip Resistor R 271 4 01155 462 2 49K Thin Film 1 50 ppm MELF Resistor R272 4 01246 462 22 1K Thin Film 1 50 ppm MELF Resistor R310 4 01431 461 10 Thick Film 5 200 ppm Chip Resistor R320 4 01431 461 10 Thick Film 5 200 ppm Chip Resistor R 321 4 01129 462 1 33K Thin Film 1 50 ppm MELF Resistor R322 4 01129 462 1 33K Thin Film 1 50 ppm MELF Resistor R323 4 01471 461 470 Thick Film 5 200 ppm Chip Resistor R324 4 01455 461 100 Thick Film 5 200 ppm Chip Resistor R325 4 01455 461 100 Thick Film 5 200 ppm Chip Resistor R326 4 01479 461 1
46. 6 003 BNC BUSHING Insulators Zo 0 00696 043 3 8X5 8 032THK Washer nylon Zo 1 00388 120 MALE BNC 4979 Connector BNC Z0 7 01412 720 EQCM Fabricated Part ZO 7 01413 720 EQCM Fabricated Part Zo 9 00267 917 GENERIC Product Labels ASRS QCM200 Quartz Crystal Microbalance 92 QCM Circuit Description Chapter 4 QCM200 Quartz Crystal Microbalance SRS Frequency Counter Selection Criteria 99 Appendix A Frequency Counter Selection Criteria The QCM200 includes a Frequency Output port BNC on the front panel for connection to an external frequency counter Frequency Output front panel AC signal Frequency 5 MHz nominal Level TTL square wave Source Impedance 502 Connector BNC The QCM200 Digital Controller features a built in frequency counter to measure the resonant frequency and display it on the front panel The stability and accuracy of the frequency counter is more than adequate for most QCM experiments For extremely demanding applications an external timebase such as the SRS FS725 Rubidium Frequency Standard can eliminate all frequency errors However the option to connect an external frequency counter is also available to 1 compare frequency measurements against an external counter and 2 provide connectivity to a pre existing experimental setup including an integrated frequency counter The selection criteria for a frequency counter for QCM applications include resolution
47. 6 032 31894 Termination Z0 0 00907 020 6 32X1 4 PF UC Screw Flathead Phillips Zo 0 00996 016 BUTTON CAP Power Button Zo 1 00003 120 BNC Connector BNC Z0 1 00273 171 10 COND DIL Cable Assembly Ribbon ZO 1 00472 112 2 PIN 24AWG WH Connector Amp MTA 100 ZO 2 00049 211 SPST ON NONE OF Switch Rocker Zo 6 00965 615 15V 15W 1A Power Supply Z0 7 01421 720 QCM100 P S CVR Fabricated Part Zo 7 01502 720 QCM200 CHASSIS Fabricated Part Zo 7 01503 720 QCM200 COVER Fabricated Part Zo 7 01504 709 QCM200 LEXAN Lexan Overlay Zo 9 00267 917 GENERIC Product Labels QCM200 Quartz Crystal Microbalance SRS Chapter 4 QCM200 Main Board REF C11 C12 C13 C14 C15 C16 C17 C18 C19 C31 C 32 C 33 C 34 C 36 C110 C 120 C 121 C 161 C 162 C 191 C212 C 213 C 221 C 222 C 223 C 224 C 225 C 271 C310 C 320 C 1110 C1111 C 1120 C 1130 C 1140 C 1150 C 1160 C 1170 C 1180 C 1190 C 1210 C 1220 C 1310 C 1320 C 1610 C 1620 C 1630 C 1640 SRS PART 5 00531 504 5 00531 504 5 00531 504 5 00531 504 5 00531 504 5 00531 504 5 00531 504 5 00531 504 5 00531 504 5 00376 552 5 00299 568 5 00299 568 5 00299 568 5 00399 552 5 00470 569 5 00470 569 5 00387 552 5 00393 552 5 00399 552 5 00531 504 5 00299 568 5 00299 568 5 00299 568 5 00299 568 5 00299 568 5 00299 568 5 00299 568 5 00399 552 5 00299 568 5 00299 568 5 00299 568 5 00299 568 5 00299 568 5 00299 568 5 00299 568 5 0
48. 60 Integrated Circuit Surface Mount Pkg U 32 3 00753 360 4053 Integrated Circuit Surface Mount Pkg Y1 6 00639 623 40 00MHZ 3 3V Temp Controlled Crystal Osc SRS QCM200 Quartz Crystal Microbalance 90 QCM Circuit Description QCM25 Crystal Oscillator C1 C2 C3 C4 C5 C6 C7 C8 c9 C10 C11 C12 C13 C14 C15 C16 C17 C18 C19 C20 C21 C22 C23 C24 D1 D2 J1 L1 L2 L3 P1 P2 PC1 R1 R2 R3 R5 R6 R7 R8 R9 R10 R11 R12 R13 R14 R15 R16 REF SRS PART 5 00318 569 5 00299 568 5 00299 568 5 00299 568 5 00299 568 5 00298 568 5 00299 568 5 00299 568 5 00299 568 5 00387 552 5 00299 568 5 00387 552 5 00387 552 5 00299 568 5 00299 568 5 00299 568 5 00299 568 5 00299 568 5 00364 552 5 00372 552 5 00372 552 5 00380 552 5 00376 552 5 00384 552 3 00010 303 3 00803 360 1 00505 100 6 00236 631 6 00013 606 6 00171 606 4 00486 441 4 00486 441 7 01426 701 4 01471 461 4 01431 461 4 01431 461 4 01447 461 4 01447 461 4 01175 462 4 01117 462 4 00217 408 4 00217 408 4 01463 461 4 00992 462 4 01447 461 4 01527 461 4 01527 461 4 01447 461 VALUE 2 2U T35 AU AU AU AU 01U AU AU AU 1000P AU 1000P 1000P AU AU AU AU AU 12P 56P 56P 270P 120P 560P GREEN MMBV609 RJ45 MODULAR FR47 2 2UH 5PH 4 7UH 5PH 50 50 QCM25 470 10 10 47 47 4 02K 1 00K 1 000K 1 000K 220 49 9 47 100K 100K 47 DESCRIPTION Cap Tan
49. 994 518 24 Adrian W Bott Characterization of Films Immobilized on an Electrode Surface Using the EQCM Current Separations 18 3 1999 79 Mark Deakin and Daniel Buttry Electrochemical Applications of the Quartz Crystal Microbalance Anal Chem 61 20 1989 183 QCM200 Quartz Crystal Microbalance SRS Chapter 2 Theory Operation and Calibration 45 Daniel Buttry and Michael Ward Measurement of Interfacial Processes at electrode surfaces with the EQCM Chem Rev 92 6 1992 1355 28 Cheryl Chagnard Patty Gilbert A Neal Watkins Theodore Beeler and David Paul An electronic Oscillator with automatic gain control EQCM Applications Sensors and actuators B 32 1996 129 136 Note the same experiment as described in Figure 10 is described in page 134 of this publication The numbers required to calculate the change in viscosity in the Nernst layer were obtained from M D Ward et al Anal Chem 65 1993 3232 Wolfgang Stockel and Rolf Schumacher In situ Microweighing at the Junction Metal Electrolyte Ber Bunsenges Phys Chem 91 1987 345 28 C Gabrielli M Keddam and R Torrei Calibration of the Electrochemical Quartz Crystal Microbalance J Electrochem Soc 139 9 1991 2657 Note A calibration procedure based on the deposition of Ag on Au electrodes is described Graeme Andrew Snook Investigation of Solid State Reactions by Electrochemical and Quartz Crystal Microbala
50. C or TX_TFC D11 on the Display board is a bi color green red LED that lights green when LED_TRAFFIC is asserted high The MCU pulses COM_ERR high whenever it detects an illegal or malformed command from the RS232 The CPLD asserts LED_ERR high for 132ms when COM_ERR is active D11 on the Display board lights red when LED_ERR is active Display board The 12 character LED display consists of a 4 character display U11 and an 8 character display U12 The MCU controls the on off state of the 420 individual LED by asserting DISP_CE low and clocking toggling SCLK while setting or clearing SDATA The LED state is clocked with DISP_RS held low An 8 bit control header is clocked in first with DISP_RS held high The momentary push button signals BUTTONO and BUTTON assert low when the button is pressed If the user holds the SELECT button pressed for 2 seconds BUTTON1 the MCU asserts REL_LED high and saves the current value of F or R as the Offset value to use in the Relative F or R calculation The resistors supplying the bicolor RS 232 LED are always passing current Normally the CPLD signals LED_ERR and LED_TFC are low which shunts the current away from D11 on the Display board The CPLD drives the cathode of D12 or D13 high steer the current though D11 and light the LED QCM200 Quartz Crystal Microbalance SRS Chapter 4 Parts Lists QCM Circuit Description Analog Board and Display Board REF SRS PART VALUE
51. DNA protein interactions protein adsorption cell adhesion biofouling biocompatibility polymer degradation and hydration biofilm formation self assembled monolayers etc Installation The flow cell is used in place of the Crystal Retainer Ring of the Crystal Holder Once installed the cell creates a flow chamber of small volume 0 15 mL The flow cell is made of chemically resistant Kynar and includes two inlet and outlet ports with 0 040 ID thru hole and fitted with barbed hose adapters for 0 062 ID tubing Simply slide your tube over the barbed stems to create a reliable low pressure connection to a syringe siphon system or peristaltic pump Consult Chapter 3 for additional tips on the operation of liquid flow cells Tip For flowing QCM setups requiring connection to a flow injection or sequential injection analysis system it is common practice to interface the capillary tubing to the flow cell using a short section of 1 16 ID PHARMED tubing for example part 1557 from www upchurch com Eliminating gas bubbles trapped inside the crystal chamber is essential for accurate measurements Please consult the Bubbles and Liquid Flow Cells section in Chapter 3 for some useful bubble elimination tricks QCM200 Quartz Crystal Microbalance SRS Chapter 1 Getting Started 13 Operation Two modes of operation are common for QCM flow cells Batch Mode The crystal is exposed to a sequence of sample solve
52. L Calvo Gravimetric measurement in redox polymer electrodes with the EQCM beyond the Sauerbrey limit Electrochemistry Communications 1 5 1999 167 R A Etchenique and E J Calvo Electrochemical Quartz Crystal Impedance Study of Redox Hydrogen Mediators for Amperometric Enzyme Electrodes Anal Chem 69 1997 4833 3 E J Calvo R Etchenique P N Bartlett K Singhal and Santamaria Quartz Crystal Impedance studies at 10 MHz of viscoelastic liquids and films Faraday Discuss 107 1997 141 Diethelm Johannsmann Viscoelastic Analysis of Organic Thin Films on quartz resonators Macromol Chem Phys 200 1999 501 SRS QCM200 Quartz Crystal Microbalance 46 Theory Operation and Calibration Chapter 2 C E Reed K Keiji Kanazawa and J Kaufman Physical description of a viscoelastically loaded AT cut quartz resonator J Appl Phys 68 5 1990 1993 3 D S Ballantine R M White S J Martin A J Rico E T Zellers G C Frye and H Woltjen Acoustic Wave Sensors Theory Design and Physico Chemical Applications Acad Press London UK 1997 Chapter 5 Chemical and Biological Sensors p 222 36 G G Guilbault and J Jordan Analytical uses of piezoelectric crystals CRC Reviews 19 p 1 28 W H King Piezoelectric Sorption Detector Anal Chem 36 1964 1735 37 Iddo Ben Dov and Itamar Willmer Piezoelectric Immunosensors for Urine Specimens of Chlamidia trachom
53. LMC6082IM Integrated Circuit Surface Mount Pkg U11 3 01143 306 HCMS 2965 LED Rectangular U11 3 01370 360 OPA277UA Integrated Circuit Surface Mount Pkg U 12 3 00372 360 LM13700M Integrated Circuit Surface Mount Pkg SRS QCM200 Quartz Crystal Microbalance 86 QCM Circuit Description Chapter 4 REF SRS PART VALUE DESCRIPTION U12 3 01144 306 HCMS 2975 LED Rectangular U13 3 01445 360 LMC6082IM Integrated Circuit Surface Mount Pkg U 14 3 00752 360 4052 Integrated Circuit Surface Mount Pkg U 15 3 00728 360 LM393 Integrated Circuit Surface Mount Pkg U 16 3 00728 360 LM393 Integrated Circuit Surface Mount Pkg U 26 3 00112 329 7805 Voltage Reg TO 220 TAB Package Y1 6 00958 620 76 8KHZ Crystal Zo 0 00002 008 2607 Dial Zo 0 00009 000 FOOT Hardware Misc Zo 0 00011 057 GROMMET Grommet Z0 0 00025 005 3 8 Lugs Zo 0 00043 011 4 40 KEP Nut Kep Zo 0 00079 031 4 40X3 16 M F Standoff Zo 0 00098 042 6 LOCK Washer lock Z0 0 00141 032 2 520194 2 Termination Zo 0 00185 021 6 32X3 8PP Screw Panhead Phillips Zo 0 00187 021 4 40X1 4PP Screw Panhead Phillips Z0 0 00197 002 3ED8 Power Entry Hardware ZO 0 00210 020 4 40X5 16PF Screw Flathead Phillips ZO 0 00222 021 6 32X1 4PP Screw Panhead Phillips Zo 0 00240 026 4 40X3 8PF Screw Black All Types Z0 0 00297 026 6 32 X 3 16 Screw Black All Types ZO 0 00434 054 2 26 WHITE Wire 26 UL1061 Z0 0 0051 7 000 BINDING POST Hardware Misc Zo 0 0053
54. Monolayer on Gold Langmuir 13 1997 4031 Yamaguchi et al Adsorption Immobilization and Hybridization of DNA Studies by the use of QC Oscillators Anal Chem 65 1993 1925 F Caruso et al QCM Study of DNA Immobilization and Hybridization for Nucleic Acid Sensor Development Anal Chem 69 1997 2043 R Suri et al Biosensors and Bioelectronics 9 1994 325 S Yamaguchi et al Adsorption Immobilization and Hybridization of DNA Studies by the use of QC Oscillators Anal Chem 65 1993 1925 P E Hockberger et al Cellular engineering control of cell substrate interactions in Nanofabrication and Biosystems H C Hoch L W Jelinski and H G Craighead Eds Cambridge University press 1996 276 299 Dirk Jope Joachim Sell Howard W Pickering Konrad G Weil Application of a Quartz Crystal Microbalance to the Study of Copper Corrosion in Acid Solution Inhibited by Triazole Iodide Protective Films J Electrochem Soc 142 1995 2170 2173 The CH100 Crystal Holder is also compatible with Maxtek s 1 inch diamter crystals and is also a replacement for its crystal holders model CHC 100 CHT 100 and CHK 100 Operation in liquids requires that the crystal be mounted in a holder such that only the front surface of the crystal is in contact with the fluid while at the same time providing an electrical connection to both electrodes SRS QCM200 Quartz Crystal Microbalance 74 S
55. Operation and Service Manual QCM200 Quartz Crystal Microbalance Digital Controller QCM25 5 MHz Crystal Oscillator y S RS Stanford Research Systems Revision 2 2 2 2009 Certification Stanford Research Systems certifies that this product met its published specifications at the time of shipment Warranty This Stanford Research Systems product is warranted against defects in materials and workmanship for a period of one 1 year from the date of shipment Service For warranty service or repair this product must be returned to a Stanford Research Systems authorized service facility Contact Stanford Research Systems or an authorized representative before returning this product for repair Information in this document is subject to change without notice Copyright Stanford Research Systems Inc 2004 All rights reserved Stanford Research Systems Inc 1290 C Reamwood Avenue Sunnyvale California 94089 www thinkSRS com Printed in U S A QCM200 Quartz Crystal Microbalance ASRS Safety and Preparation For Use i Safety and Preparation for Use Line Voltage The QCM200 Controller operates from a 90 132 or 175 264 VAC power source having a line frequency between 47 and 63 Hz Power consumption is 20 VA total Power Entry Module A power entry module labeled A C POWER on the back panel of the QCM200 provides connection to the power source and to a protective ground Power Cord The QCM200 package includ
56. P Mason and R N Thurston Eds Academic Press NY 1982 p 37 171 7 Stephen Martin et al Effect of Surface Roughness on the Response of Thickness Shear Mode Resonators in Liquids Anal Chem 65 1993 2910 Michael Ward and Edward J Delawski Radial Mass Sensitivity of the Quartz Crystal Microbalance in Liquid Media Anal Chem 63 1991 886 8 S J Martin et al Effect of Surface Roughness on the Response of Thickness Shear Mode Resonators in Liquids Anal Chem 65 1993 2910 C K Sullivan and G G Guilbault Commercial Quartz Crystal Microbalances theory and applications Biosensors and Bioelectronics 14 1999 663 670 10 US Patent number 5 233 261 H See for example Rupa Patel R Zhou K Zinszer F Josse and R Cernozek Real time Detection of Organic Compounds in Liquid Environments Using Polymer coated Thickness Shear Mode Quartz Resonators Anal Chem 72 2000 4888 12 G Sauerbrey Z Phys 155 1959 206 Electroanalytical Chemistry edited by Allen Bard Marcel Dekker 1991 p 23 33 14 C Gabrielli et al Calibration of the Electrochemical Quartz Crystal Microbalance J Electrochem Soc 139 9 1991 2657 QCM200 Quartz Crystal Microbalance SRS Chapter 3 Sensor Crystals and Holders 71 P D R Denison Linearity of Heavily Loaded Quartz Crystal Microbalance J Vac Sci Technol 10 1973 126 K H Behrndt Long Term Operation of Crysta
57. R Cap Ceramic 50V SMT 1206 10 X7R Cap Ceramic 50V SMT 1206 10 X7R Cap Ceramic 50V SMT 1206 10 X7R Cap Ceramic 50V SMT 1206 10 X7R Capacitor Chip SMT1206 50V 5 NPO Cap Ceramic 50V SMT 1206 10 X7R Cap Ceramic 50V SMT 1206 10 X7R Cap Ceramic 50V SMT 1206 10 X7R Cap Ceramic 50V SMT 1206 10 X7R Cap Ceramic 50V SMT 1206 10 X7R Cap Ceramic 50V SMT 1206 10 X7R Cap Ceramic 50V SMT 1206 10 X7R Cap Ceramic 50V SMT 1206 10 X7R Cap Ceramic 50V SMT 1206 10 X7R Cap Ceramic 50V SMT 1206 10 X7R Cap Ceramic 50V SMT 1206 10 X7R Cap Ceramic 50V SMT 1206 10 X7R Cap Ceramic 50V SMT 1206 10 X7R Cap Ceramic 50V SMT 1206 10 X7R Cap Ceramic 50V SMT 1206 10 X7R Cap Ceramic 50V SMT 1206 10 X7R Cap Ceramic 50V SMT 1206 10 X7R Cap Tantalum SMT all case sizes Cap Ceramic 50V SMT 1206 10 X7R Cap Tantalum SMT all case sizes 87 SRS QCM200 Quartz Crystal Microbalance 88 QCM Circuit Description Chapter 4 REF SRS PART VALUE DESCRIPTION C1710 5 00471 569 10U T16 Cap Tantalum SMT all case sizes C 1720 5 00299 568 AU Cap Ceramic 50V SMT 1206 10 X7R C 2310 5 00299 568 AU Cap Ceramic 50V SMT 1206 10 X7R C 2320 5 00528 568 2 2U Cap Ceramic 50V SMT 1206 10 X7R C 2410 5 00519 569 33U T35 Cap Tantalum SMT all case sizes C 2420 5 00299 568 AU Cap Ceramic 50V
58. RS Chapter 3 ASRS Sensor Crystals and Holders 61 Tip Thiolization agents specifically designed for SAM immobilization of proteins and DNA on metallic surfaces have recently become commercially available Consult the factory for up to date recommendations A silane layer silanization is another common material used for SAMs However since the coating can react irreversibly with the quartz material the QCM crystal cannot be used repeatedly in this application SAMs vs Polymer films Most conventional methods used for the development of QCM immunosensors have relied heavily on polymeric coatings deposited on the electrodes and capable of forming hydrophobic or covalent bonds with antibodies Polymeric films suffer of several disadvantages 1 polymer films attach to the electrode surface through weak hydrophobic bonds which can be easily broken by mechanical interaction washing and even changes in pH and 2 swelling of the polymer films in aqueous solution can lead to reduced sensitivity and reproducibility of the immunosensor Electroless Deposition Pre treatment QCMs are used to measure 1 plating rates and thicknesses in both electrolytic and electroless baths 2 plating efficiencies in electrolytic baths and 3 etching rates in chemical etching processes It is important to assure that the sensor crystal is properly preconditioned during the electroless deposition of metals Plating initiation must be complete and
59. S Rerystat Characteristic The amplified AGC voltage and ground reference are sent to the QCM200 via two 1 000 kQ resistors over a twisted pair The signal is received in the QCM200 by a differential amplifier to remove common mode signals The AGC signal is filtered and amplified by 2 5x before being output on the front panel Veond BNC The 5 MHz signal on the primary of T1 is converted to a TTL signal by U2 a DS8921A RS 485 transceiver The 5 MHz TTL signal is converted by U2 into a differential RS 485 signal which drives one pair of the Cat 5 cable connected to the QCM200 This pair is terminated into 100 Q and converted to TTL in the QCM200 QCM200 Quartz Crystal Microbalance SRS Chapter 4 QCM Circuit Description 77 The front face of the crystal is connected to the shield of the BNC connector which is connected to the binding post connector on the QCM25 The back face of the crystal is connected to the front face via the RF transformers and so both faces of the crystal are at the same dc potential Both faces are electrically isolated at dc from all circuits in the QCM25 and the QCM200 allowing the user to make unburdened measurements of dc currents on and off the front face of the crystal as might occur in electrochemistry measurements The QCM25 chassis ground is ac coupled to the circuit ground via the series combination of C9 0 1 uF and R5 47 Q The front face of the crystal and so the bias point binding post are ac coupled to
60. This example shows the immobilization of mouse gamma globulin antigen on a bare gold surface Step 1 and the subsequent binding of an antibody directed against the gamma globulin Step 3 Since the gold surface is not completely covered by antigen in Step 1 a blocking solution of concentrated ovalbumin is used in Step 2 to block all uncovered sites Figure 28 is an example of an application of the QCM200 system as a protein biosensor and a demonstration of the sensitivity of the technology towards protein protein interactions The entire experiment took place on a polished Au Cr QCM crystal housed within an axial flow cell connected to a standard flow injection analysis system consisting of a single syringe pump and a 6 port injection valve Typical flow rates were 50 L min temperature stability was 0 1 C at 27 C and the buffer solution was PBS pH7 5 Antigen mouse gamma globulin was first introduced into the cell Step 1 QCM200 Quartz Crystal Microbalance 40 Theory Operation and Calibration Chapter 2 resulting in a 35Hz frequency step caused by the non specific metal protein binding interactions between the protein and the bare gold surface i e physical adsorption The remaining non specific binding sites were then blocked with excess ovalbumin Step 2 resulting in the second and smaller frequency step Finally Step 3 antibody goat anti mouse IgG was flowed over the immobilized protein layer and the specific interaction be
61. a turns ratio of 1 1 This transformer allows galvanic isolation of the crystal from the oscillator circuit 7 A load resistance R of 50 Q The network of Rs Rm and R provide a network attenuation A which depends on the crystal s motional resistance Ri A SS A E e n 2 RJAR tR ean 8 An RF amplifier with an adjustable gain Ap of about 4 43 x The gain of this amplifier Ag is set during calibration to compensate for gain variations of all the other circuit elements 9 A low pass filter This filter is a 5 order Bessel low pass filter with fy 3 7 MHz adjusted so as to provide 180 of phase shift at 5 MHz The phase shift of this filter together with the 180 phase shift of the inverting amplifier A provides the 360 of phase shift necessary for oscillation The low pass filter is required to suppress spurious oscillations which would occur due to the high bandwidth of the loop amplifiers The low pass filter attenuates a signal at 5 MHz by about A 7 8 dB or 0 407X The motional resistance of the crystal at series resonance can now be computed The product of the gain or attenuation of all of the elements around the loop is exactly one when the circuit is oscillating at constant amplitude Hence Aa A Ap An Ao Ay 1 eqn 3 Rearranging and substituting the equation for A and solving for Rm a EL L A Ay Ay Aa As eqn 4 n L R Rm Ri Aa Ai Ar Az Ay Ri 7 eqn 5 From the chara
62. above the optimum set point then increasing the varactor bias will decrease the AGC voltage If the varactor voltage is modulated then the AGC will also be modulated The AGC modulation will be in phase with the varactor modulation if the dial is below the optimum set point and the AGC modulation will be out of phase with the varactor modulation if the dial is above the optimum set point The AGC modulation will go to zero when the dial is set to the optimum set point The QCM200 uses a synchronous detector i e lock in amplifier to measure the AGC modulation The user need only adjust the dial to null the detected AGC voltage as indicated by four front panel LEDs If the HIGH LED is on the dial should be moved to a lower setting If the LOW LED is on the dial should be moved to a higher setting Both NULL LEDs will be on when the dial is in the optimum position The reproducibility of this procedure is typically 0 01 pF Nulling the crystal capacitance is only important if the motional loss i e crystal resistance is high The variation of AGC voltage will be very small when the crystal losses are low and so it may not be possible to use this method in low loss situations Dry crystals will oscillate very near their series resonance frequency even when the capacitance has not been nulled Wet crystals or any situation for which the crystal s motional losses are high will require capacitive cancellation in order to oscilla
63. affect QCM measurements For reproducible measurements keep the following tips in mind Check for Chemical Compatibility Before starting an experiment check for chemical compatibility between the sample gases holder flow cell o rings and crystals If necessary consider replacing components with alternative materials Operate in a flowing gas configuration In order to avoid frequency transients due to sudden air movements around the crystal operate the QCM sensor in a flowing gas configuration Frequency transients as large as 10 Hz can be registered by simply walking past a QCM crystal fully exposed to air Operation within a flow cell also facilitates achieving proper temperature equalization between the crystal and the gas sample Wait for the temperature to stabilize In order to avoid frequency transients due to temperature changes it is best to temperature stabilize the flow cell crystal holder and eliminate temperature differences between the gas samples and the holder Immersion in a temperature stabilized water bath often does the job and allows the preheating loop to equalize the gas temperature with the sensor Keep in mind that changes in frequency are not only related to static changes in temperature around the crystal but also to the rate of change of temperature with time Use small and constant flow rates During flow experiments flowrates should be kept small and constant to eliminate signal transients due to pressure a
64. al Comparison of Different protein immobilization methods on QCM surface in flow injection immunoassay Anal Biochem 299 2001 130 135 Storri S Santoni T Mascini M A piezoelectric biosensor for DNA hybridization detection Anal Lett 31 11 1998 1795 1K L Prime G M Whitesides Science 252 1991 1164 K Prime G Whitesides J Am Chem Soc 1993 v 115 10714 10721 A Model System Using Self Assembled Monolayers Ramon Colorado Jr Ramon J Villazana and T Randall Lee Self Assembled Monolayers on Gold Generated from Aliphatic Dithiocarboxylic Acids Langmuir 14 1998 6337 6340 Spangler B D and Tyler B Capture Agents for a Quartz Crystal Microbalance Continuous Flow Biosensor Functionalized Self assembled Monolayers on Gold Anal Chim Acta 399 1999 51 62 Note Professor Spangler is also CEO of SensoPath Technologies a company specialized in the development of materials for the design and fabrication of SAMs on gold surfaces www sensoPath com 8 D S Karpovich and G J Blanchard Direct Measurement of the Adsorption Kinetics of Alkanethiolate Self Assembled Monolayers on a Microcrystalline Gold Surface Langmuir 10 1994 3315 C R Suri et al Biosensors and Bioelectronics 9 1994 325 S Yamaguchi et al Adsorption Immobilization and Hybridization of DNA Studies by the use of QC Oscillators Anal Chem 65 1993 1925 P E Hock
65. al s electrode and holder capacitance By canceling this current the capacitances are effectively eliminated from the oscillator circuit allowing the crystal to oscillate at its series resonance frequency The varactor capacitance is controlled by the ten turn potentiometer on the front panel Cancellation is achieved when the varactor capacitance is equal to the crystal s electrode and holder capacitance Increasing the dial setting increases the reverse bias on the varactor which decreases the varactor capacitance The dial should be set to the position which minimizes the gain required to sustain oscillation it is at this point where the capacitive currents cancel The gain required to sustain oscillation can be inferred from the AGC voltage the higher the AGC voltage the lower the gain required to sustain oscillation This can be done manually by finding the dial setting for which the AGC voltage is at a maximum or by modulating the varactor voltage and detecting the minimum gain setting using synchronous detection The second method is much faster and more accurate and is used by the QCM200 When the ADJUST HOLD switch on the front panel is placed in the ADJUST position the varactor voltage will be modulated by 5 around the dial set point The modulation frequency is 75 Hz and the waveform is sinusoidal If the dial is set below the optimum set point then increasing the varactor bias will increase the AGC voltage If the dial is set
66. al requires careful handling and cleaning procedures that do not harm the quartz material its electrode pads and its coatings Many practitioners consider their QCM crystals expendable and always discard them at the end of their measurements Traces of consumption and wear can often be detected visually e Edges of the sensor crystal might become cracked and the coating start to show scratches and holes e In electrochemistry experiments it is not unusual to observe changes in the adhesion layer of the liquid surface electrode which ultimately result in peeling of the metal pad A common problem is loss of the Cr adhesion layer in Au Cr electrodes These changes are visible from the contact side of the crystal e The liquid surface electrode might become irreversibly discolored or stained from chemical reaction with the analytes buffers or solvent When a crystal is close to being consumed the measurement signal will become noisy possibly even shaky It might even be difficult to obtain a stable baseline Spurious signals might become evident in electrochemical QCM experiments As the sensor crystal is coated the series resonance resistance increases indicating a loss of crystal Q When this occurs the circuit may occasionally resonate at one of the anharmonic frequencies The oscillation may switch to an anharmonic mode or it may alternate between the fundamental and anharmonic frequencies a condition known as mode hopping T
67. ample a 4 Q C change in resistance is to be expected in water around room temperature QCM200 Quartz Crystal Microbalance 26 Theory Operation and Calibration Chapter 2 Noise Analysis Ve varies logarithmically with Rm over most of the range of interest There is an important advantage in this the fractional resolution of the resistance is nearly independent of the resistance and so allows detailed and low noise measurement of the viscous losses To estimate the noise in resistance measurements we can take the derivative of the equation for the motional resistance units are Ohms and Ohms Volt Rm 10 000 10 75 eqn 7 dR _ V 5 1 _ V 8 10 000 10 In 10 a 2 000 In 10 10 eqn 8 c DR _ Ve 5 4605 10 0 4605 Rm 75 eqn 9 c Noise on the V signal AV is typically 50 uV with one second averaging Rm for a 5 MHz crystal in water is about 375 Q The fractional noise in the resistance measurement is then ARa _AV dR AV Ra R dV R 10 4605 R 75 28 ppm eqn 10 m This low noise floor for fractional resistance measurements allows very small changes in dissipation losses to be measured This is why a high precision voltmeter i e with at least six digits of resolution is recommended for measuring the analog conductance output and why a very high resolution 24 bit A D converter is used by the QCM200 to calculate resistance readings Calibrati
68. ant frequency but also in damping of the resonant oscillation the viscous loss is manifested as an increase in series resonance resistance R of the QCM resonator Thus R serves as an excellent independent measure of viscous loading by the medium liquid or soft film at the crystal s surface Af and AR measurements are both routinely used as independent indicators of mass loading and viscosity at the crystal liquid interface of the QCM resonator during chemical and electrochemical depositions in solution In a separate study a Butterworth Van Dyke equivalent circuit model Figure 16 was applied to derive a linear relationship between the change in series resonance resistance AR of the quartz oscillator and p 1 under liquid loading 1 2 AR T24 205PL ML eqn 16 n Pallq SRS QCM200 Quartz Crystal Microbalance 30 Theory Operation and Calibration Chapter 2 Where AR change in series resonance resistance in Q n number of sides in contact with liquid angular frequency at series resonance 27 fs Lu inductance for the unperturbed dry resonator usually in mH The QCM200 System was specifically designed for operation under heavy viscous loading The standard Crystal Holder supports operation in gas and liquid environments and provides single electrode exposure to liquids i e n 1 in eqn 16 as required for compatibility with electrochemical QCM measurements The Crystal Oscillator prov
69. atis Employing QCM Microgravimetric Analysis Anal Chem 69 1997 3506 Storri et al Surface modifications for the development of piezoimmunosensors Biosensors and Bioelectronics 13 1998 347 Tajima I et al Monitor of antibodies in human saliva using a piezoelectric QC biosensor Anal Chim Acta 365 1998 147 149 38 Makoto Muratsugu et al QCM for the detection of microgram quantities of human serum albumin Relationship between the frequency change and the mass of protein adsorbed Anal Chem 65 1993 2933 2937 M Malmsteen J Coll Interf Sci 172 1995 106 Note the data in these papers is in very good agreement with what was observed at SRS with the QCM200 system and BSA as the test protein 3 A Hengerer C K sslinger1 J Decker S Hauck1 I Queitsch2 H Wolf and S D bel2 Determination of Phage Antibody Affinities to Antigen by a Microbalance Sensor System BioTechniques 26 956 964 May 1999 G G Guibault Analytical uses of immobilized Enzymes Modern Monographs in Analytical Chemistry Vol 2 Marcel Dekker New York 1984 G M Minunni M Mascini G G Guilbault B Hock The Quartz Crystal Microbalance as Biosensor A Status Report on its Future Anal Lett 28 5 1995 749 S Tombelli M Mascini Piezoelectric Quartz Crystal Biosensor Recent Immobilisation Schemes Anal Lett 33 11 2000 pp 2129 2151 Kim R Rogers Principles of A
70. ayer of Fe CN s reduction adjacent to the QCM electrode Calibration ASRS It has been amply demonstrated in the literature that when experiments involve only relative frequency shifts which are measured in a fixed solution the offset caused by the viscous loading of the liquid has negligible effect on the accuracy of the Sauerbrey equation for the determination of small mass changes in rigid deposits Quantitative interpretation of the EQCM data in those cases is based on the combination of the Sauerbrey equation eqn 1 and Faraday s law The former relates change in frequency to change in mass for thin rigid deposits whereas the latter relates charge passed in an electrochemical experiment to the number of moles of material electrolyzed Therefore frequency changes can be related to the total charge passed An example would be the electrodeposition of Ag on a Pt electrode QCM crystal The charge Q is an integral measure of the total number of electrons delivered at the interface during the reduction process To the extent that each electron supplied results in the deposition of one atom of Ag there should be a linear relationship between Q and Af as is given by equation 8 nFA Af eqn 17 where QCM200 Quartz Crystal Microbalance 36 Theory Operation and Calibration Chapter 2 Af frequency change in Hz Mw apparent molar mass of the depositing species in grams mole C Sauerbrey s sensitivity factor f
71. balance SRS Chapter 4 QCM Circuit Description 85 REF SRS PART VALUE DESCRIPTION R 42 4 01660 462 2 00M Thin Film 1 50 ppm MELF Resistor R 43 4 01660 462 2 00M Thin Film 1 50 ppm MELF Resistor R 44 4 01215 462 10 5K Thin Film 1 50 ppm MELF Resistor R50 4 01191 462 5 90K Thin Film 1 50 ppm MELF Resistor R51 4 01479 461 1 0K Thick Film 5 200 ppm Chip Resistor R52 4 01242 462 20 0K Thin Film 1 50 ppm MELF Resistor R53 4 01242 462 20 0K Thin Film 1 50 ppm MELF Resistor R54 4 01660 462 2 00M Thin Film 1 50 ppm MELF Resistor R55 4 01338 462 200K Thin Film 1 50 ppm MELF Resistor R56 4 01527 461 100K Thick Film 5 200 ppm Chip Resistor R57 4 01213 462 10 0K Thin Film 1 50 ppm MELF Resistor R58 4 01213 462 10 0K Thin Film 1 50 ppm MELF Resistor R59 4 01471 461 470 Thick Film 5 200 ppm Chip Resistor R 60 4 01338 462 200K Thin Film 1 50 ppm MELF Resistor R 61 4 01184 462 4 99K Thin Film 1 50 ppm MELF Resistor R 62 4 01213 462 10 0K Thin Film 1 50 ppm MELF Resistor R 63 4 01213 462 10 0K Thin Film 1 50 ppm MELF Resistor R 64 4 01660 462 2 00M Thin Film 1 50 ppm MELF Resistor R65 4 01660 462 2 00M Thin Film 1 50 ppm MELF Resistor R 66 4 01213 462 10 0K Thin Film 1 50 ppm MELF Resistor R 67 4 01191 462 5 90K Thin Film 1 50 ppm MELF Resistor R 68 4 01519 461 47K Thick Film 5 200 ppm Chip Resistor R69 4 01479 461 1 0K Thick Film 5 200 ppm
72. bbles Connect a gt 3 mL syringe loaded with the solution you wish to inject into the QCM chamber to the inlet port of the flow cell Connect the outlet port to the body of a 3 mL syringe with its plunger removed and mounted vertically to act as a waste collector Push about 1 2 mL of solution through the chamber into the waste container Press the syringe back and forth a few times until no more bubbles are seen to evolve into the waste container The number of bubbles will decrease after each back and forth action until no more bubbles are visible Flow reversals are very efficient at displacing bubbles out of the chamber For siphon systems see Figure 33 a similar method can be employed to remove bubbles from a freshly filled chamber in this case the sample reservoir with the sample solution is connected to the inlet port and a 3 5 mL syringe loaded with gt 2 mL of the same sample is connected to the output port Pull the syringe plunger up to 1 force liquid into the chamber and 2 eliminate the bubbles formed from the fresh syringe connection Press the syringe back and forth a few times until no more bubbles evolve into the sample reservoir Stop the flow at the inlet and disconnect the syringe when no more bubbles are seen It is generally preferable to position the output port above the inlet port in flowing systems Fewer bubbles are generally trapped if the chamber is filled slowly from the bottom up with the output port being t
73. berger et al Cellular engineering control of cell substrate interactions in Nanofabrication and Biosystems H C Hoch L W Jelinski and H G Craighead Eds Cambridge University press 1996 276 299 D S Karpovich and G J Blanchard Direct Measurement of the Adsorption Kinetics of Alkanethiolate Self Assembled Monolayers on a Microcrystalline Gold Surface Langmuir 10 1994 3315 H M Schessler et al Quantitating the Balance between Enthalpic and Entropic Forces in Alkanethiol Gold Monolayer Self Assembly J Am Chem Soc 118 1996 9645 D S Karpovich and G J Blanchard Vapor adsorption onto metal and modified interfaces Evidence for adsorbate penetration of an alkanethiol Monolayer on Gold Langmuir 13 1997 4031 D S Karpovich and G J Blanchard An Undergraduate Laboratory Experiment for he Direct Measurement of Monolayer Formation Kinetics J Chem Education 72 1995 466 ASRS QCM200 Quartz Crystal Microbalance 48 Theory Operation and Calibration Chapter 2 J Justin Gooding and D Brynn Hibbert The application of alkanethiol self assembled monolayers to 52 S enzyme electrodes TrAC Trends in Analytical Chemistry 18 8 1999 525 Zhao Yang Wu et al QCM Immunosensor for Schistsoma Japonicum Infected Rabbit Serum Analytical Sciences 19 2003 437 Yung Chuan Liu Chih Ming Wang and Kuang Pin Hsiung Comparison of Different Protein Immo
74. bias voltage required by the varactor Cy and 2 a switch to set the controller into the Adjust Mode for nulling Co There are two ways to operate the QCM200 Analog Controller to null Co 1 The unit to unit variations in C are small enough and the reproducibly of Cy is good enough 2 pF that most users can just set the varactor bias to a fixed value and forget about the whole issue Set the ten turn dial to 8 0 which will provide 9 0 volts of reverse bias to the varactor making C about 18 pF This method is recommended for dry applications where Rm is low This is not recommended for sticky applications such as solutions of glycerol where Rm can be very high Null C with the conductance lock in peak detection circuit In the Adjust Mode the unit will modulate the varactor bias with a 75 Hz sine wave and indicate if the Co compensation is High Low or Nulled Start with the ten turn dial set to 8 0 the LED should indicate that the crystal is oscillating and switch to Adjust Mode Reduce the setting on the dial if the High LED is on increase the setting if the Low LED is on and lock the dial at the middle of the range for which both Null LEDs glow with equal intensity Return the switch to the HOLD Mode setting when done As A General Rule SRS Capacitance cancellation is essential for accurate measurements of liquids and lossy i e soft films Capacitance cancellation should be checked and readjusted every tim
75. bilization Methods on Quartz Crystal Microbalance Surface in Flow Injection Immunoassay Analytical Biochemistry 299 2001 130 135 Yamaguchi et al Adsorption Immobilization and Hybridization of DNA Studies by the use of QC Oscillators Anal Chem 65 1993 1925 F Caruso et al QCM Study of DNA Immobilization and Hybridization for Nucleic Acid Sensor Development Anal Chem 69 1997 2043 Ito K et al Quantitative analysis for solid phase hybridization reaction and binding reaction of DNA binder to hybrids using a QCM Anal Chim Acta 32 1996 29 35 Caruso F et al In situ measurement of DNA immobilization and hybridization using a 27MHz QCM Colloids Surf B Biointerfaces 10 1998 199 204 Yung Chuan Liu Chih Ming Wang and Kuang Pin Hsiung Comparison of Different Protein Immobilization Methods on Quartz Crystal Microbalance Surface in Flow Injection Immunoassay Analytical Biochemistry 299 2001 130 135 34 Michael Rodahl Fredrik Hook Anatol Krozer Peter Brzezinski and Bengt Kasemo QCM setup for 33 S frequency and Q factor measurements in gaseous and liquid environments Rev Sci Instrum 66 7 1995 3924 J Geelhood C W Frank and K Kanazawa Transient QCM Behaviors Compared J of the Electrochemical Society 149 1 2002 H33 QCM200 Quartz Crystal Microbalance SRS Sensor Crystals and Holders 49 Chapter 3 Sensor Crystals and Holders This
76. c 50V SMT 1206 10 X7R Cap Ceramic 50V SMT 1206 10 X7R Cap Stacked Metal Film 50V 5 40 85c Cap Stacked Metal Film 50V 5 40 85c Cap Stacked Metal Film 50V 5 40 85c Cap Stacked Metal Film 50V 5 40 85c Cap Ceramic 50V SMT 1206 10 X7R Cap Ceramic 50V SMT 1206 10 X7R Cap Ceramic 50V SMT 1206 10 X7R Cap Ceramic 50V SMT 1206 10 X7R Cap Stacked Metal Film 50V 5 40 85c Cap Stacked Metal Film 50V 5 40 85c Cap Stacked Metal Film 50V 5 40 85c Cap Stacked Metal Film 50V 5 40 85c Cap Stacked Metal Film 50V 5 40 85c Cap Ceramic 50V SMT 1206 10 X7R Capacitor Chip SMT1206 50V 5 NPO Cap Ceramic 50V SMT 1206 10 X7R Cap Ceramic 50V SMT 1206 10 X7R Cap Ceramic 50V SMT 1206 10 X7R Cap Ceramic 50V SMT 1206 10 X7R Cap Ceramic 50V SMT 1206 10 X7R Cap Ceramic 50V SMT 1206 10 X7R Cap Ceramic 50V SMT 1206 10 X7R LED T1 Package LED T1 Package LED T1 Package LED T1 Package LED T1 Package LED T1 Package LED T1 Package Integrated Circuit Surface Mount Pkg Integrated Circuit Surface Mount Pkg LED T1 Package Connector Male Right Angle Connector Misc SS a ee ee wewrewrwe rere aS QCM200 Quartz Crystal Microbalance 84 QCM Circuit Description Chapter 4 REF SRS PART VALUE DESCRIPTION P 1 4 00370 441 500 Pot Multi Turn Trim 3 8 Square Top Ad P2 4 00019 443 20K Pot 10 Turn Panel PC1 7 01422 70
77. ck Film 5 200 ppm Chip Resistor R13 4 01455 461 100 Thick Film 5 200 ppm Chip Resistor R14 4 01455 461 100 Thick Film 5 200 ppm Chip Resistor R15 4 01455 461 100 Thick Film 5 200 ppm Chip Resistor R16 4 01455 461 100 Thick Film 5 200 ppm Chip Resistor R17 4 01455 461 100 Thick Film 5 200 ppm Chip Resistor R18 4 01455 461 100 Thick Film 5 200 ppm Chip Resistor R19 4 01455 461 100 Thick Film 5 200 ppm Chip Resistor R21 4 01511 461 22K Thick Film 5 200 ppm Chip Resistor R 22 4 01519 461 47K Thick Film 5 200 ppm Chip Resistor R 23 4 01467 461 330 Thick Film 5 200 ppm Chip Resistor R31 4 01431 461 10 Thick Film 5 200 ppm Chip Resistor R 32 4 01455 461 100 Thick Film 5 200 ppm Chip Resistor R 33 4 01167 462 3 32K Thin Film 1 50 ppm MELF Resistor R 34 4 01455 461 100 Thick Film 5 200 ppm Chip Resistor R 35 4 01455 461 100 Thick Film 5 200 ppm Chip Resistor R 36 4 01117 462 1 00K Thin Film 1 50 ppm MELF Resistor R 37 4 01117 462 1 00K Thin Film 1 50 ppm MELF Resistor R 120 4 01471 461 470 Thick Film 5 200 ppm Chip Resistor R 121 4 01213 462 10 0K Thin Film 1 50 ppm MELF Resistor R122 4 01213 462 10 0K Thin Film 1 50 ppm MELF Resistor QCM200 Quartz Crystal Microbalance SRS Chapter 4 QCM Circuit Description 89 REF SRS PART VALUE DESCRIPTION R123 4 01280 462 49 9K Thin Film 1 50 ppm MELF Resistor R124 4 01021 462 100 Thin Film 1
78. cosity and or elasticity of the liquid or film in contact with its surface Maximum Loads SRS QCM sensor crystals can be coated with virtually any material as long as it can be deposited in a sufficiently thin uniform and well attached layer Layer thicknesses typically vary from a few Angstrom to a few micrometers The maximum layer thickness depends on the viscoelastic properties of the coating material As a general rule thicker layers are possible for more rigid coating materials The maximum load on a crystal is limited by two factors 1 total damping or 2 lost sensitivity For highly viscous or solid materials the damping of the crystal increases with increasing layer thickness At a certain thickness usually a couple of micrometers QCM200 Quartz Crystal Microbalance 54 Sensor Crystals and Holders Chapter 3 the damping becomes so high that the crystal can no longer be driven i e the measurement fails due to lack of oscillation More elastic materials do not couple completely to the crystal s oscillation With increasing layer thickness the outermost parts of the attached layer will couple weakly and at a certain thickness usually a few micrometers it is lost completely Oscillation is still detected and a frequency is still measured but the equipment can only sense the part of the layer in the vicinity of the crystal Useful Life Sensor crystals are often reusable several times However reusing a cryst
79. crobalance as a biosensor Anal Lett 28 1995 749 Rupa Patel R Zhou K Zinszer F Josse and R Cernozek Real time Detection of Organic Compounds in Liquid Environments Using Polymer coated Thickness Shear Mode Quartz Resonators Anal Chem 72 2000 4888 3 R Rella et al Optochemical vapor detection using spin coated thin films of metal substituted phthalocyanine Sensors and Actuators B Chemical 89 2003 86 36 T G Stange et al STM and AFM Characterization of Polystyrene Spin coated onto Silicon Surfaces Langmuir 8 1992 920 7 J R Vig UV Ozone cleaning of surfaces A review in Surface contamination Genesis Detection and Control K L Mittal Ed Plenum Press NY 1979 Pages 235 253 A Krozer and Michael Rodahl X ray Photoemission spectroscopy study of UV ozone oxidation of Au under ultrahigh vacuum conditions J Vac Sci Technol A 15 3 1997 1704 38 Advincula R Park M Yang J Mays J Subphase Adsorption of Polyelectrolyte Block Copolymer Amphiphiles at the Air Water Interface In situ Investigations using the Quartz Crystal Microbalance Technique and the Langmuir Blodgett Trough Polymer Preprints 1999 40 1084 QCM200 Quartz Crystal Microbalance SRS Chapter 3 Sensor Crystals and Holders 73 S Ryeol Kim JD Kim MS Park YK Chang and SM Chang The Characteristics of Quartz Crystal Microbalance Coated with Lipid Langmuir Blodgett Films as an olfactor
80. cteristics of the voltage variable attenuator described above Aa 1075 where Ve is the voltage at the Conductance output BNC on the QCM200 Az is adjusted QCM200 Quartz Crystal Microbalance SRS Chapter 2 Theory Operation and Calibration 25 during factory calibration so that the product of the gains A A Ap A 200 So we have Rm 10 000 x 10 75 eqn 6 Where Rm is the motional series resonance resistance in Q and V is the conductance voltage output in V The motional resistance of the crystal at series resonance Rm can be computed from the above equation Figure 21 below graphs Rm vs Ve Motional Resistance vs Conductance Voltage Rm 10 000 x 104 Vc 5 75 Ohms 10000 1000 Motional Resistance Ohms 3 O 0 1 2 3 4 5 6 7 8 9 10 11 Conductance Voltage Volts Figure 21 Motional series resonance resistance vs conductance voltage Error Analysis ASRS Errors in the measurement of Rm will be less than 3 Q 3 of Rm for Rm lt 2 KQ and are dominated by the departure of the voltage controlled attenuator from its nominal voltage gain characteristic Keep in mind that the resistance measurement in liquids and soft films is also affected by temperature mostly through the temperature coefficient of the viscosity For ex
81. d environments In this case the crystal is driven at its resonant frequency by an oscillator that can be intermittently disconnected causing the crystal oscillation amplitude to decay exponentially From the recorded decay curve the absolute Q factor inversely proportional to R and the frequency of the oscillator are simultaneously obtained Independent studies have shown that as long as the effect of the parasitic capacitance Co is properly cancelled i e as easily accomplished with the QCM200 the results provided by the Dissipation Technique should be in good agreement with the measurements provided by the QCM200 System QCM200 Quartz Crystal Microbalance SRS Chapter 2 Theory Operation and Calibration 43 References 1 G Sauerbrey Z Phys 155 1959 206 Daniel Buttry Applications of the QCM to Electrochemistry in A Series of Advances in Electroanalytical Chemistry edited by Allen Bard Marcel Dekker 1991 p 23 33 3 John Henderson Electronic Devices Concepts and Applications Prentice Hall NJ 1991 p 357 For example standard Crystal Holder with a 1 inch 5 MHz crystal connected directly to an SRS QCM25 Crystal Oscillator IG Chagnard P Gilbert N Watkins T Beeler and David W Paul An electronic oscillator with automatic gain control EQCM Applications Sensors and Actuators B 32 1996 129 136 A Arnau T Sogorb and Y Jimenez Circuit for continuous motional series resonant freq
82. de Acoustic Wave Sensor in the liquid Phase Anal Chem 65 1993 1158 20 S J Martin R W Cernosek and J J Spates Sensing Liquid Properties with Shear mode Resonator Sensors in Proceeds from Transducers Eurosensors IX Stockholm Sweden 1995 Mark R Deakin and Owen Melroy Underpotential Metal Deposition on Au monitored in situ with a Quartz Microbalance J Electroanal Chem 239 1988 321 O Melroy K Kanazawa J G Gordon II and D Buttry Direct Determination of the Mass of an Underpotentially Deposited Monolayer of Lead on Gold Langmuir 2 1986 697 Masahiro Seo Masaki Aomi and Kengo Yoshida A combined Piezoelectric and EQCM study of Underpotential Deposition of Silver on Gold Electrodes Electrochimica Acta 39 8 9 1994 1039 Youngran Lim and Euijin Hwang An Electrochemical QCM study of Oxygen reduction during the Underpotential Deposition of Lead on a Gold Electrode Bull Korean Chem Soc 17 12 1996 1091 EQCM Wall Jet Split Ring Disk Electrode study on Copper dissolution in Chloride Aqueous solution Anal Sciences 16 2000 1049 Michael Benje Matthias Eiermann Udo Pittermann and Konrad G Weil An improved Quartz microbalance Applications to Electrocrystallization and dissolution of Niquel Ber Bunsenges Phys Chem 90 1986 435 23 Jorg Auge Peter Hauptmann Frank Eichelbaum and Stephen Rosler QCM sensor in liquids Sensors and Actuators B 18 19 1
83. duction The QCM200 Quartz Crystal Microbalance Controller may be remotely programmed via the standard RS 232 serial interface Any host computer interfaced to the QCM200 can easily configure diagnose and operate the quartz crystal microbalance using simple ASCII commands RS 232 Port The QCM200 comes standard with an RS 232 communications port The RS 232 interface connector is a standard 9 pin type D female connector configured as a DCE transmit on pin3 receive on pin2 The communication parameters are fixed at 9600 Baud rate 8 Data bits 1 Stop bit No Parity No Flow Control Front Panel Indicator To assist in programming the QCM200 has a front panel RS 232 LED located above the Measurement display The RS 232 LED is an activity indicator that flashes every time a character is received or transmitted over the RS 232 lines Command Format Communications with the QCM200 uses ASCII characters A command to the QCM200 consists of a one letter mnemonic with optional an argument if necessary and a command terminator Commands may be either UPPER or lower case Carriage return lt CR gt ASCII 0x0D is the only valid terminator Extra characters such as spaces or too many digits are not allowed No command processing occurs until a lt CR gt terminator is received Any command syntax errors will result in the port ignoring the command and waiting for the next carriage return to be received The QCM200 has a
84. e Ohms L 4 1500 7 o 1000 0 10 20 30 40 50 60 70 80 90 100 Wt Glycerol Figure 22 Frequency Shift Hz and Resistance Shift Ohms versus glycerol weight percentage in water as predicted by theory and as measured with QCM200 and a 5 MHz polished crystal ASRS QCM200 Quartz Crystal Microbalance 32 Theory Operation and Calibration Chapter 2 Immersion Test A comparison against the theoretical predictions of equations 6 and 7 is usually a good starting point when testing a new experimental liquid QCM200 setup Two common checkup procedures are described Water Immersion For a gold coated 5 MHz polished crystal and assuming that the electrode capacitance has been properly cancelled a decrease in frequency of 715 Hz and an increase in series resonance resistance of 380 Q is expected when switching from air to complete immersion in water at 20 C Glycerol H20 Immersion Figure 22 shows resistance and frequency change values expected for a polished 5 MHz crystal immersed in a series of viscous glycerol water solutions at 20 C Operation at increasing glycerol concentrations is an excellent test of a QCM experimental setup and should provide predictable results up to more than 88 glycerol In both procedures an agreement between measured and expected values within 25 is generally considered acceptable for glycerol concentrations up to 70 Frequency shifts are much larger at least a facto
85. e the environment around the crystal is changed For example when transitioning from air to a liquid phase The cancellation adjustment must be performed with the Crystal Holder and crystal in the actual measurement environment The switch must be in HOLD position during actual QCM measurements QCM200 Quartz Crystal Microbalance 20 Theory Operation and Calibration Chapter 2 Frequency Measurement QCM200 Frequency Outputs The QCM200 system is a stand alone instrument with a built in frequency counter and resistance meter Series resonance frequency and resistance are measured and displayed directly on the front panel without the need for an external frequency counter or precision voltmeter There is also an analog output proportional to the Relative Frequency which can be used to interface with potentiostats i e for EQCM applications The Frequency Output port BNC on the front panel is for direct connection to an external frequency counter if desired Frequency Measurement Internal Reference 1 5 ppm 0 01 Hz for 1 sec 0 05 Hz for 10 sec or longer Frequency Analog Out back panel DC 10 V 20 bit 20 kHz V 10 kHz V 5 kHz V 2 kHz V 1kHz V 500 Hz V 200 Hz V Frequency Output front panel AC Accuracy Stability Range full scale Resolution Scales Vout Relative Frequency Scale Frequency 5 MHz nominal Level TTL square wave Source impedance 50 Q Connector BNC
86. een the signal and its inverse at 75 Hz to synchronously detect the modulation on the AGC signal The detected signal is filtered by U3A a two pole Butterworth filter with a low pass set to 0 8 Hz The detected signal will be a positive if the dial setting is too high and will be negative if the dial setting is too low The quad comparators U15 and U16 activate front panel LEDs to indicate to the user how to adjust the dial If the HIGH LED is on the dial should be set lower and if the LOW LED is on the dial should be set higher The NULL LEDs indicate that the dial is set correctly A sawtooth waveform at 16x the modulation frequency is added to the detected signal via R68 in order to blur the comparator response Even with this blurring the sensitivity and reproducibility is QCM200 Quartz Crystal Microbalance 80 QCM Circuit Description Chapter 4 remarkable the crystal s electrode and holder capacitance can be nulled with a resolution of about 0 01 pF The 75 Hz modulation on the varactor voltage will also modulate the frequency of the 5 MHz signal which is used to detect mass accumulation on the crystal face Most users will want to turn this modulation off while making mass measurements However the effect of this modulation and frequency modulations caused by the line frequency will be virtually eliminated if gate times for the frequency measurement are an integral multiple of 0 2 S so that there are an integral nu
87. ellent linearity is generally observed in Af vs Q plots for depositions within 1 ug cm providing a very reliable way to calibrate the proportionality constant of eqn 17 Several calibration procedures are also described in the electrochemistry literature and users are referred to the publications list at the end of this chapter for details Polymer Modified Electrodes The EQCM has been extensively used to study polymer modified electrodes particularly as a gravimetric tool to follow redox processes However for the linear frequency to mass relationship described by eqn 17 to hold true the polymer overlayer must exhibit no changes in rigidity during the electrochemical process Otherwise the viscoelastic changes will also contribute to the frequency change leading to an erroneous interpretation of the mass changes As a consequence it is essential to determine whether or not viscoelastic properties of the polymer film nfluence the frequency measurement during polymer film experiments QCM200 Quartz Crystal Microbalance SRS Chapter 2 Bis Frequency Shift H2 Theory Operation and Calibration 37 0 1M Pyrrole in 0 1M HCLO 295 00 40 00 300 00 5 20 00 305 00 ee ooo oe 0 00 20 00 E i d itt on 7 aS aT 60 00 320 00 ai AT 80 00 POO o 325 00 Laf 100 00 HAN y 335 00 lt q i 140 00 160 00 Deen jf 180 00 345 00 lt LH EEE
88. ensor Crystals and Holders Chapter 3 1 Kynar polyvinilidene fluoride a homopolymer of 1 1 di fluoro ethene is a tough thermoplastic that offers unique properties including high chemical inertness low permeability to gases and liquids resistance to radiation and excellent mechanical strength and toughness For detailed material information consult www atofinachemicals com Erich Uttenhaler et al Ultrasensitive QCM Sensors for detection of M13 Phages in liquids Biosensors and Bioelectronics 16 2001 735 743 18 Greenspan L Humidity fixed points of binary saturated aqueous solutions Journal of Research NIST 81A 1977 89 96 QCM200 Quartz Crystal Microbalance SRS QCM Circuit Description 75 Chapter 4 QCM Circuit Description The Quartz Crystal Microbalance system consists of two circuits QCM25 Crystal Oscillator located in a small enclosure that attaches directly to the crystal holder QCM200 Controller The QCM25 attaches to the QCM200 via a Cat 5 cable wired straight through to RJ 45 connectors This section describes the circuitry of the QCM25 and the QCM200 Introduction The Quartz Crystal Microbalance consists of two circuits the QCM25 Crystal Oscillator located in a small enclosure that attaches directly to the crystal holder and the QCM200 Controller The QCM25 attaches to the QCM200 via a Cat 5 cable wired straight through to RJ 45 connectors This cable can be up to 25 feet in length
89. ent of a short circuit at the output BNC T11 accurately couples the output signal to the BNC while rejecting ground noise from the circuit board U18 supplies an extremely stable 2 5V reference for the DAC A voltage signal representing the log of the crystal conductance is connected from the analog board to J171 on the QCM200 main board The conductance signal is attenuated by R172 and R173 to accommodate the OV to 2 5V input range of the 24 bit Delta Sigma ADC U17 The ADC completes a conversion in about 135 ms The MCU samples the conversion complete signal ADCD0 by asserting ADC_CS low When the ADC has completed the conversion it responds by pulling ADCDO low and the MCU clocks out the conversion result by toggling SCLK and sampling ADCDO The MCU scales the sample by a calibration constant determined by the factory calculates the antilog and subtracts 75 ohms The final Resistance is displayed and subtracted from the R offset to yield the delta Resistance U13 supplies a stable 5V reference for the ADC The Phase Lock Loop PLL circuitry enables QCM200 to synchronize with an external 10 MHz signal The External Reference signal is fed into the main board via J31 and is converted to a digital signal EXT_REF using a high speed differential comparator U31 C31 and R326 remove any DC bias from the external reference signal R32 protects the comparator from damage R33 and R34 provide hysteresis to prevent oscillations near the zero cr
90. er the mnemonic A query is formed by including the question mark after the command mnemonic and omitting the queried parameter from the command The query parameters shown in are NOT sent with a query The query returns the values of these parameters Values are returned as a string of ASCII characters Do NOT send or or spaces as part of the command QCM200 Quartz Crystal Microbalance SRS Appendix B QCM200 Remote Programming 103 Command List D i Display Mode Set query the Display Mode The parameter i selects a Display Mode below Display Mode F Absolute Frequency f Relative Frequency m Mass Displacement R Absolute Resistance r Relative Resistance Gate Gate time Scale Analog Frequency Scale Factor NNBWNrF OF Example DO lt CR gt Set the Measurement display to Absolute Frequency D lt CR gt Returns the Display Mode i V i Analog Frequency Scale Set query the Analog Frequency Out Scale Factor The Scale Factor sets the Analog Frequency Output voltage level according to Analog Frequency Out V Relative frequency Scale Factor The parameter i selects a Scale Factor below 1 Scale Factor 0 200 Hz V 1 500 Hz V 2 1 kHz V 3 2 kHz V 4 5 kHz V 5 10 kHz V 6 20 kHz V Example D3 lt CR gt Set the Scale factor to 2 kHz V D lt CR gt Returns the Scale Factor 1 P i Gate Time Set query the Gate time The Gate Time is the time interval spent by the frequency counter
91. es located between the pump and the crystal are often used in Flow Injection Analysis setups although noise reduction is not always as good as expected In order to avoid excessive stress to the crystal and leaks over the o ring seals flowrates should not exceed 5 mL min under any circumstances External temperature i e heating loop stabilization of the liquid samples is recommended for flow rates above 0 2 mL min Do not tighten the crystal retainer during experiments Tightening of the crystal retainer will exert additional stress on the crystal and change its frequency of oscillation Tighten the retainer at the beginning of an experiment and do not touch it again until all measurements are finished O rings often swell when coming in contact with liquids and that can contribute additional drift in the frequency when immersing a crystal holder in a new liquid Dry QCM crystals carefully A common trick used to eliminate residual water from QCM crystals that need to be immersed in dry organic solvents is to rinse the cleaned dried QCM crystals with tetrahydrofurane THF before immersion followed by drying in a flow of dry nitrogen QCM200 Quartz Crystal Microbalance SRS Chapter 3 Sensor Crystals and Holders 67 Tips for Operation in Gases To minimize errors in QCM measurements all gas phase experiments i e gas sensor development should be designed carefully Changes in temperature flow rates and gas pressure will adversely
92. es a detachable three wire power cord for connection to the power source and protective ground The exposed metal parts of the box are connected to the power ground to protect against electrical shock Always use an outlet which has a properly connected protective ground Consult with an electrician if necessary Keep all electrical wiring in your experimental setup neatly organized and in good working condition Inspect all HV wires periodically for problems as part of your safety checkups Grounding A chassis grounding lug is available on the back panel of the QCM200 Connect a heavy duty ground wire 12AWG or larger from the CHASSIS GROUND lug directly to a facility earth ground to provide additional protection against electrical shock BNC shields are connected to the chassis ground and the AC power source ground via the power cord Do not apply any voltage to the shield GFCI Ground Fault Circuit Interrupter GFCI protected outlets are often available in production and laboratory environments particularly in proximity to water sources GFCI s are generally regarded as an important defense against electrocution However the use of GFCI in conjunction with the QCM200 must not be regarded as a substitute for proper grounding and careful system design GFCI s must also be tested regularly to verify their functionality Always consult an electrician when in doubt Line Fuse The LINE FUSE is internal to the instrument and
93. et by 0 New R value 1 New F value 2 Frequency Over Range 3 Frequency Under Range 4 Communication Error 5 unused 6 unused 7 unused Example B lt CR gt Returns the Status Byte in decimal format Executing this query clears the Status bits QCM200 Quartz Crystal Microbalance SRS Appendix B QCM200 Remote Programming 105 T i Timebase Set query the timebase An ultra stable external timebase if available can improve the stability of the frequency measurements 1 Timebase 0 internal TCXO 1 lock the TCXO to the external 10 MHz timebase rear panel Example T1 lt CR gt Set the timebase to external T lt CR gt Returns the timebase i If no signal is present at the rear panel 10 MHz BNC then the QCM200 will revert to using the internal TCXO A timebase query will return 0 in this case ASRS QCM200 Quartz Crystal Microbalance 106 QCM200 Remote Programming Appendix B QCM200 Quartz Crystal Microbalance SRS
94. f 37 Hz deviation x 500 Hz 0 0185 when operated 500 Hz from 5 MHz This will cause a dry crystal to run 0 0185 0 20 Hz 0 092 Hz off series resonance or a wet crystal to run 0 0185 0 04 Hz 0 462 Hz off series resonance Since the d df of the low pass filter is 1000x smaller than the d df of a wet crystal the low pass filter does not contribute a significant error to the measurement of the series resonant frequency By modulating the varactor capacitance which nulls Co and using synchronous detection to locate the minimum gain operating point the QCM200 allows the user to reproducibly null C to 0 01 pF The corresponding phase error for a wet crystal is 0 01 pF x 0 81 pF 0 0081 which gives rise to a frequency reproducibility of 0 008 1 0 04 Hz 0 20 Hz for a wet crystal This error is virtually insignificant In water the dominant source of frequency drift comes from the temperature dependence of the viscosity of the liquid The series resonant frequency of a 5 MHz AT cut crystal in water will increase by about 8 Hz C The importance of temperature stabilization in liquid experiments is evident from the following table With proper temperature stabilization and or compensation it is possible to perform QCM measurements in water with detection limits well below 0 1 Hz rms Summary of sources of frequency error in Water Af 700 Hz Source of Error Typical magnitude of Error for we
95. faces in Treatise on Clean Surface Technology Vol 1 ed by K L Mittal Plenum Press pp 1 26 1987 J R Vig and J W LeBus UV Ozone Cleaning of Surfaces IEEE Trans on Parts Hybrids and Packaging Vol PHP 12 pp 365 370 1976 J R Vig UV Ozone cleaning of surfaces J Vac Sci Technol A3 1985 1027 L Layden and D Wadlow High Velocity carbon dioxide snow for cleaning vacuum system surfaces J Vac Sci Technol A 8 5 1990 3881 Dave Laube Limitations of CO Cleaning for Semiconductor Process Tools Advancing Applications in Contamination Control Feb 2001 p 9 30 There are many different Plasma Cleaner manufacturers Look for a small system which supports cleaning of wafers for semiconductor industry or optics for IR internal reflectance applications 3 W Kern and D A Puotinen Cleaning solutions based on hydrogen peroxide for use in silicon semiconductor technology RCA Review 31 2 1970 187 3 K Harewood and J S Wolf Anal Biochem 55 1973 573 H M Schessler et al Quantitating the Balance between Enthalpic and Entropic Forces in Alkanethiol Gold Monolayer Self Assembly J Am Chem Soc 118 1996 9645 34 Y_ Cohen S Levi S Rubin and I Willner Modified Monolayer electrodes for electrochemical and PZ analysis Novel immunosensor electrodes J ElectroAnal Chem 417 1996 65 Minunni M Guilbault G G and Hock B Quartz Crystal mi
96. ffinity Based Biosensors Molecular Biotechnology 14 2000 109 4 A Hengerer et al Determination of Phage Antibody Affinities to Antigen by a Microbalance Sensor System BioTechniques 26 1999 956 Note the affinity results are compared against ELISA and SPR numbers showing excellent agreement Fredrik Hook et al Structural changes in hemoglobin during adsorption to solid surfaces effects of pH ionic strength and ligand binding Proc Natl Acad Sci USA 95 1998 12271 B C Fredriksson S Kihlman M Rodahl and B Kasemo The Piezoelectric Quartz crystal Mass and Dissipation Sensor A means of studying Cell adhesion Langmuir 19 1998 248 Ann Sofie Cans et al Measurement of the Dynamics of Exocytosis and Vesicle Retrieval at Cell Populations Using a QCM Anal Chem 73 2001 5805 QCM200 Quartz Crystal Microbalance SRS Chapter 2 Theory Operation and Calibration 47 C A Keller and B Kasemo Surface Specific Kinetics of Lipid Vesicle Adsorption Measured with a QCM Biophysical Journal 75 1998 1397 Wei W Z et al Selective pharmaceutical analysis technique with sensitive piezoelectric quartz sensors Anal Lett 26 11 1993 2371 Brenda D Spangler and Bonnie J Tyler Capture agents for a QCM continuous flow biosensor functionalized self assembled monolayers on gold Analytica Chimica Acta 399 1999 51 62 See also www sensopath com Y C Liu et
97. h a new liquid medium and measure the temperature of the solution around the crystal during the experiments to perform temperature compensation Careful control of the temperature is required in high accuracy measurements to avoid frequency hysteresis effects the dependence of resonator frequency at a specific temperature on its prior temperature history For example it is often observed that the frequency vs temperature curve obtained going from T to T will not coincide with the one obtained immediately after going from T to T The causes of hysteresis and retrace are not well understood the experimental evidence to date is inconclusive The mechanisms that can cause these effects include strain changes changes in the quartz contamination redistribution in the crystal enclosure and apparent hysteresis or retrace due to thermal gradients In electrochemical experiments temperature control is often required to control reaction rates and is typically achieved with temperature controlled baths and jacketed cells Tight temperature control is necessary for QCM measurements involving protein adsorption protein protein interaction immunosensor development self assembled monolayers Langmuir films and DNA hybridization studies Temperature stabilization better than 0 05 C is generally required to eliminate temperature related transients and drifts in lengthy measurements This level of temperature control is particularly important if sma
98. h the circular list of possible values for the current parameter The displayed value becomes active immediately Pressing the PARAMETER key stores the new value and moves the menu display to the next parameter Relative Measurements Hold down the VALUE key for 2 seconds while in the Absolute or Relative Resistance display modes to 1 set the Resistance Offset to the current Absolute Resistance value and 2 zero the Relative Resistance readings Hold down the VALUE key for 2 seconds while in any other display mode to 1 set the Frequency Offset to the current Absolute Frequency value and 2 zero the Relative Frequency readings The ZERO LED flashes to indicate zeroing of the Relative Frequency or Relative Resistance displays Frequency Output Connector The Frequency Output connector outputs the crystal oscillator frequency The signal has TTL square wave levels and a source resistance of 50 Q Use this output to connect to an external frequency counter optional The BNC shield is connected to chassis ground Conductance Output Connector The Conductance Output connector outputs the conductance signal V related to the series resonance resistance of the QCM crystal by Ne R 10 000 d 0 jsa Voltage levels span 0 to 10 625 VDC and the source impedance is 1 KQ Use this output to connect to an external high precision multimeter optional The BNC shield is connected to chassis ground QCM200 Quartz Crystal Microbalance SRS
99. he BVD crystal model driven by an automatic gain control amplifier AGC and terminated into a load resistor RL By returning the voltage on R_ to the input of the AGC amplifier the circuit will oscillate at a frequency for which the phase shift around the loop is 0 or an integral multiple of 360 provided there is sufficient gain the Barkhausen condition Absent Co it is easy to see that the phase condition is satisfied at the series resonance of Cm and Ly fsr 1 27 LmCm At series resonance the reactance of Cm and Lm cancel leaving only Rm In this case an amplifier gain of Ay Rm R1 R will provide a loop gain of 1 to sustain oscillation Unfortunately C cannot be ignored in QCM applications In the circuit shown in Figure 17 C injects a leading current into RL which must be canceled by a lagging current via the motional arm in order to achieve the zero phase condition This requires the circuit run above series resonance where the net reactance of Cm and Ly is inductive In fact if Rm is large enough it is possible that the motional arm will not be able to contribute enough lagging current to cancel the leading current via Co and the circuit will not oscillate at all A method to cancel C is shown in Figure 18 In this circuit the AGC amplifier drives a transformer with two secondary windings One secondary drives the crystal and load as before while the other secondary inverts the voltage The inverted voltage
100. he changes in series resonance resistance that take place at the QCM sensor i e working electrode during a cyclic voltammetric scan of a 50 mM solution of K Fe CN in 1M Na SO4 50 mV sec scan rate As the potential of the electrode becomes less positive Fe CN is depleted and replaced by a layer of Fe CN adjacent to the sensor crystal Since solutions of Fe CN are more viscous than Fe CN the resistance readings increase at more negative voltages as the more viscous reduced product exerts additional loading on the crystal The resistance change corresponding to the conversion of Fe CN ie to Fe CN is 4 Ohms in complete agreement with a 0 9 estimated relative change in pn calculated from previously reported calibration curves QCM200 Quartz Crystal Microbalance ASRS Chapter 2 Theory Operation and Calibration 35 Series Resonance al EQCM Resistance Measurement Cyclic Voltammogram 7000 440 6000 439 5000 438 AR 4 Ohms 4000 89 437 3000 436 2000 435 1000 434 Current microA o 433 1000 432 2000 431 3000 0 5 0 4 0 3 0 2 0 1 0 Volts vs Ag AgCI 430 Figure 25 Changes in series resonance resistance at the QCM sensor during the electrochemical oxidation reduction of Fe CN 5 Fe CN j The resistance potential diagram shows a resistance increase in perfect sync with the generation of a viscous l
101. he last section of the internal chamber to come in contact with liquid QCM200 Quartz Crystal Microbalance SRS Chapter 3 Sensor Crystals and Holders 69 Figure 33 Simple siphon setup with axial flow cell syringe body sample reservoir and flow clamp The presence or relocation of bubbles on the surface of a crystal is generally detected by paying careful attention to the frequency and resistance readings from the sensor Bubbles displace liquid from the surface of the QCM crystal resulting in increased frequency and reduced resistance readings Tapping gently on a flow cell with a hard object can change the number or location of bubbles if a sharp and opposite sudden shift in frequency and resistance readings is observed the presence of trapped bubbles must be suspected It is sometimes possible to infer the presence of bubbles if the frequency and resistance of the crystal are premeasured by direct immersion of the holder crystal into the same sample solution used in the flow setup Resistance values significantly smaller than the immersion results should prompt the presence of trapped bubbles within the flow chamber Temperature stabilization usually requires immersion of the flow cell into a constant temperature liquid bath In many cases the liquid bath is operated above room temperature If the flowrates are high i e greater than 0 2 mL min or the temperature of the bath is far away from the temperature of the sample liquid i e
102. hifted by the two pole Butterworth filter U10B The AC component of this signal is amplified by 100x by U11 an OPA277 low offset voltage operational amplifier The output of U11 is further amplified by a voltage controlled gain amplifier consisting of U12 an LM13700 dual operational transconductance amplifier and U13B The gain of the voltage controlled amplifier U12 is controlled by the AGC voltage The gain increases exponentially with the AGC voltage varying between 1x and 100x as the AGC voltage goes from 0 VDC to 10 VDC As mentioned previously there is little modulation of the AGC voltage when the crystal losses are low i e when the AGC voltage is high The purpose of this gain control is to increase the gain for the AGC modulation when the crystal losses are low so that the apparent sensitivity of the front panel dial is more nearly constant over a wide variety of crystal resistances The gain of U12 is proportional to its bias current In this circuit the lower half of U12 is used as the amplifier channel The top half of U12 together with the Darlington pairs that are normally used as output buffers are used to generate an amplifier bias current which varies exponentially with the AGC voltage The output of the transconductance amplifier pin 12 on U12 is a current This current is converted to a voltage by U13B which is arranged as a transimpedance amplifier U13A inverts the output of U13B and the multiplexer switches betw
103. his is a potentially dangerous scenario since it might lead to early termination of a deposition or film growth process Notice that there is no outward evidence of mode hopping except for a discontinuity in the film thickness Also even though the film thickness changes dramatically the mass sensitivity and rate of growth change by only a few percent Some experiments can cause irreversible changes on the crystal surface For example the use of silver depositions on gold electrodes for calibration of electrochemical QCMs is not always recommended because silver is hard to remove reversibly from gold electrodes Copper or lead are often recommended instead Crystals exposed to etching solutions i e Piranha solution usually need to be replaced after two to three experiments Film stress can be particularly damaging Stress can bend the crystal and induce a frequency change not related to mass It can cause the electrode to tear from the quartz and in the worst case it can even cause the quartz itself to fracture 23 QCM200 Quartz Crystal Microbalance SRS Chapter 3 SRS Sensor Crystals and Holders 55 Temperature effects The intrinsic dependence of the resonant frequency of a quartz crystal on temperature is well known and generally quite small In fact the AT cut quartz crystals commonly used in QCM experiments owe their popularity to their near zero temperature coefficient at room temperature As a result the intrinsic
104. ical Compatibility Before starting an experiment check for chemical compatibility between sample solutions solvents holder flow cell o rings and crystals For example avoid contact between Viton o rings and DMSO solvent If necessary consider replacing incompatible components with alternative materials Check the POGO contacts regularly It is good practice to check the POGO contacts regularly for signs of corrosion and wear Replace the pins with new ones if necessary see Head Cleaning above Degas the sample liquid Whenever possible sample liquids should be degassed to avoid the growth of air bubbles on the surface of immersed crystals Presoak the crystal in the sample liquid To minimize long term i e hours long signal drift it is best to immerse the quartz crystal premounted on its holder in the sample solution several hours before measurements are started Temperature independent frequency drifts as large as 10 Hz and resistance drifts as large 2 Ohms are to be expected over a 24 hr period even in the purest deionized water bath Long term drifts have many different origins including chemical interaction between the liquid and the electrodes swelling of the o rings diffusion of liquid into the quartz changes in coatings etc In flowing systems expose the crystal to the carrier solution for as long as practically possible prior to sample injection Wait for the temperature to stabilize To avoid the genera
105. ides both frequency and resistance change signals and will maintain oscillation up to a series resonance resistance of about 5 KQ it will support crystal operation in highly viscous solutions up to 88 w w glycerol in water Transformer isolation of the oscillator circuit provides compatibility with virtually any potentiostat As an example eqn 15 predicts a decrease in f of 715 Hz on transfer from vacuum to pure water at 20 C in agreement with the results observed with a QCM200 using 1 inch diameter polished gold coated 5 MHz crystals mounted on a standard Crystal Holder Excellent agreement between the frequency and resistance equations and the experimental results has been proved making the QCM an excellent tool for the evaluation of fluid properties Application examples include in situ monitoring of lubricant and petroleum properties The tight correspondence between theory eqns 15 amp 16 and experiment is clearly illustrated by Figure 22 QCM200 Quartz Crystal Microbalance SRS Chapter 2 Theory Operation and Calibration 31 QCM100 nii EE A Ee Theory 1000 2000 3000 i 4000 5000 6000 Af Hz 7000 8000 9000 10000 11000 12000 t t t A t t t t t t 0 10 20 30 40 50 60 70 80 90 100 Wt glycerol QCM100 Theory 5000 4500 4000 3500 3000 2500 f 2000 Resistanc
106. illation which is related to the mass displaced during the vibration Typical values for a 1 diameter 5 MHz crystal used in the QCM200 System are Cm 33 fF Lm 30 mH and Rm 10 Q for a dry crystal Rm 400 for a crystal with one face in water or Rm 3500 Q for a crystal with one face in 85 glycerol The motional arm is shunted by the parasitic capacitance Co which represents the sum of the static capacitances of the crystal s electrodes holder and connector capacitance In the QCM200 System Co is about 20 pF a value which has been kept small by placing the electronics directly on the Crystal Holder thereby eliminating any cable capacitance QCM200 Quartz Crystal Microbalance SRS Chapter 2 SRS Theory Operation and Calibration 17 In a QCM application the motional inductance Lm is increased when mass is added to the crystal electrode the frequency shift of the series resonance is a sensitive indicator of the added mass Films of less than 1 ng cm can easily be resolved by the QCM The motional resistance Rm can also provide important information about a process since soft films and viscous liquids will increase motional losses and increase the value of Rm AGC Amp ES Figure 17 Oscillator Circuit consisting of AGC Amplifier Quartz Resonator and Load Resistor Placing the crystal in an oscillator circuit provides a simple way to measure its motional parameters Figure 17 shows t
107. in theory the QCM mass sensor does not require calibration However it must be kept in mind that the Sauerbrey equation is only strictly applicable to uniform rigid thin film deposits Vacuum and gas phase thin film depositions which fail to fulfill any of these conditions actually exhibit more complicated frequency mass correlations and often require some calibration to yield accurate results For many years QCMs were regarded as just gas phase mass detectors however recently their application has been extended since scientists realized that they can be operated in contact with liquids and viscoelastic deposits In this case both resonance frequency and series resonance resistance of the quartz oscillator are important to completely characterize the material in contact with the crystal electrode The development of QCM systems for use in fluids opened a new world of applications including electrochemistry and microrheology More recent developments have focused on tailoring electrode surface chemistry i e specialized polymer coatings so that these devices can be applied as discriminating mass detectors for 1 specific gas detection QCM200 Quartz Crystal Microbalance 16 Theory Operation and Calibration Chapter 2 2 environmental monitoring 3 biosensing and 4 basic surface molecule interaction studies The purpose of this chapter is to provide a brief introduction to the different measurement and calibration techniques avai
108. ing the QCM crystal in an electrochemical setup EQCM Transformer isolation between the crystal electrodes and the oscillator circuit makes the QCM200 system ideal for electrochemical research and compatible with virtually all potentiostats QCM200 Quartz Crystal Microbalance x Overview 5 MHz Crystal Use this BNC connector to connect the QCM25 Crystal Oscillator to the Crystal Holder or directly to your custom 5 MHz QCM crystal holder 1 4 20 MTG Hole Use this threaded hole to mount the QCM25 Crystal Oscillator in your experimental setup using a 1 4 20 threaded fastener Power LED This LED lights up to that the QCM25 is powered on This requires connection to a powered QCM200 Controller QCM200 Quartz Crystal Microbalance SRS Specifications QCM200 Frequency Measurement Display Gate times 0 1 s 1 s 10s Resolution 0 01 Hz 10 s gate 0 1 Hz 1 s gate 1 0 Hz 0 1 s gate Measurement internal TCXO Stability lt 2x10 typical 10 s Allan variance Accuracy 1 5 ppm Analog Frequency Output Output 10 V full scale 20 bit Ranges 200 kHz 100 kHz 50 kHz 20 kHz 10 kHz 5 kHz 2 kHz Frequency Output Frequency 5 MHz nominal Level TTL square wave Source impedance 50 Q Connector BNC Resistance Measurement Display Range 0 to 5000 Resolution 5 digits 0 001 R lt 100 0 01 100 R lt 1000 0 1 1000 R lt 5000 Conductance Output Vc Resistance R 10 000 x 10
109. is that you have a greater chance of experiencing interferences This issue has been addressed in various ways so that the device will only respond to the analyte of interest Those ways usually involve a chemically or biologically sensitive layer i e a coating applied to the surface of the crystal Often the hardest part of the problem is deciding what kind of chemically sensitive material you are going to put on top of the crystal so that it responds specifically to what you are trying to measure In biosensor research the chemical stability of the sensor substrate often limits the quality of the data generated The continuous oxidation of metal electrodes can make it very difficult to reach a drift free signal baseline in aqueous media Polyimide polystyrene and PVC are amongst the polymeric materials recommended to protect QCM devices Tip A Crystal Cleaning Basket SRS Part O100CCB described at the end of this chapter is available directly from Stanford Research Systems This accessory makes cleaning and surface modification treatment of the standard 1 QCM crystals very safe and easy The cleaning basket holds four crystals is made entirely of Teflon and it is specifically designed for immersion into a 100 mL beaker Several examples of surface modification techniques are described below While not exhaustive they may serve as useful guidelines while developing your own protocols QCM200 Quartz Crystal Microbalance
110. ives a 5 order Bessel low pass filter The filter serves two purposes The first is to attenuate very high frequency signals so that the loop will only oscillate at the crystal s fundamental mode The second is to provide 180 of phase shift at 5 MHz The filter s phase shift together with the 180 of phase shift from the inverting amplifier U1 gives the 360 of phase shift required to sustain oscillation The filter is adjusted during factory calibration so that the loop oscillates at 5 MHz when the crystal is replaced by a 50 Q resistor The gain of U1 is controlled by the voltage Vc at pin 5 The gain is equal to 45 50xVc dB where Vc is between 0 and 1 Vdc Increasing Vc decreases the amplifier gain The SLD output current on pin 6 will ramp Vc up to decrease the gain if the detected signal at the amplifier output pin 10 is greater than 1 Vpp The SDL output sinks a current to increase the amplifier gain if the detected amplifier output is less than 1 Vpp In this way U1 adjusts the loop gain to maintain the oscillation at constant amplitude R11 and C4 determine the AGC loop characteristics and have been selected to provide a critically damped response The AGC voltage is buffered and amplified by U3 an OPA337 operational amplifier The gain which is about 5x is adjusted during factory calibration to calibrate the slope of the AGC curve The slope and offset of the AGC voltage is adjusted to assure compliance to the Voond V
111. l Oscillators in Thin Film Deposition J Vac Sci Technol 8 5 1971 622 Chih shun Lu Mass determination with piezoelectric quartz crystal resonators J Vac Sci Technol 12 1 1975 578 Ward M D and Delawski E J Radial Mass Sensitivity of the Quartz Crystal Microbalance in Liquid Media Anal Chem 63 1991 886 R W Cernosek et al Analysis of the radial dependence of mass sensitivity for Modified electrode quartz crystal resonators Anal Chem 50 1998 237 17 S J Martin R J Huber et al Resonator Oscillator Response to Liquid Loading Anal Chem 69 1997 2050 18 S Martin H Bandey R Cernozek A R Hillman and M J Brown Equivalent circuit model for the thickness shear mode resonator with a viscoelastic film near film resonance Anal Chem 72 2000 141 1 Consult ref 17 Celia Henry Measuring the masses Quartz Crystal Microbalances Anal Chem News and Features October 1 1996 p 626A Daniel A Buttry and Michael Ward Measurement of Interfacial Processes at Electrode Surfaces with the Electrochemical Quartz Crystal Microbalance Chem Rev 92 6 1992 1355 Graeme Andrew Snook Investigation of Solid State Reactions by Electrochemical and Quartz Crystal Microbalance Measurements Ph D Thesis 2000 Department of Chemistry Monash University Clayton 3168 Melbourne Australia and Division of Minerals CSIRO Clayton South 3169 Melbour
112. l in g cm Am change in mass per unit area in g cm calculated from Sauerbrey s equation T thickness of the film in cm SRS QCM200 Quartz Crystal Microbalance 28 Theory Operation and Calibration Chapter 2 Z match Method It is generally accepted that when the mass loading from the deposit causes a change in frequency of less than 2 of the frequency of the unloaded crystal Sauerbrey s equation can be used to obtain accurate results in thin film thickness calculations As the thickness of the film increases the Sauerbrey equation must be extended to incorporate the elasticity of the deposit Lu and Lewis gave a simple equation eqn 14 for the calculation of the dependence of Af on Am which is currently applied by most QCM users to calculate rigid thin film thicknesses in gas phase depositions Ea tan z tan e eqn 14 nZ U where Am change in mass per unit area in g cm Ng Frequency Constant for AT cut quartz crystal 1 668 x 10 Hz A Pg density of quartz 2 648 g cm fu frequency of unloaded crystal prior to deposition in Hz fL frequency of loaded crystal in Hz Z Z Factor of film material Pglq Pudl pi density of film material in g cm Uq shear modulus of quartz 2 947 x 10 gem s W shear modulus of film material This analysis of frequency changes including the acoustic impedances of the quartz and film is often called the Z match
113. l methods for mounting sensor crystals have been described in the scientific QCM literature The mounting fixture requires serious consideration because of the influence of stress on the absolute frequency of oscillation and because simple and rapid exchange of crystals is required when the thin film electrodes become damaged or used up For electrochemical applications in solution it must be feasible to expose only one side of the QCM disk to the liquid bath This is necessary to prevent the two QCM electrodes from being capacitively shunted by the solution which can cause cessation of the oscillation The Crystal Holder was specifically designed to address all the above issues while at the same time providing optimal crystal performance when connected to a QCM25 Crystal Oscillator and a QCM200 Controller QCM200 Quartz Crystal Microbalance ASRS Chapter 3 Sensor Crystals and Holders 63 Head Cleaning It is not uncommon for crystals to break or for o ring seals to leak during normal operation If chemical leakage into the crystal cavity is suspected it is very important to act fast and rinse the cavity the POGO contacts and the POGO contact sockets to remove any traces of solution that might lead to damage of the holder Start by removing the crystal from the Crystal Holder and exposing the POGO pins Putting your thumbnail or the flat head of a jeweler screwdriver under the POGO head pull firmly up to remove each contact pin from i
114. lable to QCM200 users and to briefly describe the most popular theoretical models used to interpret QCM results A complete coverage of these subjects is beyond the scope of this manual However many articles have been published on the operation and calibration of QCMs in applications ranging from vacuum thin film deposition to electrochemical experiments and QCM users are referred to the publications list at the end of this chapter for more detailed information The QCM Oscillator The Butterworth van Dyke BVD electrical model for a quartz crystal resonator is shown in Figure 16 This model is often used to represent the electrical behavior of a crystal resonator near series resonance The model has also been useful in predicting the frequency shifts and losses of an AT cut quartz crystal in QCM applications Co Hw Figure 16 Butterworth van Dyke model of Quartz Crystal Resonator The BVD electrical model consists of two arms The motional arm has three series components modified by the mass and viscous loading of the crystal 1 Rm resistor corresponds to the dissipation of the oscillation energy from mounting structures and from the medium in contact with the crystal i e losses induced by a viscous solution 2 Cm capacitor corresponds to the stored energy in the oscillation and is related to the elasticity of the quartz and the surrounding medium 3 Lm inductor corresponds to the inertial component of the osc
115. layed directly on the front panel and there is an analog output proportional to the relative frequency to interface directly with potentiostats EQCM applications The QCM200 may be locked to a user supplied 10 MHz clock for ultra stable frequency measurements In addition the QCM200 has an RS 232 interface and comes with both Windows and Mac software providing real time display analysis and storage of your QCM data ASRS QCM200 Quartz Crystal Microbalance 2 Getting Started Chapter 1 Unpacking Before You Open the Box Read the entire Safety and Preparation for Use section of this manual before starting any setup procedure Read and follow all installation and operation instructions in this manual to ensure that the performance of this instrument is not compromised Checklist Open the box es and inspect all components of the QCM200 System Report any damage to Stanford Research Systems immediately Compare the contents of the shipping boxes against your original order and the checklist below Report any discrepancies to Stanford Research Systems immediately Standard Equipment Supplies QCM200 Quartz Crystal Microbalance Controller QCM25 Crystal Oscillator Operation and Service Manual Power cord 3 foot Cat 5 Cable Crystal Holder Three 3 chromium gold QCM crystals polished Optional Equipment Replacement Crystals SRS Part O100RX1 Replacement ITO Crystals SRS Part O100RX2 Axial Flow Cell SRS Par
116. ld be worthwhile specially if the material properties of the film could be derived This would allow correlation of the electrochemical behavior of the film with its material properties The unique property of the QCM technique is its ability to determine the mass of very thin layers while simultaneously giving information about their viscoelastic properties The ability to measure both mass and structural changes means it is possible to detect phase transitions cross linking and swelling in polymeric thin films QCM200 Quartz Crystal Microbalance 38 Theory Operation and Calibration Chapter 2 Chemical and Biological Sensors Anything that has mass can generate a response from a QCM sensor The universal response of the device is the reason for the wide range of application of the technology However the downside of such universal sensitivity is that you always have a great danger of interference For analytical purposes it is imperative to find ways of getting the QCM sensor to respond only to what you are interested in i e build specificity into the doce aoe usually involves the addition of a sensitive layer on the surface of the crystal Organic polymers comprise the most common type of coating used with QCM chemical sensors due to their capability to reversibly sorb vapors and liquids In much of the work published on the use of polymer coatings for vapor sensing the acoustic properties of the polymer material have been
117. lied to an XOR phase comparator inside the CPLD If the user selects the external timebase then the output of the phase comparator PLL_PHASE_DET is filtered and sent to the TCXO frequency adjust pin via the MUX U32 This locks the QCM200 TXCO frequency reference to the external timebase The TCXO frequency is accurate to 1 5ppm but can be pulled up to 10ppm to accommodate an external reference The QCM200 uses a PIC16F873A MCU U21 to communicate with a remote computer via its built in UART monitor the front panel buttons collect data from the CPLD and ADC calculate the frequency and resistance and update the DAC value and LED display The MCU communicates with the XC95288 CPLD U14 LT2410 ADC U17 DAC1220 DAC U16 and the HCMS 2975 and 2965 LED displays serially using a common clock SCLK Each of these peripherals has a dedicated chip select from the MCU The CPLD DAC and LED display receive data from the MCU on a single data line SDATA The ADC transmits data to the MCU on ADCDO and the CPLD transmits to the MCU using two data lines SIG_COUNT_Q and SIG_COUNT_QB R211 charges C213 to provide a delayed reset active low directly to the MCU and to the QCM200 Quartz Crystal Microbalance SRS Chapter 4 SRS QCM Circuit Description 81 display DISP_RESET via R215 Connector J212 is for factory use only the QCM200 can be damaged or destroyed by external voltages on J212 The unknown frequency signal
118. ll series resonance resistance changes need to be detected and measured Each individual QCM user must determine the effect of temperature on the experiments being performed and either control the temperature accordingly or measure the temperature and compensate for it The table below summarizes some of the most QCM200 Quartz Crystal Microbalance 56 Sensor Crystals and Holders Chapter 3 relevant static temperature coefficients for 5 MHz QCM crystals around room temperature Some very important temperature coefficients are listed below Temperature coefficient in air 1 3 Hz C Temperature coefficient in water 8 Hz C 4Q C Tip Whenever practical the use of flow cells is recommend for both gas and liquid studies to minimize temperature transient effects Temperature stabilization better than 0 05 C is generally required to eliminate temperature related transients and drifts in lengthy measurements Crystal Handling Please follow these instructions about general handling of sensor crystals e Keep the crystals in a clean and dry place When not in use store them in their original box and wrapper e Avoid touching the metal electrodes of the crystal e Rinse only with deionized water or another appropriate residue free solvent before drying the crystal e Always use a flow of dry oil free inert gas e g nitrogen to blow dry the crystal It is better to blow the liquid off the crystal than to let it evaporate on
119. log Out connector outputs a voltage linearly related to the Relative Frequency display of the QCM200 controller Voltage levels span 0 to 10VDC 20 bit resolution and the source impedance is 1 KQ Full scale ranges are user selectable 200 kHz 100 kHz 50 kHz 20 kHz 1 kHz 5 kHz and 2 kHz Use this output to connect to the external A D Input connector of your potentiostat for EQCM applications The BNC shield is connected to chassis ground QCM200 Quartz Crystal Microbalance viii Overview External 10 MHz Input Connector The QCM200 features a built in frequency counter to measure the resonant frequency and display it on the front panel The stability and accuracy of the frequency counter is more than adequate for most QCM experiments For extremely demanding applications an external timebase such as the SRS FS725 Rubidium Frequency Standard can eliminate all frequency errors The external 10 MHz input allows the input of an ultra high stability timebase signal This input presents a 1 kQ input impedence and takes a 1 volt peak to peak nominal input amplitude The BNC shield is connected to chassis ground The QCM200 has an internal 1 5ppm TCXO oscillator The internal oscillator will attempt to phase lock with a user supplied external 10 MHz signal when T External is selected from the front panel or the T1 command is sent via the remote RS 232 interface The internal oscillator frequency may be pulled up to
120. ls and Holders 57 Note Before starting a surface cleaning ensure that the crystal material will not be damaged by the chemicals Perform a practice test on a discarded crystal whenever possible Avoid basic high pH cleaners since they will etch all exposed quartz surfaces Tip A Crystal Cleaning Basket SRS Part O100CCB described later in this chapter is available directly from Stanford Research Systems This accessory makes cleaning and surface modification treatment of the standard 1 QCM crystals very safe and easy The cleaning basket holds four crystals is made entirely of Teflon and it is specifically designed for immersion into a 100 mL beaker Several cleaning procedures are described below which can be used as guidelines to develop your own Proper crystal handling practices must be used throughout any cleaning process General Purpose For general purpose applications such as electrochemistry liquid and viscoelastic film studies it is usually sufficient to sonicate the crystals in a solution of non basic detergent in deionized water Immediately rinse liberally with deionized water and dry in a gentle flow of nitrogen gas Hydrocarbon contaminants UV ozone treatment CO snow cleaning and plasma cleaning are some low cost and very efficient methods used for cleaning hydrocarbon impurities adsorbed from the ambient air Neither method affects the quartz gold surfaces They are both often applied to componen
121. lution on to a polished unmodified gold surface i e physical adsorption The adsorbed mass is small compared to the mass of the quartz crystal evenly distributed and rigidly attached to the gold surface resulting in a frequency decrease of 9 Hz proportional to the mass of protein adsorbed on the polished gold electrode The sensitivity of the QCM200 for the detection of microgram quantities of proteins is clearly demonstrated by this very simple experiment Sensitive selective detection of biochemically active compounds can be achieved by employing antigen antibody enzyme substrates and other receptor protein pairs The potential analytical uses of these materials has been reviewed particularly with respect to the development of biochemical sensors QCM studies have provided detailed information about the functionalized surfaces developed for a range of biochip and biosensor applications QCM Immunosensor Antigen Antibody I nteraction Step 1 Antigen non specific adsorption to bare gold Mouse Gamma Globulin 400 microg mL 10 10 Step 2 Blocking of remaining non specific sites Ovalbumin va 20 30 Step 3 Antigen Antibody specific binding Goat anti mouse IgG 40 microg mL 40 50 60 70 80 90 100 0 1000 2000 3000 4000 5000 6000 7000 Time s Figure 28 Antigen antibody reaction monitored with a QCM200 system
122. mber of modulation cycles during each measurement QCMZ200 Digital Boards The QCM200 digital boards contain all of the digital circuitry for the microprocessor controlled frequency counter A D and D A converter RS 232 interface and display See the previous section for a description of the analog circuitry inside the QCM200 The digital section consists of two boards Main Board and Display Board The Main board measures the QCM crystal frequency and conductance voltage supplies an output voltage proportional to the relative frequency accepts a 10 MHz timebase and provides an RS 232 computer interface The display board holds a 12 character alphanumeric LED display and 2 momentary contact pushbuttons The 15V output of the universal switcher supplies the Main board The 15V is regulated down to 12V U26 5V Analog U24 VCC U26 and VCCINT U23 A switching inverter U27 generates 12V which is regulated down to 5V U28 The 2VDC and 3VDC supplies are used in analog circuits VCC 5V digital powers the PIC processor and the 12 character LED display The VCCINT 3 3V digital powers the CPLD U14 the TCXO Y1 the external reference detector Q12 and the TCXO control voltage MUX U32 The CPLD divides the 40 MHz from the TCXO Y1 down to 10 MHz to clock the MCU 5 MHz for a test signal and to 2 MHz to clock the DAC If an external timebase is detected then the 10 MHz MCU clock and the external timebase 10 MHz are app
123. motion is not restricted They should drop to a level well below the surface of the probe o ring by an amount at least equal to the thickness of the crystal When fully extended they should protrude above the surface of the o ring by an amount equal or larger than the thickness of the sensor crystal Inspect the sensor crystal at this time and clean it if necessary QCM200 Quartz Crystal Microbalance 8 Getting Started Chapter 1 6 Hold the crystal Contact Surface down above the Crystal Holder s head and point the wrap around electrode towards the reference pin at end of probe See Figure 8 below Figure 8 QCM Crystal in Crystal Holder cavity with wrap around electrode pointing towards reference pin 7 Turn the crystal 90 clockwise before laying it centered onto the head o ring Turning the crystal as instructed assures a fresh contact surface develops between the crystal electrodes and the POGO pins The crystal should end up as shown in Figure 9 below Figure 9 Crystal in place with correct electrode orientation QCM200 Quartz Crystal Microbalance SRS Chapter 1 Getting Started 9 8 Place the retainer ring or Flow Cell over the crystal with its notch mating with the reference pin as shown in Figure 10 below Figure 10 Retainer ring in place 9 Attach the retainer cover and thread the first quarter turn Inspect the retainer ring to make sure the alignment notch remained mated with the reference pin
124. mpact and easy to use laboratory spin coaters compatible with QCM crystals are commercially available Consult the factory for recommendations Langmuir Blodgett films Langmuir Blodgett films LBFs are artificial structures prepared by sequential transfer of monomolecular layers one molecule thick performed on a liquid surface usually H O onto a solid substrate such as a glass slide or a silicon wafer LBFs are very thin and very well ordered This technology is attractive to researchers because of its ability to produce thin films 1 whose thicknesses can be precisely varied and 2 which can be modified to produce smart sensing devices Self Assembled Monolayers SAM Self assembled monolayer SAM techniques offer a new strategy for the immobilization of antibodies antigens and DNA on the surface of quartz crystal electrodes SAMs can be deposited on gold or silver electrodes by thiolization Since sulfur donor atoms strongly coordinate on metal substrates Au Ag Pt etc sulfur containing molecules such as disulfides R SS R sulfides R S R and thiols can form various functionalized SAMs with highly organized and compact construction Besides good mechanical and chemical properties an additional advantage of SAMs is that they make it possible to tailor electrode surfaces at the molecular level for the immobilization of specific biomolecules such as proteins or DNA QCM200 Quartz Crystal Microbalance S
125. n used in cell adhesion studies when visualization of the sample cells is required during the experiments ITO coated QCM crystals can be specia ordered directly from Stanford Research Systems or through your local SRS representative In principle any type of material that can be deposited onto the surface of the underlying metal electrode can be used on the sensor crystals The only limitation on the use of such materials is that their deposition must be carried out in such a way that the temperature of the quartz crystal does not exceed 573 C above which O quartz loses its piezoelectric activity Strict attention to cleanliness is required while performing a custom electrode deposition It is important to keep in mind that mass changes at the QCM active electrode surface influence the frequency because these electrodes are part of the composite resonator composed of 1 the quartz crystal 2 its metal electrodes 3 any film deposited on the electrodes and 4 any liquid adjacent to the electrode surface which experiences shear forces For this reason when electrodes become delaminated due to poor adhesion of the underlayer or stress caused by the deposit discontinuous changes in frequency occur which render the crystal useless Mass Sensitivity The quartz crystal microbalance is an extremely sensitive sensor capable of measuring mass changes in the nanogram cm range with a wide dynamic range extending into the 100 ug cm ra
126. nce Measurements Ph D Thesis 2000 Department of Chemistry Monash University Clayton 3168 Melbourne Australia and Division of Minerals CSIRO Clayton South 3169 Melbourne Australia under the supervision of Professor Alan Maxwell Bond Monash and Professor Stephen Fletcher CSIRO Available for download from http www bond chem monash edu au theses Note the use of Lead acetate is proposed as a better alternative to Cu and Ag deposition Bruckenstein S and Shay M Experimental aspects of use of the quartz crystal microbalance in solution Electrochim Acta 30 1985 1295 Duke Orata and Daniel A Buttry Determination of Ion Populations and Solvent Content as functions of Redox State and pH in Polyaniline J Am Chem Soc 109 1987 3574 3 Michael Ward Investigation of Open Circuit Reactions of Polymer Films Using the QCM Reactions of Polyvinylferrocene Films J Phys Chem 92 1988 2049 Charles K Baker and John R Reynolds A quartz microbalance study of the electrosynthesis of polypyrrole J Electroanal Chem 251 1988 307 Stephen Martin Victoria Edwards Granstaff and Gregory C Frye Characterization of a Quartz Crystal Microbalance with Simultaneous Mass and Liquid Loading Anal Chem 63 1991 2272 Ralf Lucklum and Peter Hauptmann The Df DR QCM technique an approach to an advanced sensor signal interpretation Electrochimica Acta 45 2000 3907 R A Etchenique and E
127. nd temperature fluctuations Control humidity if necessary Adjustment of the humidity is often a requirement for accurate gas phase measurements It is generally recommended to adjust control the humidity of the gas before flowing into the measurement chamber A common procedure consists of exposing the gas to saturated salt solutions with well known humidity values SRS QCM200 Quartz Crystal Microbalance 68 Sensor Crystals and Holders Chapter 3 Bubbles and Liquid Flow Cells Eliminating gas bubbles trapped inside flow cell chambers is essential for accurate long term QCM measurements The highest risk of bubble formation is when liquid enters an empty chamber Bubbles can also form spontaneously if liquids are not previously degassed and the chamber temperature is greater AT gt 2 C than the liquid temperature This section describes some simple tricks known to effectively prevent and remove bubble trapping in flowing QCM systems and also presents some of the common indicators used to detect the presence of bubbles in liquid flow chambers Eliminating dissolved gases from all sample solutions is the most basic precaution recommended for the minimization of bubble trapping Commercially available online degassing stages and bubble traps are recommended for flow injection analysis setups When filling an empty chamber with a syringe pump for the first time the following procedure generally works very well to displace all trapped bu
128. ne Australia under the supervision of Professor Alan Maxwell Bond Monash and Professor Stephen Fletcher CSIRO Available for download from http www bond chem monash edu au theses Note the use of Lead acetate is proposed as a better alternative to Cu and Ag deposition Scott Grimshaw Quartz Crystal Thin Film Monitoring Forges Ahead Photonics Spectra April 2003 p 82 24 John R Vig and Arthur Ballato Ultrasonic Instruments and Devices Academic Press 1999 Chapter 7 Frequency Control Devices Note this is probably the most thorough paper on the properties of QCM quartz crystal resonators gt Ballato A and Vig J R Static and dynamic frequency temperature behavior of singly and doubly rotated oven controlled quartz resonators Pmt 32nd Ann Symp Freq Conk NTIS Accession No AD A955718 pp 180 188 1978 M N Rocklein and S M George Temperature Induced Apparent Mass Changes Observed during QCM Measurements of Atomic Layer Deposition Anal Chem 75 2003 4975 Note This is a dramatic demonstration of thermally induced frequency transients caused by temperature transients in the gas phase SRS QCM200 Quartz Crystal Microbalance 72 Sensor Crystals and Holders Chapter 3 7 Kusters J A and Vig J R Thermal hysteresis in quartz resonators a review Proc 44th Ann Symp Freq Contr IEEE Catalog No 90CH2818 03 pp 165 175 1990 8 JR Vig UV Ozone Cleaning of Sur
129. nge Sauerbrey was the first to recognize the potential usefulness of the technology and demonstrate the extremely sensitive nature of these piezoelectric devices towards mass changes at the surface of the QCM electrodes The results of his work are embodied in the Sauerbrey equation which relates the mass change per unit area at the QCM electrode surface to the observed change in oscillation frequency of the crystal Af C AM QCM200 Quartz Crystal Microbalance SRS Chapter 3 Sensor Crystals and Holders 53 where Af the observed frequency change in Hz Am the change in mass per unit area in g cm C the sensitivity factor for the crystal 56 6 Hz ug cm for a 5 MHz crystal at room temperature The minimum detectable mass change is typically a few ng cm and limited by the noise specifications of the crystal oscillator and the resolution of the frequency counter used to measure frequency shifts For example based on Sauerbrey s equation a minimum detectable mass specification of 0 18 ng cm should be expected from a QCM system with a 0 01 Hz frequency measurement resolution As a comparison consider that a monolayer of a 20 kDa protein 100 coverage adsorbed on a QCM crystal amounts to roughly 10 Hz frequency shift or 180 ng cm The Sauerbrey equation relies on a sensitivity factor C which is a fundamental property of the QCM crystal Thus in theory the QCM mass sensor does not require calibration
130. nium Gold Polished 149238 1 6 00617 O100RX4 Titanium Platinum Polished 149240 1 Principle of Operation AT cut quartz crystals are most commonly used as QCM sensors because of their superior mechanical and piezoelectric properties and because they can be cut to give nearly zero temperature coefficients at room temperature Due to the piezoelectric properties and crystalline orientation of AT cut quartz the application of a voltage between the sensor crystal electrodes results in the production of internal mechanical stress An oscillating electric field of the proper frequency applied across the disk induces a pure shear mode oscillation that propagates through the crystal The designation of the oscillation as a pure shear mode indicates that the motion of the disk surface 8 perfectly parallel to the disk s face For shear mode oscillation there are several frequencies that correspond to resonant conditions For all resonant modes displacement maxima occur at the crystal faces making the device sensitive to surface perturbations The perturbations to be considered include surface loading by e a thin film mass layer e a contacting Newtonian fluid e a viscoelastic layer of finite thickness Frequency The nominal frequency of oscillation of all standard QCM Sensor Crystals is 5 MHz fundamental mode The unperturbed crystals will normally be within 1 000 ppm of their nominal frequency Operati
131. nt batches through a series of load rinse exchanges Syringes and the siphon principle are commonly used to manually inject new solutions into the crystal chamber Flow Mode A constant flow of solution solvent runs over the crystal in an open or closed flow configuration In open flow systems the siphon principle is recommended to implement the lowest noise flow setup Syringe pumps and 6 port injection valves are commonly used to expose the crystal to a sequence of analytes see Figure 15 Most standard Flow Injection Analysis FIA and Sequential Injection Analysis SIA equipment is compatible with QCM flow cell operation Peristaltic pumps are often applied to closed flow systems but they always add noise to the frequency signal due to pressure transients and coupled vibrations pulse dampening modules are always recommended In all cases the flow rate must be kept under 5 mL min to avoid excessive stress on the sensor and to avoid leaks of liquid over the o ring 6 port Injection Valve Buffer w pump ee Waste Waste i QCM w Axial Flow Cell QCM200 Figure 15 A Flow Injection Analysis QCM200 system consisting of syringe pump for buffer solution 6 port injection valve for analyte injection and Axial Flow Cell for QCM Flow Chamber ASRS QCM200 Quartz Crystal Microbalance 14 _ Getting Started Chapter t Specifications Flow Volume crystal chamber 0 15 mL In Out Ports Barbed hose adapters for 1 16
132. o Piranha solution damages QCM crystals The failure mechanism is believed to involve chemical degradation of the Cr bonding layer located between the quartz and the gold electrode Typically a QCM crystal can be exposed to Piranha solution a maximum of three times before noticeable degradation of performance occurs The first signs of crystal degradation are reduced stability in the frequency baseline QCM200 Quartz Crystal Microbalance SRS Chapter 3 Sensor Crystals and Holders 59 Polystyrene removal 1 Immerse the crystal into a 1 1 solution of hexane and deionized water and treat it in an ultrasonic bath for 1 minute 2 Rinse thoroughly with deionized water and blow dry with nitrogen gas Crystal rinsing Rinse sensor crystals with deionized or distilled water or another appropriate pure liquid In order to prevent recontamination follow these steps 1 Hold the crystal with a pair of tweezers from underneath to prevent transferring contaminants from the tweezers onto the crystal This is generally most critical in biological applications Blow the remaining liquid off the crystal with a gentle flow of nitrogen gas 3 Use a clean lint free cloth to wick off any liquid remaining on the edge of the crystal Surface Modifications SRS The biggest drawback of the QCM sensor is that it is inherently non specific anything that has mass can generate a response from the device The danger of this universal response
133. oltage is amplified by 5x in the QCM25 Crystal Oscillator and by 2 5 x in the QCM200 Controller before being output via the Conductance BNC on the front panel of the QCM200 Hence referenced to the voltage V at the QCM200 Conductance output BNC A 10 2 A fixed gain amplifier with gain A 45 dB 20 log 250 200 46 94 dB or 222 x This inverting amplifier has a bandwidth of 500 MHz and so introduces very little extraneous phase shift SRS QCM200 Quartz Crystal Microbalance 24 Theory Operation and Calibration Chapter 2 3 A source resistance Rs of 100 Q This source resistance consists of two series 50 Q resistors one of which is inside the amplifier A4 This source impedance is reduced by a factor of 4 x to 25 Q by the 2 1 transformer which follows 4 An isolation transformer with a 2 1 turns ratio hence an attenuation of A 0 5 This transformer allows galvanic isolation of the crystal from the oscillator circuit which is important in electrochemistry applications In addition to reducing the source impedance by 4 x the transformer also increases the load impedance seen at the input of the transformer by 4 x so that when Rm 0 Q the load will be 200 Q 5 Rm the motional resistance of the crystal at series resonance Rm can vary from about 10 40 Q for a dry crystal to about 375 Q for a crystal in water to about 5 KQ for a crystal in 90 w w glycerol water solution 6 A second isolation transformer with
134. on at 5 MHz is regarded as optimal for laboratory use since it provides 1 acceptable submonolayer sensitivity 2 robustness 331 um crystal thickness and 3 stable oscillation in most viscous media QCM200 Quartz Crystal Microbalance SRS Chapter 3 Sensor Crystals and Holders 51 Geometry Figure 30 shows a top and bottom view of a standard linch diameter QCM Sensor Crystal with what is called a wrap around electrode configuration A conductive metallic pad i used to allow connection to the front electrode liquid surface from the back of the crystal electrical contact surface This is required for mounting of the crystal into its Crystal Holder and for proper operation in conductive liquids The exposed area of the front electrode in contact with the liquid is 1 37 cm however the active electrode oscillation i e displacement area is mostly restricted to the area of overlap between the two circular pad electrodes or 0 40 cm All standard 1 inch QCM sensor crystals are planar with both faces parallel to within 1 um Crystal thickness is 331 um as required for fundamental oscillation at 5 MHz The large diameter of the crystal 1 inch and the relatively much smaller oscillation area assures good separation between the active electrode pads and the mounting structure of the holder and minimizes the coupling of other resonant modes to the thickness shear oscillation Surface Finish Electrode surface r
135. on of Rm Resistance measurements for the QCM25 Crystal Oscillator QCM200 are calibrated by replacing the crystal with a precision resistor in parallel with a 18 pF capacitor Two resistor values are used 25 Q and 925 Q The equation for Rm may be inverted to determine the calibration value for Vs Motional resistance Rm in Q and conductance voltage output Vo in volts 10 000 Rm 10 000 10 75 and V 5log oe eqn 11 The low pass filter is adjusted so that the QCM25 Crystal Oscillator oscillates at 5 MHz with the 25 resistor in place of the crystal The varactor dial is adjusted so that the Crystal Controller oscillates at 5 MHz with the 925 Q resistor in place of the crystal Calibration potentiometers in the QCM25 Crystal Oscillator are adjusted so that P1 pot Ve 10 000 0 005 Vdc with a calibration resistor of 25 Q and P2 pot V 5 000 0 005 Vdc with a calibration resistor of 925 Q Iterate P1 and P2 adjustments as necessary QCM200 Quartz Crystal Microbalance SRS Chapter 2 Theory Operation and Calibration 27 Gas Phase Measurements The first use of QCMs was as mass sensors and thickness monitors in gas phase thin film depositions To this date this continues to be an important area of application for this technology Sauerbrey Equation Sauerbrey s equation eqn 12 is often used to calculate mass loadings and thin film thicknesses in vacuum depositions The basic assumption is that the incremental change
136. or the crystal used see eqn 1 Q integrated charge during the reduction in Coulombs A active deposition area of the working liquid contact electrode in cm F Faraday s constant 9 648 x 10 Coulomb mole n number of electrons transferred to induce deposition i e n 1 for Ag deposition The factor of 10 provides for the unit conversion from ug in Cp to g in My A plot of Af vs Q will deliver the apparent mass per electron of the deposited species when n is taken into account This is often used to elucidate the mass changes that accompany redox processes and hence is very useful for characterizing the mechanisms of electron transfer reactions However before any calculations can be performed based on eqn 17 the EQCM must be calibrated in order to properly derive 1 the proportionality constant C of the Sauerbrey equation in solution and 2 to account for the effective area of the working electrode This is generally done using a well behaved electrochemical reaction typically electrodeposition of silver copper or lead on a Au or Pt electrode The EQCM calibration method favored by Stanford Research Systems for its QCM200 System is based on the galvanostatic deposition of Ag A 50 mM solution of AgNO in 0 5 M HNO is subjected to a reducing potential and Ag is deposited with a fixed cathodic current density of 50 500 A cm The cathodic current is integrated to obtain the charge as a function of time Exc
137. ossings The CPLD buffers EXT_REF to produce EXT_REF_CPLD R35 C32 R37 D13 Q12 R36 and C33 form an AC coupled rectifier EXT_REF_DET active low indicates that an external timebase signal is present When the user selects Timebase External the MCU de asserts pulls low PLL_DISABLE_PIC to the CPLD If both PLL_DISABLE_PIC and EXT_REF_DET are low then the CPLD pulls TCXO_ALONE low which allows the PLL_PHASE_DET signal to control the TCXO frequency The loop is considered locked when PLL_PHASE_DET is stable and within the TCXO control range 1 65V V The MCU displays the voltage at PLL_PHASE_DET scaled to 100 of the available 3 V QCM200 Quartz Crystal Microbalance 82 QCM Circuit Description Chapter 4 TCXO control range If either EXT_REF_DET or PLL_DISABLE_PIC is high then the voltage at trimmer R327 is selected and the MUX U32 passes this DC voltage to the TCXO control pin Y1 pin1 R323 C34 R324 R325 and C36 filter the TCXO control voltage to maintain a stable system clock under all operating conditions RS 232 communication to a remote user or program are provided by the Universal Asynchronous Receiver Transmitter UART within the MCU TX and RX signals are buffered and translated to RS 232 levels 6V by the transceiver U22 The charge pump inverter inside U22 uses C222 through C225 to generate the required RS 232 voltages The CPLD asserts LED_TRAFFIC high for 16mS when it detects RS 232 activity on RX_TF
138. oughness can cause large apparent mass loadings due to the liquid that is trapped within pores at the crystal surface As a general rule optically polished crystals 50 A average surface roughness are required to obtain good agreement between theory and experiment during liquid immersion experiments The QCM200 1 inch sensor crystals are available in two finishes unpolished 3 um average surface roughness typical or polished optically clear 50 A average surface roughness typical Rough surfaces are popular because they are less expensive and provide enhanced surface area However they suffer from a quantitatively unpredictable dependence of the oscillation frequency in a liquid due to trapping of fluid in the pores and pits on the surface Tip For liquid phase applications optically polished crystals are required if crystal to crystal reproducibility is to be expected A water Immersion Test refer to Chapter 2 usually provides a quick and easy way to test the quality of a crystal finish for liquid QCM applications Electrode Materials Gold electrodes 100 1000 nm thick are the most commonly used in QCM applications because of the ease with which gold is evaporated However other metals such as Pt Cu Al and Ni have also been used A thin 2 20 nm adhesion layer of either Cr Ti or Si is often deposited directly on the quartz to aid in the adhesion of the metal electrode Chromium is recommended for SRS QCM200 Q
139. pm MELF Resistor Resistor Metal Film 1 8W 0 1 25ppm Resistor Metal Film 1 8W 0 1 25ppm Thick Film 5 200 ppm Chip Resistor Thin Film 1 50 ppm MELF Resistor Thick Film 5 200 ppm Chip Resistor Thick Film 5 200 ppm Chip Resistor Thick Film 5 200 ppm Chip Resistor Thick Film 5 200 ppm Chip Resistor Chapter 4 QCM200 Quartz Crystal Microbalance SRS Chapter 4 QCM Circuit Description 91 REF SRS PART VALUE DESCRIPTION R17 4 00992 462 49 9 Thin Film 1 50 ppm MELF Resistor R18 4 01184 462 4 99K Thin Film 1 50 ppm MELF Resistor R19 4 01184 462 4 99K Thin Film 1 50 ppm MELF Resistor R 20 4 01431 461 10 Thick Film 5 200 ppm Chip Resistor R21 4 01076 462 374 Thin Film 1 50 ppm MELF Resistor R 22 4 01021 462 100 Thin Film 1 50 ppm MELF Resistor R 23 4 01021 462 100 Thin Film 1 50 ppm MELF Resistor T1 6 00622 610 ADT1 6T Transformer T2 6 00622 610 ADT1 6T Transformer U1 3 00369 340 AD8367ARU Integrated Circuit Thru hole Pkg U2 3 00375 360 DS8921AM Integrated Circuit Surface Mount Pkg U3 3 00686 360 OPA337UA Integrated Circuit Surface Mount Pkg U4 3 00898 360 AD8009 Integrated Circuit Surface Mount Pkg ZO 0 00025 005 3 8 Lugs Zo 0 00150 026 4 40X1 4PF Screw Black All Types Zo 0 00241 021 4 40X3 16PP Screw Panhead Phillips ZO 0 00276 102 PCB POST RED Binding Post ZO 0 00277 053 4 24 BLK Wire 24 UL1007 Strip 1 4x1 4 Tin Zo 0 0038
140. r of two and unpredictable for unpolished crystals so they are not recommended for system checkup Electrochemical Quartz Crystal Microbalance In most electrochemical experiments mass changes occur as material is deposited or lost from the working electrode It is of interest to monitor those changes simultaneously with the electrochemical response and the QCM is the standard means of doing so As a gravimetric probe the QCM has been used in many types of electrochemical studies including underpotential deposition of metals corrosion oxide formation dissolution studies adsorption desorption of surfactants and changes in conductive polymer films during redox processes The basic principles and applications of the QCM to electrochemical processes have been extensively reviewed in the electrochemical literature and will only be discussed briefly in this manual Please refer to the publications list at the end of this chapter for more detailed information Electrochemical Apparatus A schematic diagram of the apparatus for electrochemical quartz crystal microbalance EQCM experiments is given in Figure 23 In this example a 1 inch diameter polished QCM crystal is mounted on a Crystal Holder with only one electrode exposed to the conductive solution The Crystal Holder is connected to a QCM25 Crystal Oscillator and QCM200 Quartz Crystal Microbalance SRS Chapter 2 SRS Theory Operation and Calibration 33
141. r the frequency counter 0 1 second Gate 100 mS Resistance QCM200 Quartz Crystal Microbalance ASRS Chapter 1 Getting Started 5 Parameter Value Symbol Display 200 Hz Scale 200 Hz 500 Hz Scale 500 Hz Voltage Scaling Factor for the Analog Frequency Output voltage 1 kHz Scale 1 kHz Hz V or kHz V Scale Analog Frequency Out V 5 kHz Scale 5 kHz Relative Frequency Scale Factor 10 kHz Scale 10 kHz Frequency counter is using the Internal T Internal internal TCXO as the timebase reference Frequency counter is using the external timebase connected to the rear panel Display shows how far T T Ext 100 the internal oscillator is being pulled to lock to the external timebase percentage of full range A stable number indicates a stable lock External External 10 MHz input not detected T Ext NA Internal oscillator is being used instead Check external source Relative Frequency Resistance Readings Hold down the VALUE key for 2 seconds while in the Absolute or Relative Resistance display modes to 1 set the Resistance Offset to the current Absolute Resistance value and 2 zero the Relative Resistance readings Hold down the VALUE key for 2 seconds while in any other display mode to 1 set the Frequency Offset to the current Absolute Frequency value 2 zero the Relative Frequency readings 3 zero the Mass Displacement display and 4 zero the Frequency Analog Out voltage output
142. ru cable is used to connect the two boxes The green OSC LED lights up indicating the presence of an oscillating crystal in the circuit when the Conductance Output is gt 2 V Co Compensation A switch is available to set the controller into Adjust Mode for nulling Co A ten turn dial controls the bias voltage varactor bias required by the QCM25 Crystal Oscillator to null C Four LEDs HIGH NULL LOW provide visual feedback while nulling Co Set the Co Compensation switch back to HOLD after nulling Co Measurement Display RS 232 and ZERO LEDs An alphanumeric LED display in the QCM200 Digital Controller displays frequency mass and resistance measurements and also important instrument settings The RS 232 LED is an activity indicator that flashes whenever characters are received or transmitted over the RS 232 interface The ZERO LED flashes to indicate zeroing of the Relative Frequency and Relative Resistance readings after the VALUE key is held down for 2 seconds QCM200 Quartz Crystal Microbalance vi Overview PARAMETER and VALUE keys The PARAMETER and VALUE keys on the QCM200 are used to 1 select display modes 2 program instrument settings and 3 zero the Relative Resistance r and Relative Frequency f readings Use these keys to navigate through the menu system The PARAMETER key jumps to the next parameter and the VALUE key selects the next available value for the current parameter The VALUE key walks throug
143. speed resolution of a counter is also important The accumulated mass can change rapidly in a typical QCM measurement and it is desirable to make frequency measurements with a resolution of 1 10 in a one second interval to not significantly degrade the mass resolution of or add noise to the measurement Simply counting cycles of the frequency output over a one second interval can not provide resolution better than 1 in 5x10 and so a more elaborate counter architecture is required A reciprocal interpolating counter can provide a much better frequency resolution than 1 cycle per gate interval Virtually all frequency counters can measure the frequency of the 2 4 V square wave into 50 Q provided by the QCM200 Frequency Output Counters are available with RS 232 and or IEEE 488 interfaces to facilitate computer data acquisition The speed of the interface is not very critical as typically only one reading is taken each second Counters are relatively simple to set up and read via their computer interfaces Software drivers for National Instruments LabView products or other data acquisition programs are often available Frequency counters used at SRS for QCM measurements are listed below Manufacturer Model Digits Second Stanford Research Systems SR620 10 Agilent 53131 10 Agilent 53132 12 QCM200 Quartz Crystal Microbalance SRS QCM200 Remote Progamming 101 Appendix B QCM200 Remote Programming Intro
144. t O100FC Crystal Cleaning Basket SRS Part O100CCB Replacement Crystal Holder 0100RH Ultra stable Rubidium Frequency Standard SRS model FS725 QCM200 Quartz Crystal Microbalance SRS Chapter 1 Getting Started 3 Quick Start Instructions SRS 1 10 11 12 With the power switch in the Off position connect the QCM200 Controller to a grounded outlet using the power cord provided Connect the QCM200 Controller to the QCM25 Crystal Oscillator using the Cat 5 cable 3 feet long straight thru RJ 45 end connectors Mount a fresh quartz crystal in the Crystal Holder See special instructions in the following Crystal Installation section Connect the Crystal Holder to the 5 MHz Crystal BNC connector of the QCM25 Crystal Oscillator If required connect the Frequency Analog Output to 1 the Ext A D Input of your potentiostat EQCM or 2 a precision voltmeter or 3 an analog to digital converter If required connect the RS 232 port to your Host PC and download and install the QCM software www thinksrs com downloads soft htm Set the C Compensation switch to Hold and the ten turn dial to 8 0 Dry Operation Setting Turn the Power switch on and check that the Power LEDs in the QCM200 and QCM25 boxes light up The OSC LED of the QCM controller turns on as soon as proper quartz oscillation is established in the dry crystal After a short initialization period an Absolute Frequency F very close to 5 MH
145. t crystal Phase shift in low pass filter 0 65 Hz lt 0 1 Reproducibility of Co null lt 0 20 Hz Temperature dependence of 0 8 Hz 0 1 C viscosity static QCM200 Quartz Crystal Microbalance 22 Theory Operation and Calibration Chapter 2 Resistance Measurement QCMZ200 Resistance Outputs The QCM200 system is a stand alone instrument with a built in frequency counter and resistance meter Series resonance frequency and resistance are measured and displayed directly on the front panel without a need for an external frequency counter or precision voltmeter Resistance Display Absolute and Relative Resistance Range 0 to 5000 2 Resolution 5 digits 0 001 Q for R lt 100 Q 0 01 Q for 100 Q R lt 1000 Q 0 1 Q for 1000 Q R lt 5000 Q Conductance Output V front panel Resistance Calculation R 10 000 x 10 75 Q Resistance range 0 to 5000 Q Impedance 1 kQ Voltage level 0 to 10 625 VDC log scale Connector BNC If desired due to existing system integration or other issues the Conductance Voltage output V may be read with a high precision digital voltmeter with at least 6 digits of resolution and a computer interface The calculation of Rm is then performed by the computer QCM200 Quartz Crystal Microbalance SRS Chapter 2 Theory Operation and Calibration 23 Resistance Calculation L ag X2 5 Figure 20 QCM Gain Model 50dB V A gain model of
146. t excessive viscous loading would prohibit use of the QCM in liquids In fact operation in liquids is indeed possible and the response of the QCM is still extremely sensitive to mass changes at the crystal solution interface For many years QCMs have been used in direct contact with liquids and or viscoelastic films to assess changes in mass and viscoelastic properties during chemical and electrochemical surface processes When the QCM comes in contact with a solution there is a decrease in frequency that is dependent upon the viscosity and the density of the solution A quantitative understanding of the resonator behavior is a prerequisite for proper interpretation of experimental results under total liquid immersion This problem was first treated by Glassford and later by Kanazawa and Gordon Kanazawa s treatment of the influence of the solution properties on the crystal eqn 15 permits the prediction of the change in resonance frequency which accompanies immersion of the crystal into a viscous medium 1 2 Af f3 eqn 15 PHa where fu frequency of oscillation of unloaded crystal Pq density of quartz 2 648 gem U shear modulus of quartz 2 947 x 10 gem s p density of the liquid in contact with the electrode NL viscosity of the liquid in contact with the electrode Viscous coupling of the liquid medium to the oscillating crystal surface results not only in a decrease in the series reson
147. talum SMT all case sizes Cap Ceramic 50V SMT 1206 10 X7R Cap Ceramic 50V SMT 1206 10 X7R Cap Ceramic 50V SMT 1206 10 X7R Cap Ceramic 50V SMT 1206 10 X7R Cap Ceramic 50V SMT 1206 10 X7R Cap Ceramic 50V SMT 1206 10 X7R Cap Ceramic 50V SMT 1206 10 X7R Cap Ceramic 50V SMT 1206 10 X7R Capacitor Chip SMT1206 50V 5 NPO Cap Ceramic 50V SMT 1206 10 X7R Capacitor Chip SMT1206 50V 5 NPO Capacitor Chip SMT1206 50V 5 NPO Cap Ceramic 50V SMT 1206 10 X7R Cap Ceramic 50V SMT 1206 10 X7R Cap Ceramic 50V SMT 1206 10 X7R Cap Ceramic 50V SMT 1206 10 X7R Cap Ceramic 50V SMT 1206 10 X7R Capacitor Chip SMT1206 50V 5 NPO Capacitor Chip SMT1206 50V 5 NPO Capacitor Chip SMT1206 50V 5 NPO Capacitor Chip SMT1206 50V 5 NPO weSewewrewre ar Saa Capacitor Chip SMT1206 50V 5 NPO Capacitor Chip SMT1206 50V 5 NPO LED T1 Package Integrated Circuit Surface Mount Pkg Connector Misc Ferrite bead SMT Inductor Variable Inductor Variable Pot Multi Turn Trim 3 8 Square Top Ad Pot Multi Turn Trim 3 8 Square Top Ad Printed Circuit Board Thick Film 5 200 ppm Chip Resistor Thick Film 5 200 ppm Chip Resistor Thick Film 5 200 ppm Chip Resistor Thick Film 5 200 ppm Chip Resistor Thick Film 5 200 ppm Chip Resistor Thin Film 1 50 ppm MELF Resistor Thin Film 1 50 p
148. te at series resonance or in some cases to oscillate at all QCM200 Quartz Crystal Microbalance SRS Chapter 4 SRS QCM Circuit Description 79 The 75 Hz modulation frequency is provided by U4 a CD4060 oscillator with a 14 stage binary divider A 76 8 kHz crystal is used in the oscillator circuit The oscillator frequency is divided by 2 providing a 75 Hz square wave The 75 Hz square wave is level shifted by R9 R10 to produce a square wave between 6 and 12 VDC That square wave is used to switch a dual 1 4 analog multiplexer U14 The analog multiplexer is used to generate the 5 modulated varactor voltage and to synchronously detect a 75 Hz signal on the amplified AGC voltage U7 a MAX6250 provides 5 00 VDC used as the varactor reference voltage The front panel 10 turn potentiometer P2 divides the reference voltage which is amplified and buffered by U8A The output of U8A is 1 05x the varactor hold voltage The resistive divider R20 R23 provides 1 00x and 0 95x the varactor hold voltage When in the HOLD mode the multiplexer sends the 1 00x tap to the varactor via the output filter buffer U8B When in the ADJUST mode the multiplexer switches between the 1 05x and 0 95x taps at 75 Hz This 75 Hz offset square wave is filtered by the output filter buffer to produce an offset and 90 phase shifted sine wave to modulate the varactor voltage The AGC voltage from the differential amplifier U9A is filtered and 90 phase s
149. temperature dependence of the QCM sensor crystals is negligible at or around room temperature 1 3 Hz C and is generally ignored for monolayer adsorption desorption processes in the gas phase A thermal effect less often discussed in connection with quartz crystal oscillators is based on the fact that dynamic changes in temperature around a crystal unit can produce thermal gradients which induce frequency transients dependent on the rate of temperature change around the sensor The static frequency vs temperature characteristic is modified by this thermaltransient effect resulting from the thermal gradient induced stresses Proper thermal compensation requires consideration of both static and dynamic i e rate of change frequency temperature behavior of the QCM crystals Larger changes in frequency with temperature should be expected when QCM crystals are immersed in liquids This is due to the coupling of the shear mode oscillation with the temperature dependent viscosity and density of the fluid The temperature coefficient due to this effect is 8 Hz C and 4 Q C for water As a result for experiments in liquid phase in which the frequency is to be monitored at length the temperature must be controlled to at least 0 1 C and preferably better If temperature control is not possible or practical it is always good practice to wait at least 30 minutes before performing any accurate measurements after the crystal comes in contact wit
150. the QCM25 Crystal Oscillator is shown in Figure 20 At series resonance the reactance of the crystal s motional inductance and motional capacitance cancel and so the crystal may be represented by just Rm the motional resistance of the crystal It is also assumed that the static capacitance Co has been nulled as previously described The circuit will oscillate at the frequency for which the net phase shift around the loop is 360 provided there is sufficient gain to overcome the circuit losses Two network elements in the model provide a phase shift The inverting amplifier provides 180 of phase shift The low pass filter is adjusted to provide 180 of phase shift at 5 MHz Hence the circuit will oscillate at the frequency for which the crystal is resistive i e at series resonance The loop gain is the product of the gain or attenuation of each of the network elements If the loop gain is exactly one then the oscillation amplitude will be maintained at a fixed level An AGC circuit controls the loop gain via a voltage controlled variable attenuator From left to right the circuit consists of the following 1 A voltage controlled variable attenuator with attenuation of A An automatic gain control circuit generates a voltage to maintain the oscillation amplitude at a fixed level of 1 Vp The attenuator is controlled by this voltage between 0 and 1 Vdc providing an attenuation of 50 dB volt so that A 10 The AGC v
151. the crystal must be in close proximity to the action taking place in the rest of the tank Preplating is recommended if adhesion problems are observed with untreated crystals Pre treatment with catalyst may be prescribed in some cases It is recommended not to expose the entire Crystal Holder to catalysis during pre treatment to avoid excessive metallization of the holder during deposition QCM200 Quartz Crystal Microbalance 62 Sensor Crystals and Holders Chapter 3 Crystal Holder Description The standard Crystal Holder bundled with the QCM200 system is specifically designed to provide users with a rugged compact and easy to use sensor crystal housing for QCM experiments in air or liquids Figure 31 The Crystal Holder with a 1 inch sensor crystal mounted Its main features include e rugged design e compatibility with all standard 1 inch diameter QCM sensor crystals e compatible with Crystal Oscillator SRS Model QCM25 e liquid and gas compatibility leak proof design e single electrode exposure to liquids for compatibility with electrochemical QCM measurements e chemical resistance Kynar material with Viton O rings e broad temperature range 25 C to 110 C e easy crystal replacement a simple hand removable retainer cover permits easy crystal replacement without tools e standard female BNC connector for easy electrical connection e flow cell adapters available SRS Part O100FC Severa
152. tion of air bubbles and reduce temperature related signal changes the sample liquid should be at approximately the same temperature as the sensor holder and the entire experimental setup should be temperature stabilized The generation of air bubbles is facilitated when the temperature of the liquid is lower than that of the holder flow cell Avoid temperature differences greater than 2 C between the sample liquid and the crystal holder Keep in mind that frequency readings are not just affected by the static temperature but also by the rate of change of temperature around the sensor This is very important during the implementation of temperature compensation or stabilization schemes For example PI PID and Fuzzy Logic stabilized temperature controllers are recommended instead of On Off controllers for temperature stabilization QCM200 Quartz Crystal Microbalance SRS Chapter 3 SRS Sensor Crystals and Holders 65 To ensure signal stability for flowrates greater than 0 2 mL min use external temperature stabilization as necessary to make sure that the sample liquid is temperature equilibrated prior to flowing into the flow chamber Immersing the flow cell crystal holder in a water bath and running the sample fluid through the same bath i e heating loop prior to entering the QCM chamber is a simple way to assure temperature equalization between the holder and its liquid sample solutions Prepare your solutions carefully To avoid
153. ts socket Rinse the pins and the sockets with deionized water to remove all traces of chemicals Replace the POGO pins with new ones if necessary Keep in mind that even though the POGO contacts and sockets are gold coated unrinsed chemicals can still lead to corrosion and permanent damage to the holder This is specially true in electrochemical applications where oxidizing acids are often components of the liquid solution in contact with the crystal Crystal Cleaning Basket A Crystal Cleaning Basket SRS Part O100CCB is available directly from Stanford Research Systems This accessory makes cleaning and surface modification treatment of the standard 1 QCM crystals very safe and easy The cleaning basket is shown in Figure 32 it holds four crystals is made entirely of Teflon and it is specifically designed for immersion into a 100 mL beaker Figure 32 Crystal Cleaning Basket SRS Part O1O0CCB The entire basket is made out of Teflon and is shown here holding its maximum load of 4 crystals not included ASRS QCM200 Quartz Crystal Microbalance 64 Sensor Crystals and Holders Chapter 3 Tips for Operation in Liquids To minimize measurement errors in liquid phase QCM experiments the sample fluids should be prepared carefully Changes in temperature flow rates properties of the solvent as well as air bubbles will affect the sensor signal For reproducible measurements keep the following tips in mind Check for Chem
154. ts used in high vacuum environments Biomaterials lipids proteins and similar biomolecules 1 Treat the crystal in a UV ozone or plasma cleaning chamber for 10 minutes 2 Immerse the crystal into a 1 1 5 solution of hydrogen peroxide 30 ammonia 25 and deionized water heated to a temperature of about 75 C for 5 minutes 3 Immediately rinse with deionized water and dry with nitrogen gas 4 Treat the crystal again with UV ozone for 10 minutes immediately before measurement this removes any remaining surface contaminants Lipid vesicles 1 Treat the crystal in a UV ozone or plasma cleaning chamber for 10 minutes 2 Immerse the crystal into water with 2 of sodium dodecyl sulfate SDS at room temperature for 30 minutes 3 Immediately rinse with deionized water and blow dry with nitrogen gas 4 Treat the crystal again with UV ozone for 10 minutes immediately before measurement this removes any remaining surface contaminants QCM200 Quartz Crystal Microbalance 58 Sensor Crystals and Holders Chapter 3 Self assembled Monolayers It is common practice to wash crystals with piranha solution see next section at the end of a QCM immunoassay Piranha solution is also often used to precondition the crystals for a SAM deposition 1 Treat the crystal s with piranha solution for three minutes 2 Repeat treatment step 1 two more times with fresh piranha solution 3 Rinse liberally with deionized water and dr
155. tting Started Chapter 1 towards the flat surface of the QCM crystal The stagnation point is located at the center of the crystal electrode overlapping the area of highest sensitivity of the flat QCM oscillator The hydrodynamics associated with stagnation point flow are well understood At the stagnation point there is zero hydrodynamic flow i e without surface shear forces While the injected solution flows about the stagnation point any exchange with the surface of the crystal is diffusion limited Thus the rate of adsorption of the sample molecules or particles to the crystal surface is diffusion limited as well The hydrodynamics and deposition of molecules in stagnation point flow conditions have been investigated by Dabros and Van de Ven and the user is referred to their publications for details Dabros T van de Ven T G M A direct method for studying particle deposition onto solid surfaces Colloid and Polymer Science 261 1983 694 707 Dabros T and T G M Van de Ven Deposition of latex particles on glass surfaces in an impinging jet Physicochem Hydrodynamics 8 1987 161 172 The stagnation point flow cell was specifically designed for the study of adsorption kinetics of particles micelles and chemical and biological molecules at solid liquid interfaces under well controlled hydrodynamic conditions Examples of surface volume processes that have been studied with the aid of stagnation flow cells include
156. tween antigen and antibody proteins resulted in the final 40Hz frequency step The real advantage of the QCM technology in this application is that it is label free the sample flowed over the immobilized surface layer does not need to be modified or labeled in any way Thus it is much more physiologically relevant because labeling something with a fluorescent probe i e ELISA often changes its properties The ability to see changes in the QCM signal after every individual step provides an additional advantage over standard immunoassays such as ELISA where no user feedback is available until the entire process is completed TIP Using a QCM biosensor you cannot only tell whether something binds to a given protein immobilized on the crystal but you can also tell how tightly it binds this is very useful additional information QCM Systems are applied routinely by biologists immunologists and biochemists to obtain information about processes such as 1 protein adsorption desorption 2 cell adhesion 3 Protein protein interaction 4 Degradation of polymers 5 biofouling and biofilm formation 6 drug analysis 7 self assembled monolayers and 8 DNA biosensors For more detailed information please consult the references listed at the end of this chapter QCM200 Quartz Crystal Microbalance SRS Chapter 2 Theory Operation and Calibration 41 Self Assembled Monolayers A self assembled monolayer SAM is defined
157. uartz Crystal Microbalance 52 Sensor Crystals and Holders Chapter 3 polished blank surfaces and also for crystals operated in a harsh environment However Cr can be a problem in some electrochemical applications spurious electrochemical responses can sometimes result if diffusion of the adhesion material to the electrode surface occurs In that case Titanium is recommended as a substitute adhesive layer If Ti is still a problem Palladium can be utilized as a barrier metal between the Cr or Ti and the primary metallization consult Stanford Research Systems for availability of alternative electrode materials A zinc layer sandwiched between the adhesion layer and the electrode pad on the front or deposition side of the crystal has a relatively low bulk modulus and has been shown to absorb stress imposed by the deposited materials The buffer layer prolongs useful crystal life particularly when depositing dielectric materials The crystal should have a modest surface roughness as keying in structure The buffer layer can be a zinc layer of 600 nm sandwiched between a titanium or chromium adhesion layer of 10 to 16 nm and a gold silver or aluminum outer electrode layer of about 200 nm For applications requiring transparent electrodes tin doped indium oxide ITO electrodes are recommended ITO is routinely used to make transparent conductive coatings which are applied in a wide variety of applications Transparent electrodes are ofte
158. uency and motional resistance monitoring of quartz crystal resonators by parallel capacitance cancellation Rev Sci Instrum 73 7 2002 2724 For example from the Conductance Output of the QCM200 7 Conductance is the inverse of resistance Conductance 1 Resistance or Resistance 1 Conductance The units of resistance are Ohms Q V A and the units of conductance are Siemens S A V For example Agilent 34401A with 6 digit resolution or 3458 with eight digits resolution D R Denison Linearity of a Heavily Loaded Quartz Crystal Microbalance J Vac Sci Technol 10 1 1973 126 Klaus H Behrndt Long Term Operation of Crystal Oscillators in Thin Film Deposition J Vac Sci technol 8 5 1971 622 10 C Lu and O Lewis Investigation of film thickness determination by oscillating quartz resonators with large mass load J Appl Phys 43 1972 4385 Chih shun Lu Mass determination with piezoelectric quartz crystal resonators J Vac Sci Technol 12 1 1975 578 1 D R Denison Linearity of Heavily Loaded Quartz Crystal Microbalance J Vac Sci Technol 10 1973 126 K H Behrndt Long Term Operation of Crystal Oscillators in Thin Film Deposition J Vac Sci Technol 8 5 1971 622 12 T Nomura and M Okuhara Anal Chim Acta 142 1982 281 1 A P M Glassford Response of a Quartz Crystal Microbalance to a liquid Deposit J Vac Sci Technol 15 6 1978
159. y in a gentle flow of nitrogen gas Piranha Solution Piranha solutions are used to remove organic residues from substrates particularly in microfabrication hbs The traditional piranha solution is a 3 1 mixture of sulfuric acid and 30 hydrogen peroxide The solution may be mixed before application or prepared on the sample applying the sulfuric acid first followed by the peroxide Warnings Piranha solutions are extremely reactive and may result in explosion or skin burns if not handled with extreme caution e Prepare the smallest possible volume Some QCM users mix the cleaning solution on the crystal surface pipetting the proper ratio of sulfuric acid and hydrogen peroxide directly on the liquid surface electrode of the quartz resonator e Do not expose the crystal holder to Piranha solution Wash separately e Wear gloves goggles and a lab coat e Work in a fume hood e The mixture of hydrogen peroxide and sulfuric acid is very exothermic e Do not touch the glassware after mixing HOT up to 120 C e Use heat resistant glassware This mixture can get really hot and shutter non thermal graded glass e Rinse thoroughly e Keep the etching solution away from organic solvents e Treat with very healthy respect e Properly clean and dispose of all chemicals e Consider safer alternatives compatible with your application e If not sure how to proceed STOP and seek help from an experienced chemist e Prolonged exposure t
160. y sensing system Sensors and Materials 8 8 1996 513 521 K L Prime G M Whitesides Science 252 1991 1164 K Prime G Whitesides A Model System Using Self Assembled Monolayers J Am Chem Soc 1993 v 115 10714 10721 Ramon Colorado Jr Ramon J Villazana and T Randall Lee Self Assembled Monolayers on Gold Generated from Aliphatic Dithiocarboxylic Acids Langmuir 14 1998 6337 6340 Zhao Yang Wu et al QCM Immunosensor for Schistsoma Japonicum Infected Rabbit Serum Analytical Sciences 19 2003 437 Spangler B D and Tyler B Capture Agents for a Quartz Crystal Microbalance Continuous Flow 41 S 42 C Biosensor Functionalized Self assembled Monolayers on Gold Anal Chim Acta 399 51 62 1999 Note Professor Spangler is also CEO of SensoPath Technologies a company specialized in the development of materials for the design and fabrication of SAMs on gold surfaces www sensoPath com D S Karpovich and G J Blanchard Direct measurement of the adsorption kinetics of alkanethiolate SAMs on a microcrystalline gold surface Langmuir 10 1994 3315 H M Schessler et al Quantitating the Balance between Enthalpic and Entropic Forces in Alkanethiol Gold Monolayer Self Assembly J Am Chem Soc 118 1996 9645 D S Karpovich and G J Blanchard Vapor adsorption onto metal and modified interfaces Evidence for adsorbate penetration of an alkanethiol
161. z nominal dry frequency should be present on the front panel Measurement display Press the PARAMETER key once to display Absolute Resistance R a value lt 75 Ohms should be present at this time The QCM200 System is now ready for mass and viscosity measurements For operation under liquid immersion record the dry frequency and conductance readings and immerse the entire crystal in the solution of interest For accurate measurements i e at true series resonance perform a Capacitance Cancellation procedure as described in Chapter 2 Consult Chapter 3 for additional tips on QCM operation in liquids For operation with a flow cell see Figure 13 pay special attention when filling the flow chamber for the first time so that no air bubbles get trapped in the measurement volume Consult Chapter 3 for useful tips on QCM operation in liquid flow cells including bubble elimination techniques Temperature stabilization to better than 0 1 C is essential for high accuracy measurements in aqueous solutions due to the large temperature coefficient of viscosity For operation in an electrochemistry setup consult the Electrochemical Quartz Crystal Microbalance EQCM section in Chapter 2 QCM200 Quartz Crystal Microbalance 4 Getting Started Chapter 1 QCM200 User Interface The QCM200 user interface consists of e Measurement Display e Menu System e RS 232 interface with complete command set Measurement Display RS 23

Download Pdf Manuals

Related Search

Related Contents

Sony 17" Black Flat Panel LCD  2004 Infiniti M45 Navigation Guide  平成16年12月2日  König CSNBSLV200BU  Cardio 60 のみ - BrytonSport  Extech SC50 Handheld Digital Scale - User`s Manual  Ati A3000 - Vendita Materiale Elettrico ed Elettronico  ？OVAIRE - World Health Organization  Qguard NVR/CMS ANVR832/ANVR864 USER MANUAL  Metra 70-8112 power cable  

Copyright © All rights reserved. Failed to retrieve file