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List of commands - Metrohm Autolab

1. updated showing the commands and settings used in this example procedure see Figure 16 Commands Parameters Links Cyclic voltammetry with EQCM Remarks Example of ECM measurement using the dedicated EQCM module a End status Autolab m Signal sampler Time EQQCMO1 Temperature EQCM 1 Driving force EQCMT AFr Options 1 Options al Instrument ALT84139 Instrument description E Timed procedure H Autolab control ma Set potential 0 800 H Set cell On aa Vat time s z Optimize current range 5 Reset EOCM AFrequency H CY staircase 0 600 1 000 0 600 0 600 2 0 0200000 set cell Mt im lt gt lt gt Figure 16 Detailed view of the Cyclic voltammetry with EQCM procedure This tutorial procedure will be described step by step in order to explain how the EQCM module is used in NOVA Note for more information on the use of the NOVA software please consult the NOVA User Manual 17 Page Autolab EQCM User Manual OY Metrohm 3 3 1 Connections for electrochemical measurements To perform electrochemical measurements the crystal needs to be installed in the cell as explained in section 2 3 1 The cell must then be filled with the solution and the lid carrying the counter electrode must be fitted onto the cell Note remember that the maximum volume is 3 ml Warning be careful when installing the lid onto the cell that the electrodes reference and counter do not touch the surface of the crystal to p
2. Temperature EQCM 1 Driving force EQCM 1 AFF c Options 1 Options ma Instrument ALT54139 Instrument description E Timed procedure ____EOCM Active Figure 32 A simple EQCM warm up procedure Note this procedure only used the Autolab control command to switch on the EQCM No other commands are used and no measurement is performed 4 3 Caring for the reference electrode The reference electrode included in the EQCM kit cannot be refilled and has a limited lifetime The reference electrode is based on a gel electrolyte 3 M KCl that minimizes leakage The electrode is shipped with a yellow sealing cap see Figure 33 30 Page N Metrohm Autolab EQCM User Manual Figure 33 The reference electrode shipped with the EQCM kit The yellow cap contains excess electrolyte gel that ensures that the electrode will not dry out estimated shelf life 1 year However once the cap is removed for first use the cap must be discarded and the electrode must be stored in a saturated aqueous solution of KCI or 3 M KCI to prevent the electrode from drying out Do not refit the yellow cap onto the EQCM as this will trap an air bubble inside the cap that will significantly decrease the lifetime of the electrode 4 4 Prevent damage to the crystal surface and holding springs When the measurements are finished it is recommended to disassemble the cell complete to clean the crystal surface and mounting spring and t
3. Aj Ti crystal to different concentrations of glycerol in water measured with respect to the oscillation frequency in pure water red curve compared with the theoretical calculated plot using the equation 8 blue curve 1 gt K K Kanazawa and J G Gordon Anal Chim Acta 99 1985 175 37 Page Autolab EQCM User Manual L Metrohm Sa So gt Y Experimental values gt Y Theory n ro So ww OO N N s ano a o a oe gt amp O G amp S amp O O O O O0 requency Hz F IS S 0 5 10 15 20 25 30 35 40 45 Glycerol Mass Figure 37 Change in frequency measured during exposure to different water glycerol solutions red vs theoretical predictions blue The values of AFrequency were normalized with respect to water Note the EQCM is able to sustain stable oscillation in 100 pure glycerol Note the deviation between the theoretical and the experimental plot is normal as the theoretical model fails to take into account the viscoelastic properties of the solution As the of glycerol increases these properties become more dominant 6 4 Example of data analysis for metal electrodeposition on QCM crystals In the case of experiments which measure relative change in frequency due to deposits of metal films on the electrode measured in the same solution electrolyte the Sauerbrey equation can be accurately applied because the viscous loading of the liquid has a negligible eff
4. Determine EQCM zero frequency window During the measurement the EQCM 1 Temperature EQCM 1 Driving force and EQCM 1 AFrequency signals will be recorded alongside the other electrochemical signals defined in the signal sampler see Figure 20 and section 3 3 2 8 The cell will be switched off as soon as cyclic voltammetry is finished Whenever the software encounters the Reset FQCM AFrequency in the procedure the Determine EQCM zero frequency window will be displayed see Figure 26 Both the driving force and the AFrequency value can be adjusted through the Determine EQCM zero frequency 25 Page Autolab EQCM User Manual Determine EQCM zero frequency Latest value EQICM 1 AFrequency 0 3890 Hz EGCM 1 Orwving force O de4 EQCM 1 Temperature Eel la I Time to average a _ D oO 4 5 Time 3 AVErAQes 2 Metrohm Minimum 0 346 Hz Maza Zela 10 Figure 26 The Determine EQCM zero frequency window appears each time the software encounters the Reset EQCM AFrequency command in the procedure The Determine EQCM zero freguency window contains three sections The topmost section shown in Figure 27 displays real time information on the measured signals provided by the EQCM Latest value EQICM 1 AFrequency 0 3890 Hz EQICM 1 Oriving force IREE EQICM 1 Temperature eal a NE Time to average AVErAQes Minimum 0 346 Hz 0 925 T a2 zao E 10 Figure 27 The t
5. buttons that can be used to control the behavior of the Determine EQCM zero frequency Zero Af Clear plot Aabot oK __Zeroaf N plot i Figure 29 The bottom section of the Determine EQCM zero frequency window displays the measured values in real time Zero Af set the value of the measured AFrequency to zero Setting the value to zero requires five iterations During this adjustment the Zero Af button will be grayed out Clear plot this button can be used to clear the plot displayed in the window The measurement resumes after the button is pressed The values shown in the topmost part of the window are not cleared Abort closes the Determine EQCM zero frequency window and terminates the complete procedure 27 Page Autolab EQCM User Manual 2 Metrohm e OK closes the Determine EQCM zero frequency window and proceeds with the rest of the procedure 3 3 5 1 Adjusting the driving force The driving force is adjusted using the provided tool Insert the tool vertically into the hole labelled Trimmer on the EQCM external oscillator and make sure that the tool fits into the trimmer located on the PCB enclosed in the EQCM oscillator Do not apply to much pressure The trimmer should rotate without significant torque If you find it difficult to rotate the trimmer remove the tool and insert it again paying careful attention to the position of the tool with respect to the trimmer Warning to avoid damaging the tri
6. deposited films are the same as of quartz 6 2 Z match equation In order to overcome the limitations of the Sauerbrey equations with its assumptions the Z match equation 4 was developed by Lu and Lewis where a new term is introduced which takes into account the ratio of the acoustic impedance of quartz and the acoustic impedance of the deposited material _ Nu Pa 1 l h i am Pt han renla r 4 N VP a 5 q 2P Ry e 6 Pi My where Am is the change in mass per unit area g cm N is the frequency constant of the AT cut quartz crystal 1 668 10 Hz cm p is the density of quartz 2 648 g cm f is the resonant frequency of the unloaded crystal Hz f is the resonant frequency of the loaded crystal Hz Rz is the Z factor of the film material acoustic impedance ratio p is the density of the material g cm uq is the shear modulus of quartz 2 947 10 g cm s us is the shear modulus of the film material g cm s When Rz the acoustic impedance ratio is equal to 1 quartz on quartz then the new equation will become the Sauerbrey equation 14 C S Lu O Lewis J Appl Phys 43 1972 4385 36 Page L Metrohm Autolab EQCM User Manual This equation applies strictly to elastic films and is considered to describe more accurately the experimental results for frequency changes up to 40 of the unloaded crystal Films with viscoelasticity thick layer of organic polymer will exhibit
7. polished 6 MHz EQCM crystal Au TiO2 polished 25 pcs 6 MHz EQCM crystal Pt TiO2 polished Reference electrode Ag AgCl KCI saturated Gold counter electrode O ring set of EQCM cell 1 1 mm 1 3 5 1 5 mm 1 8 1 5 mm 4 14 1 mm 1 O ring set for crystal fixture 8 1 5 mm 10 Hex screws M3 16 10 EQCM driving force adjustment tool Polypropylene cell cover Hex key 2 5 mm PVDF cell for EQCM Cable to connect the EQCM with oscillator interface L Metrohm Autolab EQCM User Manual Appendix 2 Chemical resistance of polypropylene to common chemicals The chemical stability tables for polypropylene are listed in this appendix The resistance to a given medium is provided by a grade between 1 and 5 see Table 1 Resistance rating Indication 1 Excellent no attack 2 Good no significant attack 3 Acceptable light attack limited use 4 Unacceptable significant attack 5 Inferior cracking or dissolving Table 1 Overview of the grades used to indicate the chemical resistance of polypropylene towards different media Polypropylene must not be exposed to media characterized by a rating of 4 or 5 Contact with media with a rating of 3 must be avoided if possible An alternative cell in PVDF is available on request contact info metrohm autolab com for more information The following tables are provided in this appendix e Table 2 lists the resistance ratings towards common acids e Table 3 lists the resistan
8. 998 S 000 5002 5004 S006 S008 5010 0012 0014 5016 5018 5020 AFrequency Hz EQCM 1 44 548 4455 44 5527 44 554 44 556 44 5538 44 56 44 562 44 564 Time sS Figure 34 An example showing multiple duplicates of the EQCM signals Since the interval time is significantly smaller than the rate with which the EQCM can provide a new valid data point the same data point can be displayed several consecutive times 32 Page L Metrohm Autolab EQCM User Manual 5 2 Dynamic measurement window The EQCM module uses a dynamic window of frequency of 1000 Hz Rather than measuring the variation of frequency in the whole measurable range of 80000 Hz the EQCM focuses on a sub range or window of 1000 Hz This ensures that the frequency is measured with the highest possible resolution In practice this means that no interruptions are observed as long as the variation of frequency is smaller than 1000 Hz during the course of the experiment However when changes in frequency larger than 1000 Hz are measured the software needs to readjust the measurement window downwards or upwards depending on the direction of the frequency change This software rewindowing is triggered when measured AFrequency reaches the upper limit of the window at 900 Hz or the lower limit of the window at 100 Hz This ensures a 10 overlap between two consecutive AFrequency windows The duration of the window adjustment is 100 ms During th
9. CM User Manual Note it is possible to test the water tightness of the cell by adding a few ml of water into the cell and checking for leakage 2 3 1 Installing or changing the crystal In order to install or change the quartz crystal follow these steps carefully 1 Remove the three fixing screws 10 on the top of the cell 2 Remove the top of the cell 3 Remove the old crystal do not pull on too hard on the holder as it can easily break The crystals can be used on both sides as they are totally identical both sides of the crystal have a WE surface mounted 4 Replace it with a new one 5 Verify that the O rings are positioned properly 6 Retrace steps 2 and 1 On average a crystal can be reused about 20 times supposing that no physical damage occurred The life expectancy of the crystals depends on the following e The quality of the quartz e The amount of the deposited material and the stress generated due to it e The acoustic losses in the deposited material e The type of the deposited material e Formation of non uniform films and flakes of the deposited material e Physical damage scratches on the metal layer cracks e Electrolysis of the deposited film material by using improper experimental parameters i e applied potential e Accidental contact of the crystal with the counter electrode CE or the reference electrode RE Note The O rings 5 on the reference and counter electrode must be u
10. EQC M User manual Please read this manual carefully before starting to use the Autolab EQCM module The next sections deal with appearance and use of the module and contain necessary information regarding operation and installation SAFETY PRACTICES General e The following safety practices are intended to ensure safe operation of the equipment and must be observed during all phases of operation service and repair of the instrument e Failure to follow these instructions may cause unsafe operation e Autolab Instruments is not liable for any damage caused by not complying with the safety requirements e Failure to follow these instructions may void any warranty provided to this module Electrical hazards e To avoid electric shock hazard always ground the instrument by using the provided power cable with earth connections e There are no _ user serviceable parts Module installation component replacement and internal adjustments must be done only by qualified personnel e Removal of the module card from the Autolab PGSTAT and or opening the external oscillator poses a risk of exposure to potentially dangerous voltages Always disconnect the potentiostat from all power sources before removing protective panels e Please also refer to the Electrical Hazards described separately for the Autolab instrument used General precautions e Use only stable surfaces for setting up the system e Do not expose the EQCM module and t
11. Electrode connections 18 Electrodes 43 EQCM accessories 6 EQCM cell 7 EQCM cell volume 10 EQCM connections 6 EQCM crystal care 31 EQCM description 5 EQCM installation 6 EQCM module 6 EQCM power 21 EQCM principles 34 EQCM signals 19 EQCM test 11 13 EQCM test results 15 EQCM tutorial 16 EQCM tutorial procedure 16 EQCM 1 Driving force 27 EQCM 1 Temperature 27 EQCM 1 AFrequency 26 Example data 30 Exchanging the crystal 9 External oscillator 13 18 28 Faraday cage 30 Frequency to mass conversion 38 General specifications 43 Hardware setup 10 Autolab EQCM User Manual Index Import procedure 12 16 Installing the crystal 9 Interruption in data 33 Lead deposition example 29 Leakage 18 LED indicator 28 List of spareparts 44 Maximum cell volume 18 Maximum sampling rate 32 Measurement restrictions 32 Measurement sequence 25 Measurement window 33 Measurements in liquids 37 Minimization of the driving force 14 24 Minimum interval time 32 Noise reduction 30 OPD 40 Oscillation sustainability 27 Oscillator 18 Overpotential deposition 40 Piezoelectric effect 34 Plotting AFrequency 23 Practical tips 30 Preview changes 21 PVDF 45 Quantification 35 38 Quick test of the EQCM 11 13 Recommendations for Viton 49 Reference electrode 30 Reference electrode lifetime 30 Reference electrode storage 30 Removing the crystal 9 Reset EQCM
12. F Hf Hf HP fs Table 4 Chemical resistance ratings of Polypropylene towards common organic solvents 48 Page 2 Metrohm Autolab EQCM User Manual Appendix 3 Recommendations regarding Viton All the seals and gaskets used in the EQCM are made of Viton This material will exhibit swelling when exposed to organic environments The swelling will increase the pressure on the crystal and could damage the crystal if it becomes too significant Care must be taken when using Viton in the following organic environments e Acid anhydrides e Acetone e Acetonitrile e Amines e Dioxane e DMF e DMSO e Ethylacetate e Freon 22 e Methanol e Pyridine e THF 49 Page Autolab EQCM User Manual 2 Metrohm Appendix 4 Troubleshooting guide Table 5 displays a list of troubleshooting hints that can be followed when problems are encountered using the EQCM If the hints provided in this table do not help in solving the problem please contact service metrohm autolab com Problem description Suggested solution Neither the red nor green LED Check if the PCB card is inserted does not light after the procedure properly it has to be fixed to the main is started Autolab frame with the provided screws Check all the connections Check if the Autolab EQCM is turned on in the Autolab control command Check if the crystal is not damaged and the pins make good contact with the metalized surface Green LED will not light even after Sol
13. Figure 10 The determine EQCM zero frequency window can be used to adjust the driving force Using the provided adjustment tool rotate the trimmer on the EQCM oscillator in order to minimize the driving force The trimmer range does is not limited it can be turned 360 in either direction It recommended to slowly rotate the trimmer one full turn and then adjust the driving force in order to match the lowest recorded value displayed in the Minimum value field in the Determine EQCM zero frequency window When the driving force has been properly minimized the LED on the EQCM oscillator must be green Click the button in the Determine EQCM zero frequency window to zero the value of the EQCM 1 AFrequency signal After minimizing the AFrequency signal click the OK button to proceed with the measurement The procedure records the three signals provided by the EQCM module during ten seconds The EQCM 1 AFrequency and EQCM 1 Temperature Signals are shown on plot 1 and the EQCM 1 Driving force signal is shown on plot 2 see Figure 11 14 Page NQ Metrohm Autolab EQCM User Manual 23 97 0 925 0 2 23 565 015 0 924 a O s 0 1 23 555 v 0 923 gt 5 0 05 23 55 3 al aa D 0 922 L 23 545 LL 0 D a lt nae 23 54 gt 0 921 l S 23 535 5 ane sake a W 0 92 0 15 23 525 0 919 02 23 52 0 5 10 15 20 5 10 15 20 Index Index Figure 11 The data recorded during the TestEQCM procedure Note sw
14. ace area 42 Page L Metrohm Autolab EQCM User Manual 7 General specifications Oscillator Oscillation frequency Frequency resolution Frequency accuracy Available frequency range Temperature sensor resolution Temperature sensor accuracy Operation environment Input Driving force adjustment Housing EQCM cell and electrodes Connections to crystal holder Cell material Cell volume Crystal diameter Electrode diameter Thickness of Au coating Thickness of the adhesion layer Reference electrode Counter electrode 6 MHz 0 07 Hz 1 Hz Moving window of 1000 Hz Absolute range 80 kHz from fo 5000 Hz to fo 75000 Hz 0 1 C 1 C 10 40 C WE S electrode connections External trimmer Autolab module 9 Pin Sub D connector 2 m long Polypropylene 3 ml maximum 1 36 cm 0 538 0 67 cm 0 267 1000 A 100A Ag AgCl 3 M KCI in gel Au wire 1e Please refer to Appendix 2 for more information on the chemical stability of Polypropylene 43 Page Autolab EQCM User Manual 2 Metrohm Appendix 1 Accessories and spare parts Code EQCM EQCM AU EQCM AU PCK25 EQCM PT EQCM REF EL EQCM CE EQCM O SET EQCM O CRSTL EQCM SCRWS EQCM AD3J EQCM CELL EQCM HEX25 EQCM CELL PVDF EQCM CABLE 44 Page Description EQCM module installed in Autolab Contains complete cell with temperature sensor external oscillator box 2 m long 9 Pin Sub D connector cable 6 MHz EQCM crystal Au TiO2
15. anual Commands Farameters Links Cyclic voltammetry with EQCM Remarks Example of ECM measurement using the dedicated EQCM module End status Autolab m Signal sampler Time EQICMO Temperature ECMO ArFrequency ECMO Driv c Lotions 1 Options a Instrument ALT O47 39 Instrument description E Timed procedure Autolab control Set potential 0 500 Set cell On aa Vait time 3 z Optimize current range s Reset EQCM AFrequency CY staircase 0 600 1 000 0 600 0 500 2 0 0200000 Set cell Cit lt gt lt gt Figure 25 The Reset EQCM AFrequency command is located just before the CV staircase command In the tutorial procedure the following sequence will occur when the procedure is executed 1 The EQCM module is switched ON alongside other settings defined in the Autolab contro command 2 A potential of 0 8 V will be applied on the working electrode with respect to the reference electrode 3 The cell will be switched ON The LED located on the external oscillator is lit green or red 4 The working electrode will be kept at 0 8 V for 5 seconds Wart time 5 The most suitable current range to continue with the measurement will be determined by the software Optimize current range 6 The Reset EQCM AFfrequency command will be executed triggering the display of the Determine EQCM zero frequency window see Figure 26 7 The cyclic voltammetry will start immediately after the user closes the
16. b control E E Set potential 0 800 Set cell On Wait timet E Optimize 5p 2 e T m E E j etm 200200000 OOO Set cell IvsE lt gt iat lt gt Logi vs E Logi vs Logit E vsi E vs Logf i AFrequency vs E gt Figure 24 Adding the AFrequency vs E plot to the CV staircase command Note the AFrequency vs E plot is already included in the tutorial procedure Note it is also possible to add additional plots to the CV staircase command by dragging and dropping plot commands located in the Plot general group of commands onto the CV staircase command It is also possible to add custom plots to the CV staircase command by picking the Custom plot from the quick access toolbar 10 Please refer to the NOVA User Manual for more information 23 Page Autolab EQCM User Manual L Metrohm 3 3 5 Adjusting the driving force and zeroing the EQCM AFrequency The final item that should be included in an EQCM procedure as illustrated in the Cyclic voltammetry with EQCM procedure is the setting the AFrequency value measured by the EQCM module to zero Hz Additionally whenever a measurement is performed using the EQCM it is necessary to set the EQCM driving force to the minimum value This must be done any time the environment to which the crystal is exposed is changed The driving force needs to be minimized in order to maximize the measurable range of the EQCM and optimize the quality of the signal This
17. ce ratings towards common bases e Table 4 lists the resistance ratings towards common organic solvents 45 Page Autolab EQCM User Manual Acids Chemical CseHsCOOH H3BO3 HBr 25 CeHgO7 citric acid HCN HF HPO 25 HPO 85 CsH6O phthalic acid H2CrO C4H40 maleic acid CisH340 gt 2 oleic acid C gt H20 oxalic acid HNO 5 HNO 65 HCl 10 HCl 37 H2SO 10 H2SO 4 78 H2SO 4 93 CH3COOH 10 CH3COOH 50 CH3COOH 75 CH3COOH 100 HClO 46 Page 2 Metrohm Resistance rating 20 C MN WN Ne BRN S N HS SH HSH SH HNN HSH N HS 60 C Table 2 Chemical resistance ratings of Polypropylene towards common acids L Metrohm Autolab EQCM User Manual Bases Chemical Resistance rating 20 C 60 C NH3 Ca OH 2 KOH NaOH K2CO3 KMnO NaCN Na Fe CN e 3 NaClO N _ _ e u u UJ N N N e mne n Table 3 Chemical resistance ratings of Polypropylene towards common bases 47 Page Autolab EQCM User Manual LL Metrohm Organic solvents Chemical Resistance rating 20 C 60 C Acetone Benzol Petrol Butyl alcohol Ethyl acetate Ethyl alcohol Ethyl dichloride Ethyl ether Phenol Formalin 37 Heptane Chlorobenzene Chloroform Carbon disulphide Carbon tetrachloride Methyl alcohol Methylene chloride Methylene dichloride Methyl ethyle ketone Nitrobenzene Toluene WwW w WwW Aa A aAA RARA UU NPWH NH HW W AAAA He PAPA HnrmNnN FS
18. cription E Timed procedure Autolab control z Set potential 0 500 Set cell On z Wart time 3 p Optimize current range p Reset EOCM AFrequency CY staircase U G00 1 000 0 600 O 600 2 0 0200000 set cell Ot m lt gt gt Figure 19 Click the button in the quick access toolbar to open the signal sampler 19 Page Autolab EQCM User Manual L Metrohm The Edit Sampler window will be displayed indicating a list of signals available for the connected instrument The three signals provided by the EQCM module can be found in this list see Figure 20 Note in the tutorial procedure all three signals are already selected on Edit Sampler aome Signal sample Optimized Sampler configuration WE 1 Current v Ei Sampler WE 1 Potential GetValues EQCM 1 Temperature i EQCM 1 Temperature EQCM 1 Driving force EQCM T Driving force 7 o b EQCM 1 AFrequency Ta EEH Segment Optimized l 1 Current j External 1 ADC164 1 3 1 External Time ADC b4 2 sample alternating Figure 20 The Edit Sampler window Note the electrochemical signals provided by the EQCM are not sampled through the ADC164 module These signals are directly provided by the EQCM module This means that these signals cannot be sampled in optimized mode Hardware note the highest possible sampling rate of the EQCM module is 50 samples s 20 ms interval time Clicking the OK button validates the selecte
19. d signals and displays the Preview changes window This window shows a list of measurement commands available in the procedure for which the modified sampler can be applied see Figure 21 8 If measurements with shorter interval times are performed the last values of the EQCM signals will be recorded multiple times until new samples are obtained for these signals 20 Page 2 Metrohm Autolab EQCM User Manual Preview changes Sampler Apply sampler settings to Fa Optimize current range iw CY staircase Select all Select none Invert selection es Figure 21 The preview changes window can be used to apply the modified sampler to one or more measurement commands in the procedure Note each measurement command has a local sampler that indicates what Signals need to be acquired when that command is running during the measurement It is therefore possible to adjust the signal samplers for each measurement command in order to customize the data acquisition Please refer to the User Manual of NOVA for more information on the local and global signal Samplers 3 3 3 Switching the EQCM on Once the sampler is defined the next step is to switch the EQCM module on The default power up settings of the module keeps the module powered off until activated by the user Switching the EQCM on or off can be done at any time during a procedure using the Autolab contro command The Autolab control command is a gen
20. e crystal Proper care needs to be taken to prevent damage to these clamps since no valid measurements will be possible in case of damage When the cell is assembled with the quartz crystal in its position fill up the cell with clean water or electrolyte and inspect for any leakage around the contact pins If leakage appears disassemble the cell and start again Do not over tighten the screws Note The maximum volume of the cell is 3 ml 3 Software setup If the cell has been assembled successfully with the crystal properly installed and connected to the external oscillator the next step is to set up the NOVA software The following step by step description will help to make the necessary settings in NOVA before measurements can be performed 3 1 Installation of the EQCM module Turn on the PGSTAT and NOVA and select the EQCM module in the Hardware setup in NOVA see Figure 5 The general details about the NOVA software can be found in the NOVA User Manual 10 Page NQ Metrohm Autolab EQCM User Manual Hardware setup File Tools Main Module Additional Module s Ed PGSTAT302N FRAI2M PGSTATS02F FRAZ PGSTAT302 A0cioM PGSTAT30 JADC 50 PGSTAT128N ADC 50r4 _ PGSTAT12 SCAN250 _ PRSTAT TOON F TECANGEN L PGSTAT100 H FIBA L PGSTATTON BIPOT ARRAY O a Ill JECD FI20 Filter F wAutolab I _ PGSTAT20 Fl20 Integrator PGSTATIO Booster204 Bo
21. ect Therefore for thin lossless deposited films it is possible to make quantitative correlation between the change in frequency Af and the total charge passed Q by combining the Sauerbrey equation with the Faraday law The total charge measured is directly proportional to the total number of electrons involved in the electrochemical process which is directly proportional to the total number of metal atoms mass deposited Therefore there is a linear relationship between Af and Q 7 _ 10 My C Q A n F A 9 where Af in the change in frequency Hz Mw is the apparent molar mass of the deposited metal g mole Cp is the Sauerbrey sensitivity factor for the used crystal Q is the integrated charge during the electrodeposition C n is the 38 Page L Metrohm Autolab EQCM User Manual number of electrons transferred during the deposition process A is the total deposition area of the working electrode cm F is the Faraday constant 9 648 104 C mole This calibration procedure can be used with simple electrodeposition processes e g Ag Pb Cu on Pt or Au EQCM crystals Next two examples of data analysis for Pb deposition on Au Ti crystals are presented 6 4 1 Pb underpotential deposition on Au Ti crystals When the potential was stepped from 0 8 V a value where no Pb is deposited on the Au surface to 0 4 V potential where Pb UPD occurs the average change in frequency was measured as being 26 25 Hz see Fig
22. ectrolyte before measurements using proper tubing and a third hole on the cover not drilled Figure 4 Schematic representation of the EQCM cell front view A section in the lateral view B connection socket to the oscillator C and quartz crystal mounted used in the measurements D A full list of items is provided below Main body of the EQCM cell Upper body of the EQCM cell removable EQCM cell cover with holes for reference and counter electrode EQCM quartz crystal mounted Viton O rings Reference electrode Ag AgCl 3 M KCI in gel Counter electrode Au spiral shaped Output pins from the temperature sensor Output pins from the mounted quartz crystal 10 Fixing screws set of three 11 Connection socket connecting to the EQCM oscillator 12 Cable to the EQCM oscillator 13 Temperature sensor ee et ee The quartz crystal 4 is fixed between two O rings 5 between the upper 2 and the main body of the cell 1 by using 3 screws only one shown in Figure 4 10 There is no need to over tighten the screws In this way a solid liquid tight assembly is obtained e The O rings are in Viton Because of the possible swelling of the O rings in organic solvents there is a risk of applying extra pressure which can damage the crystal when working in these solvents Please see Appendix 3 at the end of this document for the chemical compatibility of Viton 8 Page L Metrohm Autolab EQ
23. ene eee arr 30 4 1 Optimization of the signal to NOISE ratio ccc eecccccccccecccceeeeeeeeeneees 30 4 2 Warming up of the EQCM oscillator ccccccscsssseeceeeeeeeeeeeeeeeees 30 4 3 Caring for the reference electrode vaiases c ics coediatorna ouisacedinigiaastanidndsy 30 4 4 Prevent damage to the crystal surface and holding SpringsS 31 5 Measurement restrictions ccccceccccseececceeeceeceeecesceeecesseaceessuaseeseeseeseaees 32 t aM Tae eea A T AN 32 5 2 Dynamic measurement WINdOW cccccccceeeceeeeeeeccceeeeseseaeeaeeeeeees 33 6 Tneoreicaas peT ea A estat Ania tae hoe 34 6 1 The Sauerbrey CQUAUON igss tea caniearnwtatiseaelons ceandaulibaiecsnarmedesiiaionbeante 35 Clg IGG OA ON leases grates rasa E EE Mewta wa toseton Sastto iocenone 36 63 Measurements IM NAUS sci cecesricaesstortatincencauindencebnumsidamsniensabantantnnehs 37 6 4 Example of data analysis for metal electrodeposition on QCM crystals Be ea cee cee ae ee ac ai ac tae ac crenata cies oes ee aeteriasema untae scan teas 38 6 4 1 Pb underpotential deposition on Au TI crystals eee 39 6 4 2 Pb overpotential deposition on Au Ti crystals ccceeccceeeees 40 7 PGCE lal specca O erora 43 Appendix 1 Accessories and spare Darts cccccceecccceeeeeeseececeeeeeeeeeeeeeeanees 44 Appendix 2 Chemical resistance of polypropylene to common chemicals 45 Appendix 3 Recomme
24. eral purpose command that can be used to control all the instrumental settings of Autolab including the settings of the modules installed in the Autolab Note the Auto ab contro command can be found in the Measurement general group of commands To switch the EQCM on at the beginning of the procedure click the J button located next to the Auto ab control command in the procedure editor see Figure 22 2 More information on the Autolab control command can be found in the Autolab control tutorial available from the Help menu 21 Page Autolab EQCM User Manual 2 Metrohm MUTOIGD B V Commands Parameters Links Cyclic voltammetry with EQCM Remarks Example of ECM measurement using the dedicated EACM module a End status Autolab m Signal sampler Time EGC Temperature EQCM1 AFrequency EQCM1 Orii Options 1 Options al Instrument ALT34139 Instrument description E Timed procedure of Autolab control set potential 0 800 set cell On Wait time s a Optimize current range a Reset EOCM AFrequency CY staircase 0 600 1 000 0 600 0 600 2 O 0200000 set cell Ott al lt gt lt gt Figure 22 Click the button to open the Autolab control editor The Autolab control window will be displayed The on off switch of the EQCM module can be found on the EQCM 1 tab see Figure 23 Autolab control DIO DACH Active On Active Unchanged Active Off Active On Figure 23 The on off switch o
25. f the EQCM module can be found on the EQCM 1 tab Note once the EQCM module is switched on it will remain powered on until the Autolab control command is used again to switch off the module When the module is switched on the LED located on the front panel of the external oscillator will be lit green or red when connected to the EQCM module 22 Page N Metrohm Autolab EQCM User Manual Tip it is recommended to allow the EQCM to warm up for about 15 30 minutes before starting measurements The EQCM can be left switched ON even when the measurements requiring the EQCM signals are finished this will not interfere with experiments 3 3 4 Plotting the EQCM data Since the signals recorded during the procedure can also be plotted in real time additional plot can be added to the procedure To add a plot to a procedure the quick access toolbar can be used This toolbar will list the available common plots depending on the sampled signals Click the CV staircase command in the procedure editor and click the button in the quick access toolbar to add the AFrequency vs E plot to the measurement see Figure 24 Commands Parameters Links Cyclic voltammetry with EQCK Remarks Example of EQCM measurement using the dedicated EQCM module End status Autolab oignal sampler Time EQCM 1 Temperature EQCM Driving force EQCMO AFT Options 1 Options m Instrument ALT54139 Instrument description E Timed procedure Autola
26. he Autolab instrument to damp or wet conditions Table of Contents I DeESChiD TOMO rine EOC MOGUlGs senrose aii 5 PANACEA IS WOM cast dtcticeta E E S EE E N 6 2 1 Installation of the EQCM module ccccccceccacccecceccesceuccecceseuseuass 6 Ded NE EOCMEONS tals aaa A SN Gaal 7 2 3 The EOQCM re Pease tee ere ie Sear ee ee Orne OE Ree en Nee meee rr 7 2 3 1 Installing OF changing the CryStal sevecncwsesdnsacsiPacumqrderaawiniadeendon 9 2 3 2 Cleaning and handling the crystal ccccccccccceseeeeseeeeeeeeeeneees 9 DEF SOW ANG E E E E E T E E E 10 3 1 Installation of the EQCM module c cccceccacccceeccecceceeeceeceuseaeeees 10 3 2 Quick test of the EQCM Module ccccccecceccecccecceccecceecceseuseaeeues 11 3 3 Using the EQCM tutorial procedure eee cccccccceeeecccceeeeeeeeeeeeeeeeaees 16 3 3 1 Connections for electrochemical measurement 0 06 18 De did OMe San MIO C i mea edad ee cesenee 18 3 3 5 SWC The EOC M Oaea a a a 21 DGS Potting tne HEC Cl ViGlalidy 3 masa aa E R 23 3 3 5 Adjusting the driving force and zeroing the EQCM AFrequency AEE PEE EE A AE A EE E EEE I T dees T E E E E A A 24 3 3 92 AGIUSUNG the driving TOrCE irois 28 3 3 5 2 Adjusting the zero AFreQuency sssssinessssirieessrrrreeen 29 3 3 6 Example of Cyclic voltammetry with EQCM procedure 29 aE eo EEE jc ene eae E ie Pee a ee ere ee Dent ee Rone
27. he button will be grayed out After minimizing the driving force and zeroing the AFrequency signal if necessary click the OK button to proceed with the measurement The procedure records the EQCM signals during the cyclic voltammetry measurement 3 3 6 Example of Cyclic voltammetry with EQCM procedure Figure 31 shows an example of a cyclic voltammogram recorded using the Cyclic voltammetry with the EQCM tutorial procedure This example corresponds to the bulk deposition overpotential deposition of lead on a gold coated QCM crystal in a 0 01 M Pb II perchlorate solution HClO 0 1 M during a potential scan between 0 6 V and 1 V at a scan rate of 0 020 V s All frequency changes are measured with respect to the zero AFrequency which was set using the Reset EQCM AFrequency command while the working electrode at was kept at 0 8 V vs Ag AgCl KCI 3 M reference 0 0035 0 0 008 200 0 0025 40C L z 0 002 600 gt 00015 800 T 5 0 001 1 000 8 s 0 0005 1200 Z o 1400 1600 amp 0 0005 G 0 001 AN 0 0015 a 0 8 0 6 04 0 2 d 0 2 0 4 0 6 J E Potential applied W Figure 31 An example of cyclic voltammetry blue left axis recorded simultaneously with the EQCM signal red right axis using the Cyclic voltammetry with EQCM procedure 0 01M lead II perchlorate in 0 1 M perchloric acid 11 The file corresponding to this measurement is included in the Demo database Demo 02 Plea
28. hen dry the crystal surface and holding springs to prevent damage to the surface and extending the lifetime of the crystals When the crystals are not used it is best to keep them in the metallic enclosure they are shipped with Prevent accidental contact of the reference or the counter electrode with the surface of the crystal during the measurement or when handling the cables and connectors Remember that the crystals are double sided both sides can be used 31 Page Autolab EQCM User Manual 2 Metrohm 5 Measurement restrictions Two restrictions apply when working with the Autolab EQCM module e The sampling rate of the EQCM is 50 samples s e The measurable range is fixed to a mobile frequency window of 1000 Hz Both restrictions are illustrated in the following sections 5 1 Sampling rate The EQCM module is capable of providing one new set of values for the measured signals AFrequency Driving force Temperature with an interval time of 20 ms 50 samples s When the sampling rate specified in the procedure is smaller than 20 ms the EQCM module is not able to provide new data points quickly enough In practice this means that last available data point provided by the EQCM module will be measured several times until a new data point Is available Figure 34 shows a practical example of a measurement in which the interval time defined in the procedure was set to a value smaller than 20 ms the interval time is 1 ms 4
29. ir the typical driving force is close to O V In water the driving force should be 0 9 0 25 V e EQCM 1 AFrequency the AFrequency signal corresponds to the relative change in oscillation frequency of the quartz crystal This variation is expressed with respect to an arbitrary user defined reference frequency zero Hz These three signals can be selected using the Signal sampler in the procedure editor To edit the sampler click the button located next to the Signal sampler item in the procedure editor see Figure 18 Commands Parameters Links Cyclic voltammetry with EQCM Remarks Example of ECM measurement using the dedicated EOC module a End status Autolab al Signal sampler Time EQCM 1 Temperature EQCM 1 Driving torce EQCM 1 AFrequl Options 1 Options a Instrument ALT 347 34 Instrument description E Timed procedure Autolab control set potential 0 500 Set cell On xual Vat time s a Optimize current range p Reset EOCM AFrequency CY staircase 0 600 71 000 0 600 0 600 2 0 0200000 Set cell ff m lt gt lt gt Figure 18 Click the button to open the signal sampler editor Alternatively it is possible to click the button from the quick access toolbar see Figure 19 Commands Cyclic voltammetry with ECM Remarks End status Autolak ial Signal sampler Time EQICMO Temperature ECMO Driving force EQCMET AFT Lotions 1 Options a Instrument ALT84139 Instrument des
30. is adjustment the EQCM is not able to supply new data points and this can be seen in the measured data as shown in Figure 35 2860 2870 2880 PR 2890 2900 2910 1AFreguency Hz s290 FQCM 1 2930 2940 a 0 40 485 40 5 40 52 40 54 40 56 40 58 40 6 Time S Figure 35 When the EQCM needs to adjust the window the data feed is interrupted during 100 ms The windowing scheme is illustrated in Figure 36 schematically 33 Page Autolab EQCM User Manual LL Metrohm 80 kHz 5 kHz 6 MHz 1000 Hz window 100 Hz 100 Hz 100 Hz Rewindowing 800 Hz 100 Hz 100 Hz Figure 36 Windowing scheme used in the EQCM top complete measurement range and measurement window bottom rewindowing adjustement The top graphic of Figure 36 shows the whole measurable range of the EQCM relative to the nominal frequency of 6 MHz The module can measure positive variation up to 5000 Hz and negative variations down to 75000 Hz The actual measured range is 1000 Hz represented by the small slice located in the 80000 Hz The bottom part of Figure 36 shows the details of the windowing adjustment The measurable range is 1000 Hz Whenever the variation of frequency reaches the first or last 100 Hz segment of the window in absolute value the EQCM detects that a readjustment of the window is required The window is shifted upwards or downwards depending on the variation of frequency with an over
31. is an important adjustment that needs to be carried before zeroing the AFrequency Note it is not necessary to set the driving force to the absolute minimum value Any value close the minimum will be acceptable qualitative adjustment Both adjustments can be done at any time in a procedure using the Reset FQCM AFrequency command Note the Reset EQCM AFrequency command can be found in the Measurement general group of commands The usual strategy used in electrogravimetric experiments using the EQCM consists in zeroing the value of the AFrequency while the working electrode located on the surface of the crystal is kept in an electrochemical control condition For metal deposition or electropolymerization experiments for example this is typically done by keeping the working electrode at a potential with respect to the reference electrode at which no deposition occurs The AFrequency value can then be zeroed in this condition and when the potential is changed with respect to this control situation any change in AFrequency will be measured relative to this arbitrary zero Hz point Note it is possible to zero the AFrequency and adjust the driving force as many times as required by adding the Reset EQCM AFfrequency command to the procedure in the required locations In the tutorial procedure the Reset FQCM AFrequency command is located just before the CV staircase command see Figure 25 24 Page N Metrohm Autolab EQCM User M
32. itch the measurement view to 7wo plots vertically tiled mode by pressing the button in the toolbar At the end of the measurement a message is displayed providing qualitative validation criteria for the measured data see Figure 12 TestEOQCM The driving force should be 0 90 0 25 W The Af should be stable around 0 Hz amp Hz Figure 12 A message is displayed at the end of the measurement Switch to the Analysis view and load the data for evaluation The data set includes two groups of data points see Figure 13 TestEULM 5 E TesEQCM Measured dataj Af vs t Measured data F T vs tiMeasured data Driving force vs t Measured data ll TestEQCM Reference dataj oo Afve t Reference data Tvs t Reference data Driving force vs t Reference data Figure 13 The data obtained with the TestEQCM procedure 15 Page Autolab EQCM User Manual L Metrohm The first group contains the measured data points The other group contains data points from a reference measurement This data can be used for comparison with the data points obtained during the test The EQCM measurements depend on the temperature and the crystal used during the experiment Comparison with the provided reference data points should be performed qualitatively 3 3 Using the EQCM tutorial procedure The procedure tutorials are installed in the NOVA folder created in the Program Files folder From the File menu in Nova
33. lap of 100 Hz 6 Theoretical aspects The Electrochemical Quartz Crystal Microbalance EQCM is widely used to monitor simultaneously with the electrochemical signal the change in frequency which is directly related to the mass changes due to deposition or adsorption of a species to or dissolution of a species from the working electrode The principle of operation of the EQCM relies on the piezoelectric properties of the quartz which will oscillate at a given frequency when a sinusoidal external electric 34 Page L Metrohm Autolab EQCM User Manual field is applied to it The oscillation frequency of the crystal depends on a number of parameters such as size the thickness of the crystal temperature and the oscillating media The crystals used for the system described are the so called AT cut crystals with a small temperature coefficient with a base frequency of 6 MHz They are covered with different metals e g Au Pt on top of an adhesion layer e g Ti or Cr oxides The crystals will also act as working electrodes WE being in contact with the electrolyte solution broadening in this way the application areas of this technique 6 1 The Sauerbrey equation As mentioned above the change on the frequency of the oscillation Af is sensitive to the change in mass deposited on the crystal surface Am meaning that any variation in mass of the electrode or thickness of the deposited material will proportionally change the fre
34. le 3 TestCV 6 16 2011 1 51PM NOX File 245 KB E TestECD 6 16 2011 1 51PM NOX File 227 KB E TestECN 6 16 2011 1 51PM NOX File 284 KB 1 TestEQCM 6 16 2011 1 51PM NOX File 60 KB E TestFl20 Filter 6 16 2011 1 51PM NOX File 171 KB E Testfl20 Integrator 6 16 2011 1 52 PM NOX File 315 KB E TestFl20 Integrator P 6 16 2011 1 51 PM NOX File 406 KB E TestFRA 6 16 2011 1 51PM NOX File 119 KB E TestMuUx 6 16 2011 1 51PM NOX File 409 KB E Testpx 6 16 2011 1 51PM NOX File 191 KB ___ Libraries amp Computer a Network NOX Files NOVA 1 3 or late Figure 7 The TestEQCM procedure can be found in the NOVA SharedDataBases Module test folder Filename TesthQCM The TestEQCM procedure can be used to test the correct functionality of the filter circuit of the EQCM 12 Page NA Metroh Autolab EQCM User Manual Autolab s v Insert a 6 MHz EQCM crystal in the EQCM cell as explained in section 2 3 1 Fill the cell with ca 2 ml of water and check for leakage Do not install the lid Connect the cell to the EQCM oscillator and the oscillator to the Autolab PGSTAT using the provided cable Leave the cell connectors from the PGSTAT disconnected Press the start button to start the measurement Two messages will be displayed when the measurement starts see Figure 8 TestEQCM TestEOCM This procedure is designed to test the basic Yerity thatthe LED on the EQCM oscillator is ON Wait functionality of the ECM mod
35. mmer use only the provided tool for the adjustment Once the tool is properly inserted in the oscillator rotate the trimmer slowly while monitoring the driving force shown graphically and numerically in the Determine EQCM zero frequency window At the same time the LED located on the front panel of the oscillator will indicate the oscillation status e Green stable oscillation is detected and the measurements can be performed e Red unstable or unsustainable oscillation is detected Measurements are not possible and the EQCM signals are invalid The trimmer range is not limited it can be turned 360 in either direction see Figure 30 Trimmer O Red No oscillation Green Oscillation il RON EQCM OSCILLATOR Figure 30 The EQCM trimmer can be rotated in any direction 360 It recommended to slowly rotate the trimmer one full turn and then adjust the driving force in order to match the lowest recorded value displayed in the Minimum value field in the Determine EQCM zero frequency window 28 Page L Metrohm Autolab EQCM User Manual Note it is possible to press the button to clear the graphical display of the driving force 3 3 5 2 Adjusting the zero AFrequency When the driving force has been properly minimized the LED on the EQCM oscillator must be green Click the button in the Determine EQCM zero frequency window to zero the value of the EQCM 1 AFrequency signal While the AFrequency is zeroed t
36. ndations regarding VION ccccccccceeeesssseeeeeeeeeeeenes 49 Appendix 4 Troubleshooting guide tien ceiiacicaiertien isn akeesiei i ahiewes 50 L Metrohm Autolab EQCM User Manual Autolab s v 1 Description of the EQCM module This manual gives a detailed description of the Autolab EQCM kit instructions for the installation of the module and EQCM cell and also for the necessary software setup NOVA 1 4 or higher The EQCM consists of a module that fits inside the Autolab and its accessories as shown in Figure 1 0888688898 s E Figure 1 The EQCM module complete with oscillator cell electrodes and accessories Shown in Figure 2 is a picture of all items which are included in the Autolab EQCM kit 5 Page Autolab EQCM User Manual 2 Metrohm A Ol AUTOLAB B z i lmm gt F aapna l ems buens area i f x R j NS LL A d VR 7 y A 3 H N Figure 2 Overview of the Autolab EQCM kit A Module B Accessories As shown in Figure 2 the Autolab EQCM kit contains the following 1 W N Po oS S 9 EQCM module to be installed in the Autolab PGSTAT or alongside the M101 module in a Multi Autolab Cabinet Figure 2 A 1 EQCM oscillator Figure 2 B 2 A 9 Pin Sub D connector cable 2 m long to connect the EQCM module and the oscillator Figure 2 B 3 EQCM cell detachable Figure 2 B 4 A gold counter electr
37. ode Figure 2 B 5 A Ag AgCl in 3 M KCI gel reference electrode with O ring Figure 2 B 6 Two Au TiO2 polished EQCM crystals Figure 2 B 7 Tool kit for the driving force adjustment and assembly disassembly of the cell Figure 2 B 8 One set of spare O rings not shown in Figure 2 2 Hardware installation The EQCM module can be installed in any of the following Autolab PGSTAT which has a USB interface PGSTAT 12 30 302 302N 128N The EQCM module can also be installed in a Multi Autolab Cabinet alongside a M101 module In this manual we will refer to all compatible instruments generically as PGSTAT 2 1 Installation of the EQCM module Presented below is a step by step description for the installation of the EQCM module 1 Please refer to Section 2 3 of this document for more information on the electrochemical cell 2 Please refer to Section 4 3 of this document for more information on the reference electrode and the care information of this electrode gt Please refer to Section 2 2 of this document for more information on the EQCM crystals 6 Page 2 Metrohm Autolab EQCM User Manual Autolab e v 1 Connect the oscillator to the EQCM module already installed in the instrument with the provided 9 Pin Sub D connector cable 2 Prepare the EQCM cell see Section 2 3 for more information 3 Connect the cell cables of the PGSTAT WE and S to the oscillator CE and RE to the counter and reference elect
38. opmost section of the Determine EQCM zero frequency window displays the measured values in real time e EQCM 1 AFrequency Latest value Averages these fields show the latest and averaged AFrequency values measured by the EQCM respectively The average is obtained from a moving average over the last ten values 26 Page 2 Metrohm Autolab EQCM User Manual EQCM 1 Driving force Latest Averages Minimum these fields show the latest the averaged and the minimum value of the driving force respectively The driving force is a measure of the sustainability of the oscillation The average value is obtained from a moving average over the last ten values The measurable range of driving force is between 0 V and 2 5 V The minimum field shows the absolute minimum value recorded EQCM 1 Temperature Latest Averages these fields show the latest and averaged temperature values measured by the EQCM respectively The average is obtained from a moving average over the last ten values Time to average this field indicates the number of values used in the moving average determination hardcoded to 10 The middle section shown in Figure 28 displays the recorded values of the driving force plotted versus time Driving force ty Time 3 Figure 28 The middle section of the Determine EQCM zero frequency window displays the measured driving force plotted versus time The bottom section shown in Figure 29 displays a series of
39. oster 0A E External IME303 IME663 MIK Fower Supply Frequency 50 Hz x Import FRA Calibration Say o OK Auto Cancel C Program Data Metrohm Autolab 10 0 HarcdwareSetup xml Figure 5 Selecting the EQCM module in NOVA 3 2 Quick test of the EQCM module Nova provides a ready to use test procedure that can be used at anytime to verify that the EQCM is working properly This procedure is installed in the NOVA folder created in the Program Files folder during installation of the software From the File menu in Nova select the Import procedure option and navigate to the EQCM tutorial folder see Figure 6 11 Page Autolab EQCM User Manual LL Metrohm Autolab s v View Profile Run Tools Help New Procedure Ctl h Save Procedure Ctl S Save Procedure as New New Mult Autolab Configuration Open Mult Autolab Configuration Save Mult Autolab Configuration Page Setup Print Preview Print Procedure Import Procedure Export Procedure Exit Alt F4 Figure 6 Use the Import procedure option from the File menu to load the EQCM test procedure The TestEQCM procedure can be found in NOVA SharedDataBases Module test folder see Figure 7 oC ec Fc tea naart gO Organize New folder 5j ki Nova L8 Shared Databases Module test v 4 ats k Favorites Name Date modified Type TestCV PGSTAT302F 6 16 2011 1 51PM NOX Fi
40. quency at which the crystal oscillates The relationship between Af and Am is given by the Sauerbrey equation 1 Af C Am 1 2n f C 2 f P M 2 Where Af is the change in frequency Hz Cr is the sensitivity factor of the crystal 0 0815 Hz ng cm for a 6 MHz at 20 C and Am is the change in mass per unit area g cm Gr is provided by equation 2 shown above in which n is the number of harmonic at which the crystal is driven this factor is set to 1 by design f is the resonant frequency of the fundamental mode of the loaded crystal HZ p is the density of quartz 2 648 g cm and yu is the shear modulus of quartz 2 947 10 g cm s From the equations 1 and 2 the change in mass can be calculated as following ama Af _ a f yPa Ha 3 C 2n f 12 The term AT describes the specific angle at which the quartz is cut 13 G Sauerbrey Z Phys 155 1959 206 35 Page Autolab EQCM User Manual 2 Metrohm Equations in NOVA It is possible to use the data handling commands in Nova to automatically calculate the values of interest by using the calculate signal tool and inserting the equations either directly in the procedure or in the data analysis window For more details please see the NOVA User Manual It is very important to keep in mind that the Sauerbrey equation is strictly applicable to uniform thin films in vacuum as it assumes that the acousto elastic properties of the
41. revent accidental damage If there is no leakage in the EQCM cell connect the cell to the oscillator using the connection socket 11 Insert the reference electrode and connect it to the PGSTAT Also connect the counter electrode to the CE plug of the PGSTAT using a crocodile clamp Connect the WE and the S from the PGSTAT to their respective connectors on the EQCM oscillator see Figure 17 Trimmer O Red No oscillation Green Oscillation WRQVQN EQCM OSCILLATOR Figure 17 The EQCM oscillator showing the WE and S connections on the side Note WE and S have different connections on the oscillator box 3 3 2 Signal sampler Whenever a measurement involving the EQCM module is performed the Signal Sampler of the procedure must be modified in order to indicate which signals provided by the EQCM module have to sampled alongside the usual electrochemical signals The EQCM module provides three different signals in the Signal sampler e EQCM 1 Temperature the temperature signal is measured by the sensor located at the bottom of the EQCM cell This signal is provided in C e EQCM 1 Driving force the driving force signal corresponds to a voltage value between 0 V and 2 5 V This value represents the amount of energy required to sustain the oscillation of the crystal When the loading of the 18 Page 2 Metrohm Autolab EQCM User Manual Autolab s v crystal increases the driving force also increases In a
42. rode respectively 2 2 The EQCM crystals Figure 3 shows a picture of the EQCM crystal Figure 3 Schematic view of the quartz crystals The crystals are spring mounted and packed in a metallic casing The two pins extending from the holder are used to provide contacts to the metallic layers located on both sides of the crystal The crystals have a nominal frequency of 6 MHz Typically the metal layers have a thickness of 100 nA and an adhesion layer is used to attach the layer to the surface of the crystal The adhesion layer has a typical thickness of 10 nA 2 3 The EQCM cell A schematic representation of the EQCM cell is shown in Figure 4 The main 1 and the upper body 2 of the cell and the cover 3 are made of polypropylene PP a chemical resistant material which is suitable for most of the electrochemical applications The detachable cover which contains two holes is designed to fix the Ag AgCl reference electrode 6 and the Au counter electrode 4 EQCM cells made of Kel F PCTFE can be obtained on request Item code EQCM CELL PVDF gt A chemical compatibility table for polypropylene is provided in Appendix 2 at the end of this document Please check this table carefully before exposing the cell to a solvent for the first time 7 Page Autolab EQCM User Manual LL Metrohm 7 during the measurement Whenever needed deaeration of the electrolyte is also possible by purging an inert gas through the el
43. se refer to the NOVA User Manual for more information 29 Page Autolab EQCM User Manual 2 Metrohm As the potential is scanned in the negative direction the bulk deposition of lead onto gold is triggered at around 0 43 V This is followed by a sharp increase of cathodic current at around 0 5 V which is detected by a sharp decrease in EQCM AFrequency The frequency continues to decrease after the lower vertex potential is reached until the current passes through O and become positive again This triggers an increase of the frequency and the AFrequency value finally returns to roughly O Hz at the positive end of the scan as the lead adlayer is removed from the surface 4 Practical tips The following section provides additional tips to consider when using the EQCM 4 1 Optimization of the signal to noise ratio For the best signal to noise ratio during the measurement the EQCM cell should be placed in a grounded Faraday cage The EQCM oscillator and cell will fit in the standard Autolab Faraday cage 4 2 Warming up of the EQCM oscillator It is recommended to allow the EQCM oscillator to warm up before starting electrochemical measurement Running a simple procedure like the one shown in Figure 32 can be used to switch on the oscillator and warm it up Commands Parameters Links Cyclic voltammetry with EQUI Remarks Example of EQCM measurement using the dedicated EQCM module s End status Autolab ma signal sampler Time EQCM 1
44. sed to prevent the electrodes from sliding down into the cell and eventually touching the crystal 2 3 2 Cleaning and handling the crystal To reduce the measurement errors as much as possible it is very important to keep the crystals very clean and free of any extraneous materials The following guidelines can be used to extend the lifetime of the crystals e Do not touch the crystal with bare hands use gloves and tweezers e Always store the crystals in their original package e Never touch the metallic layer of the crystal e Use always pure deionized water or pure solvents for cleaning 9 Page Autolab EQCM User Manual 2 Metrohm e Check the compatibility of the metal deposited on the crystal with the cleaning agent so that they will not react with each other e Do not wipe the crystal always use a jet of clean gas to dry the crystal e If possible use electrochemical cleaning to remove the deposited material e After the measurement remove the crystal rinse with clean water dry it and store it in the original casing not mounted in the cell Note it is recommended to always dry the crystal using a clean and dry air N2 Ar jet rather than leaving it to dry in air Warning the EQCM crystals are spring mounted The metal clamps holding the crystal are very fragile and can be easily damaged when in contact with a corrosive environment These clamps also serve as electrical contacts to the metal layers coated on th
45. select the Import procedure option and navigate to the EQCM tutorial folder see Figure 14 File View Profile Run Tools Help _ New Procedure Col N Wi Save Procedure Ctl 5 Save Procedure as New New Mult Autolab Configuration Open Mult Autolab Configuration Save Mult Autolab Configuration Page Setup Print Preview st Print Procedure Ctrl F Ey Import Procedure X d Export Procedure Exit Alt F4 Figure 14 Use the Import procedure option from the File menu to load the EQCM tutorial procedures The EQCM tutorial procedures are in the NOVA SharedDataBases Tutorials EQCM tutorial folder see Figure 15 16 Page NQ Metrohm Autolab EQCM User Manual praan ave Import procedure x rae a A G vih Nova 1 8 gt Shared DataBases gt Tutorials EQCM tutorial Search EQCM tutorial p Organize 7 New folder z i Favorites Name Date modified Type Size Chrono amperometry with EQCM 6 16 2011 1 51 PM NOX File 69 KB Libraries Cyclic voltammetry with EQCM 6 16 2011 L 51PM NOX File 133 KB amp Computer Network File name Cyclic voltammetry with EQCM v INOX Files NOVA 1 3 or late 4 s Figure 15 The EQCM tutorial procedures can be found in the NOVA SharedDataBases Tutorials EQCM tutorial folder Select the Cyclic voltammetry with EQCM procedure and click the button to import this procedure in the procedure editor The procedure editor will be
46. significant deviations from both theories described above Furthermore the thickness of the deposited layer can be also calculated using equation 7 N f f TK e an R tan z 1 Ji 7 P TR t f where TK is the thickness of the film cm Am is the change in mass per unit area g cm calculated from Z match equation pris the density of the material g cm N is the frequency constant of the AT cut quartz crystal 1 668 10 Hz cm p is the density of quartz 2 648 g cm f is the resonant frequency of the unloaded crystal Hz f is the resonant frequency of the loaded crystal Hz Rz is the Z factor of the film material acoustic impedance ratio uq is the shear modulus of quartz 2 947 10 g cm s us is the shear modulus of the film material g cm s 6 3 Measurements in liquids The decrease in frequency due to the change of the viscosity and density of the liquid which comes in contact with the crystal is described by Kanazawa s equation 8 3 A 7 n PL 8 T Ha Pa where f is the resonant frequency of the unloaded crystal Hz pq is the density of quartz 2 648 10 kg m uq is the shear modulus of quartz 2 947 10 Pa p Is the density of liquid in contact with the electrode kg m n is the viscosity of the liquid in contact with the electrode N s m In Figure 37 is presented the measured experimental change in frequency Hz resulting from the exposure of the
47. t using the following formula doc op _ doc 10 dQ dn ao where F is the Faraday constant 96485 C mol and z is the electrovalence of the electroactive species Pb 40 Page 2 Metrohm Autolab EQCM User Manual avs delta F Fb deposition at 0 45 Feit AF requency Hz 0 008 0 007 0 006 0 005 0 004 0 003 0 002 0 001 a Charge C Figure 39 Change in frequency vs charge red and the linear regression through the experimental data points black for Pb bulk deposition From Figure 39 the slope of the linear regression of Af vs Q is dAf SM 263530Hz C Applying equation 10 dAfocm a dAfocm dQ dn 50 6 10 Hz mol Knowing the crystal coefficient C 0 0815 Hz ng cm for a 6 MHz crystal it is possible to calculate the equivalent coefficient of the crystal for a known area A 0 361 cm making it possible to calculate the coefficient K g Hz 2 a ee C 0 0815Hz ng cm With these two values it is possible to calculate the experimental molar mass of the electroactive species dAf M n K 224 1g mol 41 Page Autolab EQCM User Manual 2 Metrohm When comparing the experimental value of the molar mass Mpp 224 1 g mol with the theoretical one Mr 207 2 g mol a very good agreement is obtained Note The main disadvantage of this quantitative method is that the exact surface area must be known the real surface area is not always equal to the geometric Surf
48. ule Connect the EOCM approx 15 minutes forthe EACH to warm up Click OF oscillator to the Autolab Inset a b MHz crystal into the _ to continue 4 new window willbe displayed Using EQICM cell Fill with approx 2 ml of water Connect the the provided timmer adjustthe driving force ofthe cell to the EQCM oscillator ater checking tor leakage EQCM as described in the user manual hen the Leave the cell cables from the Autolab disconnected driving farce is minimized press the Zero Afbuttonto Fress OF to continue zero the frequency Figure 8 Two messages are displayed at the beginning of the measurement When the second message appears verify that the LED on the EQCM oscillator box is ON red or green The LED is located on the front panel of the oscillator next to the trimmer hole see Figure 9 Trimmer O Red No oscillation Green Oscillation EQCM OSCILLATOR Figure 9 The EQCM status LED is located next to the Trimmer Note wait 15 minutes for the EQCM to warm up Click OK to continue The Determine EQCM zero frequency window will appear see Figure 10 13 Page Autolab EQCM User Manual 2 Metrohm Determine EQCM zero frequency Latest value AVErAQes Minimum EQICM 1 AFrequency 0 3890 Hz 0 346 Hz EQCMI 1 Driving force 0gig Maza EGCM 1 Temperature Eel la E olla E Time to average 10 a _ D oO Time is Zero ef Clear plot __Zeroaf N Clear piot _
49. ure 38 Using Sauerbrey s equation 1 the change in frequency can be correlated to the change in mass Af C Am If C 0 0815 Hz ng cm the sensitivity factor of a 6 MHz crystal the mass of the Pb monolayer can be calculated using the measured value of Af ap e 322 085Nng cm 0 0815HZz ng cm 140 35 623 0 14 EACT ASFreguency Hz ha m 25 45 61124 26 13 30 40 50 50 70 so o0 Time s Figure 38 The change in frequency due to the Pb UPD when the potential was stepped from 0 8 V to 0 4 V 39 Page Autolab EQCM User Manual L Metrohm The theoretical value for a Pb monolayer on Au 111 using Qr 302 uC cm and a 2 electron transfer process n 2 is Am 2 Mp 324 54ng cm Comparing the theoretical value Am with the experimental one Am a very good agreement can be seen 6 4 2 Pb overpotential deposition on Au Ti crystals In Figure 39 the linearity of the change in frequency Af vs charge Q is shown for the Pb bulk deposition when a potential step was applied between 0 8 V and 45 V Beside the clear indication of the linear dependence of the two parameters see Figure 39 linear regression black line experimental data points red line there is the possibility to calculate the molar mass of Pb Mey from the slope of this plot and compare it with the theoretical value Mr 207 2 g mol The slope in Hz C can be reconverted into Hz mol equivalen
50. ution too viscous Use a less viscous adjusting the trimmer electrolyte Crystal damaged Change the crystal Noise and oscillations mostly in Make sure that the RE is not touching the electrochemical signal the WE the crystal Measurement is unstable Adjust the driving force Make sure that the LED on top of the oscillator in green To avoid damaging the trimmer use only the provided tool for the adjustment The cell is leaking Disassemble and reassemble the cell Check and if needed change the O rings Table 5 Troubleshooting guide 50 Page 2 Metrohm Abort measurement 27 Acoustic impedance 36 Acoustic sensor 34 Add plot 23 Adhesion layer 35 Adjusting the driving force 28 Adjustment of driving force 14 Article codes 44 AT cut crystal 35 Autolab control 22 Bulk deposition 30 40 Caring for the reference electrode 30 Cell and accessories 43 Cell volume 18 Chemical stability of polypropylene 45 Cleaning the crystal 9 Clear plot 14 27 Connections for electrochemical measurements 18 Connections to the external oscillator 18 Crystal damage 31 Crystal installation 9 Crystal lifetime 9 Determine EQCM zero frequency 24 Determine EQCM zero frequency window 14 Driving force 14 24 28 Driving force minimization 28 Duplicated data 32 Edit sampler window 20 Edit signal sampler 20 Electrochemical cell 7 Electrochemical measurements 18 Electrochemical signals 18
51. zero frequency window 26 Reset AFrequency command 24 Resetting the frequency 29 Resetting the AFrequency 24 Results of the quick test of the EQCM 15 Rewindowing artefacts 33 Safety pratices 3 Sauerbrey equation 35 Sensitivity factor 35 Signal sampler 18 Signal to noise optimization 30 Software installation 10 Stable oscillation 27 28 Switching the EQCM off 23 Switching the EQCM on 21 Temperature measurement 27 Temperature sensor 27 Theory 34 Thickness 37 Thickness monitor 35 Trimmer 28 Troubleshooting guide 50 Typical measurement 25 Underpotential deposition 39 UPD 39 Variation of thickness 35 Viscoelastic films 37 Viton 49 51 Page Autolab EQCM User Manual 2 Metrohm Warm up 30 Zero Af 14 Warming up 13 Zero AFrequency 29 Warming up the oscillator 30 Zeroing the frequency 14 29 Water tightness 10 Z Match equation 36 Zero frequency 24 52 Page 7 2011 Kanaalweg 29 G 3526 KM Utrecht The Netherlands 2 Metrohm Autolab s v

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