Title of Invention

" AN ELECTRO CHEMICAL MICROBALANCE DEVICE USEFUL FOR IN SITU STUDY OF ADSORPTION AND DESORPTION PROCESS IN ELECTRO CHEMICAL INTERFACES"

Abstract An electro chemical microbalance device useful for in situ study of adsorption and desorption processes in electro chemical interfaces which comprises, a conventional personal computer (1), having of a monitor (9), plotter (10), a parallel bus connector (7) and an input/output (I/O) interface (8), characterized in that the said I/O interface being connected to a sweep generator (2), the output of the said sweep generator being connected through a potentiostat (2A) to a three electrode cell (3), the said cell (3) consisting of a gold coated quartz crystal as working electrode, a reference electrode and a counter electrode, the said quartz crystal working electrode being driven by an oscillator circuit (4), the output of the said oscillator being connected to a programmable frequency counter (5) & the said multimeter (6) being connected to the said personal computer through the said parallel bus connector (7).
Full Text This invention relates to an electro chemical microbalance device useful for in situ study of adsorption and desorption processes in electro chemical interfaces. This invention particularly relates to a device useful as an electro chemical microbalance for in situ study of adsorption and desorption process in electro chemical interfaces for sensitive in-situ monitoring of changes in morphology of electrode during electro chemical reactions and for in situ detection and quantification of electroactive species to an accuracy of the order not available through other electroanalytical methods.
The study of adsorption and desorption processes at electro chemical interfaces with detection and quantification of species at electrode surfaces was carried out earlier using electroanalytical techniques such as cyclic voltammetry. These methods were limited to study of surface layers weighing a few milligrams.
The schematic diagram of the device employed for cyclic voltammetric study is shown in fig.1 of the drawing accompanying this specification. In cyclic voltammetric method employed the device shown in fig.1, a time varying potential (eg. Triangle wave) is applied to experimental system through two electrodes (WE-Working Electrode and CE-Counter Electrode). The Reference Electrode (RE) generates a standard Reference Potential to enable comparison between experiments. This current flow between the CE and the WE as results of the reactions can be monitored as function of the portential and displayed. Since the potential is at a known rate the current variation with time is also known.
In cyclic voltammetry method the mass of e1ectroactive species deposited on the working electrode is related to the current due to the diffusion of the species towards the electrode. Here the variation of current as a result of applied time varying potential is measured. The measurement of the current and the integration of thesame with respect to time gives the charge due to the species and from this the mass or quantity deposited at the electrode can be determined. Under the usual experimental conditions (mV/sec to several V/sec) accuracies in the measurement of current limit mass determination accuracies to milligrams. This method has the drawback that the quantitative detection is limited to monolayer level weighing a few milligrams.
The main object of the present invention is to provide a device useful as an electro chemical microbalance for in situ study of adsorption and desorption process in electro chemical interfaces for sensitive in situ monitoring of changes in morphology of electrode during electro chemical reactions and for in situ detection and quantification of e1ectroactive species in nanogram level.
The main principle by which the device of the present invention has been developed by replacing the conventional working electrodes by a gold coated quartz wafer oscillating at its fundamental frequency and correlating the frequency changes to the deposited mass which will extend the in-situ detection accuracy to nanogram level.

The block diagram of the device of the present invention which operates on an AC power supply is shown in fig.2 of the drawings accompanying this specification.
Accordingly, the present invention provides an electro chemical microbalance device useful for in situ study of adsorption and desorption processes in electro chemical interfaces which comprises, a conventional personal computer (1), having of a monitor (9), plotter (10), a parallel bus connector (7) and an input/output (I/O) interface (8), characterized in that the said I/O interface being connected to a sweep generator (2), the output of the said sweep generator being connected through a potentiostat (2A) to a three electrode cell (3), the said cell (3) consisting of a gold coated quartz crystal as working electrode, a reference electrode and a counter electrode, the said quartz crystal working electrode being driven by an oscillator circuit (4), the output of the said oscillator being connected to a programmable frequency counter (5) & the said multimeter (6) being connected to the said personal computer through the said parallel bus connector (7).
The device of the present invention is built around a personal computer,
comprises of a quartz crystal controlled oscillator, a frequency counter, a
programmable multimeter, a potentiostat with sweep generator, a three electrode
cell with At-cut quartz crystal plated with gold on both sides as working electrode
and date acquisition and control hardware. The system is linked
to the personal computer through preferably a IEEE488
standard parallel bus and through the add-on I/O bus in the PC. An user friendly software written in BASIC takes care of the data
acquisition and control and provides on-line graphical presentation of the results.
The Quartz crystal vibrators are coated with gold electrodes on both sides and silver wire soldered on the edge for contact. Crystal holder made of teflon was designed to mount the crystal with one side of the gold electrode facing the solution. Electroless copper deposition from an EDTA, formaldehyde solution was carried out to illustrate the application of the device.
Solutions were prepared from CuSO4, disodium ethylenediaminetet-
raacetic acid (Na2EDTA), NAOH, formaldehyde, and Na SO , with
deionized water. The potential of the working electrode connected to the potentiostat was stepped up from -0.9 to -0.5V in 10mV increments. The frequency change was recorded through the frequency counter and stored in the computer memory. The current was also recorded through the programmable multimeter and transferred to the computer memory. By studying the variation of frequency and current with respect to the potential sweep, the partial currents corresponding to the oxidative and reductive half-reactions for electroless copper deposition can be determined. The variation in frequency of the quartz vibrator can be monitored by the appropriate software. Various sweep rates and the type of the signal to be applied like normal sweep, staircase, etc., can also be selected using the appropriate software.
In the method employing the device of the present invention changes in surface layers are related to frequency changes of quartz crystal oscillating at several MHz. This leads
to higher accuracy in mass determination by extending mass detection range down to a level of several tens of nanograms. The imposition of various experimental conditions for carrying out the required reactions and detection of the resulting frequency change is through a personal computer. The. following are the main advantages of the invention :
1. Precise quantitative and qualitative monitoring of monolayer
formation, polymerization and the e1ectrodeposition process
is possible using this device.
2. In-situ on-line monitoring of the above processes is possi
ble using the device.
3. Using this device the detection limit of an added mass of an
e1ectroactive species over an electrode surface can be
extended to the level of nanogram.





We claim :
1. An electro chemical microbalance device useful for in situ study of
adsorption and desorption processes in electro chemical interfaces which
comprises, a conventional personal computer (1), having of a monitor (9),
plotter (10), a parallel bus connector (7) and an input/output (I/O)
interface (8), characterized in that the said I/O interface being connected
to a sweep generator (2), the output of the said sweep generator being
connected through a potentiostat (2A) to a three electrode cell (3), the
said cell (3) consisting of a gold coated quartz crystal as working
electrode, a reference electrode and a counter electrode, the said quartz
crystal working electrode being driven by an oscillator circuit (4), the
output of the said oscillator being connected to a programmable
frequency counter (5) & the said multimeter (6) being connected to the
said personal computer through the said parallel bus connector (7).
2. An electro chemical microbalance device useful for in situ study of
adsorption and desorption processes in electro chemical interfaces substantially as herein described with reference to the examples.

Documents:

598-del-1995-abstract.pdf

598-del-1995-claims.pdf

598-del-1995-complete specification (granted).pdf

598-del-1995-correspondence-others.pdf

598-del-1995-correspondence-po.pdf

598-del-1995-description (complete).pdf

598-del-1995-description (provisional).pdf

598-del-1995-drawings.pdf

598-del-1995-form-1.pdf

598-del-1995-form-2.pdf

598-del-1995-form-4.pdf

598-del-1995-form-5.pdf

598-del-1995-form-6.pdf

598-del-1995-form-9.pdf

abstract.jpg


Patent Number 189680
Indian Patent Application Number 598/DEL/1995
PG Journal Number 14/2003
Publication Date 05-Apr-2003
Grant Date 27-Jan-2004
Date of Filing 31-Mar-1995
Name of Patentee COUNCIL OF SCIENTIFIC AND INDUSTRIAL RESEARCH
Applicant Address RAFI MARG,NEW DELHI-110001,INDIA.
Inventors:
# Inventor's Name Inventor's Address
1 RAMNATH RAVI CENTRAL ELECTRO CHEMICAL RESEARCH INSTITUTE KARAIKUDI,TAMIL NADU, INDIA.
2 GANESAN RADHAKRISHNAN CENTRAL ELECTRO CHEMICAL RESEARCH INSTITUTE KARAIKUDI,TAMIL NADU, INDIA.
3 ERODE SUBRAMANIA RAJAGOPAL CENTRAL ELECTRO CHEMICAL RESEARCH INSTITUTE KARAIKUDI,TAMIL NADU, INDIA.
PCT International Classification Number B01J 1/22
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 NA