Title of Invention	"A NOVEL METHOD FOR THE ELECTROCATALYTIC SENSING OF CHEMICAL AGENTS SULPHUR MUSTARD"
Abstract	The present invention relates to a novel method for the electrocatalytic sensing of chemical agents sulphur mustard. The method for producing said surface modified electrode comprises of coating the substrate with mercaptosilane and using the coated electrode in an electrochemical cell; the electrode is capable of in-situ generating a nanoparticle size redox catalyst and provides a detection system for sensing of chemical agents. The present invention also relates to a surface modified electrode capable of oxidizing the chemical agents. The electrode comprises of a (i) a substrate; (ii) a mercaptosilane coating on the surface of the substrate; and (iii) in-situ electro generated metallic nano particle sized redox catalyst on the surface of the coated substrate. The electrode is reusable for the sensing of sulphur mustard by avoiding decontamination process.

Title of Invention

"A NOVEL METHOD FOR THE ELECTROCATALYTIC SENSING OF CHEMICAL AGENTS SULPHUR MUSTARD"

Abstract

The present invention relates to a novel method for the electrocatalytic sensing of chemical agents sulphur mustard. The method for producing said surface modified electrode comprises of coating the substrate with mercaptosilane and using the coated electrode in an electrochemical cell; the electrode is capable of in-situ generating a nanoparticle size redox catalyst and provides a detection system for sensing of chemical agents. The present invention also relates to a surface modified electrode capable of oxidizing the chemical agents. The electrode comprises of a (i) a substrate; (ii) a mercaptosilane coating on the surface of the substrate; and (iii) in-situ electro generated metallic nano particle sized redox catalyst on the surface of the coated substrate. The electrode is reusable for the sensing of sulphur mustard by avoiding decontamination process.

Full Text	FIELD OF INVENTION The invention relates to a novel surface modified electrode capable of electrosensing and degrading the chemical agents like sulphur mustard and a method of its preparation. The electrode has a mercaptosilane coated surface and redox catalyst which is electrogenerated in-situ on the surface of the electrode. BACKGROUND OF INVENTION Detection of chemical agent Sulphur Mustard (known for its ability to alkylate the biological species upon exposure), plays a vital role during a normal time, chemical emergency and also in a war scenario in order to take appropriate counter measures including protection, decontamination and other related measures. A fleet of detection equipment is commercially available for the detection of chemical agents like sulphur mustard based on many techniques known in the art US4974963: describes method by flame photometric detection system. The method is having disadvantages such as sensing all sulphur containing compounds and also requiring very high temperature for exciting the sulphur atom. US5345213: describes a metal oxide based detection system, the main disadvantage of the system is that the sensor part is required to be kept at high temperature. US 7071465 and US20020000811: involves the mobility of ions and the shortcomings of the invention are the usage of membrane, ionization source and requirement of changing the polarity depending on the nature of agents. US5469369: describes a detection system method based on surface acoustic wave. The disadvantages of the system is that it requires different quartz chips coated with different polymers based upon the kind of agent. A reference chip is also used in parallel to the working chip. US2006191320: describes a method based on array of modified micro cantilevers for the detection of sulphur mustard, and its disadvantage is use of specific coating requirement US 4797180 and US4707242: describes yet another method is electrochemical based sensors for toxic gases which are not used for sulphur mustard sensing. EP0297738: describes a method for treatment of halogenated compound and decomposition of organic waste matter, by the use of electrochemically generated silver ions. The problems faced are insolubility and consequent precipitation of resulting silver ions in the solution. None of the method as described in the prior art is based on simple electrochemical technique for toxic gases like Sulphur mustard sensing due to high penetrative and adsorptive nature of agent towards electrodes and other materials. OB JECTTVES OF THE PRESENT INVENTION The objective of the present invention is to provide a surface modified electrode for oxidizing chemical agents like sulphur mustard. Further objective of the present invention is to provide a detection system for sensing of chemical agents alike sulphur mustard. Another objective of the invention is to provide an electrode capable of in situ generating a nanoparticle size redox catalyst. Another objective of the present invention is to utilize the modified electrode in the sensing and degradation of sulphur mustard in an undivided electrochemical cell in an alkali nitrate solution. Yet another objective of the present invention is to provide a reusable electrode for the sensing of sulphur mustard by avoiding decontamination process. STATEMENT OF INVENTION: According to the present invention there is provided a surface modified electrode capable of oxidizing the chemical agents comprising of: (i) a substrate; (ii) a mercaptosilane coating on the surface of the substrate; and (iii) in-situ electro generated metallic nano particle sized redox catalyst on the surface of the coated substrate. There is also provided a method for producing a surface modified electrode capable of oxidizing the chemical agents , comprising the steps of: (i) immersing the substrate into a solution of mercaptosilane solution for 60 to 300 minutes; (ii) removing the mercaptosilane surface coated substrate and dry it for 30 to 120 minutes; (iii) immersing the dried surface coated substrate from the solution into an electrochemical cell wherein the said electrochemical cell has: a reference electrode of the kind of Ag/AgCl electrode; and a counter electrode selected from platinum and glassy electrode; the reference electrode and the counter electrode being immersed in electrolyte of 0.01 to 0.5 M KN03 having 0.0001 to 0.01 M silver nitrate; (iv) applying a voltage of 1.0 V and changing the voltage to -1.0 V and repeating the cycle 3 to 20 times; and (v) withdrawing the electrode and drying to obtain the surface modified electrode. SUMMARY: The present invention relates to a surface modified electrode capable of oxidizing the chemical agents comprising of: (i) a substrate; (ii) a mercaptosilane coating on the surface of the substrate; and (iii) in-situ electro generated nano metallic redox catalyst on the surface of the coated electrode. The mercaptosilane coating is done on the surface of the metallic substrate to avoid the adsorption of the sulphur mustard an the electrode surface and thereby it is easy to clean the electrode surface without any decontamination process. The in-situ electrogenerated redox catalyst oxidize the sulphur mustard which in turn helps the detection of the sulphur mustard. The electrode is prepared by immersing the metallic substrate into the solution of mercaptosilane, removing and drying it The coated substrate is then used in an undivided electrochemical cell with a three electrode configuration having a reference electrode and a counter electrode. The coated metallic substrate works as a working electrode. The electrodes are dipped in an electrolyte. The variable potential is applied on the electrode from about -1.0 to 1.0 volts with respect to the potential of the reference electrode. The invention is further directed to a method for the oxidative sensing of sulphur mustard using electrochemical cell. DETAILED DESCRIPTION OF DRAWINGS: Figure 1 is cyclic voltammograms with a bare metal electrode (a) in absence of sulphur mustard and (b) in presence of sulphur mustard. Figure 2 is electrochemical impedance spectra Nyquist plot with a bare metal electrode (a) in absence of sulphur mustard and (b) in presence of sulphur mustard. Figure 3 is cyclic voltammograms with surface coated electrode (a) in absence of sulphur mustard and (b) in presence of sulphur mustard. Figure 4 is electrochemical impedance spectra Nyquist plot with surface coated electrode (a) in absence of sulphur mustard and (b) in presence of sulphur mustard. Figure 5 is cyclic voltammograms with surface coated electrode with in-situ electrogenerated redox catalyst (a) in absence of sulphur mustard and (b) in presence of sulphur mustard. Figure 6 is electrochemical impedance spectra Nyquist plot with surface coated electrode with in-situ electrogenerated redox catalyst (a) in absence of sulphur mustard and (b) in presence of sulphur mustard. Figure 7 shows the effect of scan rate on the oxidation of sulphur mustard with surface coated electrode with in-situ electrogenerated redox catalyst. DETAILED DESCRIPTION OF THE INVENTION: The purpose of the present invention is to provide a surface modified electrode which is capable of oxidizing the chemical agents like sulphur mustard. The surface modified electrode comprises of: (i) a substrate; (ii) a mercaptosilane coating on the surface of the substrate; and (iii) in-situ electro generated metallic nano particle sized redox catalyst on the surface of the coated electrode. The substrate of the electrode is selected from the group consisting of platinum, gold, graphite and glassy carbon. The substrate is coated with a layer of mercaptosilane. The hydrophobic nature of the silanes avoids the adsorption of sulphur mustard on the electrode surface and thereby it is easy to clean the electrode surface by a simple wash which overcomes extra decontamination process required for the electrode cleaning. The silane used can have a chain length of 3 to 10 carbon atoms and even more. The redox catalyst is generated in-situ on the surface coated electrode. The nanometallic catalyst is selected from electroactive metals like palladium, silver, platinum, iridium, ruthenium, bismuth, cadmium, chromium, manganese, molybdenum, nickel, antimony, tin and the kind, preferably silver. The particle size of metallic nano particle sized redox catalyst lies in the range of 5 to 80 nm. The invention also provides a method for preparation of the surface modified electrode capable of oxidizing the chemical agents of the kind sulphur mustard. The process step comprises of: (i) immersing the substrate into a solution of mercaptosilane solution of 0.01 to 0.25 M for 60 to 300 minutes; (ii) removing the mercaptosilane surface coated substrate and dry it for 30 to 120 minutes; (iii) immersing the dried surface coated substrate from the solution into an electrochemical cell wherein the said electrochemical cell is having: a reference electrode; and a counter electrode; the reference electrode and die counter electrode being immersed in electrolyte of 0.01 to 0.5 M KN03 having 0.0001 to 0.01 M silver nitrate; (iv) applying a voltage of 1.0 V and changing the voltage to -1.0 V and repeating the cycle 3 to 20 times; (v) withdrawing the electrode and drying to obtain the surface modified electrode. The reference electrode which has a stable and well known electrode potential is used like silver/silver chloride electrode. The counter electrode ensure mat current does not run through the reference electrode. The counter electrode used is made up of platinum or a glassy carbon. Mercaptosilane used has a molarity of 0.01 to 0.25 M. The potential of the cell is 3 to 20 times cycled between 1.0 volt to -1.0 volt in order to in-situ electrogenerate the metallic nano particle sized catalyst on the surface of the coated electrode . The electrode is then withdrawn from the electrochemical cell and dried. After this, the electrode is pretreated to get stable current and utilized for the oxidative sensing of chemical agents in micromole concentrations in a 0.1 to 0.5 M KN03 solution by cyclic voltametrically between -1.0 to 1.0 volt. In addition, the modified electrode is also characterized by impedance spectroscopy. This invention may also be useful for sensing other chemical agents by changing the cycling potential appropriately. The other chemical agents detected by the present invention are nerve agents such as Sarin, Soman, Tabun, VX and blister agents such as Nitrogen mustard. One can change the potential window until getting the electrochemical catalytic activity for the respective agent and utilizes the same potential window for the sensing and degradation of other chemical agents. Figures 1 and 2 are cyclic voltammogram and electrochemical impedance spectrum for bare gold electrode respectively. In Fig. 1, it is observed that the CV oxidation current with sulphur mustard in KN03 is less (Fig lb) when compared to CV oxidation (Fig. la) oxidation current without sulphur mustard in KN03. This observation is due to the strong adsorption of sulphur mustard on the bare gold electrode and this process is confirmed from the Fig. 2 which is electrochemical impedance spectrum with sulphur mustard (Fig. 2b) and without sulphur mustard in KN03 (Fig. 2a). It is observed from Fig. 2 that impedance with sulphur mustard is more when compared to in absence of sulphur mustard, this result confirms the blocking of electrochemical activity on the gold electrode surface by sulphur mustard adsorption. Figs. 3 and 4 are cyclic voltammogram (CV) and electrochemical impedance spectrum for silane surface coated electrode, respectively. Fig. 3 is entirely different from Fig.l and this observation is due to the presence of silane coating on the surface of gold electrode electrode. Moreover, Fig. 4 shows a very huge impedance (Fig. 4a) when compared to Fig. 2a due to presence of silane coating on the surface of gold electrode. However, the impedance in Fig. 2 with sulphur mustard is increased (Fig. 2b) when compared to a decrease in impedance with sulphur mustard on silane surface coated gold electrode in Fig. 4b. This observation confirms the non-adsorption of sulphur mustard on silane layer due to the hydrophobic nature of silane. Figs. 5 and 6 are cyclic voltammogram and electrochemical impedance spectrum for surface modified electrode (silane coated on surface with in-situ generated nanoparticle redox catalyst), respectively. Fig. 5a is entirely different from Fig. la and Fig. 3a and this observation is due to the presence of electrogenerated redox catalyst on the silane coated surface of gold electrode. Moreover, Fig. 4a shows a very huge impedance when compare to Fig. 2a due to the presence of silane on the surface of gold electrode in absence of sulphur mustard, in contrast Fig. 6a shows very less impedance due to the presence of electrogenerated redox catalyst on the silane coated surface of gold electrode in the absence of sulphur mustard and also in presence of sulphur mustard (Fig. 6b). However, after the addition of sulphur mustard a huge increase of current due to the oxidation of sulphur mustard is observed in Fig. 5b. this confirms the electrocatalysis on the electrode surface as well as oxidation of sulphur mustard. In addition, the impedance in Fig. 6 is almost same with sulphur mustard (Fig. 6b) and without sulphur mustard (Fig. 6 a). Moreover, the impedance in Fig. 6a is very less when compared to in Fig. 2 a and Fig. 4 a and this is due to the presence of the electrogenerated catalyst silver on the silane coated gold electrode. The huge sulphur mustard oxidation current observed in Fig. 5 b confirms the applicability of this electrogenerated catalyst on the silane coated gold electrode modification for the sensing and degradation of sulphur mustard. The main advantage of this modification is avoiding the surface adsorption of sulphur mustard by silane layer based on its hydrophobicity and thereby reusing this electrode for sensing and modifications without decontaminating the electrode surface. The stability of the modification is indicated in Fig. 7 by taking scan rate variation studies which showed good current increase with respect to increase with respect to increase in the scan rate. EXAMPLE: A gold disk electrode is immersed into a solution of 3-Mercaptopropyl trimethoxysilane and kept for 90 minutes. The electrode is removed and dried for 60 minutes. The surface coated electrode is now immersed into the electrochemical cell in which 0.002 M of silver nitrate is dissolved in 0.1 M KN03. The reference electrode used is silver/silver chloride electrode and counter electrodes of the cell is platinum wire. The potential of the cell is men cycled 10 times between 0.4 V and -0.8 V in order to in-situ electrogenerate the redox nanoparticle catalyst on the silane coated surface of the gold electrode. The electrode is then withdrawn from the electrochemical cell and dried. The electrode is pre-treated to get stable currents and utilized for the oxidative sensing of sulphur mustard in micromole concentrations in 0.1 M KNO3 solution by cyclic voltammetrically between -0.2 V and 0.7 V. We Claim: 1. A surface modified electrode capable of oxidizing the chemical agents comprising of: (i) a substrate; (ii). a mercaptosilane coating on the surface of the substrate; and (iii) in-situ electro generated metallic nano particle sized redox catalyst on the surface of the coated substrate. 2. A surface modified electrode capable of oxidizing the chemical agents as claimed in claim 1, wherein the substrate is selected from the group consisting of platinum, gold, graphite and glassy carbon. 3. A surface modified electrode capable of oxidizing the chemical agents as claimed in claim 1, wherein the mercaptosilane coated surface consists of mercaptosilane having 3 to 10 carbon atoms. 4. A surface modified electrode capable of oxidizing the chemical agents as claimed in claim 1, wherein the metallic nano particle sized redox catalyst is an electroactive metal preferably silver. 5. A surface modified electrode capable of oxidizing the chemical agents as claimed in claim 1, wherein the particle size of metallic redox catalyst is 5 to 80 nm. 6. A method for producing a surface modified electrode capable of oxidizing the chemical agents, comprising the steps of: (i) immersing the substrate into a solution of mercaptosilane solution for 60 to 300 minutes; (ii) removing the mercaptosilane surface coated substrate and drying it for 30 to 120 minutes; (iii) immersing the dried surface coated substrate from the solution into an electrochemical cell wherein the said electrochemical cell has: a reference electrode of the kind of Ag/AgCl electrode; and a counter electrode selected from platinum and glassy electrode; the reference electrode and the counter electrode being immersed in electrolyte of 0.01 to 0.5 M KN03 having 0.0001 to 0.01 M silver nitrate; (iv) applying a voltage of 1.0 V and changing the voltage to -1.0 V and repeating the cycle 3 to 20 times; and (v) withdrawing the electrode and drying to obtain the surface modified electrode. 7. A method for producing a surface modified electrode capable of oxidizing the chemical agents as claimed in claim 6 wherein the mercaptosilane used has a molarity of 0.01 to 0.25. 8. A surface modified electrode capable of oxidizing the chemical agents as and when used in electrosensing and degradation of chemical agents like Sarin, Soman, Tabun, VX and Nitrogen mustard. 9. A surface modified electrode capable of oxidizing the chemical agents as hereinbefore described with reference to the foregoing examples and accompanying drawings. 10. A method for producing a surface modified electrode capable of oxidizing the chemical agents as hereinbefore described with reference to the foregoing examples and accompanying drawings.

Full Text

FIELD OF INVENTION
The invention relates to a novel surface modified electrode capable of electrosensing and degrading the chemical agents like sulphur mustard and a method of its preparation. The electrode has a mercaptosilane coated surface and redox catalyst which is electrogenerated in-situ on the surface of the electrode.
BACKGROUND OF INVENTION
Detection of chemical agent Sulphur Mustard (known for its ability to alkylate the biological species upon exposure), plays a vital role during a normal time, chemical emergency and also in a war scenario in order to take appropriate counter measures including protection, decontamination and other related measures. A fleet of detection equipment is commercially available for the detection of chemical agents like sulphur mustard based on many techniques known in the art
US4974963: describes method by flame photometric detection system. The method is having disadvantages such as sensing all sulphur containing compounds and also requiring very high temperature for exciting the sulphur atom.
US5345213: describes a metal oxide based detection system, the main disadvantage of the system is that the sensor part is required to be kept at high temperature.
US 7071465 and US20020000811: involves the mobility of ions and the shortcomings of the invention are the usage of membrane, ionization source and requirement of changing the polarity depending on the nature of agents.

US5469369: describes a detection system method based on surface acoustic wave. The disadvantages of the system is that it requires different quartz chips coated with different polymers based upon the kind of agent. A reference chip is also used in parallel to the working chip.
US2006191320: describes a method based on array of modified micro cantilevers for the detection of sulphur mustard, and its disadvantage is use of specific coating requirement
US 4797180 and US4707242: describes yet another method is electrochemical based sensors for toxic gases which are not used for sulphur mustard sensing.
EP0297738: describes a method for treatment of halogenated compound and decomposition of organic waste matter, by the use of electrochemically generated silver ions. The problems faced are insolubility and consequent precipitation of resulting silver ions in the solution.
None of the method as described in the prior art is based on simple electrochemical technique for toxic gases like Sulphur mustard sensing due to high penetrative and adsorptive nature of agent towards electrodes and other materials.
OB JECTTVES OF THE PRESENT INVENTION
The objective of the present invention is to provide a surface modified electrode for oxidizing chemical agents like sulphur mustard.
Further objective of the present invention is to provide a detection system for sensing of chemical agents alike sulphur mustard.

Another objective of the invention is to provide an electrode capable of in situ generating a nanoparticle size redox catalyst.
Another objective of the present invention is to utilize the modified electrode in the sensing and degradation of sulphur mustard in an undivided electrochemical cell in an alkali nitrate solution.
Yet another objective of the present invention is to provide a reusable electrode for the sensing of sulphur mustard by avoiding decontamination process.
STATEMENT OF INVENTION:
According to the present invention there is provided a surface modified electrode capable of oxidizing
the chemical agents comprising of:
(i) a substrate;
(ii) a mercaptosilane coating on the surface of the substrate; and
(iii) in-situ electro generated metallic nano particle sized redox catalyst on the surface of the
coated substrate.
There is also provided a method for producing a surface modified electrode capable of oxidizing the
chemical agents , comprising the steps of:
(i) immersing the substrate into a solution of mercaptosilane solution for 60 to 300 minutes; (ii) removing the mercaptosilane surface coated substrate and dry it for 30 to 120 minutes; (iii) immersing the dried surface coated substrate from the solution into an electrochemical
cell wherein the said electrochemical cell has:
a reference electrode of the kind of Ag/AgCl electrode; and
a counter electrode selected from platinum and glassy electrode;
the reference electrode and the counter electrode being immersed in electrolyte of 0.01
to 0.5 M KN03 having 0.0001 to 0.01 M silver nitrate; (iv) applying a voltage of 1.0 V and changing the voltage to -1.0 V and repeating the cycle 3
to 20 times; and (v) withdrawing the electrode and drying to obtain the surface modified electrode.

SUMMARY:
The present invention relates to a surface modified electrode capable of oxidizing the chemical agents
comprising of:
(i) a substrate;
(ii) a mercaptosilane coating on the surface of the substrate; and
(iii) in-situ electro generated nano metallic redox catalyst on the surface of the coated
electrode.
The mercaptosilane coating is done on the surface of the metallic substrate to avoid the adsorption of
the sulphur mustard an the electrode surface and thereby it is easy to clean the electrode surface
without any decontamination process.
The in-situ electrogenerated redox catalyst oxidize the sulphur mustard which in turn helps the
detection of the sulphur mustard.
The electrode is prepared by immersing the metallic substrate into the solution of mercaptosilane,
removing and drying it The coated substrate is then used in an undivided electrochemical cell with a
three electrode configuration having a reference electrode and a counter electrode. The coated metallic
substrate works as a working electrode. The electrodes are dipped in an electrolyte. The variable
potential is applied on the electrode from about -1.0 to 1.0 volts with respect to the potential of the
reference electrode. The invention is further directed to a method for the oxidative sensing of sulphur
mustard using electrochemical cell.
DETAILED DESCRIPTION OF DRAWINGS:
Figure 1 is cyclic voltammograms with a bare metal electrode (a) in absence of sulphur mustard and (b) in presence of sulphur mustard.

Figure 2 is electrochemical impedance spectra Nyquist plot with a bare metal electrode (a) in absence of sulphur mustard and (b) in presence of sulphur mustard.
Figure 3 is cyclic voltammograms with surface coated electrode (a) in absence of sulphur mustard and (b) in presence of sulphur mustard.
Figure 4 is electrochemical impedance spectra Nyquist plot with surface coated electrode (a) in absence of sulphur mustard and (b) in presence of sulphur mustard.
Figure 5 is cyclic voltammograms with surface coated electrode with in-situ electrogenerated redox catalyst (a) in absence of sulphur mustard and (b) in presence of sulphur mustard.
Figure 6 is electrochemical impedance spectra Nyquist plot with surface coated electrode with in-situ electrogenerated redox catalyst (a) in absence of sulphur mustard and (b) in presence of sulphur mustard.
Figure 7 shows the effect of scan rate on the oxidation of sulphur mustard with surface coated electrode with in-situ electrogenerated redox catalyst.
DETAILED DESCRIPTION OF THE INVENTION:
The purpose of the present invention is to provide a surface modified electrode which is capable of
oxidizing the chemical agents like sulphur mustard.
The surface modified electrode comprises of:
(i) a substrate;
(ii) a mercaptosilane coating on the surface of the substrate; and
(iii) in-situ electro generated metallic nano particle sized redox catalyst on the surface of the

coated electrode.
The substrate of the electrode is selected from the group consisting of platinum, gold, graphite and glassy carbon.
The substrate is coated with a layer of mercaptosilane. The hydrophobic nature of the silanes avoids the adsorption of sulphur mustard on the electrode surface and thereby it is easy to clean the electrode surface by a simple wash which overcomes extra decontamination process required for the electrode cleaning. The silane used can have a chain length of 3 to 10 carbon atoms and even more.
The redox catalyst is generated in-situ on the surface coated electrode. The nanometallic catalyst is selected from electroactive metals like palladium, silver, platinum, iridium, ruthenium, bismuth, cadmium, chromium, manganese, molybdenum, nickel, antimony, tin and the kind, preferably silver. The particle size of metallic nano particle sized redox catalyst lies in the range of 5 to 80 nm.
The invention also provides a method for preparation of the surface modified electrode capable of oxidizing the chemical agents of the kind sulphur mustard. The process step comprises of:
(i) immersing the substrate into a solution of mercaptosilane solution of 0.01 to 0.25 M for
60 to 300 minutes; (ii) removing the mercaptosilane surface coated substrate and dry it for 30 to 120 minutes; (iii) immersing the dried surface coated substrate from the solution into an electrochemical
cell wherein the said electrochemical cell is having:
a reference electrode; and
a counter electrode;
the reference electrode and die counter electrode being immersed in electrolyte of 0.01
to 0.5 M KN03 having 0.0001 to 0.01 M silver nitrate; (iv) applying a voltage of 1.0 V and changing the voltage to -1.0 V and repeating the cycle 3
to 20 times; (v) withdrawing the electrode and drying to obtain the surface modified electrode.
The reference electrode which has a stable and well known electrode potential is used like silver/silver
chloride electrode.
The counter electrode ensure mat current does not run through the reference electrode. The counter
electrode used is made up of platinum or a glassy carbon.
Mercaptosilane used has a molarity of 0.01 to 0.25 M.
The potential of the cell is 3 to 20 times cycled between 1.0 volt to -1.0 volt in order to in-situ

electrogenerate the metallic nano particle sized catalyst on the surface of the coated electrode . The electrode is then withdrawn from the electrochemical cell and dried. After this, the electrode is pretreated to get stable current and utilized for the oxidative sensing of chemical agents in micromole concentrations in a 0.1 to 0.5 M KN03 solution by cyclic voltametrically between -1.0 to 1.0 volt. In addition, the modified electrode is also characterized by impedance spectroscopy.
This invention may also be useful for sensing other chemical agents by changing the cycling potential appropriately. The other chemical agents detected by the present invention are nerve agents such as Sarin, Soman, Tabun, VX and blister agents such as Nitrogen mustard. One can change the potential window until getting the electrochemical catalytic activity for the respective agent and utilizes the same potential window for the sensing and degradation of other chemical agents.
Figures 1 and 2 are cyclic voltammogram and electrochemical impedance spectrum for bare gold electrode respectively. In Fig. 1, it is observed that the CV oxidation current with sulphur mustard in KN03 is less (Fig lb) when compared to CV oxidation (Fig. la) oxidation current without sulphur mustard in KN03. This observation is due to the strong adsorption of sulphur mustard on the bare gold electrode and this process is confirmed from the Fig. 2 which is electrochemical impedance spectrum with sulphur mustard (Fig. 2b) and without sulphur mustard in KN03 (Fig. 2a). It is observed from Fig. 2 that impedance with sulphur mustard is more when compared to in absence of sulphur mustard, this result confirms the blocking of electrochemical activity on the gold electrode surface by sulphur mustard adsorption.
Figs. 3 and 4 are cyclic voltammogram (CV) and electrochemical impedance spectrum for silane surface coated electrode, respectively. Fig. 3 is entirely different from Fig.l and this observation is due to the presence of silane coating on the surface of gold electrode electrode. Moreover, Fig. 4 shows a very huge impedance (Fig. 4a) when compared to Fig. 2a due to presence of silane coating on the surface of gold electrode. However, the impedance in Fig. 2 with sulphur mustard is increased (Fig. 2b) when compared to a decrease in impedance with sulphur mustard on silane surface coated gold electrode in Fig. 4b. This observation confirms the non-adsorption of sulphur mustard on silane layer due to the hydrophobic nature of silane.
Figs. 5 and 6 are cyclic voltammogram and electrochemical impedance spectrum for surface modified electrode (silane coated on surface with in-situ generated nanoparticle redox catalyst), respectively. Fig. 5a is entirely different from Fig. la and Fig. 3a and this observation is due to the presence of electrogenerated redox catalyst on the silane coated surface of gold electrode. Moreover, Fig. 4a shows a very huge impedance when compare to Fig. 2a due to the presence of silane on the surface of gold electrode in absence of sulphur mustard, in contrast Fig. 6a shows very less impedance due to the

presence of electrogenerated redox catalyst on the silane coated surface of gold electrode in the absence of sulphur mustard and also in presence of sulphur mustard (Fig. 6b). However, after the addition of sulphur mustard a huge increase of current due to the oxidation of sulphur mustard is observed in Fig. 5b. this confirms the electrocatalysis on the electrode surface as well as oxidation of sulphur mustard. In addition, the impedance in Fig. 6 is almost same with sulphur mustard (Fig. 6b) and without sulphur mustard (Fig. 6 a). Moreover, the impedance in Fig. 6a is very less when compared to in Fig. 2 a and Fig. 4 a and this is due to the presence of the electrogenerated catalyst silver on the silane coated gold electrode. The huge sulphur mustard oxidation current observed in Fig. 5 b confirms the applicability of this electrogenerated catalyst on the silane coated gold electrode modification for the sensing and degradation of sulphur mustard. The main advantage of this modification is avoiding the surface adsorption of sulphur mustard by silane layer based on its hydrophobicity and thereby reusing this electrode for sensing and modifications without decontaminating the electrode surface. The stability of the modification is indicated in Fig. 7 by taking scan rate variation studies which showed good current increase with respect to increase with respect to increase in the scan rate.
EXAMPLE:
A gold disk electrode is immersed into a solution of 3-Mercaptopropyl trimethoxysilane and kept for
90 minutes. The electrode is removed and dried for 60 minutes. The surface coated electrode is now
immersed into the electrochemical cell in which 0.002 M of silver nitrate is dissolved in 0.1 M KN03.
The reference electrode used is silver/silver chloride electrode and counter electrodes of the cell is
platinum wire.
The potential of the cell is men cycled 10 times between 0.4 V and -0.8 V in order to in-situ
electrogenerate the redox nanoparticle catalyst on the silane coated surface of the gold electrode. The
electrode is then withdrawn from the electrochemical cell and dried.
The electrode is pre-treated to get stable currents and utilized for the oxidative sensing of sulphur
mustard in micromole concentrations in 0.1 M KNO3 solution by cyclic voltammetrically between -0.2
V and 0.7 V.

We Claim:
1. A surface modified electrode capable of oxidizing the chemical agents comprising of:
(i) a substrate;
(ii). a mercaptosilane coating on the surface of the substrate; and
(iii) in-situ electro generated metallic nano particle sized redox catalyst on the surface of the coated substrate.
2. A surface modified electrode capable of oxidizing the chemical agents as claimed in claim 1, wherein the substrate is selected from the group consisting of platinum, gold, graphite and glassy carbon.
3. A surface modified electrode capable of oxidizing the chemical agents as claimed in claim 1, wherein the mercaptosilane coated surface consists of mercaptosilane having 3 to 10 carbon atoms.
4. A surface modified electrode capable of oxidizing the chemical agents as claimed in claim 1, wherein the metallic nano particle sized redox catalyst is an electroactive metal preferably silver.
5. A surface modified electrode capable of oxidizing the chemical agents as claimed in claim 1, wherein the particle size of metallic redox catalyst is 5 to 80 nm.
6. A method for producing a surface modified electrode capable of oxidizing the chemical agents, comprising the steps of:
(i) immersing the substrate into a solution of mercaptosilane solution for 60 to 300 minutes; (ii) removing the mercaptosilane surface coated substrate and drying it for 30 to 120
minutes; (iii) immersing the dried surface coated substrate from the solution into an electrochemical
cell wherein the said electrochemical cell has:
a reference electrode of the kind of Ag/AgCl electrode; and
a counter electrode selected from platinum and glassy electrode;
the reference electrode and the counter electrode being immersed in electrolyte of 0.01
to 0.5 M KN03 having 0.0001 to 0.01 M silver nitrate; (iv) applying a voltage of 1.0 V and changing the voltage to -1.0 V and repeating the cycle 3

to 20 times; and (v) withdrawing the electrode and drying to obtain the surface modified electrode.
7. A method for producing a surface modified electrode capable of oxidizing the chemical agents as claimed in claim 6 wherein the mercaptosilane used has a molarity of 0.01 to 0.25.
8. A surface modified electrode capable of oxidizing the chemical agents as and when used in electrosensing and degradation of chemical agents like Sarin, Soman, Tabun, VX and Nitrogen mustard.
9. A surface modified electrode capable of oxidizing the chemical agents as hereinbefore described with reference to the foregoing examples and accompanying drawings.
10. A method for producing a surface modified electrode capable of oxidizing the chemical agents as hereinbefore described with reference to the foregoing examples and accompanying drawings.

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Patent Number

272510

Indian Patent Application Number

1626/DEL/2008

PG Journal Number

15/2016

Publication Date

08-Apr-2016

Grant Date

05-Apr-2016

Date of Filing

07-Jul-2008

Name of Patentee

DIRECTOR GENERAL, DEFENCE RESEARCH & DEVELOPMENT ORGANISATION.

Applicant Address

DRDO BHAWAN, RAJAJI MARG,NEW DELHI-110011, INDIA.

Inventors:

#	Inventor's Name	Inventor's Address
1	BOOPATHI,MANNAN	PROTECTIVE DEVICE DIVISION, DEFENCE RESEARCH AND DEVELOPMENT ESTABLISHMENT,JHANSI ROAD, GWALIOR-474 002, MDHYA PRADESH.
2	SINGH,BEER	PROTECTIVE DEVICE DIVISION, DEFENCE RESEARCH AND DEVELOPMENT ESTABLISHMENT,JHANSI ROAD, GWALIOR-474 002, MDHYA PRADESH.
3	GANESAN,KUMARAN	PROTECTIVE DEVICE DIVISION, DEFENCE RESEARCH AND DEVELOPMENT ESTABLISHMENT,JHANSI ROAD, GWALIOR-474 002, MDHYA PRADESH.
4	VIJAYARAGHAVAN, RAJAGOPALAN	PROTECTIVE DEVICE DIVISION, DEFENCE RESEARCH AND DEVELOPMENT ESTABLISHMENT,JHANSI ROAD, GWALIOR-474 002, MDHYA PRADESH.

PCT International Classification Number

C25B

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA