WO2012070927A1

WO2012070927A1 - Method for preparing a doped polypyrrole

Info

Publication number: WO2012070927A1
Application number: PCT/MY2011/000134
Authority: WO
Inventors: Ahmad Mohd Rais; Alva Sagir; Abd Rashid Norazah; A Aziz Aiman Sajidah
Original assignee: Mimos Bhd
Current assignee: Mimos Bhd
Priority date: 2010-11-26
Filing date: 2011-06-23
Publication date: 2012-05-31
Anticipated expiration: 2013-05-26
Also published as: MY150725A

Abstract

The present invention relates to a method for preparing a doped polypyrrole conducting layer on a thick film carbon electrode comprising the steps of depositing a circular shaped silver thick film on a pre-deposited copper film and obtaining a silver conductor layer; depositing a circular shaped carbon thick film on the silver conductor layer and obtaining a carbon electrode; sonicating the carbon electrode in deionized water to clean the carbon thick film surface; preparing an electrolyte solution of hydrophilic organic salt and pyrrole monomer in a polar solvent; and electrodepositing polypyrrole on the carbon electrode with the electrolyte.

Description

Title of Invention: METHOD FOR PREPARING A DOPED

POLYPYRROLE

Technical Field

[1] The present invention relates to a method for preparing a doped polypyrrole. More particularly, the doped polypyrrole is used in preparing conductive polymers for biological or chemical sensing device or reference electrode.

Background Art

[2] Conducting polymers have been exploited for bio-chemical and bio sensing devices for two reasons - good conducting property and as reduction-oxidation electrochemical transducer. Polypyrrole, polyaniline and polythiophene are among the most widely used. Among the three, polypyrrole is the easiest to prepare and most promising for manufacturability.

[3] Both doped and undoped polypyrrole find applications in bio-chemical sensors.

Undoped polypyrrole appears as neutral oligomer with approximately at least 8 but not more than 50 monomer units and has no positive charge on the backbone. Doped polypyrrole contains at least one cationic site at the oligomer backbone and the positive charge is neutralized with anionic counterion doping X such as chloride and nitrate.

[4] Doped polypyrrole is usually prepared by electropolymerization of pyrrole monomer in aqueous solutions of salts of potassium. Pyrrole has moderate solubility in these electrolytes and homogeneity is achieved with vigorous stirring of the electrolyte solutions. Deposition of polypyrrole via electropolymerization method is not possible in miniaturized electrodes because the electrodes are inaccessible for potentiostat setup and the electrical contacts tend to short when immersed in monomer solution.

[5] Due to that, there is a need in the art to provide a method for preparing a doped

polypyrrole conducting layer on a thick film carbon electrode.

Disclosure of Invention

Technical Problem

[6]

Technical Solution

[7]

Summary

[8] According to a first aspect of the invention, there is provided a method for preparing a doped polypyrrole conducting layer on a thick film carbon electrode comprising the steps of:

1. a) depositing a circular shaped silver thick film on a pre-deposited copper film and obtaining a silver conductor layer; D

1. b) depositing a circular shaped carbon thick film on the silver conductor layer and obtaining a carbon electrode; D

1. c) sonicating the carbon electrode in deionized water to clean the carbon thick film surface; D

1. d) preparing an electrolyte solution of hydrophilic organic salt and pyrrole monomer in a polar solvent; and D

1. e) electrodepositing polypyrrole on the carbon electrode with the electrolyte. D

[9] The provision of the method is advantageous as it results in allows preparation of high concentration of pyrrole monomer electrolyte solution in organic solvent and reproducible production of electrochemical transducer.

[10] According to a second aspect of the invention, there is provided the product produced by the method is usable in preparing an electrochemical transducer in bio-chemical sensor and for ion selective electrode (ISE) or ion sensitive field effect transistor (ISFET).

Description of Drawings

[11] For a fuller understanding of the nature of the present invention, reference should be made to the following detailed description taken in connection with the accompanying drawings in which:

[12] FIG. 1: illustrates a schematic diagram on the method for for preparing a doped polypyrrole conducting layer on a thick film carbon electrode of the present invention.

[13] FIG.2: illustrates a chemical structure of a doped polypyrrole conducting polymer of the present invention.

[14] FIG.3: illustrates a chemical structure of hydrophilic organic salts used in the present invention.

[15] FIG.4: illustrates a cyclic voltammatograms of Ppy(Cl) from ethanol solvent in 0.1M

KC1 with 90 and 150 sec electropolymerisation time.

[16] FIG.5: illustrates a cyclic voltammatograms of Ppy(Cl) from 50% v/v methanol solvent in 0.1 M KC1 with 90, 150, 300 and 500 sec electropolymerisation time.

[17] FIG.6: illustrates a cyclic voltammatograms of Ppy(Cl) from 50 % v/v 2-methoxy ethanol solvent in 0.1M KC1 with 90 and 150 sec electropolymerisation time.

[18]

[19] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[20] The present invention provides a method for preparing a doped polypyrrole

conducting layer on a thick film carbon electrode comprising the steps of depositing a circular shaped silver thick film on a pre-deposited copper film and obtaining a silver conductor layer; depositing a circular shaped carbon thick film on the silver conductor layer and obtaining a carbon electrode; sonicating the carbon electrode in deionized water to clean the carbon thick film surface; preparing an electrolyte solution of hy- drophilic organic salt and pyrrole monomer in a polar solvent; and electrodepositing polypyrrole on the carbon electrode with the electrolyte. The schematic diagram of the method is shown in FIG.l. The first and second step are further comprising the step of curing at about 70 to 150°C to give dry thickness of and 50um to 200um of the silver thick film or carbon thick film.

[21] Pyrrole is only moderately soluble in aqueous solutions of chloride or nitrate salts of potassium. Vigorous shaking or continous stirring is necessary to get homogenous mixture of the aqueous electrolyte. On the contrary, pyrrole exhibits very high solubility in solutions of polar solvents, mixture of polar solvents and mixture of polar solvents with deionized water. This type of electrolytes have been employed for elec- tropolymerization of pyrrole in preparing conductive polymers for biological or chemical sensing device or reference electrode.

[22] Doped polypyrrole is prepared by electropolymerization of pyrrole monomer in

electrolyte of hydrophilic organic salts in polar organic solvents, mixture of polar organic solvents or mixture of deionized water and polar organic solvent. The pyrrole monomer has very high solubility in these electrolytes and mixing and electropolymerization can take place efficienty without continous stirring.

[23] The hydrophilic salt having the formula of:

[25] wherein, X is selected from the group of chloride, bromide, iodide, nitrate, tetrafluo- roborate, hexafluorophosphate, acetate, trifluoroacetate, tosylate or hexacyanoferrate; and R is selected from the group of hydrogen, methyl, ethyl, butyl or allyl.

[26] The organic compound is hydroxylated ammonium salts of chloride, bromide, iodide, nitrate, tetrafluoroborate, hexafluorophosphate, acetate, trifluoroacetate, tosylate and hexacyanoferrate.

[27] The polar solvent is selected from the list of ethanol, methanol, acetonitrile,

2-methoxy ethanol, dimethylsulfoxide, tetrahydrofuran or a mixture of these solvents or a mixture of any of the solvent with deionized water.

[28] Product produced by this method is usable for preparing an electrochemical transducer in bio-chemical sensor and for ion selective electrode (ISE) or ion sensitive field effect transistor (ISFET).

[29] The present invention will be explained in more detail through the examples below.

The examples is presented only to illustrate the preferred embodiments of the present invention and not intended in any way to limit the scope of the present invention.

[30] Example 1

[31] Preparation of Screen Printed Carbon Electrode

[32] Carbon paste is screen printed on copper-gold or prefabricated screen printed silver.

The optimized dry thickness of both screen printed carbon and silver are 100 micrometer. The circular shaped electrodes with 3mm diameter is printed on polyester or printed circuit board substrate and separated by 2mm spacing from each other for integrated multi-sensor application. The printed paste was cured at 120 °C to give the desired dry thickness. Solder mask insulating layer was also screen printed to define the electrode window, separate the wells and protect the printed conducting wires.

[33] Example 2

[34] Pyrrole Electropolymerization on Screen Printed Carbon Electrode from

Choline Chloride-Ethanol Electrolyte

[35] Screen printed carbon electrodes (SPE) with 4 mm diameter were cleaned ultra- sonically with deionised water for 1 min. The electrochemical polymerisation was performed in a conventional three-electrode cell with a platinum as counter electrode and the Ag/AgCl double junction as reference electrode using Autolab PGSTAT MODEL 128N for 90 and 150 sec. The polypyrrole (Ppy) films were electrodeposited with current density of 2 n A cnr² in aqueous solution of 0.5M pyrrole containing 1M choline chloride dopant and 50% v/v ethanol-water solvent. Following the electropoly- merisation process, cyclic voltammetry experiments were conducted between -1.0 V and +1.0 V with a potential sweep rate of 100 mV sec-' in 0.1M potassium chloride (KC1) solution. The cyclic voltammetry plot is provided in FIG.4.

[36] Example 3

[37] Pyrrole Electropolymerization on Screen Printed Carbon Electrode from

Choline Chloride-Methanol Electrolyte

[38] Screen printed carbon electrodes (SPE) with 4 mm diameter were cleaned ultra- sonically with deionised water for 1 min. The electrochemical polymerisation was performed in a conventional three-electrode cell with a Pt as caunter electrode and the Ag/AgCl double junction as reference electrode using Autolab PGSTAT MODEL 128N for 90, 150, 300 and 500 sec. The polypyrrole (Ppy) films were generated with current density of 2.514 mA cnr² in aqueous solution of 0.5M pyrrole containing 1M choline chloride dopant and 50% v/v or 100% v/v methanol solvent. After forming electropolymerisation, cyclic voltammetry experiments were conducted between -1.0 V and +1.0 V with a potential sweep rate of 100 mV sec ¹ in 0.1 M potassium chloride (KC1) solution. The plots were shown as FIG.5.

[39] Example 4

[40] Pyrrole Electropolymerization on Screen Printed Carbon Electrode from

Choline Chloride-2-Methoxyethanol Electrolyte

[41] Screen printed carbon electrodes (SPE) with 4 mm diameter were cleaned ultra- sonically with deionised water for 1 min. The electrochemical polymerisation was performed in a conventional three-electrode cell with a Pt as counter electrode and the Ag/AgCl double junction as reference electrode using Autolab PGSTAT MODEL 128N for 90 and 150 sec. The polypyrrole (Ppy) films were generated with current density of 2.513 mA cm ² in aqueous solution of 0.5M pyrrole containing 1M choline chloride dopant and 50% v/v 2-methoxy ethanol solvent. After forming electropoly- merisation, cyclic voltammetry experiments were conducted between -1.0 V and +1.0

V with a potential sweep rate of 100 mV sec ¹ in 0.1M potassium chloride (KC1) solution. The plots were shown as FIG.6.

[42] Although the invention has been described with reference to particular embodiment, it is to be understood that the embodiment is merely illustrative of the principles and applications of the present invention. It is therefore to be understood that numerous modifications may be made to the illustrative embodiment that other arrangements may be devised without departing from the scope of the present invention as defined by the appended claims.

Best Mode

[43]

Mode for Invention

[44]

Industrial Applicability

[45]

Sequence List Text

Claims

[Claim 1 ] 1. A method for preparing a doped polypyrrole conducting layer on a thick film carbon electrode comprising the steps of:

a) depositing a circular shaped silver thick film on a pre-deposited copper film and obtaining a silver conductor layer;

b) depositing a circular shaped carbon thick film on the silver conductor layer and obtaining a carbon electrode;

c) sonicating the carbon electrode in deionized water to clean the carbon thick film surface;

d) preparing an electrolyte solution of hydrophilic organic salt and pyrrole monomer in a polar solvent; and

e) electrodepositing polypyrrole on the carbon electrode with the electrolyte.

2. A method as claimed in Claim 1, wherein step (a) or (b) further comprising curing at about 70 to 150°C.

3. A method as claimed in Claim 1, wherein the hydrophilic organic salt in step (d) comprises the formula of:

X~

1

wherein, X is selected from the group of chloride, bromide, iodide, nitrate, tetrafluoroborate, hexafluorophosphate, acetate, trifluoroacetate, tosylate or hexacyanoferrate; and

R is selected from the group of hydrogen, methyl, ethyl, butyl or allyl.

4. A method as claimed in Claim 1, wherein the polar solvent in step (d) is selected from the list of ethanol, methanol, acetonitrile,

5. A method as claimed in Claim 1, wherein the pyrrole monomer electrolyte solution in step (d) having concentration ranges from 0.1M to 3M.

6. A method as claimed in Claim 1, wherein the hydrophilic organic salt in the polar solvent in step (d) having a concentration ranges from 0.1M to 3M.

7. A method as claimed in Claim 6, wherein the hydrophilic organic salt is choline chloride.

8. A method as claimed in Claim 1, wherein step (e) is conducted by an electrochemical polymerization of constant current method with current density of 0.1 to 10 mA per square centimetre.

9. A method as claimed in Claim 8, wherein the electrochemical polymerization utilizing cyclic voltammetry method with scan between - IV to +1V.

10. A product produced by the method of Claim 1, wherein the doped polypyrrole conducting layer on a thick film carbon electrode is usable in preparing an electrochemical transducer in bio-chemical sensor.

11. A product as claimed in Claim 5, wherein the doped polypyrrole conducting layer on a thick film carbon electrode is usable for ion selective electrode (ISE) or ion sensitive field effect transistor (ISFET).