JPH01144562A - Electrode - Google Patents

Abstract

PURPOSE:To obtain an inexpensive and high-performance cell electrode, chemical reaction tank electrode, sensor electrode, fuel cell electrode, bio-reactor electrode or the like by using a composite film made of a noble metal thin film and a mediator. CONSTITUTION:A noble metal thin film layer made of palladium or the like is formed on a nonconducting substrate made of polyethylene terephtalate or polyamide. The surface of this thin film layer is modified by a mediator made of a conducting polymer material such as polyaniline or its derivative. An inexpensive and high-performance electrode is thereby obtained.

Description

[Detailed Description of the Invention] The present invention provides a battery electrode, a chemical reaction tank electrode, a sensor electrode,
This invention relates to electrodes suitable for fuel cell electrodes, bioreactor electrodes, etc.

Conventionally, platinum, gold, mercury, nickel, iron, lead, zinc, copper, indium oxide, tin oxide, carbon, etc. have been used as electrodes for electrochemical reactions for various purposes. It is used accordingly. Among these, electrodes using noble metals such as platinum and gold have the best electrochemical reactivity, but have the disadvantage of being high in cost.

The present invention was made in view of the above circumstances, and an object of the present invention is to provide an electrode that is inexpensive, highly functional, and suitable for use as a battery electrode, a chemical reaction tank electrode, a sensor electrode, a fuel cell electrode, a bioreactor electrode, etc. shall be.

1 Method for solving ξ As a result of intensive studies to achieve the above objective, the present inventors found that by using a composite film of a thin film of a noble metal and a mediator, it was possible to solve the problem without impairing electrochemical reactivity. By forming a thin film of a noble metal such as palladium on a non-conductive substrate such as polyethylene terephthalate by a method such as sputtering, and further modifying it by forming a mediator layer such as a conductive polymer material, the cost can be reduced. It was discovered that inexpensive and highly functional electrodes could be obtained.

This has led to the completion of the present invention.

Therefore, the present invention provides an electrode characterized in that a noble metal thin film layer is formed on a non-conductive substrate, and the surface of the noble metal thin film layer is modified with a mediator.

The present invention will be explained in more detail below.

As described above, the electrode of the present invention has a noble metal thin film layer formed on a nonconductive substrate, and the surface of this noble metal thin film layer is further modified with a mediator.

In this case, the non-conductive substrate used in the electrode of the present invention may be any non-conductive substrate, including but not limited to, polyethylene terephthalate.

Non-conductive resins such as polyamide are preferred from the viewpoint of moldability. Moreover, ceramics, glass, etc. are also suitably used.

The thin noble metal film formed on the non-conductive substrate is as follows:
A single metal such as platinum, gold, mercury, silver, copper, or an alloy thereof can be used, but palladium is particularly preferred from the viewpoint of a balance between low cost and high functionality. Although the thickness of the noble metal thin film is not particularly limited, it is preferable that the surface resistance 5 is Ω/a1 or less.

The method for forming the noble metal thin film layer on the non-conductive substrate is not particularly limited, and methods such as sputtering, ion blasting, vacuum deposition, electroless plating, and a method using a thermal transfer film are suitably employed. Among these, the method using sputtering has particularly high recovery efficiency of precious metals, and is therefore preferably employed. In this case, the electrical resistance is IKΩ
It is preferable to perform sputtering until it reaches a certain level.

Next, as the mediator for modifying the surface of the noble metal thin film layer, there is no particular restriction and a variety of mediator substances can be used, such as benzoquinone, ferrocene, chloranil, thionine, potassium ferricyanide, etc., but especially polypyrrole, polythiophene, etc. , polyaniline and its derivatives are suitable, and among them polyaniline and its derivatives are most suitable. In addition, these conductive polymer substances and the above-mentioned benzoquinone, ferrocene, chloranil, and thionine.

There is no problem in using it in combination with a mediator substance such as potassium ferricyanide.

Here, as mentioned above, polyaniline and its derivatives are most suitable as the mediator, but as a derivative of polyaniline, ), etc.

Polyaniline and its derivatives are obtained by electrolytic oxidative polymerization or chemical oxidative polymerization using a reducing agent of aniline or its derivatives, and they can be used as they are, but in this case, the obtained polyaniline or its derivatives are reduced. It is preferable to use a treated and/or neutralized one in terms of noise removal due to background current when the electrode of the present invention is used as an enzyme electrode. In this case, as the reduction treatment method, a method using electrolysis or a method using a reducing agent is adopted.

A specific method for electrolytic reduction is to use an electrolytic solution with a pH higher than 8, and to achieve a voltage of -0.6 to +0.2 V compared to a silver-silver chloride electrode.
(7) Potential, 1 to 5 mA/al (7) It is preferable to reduce at a current density, and in some cases, a step of oxidizing at a potential of 0.0 to +0.7 V compared to a silver-silver chloride electrode may be included. is also possible, and in this case, the current value is 5
mA or less is suitable, -〇, 5 in the range of 2 to 0.7v
Cyclic portamograms can also be performed at ~50 mV/sac. This allows non-living ions such as borofluoric acid and hydrofluoric acid to be exchanged with living ions such as hydrochloric acid and phosphoric acid.

As the electrolytic solution used in this electrolytic reduction treatment, known buffer solutions using borofluoric acid, hydrochloric acid, acetic acid, phosphoric acid monosaline, etc., acetic acid, phosphoric acid, phthalic acid, etc. are suitably used. The preferred concentration range is 5 mol/Q to 10 mmol/Q, with 3
More preferably mol/Q to 100 mmol/Q. The treatment temperature is preferably 0 to 40°C, particularly 0 to 20°C.

The electrolysis time is preferably 5 seconds to 30 minutes.

On the other hand, as the treatment method using a reducing agent, a method of chemically reducing polyaniline or a derivative thereof using a reducing agent may be employed. In this case, the reducing agent used is one or more of hydrogen gas, hydrazine hydrochloride, hydrazine, hydrogen sulfide, sodium sulfite, magnesium, formic acid, etc., but more preferably hydrazine, phosphoric acid, acetic acid, hydrochloric acid, etc. An aqueous solution in which the pH is adjusted to 1 to 10, more preferably 5 to 9 by adding hydrazine is preferable.
Mol/Q to 50 mmol/Ω is preferable, and the acid concentration is preferably 3 mol/Q to 10 mmol/Ω.

Further, the treatment time is preferably 1 minute to 5 hours, and the treatment temperature is preferably 0 to 40°C.

Furthermore, as a method of neutralization treatment performed as a post-treatment, p
A method of immersion in a known buffer solution of pH 3 to 10, more preferably pH 5 to 9 for 1 minute to 50 hours, more preferably 10 minutes to 6 hours is adopted, and in this case, the treatment temperature is 0 to 40'.
C is preferred. Note that polyaniline synthesized in an acidic aqueous solution is in an ammonium salt state and has a PK value of 1 to 3. Therefore, normal water washing is also included in the neutralization treatment, and the PK value of polyaniline actually increases to 3 to 6 with water washing. Moreover, this neutralization treatment can be performed simultaneously with the above-mentioned reduction treatment.

There are no restrictions on the method of modifying the surface of the noble metal thin film formed on the non-conductive substrate with the above-mentioned mediator, but methods include forming a mediator film on the noble metal thin film by electrolytic polymerization, and coating and molding the mediator film by Teflon disversion. An effective method is to Note that when polyaniline is used as the mediator, a method may be adopted in which polyaniline is dissolved in a solvent such as dimethylformamide and cast on the noble metal thin film.

The electrode of the present invention can further immobilize an enzyme on the mediator, and the enzyme to be immobilized is appropriately selected depending on the substrate specificity and reaction specificity depending on the type of chemical reaction desired to proceed. Oxidase, alcohol dehydrogenase, urease, glucokinase, peroxidase, cholesterol esterase, lipase, phospholipase, catalase, lactate dehydrogenase, glucoamylase, galactose oxidase, penicillinase, tyrosinase and the like.

Methods for immobilizing enzymes are not particularly limited, but include carrier binding methods, covalent bonding methods, ionic bonding methods, adsorption methods, and crosslinking methods, among which methods include dropping a solution containing the enzyme and drying it, and glutaric A method of forming a Schiff base with an aldehyde is preferably used. The amount of enzyme to mediator is preferably 1 to 50,000 units/■.

The treatment temperature is 0 to 30°C, more preferably 5 to 20°C.
C and pH are preferably in the range of 3 to 10.

The electrode of the present invention can be used as a battery electrode or a chemical reaction tank electrode.

Suitable for use in sensor electrodes, fuel cell electrodes, bioreactor electrodes, etc.

In this case, a biosensor made by combining an oxidoreductase and the modified electrode of the present invention is suitable as a sensor configuration. In addition, when creating such a biosensor, conductive polymer substances such as benzoquinone, ferrocene, and
Mediator substances such as chloranyl, thionine, and potassium ferricyanide can be used in combination, but this has the effect of expanding the measurable substrate concentration range.

As explained above, the electrode of the present invention has high functionality suitable for use in battery electrodes, chemical reaction tank electrodes, sensor electrodes, fuel cell electrodes, bioreactor electrodes, etc. Compared to the fund a electrode? It is superior in production cost for Li electrodes.

EXAMPLES Hereinafter, the present invention will be specifically explained with reference to Examples and Comparative Examples; however, the present invention is not limited to the following Examples.

〔Example〕

Palladium was sputtered onto a 21 square polyethylene terephthalate film having a thickness of 125 μm until the electrical resistance reached IKΩ. Next, polyaniline was kneaded and coated on the sputtering surface of this film using a 10-inch Teflon disk version.

Qualified. Furthermore, glucose oxidase was immobilized using glutaraldehyde to create a # bare electrode. This electrode is used as a glucose sensor electrode, and the material cost is 50 yen.
．． It showed a current response of 6 μA.

[Comparative example]

Glucose oxidase was immobilized on a 2 cm square, 100 μ thick platinum plate using glutaraldehyde to create an enzyme electrode for a glucose sensor. The material cost of this electrode is 6
,000 yen, and the current response to 100 μ/dll of glucose was 12 μA.

Applicant Brideston Co., Ltd. Agent: Patent Attorney Takashi Kojima

Claims (1)

[Claims] 1. Forming a noble metal thin film layer on a non-conductive substrate,
An electrode characterized in that the surface of the noble metal thin film layer is modified with a mediator. 2. The electrode according to claim 1, wherein the mediator is a conductive polymer substance. 3. The electrode according to claim 2, wherein the conductive polymer material is polyaniline or a derivative thereof. 4. The electrode according to any one of claims 1 to 3, wherein the noble metal is palladium.