JPS63311157A - Ion sensor - Google Patents

Abstract

PURPOSE:To broaden the region in which the concentration of hydrogen ions can be measured, by using a specified copolymer as a sensitive material. CONSTITUTION:A copolymer film comprising two or more kinds of compounds (A), which have atoms. (atomic group) in a molecule, is deposited on the surface of a substrate comprising a conductor, a semiconductor or nonconductor. Hydrogen ions can be added to or eliminated from said atoms. It is desirable that the atoms. (atomic group) of the compound A are the radical of -NH2, -NH-, =N-, -OH or -O-. Aniline, 1,2 diaminobenzene and the like can be used as the compound A. It is desirable that the film is formed by an electrolytic oxidation copolymerization method. In this way, an ion sensor, which can measure the concentration of hydrogen ions stably in a broad rage and whose detecting part can be miniaturized, is obtained.

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to a novel ion sensor, and more specifically,
By using a copolymer of two or more compounds that can add and desorb hydrogen ions as a sensitive material, hydrogen ion concentration can be stably measured over a wide range, and the detection part can be miniaturized. Regarding possible ion sensors.

Conventional techniques and problems to be solved by the invention Conventionally, it has been known to use an ion electrode, which is a type of ion sensor, as a means of measuring the ion concentration in a solution, etc. Until now, various ion electrodes have been used. It has been developed and used in a variety of fields, including wastewater measurement, environmental pollution monitoring, process control in factories, and clinical testing in hospitals.

Among these electrodes for measuring hydrogen ion concentration,
Hydrogen electrodes, quinhydrone electrodes, glass electrodes, etc. are known, and glass electrodes in particular are widely used for their performance, but due to their structure, it is necessary to provide a reference liquid chamber inside the electrode. Therefore, the detection section becomes large, and it is not possible to meet the current demand for miniaturization of sensors. In addition, glass electrodes have drawbacks such as the large membrane resistance of the glass membrane, which requires an amplifier with high input impedance for pH measurement, and measurement difficult in solutions where there are substances that may adhere to the glass membrane. .

On the other hand, as an ion sensor that can be miniaturized and eliminates the above-mentioned problems of the glass electrode, a polymer film of hydroxy aromatic compound is directly deposited on the surface of the conductor (Japanese Patent Laid-Open No. 57
118153), and one in which a polymer film of a nitrogen-containing aromatic compound or a hydroxy aromatic compound is directly deposited on the surface of a conductor (Japanese Patent Laid-Open No. 58-32155) has been proposed.

However, the sensor using a homopolymer film of a nitrogen-containing aromatic compound or a hydroxy aromatic compound described in the examples of the above publication has a pH of about 2 to 10 even if the measured value satisfies the Nernst equation. Therefore, the measurable hydrogen ion concentration range is narrow. For this reason, the reality is that the above-mentioned sensor has not yet been put into practical use.

The present invention was made in view of the above circumstances, and an object of the present invention is to provide a practically useful ion sensor that has a wide measurable range of hydrogen ion concentration in an ion sensor using a polymer of a specific compound as a sensitive membrane. shall be.

Means and Effects for Solving the Problems In order to achieve the above object, the inventors of the present invention conducted intensive studies and found that -NH2 group, -NH- group,
Copolymerizing two or more monomers of an aromatic compound having an atom or atomic group (hereinafter simply referred to as a hydrogen ion functional part in some cases) capable of adding and desorbing hydrogen ions such as -OH group. , when a sensor is constructed by applying this copolymer as a sensitive film to a substrate made of a conductor, semiconductor, or nonconductor; when a homopolymer film of a nitrogen-containing aromatic compound or a hydroxyaromatic compound is used; The present inventors have discovered that it is possible to obtain a sensor that exhibits a Nernst response in a wider concentration range than in the conventional method, and have accomplished the present invention.

Therefore, the present invention provides a method for applying a copolymer film of two or more aromatic compounds having atoms or atomic groups capable of adding and desorbing hydrogen ions to a substrate made of a conductor, a semiconductor, or a nonconductor. An ion sensor is provided, characterized in that the ion sensor is formed by adhering to the surface of the ion sensor.

By having the above-described structure, the sensor of the present invention has a pno. A linear relationship is established between electromotive force and pH over a wide concentration range of , 5 to 13.5, and the measurement range is almost the same as that of a glass electrode.

The present invention will be explained in more detail below.

The sensor of the present invention has a copolymer film of an aromatic compound having a hydrogen ion functional moiety adhered to the surface of a substrate.

In this case, there are no limitations on the type of aromatic compound used for copolymerization, but there are -NH2 groups, -
It is preferable to use two or more types of compounds having one or more types of NH- group, diN- group, -OH group, and -〇- group, and in particular, the following general formula (1) (however, (1) to (3) ) In the formula, Ar is an aromatic nucleus, R and R' are substituents, m is O or an integer of 1 or more, n is an integer of 1 or more, and m+n does not exceed the effective valence number of Ar.However, Ar is nitrogen It may be a heteroaromatic ring containing atoms, in which case n may be 0.) Two or more of the compounds shown below are preferably used.

In this case, the compounds of formulas (1) to (3) above are specifically aniline, 2-methylaniline, 3-methylaniline, 4-methylaniline, 1,2-diaminobenzene, 1,3-diaminobenzene. , 1,4-diaminobenzene, 2-aminobenzotrifluoride, 2-aminopyridine, 2,3-diaminopyridine, 4,4'-diaminodiphenyl ether, 4,4'-methylenedianilintyramine, 4-hydroxydiphenylamine, pyrrole,
Phenol, 4-phenoxyaniline, 4-phenoxyphenol, 4-aminodiphenylamine, 2-aminophenol, 3-aminophenol, 4-aminophenol, hydroquinone, dimethylphenol, hydroxypyridine, 2-hydroxybenzaldehyde, 3-hydroxybenzaldehyde, 4-hydroxybenzaldehyde, 2-hydroxyacetophenone, 3-hydroxyacetophenone, 4-hydroxyacetophenone, 2
-Hydroxypropiophenone, 3-hydroxypropiophenone, 4-hydroxypropiophenone, 2-benzophenol, 3-benzophenol, 4-benzophenol, 2-hydroxybenzophenone, 3-hydroxybenzophenone, 4-hydroxybenzophenone,
2-carboxyphenol, 3-carboxyphenol, 4-carboxyphenol, diphenylphenol,
2-methyl-8-hydroquinoline, 1-birenamine, 1
-aminoanthracene and the like, but are not limited thereto. Among these, particularly preferred are aniline, 1,2-diaminobenzene, 4-
Hydroxydiphenylamine, phenol, 4,4'-
They are two or more of diaminophenyl ether, pyridine, 2-aminophenol, 4-phenoxyphenol, 4-phenoxyaniline, 4-aminodiphenylamine, and 1-pyrenamine.

In this case, the combination of compounds to be copolymerized is not limited, but it is particularly preferable to copolymerize two or more compounds containing aniline and/or 1,2-diaminobenzene, which widens the measurable range of ion concentration. A wide sensor can be reliably obtained.

Examples of combinations of such compounds include a combination of aniline and 1,2-diaminobenzene, a combination of aniline, 1,2-diaminobenzene and 4-hydroxydiphenylamine, and a combination of aniline, 1,2-diaminobenzene and 2-diaminobenzene. Examples include combinations of aminophenols.

Furthermore, the mixing ratio of monomers in copolymerization is not particularly limited, but the ratio (molar ratio) of the monomer added in the least amount to the monomer added in the largest amount among the monomers added is 0.05 or more, particularly 0.3. It is preferable that it is in the range of 1 to 1. If this ratio is less than 0.05, the effect of the smaller monomer added may not be apparent, and a wide measurable pH range may not be obtained.

There is no particular restriction on the method for obtaining a copolymer film from the monomers of the above compounds, and known polymerization methods such as chemical oxidation polymerization method and electrolytic oxidation polymerization method may be employed, but electrolytic oxidation copolymerization method is particularly preferred. For example, two or three types of monomers of the above compound may be used.
An electrolytically oxidized copolymer film can be obtained on a desired electrode by inserting the electrode into a solution containing at least one type of electrode and connecting an external power source so as to apply a positive voltage to the desired electrode. In this case, the method of electrolytic oxidative polymerization is not limited, and a constant current oxidative polymerization method, a constant voltage oxidative polymerization method, a potential sweep oxidative polymerization method, etc. are appropriately employed.

Furthermore, the material of the substrate used in the present invention is not particularly limited and may be appropriately selected from various conductors, semiconductors, or nonconductors, but noble metals such as platinum, gold, titanium, silver, copper,
It is preferable to use nickel, stainless steel, aluminum, carbon, silicon, germanium, silicon oxide, germanium oxide, tin oxide or indium oxide 11.

Further, the substrate may be a conductor, a semiconductor, or a nonconductor with another type of conductor, semiconductor, or nonconductor laminated on the surface by vacuum deposition, high-frequency sputtering, or the like.

There is no limit to the method of applying the copolymer film to the substrate, but for example, a method in which the substrate is used as an electrode in the electrolytic oxidation polymerization method described in (b) and the copolymer film is directly deposited and formed on this substrate (b); , a method of dissolving a copolymer film in a solvent, applying this solution to a substrate, and then removing the solvent to form a copolymer film can be suitably employed.

When measuring hydrogen ion concentration using the ion sensor of the present invention, the ion concentration is detected by electrode potential or current response, but in this case, the sensor of the present invention does not require an internal reference liquid chamber like a glass electrode. Therefore, it is possible to miniaturize the detection section, and for example, by combining it with a field effect transistor, it is possible to create an ultra-small sensor.

Moreover, it is extremely useful in practice, as it can be used alone as a pH sensor, and can also be integrated with other sensors to form a composite sensor.

Furthermore, the ion sensor of the present invention can be made by coating the copolymer membrane surface with a film of polystyrene, polycarbonate, polyvinyl chloride, polyvinylidene chloride, etc. that has hydrogen ion permeability, or by supporting a neutral carrier or an ion-sensitive substance. It may be coated with a polymer material, which can protect the copolymer film.

As described in detail, the ion sensor of the present invention is a copolymer of two or more aromatic compounds having atoms or atomic groups capable of adding and desorbing hydrogen ions in the molecule. By using a sensitive membrane, the hydrogen ion concentration can be measured over a wide range, and the detection section can be miniaturized, making it extremely useful for practical use.

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

Example 1 A 0.2M aqueous sodium sulfate solution containing 50mM aniline monomer and 50mM 1,2-diaminobenzene monomer adjusted to pH 1 with sulfuric acid was used as the polymerization solution, and a working electrode made of a platinum plate was prepared by the three-electrode method. An electrolytically oxidized thin film in which aniline and 1,2-diaminobenzene were copolymerized was formed on a (substrate) to obtain a sensor. In this case, a platinum plate was used as the counter electrode, and a silver/silver chloride electrode (Ag/Ag'') was used as the reference electrode.The thin film was prepared using a potential sweep method with voltages ranging from -0.2v to +1.2■vs. A g
/A g+ potential range at a sweep rate of 50 mV/S
This was done by performing a 0 cycle potential sweep.

Next, the obtained thin film coated sensor was washed with water, and then immersed in a pH-adjusted sample solution, and the electromotive force was measured using the reference electrode as a reference. In this case, the sample solution used was a 0.2 M sodium sulfate aqueous solution to which sulfuric acid or sodium hydroxide 11 was added to adjust the pH value, and the reference electrode was a silver/silver chloride electrode.

The relationship between the obtained electromotive force and the pH of the sample is shown by O in Figure 1, and this sensor has an inclination of 61 m in the pH range of 0.5 to 12.
It was confirmed that the sensor of the present invention had a wide measurable range, showing a highly linear V/pH response.

After the above measurement, the sensor was washed with water, dried, and placed in the air for 2 hours.
After storing for 5 days, the relationship between electromotive force and pH was investigated in the same manner as above. The results are shown in Figure 1 with a Nernstian response between the electromotive force and pH even after storage for 25 days, with a slope of 59 mV/pH in the pH range of 0.5 to 12.
It showed a response with good linearity. Therefore, from this result, it is recognized that the present sensor does not deteriorate even when stored in air and exhibits extremely excellent performance as a sensor for measuring hydrogen ion concentration.

Example 2 A 0.2M aqueous sodium sulfate solution containing 50mM aniline monomer, 50mM 1,2-diaminobenzene monomer and 50mM 4-hydroxydiphenylamine monomer was adjusted to pH 0.8 with sulfuric acid and used as a polymerization solution, Using the three-electrode method, aniline, 1,2-diaminobenzene, and 4
- Hydroxydiphenylamine was copolymerized to form an electrolytic oxidation polymerized thin film to obtain a sensor. Note that the same counter electrode and reference electrode as in Example 1 were used.

In addition, the thin film was prepared by the potential sweep method at 10.2V-+
The measurement was carried out by sweeping the potential in a potential range of 1 + 2 V vs. A g /A g+ for 40 cycles at a sweep rate of 50 mV/S.

Next, after washing the obtained thin film coated sensor with water, Example 1
The response of the electromotive force to the pH of the solution was investigated using the same method. The results are shown in Figure 2. As is clear from Figure 2,
This sensor has a slope of 33 mV/p in the pH range of 0.5 to 13.
It exhibited a highly linear H response and was extremely excellent as a sensor for measuring hydrogen ion concentration.

Comparative Example 1 0.2M containing only 50mM aniline as monomer
Using an aqueous sodium sulfate solution adjusted to pH 1 with sulfuric acid as the polymerization solution, an electrolytically oxidized polymer thin film made of polyaniline was formed on a working electrode (substrate) made of a platinum plate by a three-electrode method to obtain a sensor. Note that the same counter electrode and reference electrode as in Example 1 were used. In addition, the thin film was prepared using the potential sweep method at 10, IV-+0.8V v
s.

15 at a sweep rate of 50 mV/S over the Ag/Ag+ potential range.
This was done by performing a 0 cycle potential sweep.

Next, after washing the obtained thin film coated sensor with water, Example 1
The response of the electromotive force to the pH of the solution was investigated using the same method. As a result, this sensor showed a linear relationship with a slope of 57 mV/pH in the narrow range of p'H3 to 9, but did not show a Nernstian response in other parts.

Comparative Example 2 A 0.2M aqueous sodium sulfate solution containing only 50mM of 1,2-diaminobenzene as a monomer and adjusted to pH 1 with sulfuric acid was used as the polymerization solution, and a working electrode (substrate) made of a platinum plate was prepared by the three-electrode method. ) on poly(1,
A sensor was obtained by forming an electrolytically oxidatively polymerized thin film consisting of (2-diaminobenzene). Note that the same counter electrode and reference electrode as in Example 1 were used. In addition, the thin film was prepared by the potential sweep method at 10,2V-+ 1.2V vs. Ag/A
The test was carried out by sweeping the g+(7) potential range for 150 cycles at a sweep rate of 50 mV/S.

Next, after washing the obtained thin film coated sensor with water, Example 1
The response of the electromotive force to the pH of the solution was investigated using the same method. As a result, this sensor showed a linear relationship with a slope of 58 mV/pH in the narrow range of pH 5 to 10.5, but did not show a Nernstian response in other parts.

lb- From the above results, it was confirmed that the sensor of the present invention using a copolymer film has a wider measurable range of ion concentration than the conventional sensor using a homopolymer film.

[Brief explanation of the drawing]

FIGS. 1 and 2 are graphs showing the relationship between the pH of a sample solution and the electromotive force of the sensor of the invention when the pH of the sample solution is measured by the sensor of the invention, respectively. Applicant Brideston Co., Ltd. Agent Patent Attorney Takashi Kojima 10
ISUS; IQ
IRIP)-1 Procedural amendment (voluntary) July 14, 1988 1, Indication of the case 1988 Patent Application No. 146781 2, Name of the invention Ion sensor 3, Person making the amendment Relationship to the case Patent Applicant address: 10-1 Kyobashi-chome, Chuo-ku, Tokyo
Name (527) Representative of Brideston Co., Ltd.
House: 4th year of Showa, Agent: 104 Address: 5th floor, Dapa Create Building, 3-11-14 Ginza, Chuo-ku, Tokyo Phone: (545) 64546 Contents of amendment (2) On page 15, line 16 of the same: "150 cycles" should be corrected to "40 cycles."that's all

Claims (1)

[Claims] 1. A copolymer film of two or more aromatic compounds having atoms or atomic groups capable of adding and desorbing hydrogen ions in the molecule as a conductor, semiconductor, or nonconductor. An ion sensor characterized by being adhered to the surface of a base made of. 2. The atom or atomic group capable of adding and desorbing hydrogen ions is -NH_2 group, -NH- group, =N- group,
The ion sensor according to claim 1, which is an -OH group or an -O- group. 3. The ion sensor according to claim 1 or 2, wherein the copolymer film is formed by an electrolytic oxidation copolymerization method. 4. The ion sensor according to any one of claims 1 to 3, configured as a pH sensor.