JPH03287060A - Solid-state chemical sensor - Google Patents

Abstract

PURPOSE: To obtain a highly reliable solid chemical sensor in which drift is suppressed by providing an intermediate layer for establishing an equilibrium reaction in a polymer ion photosensitive membrane and/or a solid between them. CONSTITUTION: As a solid for forming an ion sensitive membrane, a silver plate 1 is immersed into a hydrochloric acid and a silver chloride layer 2 is formed on the surface of the silver plate 1 through electrolysis using a platinum counter electrode. The silver/silver chloride electrode is then sealed with epoxy resin 5 except a detecting part 3 and a take-out electrode 4. Subsequently, agar of KCl solution is injected into the surface of the silver plate 1 at the detecting part 3 and eventually cooled to form a gel intermediate layer 6. A potassium-sensitive membrane 7 composed of polyvinyl chloride, bis, adipate, etc., is formed on the intermediate layer 6. Consequently, the potential on the interface of the solid/intermediate layer and the intermediate layer/ion sensitive membrane is stabilized electrochemically resulting in a highly accurate analysis.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a solid chemical sensor for a chemical analysis device used for medical measurement or environmental measurement.

[Prior Art] Conventionally, sensors of chemical analyzers are used for medical measurement (for example, electrolytes in blood) or environmental measurement.

Ion-sensitive membranes were formed directly on solids [Analytical Chemistry (Anal, Chem), Vol.
Volume 7, No. 13 (1975) pp. 2238-2243,
Volume 46, No. 14 (1974) No. 2223-22
24 pages].

In addition, in order to improve the drift of solid-state chemical sensors in which an ion-sensitive film made of polyvinyl chloride is formed directly on a solid, carbon is coated on the Ag or A g /A g CA electrode, and an ion-sensitive film is placed on top of it. A method for forming [Ursula oesterli;
Diploma thesis, Swiss Federal Institute of Technology, Zurich (1989) (Ursula Oesterle:
Diplomarbeit.

Eidgen;5sische Technfsch
[Problems to be Solved by the Invention] In the sensors of the prior art, since the polymer ion-sensitive membrane is directly formed on a solid such as a metal or an insulator, The exchange reaction of charged particles such as ions or electrons between the solid state and the ion-sensitive membrane is not easy, and as a result, the potential at the solid/ion-sensitive membrane interface is not electrochemically determined, and the sensor suffers from large drifts and is unreliable. There was a problem that it was missing.

Further, the exchange reaction of charged particles such as ions or electrons was insufficient to the extent that the Ag or Ag/Ag CQ electrode was coated with carbon.

An object of the present invention is to provide a solid-state chemical sensor that keeps the potential between a polymer ion-sensitive membrane and a solid stable and has low drift and high reliability.6 [Means for Solving the Problems] In order to achieve the object, an intermediate layer is provided that can easily form an equilibrium reaction with a polymer ion-sensitive membrane and/or a solid, and the gist of the present invention is as follows.

(1) In a solid-state chemical sensor having a polymer ion-sensitive membrane on a metal or inorganic solid, an intermediate is provided between the polymer ion-sensitive membrane and the solid to establish an equilibrium reaction in the polymer ion-sensitive membrane and/or the solid. A solid-state chemical sensor characterized by having layers.

(2) In a solid-state chemical sensor having a polymer ion-sensitive membrane on a metal or inorganic solid, a hydrophilic gel containing a target ion or a conductive gel containing the gel is provided between the polymer ion-sensitive membrane and the solid. A solid-state chemical sensor characterized by having an intermediate layer made of powder.

(3) In a solid-state chemical sensor having a polymer ion-sensitive membrane on a metal or inorganic solid, the solid is platinum, gold, silver, silver/silver chloride, silicon dioxide, silicon nitride, or aluminum oxide.

It is a solid selected from tantalum pentoxide.

The polymer ion-sensitive membrane is composed of a base material, a plasticizer, and an ion-sensitive substance, wherein the base material is an organic polymer material and the plasticizer is bis(2-ethylhexyl)adipate [B15-(2-ethylhexyl)].
xyl) adipate), Bis(2-ethylhexyl) sebacate
) seba-cate, ) t tri-(2-ethylhexyl) trimellitite (tri-(2-ethy
lhexyl) trimellitate), ion sensitive substance is valinomycin, nonactin/monactin antibiotic, crown ether.

A solid selected from quaternary ammonium salts and metal porphyrins, characterized in that an intermediate layer is provided between the polymer ion-sensitive membrane and the solid to establish an equilibrium reaction in the polymer ion-sensitive membrane and/or the solid. chemical sensor.

(4) A solid-state chemical sensor having a polymer ion-sensitive membrane on a metal or inorganic solid, wherein the solid is silver tetraphenylborate, (sj
, 1vsr tetraphsnyl borate
), silver iodide
e), silver octadecanethiol (silver
A solid-state chemical sensor, the surface of which is chemically modified with a substance selected from octadecan thyoL.

(5) In a solid-state chemical sensor having a polymer ion-sensitive membrane on a metal or inorganic solid.

A solid-state chemical sensor characterized in that an intermediate layer made of conductive powder containing a highly lipophilic substance is provided between the polymer ion-sensitive membrane and the solid.

(6) Field-effect transistor with gate insulating film (
Insulated Gate Field Effe
A polymer ion sensitive film is provided on the surface of the polymer ion sensitive film and the insulating film, and an intermediate layer is provided between the polymer ion sensitive film and/or the insulating film to establish an equilibrium reaction in the polymer ion sensitive film and/or the insulating film. A solid-state chemical sensor characterized by:

The intermediate layer for establishing the above equilibrium reaction is a gel material containing target ions, such as agar, polyacrylamide, dextran, poly(2-
Hydroxydityl methacrylate) (p-HE
M A ) is used. Also, carbon, silver, gold,
More preferably, a conductive powder such as platinum is impregnated with the gel.

In the above structure, target ions can be easily exchanged at the interface between the ion-sensitive membrane and the gel, and electrochemical equilibrium can be easily achieved at both interfaces.

Also, using silver/silver chloride (Ag/AgCQ) as a solid,
In a system where the gel is wetted with a chloride solution of the target ion, there is a relationship between the solid (A g CQ ) and the chloride ion-containing gel (
1) The equilibrium reaction of equation 1 is established, and the gel/solid interface can also reach electrochemical equilibrium.

AgC flood: A g ” + CQ-・・・・・・・・・
・(1) Furthermore, a highly lipophilic substance such as iodine is contained in the conductive powder layer, so that iodine or iodine ions (I '', I '') flow through the conductive powder layer and the ion-sensitive membrane. It is also good to use a system that can be easily moved.

Furthermore, in order to establish an equilibrium reaction between the solid and the ion-sensitive membrane, a substance that generates lipophilic anions by dissociation, such as Ag-tetraphenylborate, is introduced onto the solid surface, and then Form an ion-sensitive membrane directly.

The above-mentioned ion-sensitive membrane can be formed by dissolving the ion-sensitive membrane material in an organic solvent and coating it, or in systems using the conductive powder, by penetrating it into the conductive powder layer by capillary action. A transition region consisting of a mixture of the membrane and the conductive powder is formed between the membrane and the conductive powder.

[Function] The intermediate layer formed between the polymer ion-sensitive membrane and the solid is
Since an equilibrium reaction is established between the two, the potential at each interface between the ion-sensitive membrane/intermediate N/solid is determined electrochemically. Therefore, the potential of a solid-state chemical sensor having an ion-sensitive membrane/intermediate layer/solid structure is stable and has small drift.

The mechanism of the equilibrium reaction differs depending on the material used as the intermediate layer.1 For example, if a gel of a chloride solution (wetted) of the target ion is used as the intermediate layer and A g /Agcfl is used as the solid, the ion-sensitive membrane and the gel layer Equilibrium is established between the gel layer and A g / A g
Since the equilibrium reaction represented by the above formula (1) is established between Cn, electrochemical equilibrium can be reached as a whole.

Also, when the conductive powder contains iodine.

Since iodine is highly lipophilic, it easily diffuses into the ion-sensitive membrane and becomes ionized, and iodine ions are exchanged between the ion-sensitive membrane and the conductive powder to reach electrochemical equilibrium.

Furthermore, if molecules such as Ag-tetraphenylborate (Ag-TPB) that generate lipophilic anions upon dissociation are formed on the Ag solid surface and an ion-sensitive membrane is formed on it, the solid and the ion-sensitive membrane An exchange reaction of TPB ions occurs between the two, resulting in an electrochemical equilibrium, and the potential at the interface between the two becomes stable.

[Example] Hereinafter, the present invention will be specifically explained with reference to Examples.

[Example 1] Figures 1 and 2 are a cross-sectional view and a perspective view of a solid-state chemical sensor of this example.

As a solid for forming an ion-sensitive membrane, a silver plate 1 was immersed in a 0.1 molar hydrochloric acid solution, and a silver chloride layer 2 was formed on the silver surface by electrolysis using a platinum electrode as a counter electrode. This silver/silver chloride electrode is shown in FIG.

The detection part 3 and the extraction electrode part 4 were left and sealed with epoxy resin 5. And on the silver chloride surface of the detection part 3.

Inject 1M KCQ solution agar and cool to a thickness of about 1m.
A gel intermediate layer 6 of m was formed.

On this gel intermediate layer 6, a potassium ion sensitive membrane 7 of about 100 μm thick was formed, which was made of polyvinyl chloride (PVC), bis(2-ethylhexyl) adipate (DOA), and valinomycin.

It was made into a solid-state chemical sensor.

Instead of the above valinomycin, bis(12-crown-
4) Or by using a tetraoctadecylammonium salt, a sodium ion-sensitive membrane and a chloride ion-sensitive membrane can be obtained, respectively.

[Example 2] Figures 3 and 4 are a cross-sectional view and a perspective view of a solid-state chemical sensor of this example.

A silver film with a thickness of approximately 1 μm was formed on a glass substrate 8 by vacuum deposition, a silver electrode 9 was patterned by photolithography, and a silver chloride layer 2 was formed on the surface of the silver electrode by the method of Example 1.

As shown in FIG. 4, a frame 10 was formed on the glass substrate 9 using epoxy resin, and the gel intermediate layer 6 of Example 1 and the potassium ion sensitive film 7 were laminated within this frame.

[Example 3] FIG. 5 is a sectional view of the solid-state chemical sensor of this example.

Two n-type regions are provided on a part of the surface of the P-type silicon substrate 11, and are used as a source 12 and a drain 13, respectively.
0nm 8102 layer 14 and 1100n Si, N,
A gate insulating film consisting of layer 15 was formed to create an insulated gate field effect transistor.

A silver electrode 9 with a thickness of 1 μm was formed on the Si and N layers by vacuum evaporation and photolithography.

A silver chloride layer 2 was formed on the surface to form a floating gate electrode. Then, the source and drain electrode portions and the floating gate electrode portion were left and sealed with epoxy resin 5.

The gel intermediate layer 6 and potassium ion sensitive membrane 7 of Example 1 were laminated on the floating gate electrode.

[Comparative example]

FIG. 6 is a cross-sectional view of the solid-state chemical sensor of this comparative example.

The surface of the silver plate 1 was coated with carbon powder dispersed in a solvent and dried at 100° C. to form a carbon powder intermediate M16. As in Example 1, the detection part and the extraction electrode part were left and sealed with epoxy resin 5, and the ion-sensitive membrane 7 described in Example 1 was formed directly on the intermediate layer.

[Example 4] FIG. 7 is a sectional view of the solid-state chemical sensor of this example.

Electricity is applied between the silver plate 1 and the counter electrode platinum in a HI solution,
A silver iodide layer 7 was formed on the surface of the silver plate. Carbon powder dispersed in a solvent was coated on the silver iodide layer, and 100%
The carbon powder intermediate layer 16 was obtained by drying at .degree. C., and then placed in an iodine atmosphere to impregnate the carbon powder intermediate layer with iodine.

The ion-sensitive membrane 7 of Example 1 was formed on the iodine-impregnated intermediate layer.

[Example 5] FIG. 8 is a sectional view of the solid-state chemical sensor of this example.

A silver plate 1 is immersed in a sodium-TPB tetrahydrofuran (THF) solution, and a positive voltage is applied to the silver plate and a negative voltage is applied to the platinum using platinum as a counter electrode to form an Ag-TPB layer 18 on the surface of the silver plate. did. Then, as in Example 1, the detection part and the extraction electrode part were sealed with epoxy resin 5, and A g -
The ion-sensitive membrane 7 of Example 1 was directly formed on the TPB layer.

Note that the fourth and fifth embodiments can be applied to FIG.

That is, by replacing the silver plate l in FIG. 7.8 with the floating gate silver electrode 9 in FIG. 5 and applying the laminated structure specific to each embodiment as is, FET
(Field Effect Transistor)
type solid-state chemical sensor can be created.

The solid-state chemical sensors of each of the examples described above were installed in the flow cell shown in FIG. 9, and their characteristics were measured.

First, the sensor 19 is installed on a printed circuit board 20 on which a wiring pattern is formed, and the sensor and the printed circuit board are connected with aluminum wires 21, and connected to an external measurement circuit via pins 22 of the printed circuit board. In addition, an acrylic protective cover 23 is bonded with epoxy resin to protect the aluminum wire from the sample solution and to allow the analysis sample solution to contact only the detection part of the sensor.

Furthermore, block 2 on which a sample solution flow path is formed
4 and secure with screws 25. In order to prevent the sample solution from leaking, the block 24 and the protective cover 23 are brought into close contact using an O-ring 26.

The above flow cell is installed in the measurement system shown in FIG.

Five types of potassium chloride (KC flood) solutions ranging from 10-1 mol to 10-s mol were added to Ij11! ! I liquid 27, valve 2
8 and pump 29 to sequentially introduce it into the flow cell 30.

A reference electrode 31 of A g / A g CQ is provided downstream of the flow cell, and a reference electrode solution 32 (saturated KC
A mixture of Q solution and saturated AgCf1 solution) is introduced into the reference electrode 31 by the pump 33. The potential difference between the solid chemical sensor in the flow cell and the reference electrode is measured by a voltmeter 35 and recorded on a recorder 36. The sample liquid and reference electrode liquid for which the measurement has been completed are led to the waste liquid bottle 34. In addition, the solid line in the figure shows the flow path, and the broken line shows the electrical system.

What is the slope sensitivity of the solid-state chemical sensor of each example?

It ranged from 55 to 58 mV/decade.

Moreover, the results of measuring the stability of the solid-state chemical sensors of each example and comparative example are shown in FIG.

Each curve in the figure shows the change in potential over time in a 10-1 molar KCl2 solution.

Furthermore, as a conventional example, it can be seen that the solid-state chemical sensor of the example without the intermediate layer, that is, the sensor in which the ion-sensitive membrane is directly formed on a solid, has a large temporal change in potential and is inferior in stability.

Furthermore, it can be seen that in the comparative example using carbon as the intermediate layer, the potential changes over time are large and the stability is poor.

As mentioned above, it can be seen that the provision of the intermediate layer of the present invention significantly improves the potential stability.

[Effects of the invention] By providing an intermediate layer that can achieve an equilibrium reaction with the solid and the ion-sensitive membrane, the solid/intermediate layer and the intermediate layer/
This has the effect of electrochemically stabilizing the potential at the interface of the ion-sensitive membrane, making it possible to obtain a highly reliable solid-state chemical sensor with small drift. Therefore, the potential of the measurement system consisting of the reference electrode, sample solution, and solid-state chemical sensor is stabilized, and highly accurate analysis can be performed.

[Brief explanation of the drawing]

1, 3, 5, 7, and 8 are cross-sectional views of solid-state chemical sensors according to embodiments of the present invention, and FIG.
4 is a perspective view of FIG. 3, FIG. 6 is a cross-sectional view of a solid-state chemical sensor of a comparative example, FIG. 9 is a flow cell equipped with a solid-state chemical sensor of each of the above embodiments, and FIG. 10 is a perspective view of FIG. is a block diagram of the measurement system, and FIG. 11 is a graph showing the stability of the characteristics of each solid-state chemical sensor. DESCRIPTION OF SYMBOLS 1... Silver plate, 2... Silver chloride layer, 3... Detection part, 4
... Extraction electrode, 5... Epoxy resin, 6... Gel intermediate layer, 7... Potassium ion sensitive membrane, 8... Glass substrate, 9... Silver electrode, 10... Frame, 11
...Silicon substrate, 12...Source, 13...Drain, 14...Sin. Layer, 15... Si□N4 calendar, 16... Carbon powder intermediate layer. 17... Silver iodide layer, 18... Ag-TPB layer, 1
9... Solid chemical sensor, 20... Printed circuit board, 2
1... Aluminum wire, 22... Pin, 23... Protective cover 24... Channel block, 25... Screw, 2
6...0 ring, 27...standard solution, 28...valve, 29.33...pump, 30...flow cell,
3.Reference electrode, 32.Reference electrode liquid, 34.
...Waste liquid bolt, 35...Voltmeter, 36...Recorder. Attorney 6 Patent attorney 1 Akiyo Takahashi (Figure 5, Figure 6, Figure 8, Figure 1, Figure 2, Figure 3, Figure 3...Detection section 4...Extraction electrode 5...Epoxy resin, Figure 4, Figure 10...・) Shi・〜mu Figure 9 Nori/Tono IL4! i Anno 1 Miwire (11' Goryoku・+41 Michikawa Shii 11), Tsu30 No II+

Claims (1)

[Claims] 1. In a solid-state chemical sensor having a polymer ion-sensitive membrane on a metal or inorganic solid, there is provided a polymer ion-sensitive membrane and/or a solid between the polymer ion-sensitive membrane and the solid. A solid-state chemical sensor characterized by having an intermediate layer that establishes an equilibrium reaction. 2. In a solid chemical sensor having a polymer ion-sensitive membrane on a metal or inorganic solid, a hydrophilic gel containing target ions or a conductive powder containing the gel is placed between the polymer ion-sensitive membrane and the solid. A solid-state chemical sensor characterized by having an intermediate layer consisting of. 3. A solid-state chemical sensor having a polymer ion-sensitive membrane on a metal or inorganic solid, wherein the solid is selected from platinum, gold, silver, silver/silver chloride, silicon dioxide, silicon nitride, aluminum oxide, and tantalum pentoxide. The polymer ion-sensitive membrane is composed of a base material, a plasticizer, and an ion-sensitive substance, wherein the base material is an organic polymer material, and the plasticizer is bis(2-ethylhexyl) adipate.
Bis(2-ethylhexyl)sebacate, tri(2-
ethylhexyl) trimellitate is selected, the ion-sensitive substance is selected from valinomycin, nonactin/monactin antibiotics, crown ether, quaternary ammonium salt, metal porphyrin, and a polymer is selected between the polymer ion-sensitive membrane and the solid. A solid-state chemical sensor comprising an ion-sensitive membrane and/or an intermediate layer that establishes an equilibrium reaction in a solid. 4. In a solid-state chemical sensor having a polymer ion-sensitive membrane on a metal or inorganic solid, the surface of the solid is chemically modified with a substance selected from silver tetraphenylborate, silver iodide, and silver octadecanethiol. Characteristic solid-state chemical sensor. 5. In a solid chemical sensor having a polymer ion-sensitive membrane on a metal or inorganic solid, an intermediate layer made of conductive powder containing a highly lipophilic substance is provided between the polymer ion-sensitive membrane and the solid. A solid-state chemical sensor characterized by: 6. A field-effect transistor having a gate insulating film is provided with a polymer ion-sensitive film on the surface thereof, and an intermediate layer is provided on the polymer ion-sensitive film and/or the insulating film to establish an equilibrium reaction. solid state chemical sensor. 7. A solid chemical sensor having a polymer ion-sensitive membrane on a metal or inorganic solid, a flow path for introducing a sample into the sensor, a lead wire connected to the solid chemical sensor, and a wire connecting the sample to the lead wire. The solid chemical sensor has a protective cover that prevents contact with the lead wire and an external connection pin for the lead wire, and the solid chemical sensor is configured to establish an equilibrium reaction between the polymer ion sensitive membrane and/or the solid. A chemical analysis device having a flow cell characterized by providing an intermediate layer.