JPH037263B2 - - Google Patents

Description

〔Technical field〕

The present invention relates to an ion selectively permeable/redox functional membrane having an ion selectively permeable layer and a redox reaction functional layer, and in particular, an ion selectively permeable and redox functional membrane that can maintain a redox reaction function for a relatively long period of time. Concerning permeable/redox functional membranes. [Prior Art and Problems] Research is becoming more active in exploring new functionality by holding various compounds on the surface of conductors. However, many compounds having functionality, such as redox reaction functionality, are difficult to stably hold on the surface of a conductor and maintain their functionality over a long period of time. Purpose of the Invention The purpose of the present invention is to provide ion selective permeability and redox function that can selectively transmit specific ions in a sample solution and maintain the redox reaction function with the ions for a relatively long period of time. The goal is to provide a sexual membrane. According to the present invention, the redox reaction functional material layer has one surface that is in contact with the conductive surface, and the polymer layer that has ion selective permeability that is in contact with the other surface. Provided is an ion-selective permselective/redox functional membrane characterized in that the functional material is comprised of a polymeric metal complex compound or a polymer-polymer charge transfer type complex. Generally, the material having the redox reaction function is a polymer metal complex compound or a polymer-polymer charge transfer type complex. Further, the polymer having ion selective permeability is selected from the group consisting of polyfluorosulfonic acid resin, cellulose polymer, polyvinyl chloride and its copolymer, polyvinylidene chloride, silicone rubber, and polysulfone. Further, the conductor is usually formed by forming a layer of gold or a platinum-based metal on the surface of a conductive material other than a platinum-based metal by vacuum accumulation. DETAILED DESCRIPTION OF THE INVENTION The present invention will be described in detail below with reference to the drawings. FIG. 1 shows an embodiment in which the ion selectively permeable/redox functional membrane of the present invention is supported on a substrate. Conductive substances such as gold and platinum and SnO ₂ ,
A semiconductor material such as TiO _{2 ,} RuO 2 or In ₂ O ₃ is formed as a conductive thin film 12 on an insulating plate 11 such as glass or film by sputtering. Further, a layer 13 made of a material having a redox reaction function is formed on the surface of the thin film 12. Materials with this redox reaction function include ferrocene derivatives, polynitrostyrene, polyaniline, etc., which are polymeric compounds with redox reaction active centers, or polymeric metals in which a metal complex is coordinated to a polymeric ligand compound. Complex compounds, e.g. ruthenium complexes coordinated to polyvinylpyridine (PVP), or polymeric complex compounds created by electrostatic interactions between polyelectrolyte compounds and ionic species, e.g. protonated These include Mo(CN) ^3-/4-8 _complex fixed in a PVP membrane, and a complex compound of polyxylyl viologen and polystyrene sulfonic acid. This layer 13 can be formed on the thin film 12 by a casting method in which a solution of the above-mentioned polymer compound or polymer complex is applied onto the thin film 12. A membrane 14 of a polymer compound having ion-selective permeability is formed to cover the layer 13 . This polymer membrane 14 is made of cellulose-based polymers (cellulose, acetylcellulose, nitrocellulose, ethylcellulose, triacetylcellulose, cellulose acetate butyrate, etc.), polyvinyl chloride and its copolymers, polyvinylidene chloride, silicone rubber, fluorine It is made of resin (for example, polytetrafluoroethylene, polyfluorosulfonic acid resin, polysulfone, etc.). This polymer membrane 14 has a function of selectively transmitting predetermined ions, and also has the function of selectively transmitting the above-mentioned oxidation-reduction in a solution. It has a function of preventing a material having a reaction function from eluting into the solution and stably fixing the layer 13 to the thin film 12. Peripheral areas of the thin film 12, the redox reaction layer 13, and the polymer film 14. An insulating layer 15 made of, for example, epoxy resin is formed to cover the lead wire 16.
is connected to the thin film 12 via a silver paste 17, for example. Specific Effects of the Invention When a conductor coated with an ion-selective permselective/redox functional membrane having the above-described structure is immersed in an aqueous sample solution and its electrochemical response is examined, it is found that the oxidation-reduction film retained on the surface of the conductive thin film is The species undergo redox reactions by transfer of counterions through the ion-selective separation membrane. On the other hand, the polymer membrane does not allow redox species to pass through, suppresses diffusion into the solution, and contributes to retention stability on the surface. Examples are shown below. Example 1 A metal film was produced on a glass plate by sputtering method,
A lead wire was taken from one corner by contacting a copper wire with silver paste. Then 4.97 on the gold thin film
mmol/polyvinylpyridine (PVP; average degree of polymerization Pn=19 methanol solution and 25.0 mmol/
A K ₄ Mo (CN) ₈ aqueous solution was mixed by the casting method and formed into a film at room temperature, then Kyuprofan (trade name of copper ammonium cellulose manufactured by Asahi Kasei Corporation) was coated on top of it, and the area around the electrode was insulated with epoxy resin. (gold thin film/PVP ^- Mo(CN) ₈ /
A composition membrane electrode (Cuprofan membrane) was prepared. A three-electrode cell was used, with the membrane-coated electrode of the present invention as the working electrode, a platinum mesh as the counter electrode, and a saturated sodium chloride calomel electrode (abbreviated as SSCE) as the reference electrode.
using 0.2MCF ₃ COONa supporting electrolyte solution (PH
1.52) Measure the cyclic voltammogram of the redox reaction of Mo(CN) ₈ (sweep rate 100 mV/
After investigating the properties of the film, the oxidation peak (+0.6V vs. SSCE) and reduction peak (+0.45V
SSCE) was observed, and each peak gradually increased and became constant after 30 minutes, and even after 1 hour, it was observed that the peaks did not decrease and remained constant values. On the other hand, directly on the gold electrode (PVP−Mo
(CN) ₈ ) In the membrane-coated electrode, a redox peak appears at almost the same potential value (V vs. SSCE) as the above electrode, but the peak current decreases by about 30% within 1 minute after the electrode is immersed in the solution. It was observed that this peak current decreased to nearly zero within 30 minutes of scanning (Figure 3). Based on these findings, it was found that the Cyprofane membrane, as an ion-selective separation membrane, significantly contributes to the stability of adhesion of (PVP-Mo(CN) ₈ ) to the electrode surface. In addition, cellulose acetate or nitrocellulose membrane was used instead of the cyprofane membrane, and (metal membrane/PVP-Mo (CN) ₈ /cellulose acetate membrane) or (metal membrane/PVP-Mo
(CN) ₈ /nitrocellulose membrane) was used to measure the cyclic voltammogram in the same manner as above, and the properties of the membrane were investigated.
0.64V vs. SSCE) and reduction peak (+0.33V vs.
The peak current of SSCE) gradually increased and remained at a constant saturation value even after 30 minutes and several hours. Therefore, it was found that the cellulose acetate membrane and the nitrocellulose membrane are protective membranes and ion selectively permeable membranes that stably hold the (PVP-Mo(CN) ₈ ) membrane on the surface of the thin gold membrane. Examples 2 to 4

[Table] As an ion permselective/redox functional membrane,
Using cyprofan and cellulose acetate,
Membrane electrodes having the compositions listed in Table 1 above were prepared by changing the chemical species retained on the electrode surface. The electrode manufacturing method will be described below. Example 2: A 4.97 mmol/PVP methanol solution and a 19.1 mmol/K ₄ W(CN) ₈ aqueous solution were mixed and formed into a film by a casting method on a gold thin film, and then a Cuprofane film was coated to produce an electrode. Example 3: 1% by weight of polym-xylylviologen (m-PXV)-polystyrene sulfonic acid (PSS) complex (mixed molar ratio 1:2) was deposited on a gold thin film.
A film was formed using a NaBr/H ₂ O/acetone (30/55/15) solution by a casting method, and then a cyprofen film was coated to prepare an electrode. Example 4: A dichloromethane solution of 1% by weight polyvinylferrocene (PVF) was formed on a gold thin film by a casting method, and then a cellulose acetate film was coated to prepare an electrode. The composition membrane electrode listed in Table 1 above
0.2MCF ₃ COONa (PH6.86) or 0.2MNaClO ₄
Example 1
As a result of measuring the cyclic voltammogram and examining the properties of the membrane using the same method as above, the peak potential values of oxidation and reduction waves were shown in Table 1, and the peak current gradually increased for all composition membrane electrodes30. After minutes,
It was observed that the peak current connects to a constant saturation value without decreasing. On the other hand, with electrodes in which only a thin gold film is coated with a (PVP-W(CN) ₈ ) film, (m-PXV-(PSS) ₂ ) film, or a PVF film, the sweep
It was observed that the peak current decreased to near zero within 30 minutes. Therefore, the ion-selective permselective/redox functional membrane of the present invention coated with a cyprofane membrane and a cellulose acetate membrane has (PVP-W(CN) ₈ ), (m-PXV-
It was found that redox substances such as (PSS) ₂ ) or PVF can be stably retained. Example 5 As shown in FIG. 4, polyamide film 21
A platinum thin film 22 is coated on the surface by a sputtering method,
Next, on the platinum thin film 22, 4.97 mmol/PVP methanol solution and 25.0 mmol/K ₄ Mo (CN) ₈ aqueous solution were mixed at room temperature by a casting method to form a film 23. A resin (trade name) membrane 24 was coated thereon, and this thinly coated electrode was packed with silicone rubber 25 having holes (φ6.4 mm) on both sides. As shown in FIG.
Sandwich it in between and secure the outside with a spring-loaded clasp.
A cyclic voltammogram was measured in the same manner as in Example 1 to examine the properties of the membrane. in this case,
Table 2 shows the peak potential of the redox wave of Mo(CN) ₈ complex.
It is shown in 5-A. It was observed that the peak current value maintained a constant saturation value without decreasing even after 30 minutes had passed after the start of potential scanning. Therefore,
It was found that the electrode with this composition can prevent the (PVP-Mo(CN) ₈ ) polymer complex supported on the conductor surface from eluting out of the electrode, and can incorporate counterions in the electrolyte solution. Ta. Same as above (polyamide/platinum thin film/
A PVP-Mo(CN) ₈ /naf ion) composition electrode was prepared, and all surfaces other than those in contact with the napf ion measurement sample solution were coated with epoxy resin. Using this electrode, we measured the cyclic voltammogram in the same manner as in Example 1 to examine the properties of the membrane. As a result, the peak current value did not decrease even after 30 minutes had passed after potential scanning, but remained at a constant saturation level. It was observed that the value persisted. As a result, it was found that the (PVP-Mo(CN) ₈ ) film was stably maintained on the conductor surface by coating with naphion. It was also found that it has an ion selective permeation function. The above results are shown in Table 2.

[Table] Example 6 A thin platinum film was coated on the surface of a polyamide film by a sputtering method, and then 4.97 mmol/PVP methanol solution and 25.0 mmol/
K ₄ Mo (CN) ₈ aqueous solution was mixed at room temperature by the casting method to form a film, then nitrocellulose was coated on top of it, packed with perforated silicone rubber from both sides, and sandwiched between frosted glass plates as shown in Figure 5. The cyclic voltamgram was measured in the same manner as in Example 1 to investigate the properties of the film.
As shown in A), it was observed that the peak current value did not decrease even after 30 minutes and maintained a constant saturation value. Therefore, the composition membrane electrode prepared in this study was supported on the surface of the conductor (PVP-Mo
(CN) ₈ ) It was found that it has the property of preventing the polymer complex from eluting outside the electrode and allowing the counter ions in the electrolyte to be taken into the electrode. Same as above (polyamide/platinum thin film/
A PVP-Mo(CN) ₈ /nitrocellulose) composition electrode was prepared, and all surfaces other than those in contact with the napfion measurement sample solution were coated with epoxy resin. Using this electrode, a cyclic voltammogram was measured in the same manner as in Example 1. As a result, the redox potential was as shown in 6-B in Table 3, and the peak current value was 30
It was observed that a constant saturation value was maintained without decreasing even after minutes had passed. As a result, it was found that the membrane of the present invention coated with nitrocellulose is a protective membrane that stably maintains the (PVP-Mo(CN) ₈ ) membrane on the surface of the conductor and a membrane permeable to counterions.

[Table] Example 7 A platinum thin film was prepared on the surface of a Nafion (manufactured by Dupont) membrane by a sputtering method or an electroless plating method, and then 4.97 mmol/PVP methanol solution and 25.0 mmol/K ₄ Mo were deposited on the platinum thin film. (CN) ₈ aqueous solution was mixed and formed into a film at room temperature by the casting method, then Nafion was coated on top of it, and the electrode was insulated with epoxy resin. Platinum thin film/PVP-Mo
(CN) ₈ /nafion) composition electrode was fabricated. This electrode was immersed in a supporting electrolyte solution of 0.2MCF ₃ COONa (PH1.5), and the cyclic voltammogram was measured in the same manner as in Example 1 to examine the membrane characteristics. As a result, the peak current gradually increased. Then, after 30 minutes,
It was observed that the peak current did not decrease and maintained a constant value. Therefore, it was found that the composition film electrode prepared in this way has the effect of stably holding a (PVP-Mo(CN) ₈ ) film on the surface of the conductor. Specific Effects of the Invention The ion selectively permeable/redox functional membrane of the present invention described above has the redox reaction function by covering the material layer having the redox reaction function with an ion selectively permeable polymer membrane. The material layer having the above structure can be stably held on the conductive surface, and its function can be fully expressed. Furthermore, since the ion electrode of the present invention has the ion selectively permeable membrane as described above, it is possible to selectively sensitize the material layer to specific ions. Therefore, the ion selective permeability/redox functional membrane of the present invention has the following characteristics:
By bonding the redox reaction functional material layer to a conductor, it can become an ion electrode for detecting the concentration of the specific ion.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the ion-selective/redox functional membrane of the present invention supported on a base, in which A is a plan view, B is a cross-sectional view along line B-B of A, and FIG. Figures 2 and 3 are cyclic voltammograms of the ion-selective/redox-functional membrane of the present invention and a comparative example, respectively, and Figure 4 is a cross-section of the ion-selective/redox-functional membrane of the present invention with another structure. Figure 5 is a cross-sectional view of an apparatus consisting of a ground glass plate and an electrolyte chamber for examining cyclic voltammograms. 12, 22... Conductor, 13, 23... Redox reaction functional film, 14, 24... Protective film.

Claims (1)

[Scope of Claims] 1. A redox-reactive functional material layer having one surface in contact with a conductive surface, and a polymer layer having ion selective permeability in contact with the other surface,
An ion selective permeability/redox functional membrane characterized in that the redox reaction functional material is composed of a polymer metal complex compound or a polymer-polymer charge transfer type complex. 2. A patent claim in which the polymer having selective ion permeability is selected from the group consisting of polyfluorosulfonic acid resin, cellulose polymer, polyvinyl chloride and its copolymer, polyvinylidene chloride, silicone rubber, and polysulfone. The ion selective permeability/redox functional membrane according to item 1.