Prussian blue-supporting carbon-coated silica gel and method for producing the same

Abstract

To provide a PB-supporting carbon-coated silica gel suitable for use in electrochemical applications and easy in a production process, and a method for producing the same.SOLUTION: The method for producing a PB-supporting carbon-coated silica gel according to the present invention comprises the steps of: adding an iron cyano complex-containing solution to a container containing carbon-coated silica gel having a porous silica gel having a plurality of mesopores in which a carbon film is formed so as to cover continuously from the inner wall of the mesopores to the outer surface of the carbon-coated silica gel, such that the iron cyano complex is supported on the outer surface of the carbon-coated silica gel from the inner wall of the mesopores; removing a solvent from the iron cyano complex-containing solution to obtain a dry powder composed of carbon-coated silica gel supporting the iron cyano complex; adding an iron ion-containing solution to the dry powder and reacting the iron cyano complex with iron ions to produce Prussian blue from the inner wall of the mesopores to the outer surface of the carbon-coated silica gel; and removing a solvent from the iron ion-containing solution.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to carbon-coated silica gel with Prussian blue supported on its surface and a method for producing the same.

Background Art

[0002] Prussian blue, which has long been known as a blue pigment, can be used as a redox species in the field of electrochemistry and as an adsorbent for the radioactive element cesium in fields such as nuclear power. It is also expected to have various other applications. In recent years, its use as a compound that reacts with hydrogen peroxide in the field of sensors has been proposed. As a cesium adsorbent using Prussian blue, a cesium adsorbent has been proposed in which Prussian blue is provided on the surface of illite using illite as a support (Patent Document 1). The cesium adsorbent according to this Patent Document 1 treats illite with acrylic acid to modify the surface of illite to have carboxyl groups. Sodium chloride solution, iron chloride solution, and potassium ferrocyanide solution are sequentially injected into the surface-modified illite, and further, iron chloride solution is additionally injected to directly synthesize Prussian blue on the surface of illite surface-modified to have carboxyl groups, thereby providing Prussian blue chemically bonded at least partially to the surface of illite.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The cesium adsorbent using Prussian blue according to Patent Document 1 mentioned above has Prussian blue at least partially chemically bonded to the surface of the illite support, and therefore has the advantage that the binding performance of Prussian blue to the support is excellent and it is suitable for use in water. However, the cesium adsorbent according to Patent Document 1 has a problem in that the support is made of illite and has low electrical conductivity, making it unsuitable for electrochemical applications such as reference electrodes, hydrogen peroxide sensors, etc. In addition, in the manufacturing process, it is necessary to perform a surface treatment with acrylic acid or the like once to modify the illite surface, and then it is necessary to inject a sodium chloride solution, an iron chloride solution, and a potassium ferrocyanide solution in that order, and then to additionally inject an iron chloride solution, which makes the manufacturing process complicated. In view of the above-mentioned problems of the prior art, the inventors have an object to provide a Prussian blue-supported carbon-coated silica gel that is suitable for use in electrochemical applications and has a simple manufacturing process, and a manufacturing method thereof. In this specification, the Prussian blue-supported carbon-coated silica gel is referred to as PB-supported carbon-coated silica gel. [Means for solving the problem]

[0005] In order to achieve the above-mentioned object, the PB-supported carbon-coated silica gel according to the present invention is characterized by comprising: a carbon-coated silica gel having a porous silica gel having a plurality of mesopores, a carbon film formed so as to continuously cover from the inner walls of the mesopores to the outer surface; and Prussian blue supported on the inner walls of the mesopores and the outer surface of the carbon-coated silica gel. The method for producing PB-supported carbon-coated silica gel according to the present invention is as follows: a step of adding a solution containing an iron-cyano complex to a container containing a carbon-coated silica gel having a porous silica gel with a plurality of mesopores, the carbon film being formed so as to continuously cover the mesopore inner walls and the outer surface of the porous silica gel, thereby supporting the iron-cyano complex from the mesopore inner walls to the outer surface of the carbon-coated silica gel; A step of removing the solvent from the solution containing the iron-cyano complex to obtain a dry powder made of carbon-coated silica gel carrying the iron-cyano complex; adding an iron ion-containing solution to the dry powder, and reacting the iron cyano complex with the iron ions to generate Prussian blue from the inner walls of the mesopores to the outer surface of the carbon-coated silica gel; and removing the solvent from the iron ion-containing solution It consists of: In addition, the method for producing PB-supported carbon-coated silica gel according to the present invention is as follows: a step of adding an iron ion-containing solution to a container containing a carbon-coated silica gel in which a carbon film is formed so as to continuously cover from the inner walls of the mesopores to the outer surface of the porous silica gel having a plurality of mesopores, thereby supporting iron ions from the inner walls of the mesopores to the outer surface of the carbon-coated silica gel; A step of removing the solvent from the iron ion-containing solution to obtain a dry powder of carbon-coated silica gel carrying iron ions; adding a solution containing an iron cyano complex to the dry powder, and reacting the iron ions with the iron cyano complex to generate Prussian blue from the inner walls of the mesopores to the outer surface of the carbon-coated silica gel; and Removing the solvent from the iron cyano complex-containing solution It consists of: The iron cyano complex-containing solution may, for example, consist of a potassium ferrocyanide solution. The iron ion-containing solution may also consist, for example, of an iron (III) chloride solution. The solvent of the solution may be a mixed solvent of ethanol and water. The step of removing the solvent may be carried out under reduced pressure within the vessel. Effect of the Invention

[0006] The PB-supported carbon-coated silica gel according to the present invention includes a carbon-coated silica gel in which a carbon film is formed so as to cover continuously from the inner walls of the mesopores to the outer surface of the porous silica gel having a plurality of mesopores, and Prussian blue supported on the inner walls and outer surface of the mesopores in the carbon-coated silica gel, so that the Prussian blue can be present in close proximity to the carbon, and coupled with the high electrical conductivity of the carbon-coated silica gel, the PB-supported carbon-coated silica gel has high electron acceptance and good responsiveness. In addition, the carbon-coated silica gel has a large specific surface area, so that a large amount of Prussian blue can be supported, and when used as a material for a reference electrode or a working electrode of a hydrogen peroxide sensor, it becomes possible to prepare a highly reactive electrode. In addition, the method for producing PB-supported carbon-coated silica gel according to the present invention comprises the steps of: adding an iron-cyano complex-containing solution to a container containing carbon-coated silica gel in which a carbon film has been formed so as to continuously cover the inner walls of the mesopores of a porous silica gel having a plurality of mesopores from the outer surface, thereby supporting the iron-cyano complex from the inner walls of the mesopores to the outer surface of the carbon-coated silica gel; removing the solvent from the iron-cyano complex-containing solution to obtain a dry powder made of the carbon-coated silica gel supporting the iron-cyano complex; adding an iron ion-containing solution to the dry powder and reacting the iron cyano complex with the iron ions to produce Prussian blue from the inner walls of the mesopores to the outer surface of the carbon-coated silica gel; and removing the solvent from the iron ion-containing solution, thereby making the production easy. In addition, the method for producing PB-supported carbon-coated silica gel according to the present invention comprises the steps of: adding an iron ion-containing solution to a container containing carbon-coated silica gel in which a carbon film has been formed so as to continuously cover the inner walls of the mesopores of a porous silica gel having a plurality of mesopores from the outer surface, thereby supporting iron ions from the inner walls of the mesopores to the outer surface of the carbon-coated silica gel; removing the solvent from the iron ion-containing solution to obtain a dry powder made of the carbon-coated silica gel supporting iron ions; adding an iron cyano complex-containing solution to the dry powder and reacting the iron ions with the iron cyano complex to produce Prussian blue from the inner walls of the mesopores to the outer surface of the carbon-coated silica gel; and removing the solvent from the iron cyano complex-containing solution, thereby making the production easy. Since a potassium ferrocyanide solution can be used as the iron cyano complex-containing solution, it is easy to procure the raw material. In addition, since an iron (III) chloride solution can be used as the iron ion-containing solution, it is easy to procure the raw material. By using a mixed solvent of ethanol and water as the solvent for the solution, it is possible to promote the introduction of the iron cyano complex-containing solution and the iron ion-containing solution into the mesopores. The removal of the solvent can be accelerated by carrying out the step of removing the solvent under reduced pressure inside the container. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is a process diagram showing an example of an outline of a process for producing PB-supported carbon-coated silica gel according to the present invention. [Diagram 2] 4(a) and 4(b) show SEM images of the appearance of the carbon-coated silica gel and the PB-supported carbon-coated silica gel, respectively, observed with a scanning electron microscope. [Diagram 3] Electrodes were prepared using carbon-coated silica gel, and PB-supported carbon-coated silica gel, and the current-potential curves of each electrode were analyzed by the CV method. [Figure 4a] 1 is a graph showing the results of analyzing, by the CV method, the potential-current curves of evaluation electrode A prepared using carbon-coated silica gel, evaluation electrode B prepared using PB-supported carbon-coated silica gel, evaluation electrode C prepared using a material obtained by mixing Prussian blue into carbon paste, and evaluation electrode D prepared using a material obtained by simply mixing Prussian blue into carbon-coated silica gel. [Figure 4b] FIG. 4b is an enlarged graph showing the portions (encircled by dotted line A in FIG. 4a) of the potential-current curves of evaluation electrodes A, C, and D in FIG. 4a. [Diagram 5]1 is a graph showing the results of confirming the hydrogen peroxide response of evaluation electrode A prepared using carbon-coated silica gel (comparative sample 1), evaluation electrode B prepared using PB-supported carbon-coated silica gel (example sample 1), and evaluation electrode E prepared using Prussian blue-supported silica gel (comparative sample 5). [Figure 6] FIG. 1(a) to (d) are diagrams conceptually illustrating the manufacturing steps of a method for manufacturing an electronic substrate using a print paste for an electronic substrate having PB-supported carbon-coated silica gel.

[0008] Hereinafter, an embodiment of the PB-supported carbon-coated silica gel and its manufacturing method according to the present invention will be described with reference to the attached drawings.

[0009] First, the PB-supported carbon-coated silica gel according to the present invention will be described. In the present invention, carbon-coated silica gel is used as a support for carrying Prussian blue. Carbon-coated silica gel is a porous silica gel with multiple mesopores that is continuously coated with a carbon film from the inner walls of the mesopores to the outer surface. Since it has extremely high electrical conductivity and a large specific surface area, it is expected to have high performance as an electrode material for sensors, batteries, etc. In the present invention, the functionality of Prussian blue is imparted to the carbon-coated silica gel by supporting Prussian blue on the carbon-coated silica gel. Specifically, Prussian blue is known as an adsorbent for cesium, a radioactive element, in the field of atomic energy and the like, while it is known as a compound that can be used as an oxidation-reduction species in electrochemistry, and in recent years, it has also been known to react with hydrogen peroxide. Therefore, by supporting Prussian blue on carbon-coated silica gel having high conductivity, it becomes possible to use it as a reference electrode due to its function as an oxidation-reduction species, and in addition, it becomes possible to use it as a working electrode of a hydrogen peroxide sensor due to its function of reacting with hydrogen peroxide. In addition, since carbon-coated silica gel has a plurality of mesopores, its specific surface area is large, and as a result, the amount of Prussian blue supported is also large, so that the reaction performance as a reference electrode and the working electrode of a hydrogen peroxide sensor is also improved, and the cesium adsorption performance as a cesium adsorbent is also improved.

[0010] FIG. 1 is a process diagram showing an outline of one embodiment of the process for producing PB-supported carbon-coated silica gel according to the present invention. Prussian blue is a compound formed by adding iron ions to an iron cyano complex, and in this example is formed by utilizing the reaction between a potassium ferrocyanide solution and an iron (III) chloride solution. First, a container containing carbon-coated silica gel is prepared (Step 1). Here, the carbon-coated silica gel is silica gel on which a carbon film is formed so as to continuously cover the inner walls of the mesopores of the porous silica gel having a plurality of mesopores, from the inner surface to the outer surface, as described above. A potassium ferrocyanide solution is added to the container containing the carbon-coated silica gel (step 2), and the solution is spread throughout the carbon-coated silica gel (step 3), and the solvent of the solution is removed by drying under reduced pressure (step 4), thereby supporting potassium ferrocyanide from the inner mesopore walls to the outer surface of the carbon-coated silica gel. An iron (III) chloride solution is added to the container containing the dry powder from which the solvent has been removed in step 4, and immediately mixed well (step 5). As a result, the potassium ferrocyanide supported on the surface of the carbon-coated silica gel reacts with the iron (III) chloride to form Prussian blue on the surface of the carbon-coated silica gel. Here, as described above, potassium ferrocyanide is supported from the inner mesopore walls to the outer surface of the carbon-coated silica gel, so that Prussian blue is formed from the inner mesopore walls to the outer surface of the carbon-coated silica gel. Next, the solvent of the iron(III) chloride solution is removed by drying under reduced pressure to obtain a dry powder (step 6), the dry powder obtained in step 6 is washed with water until the filtrate becomes transparent (step 7), and finally the washed PB-supported carbon-coated silica gel is dried in a dryer (step 8), thereby completing the PB-supported carbon-coated silica gel according to the present invention. Example 1

[0011] Next, an example of producing PB-supported carbon-coated silica gel using the above-mentioned steps 1 to 8 will be described. In this example, in step 1, 1 g of carbon-coated silica gel was weighed and placed in a recovery flask. In step 2, 1.6 mL of 6.3 w / w% potassium ferrocyanide solution was added to the recovery flask prepared in step 1. Here, a 10 vl% ethanol / water mixed solvent was used as the solvent for the potassium ferrocyanide solution. Because the surface of the carbon-coated silica gel is hydrophobic, adding alcohol can promote the introduction of the potassium ferrocyanide solution into the mesopores. In step 3, the potassium ferrocyanide solution was mixed using a vortex mixer or the like so as to spread throughout the carbon-coated silica gel in the meso flask. Next, in step 4, the solvent was dried and removed using a rotary evaporator. The treatment in step 4 was carried out by reducing the pressure inside the recovery flask at room temperature for 30 minutes using a vacuum pump, and then placing the recovery flask in a water bath (warm bath) and drying it at a temperature of 60°C while rotating it. The drying time depends on the degree of air purging and is 20 minutes to 1 hour. By reducing the pressure, the potassium ferrocyanide solution can easily enter the mesopores of the carbon-coated silica gel, and by drying while rotating, the potassium ferrocyanide adhering from the inner walls of the mesopores to the outer surface is made uniform. In step 4, the efficiency of removing the solvent is increased by reducing the pressure in the recovery flask and raising the temperature of the hot bath, but if the pressure is reduced too much or the temperature is raised too much, the sample (solvent) in the recovery flask may bump, so the pressure reduction and heating are performed while making fine adjustments such as purging a small amount of air or lowering the temperature. In step 4, a dry powder was obtained in which potassium ferrocyanide was supported on the inner walls and outer surfaces of the mesopores in the carbon-coated silica gel. In step 5, 1.6 mL of 2.4 w / w% iron (III) chloride solution was added to the dry powder obtained in step 4. When the iron (III) chloride solution was added, potassium ferrocyanide attached to the surface (inner and outer surfaces of mesopores) of the carbon-coated silica gel was dissolved in the iron (III) chloride solution and reacted with the iron ions in the solution to form Prussian blue. Therefore, the sample in the eggplant flask was thoroughly mixed using a vortex mixer or the like so that the solution was distributed throughout the dry powder in the eggplant flask at the same time as or immediately after the addition of the iron (III) chloride solution. As a result, potassium ferrocyanide supported on the surface of the carbon-coated silica gel reacts with iron (III) chloride to form Prussian blue on the surface of the carbon-coated silica gel. Here, as described above, potassium ferrocyanide is supported from the inner walls of the mesopores to the outer surface of the carbon-coated silica gel, so that Prussian blue is formed from the inner walls of the mesopores to the outer surface of the carbon-coated silica gel. Next, in step 6, the solvent was dried and removed using a rotary evaporator to obtain a dry powder consisting of carbon-coated silica gel with Prussian blue supported on its surface (from the inner walls of the mesopores to the outer surface). The treatment in step 6 was carried out by reducing the pressure inside the recovery flask at room temperature for 30 minutes using a vacuum pump, and then placing the recovery flask in a water bath (warm bath) and drying it at a temperature of 60°C while rotating it. The specific treatment contents were the same as those explained in step 4. Next, in step 7, the dried powder obtained in step 6 is filtered using a vacuum filter. The filter paper was washed with pure water. This trapped the powder consisting of PB-supported carbon-coated silica gel on the filter paper, and the excess Prussian blue was removed. The filtrate was blue at the beginning of the wash because it contained Prussian blue, but it became transparent after sufficient washing and the excess Prussian blue was removed. Finally, the powder trapped by the filter paper in step 7 was placed in a dryer and dried to obtain the PB-supported carbon-coated silica gel according to the present invention. The drying temperature is preferably 90°C to 110°C, and the silica gel is dried until it is sufficiently dry. In this example, the silica gel was dried at a temperature of 90°C for 15 hours.

[0012] 2(a) and (b) show SEM images of the appearance of the carbon-coated silica gel used in the process of Example 1 (hereinafter referred to as "Comparative Sample 1") and the PB-supported carbon-coated silica gel obtained in the process of Example 1 (hereinafter referred to as "Example Sample 1"), respectively, observed with a scanning electron microscope. As shown in the drawings, there is no significant difference in appearance between the two. Both of the above samples (Comparative Sample 1 and Example Sample 1) were analyzed using an ICP optical emission spectrometer (SPS 3100, manufactured by SII Nano Technology Co., Ltd.), and the results shown in Table 1 were obtained. [Table 1] As shown in Table 1, no Fe was detected in Comparative Sample 1, but Fe was detected in Example Sample 1. The Fe detected in Example Sample 1 was Fe contained in Prussian blue, and it was confirmed that Prussian blue was supported on the surface of the carbon-coated silica gel in Example Sample 1 obtained in the process of Example 1.

[0013] FIG. 3 is a graph showing the results of analyzing current-potential curves (cyclic voltammograms) by CV (cyclic voltammetry) using electrodes fabricated from the above-mentioned Comparative Sample 1 and the above-mentioned Example Sample 1 as working electrodes (evaluation electrodes). The measurement conditions for cyclic voltammetry are as follows. Working electrode: An evaluation electrode made using comparative sample 1 (carbon-coated silica gel) and example sample 1 (PB-supported carbon-coated silica gel) ·Reference electrode: Ag / AgCl electrode Counter electrode: platinum wire Cyclic voltammetry was performed in a 1 mol / L potassium chloride solution at a sweep rate of 10 mV / sec. In FIG. 3, the solid line indicates the value of the evaluation electrode using the comparative sample 1, and the dashed line indicates the value of the evaluation electrode using the example sample 1. 3, no redox peak current was observed in the evaluation electrode prepared using Comparative Sample 1, but redox peak currents derived from Prussian blue were observed in both the oxidation reaction and the reduction reaction in the evaluation electrode prepared using Example Sample 1. This confirmed the presence of Prussian blue electrochemically in Example Sample 1 obtained by the steps of Example 1.

[0014] FIG. 4a and FIG. 4b are Evaluation electrode A made from carbon-coated silica gel. Evaluation electrode B produced using Example Sample 1 obtained in the configuration of Example 1; Evaluation electrode C made using comparative sample 2 obtained by mixing Prussian blue with carbon paste; and Evaluation electrode D made using comparison sample 3 obtained by simply mixing Prussian blue with carbon-coated silica gel 1 is a graph showing the results of analyzing the potential-current curve (cyclic voltammogram) of the above using a CV method (cyclic voltammetry). In the figure, symbol a indicates the potential-current curve of evaluation electrode A, symbol b indicates evaluation electrode B, symbol c indicates evaluation electrode C, and symbol d indicates evaluation electrode D. From these results, in evaluation electrode A prepared using carbon-coated silica gel not containing Prussian blue, no oxidation-reduction current peak derived from Prussian blue was observed, while in evaluation electrode C prepared using comparison sample 2 obtained by mixing Prussian blue into carbon paste, and evaluation electrode D prepared using comparison sample 3 obtained by simply mixing Prussian blue into carbon-coated silica gel, oxidation-reduction current peaks derived from Prussian blue were observed, but the current values ​​were small. Compared to evaluation electrodes C and D, the potential-current curve of evaluation electrode B prepared using example sample 1 showed a peak current that was superior in both oxidation and reduction reactions. The evaluation electrodes A to D used in the analysis results shown in Figures 4a and 4b were prepared by applying a paste prepared under the following conditions to a commercially available glassy carbon electrode and drying it at 120°C for 30 minutes to obtain an electrode film. ■ Evaluation electrode A (carbon-coated silica gel) Carbon-coated silica gel 31.3mg Resin 6.2mg Mix 62.5mg of solvent ■ Evaluation electrode B (PB-supported carbon-coated silica gel) PB-supported carbon-coated silica gel 31.3 mg Resin 6.2mg Mix 62.5mg of solvent ■ Evaluation electrode C (Comparative sample 2: Prussian blue mixed carbon paste) 1g of commercially available screen printing carbon paste -Commercially available Prussian blue 2.4mg mixed ■ Evaluation electrode D (Comparative sample 3: Prussian blue mixed carbon-coated silica gel) Carbon-coated silica gel 31.3mg Resin 6.2mg Solvent 62.5mg Mix 0.3mg of commercially available Prussian blue A commercially available screen printing resin binder (vinyl chloride resin) was used to prepare the evaluation electrodes A, B, and D. The screen printing resin binder is a paste-like product in which the resin is dissolved in a solvent, and the amount of resin is a value calculated from the ratio of the resin contained in the solvent. The solvent also contains dipropylene glycol monomethyl ether. The general chemical formula of commercially available Prussian blue is Fe4[Fe(CN)6]3, which contains 45.5 wt% Fe. As described above, the ICP analysis results show that the amount of Fe contained in the PB-supported carbon-coated silica gel of Example Sample 1 is 0.54 wt%, so Example Sample 1 supports approximately 1.2 wt% of Prussian blue. Therefore, in order to match the content of Prussian blue to that of Example Sample 1, Prussian blue was added to Comparative Sample 2 in an amount equivalent to approximately 1.2 wt % relative to the conductive carbon material contained in the carbon paste, and Prussian blue was added to Comparative Sample 3 in an amount equivalent to approximately 1.2 wt % relative to the carbon-coated silica gel.

[0015] FIG. 5 is a graph showing the results of confirming the hydrogen peroxide response of electrodes prepared using Example Sample 1 and Comparative Sample 1 obtained in Example 1, as well as Comparative Sample 5 obtained by supporting Prussian blue on silica gel. Using each sample, a paste prepared under the following conditions was applied onto a commercially available glassy carbon electrode and dried at 120°C for 30 minutes to obtain an electrode film, thereby producing evaluation electrodes A, B, and E. ■ Evaluation electrode A (carbon-coated silica gel) Carbon-coated silica gel 31.3mg Resin 6.2mg Mix 62.5mg of solvent ■ Evaluation electrode B (PB-supported carbon-coated silica gel) PB-supported carbon-coated silica gel 31.3 mg Resin 6.2mg Mix 62.5mg of solvent ■ Evaluation electrode E (Prussian blue-supported silica gel) Prussian blue-loaded silica gel 31.3 mg Resin 6.2mg Mix 62.5mg of solvent Here, the comparative sample 5 (Prussian blue-supported silica gel) used in the evaluation electrode E was obtained through steps 1 to 8 shown in Example 1 using silica gel instead of the carbon-coated silica gel. The measurement conditions are as follows. Working electrodes: Evaluation electrodes A, B and E ·Reference electrode: Ag / AgCl electrode Counter electrode: platinum wire Apply 0V to the working electrode (vs. reference electrode) Measure the current that flows when hydrogen peroxide is added to a phosphate buffer solution. In Figure 5, the measurement results using evaluation electrode A are plotted as "filled diamond marks," the measurement results using evaluation electrode B are plotted as "open square marks," and the measurement results using evaluation electrode E are plotted as "open circle marks." 5, it can be seen that evaluation electrode B, which uses PB-supported carbon-coated silica gel, is responsive to hydrogen peroxide, but because carbon-coated silica gel does not respond to hydrogen peroxide, evaluation electrode A shows no change in current value in response to hydrogen peroxide, and because silica gel itself has no conductivity, evaluation electrode E also shows almost no response in current value to hydrogen peroxide. Note that evaluation electrode E supports Prussian blue on non-conductive silica gel, and therefore actually shows a slight response due to the proximity of the glassy carbon electrode and Prussian blue in some areas, but compared to evaluation electrode B, which uses Prussian blue-supported carbon-coated silica gel, the level is such that it appears to have no response. Therefore, by combining it with an enzyme that produces hydrogen peroxide, it becomes possible to prepare an enzyme sensor.

[0016] According to the above-mentioned embodiment, Prussian blue can be produced on the surface (the inner walls and outer surface of the mesopores) of the carbon-coated silica gel without complicated processes. Furthermore, by supporting Prussian blue on the inner walls and outer surface of the mesopores of the carbon-coated silica gel, it is possible to have Prussian blue in close proximity to the carbon, and this makes it possible to improve the electron transfer performance compared to a material in which Prussian blue is simply mixed into carbon-coated silica gel or a material in which carbon paste is mixed with Prussian blue. This makes it possible to obtain high responsiveness when used as a reference electrode and as a working electrode for detecting hydrogen peroxide.

[0017] In the above-described embodiment, a potassium ferrocyanide solution is added to a container containing carbon-coated silica gel, and then an iron (III) chloride solution is added to generate Prussian blue on the surface (the inner walls and outer surfaces of mesopores) of the carbon-coated silica gel. However, this method is not limited to this embodiment, and Prussian blue can also be generated on the surface (the inner walls and outer surfaces of mesopores) of the carbon-coated silica gel by first adding an iron (III) chloride solution and then adding a potassium ferrocyanide solution. Furthermore, the compound used is not limited to that in this embodiment, and any compound may be used as long as it contains an iron cyano complex and iron ions capable of generating Prussian blue.

[0018] Next, a printing paste for producing an electrode using the PB-supported carbon-coated silica gel according to the present invention will be described. Carbon-coated silica gel, which is a porous silica gel with multiple mesopores and has a carbon film formed so as to cover the inner walls of the mesopores to the outer surface, has very high electrical conductivity and a large specific surface area, so it is expected to have high performance as an electrode material for sensors, batteries, etc. However, it cannot be fixed to a substrate as it is to form an electrode. The same is true for PB-supported carbon-coated silica gel. Therefore, it is necessary to mix the PB-supported carbon-coated silica gel in an appropriate ratio with a resin as a binder for forming a film on the PB-supported carbon-coated silica gel and for bonding the PB-supported carbon-coated silica gel to each other and to the substrate, and with a solvent for dissolving the resin component, uniformly dispersing the conductive material and resin, and adjusting the viscosity to a level suitable for printing, to obtain a printing paste suitable for forming electrodes, etc. on a substrate. Here, the resin may be, for example, a material selected from acrylic, epoxy, modified epoxy, polyester, and PVC, and the solvent may be an organic solvent capable of dissolving the resin depending on the resin used, and preferably, a material selected from alkyl, aromatic, ether, ester, alcohol, and amine organic solvents is used. If the resin content is too low, poor curing results in poor adhesion, while if the resin content is too high, the resin coats the carbon-coated silica gel, reducing the effect of the high specific surface area of ​​the carbon-coated silica gel, and also causing problems such as the printed electrode becoming coarse and dense, and stringiness during printing. For this reason, it is necessary to appropriately select the resin content. Similarly, with regard to the solvent, if the content is too small, problems arise in that dispersibility decreases and viscosity increases, resulting in decreased printability, while if the content is too large, the viscosity decreases, resulting in decreased printability, and problems such as the density of the printed electrode increasing occur, so the content must be appropriately selected. The inventors have confirmed that the content of the resin is preferably in a ratio of 1:0.1 to less than 1.5 relative to the PB-supported carbon-coated silica gel, preferably in a ratio of 1:0.2 to less than 0.9, and more preferably in a ratio of 1:0.2 to less than 0.5, and that the content of the solvent is preferably in a ratio of 40 to 70% by weight, and preferably 55 to 65% by weight, relative to the total printing paste. Moreover, the particle size of the PB-supported carbon-coated silica gel is preferably 10 microns to 100 microns. More preferably, in order to adjust the electrical conductivity, conductive particles selected from carbon black, metal particles and / or metal oxide particles may be added.

[0019] Next, referring to an embodiment shown in FIG. 6, a method for manufacturing an electronic substrate having an electrode using the printing paste for electronic substrates having the above-mentioned PB-supported carbon-coated silica gel (hereinafter simply referred to as printing paste) will be described. 6(a) to (d) are diagrams conceptually showing the manufacturing steps of the method for manufacturing an electronic substrate. In the figure, reference numeral 1 denotes an insulating substrate, which may be, for example, a ceramic substrate. First, a line pattern 3 is formed on the insulating substrate 1 by stencil printing with a conductive material (FIG. 6(b)). The insulating substrate is not limited to a ceramic substrate, and may be made of a film material. The conductive material forming the line pattern 3 may be any conductive material that can overlap with the electrode portion 5 formed in the process described later (FIG. 6(c)) and ensure electrical continuity. For example, a silver paste or a platinum paste may be used. Next, the electrode part 5 is stencil-printed using a printing paste having the PB-supported carbon-coated silica gel according to the present invention (FIG. 6(c)). The size and shape may be any size and shape. Finally, an insulating film 7 is formed so as to cover the other parts except for the terminal parts 3a and the electrode parts 5. The printing paste for forming the electrode part 5 described above contains carbon-coated silica gel, and the resin content is in a ratio of 1:0.1 to less than 1.5 relative to the PB-supported carbon-coated silica gel, preferably 1:0.2 to less than 0.9, and more preferably 1:0.2 to less than 0.5, and the solvent content is 40 to 70% by weight relative to the entire printing paste, and preferably 55 to 65% by weight relative to the entire printing paste, so that the paste has a suitable paste state and hardened / adhered state when producing the electrode part 5, and further, by containing the carbon-coated silica gel in the above ratio, it is possible to form an electrode with excellent conductivity.

Claims

1. a carbon-coated silica gel having a plurality of mesopores, the carbon film being formed so as to continuously cover the inner walls of the mesopores of the porous silica gel from the inner surface to the outer surface; Prussian blue supported on the inner walls and outer surfaces of the mesopores in the carbon-coated silica gel; A Prussian blue-supported carbon-coated silica gel comprising:

2. a step of adding a solution containing an iron-cyano complex to a container containing a carbon-coated silica gel having a porous silica gel with a plurality of mesopores, the carbon film being formed so as to continuously cover the mesopore inner walls and the outer surface of the porous silica gel, thereby supporting the iron-cyano complex from the mesopore inner walls to the outer surface of the carbon-coated silica gel; A step of removing the solvent from the solution containing the iron-cyano complex to obtain a dry powder made of carbon-coated silica gel carrying the iron-cyano complex; adding an iron ion-containing solution to the dry powder, and reacting the iron cyano complex with the iron ions to generate Prussian blue from the inner walls of the mesopores to the outer surface of the carbon-coated silica gel; and removing the solvent from the iron ion-containing solution 2. A method for producing a Prussian blue-supported carbon-coated silica gel, comprising the steps of:

3. a step of adding an iron ion-containing solution to a container containing a carbon-coated silica gel in which a carbon film is formed so as to continuously cover from the inner walls of the mesopores to the outer surface of the porous silica gel having a plurality of mesopores, thereby supporting iron ions from the inner walls of the mesopores to the outer surface of the carbon-coated silica gel; A step of removing the solvent from the iron ion-containing solution to obtain a dry powder of carbon-coated silica gel carrying iron ions; adding a solution containing an iron cyano complex to the dry powder, and reacting the iron ions with the iron cyano complex to generate Prussian blue from the inner walls of the mesopores to the outer surface of the carbon-coated silica gel; and Removing the solvent from the iron cyano complex-containing solution 2. A method for producing a Prussian blue-supported carbon-coated silica gel, comprising the steps of:

4. The iron cyano complex-containing solution is a potassium ferrocyanide solution.

4. The method for producing Prussian blue-supported carbon-coated silica gel according to claim 2 or 3.

5. The iron ion-containing solution is an iron (III) chloride solution.

4. The method for producing Prussian blue-supported carbon-coated silica gel according to claim 2 or 3.

6. The solvent of the solution is a mixed solvent of ethanol and water.

4. The method for producing Prussian blue-supported carbon-coated silica gel according to claim 2 or 3.

7. The step of removing the solvent is carried out under reduced pressure inside the vessel.

4. The method for producing Prussian blue-supported carbon-coated silica gel according to claim 2 or 3.

Images