JP2007136645A - Method for manufacturing carbon nanotube (cnt) thin film and biosensor using the thin film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a CNT thin film by which a CNT thin film can be inexpensively manufactured with excellent productivity so as to obtain a device that effectively utilizes the physical properties expected for a CNT, and to provide a biosensor which uses the CNT and is operated with high sensitivity at a low voltage. <P>SOLUTION: Carbon nanotube particles are converted into a micelle dispersible or soluble in an aqueous medium by a mixture of a polymer electrolytic solution and a surfactant which can be electrochemically oxidized and reduced or can be oxidized or reduced; and the surfactant is electrochemically oxidized and reduced, or oxidized or reduced to decompose the micelle to form a thin film of the CNT dispersion particles in the micelle. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for producing a carbon nanotube (hereinafter referred to as CNT) thin film useful as a functional material or a structural material such as an electronic device or a microdevice, and a biosensor sensor using the CNT thin film obtained by this method. It is.

  CNT is a very small substance with an outer diameter on the order of nm, which is formed by nesting a plurality of cylinders with several atomic layers of rounded graphite-like carbon atoms. It was discovered in 1991 ( Non-patent document 1), attracted much attention due to its chemical characteristics, electronic characteristics, mechanical characteristics and the like. In particular, various physical properties such as chemical stability, metallic and semiconducting electrical conductivity, high electron emission ability, high mechanical strength, and high thermal conductivity are observed and expected. Currently, in order to utilize such physical properties, application possibilities are being studied in various fields such as field emission type electron-emitting devices, SPM probes, catalysts, structural reinforcing materials, battery electrodes, and biosensor materials. Among these, particularly in biosensor materials, there is a problem of a decrease in response due to the miniaturization of the device, which is characterized by excellent electrical conductivity of CNT and biomolecules derived from the microstructure of nanostructures. It is expected as an electrode material for enhancing the sensitivity of biosensors because of its action to promote electron transfer reaction. However, at this time, dispersion of CNTs and establishment of a CNT device formation technique are important issues.

  The production method of CNT is a method using arc discharge (Non-patent Documents 2 and 3) such as graphite, a thermal decomposition method using a catalyst (Non-patent document 4), a laser evaporation method (Non-patent document 5), a CVD method (non-patent document 5). Patent document 6) etc. are mentioned. Furthermore, various purification methods such as a centrifugal separation method, a filtration method, an oxidation method, and a chromatographic method have been studied, and higher-purity CNTs can be generated.

  In consideration of application to the above devices and the like, a technique for handling nanometer-order CNT fine particles as an aggregate, for example, a film formation, molding, and orientation technique is required. In particular, it is important for film formation, and CNT also uses dry film formation methods such as vapor deposition and CVD (patent documents 1 and 2), wet film formation methods such as coating, printing, and electrophoresis (non-patent document 7). Consideration is being made.

  However, the dry film forming method requires a large-scale apparatus and has problems such as low productivity. Furthermore, although it is possible to form a film of 1 μm or less, there is a disadvantage that it takes time to form a film of 1 μm or more, and a porous mold such as alumina, porous Si or the like is necessary for the film forming part. is there.

In addition, wet deposition methods such as coating and printing are widely used industrially in various organic materials, pigments, polymer materials, etc., but there are few specific applications to CNTs, and the dispersibility of CNTs However, a uniform thin film cannot be obtained. Moreover, it is common to use an organic solvent as a dispersion medium, and it cannot be said that it is excellent in terms of environmental resistance. Further, in the case of coating, when the thin film is patterned, unnecessary portions are removed by a method such as photolithography after the thin film is formed, which is not efficient as a method for forming a valuable CNT material. On the other hand, in the method using electrophoresis, it is possible to form a film only on a necessary portion, but since a high potential is required, a side reaction occurs and decomposition occurs at a relatively low potential. It is difficult to use water, and an organic solvent must be used as a dispersion medium. As in the case of coating, the problem remains in environmental resistance.
Japanese Patent Laid-Open No. 6-184738 Japanese Patent Laid-Open No. 10-265208 Nature, 354, p56, 1991 Nature, 354, p56, 1991 Nature, 358, p220, 1992 J. Phys. Chem. Solids, 54, p1841, 1993 Science, 273, p483, 1996 Science, 274, p1701, 1996 Jpn. J. Appl. Phys. Vol.35, L917, 1996

  As described above, an object of the present invention is to provide a method for producing a CNT thin film that is excellent in productivity and capable of producing a CNT thin film at low cost in order to obtain a device that effectively utilizes the physical properties expected of CNT, and the production thereof. An object of the present invention is to provide a highly sensitive biosensor using a CNT thin film produced by the method.

The present invention has the following features to solve the above-described problems.
<1> CNT particles can be electrochemically oxidized and reduced, or CNT particles are micellized by a mixture of a surfactant capable of oxidation or reduction and a polymer electrolyte solution, and dispersed or solubilized in an aqueous medium. A method for producing a CNT thin film, characterized in that an activator is electrochemically oxidized and reduced, or oxidized or reduced to decompose micelles, and the CNT dispersed particles in the micelles are thinned.
<2> Deactivate micelles by oxidizing the CNT particles into micelles and dispersing or solubilizing them in an aqueous medium near the anode and reducing near the cathode, or oxidizing near the anode or reducing near the cathode. The method for producing the first CNT thin film according to claim 1, wherein the CNT dispersed particles in the micelle are deposited on the electrode, and the CNT particles deposited on the electrode are fixed to the thin film by the polymer electrolyte membrane.
<3> The micelle is decomposed by immersing an electrode in which a metal compound nobler than the oxidation potential of the surfactant is attached to the surface of the mixture of the surfactant and the polymer electrolyte solution. The first CNT thin film manufacturing method according to claim 1, wherein the CNT dispersed particles are deposited on the anode, and the CNT particles deposited on the electrode are fixed to the thin film by a polymer electrolyte membrane.
<4> An enzyme is further added to the mixture of the surfactant and the polymer electrolyte, and the surfactant is electrochemically oxidized and reduced, or oxidized or reduced to decompose the micelle, and the CNT dispersed particles in the micelle A method for producing the first CNT thin film as described above, wherein a thin film is formed by mixing the enzyme and the enzyme.
<5> Electrochemically oxidizable and reduced, or a surfactant capable of oxidation or reduction is a micellar agent composed of a ferrocene derivative, and a polymer electrolyte solution is a micellar agent capable of immobilizing a thin film. A method for producing a CNT thin film according to any one of the first to fourth aspects.
<6> The polymer electrolyte solution is at least one of polyvinyl alcohol, gellan gum, Nafion (registered trademark), carrageenan, polyglutamic acid, polyaspartic acid, chitosan, polylysine, polyarginine, polyacrylic acid, alginic acid and polyornithene. One of the first to fifth CNT thin film manufacturing methods, wherein the number is one.
<7> The method for producing a CNT thin film according to any one of the first to sixth aspects, wherein the concentration of the polymer electrolyte solution is in the range of 30 to 80%.
<8> A biosensor using a CNT thin film obtained by any one of the fourth to seventh CNT thin film manufacturing methods as an electrode, at least an electrode, a support that supports the electrode, and an electrode A biosensor characterized by being coated with a CNT thin film.
<9> The eighth biosensor as described above, wherein a polymer electrolyte membrane is further laminated on the CNT thin film.

  In the present invention, according to the first invention, in order to obtain a device that effectively utilizes the physical properties expected of CNT, a CNT thin film can be produced with excellent productivity and low cost.

  According to the second to fourth inventions, the effect of the first invention can be realized more efficiently.

  Further, according to the fifth to seventh inventions, in addition to the effects of the first to fourth inventions, a CNT thin film can be produced more efficiently.

  Then, according to the eighth and ninth inventions, it is possible to obtain a biosensor that can be operated with high sensitivity and low voltage by using any one of the fourth to seventh CNT thin films. it can.

  The inventors of the present invention electrochemically oxidized or reduced CNT, or micelleized with a surfactant and a polyelectrolyte solution capable of being oxidized or reduced, and dispersed or solubilized in an aqueous medium. The surfactant is electrochemically oxidized and reduced, or oxidized or reduced to form a high-purity and uniform CNT thin film with excellent productivity at a low cost, and a polymer electrolyte solution is added. As a result, the present invention for firmly fixing the CNT thin film could be achieved.

  Here, the CNT in the present invention is not particularly limited to the shape or the like. For example, the CNT may be a CNT itself or may be a modified body, and further, a part or all of the CNT may be a solid body or the like. Good.

Specifically, for example, the CNT may be a single-walled CNT or a multilayered CNT, and may further have a bucky-onion structure. Moreover, in order to improve the solubilization and affinity to a solvent or polymer, and to control the alignment and orientation in the CNT, the CNT may be modified by introducing a substituent as described above. The modification method and the type of substituent are not particularly limited. As the modification method, for example, various known modification methods can be used, and as the type of substituent, for example, an alkyl group such as a C _1-10 alkyl group such as a methyl group or a t-butyl group. In addition, an aryl group such as a phenyl group, an aralkyl group such as a benzyl group, a dioxolane unit, a halogen or oxygen atom, and the like, and liquid crystal polymers, dyes, polyethylene oxide and the like may be introduced. Further, the CNT may be doped with a metal and included. Furthermore, the CNT has, for example, a circular or elliptical cross-sectional shape, a curved shape including other shapes, or a polygonal shape having n corners, and both ends or one end thereof are open. For example, both ends may be closed.

  Electrochemical oxidation and reduction, or oxidation or reduction methods used for film formation of the present invention include (A) a so-called micelle electrolysis method (Patent No. 1812057, etc.), (B) oxidation other than electrolysis Examples include a method using a reduction reaction (JP-A-3-23227, etc.), (C) other electrolysis method (JP-A-2-164435), etc., and the oxidation and / or reduction methods used in the present invention are as follows. As long as the object of the present invention can be achieved, the present invention is not limited to the above method.

  As a method for use in the electrolytic polymer film of the present invention, (A) a method using polypyrrole as a main component (JP-A-2004-304001, etc.), and (B) a method using octelthiophene as a main component (JP-A-7- 133341, etc.) and (C) a method using a monomer containing polyaniline as a main component (Japanese Patent Laid-Open No. 5-28823, etc.), the electrolytic polymer film used in the present invention achieves the object of the present invention. As long as it can be used, the method is not limited to the above method.

  In particular, the method described below is preferable as the method for forming the CNT thin film of the present invention. (1) Electrolyze micelles dispersed or solubilized in an aqueous medium by converting CNT particles into micelles with a surfactant and a polymer electrolyte solution that can be oxidized and reduced electrochemically or oxidized or reduced. Can be oxidized and reduced electrochemically, or a surfactant capable of oxidation or reduction is electrochemically oxidized and reduced, or oxidized or reduced to decompose micelles, and CNT dispersed particles in the micelles (2) Electrochemically oxidizable surfactant and a polymer electrolyte solution to form micelles of CNT particles and disperse or solubilize in an aqueous medium. Dissolve the micelles by immersing an electrode with a metal compound nobler than the oxidation potential of the surfactant on the surface, and disperse the CNTs in the micelles Child is deposited on the anode, a method of firmly immobilized thinned.

  Hereinafter, the present invention will be described more specifically. In the micelle electrolysis method of the above (1), CNT can be oxidized and reduced electrochemically, or is micellized with a surfactant capable of oxidation or reduction and dispersed or solubilized in an aqueous medium. When the support salt is added to the medium and electrolyzed as necessary, the surfactant is oxidized in the vicinity of the anode and reduced in the vicinity of the cathode, so that the micelle is decomposed, and the dispersed particles of CNT in the micelle are respectively dispersed in the anode and the cathode. Or when deposited with a polymer electrolyte solution that coexists with the anode or the cathode, the CNTs are firmly fixed on the electrode by the polymer electrolyte membrane.

  As the surfactant used in this micelle electrolysis method, a ferrocene derivative is preferable, and the ferrocene derivative surfactant used for the micellization of these CNTs is a ferrocene site required for an electrolytic reaction and a nonionic, cationic, anion. For example, JP-A 63-243298, JP-A 1-2-6894, JP-A 1-453370, JP-A 2-88387, JP-A 2- Although disclosed in Japanese Patent No. 96585 and Japanese Patent Laid-Open No. 2-250892, the present invention is not limited to these.

As the surfactant other than the ferrocene derivative, a nonionic surfactant such as polyoxyethylene alkyl ether, polyoxyethylene fatty acid ester, polyoxyethylene alkylphenyl ether, or the like is used. It is set to 0.0 to 5.0 V and the current density is set to 10 to 100 mA / cm ² .

  Examples of the polymer electrolyte solution used in this micelle electrolysis method include Nafion (registered trademark), polyvinyl alcohol, dielan gum, carrageenan, polyglutamic acid, polyaspartic acid, chitosan, polylysine, polyarginine, polyacrylic acid, alginic acid, polyornithene However, it is not limited to these.

  As an aqueous medium for the micellar electrolyte, water and a water-soluble solvent such as alcohol, acetone and the like are mixed and used as necessary. In addition, a supporting electrolyte is added to the micellar electrolyte as necessary in order to adjust the electric conductivity of the aqueous medium. As this supporting electrolyte, generally used ones such as sulfates such as alkali metals and alkaline earth metals, halides, acetates and water-soluble oxides are used.

  In order to prepare a micellar electrolyte using each of the above materials, a CNT, a redox capable surfactant, and a supporting electrolyte, if necessary, are placed in the aqueous medium, and a homogenizer, a three-roll mill, a sand mill. It is uniformly dispersed or solubilized by a dispersion method such as pearl mill, stirrer or ultrasonic wave. The surfactant concentration is preferably 0.02 to 1.0 mol / L, and the CNT particle concentration is preferably 1 to 500 g / L.

  Also, CNTs are usually bundled with high aspect ratio fibrous particles having an outer diameter of about 1 to several tens of nanometers and a length of several μm or more. To disperse or solubilize them in an aqueous medium. If necessary, these bundles can be loosened using ultrasonic waves or the like, or those having an excessively high aspect ratio can be stably dispersed or solubilized by grinding.

In order to produce a thin film using the micelle electrolyte prepared in this way, the electrode substrate is immersed in the electrolyte and energized. The electrolysis conditions at this time are higher than the redox potential of the surfactant used. And at a voltage lower than the hydrogen generation potential. Specifically, 0.1 to 1.5 V and a current density of 1 mA / cm ² or less are preferable, and an electrolysis method such as constant potential or constant current is used. When electrolysis is performed under such conditions, a desired thin film is formed according to the principle of the micelle electrolysis method.

  The method (2) using an oxidation-reduction reaction other than electrolysis is the same as in (1) until micellization, but the oxidation potential of the surfactant used on the electrode forming the thin film, for example, oxidation of the ferrocene derivative When a half-cell electrode is formed in a micelle dispersion using a gold layer compound nobler than the potential, for example, in the case of a ferrocene derivative, the metal in the metal compound is simply immersed in the micelle dispersion. Since ions are reduced and Fe of the ferrocene derivative is oxidized, the micelles are decomposed and CNTs of dispersed particles are deposited on the anode. The ferrocene derivative used here is the same as (1). However, even in this method, the surfactant is not limited to the ferrocene derivative, and the reference oxidation-reduction potential is the oxidation-reduction potential of the surfactant to be used.

  When the ferrocene compound is used as the surfactant in the electrode substrate (1), a conductor having a higher precious potential than the oxidation potential of the ferrocene compound, for example, a conductive metal oxide such as gold, silver, platinum, carbon, ITO, etc. And conductive polymers. These can be used alone or on physical substrates such as sputtering, ion plating, vacuum deposition, etc. on support substrates such as various metals, ceramics, glass, and polymer films, printing methods, coating methods, chemical vapor depositions. You may form and use by chemical methods, such as a method.

  When a surfactant other than the ferrocene compound is used as the surfactant in (1), in addition to those listed above, metals such as aluminum, iron, zinc, tin, nickel, alloys, crystalline silicon, amorphous A semiconductor such as silicon can be used.

In the case of (2), a material obtained by attaching a metal compound nobler than the oxidation potential of the ferrocene compound on various metals, carbon, conductive metal oxide, conductive polymer and the like is used. Examples of the metal compound include PbO, MnO ₂ , CuO ₂ , WO, ZnO ₂ , Cu ₂ S, HgS, Ag ₂ S, etc., physical methods such as sputtering, ion plating, and vacuum deposition, printing methods It can be attached by a chemical method such as a coating method or a chemical vapor deposition method. Moreover, simple metals such as lead, manganese, aluminum and zinc can be oxidized and used.

  The adhesion of the CNT thin film can be improved by the hydrophobic treatment of the electrode substrate. Here, the hydrophobic treatment of the electrode substrate can be performed by various methods, and examples thereof include a treatment using a coupling agent. Coupling agents used at this time may be those commonly used, such as silane coupling agents, titanium coupling agents, zirconium coupling agents, acrylate coupling agents, methacrylate coupling agents, etc. is there. These coupling agents may be dissolved in a solvent, the electrode substrate to be treated may be immersed and heated to reflux to dry, or the coupling agent may be applied and dried directly, and is not limited to these processes.

  By adding an enzyme to the electrochemically oxidizable and / or reducible surfactant and polyelectrolyte solution mixture used for producing the CNT thin film, the enzyme is also immobilized on the electrode when the CNT thin film is formed. Can be used as a biosensor. In addition, it can be used as a biosensor by immobilizing an enzyme on the CNT thin film after forming the CNT thin film. At this time, examples of the immobilization of the enzyme include (A) a chemical bonding method using glutaraldehyde and the like, and (B) a physical adsorption fixing method to an adsorption carrier such as CMC and chitosan beads. It is not limited to.

  Here, the enzyme in the present invention can be appropriately selected according to the measurement object (measurement purpose), and is not particularly limited. For example, alcohol oxidase, glucose oxidase, galactose oxidase and the like can be used.

  In the present invention, the CNT thin film thus produced is applied to a biosensor. FIG. 1 illustrates an electrode configuration example of a biosensor using a CNT thin film. However, the biosensor using the CNT thin film of the present invention is not limited to such a configuration, and may be, for example, a two-electrode configuration using a reference electrode as a cathode.

  The arrangement pattern and the configuration pattern of the biosensor of the present invention will be further described. The biosensor of the present invention can be an electrochemical measuring instrument having a three-electrode configuration of a working electrode, a counter electrode, and a reference electrode, and a two-electrode configuration of a working electrode and a counter electrode. For example, it is possible to create a CNT thin film and a biosensor, and there is nothing defined by the arrangement pattern.

  In addition, as described above, considering that the configuration pattern can be a normal electrochemical measuring instrument, the formation of the thin film does not change depending on the configuration pattern of the electrode. Furthermore, since the method for producing a CNT thin film of the present invention is to perform the micelle decomposition of the surfactant electrochemically, it does not depend on the distance between electrodes, the thickness of the electrode plate, and the electrode size, and has a certain constant voltage. As long as it can be applied to the surfactant, the film can be formed under any conditions.

  In FIG. 1, reference numeral 1 denotes an anode (carbon electrode) that can form a CNT thin film by the above-described electrochemical method. Even if the electrode material itself forms a support substrate, an electrode is formed on another support substrate. It may be configured. 2 represents a cathode, 3 represents a reference electrode, and 5 represents a silver lead. Further, although not shown in the figure, in the present invention, for example, a two-electrode configuration using the reference electrode as a cathode may be used.

  Moreover, the cross-sectional schematic diagram of the biosensor using a CNT thin film was illustrated in FIG. On the anode 1, there are a CNT thin film 6 and a polymer electrolyte membrane 7 produced by an electrochemical method. In the biosensor of the first embodiment illustrated in FIG. 2, a CNT thin film 6 and a polymer electrolyte membrane 7 are sequentially laminated on the surface of a support 4 including the anode 1. The CNT thin film 6 covers only the surface of the working electrode, and the polymer electrolyte membrane 7 is formed so as to completely cover the CNT thin film 6. In addition, the upper limit of the size of the peripheral region is not particularly limited, but is appropriately determined in consideration of circumstances such as ease of manufacturing the biosensor and cost.

  FIG. 3 shows an example in which a functional membrane 8 is further provided on a polymer electrolyte membrane (electrolytic polymer membrane) 7 as a second embodiment of the biosensor according to the present invention.

  Further, the functional film 8 shown in FIG. 3 includes a film formation by an electrolytic polymerization method, a film formation by an electroless deposition method, a film formation by an electrolytic deposition method, a dip coating method, a film formation by a cast method, and the like. However, it is not limited to these processes.

  In the present invention, the CNT thin film thus produced can be used as the sensor device 10 in combination with the display device 9. FIG. 4 illustrates one embodiment of the sensor device according to the present invention.

  Examples of the present invention will be described below. Of course, the present invention is not limited to these examples.

<Example 1>
CNT 1 g, FTMA (manufactured by Dojindo) 30 mmol / L as a ferrocene derivative, 5% Nafion (registered trademark) as a polymer electrolyte solution were added to a 0.1 M MOPS buffer solution and ultrasonically dispersed for 30 minutes for film formation A dispersion was prepared. Using this dispersion, a polyethylene terephthalate substrate having a carbon electrode on the anode, a carbon electrode on the cathode, and a silver / silver chloride electrode (Ag / AgCl) on the reference electrode, 25 ° C., 0.3 V (vs. reference electrode) Was conducted for 2 hours, and a uniform CNT thin film of 23.74 μm could be formed on the anode.
<Example 2>
(1) CNT 1 g, FTMA (manufactured by Dojindo) 30 mmol / L, 5% Nafion (registered trademark) as a ferrocene derivative is added to a 0.1 M MOPS buffer solution and ultrasonically dispersed for 30 minutes to form a dispersion for film formation Was made. To this dispersion, 2000 U of glucose oxidase was added as an enzyme, a carbon terephthalate substrate with a carbon electrode on the anode, a carbon electrode on the cathode, and a silver / silver chloride electrode (Ag / AgCl) on the reference electrode, 25 ° C., 0.3 V (Vs. Reference electrode) was subjected to constant potential electrolysis for 2 hours, and a biosensor using a CNT thin film was formed on the anode. FIG. 5A shows the results of glucose measurement using the biosensor at an applied voltage of 0.4 V (vs. reference electrode).
(2) Moreover, the comparative example 1 of Example 2 was also performed. The implementation conditions and results of Comparative Example 1 were as follows.

1 g of graphite powder, FTMA (manufactured by Dojindo) 30 mmol / L, 5% Nafion (registered trademark) as a ferrocene derivative, ultrasonically dispersed for 30 minutes in a 0.1 M MOPS buffer, and a dispersion for film formation Was made. To this dispersion was added 2000 U of glucose oxidase as an enzyme, a polyethylene terephthalate substrate having a carbon electrode on the anode, a carbon electrode on the cathode, and a silver / silver chloride electrode (Ag / AgCl) on the reference electrode, 25 ° C., 0.3 V (Vs. Reference electrode) was subjected to constant potential electrolysis for 2 hours to form a biosensor using a graphite thin film, and compared with the biosensor prepared in Example 2 (FIG. 5B). The response current value was lower than that of the biosensor formed with a thin film.
<Example 3>
CNT 1g, FTMA (manufactured by Dojindo) 30 mmol / L, 5% Nafion (registered trademark) as a ferrocene derivative, ultrasonically dispersed in 0.1 M MOPS buffer for 30 minutes to prepare a dispersion for film formation did. To this dispersion was added 2000 U of glucose oxidase as an enzyme, a polyethylene terephthalate substrate having a carbon electrode on the anode, a carbon electrode on the cathode, and a silver / silver chloride electrode (Ag / AgCl) on the reference electrode, 25 ° C., 0.3 V (Vs. reference electrode) was subjected to constant potential electrolysis for 2 hours, an enzyme-supported CNT thin film was formed on the anode, and further immersed in an aqueous solution in which 100 mmol / L potassium ferricyanide and 100 mmol / L FeCl ₃ were dissolved. A biosensor was manufactured by energizing at a density of 40 μA / cm ² and forming a Prussian blue functional film on the electrode by electrolytic deposition. As a result of glucose measurement using the biosensor at 25 ° C. and −0.2 V (vs. reference electrode) (FIG. 6), good reactivity with the substrate was shown.
<Example 4>
(1) CNT 1 g, FTMA (manufactured by Dojindo) as a ferrocene derivative, 30 mmol / L, 5% Nafion added to 0.1 M MOPS buffer and ultrasonically dispersed for 30 minutes to prepare a dispersion for film formation did. To this dispersion, 2000 U of lactate oxidase was added as an enzyme, a polyethylene terephthalate substrate with a carbon electrode on the anode, a carbon electrode on the cathode, and a silver / silver chloride electrode (Ag / AgCl) on the reference electrode, 25 ° C., 0.3 V (vs. Reference electrode) was subjected to constant potential electrolysis for 2 hours to form a biosensor using a CNT thin film. FIG. 7A shows the results of lactic acid measurement using the biosensor and an applied voltage of 0.4 V (vs. reference electrode).
(2) Comparative Example 2 of Example 4 was also performed. The implementation conditions and results of Comparative Example 2 were as follows.

1 g of graphite powder, FTMA (manufactured by Dojindo) 30 mmol / L, 5% Nafion (registered trademark) as a ferrocene derivative, ultrasonically dispersed for 30 minutes in a 0.1 M MOPS buffer, and a dispersion for film formation Was made. 2000 U of lactate oxidase as an enzyme was added to this dispersion, a carbon terephthalate substrate with a carbon electrode on the anode, a carbon electrode on the cathode, and a silver / silver chloride electrode (Ag / AgCl) on the reference electrode, 25 ° C., 0.3 V (Vs. reference electrode) was subjected to constant potential electrolysis for 2 hours to form a biosensor using a graphite thin film and compared with the biosensor prepared in Example 4 (FIG. 7B). CNT The response current value was lower than that of the biosensor formed with a thin film.
<Example 5>
(1) CNT 1 g, FTMA (manufactured by Dojindo) as a ferrocene derivative, 30 mmol / L, 5% Nafion added to 0.1 M MOPS buffer, and ultrasonically dispersed for 30 minutes to prepare a dispersion for film formation did. To this dispersion was added 2000 U of putrescine oxidase as an enzyme, a polyethylene terephthalate substrate with a carbon electrode on the anode, a carbon electrode on the cathode, and a silver / silver chloride electrode (Ag / AgCl) on the reference electrode, 25 ° C., 0.3 V (vs. Reference electrode) was subjected to constant potential electrolysis for 2 hours, and a biosensor using a CNT thin film could be formed. FIG. 8A shows the result of putrescine measurement using the biosensor at an applied voltage of 0.4 V (vs. reference electrode).
(2) Comparative Example 3 of Example 5 was also performed. The implementation conditions and results of Comparative Example 3 were as follows.

1 g of graphite powder, FTMA (manufactured by Dojindo) 30 mmol / L, 5% Nafion (registered trademark) as a ferrocene derivative, ultrasonically dispersed for 30 minutes in a 0.1 M MOPS buffer, and a dispersion for film formation Was made. To this dispersion was added 2000 U of putrescine oxidase as an enzyme, a polyethylene terephthalate substrate with a carbon electrode on the anode, a carbon electrode on the cathode, and a silver / silver chloride electrode (Ag / AgCl) on the reference electrode, 25 ° C., 0.3 V (Vs. reference electrode) was subjected to constant potential electrolysis for 2 hours to form a biosensor using a graphite thin film, and compared with the biosensor prepared in Example 5 (FIG. 8B), CNT The response current value was lower than that of the biosensor formed with a thin film.
<Example 6>
CNT 1g, FTMA (manufactured by Dojindo) as a ferrocene derivative, 30 mmol / L, 5% polyvinyl alcohol as a polymer electrolyte solution was added to a 0.1 M MOPS buffer solution and ultrasonically dispersed for 30 minutes to disperse for film formation A liquid was prepared. To this dispersion, 2000 U of glucose oxidase was added as an enzyme, a carbon terephthalate substrate with a carbon electrode on the anode, a carbon electrode on the cathode, and a silver / silver chloride electrode (Ag / AgCl) on the reference electrode, 25 ° C., 0.3 V (vs. Reference electrode) was subjected to constant potential electrolysis for 2 hours, and a biosensor using a CNT thin film could be formed. FIG. 9 shows the results of glucose measurement using this biosensor at an applied voltage of 0.4 V (vs. reference electrode).

  As shown in FIG. 9, the biosensor reacted with glucose to increase the response current value, and was able to measure glucose.

It is the plane schematic diagram which showed an example of the electrode structure in the biosensor of this invention. It is the cross-sectional schematic diagram which showed an example of the electrode structure in the biosensor of this invention. It is the cross-sectional schematic diagram which showed another example of the electrode structure in the biosensor of this invention. It is the schematic diagram which illustrated one Embodiment of the sensor device by this invention. It is the figure which showed the result of the glucose measurement by the biosensor of this invention, (a) shows the case where the biosensor (CNT thin film) of this invention is used, (b) shows the case where a graphite thin film is used as a comparative example. ing. It is the figure which showed the result of the glucose measurement on another conditions by the biosensor of this invention. It is the figure which showed the result of the lactic acid measurement by the biosensor of this invention, (a) shows the case where the biosensor (CNT thin film) of this invention is used, (b) shows the case where a graphite thin film is used as a comparative example. ing. It is the figure which showed the result of the putrescine measurement by the biosensor of this invention, (a) shows the case where the biosensor (CNT thin film) of this invention is used, (b) shows the case where a graphite thin film is used as a comparative example. ing. It is the figure which showed the result of the glucose measurement by the biosensor of this invention, and uses polyvinyl alcohol as a polymer electrolyte solution.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Anode 2 Cathode 3 Reference electrode 4 Support body 5 Silver lead 6 CNT thin film 7 Polymer electrolyte membrane 8 Functional film 9 Display apparatus 10 Sensor device

Claims (9)

Carbon nanotube (CNT) particles are micellized by a mixture of a surfactant capable of electrochemical oxidation and reduction, or capable of oxidation or reduction, and a polyelectrolyte solution, and dispersed or solubilized in an aqueous medium. A method for producing a CNT thin film characterized in that a surfactant is electrochemically oxidized and reduced, or oxidized or reduced to decompose micelles, and the CNT dispersed particles in the micelles are thinned. The surfactant that disperses or solubilizes the CNT particles in an aqueous medium is oxidized near the anode and reduced near the cathode, or oxidized near the anode or reduced near the cathode to decompose the micelle, and in the micelle 2. The method for producing a CNT thin film according to claim 1, wherein the CNT dispersed particles are deposited on the electrode, and the CNT particles deposited on the electrode are fixed to the thin film by a polymer electrolyte membrane. The micelle is decomposed by immersing an electrode having a metal compound nobler than the oxidation potential of the surfactant on the surface in a mixture of the surfactant and the polymer electrolyte solution, and CNT dispersion in the micelle 2. The method for producing a CNT thin film according to claim 1, wherein the particles are deposited on the anode, and the CNT particles deposited on the electrode are fixed to the thin film by a polymer electrolyte membrane. An enzyme is further added to the mixture of the surfactant and the polymer electrolyte, and the surfactant is electrochemically oxidized and reduced, or oxidized or reduced to decompose the micelle, and the CNT dispersed particles and the enzyme in the micelle are separated. The method for producing a CNT thin film according to claim 1, wherein a mixed thin film is formed. It is characterized in that the surfactant that can be oxidized and reduced electrochemically or that can be oxidized or reduced is a micellar agent comprising a ferrocene derivative, and the polymer electrolyte solution is a micellar agent that can fix a thin film. The method for producing a CNT thin film according to any one of claims 1 to 4. The polymer electrolyte solution is at least one of polyvinyl alcohol, gellan gum, Nafion (registered trademark), carrageenan, polyglutamic acid, polyaspartic acid, chitosan, polylysine, polyarginine, polyacrylic acid, alginic acid, and polyornithene. The method for producing a CNT thin film according to any one of claims 1 to 5, wherein: The method for producing a CNT thin film according to any one of claims 1 to 6, wherein the concentration of the polymer electrolyte solution is in the range of 30 to 80%. A biosensor using, as an electrode, a CNT thin film obtained by the method for producing a CNT thin film according to any one of claims 4 to 7, comprising at least an electrode, a support for supporting the electrode, and a CNT on the electrode A biosensor comprising a thin film. The biosensor according to claim 8, further comprising a polymer electrolyte membrane laminated on the CNT thin film.