JP2012096965A - Porous titanium oxide, hydrogen detector, methods for producing them, hydrogen sensor and photoelectric conversion element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a porous titanium oxide and a method for producing the same, to provide a hydrogen gas detector having high sensitivity at room temperature, a method for producing the same, and a hydrogen gas sensor, and further to provide a photoelectric conversion element using the porous titanium oxide.SOLUTION: The porous titanium oxide includes first pores dispersed inside and second pores linked inside while continuing to the first pores in a low-crystalline state. The hydrogen gas detector includes the porous titanium oxide supporting a metal catalyst having photoadsorption/photodissociation capability in the pores, which is laminated on a base portion. The hydrogen sensor includes a light source for emitting light to the hydrogen gas detector; and a light detection unit for detecting transmitted light or reflected light. The photoelectric conversion elements includes the porous titanium oxide laminated on a transparent conductive substrate, with a pigment being supported in the pores. The method of producing the porous titanium oxide comprises steps of: drying a titania sol; and heat-treating it by immersing in hot water kept at an optional temperature of 100°C or lower.

Description

  The present invention relates to porous titanium oxide, a hydrogen detector using the titanium oxide, a method for producing the same, a hydrogen sensor using the hydrogen detector, and a photoelectric conversion element using the porous titanium oxide. is there.

Titanium oxide is generally used in the industrial field because titanium dioxide (TiO ₂ : sometimes referred to as titania) has an oxidation / reduction action by a photocatalytic reaction. Therefore, a porous structure is achieved for the purpose of effectively exhibiting photocatalytic activity. As an example, a structure that forms a porous sintered body by heating a titanium compound that becomes rutile titanium oxide by heating at a high temperature is provided. (See cited reference 1). This is because the rutile type titanium oxide particles grow while consuming the surrounding anatase type titanium oxide as a seed crystal by heating to produce pores. In addition to the above, there was a marimo-like porous titanium oxide formed by assembling fine particles of titanium oxide (see cited document 2). This is because when primary particles of titanium oxide are aggregated to form marimo-shaped secondary particles, the primary particles are aggregated in a coarse state, thereby forming a porous shape having many pores (voids). It is a thing.

  On the other hand, as represented by a fuel cell, a technology for using hydrogen gas as an energy source has been developed and spread, and accordingly, a hydrogen detection material or hydrogen for detecting flammable hydrogen gas. Sensors are important. Titanium oxide is also used as a material for detecting this hydrogen gas.

  Therefore, as a conventional hydrogen detection material using titanium oxide, there is a hydrogen gas detection material in which titanium oxide is coated with palladium oxide hydrate (see Reference 3). This is to detect hydrogen gas by utilizing the fact that palladium oxide and hydrogen gas react to generate palladium black.

  Further, there has been a gas detection element in which palladium or an alloy thereof is supported on a porous thin film made of titanium oxide (see cited document 4). This is because a titanium oxide particle having an average particle diameter of 10 to 100 nm is laminated and thinned on the surface of an insulating substrate such as a glass substrate by heat treatment at a high temperature of 300 ° C. to 700 ° C., and then a metal such as palladium. The substrate was immersed in an electrodeposition solution in which a salt was dissolved in an organic solvent and irradiated with ultraviolet rays to carry palladium or the like. In the production of a thin film using titanium oxide, a dispersion slurry of titanium oxide fine particles is used as an electrophoretic solution, and particles having a particle size of 15 to 25 nm whose crystal phase is an anatase phase are used for the dispersion slurry. The titanium oxide thin film thus formed was made porous by the gap between the stacked particles.

  Titanium oxide used in a photoelectric conversion element forms a crystalline titanium oxide film formed by depositing a titanium alkoxide polycondensate on a conductive substrate by electrophoresis and then firing at a temperature of 400 ° C. or higher. (See Patent Document 5). The dye sensitizer was supported by impregnating the titanium oxide film with a dye sensitizer solution and then drying and supporting the dye sensitizer (see Patent Document 6).

JP 2000-128656 A JP 2006-89297 A JP-A-8-253742 JP 2010-71700 A JP-A-11-310898 JP 2002-93475 A

  Since the invention disclosed in Patent Document 1 transfers anatase-type titanium oxide to rutile-type titanium oxide by heating, the porous titanium oxide formed is of a rutile type. However, the titanium oxide that effectively functions the photocatalytic ability is a titanium oxide having a large proportion of anatase phase, and the above-mentioned invention that uses rutile titanium oxide does not sufficiently exhibit the photocatalytic ability. Furthermore, since it is the structure which heats a titanium compound at high temperature, the board | substrate used when laminating | stacking a titanium oxide had to be limited to what has heat resistance.

  In addition, since the invention disclosed in Patent Document 2 aggregates primary particles of anatase-type titanium oxide to form porous secondary particles, the secondary particles are naturally anatase-type titanium oxide and It will be. However, the porous titanium oxide is configured as powder as secondary particles, and does not constitute a layered or film-like porous titanium oxide.

  In the above two inventions, both are provided with pores so as to form a gap between adjacent crystals, and the photocatalytic performance is improved solely by increasing the surface area of titanium oxide. Was the purpose. Accordingly, even when the metal catalyst is supported on the porous titanium oxide, the change in light transmittance, light reflectance, hue, or electric resistance value due to the reaction of the titanium oxide with hydrogen gas does not affect the titanium oxide. Since these appeared only on the surface of the crystal and did not extend into the interior of the titanium oxide, these changes could not be detected remarkably. As a result, a hydrogen detector in which a metal catalyst is supported on titanium oxide has not been put into practical use.

  On the other hand, regarding the invention relating to the hydrogen detection material, the invention disclosed in Patent Document 3 utilizes the fact that palladium black and hydrogen gas react to produce palladium black, which is exclusively due to the color change of palladium. However, no particular effect was obtained by using titanium oxide.

  In addition, the invention disclosed in Patent Document 4 requires heat treatment at a high temperature of 300 ° C. to 700 ° C. after laminating titanium oxide fine particles by electrophoresis, so that a material having no heat resistance is used as a substrate. There was a problem that could not be. Moreover, even if the average particle diameter of the laminated titanium oxide is small, the average particle diameter is 27.2 nm. In this case, 3 to 10 nm voids and 5 to 100 nm gaps are formed between the particles. However, these voids or gaps are intended to increase the surface area of the titanium oxide thin film, and are not configured to support a metal catalyst inside the titanium oxide film. Therefore, the effect of changing the light transmittance, the light reflectance, the hue, or the electric resistance value due to the reaction of hydrogen gas or the like with titanium oxide cannot be expected.

  The invention relating to the hydrogen sensor uses the above-described hydrogen gas detection material, and when the hydrogen gas detection material detects hydrogen gas, the change in electrical resistance value, light transmittance, or light reflectance is detected. Although it was a structure to measure, the measurement accuracy was left to the hydrogen gas detection material. Therefore, unless the accuracy of the hydrogen gas detection material is improved, the effect as a hydrogen gas sensor cannot be improved. In addition, semiconductor or catalytic combustion type hydrogen sensors are usually used in a state of being heated to 300 ° C. or higher. Therefore, in the detection of hydrogen gas, which is a flammable gas, the possibility of flammability or explosion is said. There was a safety issue.

  Further, the inventions disclosed in Patent Documents 5 and 6 relating to photoelectric conversion elements are for forming a titanium oxide film layer exclusively in order to effectively utilize the photocatalytic activity, and the loading of the dye sensitizer is The surface was limited to the surface of the titanium oxide film layer, and the dye sensitizer was not supported in the pores existing inside the titanium oxide film layer. Therefore, the electrons excited by the dye sensitizer move from the surface of the titanium oxide film layer, but the electrons cannot be sufficiently absorbed by the reduction caused by contact with the reducing agent.

  Therefore, an object of the present invention is to provide a low-crystal-state porous titanium oxide in which pores are relatively uniformly dispersed, and a method for producing the same, and to use the porous titanium oxide to increase the temperature at room temperature. It is intended to provide a sensitive hydrogen gas detector, a method for producing the same, a hydrogen gas sensor using the detector, and a photoelectric conversion element using the porous titanium oxide.

  Thus, as a result of repeated research on porous titanium oxide, the present inventors have completed the following invention.

  The porous titanium oxide according to claim 1 is a titanium oxide in a low crystalline state in which a crystalline portion and an amorphous portion are mixed, and the first pores dispersed therein and the first The second pores are finer than the pores and are continuous with the first pores and chained inside.

  Here, the low crystal state means a crystal state that does not show a peak indicating crystallization in the X-ray diffraction pattern analysis.

  The porous titanium oxide according to claim 2 is the porous titanium oxide according to claim 1, wherein the first pores communicate with the surface by a chain of the second pores. .

  The porous titanium oxide according to claim 3 is the porous titanium oxide according to claim 1, wherein the crystal portion is a single phase of anatase phase.

  The porous titanium oxide according to claim 4 is the porous titanium oxide according to claim 1, wherein the crystal portion is a composite phase of an anatase phase and a rutile phase or a brookite phase.

  A method for producing a low crystalline porous titanium oxide according to claim 5 is a method for producing the porous titanium oxide according to any one of claims 1 to 4 from a titania sol, wherein the titania sol is dried. And a heat treatment by exposure in a gas maintained at an arbitrary temperature of 100 ° C. or lower.

  A method for producing a low crystalline porous titanium oxide according to claim 6 is a method for producing the porous titanium oxide according to any one of claims 1 to 4 from a titania sol, wherein the titania sol is dried. And a heat treatment step by immersing in warm water maintained at an arbitrary temperature of 100 ° C. or less.

  Note that the heat treatment as described above has a slower reaction than a high-temperature treatment such as firing, and therefore it is desirable to leave it in an environment of 100 ° or less for about 2 hours. Therefore, when processing in warm water, it will be immersed in warm water for about 2 hours.

  A hydrogen detector according to claim 7 is a hydrogen detector using the porous titanium oxide according to any one of claims 1 to 4, wherein the titanium oxide region is formed by the porous titanium oxide, And a metal catalyst having hydrogen adsorption / dissociation ability supported in at least the first pores dispersed in the titanium oxide region.

  The hydrogen detector according to claim 8 is the hydrogen detector according to claim 6, wherein the metal catalyst is palladium, platinum, gold, silver, nickel, rhodium, osmium, or an alloy thereof.

  The hydrogen detector according to claim 9 is the hydrogen detector according to claim 6 or 7, wherein the titanium oxide region is a porous titanium oxide thin film formed in a thin film on the surface of the substrate region. Is.

  The hydrogen detector according to claim 10 is the hydrogen detector according to any one of claims 7 to 9, wherein the titanium oxide region is laminated on a base material region formed of a light-transmitting material. It is what.

  The hydrogen detector according to claim 11 is the hydrogen detector according to any one of claims 7 to 10, wherein at least one of the front and back surfaces of the titanium oxide region is made of a material that reflects light. The light reflection layer to be formed is appropriately disposed.

  Note that appropriately arranging the light reflecting layer includes not only the case where the light reflecting layer is laminated on the titanium oxide region or the base material region, but also the case where the base material region itself is formed of a material that reflects light. The case where it provides in the position away from the base material area | region is also included.

  The hydrogen detector according to claim 12 is the hydrogen detector according to any of claims 7 to 11, wherein at least one of the front and back surfaces of the titanium oxide region is made of a conductive material. The conductive regions to be formed are appropriately arranged.

  Note that appropriately arranging the conductive region includes not only the case where the conductive region is laminated on the titanium oxide region or the base region, but also the case where the base region itself is formed of a conductive material. In addition, it includes the case where it is laminated on both the titanium oxide region and the base material region.

  A hydrogen detector according to a thirteenth aspect is the hydrogen detector according to any one of the seventh to ninth aspects, wherein the titanium oxide region is laminated on a surface of a core or a clad of an optical fiber.

  The method for producing a hydrogen detector according to claim 14 includes a step of applying a titania sol to at least a part of a substrate region, a step of drying the titania sol, and a gas maintained at an arbitrary temperature of 100 ° C or lower. A titanium oxide region forming step for forming porous titanium oxide, and a metal catalyst attaching step for attaching a solution of a metal catalyst having hydrogen adsorption dissociation ability to the porous titanium oxide. And an ultraviolet irradiation step of irradiating the porous titanium oxide to which the metal catalyst solution is adhered with ultraviolet rays.

  The method for producing a hydrogen detector according to claim 15, comprising: applying a titania sol to at least a part of the base material region; drying the titania sol; and warm water maintained at an arbitrary temperature of 100 ° C. or less. A titanium oxide region forming step for forming porous titanium oxide, and a metal catalyst attaching step for attaching a solution of a metal catalyst having hydrogen adsorption dissociation ability to the porous titanium oxide. And an ultraviolet irradiation step of irradiating the porous titanium oxide to which the metal catalyst solution is adhered with ultraviolet rays.

  A hydrogen sensor according to claim 16 is a hydrogen sensor using the hydrogen detector according to claim 10 or 11, wherein light is applied to the hydrogen detector and a titanium oxide region constituting the hydrogen detector. And a light detector that detects light transmitted or reflected by the hydrogen detector.

  A hydrogen sensor according to claim 17 is a hydrogen sensor that uses the hydrogen detector according to claim 12, and a power source capable of energizing the titanium oxide region that constitutes the hydrogen detector. And an electric resistance detector for detecting an electric resistance value change when the titanium oxide region is energized.

  The hydrogen sensor according to claim 18 is a hydrogen sensor using the hydrogen detector according to claim 13, and is configured to be continuous with the optical fiber or a part of the optical fiber. The hydrogen detector, a light source that supplies light into the optical fiber, and a light detector that detects light after passing through the optical fiber.

  A photoelectric conversion element according to claim 19 is a photoelectric conversion element using the porous titanium oxide according to any one of claims 1 to 3, wherein the porous titanium oxide is laminated on a transparent conductive substrate. Among the pores dispersed in the porous titanium oxide, a dye is supported in at least the first pore.

  Here, examples of the transparent conductive substrate on which porous titanium oxide is laminated include indium tin oxide (ITO) and fluorine-doped tin oxide (FTO).

  According to the porous titanium oxide according to claim 1, the first and second pores are present inside the porous titanium oxide, and the second pores linked to each other are the first pores. Therefore, the chain of the second pores can function as a movement path of the substance with respect to the first pores formed dispersed inside. For example, a metal catalyst or a dye can be supplied to the first pore through the second pore, and the metal catalyst or the dye can be supported on the first pore. In this case, it is possible to increase the amount of these supported not only by supporting a metal catalyst on the surface of a general titanium oxide but also by supporting it inside.

  According to the porous titanium oxide according to claim 2, in addition to the effect of the porous titanium oxide according to claim 1, the first pore communicates with the surface by the second pore. A substance can be supplied to the first pores from the surface of the porous titanium oxide. For example, when a metal catalyst or pigment is supported on the surface of the porous titanium oxide, the metal catalyst or pigment can be supported on the first pore via the second pore. .

  According to the porous titanium oxide according to claim 3, since the crystallized portion is an anatase phase, in addition to the effect of the porous titanium oxide according to claims 1 and 2, the photocatalytic ability is exhibited. I can do it. That is, when the crystal structure of titanium oxide is anatase, the photocatalytic ability is more easily exhibited than that of rutile. The effect by can be acquired. Accordingly, the photocatalytic ability can be effective not only in the surface of the porous titanium oxide but also in the first pores formed in a dispersed manner.

  According to the porous titanium oxide according to claim 4, since the crystallized portion is a mixture of anatase phase and rutile phase or brookite phase, the porous titanium oxide according to claim 2 has photocatalytic activity. However, the stability of the crystal can be improved, that is, the deterioration of the crystal portion can be suppressed. Therefore, for example, even when the titanium oxide is configured in a film shape or a thin film shape, it has an effect of suppressing deterioration of the surface of the film shape or the thin film shape.

  According to the method for producing porous titanium oxide according to claim 5, since the treatment is performed at a low temperature of 100 ° C. or less, low-crystal titanium oxide with suppressed crystallization can be produced. Then, by mixing the crystallized portion and the amorphous portion, pores can be formed in the amorphous portion. Here, since the treatment is performed at a low temperature, a part of the non-crystalline part is obtained by taking in the non-crystallized part around the crystallized part in the process of gradually crystallizing a part of the titania sol. Cavities, resulting in the formation of pores. At that time, the pores to be formed have a first pore and a finer second pore, but the first pore is formed in a state where the fine second pores are aggregated. It is what is done. Furthermore, since it is processed at a low temperature of 100 ° C. or lower, it has an effect that titanium oxide can be laminated on the surface of a material having poor heat resistance.

  According to the method for producing porous titanium oxide according to claim 6, since the titania sol is treated by being immersed in warm water of 100 ° C. or lower, in addition to the effect of the porous titanium oxide according to claim 4 Thus, stable low temperature treatment can be performed under atmospheric pressure by controlling the temperature of the hot water (ie, controlling the temperature of the hot water rather than the temperature of the titania sol).

  According to the hydrogen detector according to claim 7, the metal catalyst having hydrogen adsorption dissociation ability in the pores (at least the first pores) formed in the titanium oxide region of the porous titanium oxide described above. Because it is supported, the metal catalyst in the pores adsorbs and dissociates the hydrogen present on the surface of the titanium oxide region, and the titanium oxide is hydrogenated inside the titanium oxide region by the dissociated atomic hydrogen. It becomes. Thereby, almost the entire region of the titanium oxide region is hydrogenated, and a hydride is formed over the entire region. Along with this, the absorbance changes greatly over the range of visible light to near infrared light in the titanium oxide region, so that the amount of change can be significant. Therefore, by irradiating the hydrogen detector with light, the presence or absence of hydrogen and the hydrogen concentration can be detected with high sensitivity using the fact that the amount of change or response speed of the light transmittance or reflectance is different. It becomes possible. Further, as described above, since this hydrogen detector uses porous titanium oxide having photocatalytic activity, it can be self-cleaned by irradiating with ultraviolet rays. Therefore, in the case where the detection action is reduced due to adsorption of an organic substance on the surface of the porous titanium oxide, the detection action can be recovered by self-cleaning by ultraviolet irradiation. .

  According to the hydrogen detector according to claim 8, palladium, platinum, gold, silver, nickel, rhodium, osmium, or an alloy thereof is supported on pores formed inside the titanium oxide region. In addition to the effect of the hydrogen detector according to claim 7, the action of adsorbing and dissociating hydrogen becomes efficient. Therefore, the hydrogen adsorption amount and the adsorption speed are improved, which can contribute to a high-speed response of hydrogen detection.

  According to the hydrogen detector of claim 9, since the titanium oxide region is formed into a thin film, in addition to the effect of the hydrogen detector of claim 7 or 8, for example, the hydrogen detector is irradiated with light. However, when hydrogen is detected by the change in the transmittance, the distance that the light passes through the titanium oxide becomes extremely small, and the light transmittance is improved.

  According to the hydrogen detector according to claim 10, since the titanium oxide region is laminated on the substrate region having light permeability, the effect of the hydrogen detector according to claim 7. In addition, it can be used to measure the presence or concentration of hydrogen by measuring the change in light transmittance or the change in response speed. Also, when measuring the amount of change in the light reflectance in the titanium oxide region, the change in the amount of change or the response speed is utilized by utilizing the fact that the reflectance in the titanium oxide region changes due to hydrogen adsorption / dissociation. Can also be used to measure the presence or concentration of hydrogen. In addition, when hydrogen is detected, the presence or absence of hydrogen is detected by the change in the transmittance or reflectance of the irradiated light, so it can be used as a hydrogen detector that operates at room temperature and can detect hydrogen at room temperature. Is something that can be done.

  According to the hydrogen detector according to claim 11, since the light reflecting layer is arranged on at least one of the front and back surfaces of the titanium oxide region, when the titanium oxide region is irradiated with light, Light that has passed through the titanium oxide region is reflected by the light reflecting layer, can pass through the titanium oxide region again, and be emitted to the light irradiation side. Accordingly, since the irradiated light passes through the titanium oxide region twice, it is possible to measure the change in light transmittance remarkably, and to improve the measurement sensitivity. Further, for example, when the light reflecting layers are laminated on both the front and back surfaces of the titanium oxide region, the reflection can be repeated a plurality of times in the titanium oxide region. In this case, with respect to the range in which the irradiated light can be incident and the range in which the reflected light can be emitted, it is possible to detect the light that has been repeatedly reflected a plurality of times by adopting a configuration in which the light reflecting layer is not laminated. In this case, the measurement sensitivity can be improved.

  According to the hydrogen detector according to claim 12, since the conductive region is disposed on at least one of the front and back surfaces of the titanium oxide region, the hydrogen according to any one of claims 7 to 11. In addition to the effect of the detector, it is possible to detect a change in electrical resistance value in the titanium oxide region. That is, by energizing the titanium oxide region and measuring the electric resistance value in the energized state, hydrogen can be detected by the change in the resistance value. Therefore, for example, when it is necessary to detect hydrogen in a bright environment, hydrogen can be detected without measuring the light transmittance. In addition, such a hydrogen detector can also be used as a hydrogen detector that operates at room temperature because hydrogen can be detected by a change in the resistance value of the titanium oxide region at room temperature. Furthermore, for example, when the base material region and the conductive region are light transmissive, it is possible to detect hydrogen from the amount of change in both the light transmittance and the electrical resistance value.

  According to the hydrogen detector according to claim 13, since the titanium oxide region is laminated on the surface of the core or the clad of the optical fiber, a part of a continuous long optical fiber is used as the hydrogen detector. Can function. Therefore, while the optical fiber is placed in the gas to be detected, light is incident from one end of the optical fiber and received at the other end, so that the presence or concentration of hydrogen is detected by a change in the intensity of the received light. It becomes possible to do.

  According to the method for producing a hydrogen detector according to claim 14, the porous titanium oxide having pores can be laminated on a part of the base material region, and a metal catalyst is supported in the pores. The hydrogen detector can be manufactured. At this time, since a titania sol is applied to a part of the base material region and this is processed to laminate porous titanium oxide, the range to be applied is not limited to a flat surface (for example, a curved surface (for example, Porous titanium oxide can be laminated on the surface of an optical fiber core or cladding). In addition, since the titanium oxide layer is processed in an environment of 100 ° C. or lower, even if the material of the base material used as the base material region is an organic polymer resin having poor heat resistance, it is laminated. It becomes possible.

  According to the method for producing a hydrogen detector according to claim 15, since the titania sol is applied to the surface of the substrate region and then immersed in warm water of 100 ° C or lower, the method according to claim 14. In addition to the effect of the porous titanium oxide, the temperature of the hot water can be easily maintained at a constant temperature, and a stable low-temperature treatment can be performed under atmospheric pressure.

  According to the hydrogen sensor according to claim 16, since the light irradiated to the titanium oxide region transmits or reflects through the titanium oxide region and detects the light, power is supplied to the region where hydrogen detection is to be performed. Hydrogen detection is possible in a situation where it is not possible or in an environment where wiring from an area where hydrogen detection is not permitted. In addition, since the metal catalyst is supported in the pores inside the titanium oxide region, the metal catalyst adsorbs and dissociates hydrogen, and this dissociated hydrogen oxidizes the entire region including the inside of the titanium oxide region. Since titanium is hydrogenated and the change in transmittance becomes remarkable, a sensor suitable for hydrogen detection can be configured.

  In addition, when using a hydrogen detector in which a light reflection layer is disposed, the light incident from the titanium oxide region is reflected, and the light detection unit detects this reflected light. The light that has passed through the inside is detected twice, and the change in transmittance can be detected more remarkably. Therefore, the detection sensitivity such as the presence / absence and concentration of hydrogen is improved. For example, when a light reflection layer is partially laminated on both the front and back surfaces of the titanium oxide region, reflection can be repeated a plurality of times in the titanium oxide region. In this case, with respect to the range in which the irradiated light can be incident and the range in which the reflected light can be emitted, it is possible to detect the light that has been repeatedly reflected a plurality of times by adopting a configuration in which the light reflecting layer is not laminated. The detection sensitivity can also be improved.

  In any of the above cases, since hydrogen gas is detected by a change in the transmittance or reflectance of the irradiated light, a room temperature operation type sensor that operates at room temperature can be provided.

  According to the hydrogen sensor of the seventeenth aspect, hydrogen sensing can be performed by utilizing a change in electric resistance value caused by hydrogenation of titanium oxide. If this sensor is used, even if light transmittance cannot be detected in a bright environment, the presence of hydrogen can be measured over time if the power supply from the power source is continuous. It becomes possible. Therefore, when detecting leakage of hydrogen used in the fuel cell, the power source generated by the fuel cell can be used, and it is possible to sequentially detect leakage of hydrogen gas while the fuel cell is operating. Become. Also in this hydrogen sensor, since hydrogen gas is detected by a change in electrical resistance value at room temperature, a room temperature operation type sensor that operates at room temperature can be provided.

  According to the hydrogen sensor of claim 18, the hydrogen detector in which the titanium oxide region is laminated on the core or the clad of the optical fiber is continuous with the optical fiber continuous with the light source, and the optical sensor continuous with the light source Since it is configured to receive the light from the light source and receive the light after passing through the hydrogen detector, the state of the received light changes as the absorbance changes in the titanium oxide region constituting the hydrogen detector. Thus, hydrogen can be detected in the optical fiber constituting the hydrogen detector. At this time, in the case of an optical fiber in which a portion of the titanium oxide region is laminated in the middle of the optical fiber that propagates the light of the light source to the light receiving unit, hydrogen detection is possible at the part where the part is arranged. can do. Moreover, it can also be set as the optical fiber which comprises a hydrogen detection body about all the optical fibers from a light source to a light-receiving part.

  According to the photoelectric conversion element of claim 19, since the dye (dye sensitizer) is supported in the pores existing inside the porous titanium oxide, the surface of the porous titanium oxide is The reducing action of the dye sensitizer due to the reducing agent (for example, iodine electrolyte solution) to be provided can be suppressed. Therefore, the electrons excited by the dye sensitizer can be sufficiently absorbed.

(A) is a flowchart which shows the manufacturing process of titania sol, (b) is a flowchart which shows the manufacturing process of porous titanium oxide. (A) is a model diagram of porous titanium oxide, (b) is a model diagram of a state in which palladium is deposited, and (c) is a model diagram of a state in which palladium is deposited on titanium oxide by a conventional method. (A) is a model figure which shows 1st embodiment of a hydrogen detector, (b) is a model figure which shows 2nd embodiment, (c) is a model figure which shows 3rd embodiment. It is a model figure which shows embodiment which used the base as the optical fiber. (A) is a flowchart which shows the manufacturing process of titania sol, (b) is a flowchart which shows the manufacturing process of 1st embodiment of a hydrogen detector. It is a flowchart which shows the manufacturing process of 2nd and 3rd embodiment of a hydrogen detector. It is the schematic of the hydrogen sensor which uses 1st embodiment of a hydrogen detector as a light transmissive type. It is the schematic of the hydrogen sensor which uses 2nd or 3rd embodiment of a hydrogen detector as a light reflection type. It is the schematic of the hydrogen sensor which uses the hydrogen detection body which used the base as the optical fiber. It is the schematic of the hydrogen sensor which uses 1st embodiment of a hydrogen detection body as an electrical resistance detection type. It is the schematic of the example of a change of the hydrogen sensor which uses 1st embodiment of a hydrogen detection body as an electrical resistance detection type | mold. It is the schematic which shows the example of a 2nd hydrogen sensor. It is the schematic which shows the example of a 3rd hydrogen sensor. It is an X-ray diffraction pattern of a porous titanium oxide film and a porous titanium oxide film carrying palladium. (A) is a TEM image of a porous titanium oxide layer, and (b) and (c) are TEM images of a porous titanium oxide layer supporting palladium. It is the schematic of the experiment apparatus for experimenting about 1st embodiment of a hydrogen detector. It is the schematic of the experimental apparatus for experimenting about 2nd embodiment of a hydrogen detector. 6 is a graph showing the experimental results of Experimental Example 1. 10 is a graph showing an experimental result of Experimental Example 2. It is a graph which shows the result of having experimented the response with respect to hydrogen gas about 1st embodiment of a hydrogen detector. It is a graph which shows the result of having experimented the response with respect to hydrogen gas about 2nd embodiment of a hydrogen detector. It is a graph which shows the result of the comparison experiment with the case where titanium oxide is heat-processed. It is a graph which shows the experimental result at the time of laminating | stacking a titanium oxide on a plastic substrate.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[Method for producing porous titanium oxide]
First, an embodiment according to a method for producing porous titanium oxide will be described. In this embodiment, titanium oxide is produced by a sol-gel method. FIG. 1 (a) is a flow chart showing the production process of titania sol, and FIG. 1 (b) is a flow chart showing the production process of porous titanium oxide.

As shown in FIG. 1 (a), in the titania sol, ethanol is first added to tetranormal butoxytitanium (Ti (O-nBu) ₄ ) and stirred, and further diluted hydrochloric acid, ethanol and ethyl acetoacetate are added and stirred. To generate. For example, dilute hydrochloric acid diluted to about 3% is used and mixed in a weight ratio of tetranormal butoxy titanium: ethanol: dilute hydrochloric acid: ethyl acetoacetate = 1: 20: 1: 1. Can be cited as an example. A polymer material that is soluble in water such as polyethylene glycol may be added. Next, as shown in FIG. 1B, the titania sol is dried, and then subjected to heat treatment (sometimes referred to as low temperature treatment) in an environment of 100 ° C. or lower to produce titanium oxide. The titania sol is generally coated on a substrate such as a glass plate, but here, since it is described specifically for producing porous titanium oxide, description of this type of coating is omitted.

  As a method of low temperature treatment, it is carried out by exposing it to an environment of 100 ° C. or lower for a predetermined time. Specifically, it is exposed to a gas of 100 ° C. or lower or heated to 100 ° C. or lower of hot water. There is a method of immersion. In any case, the temperature may be normal temperature (about 20 ° C.) or higher, and processing can be performed at a relatively low temperature with a long processing time. In this embodiment, a method of exclusively immersing in warm water is employed. And the titanium oxide manufactured by such a process is porous which has a structure where innumerable pores were dispersed inside. Furthermore, the titanium oxide produced in this way is in a low crystalline state. The low crystalline state means a state in which a crystalline part and an amorphous part are mixed, and in particular, in a X-ray diffraction pattern analysis, it is a crystalline state that does not show a clear diffraction peak indicating crystallization. The crystal phase of the crystal portion is a single phase of the anatase phase. However, depending on production conditions, a rutile phase or a brookite phase can be mixed in addition to the anatase phase. Thus, the photocatalytic ability can be sufficiently exhibited by the configuration including the anatase phase.

[Porous titanium oxide]
Next, an embodiment of porous titanium oxide will be described. The present embodiment is porous titanium oxide manufactured by the above-described manufacturing method. Fig.2 (a) is the figure which modeled the cross section of the porous titanium oxide 1 formed in the layer form which has an area suitably. As shown in this figure, the porous titanium oxide 1 of the present embodiment has a large number of first pores 2 as a whole, and second pores 3 finer than the pores 2, There are many more. Note that mesopores may be formed as the first pores 2, and micropores may be formed as the second pores 3. A mesopore refers to a pore having a maximum dimension in the range of 2 nm to 50 nm, and a micropore refers to a pore having a maximum dimension of 2 nm or less.

  As described above, the background to the formation of the pores 2 and 3 having different sizes is that in the process of crystallization gradually under a low temperature environment, the crystallized portion is used as a nucleus, and the surroundings are uneven. This is due to the formation of pores, but the fine second pores 3 gather to form the first pores. The pores 2 and 3 having different sizes are not formed only by mesopores and micropores, and the present invention is not limited to the above combination. For the purpose of clearly distinguishing the first pore 2, the first pore 2 is referred to as a mesopore 2, and the second pore 3 is referred to as a micropore 3.

  The mesopores 2 in the present embodiment are moderately and widely dispersed in the porous titanium oxide 1 without concentrating on the front surface 1a and the back surface 1b of the porous titanium oxide 1. The micropores 3 are also dispersed in a wide range inside the porous titanium oxide 1. Here, a part of the mesopores 2 is formed in the vicinity of the surface, but most of the other are present inside the porous titanium oxide 1 (that is, a position away from the front surface 1a or the back surface 1b). Dispersed and formed micropores 3 exist around these mesopores 2. The micropores 3 exist so as to be continuous with the mesopores 2, and further, other micropores 3 are successively linked to the microholes 3, and this chain causes a state like a narrow path 3 a (hereinafter simply referred to as a narrow path). May be described). As shown in the figure, the mesopores 2a are continuous with the front surface 1a (or the back surface 1b) of the porous titanium oxide 1 through this narrow path 3a, and the mesopores 2b in the vicinity are continuous. That is, the micropores 3 communicate with the outside of the porous titanium oxide 1 and the mesopores 2 and communicate with the mesopores 2 and the neighboring mesopores 2. Further, the neighboring meso holes 2b and 2c may be directly continuous. In this case, both 2b and 2c are continuous without passing through the micro hole 3, but the mesopores 3b and 3c are also connected to the front surface 1a or the back surface 1b by a continuous path formed by the micro holes 3. It is continuous.

  Since the porous titanium oxide of the present embodiment has the above-described configuration, when a metal catalyst having hydrogen adsorption / dissociation ability is supported on the porous titanium oxide, the metal catalyst passes through the micropores 3. Thus, it can be carried inside the mesopores 2. FIG. 2 (b) is a diagram modeling a cross section in a state where the metal catalyst 4 is supported from one surface 1 a of the porous titanium oxide 1. As shown in this figure, a metal catalyst 4 is supported inside mesopores 2 formed by being dispersed inside porous titanium oxide 1. For supporting the metal catalyst 4, there is a method of supporting the metal catalyst 4 by a photo-deposition method (also called a photoprecipitation method) using the photocatalytic ability of the titanium oxide 1. The loading of the metal catalyst 4 by such a method is referred to as “deposition” (hereinafter, this deposition will be described as a representative example). According to the above method, the metal catalyst 4 is naturally deposited on the surface 1a of the porous titanium oxide, but is also deposited inside the mesopores 2. This is because atoms constituting the metal catalyst 4 move from the surface of the porous titanium oxide 1 to the mesopores 11 via the internal micropores 3. The metal catalyst 4 is precipitated in the mesopores 2 having an appropriate surface area, but may also occur on the surfaces of the micropores 3. Moreover, since the porous titanium oxide 1 of this embodiment can fully exhibit the photocatalytic ability, it can also exhibit the self-cleaning effect by ultraviolet irradiation.

  Thus, the surface 1a of the porous titanium oxide 1 is obtained by depositing the metal catalyst 4 having hydrogen adsorption dissociation ability in a large number of mesopores 2 dispersed and formed inside the porous titanium oxide 1. The hydrogen gas can be adsorbed and dissociated in the porous titanium oxide 1 when the hydrogen gas is present in the porous titanium oxide 1, and the hydrogen is diffused into the titanium oxide through the interface where the metal catalyst and the titanium oxide are in contact with each other. As a result, hydrogenation of titanium oxide occurs. Examples of metal catalysts that can adsorb and dissociate hydrogen include palladium, platinum, gold, silver, nickel, rhodium, and osmium. In addition to using only one of these metals, Alloys from more than species can be used.

  For comparison with the present embodiment, FIG. 2C shows a state in which a metal catalyst is deposited on titanium oxide by a conventional method. As shown in this figure, in the titanium oxide 101 according to the conventional method, since no voids are formed in the titanium oxide 1, the metal catalyst 104 is deposited only on the surface 101 a of the titanium oxide 101. . Such a difference makes a big difference when hydrogen is adsorbed and dissociated. That is, when using the conventional titanium oxide 101, the metal catalyst 104 adsorbs hydrogen on the surface 101a of the titanium oxide 101, and the hydrogen remains on the metal catalyst 104 as it is (this state is sometimes referred to as occlusion). However, in the case of the porous titanium oxide of the present embodiment, the metal catalyst 4 adsorbs and dissociates hydrogen by the metal catalyst 4 deposited in the mesopores 2 existing inside the porous titanium oxide 1. Then, this is discharged | emitted with respect to the porous titanium oxide 1, and the porous titanium oxide 1 will be hydrogenated entirely.

[Hydrogen detector]
Next, an embodiment of a hydrogen detector using the porous titanium oxide will be described. FIG. 3 is a diagram modeling a cross section of an embodiment of a hydrogen detector in which porous titanium oxide 1 is laminated on a base 5 having an appropriate area. As shown in this figure, the base 5 is made of a material having a predetermined property, and a region (this is called a base material region) that can exhibit the characteristics of the material is formed. In addition, the porous titanium oxide 1 is formed in a layer shape when laminated on the base portion 5, but can be laminated in a film shape of less than 1 mm and a thickness of 1 μm or more, or a thin film shape of 1 μm or less. . In any case, the porous titanium oxide 1 is laminated to form a region where the porous titanium oxide exists (this is called a titanium oxide region). 3A shows the first embodiment, FIG. 3B shows the second embodiment, and FIG. 3C shows the third embodiment.

  In the first embodiment of the hydrogen detector 10, as shown in FIG. 3A, the porous titanium oxide 1 on which the metal catalyst 4 is deposited is laminated on the surface 5 a of the base 5. As described above, the porous titanium oxide 1 has a mesopore 2 formed therein, and a metal catalyst 4 is deposited inside the mesopore 2 (see FIG. 2B). The hydrogen detector 10 having such a configuration has a two-layer structure of the base 5 and the porous titanium oxide 1, but the base 5 is formed by a base material region having different properties depending on the material, and is porous titanium oxide. As described above, a region (titanium oxide region) in which hydrogen can be adsorbed and dissociated to hydrogenate titanium oxide is formed.

  Here, as the base 5, when configured as a light transmission type or light reflection type hydrogen detector, transparent glass or plastic is used, and when configured as an electric resistance type hydrogen detector, a metal is used. A substrate made of semiconductor or a semiconductor substrate is used. Further, glass, plastic, or conductive plastic with a transparent conductive film laminated thereon can be used as a base so that it can be used as a light transmission type or an electric resistance type. As the conductive film, for example, indium tin oxide (ITO), fluorine-doped tin oxide (FTO), or the like can be used. And such an electroconductive film can also be set as the structure laminated | stacked partially besides the case where it laminates | stacks on the whole surface of a base. By laminating the conductive film in at least two places, the conductive film can function as an electrode when detecting the electric resistance value.

  The light-transmitting hydrogen detector is a hydrogen detector that is used to irradiate light to porous titanium oxide and exclusively detect changes in light transmittance due to the porous titanium oxide. The hydrogen detector of the type is used to detect the change in the intensity of light reflected by the light reflecting layer after irradiating the porous titanium oxide with light. The hydrogen detector is a hydrogen detector used exclusively to detect changes in the electrical resistance value of the porous titanium oxide.

  The base 5 is not limited in shape as long as the base material region is formed with a predetermined thickness, and may be curved as well as flat. Each of FIGS. 3A and 3B shows a cross section, and at first glance, it seems that a flat plate shape is illustrated. However, the shape is not limited to the shape shown in the cross sectional view. Further, since the porous titanium oxide 1 is heat-treated in a low-temperature environment as described above, the base portion 5 is not required to have heat resistance. Therefore, it is possible to use a curved surface that does not have heat resistance, such as an optical fiber core or cladding, as the base 5.

  Since this embodiment is configured as described above, when the base portion 5 is made of a transparent material, a light-transmitting hydrogen detector is obtained. That is, by irradiating light from either the front surface 1a of the porous titanium oxide 1 or the back surface 5b of the base portion 5, the light passes through the porous titanium oxide 1 and the base portion 5 and is emitted to the opposite side. It will be. Therefore, hydrogen can be detected by measuring the change in the amount of light after transmission. This is because the light transmittance and light reflectance change due to the change in the absorbance (optical density) of titanium oxide due to hydrogenation, so that the presence and concentration of hydrogen can be detected according to the amount of change. is there.

  On the other hand, when the base 5 having the above structure is made of a metal substrate, a semiconductor substrate, or another conductive material, or when a conductive film is laminated on the surface 5a of the base 5, an electric resistance type hydrogen detector is used. Will function as. That is, when a current is passed between the base 5 or the conductive film and the porous titanium oxide, a change in resistance value at that time can be measured, and hydrogen is detected based on the change in resistance value. This is because the electrical resistance value is increased by hydrogenating titanium oxide, so that it is possible to detect the presence and concentration of hydrogen according to the amount of change.

  If the conductive material or the conductive film is transparent, a combination type hydrogen detector that can detect a change in electrical resistance and can also detect a change in transmittance by transmitting light. It can be. In this case, both the change amounts can be measured simultaneously, and either one of the change amounts can be selected.

  In the second embodiment of the hydrogen detector, as shown in FIG. 3 (b), porous titanium oxide 1 is layered on the surface 5 a of the base portion 5, and further on the surface 1 a of the porous titanium oxide 1. The light reflection layer 6 is laminated. As in the hydrogen detector 10 of the first embodiment, the porous titanium oxide 1 has mesopores 11 dispersed therein, and the metal catalyst 4 is deposited inside the mesopores 11. .

  Here, when a transparent material that transmits light is used as the base material region constituting the base portion 5, a light-reflecting hydrogen detector is obtained. That is, when light is irradiated from the back surface 5b of the base portion 5, the light can sequentially pass through the base portion 5 and the porous titanium oxide 1, and the light transmitted through the base portion 5 and the porous titanium oxide 1 is reflected by the light reflecting layer 6. It will be reflected by. Further, the reflected light is transmitted again through the porous titanium oxide 1 and the base portion 5 and is emitted from the back surface 5 b of the base portion 5. Therefore, hydrogen can be detected by the change in the amount of reflected light. This is because, similarly to the hydrogen detector 10 of the first embodiment described above, the reflectance of light irradiated on the porous titanium oxide 1 is changed along with the change in transmittance when the light passes through the porous titanium oxide 1. This is due to the change in the state of the light finally emitted due to the change in.

  Further, when the base 5 having the above-described configuration is made of a conductive material (the base 5 is used as a conductive region), or when a conductive film (conductive region) is laminated on the surface 5a of the base 5, the electric resistance It is also possible to function as a hydrogen detector of the type. In this case, the light reflection layer 6 is formed by laminating a conductive metal material. The electrical resistance value of the porous titanium oxide 1 can be measured by energizing the base 5 or the conductive film and the light reflecting layer 6 as electrodes, and hydrogen can be detected by the change in the electrical resistance value. To.

  Furthermore, if the metal substrate or the semiconductor substrate or the conductive film is transparent, it can be used as a hydrogen detector using both the electric resistance type and the light reflection type. In this case, either type may be selected, and both may function simultaneously.

  The light reflecting layer 6 in the hydrogen detector 20 is not laminated on the entire surface 1a of the porous titanium oxide 1, and a part of the light reflecting layer 6 is exposed so that hydrogen can be adsorbed and dissociated. Can do. And since it becomes the part where the light reflection layer 6 is laminated | stacked as a range which can reflect light, when irradiating light, it is limited to the range in which the said light reflection layer 6 exists. Become.

  As shown in FIG. 3C, the third embodiment of the hydrogen detector differs from the hydrogen detector 20 of the second embodiment in that the light reflecting layer 6 is laminated on the back surface 5b of the substrate 5. Is. By constituting the base 5 with a transparent material, a light reflecting hydrogen detector 30 is obtained. That is, by irradiating light from the surface 1a of the porous titanium oxide 1, the light transmitted through the porous titanium oxide 1 and the base portion 5 is reflected by the light reflecting layer 6, and the base portion 5 and the porous titanium oxide 1 are again formed. The light passes through and is released to the surface 1 a of the porous titanium oxide 1. Therefore, hydrogen detection is enabled by measuring the change in the state of the reflected light.

  In the hydrogen detector 30 of the third embodiment, as described above, since the light reflecting layer 6 is laminated on the back surface 5b of the base 5, the laminated state of the base 5 and the porous titanium oxide 1 is the first. This is the same as the hydrogen detector 10 of one embodiment. Therefore, when the base 5 is made of a conductive material, or when a conductive film is laminated on the surface 5a of the base 5, it can function as an electric resistance type hydrogen detector. .

  As the light reflecting layer 6 used in the hydrogen detectors 20 and 30 of the second and third embodiments, a metal material layer can be used. For example, the light reflecting layer 6 is formed by laminating an aluminum thin film or a silver thin film. Layer 6 may be used. In addition, the near-infrared light can be used as the light to be irradiated when functioning as a light transmission type hydrogen detector. This is because when titanium oxide is hydrogenated, it has the property of reducing the light transmittance and light reflectance of visible light and near infrared light.

  Furthermore, it can be set as the structure which uses together the structure of the hydrogen detection bodies 20 and 30 of 2nd and 3rd embodiment. In this case, the light reflecting layer 6 is laminated on the front surface 1 a of the porous titanium oxide 1, and the light reflecting layer 6 is also laminated on the back surface 5 b of the substrate 5. In such a form, for example, by setting the light reflection layer 6 laminated on the surface 1a of the porous titanium oxide 1 as a partial range and irradiating light from a range where the light reflection layer 6 is not laminated, The light can be repeatedly reflected a plurality of times in the middle between the light reflecting layers 6 and 6. Then, by emitting light from another range where the light reflecting layer 6 is not laminated, it is possible to measure the light that has been reflected a plurality of times and detect the presence or absence of hydrogen.

  Next, the state used for an optical fiber is shown in FIG. FIG. 4 (a) shows a structure in which porous titanium oxide 1 is laminated on the outer peripheral surface of the clad 105 as a base, and FIG. 4 (b) shows the formation of porous titanium oxide 1 on the surface of the core 205 as a base. It is what. As is well known, the optical fiber propagates light only to the core due to the difference in refractive index between the clad and the core, and both are made of synthetic resin such as quartz glass or plastic having high light transmittance. Some of these materials do not have heat resistance, but the above-described porous titanium oxide 1 can be laminated on a material that does not have heat resistance. It is.

  When the porous titanium oxide 1 is laminated on the outer peripheral surface of the clad 105 (see FIG. 4A), hydrogen can be detected by a change in the absorption or reflectance of evanescent light generated in the clad 105. That is, the evanescent light oozes out to the side of the clad at the boundary between the clad and the core, but when particles such as impurities are present in this region, it causes scattering and refraction and becomes ordinary light. Therefore, hydrogen can be detected by a change in the absorptance or reflectance when this light is absorbed or reflected by the porous titanium oxide 1 laminated on the outer periphery of the clad 105. Therefore, the porous titanium oxide 1 laminated on the outer peripheral surface of the clad is adsorbed and dissociated by the catalyst by using an optical fiber in which particles are mixed in advance in the clad near the boundary between the clad and the core. Hydrogen can be detected by comparing the state of the propagated light between when it reacts with hydrogen and when it does not react. In this case, the outer surface of the porous titanium oxide 1 is exposed so that the porous titanium oxide can come into contact with hydrogen gas.

  When the porous titanium oxide 1 is laminated on the core 205 (see FIG. 4B), the porous titanium oxide 1 layer functions as a cladding. That is, light is propagated by the core 205 due to the difference in light transmittance with the core 205. Therefore, the porous titanium oxide 1 functioning as a clad changes its light absorption rate or transmittance when hydrogenated, so that the light propagation state in a non-hydrogenated state and the hydrogenated light absorption rate or transmittance. This is different from the light propagation state when the rate is changed. Therefore, hydrogen can be detected by detecting a change in the state of light propagated by the core 205.

  Thus, materials having various properties are assumed for the base portion 5 on which the porous titanium oxide 3 is to be laminated, and the thickness of the base portion 5 (the range of the base material region) inevitably depends on these types. It will be different. On the other hand, the thickness of the porous titanium oxide 1 can be changed as appropriate according to the shape of the base 5 and the form of the hydrogen detector. In this case, the thickness of the porous titanium oxide 1 (the range of the titanium oxide region) may be a film shape of 1 μm or more and less than 1 mm, or a thin film shape of less than 1 μm. Furthermore, it may be laminated to a thickness of 1 mm or more.

  In any form of light transmission type, electric resistance type and combination type hydrogen detectors, and hydrogen detectors using optical fibers, the temperature does not rise due to heating, etc., so hydrogen detection is performed at room temperature. Is possible. This is the same when used for a hydrogen sensor described later.

[Method for producing hydrogen detector]
Next, a method for manufacturing the above-described hydrogen detector will be described. First, the manufacturing method of 1st embodiment (henceforth the hydrogen detector of the 1st form. Refer to Drawing 3 (a)) of a hydrogen detector is explained. The manufacturing process is roughly divided into two processes. The first process is a titania sol manufacturing process, and the second process is a hydrogen detector manufacturing process including a heat treatment of the titania sol. FIG. 5A shows a manufacturing process of titania sol for forming porous titanium oxide, and FIG. 5B shows a process of manufacturing the hydrogen detector 10 of the first embodiment using titania sol. Is shown. In addition, since the manufacturing process of the titania sol which is a 1st process is the same as that of the manufacturing method of the porous titanium oxide 1 mentioned above, suppose that the description is omitted.

  In order to manufacture the hydrogen detector 10 using the titania sol, as shown in FIG. 5 (b), the titania sol is coated on the surface of the base, and after drying and heat treatment at low temperature, the metal catalyst is deposited. is there. Here, a spin coating method, a spray coating method, a dip coating method, or the like can be employed as a coating method on the surface of the base. In addition, various coating methods such as a casting method, a barcode method, or a roll coating method can be used. The titania sol coating appropriately adjusts the film thickness of the coating film, assuming the film thickness of the porous titanium oxide layer formed after the low-temperature treatment, which is a subsequent process.

  After completion of the titania sol coating, the coating is dried at room temperature for about 1 hour, followed by low-temperature treatment. The low temperature treatment is a heat treatment in a relatively low temperature environment of 100 ° C. or lower, as in the above-described method for producing porous titanium oxide. And in this embodiment, 90 degreeC warm water is used, and a low temperature process is performed by being immersed in this warm water for about 2 hours. Thus, the heat treatment immersed in warm water of 100 ° C. or less may be referred to as warm water treatment below. In the hot water treatment, the titania sol can be treated at a temperature equal to or higher than normal temperature (about 20 ° C.). However, if the temperature of the hot water is lowered, the treatment speed is slowed down, so that the immersion time is lengthened. It will be necessary.

  In this way, porous titanium oxide is laminated on the surface of the base. The porous titanium oxide at this time is in a low crystalline state in which mesopores and micropores are dispersed in the inside, as well as in the above-described case, and an amorphous portion is mixed. Further, the crystal phase of the crystal part at this time is exclusively anatase phase, but the rutile phase and brookite phase may be mixed as described above. In addition, in the case where a rutile phase and a brookite phase are mixed, it is assumed that when the ratio of the anatase phase is high, the photocatalytic ability can be efficiently exhibited in the precipitation of the metal catalyst by the next step. The metal catalyst can be deposited even in the crystalline phase.

  Subsequently, a metal catalyst is deposited on the porous titanium oxide. The metal catalyst is deposited by a metal catalyst adhesion process and an ultraviolet irradiation process. In the metal catalyst attaching step, a metal catalyst solution having hydrogen adsorption / dissociation ability is attached to porous titanium oxide. The metal catalyst solution may be attached by spraying or coating the porous titanium oxide in addition to the method of immersing in the metal catalyst solution. As the metal catalyst, palladium, platinum, gold, silver, nickel, rhodium or osmium, or an alloy thereof can be used. Explaining the case where palladium is used as an example, the laminate of the base and porous titanium oxide generated in the above step is immersed in a solution in which a palladium chloride aqueous solution and an oxidizing sacrificial agent such as methanol or ethanol are mixed, The solution can be attached to porous titanium oxide. In addition, when immersed in the solution of a metal catalyst, it can also serve as the said warm water treatment. That is, by appropriately setting the temperature of the metal catalyst solution, the dried titania sol is treated with warm water in the solution. If the appropriate temperature at this time is normal temperature (about 20 °) or more, the same effect as the warm water used in the warm water treatment described above can be obtained.

  Furthermore, the metal catalyst is deposited by a step of irradiating the porous titanium oxide with ultraviolet rays (ultraviolet irradiation step). Since titanium oxide has a photocatalytic ability, palladium is photo-deposited on the surface of the porous titanium oxide while being crystallized by irradiation with ultraviolet rays. As a result, the palladium is deposited on the surface of the porous titanium oxide. The ultraviolet irradiation step may be performed, for example, at the same time as being immersed in the metal catalyst solution or after the metal catalyst solution is adhered to the porous titanium oxide.

  Here, as described above, the porous titanium oxide laminated on the base in this embodiment has mesopores and micropores dispersed therein, and the micropores are narrow paths from the surface of the porous titanium oxide to the mesopores. Thus, palladium is also deposited on the inner surface of the mesopores via the micropores.

  As described above, the first form of the hydrogen detector 10 is manufactured, in which porous titanium oxide is laminated on the surface of the base, and palladium is deposited not only on the surface of the porous titanium oxide but also on the internal mesopores. can do. The method of laminating porous titanium oxide on the surface of the base by such a process and further depositing the metal catalyst can be similarly applied to the core or clad of the optical fiber.

  Next, a second embodiment of the hydrogen detector (hereinafter referred to as a second form of hydrogen detector; see FIG. 3B) and a third embodiment (hereinafter referred to as a third form of hydrogen detector). 3 (c)) will be described. Since the hydrogen detectors 20 and 30 of the second and third embodiments are obtained by further laminating the light reflecting layer 6 with respect to the hydrogen detector 10 of the first embodiment, a laminate of a base and porous titanium oxide is provided. The manufacture of the body and the deposition step of the metal catalyst are the same as in the case of manufacturing the first embodiment 10 of the hydrogen detector. FIG. 6 is a diagram showing steps after the titania sol coating in the above manufacturing method.

  As shown in this figure, the titania sol coating, drying, heat treatment (warm water treatment), immersion in a mixed solution of palladium chloride aqueous solution and methanol or ethanol, and ultraviolet irradiation (metal catalyst deposition step) are as described above. It is the same.

  At the end of the above step, the metal catalyst is deposited on the porous titanium oxide laminated on the surface of the base. Therefore, as the next step, a metal film to be a light reflecting layer is laminated on the surface of the porous titanium oxide. As a metal film, there is a method in which a metal thin film is prepared in advance and adhered to the surface of porous titanium oxide. An example of the metal thin film is an aluminum thin film, and an adhesion method is a method using adhesion.

  Further, a smooth light reflecting layer can be laminated by laminating a transparent plastic plate or the like having a smooth surface on the surface of the porous titanium oxide, and further sticking an aluminum thin film on the surface. Since porous titanium oxide is made porous in a heat treatment step or the like, unevenness may occur on the surface thereof. In such a case, it is preferable to use a plate material having a smooth surface in order to avoid irregular reflection of light. In addition, although superimposition of a transparent board | plate material can also be directly affixed on the surface of porous titanium oxide, you may laminate | stack a base part and the said board | plate material mechanically. The mechanical lamination means a state in which the base portion and the end portion of the plate material are connected to hold them together.

  By performing the lamination process exemplified above, the hydrogen detector 20 of the second form (see FIG. 3B) can be manufactured. In addition, when laminating | stacking a metal film on the surface of porous titanium oxide, it does not cover the whole surface of the said porous titanium oxide with a metal film, but is limited to the range which should reflect light. Thereby, the range which can contact porous titanium oxide with hydrogen is ensured.

  On the other hand, when laminating the light reflecting layer on the back surface of the base portion, it is possible to stick an aluminum thin film on the back surface of the base portion as a metal film. Furthermore, it is also possible to partially change the order of the manufacturing process and previously laminate the light reflecting layer on the back surface of the base before coating the titania sol on the surface of the base. In this case, the titania sol is coated by using the base having the aluminum thin film already attached to the back surface. And in such a process, when a base has heat resistance, it is also possible to laminate | stack a light reflection layer by vapor-depositing a metal material. Examples of the vapor deposition method include sputtering, vacuum vapor deposition, and ion plating. Through the steps exemplified above, it is possible to manufacture a hydrogen detector (see Embodiment 30 of the third embodiment, FIG. 3C) in which a light reflecting layer is laminated on the back surface of the substrate.

  In the various hydrogen detectors manufactured by the above manufacturing method, when hydrogen gas is present in the vicinity, the metal catalyst (palladium in the above example) adsorbs and dissociates the hydrogen gas, and atomic hydrogen is converted into titanium oxide. When the titanium oxide is supplied and hydrogenated, the light transmittance or reflectance is changed. Then, by utilizing the change in transmittance or reflectance of light, that is, by irradiating light with a constant illuminance (light intensity) and observing the state of light after passing through titanium oxide It can be applied as a hydrogen sensor.

  In addition, the manufacturing method of the hydrogen detector demonstrated above has illustrated the case on the assumption that the surface of the base which has a general base material area | region is coated with titania sol. However, when the surface of the base material region (base) has a special configuration, the manufactured hydrogen detector has a different configuration. That is, for example, when a conductive film is laminated on the surface of the base material region (base), the titania sol is coated on the surface of the conductive film. In other words, the conductive film is present between the porous titanium oxide and the porous titanium oxide. In addition, when a base material region (base) is formed of an insulating material and a conductive film is laminated on at least two portions of the surface, the titania sol has both the base surface of the insulating material and the surface of the conductive film. A continuous titanium oxide layer can be laminated.

[Hydrogen sensor]
An embodiment of a hydrogen sensor using the hydrogen detector will be described. First, a case where the above-described hydrogen detectors 10, 20, and 30 are used as a light transmission type or a light reflection type detector will be described, and then a case where an electric resistance type detector is used will be described. And FIG. 7 shows an outline of a light transmission type hydrogen sensor using the first embodiment 10 of the hydrogen detector, and FIG. 8 shows a light reflection type hydrogen sensor using the second or third embodiments 20 and 30. An outline of the sensor is shown.

  As shown in FIG. 7, the hydrogen sensor in the case of using the light transmission type hydrogen detector 10 includes a hydrogen detector 10, a light source 7 that can emit light to the hydrogen detector 10, and the hydrogen detector 10. And a light detection unit 8 that detects light transmitted through the light. The light detection unit 8 includes a light receiving unit 81 and a spectroscope 82 that measures a spectrum of light incident from the light receiving unit 81, and can measure the intensity of light having a predetermined wavelength with respect to transmitted light. . Note that the measured value by the spectroscope 82 is further output to the analyzer 83. The analyzer 83 compares the intensity of the transmitted light having a single or a plurality of specific wavelengths, analyzes the change in the light transmittance or reflectance of the hydrogen detector 10, and determines the presence / absence and concentration of hydrogen gas. The

  The analysis method by the analysis device 83 is based on the intensity of transmitted light when the hydrogen detector 10 is irradiated with light in an environment where hydrogen gas is not present, and the intensity of transmitted light is changed compared to the reference intensity. In this case, the presence of hydrogen gas is determined. The transmitted light to be compared uses light of a specific wavelength, but the change in transmittance or reflectance varies depending on the specific wavelength. Since light having a wavelength around 640 nm (corresponding to the wavelength of a commercially available red LED) has the most significant change in transmittance, and near infrared light near a wavelength of 1000 nm also has comparable changes, these lights Can be used to enable hydrogen detection.

  Here, the hydrogen detector 10 is preferably installed inside the shield 9 made of a material that does not transmit light in an environment where the hydrogen detector 10 is used in a bright place. This is because only the light irradiation from the light source 7 is transmitted. Windows 91 and 92 through which light can pass are provided only at the position where light is emitted and the position where light is emitted. The tip is arranged and the other end is continuous with the light source 7. Various light sources can be used, but in the present embodiment, a white LED or a halogen lamp is used.

  In addition, the tip of the optical fiber 84 is also disposed in the window 92 on the side from which light is emitted, and the light receiving portion 81 of the light detecting portion 7 is continuous with the other end. The transmitted light can propagate to the light receiving unit 81.

  The shield 9 is provided with a gas supply unit 93 and a discharge unit 94, and a gas that should detect the mixing of hydrogen gas (a gas that may be mixed with hydrogen gas, hereinafter referred to as a gas to be detected) is shielded 9. The supply portion 93 is forced to flow in, and the discharge portion 94 can be discharged to the outside of the shield 9. Therefore, by continuously measuring the intensity of light transmitted through the hydrogen detector 10 while forcibly supplying the gas to be detected to the shield 9, the change in transmittance or reflectance is compared with the change in intensity. That is, hydrogen gas can be detected. In this way, the presence or absence of hydrogen gas is continuously detected from sequentially supplied gases. Further, by connecting an alarm device to the analyzing means 83, an alarm sound can be generated when hydrogen gas is detected.

  In the hydrogen sensor using the light reflection type hydrogen detectors 20 and 30, as shown in FIG. 8, the optical fiber 71 continuous to the light source 7 and the tip of the optical fiber 84 continuous to the light detection unit 8 are formed of hydrogen. It is the structure arrange | positioned toward the same surface of the detection bodies 20 and 30. FIG. At this time, the hydrogen detector 20 transmits the porous titanium oxide in such a manner that the light of the light source 7 irradiated through the optical fiber 71 passes through the porous titanium oxide and is reflected by the light reflecting layer. The side closer to the tip of the optical fiber 71 is set, and the light reflection layer is directed to the side far from the tip of the optical fiber 71. In addition, the position of the tip of the optical fiber 84 that is continuous with the light detection unit 8 is such that the incident angle of the light applied to the surface of the light reflection layer can receive the light reflected by the light reflection layer. It is adjusted according to.

  The hydrogen sensor having such a configuration passes through the porous titanium oxide before the irradiated light reaches the light reflecting layer, and passes through the porous titanium oxide even after being reflected by the light reflecting layer. Therefore, since the irradiated light passes through the porous titanium oxide twice, a change in the transmittance or reflectance of the porous titanium oxide can be significant. In particular, when porous titanium oxide is laminated in the form of a thin film, the optical path length through which light is transmitted despite the thin film is enlarged, and the change in the intensity of transmitted light can be sufficiently measured.

  For the light spectrum measurement in the light detection unit 8, the output to the analysis device 83 for analyzing the measurement value, and the analysis method in the analysis device 8, the above-described light transmission type hydrogen detector 10 is used. It is the same as the case of doing.

  The light-reflecting hydrogen detectors 20 and 30 are also installed inside the shield 109 made of a material that does not transmit light when the hydrogen sensor is used in a bright environment. This shield 109 is different from the case where a light transmission type hydrogen detector is used. That is, the shield 109 has a single window 191 that is used for both light irradiation and light emission.

  Further, when the base of the hydrogen detector 10 of the first form is made of a material capable of reflecting light, the light reflection is similar to the hydrogen detectors 20 and 30 of the second and third embodiments described above. Can be used as a mold. In this case, as a matter of course, the porous titanium oxide is the side close to the tip of the optical fiber 71 continuous with the light source 7, and the base is directed to the side far from the tip of the optical fiber 71.

  FIG. 9 schematically shows a hydrogen sensor using a hydrogen detector in which porous titanium oxide is laminated with the core or clad of the optical fiber as a base. FIG. 9 (a) is based on the cladding, and FIG. 9 (b) is based on the core. As shown in these drawings, in this hydrogen sensor, a hydrogen detector is partially formed between the light source 7 to be irradiated and the light source 8 with this light source. The optical fiber 71 connected to the light source 7 is common to the optical fiber 84 connected to the light detection unit 8, and the porous titanium oxide 1 is laminated in the middle so as to function as a hydrogen detector. . This hydrogen detector may be configured separately from the optical fiber 71 connected to the light source 7 and the optical fiber 84 connected to the light detection unit 8. In this case, the light from the light source 7 is continuously detected. You may connect so that it can propagate between part 8.

  In the configuration as described above, it is not necessary to surround the hydrogen detector by the shield 9 described above, and easy measurement is possible by installing it in a place where hydrogen needs to be detected. Further, since the optical fiber can be bent, it can be installed in a narrow space.

  Next, a hydrogen sensor when used as an electric resistance type hydrogen detector will be described. FIG. 10 is a diagram showing the outline. As shown in this figure, electrodes 181 and 182 are provided at appropriate intervals on the surface of porous titanium oxide 1 in the hydrogen detector 10 of the first embodiment, and the resistance value between these electrodes is detected. The electrodes 181 and 182 are connected to the electrical resistance value measuring device 108. The electrical resistance value measuring device 108 includes a power source that can apply a predetermined voltage, and can measure the electrical resistance between both electrodes 181 and 182 (functions as an electrical resistance detection unit).

  Further, the measurement value measured by the electric resistance value measuring instrument 108 is output to the analysis device 183, and the change in the electric resistance value can be analyzed. Specifically, the increase / decrease in the electrical resistance value at the time of hydrogen detection is compared based on the electrical resistance value between the two 1 and 5 in an environment where hydrogen gas is not present. The electrical resistance value when hydrogen gas is not present around the hydrogen detector 10 is the same as the reference value. However, when hydrogen gas is present, hydrogen adsorbed and dissociated by the catalyst reacts with titanium oxide. The electrical resistance value changes due to hydrogenation of titanium oxide. Therefore, the presence of hydrogen is determined by this change in electrical resistance value.

  A modification of the hydrogen sensor will be described. When the base portion of the hydrogen detector 10 of the first form is a conductive material, one electrode 181 is connected to the base portion 5 as shown in FIG. The electrode 182 may be connected, and the electric resistance value between the electrodes 181 and 182 may be detected by the electric resistance value measuring device 108. In the case of such a configuration, the entire electric resistance value including the electric resistance value of the porous titanium oxide 1 can be measured. In this case, the electric resistance value of the base portion 5 is also measured at the same time. However, since the base portion 5 does not change depending on the presence or absence of hydrogen, the change in the electric resistance value of the porous titanium oxide is substantially analyzed. It is.

  Further, this hydrogen sensor has a configuration in which an electrode 181 is connected to the conductive film in a hydrogen detector in which a conductive film is laminated between the base 5 and the porous titanium oxide 1. In this case, since the other electrode 182 is connected to the surface of the porous titanium oxide 1, the electric resistance value of the porous titanium oxide can be detected. And when setting it as such a structure, it is not necessary to comprise the base 5 with an electroconductive material.

  Next, an example of the second hydrogen sensor will be described. In this hydrogen sensor, as shown in FIG. 12, as a hydrogen detector, two conductive films 51 and 52 are laminated on the surface of a base portion 5 made of an insulating material, and porous so as to straddle it. What laminated | stacked the titanium oxide 1 is used. Therefore, the electrical resistance value of the porous titanium oxide 1 can be detected by connecting the electrodes 181 and 182 to these conductive films 51 and 52.

  Furthermore, a third example of the hydrogen sensor will be described. This uses the hydrogen detector 20 of the second form. This hydrogen sensor is shown in FIG. As shown in this figure, the hydrogen detector 20 of the second form has a configuration in which porous titanium oxide is present between the base 5 and the light reflecting layer 6, so that the base 5 and the light reflecting When both layers 6 are conductive materials, the electrical resistance value of the porous titanium oxide can be measured by connecting the electrode of the electrical resistance measuring device 108 to the base 5 and the light reflecting layer 6. It is. Even in this case, naturally, the electrical resistance values of the base 5 and the light reflecting layer 6 are included and measured. However, the electrical resistance value changes in response to hydrogen gas in the porous titanium oxide 1. Therefore, it is possible to detect hydrogen by detecting a change in the overall electric resistance value.

[Photoelectric conversion element]
On the other hand, in the case of constituting a photoelectric conversion element, the porous titanium oxide is laminated on a transparent conductive film, and a dye (dye sensitizer) is used instead of the metal catalyst such as palladium as a mesopore of the porous titanium oxide. What is necessary is just to make it carry in. Specifically, among the electrodes constituting the solar cell, the transparent conductive film is coated on a transparent conductive film installed on the electrolyte side of one electrode, and the transparent conductive film is heat-treated in warm water of 100 ° or less after drying. A porous titanium oxide is laminated thereon. The dye is supported on the mesopores dispersed and present inside the porous titanium oxide layer. The dye can be selected from metal complex dyes, organic dyes, and inorganic dyes. The metal complex dye can be selected from complexes such as hemin, ruthenium, osmium, or iron in addition to metal phthalocyanine such as copper phthalocyanine.

  According to the above photoelectric conversion element, since the dye (dye sensitizer) is deposited in the mesopores dispersed and present inside the porous titanium oxide, it is provided on the surface of the porous titanium oxide. The reducing agent (for example, iodine electrolyte solution) to be used can suppress the reducing action of the dye sensitizer. Therefore, the electrons excited by the dye sensitizer can be sufficiently absorbed.

  The embodiment of the present invention is as described above, but the configuration described in the embodiment is an example, and it is added that the present invention is not limited to this.

  Next, examples of porous titanium oxide will be described. Porous titanium oxide was formed by the manufacturing method described above, and the state of the porous titanium oxide was observed. Specifically, porous titanium oxide was formed according to the manufacturing process shown in FIG. 5 and analyzed using an X-ray diffractometer (XRD) and a transmission electron microscope (TEM). Furthermore, the state in which palladium was deposited (hydrogen detector) was similarly analyzed.

The titania sol was produced by adding ethanol to tetranormal butoxytitanium (Ti (O-nBu) ₄ ) and stirring, and further adding dilute hydrochloric acid, ethanol and ethyl acetoacetate and stirring. As described above, as an example, the addition amount at this time was diluted with about 3% of diluted hydrochloric acid and mixed in a weight ratio of tetranormal butoxy titanium: ethanol: dilute hydrochloric acid: ethyl acetoacetate = 1: 20: 1: 1. . A water-soluble polymer such as polyethylene glycol may be added to the sol, but it is not added in this example. The titania sol is coated on the surface of a plate-like base portion made of transparent glass (hereinafter, this type of base portion is referred to as a substrate) by spin coating, dried at room temperature for 1 hour, and further heated to 90 ° C. or less. Soaked for 2 hours.

  A graph of the X-ray diffraction pattern of the porous titanium oxide is shown in FIG. 14, and a TEM image is shown in FIG. As is clear from this X-ray diffraction pattern, the produced titanium oxide does not show a clear diffraction peak indicating crystallization. Further, it can be confirmed from the TEM image that the titanium oxide is partially crystallized (white portion). It can also be confirmed that dispersed mesopores and micropores (black portions) are present inside the titanium oxide. Thus, the titanium oxide treated in a low-temperature environment cannot confirm the presence of crystals in the X-ray diffraction pattern, but is in a crystalline state that can be confirmed by a transmission electron microscope (this is called a low crystalline state). It is. And since mesopores and micropores (both are sometimes referred to as pores) are dispersed inside, titanium oxide in such a state is called porous titanium oxide. . In the crystalline state as described above, rutile or brookite may be included as long as the crystal part includes anatase. Even when rutile or brookite is mixed in addition to anatase, there is no difference in the porous state inside the titanium oxide because it is in a low crystalline state that does not show a crystallization peak in the diffraction pattern.

  Next, palladium was deposited on the porous titanium oxide. In order to deposit palladium, ultraviolet rays were irradiated for 1 hour while immersing the laminate of the substrate and porous titanium oxide in a solution in which a palladium chloride aqueous solution and methanol as an oxidation sacrificial agent were mixed. The state of the porous titanium oxide in this state was analyzed by X-ray diffraction and a transmission electron microscope.

  A graph of the X-ray diffraction pattern is shown in FIG. 14, and TEM images are shown in FIGS. 15 (b) and (c). In this diffraction pattern, although a peak indicating a palladium crystal (111) plane appears, a crystal of titanium oxide is still not confirmed. Further, in the TEM image (FIG. 15B) in which the titanium element is mapped, the presence of a portion where the titanium element does not exist (black portion) can be confirmed. In the TEM image in which the palladium is mapped (FIG. 15C), the oxidation is performed. It was confirmed that palladium (white part) was dispersed and present inside the titanium.

[Experimental example]
Next, experimental examples relating to the hydrogen detector 10 of the first embodiment and the hydrogen detector 20 of the second embodiment described in the above embodiment will be described. The purpose of the experiment is to verify whether hydrogen gas can be detected by the configuration of this embodiment.

〔experimental method〕
As a hydrogen sensor in the case of using the light transmission type hydrogen detector 10 and the light reflection type hydrogen detector 20, an experimental apparatus similar to the configuration already described in the embodiment is manufactured. Experiment whether to change the transmittance or light reflectance. Both the light-transmissive hydrogen detector 10 and the light-reflective hydrogen detector 20 are obtained by stacking titanium oxide on a glass substrate and depositing palladium by the manufacturing method in the above embodiment. The light-reflecting hydrogen detector 20 uses a metal thin film (aluminum thin film) laminated on the back surface of a glass substrate. As the experimental apparatus, the light transmission type hydrogen detector 10 shown in FIG. 16 is used, and the light reflection type hydrogen detector 20 shown in FIG. 17 is used. The difference from the hydrogen sensor described in the embodiment is that either one of hydrogen gas and air or a mixed gas can be supplied to the gas introduction portions 93 and 193. In order to switch the supply of these gases, valves 95 and 195 are provided in the air supply pipe, and valves 96 and 196 are provided in the hydrogen supply pipe. The measurement value by the light detection unit 8 is output to the analysis device 83, and the analysis device 83 analyzes the state of transmitted light or reflected light. As an experimental analysis device 83, a personal computer is used, and light of many wavelengths is analyzed simultaneously. All experiments were performed at room temperature without any particular heating. In the comparative experiment, the state before depositing palladium is used as a sample.

[Experimental Example 1]
First, the transmittance of visible light and near-infrared light in a state where hydrogen gas was supplied was detected with respect to the wavelength by the experimental apparatus shown in FIG. The result is shown in FIG. As is clear from this result, it can be seen that the transmittance of light of a specific wavelength is greatly reduced. What is judged from this experimental result is that there is the most remarkable change in transmittance for light having a wavelength around 640 nm (corresponding to the wavelength of a commercially available red LED). Moreover, the reduction | decrease of the light transmittance was able to be confirmed also in the near infrared light of wavelength 1000nm vicinity.

[Experimental example 2]
Next, an experiment similar to the above was performed using the experimental apparatus shown in FIG. The result is shown in FIG. Also from this experimental result, the reflectivity for light of a specific wavelength is greatly reduced. According to this experimental result, light having a wavelength near 660 nm has the largest reduction in reflectance, but the reflectance is also sufficiently reduced for light having a wavelength near 640 nm. Furthermore, it was possible to confirm a decrease in reflectivity for wavelengths near 1000 nm, which is a near infrared light region.

  From both the above results, it was found that the hydrogen detectors A and B used in the experiment can detect hydrogen gas with high sensitivity if light having a wavelength near 640 nm is used. Furthermore, it has been found that hydrogen gas can be detected by using not only visible light but also near infrared light.

[Experimental Example 3]
Next, using the experimental apparatus shown in FIGS. 16 and 17, hydrogen and air are alternately supplied from the introduction parts 93 and 193 to the shields 9 and 109, and light having a wavelength near 640 nm at that time is supplied. Transmittance and reflectance were measured. The result about the transmittance is shown in FIG. 20, and the result about the reflectance is shown in FIG. “H ₂ ON” in the figure indicates the time when the supply of hydrogen gas into the shield is started, and “H ₂ OFF” indicates the time when the supply of air is stopped after the introduction of hydrogen is stopped.

  From this result, the light transmittance and reflectance are greatly reduced immediately after the supply of hydrogen gas is started, and the light transmittance and reflectance are recovered soon after switching from hydrogen gas to air. Therefore, it has been found that if hydrogen gas is present in the vicinity of the hydrogen detectors 10 and 20, the presence of hydrogen gas can be detected quickly. It was also found that if hydrogen gas disappeared, it was restored to its original state after a while. In other words, the absence of hydrogen gas (safety) can be detected by the disappearance of the hydrogen gas after the detection of the hydrogen gas.

[Comparison experiment]
Next, a comparative experiment was conducted between a hydrogen detector in which palladium was deposited on porous titanium oxide treated with hot water at 100 ° C. or lower and a hydrogen detector in which palladium was deposited on titanium oxide treated at a high temperature. What was processed at high temperature was produced on the same conditions as the case of processing with warm water except having dried the titania sol and then processing at 400 ° C. In this experiment, only the change in light transmittance was measured, so that only the light transmission type hydrogen detector 20 was used as the hydrogen detector.

  The result of the experiment is shown in FIG. As shown in this figure, the light transmittance at the time of hydrogen detection increases in the case of using a titanium oxide layer processed at a high temperature. This is because palladium is deposited on the surface of titanium oxide, so the light transmittance in a state in which hydrogen is not adsorbed is low, and the metal hydride is generated by the absorption of hydrogen by palladium. It is judged that the rate has been improved. On the other hand, a part of the hydrogen adsorbed on palladium hydrogenates titanium oxide, so the light transmittance decreases, but the light transmittance is slightly increased by canceling both actions. It becomes. Therefore, the amount of change in light transmittance is extremely small.

[Experimental Example 4]
Finally, an experiment was also conducted on a light detector having a structure in which porous titanium oxide was laminated on a transparent plastic substrate. In the experiment, a plastic substrate was used instead of the glass substrate described in the above experimental method. Other than changing the substrate, the experiment method is the same as described above. In this experiment, in order to measure the reflectance of light, a light reflection type hydrogen detector 20 was used.

  The result of the experiment is shown in FIG. From the results of this experiment, it was found that even when a hydrogen detector using a plastic substrate was used, the light reflectance was sufficiently reduced. Accordingly, even when a plastic resin having inferior heat resistance is used as the substrate, it similarly functions as a hydrogen detector. In addition, although it seems that the fall rate of light reflectivity was slightly worse than the light reflectivity (refer FIG. 14) at the time of using a glass substrate, the change of the hydrogen permeability at the time of processing titanium oxide at high temperature Since it is possible to grasp a remarkable change as compared with the above, it is sufficiently practical as a hydrogen detector.

1 Porous titanium oxide 2 Mesopore 3 Micropore 4 Metal catalyst (palladium)
5 Base 6 Light reflecting layer (metal layer)
7 Light source 8 Light detector 9, 109 Shield 10 First form hydrogen detector 20 Second form hydrogen detector 30 Third form hydrogen detector 81 Light receiver 82 Spectrometer 83, 183 Analyzing device 93, 193 Introducing section 105 Cladding 108 Electrical resistance measuring device 181, 182 Electrode 205 Core

Claims (19)

Titanium oxide in a low crystalline state in which a crystalline portion and an amorphous portion are mixed, the first fine pores dispersed inside, and finer than the first fine pores, the first fine pores A porous titanium oxide characterized in that second pores are formed which are continuous with the pores and chained inside. 2. The porous titanium oxide according to claim 1, wherein the first pore communicates with the surface by a chain of the second pores. The porous titanium oxide according to claim 1 or 2, wherein the crystal part is a single phase of anatase phase. The porous titanium oxide according to claim 1 or 2, wherein the crystal part is a mixture of an anatase phase and a rutile phase or a brookite phase. A method for producing the porous titanium oxide according to any one of claims 1 to 4, wherein the titania sol is dried and exposed to a gas maintained at an arbitrary temperature of 100 ° C or lower. And a step of heat-treating the porous titanium oxide. A method for producing the porous titanium oxide according to claim 1 from a titania sol, wherein the titania sol is dried, and immersed in warm water maintained at an arbitrary temperature of 100 ° C or lower. And a step of heat-treating the porous titanium oxide. A hydrogen detector using the porous titanium oxide according to any one of claims 1 to 4, wherein the titanium oxide region is formed by the porous titanium oxide and at least dispersed in the titanium oxide region. A hydrogen detector comprising a metal catalyst having a hydrogen adsorption / dissociation ability supported in the first pore. The hydrogen detector according to claim 7, wherein the metal catalyst is palladium, platinum, gold, silver, nickel, rhodium, osmium, or an alloy thereof. The hydrogen detector according to claim 7 or 8, wherein the titanium oxide region is a porous titanium oxide thin film formed in a thin film shape. 10. The hydrogen detector according to claim 7, wherein the titanium oxide region is laminated on a base material region formed of a light-transmitting material. 11. The light reflecting layer formed of a material that reflects light is appropriately disposed on at least one of the front and back surfaces of the titanium oxide region. Hydrogen detector. The hydrogen detector according to claim 7, wherein a conductive region formed of a conductive material is appropriately disposed on at least one of the front and back surfaces of the titanium oxide region. . The hydrogen detector according to claim 7, wherein the titanium oxide region is laminated on a surface of a core or a clad of an optical fiber. Including a step of applying a titania sol to at least a part of the substrate region, a step of drying the titania sol, and a heat treatment by exposure to a gas maintained at an arbitrary temperature of 100 ° C. or lower, A titanium oxide region forming step of forming quality titanium oxide;
A metal catalyst attaching step of attaching a metal catalyst solution having hydrogen adsorption dissociation ability to the porous titanium oxide;
A method for producing a hydrogen detector, comprising: an ultraviolet irradiation step of irradiating the porous titanium oxide to which the metal catalyst solution is adhered with ultraviolet rays. Including a step of applying a titania sol to at least a part of the base material region, a step of drying the titania sol, and a step of heat-treating by immersing in warm water maintained at an arbitrary temperature of 100 ° C. or lower, A titanium oxide region forming step of forming quality titanium oxide;
A metal catalyst attaching step of attaching a metal catalyst solution having hydrogen adsorption dissociation ability to the porous titanium oxide;
A method for producing a hydrogen detector, comprising: an ultraviolet irradiation step of irradiating the porous titanium oxide to which the metal catalyst solution is adhered with ultraviolet rays. A hydrogen sensor using the hydrogen detector according to claim 10 or 11, wherein the hydrogen detector, a light source for irradiating light to a titanium oxide region constituting the hydrogen detector, and the hydrogen detector. A hydrogen sensor, comprising: a light detection unit that detects light that has been transmitted or reflected. A hydrogen sensor using the hydrogen detector according to claim 12, wherein the hydrogen detector, a power source capable of energizing a titanium oxide region constituting the hydrogen detector, and an electrical resistance of the titanium oxide region A hydrogen sensor comprising: an electric resistance detection unit that detects a change in value. 14. A hydrogen sensor using the hydrogen detector according to claim 13, wherein the hydrogen detector is configured to be an optical fiber, continuous with the optical fiber, or configured as a part of the optical fiber, and the optical fiber. A hydrogen sensor comprising: a light source that supplies light therein; and a light detection unit that detects light after passing through the optical fiber. It is a photoelectric conversion element using the porous titanium oxide in any one of Claim 1 thru | or 3, Comprising: The said porous titanium oxide is laminated | stacked on a transparent conductive substrate, It is disperse | distributed inside this porous titanium oxide. A photoelectric conversion element, wherein a dye is supported in at least the first pore among the fine pores.