JP2009292680A - Photocatalyst nanosheet, photocatalyst material, and their manufacturing methods - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a photocatalyst nanosheet substitutable for titanium oxide nanosheet, and a photocatalyst material and their manufacturing methods. <P>SOLUTION: The photocatalyst nanosheet comprised of NbO<SB>6</SB>and/or TiO<SB>6</SB>octahedral units, and is characterised by being formed of nanosheet selected from the group consisting of Nb<SB>3</SB>O<SB>8</SB>, Nb<SB>6</SB>O<SB>17</SB>, TiNbO<SB>5</SB>, Ti<SB>2</SB>NbO<SB>7</SB>, Ti<SB>5</SB>NbO<SB>14</SB>, Ca<SB>2</SB>Nb<SB>3</SB>O<SB>10</SB>and LaNb<SB>2</SB>O<SB>7</SB>. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

The present invention relates to a photocatalyst nanosheet, a photocatalyst material using the same, and a production method thereof, and more specifically, a photocatalyst nanosheet whose crystal is composed of NbO ₆ and / or TiO ₆ octahedral units, a photocatalyst material using the same, and , And a manufacturing method thereof.

  Titanium dioxide such as anatase and rutile is known to exhibit photocatalytic and photoinduced hydrophilization properties. By coating these titanium dioxide as a thin film on various materials such as window materials and building materials, it has attracted a lot of attention that it has the effect of keeping the surface of the member clean by its photocatalytic property and photo-induced hydrophilic property, Application has begun as a self-cleaning coating technology for building windows, walls, and tent exteriors.

  These titanium dioxides are usually coated by a liquid phase process typified by a sol-gel method, a gas phase process typified by a sputtering method, or the like. However, the coated titanium dioxide thin film has a structure in which spherical titanium dioxide particles are bonded to each other and spread in a two-dimensional direction. Therefore, the surface unevenness | corrugation by a titanium dioxide particle is intense, and there exists a problem that initial antifouling property is scarce.

  For such a problem, a technique of coating a titanium oxide nanosheet instead of titanium dioxide is known (see, for example, Patent Document 1). According to Patent Document 1, a titanium oxide nanosheet having a molecular level thinness and a lateral size of micron or more is synthesized by peeling a layered titanium oxide into a single layer.

  This titanium oxide nanosheet has extremely high two-dimensional anisotropy not found in a titanium dioxide thin film, in addition to exhibiting photocatalytic properties and photoinduced hydrophilization properties like titanium dioxide such as anatase. In addition, since titanium oxide nanosheets are obtained as colloids dispersed in a liquid medium, the thickness can be precisely controlled at the nano level, so that the film-forming property is excellent and large-area coating can be performed easily and inexpensively. There is an advantage. Moreover, the surface of the titanium oxide nanosheet obtained in this way has a feature that it is smooth at the nano level.

  With such a titanium oxide nanosheet, a photocatalytic thin film excellent in initial antifouling property is expected. However, the thin film formed by coating the titanium oxide nanosheet has a problem that the photocatalytic property is not necessarily sufficient as compared with the photocatalytic thin film formed by sol-gel method using titanium dioxide particles.

JP-A-9-227123

  In view of the above circumstances, the present invention is a photocatalyst nanosheet that exhibits photocatalytic properties and photoinduced hydrophilization characteristics that are similar to or better than titanium dioxide while having excellent smoothness similar to titanium oxide nanosheets. It is an issue to provide.

  It is another object of the present invention to provide a photocatalyst nanosheet made of a nanosheet having such a function and excellent adhesion to a member.

  It is another object of the present invention to provide a photocatalyst material using a photocatalyst nanosheet having such a function and a method capable of producing it in a high yield.

(1) The photocatalyst nanosheet according to the present invention is composed of NbO ₆ and / or TiO ₆ octahedral units, and includes Nb ₃ O ₈ , Nb ₆ O ₁₇ , TiNbO ₅ , Ti ₂ NbO ₇ , Ti ₅ NbO ₁₄ , and Ca ₂ Nb _3. characterized by comprising the O ₁₀ and LaNb nanosheet selected from the group consisting of ₂ O _7.
(2) The photocatalyst nanosheet according to (1), wherein the selected nanosheet is peeled from a layered compound containing an alkali metal.
(3) The method of producing a photocatalyst nanosheets according to the present _{invention, MNb 3 O 8, M 4} Nb 6 O 17, MTiNbO 5, MTi 2 NbO 7, M 3 Ti 5 NbO 14, MCa 2 Nb 3 O 10 and MLaNb ₂ O Hydrogen ion exchange in which a layered compound containing an alkali metal selected from the group consisting of ₇ (where M is an alkali metal) is acid-treated using an acid aqueous solution, and the alkali metal in the layered compound is exchanged And a step of reacting the hydrogen ion exchanger with a basic substance to obtain a colloidal solution composed of nanosheets from which the hydrogen ion exchanger has been peeled off.
(4) A photocatalytic material comprising a photocatalytic thin film provided on a substrate according to the present invention, wherein the photocatalytic thin film comprises the photocatalytic nanosheet according to either (1) or (2). To do.
(5) The photocatalytic material according to (4), wherein the photocatalytic thin film has a maximum surface roughness of 2 nm.
(6) The method for producing a photocatalytic material according to the present invention comprises Nb ₃ O ₈ , Nb ₆ O ₁₇ , TiNbO ₅ , Ti ₂ NbO ₇ , Ti ₅ NbO ₁₄ , Ca ₂ Nb ₃ O ₁₀ and LaNb ₂ O _7. A step of applying a colloidal solution containing a nanosheet selected from
(7) The method according to (6), further including a step of performing a heat treatment in a temperature range of 100 ° C. or higher and lower than 900 ° C. following the applying step.
(8) In the method according to (6), the applying step is selected from the group consisting of an alternating adsorption method, an LB method, a drop method, a spin coating method, and a dip coating method.

Since the photocatalyst nanosheet by this invention shows photocatalytic property, it functions as a photocatalyst nanosheet for photocatalyst thin films. Among them, Nb ₃ O ₈ , TiNbO ₅ , Ca ₂ Nb ₃ O _10, and LaNb ₂ O ₇ exhibit higher photo-induced hydrophilization characteristics than existing anatase, and thus have excellent self-cleaning function, dust-proof function, and cooling function. Yes. In addition, the photocatalyst nanosheet according to the present invention maintains the nanosheet structure even after high-temperature heat treatment at 800 ° C., and exhibits higher photo-induced hydrophilization characteristics than existing anatase, so that it can function even by heat treatment when applied to a member. Will not be damaged. Moreover, since the photocatalyst nanosheet by this invention is obtained by peeling a layered compound, it has a sheet | seat thickness of a molecular level. If such a photocatalyst nanosheet is made into a thin film, a photocatalytic thin film excellent in initial antifouling property without unevenness can be obtained. In addition, the photocatalytic nanosheet according to the present invention is advantageous in a practical process because the photocatalytic property and the photoinduced hydrophilization property are not impaired even by high-temperature heat treatment.

  According to the photocatalyst material of the present invention, the photocatalyst material comprises a base material and a photocatalyst thin film comprising the above-described photocatalyst nanosheet provided thereon. The photocatalyst thin film can adhere to a substrate having an arbitrary shape and an arbitrary surface state by utilizing the high flexibility in the in-plane direction of the photocatalyst nanosheet. For this reason, there is no restriction | limiting in the material and shape of a base material, and it is suitable. In addition, the photocatalytic thin film also exhibits the photocatalytic properties and photoinduced hydrophilization characteristics of the photocatalyst nanosheet, and has unevenness (2 nm at the maximum) reflecting the sheet thickness of the photocatalyst nanosheet, and thus has excellent initial antifouling properties.

  According to the method for producing a photocatalyst nanosheet of the present invention, a photocatalyst nanosheet is obtained by peeling a single layer using a layered compound containing an alkali metal as a starting material. Since only an acid treatment and a reaction with a basic substance are required, a complicated apparatus is unnecessary, and a photocatalyst nanosheet can be provided simply and inexpensively.

  According to the method for producing a photocatalyst material of the present invention, a photocatalyst material is obtained by applying a colloidal solution comprising photocatalyst nanosheets to a substrate. The structural flexibility of the photocatalyst nanosheet allows the application of a substrate having an arbitrary shape and an arbitrary surface state, which is advantageous without limitation of use. The application to the substrate is easily performed by various wet processes, and the film thickness, size, etc. of the photocatalytic thin film can be controlled according to the application.

The present inventors have paid attention to titanium and / or niobium-based layered oxides containing alkali metals as materials that can be substituted for titanium oxide nanosheets. Examples of the titanium and / or niobium-based layered oxide containing an alkali metal include, for example, KNb ₃ O ₈ , K ₄ Nb ₆ O ₁₇ , KTiNbO ₅ , CsTi ₂ NbO ₇ , K ₃ Ti ₅ NbO ₁₄ , and KCa ₂ Nb. _{There are 3} O ₁₀ and KLaNb ₂ O ₇ .

  A nanosheet of a layered compound containing an alkali metal (hereinafter simply referred to as an alkali metal-containing layered compound) has a semiconducting band electronic structure derived from a Ti3d orbital or an Nd4d orbital and an O2p orbital. Based on such a band electronic structure, the present inventors have revealed that these nanosheets exhibit photocatalytic properties and are effective as a photocatalytic thin film and a photocatalytic material.

In addition, some of the alkali metal-containing layered compounds described above (compounds excluding K ₃ Ti ₅ NbO ₁₄ ) have been reported to be nanosheets, but good quality nanosheets have not been obtained. Therefore, the present inventors established a synthesis and production process of an alkali metal-containing layered compound as a raw material in order to obtain these nanosheets with good quality and high yield.

  Furthermore, the present inventors succeeded in making nanosheets obtained from these alkali metal-containing layered compounds into thin films and controlling the film thickness, surface structure, roughness, and in-film structure at the nano level.

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

(Embodiment 1)
FIG. 1 is a schematic view of a photocatalyst nanosheet according to the present invention.

Photocatalyst nanosheet 100 according to the _invention, selected from the group consisting of _{Nb 3 O 8, Nb 6 O} 17, TiNbO 5, Ti 2 NbO 7, Ti 5 NbO 14, Ca 2 Nb 3 O 10 and lanB ₂ O ₇ nanosheet Consists of.

The photocatalytic nanosheet according to the present invention is selected from the group consisting of MNb ₃ O ₈ , M ₄ Nb ₆ O ₁₇ , MTiNbO ₅ , MTi ₂ NbO ₇ , M ₃ Ti ₅ NbO ₁₄ , MCa ₂ Nb ₃ O ₁₀ and MLaNb ₂ O _7. It is obtained by exfoliating a single layer of the alkali metal-containing layered compound 110 to be formed. Here, M is any one of alkali metal, Li, Na, K, Rb and Cs, and K and Cs are preferable from the viewpoint of ease of synthesis.

  FIG. 2 is a schematic diagram of various photocatalyst nanosheets according to the present invention.

Each photocatalytic nanosheet according to the present invention shown in FIG. 2 includes Nb ₃ O ₈ (FIG. 2A), Nb ₆ O ₁₇ (FIG. 2B), TiNbO ₅ (FIG. 2C), Ti ₂ NbO. ₇ (FIG. 2D), Ti ₅ NbO ₁₄ (FIG. 2E), Ca ₂ Nb ₃ O ₁₀ (FIG. 2F) and LaNb ₂ O ₇ (FIG. 2G). All of the photocatalytic nanosheets are based on octahedral units 200 of NbO ₆ and / or TiO ₆ , and the units 200 are two-dimensional crystals in a predetermined arrangement. The photocatalyst nanosheet according to the present invention based on such a unit 200 has various structures in which elements are regularly arranged and rich in variety.

With such a rich structure, various effects can be obtained depending on the nanosheet to be selected. For example, Ca ₂ Nb ₃ O ₁₀ shown in FIG. 2F has a rigid crystal structure and can easily form the alkali metal layered compound 110. Therefore, there exists an effect that the big nanosheet 100 is easy to be obtained. 2D and 2E, Ti ₂ NbO ₇ and Ti ₅ NbO ₁₄ have a relatively simple crystal structure, and thus have an effect that a nanosheet with high structural flexibility can be easily obtained. Furthermore, since there are strengths of photocatalytic properties and photoinduced hydrophilization properties depending on the type of nanosheets, it is advantageous because nanosheets can be selected according to requirements.

All of these nanosheets exhibit photocatalytic properties and photoinduced hydrophilization properties as well as existing titanium oxides such as anatase. Among these, TiNbO ₅ , LaNb ₂ O ₇ , Nb ₃ O ₈ and Ca ₂ Nb ₃ O ₁₀ are confirmed to exhibit higher photo-induced hydrophilization characteristics than titanium oxide, and are self-cleaning function, dust-proof function and cooling. Effective for function. These characteristics will be described in detail in Examples described later.

  As described above, the thickness (sheet thickness) of the nanosheet obtained by peeling off the alkali metal-containing layered compound is at the molecular level, whereas the lateral size is on the order of microns. The theoretical sheet thickness obtained from the crystal structure is about 1 to 2 nm. By making such a photocatalyst nanosheet into a thin film, a photocatalyst thin film having no irregularities reflecting the sheet thickness can be obtained. It is advantageous for improvement. Specifically, as will be described later, the photocatalytic thin film has a single-layer structure or a multilayer structure of photocatalyst nanosheets. The unevenness (surface roughness) of the photocatalyst thin film is determined by the partial overlap of the photocatalyst nanosheets on the surface or the gaps that can occur between the photocatalyst nanosheets. 2 nm. A method for producing such a photocatalytic thin film will be described in detail in Embodiment 2.

Further, since the size in the surface direction is on the order of microns, it is advantageous for obtaining a photocatalytic thin film having a large area. Furthermore, as described above, the photocatalyst nanosheet according to the present invention is at the molecular level in the thickness direction, but has a micron order spread in the plane direction, and has structural flexibility unique to the nanosheet. Thereby, if the photocatalyst nanosheet according to the present invention is made into a thin film, a flexible photocatalyst thin film can be obtained. Therefore, there is no limitation on the shape of use and the versatility is high.

Furthermore, it was found that these photocatalytic nanosheets 100 maintain their crystal structure even when subjected to a high-temperature heat treatment at 800 ° C., for example. This is considered because the two-dimensional sheet structure in which the octahedral units 200 of NbO ₆ or TiO ₆ are bonded is stable. Due to such characteristics, the photocatalytic property and the photo-induced hydrophilic property are not impaired even after the high-temperature heat treatment. Such characteristics are extremely advantageous because the heat treatment in the process can be performed when the photocatalyst nanosheet 100 of the present invention is put into practical use.

  Such a photocatalyst nanosheet 100 is usually dispersed in a solvent and held as a colloidal solution. Such holding makes it possible to store for a long time, and is easy to carry and transport. Furthermore, the location for thinning the photocatalytic nanosheet 100 is not specified, which is advantageous in terms of process.

  FIG. 3 shows a schematic diagram of a photocatalytic material according to the present invention.

  The photocatalytic material 300 includes a base material 310 and a photocatalytic thin film 320 positioned thereon. The photocatalyst thin film 320 is composed of the photocatalyst nanosheet 100 described with reference to FIGS. 1 and 2.

  The base material 310 is an arbitrary material to which the photocatalytic thin film 320 is applied, and examples thereof include window materials such as buildings and vehicles, outer wall materials, and ceramic materials. As described above, since the photocatalyst nanosheet 100 has structural flexibility, the photocatalytic thin film 320 formed from the photocatalyst nanosheet 100 also has structural flexibility. Therefore, the photocatalytic thin film 320 can be positioned on the base material 310 reflecting such a shape even if the surface of the base material 310 has curvature or unevenness. The photocatalytic material 300 according to the present invention is effective as any material that requires photoinduced hydrophilization characteristics such as photocatalytic property and self-cleaning function because the material and surface shape of the substrate 310 are not limited.

  The photocatalytic thin film 320 may have a single layer structure or a multilayer structure of the photocatalyst nanosheet 100. When the photocatalyst thin film 320 has a single-layer structure of the photocatalyst nanosheet 100, the photocatalyst thin film 320 intends a state in which the photocatalyst nanosheets 100 are integrated and arranged in the plane direction. When the photocatalyst thin film 320 is a multilayer structure of the photocatalyst nanosheet 100, the photocatalyst thin film 320 intends the state where the photocatalyst nanosheet 100 was laminated | stacked on both sides of counter ion. The counter ions function to maintain the bonds between the photocatalyst nanosheets 100.

  Thus, the film thickness of the photocatalyst thin film 320 can be controlled on the nano order (molecular level) by the single layer structure or the multilayer structure of the photocatalyst nanosheet 100. Note that the surface roughness (unevenness) of the photocatalyst thin film 320 is dependent on the degree of partial overlap of the photocatalyst nanosheets 100 or the degree of gaps that can occur between the photocatalyst nanosheets 100, regardless of whether it is a single layer structure or a multilayer structure. However, it has been found that the maximum can be suppressed to 2 nm. In order to improve the initial antifouling property, it is said that the smaller the surface roughness is, the better. It is suggested that the photocatalytic thin film 320 according to the present invention is extremely excellent in the initial antifouling property.

  The photocatalytic material 300 according to the present invention is applicable to any application that requires photocatalytic properties (for example, an antibacterial function) by the photocatalytic thin film 320. For example, in the case where the substrate 310 is a tile, the photocatalytic material 300 functions as an antibacterial tile that decomposes dirt and germs by ultraviolet light irradiation. In addition, the photocatalytic material 300 can be applied to any application that requires photoinduced hydrophilization characteristics (self-cleaning function, dustproof function, cooling function) by the photocatalytic thin film 320. For example, when the substrate 310 is an external window material, the photocatalyst material 300 functions as a window material having a self-cleaning function that is washed with rainwater, and when the substrate 310 is a mirror, the photocatalyst material 300 is a photocatalyst material. The material 300 functions as a mirror having an anti-fogging function because water droplets are not formed on the surface (that is, a thin water film). When the substrate 310 is a building material, the photocatalytic material 300 is a building material. Since it can be covered with a small amount of water, it functions as an energy-saving building material that enables air cooling and wall cooling. As a matter of course, the photocatalyst material 300 is also within the scope of the assumption that the photocatalyst material 300 is used for a combination of functions of the photocatalyst nanosheet 100.

(Embodiment 2)
Next, a method for producing the photocatalyst nanosheet 100 and the photocatalyst material 300 described in Embodiment 1 will be described.

  FIG. 4 is a flowchart showing a manufacturing process of the photocatalyst nanosheet according to the present invention.

  Each step will be described.

Step S410: The alkali metal-containing layered compound 110 (FIG. 1) is acid-treated using an acid aqueous solution to generate a hydrogen ion exchanger. The alkali metal-containing layered compound 110 is composed of MNb ₃ O ₈ , M ₄ Nb ₆ O ₁₇ , MTiNbO ₅ , MTi ₂ NbO ₇ , M ₃ Ti ₅ NbO ₁₄ , MCa ₂ Nb ₃ O ₁₀ and MLaNb ₂ O _7. Selected. Here, M is an alkali metal that is a group 1 element in the periodic table. As described above, M is preferably K or Cs from the viewpoint of synthesis. The alkali metal-containing layered compound 110 has a layered structure of an alkali metal M and a titanium / niobium-based nanosheet. For example, when the alkali metal-containing layered compound 110 is MTiNbO ₅ , the MTiNbO ₅ has a layered structure of an alkali metal M and TiNbO ₅ . As the acid aqueous solution, an inorganic acid or an organic acid can be used, but it is usually selected from the group consisting of hydrochloric acid, sulfuric acid, nitric acid, acetic acid and carbonic acid.

  When the alkali metal-containing layered compound 110 is acid-treated with an acid aqueous solution, the alkali metal M ions in the alkali metal-containing layered compound 110 are replaced with hydrogen ions or oxonium ions to generate a hydrogen ion exchanger (not shown). .

  As for the acid treatment conditions, the regulation of the acid aqueous solution is 0.1 or more, and the reaction is performed at room temperature (10 ° C. to 30 ° C.) for at least 24 hours. When the regulation of the acid aqueous solution is smaller than 0.1 regulation, ion exchange does not proceed sufficiently, and the peeling reaction described later may be difficult to occur.

Step S420: A hydrogen ion exchanger and a basic substance are reacted to obtain a colloidal solution containing nanosheets. The basic substance is a substance that functions to exfoliate the layered structure of the hydrogen ion exchanger obtained in step S420, and specifically includes tetrabutylammonium ion (TBA ⁺ ), tetrapropylammonium ion, tetraethylammonium. An aqueous solution containing ions, tetramethylammonium ions, n-propylamine, n-ethylamine and ethanolamine. Among these, an aqueous solution of TBA ⁺ is desirable from the viewpoint of yield.

  The molar ratio of protons in the hydrogen ion exchanger to the basic substance is preferably in the range of 1-10. If the molar ratio is less than 1 or exceeds 10, peeling may not proceed sufficiently. It should be noted that the optimum molar ratio varies depending on the alkali metal-containing layered compound used.

  In the peeling reaction, the hydrogen ion exchanger and the basic substance may be simply mixed at room temperature, but may be shaken in addition to the mixing. Thereby, since peeling accelerates | stimulates, a yield improves. The peeling reaction can be obtained at a yield of 100% by shaking for several days (for example, 4 days) or more. As peeling progresses, it becomes a milky white solution, so the reaction may be stopped by visual inspection.

  In this way, a colloidal solution in which the photocatalyst nanosheet 100 according to the present invention is dispersed, from which the alkali metal-containing layered compound 110 has been peeled, can be obtained. According to the method of the present invention, the alkali metal layered compound 110 may be simply acid-treated and peeled off, so that a dedicated apparatus is unnecessary. Therefore, manufacturing is simple and suitable for mass production.

  Next, the manufacturing method of the photocatalyst material 300 (FIG. 3) is demonstrated.

  The photocatalytic material 300 is obtained by applying a colloidal solution containing the photocatalytic nanosheet 100 (FIG. 1) to the substrate 310 (FIG. 3). For example, the colloidal solution may be applied to the substrate following Step S420 described with reference to FIG. A colloidal solution is prepared using step S410 and step S420.

  As described in Embodiment 1, the base material 310 to which the colloidal solution is applied can be applied with any material and shape that should exhibit photocatalytic properties. The base material 310 is preferably subjected to a hydrophilic treatment. Thereby, since the wettability of the base material 310 is improved, the application of the colloidal solution to the base material 310 is facilitated.

  Application to the substrate 310 can be performed by any method through a liquid phase process, but preferably includes an alternate adsorption method, a Langmuir-Blodget (LB) method, a spin coating method, a drop method, and a dip coating method. A method selected from the group is adopted. Each method will be described in further detail.

(1) Alternate Adsorption Method FIG. 5 is a diagram showing a process for producing a photocatalytic material using an alternate adsorption method.

  Step S510: A cationic polymer 540 is applied as a counter ion to the substrate 310. As the cationic polymer 540, any polymer that makes the surface of the substrate 310 cationic can be applied. Illustratively, poly (diallyldimethylammonium chloride) (PDDA), polyethyleneimine (PEI), polyallylamine hydrochloride ( PAH). Among these, PDDA and PEI are preferable because of their versatility.

  By applying the cationic polymer 540 to the base material 310, the surface of the base material 310 becomes cationic and bonds more strongly with the anionic photocatalytic nanosheet 100.

  Step S520: A colloidal solution containing the photocatalytic nanosheet 100 (for example, the colloidal solution obtained in Step S420) is applied to the substrate 310 to which the cationic polymer 540 has been applied. The concentration of the colloidal solution is adjusted as necessary. The photocatalyst nanosheet 100 is bonded and self-aligned on the cationic polymer 540 by electrostatic interaction, whereby the photocatalytic thin film 320 is formed.

  Step S530: Steps S510 and S520 are repeated as necessary until the photocatalytic thin film 320 has a desired thickness. When the photocatalyst thin film 320 has the single layer structure of the photocatalyst nanosheet 100, step S530 may be omitted.

  In this way, the photocatalytic material 300 including the photocatalytic thin film 320 having a single layer structure or a multilayer structure is obtained. The alternating adsorption method is preferable because the film thickness of the photocatalytic thin film 320 can be controlled on the nano-order (molecular level). Since the alternate adsorption method does not require an expensive apparatus, the photocatalytic material 300 can be provided at a low cost. Further, the area of the photocatalytic material 300 can be increased depending on the size of the substrate 310 and the volume of the colloidal solution.

  Note that following step S530, the cationic polymer 540 may be removed by irradiation with light such as ultraviolet rays.

(2) LB Method FIG. 6 is a diagram showing a process for producing a photocatalytic material using the LB method.

  Step S610: The base material 310 is immersed in the developing solution. As a developing solution, a colloid solution containing the photocatalyst nanosheet 100 (for example, the colloid solution obtained in step S420) is diluted and prepared. The developing solution (prepared colloidal solution) is developed in a trough (water tank), and a part of the photocatalyst nanosheet 100 floats at the gas-liquid interface.

  Step S620: Pull up the substrate 310 to form a photocatalytic thin film 320 made of the photocatalyst nanosheet 100 on the substrate 310. In the LB method, after the substrate 310 is immersed in the trough, the surface of the developing solution is compressed to a certain surface pressure to form the photocatalytic thin film 320 at the gas-liquid interface, and the substrate 310 is removed from the colloidal solution by the vertical pulling method. By pulling up, the photocatalyst thin film 320 is transferred (formed) onto the substrate 310.

  In this way, the photocatalytic material 300 including the photocatalytic thin film 320 having a single layer structure of the photocatalytic nanosheet 100 on the substrate 310 is obtained. In the case of the LB method, the photocatalyst thin film 320 having a single layer structure (such a single layer structure is referred to as a single layer film) that is accumulated in the plane direction without the photocatalyst nanosheets 100 overlapping each other on the surface of the developing solution is a gas-liquid interface. Therefore, it is possible to form the photocatalytic thin film 320 of a single layer film that is extremely homogeneous and of good quality on the substrate 310. It is suitable for applications where a high-quality photocatalytic thin film 320 is required.

(3) Spin coating method As in the known spin coating method, a colloid solution containing the photocatalyst nanosheet 100 is used as the spin coating material (for example, the colloid solution obtained in step S420). A colloidal solution is dropped on the substrate 310 rotating at high speed, and a uniform photocatalytic thin film 320 is obtained by centrifugal force. In this case, unlike the LB method, the photocatalyst thin film 320 having a single layer structure of the photocatalyst nanosheet 100 is not necessarily obtained, but a uniform photocatalytic thin film 320 can be obtained relatively easily.

(4) Drop method (Drip method)
Similar to the known drop method, a colloidal solution containing the photocatalyst nanosheet 100 (for example, the colloidal solution obtained in step S420) is dropped on the substrate 310 with a pipette or the like and dried to obtain the photocatalytic thin film 320. In this case, a photocatalytic thin film 320 having a multilayer structure in which the photocatalytic nanosheets 100 overlap each other is obtained. Although it is difficult to obtain the photocatalyst material 300 having the uniform photocatalytic thin film 320, it is effective for applications where quality is not required.

(5) Dip coating method (dipping method)
Similar to the known dip coating method, the substrate 310 is immersed in a colloid solution containing the photocatalyst nanosheet 100 (for example, the colloid solution obtained in step S420), pulled up, and dried to obtain the photocatalyst thin film 320. Also in this case, a photocatalytic thin film 320 having a multilayer structure in which the photocatalyst nanosheets 100 overlap each other is obtained as in the drop method. Although it is difficult to obtain the photocatalyst material 300 having the uniform photocatalytic thin film 320, it is effective for applications where quality is not required.

  In the photocatalyst material 300 obtained in this way, in order to further improve the adhesion between the base material 310 and the photocatalyst thin film 320, the photocatalyst material 300 may be heat-treated following application of the colloid solution to the base material 310. Good. By the heat treatment, a reaction occurs between the substrate 310 and the photocatalytic thin film 320, and the adhesiveness is improved by the resulting bond. Here, the temperature condition for the heat treatment is at least 100 ° C. and less than 900 ° C. If it is 100 degreeC or more, since the reaction between the base material 310 and the photocatalyst thin film 320 can be produced, the improvement of adhesiveness can be anticipated. If it exceeds 900 ° C., the chemical change of the photocatalytic thin film 320 and the deterioration of the film quality occur, which is not preferable. A more preferable temperature condition for the heat treatment is a temperature range from 300 ° C. to 800 ° C. If it is 300 degreeC or more and 800 degrees C or less, adhesiveness can be reliably improved in a short time, without impairing film quality, photocatalytic property, and a photo-induced hydrophilic property.

(Embodiment 3)
Next, the manufacturing method of the alkali metal containing layered compound 110 (FIG. 1) suitable for this invention is demonstrated. In order to obtain the photocatalyst nanosheet 100 according to the present invention with high yield and high quality, it is desirable that the alkali metal-containing layered compound used in Step S410 (FIG. 4) of Embodiment 2 does not contain impurities. The inventors of the present invention have established a method for producing an alkali metal-containing layered compound by diligent efforts, and as a result, have succeeded in obtaining the photocatalyst nanosheet 100 and the photocatalyst material 300 with high yield and high quality.

  FIG. 7 is a flowchart showing the production process of the alkali metal-containing layered compound.

  This will be described in detail for each step.

Step S710: Adjusting the raw material mixture. The raw material mixture is a mixture of compounds of elements (excluding oxygen) constituting the alkali metal-containing layered compound. Specifically, when producing MNb ₃ O ₅ or M ₄ Nb ₆ O ₁₇ as the alkali metal layered compound, the raw material mixture is heated with an alkali metal source that becomes an alkali oxide, heated with niobium oxide, Including niobium sources. In the case of producing MTiNbO ₅ , MTi ₂ NbO ₇ or M ₃ Ti ₅ NbO ₁₄ as the alkali metal layered compound, the raw material mixture is heated with an alkali metal source that becomes an alkali oxide, and niobium oxide that is heated to become niobium oxide. And a titanium source that is heated to titanium oxide. In the case of producing MCa ₂ Nb ₃ O ₁₀ as an alkali metal-containing layered compound, the raw material mixture is heated with an alkali metal source that becomes an alkali oxide, a niobium source that becomes niobium oxide by heating, and an oxidation by heating. And a calcium source that becomes calcium. In the case of producing MLaNb ₂ O ₇ as an alkali metal-containing layered compound, the raw material mixture is prepared by heating an alkali metal source that becomes an alkali oxide by heating, a niobium source that becomes niobium oxide by heating, a lanthanum oxide that is heated. A lanthanum source.

  More specifically, the alkali metal source that becomes an alkali oxide by heating is, for example, an alkali metal salt such as nitrate, carbonate, carboxylate, sulfate, alkali metal hydroxide, alkali metal alkoxide, or the like. . Examples of the niobium source that is heated to become niobium oxide include niobium alkoxide, niobium hydroxide, niobium salt, and the like. Examples of the titanium source that is heated to be titanium oxide include titanium alkoxide, titanium hydroxide, and titanium salt. The calcium source that is heated to become calcium oxide is a calcium salt such as calcium alkoxide, calcium hydroxide, or calcium carbonate. The lanthanum source that becomes lanthanum oxide by heating is lanthanum alkoxide, lanthanum hydroxide, lanthanum salt, or the like.

  The alkali metal source is preferably an alkali metal salt from the viewpoint of ease of handling and availability and synthesis, and among them, an alkali metal nitrate or carbonate that is stable at normal temperature and pressure is preferred. Similarly, the calcium source is preferably a calcium salt, and calcium carbonate that is stable at room temperature and normal pressure is preferable from the viewpoint of ease of handling and availability and synthesis. Further, niobium oxide which is stable at normal temperature and normal pressure, niobium oxide as a titanium source, titanium oxide as a titanium source, and lanthanum oxide as a lanthanum source may be used.

  Thus, by using a compound of each element (excluding oxygen) constituting the alkali metal-containing layered compound as a raw material mixture, a high-purity compound can be used as the compound of each element. Mixing can be suppressed. As a result, the purity of the obtained alkali metal-containing layered compound can be improved.

  For example, each compound is mixed and ground for 60 minutes using an alumina mortar. Sufficient pulverization and mixing is preferable because the reaction between the compounds is accelerated.

  Step S720: Firing the raw material mixture. Note that the firing may be performed in two stages, that is, preliminary firing and main firing. The preliminary firing may be pulverized and mixed again to promote the reaction in the main firing. Firing conditions vary depending on the desired alkali metal-containing layered compound.

  Next, a suitable manufacturing method is demonstrated about each alkali metal containing layered compound.

(1) MNb ₃ O ₈
An alkali metal nitrate as an alkali metal source and niobium oxide as a niobium source are mixed to obtain a raw material mixture (step S710). Here, the alkali metal nitrate and niobium oxide are mixed in a stoichiometric ratio satisfying MNb ₃ O ₈ .
Next, the raw material mixture is temporarily fired by a predetermined temperature program (step S720). The predetermined temperature program increases the temperature from 550 ° C. to 650 ° C. over a period of 1.5 hours to 2.5 hours, and increases the temperature within a range of 550 ° C. to 650 ° C. for 1.5 hours to 2. Held for 5 hours or less, and then heated from a temperature range of 550 ° C. to 650 ° C. to a temperature range of 850 ° C. to 950 ° C. for 1.5 hours to 2.5 hours, Cool down quickly. Thus, since it heats up with a comparatively small temperature increase rate, bumping of the water molecule contained in the alkali metal nitrate as an alkali metal source is suppressed. Thus, it has been found that the purity can be further improved by using an alkali metal nitrate and using a predetermined temperature program.

After the preliminary firing, the raw material mixture is finally fired (step S720). Baking at a temperature range of 850 ° C. to 950 ° C. for at least 20 hours. If it is less than 20 hours, impurities of M ₂ Nb ₆ O ₁₁ may be generated.

(2) M ₄ Nb ₆ O ₁₇
A raw material mixture composed of an alkali metal carbonate as an alkali metal source and niobium oxide as a niobium source is mixed (step S710). Here, the alkali metal carbonate and niobium oxide are mixed so that the alkali metal carbonate is richer than the stoichiometric ratio satisfying M ₄ Nb ₆ O ₁₇ , for example, 10% rich in molar ratio. Is done. This is because the alkali metal may evaporate during firing.

Next, the raw material mixture is temporarily fired (step S720). In the preliminary firing, the raw material mixture is fired in a temperature range of 850 ° C. to 950 ° C. for 0.5 hours to 1.5 hours and rapidly cooled. After mixing and grinding, the raw material mixture is subjected to main firing (step S720). Specifically, the raw material mixture is fired at a temperature range of 1000 ° C. or higher and lower than 1100 ° C. for at least 20 hours. If less than 20 hours, impurities of MNbO ₃ may be generated.

(3) MTiNbO ₅
A raw material mixture composed of an alkali metal carbonate as an alkali metal source, niobium oxide as a niobium source, and titanium oxide as a titanium source is mixed (step S710). Here, the alkali metal carbonate, niobium oxide, and titanium oxide are richer in alkali metal carbonate than the stoichiometric ratio satisfying MTiNbO ₅ , for example, 5% rich in molar ratio. Mixed. This is because the alkali metal may evaporate during firing.

Next, the raw material mixture is temporarily fired (step S720). In the preliminary firing, the raw material mixture is fired in a temperature range of 850 ° C. to 950 ° C. for 0.5 hours to 1.5 hours and rapidly cooled. After mixing and grinding, the raw material mixture is subjected to main firing (step S720). Specifically, the raw material mixture is fired for at least 20 hours in a temperature range higher than 1050 ° C. and lower than 1150 ° C. When it is fired at 1050 ° C. or lower and 1150 ° C. or higher, M ₂ Ti ₆ O ₁₃ impurities may be generated.

(4) MTi ₂ NbO ₇
A raw material mixture composed of an alkali metal nitrate as an alkali metal source, niobium oxide as a niobium source, and titanium oxide as a titanium source is mixed (step S710). Here, the alkali metal nitrate, niobium oxide, and titanium oxide are richer in alkali metal nitrate than the stoichiometric ratio satisfying MTi ₂ NbO ₇ , for example, 10% rich in molar ratio. Mixed. When the raw material mixture is in the stoichiometric ratio, impurities may be generated by evaporation of the alkali metal.

  Next, the raw material mixture is temporarily fired by a predetermined temperature program (step S720). The predetermined temperature program raises the temperature to a temperature range of 350 ° C. or more and 450 ° C. or less for 0.5 hour or more and 1.5 hours or less, and to a temperature range of 700 ° C. or more and 800 ° C. or less for 3.5 hours or more The temperature is further raised for 5 hours or less, and held at a temperature range of 700 ° C. or higher and 800 ° C. or lower for at least 30 minutes. The temperature is raised in between, kept at a temperature range of 900 ° C. to 1000 ° C. for at least 30 minutes, and then rapidly cooled to room temperature. In this manner, since the temperature is raised at a relatively low temperature increase rate and baked stepwise, bumping of water molecules contained in the alkali metal nitrate is suppressed. Thus, it has been found that the purity can be further improved by using an alkali metal nitrate and using a predetermined temperature program.

  After the preliminary firing, the raw material mixture is finally fired (step S720). Specifically, the raw material mixture is fired at a temperature range of 1050 ° C. to 1150 ° C. for at least 20 hours.

(5) M ₃ Ti ₅ NbO ₁₄
A raw material mixture composed of an alkali metal carbonate as an alkali metal source, niobium oxide as a niobium source, and titanium oxide as a titanium source is mixed (step S710). Here, the alkali metal carbonate, niobium oxide, and titanium oxide are mixed in a stoichiometric ratio satisfying MTiNbO ₅ .

Next, the raw material mixture is temporarily fired (step S720). In the preliminary firing, the raw material mixture is fired in a temperature range of 850 ° C. to 950 ° C. for 0.5 hours to 1.5 hours and rapidly cooled. After the preliminary firing, the raw material mixture is finally fired (step S720). Specifically, the raw material mixture is fired at a temperature range of 950 ° C. or higher and 1050 ° C. or lower for at least 10 hours. When firing at a temperature lower than 950 ° C., impurities of K ₂ Ti ₂ O ₅ may be generated.

(6) MCa ₂ Nb ₃ O ₁₀
A raw material mixture composed of an alkali metal carbonate as an alkali metal source, niobium oxide as a niobium source, and calcium carbonate as a calcium source is mixed (step S710). Here, the alkali metal carbonate, niobium oxide, and calcium carbonate are richer in alkali metal carbonate than the stoichiometric ratio satisfying MCa ₂ Nb ₃ O ₁₀ , for example, 10% rich in molar ratio, To be mixed. This is because the alkali metal may evaporate during firing.

  Next, the raw material mixture is fired (step S720). Firing only needs to be performed by a predetermined temperature program. The predetermined temperature program is to raise the temperature in the temperature range of 850 ° C. to 950 ° C. for 2.5 hours to 3.5 hours, and in the temperature range of 850 ° C. to 950 ° C. for 0.5 hours to 1. Hold for 5 hours or less, then raise the temperature in the temperature range from 1150 ° C. to 1250 ° C. for 2.5 hours to 3.5 hours, and at least 12 hours in the temperature range from 1150 ° C. to 1250 ° C. After firing, the temperature is lowered to a temperature range of 750 ° C. to 850 ° C. for 2.5 hours to 3.5 hours and then rapidly cooled.

(7) MLaNb ₂ O ₇
A raw material mixture composed of an alkali metal carbonate as an alkali metal source, niobium oxide as a niobium source, and lanthanum oxide as a lanthanum source is mixed (step S710). Here, the alkali metal carbonate, niobium oxide, and lanthanum oxide are richer in alkali metal carbonate than the stoichiometric ratio satisfying MLaNb ₂ O ₇ , for example, 15% rich in molar ratio. So that they are mixed. This is because the alkali metal may evaporate during firing.

  Next, the raw material mixture is fired (step S720). Firing only needs to be performed by a predetermined temperature program. Predetermined temperature program is a temperature range of 1100 ° C to 1200 ° C for 2.5 hours to 3.5 hours, and a temperature range of 1100 ° C to 1200 ° C for 0.5 hours to 1.5 hours And cool to room temperature.

  The manufacturing process of the alkali metal-containing layered compound described in the third embodiment may be performed prior to step S410 in FIG. 4 described in the second embodiment. Thereby, a photocatalyst nanosheet and also a photocatalyst material are obtained with high purity and high yield.

  Hereinafter, examples will be described. In the examples, optimization conditions (combination of compounds, firing conditions) in the production of an alkali metal-containing layered compound, and optimization conditions (number of acid treatments, concentration) for obtaining a hydrogen ion exchanger are shown. Note that the examples are not limiting. The synthesis conditions and the like of the examples and comparative examples are summarized in Table 1.

A photocatalyst material 300 (FIG. 3) provided with a photocatalytic thin film 320 (FIG. 3) made of Nb ₃ O ₈ nanosheets on a quartz glass substrate and a silicon (Si) substrate as a base material 310 (FIG. 3) using an alternate adsorption method. 3) was produced. Prior to the production of the photocatalytic material, an alkali metal-containing layered compound of KNb ₃ O ₈ whose alkali metal is K was synthesized.

KNO ₃ (4.5357 g, manufactured by Wako Pure Chemical Industries, special grade) and Nb ₂ O ₅ (17.8871 g, manufactured by Rare Metallic, purity 99.99%) were mixed to obtain a raw material mixture (FIG. 7). Step S710). The molar ratio of KNO ₃ to Nb ₂ O ₅ was 2: 3 so as to satisfy the stoichiometric ratio of KNb ₃ O ₈ . The raw material mixture was pulverized and mixed for 60 minutes using an alumina mortar.

  Next, the raw material mixture was temporarily fired using a predetermined temperature program (step S720 in FIG. 7). The raw material mixture was transferred to a platinum crucible and placed in an electric furnace. The predetermined temperature program is to raise the temperature from room temperature to 600 ° C. in 2 hours, hold at 600 ° C. for 2 hours, and then raise the temperature from 600 ° C. to 900 ° C. in 2 hours. And quenched at room temperature.

Heat was removed for about 10 minutes at room temperature, and the sample in the platinum crucible was pulverized and mixed in an alumina mortar. The crushed and mixed sample was transferred again to the platinum crucible, placed in an electric furnace heated to 900 ° C., and finally baked for 20 hours (step S720 in FIG. 7). Thereafter, the platinum crucible was taken out of the electric furnace and rapidly cooled at room temperature to obtain an alkali metal-containing layered compound 110 (FIG. 1). The alkali metal-containing layered compound 110 thus obtained was subjected to powder X-ray diffraction and confirmed to be a KNb ₃ O ₈ single phase. In the main baking, when the baking time was changed to 5 hours and 10 hours under the same temperature condition, an impurity of K ₂ Nb ₆ O ₁₁ was generated. From this, it was found that a controlled temperature program and main baking for 20 hours or more are preferable.

Next, a photocatalyst nanosheet Nb ₃ O ₈ was synthesized using the alkali metal-containing layered compound KNb ₃ O ₈ thus obtained.

The alkali metal-containing layered compound KNb ₃ O ₈ was acid-treated using an aqueous nitric acid solution (13.5 N, manufactured by Wako Pure Chemical Industries, special grade) as an aqueous acid solution to produce a hydrogen ion exchanger (step S410 in FIG. 4). ). An aqueous nitric acid solution was prepared using ultrapure water (> 18 MΩcm) so as to be 2N.

Specifically, KNb ₃ O ₈ (1 g) and an aqueous nitric acid solution (100 mL) were allowed to act in a 200 mL Erlenmeyer flask and stirred once every 12 hours to promote the reaction. The aqueous nitric acid solution was changed every 24 hours, and the reaction was performed for 72 hours. After completion of the reaction, the product was filtered with ultrapure water and air-dried in air to obtain a hydrogen ion exchanger.

Next, 0.4 g of hydrogen ion exchanger was reacted with 100 mL of tetrabutylammonium hydroxide aqueous solution (TBAOHaq.) As a basic substance (made by Wako Pure Chemical Industries, special grade; concentration 10%) to peel off the hydrogen ion exchanger. to obtain a colloidal solution comprising _Nb 3 _{O 8} nanosheets (step S420 in FIG. 4).

The specific reaction is TBAOHaq. The molar ratio of TBA ⁺ in the H ⁺ to H ⁺ in the hydrogen ion exchanger was adjusted to 10: 1. Place 77.1 mL of ultrapure water in a 200 mL Erlenmeyer flask, and then add TBAOHaq. 22.9 mL was added to give a total of 100 mL of solution. To this solution, 0.4 g of a hydrogen ion exchanger was added and shaken with a shaker at 180 rpm for 10 days. It was confirmed that the solution in the Erlenmeyer flask became a milky white solution and the hydrogen ion exchanger was completely peeled off. In this way, a colloid solution composed of Nb ₃ O ₈ nanosheets (hereinafter referred to as Nb ₃ O ₈ colloid solution) was obtained.

The Nb ₃ O ₈ colloidal solution was applied to each of the quartz glass substrate and the Si substrate using an alternate adsorption method. Prior to the application, the quartz glass substrate and the Si substrate were hydrophilized. Specifically, the surfaces of the quartz glass substrate and the Si substrate were wiped with bem cotton containing acetone, and immersed in a mixed solution in which methanol and hydrochloric acid were mixed at a ratio of 1: 1 for 30 minutes. As a result, contamination such as organic substances on the surfaces of the quartz glass substrate and the Si substrate was removed. Thereafter, the quartz glass substrate and the Si substrate were washed with ultrapure water and immersed in an ethanol / hydrochloric acid (1: 1) mixed solution and a concentrated sulfuric acid solution for 30 minutes, respectively. Thereby, the surfaces of the quartz glass substrate and the Si substrate were hydrophilized.

Poly (diallyldimethylammonium chloride) (PDDA) was applied as a cationic polymer to the hydrophilized quartz glass substrate and Si substrate (step S510 in FIG. 5). Specifically, sodium chloride (NaCl) was added to a PDDA aqueous solution adjusted to a concentration of 23 gL ⁻¹ to adjust to 0.01M. Since NaCl improves the surface charge of PDDA, formation of a multi-layered photocatalytic thin film by an alternate adsorption method can be promoted. In addition, when it exceeds 0.01M, NaCl becomes an obstacle to the formation of the multilayer structure, which is not preferable. On the other hand, if NaCl is not added, the surface charge of PDDA is not improved, and it becomes difficult to form a multilayer structure. To a PDDA aqueous solution to which NaCl was added, TBAOH aq. Was added dropwise to adjust the pH of the PDDA aqueous solution to 9. In the PDDA aqueous solution thus prepared, the quartz glass substrate and the Si substrate subjected to the hydrophilic treatment were each immersed for 20 minutes. Thereafter, the quartz glass substrate and the Si substrate were washed with ultrapure water, and a nitrogen gas flow was performed to dry the surface.

Next, the Nb ₃ O ₈ colloidal solution was applied to the quartz glass substrate and the Si substrate to which PDDA was applied (Step S520 in FIG. 5). The Nb ₃ O ₈ colloidal solution was adjusted to a concentration of 0.4 gL ⁻¹ using ultrapure water and pH 9 using a hydrochloric acid solution. The application was performed by immersing the quartz glass substrate to which PDDA was applied and the Si substrate in an Nb ₃ O ₈ colloidal solution for 20 minutes. Thereafter, the quartz glass substrate and the Si substrate were washed with ultrapure water, and a nitrogen gas flow was performed to dry the surface.

Step S510 and step S520 were repeated 10 times (step S530 in FIG. 5). The photocatalytic materials thus obtained are referred to as (Nb ₃ O ₈ / PDDA) _n / glass and (Nb ₃ O ₈ / PDDA) _n / Si. Here, n indicates the number of repetitions of step 530 in FIG.

The photocatalytic properties of the Nb ₃ O ₈ nanosheets were evaluated using (Nb ₃ O ₈ / PDDA) ₁ / glass as a sample. In the evaluation method, methylene blue was adsorbed as an organic dye on the surface (Nb ₃ O ₈ / PDDA) ₁ / change in the amount of adsorbed dye accompanying photolysis of glass was measured. For the measurement, UV-vis absorption spectrum measurement was used, and the photocatalytic activity of (Nb ₃ O ₈ / PDDA) ₁ / glass was determined from the photodegradation rate of the dye.

Specifically, as a pretreatment of (Nb ₃ O ₈ / PDDA) ₁ / glass, ultraviolet light (1 mWcm ⁻² , λ <300 nm) was irradiated for 72 hours to remove surface stains such as TBA ⁺ . Thereafter, a 0.1 M methylene blue solution was dropped on the surface of (Nb ₃ O ₈ / PDDA) ₁ / glass, and dried and fixed in air for 24 hours. Ultraviolet light (10 mWcm ⁻² , λ <300 nm) was irradiated using a xenon lamp as a light source, and the change in absorbance of methylene blue was measured. The results are shown in FIG. 8, Table 2 and Table 3 and will be described in detail.

Next, the light-induced hydrophilization property of the Nb ₃ O ₈ nanosheet was evaluated using (Nb ₃ O ₈ / PDDA) ₁ / glass as a sample. As in the photocatalytic evaluation, after irradiating with ultraviolet light and pretreating (Nb ₃ O ₈ / PDDA) ₁ / glass, (Nb ₃ O ₈ / PDDA) ₁ / glass was stored for 1 month in the dark. . Thereafter, water droplets were dropped on (Nb ₃ O ₈ / PDDA) ₁ / glass, and ultraviolet light was irradiated again under the same conditions. The relationship between the water contact angle of the water droplet and the ultraviolet light irradiation time was investigated. The water contact angle measuring device was used for the measurement, and the hydrophilization reaction rate was determined. The results are shown in FIG. 9, Table 4 and Table 5 and will be described in detail.

Each time step S530 of FIG. 5 is repeated in order to investigate the multilayer structure by the alternate adsorption method (that is, (Nb ₃ O ₈ / PDDA) _n / n = 1 to 10 of glass), the UV-vis absorption spectrum is obtained. It was measured. The results are shown in FIG.

As a photocatalytic material having a multilayer photocatalytic thin film, the structure of (Nb ₃ O ₈ / PDDA) ₁₀ / Si was evaluated by X-ray diffraction (XRD). The results are shown in FIG.

The photocatalytic property of (Nb ₃ O ₈ / PDDA) ₁₀ / glass was examined as a photocatalytic material having a multilayer photocatalytic thin film. Specifically, XRD measurement was performed before and after irradiation with ultraviolet light (1 mWcm ⁻² , λ <300 nm), and the interlayer distance was measured. The results are shown in FIG.

As a photocatalytic material having a multilayered photocatalytic thin film, the surface state of (Nb ₃ O ₈ / PDDA) ₁₀ / Si was observed with an atomic force microscope (AFM). The results are shown in FIG. 19 and Table 6 and will be described later.

A photocatalytic material 300 (FIG. 3) provided with a photocatalytic thin film 320 (FIG. 3) made of Nb ₆ O ₁₇ nanosheets on a quartz glass substrate and a Si substrate as a base material 310 (FIG. 3) using an alternate adsorption method. Manufactured. Prior to the production of the photocatalytic material, an alkali metal-containing layered compound of K ₄ Nb ₆ O _{17 in which} the alkali metal is K was synthesized.

K ₂ CO ₃ (5.5824 g, manufactured by Rare Metallic, purity 99.99%) and Nb ₂ O ₅ (15.3379 g, manufactured by Rare Metallic, purity 99.99%) were mixed to obtain a raw material mixture. (Step S710 in FIG. 7). Here, K ₂ CO ₃ was added in a molar ratio of 10% more than the stoichiometric ratio of K ₄ Nb ₆ O ₁₇ , and the molar ratio of K ₂ CO ₃ and Nb ₂ O ₅ was 2.2: 3. Met. The raw material mixture was pulverized and mixed for 60 minutes using an alumina mortar.

  Next, the raw material mixture was temporarily fired (step S720 in FIG. 7). The raw material mixture was transferred to a platinum crucible and placed in an electric furnace heated to 900 ° C. and held for 1 hour. Thereafter, the platinum crucible was removed from the electric furnace and rapidly cooled at room temperature.

Heat was removed for about 10 minutes at room temperature, and the sample in the platinum crucible was pulverized and mixed in an alumina mortar. The crushed and mixed sample was transferred again to the platinum crucible, placed in an electric furnace heated to 1050 ° C., and finally baked for 20 hours (step S720 in FIG. 7). Thereafter, the platinum crucible was taken out of the electric furnace and rapidly cooled at room temperature to obtain an alkali metal-containing layered compound 110 (FIG. 1). The alkali metal-containing layered compound 110 thus obtained was subjected to powder XRD measurement and confirmed to be a K ₄ Nb ₆ O ₁₇ single phase. In the main baking, when baking was performed at 1100 ° C. for 10 hours, an impurity of KNbO ₃ was generated. From this, it was found that the main firing for at least 20 hours is preferable.

Next, a photocatalyst nanosheet Nb ₆ O ₁₇ was synthesized using the alkali metal-containing layered compound K ₄ Nb ₆ O ₁₇ thus obtained.

The alkali metal-containing layered compound K ₄ Nb ₆ O ₁₇ was acid-treated using a hydrochloric acid aqueous solution (12 N, manufactured by Wako Pure Chemical Industries, special grade) as an acid aqueous solution to produce a hydrogen ion exchanger (step S410 in FIG. 4). ). The aqueous hydrochloric acid solution was adjusted to 1 N using ultrapure water (> 18 MΩcm). In addition, it acid-treated on the conditions similar to Example 1 except having used hydrochloric acid aqueous solution, and obtained the hydrogen ion exchanger.

Next, 0.4 g of hydrogen ion exchanger was reacted with 100 mL of tetrabutylammonium hydroxide aqueous solution (TBAOHaq.) As a basic substance (made by Wako Pure Chemical Industries, special grade; concentration 10%) to peel off the hydrogen ion exchanger. to obtain a colloidal solution comprising _Nb 6 _{O 17} nanosheet (step S420 in FIG. 4).

The specific reaction is TBAOHaq. The molar ratio of TBA ⁺ in the H ⁺ to H ⁺ in the hydrogen ion exchanger was adjusted to 10: 1. In a 200 mL Erlenmeyer flask, 50.5 mL of ultrapure water was added, and then TBAOHaq. 49.5 mL was added to give a total of 100 mL of solution. To this solution, 0.4 g of a hydrogen ion exchanger was added and shaken with a shaker at 180 rpm for 10 days. It was confirmed that the solution in the Erlenmeyer flask became a milky white solution and the hydrogen ion exchanger was completely peeled off. There _was thus obtained colloidal consisting Nb _{6 O 17} nanosheet solution (referred to as _Nb 6 _{O 17} colloidal solution later).

The Nb ₆ O ₁₇ colloidal solution was applied to the quartz glass substrate and the Si substrate using an alternate adsorption method. The application of the Nb ₆ O ₁₇ colloid solution to the quartz glass substrate and the Si substrate was performed in the same procedure using the Nb ₆ O ₁₇ colloid solution adjusted to the same concentration as in Example 1, and thus the description thereof is omitted. As in Example 1, the obtained photocatalytic materials are referred to as (Nb ₆ O ₁₇ / PDDA) _n / glass and (Nb ₆ O ₁₇ / PDDA) _n / Si. Here, n indicates the number of repetitions of step 530 in FIG.

As in Example 1, (Nb ₆ O ₁₇ / PDDA) ₁ / glass was used as a sample, and the photocatalytic property and photoinduced hydrophilization property of the Nb ₆ O ₁₇ nanosheet were evaluated. The results of the photo-induced hydrophilization characteristics are shown in FIG. 9, Table 4 and Table 5 and will be described in detail.

As a photocatalytic material having a multilayered photocatalytic thin film finally obtained, the surface state of (Nb ₆ O ₁₇ / PDDA) ₁₀ / Si was observed with an atomic force microscope (AFM). The results are shown in FIG. 20 and Table 6 and will be described later.

A photocatalytic material 300 (FIG. 3) provided with a photocatalytic thin film 320 (FIG. 3) made of TiNbO ₅ nanosheets was manufactured on a quartz glass substrate and a Si substrate as a base material 310 (FIG. 3) by using an alternate adsorption method. . Prior to the production of the photocatalytic material, an alkali metal-containing layered compound of KTiNbO ₅ whose alkali metal is K was synthesized.

K ₂ CO ₃ (5.5839 g, Rare Metallic, purity 99.99%), TiO ₂ (6.1473 g, Rare Metallic, purity 99.99%), Nb ₂ O ₅ (10.2821 g, Rare) Metallic product, purity 99.99%) was mixed to obtain a raw material mixture (step S710 in FIG. 7). Than the stoichiometric ratio of KTiNbO ₅ was added _K 2 CO ₃ 5% excess at a molar _ratio, the molar ratio of K 2 CO ₃ and TiO ₂ and _Nb 2 _{O 5} is 1.05: 2: 1 met It was. The raw material mixture was pulverized and mixed for 60 minutes using an alumina mortar.

  Next, the raw material mixture was temporarily fired (step S720 in FIG. 7). The raw material mixture was transferred to a platinum crucible and placed in an electric furnace heated to 900 ° C. and held for 1 hour. Thereafter, the platinum crucible was removed from the electric furnace and rapidly cooled at room temperature.

Heat was removed for about 10 minutes at room temperature, and the sample in the platinum crucible was pulverized and mixed in an alumina mortar. The crushed and mixed sample was transferred again to the platinum crucible, placed in an electric furnace heated to 1100 ° C., and finally baked for 20 hours (step S720 in FIG. 7). Thereafter, the platinum crucible was taken out of the electric furnace and rapidly cooled at room temperature to obtain an alkali metal-containing layered compound 110 (FIG. 1). The alkali metal-containing layered compound 110 thus obtained was subjected to powder XRD measurement, and confirmed to be a KTiNbO ₅ single phase. In the main firing, impurities of K ₂ Ti ₆ O ₁₃ were generated when the temperature was changed to 1000 ° C. and 1150 ° C. and when a raw material mixture having a stoichiometric ratio of KTiNbO ₅ was used. From this, it was found that in order to obtain a single phase of KTiNbO _5, it is preferable to suppress evaporation of K ₂ CO ₃ in the raw material mixture and to perform main firing in a temperature range of 1050 ° C. or higher and lower than 1150 ° C. .

Next, using the alkali metal-containing layered compound KTiNbO ₅ thus obtained, a photocatalyst nanosheet TiNbO ₅ was synthesized.

The alkali metal-containing layered compound KTiNbO ₅ was acid-treated using an aqueous hydrochloric acid solution (12 N, manufactured by Wako Pure Chemical Industries, special grade) as an acid aqueous solution in the same manner as in Example 2 to produce a hydrogen ion exchanger (FIG. 4). Step S410).

Next, 0.4 g of hydrogen ion exchanger was reacted with 100 mL of tetrabutylammonium hydroxide aqueous solution (TBAOHaq.) As a basic substance (made by Wako Pure Chemical Industries, special grade; concentration 10%) to peel off the hydrogen ion exchanger. to obtain a colloidal solution comprising TiNbO ₅ nanosheet (step S420 in FIG. 4).

The specific reaction is TBAOHaq. The molar ratio of TBA ⁺ in the hydrogen ion exchanger to H ⁺ in the hydrogen ion exchanger was adjusted to 5: 1. Into a 200 mL Erlenmeyer flask was placed 77.3 mL of ultrapure water, and then TBAOHaq. 22.7 mL was added to give a total of 100 mL of solution. To this solution, 0.4 g of a hydrogen ion exchanger was added and shaken with a shaker at 180 rpm for 10 days. It was confirmed that the solution in the Erlenmeyer flask became a milky white solution and the hydrogen ion exchanger was completely peeled off. In this way, (and later referred to as TiNbO ₅ colloidal solution) colloidal solution consisting TiNbO ₅ nanosheets was obtained.

The TiNbO ₅ colloidal solution was applied to the quartz glass substrate and the Si substrate using the alternate adsorption method. The application of the TiNbO ₅ colloid solution to the quartz glass substrate and the Si substrate was carried out in the same procedure using the TiNbO ₅ colloid solution adjusted to the same concentration as in Example 1, and thus the description thereof is omitted. As in Example 1, the obtained photocatalytic materials are referred to as (TiNbO ₅ / PDDA) _n / glass and (TiNbO ₅ / PDDA) _n / Si. Here, n indicates the number of repetitions of step 530 in FIG.

In the same manner as in Example 1, (TiNbO ₅ / PDDA) ₁ / glass was used as a sample, and the photocatalytic property and photoinduced hydrophilization property of the TiNbO ₅ nanosheet were evaluated. Each result is shown in FIG. 8, FIG. 9, and Table 2-Table 5, and is explained in full detail.

As in Example 1, UV-vis absorption spectrum measurement of multilayer structure by alternating adsorption method, XRD measurement of (TiNbO ₅ / PDDA) ₁₀ / Si, (TiNbO ₅ / PDDA) ₁₀ / photocatalytic property of glass, and ( It was evaluated by AFM measurement of TiNbO ₅ / PDDA) ₁₀ / Si. These results are shown in FIG. 11, FIG. 14, FIG. 16, FIG.

A photocatalytic material 300 (FIG. 3) provided with a photocatalytic thin film 320 (FIG. 3) made of a Ti ₂ NbO ₇ nanosheet on a quartz glass substrate and a Si substrate as a base material 310 (FIG. 3) using an alternate adsorption method. Manufactured. Prior to the production of the photocatalytic material, an alkali metal-containing layered compound of CsTi ₂ NbO ₇ in which the alkali metal is Cs was synthesized.

CsNO ₃ (9.8901 g, manufactured by Rare Metallic, purity 99.99%), TiO ₂ (7.3694 g, manufactured by Rare Metallic, purity 99.99%), and Nb ₂ O ₅ (6.1308 g, manufactured by Rare Metallic) , Purity 99.99%) to obtain a raw material mixture (step S710 in FIG. 7). CsNO ₃ was added at a molar ratio of 10% in excess of the stoichiometric ratio of CsTi ₂ NbO ₇ , and the molar ratio of CsNO ₃ , TiO ₂ and Nb ₂ O ₅ was 2.2: 4: 1. . The raw material mixture was pulverized and mixed for 60 minutes using an alumina mortar.

  Next, the raw material mixture was temporarily fired using a predetermined temperature program (step S720 in FIG. 7). The raw material mixture was transferred to a platinum crucible and placed in an electric furnace. The predetermined temperature program is to raise the temperature from room temperature to 400 ° C. in 1 hour, from 400 ° C. to 750 ° C. in 4 hours, hold at 750 ° C. for 30 minutes, and then from 750 ° C. to 950 ° C. in 1 hour. The temperature was raised and firing was performed at 950 ° C. for 30 minutes. Thereafter, the platinum crucible was removed from the electric furnace and rapidly cooled at room temperature.

Heat was removed for about 10 minutes at room temperature, and the sample in the platinum crucible was pulverized and mixed in an alumina mortar. The crushed and mixed sample was transferred again to the platinum crucible, placed in an electric furnace heated to 1100 ° C., and finally baked for 20 hours (step S720 in FIG. 7). Thereafter, the platinum crucible was taken out of the electric furnace and rapidly cooled at room temperature to obtain an alkali metal-containing layered compound 110 (FIG. 1). The alkali metal-containing layered compound 110 thus obtained was subjected to powder XRD measurement and confirmed to be a CsTi ₂ NbO ₇ single phase. In addition, when the raw material mixture was adjusted by the stoichiometric ratio and fired under the same temperature condition, an unknown impurity was generated. This also indicates that it is important to suppress evaporation of CsNO ₃ in the raw material mixture in order to obtain a single phase of CsTi ₂ NbO ₇ .

Next, a photocatalyst nanosheet Ti ₂ NbO ₇ was synthesized using the alkali metal-containing layered compound CsTi ₂ NbO ₇ thus obtained.

The alkali metal-containing layered compound CsTi ₂ NbO ₇ was acid-treated using an aqueous hydrochloric acid solution (12 N, Wako Pure Chemical Industries, Special Grade) as an aqueous acid solution in the same manner as in Example 2 to produce a hydrogen ion exchanger (FIG. 4 step S410).

Next, 0.4 g of hydrogen ion exchanger and 100 mL of tetrabutylammonium hydroxide aqueous solution (TBAOHaq.) As a basic substance (made by Wako Pure Chemical Industries, special grade) are reacted to peel off the hydrogen ion exchanger, and Ti ₂ NbO _A colloidal solution consisting of ₇ nanosheets was obtained (step S420 in FIG. 4).

The specific reaction is TBAOHaq. The molar ratio of TBA ⁺ in the hydrogen ion exchanger to H ⁺ in the hydrogen ion exchanger was adjusted to 5: 1. Into a 200 mL Erlenmeyer flask was placed 84.6 mL of ultrapure water, and then TBAOHaq. 15.4 mL was added to give a total of 100 mL of solution. To this solution, 0.4 g of a hydrogen ion exchanger was added and shaken with a shaker at 180 rpm for 10 days. It was confirmed that the solution in the Erlenmeyer flask became a milky white solution and the hydrogen ion exchanger was completely peeled off. In this way, a colloidal solution composed of Ti ₂ NbO ₇ nanosheets (hereinafter referred to as Ti ₂ NbO ₇ colloidal solution) was obtained.

A Ti ₂ NbO ₇ colloidal solution was applied to the quartz glass substrate and the Si substrate using an alternating adsorption method. The application of the Ti ₂ NbO ₇ colloidal solution to the quartz glass substrate was performed in the same procedure using the Ti ₂ NbO ₇ colloidal solution adjusted to the same concentration as in Example 1, and thus the description thereof is omitted. As in Example 1, the resulting photocatalytic materials are referred to as (Ti ₂ NbO ₇ / PDDA) _n / glass and (Ti ₂ NbO ₇ / PDDA) _n / Si. Here, n indicates the number of repetitions of step 530 in FIG.

As in Example 1, (Ti ₂ NbO ₇ / PDDA) ₁ / glass was used as a sample, and the photocatalytic property and photoinduced hydrophilization property of the Ti ₂ NbO ₇ nanosheet were evaluated. Each result is shown in FIG. 8, FIG. 9, and Table 2-Table 5, and is explained in full detail.

Similar to Example 1, UV-vis absorption spectrum measurement of multilayer structure by alternating adsorption method, XRD measurement of (Ti ₂ NbO ₇ / PDDA) ₁₀ / Si, (Ti ₂ NbO ₇ / PDDA) ₁₀ / photocatalytic property of glass AFM measurement of (Ti ₂ NbO ₇ / PDDA) ₁₀ / Si was performed. These results are shown in FIGS. 12, 14, 17, 22 and Table 6 and will be described later.

A photocatalytic material 300 (FIG. 3) provided with a photocatalytic thin film 320 (FIG. 3) made of a Ti ₅ NbO ₁₄ nanosheet on a quartz glass substrate and a Si substrate as a base material 310 (FIG. 3) was produced. Prior to the production of the photocatalytic material, an alkali metal-containing layered compound of K ₃ Ti ₅ NbO _{14 in which} the alkali metal is K was synthesized.

K ₂ CO ₃ (6.1553 g, Rare Metallic, purity 99.99%), TiO ₂ (11.586 g, Rare Metallic, purity 99.99%), Nb ₂ O ₅ (3.9461 g, Rare) Metallic product, purity 99.99%) was mixed to obtain a raw material mixture (step S710 in FIG. 7). The molar ratio of K ₂ CO ₃ , TiO ₂ and Nb ₂ O ₅ was 3: 10: 1 so as to satisfy the stoichiometric ratio of K ₃ Ti ₅ NbO ₁₄ . The raw material mixture was pulverized and mixed for 60 minutes using an alumina mortar.

  Next, the raw material mixture was temporarily fired (step S720 in FIG. 7). The raw material mixture was transferred to a platinum crucible and placed in an electric furnace heated to 900 ° C. and held for 1 hour. Thereafter, the platinum crucible was removed from the electric furnace and rapidly cooled at room temperature.

Heat was removed for about 10 minutes at room temperature, and the sample in the platinum crucible was pulverized and mixed in an alumina mortar. The crushed and mixed sample was transferred again to the platinum crucible, placed in an electric furnace heated to 1000 ° C., and baked for 12 hours (step S720 in FIG. 7). Thereafter, the platinum crucible was taken out of the electric furnace and rapidly cooled at room temperature to obtain an alkali metal-containing layered compound 110 (FIG. 1). The alkali metal-containing layered compound 110 thus obtained was subjected to powder XRD measurement, and confirmed to be a K ₃ Ti ₅ NbO ₁₄ single phase. In the main baking, when baking was performed at 800 ° C. and 900 ° C., an impurity of K ₂ Ti ₂ O ₅ was generated. Also from this fact, it was found that in order to obtain a single phase of K ₃ Ti ₅ NbO ₁₄ , firing at least at 950 ° C. is preferable.

Next, using the alkali metal-containing layered compound K ₃ Ti ₅ NbO ₁₄ thus obtained, a photocatalyst nanosheet Ti ₅ NbO ₁₄ was synthesized.

The alkali metal-containing layered compound K ₃ Ti ₅ NbO ₁₄ was acid-treated using an aqueous hydrochloric acid solution (12 N, manufactured by Wako Pure Chemical Industries, special grade) as an aqueous acid solution in the same manner as in Example 2 to produce a hydrogen ion exchanger. (Step S410 in FIG. 4).

Next, 0.4 g of hydrogen ion exchanger and 100 mL of tetrabutylammonium hydroxide aqueous solution (TBAOHaq.) As a basic substance (made by Wako Pure Chemical Industries, special grade) are reacted to peel off the hydrogen ion exchanger, and Ti ₅ NbO _A colloidal solution consisting of ₁₄ nanosheets was obtained (step S420 in FIG. 4).

The specific reaction is TBAOHaq. The molar ratio of TBA ⁺ in the hydrogen ion exchanger to H ⁺ in the hydrogen ion exchanger was adjusted to 1: 1. Place 94.6 mL of ultrapure water in a 200 mL Erlenmeyer flask and then add TBAOHaq. 5.4 mL was added to give a total of 100 mL of solution. To this solution, 0.4 g of a hydrogen ion exchanger was added and shaken with a shaker at 180 rpm for 10 days. It was confirmed that the solution in the Erlenmeyer flask became a milky white solution and the hydrogen ion exchanger was completely peeled off. In this way, a colloidal solution composed of Ti ₅ NbO ₁₄ nanosheets (hereinafter referred to as Ti ₅ NbO ₁₄ colloidal solution) was obtained.

The Ti ₅ NbO ₁₄ colloidal solution was applied to the quartz glass substrate and the Si substrate using an alternating adsorption method. The application of the Ti ₅ NbO ₁₄ colloid solution to the quartz glass substrate and the Si substrate was carried out by the same procedure using the Ti ₅ NbO ₁₄ colloid solution adjusted to the same concentration as in Example 1, and thus the description thereof is omitted. As in Example 1, the obtained photocatalytic materials are referred to as (Ti ₅ NbO ₁₄ / PDDA) _n / glass and (Ti ₅ NbO ₁₄ / PDDA) _n / Si. Here, n indicates the number of repetitions of step 530 in FIG.

As in Example 1, (Ti ₅ NbO ₁₄ / PDDA) ₁ / glass was used as a sample, and the photocatalytic property and photoinduced hydrophilization property of the Ti ₅ NbO ₁₄ nanosheet were evaluated. Each result is shown in FIG. 8, FIG. 9, and Table 2-Table 5, and is explained in full detail.

Similar to Example 1, UV-vis absorption spectrum measurement of multilayer structure by alternating adsorption method, XRD measurement of (Ti ₅ NbO ₁₄ / PDDA) ₁₀ / Si, (Ti ₅ NbO ₁₄ / PDDA) ₁₀ / photocatalytic property of glass Evaluation and AFM measurement of (Ti ₅ NbO ₁₄ / PDDA) ₁₀ / Si were performed. These results are shown in FIG. 13, FIG. 14, FIG. 18, FIG. 23 and Table 6 and will be described later.

A photocatalytic material 300 (FIG. 3) provided with a photocatalytic thin film 320 (FIG. 3) made of a Ca ₂ Nb ₃ O ₁₀ nanosheet is manufactured on a quartz glass substrate as a base material 310 (FIG. 3) by using an alternate adsorption method. did. Prior to the production of the photocatalytic material, an alkali metal-containing layered compound of KCa ₂ Nb ₃ O ₁₀ in which the alkali metal is K was synthesized.

K ₂ CO ₃ (2.7246 g, manufactured by Rare Metallic, purity 99.99%), CaCO ₃ (7.1751 g, manufactured by Rare Metallic, purity 99.99%), Nb ₂ O ₅ (14.2919 g, Rare) Metallic product, purity 99.99%) was mixed to obtain a raw material mixture (step S710 in FIG. 7). KCa ₂ Nb ₃ O ₁₀ and _K 2 CO ₃ than the stoichiometric ratio is added 10% excess at a molar ratio _of, K 2 CO ₃ and CaCO ₃ and _Nb 2 _{O 5} molar ratio of 1.1: 4 : 3. The raw material mixture was pulverized and mixed for 60 minutes using an alumina mortar.

Next, the raw material mixture was baked (step S720 in FIG. 7). The raw material mixture was transferred to a platinum crucible and placed in an electric furnace. The temperature was raised from room temperature to 900 ° C. over 3 hours and held at 900 ° C. for 1 hour. Next, the temperature was raised from 900 ° C. to 1200 ° C. over 3 hours, and calcined at 1200 ° C. for 12 hours. Thereafter, the temperature was lowered from 1200 ° C. to 800 ° C. in 3 hours, and the platinum crucible was taken out of the electric furnace to obtain an alkali metal-containing layered compound 110 (FIG. 1). Powder XRD measurement was performed on the alkali metal-containing layered compound 110 thus obtained, and it was confirmed that it was a KCa ₂ Nb ₃ O ₁₀ single phase. In addition, when the raw material mixture was adjusted with the molar ratio of KCa ₂ Nb ₃ O ₁₀ , impurities were generated by evaporation of K ₂ CO ₃ . This also indicates that it is important to suppress evaporation of K ₂ CO ₃ in the raw material mixture in order to obtain KCa ₂ Nb ₃ O ₁₀ single phase.

Next, a photocatalyst nanosheet Ca ₂ Nb ₃ O ₁₀ was synthesized using the alkali metal-containing layered compound KCa ₂ Nb ₃ O ₁₀ thus obtained.

The alkali metal-containing layered compound KCa ₂ Nb ₃ O ₁₀ was acid-treated using an aqueous nitric acid solution (13.5 N, manufactured by Wako Pure Chemical Industries, special grade) as an aqueous acid solution to produce a hydrogen ion exchanger (FIG. 4). Step S410). An aqueous nitric acid solution was prepared using ultrapure water (> 18 MΩcm) so as to be 5N.

Specifically, KCa ₂ Nb ₃ O ₁₀ (5 g) and nitric acid aqueous solution (200 mL) were stirred using a stirrer in a 500 mL beaker and reacted for 72 hours. After completion of the reaction, the product was filtered with ultrapure water and air-dried in air to obtain a hydrogen ion exchanger.

Next, 0.4 g of a hydrogen ion exchanger and 100 mL of a tetrabutylammonium hydroxide aqueous solution (TBAOHaq.) As a basic substance (made by Wako Pure Chemical Industries, special grade) are reacted to peel off the hydrogen ion exchanger, and Ca ₂ Nb. _A colloidal solution consisting of ₃ O ₁₀ nanosheets was obtained (step S420 in FIG. 4).

The specific reaction is TBAOHaq. The molar ratio of TBA ⁺ in the hydrogen ion exchanger to H ⁺ in the hydrogen ion exchanger was adjusted to 2: 1. Place 96.2 mL of ultrapure water in a 200 mL Erlenmeyer flask and then add TBAOHaq. 3.8 mL was added to give a total of 100 mL of solution. To this solution, 0.4 g of a hydrogen ion exchanger was added and shaken with a shaker at 180 rpm for 4 days. It was confirmed that the solution in the Erlenmeyer flask became a milky white solution and the hydrogen ion exchanger was completely peeled off. In this way, a colloidal solution composed of Ca ₂ Nb ₃ O ₁₀ nanosheets (hereinafter referred to as Ca ₂ Nb ₃ O ₁₀ colloidal solution) was obtained.

A Ca ₂ Nb ₃ O ₁₀ colloidal solution was applied to a quartz glass substrate using an alternating adsorption method. As in Example 1, the quartz glass substrate was hydrophilized.

Polyethyleneimine (PEI) was applied as a cationic polymer to the hydrophilized quartz glass substrate (step S510 in FIG. 5). Specifically, the concentration and pH of the PEI aqueous solution were adjusted to 2.5 gL ⁻¹ and 9, respectively. A hydrochloric acid solution was used to adjust the pH.

  The hydrophobized quartz glass substrate was immersed in the PEI aqueous solution thus prepared for 20 minutes. Thereafter, the quartz glass substrate was washed with ultrapure water, nitrogen gas flow was performed, and the surface was dried.

Next, a Ca ₂ Nb ₃ O ₁₀ colloid solution was applied to the quartz glass substrate to which PEI was applied (Step S520 in FIG. 5). The Ca ₂ Nb ₃ O ₁₀ colloid solution was centrifuged at 1500 rpm for 10 minutes to remove unexfoliated material, and then adjusted to a concentration of 0.4 gL ⁻¹ and pH 9. Again, a hydrochloric acid solution was used to adjust the pH. For application, a quartz glass substrate provided with PEI was immersed in a colloidal solution of Ca ₂ Nb ₃ O ₁₀ for 20 minutes. Thereafter, the quartz glass substrate was washed with ultrapure water, nitrogen gas flow was performed, and the surface was dried. In Example 6, unlike Example 1, Step S530 in FIG. 5 was not performed, and a photocatalytic thin film having a single-layer structure was formed, and the process was completed.

As in Example 1, (Ca ₂ Nb ₃ O ₁₀ / PDDA) ₁ / glass was used as a sample to evaluate the photocatalytic properties and photo-induced hydrophilization properties of Ca ₂ Nb ₃ O ₁₀ nanosheets and to perform AFM observation. . The photoinduced hydrophilization characteristics and the results of AFM observation are shown in FIG. 9 and Tables 4 to 6 and will be described in detail.

A photocatalyst material 300 (FIG. 3) provided with a photocatalytic thin film 320 (FIG. 3) made of a LaNb ₂ O ₇ nanosheet was manufactured on a quartz glass substrate as a base material 310 (FIG. 3) using an alternate adsorption method. Prior to the production of the photocatalytic material, an alkali metal-containing layered compound of KLaNb ₂ O ₇ in which the alkali metal is K was synthesized.

K ₂ CO ₃ (3.3403 g, manufactured by Rare Metallic, purity 99.99%), La ₂ O ₃ (6.8474 g, manufactured by Rare Metallic, purity 99.99%), and Nb ₂ O ₅ (1.1728 g) , Manufactured by Rare Metallic, purity 99.99%) to obtain a raw material mixture (step S710 in FIG. 7). K ₂ CO ₃ was added in a molar ratio of 15% in excess of the stoichiometric ratio of KLaNb ₂ O ₇ , and the molar ratio of K ₂ CO ₃ , La ₂ O ₃ and Nb ₂ O ₅ was 1.15: 2 : 1. The raw material mixture was pulverized and mixed for 60 minutes using an alumina mortar.

Next, the raw material mixture was baked (step S720 in FIG. 7). The raw material mixture was transferred to a platinum crucible and placed in an electric furnace. The temperature was raised from room temperature to 1150 ° C. over 3 hours and held at 1150 ° C. for 1 hour. Thereafter, the temperature was lowered from 1150 ° C. to room temperature, and the platinum crucible was taken out of the electric furnace to obtain an alkali metal-containing layered compound 110 (FIG. 1). The alkali metal-containing layered compound 110 thus obtained was subjected to powder XRD measurement, and confirmed to be a KLaNb ₂ O ₇ single phase. In addition, when the raw material mixture was adjusted by the stoichiometric ratio of KLaNb ₂ O ₇ , impurities were generated by evaporation of K ₂ CO ₃ . This also indicates that it is important to suppress evaporation of K ₂ CO ₃ in the raw material mixture in order to obtain a single phase of KLaNb ₂ O ₇ .

Next, a photocatalyst nanosheet LaNb ₂ O ₇ was synthesized using the alkali metal-containing layered compound KLaNb ₂ O ₇ thus obtained.

The alkali metal-containing layered compound KLaNb ₂ O ₇ was acid-treated using an aqueous hydrochloric acid solution (12 N, manufactured by Wako Pure Chemical Industries, special grade) as an acid aqueous solution in the same manner as in Example 2 to produce a hydrogen ion exchanger (FIG. 4 step S410).

Next, 0.4 g of a hydrogen ion exchanger and 100 mL of a tetrabutylammonium hydroxide aqueous solution (TBAOHaq.) (Basic grade, manufactured by Wako Pure Chemical Industries, Ltd.) as a basic substance are reacted to release the hydrogen ion exchanger, and LaNb ₂ O _A colloidal solution consisting of ₇ nanosheets was obtained (step S420 in FIG. 4).

The specific reaction is TBAOHaq. The molar ratio of TBA ⁺ in the hydrogen ion exchanger to H ⁺ in the hydrogen ion exchanger was adjusted to 5: 1. Into a 200 mL Erlenmeyer flask was placed 88.5 mL of ultrapure water, then 10% TBAOH aq. 11.5 mL was added to give a total of 100 mL of solution. To this solution, 0.4 g of a hydrogen ion exchanger was added and shaken with a shaker at 180 rpm for 10 days. It was confirmed that the solution in the Erlenmeyer flask became a milky white solution and the hydrogen ion exchanger was completely peeled off. In this way, a colloid solution composed of LaNb ₂ O ₇ nanosheets (hereinafter referred to as LaNb ₂ O ₇ colloid solution) was obtained.

A LaNb ₂ O ₇ colloidal solution was applied to a quartz glass substrate using an alternating adsorption method. The application of the LaNb ₂ O ₇ colloid solution to the quartz glass substrate is the same except that the LaNb ₂ O ₇ colloid solution adjusted to the same concentration as in Example 1 is used and step S530 in FIG. 5 is not repeated. Is omitted.

As in Example 1, (LaNb ₂ O ₇ / PDDA) ₁ / glass was used as a sample to evaluate the photocatalytic properties and photoinduced hydrophilization properties of the LaNb ₂ O ₇ nanosheets and to perform AFM observation. The photoinduced hydrophilization characteristics and the results of AFM observation are shown in FIG. 9 and Tables 4 to 6 and will be described in detail.

A photocatalytic material 300 (FIG. 3) provided with a single-layer photocatalytic thin film 320 (FIG. 3) made of Nb ₃ O ₈ nanosheets on a silicon (Si) substrate as a base material 310 (FIG. 3) using the LB method. ) Was manufactured.

The Nb ₃ O ₈ colloidal solution prepared in Example 1 was prepared so as to have a concentration of 16 mg L ⁻¹ and developed on a trough. The Si substrate hydrophilized as in Example 1 was immersed in a trough and allowed to stand for 30 minutes to stabilize the air-water interface, and the temperature of the lower layer liquid was kept constant (25 ° C.) (step S610 in FIG. 6). ).

The Nb ₃ O ₈ nanosheet adsorbed on the air-water interface was compressed at a compression rate of 0.5 mmsec ⁻¹ to form a single-layer photocatalytic thin film 320 composed of the Nb ₃ O ₈ nanosheet on the air-water interface. Next, the surface pressure was maintained at 12 mNm ⁻¹ and left to stand for 30 minutes to stabilize the photocatalytic thin film 320. Thereafter, the Si substrate was pulled vertically at a speed of ¹ mmsec ⁻¹ while maintaining the surface pressure (step S620 in FIG. 6).

The surface state of the photocatalyst material Nb ₃ O ₈ / Si thus obtained was observed by AFM. The results are shown in FIG. 24 and will be described later.

A photocatalytic material 300 (FIG. 3) provided with a single layer photocatalytic thin film 320 (FIG. 3) made of TiNbO ₅ nanosheets on a silicon (Si) substrate as a base material 310 (FIG. 3) using the LB method. Manufactured.

The TiNbO ₅ colloidal solution prepared in Example 3 was prepared to a concentration of 16 mg L ⁻¹ and developed on a trough. A photocatalytic material was obtained by the same procedure as in Example 8 except that the surface pressure was 15 mNm- ¹ .

The surface state of the photocatalytic material TiNbO ₅ / Si thus obtained was observed by AFM. The results are shown in FIG. 25 and will be described later.

A photocatalytic material 300 (FIG. 3) provided with a single-layered photocatalytic thin film 320 (FIG. 3) made of a Ti ₂ NbO ₇ nanosheet on a silicon (Si) substrate as a base material 310 (FIG. 3) using the LB method. ) Was manufactured.

The Ti ₂ NbO ₇ colloidal solution prepared in Example 4 was prepared to a concentration of 16 mg L ⁻¹ and developed on a trough. A photocatalytic material was obtained by the same procedure as in Example 8 except that the surface pressure was 15 mNm- ¹ .

The surface state of the photocatalyst material Ti ₂ NbO ₇ / Si thus obtained was observed by AFM. The results are shown in FIG. 26 and will be described later.

A photocatalyst material 300 (FIG. 3) provided with a single layer structure photocatalytic thin film 320 (FIG. 3) made of Ti ₅ NbO ₁₄ nanosheets on a silicon (Si) substrate as a base material 310 (FIG. 3) using the LB method. ) Was manufactured.

The Ti ₅ NbO ₁₄ colloidal solution prepared in Example 5 was prepared so as to have a concentration of 16 mg L ⁻¹ and developed on a trough. A photocatalytic material was obtained by the same procedure as in Example 8 except that the surface pressure was 17 mNm- ¹ .

The surface state of the photocatalytic material Ti ₅ NbO ₁₄ / Si thus obtained was observed by AFM. The results are shown in FIG. 27 and will be described later.

A photocatalytic material 300 (FIG. 3) provided with a single-layer photocatalytic thin film 320 (FIG. 3) made of Ca ₂ Nb ₃ O ₁₀ nanosheets on a silicon (Si) substrate as a base material 310 (FIG. 3) using an LB method. FIG. 3) was produced.

The Ca ₂ Nb ₃ O ₁₀ colloidal solution prepared in Example 6 was prepared to a concentration of 32 mg L ⁻¹ and developed on a trough. A photocatalytic material was obtained by the same procedure as in Example 8, except that the surface pressure was 8.5 mNm- ¹ .

The surface state of the photocatalyst material Ca ₂ Nb ₃ O ₁₀ / Si thus obtained was observed by AFM. The results are shown in FIG. 28 and will be described later.

A photocatalyst material 300 (FIG. 3) provided with a photocatalytic thin film 320 (FIG. 3) made of Nb ₃ O ₈ nanosheets was manufactured on a silicon (Si) substrate as a base material 310 (FIG. 3) using a dropping method. .

The Nb ₃ O ₈ colloidal solution prepared in Example 1 was prepared to a concentration of 0.2 gL ⁻¹ . The surface of the Si substrate was washed with bem cotton containing acetone. One drop of Nb ₃ O ₈ colloidal solution whose concentration was adjusted by a Pasteur pipette was dropped on the Si substrate surface, and then air-dried for 5 to 7 hours to evaporate water.

The surface state of the photocatalyst material Nb ₃ O ₈ / Si thus obtained was observed by AFM. The results are shown in FIG. 29 and will be described later.

A photocatalytic material 300 (FIG. 3) provided with a photocatalytic thin film 320 (FIG. 3) made of a TiNbO ₅ nanosheet was produced on a silicon (Si) substrate as a base material 310 (FIG. 3) by a dropping method.

The TiNbO ₅ colloidal solution prepared in Example 3 was prepared to a concentration of 16 mgL- ¹ . As in Example 13, a drop of TiNbO ₅ colloidal solution adjusted in concentration by a Pasteur pipette was dropped on the Si substrate surface that had been hydrophilized in the same manner as in Example 1, and then air-dried for 5 to 7 hours to remove moisture. Evaporated.

The surface state of the photocatalytic material TiNbO ₅ / Si thus obtained was observed by AFM. The results are shown in FIG. 30 and will be described later.

A photocatalyst material 300 (FIG. 3) provided with a photocatalytic thin film 320 (FIG. 3) made of a Ti ₂ NbO ₇ nanosheet was produced on a silicon (Si) substrate as a base material 310 (FIG. 3) using a dropping method. .

The Ti ₂ NbO ₇ colloidal solution prepared in Example 4 was prepared to a concentration of 50 mgL ⁻¹ . A drop of Ti ₂ NbO ₇ colloidal solution whose concentration was adjusted with a Pasteur pipette was dropped on the Si substrate surface that had been hydrophilized in the same manner as in Example 1 and then air-dried for 5 to 7 hours. Water was evaporated.

The surface state of the photocatalyst material Ti ₂ NbO ₇ / Si thus obtained was observed by AFM. The results are shown in FIG. 31 and will be described later.

A photocatalytic material 300 (FIG. 3) provided with a photocatalytic thin film 320 (FIG. 3) made of a Ti ₅ NbO ₁₄ nanosheet was manufactured on a silicon (Si) substrate as a base material 310 (FIG. 3) using a dropping method. .

The Ti ₅ NbO ₁₄ colloidal solution prepared in Example 5 was prepared to a concentration of 16 mg L ⁻¹ . A drop of Ti ₅ NbO ₁₄ colloidal solution whose concentration was adjusted by a Pasteur pipette was dropped on the Si substrate surface that had been hydrophilized in the same manner as in Example 1, and then air-dried for 5 to 7 hours. Water was evaporated.

The surface state of the photocatalytic material Ti ₅ NbO ₁₄ / Si thus obtained was observed by AFM. The results are shown in FIG. 32 and will be described later.

The photocatalyst material (Nb ₃ O ₈ / PDDA) ₁ / glass obtained in Example ₁ and the photocatalyst material Nb ₃ O ₈ / Si obtained in Example 8 were each set at a set temperature (100 And 200 ° C, 300 ° C, 400 ° C, 500 ° C, 600 ° C, 700 ° C, 800 ° C and 900 ° C) for 1 hour. As heating conditions, a photocatalytic material was placed in an electric furnace, the temperature was raised from room temperature (30 ° C.) to each set temperature at 5 ° C./min, held at each set temperature for 1 hour, and then cooled to room temperature.

The surface state of Nb ₃ O ₈ / Si after heating at each set temperature was observed by AFM. The observation results are shown in FIG. 33 and will be described later. In addition, Nb ₃ O ₈ / Si after heating at each set temperature was subjected to in-plane X-ray diffraction measurement (in-plane XRD) using Photon Factory BL-6 (High Energy Accelerator Research Organization), and structural changes were made. Examined. The results are shown in FIG. 34 and will be described later.

About (Nb ₃ O ₈ / PDDA) ₁ / glass after heating at each set temperature, the light-induced hydrophilization characteristics were evaluated in the same manner as in Example 1. The results are shown in FIG. 35 and Table 8, and will be described later.

Comparative Example 1

Lepidocrocite potassium site type layered titanate _{K x Ti 2-x / 3} Li x / 3 O 4 and (x = 0.7), by the same procedure as in Example 1, and the acid treatment, the layered as a hydrogen ion exchanger titanate powder _{(H 4x / 3 Ti 2-} x / 3 O 4 · nH 2 O) was obtained. 0.5 g of layered titanic acid powder was added to TBAOHaq. Reaction with 100 mL gave a milky white solution. The reaction was shaken at 150 rpm with a shaker at room temperature for 7 days. In this way, a colloidal solution composed of Ti _0.87 O ₂ nanosheets (hereinafter referred to as Ti _0.87 O ₂ colloidal solution) was obtained.

Ti _0.87 O ₂ colloidal solution diluted 50 times was applied to a quartz glass substrate using an alternate adsorption method. The quartz glass substrate was hydrophilized in the same manner as in Example 1. The subsequent procedure is the same as that of the first embodiment except that step S530 of FIG. Using the photocatalyst material (Ti _0.87 O ₂ / PDDA) ₁ / glass thus obtained, the light-induced hydrophilization characteristics of Ti _0.87 O ₂ nanosheets were evaluated in the same manner as in Example 1. The results are shown in FIG. 9, Table 4 and Table 5 and will be described in detail.

  Hereinafter, the results of Examples 1 to 17 and Comparative Example 1 will be shown and described in detail.

  FIG. 8 is a diagram showing the photocatalytic properties of Examples 1 and 3-5.

All showed a decrease in absorbance by irradiation with ultraviolet light. This indicates that methylene blue was decomposed by irradiation with ultraviolet light, and it was found that both have photocatalytic properties. Among them, Ti ₂ NbO ₇ photocatalyst nanosheet (Example 4) is replaced with other Nb ₃ O ₈ photocatalyst nanosheet (Example 1), TiNbO ₅ photocatalyst nanosheet (Example 3), Ti ₅ NbO ₁₄ photocatalyst nanosheet (Example 5). In comparison, a dramatic decrease in absorbance was observed by short-time ultraviolet irradiation, indicating that the photocatalytic property was high. In the following, for simplicity, only the material name is described. Although not shown, other Nb ₆ O ₁₇ , Ca ₂ Nb ₃ O ₁₀ and LaNb ₂ O ₇ also showed a decrease in absorbance in the same manner, confirming that they had photocatalytic properties. For reference, Table 2 shows the amount of change in absorbance.

  The change rate of the absorbance of methylene blue was determined for each photocatalyst nanosheet from the relationship between the change in absorbance in FIG. 8 and Table 2 and the ultraviolet light irradiation time. The results are shown in Table 3.

From Table 3, it was found that the photocatalytic property of Ti ₂ NbO ₇ was extremely high.

  FIG. 9 is a diagram showing the light-induced hydrophilization characteristics of Examples 1 to 7 and Comparative Example 1.

  In either case, irradiation with ultraviolet light increased the reciprocal of the contact angle (defined as the hydrophilization rate), that is, decreased the contact angle. Specifically, by irradiating with ultraviolet light, the reciprocal of the contact angle increases from 0.2 to 0.4, that is, the contact angle decreases from 2.5 ° to 5 °. It became clear that it became a hydrophilic state. For reference, Table 4 shows the reciprocal value of the water contact angle.

  The hydrophilization reaction rate was calculated | required about each photocatalyst nanosheet from the relationship between the reciprocal number of the water contact angle of FIG. 9 and Table 4, and ultraviolet light irradiation time. The results are shown in Table 5.

According to Table 5, among the photocatalyst nanosheets of the present invention, Nb ₃ O ₈ (Example 1), TiNbO ₅ (Example 3), Ca ₂ Nb ₃ O ₁₀ (Example 6), LaNb ₂ O ₇ (Example) 7) was found to have a large hydrophilization reaction rate as compared with the existing titanium oxide Ti _0.87 O ₂ (Comparative Example 1). These photocatalytic nanosheets are suggested to be particularly effective for self-cleaning, dustproofing and cooling applications that utilize photoinduced hydrophilization properties. Thus, according to the present invention, it is possible to appropriately select and design a photocatalyst nanosheet having photocatalytic properties and photoinduced hydrophilization properties according to the use and demand.

10 is a view showing a UV-vis absorption spectrum of Example 1. FIG.
FIG. 11 is a diagram showing the UV-vis absorption spectrum of Example 3.
12 is a graph showing a UV-vis absorption spectrum of Example 4. FIG.
FIG. 13 is a diagram showing the UV-vis absorption spectrum of Example 5.

  10 to 13, in each case, a certain amount of increase in absorbance was observed with each repetition of step S530 in FIG. This indicates that a photocatalytic thin film having a multilayer structure in which photocatalytic nanosheets and PDDA are regularly accumulated is formed on a quartz glass substrate.

  FIG. 14 is a diagram showing XRD patterns of Examples 1 and 3-5.

  All XRD patterns showed a large diffraction peak around 2θ = 5 °. This also indicates that a photocatalytic thin film having a multilayer structure in which photocatalyst nanosheets and PDDA are regularly accumulated is formed on the Si substrate.

FIG. 15 is a diagram showing XRD patterns before and after ultraviolet light irradiation in Example 1.
FIG. 16 is a diagram showing XRD patterns before and after ultraviolet light irradiation in Example 3.
FIG. 17 is a diagram showing XRD patterns before and after ultraviolet light irradiation in Example 4.
18 is a diagram showing XRD patterns before and after ultraviolet light irradiation in Example 5. FIG.

  According to FIGS. 15-18, it turned out that the peak of 2 (theta) = 5 degree shifts to the high angle side by irradiating ultraviolet light in any case. This means that the surface separation, that is, the interlayer distance is reduced. Specific changes in the interlayer distance are shown in FIGS.

  Such a change in the interlayer distance is due to the decomposition of PDDA present between the layers by the photocatalytic action of these nanosheets by ultraviolet light irradiation. The amount of change in the interlayer distance (about 0.3 nm to 0.6 nm) approximately corresponds to one layer of PDDA. This also confirmed that these nanosheets function as photocatalytic nanosheets.

19 is a diagram showing an AFM image of the surface of Example 1. FIG.
20 is a diagram showing an AFM image of the surface of Example 2. FIG.
FIG. 21 is a diagram showing an AFM image of the surface of Example 3.
FIG. 22 is a diagram showing an AFM image of the surface of Example 4.
FIG. 23 is a diagram showing an AFM image of the surface of Example 5.

FIG. 19 and FIGS. 21 to 23 show that the nanosheets accumulated in the plane direction densely cover the surface of the base material although they partially overlap. Thereby, it turned out that the photocatalyst thin film which consists of a photocatalyst nanosheet formed by the alternate adsorption method is comparatively uniform. Both FIG. 19 and FIGS. 21 to 23 were smooth with a surface roughness between 0.8 nm and 1.1 nm. Nb ₆ O ₁₇ (FIG. 20) showed a rounded sheet shape as compared with other nanosheets. This indicates that in the production of a photocatalytic thin film composed of a Nb ₆ O ₁₇ photocatalytic nanosheet, further scrutiny is required in order to improve the adhesion to the substrate.

  Moreover, as Table 6 showed, the thickness of the nanosheet was 1 nm-2 nm. This thickness is almost the same as the thickness calculated from the crystal structure (for example, FIG. 2), suggesting that the alkali metal-containing layered compound as the starting material has been peeled off as a single layer.

FIG. 24 is a diagram showing an AFM image of the surface of Example 8.
FIG. 25 is a diagram showing an AFM image of the surface of Example 9.
FIG. 26 is a view showing an AFM image of the surface of Example 10. FIG.
FIG. 27 is a diagram showing an AFM image of the surface of Example 11.
FIG. 28 is a diagram showing an AFM image of the surface of Example 12.

  According to FIGS. 24-28, all showed a very smooth surface, and the surface roughness was between 0.15 nm and 0.26 nm. Further, from FIG. 24 to FIG. 28, according to the LB method, it is possible to obtain a photocatalytic thin film composed of a monolayer structure in which photocatalyst nanosheets are accumulated in the plane direction, specifically, a monolayer film in which nanosheets are accumulated without overlapping. I understood.

FIG. 29 is a view showing an AFM image of the surface of Example 13. FIG.
30 is a diagram showing an AFM image of the surface of Example 14. FIG.
FIG. 31 is a diagram showing an AFM image of the surface of Example 15.
32 is a view showing an AFM image of the surface of Example 16. FIG.

  As shown in FIG. 29 to FIG. 32, all had a surface roughness between 0.72 nm and 1.6 nm, and showed a structure in which nanosheets overlapped. From this, the dropping method is preferable because the photocatalytic thin film composed of the photocatalyst nanosheet is easily formed although the smoothness is inferior.

  Table 7 summarizes the smoothness of the photocatalytic thin film obtained from FIGS. 19 to 32.

  From Table 7, it can be seen that the LB method is optimal for obtaining a highly smooth photocatalytic thin film having high smoothness. In addition, the alternate adsorption method is optimal for obtaining a photocatalytic thin film with a controlled film thickness. Thus, it is desirable to select a production method according to the film quality (smoothness, film thickness, etc.) required for the application to which the photocatalytic thin film is applied.

  FIG. 33 is a view showing an AFM image of the surface after the heat treatment according to Example 17.

FIG. 33 also shows the AFM image of Example 8 as the state of the surface before the heat treatment. According to FIG. 33, the surface state of the Nb ₃ O ₈ photocatalyst nanosheet was not changed even after the heat treatment at 800 ° C. When heat treatment at 900 ° C. was performed, the nanosheets changed to needles. This is considered to be due to the change from Nb ₃ O ₈ to Nb ₂ O ₅ . This suggests that the heating of the nanosheet is preferably below 900 ° C. As a result, even if heat treatment for improving the adhesion between the nanosheet and the base material is performed, and even if heat treatment is performed on the process, the smoothness of the surface of the nanosheet can be maintained, which is extremely advantageous. is there.

  FIG. 34 is a diagram showing an in-plane XRD pattern after the heat treatment according to Example 17.

FIG. 34 also shows the XRD pattern before the heat treatment. According to the XRD pattern of FIG. 34, the XRD pattern before the heat treatment was almost the same as that after the heat treatment at each temperature of 100 ° C. to 800 ° C. In the XRD pattern after heat treatment at 900 ° C., a peak was observed on the low angle side. These peaks were confirmed to coincide with the diffraction peak of Nb ₂ O ₅ . From this, it was found that Nb ₃ O ₈ is changed to Nb ₂ O ₅ by heat treatment at 900 ° C. or higher, so that the heat treatment is preferably less than 900 ° C. As described above, the crystal structure is maintained even when Nb ₃ O ₈ is subjected to high-temperature heat treatment because the two-dimensional sheet structure in which octahedral units of NbO ₆ are bonded is extremely stable.

  FIG. 35 is a diagram showing the light-induced hydrophilization characteristics after the heat treatment according to Example 17.

For reference, FIG. 35 also shows the light-induced hydrophilization characteristics before heat treatment. As the heat treatment temperature increased, the light-induced hydrophilization characteristics decreased. However, it should be noted that even after heat treatment at 800 ° C., the Nb ₃ O ₈ photocatalytic nanosheets had photo-induced hydrophilization properties that exceeded Ti _0.87 O ₂ (see, eg, FIG. 9). . This indicates that the Nb ₃ O ₈ photocatalyst nanosheet is expected to have the same effect not only on the photoinduced hydrophilization property but also on the photocatalytic property. In addition to Nb ₃ O ₈ , similar effects are expected for TiNbO ₅ , Ca ₂ Nb ₃ O _10, and LaNb ₂ O ₇ having photo-induced hydrophilization characteristics exceeding Ti _0.87 O ₂ in FIG. 9. Is done.

  From the relationship between the reciprocal of the water contact angle in FIG. 35 and the ultraviolet light irradiation time, the hydrophilization reaction rate was determined for the heat treatment temperature. The results are shown in Table 8.

According to Table 8, the hydrophilization reaction rate (0.018 ° / min) of Nb ₃ O ₈ after heat treatment at 800 ° C. is that of the comparative example (Ti _0.87 O ₂ ) shown in Table 5 ( It was found to be larger than 0.011 ° / min.

As described above, from FIG. 33 to FIG. 35, among the photocatalytic nanosheets according to the present invention, Nb ₃ O ₈ , TiNbO ₅ , Ca ₂ Nb ₃ O _10, and LaNb ₂ O ₇ are film surface states and photoinduced hydrophilization even after heat treatment. Since the characteristics are maintained, a heat treatment for improving adhesion to the substrate and a heat treatment in the process are possible, which is extremely advantageous in practice.

  According to the present invention, there are provided photocatalyst nanosheets made of a material different from titanium oxide nanosheets and existing anatase, which can be appropriately selected according to use and can be variously designed. According to the photocatalyst material obtained by thinning the photocatalyst nanosheet on the base material, the photocatalyst material reflecting an arbitrary shape and surface form is provided by the unique flexibility of the photocatalyst nanosheet. The photocatalytic property and the photo-induced hydrophilization property can be developed for the intended use. As a matter of course, the photocatalyst nanosheet and the photocatalyst material of the present invention can be applied to any application that requires photocatalytic properties and photoinduced hydrophilization properties.

Schematic diagram of photocatalyst nanosheet according to the present invention Schematic diagram of various photocatalytic nanosheets according to the present invention Schematic diagram of photocatalytic material according to the present invention The flowchart which shows the manufacturing process of the photocatalyst nanosheet by this invention Diagram showing manufacturing process of photocatalytic material using alternating adsorption method The figure which shows the manufacturing process of the photocatalyst material using LB method Flow chart showing production process of alkali metal-containing layered compound The figure which shows the photocatalytic property of Example 1 and 3-5 The figure which shows the light-induced hydrophilization characteristic of Examples 1-7 and Comparative Example 1 The figure which shows the UV-vis absorption spectrum of Example 1 The figure which shows the UV-vis absorption spectrum of Example 3 The figure which shows the UV-vis absorption spectrum of Example 4 The figure which shows the UV-vis absorption spectrum of Example 5 The figure which shows the XRD pattern of Example 1 and 3-5 The figure which shows the XRD pattern before and behind ultraviolet light irradiation of Example 1. The figure which shows the XRD pattern before and behind ultraviolet light irradiation of Example 3. The figure which shows the XRD pattern before and behind ultraviolet light irradiation of Example 4. The figure which shows the XRD pattern before and behind ultraviolet light irradiation of Example 5. The figure which shows the AFM image of the surface of Example 1 The figure which shows the AFM image of the surface of Example 2 The figure which shows the AFM image of the surface of Example 3 The figure which shows the AFM image of the surface of Example 4 The figure which shows the AFM image of the surface of Example 5 The figure which shows the AFM image of the surface of Example 8 The figure which shows the AFM image of the surface of Example 9 The figure which shows the AFM image of the surface of Example 10 The figure which shows the AFM image of the surface of Example 11 The figure which shows the AFM image of the surface of Example 12 The figure which shows the AFM image of the surface of Example 13 The figure which shows the AFM image of the surface of Example 14 The figure which shows the AFM image of the surface of Example 15 The figure which shows the AFM image of the surface of Example 16 The figure which shows the AFM image of the surface after the heat processing by Example 17 The figure which shows the in-plane XRD pattern after the heat processing by Example 17 The figure which shows the light-induced hydrophilization characteristic after the heat processing by Example 17

Explanation of symbols

100 photocatalyst nanosheet 110 alkali metal-containing layered compound 200 NbO ₆ or octahedron unit 300 photocatalytic material 310 substrate 320 photocatalytic film of TiO ₆

Claims (8)

A photocatalytic nanosheet consisting of NbO ₆ and / or TiO ₆ octahedral units, Nb ₃ O ₈ , Nb ₆ O ₁₇ , TiNbO ₅ , Ti ₂ NbO ₇ , Ti ₅ NbO ₁₄ , Ca ₂ Nb ₃ O ₁₀ and LaNb ₂ A photocatalytic nanosheet comprising a nanosheet selected from the group consisting of O ₇ .   2. The photocatalyst nanosheet according to claim 1, wherein the selected nanosheet is peeled from a layered compound containing an alkali metal. 3. A method for producing a photocatalyst nanosheet,
Containing an alkali metal selected from the group consisting of MNb ₃ O ₈ , M ₄ Nb ₆ O ₁₇ , MTiNbO ₅ , MTi ₂ NbO ₇ , M ₃ Ti ₅ NbO ₁₄ , MCa ₂ Nb ₃ O ₁₀ and MLaNb ₂ O ₇ A step of acid-treating a layered compound (where M is an alkali metal) with an aqueous acid solution to produce a hydrogen ion exchanger in which the alkali metal in the layered compound is exchanged;
Reacting the hydrogen ion exchanger with a basic substance to obtain a colloidal solution consisting of nanosheets from which the hydrogen ion exchanger has been peeled off. A photocatalytic material comprising a photocatalytic thin film applied on a substrate,
The photocatalyst material, wherein the photocatalyst thin film comprises the photocatalyst nanosheet according to claim 1 or 2.   5. The photocatalytic material according to claim 4, wherein the photocatalytic thin film has a maximum surface roughness of 2 nm. A method for producing a photocatalytic material, comprising:
_{Nb 3 O 8, Nb 6 O} 17, TiNbO 5, Ti 2 NbO 7, Ti 5 NbO 14, Ca 2 Nb 3 O 10 and LaNb substrate a colloidal solution containing the selected nanosheet from the group consisting of ₂ O ₇ A manufacturing method comprising the steps of:   The method according to claim 6, further comprising a step of performing a heat treatment in a temperature range of 100 ° C. or higher and lower than 900 ° C. following the applying step.   The method according to claim 6, wherein the applying step is selected from the group consisting of an alternating adsorption method, an LB method, a drop method, a spin coating method, and a dip coating method.