JP2005087880A - Photocatalyst composite material, photocatalyst particle, and coating material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a highly active photocatalyst material having a crystal orientation face causing a photocatalytic reaction to suitably act. <P>SOLUTION: A photocatalyst composite material made by immobilizing on a substrate a zinc oxide membrane in which crystals grow to expose the (110) face of a wurtzite structure to its surface has zinc oxide doped with nitrogen. A photocatalyst particle composed of zinc oxide has the crystals growing so as to make the (110) face of a wurtzite structure occupy the face having the maximum surface area among the surfaces of the particle and having the above zinc oxide doped with nitrogen. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a photocatalytic material having a highly active photocatalytic activity.

  When the photocatalytic material is irradiated with light having energy greater than or equal to the band gap, electrons and holes are excited and diffused on the surface, so that an oxidation-reduction reaction or a hydrophilization reaction appears. Taking advantage of this function, photocatalytic materials are used in various fields such as environmental purification, antifouling, self-cleaning, and antifogging.

  Since the photocatalytic reaction occurs when the photoexcited carrier moves to the surface of the material, the photocatalytic activity is higher as the number of oxygen vacancies and crystal grain boundaries that are carrier scattering sources is smaller in the photocatalytic material. The photocatalytic activity also depends on the surface crystal orientation. In general, since oxygen atoms on the surface act as active sites for the photocatalytic reaction, the reaction rate of crystal planes where oxygen is present on the surface is fast (see, for example, Non-Patent Document 1).

  Zinc oxide is known as one of photocatalytic materials. In zinc oxide, since the lower end of the conduction band is on the negative side of the reduction potential of water and the upper end of the valence band is on the positive side of the oxidation potential of water, zinc oxide has a strong redox power. Zinc oxide is a white pigment, varistor, surface acoustic wave (SAW) element, gas sensor, piezoelectric element, pyroelectric element, Schottky diode, laser light emitting element, thin film transistor (TFT), acoustic resonance element, ultraviolet light detecting element. It is used in a wide range of fields such as transparent magnetic materials.

In particular, in the field of electronics, thinning of zinc oxide single crystals by heteroepitaxial growth is being studied. Zinc oxide can make crystal planes according to the material of the substrate. For example, as a research example of zinc oxide having in-plane orientation, a high-frequency magnetron sputtering method (see, for example, Patent Document 1, Non-Patent Document 2, and Non-Patent Document 3), a CVD method (see, for example, Non-Patent Document 4), Examples include film formation on a sapphire substrate by MOCVD method (for example, see Non-Patent Document 5) and PEMOCVD method (for example, see Non-Patent Document 6). However, in Patent Document 1, since the sputtering gas pressure is 4 × 10 ⁻³ torr, the mean free path of plasma is increased and damage during film formation is large. In Non-Patent Document 2, the volume resistivity of the thin film is increased. In Non-Patent Document 3, the sputtering gas pressure is 5 × 10 ⁻³ torr, so that the mean free path of plasma is increased and the damage during film formation is large. When the thin film is exposed to the atmosphere, the volume resistivity decreases to 10 ⁴ Ω · cm or less (see Non-Patent Document 7). In Non-Patent Document 5, the CL (cathode luminescence) spectrum of the thin film is measured at room temperature. In addition, a broad peak is seen in the vicinity of λ = 600 nm of the spectrum, and in Non-Patent Document 6, since both CVD and argon gas plasma are used together during film formation, all the thin films have many oxygen defects and are photocatalytic materials. In Considered that there was no is.

On the other hand, the present inventors have proposed doping of nitrogen ions as a technique for reducing oxygen defects in the zinc oxide thin film (see, for example, Patent Document 2). When nitrogen ions are doped, the generation of oxygen defects is suppressed by the charge compensation effect of nitrogen ions. In Patent Document 2, the relationship between orientation and photocatalytic activity has not been studied.
Japanese Patent Laid-Open No. 2003-63893 Japanese Patent Application No. 2003-85565 J. Phys. Chem. B, 1999, 103, 12, 2188-2194 J. Appl. Phys., 1980, 51, 5, 2464-2470 J. Vac. Sci. Technol. A, 1997, Vol. 15, No. 3, pp. 1103-1107 Appl. Phys. Lett., 1980, 36, 4, 318-320 J. Cryst. Groth, 2000, 221, 431-434 Proc. IEEE Ultrasonics Symposium, 1981, 1981, pp. 498-501 Thin Solid Films, 1976, 38, 131-141

  Provided is a highly active photocatalytic material having a crystal orientation plane on which a photocatalytic reaction suitably acts and having a structure with reduced crystal grain boundaries and oxygen defects.

In the present invention, there is provided a photocatalyst composite material in which a layer made of zinc oxide crystal-grown so that the (110) face of the wurtzite structure is the surface is fixed on a base material, Is provided. A photocatalytic composite material is provided.
On the surface of the (110) plane of the wurtzite structure, oxygen atoms that serve as active sites exist. Further, when nitrogen is doped, the generation of oxygen defects is suppressed by the charge compensation effect, so that high photocatalytic activity can be realized.

  In the present invention, a zinc oxide photocatalytic material is provided in which crystal growth is performed such that the (110) crystal plane of the wurtzite structure is the surface, and nitrogen is doped. High photocatalytic activity (oxidative decomposition power, hydrophilicity) was demonstrated by optimizing the crystal orientation and reducing oxygen defects.

  As a usage form of the photocatalyst material of the present invention, immobilization of a photocatalyst material on a substrate can be mentioned. The material of the base material is not particularly limited, but a metal material and an inorganic material are preferable. In a particularly preferred embodiment, a sapphire R plane is used as the substrate.

  In the present invention, the surface of the zinc oxide thin film is a (110) plane having a wurtzite structure. On the surface of the (110) plane of the wurtzite structure, oxygen atoms that serve as active sites for the photocatalytic reaction are present. For example, in the (001) plane of a wurtzite structure, which has been reported as a zinc oxide heteroepitaxial film, the most stable energy is when the outermost surface has only zinc atoms. The photocatalytic activity is greatly improved by forming the surface with the (110) plane of the wurtzite structure.

  In a preferred embodiment of the present invention, the zinc oxide thin film is doped with nitrogen. In addition to nitrogen, sulfur, phosphorus, and carbon are also known as dopants. Nitrogen is preferable from the viewpoint of ease of process. When nitrogen is doped, the generation of oxygen defects can be suppressed by the charge compensation effect, and as a result, high photocatalytic activity can be expressed. The position where the impurity is doped may be any one of lattice oxygen substitution, interstitial space of the photocatalytic material, crystal grain boundary, or a combination thereof. Doping can be done either on the surface or even inside the thin film

  In a preferred embodiment of the present invention, the zinc oxide thin film has in-plane orientation. By having in-plane orientation, crystal grain boundaries are reduced, whereby the mobility of electrons and holes is improved, and as a result, high photocatalytic activity can be expressed.

  The film thickness of the zinc oxide thin film is preferably 10 nm or more and 2 μm or less. If it is less than 10 nm, the film becomes non-uniform (sea-island structure), and if it exceeds 2 μm, the transparency of the film is lost.

  The surface roughness of the photocatalytic material is preferably 2 nm or more and 200 nm or less. More preferably, it is 15 nm or more and 200 nm or less. When surface roughness is imparted, the surface area increases, and the number of reaction sites increases accordingly, so that the photocatalytic activity increases. Further, when the surface roughness is imparted, the contact angle with the surface water is lowered, which is advantageous for applications such as anti-fogging and self-cleaning utilizing the hydrophilization phenomenon. When the surface roughness is less than 2 nm, the surface area of the film is small, so the amount of reaction sites contributing to the photocatalytic reaction is small. When the surface roughness exceeds 200 nm, the transparency of the film is lost by visible light scattering, which is not suitable for some applications.

  In the preferable aspect of this invention, a base material is a sapphire R surface. When the sapphire R-plane is used as a substrate, crystals are grown by heteroepitaxial growth so that the (110) plane of the wurtzite structure becomes the surface.

  In a preferred embodiment of the present invention, the zinc oxide is produced by a sputtering method. Inside the chamber of the sputtering apparatus, the introduced nitrogen gas is dissociated to generate high-energy nitrogen plasma, so that the photocatalytic material can be easily doped with nitrogen.

In the production method by the sputtering method, the total pressure of the reaction gas is preferably 6.0 × 10 ⁻³ torr or more. If it is less than 6.0 × 10 ⁻³ torr, the mean free path of the plasma increases and damage may increase during film formation.

  Sputtering devices include DC sputtering, high frequency sputtering, magnetron sputtering, ion beam sputtering, ECR sputtering, and the like, and any of these types can form a film.

  In the sputtering method, the target material is preferably a metal target. When an oxide target is used, the particles ejected by the sputtering phenomenon are formed by a group (cluster) of oxide molecules, so that uniform nitrogen doping into the crystal becomes difficult.

In the manufacturing method by the sputtering method, a mixed gas of oxygen and nitrogen is used as the gas. By using nitrogen, the generation of oxygen defects can be suppressed. The gas mixing ratio O ₂ / N ₂ is preferably 10/90 to 30/70. If the amount of nitrogen is less than 70, doping is insufficient because the amount of nitrogen is insufficient, and if the amount of nitrogen exceeds 90, amorphous or nitride may be formed.

  In the manufacturing method by the sputtering method, the plasma output is preferably 600 W or less. If it exceeds 600 W, the mean free path of plasma increases, and damage may increase during film formation.

  CVD, vapor deposition, MBE, laser ablation, and ion plating can be used as manufacturing methods different from sputtering. In this case, a radical source is required to dissociate nitrogen molecules into plasma. It is.

  As a method of doping the zinc oxide thin film of the present invention with nitrogen, there is a method in which a zinc oxide thin film or a zinc oxide precursor thin film is heat-treated in an air stream containing ammonia. In the case of doping with carbon, phosphorus, or sulfur other than nitrogen, there is a method of performing heat treatment in an air stream containing at least one of various reactive gases selected from the group consisting of hydrocarbon, phosphoric acid, and hydrogen sulfide.

  The present invention also provides a photocatalytic material comprising zinc oxide particles, wherein the (110) surface of the wurtzite structure is crystal-grown so as to be a surface having the maximum surface area of the surface of the particles, and the zinc oxide Provided is a photocatalytic material which is doped with nitrogen. In the case of a fiber for air treatment, a fiber such as a filter for water treatment, application to a honeycomb, a coating material or a coating agent, it is preferably in the form of particles. In order to sufficiently obtain the effects of the present invention, the particle diameter is preferably 5 nm or more and 100 μm or less. If it is less than 5 nm, the crystallinity of the particles is insufficient. If it exceeds 100 μm, the particles are likely to precipitate when formed into a paint.

  In a preferred embodiment of the present invention, as the method for producing the particles, a zinc oxide single crystal is precipitated so that the wurtzite type (110) crystal plane is the plane having the maximum surface area of the particle surface in the liquid phase or gas phase. Let Specifically, single crystal production such as the Bridgeman method, pulling method (Czochralski method), floating zone melting method, aqueous solution method, flux method, evaporation method, chemical vapor transport method, hydrothermal synthesis method, solid phase method, etc. Technology is available.

  In the present invention, the zinc oxide particles are doped with nitrogen. In addition to nitrogen, sulfur, phosphorus, and carbon are also known as dopants. Nitrogen is preferable from the viewpoint of ease of process. When nitrogen is doped, the generation of oxygen defects can be suppressed by the charge compensation effect, and as a result, high photocatalytic activity can be expressed. The position where the impurity is doped may be any one of lattice oxygen substitution, interstitial space of the photocatalytic material, crystal grain boundary, or a combination thereof. Doping may be performed only on the surface or inside the particles.

  As the method for producing nitrogen-doped zinc oxide particles of the present invention, the particles can be produced by heat treatment in an air stream containing ammonia. Alternatively, the zinc oxide precursor particles may be heat-treated in an air stream containing ammonia.

  The photocatalytic material of the present invention can be used as a paint in combination with a solvent. In this case, the photocatalyst material and the solvent of the present invention are used in combination with a binder, a colorant, a filler, a surfactant, a film-forming aid, a thickener and the like, if necessary.

  By using paint, it can be applied to substrates that are difficult to apply a dry process or to substrates with particularly low heat resistance such as resin, and can also be applied to the exterior walls of outdoor buildings. Become.

As a binder when used as the coating material, for example, a substance having a siloxane bond can be preferably used. Silanol groups with high affinity for water are present on the surface of the compound having a siloxane bond, which has the effect of imparting or strengthening hydrophilicity in the dark, and is self-cleaning due to rain The effect is easy to express. As the substance having a siloxane bond, an alkali silicate such as water glass, colloidal silica, or an aluminosilicate compound may be used. The aluminosilicate compound is a compound in which a part of Si of the silicate compound is substituted with Al, and in order to further compensate the charge, such as H ⁺ , Li ⁺ , Na ⁺ , K ⁺ , Rb ⁺ , Cs ⁺ , Fr ^+, etc. Alkali metal ions and alkaline earth metal ions such as Be ²⁺ , Mg ²⁺ , Ca ²⁺ , Sr ²⁺ , Ba ²⁺ , and Ra ²⁺ may be contained. A substance obtained by substituting a part of Si of the compound having a silicate bond with Al, zeolite, or the like can also be used.

  In a more preferred embodiment, a silicone emulsion can be used as the substance having a siloxane bond. Examples of silicone emulsions include methyltrichlorosilane, methyltribromosilane, methyltrimethoxysilane, methyltriethoxysilane, methyltriisopropoxysilane, methyltrit-butoxysilane; ethyltrichlorosilane, ethyltribromosilane, ethyltrimethoxysilane, Ethyltriethoxysilane, ethyltriisopropoxysilane, ethyltri-t-butoxysilane; n-propyltrichlorosilane, n-propyltribromosilane, n-propyltrimethoxysilane, n-propyltriethoxysilane, n-propyltriisopropoxy Silane, n-propyltri-t-butoxysilane; n-hexyltrichlorosilane, n-hexyltribromosilane, n-hexyltrimethoxysilane, n-hexyltrieto Sisilane, n-hexyltriisopropoxysilane, n-hexyltri-t-butoxysilane; n-decyltrichlorosilane, n-decyltribromosilane, n-decyltrimethoxysilane, n-decyltriethoxysilane, n-decyltriisoiso Propoxysilane, n-decyltri-t-butoxysilane; n-octadecyltrichlorosilane, n-octadecyltribromosilane, n-octadecyltrimethoxysilane, n-octadecyltriethoxysilane, n-octadecyltriisopropoxysilane, n-octadecyltri t-butoxysilane; phenyltrichlorosilane, phenyltribromosilane, phenyltrimethoxysilane, phenyltriethoxysilane, phenyltriisopropoxysilane, phenyltrit-butoxysilane Tetrachlorosilane, tetrabromosilane, tetramethoxysilane, tetraethoxysilane, tetrabutoxysilane, dimethoxydiethoxysilane; dimethyldichlorosilane, dimethyldibromosilane, dimethyldimethoxysilane, dimethyldiethoxysilane; diphenyldichlorosilane, diphenyl Dibromosilane, diphenyldimethoxysilane, diphenyldiethoxysilane; phenylmethyldichlorosilane, phenylmethyldibromosilane, phenylmethyldimethoxysilane, phenylmethyldiethoxysilane; trichlorohydrosilane, tribromohydrosilane, trimethoxyhydrosilane, triethoxyhydrosilane , Triisopropoxyhydrosilane, tri-t-butoxyhydrosilane; vinyltrichlorosilane, vinyltribro Silane, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltriisopropoxysilane, vinyltrit-butoxysilane; trifluoropropyltrichlorosilane, trifluoropropyltribromosilane, trifluoropropyltrimethoxysilane, trifluoropropyltriethoxysilane , Trifluoropropyltriisopropoxysilane, trifluoropropyltri-t-butoxysilane; γ-glycidoxypropylmethyldimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ -Glycidoxypropyltriethoxysilane, γ-glycidoxypropyltriisopropoxysilane, γ-glycidoxypropyltri-t-butoxysilane; γ-methacryloxy Propylmethyldimethoxysilane, γ-methacryloxypropylmethyldiethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropyltriethoxysilane, γ-methacryloxypropyltriisopropoxysilane, γ-meta Acryloxypropyltri-t-butoxysilane; γ-aminopropylmethyldimethoxysilane, γ-aminopropylmethyldiethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, γ-aminopropyltriisopropoxysilane Γ-aminopropyltri-t-butoxysilane; γ-mercaptopropylmethyldimethoxysilane, γ-mercaptopropylmethyldiethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-merca P-propyltriethoxysilane, γ-mercaptopropyltriisopropoxysilane, γ-mercaptopropyltri-t-butoxysilane; β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, β- (3,4-epoxycyclohexyl) A partial hydrolyzate or dehydration polycondensate of ethyltriethoxysilane can be preferably used.

  Furthermore, a fluororesin emulsion can be used as a binder when used as the paint. A coating film containing a fluororesin emulsion has high chemical stability and high weather resistance.

  Examples of the fluororesin emulsion include polytetrafluoroethylene, polyvinylidene fluoride, polyvinyl fluoride, polychlorotrifluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer, ethylene-tetrafluoroethylene copolymer, and ethylene-chlorotrifluoroethylene copolymer. , Tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, perfluorocyclopolymer, vinyl ether-fluoroolefin copolymer, vinyl ester-fluoroolefin copolymer, tetrafluoroethylene-vinyl ether copolymer, chlorotrifluoroethylene-vinyl ether copolymer, tetrafluoroethylene urethane crosslinked product , Tetrafluoroethylene epoxy crosslinked product, La fluoroethylene acrylic crosslinked body, at least one selected from the emulsion such as polymers containing tetrafluoroethylene melamine crosslinked body and the like fluoro group can be suitably used.

  Furthermore, a resin emulsion other than silicone and fluorine may be used as a binder when used as the paint. For example, acrylic resin type, urethane resin type, vinyl acetate resin type, vinyl chloride resin type, and rubber resin type emulsion can be mentioned. Acrylic emulsions and the like are less expensive than silicone and fluorine emulsions, and can reduce costs. However, since the weather resistance is slightly inferior, it is preferably used in combination with silicone and fluorine.

  When used as the paint, the solvent is not particularly limited as long as the photocatalytic material and the binder are dispersed. For example, water, alcohols, ethers; ketones such as acetone, 2-butanone, methyl propyl ketone, methyl butyl ketone, dipropyl ketone; ethyl acetate, propyl acetate, isopropyl acetate, butyl acetate, amyl acetate, ethyl butyrate, etc. Esters such as: general solvents such as benzene, toluene, xylene, chloroform, pentane, hexane, cyclohexane, and other aliphatic, aromatic, alicyclic hydrocarbons, petroleum, etc. Can be used.

  The photocatalytic material preferably has a columnar structure grown in a direction perpendicular to the substrate. The columnar structure can be realized by forming a film by sputtering. In the columnar structure, the surface area is increased, so that the photocatalytic activity is increased. In addition, since the surface roughness is imparted to the columnar structure, the contact angle with water on the surface is lowered, which is advantageous for applications such as anti-fogging and self-cleaning utilizing the hydrophilization phenomenon.

  In the present invention, as a base material to which the photocatalyst material can be applied, examples of applications where a self-cleaning effect can be expected include, for example, building exteriors such as outer walls and roofs, window frames, automobiles, railway vehicles, aircraft, ships, bicycles, and motorcycles. Such as exterior and painting of vehicles, window glass, signs, traffic signs, sound barriers, plastic houses, insulators, vehicle covers, tent materials, reflectors, shutters, screen doors, solar cell covers, solar water heaters, etc. Heater cover, street light, pavement, outdoor lighting, artificial waterfall, artificial fountain stone, tile, bridge, greenhouse, outer wall material, sealer between walls and insulators, guardrail, veranda, vending machine, air conditioner outdoor unit, outdoor bench , Various display devices, shutters, toll booths, toll boxes, roof gutters, vehicle lamp protection covers, dustproof covers and coatings, painting of machinery and articles, exterior of advertising towers and Instrumentation, structural members, and adhered possible film thereto articles, patch and the like.

  In the present invention, as a base material to which the photocatalytic material can be applied, in an anti-fogging application, for example, a mirror for bathroom or toilet mirror, a back mirror for vehicles, a dental tooth mirror, a road mirror, a spectacle lens, an optical Lenses such as lenses, camera lenses, endoscope lenses, illumination lenses, semiconductor manufacturing lenses; prisms; window glass of buildings and surveillance towers; automobiles, railway vehicles, aircraft, ships, submersibles, snow vehicles, -Pway gondolas, amusement park gondola, spacecraft-like vehicle windows; automobiles, rail vehicles, aircraft, ships, submersibles, snow vehicles, snowmobiles, motorbikes, ropeway gondola Windshields for vehicles such as amusement park gondola; protective or sports goggles or masks (including diving masks) shields; helmet shields; frozen food display cases Ga Scan; Hippo instrumentation - capable adhered to the glass, and their articles films, emblems are like

  The electrical resistivity, Hall electromotive force, carrier density, mobility, and carrier attributes of the photocatalytic material of the present invention can be measured by a Hall effect measuring device and a Seebeck coefficient measuring device.

  The particle diameter of the photocatalytic material of the present invention can be measured with a photon correlation spectrophotometer. Here, the particle diameter is the mode value of the volume average particle diameter measured by photon correlation spectroscopy (PCS).

(Example 1)
A sapphire substrate (made by Orbe Pioneer, cutting plane: R, C, A, diameter: 4 inch, thickness: 1 mm, polishing: double-sided mirror polishing), or glass substrate (Corning 7059) is placed inside the chamber of the high-frequency magnetron sputtering apparatus. The sample (# 1-5) was prepared under the conditions (# 1-5) described in Table 1. HSM-752 manufactured by Shimadzu Corporation was used as the high-frequency magnetron sputtering apparatus, and Zn manufactured by High-Purity Chemical Laboratory (purity: 99.999%) was used as the Zn target.

Next, the crystal structures of samples # 1 to # 5 (crystal structure of crystal plane parallel to the sample surface), in-plane orientation (in-plane orientation of the crystal structure), surface roughness, volume resistivity, hole occurrence Power, carrier density, mobility, and carrier attributes were measured. XRD for measurement of crystal structure (MXP-18 made by Mac Science), XRD for measurement of in-plane orientation (RINT-2100 made by Rigaku), SEM for measurement of film thickness (S-4100 made by Hitachi, Ltd.), AFM (Nanoscope 3a manufactured by Digital Instruments) was used for the measurement of the surface roughness. XRD scan axes are θ for Mac Science MXP-18, θ, φ (tilt angle), and β (rotation angle) for Rigaku RINT-2100. In the measurement of the crystal structure, a 2θ-θ scan was performed under the measurement conditions described in Table 2. In the in-plane orientation measurement, θ and φ were fixed at an angle at which the (101) plane of the wurtzite structure was diffracted, and β scan was performed under the conditions described in Table 3.
In the measurement of the surface roughness, 10 μm × 10 μm of the sample surface was scanned in the tapping mode with AFM, and the surface roughness (R _A ) was calculated with the attached software of the apparatus. In addition, volume resistivity, Hall electromotive force, carrier density, mobility, and carrier attributes were measured with a Hall effect measuring device (RESITEST8200 manufactured by Toyo Technica). As a result, the film thicknesses of # 1-5, surface roughness of # 1-3, electrical resistivity of # 1-4, Hall electromotive force, carrier density, mobility, and carrier attributes are shown in Table 4, The crystal structures of # 1-5 are shown in FIGS. 4-8, the in-plane orientations of # 1-4 are shown in FIGS. 9-12, and the AFM images of # 1- # 3 are shown in FIGS. 13-15, respectively. In Table 4, the volume resistivity, Hall electromotive force, carrier density, mobility, and carrier attribute of # 5 are described as “−” because the volume resistivity of the sample exceeded the measurement limit, and # 4, Since the surface roughness of 5 was not measured, “*” was written. Regarding the crystal structure, # 1 shows the (110) plane of the wurtzite structure, and # 2 to 5 show the (001) plane of the wurtzite structure. As for the in-plane orientation, a 4-fold symmetry peak was observed in # 1, and a hexagonal symmetry peak was observed in # 2 and 3, and in-plane orientation was shown, but no rotationally symmetric peak was observed in # 4. In-plane orientation was not exhibited. The surface roughness is 16 nm for # 1, 17 nm for # 2, and 24 nm for # 3, and the results are reflected in the density of white spots in the AFM image (displaying heights from 150 nm to 200 nm from the lowest unevenness point). Has been.

Subsequently, the photocatalytic activity of samples # 1 to 5 was evaluated by a dry methylene blue decomposition test. The measuring method is as follows.
1. Cut the sample to 10 mm x 15 mm.
2. The absorbance spectrum of the sample is measured with a spectrophotometer. The wavelength range is 500 to 700 nm, the wavelength interval is 1 nm, and the measurement speed is 400 nm · min ⁻¹ . At this time, the absorbance at the wavelength λ (500 nm ≦ λ ≦ 700 nm) is defined as A _λ0 .
3. A booth having the configuration shown in FIG. 16 is prepared, and the height of the black light fluorescent lamp is adjusted so that the ultraviolet intensity (λ = 360 nm) is 3 mW · cm ⁻² on the sample surface. Here, a portable ultraviolet intensity meter can be used to adjust the ultraviolet intensity.
4). Place the sample in the booth and irradiate with UV light for 24 hours.
5). Prepare an aqueous methylene blue solution having a concentration of 1.0 × 10 ⁻³ M, and immerse the sample in the solution for 5 minutes.
6). Remove the sample and dry in air at room temperature.
7). The excess methylene blue on the substrate surface is wiped off so that the methylene blue remains only on the photocatalyst surface.
8). The absorbance spectrum of the sample is measured with a spectrophotometer. At this time, the absorbance at the wavelength λ is A _λ1 .
9. In the booth of FIG. 16, the height of the black light fluorescent lamp is adjusted so that the ultraviolet intensity (λ = 360 nm) is 1 mW · cm ^{−2 on} the sample surface.
10. Place the sample in the booth and irradiate with UV light for 15 minutes.
11. Subsequently, the sample is left in the dark for 90 minutes.
12 The absorbance spectrum of the sample is measured with a spectrophotometer. At this time, the absorbance at the wavelength λ is A _λ2 .
13. From Formula 1, the photocatalytic activity (Δabs.) Is calculated.

  In this measurement, methylene blue tetrahydrate (137-06982) manufactured by Wako Pure Chemical Industries as the methylene blue reagent, Ubest-55 manufactured by JASCO Corporation as spectrophotometer, UD-36 manufactured by Topcon as UV intensity meter, black light fluorescent lamp The FL20S BLB manufactured by Toshiba Lighting & Technology was used. The photocatalytic activity of # 1-5 is shown in FIG. # 1 where the substrate is a sapphire R surface is an example, and other # 2 to 5 are comparative examples. In # 1, an oxygen atom was present on the outermost surface of the sample, which acted as a reaction site for the photocatalytic reaction, and thus exhibited a high photocatalytic activity.

(Example 2)
The photocatalytic activity of the samples (# 1-5) was evaluated by hydrophilization characteristics. The measuring method is as follows.
1. Immerse the sample in ethanol for 30 minutes.
2. Remove the sample and dry in air at room temperature.
3. Prepare a booth with the configuration shown in Fig. 17, and set the height of the mercury xenon lamp and bandpass filter (center wavelength: 355 nm) so that the UV intensity (λ = 360 nm) is 3 mW · cm ^-2 on the sample surface. adjust. Here, a portable ultraviolet intensity meter can be used to adjust the ultraviolet intensity.
4). The contact angle of the sample with water is measured with a contact angle meter.
5). Blow off the adhering water with air to dry the sample surface.
6). Place the sample in the booth and irradiate with ultraviolet rays. The irradiation time is 0.5 to 2 hours for samples # 1 to 3 and 70 hours for samples # 4 and 5.
7). After irradiation with ultraviolet rays for a predetermined time, the contact angle of the sample with water is measured with a contact angle meter.

  In this measurement, CA-X150 manufactured by Kyowa Interface Science as a contact angle meter, Lumina Ace LA-210UV manufactured by Hayashi Watch Industry as a mercury xenon lamp, UV-D36B manufactured by Asahi Techno Glass as a bandpass filter, and Topcon manufactured as a UV intensity meter. UD-36 was used. The hydrophilization characteristics of # 1-3 are shown in FIG. 2, and the hydrophilization characteristics of # 4-5 are shown in FIG. # 1 where the substrate is a sapphire R surface is an example, and other # 2 to 5 are comparative examples. Sample # 1 showed superior hydrophilization properties compared to samples # 2-5. Since oxygen atoms exist on the outermost surface of the sample, the oxygen atoms react with adsorbed water and adsorbed oxygen during ultraviolet irradiation, resulting in a structural change of the sample surface.

It is a graph which shows the photocatalytic activity of sample # 1- # 5. It is a graph which shows the hydrophilization characteristic of sample # 1- # 3. It is a graph which shows the hydrophilization characteristic of sample # 4-# 5. It is a graph which shows the crystal structure of sample # 1. It is a graph which shows the crystal structure of sample # 2. It is a graph which shows the crystal structure of sample # 3. It is a graph which shows the crystal structure of sample # 4. It is a graph which shows the crystal structure of sample # 5. It is a graph which shows the in-plane orientation of sample # 1. It is a graph which shows the in-plane orientation of sample # 2. It is a graph which shows the in-plane orientation of sample # 3. It is a graph which shows the in-plane orientation of sample # 4. It is a figure which shows the AFM image of sample # 1. It is a figure which shows the AFM image of sample # 2. It is a figure which shows the AFM image of sample # 3. It is a figure which shows the evaluation apparatus of photocatalytic activity (oxidative decomposition power). It is a figure which shows the evaluation apparatus of photocatalytic activity (hydrophilic property).

Claims (8)

A photocatalytic composite material in which a film made of zinc oxide crystal-grown so that the (110) face of the wurtzite structure is the surface is fixed on a base material, wherein the zinc oxide is doped with nitrogen A photocatalytic composite material characterized by comprising: The photocatalyst composite material according to claim 1, wherein the film made of zinc oxide has in-plane orientation. 3. The photocatalyst composite material according to claim 1, wherein a film thickness of the zinc oxide film is 10 nm or more and 2 μm or less. The photocatalyst composite material according to any one of claims 1 to 3, wherein the zinc oxide layer has a surface roughness of 2 nm or more and 200 nm or less. The photocatalyst composite material according to any one of claims 1 to 4, wherein the base material is a sapphire R surface. The photocatalyst composite material according to any one of claims 1 to 5, wherein the zinc oxide is produced by a sputtering method, and a total pressure of a reaction gas during sputtering is 6.0 × 10 ^-3 torr or more. Photocatalyst particles made of zinc oxide, crystal-grown so that the (110) plane of the wurtzite structure is the plane having the maximum surface area of the surface of the particles, and the zinc oxide is doped with nitrogen Photocatalyst particles characterized by the above. A coating composition comprising the photocatalyst particles according to claim 7 and a solvent.

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