WO2015064773A1

WO2015064773A1 - Photocatalytic coating and method of making same

Info

Publication number: WO2015064773A1
Application number: PCT/JP2014/079659
Authority: WO
Inventors: Guang Pan; Tao Gu; Ekambaram Sambandan; Brett T. Harding
Original assignee: Nitto Denko Corporation
Priority date: 2013-11-04
Filing date: 2014-10-31
Publication date: 2015-05-07
Also published as: TW201521871A

Abstract

The present invention is aimed at improving the adhesion of a photocatalytic material to a substrate. An embodiment of the present invention relates to a method for making a photocatalytic element comprising: providing a suspension comprising a binder and a photocatalytic material, wherein the weight ratio of the binder to the photocatalytic material is about 0.5 to 2.0 parts binder to about 1 part photocatalytic material; and applying the suspension to a substrate surface.

Description

DESCRIPTION

PHOTOCATALYTIC COATING AND METHOD OF MAKING SAME Technical Field

Some embodiments are related to a process for producing a substrate provided with an inorganic particle-containing photocatalytic film.

Background Art

Visible light activated photocatalysts can be deployed for self-cleaning, air and water purification and many other interesting applications usually without any post- deployment non-renewable energy costs. This is because the photocatalysts are able to decompose pollutants (like dyes, volatile organic compounds and NO_x) using light available in the ambient like solar radiation or indoor and outdoor lighting. With the anticipated rapid adoption of UV-free indoor lighting (like LEDs and OLEDs), it is imperative to find ways to deploy visible-light activated photocatalysts in indoor applications for instance in cleaning room air in domestic, public and commercial spaces especially in confined areas like aircraft, public buildings, etc. Moreover, additional applications for antibacterial surfaces and self-cleaning materials can have wide applicability in the food service, transportation, health care and hospitality sectors.

Various methods have been proposed to fix titanium oxide. See, for example, Patent Literatures 1 to 5. Thus there is a need for affixation of titanium oxide to substrate surfaces. Citation List Patent Literature

PTL1 : Unites States Patent No. 5,897,958

PTL2 : Unites States Patent No. 6,228,480

PTL3 : Unites States Patent No. 6,407,033

PTL4 : Unites States Patent No. 7,510,595

PTL 5: United States Reissue Patent No. RE38,850

Summary of Invention

The present invention is aimed at improving the adhesion of a photocatalytic material to a substrate.

Namely, some embodiments of the present invention relate to a method for making a photocatalytic element comprising: providing a suspension comprising a binder and a photocatalytic material, wherein the weight ratio of the binder to the photocatalytic material is about 0.5 to 2.0 parts binder to about 1 part photocatalytic material; and applying the suspension to a substrate surface.

In some embodiments, applying the suspension to a substrate may further comprise casting the suspension upon the substrate.

In some embodiments, applying the suspension to a substrate may further comprise spin coating the suspension on the substrate at about 500 revolutions per min to about 3000 revolutions per min for between about 5 seconds to about 30 seconds.

In some embodiments, the method may further comprise surface treating the substrate surface. In some embodiments, the method may further comprise applying a silane coupling agent to the substrate surface. The silane coupling agent may be

aminopropyltriethoxy silane.

In some embodiments, the method may further comprise adding a binder catalyst material to the suspension. The binder catalyst material may be D25.

In some embodiments, providing the suspension may further comprise dissolving a silicone resin in a propylene glycol solvent. The propylene glycol solvent may be propylene glycol methyl ether acetate. In addition, the silicone resin may be a silicone alkyd resin, a silicone epoxy resin, a silicone acrylic resin, or a silicone polyester resin. Furthermore, the silicone resin may be a silicone polyester resin. Moreover, the silicone polyester resin may be KR5230.

In some embodiments, the photocatalytic material may comprise a copper oxide loaded metal oxide.

In some embodiments, the photocatalytic material may comprise doped or undoped Ti0₂.

In some embodiments, there is provided a method for making a photocatalytic element comprising:

providing a solution comprising 10% of KR5230 and 90% of propylene glycol monomethyl ether acetate (PGMEA);

adding a photocatalytic copper loaded plural phase titanium oxide material powder to the solution, at a ratio of 10:1 (w/w) binder:photocatalytic material;

pretreating a PET surface with corona treatment; and

spin coating the solution on the pretreated PET surface, at about 100 to about 2000 rpm for about 30 to about 60 seconds. In some embodiments, there is provided a photocatalytic element made according to the methods described above.

In some embodiments, there is provided a photocatalytic element comprising a silicone polyester resin and a photocatalytic material, wherein the weight ratio of the resin to the photocatalytic material is between about 0.5 to about 2.0 to about 1 (0.5-2 parts resin to 1 part photocatalytic material). The silicone polyester resin may be selected from KR500, KR5230 and KR5235. In addition, the photocatalytic material may be selected from copper oxide loaded plural phase titanium oxide, copper oxide loaded Sn/C doped titanium oxide, and unloaded doped titanium oxide.

Furthermore, some embodiments of the present invention relate to a method for making a photocatalytic element comprising: providing a suspension comprising a binder, photocatalytic material, a photo-initiator and an organic solvent, wherein the weight ratio of the binder to the photocatalytic material is about 1.0 to 20 parts binder to about 1 part photocatalytic material; and applying the suspension to a substrate surface.

Furthermore, some embodiments of the present invention relate to a method for making a photocatalytic element comprising: providing a solution comprising a binder, photocatalytic material, a photo-initiator and an organic solvent; providing a suspension comprising a binder, photocatalytic material, a photo-initiator and an organic solvent, wherein the weight ratio of the binder to the photocatalytic material in the suspension is about 1.0 to 20 parts binder to about 1 part photocatalytic material; applying the solution to a substrate surface to form an intervening layer on the substrate surface; and applying the suspension to the intervening layer on the substrate surface.

In some embodiments, applying the suspension to a substrate may further comprise casting the suspension upon the substrate. In some embodiments, the method may further comprise surface treating the substrate surface. The binder may comprise an ultraviolet curable urethane resin. In addition, the ultraviolet curable urethane resin may comprise a urethane acrylate resin.

In some embodiments, the organic solvent may be a C1-C7 ketone.

In some embodiments, the organic solvent may be a C 1 -C7 alcohol.

In some embodiments, the organic solvent may be selected from cyclopentanone, propylene glycol monomethyl ether acetate (PGMEA), N- methylpyrrolidone (NMP), methyl ethyl ketone (MEK), toluene, ethyl acetate and butyl acetate.

In some embodiments, the suspension may further comprise a dispersing agent. The dispersing agent may be selected from a cationic dispersing agent, an anionic dispersing agent, and a non-ionic dispersing agent.

In some embodiments, the photoinitiator may be selected from IRGACURE 907 and IRGACURE 2022.

In some embodiments, there is provided a method for making a photocatalytic element comprising: providing a solution comprising 10% by weight of a urethane acrylate resin, less than 1.0% by weight of a photoinitiator and 90% by weight of cyclopentone; adding a photocatalytic copper loaded plural phase titanium oxide material powder to the solution, at a ratio of 5: 1 (w/w) binder :photocatalytic material; pretreating a PET surface with corona treatment; and tape casting the suspension on the pretreated PET surface.

In some embodiments, there is provided a method for making a photocatalytic element comprising: providing a solution comprising 10% by weight of a urethane acrylate resin, less than 1.0% by weight of a photoinitiator and 90% by weight of cyclopentone; pretreating a PET surface with corona treatment; tape casting the solution on the pretreated PET surface to form a binder coating on the PET surface; providing a solution comprising 10% by weight of a urethane acrylate, less than 1.0% by weight of a photoinitiator, 90% by weight of cyclopentone and a photocatalytic copper loaded plural phase titanium oxide material powder to the suspension, at a ratio of 5:1 (w/w) bindenphotocatalytic material; and tape casting the suspension on the binder coating.

In some embodiments, there is provided a photocatalytic element made according to the methods described above.

In some embodiments, there is provided a photocatalytic element comprising a urethane acrylate resin and a photocatalytic material, wherein the weight ratio of the resin to the photocatalytic material is between about 0.5 to about 10 to about 1 (0.5-10 parts urethane acrylate resin to 1 part photocatalytic material), preferably between about 1.5 to about 10 to about 1 (1.5-10 parts urethane acrylate resin to 1 part photocatalytic material). The urethane acrylate resin may be selected from UNIDIC 17806, EBECRYL 8701, EBECRYL 8301, EBECRYL 8405, OC-3021, OC-4021, OC-4122, HC-5619, and UVHC3000. In addition, the photocatalytic material may be selected from copper oxide loaded plural phase titanium oxide, copper oxide loaded Sn/C/N doped titanium oxide, and unloaded doped titanium oxide. According to the present invention, the adhesion of a photocatalytic material to a substrate can be improved.

Brief Description of Drawings

FIG. 1 is a schematic of embodiments of an experiment described herein.

FIG. 2A and 2B are schematics of embodiments of photocatalytic elements described herein.

FIG. 3 is a schematic of an embodiment of a photocatalytic element described herein.

FIG. 4 is a schematic of an embodiment of a photocatalytic element described herein.

FIG. 5 is a graph showing the antibacterial (E.Coli) activity of an embodiment described herein (Example A).

FIG. 6 is a graph showing the antibacterial (E.Coli) activity of an embodiment described herein (Example B).

FIG. 7 is a graph showing the antibacterial (E.Coli) activity of an embodiment described herein (Example C).

FIG. 8 is a graph showing the antibacterial (E.Coli) activity of an embodiment described herein (Example D).

FIG. 9 is a graph showing the antibacterial (E.Coli) activity of an embodiment described herein (Example E).

FIG. 10 shows SEM surface and cross section images of an embodiment (Example A) on PET substrate. FIG. 11 is a graph showing the antibacterial (E.Coli) activity of embodiments described herein (Examples AA-AF) performance of photocatalytic (copper oxide (Cu_xO) loaded plural phase Ti0₂ [87% anatase phase Ti0₂/13% rutile phase Ti0₂]) coating with KR5230 as binder. (Photocatalytic loading=11.8 vol%, 21.1 vol% and 34.8 vol%)

FIG. 12 is a schematic of embodiments of an experimental described herein. FIG. 13 is a schematic of embodiments of an experimental described herein. FIG. 14 is a schematic of an embodiment of a photocatalytic element described herein.

FIG. 15 is a schematic of an embodiment of a photocatalytic element described herein.

FIG. 16 is a graph showing the antibacterial (E.Coli) activity of an embodiment described herein (Example I and Example II).

FIG. 17 is a graph showing the antibacterial (E.Coli) activity of an embodiment described herein (Examples 1 1 to 15) under light.

FIG. 18 is a graph showing the antibacterial (E.Coli) activity of an embodiment described herein (Examples 1 1 to 15) under dark.

FIG. 19 is a SEM surface image of an embodiment (Example 11) on PET substrate.

FIG. 20 is a SEM surface image of an embodiment (Example 11) on PET substrate.

FIG. 21 is a SEM surface image of an embodiment (Example 15) on PET substrate. FIG. 22 is a SEM surface image of an embodiment (Example 15) on PET substrate

Description of Embodiments

Embodiments of the present invention are described in greater detail below.

Photocatalytic coatings described herein can comprise inorganic particles at nanometer scale dispersed in polymer resins. Polymer resins can be used as binders to hold the nanometer scale particles to a substrate surface with increased adhesion and scratch resistance. Polymer resins can be used as binders to provide the coating with increased hardness to resist the damage caused by scratching. Photocatalyst coatings can be formed by applying the photocatalytic suspension made of polymer binders and photocatalyst particles on substrate. In an embodiment, the photocatalyst particles comprise semiconductor nano-particles which have a bandgap or bandgaps associated with absorption in the wavelength range of visible light. The photocatalyst particles can be doped or loaded with copper oxide (e.g., a plural Cu¹⁺ and Cu²⁺ oxide) which provides the coating with the function or functions of inactivating microbes such as bacteria, or viruses, decomposing VOC (Volatile Organic Compounds) or decomposing the dyes in liquid as indicator of maintenance of phtocatalyst activity. Multiple coatings can be formed on substrates to give multiple functions integrated on one substrate.

As shown in FIG. 1, the current disclosure provides a method (S 10) for making a photocatalytic element comprising providing a binder and photocatalytic material solution, wherein the binder to photocatalytic material is provided in a ratio of about 0.5-2.0 parts binder to about 1 part photocatalytic material (weight ratio [w/w]) (SI 2); and applying the mixture to a substrate (SI 6). Those skilled in the art will recognize that 0.5-2.0 parts binder to 1 part photocatalytic material corresponds to about 5% to about 35 vol% of photocatalytic material in the coating as calculated by the density of the photocatalytic material and resin. In some embodiments, 5-20 parts of a 10% binder (by weight) solution to 1 part photocatalytic material (by weight) is provided. In some embodiments, the method further comprises treating the surface of the substrate (SI 4). In some embodiments, the method further comprises drying the applied binder/photocatalytic material suspension on the substrate surface to remove the solvent (SI 8). In some embodiments, the solvent is substantially all removed.

FIG. 2A shows a photocatalytic element 10 including a substrate 12 and a photocatalytic coating 14. In some embodiments, a primer layer 16 is interposed between the substrate 12 and photocatalytic coating 14. In some embodiments, the primer layer comprises a silane coupling agent. In some embodiments, the primer layer is disposed upon a first surface 18 of the substrate 12. In some embodiments, the primer layer can be a first portion of the substrate 12. In some embodiments, the first portion is integral with the substrate. In some embodiments, the photocatalytic coating 14 is disposed upon or contacting the primer layer 16. As shown in FIG. 2B, in some embodiments, the photocatalytic coating 14 is disposed upon, in contact with or a portion of the substrate 12. In some embodiments, the primer layer can comprises a treated substrate surface 18.

In FIG. 3, there is shown a photocatalytic element 10, including a substrate 12, a first photocatalytic coating 14A and a second photocatalytic coating 14B. In some embodiments, the photocatalytic coating 14A is disposed upon, in contact with or a portion of the substrate 12. In some embodiments, the second photocatalytic coating 14B is disposed upon, in contact with or a portion of the first photocatalytic coating 14A. In some embodiments, plural apertures 20 are defined within photocatalytic coating 14B to communicate the surface 22 of photocatalytic coating 14A with the ambient environment 8. This provides plural photocatalytic layers (14A and 14B) in contact with the ambient environment 8.

In FIG. 4, there is shown a photocatalytic element 10, including a substrate 12, a primer layer 16, and plural photocatalytic coatings, e.g., a first photocatalytic coating 14A and a second photocatalytic coating 14B. In some embodiments, the photocatalytic coatings 14A and 14B can be disposed upon, in contact with the primer layer 16. As previously described with regard to FIG. 2A and 2B, in some embodiments, the first photocatalytic coating 14A and second photocatalytic coating 14B can be disposed upon, in contact with or a portion of the substrate 12. In this embodiment, both photocatalytic coatings are in direct communication or in contact with the environment 8.

In some embodiments, the photocatalytic material can be an oxide comprising an element that can be, for example, titanium, tungsten, tantalum, tin, zinc or strontium. In some embodiments, the oxide can be doped or undoped, and/or loaded or unloaded. In some embodiments, the oxide can have a valence band deeper than that of the copper loaded materials valence bands. In some embodiments, the photocatalytic material can be a plural phase composite of photocatalytic materials. In some embodiments, the photocatalytic material can be ananatase, rutile, wurtzite, spinel, perovskite, pyrocholore, garnet, zircon and/or tialite phase material or mixtures thereof. Each of these options is given its ordinary meaning as understood by one having ordinary skill in the semiconductor art. Comparison of an X-ray diffraction pattern of a given standard and the produced sample is one of a number of methods that may be used to determine whether the sample comprises a particular phase. Exemplary standards include those XRD spectra provided by the National Institute of Standards and Technology (NIST) (Gaitherburg, MD, USA) and/or the International Centre for Diffraction Data (ICDD, formerly the Joint Committee on Powder Diffraction Standards [JCPDS]) (Newtown Square, PA, USA).

In some embodiments, the plural phase photocatalytic materials comprise anatase phase and rutile phase compounds. In some embodiments, the plural phase photocatalytic materials can be titanium oxides. In some embodiments, the anatase phase can be 2.5% to about 97.5%, 5% to about 95%, and/or about 10% to about 90%; and the rutile phase can be 97.5% to about 2.5%, 95% to about 5%, and/or about 10% to about 90%. A non-limiting example of a suitable material includes, but is not limited to a Ti0₂ mixture sold under the brand name P25 (83%Anataste Ti0₂+17%Rutile Ti0₂) sold by Evonik (Parissipany, NJ, USA)).

In some embodiments, the photocatalytic materials comprise compounds having an average particle diameter of between about 10 - 100 nm. In some embodiments, the average particle diameter can be between about 20 nm to about 60 nm.

In some embodiments, the photocatalytic material can be a copper oxide (a copper oxide [Cu_xO], comprising Cu and Cu + valence state atoms present in the copper oxide) loaded photocatalytic composite as described in United States Patent Application 13/840,859, filed March 15, 2013 (United States Publication No. 2014/0271,916, published September 18, 2014); and/or United States Provisional Application 61/835,399, filed June 14, 2013; and United States Patent Application 13/741,191, filed January 14, 2013 (United States Publication No. 2013/0192976, published August 1, 2013), each of which is incorporated by reference in its entirety. In some embodiments the presence of Cu²⁺ is greater than Cu^I+ (e.g., Cu²⁺ is greater than 50%). In some embodiments, Cu²⁺ can be about 50% to about 95%, e.g., about 79%, and Cu¹⁺ can be about 50% to about 5% of the Cu oxide, e.g., about 21%. The amount of Cu²⁺ and/or Cu¹⁺ can be determined by X-ray absorption fine structure analysis (XAFS).

In some embodiments, a photocatalyst as the photocatalytic material may be an inorganic solid, such as a solid inorganic semiconductor, that absorbs ultraviolet or visible light. For some materials, photocatalysis may be due to reactive species (able to perform reduction and oxidation) being formed on the surface of the photocatalyst from the electron-hole pairs generated in the bulk of the photocatalyst by said absorption of electromagnetic radiation. In some embodiments, the photocatalyst has a conduction band with an energy of about 1 eV to about 0 eV, about 0 eV to about -1 eV, or about -1 eV to about -2 eV, as compared to the normal hydrogen electrode. Some photocatalyst may have a valence band with energy of about 3 eV to about 3.5 eV, about 2.5 eV to about 3 eV, or about 2 eV to about 3.5 eV, or about 3.5 eV to about 5.0 eV as compared to the normal hydrogen electrode. In some embodiments, the photocatalyst comprises a copper loaded oxide. Suitable copper loaded oxides are described in United States Patent Application 13/840,859 filed March 15, 2013 (United States Publication No. 2014/0271,916, published September 18, 2014); and United

States Provisional Application, 61/835,399, filed June 14, 2013, which are incorporated by reference in their entireties. Copper loaded oxides can exhibit anti-bacterial effects.

Some photocatalysts can be activated only by light in the UV regime i.e.

wavelength less than 380 nm. This is because of the wide bandgap (> 3 eV) of most semiconductors. However, in recent years by appropriately selecting materials or modifying existing photocatalysts, visible light photocatalysts have been synthesized (Asahi et al., Science, 293: 269-271, 2001 and Abe et al., Journal of the American Chemical Society, 130(25): 7780-7781, 2008). A visible light photocatalyst includes a photocatalyst which is activated by visible light, e.g. light that is normally visually detectable by the unaided human eye, such as at least about 380 nm in wavelength. In some embodiments, visible light photocatalysts can also be activated by UV light below 380 nm in wavelength in addition to visible wavelengths. Some visible light photocatalyst may have a band gap that corresponds to light in the visible range, such as a band gap greater than about 1.5 eV, less than about 3.5 eV, about 1.5 eV to about 3.5 eV, about 1.7 eV to about 3.3 eV, or 1.77 eV to 3.27 eV. Some photocatalysts may have a band gap of about 1.2 eV to about 6.2 eV, about 1.2 eV to about 1.5 eV, or about 3.5 eV to about 6.2 electron eV.

It is preferable that the photocatalyst contains a metallic compound (such as an oxide, a nitride oxide, an oxynitride carbide, or a halide), and more preferably contains a titanium compound, a tin compound, or a tungsten compound.

Some photocatalysts include oxide semiconductors such as Ti0₂, ZnO, W0₃, Sn0₂, etc., and modifications thereof. Contemplated modifications include doping and/or loading. Other materials like complex oxides (SrTi0₃, B1VO₄) and some sulfides (CdS, ZnS), nitrides (GaN) and some oxynitrides (e.g. ZnO:GaN) may also display photocatalytic properties. Photocatalysts can be synthesized by those skilled in the art by a variety of methods including solid state reaction, combustion, solvothermal synthesis, flame pyrolysis, plasma synthesis, chemical vapor deposition, physical vapor deposition, ball milling, and high energy grinding. The average oxidation number or formal charge of titanium in the titanium compound is preferably +1 to +6, more preferably +2 to +4, further preferably +1 to +3. The average oxidation number or formal charge of tin in the tin compound is preferably +2 to +8, more preferably +1 to +6, further preferably +1 to +4. The average oxidation number or formal charge of tungsten in the tungsten compound is preferably +1 to +8, more preferably +1 to +6, further preferably +1 to +4.

More specifically, the photocatalyst preferably contains at least one selected from titanium(IV) oxide (Ti0₂), tin(IV) oxide (Sn0₂), tungsten(III) oxide (W₂0₃), tungsten(IV) oxide (W0₂), and tungsten(VI) oxide (W0₃). As the titanium(IV) oxide (Ti0₂), an anatase-type titanium(IV) oxide (Ti0₂) is preferred.

Incidentally, in the present specification, the phrase that "the photocatalyst contains (or comprises) tungsten(VI) oxide (W0₃)" includes not only a case where the photocatalyst is a pure tungsten(VI) oxide (WO3) but also a case where the

photocatalyst contains a tungsten(VI) oxide (W0₃) doped with another element or compound. (The same applies to photocatalysts and co-catalysts other than tungsten oxide.)

Especially, it is preferable that the photocatalyst contains tungsten(VI) oxide (W0₃) because it makes it possible to form a photocatalytic element that shows a sufficient photoactivity with visible light.

In some embodiments, the respective Ti or W compounds can be a respective oxide, oxycarbide, oxynitride, oxyhalide, halide, salt, doped or loaded compound. In some embodiments, the respective Ti or W compounds can be Ti0₂, W0₃, or

Ti(0,C,N)₂:Sn, such as Ti(0,C,N)₂:Sn wherein the molar ratio of Ti:Sn is about 90: 10 to about 80:20, about 85: 15 to about 90:10, or about 87: 13. Suitable Ti(0,C,N)₂:Sn compounds are described in United States Patent Application, 13/738,243, filed January 10, 2013 (United States Patent Publication US2013/0180932, published July 18, 2013), which is incorporated by reference in its entirety. In some embodiments, the respective Ti or W compounds can be nanopowders, nanoparticles, and or layers comprising the same. In some embodiments, examples of the photocatalyst may include metal oxides such as tungsten(III) oxide (W₂0₃), tungsten(IV) oxide (W0₂), tungsten(VI) oxide (W0₃), zinc oxide (ZnO), zirconium oxide (Zr0₂), tin(II) oxide (SnO), tin(IV) oxide (Sn0₂), tin(VI) oxide (Sn0₃), cerium(II) oxide (CeO), cerium(IV) oxide (Ce0₂), strontium titanate (SrTi0₃), barium titanate (BaTi0₃), indium(III) oxide (ln₂0₃), bismuth vanadate (BiV0₄), iron(III) oxide (Fe₂0₃), bismuth(III) oxide (Bi₂0₃), copper(I) oxide (Cu₂0), copper(II) oxide (CuO), Cu_xO, potassium tantalate (KTa0₃), and potassium niobate (KNb0₃); metal sulfides such as cadmium sulfide (CdS), zinc sulfide (ZnS), and indium sulfide (InS); metal selenides such as cadmium selenate (CdSe0₄), and zinc selenide (ZnSe); and metal nitrides such as gallium nitride (GaN). Cu_xO is described in United States Patent Application 13/840,859 which is hereby incorporated in its entirety by reference. In some embodiments, the photocatalyst comprises Ti0₂. In some embodiments, the photocatalyst comprises anatase and/or rutile titanium(IV) oxide (Ti0₂). In some embodiments, the photocatalyst does not include TiO_x. In some embodiments, the photocatalyst does not include Ti0₂. In some embodiments, the photocatalyst comprises W0₃.

Any useful amount of photocatalyst may be used. In some embodiments, the photocatalyst material is about 0.01 molar % to 100 molar %, or at least about 0.01 molar % and less than 100 molar % of the composition. In some embodiments, the photocatalyst material is about 20 molar % to about 80 molar %, about 30 molar % to about 70 molar %, about 40 molar % to about 60 molar %, or about 50 molar % of the composition.

Photocatalysts such as Ti0₂ and W0₃ compounds, e.g., nanopowders, can be prepared by many different methods including plasma synthesis such as thermal plasma (direct current and including radio frequency inductively-coupled plasma (RF-ICP)), solvothermal, solid state reaction, pyrolysis (spray and flame), and combustion. Radio frequency inductively-coupled plasma (e.g. thermal) methods as described in US Patent 8,003,563, which is hereby incorporated in its entirety by reference, may be useful because of low contamination (no electrodes) and high production rates and facile application of precursors either in the gas, liquid or solid form. Hence, radio frequency inductively-coupled plasma processes are preferred. For example, when preparing W0₃ nanopowders, a liquid dispersion of ammonium metatungstate in water (5-20 wt% solid in water) can be sprayed into the plasma volume using a two-fluid atomizer. Preferably, the precursor can be present to about 20 wt% solid in water. The plasma can be operated at about 25 kW plate power with argon, nitrogen and/or oxygen gases. The particles formed from the condensed vapor from the plasma can then be collected on filters. In some embodiments, the particle surface areas range as measured using BET from about 1 m²/g to about 500 m²/g, about 15 m²/g to 30 m²/g, or about 20 m /g. In some embodiments, the obtained W0₃ may be heated from about 200°C to about 700°C or about 300°C to about 500°C.

In some embodiments, a photocatalyst can be doped with at least one naturally occurring element e.g. non-noble gas elements, to improve the activity of the photocatalyst. ^' Such an element may be called a "dopant". Doped elements (dopants) can be provided as precursors added generally during synthesis. Doped elements (dopants) can be elements that are incorporated into the crystal lattice of the Ti or W compound, for example as substituted within defined positions within the crystal lattice or otherwise interstitially included within the crystal. In some embodiments, the dopant can be selected from one of more elements including alkali metals such as lithium (Li), sodium (Na), potassium (K), and cesium (Cs); alkali earth metals such as magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba); noble metals such as gold (Au), silver (Ag), platinum (Pt), rhodium (Rh), iridium (Ir), palladium (Pd), and ruthenium (Ru); transition metals such as iron (Fe), copper (Cu), zinc (Zn), vanadium (V), titanium (Ti) (for example for W-based compounds), tungsten (W) (for example for Ti-based compounds), manganese (Mn), Mo, zirconium (Zr), niobium (Nb), chromium (Cr), cobalt (Co), cerium (Ce) and nickel (Ni); lanthanide and actinide metals; halogens; Group III elements (from the Dmitri Mendeleev/Lothar Meyer style modern periodic table with elements arranged according to increasing atomic number) including B, Al, Ga, In and Tl, Group IV elements including Ca, Si, Ge, Sn; Group V elements like N, P, As, Bi; and Group VI elements like S and Se. In some embodiments, the photocatalyst can be doped with at least one element selected from C, N, S, F, Sn, Zn, Mn, Al, Se, Nb, Ni, Zr, Ce and Fe. In some embodiments, the photocatalyst may be self-doped, e.g., Ti³⁺ in place of Ti⁴⁺ in a Ti0₂ matrix. Details of suitably doped photocatalytic materials are presented in the United States Provisional Patent Application No.

61/587,889, which is hereby incorporated by reference in its entirety. In this specification, a photocatalyst doped with a dopant may be referred to as "doped-type photocatalyst".

The term "doping" means adding an arbitrarily chosen element (dopant) to the host compound crystals within a range that essentially does not change the basic crystalline structure of the photocatalyst. Whether the photocatalyst is doped or not can be confirmed by, for example, a peak shift in XPS (X-ray photoelectron

spectroscopy). Methods used for forming the doped-type photocatalyst are not particularly limited, and may be, for example, a sol-gel method, a solid-phase reaction method, and an ion implantation method.

When the photocatalyst is a doped-type photocatalyst, the molar ratio of the host compound (compound subjected to doping) and the dopant in the photocatalyst is not particularly limited, and is preferably 99.9:0.1 to 80:20, more preferably 99.9:0.1 to 85: 15, further preferably 99.9:0.1 to 87: 13.

Preferably, the doped-type photocatalyst is doped with at least one selected from carbon (C), nitrogen (N), sulfur (S), fluorine (F), tin (Sn), zinc (Zn), manganese (Mn), aluminum (Al), selenium (Se), niobium (Nb), nickel (Ni), zirconium (Zr), cerium (Ce), and iron (Fe).

The photocatalyst may be a p-type or an n-type. A p-type photocatalyst may be obtained, for example, by doping a photocatalyst with high valance elements (for example, such as arsenic (As)). An n-type photocatalyst may be obtained, for example, by doping a photocatalyst with low valence elements (for example, such as boron (B)).

In some embodiments, the photocatalytic material can comprise one or more of n-type UV photocatalytic material, n-type visible light photocatalytic material, p-type UV photocatalytic material and/or p-type visible photocatalytic material. In some embodiments, the n-type visible band gap semiconductors can optionally be W0₃, Ti(0,C,N)₂:Sn, or Ce0₂. In some embodiments, the n-type UV photocatalytic material can optionally be Ce0₂, Ti0₂, Sn0₂, SrTi0₃, ATa0₃, ANb0₃ etc.; A = alkali metal ion, wherein A can Ca, Ba, and/or Sr. In some embodiments, p-type visible band gap semiconductors can optionally be SiC, CuM0₂, M = Al, Cr. In some embodiments, the p-type UV photocatalytic material can optionally be Znlr0₂, ZnRh0₂, CuO, SnO, NiO, Mn₂0₃, Co₃0₄, and/or Fe₂0₃.

In some embodiments, the photocatalyst can be loaded with at least one metal.

Loaded elements can be provided by post synthesis methodologies like impregnation (Liu, M., Qiu, X., Miyauchi, M., and Hashimoto, K., Cu(II) Oxide Amorphous

Nanoclusters Grafted Ti³⁺ Self-Doped T1O₂: An Efficient Visible Light Photocatalyst. Chemistry of Materials, published online 201 1), photo-reduction (Abe et al., Journal of the American Chemical Society, 130(25): 7780-7781, 2008), and sputtering. Loading metals on photocatalysts may be carried out as described in US Patent Publication Number US2008/0241542 which is incorporated herein its entirety by reference. In some embodiments, the loaded element is selected from noble elements. In some embodiments, the loaded element can be selected from at least one noble element, oxide, and/or hydroxide. In some embodiments, the noble elements can be selected from Au, Ag, Pt, Pd, Ir, Ru, Rh or their oxides and/or hydroxides. In some embodiments, the loaded element is selected from transition metals, their oxides and/or hydroxides. In some embodiments, the loaded element is selected from Fe and Cu and Ni or their oxide and hydroxides. In some embodiments, the loaded elements may be chosen from different groups of elements including at least one transition metal and at least one noble metal or their respective oxides and hydroxides. In some embodiments, a suitable loaded metal oxide is described in United States Patent Application 13/840,859 filed March 15, 2013; and United States Provisional Application, 61/835,399, filed June 14, 2013, which are incorporated by reference in their entireties. In some embodiments, the photocatalyst preferably has a refractive index (Rl) of 1.0 to 4.0, more preferably 1.0 to 3.0, particularly preferably 1.5 to 2.5 at a wavelength of 589 nm. With the photocatalyst refractive index (Rl ) falling in the range of 1.0 to 4.0, it becomes easier to reduce the refractive index difference from the co-catalyst, and thus becomes easier to form a translucent layer. Note that the refractive index values of the photocatalyst are measured values obtained with an Abbe refractometer according to the "Solid Sample Measurement Method" specified by JIS K 0062.

The shape of the photocatalyst is not particularly limited, and the photocatalyst is preferably particulate in shape. Many kinds of photocatalysts are poorly soluble in solvent. With the particulate shape, the photocatalyst can be dispersed in a dispersion medium to produce a dispersion liquid, which can then be used to easily form a layer by being coated and dried.

When the photocatalyst is particulate in shape, the average particle size of the photocatalyst is not particularly limited, and is preferably 5 nm to 1,000 nm, more preferably 5 nm to 100 nm, further preferably 5 nm to 30 nm. When the average particle size of the photocatalyst exceeds 1 ,000 nm, the overall surface area of the photocatalyst becomes smaller, and a sufficient photocatalytic activity may not be shown. On the other hand, when the average particle size of the photocatalyst falls below 5 nm, particle aggregation tends to occur, and the translucency of the layer containing the photocatalyst may suffer.

Note that the average particle size of the photocatalyst is a volume-based 50% cumulative distribution diameter (D50) of photocatalyst particles dispersed in an arbitrary dispersion liquid as determined by dynamic light scattering frequency analysis (FFT-heterodyne method).

Co-catalysts are a substance that accelerates the photocatalytic activity of the photocatalyst. The co-catalyst may be used in combination with the photocatalyst, as desired. The co-catalyst may be one that shows or does not show photocatalytic activity by itself. In cooperation with the photocatalyst, the co-catalyst can increase the reaction rate of the photocatalyst by 1.2 fold or more, preferably 1.5 fold or more, further preferably 2.0 fold or more, particularly preferably 3.0 fold or more from that when the photocatalyst is used alone. The reaction rate of the photocatalyst may be based on, for example, the decomposition rate of acetaldehyde, a type of volatile organic compounds (VOCs). Co-catalysts may also be generically referred to as T- Binder throughout this document.

Specifically, the photocatalyst, either alone or with the co-catalyst mixed with or supported by the photocatalyst, is put in a closed space charged with certain quantities of compressed air and acetaldehyde (calibration gas), and irradiated with visible light (wavelength 455 nm, irradiation intensity 200 mW/cm²) for 1 hour. The acetaldehyde concentrations in the closed space before and after the irradiation are then compared to calculate the factor by which the reaction rate of the photocatalyst increased. For example, the acetaldehyde decomposition rate can be said to have increased 3 fold (a 3- fold increase of photocatalytic activity) when the acetaldehyde concentration in a closed space charged with the photocatalyst and the co-catalyst (either mixed with the photocatalyst or supported on the photocatalyst) becomes 20 ppm after the irradiation of the closed space containing 80 ppm of acetaldehyde (i.e., 60 ppm of acetaldehyde has decomposed) as compared to when the acetaldehyde concentration in a closed space charged with the photocatalyst alone becomes 60 ppm after the irradiation of the closed space containing 80 ppm of acetaldehyde (i.e., 20 ppm of acetaldehyde has

decomposed).

Some co-catalyst may be compounds or semiconductors that are capable of being reduced by electron transfer from the conduction band of the photocatalyst. For example, a co-catalyst may have a conduction band having a lower energy than the conduction band of the photocatalyst, or a co-catalyst may have a lowest unoccupied molecular orbital having a lower energy than the conduction band of the photocatalyst. When a term such as "lower energy" and "higher energy" is used to compare a band of a semiconductor or a molecular orbital with another band or molecular orbital, it means that an electron loses energy when it is transferred to the band or molecular orbital of lower energy, and an electron gains energy when it is transferred to the band for molecular orbital of higher energy.

The co-catalyst may be simply mixed with the photocatalyst, or may be supported on the photocatalyst. In this specification, a photocatalyst supporting the co-catalyst is referred to as "supporting-type photocatalyst". As used herein, the term "supporting" refers to the state where a substance different from the photocatalyst is adhering to the photocatalyst surface. Such an adhering state can be observed, for example, by scanning electron microscopy. Methods used for forming the supporting- type photocatalyst are not particularly limited, and may be, for example, an

impregnation method, a photoreduction method, or sputtering. The supporting-type photocatalyst may be formed by using the method described in, for example, US Patent Application 2008/0241542. The co-catalyst may be doped with a dopant. A co- catalyst doped with a dopant will be referred to as doped-type co-catalyst. The compounds and elements used to dope the co-catalyst are as exemplified above in conjunction with the photocatalyst.

It is believed that some metal oxides that are co-catalysts are capable of reducing 0₂. For example, it is believed that Ce0₂ can reduce 0₂ gas by electron transfer. In doing so, it is believed that Ce³ transfers an electron to 0₂ and is converted to Ce⁴⁺ as a result. In a photocatalyst composition, a photocatalyst may transfer an electron to Ce0₂, thus converting Ce⁴⁺ to Ce³⁺, and the Ce³⁺ may then reduce 0₂. Ce³⁺ may also be present as a result of equilibrium processes involving Ce0₂ and 0₂, and superoxide radical ion (0₂ ^"). 0₂ and superoxide radical ion in such an equilibrium process may be adsorbed to the surface of solid Ce0₂ or present in the atmosphere. Ce³⁺ may also be present as a result of oxidation and reduction reactions with cerium species of different oxidation states that may be added intentionally or present as impurities.

It is believed that some co-catalysts may be capable of effecting multi-electron reduction of oxygen. For example, some co-catalysts can effect two electron, four electron, 6 electron and/or up to 8 electron reduction of oxygen. It is believed the co- catalyst can store electrons in the conduction band of the co-catalyst, these stored electrons can then be used for oxygen reduction.

Some co-catalysts may be capable of converting atmospheric 0₂ to superoxide radical ion. For example, Ce0₂ is capable of converting atmospheric oxygen to superoxide radical ion. It is believed that some of the equilibrium and/or electron transfer processes described above may contribute to this property of Ce0₂. Such a conversion may occur under a variety of conditions, such as ambient conditions, including for example, normal atmospheric oxygen concentrations, such as molar concentrations of about 10% to about 30%, about 15% to about 25%, or about 20% oxygen; ambient temperature, such as about 0°C to about 1000°C, about 0°C to about 100°C, about 10°C to about 50°C, or about 20°C to about 30°C; and pressure, such as about 0.5 to about 2 atm, about 0.8 atm to about 1.2 atm, or about 1 atm. Such a conversion may also occur under elevated or reduced temperature, pressure, or oxygen concentration. Other materials that may be capable of reducing 0₂ or converting atmospheric 0₂ to superoxide radical ion include various other materials such as Ce_xZr_y0₂ (where x/y = 0.99-0.01), BaYMn₂05₊s, and lanthanide-doped Ce0₂ including Ce_xZr_yLa_z0_2, Ce_xZryPr_z0_2j and Ce_xSm_y0₂.

Some co-catalysts may have a valence band or a highest occupied molecular orbital at a higher energy than a valence band of the photocatalyst. This may allow a hole in a valence band of the photocatalyst to be transferred to a highest occupied molecular orbital or a valence band of the co-catalyst. The hole in the valence band or highest occupied molecular orbital of co-catalyst may then oxidize H₂0 or OH^' to OH-. For example, if W0₃ is chosen as a photocatalyst, examples of such a co-catalyst may include anatase Ti0₂, SrTi0₃, KTa0₃, SiC or KNb0₃.

In some embodiments, the co-catalyst can be inorganic. In some embodiments, the inorganic co-catalyst can be a binder. In some embodiments, the co-catalyst can be an oxide, such as a metal dioxide, including Ce0₂, Ti0₂, or the like. Suitable co- catalysts are described in United States Patent Application 13/738,243, filed January 10, 2013 (United States Patent Publication, US2013/180932, published July 18, 2013), which is incorporated by reference in its entirety.

In some embodiments, examples of the co-catalyst may include copper(I) oxide (Cu₂0), copper(II) oxide (CuO), molybdenum(VI) oxide (M0O3), manganese(III) oxide (Mn₂0₃), yttrium(III) oxide (Y₂0₃), gadolinium(III) oxide (Gd₂0₃), anatase-type and/or rutile-type titanium(IV) oxide (Ti0₂), strontium titanate (SrTi0₃), potassium tantalate (KTa0₃), silicon carbide (SiC), potassium niobate (KNb0₃), silicon oxide (Si0₂), tin(IV) oxide (Sn0₂), aluminum(III) oxide (A1₂0₃), zirconium oxide (Zr0₂), iron(III) oxide (Fe₂0₃), iron(II, III) oxide (Fe₃0₄), nickel(II) oxide (NiO), niobium(V) oxide (Nb₂0₅), indium oxide (ln₂0₅), tantalum oxide (Ta₂0₅), cerium(II) oxide (CeO), cerium(IV) oxide (Ce0₂), A_rX_tO_s (where A is a rare earth element, X is an element other than rare earth elements, or a combination of elements other than rare earth elements, r is 1 to 2, t is 0 to 3, and s is 2 to 3), ammonium phosphomolybdate trihydrate ((NH₄)₃[PMoi₂O₄₀]), 12-tungstophosphoric acid (PWi₂O₄₀), tungsten silicide (H₄[SiWi₂0₄o]), phosphomolybdic acid (12Μο0₃·Η₃Ρ0₄), and cerium-zirconium composite oxide (Ce_xZr_y0₂) (y/x = 0.001 to 0.999). In some embodiments, the co- catalyst comprises ln₂0₅, Ta₂0₅, anatase Ti0₂, rutile Ti0₂, a combination of anatase and rutile Ti0₂, or Ce0₂. In some embodiments, the co-catalyst comprises Ti0₂. In some embodiments, the co-catalyst comprises anatase Ti0₂. In some embodiments, the co- catalyst does not include Cr₂0₃, Ce0₂, A1₂0₃, or Si0₂. In some embodiments, the co- catalyst does not include Cr₂0₃. In some embodiments, the co-catalyst does not include Ce0₂. In some embodiments, the co-catalyst does not include A1₂0₃. In some embodiments, the co-catalyst does not include Si0₂.

In some embodiments, the co-catalyst can be Re_rE_tO_s, Re_rE_tO, or Re_rE_t0₂, wherein in Re is a rare earth element, E is an element or a combination of elements, and O is oxygen; and r is 1 to 2, such as about 1 to about 1.5 or about 1.5 to about 2; s is 2 to 3, such as about 2 or about 3; and t is 0 to 3, such as about 0.01 to about 1, about 1 to about 2, or about 2 to about 3. In some embodiments, the co-catalyst can be Re_rO_s where Re can be a rare earth metal and r can be greater than or equal to 1 and less than or equal to 2, or can be between 1 and 2, and s can be greater than or equal to 2 and less than or equal to 3, or can be between 2 and 3. Examples of suitable rare earth elements include scandium, yttrium and the lanthanide and actinide series elements. Lanthanide elements include elements with atomic numbers 57 through 71. Actinide elements include elements with atomic numbers 89 through 103. In some embodiments, the co- catalyst can be Ce_xZr_y0₂ wherein the y/x ratio = 0.001 to 0.999.

The co-catalyst preferably contains at least one selected from a cerium compound, a copper compound, a potassium compound, a strontium compound, a tantalum compound, a niobium compound, and a titanium compound. More preferably, the co-catalyst contains a cerium compound, or a copper compound. The average oxidation number or formal charge of the cerium compound is preferably +2 to +4. The average oxidation number or formal charge of the copper compound is preferably +1 to +2. In some embodiments, the co-catalyst can be CeO_a (a < 2). In some embodiments, the co-catalyst can be CeO. In some embodiments, the co-catalyst can be cerium oxide (Ce0₂).

In some embodiments, the co-catalyst contains cerium oxide, more preferably cerium(IV) oxide (Ce0₂). This embodiment is suited for use in decomposition of volatile organic compounds (VOCs). When the co-catalyst contains cerium(IV) oxide (Ce0₂), it is preferable to dope the cerium(IV) oxide, preferably with tin (Sn). In the tin (Sn)-doped cerium(IV) oxide (Ce0₂:Sn), the tin (Sn) accounts for preferably 1 mol% to 50 mol%, more preferably 1.5 mol% to 10 mol%, further preferably 1.5 mol% to 10 mol%, particularly preferably 1.5 mol% to 4.5 mol% of the total co-catalyst (Ce0₂:Sn).

In some embodiments, the photocatalyst can be W0₃ and the co-catalyst can be

In some embodiments, the co-catalyst maybe a Keggin unit e.g. ammonium phosphomolybdate ((NH₄)₃[PMoi₂O₄₀]), 12-phosphotungstic acid, silicotungstic acid and phosphomolybdic acid. The overall stability of the Keggin unit allows the metals in the anion to be readily reduced. Depending on the solvent, acidity of the solution and the charge on the a-Keggin anion, it can be reversibly reduced in one- or multiple electron step.

While not wanting to be limited by theory, the inventors believe that Ce0₂ may be useful in conjunction with tungsten oxide because of the relative band positions of these materials. Furthermore, it is noteworthy that the index of refraction of Ce0₂ is substantially the same as tungsten oxide, about 90% to about 1 10%. In another embodiment about 95% to about 105%o. In some embodiments, the high transparency of the photocatalytic compositions can provide a composition/layer/element of transparency greater than about 50%, 60%, 65% and/or 70%. The low scattering losses due to matched refractive indices contributes directly to a transparent composition.

In some embodiments, the co-catalyst contains copper oxide, more preferably copper(I) oxide (Cu₂0) and/or copper(II) oxide (CuO). This embodiment is suited for anti-mi crobial applications. When the co-catalyst contains copper(I) oxide (Cu₂0) and/or copper(II) oxide (CuO), it is preferable that the copper(I) oxide (Cu₂0) and/or copper(II) oxide (CuO) are supported on the photocatalyst.

The shape of the co-catalyst is not particularly limited, and the co-catalyst is preferably particulate in shape for the same reasons described for the photocatalyst. When the co-catalyst is particulate in shape, the average particle size of the co-catalyst is not particularly limited, and is preferably 1 nm to 1,000 nm, more preferably 1 nm to 100 nm, further preferably 1 nm to 30 nm.

The co-catalyst has a refractive index (R2) of preferably 1.0 to 4.0, more preferably 1.0 to 3.0, particularly preferably 1.5 to 2.5 at 589 nm wavelength. With the co-catalyst refractive index (R2) falling in the range of 1.0 to 4.0, it becomes easier to reduce the refractive index difference from the photocatalyst, and form a desirably translucent layer.

Examples of the photocatalyst described above include a UV responsive photocatalyst that shows photocatalytic activity only with ultraviolet rays of less than 380 nm wavelength, and a visible-light responsive photocatalyst that shows

photocatalytic activity also with visible light of 380 nm to 780 nm wavelengths. In the present invention, the photocatalyst may be a UV responsive photocatalyst or a visible- light responsive photocatalyst, and is preferably a visible-light responsive photocatalyst. The visible-light responsive photocatalyst shows some photoactivity with visible light even without the co-catalyst. The visible-light responsive photocatalyst, in

cooperation with the co-catalyst, can thus show even higher photoactivity with visible light. When the photocatalyst is a visible-light responsive photocatalyst, the band gap is, for example, 1.5 eV to 3.5 eV, preferably 1.7 eV to 3.3 eV, more preferably 1.77 eV to 3.27 eV. Note that the photocatalyst may show a visible-light responsiveness in certain photocatalyst and co-catalyst combinations even when the photocatalyst is a UV responsive photocatalyst.

In some embodiments, the photocatalyst is preferably one that shows a visible- light responsiveness. A visible-light responsive photocatalyst can show photocatalytic activity also with a visible-light emitting light source such as a fluorescence lamp and an LED, and enables avoiding use of ultraviolet light, which can be harmful to the human body.

Photocatalysts may be used either alone or as a mixture of two or more. When two or more photocatalysts are used as a mixture, one of the photocatalysts may function as the co-catalyst of the other photocatalyst. Co-catalysts may also be used alone or as a mixture of two or more.

When the photocatalyst and the co-catalyst are used in combination, any useful ratio of photocatalyst to co-catalyst may be used. The ratio (molar ratio) of the total photocatalyst and the total co-catalyst is preferably 99.5:0.5 to 16.7:83.3, more preferably 99.5:0.5 to 20:80, further preferably 99.5:0.5 to 50:50.

When the photocatalyst content is less than the lower limit of the foregoing ranges, the co-catalyst will be in excess of the photocatalyst amount, and a sufficient photocatalytic activity may be not be exerted. On the other hand, when the photocatalyst content exceeds the upper limit of the foregoing ranges, the co-catalyst will be deficient relative to the photocatalyst amount, and a sufficient photocatalytic activity may not be exerted.

In the present invention, when the photocatalyst and the co-catalyst are used in combination, the combination of the photocatalyst and the co-catalyst is not particularly limited.

In some embodiments, a photocatalytic material can comprise tungsten oxide and a rare earth oxide at a molar ratio of about 0.5:1 to 2:1 or about 1 : 1 (tungsten oxide :rare earth oxide). In some embodiments, the rare earth oxide is cerium oxide (Ce0₂). In some embodiments, the photocatalytic composition may include W0₃ and Ce0₂, having a molar ratio (W0₃:Ce0₂) of about 1 :5 to about 5: 1 , about 1 :3 to about 3: 1, about 1 :2 to about 2: 1, or about 1 : 1.

In a preferred embodiment, the photocatalyst contains tungsten(VI) oxide (W0₃), and the co-catalyst contains cerium(IV) oxide (Ce0₂). A photocatalytic element that is excellent in visible-light responsiveness and photocatalytic activity, and is also particularly excellent in the ability to decompose volatile organic compounds (VOCs) can be formed by using tungsten(VI) oxide (W0₃) as the photocatalyst, and cerium(IV) oxide (Ce0₂) as the co-catalyst.

In another preferred embodiment, the photocatalyst contains titanium(IV) oxide (Ti0₂) or tin(IV) oxide (Sn0₂), and the co-catalyst contains copper(I) oxide (Cu₂0) and/or copper(II) oxide (CuO). In this case, the co-catalyst containing copper(I) oxide (Cu₂0) and/or copper(II) oxide (CuO) is preferably supported on the photocatalyst containing titanium(IV) oxide (Ti0₂) or tin(IV) oxide (Sn0₂). A photocatalytic element that is excellent in visible-light responsiveness and photocatalytic activity, and is also particularly excellent in anti-microbial properties can be formed by using titanium(IV) oxide (Ti0₂) or tin(IV) oxide (Sn0₂) as the photocatalyst, and copper(I) oxide (Cu₂0) and/or copper(II) oxide (CuO) as the co-catalyst. In this specification, a co-catalyst-supporting type photocatalyst supporting a co_^catalyst Cu_xO on a photocatalyst Ti0₂ may be represented by Cu_xO-Ti0₂. Similarly, a co-catalyst- supporting type photocatalyst supporting a co-catalyst Cu_xO on a photocatalyst Sn0₂ may be represented by Cu_xO-Sn0₂. Here, "Cu_xO" is intended to mean a state where two types of copper oxides, CuO (X = 1 ; copper(II) oxide) and Cu₂0 (X = 2; copper(I) oxide) are present. In some embodiments, the binder material can be a silicone resin. In some embodiments, the silicone resin can be, for example, a silicone alkyd resin, a silicone epoxy resin, a silicone acrylic resin, or a silicone polyester resin. In some embodiments, the silicone resin is a silicone polyester resin. In some embodiments, the suitable silicone polyester resins can be commercially available products, e.g., KR5230 and /or KR5235 (Shin-Etsu Chemical Co., Ltd, Tokyo, Japan). KR5230, can be a silicone polyester resin with a silicone content of about 4% to about 44%, or about 6% to about 46%, or about 8% to about 48%, or about 10% to about 50%, or about 12% to 52%, or about 14% to about 54%, or about 16% to about 56%, or the like.

In some embodiments, the binder material can be a silane compound. In some embodiments, the silane compound can be at least one of tetrachlorosilane, tetramethoxysilane, tetraethoxysilane, tetra-n-propoxysilane, tetra-i-propoxysilane, tetra-n-butoxysilane and tetra-sec-butoxysilane; trichlorosilane, trimethoxysilane, triethoxysilane, tri-n-propoxysilane, tri-i-propoxysilane, tri-n-butoxysilane, tri-sec- butoxysilane, fluorOtrichlorosilane, fluorotrimethoxysilane, fluorotriethoxysilane, fluorotri-n-propoxysilane, fluorotri-i-propoxysilane, fluorotri-n-butoxysilane, fluorotri- sec-butoxysilane, methyl trichlorosilane, methyl trimethoxysilane, methyl triethoxysilane, methyl tri-n-propoxysilane, methyl tri-i-propoxysilane, methyl tri-n- butoxysilane, methyl tri-sec-butoxysilane, 2-(trifluoromethyl)ethyltrichlorosilane, 2- (trifluoromethyl)ethyltrimethoxysilane, 2-(trifluoromethyl)ethyltriethoxysilane, 2- (trifluorornethyl)ethyltri-n-propoxysilane, 2-(trifluoromethyl)ethyltri-i-propoxysilane, 2-(trifluoromethyl)ethyltri-n-butoxysilane, 2-(trifluoromethyl)ethyltri-sec-butoxysilane, 2-(perfluoro-n-hexyl)ethyltrichlorosilane, 2-(perfluoro-n-hexyl)ethyltrimethoxysilane, 2-(perfluoro-n-hexyl)ethyltriethoxysilane, 2-(perfluoro-n-hexyl)ethyltri-n- propoxysilane, 2-(perfluoro-n-hexyl)ethyltri-i-propoxysilane, 2-(perfluoro-n- hexyl)ethyltri-n-butoxysilane, 2-(perfluoro-n-hexyl)ethyltri-sec-butoxysilane, 2- (perfluoro-n-octyl)ethyltrichlorosilane, 2-(perfluoro-n-octyl)ethyltrimethoxysilane, 2- (perfluoro-n-octyl)ethyltriethoxysilane, 2-(perfluoro-n-octyl)ethyltri-n-propoxysilane, 2- (perfluoro-n-octyl)ethyltri-i-propoxysilane, 2-(perfluoro-n-octyl)ethyltri-n-butoxysilane,

2- (perfluoro-n-octyl)ethyltri-sec-butoxysilane, hydroxymethyltrichlorosilane, hydroxymethyltrimethoxysilane, hydroxyethyltrimethoxysilane, hydroxymethyltri-n- propoxysilane, hydroxymethyltri-i-propoxysilane, hydroxymethyltri-n-butoxysilane, hydroxymethyltri-sec-butoxysilane, 3-(meth)acryloxypropyltrichlorosilane, 3- (meth)acryloxypropyltrimethoxysilane, 3-(meth)acryloxypropyltriethoxysilane, 3- (meth)acryloxypropyltri-n-propoxysilane, 3-(meth)acryloxypropyltri-i-propoxysilane, 3 -(meth)acryloxypropyltri-n-butoxysilane, 3 -(meth)acryloxypropyltri-sec-butoxysilane,

3- mercaptopropyltrichlorosilane, 3-mercaptopropyltrimethoxysilane, 3- mercaptopropyltriethoxysilane, 3 -mercaptopropyltri-n-propoxysilane, 3 - mercaptopropyltri-i-propoxysilane, 3-mercaptopropyltri-n-butoxysilane, 3- mercaptopropyltri-sec-butoxysilane, vinyltrichlorosilane, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltri-n-propoxysilane, vinyltri-i-propoxysilane, vinyltri-n- butoxysilane, vinyltri-sec-butoxysilane, allyltrichlorosilane, allyltrimethoxysilane, allyltriethoxysilane, allyltri-n-propoxysilane, allyltri-i-propoxysilane, allyltri-n- butoxysilane, allyltri-sec-butoxysilane, phenyltrichlorosilane, phenyltrimethoxysilane, phenyltriethoxysilane, phenyltri-n-propoxysilane, phenyltri-i-propoxysilane, phenyltri- n-butoxysilane and phenyltri-sec-butoxysilane; compounds of the formula (1) in which m is 2, such as methyldichlorosilane, methyldimethoxysilane, methyldiethoxysilane, methyldi-n-propoxysilane, methyldi-i-propoxysilane, methyldi-n-butoxysilane, methyldi-sec-butoxysilane, dimethyldichlorosilane, dimethyldimethoxysilane, dimethyldiethoxysilane, dimethyldi-n-propoxysilane, dimethyldi-i-propoxysilane, dimethyldi-n-butoxysilane, dimethyldi-sec-butoxysilane, (methyl) [2-(perfluoro-n- octyl)ethyl]dichlorosilane, (methyl)[2-(perfluoro-n-octyl)ethyl]dimethoxysilane, (methyl)[2-(perfluoro-n-octyl)ethyl]diethoxysilane, (methyl)[2-(perfluoro-n- octyl)ethyl]di-n-propoxysilane, (methyl) [2-(perfluoro-n-octyl)ethyl]di-i-propoxysilane, (methyl)[2-(perfluoro-n-octyl)ethyl]di-n-butoxysilane, (methyl) [2-(perfluoro-n- octyl)ethyl]di-sec-butoxysilane, (methyl)(gamma-glycidoxypropyl)dichlorosilane, (methyl)(gamma-glycidoxypropyl)dimethoxysilane, (methyl)(gamma- glycidoxypropyl)diethoxysilane, (methyl)(gamma-glycidoxypropyl)di-n-propoxysilahe, (methyl)(gamma-glycidoxypropyl)di-i-propoxysilane, (methyl)(gamma- glycidoxypropyl)di-n-butoxysilane, (methyl)(gamma-glycidoxypropyl)di-sec- butoxysilane, (methyl)(3-mercaptopropyl)dichlorosilane, (methyl)(3- mercaptopropyl)dimethoxysilane, (methyl)(3-mercaptopropyl)diethoxysilane, (methyl)(3 -mercaptopropyl)di-n-propoxysilane, (methyl)(3 -mercaptopropyl)di-i- propoxysilane, (methyl)(3 -mercaptopropyl)di-n-butoxysilane, (methyl)(3 - mercaptopropyl)di-sec-butoxysilane, (methyl)(vinyl)dichlorosilane, (methyl)(vinyl)dimethoxysilane, (methyl)(vinyl)diethoxysilane, (methyl)(vinyl)di-n- propoxysilane, (methyl)(vinyl)di-i-propoxysilane, (methyl)(vinyl)di-n-butoxysilane, (methyl)(vinyl)di-sec-butoxysilane, divinyldichlorosilane, divinyldimethoxysilane, divinyldiethoxoysilane, divinyldi-n-propoxysilane, divinyldi-i-propoxysilane, divinyldi- n-butoxysilane, divinyldi-sec-butoxysilane, diphenyldichlorosilane, diphenyldimethoxysilane, diphenyldiethoxysilane, diphenyldi-n-propoxysilane, diphenyldi-i-propoxysilane, diphenyldi-n-butoxysilane and diphenyldi-sec- butoxysilane; and compounds of the formula (1) in which m is 3, such as chlorodimethylsilane, methoxydimethylsilane, ethoxydimethylsilane, chlorotrimethylsilane, bromotrimethylsilane, iodotrimethylsilane, methoxytrimethylsilane, ethoxytrimethylsilane, n-propoxytrimethylsilane, i- propoxytrimethylsilane, n-butoxytrimethylsilane, sec-butoxytrimethylsilane, t- butoxytrimethylsilane, (chloro)(vinyl)dimethylsilane, (methoxy)(vinyl)dimethylsilane, (ethoxy)(vinyl)dimethylsilane, (chloro)(methyl)diphenylsilane, (methoxy)(methyl)diphenylsilane and (ethoxy)(methyl)diphenylsilane.

Herein, the formula (1) mentioned above is shown below.

(wherein Y is a chlorine atom, bromine atom, iodine atom, or linear, branched or cyclic alkoxyl group having 1 to 20 carbon atoms, R is a hydrogen atom, fluorine atom, linear, branched or cyclic alkyl group having 1 to 20 carbon atoms, linear, branched or cyclic substituted alkyl group having 1 to 20 carbon atoms, linear, branched or cyclic alkenyl group having 2 to 20 carbon atoms, aryl group having 6 to 20 carbon atoms, or aralkyl group having 7 to 20 carbon atoms, and m is an integer of 0 to 3).

In some embodiments, the silane compound can be at least one of tetramethoxysilane, tetraethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, 3 -(meth)acryloxypropyltrimethoxysilane, 3 -(meth)acryloxypropyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, allyltrimethoxysilane, allyltriethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, dimethyldimethoxysilane and dimethyldiethoxysilane.

Commercially available products of the partial condensate of the silane compound include, for example, KC-89, KC-89S, X-21-3153, X-21-5841, X-21-5842, X-21-5843, X-21-5844, X-21-5845, X-21-5846, X-21-5847, X-21-5848, X-22-160AS, X-22-170B, X-22-170BX, X-22-170D, X-22-170DX, X-22-176B, X-22-176D, X-22- 176DX, X-22-176F, X-40-2308, X-40-2651, X-40-2655A, X-40-2671, X-40-2672, X- 40-9220, X-40-9225, X-40-9227, X-40-9246, X-40-9247, X-40-9250, X-40-9323, X- 41-1053, X-41-1056, X-41-1805, X-41-1810, KF6001, KF6002, KF6003, KR212, KR- 213, KR-217, KR220L, KR242A, KR271, KR282, KR300, KR31 1 , KR401N, KR500, KR510, KR5206, KR5230, KR5235, KR9218 and KR9706 (of Shin-Etsu Silicones KK); Glass Resin (of Showa Denko K.K.); SH804, SH805, SH806A, SH840, SR2400, SR2402, SR2405, SR2406, SR2410, SR241 1 , SR2416 and SR2420 (of Toray Dow Corning Silicone Co., Ltd.); FZ371 1 and FZ3722 (of Nippon Unicar Co., Ltd.); DMS- S 12, DMS-S15, DMS-S21, DMS-S27, DMS-S31, DMS-S32, DMS-S33, DMS-S35, DMS-S38, DMS-S42, DMS-S45, DMS-S51, DMS-227, PDS-0332, PDS-1615, PDS- 9931 and XMS-5025 (of Chisso Corporation); Methyl Silicate MS51 and Methyl Silicate MS56 (of Mitsubishi Chemical Corporation); Ethyl Silicate 28, Ethyl Silicate 40 and Ethyl Silicate 48 (of Colcoat Co., Ltd.); and GR100, GR650, GR908 and GR950 (of Showa Denko K.K.), SMP100 (of Wacker Chemie AG), In the present embodiments, the above silane compounds and partial condensates thereof may be used alone or in combination of two or more.

In some embodiments, a binder catalyst can be added to the binder/photocatalytic suspension. In some embodiments the binder catalyst can be a tiatanium alkoxide. One suitable example can be a titanium alkoxide commercially available from Shin-Etsu Chemical Co., Ltd. (D25).

In some embodiments, a photocatalytic suspension is provided, comprising the photocatalytic material, binder and an organic solvent. In some embodiments, the binder can be dissolved in an organic solvent. In some embodiments, the photocatalytic material is substantially insoluble in the organic solvent. In some embodiments, the organic solvent can be, for example, a hydrocarbon, ketone, ester, ether or alcohol.

Examples of the above hydrocarbon include toluene and xylene; examples of the above ketone include methyl ethyl ketone, methyl isobutyl ketone, methyl n- amylketone, diethyl ketone and cyclohexanone; examples of the above ester include ethyl acetate, n-butyl acetate, i-amyl acetate, propylene glycol monomethyl ether acetate, 3-methoxybutyl acetate and ethyl lactate; examples of the above ether include ethylene glycol dimethyl ether, ethylene glycol diethyl ether, tetrahydrofuran and dioxane; and examples of the above alcohol include 1-hexanol, 4-methyl-2-pentanol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol mono-n-propyl ether, ethylene glycol mono-n-butyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether and propylene glycol mono-n- propyl ether. In some embodiments, providing the binder and photocatalytic material suspension further comprises dissolving a silicone-modified polyester resin in a propylene glycol solvent. In some embodiments, the propylene glycol solvent can be propylene glycol methyl ether acetate. In some embodiments, the propylene glycol solvent is propylene glycol methyl ether acetate.

These organic solvents may be used alone or in combination of two or more.

In some embodiments, the binder to photocatalytic material is provided in a ratio of about 0.5 to 2.0 parts binder (weight ratio) to about 1 part (weight ratio) photocatalytic material. Those skilled in the art should recognize that 1 :5 wt ratio can be about 34.8 vol%; and 1 :20 wt% can be about 11.8 vol%. In some embodiments, the binder to photocatalytic material is provided in a ratio of about 0.5-2.0 parts binder to about 1 part photocatalytic material (by weight). In some embodiments, the binder to photocatalytic material is provided in a ratio of about 8-12 parts binder (binder in 10% solution) to about 1 part photocatalytic material, e.g., about 0.5 parts binder to about 1 part photocatalytic material, by weight. While not wanting to be limited by theory, having a ratio of less than 0.5 parts binder to about 1 part photocatalytic material can result in insufficient adhesion of photocatalytic material to the surface of the substrate. Those skilled in the art can recognize that a suitable method for assessing the adhesion can be by, but is not limited to, ASTM D3359. While not wanting to be limited by theory, having a ratio of greater than 2.0 parts binder to 1.0 part photocatalytic material (weight %) can result in insufficient presence of photocatalytic material exposed beyond the surface of the coating.

In some embodiments, the photocatalytic/binder material is applied to a substrate. In some embodiments the substrate can be a thermoplastic polymer. In some embodiments, the substrate can be a thermosetting polymer. In some embodiments, the substrate can be any of polyethylene, polypropylene, polyester, polystyrene, polyamide, polyimide, polysulfone, polyethersulfone (PES), polyacrylate, polkyacrylonitrile, polycarbonate (PC), polymethyl methacrylate (PMMA), polyvinylchloride (PVC), ethylene vinyl acetate (EVA), polyvinylidene difluoride (PVDF), polyether ether ketone (PEEK) and /or mixtures thereof. In some embodiments, the substrate can comprise a polyester. In some embodiments, the polyester can be, for example, polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN). In some embodiments, the substrate can comprise a thermosetting resin. In some embodiments, the thermosetting resin can comprise a phenol formaldehyde resin. In some embodiments, the thermosetting resin can comprise polyoxybenzylmethyleneglycoanhydride (Bakelite), epoxy/fiberglass, epoxy/carbon fiber, and any fiber reinforced plastic material. In some embodiments, the epoxy- fiberglass composite can be in the form of a stethoscope diaphragm (e.g., commercial embodiments sold by Littman [3M, Minneapolis, MN]).

In some embodiment, the substrates comprise polymer films which were subject to pre-treatment for increasing the adhesion between coating and substrates. In some embodiments the pretreated films and or substrates were chemically treated, corona treated or heated treated to increase adhesion of the coating to the substrates. Commercially available products of suitable chemically treated films include, but are not limited to, 3 SAB/3 SAC; 3LD4; 4407/4507; 2SABN/2SACN (Mitsubishi Polyester Films, Greer, SC, USA). In some embodiments, the substrates were pre-treated with a coupling agent to promote the adhesion between polymer binders and substrates. In some embodiments, the couplings agent can be any of the previously listed coupling agents. In some embodiments, the coupling agent can be aminopropyltriethoxy silane, allyltrimethoxysilane, (3-aminopropyl)triethoxysilane, 3- amiopropyl(diethoxy)methylsilane, (3-amino)trimethoxysilane aminopropyltriethoxy silane (APTES). Suitable amounts of the coupling agent have been described in "A Study of Adhesion of Silicon Dioxide on Polymeric Substrates for Optoelectronic Applications" (Optoelectronic Devices & Properties, ed., Sergiyuenko, Oleg. InTech Europe, Rijeka, Croatia (201 1), Chapter 2, pg 23-40, 26). In some embodiments, applying the mixture to a substrate further comprises spin-coating the binder- photocatalytic material solution on the substrate at about 500 revolution per minute to about 3000 revolutions per minute for between about 5 seconds to about 30 seconds. In one embodiment, the spin coating can be about 1200 RPM for about 20 sec.

In some embodiments, applying the mixture to a substrate further comprises casting the mixture upon the substrate. A suitable casting procedure has been described in United States Patent Number 8,283,843, issued October 9, 2012, which is incorporated by reference inits entirety. In some embodiments, the blade gap can be between 0.5 mils to about 50 mils, between about 2.0 mils to about 35 mils; or between about 3.5 mils to about 20 mils. In some embodiments, the photocatalytic coating can be formed by applying the photocatalytic suspension on substrates by wire wound lab rod with wire size in the range of 0.003 to 0.020 inches (Paul N. Gardner Inc.).

In some embodiments, the method further comprises treating the surface of the substrate. In some embodiments, the treatment of the surface further includes adding additional adhesion materials to the substrate surface and/or to the photocatalytic layer, and/or disposing an additional layer of adhesion materials therebetween. In some embodiments the additional layer can be a primer layer between the substrate and photocatalytic coating. In some embodiments, the primer layer is disposed upon or in contact with substrate surface. In some embodiments, the primer layer comprises an organic solvent and a silane coupling agent. In some embodiments, the silane coupling agent can include any of aminopropyltriethoxysilane, allyltrimethoxysilane, (3- aminopropyl)triethoxysilane, 3-amiopropyl(diethoxy)methylsilane, (3 - amino )trimethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, 2-(3,4- epoxycyclohexyl)ethyltrimethoxysilane, 3 -glycidoxypropyltrimethoxysilane, 3 - glycidoxypropylmethyldiethoxysilane, 3-glycidooxypropyltriethoxysilane, p- styryltrimethoxy silane, 3 -methacryloxypropylmethyldimethoxysilane, 3 - methacry loxypropyltrimethoxysilane, 3 -methacryloxypropylmethyldiethoxysilane, 3 - methacryloxypropyltriethoxysilane, 3 -acryloxypropyltrimethoxy silane, N-2- (aminoethyl)-3-aminopropylmethyldimethoxysilane, N-2-(aminoethyl)-3- aminopropyltrimethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane, N- (vinylbenzyl)-2-aminoethyl-3-aminopropyltrimethoxysilane hydrochloride, 3- ureidopropyltriethoxysilane, 3 -mercaptopropylmethyldimethoxysilane, 3 - mercaptopropyltrimethoxysilane, bis(triethoxysilylpropyl)tetrasulfide, and/or 3- isocyanatepropyltriethoxysilane. In some embodiments, the coupling agent can be aminopropyltriethoxy silane (APTES).

In some embodiments, the treating of the surface can be by, and not limited to, chemically treating, e.g., acid treating, base treating, solvent treating the surface, ozone treating, corona treating and/or heat treating the substrate surface to increase the adhesion of the coating to the substrate. Surface treatment of substrate can also be applied with use of sulfuric acid (10wt% to 60wt%). Suitable chemically treated films include polyester films treated with a corona plasma. In some embodiments, the photocatalytic material comprises Cu_xO loaded onto a plural phase titanium oxide, e.g., P25 commercially available from Evonik. In some embodiments, the photocatalytic material can be any or all of Ti:Sn(C,N,0)₂, Cu_xO, P25, Sn0₂.

In some embodiments, the method comprises drying the binder/photocatalytic suspension on the substrate surface at a time and temperature sufficient to remove substantially all of the solvent. In some embodiments the drying is performed at a temperature and for a time that partially cures the binder, yet does not deform the substrate. For example, in one embodiment, a PET substrate with photocatalytic coating thereon can be dried at ambient atmosphere at 1 10°C for about lhr.

In some embodiments, the method for making a photocatalytic element comprises providing a KR-5230 (10% by wt) / PGMEA (90% by wt) solution; adding a photocatalytic Cu_xO/plural phase Ti0₂ mixed powder to the solution, at a ratio of 10: 1 (w/w) bindenPhotocatalytic; pretreating a PET surface with corona treatment; and spin coating the solution on the pretreated PET surface, at about 20-80 rps for about 30-60 seconds.

In some embodiments, the plural phase Ti0₂ comprises anatase phase Ti0₂ and rutile phase Ti0₂. In some embodiments, the plural phase Ti0₂ comprises about 50% to about 90% anatase phase Ti0₂ and about 50% to about 10% rutile phase Ti0₂. In some embodiments, the plural phase Ti0₂ comprises about 83% anatase phase Ti0₂ and about 17% rutile phase Ti0₂, e.g., available commercially from Evonik (P25).

In some embodiments, a photocatalytic element can be made according to the methods described above. In some embodiments, a photocatalytic element comprises a silicone polyester resin and a photocatalytic material, wherein the ratio of resin to photocatalytic material is between about 0.5 to about 2.0 to about 1, e.g., 1 :2. In some embodiments, the silicone polyester resin is selected from KR500, KR5230 and KR5235. In some embodiments, the photocatalytic material can be selected from doped or undoped, loaded or unloaded previously described oxides. In some embodiments, the photocatalytic material can be copper oxide loaded (Cu_xO) plural phase titanium oxide (e.g., P25), copper oxide loaded (Cu_xO) Sn/C N doped titanium oxide (Ti:Sn(CNO)₂)and/or unloaded Ti:Sn(C,N,0)₂. In some embodiments, the nominal thickness of a plurality of photocatalytic materials disposed in or upon the coated surface can be measured by the Quartz Crystal microbalance, which measures the mass deposited onto it, and can be about 0.0001 nm to about 2 nm or about 0.001 nm to about 0.75 nm. In some embodiments, the photocatalytic coating comprises a binder matrix and a photocatalytic material. In some embodiments, the photocatalytic coating can be a discontinuous layer defining apertures or voids between islands of photocatalytic material.

In some embodiments, nominal thickness of coating onto substrate can be between about 0.01 μιη to about 1000 μηι (1 mm). The nominal thickness can be as measured by stylus surface profiler (Dektek). In some embodiments, the photocatalytic coating can be a discontinuous layer defining apertures or voids between islands of photocatalytic material (see FIG. 10, for example). In some embodiments, the plurality of photocatalytic nanomaterials can have a total mass of about 1 ng to about 500 ng, about 10 ng to about 100 ng, or about 20 ng to about 60 ng for each cm of area of the surface of the light-emitting layer.

In some embodiments, a method for making a photocatalytic element is provided, the method comprising providing a suspension comprising a binder, a photocatalytic material, a photo-initiator and an organic solvent, wherein the weight ratio of binder to photocatalytic material is about 1.0 to 20 parts binder to about 1 part photocatalytic material; and applying the suspension to a first surface. In some embodiments, the first surface can be of a substrate surface. In some embodiments, the first surface can be a surface of an at least one intervening layer. In some embodiments, the at least one intervening layer is disposed upon a substrate. In some embodiments, the intervening layer can comprise a binder. In some embodiments, the binder is an organic binder. In some embodiments, the binder can be an organic polymer. In some embodiments, the intervening layer can further comprise a photo- initiator and/or an organic solvent.

In some embodiments, a method for making a photocatalytic element is provided, the method comprising providing a suspension comprising a binder, a photocatalytic material, a photo-initiator and an organic solvent, wherein the weight ratio of binder to photocatalytic material is about 1.0 to 20 parts binder to about 1 part photocatalytic material; and applying the suspension to a substrate surface.

In some embodiments, a method for making a photocatalytic element is provided, the method comprising providing a solution comprising a binder, a photocatalytic material, a photo-initiator and an organic solvent; providing a suspension comprising a binder, photocatalytic material, a photo-initiator and an organic solvent, wherein the weight ratio of binder to photocatalytic material is about 1.0 to 20 parts binder to about 1 part photocatalytic material; applying the solution to a substrate surface to form an intervening layer (such as, for example, a binder coating) on the substrate surface; and applying the suspension to the intervening layer (such as, for example, a binder coating) on the substrate surface.

As shown in FIG. 12, the current disclosure provides a method (S 10') for making a photocatalytic element comprising providing a binder and photocatalytic material solution, wherein the binder to photocatalytic material is provided in a ratio of about 1.0-20.0 parts binder to about 1 part photocatalytic material (weight ratio [w/w]) (SI 2'). In some embodiments, 1-20 parts of a 10% binder (by weight) solution to 1 part photocatalytic material (by weight) is provided. In some embodiments, the method further comprises treating the surface of the substrate (S14'). In some embodiments, method comprises applying the suspension to the substrate surface (SI 6'). In some embodiments, the method comprises heating the applied binder/photocatalytic material suspension on the substrate surface to remove the solvent (S I 8'). In some embodiments, the method comprises curing the applied binder/photocatalytic material suspension on the substrate surface (S20').

As shown in FIG. 13, the current disclosure provides a method (SI 10) for making a photocatalytic element can comprise providing a binder solution (SI 12). In some embodiments, the method can comprise providing a binder and photocatalytic material suspension, wherein the binder to photocatalytic material can be provided in a ratio of about 1.0-20.0 parts binder to about 1 part photocatalytic material (weight ratio [w/w]) (SI 14). In some embodiments, 1-20 parts of a 10% binder (by weight) solution to 1 part photocatalytic material (by weight) is provided. In some embodiments, the method can comprise treating the surface of the substrate (SI 16). In some embodiments, the method can comprise applying an intervening layer to the substrate surface (SI 18). In some embodiments, the intervening layer can be a layer comprising a binder. In some embodiments, the binder in the intervening layer is the same as in the photocatalytic suspension. In some embodiments, the method can comprise heating the applied binder solution on the substrate surface and/or the applied binder/photocatalytic material suspension on the intervening layer surface to remove the solvent (SI 20). In some embodiments, the method comprises curing the binder solution on the substrate surface and/or applied binder/photocatalytic material suspension on the intervening layer surface (SI 22). In some embodiments, the intervening layer can be cured prior to the addition of the photocatalytic suspension. In some embodiments, the intervening layer and the photocatalytic suspension can be cured concurrently/together.

As shown in FIG. 14, there is shown a photocatalytic element 1 10 including a substrate 1 12 and a photocatalytic coating 1 14. In some embodiments, the photocatalytic coating is disposed upon, in contact with or a portion of the first surface 1 18 of the substrate 1 12. In some embodiments, the substrate 1 12 can comprise a treated substrate surface 1 18. In some embodiments, the photocatalytic coating 1 14 includes a photocatalytic material 120 disposed in and/or upon a binder 122. In some embodiments, a sufficient amount of the photocatalytic material 120 is exposed on the surface of the photocatalytic coating to provide a desired antibacterial effect.

FIG. 15 shows a photocatalytic element 1 10 including a substrate 1 12, a photocatalytic coating 1 14, and an intervening layer 124. In some embodiments, the intervening layer 124 is disposed upon, in contact with or a portion of the first surface 1 18 of the substrate 112. In some embodiments, the photocatalytic coating is disposed upon, in contact with or a portion of the first surface 126 of the intervening layer 124. In some embodiments, the intervening layer can be of the same binder, photo-initiator and/or solvent as the photocatalytic coating. In some embodiments, the substrate 1 12 can comprise a treated substrate surface 1 18. In some embodiments, the photocatalytic coating 1 14 includes a photocatalytic material 120 disposed in and/or upon a binder 122. In some embodiments, a sufficient amount of the photocatalytic material 120 is exposed on the surface of the photocatalytic coating to provide a desired antibacterial effect.

In some embodiments, a photocatalytic suspension is provided, comprising the at least one photocatalytic material, at least one binder, at least one photo-initiator and at least one organic solvent. In some embodiments, a binder solution is provided, comprising at least one binder, at least one photo-initiator and at least one organic solvent.

In some embodiments, the photocatalytic material can be those as mentioned above.

In some embodiments, the binder material can be an organic binder/material. In some embodiments, the binder material can be an organic polymer. In some embodiments, the binder material can be a UV curable resin. In some embodiments, the UV curable resin can be a urethane resin. In some embodiments, the UV curable resin does not include silicon. In some embodiments, the urethane resin can be a urethane acrylic resin. In some embodiments, the urethane resin can be a urethane acrylate resin. In some embodiments, the urethane acrylate resin comprises at least 2, at least 3, and/or at least 5 acryloyl groups per molecule. In some embodiments, the suitable urethane resins can be commercially available products, e.g., UNIDIC 17-806 (80% by mass of the non- volatile content; polyfunctional urethane acrylate by DIC International (USA), LLC, Parsippany, NJ, USA); Ebecryl 8701 (aliphatic urethane triacrylate), Ebecryl 8301-R (aliphatic urethane hexaacrylate), Ebecryl 8405 (aliphatic urethane tetraacrylate) (Allnex USA, Smyrna, GA, USA), OC-3021, OC-4021, OC- 4122 (Dymax Oligomers and Coatings, Torrington, CT, USA); HC-5619 (Addison Clearwave Coatings, Inc., St. Charles, IL, USA); and Silfort UVHC3000 (Momentive Performance Materials, Inc., Albany, NY, USA).

In some embodiments, the binder to photocatalytic material is provided in a ratio of about 1.0 to about 20.0 parts binder (weight %), preferably about 1.5 to about 10.0 parts binder (weight %), to about 1 part (weight %) photocatalytic material. Those skilled in the art should recognize that 1 :5 wt% can be about 34.8 vol%; and 1 :20 wt% can be about 1 1.8 vol%. In some embodiments, the binder to photocatalytic material is provided in a ratio of about 1.0-20.0 parts binder to about 1 part photocatalytic material (by weight). In some embodiments, the binder to photocatalytic material is provided in a ratio of about 1.7, 2.5, 5.0, and/or 10.0 parts binder to about 1 part photocatalytic material (by weight). In some embodiments, the binder to photocatalytic material is provided in a ratio of about 1.5-12 parts binder (binder in 10% solution) to about 1 part photocatalytic material, e.g., about 5 parts binder to about 1 part photocatalytic material, by weight. While not wanting to be limited by theory, having a ratio of less than 1.0 part binder to about 1 part photocatalytic material can result in insufficient adhesion of photocatalytic material to the surface of the substrate. Those skilled in the art can recognize that a suitable method for assessing the adhesion can be by, but is not limited to, ASTM D3359. While not wanting to be limited by theory, having a ratio of greater than 20.0 parts binder to 1.0 part photocatalytic material (weight %) can result in insufficient presence of photocatalytic material exposed beyond the surface of the coating.

In some embodiments, the photocatalytic suspension further includes a dispersing agent. In some embodiments, the dispersing agent can be a cationic, anionic, non-ionic dispersing agent. In some embodiments, the suitable dispersing agent can be commercially available products, e.g., Additol XL 203 (cationic dispersing agent, Allnex USA, Smyrna, GA, USA), Additol XL 251 (anionic dispersing agent, Allnex USA, Smyrna, GA, USA), Additol VWX 6208/60 (polymeric non-ionic dispersing agent, Allnex USA, Smyrna, GA, USA) and Flowlen G700 (polycarboxylic acid-based, molecular weight M_w=230, KYOEISHA CHEMICAL Co., LTD, Osaka, JP). In some embodiments, the suitable dispersing agent can be Disperbyk-1 10 (copolymer with acidic groups) and/or Disperbyk-118, (linear copolymer with highly polar, different affinic groups) (BYK USA, Inc., Wallingford, CT, USA).

In some embodiments, the photoinitiator can be an alpha amino ketone, a bis acyl phosphine (BAPO), an alpha hydroxyl ketone and/or combinations and/or mixtures thereof. In some embodiments, the suitable photoinitiator can be 2-methyl-l -[4- (methylthio)phenyl]-2-(4-morpholinyl)-l-propanone (IRGACURE 907), phosphine oxide (phenyl bis(2,4,6-trimethyl benzoyl) [IRGACURE 819]), and/or 2-hydroxy-2- methyl-1 -phenyl- 1-propanone [DAROCUR 1 173]. In some embodiments, the suitable photoinitiator can be commercially available products, e.g., IRGACURE 907, and/or IRGACURE 2022 (20 wt% IRGACURE 819/80% DAROCUR 1 173]).

In some embodiments, the binder can be dissolved in an organic solvent. In some embodiments, the photocatalytic material is substantially insoluble in the organic solvent. In some embodiments, the organic solvent can be, for example, a hydrocarbon, ketone, ester, ether or alcohol.

Examples of the above hydrocarbon, ketone, ester, ether and alcohol can be those as mentioned above. In some embodiments, the organic solvent can be a C1-C7 alcohol. In some embodiments, the organic solvent can be a C1-C7 ketone. In some embodiments, the organic solvent can be cyclopentanone, propylene glycol monomethyl ether acetate (PGMEA), N-methylpyrrolidone (NMP), methyl ethyl ketone (MEK), toluene, ethyl acetate and/or butyl acetate. In some embodiments, providing the binder and photocatalytic material suspension further comprises dissolving a urethane resin in a cyclopentanone solvent. These organic solvents may be used alone or in combination of two or more. In some embodiments, the photocatalytic/binder material can be applied to a first surface. In some embodiments, the photocatalytic/binder material can be applied to a surface of an at least one intervening layer. In some embodiments, the intervening layer can comprise any or all of the aforedescribed materials of the photocatalytic/binder suspension, except for the photocatalytic material, e.g. binders, solvents, photo-initiators, etc. as earlier described. In some embodiments, the intervening layer and the photocatalytic binder layer can comprise the same and/or different materials. In some embodiments, the photocatalytic/binder material can be applied to a surface of a substrate. In some embodiments the substrate can be a thermoplastic polymer. In some embodiments, the substrate can be a thermosetting polymer. In some embodiments, the substrate can be any of polyethelene, polypropylene, polyester, polystyrene, polyamide, polyimide, polysulfone, polyethersulfone (PES), polyacrylate, polkyacrylonitrile, polycarbonate (PC), polymethyl methacrylate (PMMA), polyvinylchloride (PVC) and /or mixtures thereof. In some embodiments, the substrate can comprise a polyester. In some embodiments, the polyester can be, for example, polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN).

In some embodiments, the substrate can comprise a thermosetting polymer. In some embodiments, the thermosetting resin can comprise a phenol formaldehyde resin. In some embodiments, the thermosetting resin can comprise polyoxybenzylmethyleneglycoanhydride (Bakelite), epoxy/carbon fiber, and any fiber reinforced plastic sheets. In some embodiments, the epoxy-fiberglass composite can be in the form of a stethoscope diaphragm (e.g., commercial embodiments sold by Littman [3M, Minneapolis, MN]). In some embodiments, the substrates can comprise polymer films which were subject to pre-treatment for increasing the adhesion between coating and substrates. In some embodiments the pretreated films and or substrates were chemically treated, corona treated or heated treated to increase adhesion of the coating to the substrates. Commercially available products of suitable chemically treated films include, but are not limited to, 3SAB/3SAC; 3LD4; 4407/4507; 2SABN/2SACN (Mitsubishi Polyester films, Greer, SC, USA). In some embodiments, the substrates were pre-treated with coupling agents to promote the adhesion between polymer binders and substrates. In some embodiments, the couplings agents can be aminopropyltriethoxy silane, allyltrimethoxysilane, (3-aminopropyl)triethoxysilane, 3- amiopropyl(diethoxy)methylsilane, and/or (3-amino)trimethoxysilane.

In some embodiments, applying the mixture to an intervening layer and/or a substrate further comprises spin-coating the binder-photocatalytic material solution on the substrate at about 500 revolutions per min to about 3000 revolutions per min for between about 5 seconds to about 30 seconds. In one embodiment, the spin coating can be about 1200 rpm for about 20 sec.

In some embodiments, applying the mixture to an intervening layer and/or a substrate further comprises casting the mixture upon the substrate. A suitable casting procedure is already mentioned above.

In some embodiments, the method further comprises treating the surface of the substrate to increase the adhesion of the coating to the substrate. In some embodiments, the treating of the surface can be by, and not limited to, chemically treating, e.g., acid treating, base treating, solvent treating the surface, ozone treating, corona treating and/or heat treating the substrate surface to increase the adhesion of the coating to the substrate. Suitable chemically treated films include polyester films treated with a corona plasma. In some embodiments, the photocatalytic material comprises Cu_xO loaded onto P25 mixed phase photocatalytic material. In some embodiments, the photocatalytic material can be any or all of Ti:Sn(C,N,0)₂, Cu_xO, P25, Sn0₂.

In some embodiments, the method comprises drying the binder/photocatalytic suspension and/or the intervening layer on the substrate surface at a time and temperature sufficient to remove substantially all of the solvent. In some embodiments the drying is performed at a temperature and for a time that partially cures the binder, yet does not deform the substrate. In some embodiments, the intervening layer is partially cured before photocatalytic/binder suspension is applied thereto. In some embodiments, the intervening layer is substantially completely cured before photocatalytic/binder suspension is applied thereto. For example, in one embodiment, a PET substrate with photocatalytic coating thereon can be dried at ambient atmosphere at 90° C for about 2 min.

In some embodiments, the method comprises curing the binder/photocatalytic suspension on the substrate surface and/or the intervening layer with sufficient UV irradiation to cure suspension. In some embodiments, the method comprises curing the intervening layer on the substrate surface with sufficient UV irradiation to cure intervening layer. In some embodiments the curing is performed at an ultraviolet intensity and for a time that partially cures the binder, yet does not degrade the UV curable material. In certain embodiments, UV having an energy of 0.2-20 J/cm² and a wavelength in the range of 100-400 nm, preferably 200-400 nm can be used for cross- linking and curing the binder/photocatalytic suspension on the substrate surface. For example, in one embodiment, the UV energy is about 0.5 J/cm² to about 1.5 J/cm². Such UV can be applied by using an ultra-high-pressure mercury-vapor lamp, high- pressure mercury-vapor lamp, low-pressure mercury-vapor lamp, carbon arc, metal halide lamp or the like. For example, in one embodiment, a PET substrate with urethane binder/photocatalyst/photoinitiator composite coating thereon can be irradiated at about 25 mW/cm² for about 5 minutes. For example, in another embodiment, a PET substrate with urethane binder/photocatalyst/photoinitiator composite coating thereon can be irradiated at about 225 mW/cm for about 5 minutes. For example, the substrate can be irradiated with a Loctite® Zeta® 741 1 UV Flood Curing System or a Dymax UV conveyor system.

In some embodiments, the method for making a photocatalytic element comprises providing a urethane acrylate resin (e.g., UNIDEC 17 806) (10% by wt) / organic solvent (cyclopentanone) (90% by wt) / 0.24 wt% photo-initiator (IRGACURE 907) solution; adding a photocatalytic Cu_xO/plural phase Ti0₂ mixed powder to the solution, at a ratio of five to 1 (w/w) bindenphotocatalytic material; pretreating a PET surface with corona treatment; casting the solution/suspension on the pretreated PET surface; and curing the binder/photocatalytic solution/suspension on the PET surface. In some embodiments, a dispersing agent is added to the binder/solvent/photo-initiator solution/suspension. In some embodiments, the cast solution is cured upon the pretreated PET surface.

In some embodiments, the plural phase Ti0₂ can be those as mentioned above. In some embodiments, a photocatalytic element can be made according to the methods described above.¹ In some embodiments, a photocatalytic element comprises a urethane acrylate resin and a photocatalytic material, wherein the ratio of resin to photocatalytic material is between about 1.0 to about 20.0 to about 1, e.g., 20 parts resin: one part photocatalytic material. In some embodiments, the urethane acrylate resin can be selected from UNIDIC 17806, EBECRYL 8701, EBECRYL 8301, EBECRYL 8405, OC-3021, OC-4021, OC-4122, HC-5619, and/or UVHC3000. In some embodiments, the photocatalytic material can be selected from doped or undoped, loaded or unloaded previously described oxides. In some embodiments, the photocatalytic material can be copper loaded (Cu_xO) P25, copper loaded (Cu_xO) Ti:Sn(CNO)₂ and/or unloaded Ti:Sn(C,N,0)₂.

In some embodiments, the nominal thickness of a plurality of photocatalytic materials disposed in or upon the coated surface can be measured by the Quartz Crystal microbalance, which measures the mass deposited onto it, can be about 0.0001 nm to about 2 nm or about 0.001 nm to about 0.75 nm. In some embodiments, the photocatalytic coating comprises a binder matrix and a photocatalytic material. In some embodiments, the photocatalytic coating can be a discontinuous layer defining apertures or voids between islands of photocatalytic material.

In some embodiments, the plurality of photocatalytic nanomaterials may have a total mass of about 1 ng to about 500 ng, about 10 ng to about 100 ng, or about 20 ng to about 60 ng for each cm² of area of the surface of the light-emitting layer.

In some embodiments, the photocatalytic coating can have a thickness of between about 100 nm to about 10 microns. In some embodiments, wherein the photocatalytic layer is disposed on the substrate surface, the photocatalytic coating can have a thickness of between about 100 nm to about 10 microns.

In some embodiments, wherein the photocatalytic material /binder layer is used in conjunction with binder layer, the binder layer substantially free of photocatalytic material, the intervening binder layer disposed between photocatalytic material/binder layer and the substrate, the photocatalytic binder layer can be thinner. In some embodiments, the photocatalytic /binder layer can be between about 50 nm, 75 nm, 100 nm to about 250 nm, 300 nm, 400 nm and/or about 500 nm.

In some embodiments, the photocatalytic coating is characterized by an adhesion of about at least 35%, at least 45%, at least 55%, at least 65%, at least 75%, at least 80%, at least 90%, at least 95%, at least 97%, or at least 99% adhesion. In some embodiments, greater than 65% (0B); between about 35% to about 65% (IB); between about 15-35% (2B); between about 5-15% (3B); less than about 5%(4B); and substantially no photocatalytic materials are removed from the film coating (5B). The term adhesion refers to the percentage of the coating remaining on the substrate after a standard tape removal test method for measuring adhesion. One method of ascertaining the adhesion is by the procedures described in ASTM-D3359. In some embodiments, the layers are characterized by a hardness test of at least 2H, of at least 3H, of at least 4H. One method of ascertaining the surface hardness (scratch resistance) is by the procedures described in ASTM-3363.

EXAMPLES

Embodiments of the photocatalytic elements described herein improve the adhesion of a photocatalytic material to a substrate. These benefits are further shown by the following examples, which are intended to be illustrative of the embodiments of the disclosure, but are not intended to limit the scope or underlying principles in any way. EXAMPLE 1 (P-CAT (Cu_xO/Ti0₂:Sn) coating on PET substrate)

Commercial available PET (polyethylene terephthalate) film (Eplastics Inc. San Diego, CA USA) with a thickness of about 120 micrometers (microns) was used as substrate for a photocatalytic coating. The substrate was cut into piece with dimension of 7.5 cm by 5 cm. The cut PET substrate was cleaned with a sequence of soap and water; acetone; and methanol; and then dried.

A binder solution containing 10wt% silicone modified polyester resin was made by mixing a modified silicone polyether resin (sold under the brand designation, R5230 or "KR-5230", by ShinEtsu Silicones, JAPAN) with PGMEA (Propylene Glycol Monomethyl Ether Acetate, reagent >99.5%, Sigma-Aldrich). The mixing was conducted with planetary centrifugal mixer (THINKY AR-310) at about 2000 rpm for 2 min for mixing and then at about 2200 rpm for about lmin for defoaming.

To make a coating suspension, one part of IiSn(CNO)₂ photocatalytic powder by weight was mixed with 10 part, by weight, of binder solution (10wt% silicone-modified polyester resin (KR-5230) dissolved in PGMEA). The photocatalytic powder was made according to that described in United States Patent Application 13/840,859, filed March 15, 2013; and United States Provisional Application 61/835,399, filed June 14, 2013; and United States Patent Application 13/741,191, filed January 14, 2013 (United States Publication No. 2013/0192976, published August 1, 2013), each of which are incorporated by reference in their entirety. The photocatalytic-cat (P-cat) powder comprises copper oxide loaded titanium oxide doped with carbon, nitrogen and tin to increase the light absorption in visible light range. The nominal copper content in P- cat was lwt%. 1 gm of photocatalytic powder was dispersed in the binder solution (about 10 gm, 10% solution) by keeping the glass vial containing the mixture in a sonication bath for about one hour. The obtained suspension was passed through an inline filter with stainless steel screen with opening of 30 micrometers.

Prior to coating, the cleaned PET substrate was subject to corona discharge treatment to increase the hydrophilicity of substrate surface for good wettability of coating suspension. A corona treatment apparatus (TEWC-4AX, KASUGA DENKI Inc. JAPAN) was used at discharge power of 100W and scan speed of 0.5m/sec for two scans.

The coating of the substrate (Ex-1) was performed on the prepared PET substrate by spin coating with spin coater (SCS 6800 series, Specialty Coating System) at about 1200 rpm for about 20 sec.

An additional example (Εχ- ) was prepared in a manner similar to Ex-1 , except that the photocatalytic coating was formed on the prepared PET substrate by tape casting with use of doctor blade and tape caster (AFA-II, MTI Corporation) by the method described in United States Patent 8,283,843, filed January 28, 201 1, issued October 9, 2012. The gap of doctor blade was kept in the range of 3 mil to 20 mils (one mil equals to 1/1000 inch or 25.4 micrometers). PET substrate with photocatalytic coating was dried at ambient atmosphere at 1 10°C for about lhr. Additional examples (Ex- A to Ex-F) were prepared in a manner similar to Ex-1, except that the binder solution wt% and the ratio of photocatalytic material to binder solution was varied as indicated in Table 1.

An additional example (Ex-G) was prepared in a manner similar to Ex-1 , except that the substrate was a 2.5 cm diameter disk of stethoscope diaphragm substrate. A commercial diaphragm of stethoscope (3M, Minneapolis, MN, USA, Littmann™) was used as a substrate for photocatalyst coating. Suspension was made of copper oxide loaded plural phase Ti0₂ (P25) and binder solution made of 10wt% of KR5230 in PGMEA was applied onto the diaphragm by spin coating at 1000 rpm for 20 sec and then dried in ambient atmosphere for lhr at 1 10°C.

Adhesion

Adhesion of photocatalytic coating was evaluated by following the procedures described in ASM-D3359.

Coating hardness was evaluated by following the procedures described in ASTM-3363.

Table 1 Adhesion and pencil hardness of photocatalytic (Cu_xO/Ti(0,C,N)₂:Sn coating on PET substrate

Removed percentage : 0B>65%; 1Β:35-65%; 2B: 15-35%; 3B:5-15%; 4B<5%; 5B:0%

Antibacterial performance

Antibacterial performance was evaluated by following the procedures.

Substrate (Γ' x 2" glass slide) was prepared by sequential application of 70% IPA (Isopropyl Alcohol), 100% ethanol (EtOH) and then dried in air. Ex-1 was dispersed in 100% EtOH at 2mg/mL concentration and then about 100 uL of the suspension was applied to the substrate, and then dried. The application process was repeated 5 times to attain about 1 mg of Ex-1 on the substrate. The substrate was then dried at room temperature. The coated substrates were placed in a glass dish with a water soaked filter paper for maintaining moisture, and glass spacers were inserted between the substrate and the filter paper to separate them.

E. coli (ATCC 8739) was streaked onto a 10 cm diameter petri dish containing about 20 ml of LB (lysogeny broth/ luria broth) agar, and incubated at about 37°C overnight. For each experiment, a single colony was picked to inoculate about 3 mL nutrient broth, and the inoculated culture was incubated at about 37°C for about 16 hours to create an overnight culture (~10⁹ cells/mL). A fresh log-phase culture of the overnight culture was obtained by diluting the overnight culture xlOO, inoculating another 5 cm petri dish with LB agar and incubated about at 37°C for about 2.5 hr. The fresh culture was diluted 50x with 0.85% saline, which will gave a cell suspension of about 2 x 10⁶ cells/mL. 50 of the cell suspension was pipetted onto each deposited glass substrate. A sterilized (in 70% and then 100% EtOH) plastic film (20 mm x 40 mm) was placed over the suspension to spread evenly under the film. The specimen was kept in the dark (Cu_xO-Dark) or then irradiated under blue LED light (455 nm, 10 mW/cm²) (Cu_xO-light). At chosen time point, e.g., 30 min/60 min increments, the specimen was placed in 10 mL of 0.85% saline and vortexed to wash off the bacteria. The wash off suspension was retained, then serially diluted using 0.85% saline, and then plated on LB agar and incubated at about 37°C overnight to determine the number of viable cells in terms of CFU/Specimen. FIG. 5 to FIG. 9 shows the antibacterial (E. Coli) performance of photocatalytic coating on PET substrate with varied P-cat loading as described in Table 1 (FIG. 5- Sample Example A, FIG. 6- Sample Example B, etc.). There was a trend that adhesion increased with increasing binder content and antibacterial performance did not change significantly. To get good antibacterial performance while maintaining good adhesion of photocatalytic coating to the substrate, binder loading more than 75 vol% was favorable.

FIG. 10 showed the surface and cross section morphology of photocatalytic coating on PET substrate with silicone modified polyester resin as binder. Coating thickness was about 10 micrometers.

EXAMPLE 2 (P-CAT (Cu_xO/Ti0₂) coating on PET substrate)

Photocatalytic coating (Examples AA, AB, AC, AD, AE, AF) comprising copper loaded titanium oxide and silicone modified polyester as binder was formed on PET substrate by following the same processing procedures. 1 gram of titanium oxide powder P25 (Evonik Deggusa Corp, Parissipany, NJ, USA) loaded with lwt% of Cu_xG was used instead of the photocatalytic material of Example 1 described above. Table 2 showed the adhesion, hardness and antibacterial performance as full killing time against E.Coli. FIG. 1 1 shows the bacterial count vs. contact time to photocatalytic coatings which have varied photocatalytic material loading. Table 2

room temperature

EXAMPLE 3 (P-CAT (Cu_xO/Sn0₂) coating on PET substrate)

Photocatalytic coating comprising copper loaded tin oxide and silicone modified polyester as binder was formed on PET substrate by following the same processing procedures aforementioned. Copper content in the photocatalytic powder was 1 wt% as tin oxide. FIG. 11 showed the antibacterial performance of photocatalytic coating on PET substrate.

EXAMPLE 4 (P-CAT (Cu_xO/Ti0₂) coating on polymer pitcher with silicone oligomer as binder) Photocatalytic coating comprising copper loaded titanium oxide on a water pitcher was implemented. The coating suspension consisted of copper oxide loaded plural phase titanium oxide (Cu_xO/P25) powder dispersed in silicone oligomer (KR- 500, ShinEtshu Silicones, JAPAN) and catalyst (D-25) of 2wt% vs. KR-500 which was made by following the procedures in example 1. The water pitcher made of PMMA was first coated with primer layer consisting silane coupling agent for promoting the adhesion between PMMA and KR-500. The synthesis of silane coupling agent was listed as follows.

Silanization Procedure:

A mixture of 70:30 vol% ethanol and MiliQ (MQ) water was prepared as a solvent for the silane reaction. From this, a 7.5 wt% solution of aminopropyltriethoxy silane (APTES) was made. Its pH was adjusted to 5.5 by the addition of concentrated acetic acid. The reaction was stirred while hydrolyzing for lhr.

The interior of the container was filled with the silanization mixture and let sit for 30 minutes. The container was then rinsed with copious amounts of MQ water and allowed to dry prior to subsequent coatings.

(APTES) P-cat coating was applied on PMMA pitcher coated with primer by dip coating with the suspension and then spinning at about 400 rpm for about 5 min to get rid of extra coating suspension to get a uniform coating. The coated Pitcher was cured at ambient atmosphere and temperature for about 12 hours.

EXAMPLE 5 (Photocatalytic coating with inorganic binders)

Commercially available inorganic sols were used as binder to replace the silicone resin which include silica, alumina, zirconia and titania sols. Silica sol (SNOWTEX-O, Nissan Chemicals, JAPAN) was mixed with photocatalytic powder composed of copper loaded titanium oxide as mentioned in EXAMPLE 2 by sonication probe for 30 min. Photocatalytic material loading varied in the range of 5.6 to 37.4 vol%. The photocatalytic suspension was applied on PET substrate by spin coating at spin rate of 1200 rpm. The coating was dried at 110°C for 1 hrs to remove the solvent and water in silica sol to get coating with good adhesion to PET substrate.

EXAMPLE I (P-CAT (Cu_xO/Ti0₂) coating on PET substrate)

Commercial available PET (polyethylene terephthalate) film (Eplastics Inc. San Diego, CA USA) with a thickness of about 120 micrometers (microns) was used as substrate for a photocatalytic coating. The substrate was cut into paper size. The cut PET substrate was cleaned with acetone and then dried.

A binder solution containing 10wt% UV curable hard coat was made by mixing about 1 g UV-curable acrylate binder (sold under the brand designation, Unidic 17806, by DIC corporation, JAPAN), about 24 mg of a photo-initiator (sold under the brand designation Irgacure 907) and about 10 g Cyclopentanone (reagent> 99.5%, Sigma- Aldrich). The mixing was conducted with planetary centrifugal mixer (THINKY AR- 310) at about 2000 rpm for 2 min for mixing and then at about 2200 rpm for about 1 min for defoaming.

To make a coating suspension, one part of Cu_xO/P25 photocatalytic powder (about 0.2 g) by weight was mixed with 5 parts, by weight, of binder solution (10wt% urethane acrylate dissolved in cyclopentanone). The photocatalytic powder was made according to that described in United States Patent Application 13/840,859, filed March 15, 2013; and United States Provisional Application 61/835,399, filed June 14, 2013; and United States Patent Application 13/741,191, filed January 14, 2013 (United States Publication No. 2013/0192976, published August 1 , 2013). The photocatalytic-cat (P- cat) powder comprises copper oxide loaded titanium oxide doped with carbon, nitrogen and tin to increase the light absorption in visible light range. The nominal copper content in P-cat was lwt%. 0.2 gm of photocatalytic powder was dispersed in the binder solution (about 1 gm, 10% solution) by keeping the glass vial containing the mixture in a sonication bath for about half hour followed by probe sonication for about 20-30 mins. The obtained suspension was passed through a filter with opening of 5 micrometers.

Prior to coating, the cleaned PET substrate was subject to corona discharge treatment to increase the hydrophilicity of substrate surface for good wettability of coating suspension. A corona treatment apparatus (TEWC-4AX, KASUGA DENKI Inc. JAPAN) was used at discharge power of 100 W and scan speed of 0.5 m/sec for two scans.

The coating of the substrate (Ex-I) was performed on the prepared PET substrate by tape casting with use of doctor blade and tape caster (AFA-II, MTI Corporation) by the method described in United States Patent 8,283,843, filed January 28, 2011, issued October 9, 2012. The gap of doctor blade was kept in the range of 3 mils to 20 mils (one mil equals to 1/1000 inch or 25.4 micrometers). PET substrate with photocatalytic coating was dried at ambient atmosphere and then preheat at 90 to 100°C for about 2 min, then UV cured under Loctite® Zeta® 741 1 UV Flood Curing System. The UV light energy was monitored by the ZETA 701 1 -A Dosimeter-Radiometer with the energy intensity about 25 mw/cm . Additional examples (Ex-II, Ex-III, and Ex-IV) were prepared in a manner similar to Ex-I, except that the binder to P-cat ratio is different and varied as indicated in Table 4.

Additional examples (Ex-1 1 to Ex- 15) were prepared in a manner similar to Ex-

I, except that the different dispersing agent was added to the binder/photo- initiator/cyclopentanone and varied in the amounts as indicated in Table 6.

EXAMPLE V (P-CAT (Cu_xO/Ti0₂) coating/intervening layer/PET substrate embodiment)

The substrate in Example V was prepared as described in Example I above. The binder solutions for an intervening first layer and the photocatalyst/binder second layer were made in a similar manner to the binder layer described in Example I, except as described in the Table 3 below. Table 3

The first or intervening layer was applied to the prepared substrate in a manner similar to that described in Example I above.

A second or photocatalytic layer was then disposed upon the first layer coating. The gap of doctor blade was kept in the range of 1 mil to 3 mils. The PET substrate with first polymeric coating and second polymeric coating was dried at ambient atmosphere and then preheated at 90 to 100°C for about 2 min. The dried dual coated substrate was then UV cured under Loctite® Zeta® 741 1 UV Flood Curing System. The UV light energy was monitored by the ZETA 701 1 -A Dosimeter- Radiometer with the energy intensity about 25 mw/cm².

Haze and Transmittance

Haze and Transmittance were evaluated on UltrascanPro, which follows the procedures described in ASTM-D1003 standard.

Adhesion

Removed percentage : 0B>65%; lB:35-65%; 2B: 15-35%; 3B:5-15%; 4B<5%;

5B:0%

Hardness Coating hardness was evaluated by following the procedures described in ASTM-3363.

Solvent resistance (Rub test)

Rub test was evaluated by following the procedures described in ASTM-D5402, the solvent used including IP A, EtOH, and bleach. The cloth was clean room synthetic wiper. Double rubs were performed until the maximum of 200.

Table 4 Composition with different binder /P-cat ratio

Table 5 Haze, Transmittance, Adhesion and pencil hardness of photocatalytic

(Cu_xO/P25) coating on PET substrate

Table 6 Composition with different dispersing agent

Table 7 Haze, Transmittance, Adhesion and pencil hardness of photocatalytic

(Cu_xO/P25) coating on PET substrate

FIG. 17 is a graph showing the antibacterial (E.Coli) activity of an embodiment described herein (Ex-1 1 to Ex- 15) under light.

FIG 18 is a graph showing the antibacterial (E.Coli) activity of an embodiment described herein (Ex-1 1 to Ex- 15) under dark.

Table 8 Rub test result for example 15 (Cu_xO/P25 coating on PET substrate).

The difference between before and after test data might due to the test spot are not the same.

FIGS. 19 and 20 are SEM photographs of example 1 1. FIGS. 21 and 22 are SEM photographs of example 15. The SEM photographs depict dispersing uniformity of the photocatalytic material in or on the cured binder/photocatalyst surface.

Unless otherwise indicated, all numbers expressing quantities of ingredients, properties such as molecular weight, reaction conditions, and so forth used in the specification and claims are to be understood as being modified in all instances by the term "about." Accordingly, unless indicated to the contrary, the numerical parameters set forth in the specification and attached claims are approximations that may vary depending upon the desired properties sought to be obtained. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.

The terms "a," "an," "the" and similar referents used in the context of describing the embodiments (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., "such as") provided herein is intended merely to better illuminate the embodiments and do not pose a limitation on the scope of any claim. No language in the specification should be construed as indicating any non-claimed element essential to the practice of the embodiments.

Groupings of alternative elements or embodiments disclosed herein are not to be construed as limitations. Each group member may be referred to and claimed individually or in any combination with other members of the group or other elements found herein. It is anticipated that one or more members of a group may be included in, or deleted from, a group for reasons of convenience and/or patentability. When any such inclusion or deletion occurs, the specification is deemed to contain the group as modified thus fulfilling the written description of all Markush groups used in the appended claims.

Certain embodiments are described herein, including the best mode known to the inventors for carrying out the invention. Of course, variations on these described embodiments will become apparent to those of ordinary skill in the art upon reading the foregoing description. The inventors expect skilled artisans to employ such variations as appropriate, and the inventors intend for the embodiments to be practiced otherwise than specifically described herein. Accordingly, the claims include all modifications and equivalents of the subject matter recited in the claims as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is contemplated unless otherwise indicated herein or otherwise clearly contradicted by context.

In closing, it is to be understood that the embodiments disclosed herein are illustrative of the principles of the claims. Other modifications that may be employed are within the scope of the claims. Thus, by way of example, but not of limitation, alternative embodiments may be utilized in accordance with the teachings herein. Accordingly, the claims are not limited to embodiments precisely as shown and described.

The present application is based on a US provisional application No. 61/899,423 filed November 4, 2013, a US provisional application No. 61/931 ,387 filed January 24, 2014, and a US provisional application No. 62/007,489 filed June 4, 2014, the entire contents of which are incorporated herein by reference.

In addition, each of Unites States Patent No. 5,897,958, Unites States Patent No. 6,228,480, Unites States Patent No. 6,407,033, Unites States Patent No. 7,510,595 and United States Reissue Patent No. RE38,850 mentioned above is also incorporated herein by reference in its entirety.

Claims

1. A method for making a photocatalytic element comprising:

providing a suspension comprising a binder and a photocatalytic material, wherein the weight ratio of the binder to the photocatalytic material is about 0.5 to 2.0 parts binder to about 1 part photocatalytic material; and

applying the suspension to a substrate surface.

2. The method of claim 1, further comprising applying a silane coupling agent to the substrate surface.

3. The method of claim 2, wherein the silane coupling agent is aminopropyltriethoxy silane.

4. The method of any one of claims 1 to 3, further comprising adding a binder catalyst material to the suspension.

5. The method of claim 4, wherein the binder catalyst material is D25.

6. The method of any one of claims 1 to 5, wherein providing the suspension further comprises dissolving a silicone resin in a propylene glycol solvent.

7. The method of claim 6, wherein the silicone resin is a silicone alkyd resin, a silicone epoxy resin, a silicone acrylic resin, or a silicone polyester resin.

8. The method of claim 7, wherein the silicone resin is a silicone polyester resin.

9. The method of any one of claims 1 to 8, wherein the photocatalytic material comprises a copper oxide loaded metal oxide.

10. A method for making a photocatalytic element comprising: providing a solution comprising 10% of KR5230 and 90% of propylene glycol monomethyl ether acetate (PGMEA);

adding a photocatalytic copper loaded plural phase titanium oxide material powder to the solution, at a ratio of 10: 1 (w/w) bindenphotocatalytic material;

pretreating a PET surface with corona treatment; and

spin coating the solution on the pretreated PET surface, at about 100 to about 2000 rpm for about 30 to about 60 seconds.

11. A photocatalytic element comprising a silicone polyester resin and a photocatalytic material, wherein the weight ratio of the resin to the photocatalytic material is between about 0.5 to about 2.0 to about 1.

12. The photocatalytic element of claim 11, wherein the silicone polyester resin is selected from KR500, KR5230 and KR5235.

13. A method for making a photocatalytic element comprising:

providing a suspension comprising a binder, photocatalytic material, a photo- initiator and an organic solvent, wherein the weight ratio of the binder to the photocatalytic material is about 1.0 to 20 parts binder to about 1 part photocatalytic material; and

applying the suspension to a substrate surface.

14. The method of claim 13, wherein the binder comprises an ultraviolet curable urethane resin.

15. The method of claim 13 or 14, wherein the organic solvent is a d-C₇ ketone.

16. The method of claim 13 or 14, wherein the organic solvent is a C1 -C7 alcohol.

17. The method of claim 13 or 14, wherein the organic solvent is selected from cyclopentanone, propylene glycol monomethyl ether acetate (PGMEA), N- methylpyrrolidone (NMP), methyl ethyl ketone (MEK), toluene, ethyl acetate and butyl acetate.

18. The method of any one of claims 13 to 17, wherein the suspension further comprises a dispersing agent.

19. The method of claim 18, wherein the dispersing agent is selected from a cationic dispersing agent, an anionic dispersing agent, and a non-ionic dispersing agent.

20. The method of any one of claims 13 to 19, wherein the photoinitiator is selected from IRGACURE 907 and IRGACURE 2022.

21. The method of any one of claims 13 to 20, wherein the photocatalytic material comprises a copper oxide loaded metal oxide.

22. A method for making a photocatalytic element comprising:

providing a solution comprising 10% by weight of a urethane acrylate resin, less than 1.0% by weight of a photoinitiator and 90% by weight of cyclopentone;

adding a photocatalytic copper loaded plural phase titanium oxide material powder to the solution, at a ratio of 5: 1 (w/w) bindenphotocatalytic material;

pretreating a PET surface with corona treatment; and

tape casting the suspension on the pre treated PET surface.

23. A photocatalytic element comprising a urethane acrylate resin and a photocatalytic material, wherein the weight ratio of the resin to the photocatalytic material is between about 0.5 to about 10 to about 1.

24. The photocatalytic element of claim 23, wherein the urethane acrylate resin is selected from UNIDIC 17806, EBECRYL 8701, EBECRYL 8301, EBECRYL 8405, OC-3021 , OC-4021 , OC-4122, HC-5619, and UVHC3000.