PHOTOCATALYST AND METHOD FOR FABRICATING THE SAME

Abstract

The present invention provides a metal/metal oxide doped-WO.sub.3 flower-like assemblies as a photocatalyst applied to photocatalytic inactivation of influenza virus and bacteria under UV or visible light activation, and further provides a surface-modulator-driven synthesis method for producing WO.sub.3 flower-like assemblies, as well as doping methods for doping the metal/metal oxide to the WO.sub.3 flower-like assemblies. The metal/metal oxide doped in WO.sub.3 flower-like assemblies can further enhance the antiviral and antibacterial performances.

Claims

1. A photocatalyst comprising: a tungsten oxide (WO.sub.3) flower-like assembly comprising corners and edges at a surface of the WO.sub.3 flower-like assembly; and particles of a metal or a metal oxide, wherein the particles are distributed on the surface of the WO.sub.3 flower-like assembly.

2. The photocatalyst of claim 1, wherein the WO.sub.3 flower-like assembly comprises WO.sub.3 nanoplates aggregated to form at least a portion of the surface of the WO.sub.3 flower-like assembly for providing the corners and the edges.

3. The photocatalyst of claim 1, wherein the WO.sub.3 flower-like assembly comprises WO.sub.3 nanoplates aggregated to form the surface of the WO.sub.3 flower-like assembly for providing the corners and the edges.

4. The photocatalyst of claim 1, wherein the metal is titanium (Ti), zirconium (Zr), manganese (Mn), iron (Fe), palladium (Pd), platinum (Pt), copper (Cu), silver (Ag), zinc (Zn), aluminum (Al) or cerium (Ce); and the metal oxide is an oxide of Ti, Zr, Mn, Fe, Pd, Pt, Cu, Ag, Zn, Al or Ce.

5. The photocatalyst of claim 1, wherein each particle has a particle size between 100 nm and 900 nm.

6. The photocatalyst of claim 1, wherein the photocatalyst has a mass concentration of the particles between 0.01% and 50%.

7. The photocatalyst of claim 1, wherein the WO.sub.3 flower-like assembly has a particle size between 100 nm and 250 nm, and has a round shape, a spherical shape or a flower-like shape.

8. The photocatalyst of claim 1, wherein the WO.sub.3 flower-like assembly is further doped with a metal ion, the metal ion being an ion of Ti, Zr, Mn, Fe, Pd, Pt, Cu, Ag, Zn, Al or Ce.

9. A disinfection material comprising the photocatalyst of claim 1.

10. A method for fabricating a photocatalyst comprising: providing a modulator solution comprising a dicarboxylic acid or oxalic acid; providing a sodium tungstate dihydrate solution; mixing the sodium tungstate dihydrate solution and the modulator solution thereby forming a first mixture solution; adding an acid into the first mixture solution thereby forming a second mixture solution; heating the second mixture solution thereby forming a first precipitate; collecting the first precipitate from the second mixture solution; the first precipitate thereby forming WO.sub.3 flower-like assemblies; and doping the WO.sub.3 flower-like assemblies with particles of a metal or a metal oxide such that the particles are distributed on the surface of each WO.sub.3 flower-like assembly thereby forming the photocatalyst.

11. The method of claim 10, wherein said doping comprises mechanically mixing the WO.sub.3 flower-like assemblies and a powder comprising the particles to distribute the particles on the surface of each WO.sub.3 flower-like assembly.

12. The method of claim 10, wherein said doping comprises: dispersing the WO.sub.3 flower-like assemblies in a solution containing the particles to distribute the particles on the surface of each WO.sub.3 flower-like assembly thereby forming second precipitate; collecting the second precipitate from the solution; and drying the second precipitates thereby forming the photocatalyst.

13. The method of claim 10, wherein the metal is Ti, Zr, Mn, Fe, Pd, Pt, Cu, Ag, Zn, Al or Ce.

14. The method of claim 10, wherein the metal oxide is an oxide of Ti, Zr, Mn, Fe, Pd, Pt, Cu, Ag, Zn, Al or Ce.

15. The method of claim 10, wherein the dicarboxylic acid is 1,4-benzendicarboxylic acid.

16. The method of claim 10, wherein the sodium tungstate dihydrate solution comprises sodium tungstate dihydrate in a concentration between 0.05 mol/L and 0.30 mol/L.

17. The method of claim 10, wherein the sodium tungstate dihydrate and oxalic acid in the first mixture solution are in a mass ratio between 1:1.1 and 1:2.0.

18. The method of claim 10, wherein the acid is hydrochloric acid (HCl).

19. The method of claim 18, wherein the HCl is added into the first mixture solution to adjust pH value of the second mixture solution to be 0.1 to 1.0.

20. The method of claim 10, wherein the second mixture solution is heated at 80-100° C. for 8-12 hours.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0030] The appended drawings, where like reference numerals refer to identical or functionally similar elements, contain figures of certain embodiments to further illustrate and clarify the above and other aspects, advantages and features of the present invention. It will be appreciated that these drawings depict embodiments of the invention and are not intended to limit its scope. The invention will be described and explained with additional specificity and detail through the use of the accompanying drawings in which:

[0031] FIG. 1A depicts a method for fabricating metal oxide-doped WO.sub.3 flower-like assemblies according to certain embodiments;

[0032] FIG. 1B depicts the ROS formation mechanism by the metal oxide-doped WO.sub.3 flower-like assemblies;

[0033] FIG. 2A shows a field emission scanning microscopy (FESEM) image of WO.sub.3 flower-like assemblies of Example 1 (with H.sub.2C.sub.2O.sub.4:Na.sub.2WO.sub.4=1.4:1) with low magnification;

[0034] FIG. 2B shows a FESEM image of the WO.sub.3 flower-like assemblies high magnification;

[0035] FIG. 3A shows a FESEM image of CuO-doped WO.sub.3 nanoflowers of Example 2;

[0036] FIG. 3B shows the energy-dispersive X-ray spectroscopy (EDX) of the CuO-doped WO.sub.3 nanoflowers;

[0037] FIG. 4 shows a schematic diagram depicting an irradiation set-up for an antibacterial test;

[0038] FIG. 5A shows an antibacterial test (E. coli) result of a control glass slide sample without WO.sub.3 coating;

[0039] FIG. 5B shows an antibacterial test (E. coli) result of a WO.sub.3 flower-like assemblies-coated sample prepared by Example 1;

[0040] FIG. 6A shows an antibacterial test (E. coli) result of a control glass slide sample without WO.sub.3 coating;

[0041] FIG. 6B shows an antibacterial test (E. coli) result of a commercial WO.sub.3 particles-coated sample;

[0042] FIG. 6C shows an antibacterial test (E. coli) result of a copper(II) oxide (CuO)-doped WO.sub.3 flower-like assemblies-coated sample prepared by Example 2;

[0043] FIG. 6D shows a FESEM image of the commercial WO.sub.3 particles; and

[0044] FIG. 6E shows a FESEM image of the CuO-doped WO.sub.3 flower-like assemblies.

[0045] Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been depicted to scale.

DETAILED DESCRIPTION OF THE INVENTION

[0046] Accordingly, the present disclosure provides a metal/metal oxide-doped WO.sub.3 flower-like assemblies as a photocatalyst for antiviral and antibacterial functions and a surface-modulator-driven synthesis method for fabricating the WO.sub.3 flower-like assemblies. The metal/metal oxide-doped WO.sub.3 flower-like assemblies can be applied to photocatalytic inactivation of influenza virus and bacteria under UV or visible light activation. The metal/metal oxide doped in WO.sub.3 flower-like assemblies can further enhance the antiviral and antibacterial performance.

[0047] As the morphology of WO.sub.3 affects the charge separation and recombination during the photocatalytic process. The present WO.sub.3 flower-like assembly resembles a flower and is assembled by nanostructures (i.e., nano-building-blocks) aggregated to form the WO.sub.3 flower-like assembly resembles. The WO.sub.3 flower-like assembly includes corners and edges, and atoms located in corners and edges have more catalytic activity because of the low coordination numbers. Particularly, the WO.sub.3 flower-like assembly includes WO.sub.3 nanoplates aggregated to form the surface of the WO.sub.3 flower-like assembly. As the WO.sub.3 nanoplates have sharp corners and edges, they shows higher photocatalytic activity in comparison with the WO.sub.3 nanospheres. In addition, the flower shape of the WO.sub.3 flower-like assembly can further increase the surface area for enhancing the antiviral and antibacterial performance.

[0048] Provided herein is a photocatalyst comprising: a tungsten oxide (WO.sub.3) flower-like assembly comprising corners and the edges at the surface of the WO.sub.3 flower-like assembly; and particles of a metal or a metal oxide; wherein the particles are distributed on the surface of the WO.sub.3 flower-like assembly.

[0049] In certain embodiments, the particles are distributed partially or fully on the surface of each WO.sub.3 flower-like assembly.

[0050] In certain embodiments, the WO.sub.3 flower-like assembly comprises WO.sub.3 nanoplates aggregated to form at least a portion of the surface of the WO.sub.3 flower-like assembly for providing the corners and the edges.

[0051] In certain embodiments, the WO.sub.3 flower-like assembly comprises WO.sub.3 nanoplates aggregated to form the surface of the WO.sub.3 flower-like assembly for providing the corners and the edges.

[0052] In certain embodiments, the metal is titanium (Ti), zirconium (Zr), manganese (Mn), iron (Fe), palladium (Pd), platinum (Pt), copper (Cu), silver (Ag), zinc (Zn), aluminum (Al) or cerium (Ce); and the metal oxide is titanium oxide, zirconium oxide, manganese oxide, iron oxide, palladium oxide, platinum oxide, copper oxide, silver oxide, zinc oxide, aluminum oxide or cerium oxide.

[0053] In certain embodiments, each particle has a particle size between 100 nm and 900 nm

[0054] In certain embodiments, the photocatalyst has a mass concentration of the particles between 0.01% and 50%.

[0055] In certain embodiments, the WO.sub.3 flower-like assembly has a particle size between 100 nm and 250 nm.

[0056] In certain embodiments, the WO.sub.3 flower-like assembly has a round shape or a spherical shape.

[0057] In certain embodiments, the WO.sub.3 flower-like assembly is further doped with a metal ion, the metal ion being an ion of Ti, Zr, Mn, Fe, Pd, Pt, Cu, Ag, Zn, Al or Ce.

[0058] Provided herein is a disinfection material comprising the photocatalyst described above.

[0059] Provided herein is a method for fabricating a photocatalyst comprising: providing a modulator solution comprising a dicarboxylic acid or oxalic acid; providing a sodium tungstate dihydrate solution; mixing the sodium tungstate dihydrate solution and the modulator solution thereby forming a first mixture solution; adding an acid into the first mixture solution thereby forming a second mixture solution; heating the second mixture solution thereby forming a first precipitate; collecting the first precipitate from the second mixture solution; drying the first precipitate thereby forming WO.sub.3 flower-like assemblies; and doping the WO.sub.3 flower-like assemblies with particles of a metal or a metal oxide such that the particles are distributed on the surface of each WO.sub.3 flower-like assembly thereby forming the photocatalyst.

[0060] In certain embodiments, the particles are distributed partially or fully on the surface of each WO.sub.3 flower-like assembly.

[0061] In certain embodiments, the step of doping comprises mechanically mixing the WO.sub.3 flower-like assemblies and a powder comprising the particles to distribute the particles on the surface of each WO.sub.3 flower-like assembly.

[0062] In certain embodiments, the step of doping comprises: dispersing the WO.sub.3 flower-like assemblies in a solution containing the particles to distribute the particles on the surface of each WO.sub.3 flower-like assembly thereby forming second precipitate; collecting the second precipitate from the solution; and drying the second precipitates thereby forming the photocatalyst.

[0063] In certain embodiments, the metal is Ti, Zr, Mn, Fe, Pd, Pt, Cu, Ag, Zn, Al or Ce.

[0064] In certain embodiments, the metal oxide is titanium oxide, zirconium oxide, manganese oxide, iron oxide, palladium oxide, platinum oxide, copper oxide, silver oxide, zinc oxide, aluminum oxide or cerium oxide.

[0065] In certain embodiments, the dicarboxylic acid is 1,4-benzendicarboxylic acid.

[0066] In certain embodiments, the sodium tungstate dihydrate solution has a concentration of sodium tungstate dihydrate between 0.05 mol/L and 0.30 mol/L.

[0067] In certain embodiments, the mass ratio of sodium tungstate dihydrate and oxalic acid in the first mixture solution is between 1:1.1 and 1:2.0.

[0068] In certain embodiments, the acid is hydrochloric acid (HCl)

[0069] In certain embodiments, the HCl is added to adjust the pH value of the second mixture solution to be 0.1 to 1.0.

[0070] In certain embodiments, the second mixture solution is heated at 80-100° C. for 8-12 hours.

[0071] In certain embodiments, a method for fabricating a photocatalyst comprises: preparing a water solution of modulator by dissolving oxalic acid powder in deionized water; preparing a water solution of sodium tungstate dihydrate powder by dissolving sodium tungstate dihydrate powder in deionized water; dropwise addition of the sodium tungstate dihydrate water solution to the modulator water solution to form a first mixture solution; adding 37% HCl to the first mixture solution to from a second mixture solution with the pH value between 0.1 and 1.0; heating and stirring the second mixture solution; collecting the precipitate from the second mixture solution by centrifugation; washing the precipitate with water and ethanol; and air-drying the solid sample; and doping the solid sample with metal oxide.

[0072] The present method for fabricating WO.sub.3 flower-like assemblies is a simple surface-modulator-driven synthesis method. As shown FIG. 1A, the WO.sub.3 flower-like assemblies of the certain embodiments are prepared by using sodium tungstate dihydrate as a starting material, oxalic acid as a modulator for mediating the structure of the synthesized WO.sub.3 (e.g., assisting the formation of monoclinic), and HCl to control the pH value of the precursor aqueous solution. HCl is preferably used since alternate acid may lead to formation of by-products. The oxalic acid acts as a modulator to control the growth direction of WO.sub.3 nanoparticles for synthesizing self-assembled flower-like structure/nanoflowers. The introduction of enough amount of oxalic acid (e.g., oxalic acid/sodium tungstate dihydrate ratio of 1.5:1) provides sufficient oxalate ions to form hydrogen bonds with structural water of WO.sub.3 nanoplates, which results in the aggregation of nanoplates, and appears in a flower-like assemblies morphology (e.g., as shown in FIGS. 2A and 2B).

[0073] Referring to FIG. 1A, in step S11, sodium tungstate dihydrate solution is added into the oxalic acid by dropwise to form a first mixture solution. In step S12, HCl is added into the first mixture solution by dropwise to form a second mixture solution. In step S13, the second mixture solution is heated and refluxed to form a precipitate 101 of WO.sub.3 flower-like assemblies. In step S14, the precipitate 101 is collected by centrifugation and dried to form dry WO.sub.3 flower-like assemblies 102. In step S15, the dry WO.sub.3 flower-like assemblies 102 are dispersed in a metal ion solution for doping the WO.sub.3 flower-like assemblies with metal oxide particles 104 to form a precipitate 103 of metal oxide-doped WO.sub.3 flower-like assemblies. In this embodiment, the metal ions (e.g., Ti, Zr, Mn, Fe, Pd, Pt, Cu, Ag, Zn, Al or Ce ions) in the metal ion solution also act as a dopant doped into the WO.sub.3 flower-like assemblies. In step S16, the precipitate 103 is collected by centrifugation and dried to form dry metal oxide-doped WO.sub.3 flower-like assemblies 105, and each dry metal oxide-doped WO.sub.3 flower-like assembly includes the dry WO.sub.3 flower-like assembly 102 and the metal oxide particles 104 distributed on the dry WO.sub.3 flower-like assembly 102. Alternatively, after the step S14, the dry WO.sub.3 flower-like assemblies 102 are directly and mechanically mixed with a powder having the metal oxide particles 104 to form the metal oxide-doped WO.sub.3 flower-like assemblies 105 as shown in step S17.

[0074] The metal oxide particles 104 can enhance the photocatalytic activity of WO.sub.3 flower-like assembly 102. These co-catalysts can facilitate the multiple-electron reduction of oxygen, then the electron on the WO.sub.3 conduction band reduces oxygen to super oxide anion O.sub.2—effectively as shown in FIG. 1B. The formation of ROS is important for killing bacteria, virus, as well as organic pollutants dissociation.

Example 1: Preparation of WO.SUB.3 .Flower-Like Assemblies

[0075] As a specific example of the WO.sub.3 flower-like assemblies, sodium tungstate dihydrate (3.3 g, 0.01 mmol) was dissolved in 60 mL of deionized water to get a transparent solution of 0.17 mol/L. Oxalic acid (1.5 g, 0.015 mmol) was subsequently added into the reaction system and the obtain solution was stirred at room temperature for 30 mins. 1.5 mL of 37% HCl aqueous solution was added dropwise into the above solution under continuous stirring until pH 0.1. The reaction vessel was transferred into an oil bath of 90° C. After 4 hours reaction, the final yellow precipitates were centrifuged and washed repeatedly with deionized water and ethanol, followed by air-drying the sample in air, thus WO.sub.3 flower-like assemblies were obtained.

[0076] The SEM image of FIG. 2A shows a plurality of WO.sub.3 flower-like assemblies 20 of Example 1. As shown in FIG. 2B, the WO.sub.3 flower-like assembly 20 have a plurality of WO.sub.3 nanoplates 21 aggregated randomly to form the surface of the WO.sub.3 flower-like assembly 20, and the WO.sub.3 nanoplate 21 has corners 22 and edges 23, and atoms located in the corners 22 and the edges 23 can provide more catalytic activity for enhancing the antibacterial and antiviral performances.

Example 2: Preparation of CuO-Doped WO.SUB.3 .Flower-Like Assemblies

[0077] As a specific example of the CuO-doped WO.sub.3 flower-like assemblies, there is a mixed powder containing 99.5 wt % of WO.sub.3 flower-like assemblies and 0.5 wt % of copper (II) oxide powder. The mixed powder is prepared by grounding copper (II) oxide and WO.sub.3 flower-like assemblies together for 10 mins.

[0078] FIG. 3A shows CuO-doped WO.sub.3 nanoflower 30 of Example 2 including WO.sub.3 nanoflower 31 and CuO particles distributed on the surface of the WO.sub.3 nanoflower 31. The WO.sub.3 nanoflower 31 includes WO.sub.3 nanoplates 32 aggregated randomly to form the surface of the WO.sub.3 nanoflower 31 and the WO.sub.3 nanoplate 31 has corners 33 and edges 34. FIG. 3B shows the EDX of the CuO-doped WO.sub.3 nanoflowers 30 which indicates the presence of CuO, and the CuO-doped WO.sub.3 nanoflowers has a mass concentration of Cu with 6.54%.

[0079] To evaluate the antibacterial and antivirus properties, the WO.sub.3 flower-like assemblies of Example 1 were undergone an antibacterial property evaluation test adopted from ISO 27447:2009 and an antiviral property evaluation test adopted from ISO18184:2019.

[0080] To prepare the test specimens, the WO.sub.3 flower-like assemblies were mixed with a dispersion medium e.g., water. A dispersion process was performed by an ultrasonic disperser. A testing sample was produced by coating the obtained dispersion liquid on a test piece such as a glass plate. This general method includes dripping, spin coating, dipping, spraying or the like. The WO.sub.3 flower-like assemblies were adhered in a range of 0.02 mg/cm.sup.2 or more and 40 mg/cm.sup.2 or less on a 5×5 cm glass slide.

[0081] FIG. 4 shows a schematic diagram depicting an irradiation set-up for the antibacterial test. The irradiation set-up includes light source 41, plastic lid 42, cover slide glass 43, WO.sub.3-coated glass slide 44, wet filter paper 45, metal nut 46, metal plate 47, and bacterial suspension 48.

[0082] The percent reduction of bacteria was evaluated according to a glass adhesion test based on an adopted ISO 27447:2009 test (replacing UV light source to a visible light source 41). The bacterial suspension 48 (0.1 mL; 10.sup.5 CFU mL.sup.−1) was pipetted onto the test surface (5×5 cm.sup.2) and a cover glass applied (4×4 mm.sup.2). The sample was placed in a square Petri dish (100×100×20 mm.sup.3) equipped with wet filter paper 45 and a square metal plate 47 for support as shown in FIG. 4. At least one bacterium selected from among Staphylococcus aureus, Escherichia coli, Klebsiella pneumonia and Pseudomonas aeruginosa. A visible light lamp (1000 1×) was used as a light source. After irradiation for 4 hours, sample on the cover glass were shaken out into 3 mL of saline solution, serially diluted and spread onto an agar media. In order to determine the number of viable cells (counted as CFU mL.sup.−1), the samples were incubated at 37° C. for 24 h and the bacterial colonies were then counted.

[0083] FIGS. 5A and 5B shows the antibacterial test results of the control sample and WO.sub.3 flower-like assemblies on LB agar plate. As shown in FIG. 5A, E. coli colonies is visible on the control sample while no visible colonies appears on the WO.sub.3 flower-like assemblies-treated sample as shown in FIG. 5B, which indicates the WO.sub.3 flower-like assemblies can kill bacteria effectively.

[0084] The antiviral activity of the WO.sub.3 flower-like assemblies was evaluated according to an adopted ISO18184:2019 test method (using WO.sub.3 flower-like assemblies coated glass plates as test specimen and irradiating the sample with visible light). A visible light source (1000 1×) was used and the sample was irradiated for 4 hours. The concentrated virus was diluted with PBS to adjust the virus titer at six TCID.sub.50/ml. The reaction was carried out at room temperature (25° C.). The WO.sub.3 flower-like assemblies coated glass plate was also evaluated in a dark condition in a stainless steel box. At the indicated time, the virus spotted glass plate was taken and rinsed with 1 ml of maintenance medium for MDCK cells in a plastic bag. The recovered virus was transferred into a microtube and centrifuged to remove debree, and the resulting supernatant was titrated on MDCK cells.

[0085] The percent reduction of bacteria or virus was calculated as follows: Percent Reduction=(A−B)×100/A, where A is the number of viable microorganisms before treatment, and B is the number of viable microorganisms after treatment.

[0086] Table 1 below shows test results of the sample of CuO-doped WO.sub.3 flower-like assemblies of Example 2 according to antiviral test (H1N1). The sample of CuO-doped WO.sub.3 flower-like assemblies show 99.99% of virus reduction.

TABLE-US-00001 TABLE 1 Irradiation First test Second test Third test Average value Mean Antiviral time Testing Log(TCI Log(TCI Log(TCI Log(TCI logarithm of efficiency Virus (h) condition Group D.sub.50/ml) D.sub.50/ml) D.sub.50/ml) D.sub.50/ml) inactivation (%) A/PR8/34 4 Irradiation Control sample 5.67 6.00 6.00 5.89 5.89 >99.99 (H1N1) condition Test sample 0.00 0.00 0.00 0.00 Dark Control sample 5.67 6.00 6.00 5.89 5.89 >99.99 condition Test sample 0.00 0.00 0.00 0.00

[0087] The antibacterial and antivirus properties of WO.sub.3 flower-like assemblies can be enhanced by doping with transition metal element or their oxides. The method of combining the WO.sub.3 flower-like assemblies and the transition metal element (specifically, a single element or a metal oxide of at least one element selected from among Ti, Zr, Mn, Fe, Pd, Pt, Cu, Ag, Zn, Al and Ce) includes various combining methods such as a direct mixing method for mixing powders and an impregnation method.

[0088] To evaluate the antibacterial properties, the CuO-doped WO.sub.3 flower-like assemblies of Example 2 were undergone an antibacterial property evaluation test adopted from ISO 27447:2009.

[0089] FIGS. 6A-6C show the antibacterial test results of the control, commercial WO.sub.3 particles and WO.sub.3 flower-like assemblies on LB agar plate. As shown in FIGS. 6A and 6B, E. coli colonies are visible on the control sample and the commercial WO.sub.3 particles-coated sample while no visible colonies appears on the CuO-doped WO.sub.3 flower-like assemblies-coated sample as shown in FIG. 6C, which indicates the CuO-doped WO.sub.3 flower-like assemblies can kill bacteria effectively. Correspondingly, the morphology of the commercial WO.sub.3 particles and CuO-doped WO.sub.3 flower-like assemblies are shown in FIGS. 6D and 6E respectively. In addition, some reports revealed that Cu(II) doped WO.sub.3 nanoparticles merely provide ˜85% of antibacterial reduction which is smaller when compared with CuO-doped WO.sub.3 flower-like assemblies with >99.99% under 120 mins visible light irradiation. It indicates that the structure/morphology of the WO.sub.3 is a key factor in antibacterial/antiviral property.

[0090] Thus, it can be seen that an improved photocatalyst exerts the antibacterial and antiviral performances without requiring irradiation of UV light. Therefore, practical antibacterial performance can be obtained even when the metal/metal oxide-doped WO.sub.3 flower-like assemblies catalyst is applied to products, which are used in an indoor environment having a low illuminance, such as ceilings, walls, floors, furniture and home electric appliances in the interior. In addition, metal/metal oxide doped in WO.sub.3 flower-like assemblies can enhance the antibacterial and antiviral performances.

[0091] Although the invention has been described in terms of certain embodiments, other embodiments apparent to those of ordinary skill in the art are also within the scope of this invention. Accordingly, the scope of the invention is intended to be defined only by the claims which follow.