BACKGROUND

1. Technical Field

The present disclosure relates to photocatalytic compositions comprising photocatalytic materials, in particular, to photocatalytic compositions for improving antibacterial and antiviral activities.

2. Description of Related Art

Photocatalysts are semiconductor materials, and the most common photocatalytic semiconductor material can be made of titanium dioxide (TiCU) . When the photocatalyst is irradiated by light, the energy of the photon can be absorbed by TiCf. and then the electron is excited from its ground state to a higher energy level, thereby raising an electron in the valence band to the conduction band, and resulting in a pair of free electron and hole. The hole can produce oxygen molecules or hydroxyl free radicals (OH ) that has strong oxidizing ability. The electron can generate hydrogen peroxide (H2O2) or super oxygen (O ² ) in the presence of oxygen molecules that also has strong oxidizing ability. Therefore, the photocatalyst has potent oxidizing power, and is considered as one of the materials with antibacterial and bactericidal prospects.

In most cases, ultraviolet (UV) irradiation is required for the photocatalyst to acquire antibacterial activity; however, there may not be available ultraviolet light in indoor environment. Therefore, the photocatalyst applicable to visible light has also been developed. For example, the nano-photocatalyst TiCF is paired with other nano-ionic materials, such as CuBiS2 (CBS), CuGaS2 (CGS), Cu2ZnSnS4 (CZTS) and Ag2S, and mixed in a porous carrier material to make powder, which can be irradiated by visible light to produce the bactericidal effect.

Nevertheless, the semiconductor materials or metal ions used in the visible light-active photocatalysts can only absorb the light with certain wavelength, which may not predominantly exist in the environment, such that the bactericidal effect of a visible light-active photocatalyst is generally worse than that of the photocatalyst irradiated by ultraviolet light. Hence, there still exists an unmet need to provide a photocatalytic material that has potent antibacterial, bactericidal, and even antiviral activities under the visible light irradiation.

SUMMARY

The present disclosure provides a photocatalytic composition that can adjust the wavelength of light and its antibacterial and antiviral applications. The photocatalytic composition of the present disclosure is formed by mixing a photocatalyst with a quantum dot that can adjust the wavelength of light. Under the irradiation of ambient light, the quantum dot can emit the light whose wavelength is required by the photocatalyst, thereby supplementing the insufficient amount of ambient light, and improving the antibacterial and antiviral activities of the photocatalyst.

In at least one embodiment of the present disclosure, the photocatalytic composition of the present disclosure comprises a photocatalytic material, a silver nanoparticle, and a quantum dot, and has photocatalytic activity in the visible light spectrum. In some embodiments of the present disclosure, the photocatalytic material comprises titanium dioxide (TiCU) . In some embodiments of the present disclosure, the photocatalytic material further comprises CuBiS2, CuGaS2, Cu2ZnSnS4, Ag2S, or any combination thereof.

In at least one embodiment of the present disclosure, the quantum dot comprises CdS, CdSe, Cd/ZnS, ZnS, CdSe/ZnS, a perovskite quantum dot, or any combination thereof. In some embodiments of the present disclosure, the quantum dot is a CdS quantum dot, a CdSe/ZnS quantum dot, or a perovskite quantum dot. In some embodiments of the present disclosure, the quantum dot is a blue light-emitting quantum dot, such as a quantum dot absorbing the light with a wavelength from 360 nanometer (nm) to 780 nm, and emitting the light with a wavelength from 435 nm to 480 nm.

In some embodiments of the present disclosure, the present disclosure further provides an antimicrobial agent, such as an antibacterial agent, an antiviral agent, or a combination thereof. In some embodiments, the antimicrobial agent comprises the above-mentioned photocatalytic composition, and is formulated into a spray, a coating agent, or a thin fdm.

In some embodiments of the present disclosure, the present disclosure also provides a method of manufacturing an article having antibacterial and antiviral activities, comprising applying the above- mentioned antibacterial agent and antiviral agent on an article, and exposing the article to ultraviolet light or visible light for the article to have antibacterial and antiviral activities. In some embodiments of the present disclosure, the article is exposed to the ultraviolet light or the visible light for less than 1 hour, such as less than 50 minutes, less than 45 minutes, less than 30 minutes, less than 20 minutes, less than 15 minutes, less than 10 minutes, less than 5 minutes, less than 3 minutes, less than 1 minute, less than 30 seconds, less than 10 seconds, and less than 5 seconds.

The photocatalytic composition provided in the present disclosure has a high photocatalytic effect under the irradiation of sunlight, fluorescent lamp, visible light, or ultraviolet light, and thus can exhibit excellent antibacterial and antiviral activities in an environment where only visible light exists. The photocatalytic composition of the present disclosure can be formulated into a spray, a coating agent, a thin fdm, and the like, and it will not induce skin irritation or sensitization, and is suitable for application to various article surfaces, such as a mask, a face shield, a glove, a fdter cover, and the outer layers of other protective covers, or can be sprayed onto the surface of a target, and further inactivates bacteria and viruses by exposure to ambient light.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure can be more fully understood by reading the following descriptions of the embodiments, with reference made to the accompanying drawings.

FIG. 1 shows the absorption spectrum of Fe/TiO2 photocatalytic powders prepared by incorporating iron nanoparticles into TiO2 photocatalysts in different proportions. Abs: absorbance.

FIG. 2 shows the absorption spectrum of Ag/TiCE photocatalytic powders prepared by incorporating silver nanoparticles into TiCE photocatalysts in different proportions. Abs: absorbance.

FIG. 3 shows that the CdSe/CdS/ZnS quantum dots with different particle sizes emit fluorescence of different wavelengths under light irradiation.

FIG. 4 shows the absorption spectrum and the emission spectrum of the quantum dot whose dominant wavelength is 620 nm. FWHM: full width at half maximum.

FIG. 5 is a schematic diagram of a photocatalytic thin film formed by the photocatalytic composition according to one embodiment of the present disclosure.

FIGs. 6A and 6B show the antibacterial effect of a photocatalytic thin film without treatment or treated with UV irradiation for 15 minutes, respectively.

FIG. 7 shows the results of the cytotoxic reactivity assay of the photocatalytic composition according to one embodiment of the present disclosure. Normal control: no treatment. Negative control: high density polyethylene film. Positive control: zinc diethyldithiocarbamate polyurethane film. Treatment group: the photocatalytic composition of the present disclosure. 100x magnification. Neutral red stain.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The following examples are used for illustrating the present disclosure. A person skilled in the art can easily conceive the other advantages and effects of the present disclosure, based on the disclosure of the specification. The present disclosure can also be implemented or applied as described in different examples. It is possible to modify or alter the following examples for carrying out this disclosure without contravening its scope, for different aspects and applications.

It is further noted that, as used in this disclosure, the singular forms “a,” “an,” and “the” include plural referents unless expressly and unequivocally limited to one referent. The term “or” is used interchangeably with the term “and/or” unless the context clearly indicates otherwise.

As used herein, the term “comprising” or “comprises” is used in reference to compositions, methods, and respective component(s) thereof, which are included in the present disclosure, yet open to the inclusion of unspecified elements or steps, whether essential or not.

As used herein, the term “about” generally means within 10%, 5%, 1%, or 0.5% of a given value or range. Alternatively, the term “about” means within an acceptable standard error of the mean when considered by one of ordinary skill in the art. Unless otherwise expressly specified, all of the numerical ranges, amounts, values and percentages such as those for quantities of materials, durations of time periods, temperatures, operating conditions, ratios of amounts, and the likes disclosed herein should be understood as modified in all instances by the term “about.”

The photocatalytic composition of the present disclosure comprises a photocatalytic material, a silver nanoparticle, and a quantum dot. By the combination of the quantum dot that can adjust a wavelength of light, the photocatalyst, and the silver nanoparticle having antibacterial and antiviral activities, the photocatalytic composition of the present disclosure may exhibit excellent antibacterial and antiviral activities upon visible light irradiation, wherein the virus described in the present disclosure includes a DNA virus and an RNA virus, such as influenza virus, enterovirus, and coronavirus, e.g., SARS-CoV-2, and is not limited thereto.

In at least one embodiment of the present disclosure, the photocatalytic material comprises TiCf (e.g., rutile TiCF and anatase TiCf). such as nano-TiCf. and may further comprise other materials. For example, the photocatalytic material may comprise TiCf as the N-type layer and the other materials (e.g., CuBiS2, CuGaS2, Cu2ZnSnS4, and Ag2S) as the P-type layer, which may be paired with TiCU respectively, to form an ultraviolet light- and/or visible light-active photocatalytic composite.

In at least one embodiment of the present disclosure, the photocatalytic material can be a visible lightactive photocatalytic composite formed by incorporating an iron nanoparticle, a silver nanoparticle, a gold nanoparticle, and/or a platinum nanoparticle into a nano-TiCf photocatalyst. For example, the photocatalytic material can comprise the silver nanoparticle, the gold nanoparticle, and the platinum nanoparticle into the nano-TiCF photocatalyst. As shown in FIGs. 1 and 2, the absorption spectrums generated by the nano-TiCF photocatalysts incorporated with different amounts of Fe and Ag ions are shown respectively, and it is observed that there appears redshift moving toward the visible spectrum.

In at least one embodiment of the present disclosure, the particle size of the quantum dot in the photocatalytic composition of the present disclosure is adjustable, so as to form a quantum dot that can be irradiated by a light source with a specific wavelength to emit the light of wavelength required for the photocatalytic effect of the photocatalyst. In some embodiments of the present disclosure, the quantum dot in the photocatalytic composition of the present disclosure is a blue light-emitting quantum dot, which can absorb visible light of different wavelengths and emit blue light.

In at least one embodiment of the present disclosure, the quantum dot may be a single-component quantum dot, e.g., CdS quantum dot. In some embodiments of the present disclosure, the quantum dot may be a quantum dot with a multilayered nanocore-shell structure; for example, the multilayered structure may include the component selected from CdS, CdSe, Cd/ZnS, ZnS, CdSe/ZnS, a perovskite quantum dot, or any combination thereof. In some embodiments of the present disclosure, the quantum dot may be a mixture of multi-wavelength quantum dots that have different nanoparticle sizes. As shown in FIG. 3, CdSe/CdS/ZnS quantum dots with a multilayer structure and different particle sizes according to some embodiments of the present disclosure emit fluorescence of different wavelengths under the irradiation of a light source. Also, FIG. 4 shows the absorption spectrum and the emission spectrum of the quantum dot with a dominant wavelength of 620 nm according to some embodiments of the present disclosure.

In at least one embodiment of the present disclosure, the photocatalytic composition of the present disclosure may further comprise a fluorescent powder. In some embodiments of the present disclosure, the fluorescent powder may be a single-wavelength fluorescent powder, e.g., a SrS:Eu ²⁺ fluorescent powder, which emits red light upon the blue light irradiation. In some embodiments of the present disclosure, the fluorescent powder may also be a multi-wavelength fluorescent powder, e.g., a YAG:Ce ³⁺ fluorescent powder (YAG: yttrium aluminium garnet), which emits white light upon the blue light irradiation. In some embodiments of the present disclosure, the photocatalytic composition of the present disclosure may comprise both of the above fluorescent powders.

In at least one embodiment of the present disclosure, the photocatalytic composition of the present disclosure may further comprise a matrix, such as a soluble high molecular polymer or an insoluble high molecular polymer. In some embodiments of the present disclosure, the examples of the soluble high molecular polymer include, but are not limited to, polyfmethyl methacrylate) (PMMA), polystyrene (PS), polyethylene (PE), and polycarbonate (PC). In some embodiments of the present disclosure, the examples of the insoluble high molecular polymer include, but are not limited to, silicone.

In at least one embodiment of the present disclosure, the photocatalytic composition of the present disclosure may be formulated into an antibacterial agent or an antiviral agent, and its use form is not particularly limited; for example, the photocatalytic composition may be in a form of a spray, a coating agent, or a thin film. The thin film of the present disclosure may be a single-layer or multi-layer thin film. For example, the antibacterial agent or the antiviral agent of the present disclosure comprises a spray of the above photocatalytic composition, which is arranged in a container equipped with a nozzle, and can be sprayed through the nozzle of the container on, for example, a mask, a face shield, a glove, a protective clothing, a filter, or those that need to be protected against bacteria or viruses, e.g., a daily necessity, an utensil, a cloth, a housing facility, a cabin air filter, a medical equipment, a plastic surface, a glass surface, a metal surface, the interior of a vehicle (such as an airplane, boat, car, and mass transit), a phone panel, or a kiosk, or on a skin surface. The sprayed target can provide a protective effect against bacteria and viruses. In at least one embodiment of the present disclosure, the nozzle of the container filled with the antibacterial and antiviral spray of the present disclosure may be further equipped with a light source of ultraviolet light or visible light, such that the photocatalytic composition contained therein is directly exposed to the irradiation of ultraviolet light or visible light during the spraying process, thereby inducing the antibacterial and antiviral activities.

FIG. 5 is a schematic diagram of a photocatalytic thin film formed by the photocatalytic composition according to at least one embodiment of the present disclosure. The photocatalytic thin film 1 comprises a quantum dot 11, a photocatalytic composite 12, a fluorescent powder 13, and a matrix 14. In some embodiments of the present disclosure, the quantum dot 11 comprises a single -component quantum dot 111, a multilayered nanocore -shell quantum dot 112, or a combination thereof. The multilayered nanocore-shell quantum dot 112 may consist of a CdSe layer 1121, a CdS layer 1122, a Cd/ZnS layer 1123, and a ZnS layer 1124, and is not limited thereto. In some embodiments of the present disclosure, the quantum dot 11 has an average particle size of 25 ± 2 nm with an emission wavelength of 460 nm and a full width at half maximum (FWHM) of 28 nm. In some embodiments of the present disclosure, the photocatalytic composite 12 may be a composite formed from TiCF as the N-type semiconductor powder 121 and the other materials (e.g., CdS, CdSe, Cd/ZnS, ZnS, CdSe/ZnS, and a perovskite quantum dot) as the P-type semiconductor powder 122. In some embodiments of the present disclosure, the photocatalytic composite 12 of the present disclosure may also comprise an iron nanoparticle 123, a silver nanoparticle 124 or a combination thereof added therein. In some embodiments of the present disclosure, the fluorescent powder 13 comprises a SrS:Eu ²⁺ fluorescent powder 131, a YAG:Ce ³⁺ fluorescent powder 132, or a combination thereof, and is not limited thereto.

The present disclosure also provides a method of manufacturing an article having the antibacterial and antiviral activities, comprising applying the antibacterial agent and/or the antiviral agent of the present disclosure on an article, and exposing the article to ultraviolet light or visible light, thereby forming the article having the antibacterial and antiviral activities. In some embodiments of the present disclosure, the examples of the article include, but are not limited to, a single article composed of a general member, such as a fiber, a metal, ceramics and glass, and a composite article composed of two or more of the above members.

There is no particular limitation to the place where the antibacterial and antiviral agent of the present disclosure is used. For example, in addition to the place where any light exists, the antibacterial and antiviral agent of the present disclosure may also be used in a dark place. After being irradiated by light, the antibacterial and antiviral agent of the present disclosure can still have excellent antibacterial and antiviral activities in the dark place, and thus can continuously inactivate bacteria or viruses. For example, the antibacterial and antiviral agent of the present disclosure may be applied to wall, floor, ceiling, and the like, and may also be applied in the dark place, such as the inside of machinery, the storage room of a refrigerator, and the place in a health facility that becomes a dark place at night or when not in use.

Many examples have been used to illustrate the present disclosure. The examples below should not be taken as a limit to the scope of the present disclosure.

EXAMPLES

Example 1 : Culture of cells

Human liver cancer cell Huh7 was incubated in Dulbecco’s Modified Eagle Medium (DMEM; Gibco) containing 10% fetal bovine serum (FBS; Gibco) in a 37°C incubator with 5% CO2. After cell passage, cells were rinsed with phosphate buffered saline (PBS) twice, followed by addition of an adequate amount of 2.5% ethylenediaminetetraacetic acid (EDTA) for cell treatment. After the cells fell off the surface of the culture dish, fresh DMEM medium with 10% FBS was added to disperse and evenly distribute the cells in the culture dish, and then incubated in the 37°C incubator with 5% CO2.

Example 2: Culture of viruses

Coronavirus 229E was incubated in the Huh7 cells. Specifically, the cells were incubated in a DMEM medium containing 10% FBS, and rinsed with PBS when cultures reached to 90% confluence. Further, the cells were infected with viruses in an amount of about 0.01 MOI (multiplicity of infection), followed by addition of DMEM medium containing 10% FBS, and then incubated in a 35°C incubator with 5% CO2 for 48 hours. When the cytopathic effect (CPE) was observed in 50% of the cells, all the culture media containing viruses and the cells with CPE were collected. After centrifugation at 2,000 rpm for 10 minutes, the supernatant was collected and stored in aliquots at -80°C.

Example 3 : Preparation of a photocatalytic thin film

The photocatalyst stock solution was formed by mixing a matrix, a CdS single-component quantum dot, a silver nanoparticle, and a visible light-active photocatalyst. The matrix was a matrix composed of an insoluble high molecular polymer, such as silicone composed of silicon dioxide ( S i O2) - but was not limited thereto. In other embodiments of the present disclosure, the matrix may also be a matrix composed of a soluble high molecular polymer, such as polymethylmethacrylate (PMMA), polystyrene (PS), polyethylene (PE), and polycarbonate (PC). If the matrix was a matrix composed of an insoluble high molecular polymer, then the quantum dot, the silver nanoparticle, and the visible light-active photocatalyst may be directly mixed with silicone to form a silicone mixture. If the matrix was a matrix composed of the soluble high molecular polymer, then the high molecular polymer may be first dissolved in an organic solvent (e.g., chloroform and toluene) under stirring, and mixed with the quantum dot, the silver nanoparticle, and the visible light-active photocatalyst to form a mixture of the high molecular polymer. In at least one embodiment of the present disclosure, the photocatalyst stock solution comprised about 2.0% of the TiCh photocatalyst, about 0.0005% to about 0.001% of the silver nanoparticle, about 0.001% of the CdS quantum dot, and about 2.0% of SiCE mixed in water. In some embodiments of the present disclosure, the amount of TiCE in the photocatalyst stock solution may be about 0.1%, about 0.2%, about 0.5%, about 0.8%, about 1%, about 1.2%, about 1.5%, about 1.8%, about 2%, about 2.5%, about 3%, about 4%, or about 5%, and was not limited thereto. In some embodiments of the present disclosure, the amount of the quantum dot in the photocatalyst stock solution may be about 0.0005%, about 0.001%, about 0.0015%, about 0.002%, about 0.0025%, about 0.003%, about 0.004%, about 0.005%, about 0.01%, about 0.02%, or about 0.05%, and was not limited thereto. In some embodiments of the present disclosure, the amount of the silver nanoparticle in the photocatalyst stock solution may be about 0.0005%, about 0.0006%, about 0.0007%, about 0.0008%, about 0.0009%, about 0.001%, about 0.005%, about 0.008%, about 0.01%, about 0.02%, about 0.03%, about 0.04%, or about 0.05%. In other embodiments of the present disclosure, the amount of the silver nanoparticle in the photocatalyst stock solution may also be about 0.0015%, about 0.002%, or no greater than 0.0025%, or no greater than 0.055%.

Further, in some embodiments of the present disclosure, the photocatalytic thin fdm may be made from the mixture containing the photocatalyst through a physical sedimentation process, an electrochemical reaction process, an ultraviolet curing process, or athermal catalytic curing process.

In at least one embodiment of the present disclosure, for the physical sedimentation process, the mixture of the high molecular polymer was first subjected to an ultrasonic wave to remove bubbles therein, followed by pouring into the forming mold. After the organic solvent in the mixture was completely volatilized, the photocatalytic thin film can thus be obtained.

In at least one embodiment of the present disclosure, for the ultraviolet curing process, the mixture of the high molecular polymer or the silicone mixture was first added with an ultraviolet curable adhesive, and then drawn into a thin film after fully mixing. Such thin film was then subjected to the ultraviolet irradiation for curing.

In at least one embodiment of the present disclosure, for the thermal catalytic curing process, the silicone mixture was first placed in a vacuum box to vacuum the air and the organic solvent therein. Further, the silicone mixture was heated and cured in a curing oven to form a photocatalytic thin film.

Example 4: Anti-virus assay

For determining the antiviral activity of the photocatalytic thin film, 0.5 m of the virus stock prepared in Example 2 was reacted with the photocatalytic thin film prepared in Example 3 under the specific experimental conditions. After completion of the reaction, the reacted virus samples were collected and subjected to the following assay. First, the cells were collected with a trypsin-EDTA solution, and the cell concentration was adjusted to 6 x 10 ⁵ cells/mL by DMEM medium containing 10% FBS. Further, 1 mb of the cells were seeded in a 6-well plate and incubated in a 37°C incubator with 5% CO2 for 18 to 24 hours.

Subsequently, the reacted virus samples were ten-fold serially diluted to 1 x 10 ⁸ , and added into the 6- well plate containing the cultured cells. After the further incubation for 64 hours, the cells were fixed with 10% formalin (Riedel-de Haen) for 1 hour, and then stained with 0.1% crystal violet (J.T Baker) for 5 minutes. The number of virus plaques compared with the control group was counted to determine the antiviral activity of the photocatalytic thin film. The experimental conditions and results were further described in Test Examples 1 to 3 below.

Test Example 1

Experimental condition: The virus stock was reacted with the photocatalytic thin film containing or not containing the silver nanoparticle. UV irradiation was performed for 5 minutes at a distance of 5 cm from the light source. The results were shown in Table 1 below.

Table 1

*PFU: plaque forming unit

TA: photocatalyst and silver nanoparticle

TH: photocatalyst

Test Example 2

Experimental condition: The virus stock (in a concentration of 5x10 ⁶ PFU/mL) was reacted with the photocatalytic thin film containing different amounts of quantum dots. UV irradiation was performed for 15 minutes at a distance of 7 cm from the light source. The results were shown in Table 2 below.

Table 2

*0P: without addition; IP: 0.5%; 2P: 1%

Test Example 3

Experimental condition: The virus stock (in a concentration of 5x 10 ⁶ PFU/mL) was reacted with the photocatalytic thin film containing the quantum dots of a concentration of 2P. UV irradiation was performed for 5 or 10 minutes at a distance of 7 cm from the light source. The results were shown in Table 3 below.

Table 3

Test Example 4

The experimental condition of this test example was the same as that of Test Examples 1 to 3, except that the UV irradiation was replaced with visible light irradiation. The results showed that the photocatalytic thin film irradiated with visible light exhibited the antiviral effect equivalent to that irradiated with UV.

Example 5 : Bacteriostatic assay of the photocatalyst

For determining the bacteriostatic ability of the photocatalytic thin film prepared in Example 3, the photocatalytic thin film (containing 1% quantum dots) was reacted with bacteria under the specific experimental conditions. After completion of the reaction, the bacterial solution was serially diluted with PBS, followed by spreading and culturing for 24 hours. The number of colonies was counted to determine the bacteriostatic rate of the photocatalytic thin film.

As shown in FIG. 6A, the results showed that the bacteriostatic rate of the control group (without the treatment to form a photocatalytic thin film and without UV irradiation) for Escherichia coli (E. coli) ATCC25922 was 0% (in FIG. 6A, from left to right, the dishes cultured with the bacterial solution were diluted by 100, 10, and 1 time(s), respectively). Further, FIG. 6B showed that after 15 minutes of UV irradiation and the treatment to for a photocatalytic thin film, there was no visible colonies on the culture dishes (in FIG. 6B, from bottom to top and from left to right, the dishes cultured with the bacterial solution were diluted by 100,000, 10,000, 1,000, 100, and 10 times, respectively).

In addition, after 10 minutes of UV irradiation, the bacteriostatic rates of the photocatalytic thin film against Staphylococcus aureus (S. aureus) BAA977 and E. coli ATCC25922 were 99.99% and 100%, respectively. Also, after 1 minute or 5 minutes of UV irradiation, the bacteriostatic rate against .S', aureus BAA977 was 99.97%, and the bacteriostatic rate against E. coli ATCC25922 was 99.92% to 99.95%.

As to carbapenem -resistant Acinetohacter haumannii (CR-AB), after 10 minutes of UV irradiation, the bacteriostatic rate of the photocatalytic thin film was up to 99.99%. As to Pseudomonas aeruginosa, after 10 minutes of UV irradiation, the bacteriostatic rate of the photocatalytic thin film was up to 100%.

Furthermore, after only 10, 20, 30, and 40 seconds of UV irradiation, the bacteriostatic rates of the photocatalytic thin film against .S'. aureus BAA977 were 98.145%, 99.92%, 99.978%, and 99.955%, respectively, and the bacteriostatic rates against E. coli ATCC25922 were 99.964%, 99.995%, 99.973%, and 99.988%, respectively.

Under the condition of visible light irradiation, the bacteriostatic rate of the photocatalytic thin film irradiated with visible light for 10 minutes against A. coli ATCC25922 was 99.999%, which was equivalent to that irradiated with only UV. Also, after 20 minutes of visible light irradiation, the bacteriostatic rates against .S'. aureus BAA977 and E. coli ATCC25922 were 99.9379% and 100%, respectively. As to CR-AB and Pseudomonas aeruginosa, it was found that the bacteriostatic effect of the photocatalytic thin film irradiated with visible light was equivalent to that irradiated with only UV.

Example 6: Skin irritation assay

For determining the potential response of skin irritation of the photocatalyst stock solution, the following animal test was carried out, in which the photocatalyst stock solution to be tested contained CdSe/ZnS quantum dot, a perovskite quantum dot, titanium zeolite, rutile titanium dioxide, anatase titanium dioxide, silicon dioxide, gold nanoparticle, platinum nanoparticle, and silver nanoparticle mixed in pure water. In some embodiments of the present disclosure, the titanium zeolite can be used for preventing precipitation. In some embodiments of the present disclosure, the photocatalyst stock solution contains TiCE in an amount of from about 0.1% to about 5% (e.g., from 0.1% to 1.1%, from 0.2% to 3.5%, and from 0.3% to 2%), quantum dots in an amount of from about 0.0005% to about 0.05% (e.g., from 0.001% to 0.05%, from 0.005% to 0.02%, and from 0.008% to 0.01%), silver nanoparticles in an amount of from about 0.0005% to about 0.05% (e.g., from 0.0008% to 0.03%, from 0.001% to 0.011%, and from 0.003% to 0.008%), and silicon dioxide in an amount of from about 0.01%to about 1% (e.g., from 0.05%to 1%, from 0.1% to 0.8%, and from 0.3% to 0.5%).

Test animal: Male New Zealand white rabbits were purchased from WEI XIN HANG, Banqiao, weighing about 2.4 kilogram (kg) to 3.5 kg. One rabbit per cage, the feeding environmental condition was as follows: the temperature of 20 ± 3°C, the humidity of 50 ± 20%, and the daily lighting time of 12 hours. The animals were allowed to take the feed and water ad libitum.

Assay procedure: Prior to the assay, the fur on the dorsal skin was clipped in one direction with an electric animal shaver, and the skin surface was checked as to whether it was intact. If the skin surface had a scratch or a skin disease, such animal would not be used for the assay. The shaved skin on the back was divided into an upper back area and a lower back area.

Subsequently, 0.5 m of the photocatalyst stock solution was coated on a gauze patch of about 2.5 cm x 2.5 cm in size and covered on the upper back area of the dorsal skin. The lower back area was not subjected to any treatment and served as the control. The administration process has been suggested by the test guideline of the Organization for Economic Cooperation and Development (OECD) 404.

Next, the animals were wrapped with elastic and porous bandage. Four hours after administration, the bandage and the gauze patch were removed, and the test area was rinsed with distilled water, followed by irritant reaction evaluation.

Irritant reaction evaluation: At 1 ± 0.1 hour, 24 ± 2 hours, 48 ± 2 hours, and 72 ± 2 hours after removing the gauze patch of the photocatalyst stock solution, the skin reactions at the treated areas were observed and recorded based on the criteria of the grading system for skin reaction (OECD 404) (Table 4), and then the primary cutaneous irritation index (PCI) was calculated from the scores of erythema and oedema. Further, the irritation of the photocatalyst stock solution was determined according to the skin irritation index categories (Table 5). If the irritant reaction was observed at the 72 ^nd hours, then observation on the irritant sites and recordings were continued until the 14 ^th day to determine the reversibility of the skin injury.

Table 4. Grading system for skin reaction (OECD 404)

Table 5. Skin irritation index categories

The results were shown in Table 6 below. There were no skin reactions induced by the photocatalyst stock solution in the test animals, and the primary cutaneous index (PCI) for the photocatalyst stock solution was zero. It thus can be seen that the photocatalytic composition provided in the present disclosure will not induce skin irritation.

Table 6. Skin reaction in rabbits

Example 7 : Skin sensitization assay For determining the potential for the photocatalyst stock solution to induce a skin sensitization response, the photocatalyst stock solution as mentioned in Example 6 was used to carry out the following animal test.

Test animal: Female guinea pigs (Hartley) were purchased from WEI XIN HANG, Banqiao, weighing about 315 grams (g) to 427 g. One guinea pig per cage, the feeding environmental condition was as follows: the temperature of 20 ± 3 °C, the humidity of 50 ± 20%, and the daily lighting time of 12 hours. The animals were allowed to take the feed and water ad libitum.

Assay procedure: Animals were divided into three groups, i.e., (1) negative control, administrated with sterilized water; (2) positive control, administrated with hexyl cinnamic aldehyde (HCA) dissolved in cottonseed oil; and (3) treatment group, administrated with the photocatalyst stock solution. Prior to the assay, the fur on the animals’ back was clipped in one direction with an electric animal shaver. The clipped area was 2 cm x 4 cm in size and divided into right and left backsides.

The assay included two phases, i.e., induction phase and challenge phase. In the intradermal induction phase, the photocatalyst stock solution was mixed with an adjuvant, and then were intradermally injected to the upper back area. In the topical induction phase, the photocatalyst stock solution was directly applied to the injected area. In the challenge phase, the photocatalyst stock solution was directly applied to the lower back area. The administration process has been suggested by the test guideline of OECD 406.

On the treatment day of the intradermal induction phase, 0.1 mb of each of the following three substances were symmetrically injected into the left and right upper back areas:

Site (A): The emulsion (E-FCA) was formed from the control solvent mixed with Freund’s complete adjuvant (FCA) in a volume ratio of 1 : 1. The treatment group and the negative control group were administrated with E-FCA of the negative control solvent, and the positive control group was administrated with E-FCA of the positive control solvent;

Site (B): The photocatalyst stock solution (undiluted) was directly injected to the animals of the treatment group. The negative control animals were injected with sterile water, and the positive control animals were injected with HCA; and

Site (C): The photocatalyst stock solution (undiluted) was emulsified in E-FCA in a volume ratio of 1 : 1 and injected to the animals of the treatment group. The control solvent was emulsified in E-FCA and injected to the animals of the negative and positive control groups.

The topical induction phase was performed after one week of the intradermal induction phase. At this phase, the previously intradermally injected site was pretreated with 0.5 mb of 10% sodium dodecyl sulfate (SDS), and 24 hours later, it was covered by a patch with 0.2 mb of the photocatalyst stock solution or the control solvent. The patch was removed after 48 hours of treatment.

The challenge phase was performed after two weeks as completing the topical induction phase. At this phase, the patch with 0.1 mL of the photocatalyst stock solution (2 cm x 2 cm) was applied to the lower back area and removed after 24 hours.

Sensitization reaction evaluation: According to the grading system for skin reaction (OECD 406) (Table 7), the skin reactions were graded at 24 ± 2 hours and 48 ± 2 hours after the challenge phase. If the skin reaction grade of the control group was less than 1, the grade of the treatment group was not less than 1, or the grade of the control group was not less than 1, the grade of the treatment group was greater than that of the control group, then the test substance was determined to be sensitive to the skin.

Table 7. Grading system for skin reaction (OECD 406)

The results were shown in Table 8 and Table 9 below. It was found that the photocatalyst stock solution and the negative control group showed no visible changes on the treated skin area at 24 ± 2 hours and 48 ± 2 hours after the challenge phase. Further, in the positive control group, 60% animals exhibited positive responses. Such results meet the OECD 406 guideline; that is, at least 30% in an adjuvant test should be expected. It thus can be seen that the photocatalytic composition provided in the present disclosure will not induce delayed skin sensitization.

Table 8. Skin reaction scores in each individual guinea pig

Table 9. Incidence and severity indices of skin reaction

Group Negative control Positive control Treatment group

Number of animals 5 5 10

Photocatalyst stock

Testing sample Sterilized water HCA solution

Erythema 0/5* 3/5 0/10

Swelling 0/5 0/5 0/10

*n/n: Number of animals with erythema or swelling / Number of animals per group. Example 8: Acute oral toxicity assay

For determining the potential acute toxicity of oral dose of the photocatalyst stock solution, the photocatalyst stock solution as mentioned in Example 6 was used to carry out the following animal test.

Test animal: 8-week-old female SD rats were purchased from BioLASCO CO., Ltd. One rat per cage during the assay period, the feeding environmental condition was as follows: the temperature of 22 ± 3 °C, the humidity of 50 ± 20%, and the daily lighting time of 12 hours. The animals were allowed to take the feed and water ad libitum. Assay procedure: The photocatalyst stock solution was dissolved in sterile water to be the operation solution with a concentration of 60 mg/mL or 400 mg/mL (at a dosing volume of 5 mL/kg). After an overnight fast, each animal received a single oral dose of the formulated photocatalyst stock solution. The assay was performed based on a stepwise procedure (referring to Table 10 below). The dosing was performed sequentially to groups of 3 animals per step. The dose level of 300 mg/kg was used for step 1 and step 2, and the dose level of 2,000 mg/kg was used for step 3 and step 4. The administration process has been suggested by the test guideline of OECD 423.

Table 10. Stepwise procedure

Clinical observation and pathological examination: All animals were observed individually for general health conditions and clinical signs of illness or discomfort before administration, at 0.5 hours and 4 ± 0.5 hours after administration, and subsequently once daily for up to 14 days. Observations included changes in skin, fur, eyes and mucous membranes, and also respiratory, circulatory, autonomic and central nervous systems, and somatomotor activity, and behavior pattern. Any animal found dead during observation was subjected to necropsy. At the end of the assay, all surviving animals were subjected to necropsy after euthanized by CO2 inhalation. The appearance, oral cavity, cranial cavity, and all tissues and organs in thoracic and abdominal cavities were visually inspected, and gross findings were recorded.

The results showed that no animal deaths were found in all steps, and no abnormal clinical signs were observed in all animals. Also, none of the animals showed body weight loss over the assay period, and all animals consumed the food normally. At the end of the assay, all animals were sacrificed and examined, and such results revealed that the organs of all treated rats did not show significant gross lesions. It thus can be seen that the oral median lethal dose (LD50) of the photocatalytic composition provided in the present disclosure was ranked as exceeding 2,000 mg/kg in rats. According to globally harmonized system of classification and labeling of chemicals (GHS), the photocatalytic composition may be classified as category 5, which refers to the lowest level of acute toxicity hazard. Example 9: In vitro cytotoxicity assay

For determining the potential cytotoxicity of the photocatalyst stock solution, the photocatalyst stock solution as mentioned in Example 6 was used to carry out the following in vitro agar diffusion test according to the ISO10993-5 guideline of International Organization for Standardization.

Assay procedure: Mouse lung fibroblast cells (NCTC Clone 929, BCRC No.: RM 60091; Food Industry Research and Development Institute of Bioresource Collection and Research Center) were incubated in minimum essential medium (MEM) containing 10% fetal bovine serum, 2 mM L-glutamine, 2.2 g/L sodium bicarbonate, 0.11 g/L sodium pyruvate, and 100 U penicillin/ 100 pg/mL streptomycin in a 37°C incubator with 5% CO2. Before starting the test, two or three passages of subcultures were conducted when cultures reached to 70% to 80% confluence. Further, the cells were seeded in a 6-well plate at a density of I x IO ⁶ cells/well and incubated in a 37°C incubator with 5% CO2 for 24 hours.

Subsequently, 3% Noble agar (BD Biosciences) was autoclaved at 121°C for 30 minutes, and then mixed with an equal volume of 2x MEM medium, followed by cooling to about 39°C. After the cell culture, the medium was aspirated from the culture plates, and replaced with 2 mb agar medium. The agar medium was then allowed to solidify at room temperature.

Further, 0.1 mb of the photocatalyst stock solution was spread thoroughly on the top of I cm x 1 cm filter paper, and placed on the agar layer (the photocatalyst stock solution was directly in contact with the agar layer) for 24 hours. High density polyethylene film (HDPE; Hatano Research Institute) and zinc diethyldithiocarbamate polyurethane film (Hatano Research Institute) were served as negative and positive control samples, respectively. Both of them were cut into 1 cm x 1 cm pieces and placed on the agar layer for 24 hours. Each sample was performed in triplicates.

Next, the edges of the specimen of the photocatalyst stock solution and the control samples on the bottom of the culture dish were depicted. Each agar medium was stained with 2 mb of neutral red solution and incubated for 1 hour. After removal of the neutral red solution, the decolorization zone of each well was examined with a phase contrast microscope.

Cytotoxicity evaluation: The reactivity grades were measured by the reactivity zone in which cells were not stained with neutral red (Table 11). The achievement of a numerical grade greater than 2 was considered as a cytotoxicity effect. If a cytotoxic effect was observed for the negative control, or no cytotoxic effect was elicited by the positive control, then this test would be considered invalid.

Table 11. Reactivity grades for agar diffusion cytotoxicity test

The results were shown in Table 12 and FIG. 7. It was observed that the zone index of the negative control was 0, implying that the negative control sample had no cytotoxicity. The positive control sample exhibited moderate reactivity (Grade 3), implying that this test was valid. Under the conditions of this test, the reactivity grade of the photocatalyst stock solution was 0. That is to say, the cytotoxicity grade of the photocatalytic composition of the present disclosure was not greater than 2, and therefore met the criteria of biocompatibility guided by ISO 10993-5.

Table 12. Cytotoxicity reactivity grades ^# Biological reactivity was evaluated according to Table 11

Example 10: Environmental cleanup and disinfection assay

In this Example, for determining the long-term antibacterial and antiviral effects of the photocatalyst stock solution applied to the environment, the photocatalyst stock solution as mentioned in Example 6 was used as an environmental cleaning agent, and sprayed on the surface of an environmental object easily contaminated by pathogens. Test Example 1

Application region: The equipment frequently touched by passengers in Taoyuan Airport Mass Rapid Transit (MRT) Station Al 8 and Station A17

Application procedure: On the day of disinfection (D), the photocatalyst stock solution was used to disinfect the test equipment. During the rest of the test period, the test equipment was cleaned up with water or disinfected according to the original process of the station.

Sampling and measurement procedures:

1. The adenosine triphosphate (ATP) bioluminescence assay was employed, in which a portable ATP luminometer (Kikkoman) was used by the same person and the same sampling method.

2. The sampling point and area were fixed and framed by a paper frame. The minimum sampling area was 5 x 5 cm ² , and the maximum area was 10 x 10 cm ² . The sampling principle was that the sampling area for a sampling point with a large area was 10 x 10 cm ² , and a sampling point less than 5 x 5 cm ² was fully sampled.

3. Prior to the sampling, the surface of the application region was wiped with water. The sampling should not be performed under a condition of excessive humidity or in water droplets, so as to prevent from the failure to completely obtain ATP at the fixed area.

4. During the sampling, the ATP sampling swab was moistened. The swabbing was performed by wiping the sampling surface horizontally in a Z-shape pattern, and then vertically up and down. The swab should be rotated 360 degrees to contact the sampling surface.

5. After the completion of the sampling, the sampling swab was put back into the reaction tube, and the measurement should be carried out within 4 hours.

6. During the measurement, the sampling swab was vertically pressed forward the bottom of the reaction tube, and mixed with the reagent therein. After shaking for 5 seconds and breaking the bubble, the reaction tube was inserted to the measurement chamber of a luminometer within 30 seconds, so as to obtain the relative light unit (RLU).

Before the cleanup and disinfection by the photocatalyst stock solution, the quaternary ammonium compound was used to spray on the application region for disinfection, and the ATP assay was performed 1 hour later to obtain the original RLU value. Further, the ATP assay was performed immediately after the cleanup and disinfection by the photocatalyst stock solution, and also performed on 3 to 24 days later. The test results were shown in Table 13 and Table 14 below.

Table 13

Table 14

Test Example 2 Application region: Taoyuan International Airport Services CO., Ltd. Application procedure: The photocatalyst stock solution was used to disinfect the sampling points, and the ATP assay was performed before and after the disinfection (the sampling and measurement procedures were the same as the above) and also performed on 14 days later, so as to determine the long-term disinfection effects of the photocatalyst stock solution.

The test results were shown in Table 15 below.

Table 15

The above results showed that the photocatalytic composition provided in the present disclosure may form a coating on the surface after spraying, and the disinfection rate may continuously achieve more than 95% after 14 days. According to the commonly used pass criteria of RLU recommended by the instrument manufacturer, the RLU value for health facility and central kitchen should be 200 to 500. It thus can be seen that with the disinfection of the photocatalytic composition provided in the present disclosure, the RLU value of the environment can meet the criteria for health facility, and the effect can last for more than 24 days.

From the above, the photocatalytic composition provided in the present disclosure has a photocatalytic effect under the irradiation of sunlight, fluorescent lamp, visible light, or ultraviolet light, and thus can exhibit excellent antibacterial and antiviral activities in an environment where only visible light exists. In addition, in comparison with the commonly used disinfectants, such as alcohol, hypochlorous acid, quaternary ammonium compound, and chlorine dioxide, whose effect lasts only 1 hour at most, the photocatalytic composition of the present disclosure can penetrate pathogens physically and has a stable and long-term effect. Further, the usage amount of silver ions can be reduced, since the photocatalytic composition of the present disclosure containing silver ions in an amount lower than the silver ion tolerance of the human body (0.0025%) can effectively achieve the antibacterial and antiviral effect. Hence, the photocatalytic composition of the present disclosure provides a safe strategy against bacteria and viruses, which is convenient to use and has low impact on the human body.

While some of the embodiments of the present disclosure have been described in detail above, it is, however, possible for those of ordinary skill in the art to make various modifications and changes to the embodiments shown without substantially departing from the teaching and advantages of the present disclosure. Such modifications and changes are encompassed in the scope of the present disclosure as set forth in the appended claims.