Waveguide assisted photocatalytic methods and devices for generating dry hydrogen peroxide (DHP)

Abstract

Photocatalytic devices for generating dry hydrogen peroxide (DHP) and methods of using the same are provided herein. The photocatalytic devices of the present technology utilize optical waveguides that include optical substrates at least partially coated with a photocatalyst layer. As UV light propagates through the optical substrate, a portion can be permitted to escape and irradiate the photocatalyst. The resulting active photocatalyst can be used to convert humidity from an incoming air stream to dry hydrogen peroxide. Various designs of the optical waveguides permit enhanced flexibility for the photocatalytic devices, while also increasing both energy and reaction efficiency.

Description

WAVEGUIDE ASSISTED PHOTOCATALYTIC METHODS AND DEVICES FOR GENERATING DRY HYDROGEN PEROXIDE (DHP)RELATED APPLICATIONS

[0001] This application claims the priority benefit of U.S. Provisional Patent Application Serial No. 63 / 661,703 filed on June 19, 2024, the entire disclosure of which is incorporated herein by reference.BACKGROUND

[0002] The present technology relates to generation of dry hydrogen peroxide (DHP). In particular, it relates to use of improved photocatalytic methods and devices for generating DHP from humid air streams.

[0003] Photocatalytic conversion of humid air streams to form dry hydrogen peroxide (DHP) has been used in a wide variety of applications. Most of the existing systems utilize an illumination source such as a bulb or LED light to provide the activation energy necessary to initiate the photocatalytic reaction. As a result, there is a certain distance between the light source and the catalyst, so that as the surface area of the catalyst increases, so too does the demand for UV light - which often increases the number of light sources (e.g., bulbs or lamps) needed to meet the energy needs. Accordingly, larger and / or more efficient devices must include multiple light sources, which results in increased size, cost, and energy consumption. Furthermore, UV lamps require a source of power to operate, which oftentimes is not readily available in the most desirable locations to deploy DHP-generating devices thereby requiring the added step and expense of installing electrical wiring.

[0004] Thus, a need exists for methods and devices for generating dry hydrogen peroxide that utilizes a larger photocatalytic surface area, but fewer light sources. Advantageously, the device and method would exhibit increased reaction and energy efficiency.SUMMARY

[0005] In one aspect, the present technology concerns a method of generating dry hydrogen peroxide (DHP), the method comprising: (a) transmiting UV light through at least oneoptical waveguide, wherein the optical waveguide comprises an optical substrate at least partially coated with a photocatalyst layer; (b) permitting at least a portion of the UV light to escape the optical substrate in areas where the optical substrate is coated with the photocatalyst layer to thereby irradiate at least a portion of the photocatalyst layer with UV light; and (c) contacting at least a portion of the photocatalyst layer being irradiated with UV light with a humid air stream to generate dry hydrogen peroxide (DHP).

[0006] In one aspect, the present technology concerns a photocata lytic device for generating dry hydrogen peroxide (DHP), the device comprising: at least one optical waveguide for transmitting UV light, wherein the at least one optical waveguide comprises an optical substrate; and a photocatalyst layer coated onto at least a portion of the surface of the optical substrate. The photocata lytic device further comprises at least one UV light source coupled to one of the pair of opposite ends of the optical substrate for introducing UV light into the optical waveguide, wherein the photocata lytic device is configured to generate DHP at or near the surface of the photocatalyst layer and to discharge at least a portion of the DHP to a surrounding environment when in operation.BRIEF DESCRIPTION OF THE DRAWINGS

[0007] FIG. 1 is a schematic diagram of a longitudinal cross-section of an optical waveguide according to embodiments of the present technology;

[0008] FIG. 2a is a cross-sectional view of an optical waveguide comprising an optical fiber as the optical substrate at least partially coated by a catalyst layer;

[0009] FIG. 2b is a longitudinal cross-section of the optical waveguide shown in FIG. 2a;

[0010] FIG. 3 is a perspective view of a helical optical fiber according to embodiments of the present technology;

[0011] FIG. 4a is a cross-sectional view of an optical waveguide comprising an optical fiber as the optical substrate at least partially coated by a catalyst layer, particularly illustrating an embodiment wherein the optical fiber has an annular cross section;

[0012] FIG. 4b is a longitudinal cross-section of the optical waveguide shown in FIG. 4a;

[0013] FIG. 5a is a perspective view of a photocata lytic device according to embodiments of the present technology;

[0014] FIG. 5b is a perspective view of another photocatalytic device according to embodiments of the present technology;

[0015] FIG. 6a is a cross-sectional view of an optical waveguide including a plurality of annular cross-section optical fibers as the optical substrates, particularly illustrating embodiments wherein the optical fibers can be arranged in an alternating, stacked configuration;

[0016] FIG. 6b is a cross-sectional view of an optical waveguide including a plurality of annular cross-section optical fibers as the optical substrates, particularly illustrating embodiments wherein the optical fibers can be arranged in a repeating stacked configuration;

[0017] FIG. 7a is a partial view of an optical woven structure according to embodiments of the present technology;

[0018] FIG. 7b is a partial view of an optical textile according to embodiments of the present technology, particularly illustrating embodiments wherein multi-strand optical threads are interwoven with one another;

[0019] FIG. 7c is a partial view of an optical textile according to embodiments of the present technology, particularly illustrating embodiments wherein single strand optical fibers are interwoven with one another;

[0020] FIG. 8a is a cross-sectional view of an optical waveguide according to embodiments of the present technology, particularly illustrating embodiments wherein the optical substrate comprises a sheet of optical material;

[0021] FIG. 8b is a plan view of the optical waveguide shown in FIG. 8a;

[0022] FIG. 8c is a perspective view of another optical waveguide formed from an optical substrate that comprises a sheet of optical material and formed into a three-dimensional shape;

[0023] FIG. 9 is a perspective view of another optical waveguide according to embodiments of the present technology, particularly illustrating discontinuous application of the photocatalyst layer;

[0024] FIG. 10a is a schematic view of an optical splitter and an optical coupler suitable for use in photocatalytic devices according to embodiments of the present technology;

[0025] FIG. 10b is a schematic view of pluralities of optical fibers according to embodiments of the present technology, particularly illustrating methods of connecting multiple fibers into a single connecting waveguide;

[0026] FIG. 11 is a block flow diagram illustrating a method of configuring the optical waveguide, UV light source, and power source according to embodiments of the present technology;

[0027] FIG. 12 is a block flow diagram illustrating a method of configuring the optical waveguide, UV light source, and power source according to embodiments of the present technology; and

[0028] FIG. 13 is a block flow diagram illustrating a method of configuring the optical waveguide, UV light source, and power source according to embodiments of the present technology.DETAILED DESCRIPTION

[0029] According to embodiments of the present technology, methods and devices are provided for generating dry hydrogen peroxide (DHP). Such methods and devices can comprise a photocata lytic device including an optical waveguide that comprises an optical substrate at least partially coated by a photocatalyst layer. As light (e.g., UV light) is transmitted through the optical substrate, at least a portion of it can be permitted to escape the optical substrate and irradiate the photocatalyst layer, thereby activating the photocatalyst to form an activated photocatalyst layer. As air passes over the activated photocatalyst layer, water vapor in the air stream is reacted to generate dry hydrogen peroxide (DHP). The DHP can then be discharged from the photocatalytic device and into a surrounding environment, such as a room, building, vehicle, or other enclosed space.

[0030] In some embodiments, photocatalytic systems for generating dry hydrogen peroxide may utilize a UV-light source, such as a bulb, to irradiate a photocatalyst, which can be deposited on a substrate within the device. Although not wishing to be bound by any particular theory, when the energy of the illumination source is greater than the bandgap of the photocatalyst, the catalyst(e.g., titanium dioxide) transitions to an excited state (TiCh*). The following equation summarizes the photoexcitation process: yieldsTiO2+ hv - > TiO2(1)

[0031] More specifically, an electron in the valence band (highest occupied molecular orbital) is excited to the conduction band (lowest unoccupied molecular orbital) to move the titanium dioxide from its ground state (So) to its first excited state (Si).

[0032] The resulting TiCh* is a strong oxidant and as water passes over the surface of the activated photocatalyst, hydroxyl radicals (HO-) are generated on the surface of the photocatalyst via oxidation of the water molecules. The combination of these hydroxyl radicals occurs to produce hydrogen peroxide, which is then released from the surface of the photocatalyst. Such hydrogen peroxide is referred to as dry hydrogen peroxide (DHP).

[0033] As used herein, the terms "dry hydrogen peroxide" and "non-hydrated hydrogen peroxide" are used interchangeably and refer to a purified hydrogen peroxide gas that is typically near ideal state. Dry hydrogen peroxide gas is gaseous hydrogen peroxide (H2O2) that is substantially free of hydration (in the form of H2O2 in solution) and substantially free of ozone. DHP is not condensed nor is it present as a droplet or in any way combined with water upon formation. DHP is free of water molecules bonded by covalence, hydrogen bonding, van der Waals forces, or London forces.

[0034] Additionally, DHP is substantially free of ozone. As used herein, the term "substantially free of ozone" refers to a stream comprising less than about 0.015 ppm, less than about 0.010 ppm, or less than about 0.005 ppm of ozone, measured by an EcoTech Serinus 10 CRDS instrument. In some cases, the DHP can be "free of ozone," which refers to concentrations of ozone below the level of detection.

[0035] Methods and devices according to the embodiments of the present technology produce DHP that is non-hydrated and free of ozone. DHP is distinguishable from aerosolized aqueous hydrogen peroxide as DHP is not hydrated, non-toxic and the H2O2 molecules are present in much lower concentrations. In some embodiments, methods and devices as described herein can discharge DHP into a surrounding treatment environment to achieve an equilibrium concentration of at least about 0.25, at least about 0.5, at least about 1, at least about 2.5, at leastabout 5, or at least about 10 parts per billion by weight (ppb) and / or not more than about 350, not more than about 275, not more than about 200, not more than about 100, not more than about 50, not more than about 25, or not more than about 10 ppb. Such concentrations can be measured using a continuous sampling device operating at steady state for at least a period of 1 hour. An example of such a sampling device includes a Picarro PI2114 CRDS H2O2 sensor. In certain embodiments, the sensor data is fine-tuned to account for effects that interfere with or could be mistaken for DHP by the sensor.

[0036] According to embodiments of the present technology, in order to achieve photocata lytic production of DHP according to embodiments of the present technology, four main elements should be present: (1) photocatalyst; (2) light; (3) air flow; and (4) humidity (source of water). In particular, methods and devices as described herein utilize a photocatalyst which is accessible to air flow. Additionally, a light source can irradiate the catalyst with enough energy to activate it (as discussed previously). This means that the intensity and coverage of the light source over the catalyst should be sufficient over the entire surface area of the catalyst. Finally, air should be able to access and contact the surface of the activated catalyst during the irradiation and the air must include sufficient humidity that the water in the air can be converted to hydrogen peroxide.

[0037] In contrast to other systems or methods for making hydrogen peroxide (some of which may employ a thin, screen-like substrate coated with catalyst) devices and methods according to embodiments of the present invention utilize an optical waveguide that includes at least one optical substrate at least partially coated with a photocatalyst layer. The optical substrate can be any suitable form, such as fibers or sheets, and may be coupled to a light source, such as a UV light source. As light (UV energy) is transmitted through the optical substrate, at least a portion leaks out of (e.g., escapes) the optical substrate and irradiates the photocatalyst layer, thereby activating it. Air passing over the activated photocatalyst layer contacts its surface and DHP is produced.

[0038] In some embodiments, the passing step includes moving a stream of air over a stationary catalyst layer (or structure), while, in other cases, the passing step may include rotating or otherwise moving the catalyst layer (or structure) thereby causing air to pass over the photocatalyst layer. In some cases, both the catalyst layer (or structure) and air may be in motionto perform the passing step. The DHP generated on the catalytic surface can then be discharged into the surrounding environment, thereby building up an equilibrium concentration of DHP as described herein.

[0039] Turning now to FIG. 1, a schematic depiction of a longitudinal cross-section of a simple optical waveguide 10 is provided. The optical waveguide 10 comprises an optical substrate in the form of an optical fiber 12 and a photocatalyst layer 18 coating at least a portion of the surface 16 of the optical fiber 12. Although shown in FIG. 1 as covering the entirety of the surface 16, in some embodiments, there may be portions of the surface 16 not covered by the photocatalyst layer 18. Further, other shapes and configurations for the optical substrate may be used. Additional details regarding such embodiments are provided below.

[0040] As shown in FIG. 1, it is possible to control the amount of light (e.g., UV light) propagating through the optical fiber 12 via reflection (R) and the amount of light transmitted out of the optical fiber 12 and into the photocatalyst layer 18 (T2X). The total amount of light transmitted out of the end of the optical fiber 12 (or segment thereof as shown in FIG. 2) is shown as Tl.

[0041] In conventional optical fibers, it is desired to maximize the reflection of the light through the optical material and avoid transmitting the light energy out of the optical fiber 12. Thus, such fibers seek to minimize (to 0, if possible) T2Xand maximize Tl. However, according to embodiments of the present technology, some reflection may be desired in order to propagate energy down the length (X) of the optical fiber 12, but the amount of energy exiting the optical fiber 12 and absorbed by the photocatalyst layer 18 must be sufficient to activate the photocatalyst. In certain embodiments, it is desirable to minimize the discharge of light energy from the end of the optical fiber 12 (Tl) since such energy would not be used to irradiate the photocatalyst. In some cases, it may be desirable to create and / or maximize retroreflection of light energy back into the fiber (e.g., in the direction opposite of the original propagation; not shown in FIG. 1). This may be useful, for example, when maximizing energy transmission out of the surface 16 of the optical fiber 12, as discussed in detail herein.

[0042] However, in other embodiments, especially when a plurality of optical waveguides 10 are connected in series, it may be desirable to transmit significant light energy from the end ofoptical fiber 12 (Tl) to supply sufficient energy to downstream optical waveguides 10 for the successful operation thereof. In such embodiments, it may be desirable for the amount of light escaping the optical fiber 12 and irradiating the photocata lytic layer 18 should not far exceed the energy need of that photocatalyst layer 18 for DHP generation.

[0043] According to some embodiments, the humid air stream introduced into a photocata lytic device of the present technology can comprise at least about 50, at least about 65, at least about 70, at least about 75, or at least about 80 percent relative humidity and / or not more than about 99, not more than about 90, or not more than about 85 percent relative humidity. The temperature and pressure of the air stream can be any suitable temperature and pressure and often these are at or near ambient.

[0044] In some embodiments, the humid air stream introduced into the photocatalytic device can have a relative humidity of at least about 5, at least about 10, at least about 15, at least about 20, at least about 25, at least about 30, or at least about 35 percent and / or not more than about 50, not more than about 45, not more than about 40, not more than about 35, not more than about 30, not more than about 25, less than about 20, not more than about 15, not more than about 10, or not more than about 7.5 percent. Methods and devices as described herein may not be performed or operated in an aqueous environment, such that the device is not surrounded by, contacted with, or immersed in liquid water during operation. Thus, dry hydrogen peroxide can be the product discharged from the surface instead of hydrated or aqueous hydrogen peroxide.

[0045] In some cases, when operated at lower humidity, the reaction at the surface of the photocatalyst may be dominated by the destruction of any residual volatile organic compounds (VOCs) than the production of hydrogen peroxide. In some embodiments, the air stream passing through the photocatalytic device (over the surface of the photocatalyst) can have a total VOC content of at least about 0.5, at least about 1, at least about 2, or at least about 3.5 ppm and / or not more than about 10, not more than about 7.5, or not more than about 5 ppm, based on the total volume of the air stream. The air stream may comprise ambient air and have an oxygen concentration in the range of from about 19.75 to about 21 volume percent, with the balance being mainly nitrogen with trace amounts of other gases.

[0046] The air stream passing through the photo catalytic device and / or over the catalytic surface can have a volumetric flow rate of at least about 0.5 CFM (ft3 / min), at least about 25 CFM, at least about 50 CFM, at least about 100 CFM, at least about 250 CFM, at least about 500 CFM, at least about 750 CFM and / or not more than about to 3,000 CFM (ft3 / min). In some cases, the air stream can have a volumetric flow rate of at least about 0.5 mL per minute (mL / min), at least about 1 mL / min, at least about 2 mL / min, or at least about 5 mL / min and / or up to about 5 L / min, up to about 2.5 L / min, up to about 1 L / min, or up to about 0.5 L / min. The flow rate of the air depends, in part, on the specific configuration of the device, ambient conditions, as well as the area being treated with DHP.

[0047] In some embodiments, the photocata lytic device may be designed to maintain a turbulent or transitional flow for the air stream as it passes through the device and, in particular, as it passes over and near the surface of the activated photocatalytic layer. Although not wishing to be bound by any particular theory, it is believed that such flow regimes help facilitate increased contact with the photocatalyst layer, thereby increasing reaction efficiency. As used herein, "turbulent flow" is characterized by a Reynolds number of 2300 or more, and "transitional flow" is characterized by a Reynolds number between 1800 and 2000. The flow of air through the photocata lytic device may not be laminar, such that, for example, its Reynolds number is not below 1800.

[0048] Photocatalytic devices according to embodiments of the present technology comprise at least one optical waveguide for propagating UV light and at least one UV light source coupled to the optical waveguide for introducing UV light therein. Specific details of various embodiments of such devices, as well as methods of making the devices, according to embodiments of the present technology are provided below.Optical Waveguides

[0049] In general, an optical waveguide utilized in photocatalytic devices of the present technology include an optical substrate and a photocatalyst layer at least partially coated one to one or more surfaces of the optical substrate. The optical substrate can be formed of at least one optical material capable of passing UV light therethrough. Suitable optical materials include those that do not absorb the light introduced therein such that, for example, the absorbance of UV lightintroduced therein is less than about 10 percent, less than about 5 percent, less than about 2 percent, less than about 1 percent, or less than about 0.5 percent, measured with a Perkin-Elmer Lambda 1050+ UV / Vis / NIR spectrophotometer.

[0050] In some embodiments, the refractive index of the optical material (optical substrate) can be at least about 1.45, at least about 1.47, at least about 1.50, or at least about 1.55 and / or not more than 2.00, not more than about 1.90, not more than about 1.80, not more than about 1.75, not more than about 1.70, not more than about 1.65, or not more than about 1.60, measured according to conventional methods using a refractometer. The optical material may be polymeric or non-polymeric. Examples of suitable optical materials include quartz, sapphire, borosilicate glass, polymethyl methacrylate (PMMA), polycarbonate, and combinations thereof.

[0051] In some embodiments, the optical material used to form the optical substrate may be treated to reduce the refractive index to fall within one or more of the above ranges. For example, in some embodiments, at least a portion of the surface of the optical substrate may be treated with a coupling agent (e.g., a silane coupling agent) to increase the adhesion of the photocatalyst layer to the surface of the optical substrate. Examples of suitable coupling agents include, but are not limited to, silane coupling agents having of the formula HO2C-CH2CH2CH2- Si(OR)s, wherein R is a methyl or ethyl group. Although not wishing to be bound by any particular theory, it is hypothesized that the siloxy groups will bind to the surface of the substrate, and the carbon-oxygen group will bind to the photocatalyst material.

[0052] The optical substrate can have any suitable shape. In some embodiments, the optical substrate can include at least one elongated fiber having a generally circular or annular cross section. In other embodiments, the optical substrate can comprise a sheet or plate, configured in either a planar (or flat) configuration or shaped, bent, or otherwise formed into another three- dimensional shape, such as a cone, sphere, or cube. The specific shape of the optical substrate may depend, at least in part, on the size, shape, and end placement of the photocata lytic device. Several embodiments of optical waveguides with different shapes will be discussed in detail shortly with reference to the Figures.

[0053] Each optical waveguide further comprises a photocatalyst layer coated onto at least a portion of one or more surfaces of the optical substrate. The photocatalyst layer may include oneor more of any suitable photocatalyst capable of being activated by UV light and of initiating the conversion of water in the air (humidity) to hydrogen peroxide on contact. The photocatalyst can comprise a metal or metal oxide. Examples of suitable photocatalysts include, but are not limited to, titanium dioxide (anatase or rutile), copper, copper oxide, zinc, zinc oxide, iron, iron oxide, or mixtures thereof. In some embodiments, the photocatalyst can be doped with cocatalysts such as copper, rhodium, silver, platinum, gold, and combinations thereof. Other examples of suitable catalysts include perovskites, zeolites, and combinations thereof.

[0054] In some embodiments, the photocatalyst layer can include at least about 75, at least about 80, at least about 85, at least about 90, at least about 95, at least about 97, or at least about 98 weight percent of at least one of the above types of photocatalysts, based on the total amount of photocatalyst present in the photocatalyst layer. The catalyst may have an average crystalline size of from about 0.25 nm to about 100 nm, about 0.5 nm to about 75 nm, or about 1 nm to about 50 nm.

[0055] In some embodiments, the photocatalyst may be present in the photocatalyst layer in an amount of at least about 10, at least about 20, at least about 25, at least about 30, at least about 35, or at least about 40 percent and / or not more than about 99, not more than about 95, not more than about 90, not more than about 85, not more than about 80, or not more than about 75 percent, based on the total weight of the photocatalyst layer. In some cases, the photocatalyst layer may consist essentially of, consist of, or include 100 percent photocatalyst. In some embodiments, the photocatalyst layer can include less than about 500, less than about 250, less than about 100, or less than about 50 ppm of one or more metal nanoparticles.

[0056] In some embodiments, the refractive index of the photocata lytic layer may be greater than the refractive index of the optical substrate by at least about 0.010, at least about 0.050, at least about 0.10, at least about 0.20, at least about 0.25, at least about 0.30, at least about 0.35, or at least about 0.40 and / or not more than about 0.75, not more than about 0.70, not more than about 0.65, not more than about 0.60, not more than about 0.55, or not more than about 0.50 index units. In some embodiments, the refractive index of the photocata lytic layer can be at least about 2.00, at least about 2.10, at least about 2.20, at least about 2.30, or at least about 2.40 and / or not more than about 2.75, not more than about 2.65, not more than about 2.50, or notmore than about 2.45, while the refractive index of the optical substrate falls into one or more of the ranges provided herein.

[0057] In some embodiments, the optical substrate and / or the photocatalyst layer can include at least one inorganic metal oxide such as, for example, an inorganic metal oxide phosphor (e.g., europium oxide, EU2O3). When present, the amount of such a material in the optical substrate and / or photocatalyst layer can be at least about 0.01, at least about 0.05, at least about 0.10, or at least about 0.25 weight percent and / or not more than about 5, not more than about 3, not more than about 2, or not more than about 1 weight percent, based on the total weight of the optical substrate or the photocatalyst layer. In some cases, inclusion of such materials can provide color to the optical waveguide, particularly when UV light is passing through the optical waveguide.

[0058] Suitable inorganic metal phosphors can be chosen from WO3, CeOz, NdzOs, Tb2C>3, Tm2O3, Yb2C>3, Et2O3, HO2O3, Dy2O3, and mixed lanthanides of the form: Ln(l)2-xLn(2)xO3, metal oxide materials doped with Ln3+ions in an amount of from about 0.1 to about 5.0 percent by weight. Suitable Ln3+ions include, for example, Pr3+, Nd3+, Sm3+, Eu3+, Gd3+, Tb3+, Dy3+, Ho3+, Er3+, Tm3+, and Yb3+and the metal oxide can be chosen from ZnO, TiCh, AI2O3, Y2O3, SiCh. Additionally, metal phosphate (PO43) salts, metal sulphate (SO42) salts, metal borates (BO43), aluminates (AIO45) (AI2O3) and metal silicates (SiC4) doped with the same elements may also be used.

[0059] In some embodiments, the metal phosphor may be chosen from Tl+, Pb2+, Sn2+, Sb3+, Cr3+, Mn4+, Mn2+, and Fe3+doped metal oxides, metal phosphates, metal sulfates or metal borates including Sr2P2O7:Sn2+, Sr2B6Oi0:Sn2+, Ca5(PO4)3F:Sb3+, YPO4:Sb3+, (Ca,Zn)3(PO4)2:TI+, BaMg2Ali6O2?:TI+or BaSi20s:Pb2+, or combinations thereof.

[0060] In some embodiments, the optical substrate and / or photocatalyst layer can include at least one non-oxide dopant in an amount of at least about 0.01, at least about 0.05, at least about 0.10, or at least about 0.25 weight percent and / or not more than about 5, not more than about 3, not more than about 2, or not more than about 1 weight percent, based on the total weight of the optical substrate or the photocatalyst layer. Inclusion of such components may, for example, control the refractive index of the photocatalyst layer and / or optical substrate to a desired range, or may facilitate or strengthen the adhesion of the photocatalyst layer to the surface of the optical substrate.

[0061] The optical waveguides described herein can be made by any suitable method, including by brushing, dipping, painting, printing, or otherwise coating a slurry including the photocatalyst onto at least a portion of at least one surface of the optical substrate. In some cases, the catalyst may be deposited on the surface via vapor deposition, electrochemical deposition, powder coating, or even oxidation of a metal coated (e.g., titanium) optical substrate. The method of forming the optical waveguides is not particularly limiting, as long as the coating is applied in the desired portion or portions of the substrate at the desired thickness. After application of the catalyst slurry, the coated optical substrate may be permitted to dry, thereby creating a dried photocatalyst layer as described herein.

[0062] Several specific embodiments of optical waveguides suitable for use in photocata lytic devices of the present technology will now be discussed in detail with reference to the Figures. Turning initially to FIGS. 2a and b, cross-sectional views of an optical waveguide 110 according to embodiments of the present invention are provided. As shown in FIGS. 2a and 2b, the optical waveguide 110 comprises an optical substrate in the form of an elongated optical fiber 112 at least partially coated with a photocatalyst layer 118. As shown in FIGS. 2a and 2b, the elongated optical fiber 112 has a pair of opposite ends 114a, b and defines an outer surface 116. As shown in FIG. 2a, the optical fiber 112 may be solid (e.g., not hollow) and may have a generally circular cross- sectional shape. In other embodiments, the optical fiber 112 may have a different cross-sectional shape, such as, for example, an oval, a square, a triangle, a rectangle, or any other suitable geometric shape.

[0063] In some embodiments, the average diameter of the optical fiber 112 can be at least about 250, at least about 300, at least about 500, or at least about 750 microns and / or not more than about 7.5, not more than about 5, or not more than about 2.5 mm. When the optical fiber 112 does not have a circular cross-sectional shape, the diameter may be considered the same as the largest dimension of the non-circular cross-section and may fall within one or more ranges above.

[0064] The optical fiber 112 can have any suitable length depending on the specific configuration of the photocatalytic device in which it is utilized. In some embodiments, the optical fiber 112 may have an overall length of at least about 1 m, at least about 2 m, at least about 5 m,at least about 10 m, at least about 25 m and / or not more than about 200 m, not more than about 100 m, not more than about 75 m, or not more than about 50 m, measured between the opposite ends 114a, b of the fiber. In some cases, the optical fiber 112 may be coiled and / or twisted such that fibers having lengths of, for example, 25 cm or more may ultimately be used in relatively small photocata lytic devices. One example of a coiled optical fiber 112 optical fiber is shown in FIG. 3. In other embodiments, shorter optical fibers may be used, such as those having a length of less than 1 m, less than about 50 cm, less than about 25 cm, or less than 10 cm. In other cases, even longer optical fibers 112 may be used, such as those having lengths of greater than 200 m, greater than 300 m, or greater than 500 m.

[0065] Additionally, as shown in FIGS. 2a and 2b, the optical waveguide 110 can include a photocata lytic layer 118 coated onto at least a portion of the outer surface 116 of the optical substrate (here, optical fiber 112). In some embodiments, the average thickness of the photocata lytic layer 118 can be at least about 25 nm, at least about 50 nm, at least about 75nm, or at least about 100 nm and / or not more than about 12.5 |im, not more than about 10 |im, not more than about 7.5 |im, not more than about 5 p.m, or not more than about 2.5 microns. In some embodiments, the average thickness of the photocata lytic layer 118 can be in the range of from about 2 nm to about 250 nm, about 5 nm to about 175 nm, or about 10 nm to about 100 nm. The average thickness can be measured at 10 different locations spaced equally apart from one another in a straight line along the entire length of the optical fiber (or other substrate) or along the entire length of the photocatalyst layer 118, particularly in the case where the surface 116 of the optical substrate 112 is only partially coated with the photocatalyst layer 118.

[0066] In some embodiments, the average thickness of the photocatalyst layer 118 on the outer surface 116 of the optical substrate can be at least about 1 p.m, at least about 5 .m, at least about 25 .m, or at least about 50 pm and / or not more than about 200 pm, not more than about 150 pm, not more than about 100 pm, or not more than about 75 pm, measured as described above.

[0067] According to some embodiments, as shown in FIGS. 4a and 4b, the elongated optical fiber 112 can have an annular cross-section. In such a case, the optical fiber 112 includes a pair of opposite ends 114a, b and both an outer surface 116 and an inner surface 120. As generally shownin FIGS. 4a and 4b, the photocatalytic layer may be coated onto both the outer surface 116 and the inner surface 120, or it may be coated onto only one of the inner and outer surfaces 120, 116 (embodiment not shown).

[0068] Annular optical fibers 112 as shown in FIGS. 4a and 4b may have a similar overall diameter (measured as if the fiber had a solid cross-section) as the solid optical fiber 112 shown in FIGS. 3a and 3b. In some embodiments, the annular optical fiber can have a thickness, measured between the inner and outer surfaces 116, 120, of at least about 250 microns, at least about 500 microns, or at least about 750 microns and / or not more than about 7.5 mm, not more than about 5 mm, or not more than about 2.5 mm.

[0069] Additionally, the thickness of the photocatalyst layer 118 on the outer surface 116 and / or the photocatalyst layer 122 on the inner surface 120 of the optical fiber 112 shown in FIGS. 4a and 4b can be in the range of from about 25 nm, at least about 50 nm, at least about 75 nm, or at least about 100 nm and / or not more than about 12.5 pm, not more than about 10 pm, not more than about 7.5 |im, not more than about 5 |im, not more than about 2.5 |im, or not more than about 1 pm. In some embodiments, the average thickness of the photocatalytic layer 118 can be in the range of from about 2 nm to about 250 nm, about 5 nm to about 175 nm, or about 10 nm to about 100 nm, measured as described herein. Depending on the size of the opening, the photocatalyst layer 122 on the inner surface 120 may be slightly thinner than the photocatalyst layer 118 on the outer surface 116 of the optical fiber 112.

[0070] In some embodiments, thickness of the photocatalyst layer 118 on the outer surface 116 and / or the photocatalyst layer 122 on the inner surface 120 of the optical substrate can be at least about 1 pm, at least about 5 pm, at least about 25 pm, or at least about 50 pm and / or not more than about 200 pm, not more than about 150 pm, not more than about 100 pm, or not more than about 75 pm, measured as described above.

[0071] In some embodiments, the photocatalyst layer 122 can have a total surface area (on the entire photocatalytic device) of at least about 10 cm2, at least about 50 cm2, at least about 100 cm2, at least about 500 cm2, at least about 750 cm2, at least about 1000 cm2, at least about 5000 cm2, or at least about 1 m2and / or not more than about 10 m2, not more than about 5 m2, not morethan about 2 m2, not more than about 1 m2, not more than about 5000 cm2, or not more than about 1000 cm2, depending on the specific size and configuration of the photocatalytic device.

[0072] According to some embodiments, the optical substrate may comprise two or more optical fibers in contact with one another. Overall, such optical waveguides can include at least 5, at least 10, at least 25, at least 50, at least 75, or at least 100 optical fibers and / or not more than about 250, not more than about 200, not more than about 100, not more than about 75, not more than about 50, or not more than about 25 optical fibers. The fibers may be twisted, coiled, braided, and / or interwoven with one another and / or the fibers may be bundled or stacked to form the optical substrate. Several embodiments of multi-fiber optical waveguides formed from substrates are provided in FIGS. 5a, 5b, 6a, 6b, and 7a-c.

[0073] Turning initially to FIG. 5a, one embodiment of a photocatalytic device 210a includes a multi-fiber optical waveguide shown as a spray comprising a plurality of elongated fibers 212a and a base 250 for securing one end (not shown) of each of the fibers 212a, while the other end remains unsecured. In some cases, the base 250 can include a UV light source (not shown) for providing UV light to the fibers 212. The fibers 212 can be any type of elongated fiber discussed herein and may be at least partially coated with a photocatalyst layer (not shown).

[0074] In another embodiment shown in FIG. 5b, a photocatalytic device 210b including an optical waveguide formed from a plurality of elongated fibers 212b that are secured at both ends, with the middle portion of the fibers 212b being spread apart to permit the passage of air therethrough. In some cases, the spacing of the fibers 212b can be maintained with two spacing discs 216a, b located at opposite ends of the fibers 212b. Further, as shown in FIG. 5b, a UV light source 214a and / or 214b may be disposed at both or either end of the fibers 212b and may provide UV light into at least one end of the fibers 212b.

[0075] Turning now to FIGS. 6a and 6b, additional embodiments of optical waveguides 310 including optical substrates formed from a plurality of elongated optical fibers 312 are provided. The optical fibers 312 in the waveguides 310 have an annular cross-section and are arranged in parallel. The optical fibers 312 are stacked upon one another to form multiple rows. In some embodiments, the optical fibers 312 can be in an alternating pattern (FIG. 6a) or in a repeating pattern (FIG. 6b). Additionally, the optical waveguide 310 may further include at least one fasteningor securing device to hold the fibers 312 in position. Examples of such devices include, but are not limited to, ties or bands that fit around the circumference of the fibers and / or tubes or ducts into which the fibers can be placed.

[0076] Additionally, although shown in FIGS. 6a and 6b as comprising three rows of four fibers, any suitable number of fibers per row and any suitable number of rows can be utilized according to various embodiments of the present technology and as described herein. The number and spacing of the individual fibers may be selected to ensure sufficient air flow through the optical waveguide, which may be generally parallel to the direction of extension of the fibers (e.g., perpendicular to the structures shown in FIGS. 6a and 6b). In other words, when the optical waveguides 310 in FIGS. 6a and 6b are utilized in a photocata lytic device for generating DHP, the air flows in the annular region within the optical fibers 312, as well as the empty space between the fibers. Additional details of specific photocata lytic devices are provided below.

[0077] Turning now to FIG. 7a to 7c, several additional embodiments of waveguides including a plurality of optical fibers are shown. In some embodiments, at least a portion of the fibers 412 comprise single strand fibers (as shown, for example, in FIG. 7c), while, in some embodiments, at least a portion of the fibers 412 comprise multi-strand fibers, or threads 432. When used, the threads 432 may comprise at least two, at least three, at least four, or at least 5 individual fibers and / or not more than about 10, not more than about 8, not more than about 5, or not more than about 4 individual fibers woven, braided, or otherwise combined to form the thread 432. In some cases, each of the optical fibers within the thread may be coated by a photocatalyst layer prior to the combining to form the thread 432, while, in other cases, the optical fibers may first be combined to form the thread 432, which may then be at least partially coated with photocatalyst as described herein.

[0078] As generally shown in FIGS. 7a-c, in some embodiments, the optical fibers 412 (or optical threads 432) may be interwoven to form an optical woven structure (FIG. 7a) or optical textile 450 (FIGS. 7b and 7c). In some embodiments, a plurality of optical fibers 412 (or threads 432, as shown in FIG. 7a) may be interwoven amongst a plurality of solid supports 442 to form an optical woven structure 440 suitable for use as an optical waveguide. Such supports 442 may have similar dimensions as the optical fibers described herein, and may be formed of any suitableY1material, including, but not limited to polyethylene, polypropylene, nylon, aluminum, stainless steel, polycarbonate, polyester, and combinations thereof. Although shown in FIG. 7a as including multi-strand threads, a similar optical woven structure could be formed using single strand optical fibers.

[0079] Similarly, in some embodiments, a plurality of optical threads and / or single strand optical fibers may be interwoven to form an optical textile. Specific examples of this include interweaving two or more single strand optical fibers (FIG. 7c), two or more optical threads (FIG. 7b), or an optical fiber and an optical thread (embodiment not shown). When the optical textile includes both single fibers and threads, either one can be the weft (horizontal) or warp (vertical) fiber. Additionally, any suitable pattern of weaving can be used. In some embodiments, however, the optical substrate may not be in the form of an optical textile or fabric.

[0080] In some embodiments, the spacing between adjacent individual optical fibers, optical thread, and / or solid supports of an optical woven structure 440 or optical textile 450 in either the weft direction (shown as "y" in FIGS. 7a-c) and / or the warp direction (shown as "x" in FIGS. 7a-c) can be at least about 2, at least about 5, or at least about 10 microns and / or not more than about 1, not more than about 0.5, not more than about 0.25, or not more than about 0.10 mm. Additionally, or in the alternative, the spacing between adjacent optical fibers, optical threads, and / or solid supports in the weft or warp direction can be at least about 2, at least about 5, or at least about 10 microns and / or not more than about 1, not more than about 0.5, not more than about 0.25, or not more than about 0.10 mm. For a given optical woven structure or textile, the spacings in the weft and warp directions may be the same, these spacings may be different.

[0081] Additionally, the optical fibers and / or threads can be woven before or after application of the photocatalyst layer (not shown in FIGS. 7a-c). The types and amounts of photocatalyst present on optical woven structures and / or optical textiles according to the present technology can be within the ranges and patterns described previously with respect to optical fibers.

[0082] Turning now to FIGS. 8a-c, several embodiments of another type of optical waveguides suitable for use in photocata lytic devices as described herein are provided. The optical waveguides 510 shown in FIGS. 8a-c comprise an optical sheet 530 having a pair of opposite majorsurfaces 532a, b and a thickness, "z," defined between the surfaces 532a, b. The optical sheet 530 may be formed from any of the optical materials described herein, and may have an average thickness, z, of at least about 350, at least about 500, or at least about 750 microns and / or not more than about 7.5 mm, not more than about 5 mm, not more than about 2.5 mm, not more than about 2 mm, not more than about 1.5 mm, or not more than about 1 mm.

[0083] The other dimensions of the optical sheet 530 can be anything suitable for the particular application and the optical sheet 530 may have any shape, such as rectangular, square, triangular, circular, or any other geometrical shape. In some embodiments, the largest dimension of the major surfaces 532a, b of the optical sheet 530 used in photocatalytic devices as described can be at least about 5, at least about 10, at least about 25, at least about 50, at least about 100, or at least about 150 mm and / or not more than about 1000, not more than about 750, not more than about 500, not more than about 250, or not more than about 100 mm.

[0084] In some embodiments, the optical sheet 530 can be substantially planar (as shown in the example provided in FIGS. 8a and 8b), while in other embodiments, the optical sheet 530 may be substantially non-planar (as shown in the example provided in FIG. 8c). As used herein, the term "substantially planar" refers to a sheet whose major surfaces are at least 95 percent flat and the term "substantially non-planar" refers to a sheet whose major surfaces are less than 95 percent flat. Note that the flatness or lack of flatness of a surface refers to the overall shape of the optical sheet 530, not necessarily to deviations in the roughness or smoothness of the surface itself. Further, other non-planar configurations may be formed according to embodiments of the present invention, such as a sphere, a cylinder, or a cone (such as in FIG. 8c). Additionally, in some embodiments, multiple flat optical sheets may be combined to form a three-dimensional shape, such as a cube, prism, or pyramid, which includes multiple substantially planar faces combined to form a non-planar structure.

[0085] Additionally, as shown in FIGS. 8a-c, the optical sheet 530 may include a plurality of apertures 550 extending through the thickness of the sheet and connecting the two opposite major surfaces 532a, b. Such apertures 550 permit air to flow through the optical sheet 530 when it is utilized as part of an optical waveguide of a photocatalytic device as described herein. In some embodiments, the thickness of the optical sheet 530 (defined between the opposing major surfaces532a, b) can be in the range of from about 0.1 pm to about 10 pm, about 0.5 pm to about 7.5 urn, or about 0.75 urn to about 3 pm. In some embodiments, the maximum thickness of the optical sheet 530 can be at least about 0.5, at least about 1, at least about 2.5, at least about 5, at least about 10, at least about 25, at least about 40, or at least about 50 mm and / or not more than about 250 mm, not more than about 200 mm, not more than about 150 mm, not more than about 100 mm, not more than about 75 mm, not more than about 50 mm, or not more than about 25 mm.

[0086] The apertures 550 can comprise holes having any suitable cross-sectional shape, including circular, as shown in FIGS. 8a to 8c. When apertures 550 includes holes as generally shown in FIGS. 8a-c, the largest dimension of each aperture 550 (e.g., diameter for a hole with a circular cross-section) can be at least about 1, at least about 10, at least about 25, at least about 50, at least about 100, or at least about 500 microns and / or not more than about 5, not more than about 2.5, not more than about 1, or not more than about 0.75 microns. In some embodiments, the largest dimension of each aperture can be at least about 0.5, at least about 1, at least about 2.5, at least about 5, at least about 10, or at least about 20 mm and / or not more than about 100, not more than about 75, not more than about 50, not more than about 25, not more than about 10, or not more than about 5 mm.

[0087] At least a portion of the apertures 550 may all have the same size and shape, or the size and / or shape of at least a portion of the apertures 550 may be different. In other embodiments (not shown), the apertures 550 may comprise a series of lines or troughs spaced apart from one another along and connecting the major surfaces 532a, b of the optical sheet 530. The thickness of the apertures 550 can the same as the thickness of the optical sheet 530, particularly when the apertures 550 extend from one major surface 532a of the sheet to the other 532b.

[0088] The apertures 550 may be arranged in any suitable pattern. For example, the apertures 550 may be arranged in spaced-apart rows in an alternating or repeating (nonalternating) pattern, or the apertures 550 may be placed along the surfaces 532a, b randomly (particularly when the apertures 550 comprise holes). In some cases, a portion of the pattern of apertures 550 may be ordered (e.g., in rows or other shape or pattern), while a portion may be unpatterned or random.

[0089] Regardless of orientation, the maximum spacing between the center points of adjacent apertures 550 on an optical sheet 530 can be in the range of from about 25, at least about 50, at least about 75, or at least about 100 microns and / or not more than about 5, not more than about 2.5, not more than about 1, not more than about 0.75, not more than about 0.50 mm. According to some embodiments, the major surfaces 532a, b of the optical sheet 530 may be at least about 50, at least about 60, at least about 70, at least about 75, at least about 80, at least about 85 percent covered with apertures 550.

[0090] As shown generally in FIGS. 8a to 8c, one or both of the major surfaces 532a, b, of the optical sheet 530 may be at least partially coated with a photocatalyst layer 538. The type and thickness of the photocatalyst layer 538 can be and fall within the ranges described herein with respect to an optical fiber substrate.

[0091] Regardless of the shape of the optical substrate, the photocatalyst layer may cover a portion of, or all, of one or more surfaces of the optical substrate onto which it is coated. In some embodiments, the photocatalyst layer may cover at least about 10, at least about 25, at least about 35, at least about 50, at least about 60, at least about 65, at least about 70, at least about 75, at least about 80, at least about 85, at least about 90, at least about 95, at least about 99 percent of the surface of the optical substrate onto which it is coated or of the optical waveguide. In some cases, all (i.e., 100 percent) of the total surface area of the optical waveguide may be covered by the photocata lytic layer.

[0092] Additionally, or in the alternative, the photocatalyst layer may cover not more than about 99, not more than about 90, not more than about 85, not more than about 80, not more than about 75, not more than about 70, not more than about 65, not more than about 60, not more than about 55, or not more than about 50 percent of the total surface of the optical substrate of the optical waveguide.

[0093] In other embodiments, less than the total surface area of a surface of the optical waveguide may be coated with the photocatalyst layer. One example of this discontinuous type of photocatalyst layer 618 coating on an optical substrate 612 of an optical waveguide 610 is provided in FIG. 9. Although shown in FIG. 9 as comprising an optical fiber, the optical substrate 618 canhave any suitable size, shape, and configuration as described herein. Further, the photocatalyst layer 618 can be of any type and can be applied in any thickness as described in detail herein.

[0094] Turning now to FIG. 9, an embodiment is shown wherein the optical fiber 612 is only partially coated with the photocatalyst layer 618, thereby forming portions or areas of the optical fiber 612 that are coated with the photocatalyst layer 618 (e.g., coated areas 620) and portions or areas of the optical fiber 612 that are not coated with the photocatalyst layer 618 (e.g., uncoated areas 622). In some embodiments, the coated areas 620 of the optical substrate 612 may not be in contact with adjacent coated areas and, thus, may be spaced apart from one another by at least about 100 microns, at least about 250 microns, at least about 500 microns, or at least about 1 mm and / or not more than about 25 cm, not more than about 20 cm, not more than about 15 cm, not more than about 10 cm, or not more than about 5 cm. Although shown in an alternating pattern of generally similarly sized areas, the coated areas 620 and uncoated areas 622 can have a wide variety of patterns, depending on the specific design, configuration, and end use of the optical waveguide 610.

[0095] In some embodiments, at least one of the coated areas 620 of the optical substrate 612 may be spaced apart from at least one another coated area (and / or from the UV light source) by at least about 1 m, at least about 5 m, at least about 25 m, at least about 50 m, at least about 100 m, or at least about 150 m and / or not more than about 750 m, not more than about 500 m, not more than about 250 m, or not more than about 150 m.

[0096] The presence and placement of coated areas 620 and uncoated areas 622 on an optical waveguide 610 may help control the amount of UV light passing through the optical substrate 612 and the amount of UV light exiting the surface 616 of the optical substrate 612. As discussed herein, increasing the amount of UV light exiting the surface of the optical substrate 612 may be desirable when the surface of the optical substrate 612 is coated with the photocatalyst layer 618. In such cases, the UV energy transmitted out of the optical substrate 612 may be absorbed by the photocatalyst in the overlying photocatalyst layer 618, thereby effectively irradiating the catalyst with UV light and activating it for conversion of incoming water molecules to form DHP.

[0097] In some embodiments, a large portion or most of the UV light introduced into a coated area may be discharged out of its surface and into the photocatalytic layer. For example, in some embodiments, at least about 40, at least about 50, at least about 60, or at least about 75 percent of the total UV light introduced into one end of a coated area 620 may exit the surface 616 of the coated area 620 and be absorbed by the photocatalyst layer 618. Thus, not more than about 60, not more than about 50, not more than about 40, or not more than about 25 percent of the total amount of UV light introduced into one end of a coated area 620 may exit the other end. In some cases, a significant portion of the UV light introduced into an uncoated area 622 may be retained in the optical substrate 612 in order to ensure sufficient UV light for irradiation of a subsequent coated area 620. Such embodiments may occur when, for example, two or more optical waveguides are connected in series or where a single optical substrate (e.g., an optical fiber or optical thread) is designed to irradiate UV energy only in some portions of its length.

[0098] The UV light flux from portions of the surface 616 of the optical substrate 612 coated by the photocatalyst layer 618 can be at least about 1 pW / cm2, at least about 1.5 pW / cm2, at least about 3 pW / cm2, at least about 25 pW / cm2, at least about 50 pW / cm2, at least about 100 pW / cm2, at least about 250 pW / cm2, at least about 500 pW / cm2, or at least about 750 pW / cm2and / or definitely less than 1 W / cm2, and more preferably, not more than about 10 mW / cm2, not more than about 7.5 mW / cm2, not more than about 5 mW / cm2, not more than about 3 W / cm2, not more than about 2 W / cm2, not more than about 1 W / cm2, or not more than about 750 pW / cm2. UV flux is measured using a General UV513AB Digital Light Meter.

[0099] Similarly, in the uncoated areas 622 of the optical waveguide 610, it may be desirable to retain as much UV light in the optical substrate 612 as possible. For example, in such areas of the optical waveguide 610, larger amounts or proportions of UV energy may be passed through the optical waveguide 610 than are permitted to escape. For example, in some embodiments, at least about 85, at least about 90, at least about 95, or at least about 97 percent of the total amount of UV light introduced into one end of an uncoated area 622 is discharged from the other end.

[0100] In short, uncoated areas 622 of optical substrates 612 may be used to convey as much UV light from one area (e.g., optical waveguide) to another with little or no loss of UV energy. In some embodiments, the UV light flux from portions of the surface 616 of the uncoated areas 622can be not more than about 3 .W / cm2, not more than about 1 .W / cm2, not more than about 0.5 |iW / cm2, or not more than about 0.1 |iW / cm2. In some cases, the UV light flux from portions of the surface 616 of the uncoated areas 622 can be nearly 0 .W / cm2.

[0101] In order to further control the amount of UV light discharged from the surface 616 of the optical substrate 610, at least a portion of the surface 616 underlying the coated areas 620 of the optical substrate 610 may comprise a plurality of surface defects. Although not wishing to be bound by theory, it is hypothesized that surface roughness (e.g., increased defects in the surface) of the optical waveguide help to increase the amount of UV light directed out of its surface and into the photo catalytic layer. Examples of surface defects include knicks, cuts, scratches, and other types of imparted surface roughness. In some embodiments, at least a portion of the surface 616 in one of more of the coated areas 620 of an optical substrate 612 may comprise a surface defect density of at least about 20 percent, at least about 25 percent, at least about 30 percent, or at least about 35 percent and / or not more than about 95 percent, not more than about 90 percent, not more than about 85 percent, or not more than about 80 percent of the total surface area of the optical fiber, measured by a Lecia Z16 APO optical telescope.

[0102] Achievement of a surface defect density in the above ranges can be done by, for example, scratching or roughening at least a portion of the surface of the optical waveguide using sandpaper, steel wool, or other roughening material. In other cases, the surface of the optical waveguide can be chemically etched, such as, for example, with a strong acid such as hydrofluoric acid (HF). Another way to increase surface defect density is to twist or bend the fiber into a helical fiber or to twist, bend, or tie the fiber onto itself to form a twisted optical waveguide. An example of a helical fiber is provided is illustrated in FIG. 3.

[0103] Further, referring again to FIG. 9, in some cases, at least a portion of the uncoated areas 622 of the surface of the optical substrate 612 may include a layer of cladding 636 to further retain UV light within the optical substrate 612 (e.g., fiber). The cladding layer 636, which typically has a refractive index that is less than the refractive index of the optical material used to form the optical substrate, may be formed from any suitable material, including for example, UV absorptive or UV-blocking materials. Examples of suitable cladding materials include, but are not limited to, oils, waxes, and polymers, such as, for example, fluoride-doped silica.

[0104] The cladding layer 636 may be a single-layer or double-layer cladding and can have an average thickness of at least about 50, at least about 75, or at least about 100 microns and / or not more than about 500, not more than about 250, or not more than about 200 microns. Overall, the cladding layer 636 may be present on less than about 50, less than about 45, less than about 40, less than about 35, less than about 30, less than about 25, or less than about 20 percent of the total combined surface area of the optical waveguide 610. In some embodiments, at least about 85, at least about 90, at least about 95, at least about 97, or at least about 99 percent of the total surface 616 of the optical substrate 612 can be covered by the photocatalyst layer 618 or the cladding layer 636.

[0105] In some embodiments the refractive index of the cladding layer 636 can be lower than the refractive index of the optical substrate 612 by at least about 0.001, at least about 0.005, at least about 0.010, at least about 0.050, at least about 0.100, or at least about 0.500, The refractive index of the cladding layer 636 can be less than 1.45, less than about 1.42, less than about 1.40, less than about 1.37, or less than about 1.35 and / or it can be at least about 1.25, at least about 1.27, at least about 1.30, or at least about 1.32. Adjusting the relative refractive indices of the optical substrate 612, the photocatalyst layer 618, and the cladding layer 636, when present, can also help control the amount of UV light permitted to escape from or retained within the optical substrate 612.

[0106] The photocatalyst layers and cladding layers described herein may be applied to the optical substrates in any suitable manner. Examples of methods of applying these layers include, but are not limited to, dipping, spray coating, brushing, melt coating, and combinations thereof. Once applied, the photocatalyst layer and / or cladding layer can be heated or otherwise permitted to dry to thereby provide a photocatalyst and / or cladding layer having properties as described herein.

[0107] Regardless of its structure (e.g., fiber or sheet), optical substrates as described herein may have a total open area of at least about 10, at least about 15, at least about 20, or at least about 25 percent and / or not more than about 80, not more than about 75, not more than about 70, not more than about 65, or not more than about 60 percent. Open areas within this range apply both to optical substrates and to optical waveguides, which include an optical substratecoated with a photocatalyst layer, with the optical substrate open areas being at least slightly higher than the same substrate when coated with the photocatalyst layer. As discussed in further detail below, utilizing optical substrates with percent open areas within these ranges helps regulate the flow of air through the corresponding waveguide, thereby increasing the efficiency of DHP generation and / or the amount of DHP generated.Optical Couplers / Splitters

[0108] In some embodiments, the photocata lytic DHP devices of the present technology may include one or more optical couplers or optical splitters for connecting two or more UV light sources to an optical waveguide and / or for connecting two or more optical waveguides to one another. For example, in some embodiments, an optical coupler may connect two optical waveguides in series or may combine the UV light from two UV light sources into a single optical waveguide. Additionally, in some case, an optical splitter may divide the energy from a single UV light source or into multiple (two or more) optical waveguides.

[0109] Examples of an optical couplers 730 and an optical splitter 740 are shown in FIG. 10a. As shown in FIG. 10a, the optical coupler 730 includes a pair of inlets 712, 714 combined into a single outlet 716, while the optical splitter 740 includes a single inlet 722 split into a pair of outlets 724, 726. Although shown in FIG. 10a with relation to fibers including only one or two inlets or outlets, couplers and splitters of the present technology could include any number of inlets and outlets according to the specific design needed.

[0110] Additionally, in some embodiments, the photocatalytic DHP devices described herein can include an optical coupler and an optical splitter connected to either end of a connecting waveguide. In such embodiments, the connecting waveguide can be used to transport UV light between two or more optical waveguides. Several examples of such configurations are shown in FIG. 10b. Each example provided in FIG. 10b includes several inlet optical fibers 812 combined at a coupler 820 to form a connecting waveguide 822. The connecting waveguide 822 may extend for any suitable length before being divided by a splitter 830 into another plurality of outlet optical fibers 832. As generally shown in FIG. 10b, the connecting waveguide 822 can be formed by twisting the inlet optical fibers 812, optionally melting or fusing the fibers together, or tapering the inletfibers 812 to form a single connecting waveguide 822, which is then subsequently divided to provide a plurality of outlet fibers 832.

[0111] In other embodiments, as connecting waveguide may be used to connect one or more UV light sources to one or more optical waveguides. Thus, in some cases, the connecting waveguide may not include an optical coupler and / or optical splitter. Several embodiments of optical configurations including at least one connecting waveguide will be discussed in detail shortly with respect to FIGS. 11 to 13. Regardless of its specific configuration or function, the length of the connecting waveguide may depend on the specific application but can be in the range of from about 2 to about 25 inches, about 5 to about 20 inches, or about 7.5 to about 15 inches, or it can be in the range of from about 1 to about 350 feet, about 5 to about 250 feet, or about 10 to about 100 feet.

[0112] Optical couplers, optical splitters, and connecting waveguides may be formed from the same material as the optical substrates used in the optical waveguides but may not include a photocatalyst layer. Thus, less than about 5, less than about 2, less than about 1, or less than about 0.5 percent of the surface of the optical couplers, optical splitters, and / or connecting waveguides may be coated with a catalyst. Instead, at least about 60, at least about 75, at least about 80, at least about 90, or at least about 95 percent of the surface of the optical coupler, optical splitter, and / or connecting waveguides may be coated with a cladding, such that the UV light flux out of these optical elements can be less than about 2, less than about 1, less than about 0.5, or less than about 0.1 percent of the total input light flux, measured as described herein. This is less than the flux from the photocatalyst-coated optical waveguide. Alternatively, in some embodiments, the connecting waveguide may be at least partially coated by a photocatalyst layer as described in detail herein with regard to the optical waveguide.UV Light Source

[0113] Photocata lytic devices for generating DHP according to embodiments of the present technology further include at least one UV light source for generating UV light or energy. As used herein, the terms "UV light" and "UV energy" are interchangeable and refer to electromagnetic radiation having a wavelength of from 100 to 410 nm or from about 260 nm to about 410 nm, or about 310 nm to about 410 nm. In some cases, the UV light may be or comprise predominantlyUV-A light, which has a wavelength from 320 nm to 410 nm, or UV-C light, which has a wavelength of from 100 to 290 nm. In some cases, the UV light generated by the UV light source can have a predominant wavelength of 245 nm, 312 nm, or 365 nm. Examples of suitable UV light sources include, but are not limited to, UV bulbs, UV lamps, UV light emiting diodes (LEDs), and combinations thereof.

[0114] In some embodiments, the power of the UV light source (normalized by the total surface area of the photocatalyst on the optical substrate) can be at least about 3 W / cm2, at least about 10 pW / cm2, at least about 25 pW / cm2, at least about 50 pW / cm2, at least about 100 pW / cm2, at least about 250 pW / cm2, at least about 500 pW / cm2, or at least about 750 pW / cm2and / or mot more than about 10 W / cm2, not more than about 7.5 W / cm2, not more than about 5 W / cm2, not more than about 3 W / cm2, not more than about 2 W / cm2, not more than about 1 W / cm2, or not more than about 750 W / cm2. Power of the UV light source is measured using a General UV513AB Digital Light Meter.

[0115] The UV light source or sources utilized by the photocata lytic device can be coupled to at least one end of an optical waveguide (or optical substrate) for introducing UV light into the optical substrate. In some cases, a single optical waveguide may be coupled with only one UV light source (e.g., at one end of the optical substrate). In other cases, a single optical waveguide may be coupled to two or more UV light sources located at different locations along the optical substrate. For example, when the optical substrate comprises an optical fiber, one UV light source may be coupled to each end of the optical fiber. When the optical substrate comprises an optical sheet, one (or two, or three, or four or more) UV light sources can be coupled to various locations along the edge and / or major surfaces of the optical sheet.

[0116] A single photocata lytic device can utilize one UV light source, or two or more (at least two, at least three, at least four, or five or more), depending on its specific size and configuration. For example, in some embodiments when the optical waveguide comprises an optical textile, one or more UV light sources may be coupled to different optical fibers or optical threads within the textile. For example, each, or two or more, of the weft and warp optical fibers or optical threads in an optical textile substrate may be coupled to a UV light source. In some cases, optical combiners may be used to combine the UV light from two or more UV sources into an opticalwaveguide, and in some cases, optical splitters may be used to divide the UV light from a single source into two or more optical waveguides.

[0117] In addition to the UV light source, photocata lytic devices according to embodiments of the present technology can include one or more power sources for providing power to the UV light source. In some cases, the power source can comprise a battery (e.g., an alkaline battery or lithium battery) and, in other cases, the power course can comprise an electrical outlet. Photocata lytic devices as described herein may also be switchable between battery and electrical power sources.

[0118] Referring now to FIGS. 11 to 13, several embodiments of configurations including UV light sources and optical waveguides according to the present technology are provided in FIGS. 11 to 13. Although described separately herein with respect to an individual Figure, it should be understood that one or more elements or portions of configurations shown in these Figures can be used alone or combined with one or more other elements or portions without departing from the scope of the present technology.

[0119] Turning initially to FIG. 11, a photocata lytic waveguide configuration 900 including a pair of UV light sources 902, a pair of power sources 904, a pair of connecting waveguides 906, and an optical waveguide 910. As shown in FIG. 11, connecting waveguides 906 are connected to either end of an optical waveguide 910 and to two separate UV light sources 902, which are coupled to two separate power sources 904. Connecting waveguides 906 may not include any photocatalyst layer and may instead be coated with a cladding layer 920. In some cases, when the power source or sources 704 are close to the optical waveguide, connecting waveguides 906 may not be used.

[0120] Optical waveguide 910 can comprise any of the optical waveguides described herein and, in some cases, can comprise an optical textile coated with a photocatalytic layer 918. For example, in some cases, the optical waveguide 910 can include a single fiber twisted and / or woven upon itself with a UV light source 902 coupled to each end of the fiber. Alternatively, the optical waveguide 910 can include two fibers interwoven with one another with one end of each coupled to a UV light source 902. In other cases, the optical waveguide 910 can include a single fiber twisted, coiled, or formed in an undulating pattern with a single UV light source 902 coupledto each end. In some embodiments, optical waveguide 910 shown in FIG. 11 may include two or more waveguides (not shown) arranged in series or in parallel.

[0121] Power from the power sources 904 cause UV light generation in the UV light sources 902, which direct at least a portion of the energy into the connecting waveguides 906. The UV light then passes through the connecting waveguide 906 and into the optical waveguide 910, wherein a significant portion of the UV light escapes the optical substrate (not shown in FIG. 11) and enters the photocata lytic layer coated on at least a portion of the surface of the optical substrate (not shown in FIG. 11). The resulting activated photocatalyst may then be used to generate DHP according to embodiments of the present technology.

[0122] Referring now to FIG. 12, another photocatalytic waveguide configuration 1000 according to embodiments of the present technology is shown as comprising a single UV light source 1002, first and second optical splitters 1022a, b, an optical coupler 1024, an optional connecting waveguide 1006, and a pair of optical waveguides 1010a, 1010b arranged in series. As shown in FIG. 12, a single UV light source 1002 couple to a power source 1004 can discharge UV light into a first optical splitter 1022a, which divides the UV light into several separate fibers, which are thereafter coupled to the optical waveguide 1010a. Optical waveguide 1010a can be any type of waveguide described herein, and may include, for example, an optical substrate chosen from an optical sheet, a plurality of optical fibers, or an optical textile or woven structure. Additionally, although shown as including four outlets, the first optical splitter 1022a may include any suitable number, including at least 2, at least 3, at least 5, at least 6, at least 7, at least 8, or 9 or more outlets.

[0123] As discussed previously, UV light from the optical substrate (not shown) in the optical waveguide 1010a activates the photocatalyst layer 1018 so it can produce DHP when contacted with humid air. Remaining UV light may then pass out of the optical waveguide 1010a via optical coupler 1024 and into a single connecting waveguide 1006, which is coated with a cladding layer. Upon transmission through the length of the connecting waveguide 1006, the UV light may pass through the second optical splitter 1022a, wherein it is again divided and introduced into multiple locations along or within the second optical waveguide 1010b. Accordingly, UV light from a singlesource may be used in two or more optical waveguides in series. Alternatively, or in addition, the optical waveguides 1010a and / or 1010b may include two or more optical waveguides in parallel.

[0124] In some cases, the photocatalytic device may be a modular device with two or more optical waveguides, a plurality of connectors (e.g., optical couplers and / or optical splitters), and one or more UV light sources that can be coupled to one another within a treatment area in order to provide a desired concentration of DHP to the area. In some cases, such modular units may be permanently installed such that the device cannot be disassembled without causing damage to one or more parts (e.g., optical waveguide, UV light source, or connectors). In other cases, the modular device may be removable, such that it can be disassembled (and reassembled in the same or a different location) without substantial replacement of the component parts.

[0125] Turning now to FIG. 13, yet another photocatalytic waveguide configuration 1100 is provided. As shown in FIG. 13, configuration 1100 includes a first and second UV light source 1102a, b and an optical waveguide that includes first and second photocatalyst-coated optical fibers 1112a, b interwoven with one another to form an optical textile 1150. Although shown here with two UV light sources and two optical fibers, it should be understood that any suitable number of UV light sources and interwoven optical fibers can be used in a similar manner according to embodiments of the present technology. Further, as shown in FIG. 13, one of the UV light sources 1102a can be coupled to the first optical fiber 1112a and the second UV light source 1102b can be coupled to the second optical fiber 1112b. The same, or different power sources 1104, can be coupled to each of the UV light sources 1102a, b.

[0126] One or more of the photocatalytic waveguide configurations as described herein or modified with one or more features as also described herein may be used in a DHP generating device of the present technology. Such devices may include stand-alone devices for home, business, or industrial use, or a drop-in system that can be inserted, either during construction or as a retrofitted device, into one or more parts of a heating, ventilation, and air conditioning (HVAC) unit in a residential, business, or industrial setting (e.g., a duct of the HVAC system).

[0127] In some embodiments, in addition to an optical waveguide and a UV light source of the types and coupled as described herein, the DHP generating device can optionally include at least one enclosure defining an internal volume into which the optical waveguide can be inserted.In some cases, the UV light source may also be present in the internal volume, optionally along with the power source (e.g., battery). In other cases, the UV light source may be external to the enclosure and may be connectable to the optical waveguide within the enclosure when operation of the device is desirable. Similarly, the power source may also be located outside the device enclosure and operable to be connected and disconnected as needed to power the device. In operation, DHP generated at the surface of the photocatalyst may be discharged from at least one outlet of the enclosure and into the surrounding environment.

[0128] In other embodiments, the photocatalytic device may not include any type of enclosure such that, for example, the optical waveguides may be disposed within the treatment environment (and not within the internal volume of an enclosure) during operation. In such embodiments, the DHP leaving the catalyst surface is discharged into the surrounding environment immediately and does not have to exit any outlets of the device. Examples of such photocatalytic devices are shown, for example, in FIGS. 5a and 5b.

[0129] Further, in some embodiments, the photocatalytic device may include a fan for moving humid air into and out of the device, particularly when the device is a stand-alone device and / or when it includes an enclosure. In other embodiments, particularly when the photocatalytic device is inserted or built into the ductwork of an HVAC system, the device may not include its own fan but may utilize the fan within the HVAC system for moving air through the device and over the photocatalyst-coated optical waveguide.

[0130] Additionally, the photocatalytic device can include one or more filters upstream of the optical waveguide for removing unwanted components from the incoming air stream. For example, in some cases, at least one filter designed to remove volatile organic compounds (VOCs) can be used, alone or in combination with at least one filter for removing airborne particulates (e.g., dust, dirt, etc.) A carbon black filter may be used to remove VOCs and an air filter having a MERV rating of at least 5, at least 7, at least 9, or at least 11 and / or not more than about 15, not more than about 13, or not more than about 10 may be used to remove the particulates.

[0131] In some embodiments, each of the filters can have a removal rate of at least about 90, at least about 95, at least about 97, at least about 99, or at least about 99.9 percent. As a result, the humid air stream introduced into the optical waveguide can comprise less than about 500, lessthan about 250, less than about 100, or less than about 50 ppm of airborne particulates, and / or less than about 500, less than about 250, less than about 100, or less than about 50 ppm of volatile organic compounds (e.g., VOCs). In some embodiments, the humid air stream may comprise less than 10, less than 5, or less than 1 ppm of particulates and / or VOCs, or no particulates or VOCs may be detected in this stream.EXAMPLE

[0132] A waveguide having a configuration similar to the one shown in FIG. 5A was prepared by coating a plurality of individual quartz optical fibers with an aqueous titanium dioxide (TiCh) slurry. Both ends of the fibers were left uncoated. After drying, the resulting catalyst-coated fibers were assembled in a base that included a 2W / 0.2A LED bulb with a lambda (max) of emission of 367 nm (with 9 nm FWHM). The coated fibers were oriented within the base such that UV light emitted from the bulb entered the uncoated end of the fibers and was permitted to propagate through the core, with at least a portion of the UV light exiting the core at various points along the length of the fiber and activating the catalyst deposited along the surface of the fibers.

[0133] The assembled waveguide was placed in an environmental chamber under ambient temperature and pressure. The UV bulb was turned on and the device permitted to operate for a period of 24 hours, with the concentration of dry hydrogen peroxide (DHP) within the environmental chamber being measured over the operating period using the measurement method described herein. After an initial spike in DHP concentration (likely due to new catalyst and fully hydrated catalytic sites), the equilibrium concentration of DHP was measured to be around 0.8 ppb or less.DEFINITIONS

[0134] As used herein, the terms "a," "an," and "the" mean one or more.

[0135] As used herein, the term "and / or," when used in a list of two or more items, means that any one of the listed items can be employed by itself or any combination of two or more of the listed items can be employed. For example, if a composition is described as containing components A, B, and / or C, the composition can contain A alone; B alone; C alone; A and B in combination; A and C in combination, B and C in combination; or A, B, and C in combination.

[0136] As used herein, the terms "comprising," "comprises," and "comprise" are open- ended transition terms used to transition from a subject recited before the term to one or more elements recited after the term, where the element or elements listed after the transition term are not necessarily the only elements that make up the subject.

[0137] As used herein, the terms "having," "has," and "have" have the same open-ended meaning as "comprising," "comprises," and "comprise" provided above.

[0138] As used herein, the terms "including," "include," and "included" have the same open-ended meaning as "comprising," "comprises," and "comprise" provided above.

[0139] As used herein, the phrase "at least a portion" includes at least a portion and up to and including the entire amount or time period.CLAIMS NOT LIMITED TO DISCLOSED EMBODIMENTS

[0140] The preferred forms of the invention described above are to be used as illustration only and should not be used in a limiting sense to interpret the scope of the present invention. Modifications to the exemplary embodiments, set forth above, could be readily made by those skilled in the art without departing from the spirit of the present invention.

[0141] The inventors hereby state their intent to rely on the Doctrine of Equivalents to determine and assess the reasonably fair scope of the present invention as it pertains to any apparatus not materially departing from but outside the literal scope of the invention as set forth in the following claims.

Claims

CLAIMSWhat is claimed is -1. A method of generating dry hydrogen peroxide (DHP), said method comprising:(a) transmitting UV light through at least one optical waveguide, wherein said optical waveguide comprises an optical substrate at least partially coated with a photocatalyst layer;(b) permitting at least a portion of said UV light to escape said optical substrate in areas where said optical substrate is coated with said photocatalyst layer to thereby irradiate at least a portion of said photocatalyst layer with UV light; and(c) contacting at least a portion of said photocatalyst layer being irradiated with UV light with a humid air stream to generate dry hydrogen peroxide (DHP).

2. The method of claim 1, further comprising subsequent to step (c), discharging said DHP from said device and into a surrounding environment to achieve an equilibrium concentration of DHP in said surrounding environment is not more than 5 parts per billion by weight (ppb).

3. The method of claim 2, wherein said surrounding environment comprises a room, a building, or a vehicle.

4. The method of claim 2, wherein said surrounding environment comprises a duct of a heating, air conditioning, and ventilation (HVAC) system.

5. The method of any of claims 1-4, wherein said optical substrate has a first refractive index and said photocatalyst layer has a second refractive index higher than said first refractive index by at least about 0.050.

6. The method of claim 5, wherein the second refractive index of said photocatalyst layer is at least about 2.00.

7. The method of any of claims 1-6, wherein said photocatalyst layer has an average thickness of about 10 nm to about 100 pm.

8. The method of any of claims 1-7, wherein said photocatalyst layer covers at least about 10 percent and / or not more than 75 percent of the total surface area of said optical substrate.

9. The method of any of claims 1-8, wherein said photocatalyst layer comprises a metal oxide photocatalyst and wherein said metal oxide photocatalyst is present in said photocatalyst layer in an amount of about 10 to about 95 weight percent, based on the total weight of said photocatalyst layer.

10. The method of claim 9, wherein said metal oxide comprises titanium dioxide.

11. The method of any of claims 1-10, wherein said optical substrate comprises a plurality of optical fibers.

12. The method of any of claims 1-10, wherein said optical substrate comprises an optical sheet having a pair of opposing major surfaces and a thickness defined therebetween, wherein said optical sheet comprises a plurality of apertures extending through said thickness between said major surfaces.

13. The method of claim 12, wherein said thickness of said optical sheet is in the range of from about 1 micron to about 1 mm, wherein the thickness of said photocatalyst layer on at least a portion of said optical sheet is in the range of from about 10 nm to about 100 nm, and wherein said plurality of apertures covers at least about 50 percent of said major surfaces of said optical sheet.

14. The method of any of claims 1-13, wherein said UV light source comprises two or more UV light sources.

15. The method of any of claims 1-14, wherein said optical waveguide has a UV light flux of less than 10 mW / cm2and wherein said UV light source predominantly generates UV light having a wavelength of from about 260 nm to about 410 nm.

16. The method of any of claims 1-15, wherein the transmission of UV light out of the surface of the waveguide and into the photocata lytic layer in said areas where said optical substrate is coated with said photocatalyst layer is at least 1.5 |iW / cm2.

17. The method of any of claims 1-16, wherein the optical waveguide is not immersed in water during steps (a) through (c).

18. The method of any of claims 1-17, wherein the optical waveguide is located within an internal volume of an enclosure and subsequent to said contacting, discharging at least a portion of said DHP out of said enclosure and into a surrounding environment.

19. A photocatalytic device for generating dry hydrogen peroxide (DHP), said device comprising: at least one optical waveguide for transmitting UV light, wherein said at least one optical waveguide comprises - an optical substrate; and a photocatalyst layer coated onto at least a portion of said surface of said optical substrate; and at least one UV light source coupled to one of said pair of opposite ends of said optical substrate for introducing UV light into said optical waveguide, wherein the photocata lytic device is configured to generate DHP at or near the surface of the photocatalyst layer and to discharge at least a portion of the DHP to a surrounding environment when in operation.

20. The photocatalytic device of claim 19, wherein said optical substrate comprises a plurality of elongated fibers, wherein each of said fibers includes a first end and a second end and wherein at least the first end of each of said fibers is secured in a base and the second end of each of said fibers is unsecured.

21. The photocatalytic device of claim 19, wherein said optical substrate comprises a plurality of elongated fibers, wherein each of said fibers includes a first end and a second end, and wherein each of said first and second ends of said fibers are secured.

23. The photocatalytic device of claim 19, wherein said optical substrate comprises an optical sheet having a pair of opposing major surfaces and a thickness defined therebetween, wherein said optical sheet comprises a plurality of apertures extending through said thickness between said major surfaces.

24. The photocatalytic device of claim 19, wherein said optical substrate comprises an optical textile or woven sheet.

25. The photocata lytic device of any of claims 19-24, wherein said optical substrate comprises a pair of optical substrates coupled to one another by at least one optical coupler.

26. The photocatalytic device of any one of claims 19-25, wherein said photocatalytic device comprises a single UV light source.

27. The photocatalytic device of any of claims 19-26, wherein said photocatalytic device comprises a connecting waveguide coupling said UV light source to one of said pair of opposite ends of said optical substrate, wherein said UV light source is spaced from said optical substrate by at least 1 m, wherein said connecting waveguide is coated with a layer of cladding and has a lower UV light flux than said optical waveguide coated with said photocatalyst.

28. The photocatalytic device of any one of claims 19-27, wherein the photocatalytic device further comprises an enclosure defining an interior volume in which the optical waveguide is disposed and an air distribution mechanism for discharging DHP generated out of the enclosure and into said surrounding environment during operation.

29. The photocatalytic device of any one of the claims 19-27, wherein the photocatalytic device does not include an enclosure, and the optical waveguide is disposed within said surrounding environment during operaton.

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