PHOTOACTIVE SURFACES AND SYSTEMS IMPLEMENTING SAME

TECHNOLOGICAL FIELD

The invention generally contemplates photoactive surfaces and uses thereof.

BACKGROUND OF THE INVENTION

Photoactive materials are used in a variety of applications and devices, ranging from light-sensitive circuits, light-sensitive surfaces and switches to devices capable of converting light into an electrical signal. Photoactive materials interact with light to modify either their own properties or properties of the electromagnetic field applied.

While a great variety of photoactive materials are known, their stability over time and their ability to produce efficient interaction with materials present in various liquid or gaseous media is limited, hence limiting their practical industrial use.

Photodiodes are semiconductor diodes which purpose is to convert power from photons of light into electric current. The generation of electric current is created when the power of the photons is absorbed by the surface of a semiconductor. In certain configurations of devices utilizing photodiodes, photo -generated electrons and holes are exploited to accelerate chemical reactions, causing degradation of gas or liquid-borne pollutants. Some of the means known for achieving pollutant degradation via a photocatalytic activity are disclosed in references [1] through [9].

PUBLICATIONS

[1] Korean patent application no. KR 102279008

[2] Korean patent application no. KR 102244078

[3] International patent publication no. WO 2008/055126

[4] European patent no. EP 0636575

[5] Korean patent application no. KR 10-2342295

[6] Chinese patent application no. CN 111744520

[7] US patent no. US 10,249,836

[8] Chinese patent application no. CN 113304603

[9] International patent publication no. WO 2014/016239 GENERAL DESCRIPTION

The inventors of the technology disclosed herein have developed a novel and highly photoactive material that has demonstrated effective chemical interaction with gas- borne organic and inorganic substances, including air-borne microorganisms that may be present in aerosols, resulting in their degradation. The ability to eradicate, kill or neutralize air borne microorganism with a high effectiveness, over long periods of time, is highly unexpected. The superior photoactivity suggests a mechanism of action that may involve several mechanisms of action, including trapping or adhesion and degradation via mechanisms such as, for example, radical generation, electrostatic charge, adhesion to the surface of microbial cells, interruption of transmembrane electron transfer, disruption of cell membrane and cell wall, DNA damage, and oxidative stress. Photoactive surfaces of the invention have thus been exploited as purification and/or adsorbant surfaces in constructing purification devices such as air purification systems. The photoactive surfaces may additionally be used as self-cleaning surfaces, as building materials requiring low maintenance and potentially high durability, as compared to existing selfcleaning materials.

As devices and systems of the invention implementing photoactive surfaces, as disclosed herein, may involve a variety of chemical/biological and chemophysical mechanisms of neutralization, inactivation or degradation, the purification devices and systems have been structured and configured to be not selective towards a certain type of pollutant, contaminant or agent, but rather meet various industrial and domestic challenges, amongst these increased effectivity in neutralizing or inactivating of chemical pollutants and contaminants, including organic and inorganic volatiles, biological toxins as well as microorganisms such as bacteria, viruses, fungi, molds, etc., which may be present in a medium to be purified, e.g., air or water.

In its broadest form, the technology concerns a purification or an adsorbent (matrix) material, which comprises or consists a photoactive material as disclosed herein. The term purification or adsorbent (matrix) material" generally refers to two equivalent descriptive alternatives of the photoactive material. In the first alternative, the matrix material, i.e., generally the material which forms the main part of the photoactive component and which defines the main body of the photoactive component, is said to be a purification material (or a purificator), namely capable of clearing out or removing an agent from a medium (namely purifying the medium from said agent), wherein the mechanism of purification may involve any chemical or physical interaction with the agent. In the second alternative, the matrix material, as defined, is described as an adsorbent material capable of adsorbing an agent from a medium. The adsorption may subsequently lead to degradation or purification of the medium from the agent.

In some embodiments, the purification or adsorbent matrix material is an air- purification material intended for use in air-purification systems.

In a first of its aspects, the invention concerns a purification, e.g., an Oir- urification or an adsorbent material (or matrix material) comprising or consisting a photoactive material comprising TiO ₂ , a metal species and a carbonaceous material, wherein the metal species is a metal different from Ti and/or a metal oxide thereof. As disclosed herein the matrix material is formed by thermally treating Ti-ethylene glycol (Ti-EG) hybrid material formed in presence of the metal species on a carbonaceous material.

Thus, the invention also provides a purification or an air- purification or an adsorbent matrix material comprising a photoactive TiO ₂ /metal species formed by thermally treating a carbonaceous material provided with a film of Ti-ethylene glycol (Ti- EG) hybrid material in presence of the metal species, wherein the metal species is a metal different from Ti and/or a metal oxide thereof. In certain configurations, the metal species is associated or contained within the carbonaceous material, while in others the metal species forms a layer or material regions on a surface of the carbonaceous material. In either configuration, the metal species may be deposited on the carbonaceous material prior to formation of the film of the Ti-EG.

The photoactive material being the matrix material is a highly adsorbent photoactive material comprising a metal oxide material, such as titanium oxide, TiO ₂ , and at least one metal and/or an oxide thereof, wherein the photoactive material is formed by thermal decomposition of a metalcone material, such as a titanium-ethylene glycol (Ti- EG) hybrid material, provided on a carbonaceous material, as defined herein. The photoactive material may be formed as such or may be formed directly as a film or a coat on a surface. The photoactive material or film or coat may be implemented in a variety of systems and apparatuses for providing photocatalytic capabilities in a variety of areas.

The high adsorption of the photoactive materials of the invention may be expressed in Brunauer-Emmett-Telle (BET) values. An improved gas adsorption was observed following thermal treatment of the preactivated film. The BET values for a given carbonaceous material, such as CNT mats, provides surface areas of about -400 m ² /gr. While thermal treatment of the carbonaceous material increased the surface area by -10%, forming a preactivated layer as disclosed herein, and thermally treating same, increased the surface area by -20%. In addition to the increase in BET surface area, the thermal treatment yielded defect sites that were found to promote adsorption and formation of polar sites.

Thus, in another of its aspects, the invention provides a photoactive material of a form metal oxide/metal species/carbonaceous material.

The invention also provides a photoactive material of a form TiO ₂ /metal species/carbonaceous material.

As used herein, the expression “metal oxide/metal species/carbonaceous material encompasses any composition of matter that comprises a carbonaceous material that is associated with, coated by or generally provided with a metal oxide and a metal species, each as defined herein. The expression is not intended as limiting to any type of interaction between the components, nor to suggest a particular sequence of association between the components. According to the general meaning of the expression, the metal oxide may be associated with the carbonaceous material, which is also associated with the metal species; or the metal oxide may be associated with the metal species and both are associated with the carbonaceous material. In some configurations, the metal species is associated with or contained in the carbonaceous material and the metal oxide is associated with the surface of the carbonaceous materials. In other configurations, the metal oxide and metal species are associated with a surface of or contained within the carbonaceous material. Similarly, the expression “TiO ₂ /metal species” is not meant to suggest any particular interaction or association between the TiO ₂ and the metal species.

In some embodiments, the metal oxide/metal species/carbonaceous material is a composition of matter that comprises TiO ₂ , a metal species and a carbonaceous material, each as defined herein.

In some embodiments, the photoactive material comprises TiO ₂ /metal species (one or more metal species selected from a metal, an oxide thereof, and an oxide of a different metal), wherein the composition of matter is formed by thermally treating a hybrid metal oxide-organic material such as Ti-EG prepared by TiCl ₄ (Ti) and ethylene glycol (EG) precursors. A special set of hybrid organic-inorganic films based on metal precursors and various organic alcohols yields metal alkoxide films that can be described as "metalcones." The metacones may be formed of a variety of metals, as further disclosed below. The hybrid organic-inorganic material is provided on a carbonaceous material in the presence of a metal or a metal oxide, under conditions suitable for converting the material into a highly adsorbent photoactive material, or for imparting photocatalytic activity to said material.

The invention further provides a photoactive TiO ₂ /metal species formed by thermally treating a carbonaceous material provided with a film of a Ti-EG hybrid material in the presence of a metal or a metal oxide. As disclosed herein, the metal or metal oxide (herein a metal species) may be part of the carbonaceous material or may be added prior to thermal treatment of the carbonaceous material having a film of a Ti-EG hybrid material formed on its surface or associated therewith.

The invention further provides a photoactive metal oxide, e.g., titanium oxide, provided on a surface of a carbonaceous material or associated with a carbonaceous material, wherein the photoactive metal oxide is formed by thermal treatment of a precursor metalcone hybrid material. In such products, the photoactive material is free of a metal species, as defined herein.

The "photoactive material” of the invention is a composition of matter forming a matrix material with properties as disclosed herein. The composition of matter is of the metal oxide/metal species/carbonaceous material, such as TiO ₂ /metal species/carbonaceous material. The material is a high adsorption, high surface area solid composition of the metal oxide, e.g., titanium oxide and a metal species, being at least one metal or metal oxide, provided on a surface of a highly porous or a high surface area carbonaceous material. The photoactive material is described as a “TiO ₂ /metal species” material, in which the TiO ₂ is present with a metal species that is selected from a metal different from titanium, and which may be a metal or a metal oxide of one or more metals.

The “ metal species " present with the TiO ₂ may be selected from metals such as Fe, Au, Ag, Cu, Ni, Zn, Mn and/or metal oxides thereof, at times in combination with other non-metal based materials or non-metal atoms, such as Si-based materials or atoms, P-based materials or atoms, and S-based materials or atoms. The metal species may be two or more metals (zero valent) or a metal and an oxide thereof or an oxide of a different metal. In other words, the metal species may be selected amongst metals (zero valent) and metal oxides, wherein the metal oxides are not necessarily oxides of the zero valent metal.

In some embodiments, the metal species is Fe ⁰ and/or FeO ₂ .

In some embodiments, the photoactive material is a material composition comprising TiO ₂ and Fe ⁰ and FeO ₂ (presented in short as TiO ₂ /Fe ⁰ /FeO ₂ ); or TiO ₂ and Fe ⁰ (TiO ₂ /Fe ⁰ ); or TiO ₂ and FeO ₂ (TiO ₂ /FeO ₂ ) provided on a carbonaceous material, as defined and selected herein.

In some embodiments, the TiO ₂ /metal species is obtained by thermal treatment of a hybrid material comprising titanium and ethylene glycol (formed in the presence of water) and designated herein Ti-ethylene glycol (or Ti-EG) and formed as a film on a carbonaceous material in the presence of a metal species, as defined.

The photoactive material having the material composition TiO ₂ /metal species/carbonaceous material, namely a TiO ₂ /metal species provided on a carbonaceous material (and formed as disclosed herein), or a TiO ₂ provided in a carbonaceous material comprising the metal species, is not comparable in its photoactivity to commercially available TiO ₂ or TiO ₂ obtained by other methods. While the reason for the superior photoactivity is not entirely understood, it is clear that the TiO ₂ /metal species is uniform and highly reproducible. Comparison between TiO ₂ /metal species obtained according to the invention with TiO ₂ obtained by other methods, or such which are commercially available, supports the superior photoactivity of metal oxides of the invention. For example, the photoactivity of a material including the metal oxide formed according to the present invention on CNT as the carbonaceous material was reactive under visible light spectrum, while a commercial TiO ₂ - P25 and other types of TiO ₂ required UV light for activation of a photocatalytic oxidation. By comparing results obtained for systems of the invention to results published by companies using nanoparticles of TiO ₂ , one can identify a clear advantage: air-borne microorganisms’ deactivation and oxidation of volatile organic compounds was much faster (double and more) than the regular or commercially available titanium oxides.

The photoactive material or surface made therefore may be formed by thermal activation or thermal modification of a photo inactive or a pre-activated hybrid material or layer of Ti-EG provided in combination with or in presence of a metal species (different from Ti) or a metal precursor thereof which may be a metal of zero valency or a metal salt or a metal oxide. The thermal activation converts the photo inactive or preactivated material into a photoactive material that is different from the photo inactive or preactivated material in composition and reactivity under the visible light. UV radiation is not required. In other words, the “ photoactivity is reflected in the material ability to chemically or photo-catalytically interact with substances under visible light (solar radiation or illumination from a light source). Typically, the photoactivity comprises enabling/initiating of photocatalytic reactions or causing structural modifications in substances interacting with the photoactive material, causing their degradation. Such an interaction may involve generation of free charge carriers. It is to be clear that the photoactivity stems from contributions from each of the components making the photoactive material, including the TiO ₂ , the metal species, the carbonaceous material and any combination thereof. While a mechanistic description of such contributions is difficult to describe, results presented herein demonstrate that photoactivity of systems of the invention are superior to photoactivity demonstrated by each of the components alone, as each by itself is typically not photoactive (e.g., under visible light irradiation).

The photo inactive material or the preactivated material thermally treated to yield the photoactive material is a hybrid material that is absent of photoactivity or is substantially poor or exhibits low photoactivity. As disclosed herein, the photoactivity referred to herein is the ability to chemically or photo-catalytically interact with substances under the influence of light. The preactivated material is substantially thus unable to cause such modification, e.g., degradation.

The preactivated material may be characterized as a Ti-EG hybrid layer, wherein the titanium atom is in-layer associated with oxygen atoms and the ethylene glycol, wherein the layer is provided on a surface region of a carbonaceous material, and wherein one of the hybrid layers and the carbonaceous material comprises a metal species, as defined herein.

As disclosed herein, the metal species is a zero valent metal and/or a metal oxide, or a combination of two more such species. The metal species may be incorporated in the preactivated material prior to the thermal decomposition thereof, or may be inherently present in either the hybrid layer or the carbonaceous material. Irrespective of the source of the metal species, the metal species is not provided in a contaminating amount or a doping amount. The amount of the metal species may be between 0.5 and 10 wt%. In some embodiments, the amount of the metal species is between 3.5 and 6 wt%, or is between 1 and 10, 2 and 10, 3 and 10, 4 and 10, 5 and 10, 6 and 10, 3 and 9, 3 and 8, 3 and 7, 3 and 6, 3 and 5, 5 and 10, 5 and 9, or 5 and8 wt%.

In some embodiments, the carbonaceous material and/or metalcone precursor is enriched with or selected to contain an amount of the metal species that is greater than a doping amount, e.g., being between 0.5 and 10 wt%; or is between 3.5 and 6 wt%, or is between 1 and 10, 2 and 10, 3 and 10, 4 and 10, 5 and 10, 6 and 10, 3 and 9, 3 and 8, 3 and 7, 3 and 6, 3 and 5, 5 and 10, 5 and 9, or 5 and8 wt%.

In some embodiments, the Ti-EG is deposited on a surface of a carbonaceous material comprising an amount of the metal species as defined herein.

The carbonaceous material may be any carbon-rich material or a carbon allotrope. The carbonaceous material may be selected from carbon black, graphite, amorphous carbon, graphene, carbon wires, carbon nanowires, carbon nanotubes (CNT), carbon buds, carbon mats, carbon fullerenes, carbon nanoparticles and microparticles, glassy carbon, carbon nanofoam, carbon nitrite, and others.

In some embodiments, the carbonaceous material is a carbon allotrope.

In some embodiments, the carbonaceous material is CNT or graphene.

In some embodiments, the carbonaceous material is a carbon nanotube (CNT) or a CNT-based material. The CNT may be any of the CNTs known in the art. The CNT may be any one or a combination of carbon allotropes of the fullerene family selected from single walled carbon nanotubes, double-walled carbon nanotubes and multi-walled carbon nanotubes. The CNT may have between 1 to 10 walls and have varying dimensions. In some embodiments, the CNTs have high aspect ratios as measured by their ratio of length to diameter. The CNTs may have open or closed ends.

Where the CNT is provided in a form of a CNT assembly, it may be in a form of a collection or an array or a bundle of two or more CNTs. The assembly may be in the shape of a fiber that self-assembles into fiber bundles or a web in a random or an organized fashion. Thus, a CNT assembly used as a substrate for forming photoactive surfaces according to the invention may be a compilation of two or more CNTs, which together form a fiber or a web and/or a CNT bundle that comprises at least one CNT fiber. The CNTs within the assembly may be branched, crosslinked, or share common walls with one another. The CNTs within the assembly may have any defined shape, positioning, orientation and density. In some embodiments, the CNTs are assembled on a substrate or are collected in a macrostructure.

In some embodiments, the preactivated material is a Ti-EG hybrid layer provided on a surface region of a CNT material (e.g., individual CNTs or an assembly of CNTs, such as a CNT mat) or graphene, wherein one of the hybrid layers or the CNT material/graphene comprises Fe ⁰ and/or FeO ₂ .

In some embodiments, the photoactive material is TiO ₂ /mctal species/carbonaceous material, wherein the carbonaceous material is a CNT or a graphene associated with a layer of a composition of matter in a form TiO ₂ / Fe ⁰ /FeO ₂ or TiO ₂ /Fc ⁰ or Ti/FeO ₂ .

In some embodiments, the photoactive material is a CNT provided with a surface layer(s) of a composition of matter of TiCF and Fe ⁰ and/or FeCF; or TiCF and Fe ⁰ ; or TiCF and FeO ₂ .

In some embodiments, the photoactive material is a CNT provided with a surface layer of a composition of matter comprising TiO ₂ /Fe ⁰ / FeO ₂ or TiO ₂ /Fe ⁰ or Ti/ FeO ₂ .

In some embodiments, the TiO ₂ and the metal species are separately distributed on the carbonaceous species. In such cases, the metal species may be distributed on the surface of the carbonaceous material, while the Ti-EG hybrid layer forms a layer on the CNT or surface regions thereof.

The preactivated material may be formed by a variety of methods, including for example vapor deposition methods such as atomic layer deposition and molecular layer deposition; sol-gel deposition; spray pyrolysis technique; chemical vapor deposition (CVD), plasma enhanced (PECVD), electrospinning, spin-coating, and others.

Once the preactivated material is formed, it is converted into the photoactive form TiO ₂ /metal species/carbonaceous material under a temperature sufficient to decompose the ethylene glycol and transform the Ti component into a photoactive TiO ₂ /metal species on the carbonaceous material, as defined herein. Typically, the temperature used to form the photoactive material is above 100°C, or above 300°C. In some embodiments, the temperature is between 100 and 900°C. Depending on the composition and/or sensitivity of the substrate material, the temperature may be above or around 100, 200, 300, 400, 500, 600, 700 or 800°C.

In some embodiments, the temperature is between 200 and 900°C, 200 and 800°C, 200 and 700°C, 200 and 600°C, 200 and 500°C, 200 and 400°C, 400 and 900°C, 500 and 900°C, 600 and 900°C, 700 and 900°C, 300 and 900°C, 300 and 800°C, 300 and 700°C, 300 and 600°C, 300 and 500°C, 400 and 900°C, 400 and 800°C, 400 and 700°C, 400 and 600°C, 500 and 900°C, 500 and 800°C, or between 500 and 700°C.

In some embodiments, the temperature is between 400 and 500 °C.

Photoactivity may be imparted by thermally treating a preactivated material immediately following its production, or at any time after the material has been formed.

Thermal treatment may proceed under vacuum, or in the absence of oxidizing agents or oxygen. For obtaining highly active surface, thermal treatment may be carried under air. Also, vacuum with partial pressure of O2 may be used.

Thus, the photoactive material of the from metal oxide/metal species/carbonaceous material or of the form TiO ₂ /metal species/carbonaceous material is manufactured by a process comprising a step of forming a preactivated material, and thermally treating same under a high temperature to provide the photoactive composition of matter.

The invention further provides a process for forming a photoactive material of the form TiO ₂ /metal species/carbonaceous material, as defined herein, the process comprising thermally treating a preactivated carbonaceous material associated with a hybrid layer of Ti-ethylene glycol hybrid material, wherein the carbonaceous material or the hybrid layer further comprises a metal species, as defined herein, under conditions causing degradation of the ethylene glycol and conversion of the preactivated material into the photoactive form.

In some embodiments, the carbonaceous material is CNT or graphene, or any of the other materials disclosed herein. In some embodiments, the metal species is iron and/or iron oxide, or any of the other metals/metal oxides disclosed herein.

The “ conditions causing degradation of the organic material and conversion of the preactivated material into a photoactive f rm" comprise or consist reacting the preactivated material at a temperature selected to decompose the ethylene glycol and transform the Ti component into a photoactive TiO ₂ form in the presence of the metal species. The temperature is typically above 100°C, or above 300°C. In some embodiments, the temperature is between 100 and 900°C. Depending on the composition and/or sensitivity of the substrate material, the temperature may be above or around 100, 200, 300, 400, 500, 600, 700 or 800°C. In some embodiments, the temperature is between 400 and 500°C, or is 400, 410, 420, 430, 440, 450, 460, 470, 480 or 500°C In some cases, the conditions comprise thermal treatment under vacuum, or in the absence of oxidizing agents or oxygen, or under an inert gas.

In some cases, the conditions comprise thermal treatment under air, or in the presence of oxygen, or under a reducing atmosphere, e.g., in presence of hydrogen gas.

In some embodiments, the process comprises a step of forming a film or a coat of the preactivated material on a surface region of a substrate.

In some embodiments, the preactivated material or film is formed by spray pyrolysis. Spray pyrolysis is a technique which requires use of a precursor solution, for example, TiCl4, and a heated substrate and atomizer. In the pyrolysis process, the solution is atomized in small drops and these droplets are transferred to the heated substrate due to gas that generates thin films. The thin films produced have large surface areas of substrate coverage and potential and homogeneity of mass synthesis. The conditions of spray pyrolysis may vary.

In some embodiments, the preactivated material or film is formed by chemical vapor deposition (CVD) or by plasma enhanced chemical vapor deposition (PECVD).

In some embodiments, the preactivated material or film is formed by electrospinning or by spin-coating.

In some embodiments, the film or coat of the preactivated material is by vapor phase deposition. The vapor phase deposition method may be one or a combination of atomic layer deposition (ALD), molecular layer deposition (MLD), combined ALD/MLD, spatial ALD, and tandem catalyst ALD/MLD. ALD and MLD are vapor phase chemical techniques, which can be used separately or in combination, allowing thin-film deposition via consecutive and self-limiting surface reactions. ALD allows inorganic film depositions and MLD allows organic film depositions. Spatial ALD (S- ALD) involves layer-by-layer film deposition in which reactive precursors are separated in space rather than in time, as with conventional ALD. In tandem catalyst ALD/MLD, each sub-cycle catalyzes the deposition of the complementary sub-cycle.

Generally speaking, the process for forming the film of the preactivated material is an atomic layer deposition process (ALD) and/or a molecular layer deposition process (MLD).

As known in the art, ALD is a self-limiting process, during which an amount of a precursor material is deposited in each reaction cycle and is constant. While precursors, reagents and material sources used in an ALD step are eventually reacted in the vapor phase, the precursors can be either liquid or solid which are transported via direct vaporization, bubbling or sublimation into contact with the surface. Unlike ALD, a MLD cycle may comprise reacting a surface with a metal precursor, followed by reacting the formed metal center with organic precursors, e.g., diols, triols or higher alcohol homologues, to form a material layer that is covalently associated with the layer onto which it is deposited, thus forming the preactivated metal-organic hybrid material, as further defined herein.

The MLD steps or cycles may be repeated as many times as needed to afford a multilayered structure or shells and reach a desired thickness or functionality. In some embodiments, a multi-layer deposition scheme may be used to achieve a multilayered structure.

The ALD/MLD conditions may vary in accordance with processing parameters known in the art. The materials that may be deposited in accordance with ALD or MLD and the conditions that can be used may be adapted from the general state of the art. See for example Meng X., J. Mater. Chem. A, 2017, 5, 18326; Leskela M., Thin Solid Films, 2002, 409, 138; and Van Bui H., Chem. Commun., 2017, 53, 45. The content of any of these publications, vis-a-vis ALD/MLD conditions and materials is incorporated herein by reference.

In some embodiments, the ALD step is carried out in an ALD reactor, and the process comprises introducing into the ALD reactor at least one titanium precursor composition (comprising for example TiCL, TMA, water) under conditions permitting direct vaporization, bubbling or sublimation into contact with the surface on which the film or coat is to be formed.

In some embodiments, the ALD/MLD reactor is selected from conventional ALD reactor, fluidized bed rector, high pressure spatial ALD reactor or any other type of reactor.

The titanium precursor may be one or a collection of several precursors and/or materials. As the titanium precursor comprises a metal atom and one or more same or different ligand groups, as described herein, the at least one titanium precursor may be a composition which comprises at least one titanium source, and ethylene glycol.

The titanium source is a titanium salt or a titanium complex

The titanium salt or complex may be selected from:

- a titanium halide, wherein the halide is selected from CI, Br, I and F; - a titanium alkoxide;

- a titanium alkyl, wherein the alkyl ligand may be a long alkyl group (comprising more than 5 carbon atoms, including aryl groups), or a short alkyl group (comprising between 1 and 5 carbon atoms), wherein the alkyl is optionally substituted with one or more alcohol or amine groups;

- a titanium acetylacetonate; and

- a titanium complex with one or more ligand moieties.

In some embodiments, the titanium source is selected from cyclopentadienyl(cycloheptatrienyl)titanium (II), tetrakis (diethyl amino)titanium (IV), tetrakis(dimethylamino)titanium (IV), tetrakis(dimethylamino) titanium (IV), titanium (IV) n-butoxide, titanium (IV) t-butoxide, titanium (IV) ethoxide, titanium (IV) i- propoxide, (trimethyl)pentamethyl cyclopentadienyltitanium (IV), and tris(2, 2,6,6- tetramethyl-3,5-heptanedionato)titanium (III).

In some embodiments, the titanium source is a metal halide, e.g., TiCU-

In some embodiments, the titanium source is a titanium oxide, optionally selected as above.

In some embodiments, the preactivated material is formed from TiCU, trimethylaluminum (TMA) and a metal species such as an iron metal and/or an iron oxide.

In some embodiments, the process comprises

-forming a preactivated film or coat of Ti-EG hybrid material on a surface region of a substrate, the forming optionally comprising ALD, MLD or tandem ALD-MLD deposition, and

-thermally treating the film or coat formed on the surface, to cause degradation of the Ti-EG film or coat (and convert same) into a photoactive composition of matter.

In some embodiments, the process comprises

-forming a preactivated film or coat of a hybrid titanium-ethylene glycol material on a surface region of a substrate, the forming optionally comprising ALD, MLD or tandem ALD-MLD deposition, and

-thermally treating the film or coat formed on the surface, to form the photoactive composition of matter.

The hybrid Ti-EG material comprises a Ti component and ethylene glycol that is associated thereto. The titanium component comprises a plurality of titanium atoms that may be in-layer associated to each other directly or indirectly via linking atoms (e.g., oxygen atoms) or via organic ligands, connecting to each of the titanium atoms via a linking atom such as oxygen. The so linked titanium atoms are further associated with one or more hydroxides, oxides or alkoxides that are surface exposed.

Typically, the preactivated hybrid material is formed on a carbonaceous material as defined herein. The layering or deposition of the carbonaceous material and the preactivated hybrid material, as defined, may take place on a surface of a substrate such as glass, quartz, quartz stone, stone, tiles, ceramics, metallics, carbonaceous surfaces (e.g., carbon allotropes), silicon, fused silica and others.

Irrespective of the structure and composition of the substrate or surface material, association between the surface and the photoactive material, despite the thermal treatment employed, is believed to be physical and not chemical. Nevertheless, in some configurations, the photoactive material may be chemically associated, fully or partially, with the surface.

In some embodiments, the photoactive is provided as a powder or as a photoactive film on a surface region of a substrate.

In some embodiments, the photoactive material may be formed, according to processes of the invention, on a sacrificial surface or independent of a surface and may thereafter be used for forming a film or a coat on a substrate material.

In some embodiments, the substrate material is coated with a surface material, each being of a different composition and optionally different thicknesses, and a photoactive film or coat is formed on the surface. In some embodiments, the substrate material is coated with a coating of a different material, wherein said coating is further layered with a photoactive material of the invention.

In some embodiments, the surface is any surface of a device or an element or a member of a device, e.g., a device used for air purification.

In some embodiments, the invention provides a photoactive surface or film on a surface of a solid material configured for attachment, optionally by means of an adhesive surface, to a surface region of an object provided in an environment (indoors or outdoors) to be clear out of a pollutant or a toxin, as defined herein, or air-purified. The solid material may be a sticker having an adhesive surface capable of attachment to the object, wherein optionally is used in constructing an air purification system. In some embodiments, the surface is a surface of a membrane or a filtering medium or a filtering surface, or is a surface of a purification member or module that can be adapted to existing purification systems for achieving air-purification, water- purification or self-cleaning.

In some embodiments, the surface is a surface of nano- or microparticle of any shape.

In some embodiments, the surface is of a carbonaceous material, e.g., a carbon allotrope. In some embodiments, the surface is a carbon nanotube (CNT) or a CNT -based material. The CNT may be any of the CNTs known in the art. The CNT may be any one or a combination of carbon allotropes of the fullerene family selected from single walled carbon nanotubes, double-walled carbon nanotubes and multi-walled carbon nanotubes. The CNT may have between 1 to 10 walls and have varying dimensions. In some embodiments, the CNTs have high aspect ratios as measured by their ratio of length to diameter. The CNTs may have open or closed ends.

Where the CNT is provided in a form of a CNT assembly, it may be in a form of a collection or an array or a bundle of two or more CNTs. The assembly may be in the shape of a fiber that self-assembles into fiber bundles or a web in a random or an organized fashion. Thus, a CNT assembly used as a substrate for forming photoactive surfaces according to the invention may be a compilation of two or more CNTs, which together form a fiber or a web and/or a CNT bundle that comprises at least one CNT fiber. The CNTs within the assembly may be branched, crosslinked, or share common walls with one another. The CNTs within the assembly may have any defined shape, positioning, orientation and density.

In some embodiments, the CNTs are assembled on a substrate or are collected in a macrostructure.

A photoactive material or film or surface formed of such a photoactive material according to the invention may be implemented in a variety of devices or systems for interacting with and/or causing decomposition of air-borne or water-borne organic or inorganic substances. Without wishing to be bound by theory, the interaction of the photoactive surface with the organic and/or inorganic substances involves an initial physical interaction, during which substances coming in touch with the surface become adsorbed by or associated to or trapped in surface features, such as pores, that define the photoactive surface. Over time and upon continued exposure to visible light and as the level of free charge carriers increases due to illumination or exposure to visible light, the substances interact with the charge carriers and undergo degradation. As the photoactive surface does not substantially undergo a compositional change, and as the interaction with the organic or inorganic substances does not have an effect on the composition nor the activity of the surface, photoactivity is maintained over time. Surface regeneration may be used to remove degradation products from remaining in the surface features. The regeneration may involve flowing of an inert gas over the surface or washing same with a fluid. However, in certain configurations, as gaseous organic contaminants may be degraded to water vapor and carbon dioxide, there is no need for a regeneration step during the “life time” of the photoactive surface.

As indicated herein, photoactivity may be increased or improved when the surface is under visible light. In some cases, UV radiation is minimized or is unnecessary. As air- borne and water-borne substances are initially trapped by surface features present in the photoactive surface, exposure to visible light need not be continuous. However, to achieve substance degradation, the surface may be exposed to light over long periods of time, e.g., minutes to hours, or continuously as long as the system for removal of the substances, e.g., air purification, is in operation.

In some cases, photoactivation is most efficient under visible light, namely under a light of a wavelength between 170 to 800 nanometers. In some embodiments, the light is of a wavelength between 380 and 740 nm.

In some embodiments, UV light is excluded.

Thus, systems implementing a photoactive surface according to the invention may be provided with a light source (such as LED) for providing direct or indirect illuminating to said surface, e.g., a light source that is positioned to provide exposure of the surface to visible light.

The invention further provides a film, a system, a device or an electrode implementing a photoactive surface according to the invention, wherein the photoactive surface is one of:

-a photoactive material of the form metal oxide/metal species/carbonaceous material, wherein the metal oxide is of a metal as disclosed herein, e.g., TiO ₂ , and wherein the metal species and the carbonaceous material is as disclosed herein;

-a photoactive material of the form TiO ₂ /metal species/carbonaceous material, wherein the metal species and the carbonaceous material is as disclosed herein; -a photoactive material of the form TiO ₂ /Fe ⁰ /FeO ₂ or TiO ₂ /Fc ⁰ or Ti/FeO ₂ provided on or associated with a carbonaceous material as disclosed herein;

-a photoactive material of the form TiO ₂ /Fe ⁰ /FeO ₂ or TiO ₂ /Fc ⁰ or Ti/FeO ₂ provided on or associated with CNT;

-a photoactive material of the form TiO ₂ /carbonaceous material as disclosed herein; and

-a photoactive material of the form TiO ₂ /CNT.

Each of the aforementioned photoactive materials is formed by thermal treatment of a preactivated material, as disclosed herein.

Also provided is a system or a device implementing a photoactive surface according to the invention, the photoactive surface being provided under illumination. The expression “provided under illumination encompasses two general system configurations: a system provided with an illumination source that is configured and operable to provide illumination of the surface, and/or a system wherein the photoactive surface is provided in a geometry and/or position within the system that enables a continued or programmed natural light exposure (which may be reinforced with an illumination source).

Light exposure may be programmed or predesigned. The distance of the light source (e.g., LED) from the active surface may vary and can be determined by the device engineering. Generally speaking, the distance may be between a few centimeters to several dozens of centimeters. Exposure time may be determined by a variety of factors, including, inter alia, the type of active layer, the level of pollution, and other variables. Both the exposure time and exposure distance may be set by a sensor monitoring the degree of pollution or may be preset based on a learned behavior of, e.g., contaminants’ flow in a given environment where the system is positioned.

Thus, systems of the invention may further comprise a control unit and may also comprise a plurality of sensor units that are configured and operable to monitor and control the operation of the active layer.

The system may be selected amongst purification systems, e.g., air-purification systems - HVAC or standalone systems or water-purification systems, self-cleaning - indoor and outdoor building surfaces, widows, frames, tiles, ceramics, fabrics, etc.

In some embodiments, the system is a purification system. In some embodiments, the purification system is an air-purification system or a water-purification system. The term air purification or "water purification refers to an ability or a system ability to remove from a gaseous medium, being typically air, or a liquid medium, being typically a water medium, impurities or pollutants, both organic and inorganic, which are present. Purification suggests that the concentration of the substances, e.g., pollutants, is diminished to concentration below a predetermined threshold. The substance concentration may be reduced by 10, 20, 30, 40% or more, based on the original concentration of the substances in the volume of air or water purified.

The purification of the gaseous or water medium may be non-selective. Yet, in some cases, the photoactive surface may be configured for adsorbing and degrading substances which removal is targeted or desired. Such may be nitrogen oxides (NOx), carbon monoxides (CO), unbumed hydrocarbons (HC), sulfur dioxide, as well as CO2 and other greenhouse gases.

Generally speaking, the substances to be removed are chemical and/or biological agents in a gaseous or a fluid medium that are at least potentially toxic to humans and/or animals, when distributed via air or water. Such substances may include soluble organic materials; gaseous pollutants, such as volatile organic compounds (VOCs), including chlorinated compounds such as chlorobenzene, carbon tetrachloride and vinyl monochloride; pollutants contained in drinking water, industrial water, hospital and agricultural effluents, for example herbicides, pesticides, endocrine disrupters, persistent organic pollutants (POPs), pharmaceuticals and personal care products (PPCPs) and others.

A purification system according to the invention, implementing a photoactive surface, as disclosed, may also be used to neutralize or cause inactivation of biological toxins and microorganisms such as bacteria, viruses, fungi, molds, etc, which may be present in the air, e.g., as aerosol particles, or water to be purified.

An air-purification system implementing a photoactive surface according to the invention may generally comprise the photoactive surface or one or more photoactive elements, wherein each of the elements comprises at least one photoactive material or photoactive surface according to the invention. The system may also comprise a source of visible radiation configured and operable to illuminate the surface or a region thereof or each or some of the elements to render the surface of the region thereof or the elements photoactive to cause chemical decomposition of a substance or a material interacting with the surface, region or element, as disclosed. In some embodiments, the system may further comprise means, e.g., a fan, for flowing air or for causing air to flow onto the active surface(s) or through a photoactive element, to bring substances present in the flown air into interaction with the surface(s).

In some embodiments, the system may further comprise a pre-filter element that is positioned in front of the photoactive surface for preventing flow of particulate materials (typically 2-5 microns in average size or diameter) onto the surface. In some embodiments, a fine filter (HEPA or similar) may also be utilized.

In some embodiments, the photoactive surface, e.g., in a form of a module or photoactive members or elements, may be used as add-on features onto existing air- purification systems. Thus, in such embodiments, for example, a system used for moving air between indoor and outdoor areas, along with heating and cooling, such as heating, ventilation, and air conditioning (HVAC) systems may be provided with one or more photoactive elements and optionally further with a light source. In some embodiments, the light source is any visible light emitting device, e.g., an OLED.

Thus, in another aspect, there is provided a HVAC system implementing a photoactive surface or element according to the invention.

In some embodiments, the purification system is a water purification system comprising one or more photoactive surfaces or elements, optionally enclosed within a water-flowing pipe.

The invention further provides a self-cleaning object, the object having a surface or a surface region coated or formed of a photoactive material of the invention. As used herein, the term “self -cleaning” refers to a photoactive film or a layer of the invention that is configured or which promotes removal of contaminates present on its surface. The removal of contaminants, e.g., organic or inorganic or biological contaminants, that may come into contact with the surface, occurs by adsorption and subsequent degradation as disclosed herein. A self-cleaning surface of the invention may or may not require illumination of visible light. In some embodiments, the self-cleaning surface is capable of capturing and/or degrading a pollutant or neutralizing or inactivating a biological material or toxin without stimulation or activation.

The self-cleaning object may be a fabric, tiles, windows and any other functional or aesthetic object.

The invention further provides: A purification or an adsorbent matrix material comprising or consisting a photoactive material comprising TiO ₂ , a metal species and a carbonaceous material, wherein the metal species is a metal different from Ti and/or a metal oxide thereof.

In some configurations of a matrix material used as disclosed herein, the matrix material is formed by thermally treating a hybrid material comprising Ti-ethylene glycol in presence of the metal species on a carbonaceous material.

A purification or an adsorbent matrix material comprising a photoactive titanium oxide and metal species (TiO ₂ /mctal species) formed by thermally treating a carbonaceous material provided with a film of a Ti-Ethylene Glycol (Ti-EG) hybrid material in the presence of the metal species, wherein the metal species is a metal different from Ti and/or a metal oxide thereof.

In some configurations of a matrix material used as disclosed herein, the metal species is associated or contained within the carbonaceous material.

In some configurations of a matrix material used as disclosed herein, the metal species forms a layer or material regions on a surface of the carbonaceous material.

In some configurations of a matrix material used as disclosed herein, the metal species is deposited on the carbonaceous material prior to formation of the film of the Ti- EG film.

In some configurations of a matrix material used as disclosed herein, the metal species is a metal selected from selected from Fe, Au, Ag, Cu, Ni, Zn, and Mn, and/or a metal oxide thereof.

In some configurations of a matrix material used as disclosed herein, the metal species is provided with a Si-, P- and/or S-based material.

In some configurations of a matrix material used as disclosed herein, the metal species is Fe ⁰ and/or FeO ₂ .

In some configurations of a matrix material used as disclosed herein, the photoactive material is TiO ₂ /Fe ⁰ /FeO ₂ or TiO ₂ /Fe ⁰ or Ti/FeO ₂ provided on a carbonaceous material.

In some configurations of a matrix material used as disclosed herein, the amount of the metal species is between 0.5 and 10 wt%. In some configurations of a matrix material used as disclosed herein, the amount is between 3 and 6 wt%.

In some configurations of a matrix material used as disclosed herein, the matrix is provided as a powder or as a photoactive film on a surface region of a substrate. In some configurations of a matrix material used as disclosed herein, the carbonaceous material is a carbon allotrope. In some configurations of a matrix material used as disclosed herein, the carbonaceous material is selected from carbon black, graphite, amorphous carbon, graphene, carbon wires, carbon nanowires, carbon nanotubes (CNT), carbon buds, carbon mats, carbon fullerenes, carbon nanoparticles and microparticles, glassy carbon, carbon nanofoam, and carbon nitrite. In some configurations of a matrix material used as disclosed herein, the carbonaceous material is CNT or graphene.

In some configurations of a matrix material used as disclosed herein, the matrix material is formed or provided on a substrate.

In some configurations of a matrix material used as disclosed herein, the photoactive material is formed by forming a film of a Ti-ethylene glycol metal-organic material, and treating the film under conditions suitable to provide the photoactive material, wherein the film is formed on the carbonaceous material and wherein one of the film and the carbonaceous material comprises the metal species or a precursor form thereof.

In some configurations of a matrix material used as disclosed herein, the film is formed by vapor deposition method; sol-gel deposition; spray pyrolysis; chemical vapor deposition (CVD), plasma enhanced (PECVD), electrospinning, or spin-coating.

In some configurations of a matrix material used as disclosed herein, the matrix material is formed by a process comprising atomic layer deposition (ALD), molecular layer deposition (MLD) or tandem ALD-MLD deposition.

In some configurations of a matrix material used as disclosed herein, the matrix material is for use in forming an active surface for adsorbing, interacting or degrading air-borne materials. In some configurations of a matrix material used as disclosed herein, the air-borne materials are selected from organic and biological materials. In some configurations of a matrix material used as disclosed herein, the air-borne materials comprise air-borne bacteria, viruses, fungi, and molds, optionally provided in a form of an aerosol.

In some configurations of a matrix material used as disclosed herein, the matrix material is provided as a film of the photoactive material on a surface of a solid material configured for attachment, optionally by means of an adhesive surface, to a surface region of an object provided in an environment to be air-purified. In some configurations of a matrix material used as disclosed herein, the solid material is a sticker having an adhesive surface capable of attachment to the object.

In some configurations of a matrix material used as disclosed herein, the matrix material is for use in constructing an air purification system.

A purification or an adsorbent matrix material comprising or consisting a photoactive material comprising TiO ₂ and a carbonaceous material, wherein the TiO ₂ is formed by thermal decomposition of a Ti-ethylene glycol hybrid layer formed on the carbonaceous material.

A film formed of a matrix material according to the invention.

A system or a device implementing a matrix material according to the invention or a film according to the invention.

A system or a device implementing a matrix material comprising or consisting a photoactive material comprising TiO ₂ , a metal species and a carbonaceous material, wherein the metal species is a metal different from Ti and/or a metal oxide thereof.

In some configurations of a system used as disclosed herein, the matrix material is provided under illumination.

In some configurations of a system used as disclosed herein, the system is for adsorbing and degrading substances selected from nitrogen oxides (NOx), carbon monoxides (CO), unburned hydrocarbons (HC), sulfur dioxide, CO2 and greenhouse gases; or for neutralizing or inactivating biological toxins and/or microorganisms, wherein optionally the microorganism is selected from bacteria, viruses, fungi, and molds; or for adsorbing and degrading substances selected from soluble organic materials; gaseous pollutants; and pollutants contained in drinking water, industrial water, hospital and agricultural effluents.

An air-purification system implementing an air-purification matrix material according to the invention.

In some configurations of a system used as disclosed herein, the photoactive material is provided in a form of a photoactive surface, or one or more photoactive elements, wherein each of the elements comprises at least one photoactive material; and a source of visible light configured and operable to activate the surface or each or some of the elements to cause chemical decomposition of a substance or a material interacting with the surface. In some configurations of a system used as disclosed herein, the system further comprising means, configured and operable to flow air onto the photoactive surface(s) or through a photoactive element, to bring substances present in the flown air into interaction with the surface(s).

In some configurations of a system used as disclosed herein, the system further comprises a pre-filter element or a fine filter.

In some configurations of a system used as disclosed herein, the system is a HVAC system.

A purification system implementing an air-purification matrix material according to the invention, for use in a method for adsorbing and degrading substances selected from nitrogen oxides (NOx), carbon monoxides (CO), unbumed hydrocarbons (HC), sulfur dioxide, CO2 and greenhouse gases; for neutralize or inactivating biological toxins and/or microorganisms; or for adsorbing and degrading substances selected from soluble organic materials; gaseous pollutants; and pollutants contained in drinking water, industrial water, hospital and agricultural effluents.

A method for removing an air-borne pollutant from an environment, the method comprising flowing or allowing air in said environment to flow on a surface of a matrix material according to the invention, and permitting said air to interact with the matrix material, wherein optionally the matrix material is illuminated with visible light.

In some configurations of a method used as disclosed herein, the pollutant is selected from nitrogen oxides (NOx), carbon monoxides (CO), unburned hydrocarbons (HC), sulfur dioxide, CO2 and greenhouse gases; or the pollutant is selected from biological toxins and/or microorganisms; or the pollutant is a microorganism selected from bacteria, viruses, fungi, and molds.

In some configurations of a method used as disclosed herein, the methodis for adsorbing and degrading substances selected from soluble organic materials; gaseous pollutants; and pollutants contained in drinking water, industrial water, hospital and agricultural effluents.

In some configurations of a method used as disclosed herein, the matrix material is implemented in an air-purification system.

In some configurations of a method used as disclosed herein, the method comprises providing a purification or an air-purification matrix material. In some configurations of a method used as disclosed herein, the environment is indoors or outdoors.

In some configurations of a method used as disclosed herein, the air is caused to flow in a tangential direction to the surface of a matrix material.

In some configurations of a method used as disclosed herein, the method comprises illuminating the matrix material by visible light.

A purification or an adsorbent matrix material comprising or consisting a photoactive material comprising:

-TiO ₂ /metal species/carbonaceous material, wherein the metal species and the carbonaceous material are as defined herein;

-TiO ₂ /Fe ⁰ /FeO ₂ or TiO ₂ /Fc ⁰ or Ti/FeO ₂ provided on or associated with a carbonaceous material as defined herein;

-TiO ₂ /Fe ⁰ /FeO ₂ or TiO ₂ /Fc ⁰ or Ti/FeO ₂ provided on or associated with CNT;

-TiO ₂ /carbonaceous material, wherein the carbonaceous material is as defined herein; and

-TiCL/CNT, wherein each of the photoactive materials is formed by thermal treatment of a preactivated material comprising a Ti-metalcone formed one the carbonaceous material in presence of a metal species as defined herein.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to better understand the subject matter that is disclosed herein and to exemplify how it may be carried out in practice, embodiments will now be described, by way of non-limiting example only, with reference to the accompanying drawings, in which:

Fig. 1 - VOC test matrix.

Fig. 2 - Aerosol test chamber flow diagram.

Fig. 3 - D-Limonene percentage reduction for the flow cell testing device.

Fig. 4 - D-Limonene net percentage reduction for the flow cell testing device.

Fig. 5 - The destruction time to half-life achieved by the flow cell testing device.

Fig. 6 - Staphylococcus epidermidis particle size distribution in mass percent.

Fig. 7 - General timeline for the test trials.

Fig. 8 - Log reduction of S. epidermidis yielded by the flow cell testing device. Fig. 9 - Net log reduction of S. epidermidis yielded by the cell testing device.

Fig. 10 - Summary of net reduction of S. epidermidis yielded by the flow cell testing device.

Fig. 11 - XPS surface analysis of the CNTs with Ti-EG. Results in panels A depict CNT comprising metallic Fe(0). Results in panels B depict CNT deposited with Ti-EG and heated to 480°C for 20 minutes under air.

DETAILED DESCRIPTION OF EMBODIMENTS

While the disclosure provided herein is mainly focused on Ti-based photoactive materials, photoactive materials may be equally formed with other metals. Replacing any of the Ti-based systems disclosed herein with a metal-based system of metals such as transition metals and metalloids of the Periodic Table of the Elements. In some embodiments, the metals are transition metals or metalloids.

In some embodiments, the metals alternative to Ti exemplified herein may be selected from Al, W, Sc, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Tc, Ru, Rh, Re, Pd, Ag, Au, Cd, In, Sn, Sb, Te, Hg, Tl, Pb, Pt, Bi and Po. In some embodiments, the metal is selected from Zn, Zr, Fe, V, Cu, Ni, Bi and W.

In other embodiments, the metal is selected from Zn, Fe, V, Ni, Cu and Cr (e.g., yielding the metal oxides ZnO, Fe ₂ O ₃ , V ₂ O ₅ , NiO, CuO, CU ₂ O, CrO, respectively).

The metal source used may be similarly selected from metal halides (wherein the halide is selected from CI, Br, I and F); metal alkoxides; and any of the other metal sources disclosed hereinabove.

The organic reactive material, alternative to ethylene glycol, may be selected amongst such materials having sufficient vapor pressure and thermal stability under the conditions of the film formation. The organic reactive material may be selected amongst aliphatic materials (alkylenes), alkenylenes, alkynylenes and arylenes (which may have one or two aryl rings, e.g., phenyl rings, bonded to each other or to a backbone alkylene, alkenylene and/or alkynylene moiety). In some embodiments, the organic reactive material is an aliphatic material comprising between 2 and 5 carbon atoms and two or more alcohol and/or amine functional groups. In some embodiments, the "organic aliphatic material" is selected amongst materials having a C2-C5 carbon chain wherein one or more of said carbons are substituted with 2 or 3 functional groups selected independently from hydroxyl (-OH) and amine (-NH2). In some embodiments, the organic aliphatic material is selected amongst aliphatic alcohols and amines having sufficient vapor pressure and thermal stability under the conditions of the film formation. In some embodiments, the organic aliphatic alcohol is selected from ethylene glycol (EG), 1,3 -propanediol, 1,2-propanediol, 1,4-butanediol, 1,3 -butanediol, 1,2- butanediol, 1,5- pentanediol, 1,4-pentanediol, 1,3 -pentanediol, 1,2-pentanediol, glycerol, pentaerythritol, 1,2,4-butanetriol, 1,2-ethylenediamine 1,3 -propanediamine, 1,2- propanediamine, 1,4- butanediamine, 1,3 -butanediamine, 1,2-butanediamine, 1,5- pentanediamine, 1,4- pentanediamine, 1,3-pentanediamine, 1,2-pentanediamine, 1,2,3- propanetriamine, 1,2,4- butanetriamine, and others.

In some embodiments, where the metal is different from Ti, the organic aliphatic alcohol may be a dialcohol, e.g., ethylene glycol, EG.

Generally speaking, the preactivated film formed on the carbonaceous materail, e.g., CNT, is a metalcone layer of the general form R-X-M-X-R, wherein the metal M is connected through a heteroatom X, which may be an oxygen atom (-O-), a nitrogen atom (-N-) or a sulfur atom (-S-) to an organic moiety (R). Where the heteroatom X is oxygen, examples of metalcones are titanium-ethylene glycol, as disclosed herein, and aluminum- ethylene glycol, the oxygen atom of the ethylene glycol constitutes a point of connectivity with the metal, and the ethylene glycol is the organic moiety. Any organic moiety R may be utilized, with a variety of metals, generating metacones of zinc (zincone), aluminum (alucone), titanium (titanicone), etc. The number of M-0 (alkoxide) bonds may vary depending on the metal.

In some embodiments, the metalcone may have the structure R-N-M, wherein M is the metal, the heteroatom linking the organic moiety to the metal is a nitrogen atom (- N-), and R is the organic residue. Such materials include diamines e.g., ethylene diamine and alcohol-amines e.g., ethanolamine. As with the oxygen cases, any organic moiety R may be utilized, with a variety of metals, generating metacones of zinc (zincone), aluminum (alucone), titanium (titanicone), etc. The number of M-N (alkoxide) bonds may vary depending on the metal.

As stated herein the invention provides a process for forming a photoactive material, involving thermal treatment of a preactivated hybrid metalcone-organic material comprising an organic material associated to a metalcone material under conditions causing degradation of the organic material and conversion of the metalcone material into a photoactive metal oxide material. The preactivated film or coat is formed by material deposition, e.g., vapor phase deposition, which may be one or a combination of atomic layer deposition (ALD), molecular layer deposition (MLD), combined ALD/MLD, spatial ALD, and tandem catalyst ALD/MLD. The film or coat may be achievable according to a process disclosed in WO 2018/154572 and US application 16/486,040, each of which being incorporated herein by reference.

Example 1:

Methods', a suitable surface was selected for integration with spatial ALD to yield continuous synthesis of nanocomposite material. This included low pressure ALD, atmospheric pressure spatial ALD. Initial vapor phase processing, without solvent was followed by wet chemical processing after the wetting properties were modified in the first stage of ALD/MLD vapor phase reaction.

Example 2: Organic -inorganic hybrid films

MLD of -M-0-(R)-0-M-, as in hybrid organic-inorganic thin films, also called metalcones, such as titanium-ethylene glycol (for M=Ti and R= C2H4, Ti-EG). In addition, when Ti-EG films are thermally treated, oxygen deficient TiO ₂ oxide is formed by controlled combustion of the organic component, (R), embedded in the thin film. This gives an oxide with an adjustable electronic structure including shifting of band-edge positions and introduction of in-gap defect states that mediate efficient electron transfer.

The inventors have successfully demonstrated the first application of MLD for the preparation of highly photoactive thin films. This means that the organic components introduced by MLD can either be used as a sacrificial component to control the oxide electronic properties.

The use of MLD for tailoring metal oxide (MO) thin films with controlled compositions, doping, electronic structure, and architectures was demonstrated. A key characteristics of the as-prepared Ti-EG films, and other metalcones is the film permeability that provides a versatile handle for additional functionality and varying the interface properties. The permeability of Ti-EG films was studied and compared with conventional TiO ₂ films (by ALD). Ti-EG films prepared by MLD and thermally treated resulting in thin oxide coatings that are pin-hole free, yet retain electronic communication between the solution and the underlying conductive electrode. Doping of Ti-EG films with metal cations. Ti-EG films permeability can be used for adsorbing cations that function as dopants once the modified Ti-EG films are thermally treated. For example, Ti-EG films adsorbed with Ni and Fe were thermally treated at various temperatures and characterized. Band gap (BG) values were extracted using Tauc’s equation for the undoped, Fe-doped, and Ni-doped films for a range of thermal treatment temperatures. A monotonic BG narrowing is obtained for doped films thermally treated up to 750 °C with lowest BG values obtained for both Fe-, and Ni-doped Ti-EG of 2.74 and 2.70 eV, respectively. The facile doping of TiO ₂ was utilized for optimizing the protective layer band structure and improvement of the overall photocatalytic performance of the system.

Example 3: Forming a photoactive surface

To achieve photoactivation, the above formed films were formed on substrates such as CNT mats, activated carbon fiber cloths, quartz and fused silica capillary tubes. Activation temperature for quartz and fused silica was 650°C, while for CNT and carbon fiber the temperature was 480°C.

Example 4: Characterization of the Reduction Efficacy of a Photoactive Surface Flow Cell Against Limonene

The purpose of this study was to evaluate the volatile organic compound (VOC) elimination efficacy of the Flow Cell in a controlled test environment. The Flow Cell is a test unit that is comprised of a proprietary system that utilizes a small fan to run aerosol through a catalyst bed comprised of carbon nanotube mats that are coated with titanium oxide using molecular level deposition. The mats are activated using strips of broad- spectrum daylight LED lights. While this technology is designed to be used in a variety of applications, this study focused on its efficacy as a photocatalyst for the destruction of VOCs.

Testing was conducted in an environmentally controlled Lexan test chamber. Control trial data, or natural losses, were subtracted from test trial data to produce the net log reduction attributable to the device. For this study, the device was evaluated on a single speed. Testing was conducted in a Lexan environmentally controlled test chamber designed to simulate an individual’s personal breathing space (Im ³ ). The testing environment was maintained at ambient room conditions a temperature of 25 °C ± 3 °C with a relative humidity of approximately 45 +/- 5%.

The chamber was sealed to prevent the occurrence of air exchanges during testing. Testing was performed in triplicate test trials for the challenge species. Additionally, a control trial was run to characterize the amount of natural decay exhibited by the species without the device operating. The test matrix is presented in Fig. 1.

Limonene was nebulized into the sealed environmental aerosol test chamber containing the test device. The chamber test trial starting concentration was 10.0 parts per million (ppm). The ION Tiger Phocheck was used to monitor chamber VOC concentrations throughout testing. Chamber control reduction test data was subtracted from the operational flow cell device reduction test data to yield the net reduction in the chamber for each test trial and each sampling time point. Major Equipment Used The equipment used in this study was calibrated and certified prior to the start of testing. The calibration is performed either in house or by the manufacturer as applicable.

The Flow Cell

The Flow Cell was constructed as an air purification device that uses passive tangential flow air through titanium oxide infused carbon nanotube mats that act as a photo catalyst activated with broad spectrum visible light as a means of aerosol reduction. The device was tested on the same fan speed throughout testing.

ION Tiger Phocheck VOC Meter

The ION Tiger Phocheck VOC meter used was a general VOC meter that was used to measure the VOC concentration throughout each trial during testing. The Tiger uses an internal pump for sampling and has a range that extends down to 1.0 part per billion (ppb). The VOC meter was set to data log throughout each trial. Data was then transferred to MS Excel for analysis once testing was complete.

Collison 6- Jet Nebulizer

The 6-Jet Collison nebulizer (BGI Inc., Waltham, MA) has long been an industry standard technique for aerosolization of various liquids. The Collison nebulizer is made from 316 stainless steel and utilizes silicone rubber O-Ring sealing gaskets and features an adjustable stem for varying liquid levels. Test Chamber

The primary aerosol exposure chamber used fort the test trials was a sealed lm3 environmental chamber constructed of 3/8” Lexan and outfitted with all necessary pass- throughs, sub-systems, and sampling ports. The chamber is equipped with HEPA filtered house air to maintain a clean background environment prior to all testing and to allow rapid air flushing through the chamber after completion of each exposure. This ensures a clean background before conducting subsequent trials. During the aerosolization of the VOC, the chamber was operated in a balanced push/pull aerosol inlet and vacuum to eliminate over or under pressure in the chamber. The chamber was operated at a slightly negative pressure, -0.3 in H2O, for technician safety. Once aerosolization of the VOC at the beginning of each trial was complete, the inlet and vacuum balance were cut off and the chamber sat idly until air sample collections. The chamber is outfitted with impinger sample ports located in the corners of the chamber aimed towards the center. The chamber was equipped with two (2) mixing fans to ensure spatial homogeneity of aerosol during their aerosolization and sampling. These fans were switched on during the aerosolization of the aerosol into the chamber and remained on for the duration of the trials to ensure spatial homogeneity.

A Magnehelic® gauge (Dwyer instruments, Michigan City, IN), with a range of 0.0 +/- 0.5-inch H2O, was used to monitor and balance the system pressure during aerosol generation, aerosol purge, and testing cycles. Prior to testing, the interior walls, ceiling, and floor of the testing chamber were wiped down with 91% Isopropyl Alcohol. Fig. 2 is a flow diagram of the test chamber.

Aerosol Generation System

D-limonene was purchased from Abstrax Tech for the VOC testing. The VOC aerosol was disseminated using a Collison 6-jet nebulizer (BGI Inc., Waltham, MA) driven by purified filtered house air supply. A pressure regulator allowed for control of the disseminated particle size, use rate, and sheer force generated within the Collison nebulizer. Prior to testing, the Collison nebulizer flow rate and use rate were characterized using a calibrated TSI Model 4040 mass flow meter (TSI Inc., St Paul MN). The air supply pressure was approximately 60 psi. Species Selection

Limonene (C ₁₀ H ₁₆ ) was chosen for this study due to its prevalence in day-to-day life and its similarity to other VOC’s. Limonene is a monoterpene that is derived from citrus plant oil and is prevalent in many cleaning agents, air fresheners, polishes.

VOC Preparation

A stock of D-Limonene terpene isolate was purchased from ABSTRAX TECH for testing. The stock is ready to use with no diluting or preparation necessary. For testing 125pl of working stock was aliquoted from the stock bottle and placed into the nebulizer cup in a chemical fume hood. After aliquoting the amount needed for testing the stock was placed into a chemical cabinet and the nebulizer was sealed and moved to the lab for testing.

Testing Method

To accurately assess the test device, a pilot control test was performed with the VOC aerosol for an 8-hour period, without the test device in operation, to characterize the aerosol challenge for decay rate and concentration over time. Control testing was performed to provide baseline data to assess the actual reduction rate from the operation of the device during the testing trials and verify that VOC concentrations persisted above the required concentrations over the entire pilot control test period. For control testing, the device remained in the test chamber for consistency with test runs.

During control and test device trials, two low velocity mixing fans, located in opposite comers of the test chamber, were turned on for the duration of trial to ensure a homogenous aerosol concentration within the aerosol chamber. For each control and challenge test, the nebulizer was filled with approximately 125 μl of D-limonene. The chamber mixing fans were turned on during dissemination to assure a homogeneous concentration in the test chamber prior to the beginning of sampling. Following aerosol generation, a baseline concentration was established at a point in which the Tiger VOC monitor came to a steady state.

The chamber starting concentration goal for testing was 10 parts per million. The Tiger was set to record once every minute over the 8-hour time span. For the flow cell VOC aerosol tests, the device was operated at the highest fan speed. The highest fan speed on the unit was measured to be approximately 8 cfm (cubic feet per minute). The same device was used for each trial of the triplicate set of test runs for consistency. The nebulization procedure remained the same in the test trials as in the control trials. The test device was turned on immediately following a time 0 baseline sample and operated for the entirety of the test. Total test time was based on VOC concentrations and limits of detection.

Test chamber temperature and humidity were recorded continuously throughout the test from initiation to completion. All samples were recorded on the Tiger until the end of the trial. After the trial the files were moved from the Tiger to a PC to be analyzed in Microsoft Excel.

Post-Testing Decontamination and Prep

Between each test, the chamber was airflow evacuated/purged for a minimum of 20 minutes and monitored with the Tiger until the level of VOC’ s in the chamber reached baseline level. In between trials, the chamber was ozone treated to oxidize any remaining VOC’s that may have been left on the chamber interior from the previous test.

Data Analysis

The chamber concentration data, measured with the Tiger VOC meter, was transferred to MS Excel for data analysis. The extracted D-limonene concentration data was used to compare the test trial data to the control trial data. This data shows the percent reduction, over time, as well as the half-life of the formaldehyde during each set of trials. The half-life was calculated using the first 30 minutes of each trial to avoid reduction effects caused by chamber limits. The results are presented on the next page as the result from each trial as well as a group average.

Chamber VOC Testing Results

The flow cell device produced a reduction in D-Limonene concentration throughout the course of the test trials with a majority of the reduction coming in the first two hours of testing. At 2 hours, the average reduction of the triplicate trials was 75.8%. At the end of the 8-hour trials, the average reduction was 84.8%. A graph with the average percent of VOC remaining in the chamber for each trial, as well as the average for the control trial, can be found in Fig. 3. The maximum net log reduction for the triplicate trials, calculated by subtracting the losses from the control trial, occurred just after the 1- hour mark with an average net percent reduction of 38.9%. The test trial results, in net percent reduction, can be found in Fig. 4.

Half-Life Results

The destruction time to half-life, for each test and control trial, were calculated to give a better representative look at the devices’ performance in the VOC trials. The destruction time to half-life came out to 170.97 minutes for the control trial. The triplicate trials averaged a destruction time to half-life time of 29.84 minutes with only a 1.42- minute standard deviation between the three trials (see Fig. 5).

SUMMARY OF RESULTS

When tested against the VOC, D-limonene, the Quantum Innovations flow cell yielded a fast initial reduction for the first two hours, followed by a leveling out of the reduction trend as the VOC concentration in the chamber became lower. This trend happens because the lower the VOC concentration in the chamber, the less available VOC there is to reduce. The less VOC concentration in the chamber leads to less VOC molecules passing through the device during each chamber turnover. The more the device has to turn over the chamber air the longer the reduction takes to occur.

The net log reduction of the triplicate trials reached a maximum level of 38.9% after the 1-hour time point. After that time, the device trials had a leveling off effect while the control maintained a slowly declining D-limonene concentration. This led to the controls losing slightly more D-limonene than the trials and the net log reduction to begin to decrease. The destruction time to half-life gives an alternative way to look at this data. The control trial, with a destruction time to half-life of 170.97 minutes, had a time to half- life over five times the amount of time it took the device trials to bring the VOC to its half-life (29.84 minutes). The standard deviation of only 1.42 minutes between the three trials also showed the repeatability of the performance of the device.

Example 5: Bioaerosol Reduction Efficacy Of a Photoactive Prototype Flow Cell Against Staphylococcus epidermidis

The purpose of this study was to evaluate the Staphylococcus epidermidis bioaerosol elimination efficacy of the prototype Flow Cell device, see Fig. 2, in a controlled test environment. The Flow Cell is a test unit that is comprised of a proprietary system that utilizes a small fan to circulate room air between carbon nanotube mats that are coated with titanium oxide material using atomic deposition. The mats have catalytic properties that are activated using strips of broad- spectrum daylight LED lights. While this technology is designed to be used in a variety of applications, this study focused on its efficacy as a catalytic material for air purification.

For this study, the device was evaluated on a single speed. Testing was conducted in a Lexan environmentally controlled test chamber designed to simulate an individual’s personal breathing space (Im ³ ). The testing environment was maintained at ambient room conditions a temperature of 25 °C ± 3 °C with a relative humidity of approximately 45 +/- 5%. The chamber was sealed to allow no air exchanges throughout testing.

Testing was performed in triplicate test trials for the challenge species to characterize the amount of natural decay exhibited by the species without the device turned on. Staphylococcus epidermidis was nebulized into a sealed environmental bioaerosol test chamber containing the test device. Starting chamber concentrations were approximately 1 x 10 ⁵ - 1 x 10 ⁷ cfu/L of chamber air. This starting concentration allowed for 5-6 log reduction to quantify the efficacy of the test device.

AGI impingers were used to capture viable chamber bioaerosols at set sampling times. All impinger samples were serially diluted, plated, and enumerated in triplicate to yield viable bioaerosol concentration at each sampling point. Chamber control log reduction test data was subtracted from the operational flow cell device log reduction test data to yield net reduction in the chamber for each tested bioaerosol challenge and each sampling time point. Major Equipment Used The equipment used in this study was calibrated and certified prior to the start of testing. The calibration is performed either in house or by the manufacturer as applicable.

Flow Cell

The Flow Cell is an air purification device that uses passive tangential flow air through titanium oxide infused carbon nanotube mats that are activated with broad- spectrum daylight LED lights as a means of bioaerosol reduction. The device was tested on the same fan speed throughout testing. TSI APS

A TSI Aerodynamic Particle Sizer (APS) model 3321 (TSI Inc., Shoreview, MN) was used to measure particle size and concentration of bioaerosols prior to testing to ensure proper nebulization for the trials. The APS provides real-time aerodynamic particle characterization with a size range from 0.54-20.0 pm with 52 size bins of resolution. Sampling is continuous with a data export interval of 1 second. The APS has a continuous flow rate of 1 LPM. The APS was connected directly to a sample port located in the chamber to measure challenge aerosols. Collison 6-Jet Nebulizer The 6- Jet Collison nebulizer (BGI Inc., Waltham, MA) has long been an industry standard technique for aerosolization of various liquids including biological stock suspensions. The Collison nebulizer is made from 316 stainless steel and utilizes silicone rubber O- Ring sealing gaskets and features an adjustable stem for varying liquid levels.

Bioaerosol Chamber

The primary aerosol exposure chamber used in testing was a sealed Im ³ environmental chamber constructed of 3/8” Lexan and outfitted with all necessary pass- through and sub-systems sampling ports. The chamber is equipped with HEPA filtered house air in order to maintain a clean background environment prior to all testing and to allow rapid air flushing through the chamber after completion of each exposure to ensure a clean background at before conducting subsequent trials.

During the aerosolization of the bioaerosols, the chamber was operated in a balanced push/pull aerosol inlet and vacuum to eliminate over or under pressure in the chamber. The chamber was operated at a slightly negative pressure, -0.3 in H2O, for technician safety. Once aerosolization of the challenge organism at the beginning of each trial was complete, the inlet and vacuum balance were cut off and the chamber sat idly until air sample collections.

The chamber is outfitted with impinger sample ports located in the comers of the chamber aimed towards the center. The chamber was equipped with two (2) mixing fans to ensure spatial homogeneity of bioaerosols during their aerosolization and sampling. These fans were switched on during the aerosolization of the bioaerosol into the chamber and remained on for the duration of the trials to ensure spatial homogeneity.

A Magnehelic® gauge (Dwyer instruments, Michigan City, IN), with a range of 0.0 +/- 0.5-inch H2O, was used to monitor and balance the system pressure during aerosol generation, aerosol purge, and testing cycles. Prior to testing, the interior walls, ceiling, and floor of the testing chamber were wiped down with 91% isopropyl alcohol.

Bioaerosol Generation System

Test bioaerosols were disseminated using a Collison 6-jet nebulizer (BGI Inc., Waltham, MA) driven by purified filtered house air supply. A pressure regulator allows for control of disseminated particle size, use rate, and sheer force generated within the Collison nebulizer. A pressure regulator allows for control of disseminated particle size, use rate, and sheer force generated within the Collison nebulizer. Prior to testing, the Collison nebulizer flow rate and use rate were characterized using a calibrated TSI Model 4040 mass flow meter (TSI Inc., St Paul MN). The air supply pressure was approximately 60 psi, which obtains an output volumetric flow rate of 50-80 LPM with a fluid dissemination rate of approximately 1-2 mL/min.

Particle Size Distribution

Aerosol particle size distributions and count concentrations were measured initially to obtain challenge particle size distribution for each species. The particle size distribution of S. epidermidis can be found to the right in Fig. 6. The aerosol for S. epidermidis had a larger overall particle size distribution with most of the particles being above 1.0pm with a peak around 2.0pm.

Bioaerosol Sampling and Monitoring System

An AGI-30 impinger (Ace Glass Inc., Vineland, NJ) were used for bioaerosol collection to determine the chamber concentration. This impinger was connected to the bioaerosol chamber via a sample port located in a corner of the chamber. The AGI-30 impinger vacuum source was maintained at a minimum negative pressure of 17 inches of Hg during all sampling to assure critical flow conditions of the samplers. The AGI-30 sample impingers (Fig. 8) were flow characterized using a calibrated TSI model 4040 mass flow meters.

Species Selection

Species selection is based on BSL1 surrogates for a wide range of BSL 3 pathogenic microorganisms. It is routine in the bioaerosol field to use surrogate species to test performance against BSL3 microorganism decontamination due to the high cost and limited laboratory space associated with aerosol BSL 3 testing.

This testing utilized methicillin resistant Staphylococcus epidermidis which is a bio-safety level 1 (BSL1) pathogen. This organism is a surrogate for methicillin resistant Staphylococcus aureus which is a common pathogen with a history of being prevalent in hospitals and is known to cause pulmonary infections.

Culture Preparation

To culture the Staphylococcus epidermidis, the seed stock was obtained from the ATCC. Seed stock was added to tryptic soy broth in a vented culture flask in a class 2 biological safety cabinet and followed standard preparation methodologies. It was then placed into an incubator for 24 hours at 370C. The S. epidermidis was prepared fresh each day for testing.

Plating and Enumeration

Impinger and stock cultures were serially diluted and plated in triplicate (multiple serial dilutions) using standard small drop plaque assay technique onto Tryptic Soy Agar plates. The plated cultures were incubated for 24 hours at 37 °C, and plaques were enumerated and recorded.

Bioaerosol Testing

To accurately assess the test device, a pilot control test was performed with each bioaerosol for a 90-minute period, without the test device in operation, to characterize the aerosol challenge for particle size distribution, aerosol delivery/collection efficiency, decay rate, and viable concentration over time. Control testing was performed to provide baseline data to assess the actual reduction rate from the operation of the device during the testing trials and verify that viable bioaerosol concentrations persisted above the required concentrations over the entire pilot control test period. For control testing, the device remained in the test chamber for consistency with test runs.

During control and test device trials, two low velocity mixing fans, located in opposite comers of the bioaerosol test chamber, were turned on for the duration of trial to ensure a homogenous aerosol concentration within the aerosol chamber. For each control and challenge test, the Collison nebulizer was filled with approximately 10 mL of biological stock and 40 mL of sterile tryptic soy broth and operated at 40 psi for a period of 5 minutes. For both control and device tests, the impingers were filled with 20 mL of sterilized PBS (addition of 0.05% v/v Tween 80) for bio aero sol collection.

The chamber mixing fan was turned on during bioaerosol dissemination to assure a homogeneous concentration in the test chamber prior to the first impinger sample. Following bioaerosol generation, baseline concentrations were established for each pilot control and flow cell test by sampling simultaneously with an AGL30 impinger located at opposite comers of the chamber. AGI samples were collected for 3, 5, or 10 minutes at intervals of 15 minutes throughout the entire period. Collected impinger chamber samples were mixed and collected at each sample interval for each test. Impingers were rinsed 6x with sterile filtered water between each sampling interval and re-filled with sterile PBS using sterile graduated pipettes for sample collection.

For the flow cell bioaerosol tests, the device was operated at the highest fan speed. The highest fan speed on the unit was measured to be approximately 8 cfm (cubic feet per minute). The same device was used for each trial of the triplicate- set of test runs for consistency. The nebulization procedure remained the same in the test trials as in the control trials with approximately 10 mL of biological stock and 40 mL of sterile tryptic soy broth being nebulized at 40 psi for a period of 5 minutes. The test device was turned on immediately following a time 0 baseline sample and operated for the entirety of the test (90 minutes).

Total test time was based on viable bioaerosol concentrations, limits-of-detection, and time required to show greater than 4.0 net log reduction compared to the control test. Subsequent impinger samples were taken at intervals of 15-minute time points and then enumerated for viable concentration to measure the effective viable bio aero sol reduction during operation of the test unit. See Fig. 7 for the testing timeline.

The test chamber temperature and humidity levels were recorded continuously throughout the test from initiation to completion. All samples were plated in triplicate on Tryptic Soy Agar plates over a minimum of a 3 -log dilution range. Plates were incubated for viable PFU formation. Plates were incubated and enumerated for viable counts to calculate aerosol challenge concentrations in the chamber and reduction of viable bioaerosols.

Post-Testing Decontamination and Prep Between each test, the chamber was airflow evacuated/purged for a minimum of 20 minutes and analyzed with the APS for particle concentration decrease to baseline levels. The chamber was decontaminated between tests with aerosol/vaporous hydrogen peroxide (35%). The Collison nebulizer and impingers were cleaned at the conclusion of each day of testing by soaking them in a 10% bleach bath for 20 minutes. The nebulizer and impingers were then be submerged in a DI water bath, removed, and spray rinsed 6 times with filtered DI water until use.

Data Analysis

Impinger data was plotted to show log reduction vs. test time for control and flow cell device tests. The net LOG reduction attributable to the flow cell was calculated by subtracting the average control reduction from each of the test device trials at each sample time. The net LOG reduction for the device was plotted for each time point in every trial. All data shows individual and group average +/- standard deviation.

Chamber S. epidermidis Bioaerosol Testing Results

The flow cell device produced a steady reduction in Staphylococcus epidermidis throughout each test trial. At the 75-minute time point the device averaged a log reduction of 5.06. When the losses from the control are considered the net log reduction at that time point equated to 4.04. At the final time point the device achieved a 4.57 net log reduction which is equivalent to a 99.997% net reduction. A graph of the log reduction of each trial and the average as well as the control can be found in Fig. 8. A graph of the net log of the trials with the average can be found in Fig. 9 and a summary of the results is presented in Fig. 10.

SUMMARY OF RESULTS

When tested with the gram-positive bacteria Staphylococcus epidermidis the device yielded a steady reduction throughout each trial. At the final 90-minute time point the device yielded a net log reduction of 4.57 which is equivalent to a 99.997% reduction. A graph of the net log reduction of the triplicate trials can be found in Fig. 9. Conclusion In conclusion the device showed efficacy against S. epidermidis by achieving a net log reduction of over 99.99% in the 90 minutes. A summary table of the net log reduction of each trial at each time point as well as the percent reduction and the averages at each time point can be found in Fig. 10.

Fig. 11 presents XPS surface analysis of a carbonaceous material, i.e., CNTs with a preactivated film of Ti-EG. As you can see from the Fe2p signal, there is a shift to higher binding energy which is indicative of oxidation of the Fe from metallic (0) to Fe(II) upon thermal treatment. In addition, the Ti and O peaks show the formation of TiO ₂ on the CNT. The Fe content was measured between 0.5 and 15% w/w, depending on the carbonaceous material used. Typically, the Fe content was between 3 and 5% w/w.