FIELD

[0001] The present disclosure relates to disinfecting, self-binding suspensions, and more particularly, disinfecting, self-binding suspensions for preparing disinfecting thin-film coatings.

BACKGROUND

[0002] Surface disinfection is vital for preventing the spread of infectious diseases. Inadequate surface disinfection may accelerate the spread of contagious diseases and remains the principal infection pathway for nosocomial infections. Pathogenic microorganisms, including viruses, can survive on ordinary surfaces for an extended period, which poses a risk of spread and infection. For example, Pseudomonas aeruginosa and Escherichia coli can survive on a surface for up to 16 months. SARS-CoV-2, the virus responsible for the COVID-19 disease pandemic outbreak, can survive for up to 28 days on common surfaces, including banknotes, glass, and stainless steel.

[0003] Conventional methods of disinfection include the use of liquid disinfecting solutions. For example, liquid disinfecting solutions can be used to disinfect high-touch areas such as office equipment (e.g., mice, keyboards, printers), metal furnishings (e.g., doorknobs, handrails), touchscreens (e.g., portable tablets, mobile phone devices, automated teller machines (ATMs)), etc. Examples of such liquid disinfecting solutions can include the use of alcohol-, hypochlorite-, peroxide-, detergent-, or a combination thereof. The use of conventional liquid disinfecting solutions can result in a rapid decrease of microbial load.

SUMMARY OF THE DISCLOSURE

[0004] Provided herein are sterilizing suspensions, coated substrates prepared using sterilizing suspensions, and methods of preparing said suspensions and coated substrates. As described above, conventional surface disinfectants include liquid disinfecting solutions. However, the active ingredients of liquid disinfecting solutions either evaporate or dissolve during the use of the surface (e.g., when the surface is touched, as in high-touch surfaces) or are consumed during the disinfection chemical reaction. Frequent use of liquid disinfecting solutions can improve the amount of disinfection and minimize the spread of infectious diseases. Still, it remains infeasible to continuously disinfect high-touch surfaces to achieve adequate disinfection properties.

[0005] Accordingly, provided herein are disinfecting suspensions and thin-film coatings formed from such suspensions. Specifically, the suspensions described may be deposited onto high- touch surfaces to provide a disinfecting thin- film coating for the high-touch surface. These disinfecting thin-film coatings can help prevent the spread of infectious diseases.

[0006] The suspensions provided herein may be prepared in an aqueous/alcoholic medium using silver-doped titanium dioxide nanoparticles, quaternary ammonium salts, and silicon dioxide nanoparticles. Silicon dioxide nanoparticles act as anchors for the disinfecting suspension to irreversibly bind on a porous or non-porous substrate without the application of heat. The disclosed disinfecting suspensions may be applied to office equipment (e.g., mice, keyboards, printers), metal furnishings (e.g., doorknobs, handrails), furniture surfaces (e.g., desks, textiles, benchtops), or screens (e.g., portable tablets, mobile phone devices, automated teller machines (ATMs)), and the like to form a disinfecting thin-film coating on the surface.

[0007] Thin-film coatings may be transparent in the visible spectrum of light. If these thin films are not transparent, they could interfere with the visible light resulting in aesthetic appearance defects. Further, such films should retain their initial properties (e.g., photocatalytic activity, sterilizing activity) for a minimum of eight weeks under variable weather and abrasion conditions and exhibit suitable adhesion to the substrate, even if the substrate is a plastic, non- porous surface.

[0008] The disclosed invention presents unique advantages that can include:

• a photocatalytic disinfection mechanism activated upon low UV exposure;

• strong adhesion on various substrates and resistance to removal by abrasion;

• insoluble in an aqueous medium; and

• cost-effectiveness.

[0009] In some embodiments, provided is a disinfecting suspension composition, the composition comprising: 0.01 to 0.50 wt. % titanium dioxide nanoparticles; 0.0005 to 0.10 wt.

% silver; 2 to 8 wt. % silicon dioxide nanoparticles; and 0.01% to 2 wt. % quaternary ammonium salt.

[0010] In some embodiments of the composition, the composition comprises 0.00001 to 0.005 wt. % salt.

[0011] In some embodiments of the composition, the composition comprises 0.0001 to 0.1 wt.

% dispersant. [0012] In some embodiments of the composition, the composition- comprises 0.1 to 5 wt. % surfactant.

[0013] In some embodiments of the composition, the composition comprises 25 to 50 wt. % alcohol.

[0014] In some embodiments of the composition, the composition comprises 0.01 to 0.5 wt. % Lewis base.

[0015] In some embodiments of the composition, the composition comprises 30 to 60 wt. % water.

[0016] In some embodiments of the composition, the salt comprises at least one of Na4P207, sodium hydroxide, or sodium chloride.

[0017] In some embodiments of the composition, the alcohol comprises at least one of methanol, ethanol, n-propyl alcohol, or isopropyl alcohol.

[0018] In some embodiments, a coated substrate is provided, the coated substrate comprising: a substrate; and a thin-film coating on the substrate, the thin-film coating comprising: 0.001 to 0.25 wt. % titanium dioxide nanoparticles; 0.00005 to 0.05 wt. % silver; 0.2 to 4 wt. % silicon dioxide; and 0.001% to 1 wt. % quaternary ammonium salt.

[0019] In some embodiments of the coated substrate, the thin-fdm coating comprises 0.000001 to 0.0025 wt. % salt.

[0020] In some embodiments of the coated substrate, the thin-film coating comprises 0.00001 to 0.05 w.t % dispersant.

[0021] In some embodiments of the coated substrate, the thin-film coating comprises 0.01 to 2.5 wt. % surfactant.

[0022] In some embodiments of the coated substrate, the thin-film coating comprises 0.001 to 0.25 w.t % Lewis base.

[0023] In some embodiments of the coated substrate, the salt comprises at least one of Na4P207, sodium hydroxide, or sodium chloride. [0024] In some embodiments of the coated substrate, 0.01 to 0.15 L/m2 of a suspension composition is applied to the substrate to form the thin-film coating of the coated substrate.

[0025] In some embodiments of the coated substrate, the substrate comprises a computer mouse, a keyboard, a printer, a doorknob, a handrail, a portable tablet, a mobile phone device, or an automated teller machine.

[0026] In some embodiments, a method of producing a disinfecting coated substrate is provided, the method comprising: preparing a binder solution; preparing a silver-based suspension; preparing a titanium dioxide-based suspension; combining the binder solution, the silver-based suspension, and the titanium dioxide-based suspension to form a disinfecting suspension; and depositing the disinfecting suspension onto a substrate to form a coated substrate.

[0027] In some embodiments of the method, preparing a binder solution comprises combining two or more of alkoxysilane, a first alcohol, a Lewis base, and water.

[0028] In some embodiments of the method, preparing a silver-based suspension comprises combining two or more of water, a thickening agent, a second alcohol, and silver.

[0029] In some embodiments of the method, preparing a titanium dioxide-based suspension comprises combining two or more of water, a salt, a dispersant, and titanium dioxide.

[0030] In some embodiments of the method, the salt comprises at least one of Na4P207, sodium hydroxide, or sodium chloride.

[0031] In some embodiments of the method, the first alcohol comprises at least one of methanol, ethanol, n-propyl alcohol, or isopropyl alcohol.

[0032] In some embodiments of the method, the second alcohol comprises at least one of methanol, ethanol, n-propyl alcohol, or isopropyl alcohol.

[0033] In some embodiments of the method, depositing the disinfecting solution comprises depositing 0.01 to 0.15 L disinfecting solution per square meter of the substrate.

[0034] In some embodiments of the method, the substrate comprises a computer mouse, a keyboard, a printer, a doorknob, a handrail, a portable tablet, a mobile phone device, or an automated teller machine. BRIEF DESCRIPTION OF THE FIGURES [0035] The invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0036] FIG. 1 provides a process diagram for preparing a suspension, according to some embodiments;

[0037] FIG. 2 provides a transmission electron microscopy image of titanium dioxide nanoparticles, according to some embodiments;

[0038] FIG. 3 presents a transmission electron microscopy image of metallic silver nanoparticles, according to some embodiments; and

[0039] FIG. 4 provides photocatalytic decomposition data of nitrogen oxide from coated substrates, according to some embodiments.

DETAILED DESCRIPTION OF THE DISCLOSURE [0040] Provided herein are disinfecting, self-binding suspensions, coated substrates prepared using disinfecting, self-binding substrates, and methods of preparing disinfecting, self-binding suspensions. The suspensions described include a binary TiCh-silver system that provides improved photocatalytic activity in thin- film coatings formed by the suspension. Specifically, the binary TiCk-silver binary system provides enhanced photocatalytic activity over suspensions comprising only one of T1O2 or silver. Further, the suspensions provided herein may include monodispersed nanoparticles and comprise of agglomerates no larger than 200nm to achieve these properties.

[0041] The suspensions disclosed herein may be used to prepare thin-film coatings for products such as office equipment (e.g., mice, keyboards, printers), metal furnishings (e.g., doorknobs, handrails), furniture surfaces (e.g., desks, textiles, benchtops), or screens (e.g., portable tablets, mobile phone devices, automated teller machines (ATMs)). DISINFECTING, SELF-BINDING SUSPENSION COMPOSITIONS

[0042] Described below are disinfecting, self-binding suspensions. These disinfecting, selfbinding suspensions can be used to form thin-film coatings for various surfaces. For example, the disinfecting, self-binding suspensions described below may be used to create thin-film coatings for high-touch surfaces to help prevent the spread of infectious diseases.

[0043] Suspensions provided herein may include titanium dioxide, silver (metallic silver or silver oxide or silver cation salts (Ag ⁺ )), silicon dioxide, quaternary ammonium salts, a salt for steric or electrostatic hindrance and stabilization, a dispersant, a surfactant, alcohol, a Lewis base, and a solvent. Each component is described in detail below.

[0044] In some embodiments, a suspension may include titanium dioxide (TiCL). Titanium dioxide presents disinfection properties upon exposure to ultraviolet light (i.e., light having a wavelength below 395nm). Titanium dioxide nanocrystallites exist in three distinct crystal phases: anatase, brookite, and rutile. Of these three phases, anatase is generally preferred for photocatalytic activity because of its energy gap in the range of 3.23 eV (n-type semiconductor). When the photoactive titanium dioxide nanoparticles are irradiated by near-ultraviolet light (i.e., light having a wavelength below 390nm), electrons from the electron-filled valence band are transferred to the vacant conduction band and subsequently leave positive-charged holes in the valence band. This photo-generated charge separation is responsible for the photoreduction and photooxidation of different microorganisms surrounding the semiconductor particles. Subsequently, the outer lipidic membrane of microbes or the protein capsule of viruses oxidizes and physically ruptures, resulting in a non-selective termination of microorganisms. It is well established in the scientific literature that surface hydroxyl (-OH) groups of titanium dioxide nanoparticles cannot form covalent metal-oxygen-metal (-M-0-M-) bonds unless subjected to annealing temperatures exceeding 400°C (752°F). Therefore, titanium dioxide nanoparticles exhibit poor adhesion on substrates and removal from a substrate when exposed to abrasion. However, titanium dioxide combined with a metal, such as silver, can exhibit improved disinfection properties.

[0045] Titanium dioxide nanoparticles may be obtained from a powder. For example, a commercially available and low-cost titanium dioxide powder may be used in suspensions according to embodiments provided herein. Suitable commercially available titanium dioxide powders can include Evonik Aeroxide™ P90, Evonik Aeroxide™ P25, or Kronos KRONOClean™ 7000. In some embodiments, suspensions provided herein may include 0.01 to 0.5 wt. % titanium dioxide. In some embodiments, suspensions provided herein may include less than or equal to 0.5, 0.25, 0.1, 0.05, or 0.025 wt. % titanium dioxide. In some embodiments, suspensions provided herein may include more than or equal to 0.01, 0.025, 0.05, 0.1, or 0.25 wt. % titanium dioxide. Suspensions comprising insufficiently low concentrations of titanium dioxide may result in thin-film coatings having inferior photocatalytic activity. Conversely, suspensions comprising exceedingly high concentrations of titanium dioxide may not meet the optical criteria of coating transparency.

[0046] As explained above, suspensions provided herein can achieve desirable photocatalytic properties due to a titanium dioxide and silver binary system. Specifically, the binary system of titanium dioxide with silver (metallic silver or silver oxide or silver cation salts (Ag ⁺ )) can provide synergistic effects and performance (e.g., photocatalytic disinfection reaction rate) that cannot be achieved when either the titanium dioxide or silver (metallic silver or silver oxide or silver cation salts (Ag ⁺ )) alone. In particular, the binary system of TiCb-silver shows improved photocatalytic activity compared to pure T1O2. When the two photoactive oxides (i.e., titanium dioxide and metallic silver or silver oxide or silver cation salts (Ag ⁺ )) are combined, a material having improved photocatalytic activity is generated. The performance of titanium dioxide- based photocatalysts can be enhanced by doping with metallic silver or silver oxide or silver cation salts (Ag ⁺ ). The doping process improves the sensitivity of titanium dioxide nanoparticles to visible light and induces an efficient surface plasmon resonance effect preventing the recombination of photoexcited electron-hole pairs. Therefore, the titanium dioxide and silver nanostructured materials can be activated for light-induced disinfection by UV and visible light. The mechanism of photocatalytic activity enhancement has been disclosed in «Silver modified titanium dioxide thin films for efficient photodegradation of methyl orange», by I.M. Arabatzis et al, Applied Catalysis B: Environmental, 42 (2003) 187.

[0047] Among the titanium dioxide dopants for photocatalytic processes, silver (metallic silver or silver oxide or silver cation salts (Ag ⁺ )) is the most abundant and cost-effective. Silver is also a well-known photoactive inorganic element, which blends in and efficiently promotes the light- induced photocatalytic titanium dioxide process rate. Silver can be used to modify the surface of titanium dioxide (i.e., surface modification) or to dope the titanium dioxide (i.e., doping).

Surface modification of titanium dioxide with silver is less energy-consuming and easier than molecular doping in the crystal lattice of titanium dioxide. In particular, silver can increase the light-induced disinfection capability of titanium dioxide nanoparticles in the visible range. Other noble metals that may be used instead of silver can include gold, palladium, or platinum. [0048] The silver used to modify the titanium dioxide may include metallic silver, silver oxide, or silver cation salts (Ag ⁺ ). In some embodiments, silver compounds may include silver nanoparticles that are obtained from a sol-gel procedure. In some embodiments, a commercially available silver nitrate (AgNCfi) powder may be used as the silver source. Suitable commercially available silver nitrate powders may include Laboratorios Argenol SL Silver Nitrate EP 9.0 or Cofermin Chemicals GmbH & Co. Silver Nitrate. For example, a commercially available silver oxide (Ag ₂ 0) powder may be used as the silver source. Suitable commercially available silver oxide powders may include Helioenergia sp. z o.o. nAg OXY. In some embodiments, suspensions provided herein may include 0.0005 to 0.1% wt. % silver compound. In some embodiments, suspensions provided herein may include less than or equal to 0.1, 0.075, 0.05, 0.01, 0.0075, 0.005, 0.001, or 0.00075 wt. % silver compound. In some embodiments, suspensions provided herein may include more than or equal to 0.00075, 0.001, 0.005, 0.0075, 0.01, 0.05, 0.075, or 0.001 wt. % silver compound. Suspensions comprising insufficiently low concentrations of silver content may not assist the photocatalytic effect adequately. Conversely, suspensions comprising exceedingly high concentrations of silver content may block the photocatalytic effect.

[0049] Suspensions provided herein may also include silicon dioxide. Silicon dioxide promotes the adhesion of silver-modified titanium dioxide nanoparticles and quaternary ammonium salts on coated substrates prepared using suspensions described herein. Specifically, suspensions may include silicon dioxide powder and/or silicon dioxide nanoparticles. Silicon dioxide can encourage adhesion on porous or non-porous surfaces. In some embodiments, silicon dioxide nanoparticles may be obtained from a sol-gel procedure. For example, commercially available silicon alkoxide raw materials can be used to prepare a colloidal suspension comprising silicon dioxide powder. Suitable silicon alkoxides can be any compound with chemical formula (H ₂ NC _n H _2n O)(C _k H _{2k+ 1} 0)(CmH _2m+i 0)(CpH _2p+i 0)Si (aminosilanes) or (C _n H _2n+! 0)(C _k H _2k+i O)(C _n H _2in+i O)(C _p H _2p+i O)Si or polydimethylsiloxane (C ₂ H ₆ 0Si) _q (C„H ₂ „+ _I 0)(C _k H _2k+i 0)(C _m H _2m+i 0)Si(CiH _2i )Si(C _x H _2x+ 10)(C _y H _2y+ 10)(C _z H _2z+i O) (where n, k, 1, m, p, x, y, z are positive, integer numbers from zero to eight and q is a positive integer numbers from zero to one thousand). For example, commercially available alkoxysilanes can include DOWSIL™ Z-6162, DOWSIL™ Xiameter 6697, and/or EVONIKTM Dynasylan A. Any one of these alkoxysilanes may be used in a sol-gel process to obtain silicon dioxide. In some embodiments, the colloidal silicon dioxide nanoparticles prepared from a sol-gel technique may be preferred to silicon dioxide nanoparticles obtained from powders because they can enhance the superhydrophilicity of the final coating and act as adhesion binders to the substrate. In some embodiments, disinfecting suspensions provided herein may include 2 to 8 wt. % silicon dioxide. In some embodiments, suspensions provided herein may include less than or equal to 8, 7, 6, 5, 4, or 3 wt. % silicon dioxide. In some embodiments, a suspension provided may include more than or equal to 2, 3, 4, 5, 6, or 7 wt. % silicon dioxide. Suspensions comprising insufficiently low concentrations of silicon dioxide may result in thin-film coatings having a substrate adhesion capability that is too weak. Conversely, suspensions comprising exceedingly high concentrations of S1O2 content may cover titanium dioxide nanoparticles and prevent the expression of the photocatalytic phenomenon.

[0050] Suspensions provided may also comprise one or more salts. For example, a suspension according to some embodiments may comprise a quaternary ammonium salt. Quaternary ammonium cations have remarkable disinfection activity. Quaternary ammonium cations are positively charged polyatomic ions of the structure NR ₄ ⁺ , R being an alkyl group or an aryl group. Unlike the ammonium ion (NH4 ) and the primary, secondary, or tertiary ammonium cations, the quaternary ammonium cations are permanently charged, independent of the pH of the solution. Quaternary ammonium salts or quaternary ammonium compounds are salts of quaternary ammonium cations. Quaternary ammonium compounds have been shown to have microbicidal activity. Certain quaternary ammonium compounds, especially those containing long alkyl chains, are used as microbicides and disinfectants. Specific examples of quaternary ammonium compounds are benzalkonium chloride, benzethonium chloride, methylbenzethonium chloride, cetalkonium chloride, cetylpyridinium chloride, cetrimonium, cetrimide, dofanium chloride, tetraethylammonium bromide, didecyldimethylammonium chloride, and domiphen bromide. Also useful against fungi, amoebas, and enveloped viruses, quaternary ammonium compounds are believed to act by disrupting the cell membrane or viral envelope. Quaternary ammonium compounds are lethal to a wide variety of organisms except for endospores and non-enveloped viruses. Quaternary ammonium compounds are cationic detergents and disinfectants and can be used to remove organic material. Effective levels are at 200 ppm. They are effective at temperatures up to 100°C (212°F). Additionally, quaternary ammonium salts can improve thin-film coatings’ disinfection propierties by minimizing the amount of time between when the suspension is deposited and when the thin-film coating begins exhibiting disinfection properties.

[0051] Quaternary ammonium salts may be obtained in powder or solution form. Suitable quaternary ammonium salts can include any salt or mixture of salts in which a nitrogen atom has four carbon-nitrogen single bonds. Specifically, suitable quaternary ammonium salts may include (C _r H _2r+i O)(C _s H _2s+i O)(C _t H _2t+i O) ₂ N ⁺ or (C H2n-iO)Ar(C _t H2 _t+i O)2N ⁺ (where r, s, t, are positive, integer numbers from one to twenty- five and Ar stands for aryl organic chemistry group, which is any functional group or substituent derived from an organic aromatic ring). For example, commercially available quaternary ammonium salts can include Innospec EMPIGEN® BKC 50 or Lonza BardacTM 205M. In some embodiments, suspensions provided herein may include 0.01% to 2 wt. % quaternary ammonium salt. In some embodiments, suspensions provided herein may include less than or equal to 2, 1.5, 1, or 0.5 wt. % quaternary ammonium salt. In some embodiments, suspensions provided herein may include more than or equal to 0.01, 0.05, 0.10, 0.15, 0.20, 0.25, 0.30, 0.35, 0.40, 0.45, 0.50, 1, or 1.5 wt. % quaternary ammonium salt.

[0052] In some embodiments, suspensions provided herein may include a salt used to control the ionic strength of the preparation emulsion or suspension. For example, some salts dissociate into ions in the presence of aqueous media. Ions can be absorbed by nanoparticle surfaces and can electrostatically repel each other to prevent aggregation and sedimentation. Therefore, optimizing the amount of salt and the amount of ions present in a suspension can form more stable nanoparticle emulsions and increase their commercial exploitation potential. Examples of suitable salts include polyelectrolytes (e.g., poly(sodium styrene sulfonate), Na ₄ P ₂ C> ₇ , sodium hydroxide, or sodium chloride). In some embodiments, suspensions provided herein may include 0.00001 to 0.005 wt. % salt. In some embodiments, a suspension may comprise less than or equal to 0.005, 0.0025, 0.001, 0.0005, 0.0001, or 0.00005 wt. % salt. In some embodiments, a suspension may include more than or equal to 0.00001, 0.00005, 0.0001, 0.0005, or 0.001 wt. % salt. Suspensions, including an insufficiently low amount of salt, may present sedimentation within hours after preparation, making the resulting formulation impractical to use. Conversely, suspensions including exceedingly high salt concentrations may result in reduced photocatalytic activity, as salt ions create multilayers around nanoparticles and prevent chemical interaction with water or oxygen molecules.

[0053] Suspensions provided herein may also include a dispersant for promoting the formation and stabilization of the nanoparticles in the solution. Commercially available dispersants can include Surfynol CT-231, Tego Flow 425, carboxyl methylcellulose (CMC), dimethyl sulfoxide (DMSO), l,2-Dipalmitoyl-sn-glycero-3-phosphocholine, Tween 80, bovine serum albumin (BSA), and fetal bovine serum (FBS). In some embodiments, suspensions provided herein may include 0.0001 to 0.1 wt. % dispersant. In some embodiments, suspensions may include less than or equal to 0.1, 0.05, 0.01, 0.005, 0.001, or 0.0005 wt. % dispersant. In some embodiments, suspensions may include more than or equal to 0.0001, 0.0005, 0.001, 0.005, 0.01, or 0.05 wt. % dispersant.

[0054] Suspensions provided herein may also include a surfactant. Surfactants can help improve substrate wetting by reducing the surface tension between the suspension/thin-film coating and the substrate. Suitable commercially available surfactants may include Tego Wet 500, Tego Wet 270, and siloxane formulations. In some embodiments, suspensions provided herein may include 0.1 to 5 wt. % surfactant. In some embodiments, a suspension may include less than or equal to 5, 4, 3, 2, 1, or 0.5 wt. % surfactant. In some embodiments, suspensions may include more than or equal to 0.1, 0.5, 1, 2, 3, or 4 wt. % surfactant.

[0055] In some embodiments, a suspension may include a liquid alcohol to hydrolyze the chemical binder. A suitable alcohol may include up to five carbon atoms (e.g., methanol, ethanol, isopropanol) and up to two oxygen atoms (CiH _2i +20 or CjH2j+2C>2, where i and j are positive, integer numbers from one to five). In some embodiments, a suspension may include 25 to 50 wt. % alcohol. In some embodiments, a suspension may include less than or equal to 50,

45, 40, 35, or 30 wt. % alcohol. In some embodiments, a suspension may include more than or equal to 30, 35, 40, 45, or 50 wt. % alcohol.

[0056] In some embodiments, a Lewis base may be included to adjust the pH value during hydrolysis. In some embodiments, the pH may be adjusted and controlled to a value from 9 to 10. In some embodiments, a suspension may include 0.01 to 0.5 wt. % Lewis base. In some embodiments, a suspension may include less than or equal to 0.5, 0.4, 0.3, 0.2, 0.1, or 0.05 wt. % Lewis base. In some embodiments, a suspension may include more than or equal to 0.01, 0.05, 0.1, 0.2, 0.3, or 0.4 wt. % Lewis base.

[0057] Suspensions provided herein may include a solvent. Suitable solvents can include water (e.g., deionized) or alcohol. In some embodiments, sterilizing, self-binding suspensions provided herein may include 30 to 60 wt. % solvent. In some embodiments, suspensions may include less than or equal to 60, 55, 50, 45, 40, or 35 wt. % solvent. In some embodiments, suspensions may include more than or equal to 35, 40, 45, 50, 55, or 60 wt. % solvent.

[0058] In some embodiments, suspensions provided herein incorporate monodispersed nanoparticles comprising agglomerates not exceeding 200 nm to improve the transparency of the thin films produced from the provided suspensions. [0059] Disinfecting suspensions described may have a density of 0.9-1.2 g/cm ³ . In some embodiments, the density maybe less than or equal to 1.2, 1.1, or 1 g/cm ³ . In some embodiments, the density may be greater than or equal to 0.9, 1 , or 1.1 g/cm ³ .

[0060] In some embodiments, the pH of a disinfecting suspension may be 7-12. In some embodiments, the pH may be less than or equal to 12, 11, 10, 9, or 8. In some embodiments, the pH may be greater than or equal to 7, 8, 9, 10, or 11.

[0061] In some embodiments, the viscosity of a disinfecting suspension may be 30-60 Krebs Units (KU). In some embodiments, the viscosity may be less than or equal to 60, 55, 50, 45, 40, or 35 KU. In some embodiments, the viscosity may be greater than or equal to 30, 35, 40, 45, 50, or 55 KU.

[0062] FIG. 1 shows method 100 of preparing a disinfecting suspension, according to some embodiments. At step 102, a binder solution is prepared. This binder solution can include two or more of alkoxysilane, a first alcohol, a Lewis base, and water. At step 104, a silver-based suspension is prepared. The silver-based suspension can include two or more of water, a thickening agent, a second alcohol, and silver. At step 106, a titanium dioxide-based suspension is prepared. The titanium oxide-based suspension can include two or more of water, a salt, a dispersant, and titanium dioxide. At step 108, the binder solution, the silver-based suspension, and the titanium dioxide-based suspension are combined. The combination fonns a disinfecting suspension. At step 110, the disinfecting suspension is deposited onto a substrate to form a coated substrate.

COATED SUBSTRATES

[0063] The above-described suspensions can be used to prepare thin- film coatings for substrates (or coated substrates) for applications including, but not limited to, office equipment (e.g., mice, keyboards, printers), metal furnishings (e.g., doorknobs, handrails), furniture surfaces (e.g., desks, textiles, benchtops) or screens (e.g., portable tablets, mobile phone devices, automated teller machines (ATMs)). Discussed below are various application/deposition methods for preparing coated substrates.

[0064] In some embodiments, nanoparticles can adhere to a substrate easily. Thus, suspensions comprising nanoparticles can be considered “self-binding” due to the nanoparticles’ ability to adhere to the substrate easily. Specifically, silicon dioxide nanoparticles act as a binder. Accordingly, suspensions comprising silicon dioxide nanoparticles can be considered self- binding. In some embodiments, no heat treatment step is needed for the suspension to adhere to the substrate to form a thin-film coating.

[0065] In some embodiments, a thin-film coating prepared using a suspension provided herein may be 100-300nm thick. In some embodiments, the thickness of a thin-film coating prepared using suspensions described herein may be less than or equal to 300, 250, 200, or 150 nm. In some embodiments, the thickness of a thin-film coating prepared using suspensions described herein may be greater than or equal to 100, 150, 200, or 250 nm.

[0066] In some embodiments, a suspension may be used to form a thin-film coating on a substrate. For example, 0.001 to 0.1 L/m ² of a disinfecting suspension may be deposited to the substrate. In some embodiments, less than or equal to 0.1, 0.08, 0.06, 0.04, 0.02, 0.01, or 0.005 L/m ² suspension may be deposited on a substrate. In some embodiments, more than or equal to 0.001, 0.005, 0.01, 0.02, 0.04, 0.06, or 0.08 L/m ² suspension may be deposited on a substrate.

[0067] Suitable deposition methods include spraying, blade, rotating drum, or cloth whipping.

[0068] In some embodiments, the substrate of the coated substrate may comprise an organic or an inorganic material. Suitable substrate materials may include glass, aluminum, stainless steel, metal substrates, cement and concrete, marble, polished stone, natural stone, plasters and renders, polymer films, veneers, melamine, polycarbonate films, acrylic paint films, styrene- acrylic paint films, polyurethane paint films, and epoxy paint films.

[0069] In some embodiments, the thin-film coatings provided require a conditioning period before exhibiting disinfection properties. For example, a thin-film coating may present inadequate disinfection properties for a period of one hour to three days after deposition. However, the presence of quaternary ammonium salts can enhance earlier disinfection.

EXAMPLES

Example 1: Preparing a disinfecting suspension

[0070] Preparing the Binder Solution: 21.5kg of alkoxysilane (tetraethyl orthosilicate; DOWSIL™ Xiameter 6697, Dow Corning Europe SA) was mixed with 45.6 L of ethanol in stainless steel 200L chemical reactor. Deionized water (92 L) was added to the mixture and stirred for fifteen minutes. A water-soluble Lewis base (25 wt. % ammonium hydroxide NH4OH) was added dropwise to adjust the pH to 9.5. The mixture was stirred for 600 minutes until becoming a transparent liquid. [0071] Preparation of the TiC colloidal suspension: Deionized water (56 L) was placed into an 80 L stainless steel continuously- stirring tank reactor. A stabilizing salt (Na4P207, 0.12kg) and 0.36kg of dispersant (Surfynol CT-231, Air Products and Chemicals, Inc.) were diluted into the deionized water. The solution was vigorously stirred for 60 minutes at 600 revolutions per minute. After stirring, 3.6kg of titanium dioxide powder (Evonik Aeroxide™ P90) was added to the solution, resulting in a colloidal solution.

[0072] A Hielscher, UlPlOOOhd ultrasonic processor (power output: 800 Watts at 20 kHz) having a robust stainless-steel reactor vessel was connected to the continuous-stirring tank reactor. The ultrasonication tip was inserted into the colloidal solution. After 540 minutes of ultrasonication, the resulting material was a stable T1O2 colloidal suspension. The titanium-based solution is a milky solution. The color is due to the presence of T1O2 nanoparticles. The T1O2 nanoparticles’ size is in the range of 15 to 35nm, as shown in Figure 2.

[0073] Preparation of silver-based solution: Deionized water (56L) was placed into an 80L stainless steel continuously stirring tank reactor. 0.2kg of a thickening agent (Dupont Methocel™) was added, and the solution was stirred for 90 minutes. Subsequently, it was diluted with 38L of ethanol, and finally, 0.0025kg of silver nitrate AgNCft (Cofermin Chemicals GmbH & Co. Silver Nitrate) was added. The solution was stirred for additional 600 minutes.

[0074] The silver-based solution is a low-viscous solution with a slightly reddish color. The solution’s color is correlated to the plasmonic peak due to the metallic silver nanoparticles’ presence. The size of metallic silver nanoparticles depends on the preparation conditions and is in the range of 30-1 OOnm. Figure 3 represents the silver-based solution, taken by Transmission Electron Microscopy (TEM). The solution has a viscosity of 56KU (Krebs Units), pH of 8.16 (22.6°C), and density equal to 0.89 g/cm ³ .

[0075] Preparation of final suspension: As depicted in Figure 1 , 42kg of the binder solution was diluted with 41.52 L of deionized water in a stainless steel 200 L chemical reactor. 28kg of the silver-based solution were added, and the mixture stirred for additional 60 minutes. 8.4kg of the titanium colloidal suspension was added. After 20 minutes, a solution containing 0.84kg of quaternary ammonium compound mixture (Lonza Bardac™ 205M) was diluted in 19.6 L of ethanol and added. The combination stirred for 60 minutes at 600 revolutions per minute.

[0076] The product is stable for at least six months (i.e., no sedimentation or solid-phase precipitation). Additionally, the resulting suspension may be applied to substrates using industrial deposition methods. The resulting disinfecting suspension is milky in color with a density equal to 0.94 g/cm ³ , pH at 10.02 (22.6°C), and viscosity at 45KU (Krebs Units).

[0077] Table 1 provides the weight-percent of each of the components described with respect to Example 1. Example 2: Preparing a disinfecting suspension

[0078] Preparation of the binder solution: 8.61kg of alkoxysilane (tetraethyl orthosilicate; EVONIK™ Dynasylan A) was mixed with 18.05L isopropanol in stainless steel 80L chemical reactor. Deionized water (36.76 L) was added to the mixture and stirred for fifteen minutes. A water-soluble Lewis base (25 wt. % ammonium hydroxide NH4OH) was added dropwise to adjust the pH to 9.5. The mixture was stirred for 600 minutes until becoming a transparent liquid.

[0079] Preparation of the TiC colloidal suspension: In this example, a commercially available water paste of T1O2 nanoparticles (Cinkama™ CCA 100BS) was used. The concentration of T1O2 in the suspension is in the range of 20 to 22 wt. %. [0080] Preparation of the final suspension: 45kg of the binder solution was diluted with 71.88

L, and 1.78kg of the titanium-based suspension was added. The combination was stirred for 30 minutes at 600 revolutions per minute. 0.072kg of silver nitrate AgNCb (Cofermin Chemicals GmbH & Co. Silver Nitrate) were added to the suspension and stirred for additional 30 minutes. A solution of isopropanol (38 L) consists of: 0.15kg Surfynol 440, 0.3kg of Tego Flow 425, and 0.375kg of TegoWet 500 was added, and after fifteen minutes, 0.90kg of quaternary ammonium compound mixture (Innospec EMPIGEN® BKC 50) were added. The mixture was stirred for 60 minutes at 600 revolutions per minute. The product is stable for at least six months (i.e., no sedimentation or solid-phase precipitation). Additionally, the resulting suspension may be applied to substrates using industrial deposition methods.

[0081] Table 2 provides the weight-percent of each component described with respect to Example 2. Component wt. %

; Deionized water: 56.0830 ; Isopropyl Alcohol: 38.3810

! Alkoxysilane: 4.3050 !

! Lewis Base: 0.0960 ; i Titanium Dioxide: 0.2370 ;

I Dispersing Media: 0.5500 i

I Silver: 0.0480 j

Quaternary Ammonium Compound: 0.3000 ;

! Total: 100.0000 i

Example 3: Applying suspensions on glass substrates by spraying

[0082] A prepared suspension (e.g., the suspension of Example 1 or Example 2) was mist air- sprayed on glass substrates. Specifically, the amount of suspension deposited onto the glass substrate was 0.0285 L/m ² , as measured by the gravimetric method. The wet suspension dried and resulted in a uniform, transparent, coated glass substrate prepared using suspensions. No heat treatment was applied during the application or the curing of the suspension on the glass substrate. Curing was allowed for four hours after application on the glass substrate.

Example 4: Applying the suspensions on glass substrates by dry microfiber cloth:

[0083] A prepared suspension (e.g., the suspension of Example 1 or Example 2) was rinsed on glass substrates. Specifically, the amount of suspension deposited onto the glass substrate was 0.10 L/m ² , as measured by the gravimetric method. Before drying, the wet film was suffused by a dry, microfiber cloth on the glass substrate. The application process resulted in a uniform, transparent, coated glass substrate prepared using a suspension as described. No heat treatment was applied during the application or the curing of the suspension on the glass substrate. Curing was allowed for four hours after application on the glass substrate.

Example 5: Photocatalytic activity of the coated substrate

[0084] Coated glass substrates prepared using a suspension described herein present photocatalytic properties. The photocatalytic activity was evaluated by removing nitrogen oxides (NO _x ), as described in the International Standard EN ISO 22197-1 :2016. Nitric oxide is chosen as a typical air pollutant that is absorbed on the photocatalyst’s surface. Upon exposure to photocatalytic action, it is converted to nitrogen dioxide (NO2) and, subsequently, to nitrate ions (NO3-). The substrate of Example 3 was glass having dimensions of 98mm x 49mm x 6mm. The nitric oxide oxidation process was monitored using a HORIBA APNA-370 chemiluminescence NO _x analyzer. The conditioning procedure included exposure to lW/m ² UV-A illumination (cut off filter for wavelengths below 360nm was applied) for 72h, without the presence of any target pollutant molecule. The nitric oxide concentration in the photocatalytic evaluation reactor was adjusted to lppm, and the relative humidity was set at 50%. The photocatalytic evaluation results are graphically presented in Figure 4. The photocatalytic activity of coated glass substrates (e.g., the coated substrates of Example 3 or Example 4) are presented in the table that follows, in terms of nitric oxide decomposition, nitrogen dioxide emission, and total nitrogen oxides decomposition:

[0085] The photocatalytic activity of coated glass substrates (e.g., the coated substrates of Example 3 or Example 4) is elevated compared to industry standards. The emission of intermittent nitrogen dioxide remains lower than 0.07ppm, and the coated substrate presented stable photocatalytic performance when exposed to illumination.

Example 6: Bactericidal activity of coated substrates

[0086] Coated glass substrates (e.g., the coated substrates of Example 3 or Example 4) also present bactericidal properties. The bactericidal activity was evaluated to inhibit bacterial microorganisms’ growth or eliminate them, as described in the International Standard EN ISO 27447:2019. No conditioning procedure was applied for the coated glass substrates. Test microorganisms (i.e., Escherichia coli, gram-negative; Listeria monocytogenes, gram-positive; Staphylococcus aureus, gram-positive) were prepared by growth in a liquid culture medium. The suspension of test microorganisms was standardized by dilution in a nutritive broth. The sterilized fdter paper was placed into the bottom of a sterile glass Petri dish. Sterile water was added, and a sterile glass rod is placed on top of the sterilized filter paper. Control and test surfaces are placed on top of the glass rod. This prevents the carriers and the filter paper from touching and helps maintain moisture during the test. Control and test surfaces are inoculated with microorganisms in triplicate, and then the microbial inoculum is covered with a sterile glass. The Petri dishes containing inoculated samples are covered with moisture conservation glass. Microbial concentrations are determined at “time zero” by elution followed by dilution and plating. A control is run to verify that the neutralization/elution method effectively neutralizes the microbicidal agent in the microbicidal surface being tested. Inoculated, covered control and test carriers are allowed to incubate undisturbed under 0.566 W/m ² UV-A (cut-off filter for wavelengths below 360nm was applied) for 4 hours. Another set of inoculated, covered control and test carriers are allowed to incubate undisturbed in the dark for the contact time duration. After incubation, microbial concentrations were determined. The reduction of microorganisms relative to initial concentrations and the control surface is calculated. The bactericidal evaluation of coated glass substrates prepared using the suspensions provided herein is presented in the table below. R is the photocatalyst bactericidal activity value for the film cover method, after UV irradiation of intensity L and L is the UV irradiation intensity (mW/cm ² ).

[0087] The above table results indicate that the coated glass substrates prepared using suspensions described present significant bactericidal properties, and R values exceed the threshold of four (4).

Example 7: Bactericidal activity of coated substrates when artificially aged

[0088] Coated glass substrates prepared using a suspension described presents bactericidal properties, even when exposed to artificial aging conditions. The artificial aging procedure followed is described in the International Standard EN ISO 11507:2007. As per the scope of the artificial aging procedure, it specifies exposure conditions for paint coatings exposed to artificial weathering (i.e., artificial weathering caused by fluorescent UV lamps, condensation, or water spray, for example). The effects of weathering are evaluated by comparative testing of chosen parameters. The ultraviolet light produced by fluorescent lamps simulates only part of the UV region of natural sunlight. Consequently, the test pieces are subjected to a small but destructive portion of the spectrum. Due to the lack of visible and infrared energy in the light from such UV lamps compared to sunlight, the test pieces are not heated above the temperature of the surrounding air in the way in which they would be in practical use.

[0089] The artificial aging procedure is described in Method B of the International Standard EN

ISO 11507:2007. The following cycle repetition was used for a total testing period of 2,000 hours: (1) five hours dry at a continuous irradiance of 45 W/m ² (290nm to 400nm), a black panel temperature of 50±3°C and relative humidity less than 15%; (2) one-hour water spray at the same irradiance and a black panel temperature of 25±3°C, but with no control of the relative humidity; (3) start the dry period again. The bactericidal activity was evaluated to inhibit bacterial microorganisms’ growth or eliminate them, as described in the International Standard

EN ISO 27447:2019. No conditioning procedure was applied for the artificially aged, coated glass substrates. Test microorganisms (i.e., Escherichia coli, gram-negative; Listeria monocytogenes, gram-positive; Staphylococcus aureus, gram-positive) were prepared by growth in a liquid culture medium. The suspension of test microorganisms was standardized by dilution in a nutritive broth. Sterilized filter paper is placed into the bottom of a sterile glass Petri dish.

Sterile water is added, and a sterile glass rod is placed on top of the sterilized filter paper.

Control and test surfaces are placed on top of the glass rod. This prevents the carriers and the filter paper from touching and helps maintain moisture during the test. Control and test surfaces are inoculated with microorganisms in triplicate, and then the microbial inoculum is covered with a sterile glass. The Petri dishes containing inoculated samples are covered with moisture conservation glass. Microbial concentrations are determined at “time zero” by elution followed by dilution and plating. A control is run to verify that the neutralization/elution method effectively neutralizes the microbicidal agent in the microbicidal surface being tested. Inoculated, covered control and test carriers are allowed to incubate undisturbed under 0.566 W/m ² UV-A (cut-off filter for wavelengths below 360nm was applied) for 4 hours. Another set of inoculated, covered control and test carriers are allowed to incubate undisturbed in the dark for the contact time duration. After incubation, microbial concentrations were determined. The reduction of microorganisms relative to initial concentrations and the control surface was calculated. The bactericidal evaluation of coated glass substrates prepared using suspensions provided herein is presented in the table below. R is the photocatalyst bactericidal activity value for the film cover method, after UV irradiation of intensity L and L is the UV irradiation intensity (mW/cm ² ) .

[0090] The above table results indicate that the coated glass substrates prepared using a suspension described (i.e., the coated substrates of Example 3 or Example 4) present significant bactericidal properties, and R values exceed the threshold of four, even after exposure to artificial aging conditions. The drastic reduction of bactericidal performance under dark conditions is attributed to the decomposition of quaternary ammonium salts during the aging procedure and the coated glass substrates’ photocatalytic activity.

Example 8: Microbicidal activity of coated substrates

[0091] Coated substrates prepared using suspensions described present microbicidal properties. The screen of four operational ATMs were diagonally coated, following the procedure described in Example 4. Two of the ATM screens were coated using the upper right, lower left, upper left pattern. Two of the ATM screens were coated using the upper right, lower left, lower right pattern. Before applying a suspension on the screen of an ATM, the surface was thoroughly cleaned and dried using ultra-pure isopropyl alcohol. The half-treated ATM screens were conditioned for seven days after the application. Half-treating a screen includes coating the right lower or left upper side of a screen, divided by a bottom left comer to upper right comer diagonal. No cleaning or disinfection of the ATM screens took place during the bactericidal assessment period. Bactericidal performance was assessed by collecting samples from the coated and uncoated areas of the ATM screens employing the aseptic swabbing technique described by NIOSH (https://www.cdc.gov/niosh/topics/emres/unp-envsamp.html). Standard plate growth was used for enumerating microbial cultures growing on a solid medium (agar plates). Colonies are referred to as colony- forming units (CFU). Microbial contamination level is reported as CFU per unit area. Results are comparing the average contamination level of the treated and untreated automated teller machines screen surface. Results are summarized in the table below: [0092] The coated ATM screens prepared using suspensions described herein present a significant decrease in microbial surface contamination. The sterilization performance decreases 45 days after the day of the original coating application.

Example 9: Bactericidal activity of disinfecting suspensions

[0093] Suspensions (e.g., suspensions described in Example 1 and/or Example 2) were assessed for their bactericidal activity, according to International Standard EN ISO 1276:2019. The International Standard EN ISO 1276:2019 specifies a test method and the minimum requirements for bactericidal activity of chemical disinfectant and antiseptic products that form a homogeneous, physically stable preparation when diluted with hard water or, in the case of ready-to-use products, with soft water. Products can only be tested at a concentration of 80 % or less, as some dilution is always produced by adding the test organisms and interfering substances.

[0094] In accordance with EN 1276:2019, a test suspension of bacteria was tested against a suspension (e.g., the suspension of Example 1 and/or Example 2). According to EN 1276:2019 (> 5 log reduction), the suspension demonstrated bactericidal activity under clean conditions for 5 minutes contact time and at 20°C when tested at a concentration of 80 wt. %. The reference strains used were Pseudomonas aeruginosa, Staphylococcus aureus, Escherichia coli, and Enterococcus hirae.

Example 10: Bactericidal activity of disinfecting suspensions

[0095] Suspensions described herein (e.g., the suspensions of Example 1 and/or Example 2) were assessed for their bactericidal activity, according to International Standard EN ISO 13697:2015+A1:2019. The International Standard EN ISO 13697:2015+A1:2019 specifies a test method (phase 2/step 2) and the minimum requirements for bactericidal activity of chemical disinfectants that form a homogeneous physically stable preparation in hard water or, in the case of ready-to-use products, with water. As three concentrations are tested, dilution of the product is required in the active to the non-active range. Therefore, the product forms a homogeneous, stable preparation in hard water. Following EN ISO 13697:2015+A1:2019, a test suspension of bacteria was tested against the sterilizing, self-binding suspensions, as prepared in Example 1 and Example 2, demonstrated bactericidal activity (> 5 log reduction), under clean conditions for 5 minutes contact time, at 20°C, when tested at product concentrations: Undiluted (80%) using as test organisms the reference strains: Staphylococcus aureus and Enterococcus hirae. Example 11: Virucidal activity of disinfecting suspensions

[0096] Suspensions described herein (e.g., the suspensions of Example 1 and/or Example 2) were assessed for their virucidal activity, according to International Standard EN ISO 14476:2013+A2:2019. The International Standard EN ISO 14476:2013+A2:2019 specifies a test method and the minimum requirements for virucidal activity of chemical disinfectant and antiseptic products that form a homogeneous physically stable preparation when diluted with hard water, or in the case of ready-to-use products (i.e., products that are not diluted when applied), with water. Following EN ISO 14476:2013+A2:2019, a test suspension of the titrated virus was tested against the sterilizing, self-binding suspensions, as prepared in Example 1 and Example 2, demonstrated virucidal activity (> 4 log reduction), for 5 minutes contact time in the presence of bovine serum albumin solution (0.3g-L-l), at 20°C, when tested at product concentrations: Undiluted (97%) using as test organisms the enveloped DNA Vaccinia virus (Strain MV A) and presents the same virucidal activity against enveloped viruses, as but not limited to Coronavirus alpha, Coronavirus beta, Coronavirus MERS-CoV, Coronavirus SARS- CoV, Coronavirus SARS-CoV-2, Filoviridae, Flavivirus, Hepatitis B virus (HBV), Hepatitis C virus (HCV), Hepatitis Delta virus (HDV), Herpesviridae, Human Immunodeficiency Virus (HIV), Human T Cell Leukemia Virus (HTLV), Influenza Virus, Measles Virus, Paramyxoviridae, Poxviridae, Rabies Virus, Rubella Virus.

[0097] The foregoing description sets forth exemplary systems, methods, techniques, parameters, and the like. However, it should be recognized that such description is not intended as a limitation on the scope of the present disclosure but is instead provided as a description of exemplary embodiments.

[0098] Although the description herein uses terms first, second, etc., to describe various elements, these elements should not be limited by the terms. These terms are only used to distinguish one element from another.

[0099] The articles “a” and “an” herein refer to one or more than one (e.g., at least one) of the grammatical object. Any ranges cited herein are inclusive. The term “about” used throughout is used to describe and account for small fluctuations. For instance, "about" may mean the numeric value may be modified by ±0.05%, ±0.1%, ±0.2%, ±0.3%, ±0.4%, ±0.5%, ±1%, ±2%, ±3%, ±4%, ±5%, ±6%, ±7%, ±8%, ±9%, ±10% or more. All numeric values are modified by the term “about” whether or not explicitly indicated. Numeric values modified by the term “about” include the specific identified value. For example, "about 5.0" includes 5.0. [0100] The term “substantially” is similar to “about” in that the defined term may vary from for example, by ±0.05%, ±0.1%, ±0.2%, ±0.3%, ±0.4%, ±0.5%, ±1%, ±2%, ±3%, ±4%, ±5%, ±6%, ±7%, ±8%, ±9%, ±10% or more of the definition; for example, the term “substantially perpendicular” may mean the 90° perpendicular angle may mean “about 90°”. The term “generally” may be equivalent to “substantially”.

[0101] For any of the structural and functional characteristics described herein, methods of determining these characteristics are known in the art.