RU2793180C1 - Composition for applying a photoactive coating on the surface of porous and non-porous materials and providing oxidative degradation of chemicals - Google Patents

Abstract

FIELD: chemical industry; protection of human health; the environment.

SUBSTANCE: composition for applying a photoactive coating on the surface of materials and providing oxidative destruction of chemicals contains a polar organic solvent, an organosilicon compound, water and 1-150 g/l of nanocrystalline anatase-modified titanium dioxide or nanocrystalline anatase-modified titanium dioxide containing nitrogen impurities, or nitrogen impurities, iron and copper. The nitrogen impurity content is up to 1% of the mass of nanocrystalline titanium dioxide. The composition contains isopropyl or ethyl alcohol or ethyl acetate as a polar organic solvent, and ethyl silicate as an organosilicon compound. The composition also additionally contains an inorganic acid from the range including sulfuric, nitric, or hydrochloric acids. The volume ratio of ethyl silicate: polar organic solvent is from 1:19 to 1:1, respectively. The volume fraction of inorganic acid is 0.1-10%, and the volume fraction of water is 5-25%.

EFFECT: composition ensures the stability of the coating on the surface of porous and non-porous materials, oxidative degradation of chemicals and biomacromolecules, self-cleaning under the action of sunlight and room light sources.

2 cl, 10 dwg, 1 tbl, 23 ex

Description

The invention relates to the field of photoactive coatings and methods for cleaning the surface of materials from harmful pollutants that can have a negative impact on human health and the environment, and unwanted impurities that can adversely affect the performance properties of these materials.

Methods for removing chemicals from the surface of materials are known, which are based on the principles of destruction, modification and isolation of compounds (M. Nilsson, H. De Maeyer; M. Allen, Evaluation of Different Cleaning Strategies for Removal of Contaminating DNA Molecules, Genes. 13, 162 (2022) 1-9 https://doi.org/10.3390/genes13010162 ). As a rule, destruction is the most effective, since it leads to the complete destruction of the structure of chemicals, almost completely reducing the likelihood of their negative impact on human health and the environment.

A simple way to remove compounds from the surface of materials is to treat them with an aqueous solution of a surfactant, predominantly of a nonionic type, which additionally contains an active component that promotes the destruction of molecules. The mechanism of action of such compositions includes the enveloping of compound molecules with surfactant molecules, followed by their destruction by the active component. For example, a special composition of DNA Remover® PCR Clean™ from Minerva Biolabs GmbH ( Berlin, Germany, https://minerva-biolabs.com/de/dna-dekontaminationsreagenzien/pcr-clean), aimed at the destruction of nucleic acids, contains purified water with the addition of ethoxylated alcohols (<0.2%) and phosphoric acid (<2%). In this case, ethoxylated alcohols act as a nonionic surfactant, and orthophosphoric acid is the active component that provides acidic hydrolysis of ester bonds. The main disadvantage of this method is the low rate of molecular degradation, which leads to low efficiency of this method for reducing the amount of contaminant, especially on the surface of porous materials ( M. Nilsson, H. De Maeyer; M. Allen, Evaluation of Different Cleaning Strategies for Removal of Contaminating DNA Molecules, Genes 13, 162 (2022) 1-9 https://doi.org/10.3390/genes13010162 ). The disadvantage is also the need to periodically repeat the procedure for applying the composition. In addition, the use of this approach requires a certain type of active component for each class of compounds, which greatly complicates the procedure for use.

A method is described for inactivating compounds by using solutions of metal chelate complexes in combination with oxidizing and reducing agents (US 585865, C12Q1/68, 01/12/1999) to destroy the structure of compounds and prevent their effects on humans and the environment. As chelate complexes, complexes of pyridine or phenanthroline derivatives with transition metals, including nickel, copper, iron, zinc, ruthenium, rhodium, and cobalt, have been proposed. The oxidizing agent is mainly hydrogen peroxide in the form of a dilute aqueous solution, which actively decomposes upon interaction with transition metal complexes with the formation of highly reactive radicals, which ensure the destruction of the structure of the compounds and eliminate their negative effect. The proposed oxidizing agent makes it possible to destroy a large number of chemicals, including biomacromolecules. The main disadvantage of this method is the need for sequential treatment of the surface of materials with two solutions, one of which contains metal chelate complexes, and the second contains oxidizing and reducing agents, followed by exposure in a wetted state for a sufficiently long period of time (up to one hour) for the processes of oxidative degradation of the pollutant. The disadvantage is also the need to use in some cases additional stabilizing additives, such as dithiothreitol.

One of the effective methods of dealing with chemical contamination in laboratory premises is to treat the floor, work surfaces and utensils with a solution of a highly reactive chemical agent, such as bleach or hydrogen peroxide with a concentration of up to 30% (US 2007/0289605 A1, A61L 2/00, 20.12. 2007), which is a powerful oxidizing agent and ensures the destruction of both organic and inorganic compounds. The main disadvantage of this method is the use of caustic and aggressive substances that are dangerous to human health, as they lead to damage to the skin, mucous membranes of the respiratory system and vision, which requires the use of personal protective equipment. These substances cause corrosion of metals, and can also discolor painted materials, which requires care and limits the scope of their use.

Also known is a method for reducing the amount of harmful chemical compounds through the use of reagents that ensure the occurrence of specific interactions. For example, to reduce surface contamination of materials with nucleic acids, a method using cationic compositions has been proposed (US 2010/0216680 A1, C11B 3/37, 08/26/2010). The main disadvantage is that each type of chemical requires its own specific reagents. Another disadvantage is the need to periodically repeat the procedure for applying the composition to ensure a permanent reduction in the level of contamination of surfaces with chemical compounds in the premises of laboratories.

To ensure a permanent reduction in the level of contamination without the need for periodic treatments, self-cleaning materials are used, which, due to the presence of a modifier on the surface, are able to independently destroy chemicals, which improves the performance of materials and increases the safety of people's lives ( VA Ganesh, HK Raut, AS Nair, S. Ramakrishna, A review on self-cleaning coatings, J. Mater Chem 21 (2011) 16304-16322 ). Such materials are widely used to control microbial contamination (Self-Cleaning Materials and Surfaces: A Nanotechnology Approach, Ed.: Walid A. Daoud, 2013 2013 John Wiley & Sons, Ltd, 352 p., ISBN: 9781119991779). For example, a method for producing a textile material with antibacterial properties for workwear is described (RU 2619704, D06M 10/00, 05/20/2016), including treatment with low-temperature plasma of a low-pressure high-frequency discharge, subsequent impregnation with a colloidal aqueous solution of silver nanoparticles and drying, in which plasma treatment is carried out low-temperature plasma of a low-pressure high-frequency capacitive discharge for 120 s in a plasma-forming gas medium at a flow rate of 0.04 g/s, at a pressure in the working chamber of 26.6 Pa and a discharge power of 3.5-4.0 kW, impregnation is carried out with a colloidal aqueous solution silver nanoparticles with a concentration of 0.05-0.1 g/dm ³ . The main disadvantage of materials obtained by modifying the base with various bactericidal additives containing predominantly copper, zinc or silver compounds is their focus on combating only bacterial contamination, while chemical pollutants and macromolecular systems (nucleic acids, viruses) are not exposed to any effects and are not are removed from the surface of materials, which does not allow to completely clean their surface from contamination.

This problem can be solved by attaching photocatalyst nanoparticles on the surface of materials, which have a predominantly semiconductor structure, which have oxidative activity under the action of light due to the formation of highly reactive oxygen particles and can oxidize organic and inorganic compounds, thereby ensuring the removal of both chemical and biological pollutants. ( MN Lyulyukin, PA Kolinko, DS Selishchev, DV Kozlov, Hygienic aspects of TiO ₂ -mediated photocatalytic oxidation of volatile organic compounds: Air purification analysis using a total hazard index, Appl. Cat. B-Environ. 220 (2018) 386- 396 ). The most active photocatalyst for oxidative degradation processes is titanium dioxide, predominantly anatase modification.

Three approaches are known for forming a photoactive coating on the surface of materials. The first approach is associated with applying a composition to the surface of materials, the main component of which is a precursor of titanium dioxide, for example, titanium tetraisopropoxide from TIP/TiO ₂ P25, Fibers Polym 10 (2009) 716-723 ), which hydrolyzes to form a uniform photoactive coating with high adhesion to the surface of the material after heat treatment. The described approach is implemented in the sol-gel method and colloidal TiO ₂ nanoparticles, Cellulose 18 (2011) 811-825 ) and when applying a photocatalyst from the gas phase ( A. Sobczyk-Guzenda, H. Szymanowski, W. Jakubowski, A. Błasińska, J. Kowalski, M. Gazicki- Lipman, Morphology, photocleaning and water wetting properties of cotton fabrics, modified with titanium dioxide coatings synthesized with plasma enhanced chemical vapor deposition technique, Surf Coatings Technol 217 (2013) 51-57). For example, a method for producing a self-cleaning material is known (JP 2004057912, Feb. 26, 2004) by co-deposition of titanium tetrachloride and water vapors on the surface of glass fabric with their simultaneous hydrolysis and the formation of titanium dioxide. The main disadvantage of this method is that the TiO ₂ formed on the surface of the fiberglass has a low degree of crystallinity and, as a result, a very low photocatalytic activity in oxidation reactions. High-temperature calcination is required to improve crystallinity and photocatalytic activity, which can only be used for thermally stable materials.

Thus, the main disadvantage of the approach based on the use of a photocatalyst precursor is the difficulty of applying heat treatment to materials with low thermal stability (for example, wood and textile fabrics), which leads to the difficulty of forming a crystalline layer of a photoactive coating and a low degradation rate of chemicals.

Another approach is to deposit crystallized photocatalyst particles on the surface of materials. To do this, a suspension of the photocatalyst in water or alcohol is prepared and applied to the material by dipping (G. Di Carlo, LF Liotta, G. Calogero, C. Giuliani, GM Ingo, Green cleaning procedures based on titania-doped cotton textiles: effect of titania textural properties, J. Nanosci. Nanotechnol. 17 (2017) 3842-3847 ) and spraying ( Z. Han, VWC Chang, L. Zhang, MS Tse, OK Tan, LM Hildemann, Preparation of TiO ₂ -coated polyester fiber filter by spray -coating and its photocatalytic degradation of gaseous formaldehyde, Aerosol Air Qual. Res. 12 (2012) 1327-1335 ). This approach leads to obtaining samples that ensure the oxidation of chemical compounds at a high rate, but, as a rule, the obtained coatings have low adhesion of the photoactive component to the surface, since during deposition no chemical bonds are formed between the particles of the photocatalyst and functional groups on the surface of the material ( J Wang, J. Zhao, lu Sun, X. Wang, A review on the application of photocatalytic materials on textiles, Text Res. J. 85 (2015) 1104-1118 ).

The third approach is to fix highly active crystalline photocatalyst particles with the help of chemical compounds. This method includes the chemical fixation of a photocatalyst with carboxylic acids forming a bridge ( M. Montazer, S. Hashemikia, Textile with immobilized nano titanium dioxide for repeated discoloration of CI reactive black 5 under UV-A, Color. Technol. 128 (2012 ) 403-409 https://doi.org/10.1111/j.1478-4408.2012.00394.x ). Despite the high adhesion rates when fixing TiO ₂ by this method, the main disadvantage is the high probability of destruction of the bridge structure when the material is illuminated. This is due to the oxidative degradation of the carboxylic acid in contact with the photocatalyst, which subsequently leads to the removal of photocatalyst particles from the surface of the material ( KT Meilert, D. Laub, J. Kiwi, Photocatalytic self-cleaning of modified cotton textiles by TiO ₂ clusters attached by chemical spacers, J. Mol. Catal. A Chem. 237 (2005) 101-108 ).

A known method of obtaining self-cleaning fabric (US 2005/0227557, B32B5/02, 04/09/2004) by impregnating the washed fabric base with an aqueous suspension containing from 0.1 to 10 wt. % titanium dioxide powder and from 1 to 5 wt. % acetone and from 2 to 10 wt. % resin. Also known is a method for fixing a photoactive component (WO2009027432A1, C09D 7/00, 03/05/2009) using aqueous and/or organic dispersions of various organic binders, including acrylates, caprolactam, vinylcaprolactam, N-vinylformamide, etc., which makes it possible to obtain a photoactive coating on surfaces of various materials, including fabrics, which has high adhesion.

The main disadvantage of the methods described above using adhesive compositions based on organic binders is that a large part of the surface of the photocatalyst particles is blocked by the binding agent. This leads to a low photocatalytic activity of the resulting material, and also with prolonged irradiation of the material, the molecules of the organic binder will be destroyed by the photocatalyst, which may release hazardous chemical decomposition products, such as, for example, formaldehyde or heteroatomic compounds, onto the surface of the material or into the air atmosphere and degradation of material performance. For these reasons, the use of photocatalyst resistant inorganic binders is preferred.

A method for obtaining a fabric material for photocatalytic and adsorption purification of gaseous and aqueous media is described (RU 2559506, B01J 20/06, 06/10/2014), characterized in that the material is prepared by impregnating the washed and dried fabric base with an aqueous sol of silicon dioxide SiO ₂ , followed by drying treated tissue base in air, rinsing with distilled water and final drying; impregnating the fabric coated with silicon dioxide with a solution of titanyl sulfate (4-10 wt.%) and then immersing in an aqueous suspension of a photocatalyst based on nanocrystalline titanium dioxide, which may contain additives of noble metals such as platinum, gold or mixtures thereof, followed by washing and drying. Obtained by the described method, the coating has photocatalytic activity under the action of UV or visible radiation. The disadvantage of the described method is the complexity of its implementation due to several successive stages of applying various modifiers. A significant disadvantage of the described method is that an aqueous solution of titanyl sulfate with a concentration of 4-10 wt. % has a strongly acidic environment (pH < 1) and after impregnation can lead to degradation of the material. Also, a significant disadvantage is that due to the use of a water-based impregnating composition, it is required to immerse the treated material in the impregnating composition for a long time with additional high-intensity exposure (sonication) for effective diffusion of modifiers deep into the fabric fibers. It also prevents the impregnation composition from being applied by spraying. The use of a water-based impregnant also limits the use of materials that have hydrophobic surface properties. Another significant disadvantage is that in order to impart photocatalytic activity to the material under the action of visible light, the photocatalyst present in the composition contains particles of noble metals, mainly gold and platinum or a mixture thereof, which leads to high cost and the need to control and account for its turnover. .

Also described is an example of using a composition based on isopropyl alcohol for applying a photoactive coating on the surface of cotton fabrics by fixing nanocrystalline particles of TiO ₂ with amorphous titanium dioxide formed during the hydrolysis of tetraisopropyl orthotitanate ( M. Solovyeva, D. Selishchev, S. Cherepanova, G. Stepanov, E Zhuravlev, V. Richter, D. Kozlov, Self-cleaning photoactive cotton fabric modified with nanocrystalline TiO ₂ for efficient degradation of volatile organic compounds and DNA contaminants, Chem. Eng. J. 388 (2020) 124167. https://doi .org/10.1016/j.cej.2020.124167 ). The application of such a composition to the surface of cotton makes it possible to obtain fabric materials with a uniform photoactive coating, which ensures complete oxidation of acetone and diethyl sulfide vapors under the action of ultraviolet radiation. The main disadvantage of this composition is the low adhesion of the resulting photoactive coating to the surface of non-porous materials, such as glass, due to the fact that amorphous titanium dioxide does not provide a strong bond. This results in the composition being suitable for the functionalization of porous materials, predominantly cotton textile fabrics, but not suitable for the functionalization of non-porous materials, since the coating is gradually removed by treatment with water. It is also a disadvantage that the composition contains a photocatalyst that is active only under UV radiation, but is not active under visible light.

The composition closest in composition to the present invention is a composition for obtaining a stable coating on the surface of materials (US2002/0007006 A1, C08J 3/00, 01/17/2002), which consists of a mixture of organosilicon compounds and products of their hydrolysis and condensation, a photoactive component, including including anatase titanium dioxide, and an organic solvent, including isopropyl alcohol, to which water and acids can be added to stabilize the coating. The use of this composition makes it possible to obtain stable coatings on the surface of glass, plastic, metal and other non-porous or low-porous materials that demonstrate high hardness and adhesion, as well as photoinduced hydrophilicity, resistance to weathering, alkalis, organic compounds and stains. The main disadvantage of the described composition is the lack of the ability to remove chemical contaminants from the surface of coated materials obtained using this composition, because due to the high content of organosilicon compounds that provide high hardness and adhesion of the coating, the photocatalytic effect provided by the presence of a photoactive component, such as titanium dioxide, lies in the photoinduced hydrophilicity of the coating, and not in the ability to photocatalytic destruction of chemicals, including nucleic acids, ensuring their removal and permanent reduction of contamination. In addition, due to the complex composition of the composition and the conditions for its application, the problem arises of obtaining coatings on the surface of porous materials, such as, for example, textile fabrics, which significantly narrows the scope of the described composition. It is also a disadvantage that the composition contains a photocatalyst that is active only under UV radiation, but is not active under visible light.

The objective of the claimed invention is to create a stable coating with a composition that removes chemical contaminants from the surface of materials and permanently reduces the level of indoor pollution without the need for periodic treatments.

The technical result is the creation of a composition composition for applying a stable photoactive silicon-titanium oxide coating on the surface of porous and non-porous materials, which has the effect of self-cleaning under the action of sunlight and room light sources and provides oxidative degradation of chemicals, including biomacromolecules.

The composition for applying a photoactive coating on the surface of materials includes a polar organic solvent, which makes it possible to obtain a stable dispersion with a homogeneous distribution of particles throughout the volume, with the addition of photocatalytically active nanocrystalline titanium dioxide, which may contain impurities of nitrogen, iron and copper, as well as with the addition of an organosilicon binder - ethyl silicate, inorganic acid and water.

The spectral characteristics of the photocatalysts used, photographs of the obtained materials with applied photoactive coating, data on the effect of the composition of the claimed composition on their photocatalytic activity and the possibility of destruction of chemicals and biomacromolecules are shown in Fig. 1-10.

Fig. 1. Diffuse reflectance spectra illustrating the absorption regions of titanium dioxide and titanium dioxide containing nitrogen impurities.

Fig. 2. Photos of different materials with applied photoactive coating.

Fig 3. Effect of acid type and water wash on photoactive coating activity.

Fig. 4. Influence of the content of the organosilicon binder in the composition on the activity of the photoactive coating.

Fig. Fig. 5. Dependence of the activity of the photoactive coating on the glass surface on the concentration of the photocatalyst in the composition.

Fig. Fig. 6. Dependence of the activity of the photoactive coating on the surface of the glass fabric on the concentration of the photocatalyst in the composition.

Fig. 7. Change in the composition of the gas phase in a reactor containing benzene vapor upon illumination of a material coated with a photoactive coating.

Fig. 8. Destruction of DNA on the surface of tissue material with a photoactive coating under the action of UV-A radiation.

Fig. 9. Illustration of the removal of various RNAs from the surface of materials with a photoactive coating under the action of UV-A radiation.

Fig. 10. Illustration of the removal of RNA of biological objects on the example of the influenza virus.

As a polar organic solvent, which makes it possible to obtain a stable dispersion with a homogeneous distribution of photocatalyst particles throughout the volume, isopropyl alcohol, ethyl alcohol or ethyl acetate is mainly used.

As a photocatalyst, nanocrystalline titanium dioxide in the anatase modification with a specific surface of more than 50 m ² /g or crystalline titanium dioxide in the anatase modification containing nitrogen impurities for the possibility of absorbing visible light and iron and copper impurities to improve the separation of photogenerated charges is used. The photocatalyst is synthesized using the described technique (N. Kovalevskiy, D. Selishchev, D. Svintsitskiy, S. Selishcheva, A. Berezin, D. Kozlov, Synergistic Effect of Polychromatic Radiation on Visible Light Activity of N-Doped TiO 2 _{Photocatalyst} , Catalysis Communications 134 (2020) 105841 ), which makes it possible to obtain titanium dioxide doped with nitrogen, which is able to absorb not only UV radiation, but also visible light, which expands its spectrum of action. Diffuse reflectance spectra illustrating the presence of absorption in the visible region of titanium dioxide containing nitrogen impurities compared to conventional titanium dioxide are shown in FIG. 1. The content of nitrogen impurities in titanium dioxide can reach 1 wt. %. After synthesis, the photocatalyst is crushed in a vibrating mill until a colloidal state is reached. To improve the separation of photogenerated charge carriers and increase the activity of the photocatalyst, its surface modification with iron and copper compounds is carried out. As compounds of iron and copper, their water-soluble salts are used, which are added to the composition in an amount mainly up to 1 wt. % with respect to titanium dioxide.

Ethyl silicate is used as an organosilicon binder, which is a mixture of tetraethoxysilane and partially hydrolyzed oligoethoxysiloxanes. The total content of silicon in ethyl silicate in terms of SiO ₂ is 32-40 wt. %.

The acid used is an inorganic acid, preferably sulfuric, nitric or hydrochloric.

The volume ratio of ethyl silicate and organic solvent in the proposed composition is not less than 1:19, but not more than 1:1, while the volume fraction of acid is in the range of 0.1-10%, and the proportion of water is in the range of 5 to 25%. The concentration of the photocatalyst is preferably 1-150 g/L. Before use, the composition is intensively stirred to evenly distribute the particles of the photocatalyst throughout the volume.

The essence of the invention is illustrated by the following examples.

Isopropyl alcohol (C ₃ H ₈ O, OSCh, 99.8%, EKOS-1 JSC), ethyl alcohol (C ₂ H ₅ OH, > 99.9%, JT Baker) or ethyl acetate is used as a polar organic solvent. (C ₄ H ₈ O ₂ , chemically pure, 99.7%, JSC Base No. 1 of Chemical Reactives).

Concentrated acid is used as an acid: sulfuric acid (H ₂ SO ₄ , OSCH, SIGMATEK LLC), hydrochloric acid (HCl, OSCH, AO REAKHIM LLC), nitric acid (HNO ₃ , chemically pure, 65%, TK ANT LLC ), orthophosphoric (H ₃ PO ₄ , ChDA, OJSC TK SPEKTR-KHIM) or acetic acid (CH ₃ COOH, chemically pure, JSC Base No. 1 of Chemical Reaktivov).

As a photocatalyst, nanocrystalline titanium dioxide TiO ₂ Hombikat UV100 (Sachtleben Chemie GmbH) is used, which is 100% anatase with a specific surface of 350 m ² /g and a crystallite size of 10-15 nm, or crystalline anatase titanium dioxide with an average crystallite size of 11 nm, containing nitrogen impurities, which is synthesized according to the method described in the work (N. Kovalevskiy, D. Selishchev, D. Svintsitskiy, S. Selishcheva, A. Berezin, D. Kozlov, Synergistic effect of polychromatic radiation on visible light activity of N-doped TiO ₂ photocatalyst, Catal. Commun. 134 (2020) 105841. doi:10.1016/j.catcom.2019.105841), by precipitation of TiO ₂ from an aqueous solution of titanyl sulfate with an aqueous solution of ammonia, followed by calcination at a temperature of 400-450 ° C and crushed into vibratory mill MM500 (Retsch) to the nanoscale state. According to elemental analysis, the content of nitrogen impurities in the synthesized photocatalyst TiO ₂ -N is in the range of 0.36-0.40 wt. %.

Ethylsilicate-32 (PJSC Khimprom) is used as an organosilicon binder, which is a mixture containing tetraethoxysilane and oligoethoxysiloxanes with the general formula Si _m O _m-1 (OC ₂ H ₅ ) _2m+2 , where m = 4-7 .

To obtain a composition for applying a photoactive coating, a mixture of ethyl silicate and isopropyl alcohol is prepared in a ratio of 1:19 to 1:1 by volume, acid and water are added to it in an amount of 0.1-10 and 5-25 vol. % respectively. Next, the mixture is intensively stirred and the prepared photocatalyst is added in the amount of 1-150 g/l. The resulting composition is treated in an ultrasonic bath for 10 minutes, and then further stirred for 10-12 hours. Then it is applied in a thin layer to the surface of the prepared material with a brush, roller, airbrush or by impregnation.

As a basis for applying a photoactive coating, the surface of porous and non-porous materials made of textile fabrics, fiberglass, glass and plastic, as well as finishing elements, mainly painted surfaces, is used. Before application, the surface of the materials is cleaned of visible contaminants, wiped with a paper towel or cloth dipped in ethyl or isopropyl alcohol, and the alcohol is completely evaporated. The prepared composition with a photoactive component is applied to the surface with a thin layer with a brush, roller or sponge, or sprayed with an airbrush or spray gun. After complete evaporation of the solvent, the coating is kept at room temperature for another hour and then wiped with a cloth moistened with purified water to remove poorly fixed particles and finally wiped with a paper towel. Photographs of photoactive coatings on the surface of various materials are shown in Fig. 2.

Example 1

To 0.750 g of titanium dioxide TiO ₂ Hombikat UV 100 add 0.750 ml of ethyl silicate, 1.4 ml of distilled water, 0.1 ml of concentrated sulfuric acid and 12.75 ml of isopropyl alcohol. The composition is sonicated and then further stirred for 10-12 hours. The concentration of the photocatalyst in the prepared dispersion is 50 g/l, and the amount of binder is 5 vol. %.

Next, 100 μl of the composition for photoactive coating is applied in a thin layer on the surface of the coverslip and dried at room temperature.

The sample is labeled C-50T-5E-Ce.

Example 2

Similar to example 1 with the exception that the resulting photoactive coating is additionally washed with distilled water for 10 seconds and dried at 80°C for 1 hour.

The sample is labeled C-50T-5E-Se-O.

Example 3

Similar to example 1 with the exception that hydrochloric acid is added to the composition in an amount of 100 μl.

The sample is labeled C-50T-5E-Co.

Example 4

Similar to example 3, with the exception that the resulting photoactive coating is additionally washed with distilled water for 10 seconds and dried at 80°C for 1 hour.

The sample is labeled C-50T-5E-Co-O.

Example 5

Similar to example 1, with the exception that concentrated nitric acid is added to the composition in an amount of 100 μl.

The sample is marked as S-50T-5E-A.

Example 6

Similar to example 5, with the exception that the resulting photoactive coating is additionally washed with distilled water for 10 seconds and dried at 80°C for 1 hour.

The sample is marked as C-50T-5E-A-O.

Example 7 ( comparative ).

Similar to example 1, with the exception that phosphoric acid is added to the composition in an amount of 100 μl.

The sample is marked as S-50T-5E-F.

Example 8 ( comparative ).

Similar to example 1, with the exception that glacial acetic acid is added to the composition in an amount of 100 μl.

The sample is marked as S-50T-5E-U.

Example 9

To 0.750 g of titanium dioxide TiO ₂ Hombikat UV 100 add 1.4 ml of distilled water, 0.1 ml of concentrated nitric acid, ethyl alcohol and ethyl silicate. The amount of ethyl silicate is 0.75; 1.5; 3; 4.5; 7.5 and 9 ml to achieve a volume fraction of the binder in the prepared dispersion of 5; 10; 20; thirty; 50 and 60% respectively. Ethyl alcohol is added to a total liquid volume of 15 ml. The concentration of titanium dioxide is 50 g/l.

The resulting photoactive coating composition is applied in a thin layer on the cover slip surface using a pneumatic airbrush (FPS-20, Hammer Werkzeug GmbH, Germany) and dried at room temperature.

Samples are labeled C-50T-xE, where x is the volume fraction of ethyl silicate.

Example 10

To a portion of titanium dioxide TiO ₂ Hombikat UV 100 add 1.5 ml of ethyl silicate; 1.4 ml distilled water; 0.1 ml concentrated nitric acid and 12 ml ethyl acetate. The mass of the photocatalyst is 0; 0.015; 0.15; 0.45; 0.75; 1.05; 1.5 and 2.25 g, which corresponds to its concentration of 0; 1; 10; thirty; 50; 70; 100 and 150 g/l in the prepared mixture. The amount of binder is 10 vol. %.

Next, 100 μl of the composition for photoactive coating is applied in a thin layer on the surface of the coverslip and dried at room temperature.

Samples are labeled C-xT-10E, where x is the concentration of titanium dioxide (g/l).

Example 11.

Similar to example 10, with the exception that concentrated sulfuric acid is used as the acid, and isopropyl alcohol is used as the solvent. The resulting composition for a photoactive coating is applied to the surface of the glass fabric by impregnation. After the solvent has evaporated, the tissue pieces are kept at room temperature for one hour. Next, the samples are rinsed in distilled water and dried at 80°C for 1 hour.

The samples are labeled as ST-xT-10E, where x is the concentration of titanium dioxide (g/l).

Example 12

It is similar to example 11 with the exception that in the preparation of the composition, instead of TiO ₂ Hombikat UV100, synthesized nanocrystalline titanium dioxide containing nitrogen impurities (TiO ₂ -N) is used, which is capable of absorbing radiation in the visible range of the spectrum (Fig. 1).

When titanium dioxide is precipitated from an aqueous solution of titanyl sulfate with an aqueous solution of ammonia, followed by calcination in air, TiO ₂ is obtained containing nitrogen impurities (TiO ₂ -N), which provide absorption in the visible region of the spectrum. In this case, the synthesis conditions (pH of precipitation, aging time, calcination temperature) affect the nitrogen content in the TiO ₂ structure, which can reach 1 wt %. %. For examples, a photocatalyst with a nitrogen content of 0.36-0.40 wt. %, since it exhibits greater activity under the action of visible light compared to photocatalysts with a different nitrogen content, which were synthesized under different conditions.

Example 13

Prepare a composition with a concentration of photocatalyst 100 g/l and the amount of binder 30 vol. %. For this, 36 ml of isopropyl alcohol, 400 μl of concentrated nitric acid, 5.6 ml of distilled water and 18 ml of ethyl silicate are added to 6 g of titanium dioxide TiO ₂ Hombikat UV 100.

The resulting composition for a photoactive coating is applied to the surface of pieces of fiberglass by impregnation. After the solvent has evaporated, the tissue pieces are kept at room temperature for one hour.

The sample is marked as ST-100T-30E.

Example 14

Similar to example 13 with the exception that a sample of glass fabric with a photoactive coating is additionally rinsed in distilled water and dried at 80°C for 1 hour.

The sample is marked as ST-100T-30E-O.

Example 15

Similar to example 13 with the exception that instead of fiberglass, a mixed cotton-polyester fabric "Panacea-Cotton rich-150" is used.

The sample is marked as T-100T-30E.

Example 16

Similar to example 15 with the exception that the tissue sample with a photoactive coating is additionally rinsed in distilled water and dried at 80°C for 1 hour.

The sample is marked as T-100T-30E-O.

Example 17.

Similar to example 16, with the exception that in the preparation of the composition for the photoactive coating, instead of TiO ₂ Hombikat UV100, synthesized nanocrystalline titanium dioxide containing nitrogen impurities (TiO ₂ -N) is used.

The sample is marked as T-100TN-30E-O.

Example 18.

Similar to example 17, with the exception that a portion of iron (III) nitrate nonahydrate (Fe(NO ₃ ) ₃ × 9H ₂ O) is additionally added to the composition for a photoactive coating in an amount corresponding to 0.1% Fe by weight of the added titanium dioxide, and copper (II) nitrate trihydrate (Cu(NO ₃ ) ₂ × 3H ₂ O in an amount corresponding to 0.5% Cu by weight of added titanium dioxide.

In the range of contents up to 1 wt. % surface modification of the TiO ₂ -N photocatalyst with iron leads to an increase in its activity under the action of visible light. In this case, the activity has an extreme dependence on the iron content with a maximum at a value of 0.1 wt. %. In order to demonstrate the greatest effect for this example, the value of the iron content corresponding to the maximum activity (ie, 0.1 wt.%) was chosen.

In the range of contents up to 1 wt. % surface modification of the TiO ₂ -N photocatalyst with copper leads to an increase in its activity under the action of visible light. In this case, the activity has an extreme dependence on the copper content with a maximum at a value of 0.5 wt. %. In order to demonstrate the greatest effect for this example, the value of the copper content corresponding to the maximum activity (ie, 0.5 wt.%) was chosen.

The sample is marked as T-100TNFC-30E-O.

Example 19 (comparative).

Similar to example 16 with the exception that no photocatalyst is added to the photoactive coating composition.

The sample is labeled as T-0TN-30E-O.

To illustrate the possibility of the resulting photoactive coating to the photocatalytic degradation of chemicals under the action of ultraviolet or visible radiation, their photocatalytic activity is tested in the test reaction of acetone vapor oxidation. The tests are carried out in the ISOFA flow-circulation installation (Certificate of state registration of the computer program 2015660118, ISOFA / Kozlov D.V., Selishchev D.S., Korovin E.Yu., 10.20.2015) at a temperature of 40 ° C and a value volumetric flow rate 65±1 cm ³ /min. The source of UV radiation is a 10 W LED with a radiation power in the wavelength range of 320-400 nm, equal to 9.7 mW/cm ² . The source of visible light is a 100 W LED with a radiation power in the wavelength range of 400-500 nm, equal to 160 mW/cm ² . The concentration of reagents and products is analyzed by changing the areas of absorption bands corresponding to a certain substance in IR spectra recorded using an FT-801 IR-Fourier spectrometer (OOO NPF Simeks, Russia), equipped with a long-pass cell (Infrared Analysis, USA) with a length optical path equal to 2.4 m. The concentration of acetone in the final reaction mixture is 15-25 µmol/L. A measure of the photocatalytic activity of materials is the rate of formation of CO ₂ during the oxidation of acetone, which is calculated by the following formula:

, где:

- разность концентраций СО₂ в конечной и исходной реакционных смесях (мкмоль/л), U - объемная скорость (л/мин).

, Where:

- the difference between the concentrations of CO ₂ in the final and initial reaction mixtures (µmol/l), U - space velocity (l/min).

The results of tests to determine the photocatalytic activity of materials obtained using the proposed composition, as well as data on the resistance of the applied photoactive coating to washout under running water, are presented in Table 1.

Table 1 Example No. Sample name Washout resistance Photocatalytic activity, µmol/min UV radiation visible light 1 S-50T-5E-Se Yes 0.32 -- 2 S-50T-5E-Se-O Yes 1.66 -- 3 S-50T-5E-So Yes 0.85 -- 4 S-50T-5E-Co-O Yes 1.37 -- 5 S-50T-5E-A Yes 0.99 -- 6 S-50T-5E-A-O Yes 1.27 -- 7 S-50T-5E-F No 0.12 -- 8 S-50T-5E-U No 0.40 -- 9 S-50T-hE Yes 0-0.18 -- 10 S-xT-10E Yes 0 - 1.29 -- eleven ST-xT-10E Yes 0 -1.23 -- 12 ST-xTN-10E Yes 0 -1.11 0 - 0.36 13 ST-100T-30E Yes 0.90 -- 14 ST-100T-30E-O Yes 1.40 -- 15 T-100T-30E Yes 1.73 -- 16 T-100T-30E-O Yes 2.23 -- 17 T-100TN-30E-O Yes 1.54 0.47 18 T-100TNFC-30E-O Yes 1.64 0.79 19 T-0TN-30E-O Yes 0 0

According to the test data, all materials with a photoactive coating applied using the proposed composition have photocatalytic activity and are capable of complete oxidation of acetone vapor to carbon dioxide and water under the action of light, which confirms the possibility of cleaning at the molecular level. Materials obtained using nanocrystalline titanium dioxide anatase modification TiO ₂ Hombikat UV100 (examples 1-11, 13-16) exhibit activity under the action of near ultraviolet radiation (UV-A). UV-A radiation is part of sunlight and does not have a strong negative effect on humans. Thus, the materials obtained using the proposed composition will be active both under the action of sunlight and under the action of the radiation of room luminescent light sources, in the emission spectra of which there are bands with a wavelength of less than 400 nm. At the same time, materials obtained using nanocrystalline titanium dioxide containing nitrogen impurities (examples 12, 17 and 18) are active both under the action of UV radiation and under the action of visible light, which corresponds to a greater efficiency of sunlight conversion and the possibility of using indoor LED lighting sources.

Examples 1-8 illustrate that in order to form a stable photoactive coating on the surface of materials using the proposed composition, it is necessary to have strong acids in its composition, such as nitric, sulfuric and hydrochloric (examples 1-6), since for hydrolysis of the organosilicon binder and reliable fixation particles of the photocatalyst on the surface of the material requires the presence of a sufficient amount of protons in the composition. In the case of medium and weak acids, such as phosphoric or acetic acids (examples 7-8), it is not possible to obtain a stable coating that will not be washed off the surface of the material with a water jet. In addition to influencing the stability of the resulting photoactive coating, the type of acid added also affects its activity (Table 1, Fig. 3).

Comparison of examples 1 and 2, 3 and 4, 5 and 6 shows that additional treatment of the photoactive coating with water not only removes loose particles of the photocatalyst, but also increases its photoactivity by removing acidic groups from its surface that remain after application and protrude in the role of recombination centers for photogenerated charge carriers, providing a decrease in activity. The wash effect for each type of acid is clearly shown in Figure 3. Nitric and sulfuric acids are preferred, but hydrochloric acid can also be used.

Example 9 illustrates the effect of the content of organosilicon binder in the composition on the activity of the resulting photoactive coating. At a low content of the binder, low resistance of the photoactive coating to the loss of the photocatalyst during friction or treatment with water is observed. An increase in the content of ethyl silicate leads to the fixation of more photocatalyst and a gradual increase in activity (Fig. 4). On the other hand, with a high content of ethyl silicate, the photocatalyst is shielded, which reduces the activity of the photoactive coating down to 0. Thus, the volume ratio of ethyl silicate and organic solvent in the proposed composition is at least 1:19, but not more than 1:1.

Examples 10 and 11 illustrate that an increase in the concentration of titanium dioxide in the composition leads to an increase in the activity of the photoactive coating. The type of material the surface of which is coated affects the value of the optimal concentration of the photocatalyst. On FIG. Figure 5 shows that for example 10, with an increase in the concentration of the photocatalyst to 30 g/l, an increase in the activity of the photoactive coating on the surface of a non-porous material (i.e., glass) is observed, but a further increase in the concentration to 150 g/l has little effect on the activity of the photoactive coating. This is due to the limitation of the amount of fixed photocatalyst per unit of glass surface that will be available for illumination. On FIG. 6 shows that in the case of glass fabric (example 11), with an increase in the content of titanium dioxide in the applied composition, a monotonous increase in activity is observed, which is due to the high porosity of the structure of the glass fabric material compared to glass. It should be noted that in both cases without the addition of titanium dioxide (ie, for a concentration of 0 g/l) there is zero activity and such a coating does not have the function of self-cleaning under the influence of light. Thus, compositions containing titanium dioxide with a concentration of 1–150 g/l make it possible to apply photoactive coatings on the surfaces of both porous and non-porous materials. At the same time, when using as a photocatalyst nanocrystalline titanium dioxide containing nitrogen impurities (TiO ₂ -N), which due to these impurities is able to absorb visible radiation (Fig. 1), the resulting materials (example 12) have photocatalytic activity not only under under the action of UV radiation, but also under the action of visible light, since the oxidation of acetone vapor is observed at a high rate (Table 1). Similarly to example 11, an increase in the concentration of TiO ₂ -N in the range of 1-150 g/l leads to a monotonous increase in the activity of materials in both spectral ranges.

It should be noted that examples 1, 9 and 10 illustrate the possibility of using isopropyl alcohol, ethyl alcohol or ethyl acetate as a polar organic solvent in the preparation of a photoactive coating composition.

In addition to fabric materials based on inorganic fibers (example 13), the proposed composition for applying a photoactive coating makes it possible to modify fabrics based on natural and synthetic fibers (example 15) to obtain self-cleaning textile materials. As in the case of glass (examples 1-6), for fabric materials, additional treatment with water leads to an increase in the photoactivity of the coating (examples 14 and 16, respectively) due to the removal of acidic residues.

Similarly to example 12, when nanocrystalline titanium dioxide containing nitrogen impurities (TiO ₂ -N) is used as a photocatalyst, the resulting coating (example 17) has photocatalytic activity not only under the action of UV radiation, but also under the action of visible light, since oxidation is observed acetone vapor at high speed (Table 1). Additional introduction of transition metals into the composition for applying a photoactive coating, for example, iron and copper ions (example 18), leads to surface modification of the photocatalyst and provides a significant increase in the activity of the material under the action of visible light due to the spatial separation of photogenerated charge carriers and a decrease in their recombination.

Comparison of examples 16 and 19 emphasizes the key role of the photocatalyst in the composition of the applied coating on the surface of the fabric to impart self-cleaning properties, since in the absence of a photocatalyst, the activity of the resulting coatings is zero (Table 1). The same effect is observed in the absence of titanium dioxide in the composition of photoactive coatings on glass (example 10) and fiberglass (example 11).

Thus, the proposed composition, consisting of an organosilicon binder and nanocrystalline titanium dioxide, which may additionally contain nitrogen impurities in the volume and metal on the surface, makes it possible to apply a photoactive coating on the surface of various types of materials and provide oxidative degradation of chemicals up to the products of their complete oxidation under action of light of a wide spectral range.

Example 20.

Conduct a study of the kinetic laws of the oxidation of benzene vapor on the surface of the material with a photoactive coating, synthesized analogously to example 16 using 100% cotton fabric, in a static reactor using the method of IR spectroscopy for quantitative analysis.

To do this, a material sample is placed in a 300 ^cm3 glass reactor built into the cuvette compartment of a Nicolet 380 IR-Fourier spectrometer (Thermo Scientific, USA). The optical path length is 10 cm. The reactor is maintained at a temperature of 25°C using a liquid thermostat. Before carrying out the experiments, the samples are kept under the influence of UV radiation with a power of 10.8 mW/cm ² with a maximum at 367 nm for an hour to remove residual organic compounds. Then a stream of air saturated with water vapor is passed through the reactor to establish a relative humidity of 15%.

To carry out the experiment, an aliquot of liquid benzene (C ₆ H ₆ , KhCh, AO REAKHIM) with a volume of 0.3 μl is introduced into the reactor, the adsorption-desorption equilibrium is established, and the radiation source is turned on, which is a UV LED with the above-described characteristics. Analyzing the IR spectra in the areas of 2975-3145, 2200-2450 and 2000-2250 cm ^-1 determine the concentration of benzene, CO ₂ and CO, respectively.

Example 20 illustrates the ability of the resulting photoactive coating to clean its own surface and the surrounding area from aromatic compounds. Using benzene as an example, it was shown that the complete oxidation of the aromatic compound occurs on the illuminated surface of the material with a photoactive coating (Fig. 7). The linear decrease in the concentration of benzene under the action of radiation indicates a constant rate of its oxidation on the surface of the material with a photoactive coating, which emphasizes the possibility of a permanent reduction in the level of indoor pollution without the need for periodic treatments.

To illustrate the ability of materials coated with a photoactive coating to destroy biomacromolecules, tests are carried out using the PCR method.

Tests are carried out in accordance with the following procedure. A solution of the object (nucleic acid) for research is applied in a volume of 100 μl to a 1 cm ² fragment of the starting material and the material with a photoactive coating, kept at room temperature until completely dry, and subjected to UV-A radiation (365 nm, 5.0 mW/cm ² ) for 0-48 hours. Nucleic acids are washed off by incubating the test sample in 1.5 ml TE buffer (10 mM Tris HCl pH 7.5, 1 mM EDTA).

Nucleic acid content in wash solutions was quantified using specific oligonucleotides as primers in the BioMaster HS-qPCR SYBR Blue (2×) reaction mixture (Biolabmiks, Novosibirsk, Russia). The PCR reaction is carried out on a Light Cycler 96 instrument (Roche Diagnostics, Switzerland) with preheating to 95°C for 5 min, followed by 45 amplification cycles, including denaturation at 95°C for 10 s, primer annealing at 58°C for 10 min. for 10 s, elongation at 72°C for 20 s. Shooting the fluorescence signal is carried out at 81°C. For each reaction, the threshold cycle value (Cq) is determined in the accompanying software version 1.1.0.1320 (KJ Livak, TD Schmittgen, Analysis of Relative Gene Expression Data Using Real-Time Quantitative PCR and the 2-ΔΔCT Method, Methods. 25 (2001) 402-408 ; MW Pfaffl, Relative quantification, in: Tevfik Dorak (Ed.), Real-Time PCR, Taylor & Francis, 2006: pp. 63-82 ). The melting curve of PCR products to assess the specificity of the amplification reaction is built for the temperature range from 67 to 97°C. PCR fragment 28-2.1 (imitating the fragment of the 28S rRNA gene 4502-4548 nt) is used as an internal PCR control. Evaluation of the results for the removal of traces of NA is carried out using the formula

To illustrate, several examples are given for different materials using different nucleic acids.

Example 21.

The study of the anti-contamination activity of the photoactive coating under the action of UV-A radiation is carried out according to the above method by applying to the surface 100% cotton fabric "Premier-Cotton-350" and a material synthesized analogously to example 16 using the fabric "Premier-Cotton-350", a solution PCR product, which is a DNA fragment with a length of 71 bp and is designated as "1702".

Example 22.

Similar to example 21, with the exception that a mixture of pre-intact total RNA with a concentration of 100 ng/ml is applied to tissue materials, consisting mainly of ribosomal RNA (rRNA) and major short RNA (transfer RNA (tRNA) and small nuclear RNA (snRNA)) . Washout of nucleic acids is carried out by incubation of a fragment of the material in 1.5 ml of deionized water and primers specific for the analysis of the level of 18S rRNA and U1 snRNA are used. Also, the protocol for the reverse transcription reaction followed by amplification to assess the level of RNA contains a pre-incubation step at 45°C for 30 min (primer elongation step with reverse transcriptase).

Example 23.

It is similar to example 21 with the exception that 150 μl of a suspension of influenza A / PR / 8/34 (H1N1) virus in culture medium is applied to samples of the original cotton fabric and material with a photoactive coating 4 cm ² in size and covered with glass. Then half of the prepared samples are irradiated with UV-A radiation for 30, 60, 180 or 360 minutes, and the remaining half is used to evaluate the effect of the photoactive coating on virus degradation without irradiation. At the end of time, all samples are immersed in 2 ml of phosphate-buffered saline (PBS, Biolot) and shaken to wash away the viral particles. To determine the initial amount of virus, 150 μl of the suspension is immediately placed in 2 ml of buffer. Using the above technique, threshold cycle values are determined.

Fig. 8 illustrates the fact that DNA remains stable on the surface of the original tissue material (without photoactive coating) under the action of UV-A radiation, since the value of the threshold cycle C _q does not change significantly even under prolonged illumination. On the other hand, example 20 confirms the fundamental possibility of DNA destruction on the illuminated surface of a fabric material with a photoactive coating, since the Cq value gradually increases to the background level (Fig. 8), which indicates DNA destruction and a decrease in its concentration up to the detection limit.

Example 22 illustrates the fundamental possibility of removing various RNAs from the surface of materials with a photoactive coating (Fig. 9), and also indicates the possibility of using the developed composition to reduce the likelihood of cross-contamination in molecular biological and diagnostic laboratories.

Example 23 illustrates the possibility of removing RNA even biological objects, such as influenza virus (Fig. 10). As in the case of DNA fragments (Fig. 8), the threshold C _q cycle gradually decreases down to the background level, which indicates the destruction of viral RNA and a decrease in its concentration up to the limit of detection. This effect will ensure the absence of false positive results from biological objects, such as viruses.

Thus, the proposed composition for applying a photoactive coating, which forms a silicon-titanium oxide coating on the outer surface of porous and non-porous materials, which, due to the photoactive component based on nanocrystalline titanium dioxide, has a self-cleaning effect under the action of sunlight and room light sources, allows you to remove chemical substances, including biomacromolecules, including fragments of nucleic acids in the composition of DNA, RNA and other NC-containing biological objects, such as viruses, thereby ensuring a permanent reduction in the level of pollution in premises for various purposes.

Claims (2)

1. Composition for applying a photoactive coating on the surface of materials and providing oxidative destruction of chemicals, containing a polar organic solvent, an organosilicon compound, water and anatase modification titanium dioxide, characterized in that it contains isopropyl or ethyl alcohol, or ethyl acetate as a polar organic solvent , as an organosilicon compound - ethyl silicate, 1-150 g / l of nanocrystalline titanium dioxide or nanocrystalline titanium dioxide containing an admixture of nitrogen, or an admixture of nitrogen, iron and copper, while the composition additionally contains an inorganic acid from a series including sulfuric, nitric, or hydrochloric acid, and the volume ratio of ethyl silicate : polar organic solvent is from 1:19 to 1:1, respectively, the volume fraction of inorganic acid is from 0.1 to 10%, and the volume fraction of water is from 5 to 25%. 2. Composition according to claim 1, characterized in that the nitrogen impurity content is up to 1% of the mass of nanocrystalline titanium dioxide.

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