A TRANSPARENT PHOTOCATALYTIC COATING FOR IN-SITU GENERATION OF FREE RADICALS COMBATING MICROBES, ODORS OR ORGANIC COMPOUNDS IN VISIBLE LIGHT

Abstract

A transparent photocatalytic coating for in-situ generation of free radicals combating microbes, odors and organic compounds in visible light is disclosed, featuring a catalytic material comprising a dopant and having particle size distribution suitable for exciton-confinment to accumulatively shift the photocatalytic process into visible light range. Furthermore, the present invention features a method of producing the photocatalytic material described herein. Furthermore, the present invention discloses a method of application of the photocatalytic coating to a surface of a locus. Finally, the present invention features using the photocatalytic coating for removing contaminants and microorganisms at the locus.

Claims

1-10. (canceled)

11. A liquid composition for in-situ generation of free radicals for combating soils, microorganisms and odors at a locus, comprising: a) from 0.01 to 3 percent by weight of TiO.sub.2 nanoparticles as a photocatalytic material; b) from 0.1 to 1 percent by weight of a mineral acid as stabilizer, and c) the liquid being water; wherein the photocatalytic activity of TiO.sub.2 nanoparticles is extended to be in visible light by: Created defects within the TiO.sub.2 crystalline structure, wherein said created defects within the TiO.sub.2 structure are oxygen or titanium vacancies or substitutions obtained by one or more of the following techniques: by doping of TiO.sub.2 nanoparticles during their condensation with 0.00001 to 5 percent by weight of one or more dopants comprising (i) one or more of copper, cobalt, nickel, chromium, manganese, molybdenum, niobium, vanadium, iron, ruthenium, gold, silver, platinum ions, and (ii) one or more of nitrogen, sulfur, carbon, boron, phosphorous, iodine, and fluorine ions; optionally, by synthesis in the presence of reductants; optionally, by annealing in reducing atmospheres. The TiO.sub.2 nanoparticles being 5-10 nm, said particles capable of forming conglomerates of up to 40 nm; Optionally, combination of visible light harvesters with the TiO.sub.2; Optionally, by created defects at the TiO.sub.2 particle surface.

12. The composition according to claim 11, the composition comprising 2 percent by weight of TiO.sub.2 particles.

13. The composition according to claim 11, wherein the dopant is silver ions and the concentration of silver dopant is 0.0025 percent by weight.

14. The composition according to claim 11, wherein the combination of visible light harvesters with the TiO.sub.2 is obtained by one or more of the following techniques: by the contaminant compound/microorganism itself, having an absorption in visual light; optionally, by co-synthesis of TiO.sub.2 nanoparticles; optionally, by mixing with organic dyes.

15. The composition according to claim 11, wherein the created defects at the TiO.sub.2 particle surface are obtained by one or more of the following techniques: surface chemical modifications; or by plasma treatment.

16. The composition according to claim 11, where the photocatalytic activity of TiO.sub.2 nanoparticles is further enhanced by promoting growth of a specific particle's crystal facets, with said promoting being effected by addition of a capping agent.

17. A method for combating soils, microorganisms and odors at a locus, using the composition of any of the preceding claims, the method comprising: optionally diluting the composition by up to a factor of 10; delivering of said liquid composition to a surface in said locus so as to deliver most of the TiO.sub.2 nanoparticles and a fraction of the liquid solvent to the surface; and drying of said composition at the said surface.

18. The method of producing a liquid composition according to claim 11, said method comprising the steps of: a) mixing of a titania precursor solution with a solvent solution under stirring; the precursor solution optionally being a titanium alkoxide solution, and the solvent solution optionally comprising water, a stabilizer and a dopant precursor; b) purification to remove excess alcohol being formed during the reaction; c) peptization.

19. The method according to claim 18, wherein b) and c) are carried out simultaneously.

20. The use of a liquid composition according to claim 11 for in-situ generation of free radicals combating soils, microorganisms and odors at a locus, wherein a locus is selected from any indoor or outdoor facility, including an industrial environment, a production facility, a storage house, a vehicle, a home, a hotel, a sport facility, an educational institution, a health care facility, a food or beverage production or serving site, an animal farm, and agricultural environments, or an elements of the forgoing.

Description

DETAILED DISCLOSURE

[0041] In one aspect, a liquid composition comprising TiO2 nanoparticles is disclosed, where the photocatalytic activity of TiO2 nanoparticles is extended into the visible light by combining one or more of: defects in the crystallinic structure, defects on the surface of nanoparticles, or addition of light harvesters; and further improving the photocatalytic activity of TiO2 nanoparticles by selecting a specific mean size of the particles to be equal to the exciton Bohr radius for semiconductors, being dose to 5 nm for TiO2.

[0042] In this aspect, a liquid composition for in-situ generation of free radicals for combating soils, microorganisms and odors at a locus is disclosed, comprising:

[0043] a) from 0.01 to 3 percent by weight of TiO2 nanoparticles as a photocatalytic material;

[0044] b) from 0.1 to 1 percent by weight of a stabilizer, preferably being a mineral acid, most preferably nitric acid; and

[0045] c) the liquid being water;

[0046] Characterized in that the photocatalytic activity of TiO2 nanoparticles is extended to be in visible light by: [0047] Created defects within the TiO2 crystalline structure, where created defects within the TiO2 structure are oxygen or titanium vacancies or substitutions, obtained by one or more of the following techniques: [0048] by doping of TiO2 nanoparticles during their condensation with 0.00001 to 5 percent by weight of one or more dopants selected from the transition metals comprising copper, cobalt, nickel, cromium, manganese, molybdenum, niobium, vanadium, iron, ruthenium, gold, silver, platinum ions and from the non-metals comprising nitrogen, sulfur, carbon, boron, phosphorous, iodine, fluorine ions; [0049] optionally, by synthesis in the presence of reductants; [0050] optionally, by annealing in reducing atmospheres. [0051] The TiO2 nanoparticles being 5-10 nm, said particles capable of forming conglomerates of up to 40 nm; [0052] Optionally, combination of visible light harvesters with the TiO2; [0053] Optionally, by created defects at the TiO2 particle surface;

[0054] In second aspect, the method of combating the microbes, contaminats and odors using our inventive composition is disclosed:

[0055] A method for combating soils, microorganisms and odors at a locus, comprising: [0056] a step of diluting the composition by a factor of 1 (no dilution) to 10 (1 part of composition to 10 parts of pure water); [0057] a step of delivering of said liquid composition to a surface in said locus, comprising an application of said liquid composition, the application process being adapted to deliver most of the TiO2 nanoparticles and only a small fraction of the liquid solvent to the surface; preferably, the application is done using a spraying technique; [0058] a step of drying of said composition at the said surface, and forming a residue or layer of said photocatalytic nanoparticles on said surface, invisible to a human eye.

[0059] In a third aspect of the invention, the production method of the compositions according to the first aspect of invention is disclosed:

[0060] A method of producing a liquid composition, said production comprising the steps of:

[0061] a) mixing of Titania precursor solution with a solvent solution under stirring; preferably, precursor solution is a titanium alkoxide solution, and solvent solution comprises water, a stabilizer and a dopant presursor;

[0062] b) purification to remove excess alcohol being formed during the reaction;

[0063] c) peptization;

[0064] In a forth aspect of the invention, the use of the compositions according to the first aspect of invention at various locuses is disclosed:

[0065] The use of a liquid composition as disclosed, applied and produced according to any of the preceding claims, for in-situ generation of free radicals combating soils, microorganisms and odors at a locus, wherein a locus is selected from any indoor or outdoor facility, exemplified by but not limited to an industrial environment, a production facility, a storage house, a vehicle, a home, a hotel, a sport facility, an educational institution, a health care facility, a food or beverage production or serving site, animal farms and other agricultural environments, or elements of these environments, examples being but not restricted to, worksurfaces, ceramic tiles, sinks, baths, washbasins, water tanks, toilets, ovens, hobs, carpets, fabrics, floors, painted woodwork, metalwork, laminates, glass surfaces including windows and mirrors, room door handles, bed rails, taps, sterile packaging, mops, plastics, keyboards, telephones and the like, walls, ceilings, industrial machinery or equipment, shower cubicles, shower curtains, sanitary ware articles, building panels, or kitchen worktops.

SPECIFIC EXAMPLES OF THE INVENTION

[0066] The invention has been described with reference to a number of embodiments and aspects. However, the person skilled in the art may amend such embodiments and aspects while remaining within the scope of the appended patent claims.

[0067] Some specific novel and inventive formulations in this scope that have proven efficacy are disclosed in the following embodyments and examples.

Example 1

[0068] A liquid composition comprising a) 0.01-3 wt. % of TiO2 nanoparticles, anatase, average primary size 5-10 nm; b) 0.1-1 wt. % nitric acid; c) 0.00001-0.0025 wt. % AgCl; d) 0-0.1 wt. % isopropanol; e) 95.8975-99.88999 wt. % pure water.

[0069] The TiO2 mean particle size of 5-10 nm is equal or right above the Bohr radius. This allows to maximize the TiO2 coating surface area without loosing significant absorption of visible light due to exciton quantum confinement.

[0070] Nitric acid is used as a stabilizer to hinder nanoparticle aggregation. The acid works by protonating the surface of the particles and hence giving them a positive surface charge. Charged particles repel each others and do not aggregate. Other acids can be used, such as hydrochloric acid or sulfuric acid. Bases can also be used, and these will give a negative surface charge.

[0071] AgCl is used as a source of silver ions. Silver ions act as a dopant, replacing titanium atoms in the TiO2 structure or positioning themselves in interstitials crystal sites in between the atoms of the structure. These modifications change the electronic properties of the semiconductor and allow for absorption of light in the visible range. Other silver salts can be used as a source of silver ions, like silver nitrate AgNO3, silver tetrafluoroborate AgBF4 or silver perchlorate AgClO4. Several other elements can be used instead of silver to provide doping, the most common being copper, cobalt, nickel, cromium, manganese, molybdenum, niobium, vanadium, iron, ruthenium, gold, silver, platinum within transition metals and nitrogen, sulfur, carbon, boron, phosphorous, iodine, fluorine for the non-metals.

[0072] Isopropanol is a by-product of the reaction between the titanium precursor (titanium isopropoxide) and water. Depending of the choice of the precursor, other by-products might be present such as butanol (from titanium butoxide) or hydrochloric acid (from titanium tetrachloride).

[0073] Water used for the production and in the final product must have a low amount of ionic impurities with conductivity below 20 μS/cm (ISO Type 3, 2 and 1). Demineralized, distilled, reverse osmosis or milliQ water can be used. Tap water or generally hard water cannot be used as it will lead to nanoparticles aggregation.

[0074] The photocatalytic activity of TiO2 nanoparticles is further enhanced by favouring the growth of specific particle's crystal facets (anisotropic growth), said favouring is performed using an addition of a capping agent such as hydrofluoric acid HF. In the TiO2 nanoparticle synthesis phase, capping agents specifically bind to and stabilize highly energetic facets such as anatase {001} whose growth would instead be reduced in favour of more thermodynamically stable but less photocatalytically active facets.

Example 2

[0075] Method for delivering a liquid composition combating soils, microorganisms and odors at a locus comprising a) diluting the liquid composition, if necessary, by a factor of 1 (no dilution) to 10 (1 part of composition to 10 parts of pure water);

[0076] b) applying composition to a surface, for example, by spraying the composition with an electrostatic spraying gun at a specific distance from the target surface to be coated, so that the visible spraying plume ends 10-20 cm before the target surface; c) let the deposited particles to dry completely, which takes around 2 hours.

Example 3

[0077] A method of producing a liquid composition comprising the steps of a) fast mixing under hgh stirring of 0.1-10 wt. % titanium isopropoxide with a solution of: 88.988-99.88999 wt. % pure water, 0.01-1 wt. % nitric acid and 0.0001-0.002 wt. % AgCl; b) evaporation under vacuum pressure of 1-999 mBar of excess isopropanol being formed during the reaction and c) peptization at a temperature of 30-99 degrees centigrade. These two last steps can be carried out simultaneously for a duration of time which will depend on the initial reagent volumes. Steps b) and c) can be with an advantage performed in a same step, for example, by performing removal of excess alcohol by vacuum evaporation, using a temperature between room temperature and 100 C and absolute pressure between 0.1 mBar and ambient pressure, process time being volume dependent.

Example 4

[0078] The use of a liquid composition as composed, applied and produced according to any of the preceding claims, for in-situ generation of free radicals combating soils, microorganisms and odors at a locus, wherein a locus is selected from any indoor or outdoor facility, exemplified by but not limited to an industrial environment, a production facility, a storage house, a vehicle, a home, a hotel, a sport facility, an educational institution, a health care facility, a food or beverage production or serving site, animal farms and other agricultural environments, or elements of these environments, examples being but not restricted to, a wall, ceiling, floor, window, working surface, industrial machinery or equipment, carpet, mirror, shower cubicle, shower curtain, sanitary ware article, ceramic tile, building panel, water tank or kitchen worktop.

[0079] Biocidal active substances are called in situ generated active substances if they are generated from one or more precursors at the place of use. In our invention, the TiO2 particles are catalysing the formation of free radicals from the ambient air or water, depending on the application site. Coated on the inside surface of a fish tank, as an example, our photocatalysator wil generate in-situ free radicals out of water molecules and dissolved gases and salts present in water.

Example 5

[0080] Tests of efficacy of the liquid composition of our invention on patogens are summarized below:

TABLE-US-00001 indicates data missing or illegible when filed [0081] European Standards (abbreviated ENs owing to the more literal translation from French/German as European Norms) are technical standards drafted and maintained by CEN (European Committee for Standardization). CENELEC (European Committee for Electrotechnical Standardization) and ETSI (European Telecommunications Standards Institute). [0082] 1 log reduction=90% reduction [0083] 2 log reduction=99% reduction [0084] 3 log reduction=99.9% reduction [0085] 4 log reduction=99.99% reduction [0086] 5 log reduction=99.999% reduction [0087] 6 log reduction=99.9999% reduction

Example 1 Embodyments

[0088] 1. Composition comprising a) 0.01 wt. % of TiO2 nanoparticles, anatase; b) 0.1 wt. % nitric acid; c) 0,00001 wt. % AgCl; d) traces of isopropanol; e) balance is water. [0089] 2. Composition comprising a) 0.01 wt. % of TiO2 nanoparticles, anatase; b) 0.1 wt. % nitric acid; c) 0,0001 wt. % AgCl; d) traces of isopropanol; e) balance is water. [0090] 3. Composition comprising a) 0.01 wt. % of TiO2 nanoparticles, anatase; b) 0.1 wt. % nitric acid; c) 0,001 wt. % AgCl; d) traces of isopropanol; e) balance is water. [0091] 4. Composition comprising a) 0.01 wt. % of TiO2 nanoparticles, anatase; b) 0.1 wt. % nitric acid; c) 0.0025 wt. % AgCl; d) traces of isopropanol; e) balance is water. [0092] 5. Composition comprising a) 0.01 wt. % of TiO2 nanoparticles, anatase; b) 0.3 wt. % nitric acid; c) 0,00001 wt. % AgCl; d) traces of isopropanol; e) balance is water. [0093] 6. Composition comprising a) 0.01 wt. % of TiO2 nanoparticles, anatase; b) 0.3 wt. % nitric acid; c) 0,0001 wt. % AgCl; d) traces of isopropanol; e) balance is water. [0094] 7. Composition comprising a) 0.01 wt. % of TiO2 nanoparticles, anatase; b) 0.3 wt. % nitric acid; c) 0,001 wt. % AgCl; d) traces of isopropanol; e) balance is water. [0095] 8. Composition comprising a) 0.01 wt. % of TiO2 nanoparticles, anatase; b) 0.3 wt. % nitric acid; c) 0.0025 wt. % AgCl; d) traces of isopropanol; e) balance is water. [0096] 9. Composition comprising a) 0.01 wt. % of TiO2 nanoparticles, anatase; b) 0.7 wt. % nitric acid; c) 0,00001 wt. % AgCl; d) traces of isopropanol; e) balance is water. [0097] 10. Composition comprising a) 0.01 wt. % of TiO2 nanoparticles, anatase; b) 0.7 wt. % nitric acid; c) 0,0001 wt. % AgCl; d) traces of isopropanol; e) balance is water. [0098] 11. Composition comprising a) 0.01 wt. % of TiO2 nanoparticles, anatase; b) 0.7 wt. % nitric acid; c) 0,001 wt. % AgCl; d) traces of isopropanol; e) balance is water. [0099] 12. Composition comprising a) 0.01 wt. % of TiO2 nanoparticles, anatase; b) 0.7 wt. % nitric acid; c) 0.0025 wt. % AgCl; d) traces of isopropanol; e) balance is water. [0100] 13. Composition comprising a) 0.01 wt. % of TiO2 nanoparticles, anatase; b) 1 wt. % nitric acid; c) 0,00001 wt. % AgCl; d) traces of isopropanol; e) balance is water. [0101] 14. Composition comprising a) 0.01 wt. % of TiO2 nanoparticles, anatase; b) 1 wt. % nitric acid; c) 0,0001 wt. % AgCl; d) traces of isopropanol; e) balance is water. [0102] 15. Composition comprising a) 0.01 wt. % of TiO2 nanoparticles, anatase; b) 1 wt. % nitric acid; c) 0,001 wt. % AgCl; d) traces of isopropanol; e) balance is water. [0103] 16. Composition comprising a) 0.01 wt. % of TiO2 nanoparticles, anatase; b) 1 wt. % nitric acid; c) 0.0025 wt. % AgCl; d) traces of isopropanol; e) balance is water. [0104] 17. Composition comprising a) 0.1 wt. % of TiO2 nanoparticles, anatase; b) 0.1 wt. % nitric acid; c) 0,00001 wt. % AgCl; d) traces of isopropanol; e) balance is water. [0105] 18. Composition comprising a) 0.1 wt. % of TiO2 nanoparticles, anatase; b) 0.1 wt. % nitric acid; c) 0 wt. % AgCl; d) traces of isopropanol; e) balance is water. [0106] 19. Composition comprising a) 0.1 wt. % of TiO2 nanoparticles, anatase; b) 0.1 wt. % nitric acid; c) 0 wt. % AgCl; d) traces of isopropanol; e) balance is water. [0107] 20. Composition comprising a) 0.1 wt. % of TiO2 nanoparticles, anatase; b) 0.1 wt. % nitric acid; c) 0 wt. % AgCl; d) traces of isopropanol; e) balance is water. [0108] 21. Composition comprising a) 0.1 wt. % of TiO2 nanoparticles, anatase; b) 0.3 wt. % nitric acid; c) 0,00001 wt. % AgCl; d) traces of isopropanol; e) balance is water. [0109] 22. Composition comprising a) 0.1 wt. % of TiO2 nanoparticles, anatase; b) 0.3 wt. % nitric acid; c) 0,0001 wt. % AgCl; d) traces of isopropanol; e) balance is water. [0110] 23. Composition comprising a) 0.1 wt. % of TiO2 nanoparticles, anatase; b) 0.3 wt. % nitric acid; c) 0,001 wt. % AgCl; d) traces of isopropanol; e) balance is water. [0111] 24. Composition comprising a) 0.1 wt. % of TiO2 nanoparticles, anatase; b) 0.3 wt. % nitric acid; c) 0.0025 wt. % AgCl; d) traces of isopropanol; e) balance is water. [0112] 25. Composition comprising a) 0.1 wt. % of TiO2 nanoparticles, anatase; b) 0.7 wt. % nitric acid; c) 0,00001 wt. % AgCl; d) traces of isopropanol; e) balance is water. [0113] 26. Composition comprising a) 0.1 wt. % of TiO2 nanoparticles, anatase; b) 0.7 wt. % nitric acid; c) 0,0001 wt. % AgCl; d) traces of isopropanol; e) balance is water. [0114] 27. Composition comprising a) 0.1 wt. % of TiO2 nanoparticles, anatase; b) 0.7 wt. % nitric acid; c) 0,001 wt. % AgCl; d) traces of isopropanol; e) balance is water. [0115] 28. Composition comprising a) 0.1 wt. % of TiO2 nanoparticles, anatase; b) 0.7 wt. % nitric acid; c) 0.0025 wt. % AgCl; d) traces of isopropanol; e) balance is water. [0116] 29. Composition comprising a) 0.1 wt. % of TiO2 nanoparticles, anatase; b) 1 wt. % nitric acid; c) 0,00001 wt. % AgCl; d) traces of isopropanol; e) balance is water. [0117] 30. Composition comprising a) 0.1 wt. % of TiO2 nanoparticles, anatase; b) 1 wt. % nitric acid; c) 0,0001 wt. % AgCl; d) traces of isopropanol; e) balance is water. [0118] 31. Composition comprising a) 0.1 wt. % of TiO2 nanoparticles, anatase; b) 1 wt. % nitric acid; c) 0,001 wt. % AgCl; d) traces of isopropanol; e) balance is water. [0119] 32. Composition comprising a) 0.1 wt. % of TiO2 nanoparticles, anatase; b) 1 wt. % nitric acid; c) 0.0025 wt. % AgCl; d) traces of isopropanol; e) balance is water. [0120] 33. Composition comprising a) 1.5 wt. % of TiO2 nanoparticles, anatase; b) 0.1 wt. % nitric acid; c) 0,00001 wt. % AgCl; d) traces of isopropanol; e) balance is water. [0121] 34. Composition comprising a) 1.5 wt. % of TiO2 nanoparticles, anatase; b) 0.1 wt. % nitric acid; c) 0 wt. % AgCl; d) traces of isopropanol; e) balance is water. [0122] 35. Composition comprising a) 1.5 wt. % of TiO2 nanoparticles, anatase; b) 0.1 wt. % nitric acid; c) 0 wt. % AgCl; d) traces of isopropanol; e) balance is water. [0123] 36. Composition comprising a) 1.5 wt. % of TiO2 nanoparticles, anatase; b) 0.1 wt. % nitric acid; c) 0 wt. % AgCl; d) traces of isopropanol; e) balance is water. [0124] 37. Composition comprising a) 1.5 wt. % of TiO2 nanoparticles, anatase; b) 0.3 wt. % nitric acid; c) 0,00001 wt. % AgCl; d) traces of isopropanol; e) balance is water. [0125] 38. Composition comprising a) 1.5 wt. % of TiO2 nanoparticles, anatase; b) 0.3 wt. % nitric acid; c) 0,0001 wt. % AgCl; d) traces of isopropanol; e) balance is water. [0126] 39. Composition comprising a) 1.5 wt. % of TiO2 nanoparticles, anatase; b) 0.3 wt. % nitric acid; c) 0,001 wt. % AgCl; d) traces of isopropanol; e) balance is water. [0127] 40. Composition comprising a) 1.5 wt. % of TiO2 nanoparticles, anatase; b) 0.3 wt. % nitric acid; c) 0.0025 wt. % AgCl; d) traces of isopropanol; e) balance is water. [0128] 41. Composition comprising a) 1.5 wt. % of TiO2 nanoparticles, anatase; b) 0.7 wt. % nitric acid; c) 0,00001 wt. % AgCl; d) traces of isopropanol; e) balance is water. [0129] 42. Composition comprising a) 1.5 wt. % of TiO2 nanoparticles, anatase; b) 0.7 wt. % nitric acid; c) 0,0001 wt. % AgCl; d) traces of isopropanol; e) balance is water. [0130] 43. Composition comprising a) 1.5 wt. % of TiO2 nanoparticles, anatase; b) 0.7 wt. % nitric acid; c) 0,001 wt. % AgCl; d) traces of isopropanol; e) balance is water. [0131] 44. Composition comprising a) 1.5 wt. % of TiO2 nanoparticles, anatase; b) 0.7 wt. % nitric acid; c) 0.0025 wt. % AgCl; d) traces of isopropanol; e) balance is water. [0132] 45. Composition comprising a) 1.5 wt. % of TiO2 nanoparticles, anatase; b) 1 wt. % nitric acid; c) 0,00001 wt. % AgCl; d) traces of isopropanol; e) balance is water. [0133] 46. Composition comprising a) 1.5 wt. % of TiO2 nanoparticles, anatase; b) 1 wt. % nitric acid; c) 0,0001 wt. % AgCl; d) traces of isopropanol; e) balance is water. [0134] 47. Composition comprising a) 1.5 wt. % of TiO2 nanoparticles, anatase; b) 1 wt. % nitric acid; c) 0,001 wt. % AgCl; d) traces of isopropanol; e) balance is water. [0135] 48. Composition comprising a) 1.5 wt. % of TiO2 nanoparticles, anatase; b) 1 wt. % nitric acid; c) 0.0025 wt. % AgCl; d) traces of isopropanol; e) balance is water. [0136] 49. Composition comprising a) 3 wt. % of TiO2 nanoparticles, anatase; b) 0.1 wt. % nitric acid; c) 0,00001 wt. % AgCl; d) traces of isopropanol; e) balance is water. [0137] 50. Composition comprising a) 3 wt. % of TiO2 nanoparticles, anatase; b) 0.1 wt. % nitric acid; c) 0 wt. % AgCl; d) traces of isopropanol; e) balance is water. [0138] 51. Composition comprising a) 3 wt. % of TiO2 nanoparticles, anatase; b) 0.1 wt. % nitric acid; c) 0 wt. % AgCl; d) traces of isopropanol; e) balance is water. [0139] 52. Composition comprising a) 3 wt. % of TiO2 nanoparticles, anatase; b) 0.1 wt. % nitric acid; c) 0 wt. % AgCl; d) traces of isopropanol; e) balance is water. [0140] 53. Composition comprising a) 3 wt. % of TiO2 nanoparticles, anatase; b) 0.3 wt. % nitric acid; c) 0,00001 wt. % AgCl; d) traces of isopropanol; e) balance is water. [0141] 54. Composition comprising a) 3 wt. % of TiO2 nanoparticles, anatase; b) 0.3 wt. % nitric acid; c) 0,0001 wt. % AgCl; d) traces of isopropanol; e) balance is water. [0142] 55. Composition comprising a) 3 wt. % of TiO2 nanoparticles, anatase; b) 0.3 wt. % nitric acid; c) 0,001 wt. % AgCl; d) traces of isopropanol; e) balance is water. [0143] 56. Composition comprising a) 3 wt. % of TiO2 nanoparticles, anatase; b) 0.3 wt. % nitric acid; c) 0.0025 wt. % AgCl; d) traces of isopropanol; e) balance is water. [0144] 57. Composition comprising a) 3 wt. % of TiO2 nanoparticles, anatase; b) 0.7 wt. % nitric acid; c) 0,00001 wt. % AgCl; d) traces of isopropanol; e) balance is water. [0145] 58. Composition comprising a) 3 wt. % of TiO2 nanoparticles, anatase; b) 0.7 wt. % nitric acid; c) 0,0001 wt. % AgCl; d) traces of isopropanol; e) balance is water. [0146] 59. Composition comprising a) 3 wt. % of TiO2 nanoparticles, anatase; b) 0.7 wt. % nitric acid; c) 0,001 wt. % AgCl; d) traces of isopropanol; e) balance is water. [0147] 60. Composition comprising a) 3 wt. % of TiO2 nanoparticles, anatase; b) 0.7 wt. % nitric acid; c) 0.0025 wt. % AgCl; d) traces of isopropanol; e) balance is water. [0148] 61. Composition comprising a) 3 wt. % of TiO2 nanoparticles, anatase; b) 1 wt. % nitric acid; c) 0,00001 wt. % AgCl; d) traces of isopropanol; e) balance is water. [0149] 62. Composition comprising a) 3 wt. % of TiO2 nanoparticles, anatase; b) 1 wt. % nitric acid; c) 0,0001 wt. % AgCl; d) traces of isopropanol; e) balance is water. [0150] 63. Composition comprising a) 3 wt. % of TiO2 nanoparticles, anatase; b) 1 wt. % nitric acid; c) 0,001 wt. % AgCl; d) traces of isopropanol; e) balance is water. [0151] 64. Composition comprising a) 3 wt. % of TiO2 nanoparticles, anatase; b) 1 wt. % nitric acid; c) 0.0025 wt. % AgCl; d) traces of isopropanol; e) balance is water.