UV-PROTECTIVE COMPOSITIONS AND THEIR USE

Abstract

Disclosed are UV-protective compositions comprising Fe-doped zinc titanate having the general formula Zn.sub.2Ti.sub.(1-x)Fe.sub.xO.sub.4, wherein x is between 0.005 and 0.1. Also disclosed is Fe-doped or undoped zinc titanate being either directly dispersed in the composition and/or dispersed in a polymer matrix. Methods of preparation and uses of such compositions are also provided.

Claims

1-23. (canceled)

24. A UV-protective composition comprising Fe-doped zinc titanate crystals each independently having the chemical formula Zn.sub.2Ti.sub.(1-x)Fe.sub.xO.sub.4 as an ultraviolet-absorbing agent, wherein x is between 0.005 and 0.1, the zinc titanate crystals forming discrete nanoparticles, wherein at least 50% of a total number of said discrete nanoparticles have at least one dimension of up to 250 nm.

25. The UV-protective composition according to claim 24, wherein x is between 0.025 and 0.05.

26. The UV-protective composition according to claim 24, wherein a molar ratio of Ti to Fe is 19 to 1.

27. The UV-protective composition according to claim 24, wherein the Fe-doped zinc titanate crystals are in the form of nanoparticles consisting of said crystals, at least 50% of the total number of said nanoparticles having at least one dimension of up to about 100 nm.

28. The UV-protective composition according to claim 24, wherein the Fe-doped zinc titanate crystals are at a concentration in the range of from about 0.001% to about 40% (w/w) of the composition.

29. The UV-protective composition according to claim 24, wherein the Fe-doped zinc titanate nanoparticles are dispersed in a dispersant.

30. The UV-protective composition according to claim 29, wherein the dispersant is selected from: polyacrylic acid and salts thereof; polyhydroxystearic acid; oleic acid; octyldodecyl/PPG-3myristyl ether dimer dilinoleate; butylphthalimide combined with isoproplylphthalimide; C.sub.12-15 alkyl ethylhexanoate; cetyl esters; isononyl isononanoate combined with ethylhexyl isonononoate; C.sub.12-15 alkyl benzoate; ethylhexyl isononanoate; polyglyceryl-3 behenate; ethyl isonanoate combined with cetyl dimethicone; propanediol dicaprylate/caprate combined with diisostearyl malate; PPG-26 dimer dilinoleate copolymer combined with isononyl isononanoate and with ethylhexyl isononanoate; dimer dilinoleyl dimer dilinoleate; diethylhexyl adipate; decyl oleate; dipentaerythrityl tetrahydroxy-stearate/tetraisostearate; octyldodecyl erucate; glyceryl ester; tribehenin; trihydroxystearin; triisostearin; triethylhexanoin; isocetyl behenate; isononyl isonanoate; isostearyl ester; triisostearin/glyceryl behenate; methyl acetyl ricinoleate; neopentylglycol dicaprate/dicaprylate; oleyl lactate; ethylhexyl pelargonate; pentaerylthrityl tetraisononanoate; propanediol dicaprylate/caprate; polyglycerol-10 hexaoleate combined with polyglyceryl-6 polyricinoleate; pentaerythrityl ester; cetearyl ethylhexanoate; tridecyl enucate; tribeherin combined with caprylic/capric triglyceride; dimer dilinoelyl dimer dilinoleate combined with triisostearin; trimethylolpropane ester; and trioctyldodecyl citrate.

31. The UV-protective composition according to claim 24, wherein said discrete nanoparticles of said Fe-doped zinc titanate crystals are dispersed with a dispersant in a polymer matrix, the polymer matrix comprising a thermoplastic polymer swelled with a liquid carrier.

32. The UV-protective composition according to claim 31, wherein said polymer matrix is in the form of polymer matrix flakes wherein each flake of said polymer matrix flakes has a flake length (Lf), a flake width (Wf), and a flake thickness (Tf), said polymer matrix flakes having a dimensionless flake aspect ratio (Rf) defined by: Rf=(LfWf)/(Tf).sup.2, wherein, with respect to a representative group of at least ten polymer matrix flakes, an average Rf is at least 5.

33. The UV-protective composition according to claim 31, wherein the dispersant adapted to disperse the discrete nanoparticles of the Fe-doped zinc titanate crystals within said polymer matrix has a hydrophilic-lipophilic balance (HLB) value of at most 9.

34. The UV-protective composition according to claim 31, wherein the thermoplastic polymer in the polymer matrix comprises at least one of an ethylene-acrylic (EAA) polymer, an ethylene-methacrylic (EMMA) polymer, an ethyl vinyl acetate (EVA) polymer, or combinations thereof.

35. The UV-protective composition according to claim 24, formulated as one or more of the following: (a) a skin-care composition for application to human or non-human animal skin; (b) a hair-care composition for application to human or non-human animal hair; or (c) a coating composition for application to an inanimate surface.

36. The UV-protective composition according to claim 24, for use in protecting a subject against an effect of ultraviolet radiation.

37. The UV-protective composition according to claim 24, for use in protecting the skin or hair of a subject against an effect of ultraviolet radiation.

38. The UV-protective composition according to claim 24, for use in protecting an inanimate object against an effect of ultraviolet radiation.

39. The UV-protective composition for use according to claim 36, wherein protecting against ultraviolet radiation comprises protecting against ultraviolet A radiation and ultraviolet B radiation.

40. The UV-protective composition according to claim 24, wherein the composition has a critical wavelength of at least 370 nm.

41. The composition according to claim 24, wherein the composition has a critical wavelength of at most 400 nm.

42. The composition according to claim 24, wherein the composition has a critical wavelength in the range of 370 nm to 400 nm.

43. The UV-protective composition according to claim 24, wherein the area under the curve (AUC) formed by the UV-absorption of the Fe-doped zinc titanate crystals as a function of wavelength in the range of 280 nm to 400 nm (AUC.sub.280-400) is at least 75% of the AUC formed by the same zinc titanate crystals at the same concentration in the range of 280 nm to 700 nm (AUC.sub.280-700).

44. An article coated with the composition according to claim 24.

45. A UV-protective composition comprising zinc titanate crystals each independently having the chemical formula Zn.sub.2Ti.sub.(1-x)Fe.sub.xO.sub.4 as an ultraviolet-absorbing agent, wherein x is between 0 and 0.1, the zinc titanate crystals forming discrete nanoparticles, wherein at least 50% of a total number of said discrete nanoparticles have at least one dimension of up to 250 nm, and wherein said discrete nanoparticles are dispersed with a dispersant in a polymer matrix, the polymer matrix comprising a thermoplastic polymer swelled with a liquid carrier.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0155] Some embodiments of the invention are described herein with reference to the accompanying figures. The description, together with the figures, makes apparent to a person having ordinary skill in the art how some embodiments of the disclosure may be practiced. The figures are for the purpose of illustrative discussion and no attempt is made to show structural details of an embodiment in more detail than is necessary for a fundamental understanding of the disclosure. For the sake of clarity, some objects depicted in the figures are not to scale.

[0156] In the Figures:

[0157] FIG. 1 is a line graph showing powder absorbance of Fe-doped and undoped zinc titanate powder, prepared according to present teachings, as compared to undoped zinc oxide powder and presintered zinc titanate as reference.

[0158] FIG. 2 is a plot showing the powder X ray diffraction (PXRD) diffractogram of Fe-doped and undoped zinc titanate crystals prepared according to the present teachings.

[0159] FIG. 3 is a line graph showing Particle Size Distribution (PSD) of particles of Fe-doped and undoped zinc titanate powder after milling according to present teachings, expressed as number percentage, as compared to zinc oxide as reference.

[0160] FIG. 4 is a line graph showing absorbance of aqueous suspensions comprising different concentrations of nanoparticles of Fe-doped zinc titanate crystals, prepared according to present teachings, as compared to the same respective concentrations of undoped zinc titanate as reference.

[0161] FIG. 5 is a line graph showing absorbance of aqueous suspensions comprising a same concentration of nanoparticles of zinc titanate crystals at various levels of Fe-doping prepared according to present teachings, as compared to undoped zinc titanate crystals, undoped zinc oxide and a commercially available sunscreen as reference.

[0162] FIGS. 6A-6B are high resolution Scanning Electron Microscope (HR-SEM) images of nanoparticles of zinc titanate crystals prepared according to present teachings, where FIG. 6A shows nanoparticles of undoped zinc titanate crystals and FIG. 6B shows nanoparticles of Fe-doped zinc titanate crystals.

DETAILED DESCRIPTION

[0163] The present disclosure, in at least some embodiments, provides compositions for protection against ultraviolet radiation, uses of such compositions and methods of making such compositions.

[0164] The UV-protective compositions disclosed herein comprise one or more zinc titanate crystals each independently having the chemical formula Zn.sub.2Ti.sub.(1-x)Fe.sub.xO.sub.4, wherein x is between 0 and 0.1, which when present as large particles (e.g., dimensions in each of the X-, Y- and Z-directions being greater than 250 nanometers (nm), resulting for instance in a hydrodynamic diameter of more than 250 nm as measured by DLS) may effectively absorb radiation having wavelengths of greater than about 400 nm. Accordingly, compositions comprising such large particles of zinc titanate crystals, whether or not further substituted (doped) by iron atoms, may provide protection against ultraviolet radiation having wavelengths up to at least 400 nm. There may be instances where particles having a hydrodynamic diameter of more than 250 nm (but not more than 500 nm) are used as well, e.g. in the preparation of coatings for inanimate objects, wherein some degree of tinting is tolerable or even required, or for cosmetic compositions wherein tinting might be desirable.

[0165] However, in the case in which the UV-protective composition is a sunscreen composition which comprises doped or undoped zinc titanate crystals, but which also contains particles that absorb light at wavelengths in the range of 400-800 nm, the sunscreen will be visible on the end-user because of the absorption in the visible range (>400 nm).

[0166] It has surprisingly been found by the present Inventors that, although reduction of particle size of known inorganic UV-absorbing agents to dimensions below 1 micrometer (m), typically below 100 nm (for instance, reduction to nanometric dimensions) is known to significantly reduce the maximum wavelength of light, including UV light, which is effectively absorbed by the particles, UV-protective compositions according to the present teachings comprising particles of doped or undoped zinc titanate crystals milled to nanoparticle size still provide substantial absorption of UV radiation of wavelength from 280 nm (or even shorter wavelength) up to about 400 nm, thus providing broad-spectrum protection against both UVA and UVB radiation, even in the absence of additional ultraviolet-absorbing agents.

[0167] Thus, in some embodiments, UV-protective compositions disclosed herein, such as sunscreen compositions, comprise doped or undoped zinc titanate in the form of particles, comprising one or more said crystals, wherein at least 90% of the particles are nanoparticles, such as at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% of the particles are nanoparticles. In some embodiments, at least 95%, or at least 97.5% or at least 99% of the particles, in terms of number or volume of particles, are nanoparticles. In some embodiments, at least one dimension of the zinc titanate crystal nanoparticles is expressed in terms of the hydrodynamic diameter as measured by DLS techniques.

[0168] In some embodiments, the cumulative particle size distribution in a sample is assessed in terms of the number of particles in the sample (denoted D.sub.N). In some embodiments, the cumulative particle size distribution in a sample is assessed in terms of the volume of particles in the sample (denoted D.sub.V).

[0169] In some embodiments, the maximum diameter of the nanoparticles is assessed for population distribution measured in terms of number of particles and percentage thereof. In some embodiments, the maximum diameter of the nanoparticles is assessed for population distribution measured in terms of sample volume of particles and percentage thereof.

[0170] Dimensions of particles can also be assessed (or confirmed) by microscopy (e.g., light microscopy, confocal microscopy, SEM, STEM, etc.). Such techniques may be more suitable than DLS for particles (such as matrix flakes) having non-globular shapes. The particles may be characterized by an aspect ratio, e.g., a dimensionless ratio between the smallest dimension of the particle and the longest dimension or equivalent diameter in the largest plane orthogonal to the smallest dimension, as relevant to their shape. The equivalent diameter (Deq) is defined by the arithmetical average between the longest and shortest dimensions of that largest orthogonal plane. Particles having an almost spherical shape are characterized by an aspect ratio of approximately 1:1, whereas flake-like particles, such as matrix flakes, can have an aspect ratio of up to 1:100, or more.

[0171] As readily appreciated by a person skilled in measurement of particle size, combining a variety of techniques also allows to assess whether the particles or nanoparticles are individuals or agglomerates, and whether they would or not be well-dispersed within their respective media.

[0172] As further detailed herein-below, nanoparticles of doped or undoped zinc titanate crystals can in some embodiments be immobilised within a polymer matrix. The matrix can form distinct elements, which may assume a variety of shapes. For topical application, a platelet shape of polymer matrix element is deemed particularly suitable, as the platelets may lay flat on the skin when applied, providing a better coverage than, e.g., sphere-shaped particles. Such flat platelets of polymers can also be advantageous for industrial use, e.g., for electrostatic coatings. Such matrix flakes can be characterized by a flake length (Lf, the longest dimension in the plane of the flake), a flake width (Wf, the largest dimension in the plane of the flake, such width being transverse to the length), and a flake thickness (Tf, the largest thickness being measured orthogonally to the plane in which the length and width of the flake are defined), such that Tf is smaller than Wf, and Wf is equal or smaller than Lf (Tf<WfLf). Lf, Wf and Tf can be further used to calculate an aspect ratio (e.g., Rf as below defined) of a matrix flake.

[0173] Such characteristic dimensions can be assessed on a number of representative particles, or a group of representative particles, that may accurately characterize the population (e.g., by diameter, longest dimension, thickness, aspect ratio and like characterizing measures of the particles). It will be appreciated that a more statistical approach may be desired for such assessments. When using microscopy for particle size characterization, a field of view of the image-capturing instrument (e.g., light microscope, etc.) is analyzed in its entirety. Typically, the magnification is adjusted such that at least 5 particles, at least 10 particles, at least 20 particles, or at least 50 particles are disposed within a single field of view. Naturally, the field of view should be a representative field of view as assessed by one skilled in the art of microscopic analysis. The average value characterizing such a group of particles in such a field of view is obtained by volume averaging. In such case, D.sub.V50=[(Deq(m)).sup.3/m].sup.1/3 wherein m represents the number of particles in the field of view and the summation is performed over all m particles. As mentioned, when such methods are the technique of choice for the scale of the particles to be studied or in view of their shape, such measurements can be referred to as D50.

[0174] In some embodiments, the doped or undoped nanoparticles of zinc titanate crystals are substantially invisible to the human eye, in particular when applied to the skin or hair of a subject, or if desired when applied to an inanimate surface, due to their small size.

[0175] In some embodiments, the doped or undoped nanoparticles of zinc titanate crystals are blended into a colored composition and need not be substantially transparent and/or invisible, for instance when used in a make-up product, such as a foundation, which is slightly tinted when applied to the skin of a subject, or when used in a stain or paint applicable to inanimate surfaces.

[0176] According to some embodiments of the disclosure, there is provided a UV-protective composition comprising undoped zinc titanate crystals.

[0177] According to some embodiments of the disclosure, there is provided a UV-protective composition comprising Fe-doped zinc titanate crystals, the level of doping by iron atoms being such that the Ti:Fe molar ratio can be between 199:1 and 2:1, between 150:1 and 2:1, between 100:1 and 2:1, between 50:1 and 2:1, between 40:1 and 3:1, between 39:1 and 4:1, between 35:1 and 5:1, between 30:1 and 6:1, between 25:1 and 7:1, between 20:1 and 8:1, between 19:1 and 9:1, such as 199:1, 150:1, 100:1, 49:1, 48:1, 47:1, 46:1, 45:1, 44:1, 43:1, 42:1, 41:1, 40:1, 39:1, 38:1, 37:1, 36:1, 35:1, 34:1, 33:1, 32:1, 31:1, 30:1, 29:1, 28:1, 27:1, 26:1, 25:1, 24:1, 23:1, 22:1, 21:1, 20:1, 19:1, 18:1, 17:1, 16:1, 15:1, 14:1, 13:1, 12:1, 11:1, 10:1, 9:1, 8:1, 7:1, 6:1, 5:1, 4:1 or 3:1, in particular Ti:Fe molar ratio of 0.995:0.005 (199:1), Ti:Fe molar ratio of 0.975:0.025 (39:1) or Ti:Fe molar ratio of 0.95:0.05 (19:1).

[0178] According to a further aspect of some embodiments of the disclosure, there is provided a method of preparing doped or undoped zinc titanate nanoparticles from powders of metal oxides, metal nitrates or metal carbonates. The method comprises combining powders of zinc and titanium, each in the form of either oxides, nitrates or carbonates, in appropriate ratios so as to obtain the desired stochiometric amount. In particular embodiments, Zinc oxide (ZnO) and titanium dioxide (TiO.sub.2) are combined.

[0179] For preparing Fe-doped zinc titanate, some of the metal starting material including titanium is replaced with a starting material including iron. The extent of the replacement is determined according to the desired Fe-doping level, wherein a lower doping level of 0.5 or less results in a narrower UV-spectrum protection (which can be used for inanimate objects), and a higher doping level of above 0.5 results in a broader UV-spectrum protection, more beneficial for cosmetic use. The amount of the added ferric oxide (particularly Fe.sub.2O.sub.3) is calculated to provide the intended Fe-doping ratio, and a corresponding amount of the titanium starting material is reduced accordingly.

[0180] The powdered metal starting materials are then mixed until homogenization by any means known in the art (e.g., by a mortar grinder). As used herein, the term homogenous (and grammatical variants), refer to a mixture, which components are uniformly distributed throughout, forming a single phase.

[0181] Following homogenization, the mixture is calcinated, under conditions which can be readily determined by anyone skilled in the art without undue experimentation. In a particular embodiment, when metal oxides are used as starting materials, calcination is conducted at about 1000 C. for approximately 24 hours. Calcination is performed in order to form crystals of the Fe-doped or undoped zinc titanate substance from the individual powders of metal starting materials, while removing any volatile substance in the process.

[0182] Following calcination, the obtained doped or undoped zinc titanatef crystals are then cooled or allowed to cool down to a temperature of at most 150 C., at most 100 C., at most 70 C., at most 50 C., or at most to an ambient temperature (circa 23 C.), followed by low-energy milling (e.g. by a mortar grinder or ball mill). Low-energy milling suffices to break down the calcinated material into smaller chunks of a size suitable for the following steps.

[0183] For the nanoparticles preparation, the low-energy milled particles are combined with a dispersant, optionally in the presence of an oil-based or water-based carrier, and the obtained slurry is then high-energy milled, whereby nanoparticles of doped or undoped zinc titanate are obtained.

[0184] The types of dispersant and optional oil-based or water-based carrier that can be used in the high-energy milling step depend on the further processing of the nanoparticles, as well as the intended use of the compositions containing them.

[0185] So, for example, if the intended UV-protective composition is a sunscreen composition to be applied on the skin, such a composition might preferably be prepared using oil-based constituents, to provide water-resistance (e.g., to sweat or swimming environment). In such a case, it might be further preferred to disperse the nanoparticles of zinc titanate in a polymer matrix, and having such an illustrative purpose in mind, it would be advantageous to use an oil-based dispersant and optionally an oil-based carrier for the manufacturing of the nanoparticles, as well as an oil-based dispersant and oil-based swelling liquid or carrier for the polymeric matrix. The obtained mixture is compatible in the sense that no turbidity or phase separation is observed in the final UV-protective composition.

[0186] Suitable equipment for the nanoparticles grinding or high-energy milling may include an attritor media grinding mill, a high-energy ball mill, a dyno mill, a zeta mill and a sonicator to name a few.

[0187] While nanoparticles can in theory be prepared by various methods, only a few might be appropriate for industrial manufacturing of significant amounts of composite materials within a reasonably short time period. Bottom-up methods, e.g. growing the crystals in highly diluted solutions, may be inadequate for large scale production. Top-down methods may provide relatively more concentrated compositions than the former method, the composite material being at the end of the process for its preparation generally milled by low-energy milling methods (such as ball milling). Low-energy milling methods are typically capable of breaking-down chunks of materials into smaller macro-particles in the size range of millimetres to micrometres depending on the duration of the milling. While smaller particles could eventually be produced by low-energy milling, such sub-micron particles would typically not exceed 10% of the entire population of the particles so produced. Thus, top-down methods typically result in the formation of agglomerates and/or impure composites, depending on the preparation method. Agglomerates having at least one dimension even in the range of micrometers, will scatter incident light and will therefore be inappropriate for the preparation of transparent compositions according to aspects of the present teachings.

[0188] In contrast, the method of the present invention encompasses a top-down preparation of doped or non-doped zinc titanate nanoparticles, whereby the mixed powders are calcinated to obtain a bulk of agglomerated crystals, which is later ground by high-energy milling in the presence of a compatible dispersant, allowing to obtain discrete, individual nanoparticles. High-energy milling, in contrast with previously described low-energy method, allows for the preparation of particles predominantly in the sub-micron range, advantageously in the range of no more than 500 nm, no more than 250 nm, no more than 200 nm or no more than 100 nm. While particles milled by a high-energy milling method (e.g., a sonication), may include some particles in the range of a few micrometers, such methods are typically employed for a duration of time or at an efficiency such that the larger particles in the micron range do not exceed 10% of the entire population of particles.

[0189] Without wishing to be bound by theory, the inventors believe that for particles that absorb light in the UV-Visible range, downsizing the particles to the nanometric scale may effect a blue shift in the absorbance band, often on the order of 100 to 200 nm.

[0190] This phenomenon occurs when the downsizing produces discrete nanoparticles. For nanopowders that are not dispersed in a medium, however, the absorption profile may be substantially similar to that of the bulk material. Moreover, the inventors believe that in some cases, the size reduction process may introduce enough stress, strain, or defects into the nano-crystalline structures such that the absorption profile may be deleteriously affected. In severe cases, the obtained material may actually become useless as a UV-absorbing agent.

[0191] According to a further aspect of some embodiments of the disclosure, there is provided a UV-protective composition comprising doped or undoped zinc titanate crystals for use in protecting the skin of a subject, such as a human subject, against ultraviolet radiation, in some embodiments providing broad-spectrum protection against both ultraviolet A and ultraviolet B radiation.

[0192] According to a further aspect of some embodiments of the disclosure, there is provided a UV-protective composition comprising doped or undoped zinc titanate crystals for use in protecting the hair of a subject, such as a human subject, against ultraviolet radiation, in some embodiments against both ultraviolet A and ultraviolet B radiation.

[0193] According to a further aspect of some embodiments of the disclosure, there is provided a UV-protective composition comprising doped or undoped zinc titanate crystals for use in protecting the surface of an inanimate object against ultraviolet radiation, in some embodiments against both ultraviolet A and ultraviolet B radiation and in other embodiments mainly against ultraviolet B radiation.

[0194] According to a further aspect of some embodiments of the disclosure, there is provided a method of protecting the skin of a subject against ultraviolet radiation, the method comprising applying to the skin of the subject an efficacious amount of a UV-protective composition comprising doped or zinc titanate crystals. In some such embodiments, the UV-protective composition can be in the form of a skin-care product suitable for skin application and/or at least temporary retention thereupon.

[0195] According to a further aspect of some embodiments of the disclosure, there is provided a method of protecting the hair of a subject against ultraviolet radiation, the method comprising applying to the hair of the subject an efficacious amount of a UV-protective composition comprising doped or undoped zinc titanate crystals. In some such embodiments, the UV-protective composition can be in the form of a hair-care product suitable for hair application and/or at least temporary retention thereupon.

[0196] According to a further aspect of some embodiments of the disclosure, there is provided a method of protecting the surface of an inanimate object against ultraviolet radiation, the method comprising applying to the surface of the object an efficacious amount of a UV-protective composition comprising doped or undoped zinc titanate crystals. In some such embodiments, the UV-protective composition can be in the form of a coating product suitable for application to inanimate surfaces and/or at least temporary retention thereupon.

[0197] According to a further aspect of some embodiments of the disclosure, there is provided the use of doped or undoped zinc titanate crystals in the manufacture of a composition for protection of the skin of a subject against ultraviolet radiation.

[0198] According to a further aspect of some embodiments of the disclosure, there is provided the use of doped or undoped zinc titanate crystals in the manufacture of a composition for protection of the hair of a subject against ultraviolet radiation.

[0199] According to a further aspect of some embodiments of the disclosure, there is provided the use of doped or undoped zinc titanate crystals in the manufacture of a composition for protection of surfaces of an object against ultraviolet radiation.

[0200] According to a further aspect of some embodiments of the disclosure, there is provided a method of manufacturing a UV-protective composition, comprising combining doped or undoped zinc titanate crystals, as an ultraviolet-absorbing agent, with other ingredients in proportions and in a manner suitable to make a UV-protective composition as described herein.

[0201] In some embodiments of the composition, use or method disclosed herein, the zinc titanate crystals are present in the composition at a concentration of from about 0.001% (w/w) to about 40% (w/w), such as about 0.1, 1, 2, 3, 4, 5, 10, 15, 20, 25, 30 or 35% (w/w), from about 0.01% (w/w) to about 30% (w/w), from about 0.1% (w/w) to about 20% (w/w) or from about 0.1% (w/w) to about 15% (w/w) of the final composition.

[0202] In some embodiments, the zinc titanate crystals constitute at least 0.01 wt. %, at least 0.1 wt. %, at least 0.5 wt. %, at least 1 wt. %, at least 2 wt. %, at least 3 wt. %, at least 4 wt. %, at least 5 wt. %, at least 10 wt. %, at least 15 wt. %, at least 20 wt. %, at least 25 wt. %, at least 30 wt. %, or at least 35 wt. % of the composition. In some embodiments, the zinc titanate crystals constitute at most 40 wt. %, at most 35 wt. %, at most 30 wt. %, at most 25 wt. %, at most 20 wt. %, at most 15 wt. %, at most 10 wt. %, at most 5 wt. %, at most 4 wt. %, at most 3 wt. %, at most 2 wt. %, at most 1 wt. %, at most 0.5 wt. %, or at most 0.1 wt. % of the composition. As readily appreciated by the skilled person, the concentration of zinc titanate crystals may vary depending on the intended use of the final composition and the minimal and maximal values above provided can only be combined to form a range provided that the minimum concentration is lower than the maximum concentration. For instance, the zinc titanate nanoparticles can be present in the UV-protective composition at a concentration between 0.001% and 40%.

[0203] In some embodiments of the composition, use or method disclosed herein, the doped or undoped zinc titanate crystals are present in the composition as nanoparticles having at least one dimension or a hydrodynamic diameter of up to about 500 nm, such as up to about 10 nm, up to about 20 nm, up to about 30 nm, up to about 40 nm, up to about 50 nm, up to about 60 nm, up to about 70 nm, up to about 80 nm, up to about 90 nm, up to about 100 nm, up to about 110 nm, up to about 120 nm, up to about 130 nm, up to about 140 nm, up to about 150 nm, up to about 160 nm, up to about 170 nm, up to about 180 nm or up to about 190 nm. In some embodiments, the nanoparticles have at least one dimension or a hydrodynamic diameter in the range of from about 10 nm to about 500 nm, from about 20 nm to about 500 nm, from about 10 nm to about 400 nm, from about 10 nm to about 300 nm, from about 10 nm to about 250 nm, from about 10 nm to about 200 nm, from about 20 nm to about 150 nm, from about 20 to about 100 nm, from about 10 nm to about 80 nm, from about 10 to about 70 nm, from about 20 to about 70 nm, or from about 20 to about 60 nm, In some particular embodiments, the nanoparticles have at least one dimension or a hydrodynamic diameter of about 30 nm.

[0204] In some embodiments, the afore-mentioned dimensions or ranges of dimensions or hydrodynamic diameters apply to at least 95%, or at least 97.5% or at least 99% of the population of the nanoparticles.

[0205] In some embodiments, the aforesaid smallest dimension of doped or undoped zinc titanate crystals is estimated based on the hydrodynamic diameter of the particles as measured by DLS techniques. In some embodiments, the population distribution of the particles is expressed in terms of the cumulative particle size distribution, according to the number of particles in a sample. In some embodiments, the population distribution of the particles is expressed in terms of the cumulative particle size distribution of a sample volume of particles.

[0206] In some embodiments of the composition, use or method disclosed herein, the composition is generally devoid and/or generally free of an organic ultraviolet-absorbing agent.

[0207] In some embodiments of the composition, use or method disclosed herein, the composition is generally free of an organic ultraviolet-absorbing agent, that is to say the composition contains less than 5 wt. % organic UV-absorbing agents. In some embodiments the composition contains less than 4 wt. %, less than 3 wt. %, less than 2 wt. % or less than 1 wt. % organic UV-absorbing agents. In some embodiments the composition is largely free of organic ultraviolet-absorbing agents, i.e. the composition contains less than 0.5 wt. % organic UV-absorbing agents. In some embodiments the composition is mostly free of organic UV-absorbing agents, i.e. the composition contains less than 0.1 wt. % organic UV-absorbing agents. In some embodiments the composition is principally free of organic ultraviolet-absorbing agents, i.e. the composition contains less than 0.05 wt. % organic UV-absorbing agents. In some embodiments the composition is fundamentally free of organic UV-absorbing agents, i.e. the composition contains less than 0.01 wt. % organic UV absorbing agents. In some embodiments of the composition, use or method disclosed herein, the composition is generally devoid of organic ultraviolet-absorbing agents, considerably devoid of organic ultraviolet-absorbing agents, significantly devoid of organic ultraviolet-absorbing agents, substantially devoid of organic ultraviolet-absorbing agents, essentially devoid of organic ultraviolet-absorbing agents, substantively devoid of organic ultraviolet-absorbing agents or devoid of organic ultraviolet-absorbing agents.

[0208] In some embodiments of the composition, use or method disclosed herein, the composition is generally devoid and/or generally free of an additional inorganic ultraviolet-absorbing agent.

[0209] In some embodiments of the composition, use or method disclosed herein, the composition is generally free of an additional inorganic ultraviolet-absorbing agent, that is to say the composition contains less than 5 wt. % additional inorganic UV-absorbing agents. In some embodiments the composition contains less than 4 wt. %, less than 3 wt. %, less than 2 wt. % or less than 1 wt. % additional inorganic UV-absorbing agents. In some embodiments the composition is largely free of additional inorganic ultraviolet-absorbing agents, i.e. the composition contains less than 0.5 wt. % additional inorganic UV-absorbing agents. In some embodiments the composition is mostly free of additional inorganic UV-absorbing agents, i.e. the composition contains less than 0.1 wt. % additional UV-absorbing agents. In some embodiments the composition is principally free of additional inorganic ultraviolet-absorbing agents, i.e. the composition contains less than 0.05 wt. % additional UV-absorbing agents. In some embodiments the composition is fundamentally free of additional inorganic UV-absorbing agents, i.e. the composition contains less than 0.01 wt. % additional UV absorbing agents.

[0210] In some embodiments of the composition, use or method disclosed herein, the composition is generally devoid of additional ultraviolet-absorbing agents, considerably devoid of additional ultraviolet-absorbing agents, significantly devoid of additional ultraviolet-absorbing agents, substantially devoid of additional ultraviolet-absorbing agents, essentially additional of organic ultraviolet-absorbing agents, substantively devoid of additional ultraviolet-absorbing agents or devoid of additional ultraviolet-absorbing agents.

[0211] In some embodiments of the composition, use or method disclosed herein, the doped or undoped zinc titanate crystals are the sole ultraviolet-absorbing agent.

[0212] In some embodiments of the composition, use or method disclosed herein, the composition further comprises silver metal particles.

[0213] In some embodiments, the silver metal particles are present in the composition as nanoparticles. In some embodiments, the silver nanoparticles have at least one dimension of up to about 50 nm. In some embodiments, the silver nanoparticles have at least one dimension of up to about 40 nm. In some embodiments, the silver nanoparticles have at least one dimension of up to about 30 nm. In some embodiments, the silver nanoparticles have at least one dimension in the range of from about 10 nm to up to about 50 nm.

[0214] In some embodiments, the afore-mentioned dimensions or ranges of dimensions apply to at least 90%, or at least 95%, or at least 97.5% or at least 99% of the population of the silver nanoparticles.

[0215] In some embodiments, the aforesaid at least one dimension of the silver nanoparticles is estimated based on the hydrodynamic diameter of the particles as measured by DLS techniques. In some embodiments, the population distribution of the particles is expressed in terms of the cumulative particle size distribution according to the number of particles in a sample. In some embodiments, the population distribution of the particles is expressed in terms of the cumulative particle size distribution of a sample volume of particles.

[0216] In some embodiments, the silver nanoparticles are present in the composition at a concentration in the range of from about 0.01% to about 10% (w/w) of the total composition, such as about 0.1, 1, 2, 3, 4, 5, 6, 7, 8, or 9% (w/w) of the total composition. In some embodiments, the silver nanoparticles are present in the composition at a concentration in the range of from about 0.01% to about 5% (w/w), from about 0.05% to about 5% (w/w), or from about 0.1% to about 2% (w/w) of the total composition. In some preferred embodiments, the silver nanoparticles are present in the composition at a concentration of about 1% (w/w) or about 2% (w/w) of the total composition.

[0217] In some embodiments, the silver particles constitute at least 0.01 wt. %, at least 0.1 wt. %, at least 0.5 wt. %, at least 1 wt. %, at least 2 wt. %, at least 3 wt. %, at least 4 wt. %, at least 5 wt. % or at least 10 wt. % of the composition. In some embodiments, the silver particles constitute at most 10 wt. %, at most 5 wt. %, at most 4 wt. %, at most 3 wt. %, at most 2 wt. %, at most 1 wt. %, at most 0.5 wt. %, or at most 0.1 wt. % of the composition.

[0218] In some embodiments of the composition, use or method disclosed herein, the UV-protective composition is a composition for human or animal use, formulated as a topical composition. The topical composition may optionally be provided in a form selected from the group consisting of a cream, an emulsion, a gel, a lotion, a mousse, a paste and a spray. If desired, the topical composition can also be formulated into make-up cosmetics, for example, foundation, blusher, etc.

[0219] In some embodiments, the topical composition further comprises a dermatologically or cosmetically or pharmaceutically acceptable carrier.

[0220] In some embodiments, the topical composition further comprises one or more dermatologically or cosmetically or pharmaceutically acceptable additives or excipients, such as colorants, preservatives, fragrances, humectants, emollients, emulsifiers, waterproofing agents, surfactants, dispersants, thickeners, viscosity modifiers, anti-foaming agents, conditioning agents, antioxidants and the like. Such additives or excipients and the concentrations at which each can effectively accomplish its respective functions, are known to persons skilled in the pertinent art and need not be further detailed.

[0221] In some embodiments, the topical composition is a sunscreen composition.

[0222] In some embodiments, the UV-protective composition is in the form of a coating that can be applied to the surface of an inanimate object. The coating composition may be provided in a form selected from the group consisting of liquid coat, an emulsion, a cream, a gel, a paste, a film, a powder and a spray.

[0223] In another aspect of the present disclosure, there is provided a method for the preparation of the compositions disclosed herein.

[0224] According to a further aspect of some embodiments of the disclosure, there is provided a UV-protective composition as disclosed herein, for use in protecting a subject, such as a human subject or a non-human animal, against an effect of ultraviolet radiation, in some embodiments providing broad-spectrum protection against both ultraviolet A and ultraviolet B radiation.

[0225] In some embodiments, the composition is for use in protecting the skin of a subject, against an effect of ultraviolet radiation, in some embodiments providing broad-spectrum protection against both ultraviolet A and ultraviolet B radiation.

[0226] In some embodiments, the composition is for use in protecting the hair of a subject, such as a human subject, against an effect of ultraviolet radiation, in some embodiments against effects of both ultraviolet A and ultraviolet B radiation.

[0227] The skin may be the skin of the face, of the arms, of the legs, of the neck of the torso, or of any other area of the body that can be exposed to UV radiation.

[0228] In some embodiments, the sunscreen composition as disclosed herein is applied to the skin of the subject prior to or during exposure to UV radiation. In some embodiments, the composition is reapplied intermittently, for example every 10 hours, every 9 hours, every 8 hours, every 7 hours, every 6 hours, every 5 hours, every 4 hours, every 3 hours, every 2 hours or every hour, or any intermediate value, during exposure to UV radiation.

[0229] In some embodiments, the UV-protective composition is for protecting the hair of a subject against ultraviolet radiation and is provided in a form selected from the group consisting of a cream, an emulsion, a gel, a lotion, a mousse, a paste and a spray. In some embodiments, the composition is provided in the form of a shampoo, a conditioner or a hair mask.

[0230] In some embodiments, the composition is formulated to be applied to the hair, or is applied to the hair, for a fixed period of time (such as up to 1 minute, up to 2 minutes, up to 3 minutes, up to 4 minutes or up to 5 minutes, up to 10 minutes, up to 15 minutes, up to 20 minutes, up to 25 minutes or up to 30 minutes) prior to rinsing. In some embodiments, the conditioner or hair mask is formulated for application to the hair, or is applied to the hair without rinsing, such that the conditioner or hair mask remains on the hair.

[0231] According to a further aspect of some embodiments of the disclosure, there is provided a UV-protective composition as disclosed herein, for use in protecting an inanimate object, against an effect of ultraviolet radiation, in some embodiments providing broad-spectrum protection against both ultraviolet A and ultraviolet B radiation. In some embodiments, the UV-protective composition for use in protecting an inanimate object, is capable of protecting the object against a harmful effect of ultraviolet B radiation.

[0232] According to a further aspect of some embodiments of the disclosure, there is provided a method of protecting the skin or the hair of a subject against an effect of ultraviolet radiation, the method comprising applying to the skin and/or the hair of the subject a sunscreen composition comprising a matrix comprising a polymer and a carrier (oil-based or water-based); and particles of doped or undoped zinc titanate crystals, dispersed in the matrix.

[0233] According to a further aspect of some embodiments of the disclosure, there is provided the use of a matrix comprising a polymer and a carrier (oil-based or water-based); and particles of a UV-protective-agent comprising doped or undoped zinc titanate crystals, dispersed in the matrix, in the manufacture of a composition for protection of the skin and/or the hair of a subject against an effect of ultraviolet radiation.

[0234] According to a further aspect of some embodiments of the disclosure, there is provided the use of a matrix comprising a polymer and a carrier (oil-based or water-based); and particles of a UV-protective-agent comprising doped or undoped zinc titanate crystals, dispersed in the matrix, in the manufacture of a composition for protection of exterior surfaces of an inanimate object against an effect of ultraviolet radiation. The exterior surface may comprise the surface of any porous or non-porous material, including, but not limited to glass, fabrics, leathers, woods, cardboards, metals, plastics, rubbers, ceramics and other structural materials.

[0235] The composition for the protection of inanimate objects against UV radiation, can be formulated in any form suitable for application to the surface of the inanimate object on which it is to be used.

EXAMPLES

Materials and Methods

Materials

[0236] The following materials were purchased from Sigma Aldrich, USA:

TABLE-US-00001 ZnO (99.9% pure) CAS 1314-13-2 TiO.sub.2 (99% pure) CAS 13463-67-7 Fe.sub.2O.sub.3 (99% pure) CAS 1309-37-1 Poly Acrylic Acid Sodium base (PAA) CAS 9003-04-7

[0237] The milling media, namely Zirconia beads having an average diameter of 2 mm, were purchased from Pingxiang Lier Ceramic Co., China.

Equipment

[0238] High Resolution Scanning Electron Microscope HSEM/TEM Magellan XHR 400L FE-SEM by Nanolab Technologies, Albany, N.Y., USA.

[0239] High Resolution X-ray diffractometer XRD Rigaku SmartLab with Cu radiation generated at 40 kV and 30 mA (CuKa=1.542 A) as the X-ray source.

[0240] Particle Size Analyser (Light Scattering) Zen 3600 Zetasizer by Malvern Instruments, Malvern, UK.

[0241] Oven, Vulcan-Hart 3-1750 multi-stage programmable box furnace.

[0242] Temperature controllable circulating water bath, BL-30L 9 liter 1/3HP by MRC, Hampstead, London, UK.

[0243] Grinding Mill Model HD-01 Attritor by Union Process, Inc., Akron, Ohio, USA.

[0244] Analytical Balance XSE by Mettler-Toledo International Inc., Columbus, Ohio, USA.

[0245] Mortar Grinder Pulverisette 2 by Fritsch GmbH, Idar-Oberstein, Germany.

[0246] Double Planetary Mixer by Charles Ross & Son Company, Hauppauge, N.Y., USA.

Example 1: Preparation of Zinc Titanate Crystals

[0247] Doped and undoped zinc titanate crystals having the general formula Zn.sub.2Ti.sub.(1-x)Fe.sub.xO.sub.4 wherein x is from 0 to 0.1, were prepared by a solid solution method. The Fe-doped crystals included two molar ratios Ti:Fe 0.975:0.025 and 0.95:0.05 (i.e. wherein x=0.025 or 0.05, respectively).

[0248] In this process, the constituent metal oxides were mixed together in powder form so as to obtain the desired stoichiometric amount. ZnO, having a MW of 81.4084 g/mol and TiO.sub.2 having a MW of 79.87 g/mol were mixed in desired ratio so that the combined ZnTiO.sub.4 powder amounted to about 200 grams. When desired, Fe.sub.2O.sub.3 having a MW of 159.69 g/mol, was added while the amount of titanium dioxide was reduced, the amount of ferric oxide selected to provide the required doping ratio. The powder due to be iron doped amounted likewise to about 200 grams.

[0249] All materials were weighed using an analytical scale (Mettler Toledo, USA).

[0250] The powders of the constituent reagents were then mixed together for about 10 minutes at 70 rpm at ambient temperature in a Pulverisette 2 mortar grinder (Fritsch, Germany), so as to obtain homogeneously mixed presintered powders (to be doped or undoped, as appropriate). The mixed powders were transferred to a 500 ml alumina crucible and sintered or calcined by heating in a ceramic oven at a rate of 40 C. per minute until the temperature reached 1000 C., and maintained at this temperature for 24 hours, allowing for the formation of the desired doped or undoped zinc titanate crystals. It is believed that under such conditions, the iron atoms can substitute the titanium atoms in the orthorhombic structure of the zinc titanate crystals to provide doping without breaking the crystallographic symmetry.

[0251] After 24 hours at 1000 C., the samples were allowed to cool down to ambient temperature (circa 23 C.), at which time they were again ground to homogeneous powder for about 10 minutes at 70 rpm by the Pulverisette 2 mortar grinder.

[0252] Powders of doped or undoped zinc titanate crystals prepared as above-described were either used or analyzed as is in coarse form, or further size-reduced and used and analyzed in the form of nanoparticles, as described in following examples. It is to be understood that the coarse material was manually ground with a mortar and pestle to disassociate any gross agglomerate that may be present in the resulting powders, so as to eliminate coarse lumps of particles. In bulk size, the zinc titanate compounds displayed a white shade if undoped and a pale reddish tint if doped, the color intensity depending on the degree of iron doping.

Example 2: Absorbance Determination in Powder

[0253] Absorbance correlation of coarse powders over the wavelength range of 200-800 nm was calculated using a Cary 300 UV-Vis spectrophotometer with an integrated sphere detector (Agilent Technologies, Santa Clara, Calif., USA).

[0254] Briefly, the absorbance of the samples was qualitatively estimated by subtracting the amount of light reflected from the powder sample, gathered by the integrated sphere detector of the spectrophotometer, from the amount of light reflected from a white surface (which reflects all incident light). Since the extent of penetration of the light into the samples and the extent of scattering of the sample is unknown, this measurement provides an absorbance profile of the sample rather than a true quantitative measurement.

[0255] Results, showing correlation to absorbance as a function of wavelength, determined by diffuse reflection measurement gathered by the integrated sphere method, are presented in FIG. 1.

[0256] FIG. 1 shows the absorbance of doped (Ti:Fe 0.975:0.025 or 0.95:0.05) or undoped (x=0) zinc titanate crystals, as obtained following the sintering method of Example 1 as compared to undoped zinc oxide or to an undoped presintered mixture of zinc oxide and titanium dioxide in appropriate stoichiometric amounts.

[0257] As seen in FIG. 1, undoped zinc oxide exhibits a very sharp decrease in UV absorbance in the range of from about 380 nm to about 400 nm. The presintered mixture of zinc oxide and titanium dioxide corresponding to the undoped zinc titanate displayed an absorbance pattern similar to zinc oxide alone with a sharp decrease at 380 nm. Undoped zinc titanate, differing from its presintered version, has a relatively constant UV absorbance from 200 nm to about 310 nm, with a gradual decrease in the range of from about 310 nm to about 380 nm, followed by a sharper decrease at about 380 nm, but providing higher absorbance levels than undoped zinc oxide (or its presintered mix) in the range of from about 380 nm to about 400 nm. Crystals of doped zinc titanate (Ti:Fe 0.975:0.025 or 0.95:0.05) exhibited significantly higher UV absorbance than either undoped zinc oxide or undoped zinc titanate crystals in the 380 nm to 400 nm range, with absorbance of Ti:Fe 0.95:0.05 doped zinc titanate crystals being higher than that of the Ti:Fe 0.975:0.025 doped equivalent.

Example 3: Crystal Structure Determination

[0258] The crystal structure of undoped or doped (Ti:Fe 0.975:0.025) zinc titanate, as above-prepared, was determined by powder XRD using Rigaku TTRAX-III X-ray diffractometer. The X-ray source (Cu anode) was operated at a voltage of 40 kV and a current of 30 mA on packed powder samples. Data were collected in continuous detector scan mode at a step size of 0.02/step. Diffractograms were collected over the 20 range of 10 to 80. The results are shown in FIG. 2, wherein the pattern of undoped zinc titanate crystals is displayed as a continuous line, whereas that of the doped equivalent is shown as a dotted line. For both materials, a predominant peak is seen around 20 of about 35 and doping did not significantly affect the crystalline peaks characteristic of the zinc titanate crystals, the main ones being indicated on the figure.

Example 4: Preparation of Nanoparticles

[0259] Nanoparticles of doped (Ti:Fe 0.975:0.025 or 0.95:0.05) or undoped zinc titanate crystals were prepared from the ground sintered samples obtained in Example 1. Nanoparticles of zinc oxide were prepared for comparison from its stock powder. Generally, all such samples or stock powders contained particles having a size greater than about 5 micrometer (m) and may be referred hereinafter as the coarse materials. The coarse powders were milled in an Attritor grinding mill (HD-01 by Union Process) using a batch size of 200 g with solid loading 10% (20 g) as follows.

[0260] All materials were weighed using an analytical scale (XSE by Mettler Toledo). 20 g of PAA dispersant was weighed and dispersed in about 100 ml of deionized water. 20 g of coarse powder was weighed and introduced into the dispersant-containing liquid to provide a dispersant to inorganic material ratio of 1:1 yielding a slurry of the inorganic material. Water was added to complete batch size to 200 g, the solids constituting about 10 wt. % of the sample.

[0261] The aqueous slurry of inorganic material was then placed in a zirconia pot with 2300 g of 2 mm diameter zirconia grinding beads. The pot was placed in the grinding mill, and the grinding mill activated at 700 RPM for about 75 hours at 25 C.

[0262] The hydrodynamic diameter of the nanoparticles obtained by this method was determined by Dynamic Light Scattering, using a Zen 3600 Zetasizer from Malvern Instruments Ltd. (Malvern, UK). A sample of the milled nanoparticles was further diluted in deionized water to form a suspension having a solid concentration of about 0.5 wt. %.

[0263] Representative results, showing the percentage of number of doped (Ti:Fe 0.975:0.025 and 0.95:0.05) and undoped zinc titanate crystal particles, as well as zinc oxide as reference, having hydrodynamic diameters in the range of 10-1000 nm are presented in FIG. 3.

[0264] FIG. 3 shows that the majority of doped and undoped zinc titanate crystal particles had hydrodynamic diameters in the size range of from about 20 nm and up to about 100 nm. The predominant peaks of doped (Ti:Fe 0.975:0.025 and 0.95:0.05) and undoped zinc titanate crystals were each at around 40 nm. Results of the particle size distribution of the nanoparticles prepared as herein described, namely the maximum hydrodynamic diameter of a percentage of the population, are provided in the Table 1 below, in terms of percent of number of particles. Information on zinc oxide is provided for reference.

TABLE-US-00002 TABLE 1 Max. Hydrodynamic Diameter (nm) Material 10% 50.0% 90.0% 95.0% 97.5% 99.0% Zinc oxide 20.2 26.4 36.2 39.5 47.7 62.2 Zn.sub.2TiFeO.sub.4 29.8 40.4 60.5 70.7 83.5 110 (Fe:Ti 0.025:0.975) Zn.sub.2TiFeO.sub.4 31.9 42.4 62.2 71.3 82.4 104 (Fe:Ti 0.05:0.95) Zn.sub.2TiO.sub.4 ref 29.2 38 53.7 60.7 70.2 103

[0265] As can be seen from the above table, at least 97.5% of the nanoparticles of doped or undoped zinc titanate crystals as prepared and size-reduced according to the present teachings have a dimension of at most 100 nm.

Example 5: Absorbance of Suspended Crystal Nanoparticles

[0266] Absorbance of the nanoparticles of doped and undoped zinc titanate crystals prepared according to Example 4 was measured over the wavelength range of 200-800 nm using a Cary 300 UV-Vis spectrophotometer with quartz cuvette (10 mm light pathway). The samples were diluted in the vehicle in which the inorganic materials were milled (namely with deionized water containing 10 wt. % PAA) to provide any desired predetermined solid concentration (e.g., 0.25 wt. %, 0.5 wt. %, and 1.0 wt. %,). Results are presented in FIGS. 4 and 5. For convenience, it should be recalled that an absorbance value of 1 indicates a UV blocking of at least about 90%, whereas an absorbance value of 2 indicates blocking of up to 99% of the radiation.

[0267] In FIG. 4, the absorbance in the 200-800 nm wavelength range is shown for nanoparticles of undoped zinc titanate crystals nanoparticles and for 0.975:0.025 Ti:Fe and 0.95:0.05 Ti:Fe doped zinc titanate nanoparticles at three concentrations of 0.25 wt. %, 0.5 wt. % and 1 wt. %.

[0268] As can be seen in the figure, doped and undoped zinc titanate crystals displayed significant absorbance up to at least 360 nm at all concentrations tested, with all materials except for 0.25 wt. % undoped zinc titanate crystals displaying substantial absorbance at 400 nm. Absorbance across the tested range was shown to increase with increasing zinc titanate concentration and degree of doping at the concentrations and Fe:Ti ratios tested.

[0269] FIG. 5 shows absorbance of undoped zinc titanate crystals, doped (Ti:Fe 0.975:0.025 or 0.95:0.05) zinc titanate crystals, and zinc oxide as reference, each at a concentration of 0.5 wt. %. As shown in the figure, zinc oxide displayed an insignificant level of absorbance at wavelengths of higher than about 380 nm, displaying at 400 nm an absorbance of about 0.26. For comparison, undoped zinc titanate crystals displayed an absorbance of about 1.3 at 400 nm, while the doped variants each displayed absorbance of at least 2.1 at 400 nm. A commercial sunscreen composition (Skingard sunscreen composition by Careline (Pharmagis, Israel)) based on organic tUV blockers was included for convenient comparison.

Example 6: Scanning Electron Microscope Studies

[0270] The doped and undoped zinc titanate crystal nanoparticles were also studied by High Resolution Scanning Electron Microscopy (HR-SEM) using Magellan 400 HSEM/TEM by Nanolab Technologies.

[0271] FIG. 6A shows an image for undoped zinc titanate crystal nanoparticles, wherein FIG. 6B shows an image for Fe-doped zinc titanate crystal nanoparticles (Ti:Fe 0.95:0.05).

[0272] As shown in the figures, doped and undoped zinc titanate crystal particles having spheroid shape with diameters of less than about 100 nm, mainly less than about 70 nm, were obtained. Larger clusters are deemed non-representative, resulting from agglomeration of individual particles upon preparation of the sample for HR-SEM analysis, the drying out of the liquid carrier being known to cause such artificial outcome. The good correlation between the diameters of the particles when measured in suspension and in dried form confirm the suitability of the above-described method to prepare nanoparticles having at least one dimension (e.g. a diameter) of up to about 100 nm.

Example 7: Determination of Critical Wavelength

[0273] Based on the absorbance spectra determined according to previous Examples, critical wavelength was calculated for undoped zinc titanate crystals and for two Fe-doped variants (Ti:Fe 0.975:0.025 and 0.95:0.05), all measured at nanoparticle concentration of 0.25 wt. %, 0.5 wt. % and 1 wt. %. A suspension of nanoparticles of Zinc Oxide at 0.5 wt. % served as control.

[0274] Briefly, in order to quantify the breadth of UV protection, the absorbance of the sunscreen composition was integrated from 290 nm to 400 nm the sum reached defining 100% of the total absorbance of the sunscreen in the UV region. The wavelength at which the summed absorbance reaches 90% absorbance was determined as the critical wavelength which provided a measure of the breadth of sunscreen protection.

[0275] The critical wavelength .sub.c was defined according to the following equation:

[00001]${}_{290}^{{}_c}.Math.\mathrm{Ig}\left[1/T\left(\right)\right].Math.d.Math..Math.=0.9.Math.{}_{290}^{400}.Math.\mathrm{Ig}\left[1/T\left(\right)\right].Math.d.Math..Math.$

wherein:

[0276] .sub.c is the critical wavelength;

[0277] T() is the mean transmittance for each wavelength; and

[0278] D is the wavelength interval between measurements.

[0279] Critical wavelengths as calculated are presented in Table 2 below.

TABLE-US-00003 TABLE 2 Critical Wavelength (nm) Inorganic Material 0.25 wt. % 0.5 wt. % 1 wt. % Zinc titanate undoped 372 377 381 Fe-doped zinc titanate 373 379 383 Ti:Fe 0.975:0.025 Fe-doped zinc titanate 373 380 385 Ti:Fe 0.95:0.05 ZnO Control 362

[0280] As can be seen from the above table, according to the Critical Wavelength Method, undoped and Fe-doped zinc titanate crystal nanoparticles can be classified as providing broad spectrum protection (i.e. having a critical wavelength of 370 nm or more) at concentrations of as low as 0.25 wt. %. Such results are superior to those achieved by the control suspension consisting of ZnO nanoparticles having similar particle size distribution which even when tested at the concentration of 0.5 wt. % displayed a narrower spectrum protection, its critical wavelength being of only 362 nm.

Example 8: Preparation of Composition Comprising Polymer Matrix and Zinc Titanate

[0281] The nanoparticles of doped or undoped zinc titanate crystals prepared according to the present teachings and above-examples can be further processed so as to be embedded or immobilized within a polymer matrix. Suitable methods and polymers are described by the present Applicant in PCT Publication No. WO 2017/013633, incorporated herein by reference in its entirety as if fully set forth herein. In particular, Example 2 of the reference provides for the preparation of a polymer matrix, whereas Example 3 teaches how to blend such matrix with nanoparticles, and how to further process such mixture so as to obtain polymer embedded particles. A non-limiting example of a suitable polymer matrix comprises Nucrel (methylene-methacrylic acid copolymer) of DuPont, USA, dispersed in Isopar (paraffinic oil) of ExxonMobil Chemical Company, USA.

Example 9: Preparation of Composition Comprising Zinc Titanate in Wood Lacquer

[0282] Doped and undoped zinc titanate crystal nanoparticles are diluted in a clear wood lacquer (Tambour Clear Glossy Lacquer for Wood No. 8, Cat. No. 149-001) to a particle concentration of 1% by weight of the total lacquer composition. The resulting mixtures are sonicated for 30 seconds using a Misonix Sonicator tip (Misonix, Inc.) at amplitude 100, 15 W. The sonicated lacquer dispersions are applied upon a microscopic glass slide at an initial thickness of about 100 m (using 100 am thick spacers and a leveling rod). The lacquer coated slides are left to dry for at least 12 hours at ambient temperature (circa 23 C.) resulting in a dried layer of sample of about 5 m. The lacquer devoid of added nanoparticles serves as control. Absorbance of the dried layers of lacquer over the wavelength range of 200-800 nm is assessed using a Cary 300 UV-Vis spectrophotometer.

[0283] Although the disclosure has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, it is intended to embrace all such alternatives, modifications and variations that fall within the scope of the appended claims.

[0284] Citation or identification of any reference in this application shall not be construed as an admission that such reference is available as prior art to the disclosure.