UV-protective compositions and their use

Abstract

Disclosed are compositions comprising inorganic UV-absorbing agents and the use of such compositions, in particular for protecting a subject or the surface of an inanimate object against a harmful effect of ultraviolet radiation.

Claims

1. A UV-protective composition comprising nanoparticles of at least one inorganic UV-absorbing agent selected from the group consisting of (i) barium titanate (BaTiO3) and (ii) bismuth vanadate (BiVO4); and a dispersant associated with said nanoparticles, wherein a weight ratio of said dispersant to said inorganic UV-absorbing agent is within a range of 1:2.5 to 2.5:1, and wherein said dispersant includes a neutralized polyacrylic acid; wherein said inorganic UV-absorbing agent has a median particle diameter, on a particle number basis (DN50), of at most 80 nm; wherein a critical wavelength of said inorganic UV-absorbing agent is within a range of 330 to 400 nm; and wherein a UV absorbance selectivity is defined by
RAUC=100%.Math.(AUC.sub.280-400)/(AUC.sub.280-700) wherein: RAUC is said UV absorbance selectivity; AUC.sub.280-400 is a UV-absorbance by the composition or by said inorganic UV-absorbing agent, over a wavelength range of 280 nm to 400 nm; and AUC.sub.280-700 is a UV-absorbance by the composition or by said inorganic UV-absorbing agent, over a wavelength range of 280 nm to 700 nm; and wherein said UV absorbance selectivity of said inorganic UV-absorbing agent is at least 60%.

2. The UV-protective composition of claim 1, wherein said UV absorbance selectivity of said inorganic UV-absorbing agent is at least 70%.

3. The UV-protective composition of claim 1, wherein said UV absorbance selectivity of said inorganic UV-absorbing agent is at least 75%.

4. The UV-protective composition of claim 1, wherein said inorganic UV-absorbing agent comprises said barium titanate, and wherein said UV absorbance selectivity of said barium titanate is at least 80%.

5. The UV-protective composition of claim 1, wherein a polydispersity index (PDI) of said inorganic UV-absorbing agent is within a range of 0.13 to 0.30.

6. The UV-protective composition of claim 1, wherein said D.sub.N50 is within a range of 15 nm to 70 nm.

7. The UV-protective composition of claim 1, wherein said D.sub.N50 is within a range of 15 nm to 60 nm.

8. The UV-protective composition of claim 5, wherein said D.sub.N50 is within a range of 25 nm to 50 nm.

9. The UV-protective composition of claim 1, wherein said inorganic UV-absorbing agent comprises said bismuth vanadate, and wherein said UV absorbance selectivity of said bismuth vanadate is at least 65%.

10. The UV-protective composition of claim 1, wherein said inorganic UV-absorbing agent comprises said bismuth vanadate, and wherein said UV absorbance selectivity of said bismuth vanadate is at least 70%.

11. The UV-protective composition of claim 1, wherein said weight ratio of said dispersant to said inorganic UV-absorbing agent is within a range of 1:2.0 to 2.0:1.

12. The UV-protective composition of claim 1, wherein at least a portion of said dispersant at least partially envelops said inorganic UV-absorbing agent.

13. The UV-protective composition of claim 1, wherein said critical wavelength of said inorganic UV-absorbing agent is at least 345 nm.

14. The UV-protective composition of claim 1, wherein said critical wavelength of said inorganic UV-absorbing agent is at least 360 nm.

15. A UV-protective composition comprising nanoparticles of at least one inorganic UV-absorbing agent selected from the group consisting of (i) barium titanate (BaTiO3) and (ii) bismuth vanadate (BiVO4), and a dispersant associated with said nanoparticles, wherein a weight ratio of said dispersant to said inorganic UV-absorbing agent is within a range of 1:2.5 to 2.5:1, and wherein said dispersant includes a neutralized polyacrylic acid; wherein said inorganic UV-absorbing agent has a median particle diameter, on a particle number basis (DN50), of at most 80 nm; wherein a critical wavelength of said inorganic UV-absorbing agent is within a range of 330 to 400 nm; wherein an area under the curve formed by UV-absorption of a particular one of said inorganic UV-absorbing agent, as a function of wavelength in a range of 280 nm to 400 nm (AUC.sub.280-400), is at least 75% of the AUC formed by said particular one of said inorganic UV-absorbing agent, at the same concentration, in a range of 280 nm to 700 nm (AUC.sub.280-700), and wherein an overall polydispersity index (PDI) of said inorganic UV-absorbing agent is within a range of 0.13 to 0.30.

16. The UV-protective composition of claim 15, wherein a weight ratio of said dispersant to said inorganic UV-absorbing agent is within a range of 1:2 to 2:1.

17. A UV-protective composition comprising nanoparticles of an inorganic UV-absorbing agent selected from the group consisting of (i) barium titanate (BaTiO3) and (ii) bismuth vanadate (BiVO4), and a dispersant associated with said nanoparticles, wherein a weight ratio of said dispersant to said inorganic UV-absorbing agent is within a range of 1:2.5 to 2.5:1, and wherein said dispersant includes a neutralized polyacrylic acid; wherein said inorganic UV-absorbing agent has a median particle diameter, on a particle number basis (DN.sub.50), of at most 80 nm; and wherein a critical wavelength of said inorganic UV-absorbing agent is within a range of 330 to 400 nm.

18. The UV-protective composition of claim 17, wherein said weight ratio of said dispersant to said inorganic UV-absorbing agent is within a range of 1:2.0 to 2.0:1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) 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 invention 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 invention. For the sake of clarity, some objects depicted in the figures are not to scale.

(2) In the Figures:

(3) FIG. 1A is a correlation to a UV absorbance spectrum of barium titanate powder as compared to absorbance by titanium dioxide powder, as determined by the integrated sphere method;

(4) FIG. 1B is a correlation to a UV absorbance spectrum of bismuth oxide powder as compared to absorbance by zinc oxide powder, as determined by the integrated sphere method;

(5) FIG. 1C is a correlation to a UV absorbance spectrum of bismuth vanadate powder as compared to absorbance by zinc oxide powder, as determined by the integrated sphere method;

(6) FIG. 1D-A is a correlation to a UV absorbance spectrum of zinc oxide powder doped with either 5% manganese or 5% copper on a molar basis, as determined by the integrated sphere method, undoped zinc oxide reference being included for comparative purposes;

(7) FIG. 1D-B is a correlation to a UV absorbance spectrum of zinc oxide powder doped with different molar percentage concentrations of copper, as determined by the integrated sphere method, undoped zinc oxide reference being included for comparative purposes;

(8) FIG. 2A is a line graph showing the distribution of barium titanate nanoparticle sizes used in implementing a specific embodiment of the invention described herein, titanium dioxide reference being included for comparative purposes;

(9) FIG. 2B is a line graph showing the distribution of bismuth oxide nanoparticle sizes used in implementing a specific embodiment of the invention described herein, zinc oxide reference being included for comparative purposes;

(10) FIG. 2C is a line graph showing the distribution of bismuth vanadate nanoparticle sizes used in implementing a specific embodiment of the invention described herein, zinc oxide reference being included for comparative purposes;

(11) FIG. 2D is a line graph showing the distribution of copper-doped and manganese-doped zinc oxide nanoparticle sizes used in implementing a specific embodiment of the invention described herein, undoped zinc oxide reference being included for comparative purposes;

(12) FIG. 3A-A is a High resolution Scanning Electron Microscopy (HRSEM) image of barium titanate nanoparticles used in implementing a specific embodiment of the invention described herein;

(13) FIG. 3A-B is a HRSEM image of a titanium dioxide reference for comparative purposes;

(14) FIGS. 3B-A and 3B-B are different magnifications of High resolution Scanning Electron Microscopy (HRSEM) images of bismuth oxide nanoparticles used in implementing a specific embodiment of the invention described herein;

(15) FIG. 3C is a High resolution Scanning Electron Microscopy (HRSEM) image of bismuth vanadate nanoparticles used in implementing a specific embodiment of the invention described herein;

(16) FIGS. 3D-A, 3D-B, 3D-C and 3D-D are different magnifications of High resolution Scanning Electron Microscopy (HRSEM) images of copper-doped zinc oxide nanoparticles used in implementing a specific embodiment of the invention described herein;

(17) FIG. 4A shows UV absorbance spectra for three different concentrations of barium titanate nanoparticles according to the present teachings, titanium dioxide reference being included for comparative purposes;

(18) FIG. 4B shows UV absorbance spectra for three different concentrations of bismuth oxide nanoparticles according to the present teachings;

(19) FIG. 4C shows UV absorbance spectra for three different concentrations of bismuth vanadate nanoparticles according to the present teachings;

(20) FIG. 4D-A shows UV absorbance spectra of different concentrations of manganese-doped zinc oxide, undoped zinc oxide reference being included for comparative purposes;

(21) FIG. 4D-B shows UV absorbance spectra of different concentrations of copper-doped zinc oxide, undoped zinc oxide reference at each concentration being included for comparative purposes;

(22) FIG. 4D-C is a close-up view over a sub-range of what is shown in FIG. 4D-B;

(23) FIG. 5A is a UV absorbance spectrum of a suspension according to an embodiment of the invention comprising 9% bismuth oxide as compared to that of a sunscreen composition comprising 9% undoped zinc oxide and a commercially-available sunscreen composition comprising organic UV-absorbing agents as references;

(24) FIG. 5B is a UV absorbance spectrum of a suspension according to an embodiment of the invention comprising 2% bismuth vanadate as compared to that of a sunscreen composition comprising 2% undoped zinc oxide and a commercially-available sunscreen composition comprising organic UV-absorbing agents as references;

(25) FIG. 5C is a UV absorbance spectrum of a suspension according to an embodiment of the invention comprising 2% (w/w) copper-doped or manganese-doped (5% molar percentage) zinc oxide as compared to that of a sunscreen composition comprising 2% (w/w) undoped zinc oxide and a commercially-available sunscreen composition comprising organic UV-absorbing agents as references;

(26) FIG. 6 shows UV absorbance spectra for several embodiments of a sunscreen composition according to embodiments of the invention, each embodiment comprising 1% bismuth oxide with a different concentration of silver nanoparticles, references being included for comparative purposes;

(27) FIG. 7 is a line graph showing the distribution of bismuth oxide and bismuth vanadate nanoparticle sizes used in implementing a specific embodiment of the invention described herein;

(28) FIG. 8 is a UV absorbance spectrum of lacquer compositions according to embodiments the invention containing either bismuth oxide or bismuth vanadate, as well a lacquer composition without bismuth oxide or bismuth vanadate as a reference for comparative purposes; and

(29) FIG. 9 provides UV absorbance spectra for a composition based on barium titanate, in which the UV absorbance spectra for composition samples are characterized as a function of the milling time of the samples.

DETAILED DESCRIPTION OF SOME EMBODIMENTS

(30) As noted, above, there is provided, in accordance with an embodiment of the invention, a UV-protective composition which comprises particles of at least one inorganic UV-absorbing agent selected from the group consisting of (i) barium titanate (BaTiO.sub.3), (ii) bismuth oxide (Bi.sub.2O.sub.3), (iii) bismuth vanadate (BiVO.sub.4), and (iv) doped zinc oxide (ZnO).

(31) It is known that in addition to absorbing ultraviolet radiation, UV-absorbing agents, including the inorganic UV-absorbing agents mentioned above, when present as large particles (e.g., dimensions in each of the X-, Y- and Z-directions being greater than 100 nanometers (nm), resulting for instance in a hydrodynamic diameter of more than 100 nm as measured by DLS) may also effectively absorb radiation having wavelengths of greater than about 400 nm. Accordingly, compositions comprising such large particles of such UV-absorbing agents may provide protection against ultraviolet radiation having wavelengths up to at least 400 nm. However, in the case in which the UV-protective composition is a sunscreen composition which comprises at least one of the aforementioned inorganic UV-absorbing agents, but which sunscreen composition also contains particles that absorb light at wavelengths in the range of 400-800 nm, the behavior of the sunscreen composition is similar to some commercially-available sunscreen compositions comprising organic UV radiation absorbing agents and/or complex combinations of UV-protective agents, i.e. the sunscreen will be visible on the end-user because of the absorption in the visible range.

(32) It has surprisingly been found by the present Inventors that, although reduction of particle size of known inorganic UV-absorbing agents to nanometric dimensions (e.g., below 1 micrometer (m), typically below 100 nm) is known to significantly reduce the maximum wavelength of light, including UV light, which is effectively absorbed by the particles, compositions as described herein, such as sunscreen compositions, which contain one or more of the aforesaid inorganic UV-absorbing agents, milled to nanoparticle size, still provide substantial absorption of UV radiation of wavelength from 280 nm (or shorter wavelengths) 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.

(33) Thus, in some embodiments, compositions disclosed herein, such as sunscreen compositions, comprise particles of one or more of said inorganic UV-absorbing agents, wherein at least 50% of the particles are nanoparticles, in terms of at least one of number of particles and volume of particles. In some embodiments, at least 90% or at least 95% or at least 97.5% or even at least 99% of the particles, in terms of at least one of number of particles and volume of particles, are nanoparticles.

(34) In some embodiments, the at least one dimension of the inorganic UV-absorbing nanoparticles is expressed in terms of the hydrodynamic diameter as measured by DLS.

(35) 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).

(36) 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.

(37) In some embodiments, the inorganic UV-absorbing agent nanoparticles in the composition are substantially invisible to the human eye, in particular when applied to the skin or hair of a subject or when applied to an inanimate surface, due to their small size.

(38) In some embodiments, the inorganic UV-absorbing agent nanoparticles 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.

(39) According to an aspect of some embodiments of the invention, there is provided a sunscreen composition comprising a UV-absorbing agent selected from the group consisting of (i) barium titanate (BaTiO.sub.3), (ii) bismuth oxide (Bi.sub.2O.sub.3), (iii) bismuth vanadate (BiVO.sub.4), and (iv) doped zinc oxide (ZnO), as well as mixtures thereof.

(40) According to a further aspect of some embodiments of the invention, there is provided a sunscreen composition comprising at least one of the aforementioned inorganic UV-absorbing agents, 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.

(41) According to a further aspect of some embodiments of the invention, there is provided a sunscreen composition comprising at least one of the aforementioned inorganic UV-absorbing agents, 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.

(42) According to a further aspect of some embodiments of the invention, 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 a sunscreen composition comprising at least one of the aforementioned inorganic UV-absorbing agents. In some embodiments, the sunscreen composition is in a form selected from the group consisting of an aerosol, a cream, an emulsion, a gel, a lotion, a mousse, a paste and a spray. There is also provided a method of protecting the hair of a subject against ultraviolet radiation, the method comprising applying to the hair of the subject a hair-protective composition comprising at least one of the aforementioned inorganic UV-absorbing agents. In some embodiments, the hair protective composition is in a form of a shampoo or conditioner. There is also provided a method of protecting the surface of an inanimate object against ultraviolet radiation, the method comprising applying to the surface of the inanimate object a UV-protective composition comprising at least one of the aforementioned inorganic UV-absorbing agents. For methods of protecting the surface of inanimate objects, in addition to being in one of the forms mentioned above, the UV-protective composition may be in the form of a liquid, and applied, for example, as coating. Methods of applying UV-protective compositions to objects or sunscreen compositions to subjects or surfaces are known and need not be detailed herein.

(43) According to a further aspect of some embodiments of the invention, there is provided the use of at least one of the aforementioned inorganic UV-absorbing agents, in the manufacture of a composition for protection of the skin of a subject against ultraviolet radiation.

(44) According to a further aspect of some embodiments of the invention, there is provided the use of at least one of the aforementioned inorganic UV-absorbing agents in the manufacture of a composition for protection of the hair of a subject against ultraviolet radiation.

(45) Additionally, the aforementioned inorganic UV-absorbing agents can be used in the manufacture of a composition for protection of the surface of an object against ultraviolet radiation.

(46) According to a further aspect of some embodiments of the invention, there is provided a method of manufacturing UV-protective composition, comprising combining an inorganic UV-absorbing agent as described herein with other ingredients in proportions and in a manner suitable to make a UV-protective composition as described herein. In some embodiments, the UV-protective composition is formulated as a sunscreen composition for application to human skin. In some embodiments, the composition is formulated as a composition for application to hair, such as a shampoo or conditioner. In some embodiments, the composition is formulated for application to an inanimate surface, such as a varnish. Methods for formulating such compositions, e.g. sunscreens, shampoos, conditioners, and varnishes, are well-known in the art.

(47) In some embodiments of the compositions, use or methods disclosed herein, the inorganic UV-absorbing agent or combination thereof is present in the composition at a concentration of from about 0.001% (w/w) to about 40% (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 even from about 0.1% (w/w) to about 15% (w/w) of the final composition. In some embodiments, the inorganic UV-absorbing agent constitutes 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. %, at least 35 wt. %, or at least 40 wt. %. of the composition. In some embodiments, the inorganic UV-absorbing agent constitutes 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. %, at most 0.1 wt. % or at most 0.01 wt. % of the composition.

(48) In some embodiments of the composition, use or method disclosed herein, the inorganic UV-absorbing agent or combination thereof is present in the composition as nanoparticles having at least one dimension of up to about 100 nm. In some embodiments, the nanoparticles have at least one dimension in the range of 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 of about 30 nm.

(49) In some embodiments, the aforementioned dimensions or ranges of dimensions apply to at least 50%, at least 90%, at least 95%, at least 97.5% or at least 99% of the population of the nanoparticles on a volume basis. In some embodiments, the aforementioned dimensions or ranges of dimensions apply to at least 50%, at least 90%, at least 95%, or at least 97.5% or at least 99% of the population of the nanoparticles on a number basis.

(50) In some embodiments, the aforesaid smallest dimension of the inorganic UV-absorbing agent nanoparticles, is estimated based on the hydrodynamic diameter of the particles as measured by DLS. 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.

(51) In some embodiments of the composition, use or method disclosed herein, the composition contains less than 5 wt. % organic UV-absorbing agents. In some embodiments the composition contains less than 4 wt. %, 3 wt. %, 2 wt. % or 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.

(52) In some embodiments of the composition, use or method disclosed herein, the composition contains less than 10 wt. % additional UV-absorbing agents. In some embodiments the composition contains less than 5 wt. %, less than 4 wt. %, less than 3 wt. %, less than 2 wt. % or less than 1 wt. % additional UV-absorbing agents. In some embodiments the composition is largely free of additional ultraviolet-absorbing agents, i.e. the composition contains less than 0.5 wt. % additional UV-absorbing agents. In some embodiments the composition is mostly free of additional 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 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 UV-absorbing agents, i.e. the composition contains less than 0.01 wt. % additional UV absorbing agents. 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 additional of organic ultraviolet-absorbing agents or devoid of additional ultraviolet-absorbing agents.

(53) In some embodiments of the composition, use or method disclosed herein, the inorganic UV-absorbing agent or mixture of such agents is the sole ultraviolet-absorbing agent in the composition.

(54) In some embodiments of the composition, use or method disclosed herein, the composition further comprises silver metal particles.

(55) 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.

(56) In some embodiments, the aforementioned dimensions or ranges of dimensions apply to at least 50%, at least 90%, at least 95%, at least 97.5% or at least 99% of the population of the silver nanoparticles on a volume basis. In some embodiments, the aforementioned dimensions or ranges of dimensions apply to at least 50%, at least 90%, at least 95%, at least 97.5% or at least 99% of the population of the silver nanoparticles on a number basis.

(57) 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. 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.

(58) 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. 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. 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.

(59) In some embodiments of the composition, use or method disclosed herein, the 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 composition can also be formulated into make-up cosmetics, for example, foundation, blusher, etc.

(60) In some embodiments, the topical composition further comprises a dermatologically or cosmetically or pharmaceutically acceptable carrier.

(61) 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.

(62) In some embodiments, the topical composition is a sunscreen composition.

(63) In some embodiments, the subject is a human subject.

(64) The skin to which the composition is formulated to be applied, or to which the composition is applied, 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.

(65) In some embodiments, a 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 during exposure to UV radiation.

(66) In some embodiments, the 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.

(67) 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, up to 5 minutes, up to 10 minutes, up to 15 minutes, up to 20 minutes, up to 25 minutes or even 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.

(68) In some embodiments of the composition, use or method disclosed herein, the composition is a composition for the protection of inanimate objects against UV radiation, formulated in any form suitable for the surface of surfaces to which the composition is to be applied. The composition can be suitable for porous or non-porous surfaces, and for instance, in the form of an aerosol, a cream, an emulsion, a gel, a liquid coat, a mousse, a paste and a spray. It can be applied during the manufacturing of the object and/or periodically thereafter.

EXAMPLES

(69) Materials and Methods

(70) Materials:

(71) All materials, unless otherwise indicated, were purchased from Sigma Aldrich as follows:

(72) Barium titanate at purity of 99% (CAS 12047-27-7)

(73) Bismuth oxide at purity of 99% (CAS 1304-76-3)

(74) Bismuth vanadate at purity of 99% (CAS 14059-33-7, Alfa Aesar)

(75) Zinc oxide at purity of 99.9% (CAS 1314-13-2)

(76) Titanium dioxide at purity of 99.9% (CAS 13463-67-7)

(77) Copper oxide at purity of 99.0% (CAS 1317-38-0)

(78) Manganese oxide at purity of 99.0% (CAS 1313-13-9)

(79) Poly Acrylic Acid Sodium base (PAA) (CAS 9003-04-7)

(80) Silver particles 10 nm (Sigma Aldrich Cat. No.730785)

Example 1: Absorbance of UV Radiation by Powders of Barium Titanate, Bismuth Oxide, Bismuth Vanadate, and 5% Doped Zinc Oxide

(81) Absorbance correlation of dry powders of barium titanate, bismuth oxide, bismuth vanadate, and 5% doped zinc oxide powder 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), with dry titanium dioxide powder as reference.

(82) Preparation of Doped Zinc Oxide Powder

(83) In order to obtain 5% doped zinc oxide in molar percentage of doping agent, 500 g of zinc oxide powder (MW=81.4084 g/mol) having an average particle size of less than about 5 m was mixed with either 24.43 g copper oxide powder (CuO, MW=79.5454 g/mol) or 26.70 g manganese oxide powder (MnO.sub.2, MW=86.9368 g/mol) as source for copper or manganese dopant. Mixing was carried out in a Pulverisette 2 mortar grinder (Fritsch, GmbH) for about 10 minutes at 70 rpm to obtain a homogenous powder.

(84) The homogenous powder was transferred to a 500 ml alumina crucible and then heated in a ceramic oven (Vulcan 3-1750) at a heating rate of 40 C./min until a temperature of 1000 C. was reached. The powder was subsequently heated at this elevated temperature for 24 hours. It has been reported (Florian Norindr, Ph.D. thesis, University of Southampton Research Repository, September 2009) that at this temperature, sufficient energy is provided for the dopant ions to diffuse into the ZnO host matrix and dope it.

(85) After heating for 24 hours, the powder was allowed to cool to room temperature (circa 23 C.) and then ground again for 10 minutes at 70 rpm by the Pulverisette 2 mortar grinder.

(86) Absorbance Measurements

(87) 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.

(88) Results, showing correlation to absorbance as a function of wavelength, determined by diffuse reflection measurement gathered by the integrated sphere method, are presented in FIGS. 1A, 1B, 1C and 1D.

(89) As seen in FIG. 1A, titanium dioxide has a relatively constant UV absorbance from 200 nm to about 350 nm, with very low absorbance above 400 nm. Barium titanate has significantly higher UV absorbance from 200 nm to about 350 nm, at least comparable to that of zinc oxide (not shown), with negligible absorbance above about 410 nm.

(90) As seen in FIG. 1B, undoped zinc oxide has high UV absorbance from 200 nm to about 375 nm, with negligible absorbance above 390 nm. Bismuth oxide has high UV absorbance from 200 nm to about 440 nm, with negligible absorbance above 460 nm.

(91) As seen in FIG. 1C, undoped zinc oxide has high UV absorbance from 200 nm to about 375 nm, with negligible absorbance above 390 nm. Bismuth vanadate has high UV absorbance from 200 nm to at least about 470 nm.

(92) As seen in FIG. 1D-A, absorbance in the 380-400 nm wavelength range was significantly greater for zinc oxide powder doped with either copper or manganese as compared to the absorbance of the undoped zinc oxide reference powder. At 400 nm, absorbance of zinc oxide powder doped with copper was greater than that of zinc oxide powder doped with manganese. Doping of the zinc oxide was confirmed by XRD measurement, which showed that the crystal dimensions of the zinc oxide were altered by doping with 5% copper molar percentage, as compared to the undoped zinc oxide reference powder.

(93) FIG. 1D-B shows the absorbance of UV radiation over the wavelength range of 200-800 nm for zinc oxide doped with various molar percentage concentrations of dopant to matrix, namely with 1%, 3% and 5% copper. As seen in this figure, zinc oxide powder doped with copper at each of the tested concentrations showed significantly greater absorbance of UV radiation in the 380-400 nm wavelength range as compared to the absorbance of undoped zinc oxide reference powder in the same wavelength range. In the present experiment, doping the zinc oxide matrix with 3% or 5% of copper oxide (molar percentage) yielded similar results.

Example 2: Preparation of Nanoparticles

(94) Doped zinc oxide was prepared as described in Example 1. Nanoparticles of barium titanate, bismuth oxide, bismuth vanadate and doped zinc oxide were prepared from the corresponding powder having particle size of greater than about 5 m by milling in an Attritor grinding mill (HD-01 by Union Process, Akron, Ohio, USA) using a batch size of 200 g with solid loading 10% (20 g) as follows.

(95) All materials were weighed using an analytical scale (Mettler Toledo, Columbus, Ohio, USA). 20 g of solid PAA dispersant was weighed and dissolved in 180 g deionized water as solvent to provide a 10% (w/w) PAA solution. 20 g of the relevant powder was weighed and introduced into the PAA solution to provide a PAA dispersant:inorganic UV-absorbing agent ratio of 1:1 yielding a slurry of inorganic UV-absorbing agent.

(96) In each case, the slurry was 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 100 hours at 25 C. The resulting product was a 9% (w/w) suspension of inorganic UV-absorbing agent nanoparticles in water, the inorganic solid content being assessed by oven burning as described in more detail below.

(97) Each 9% (w/w) suspension of inorganic UV-absorbing agent nanoparticles was diluted in distilled water to obtain a concentration of 0.5%, 1.0% or 2.0% (w/w), then sonicated for 30 seconds using a Misonix Sonicator tip (Misonix, Inc.) at amplitude 100, 15 W.

(98) The hydrodynamic diameter of the nanoparticles was determined by Dynamic Light Scattering, using a Zen 3600 Zetasizer from Malvern Instruments Ltd. (Malvern, UK) using the suspension having 0.5% inorganic UV-absorbing agent nanoparticles in water.

(99) Results, showing (a) the percentage of barium titanate and reference titanium dioxide particles having hydrodynamic diameters in the range of 1-1000 nm are presented in FIG. 2A; (b) the percentage of particles of bismuth oxide and reference undoped zinc oxide having hydrodynamic diameters in the range of 1-1000 nm are presented in FIG. 2B; (c) the percentage of bismuth vanadate and reference undoped zinc oxide particles having hydrodynamic diameters in the range of 1-1000 nm are presented in FIG. 2C; (d) the percentage of particles of undoped and doped zinc oxide having hydrodynamic diameters in the range of 1-1000 nm are presented in FIG. 2D.

(100) As shown in FIG. 2A, the majority of barium titanate particles in suspension had hydrodynamic diameters in the size range of from about 20 nm and up to about 100 nm, mainly up to about 60 nm with a predominant peak around about 30 nm. Specifically, the cumulative particle size distribution for the hydrodynamic diameter of barium titanate particles at D95, D97.5 and D99 of the population, analyzed in terms of percentage of number of particles were found to be about 45 nm, about 50 nm and about 59 nm, respectively.

(101) The majority of titanium dioxide particles serving as reference in suspension had hydrodynamic diameters in the size range of from about 15 nm and up to about 100 nm, mainly up to about 60 nm with a predominant peak around about 25 nm. Specifically, the cumulative particle size distribution for the hydrodynamic diameter of titanium dioxide particles at D95, D97.5 and D99 of the population, analyzed in terms of percentage of number of particles were found to be about 40 nm, about 48 nm and about 58 nm, respectively.

(102) As shown in FIG. 2B, the majority of bismuth oxide particles in suspension had hydrodynamic diameters in the size range of from about 10 nm and up to about 100 nm, mainly up to about 50 nm with a predominant peak around about 20 nm. Specifically, the cumulative particle size distribution for the hydrodynamic diameter of the bismuth oxide nanoparticles at D95, D97.5 and D99 of the population, analyzed in terms of percentage of number of particles were found to be about 28 nm, about 31 nm and about 35 nm, respectively. For comparison, a 0.5% w/w suspension of zinc oxide serving as reference displayed maximal diameters of about 39 nm, about 48 nm and about 62 nm for same percentage of particles.

(103) As shown in FIG. 2C, the majority of bismuth vanadate particles in suspension had hydrodynamic diameters in the size range of from about 10 nm and up to about 100 nm, mainly from about 20 nm and up to about 50 nm, with a predominant peak around about 35 nm. Specifically, the cumulative particle size distribution for the hydrodynamic diameter of bismuth vanadate particles at D95, D97.5 and D99 of the population, analyzed in terms of percentage of number of particles were found to be about 36 nm, about 42 nm and about 65 nm, respectively. For comparison, a 0.5% w/w suspension of zinc oxide serving as reference displayed maximal diameters of about 39 nm, about 48 nm and about 62 nm for same percentage of particles.

(104) As shown in FIG. 2D, the majority of particles of undoped or manganese-doped zinc oxide in suspension had hydrodynamic diameters in the size range of from about 15 nm and up to about 100 nm, with a predominant peak around about 20 nm, while the majority of particles of copper-doped zinc oxide in suspension had hydrodynamic diameters in the size range of from about 8 nm and up to about 50 nm, with a predominant peak around about 15 nm. The cumulative particle size distribution for the hydrodynamic diameter (in nanometers) of undoped zinc oxide, copper-doped zinc oxide and manganese-doped zinc oxide at D95, D97.5 and D99 of the population, analyzed in terms of percentage of number of particles are shown in Table 1.

(105) TABLE-US-00001 TABLE 1 Material D95 D97.5 D99 undoped ZnO 39.5 47.7 62.2 5% Cu-doped ZnO 26.7 30.6 36.2 5% Mn-doped ZnO 32.5 37.2 43.6

(106) The nanoparticles of barium titanate, titanium dioxide, bismuth oxide, bismuth vanadate, and doped zinc oxide were also studied in dried form by High Resolution Scanning Electron Microscopy (HR-SEM) using Magellan 400 HSEM/TEM by Nanolab Technologies (Milpitas, Calif., USA). The images obtained are shown in FIGS. 3A-A (barium titanate), 3A-B (titanium dioxide), 3B-A and 3B-B (bismuth oxide), 3C (bismuth vanadate), and 3D-A, 3D-B, 3D-C and 3D-D (doped zinc oxide).

(107) As shown in FIG. 3A-A, barium titanate particles having spheroid shape with diameters of less than about 100 nm, mainly less than about 60 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 confirms 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. FIG. 3A-B, shows particles of titanium dioxide as reference for comparative purpose.

(108) As shown in FIG. 3A-B, titanium dioxide particles having spheroid shape with diameters of less than about 100 nm, mainly less than about 50 nm, were obtained. These results are provided as reference for comparative purposes.

(109) As shown in FIGS. 3B-A and 3B-B, bismuth oxide particles having spheroid shape with diameters of less than about 100 nm, mainly less than about 50 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 confirms 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.

(110) As shown in FIG. 3C, bismuth vanadate particles having spheroid shape with diameters of less than about 100 nm, mainly about 25 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 confirms 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.

(111) As shown in FIGS. 3D-A, 3D-B, 3D-C and 3D-D, each displaying a different magnification, copper doped zinc oxide particles having spheroid shape with diameters of less than about 100 nm, mainly less than about 50 nm, were obtained. Similar pictures (not shown) were obtained for manganese doped and undoped zinc oxide particles. 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 confirms 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 3: Absorbance of UV Radiation by Inorganic UV-Absorbing Nanoparticles at Different Concentrations

(112) Barium titanate nanoparticles having a D.sub.N95 of about 45 nm, a D.sub.N97.5 of about 50 nm and a D.sub.N99 of about 59 nm were prepared by milling to obtain a 9% (w/w) suspension, which was then diluted in water to obtain a concentration of 0.5%, 1.0% or 2.0% (w/w) and sonicated, as described in Example 2. Bismuth oxide nanoparticles of median hydrodynamic diameter (D50 of the number of particles) of about 20 nm and having a D.sub.N95 of about 28 nm, a D.sub.N97.5 of about 31 nm, and a D.sub.N99 of about 35 nm, were prepared by milling to obtain a 9% (w/w) suspension, which was then diluted in water to obtain a concentration of 0.5%, 1.0% or 2.0% (w/w) and sonicated, as described in Example 2. Bismuth vanadate nanoparticles having a D.sub.N95 of about 36 nm, a D.sub.N97.5 of about 42 nm and a D.sub.N99 of about 65 nm were prepared by milling to obtain a 2% (w/w) suspension, which was then diluted in water to obtain a concentration of 0.5%, 1.0% or 2.0% (w/w) and sonicated, as described in Example 2. 5% Copper-doped zinc oxide nanoparticles having a D.sub.N95 of about 27 nm, a D.sub.N97.5 of about 31 nm and a D.sub.N99 of about 36 nm, were prepared by milling to obtain a 9% (w/w) suspension, which was then diluted in water to obtain a concentration of 0.5%, 1.0% or 2.0% (w/w) and sonicated, as described in Example 2 above. 5% Manganese-doped zinc oxide nanoparticles having a D.sub.N95 of about 33 nm, a D.sub.N97.5 of about 37 nm and a D.sub.N99 of about 43 nm, were prepared by milling to obtain a 9% (w/w) suspension, which was then diluted in water to obtain a concentration of 0.5%, 1.0% or 2.0% (w/w) and sonicated, as described in Example 2 above.

(113) The weight percentage of barium titanate, bismuth oxide, bismuth vanadate, copper-doped zinc oxide and manganese-doped zinc oxide following milling, as well as of the reference titanium dioxide and undoped zinc oxide, was confirmed by burning a sample of the suspension at 500 C. for 5 hours in a Vulcan 3-1750 ceramic oven. A predetermined weight (e.g., 2 gram) of the sample was placed in an aluminum crucible and the weight of the residues after evaporation of the liquid carrier and combustion of the organic components, if any, was measured using an analytical scale. Dividing the weight of the residue by the original weight of the sample provided the concentration of inorganic materials in the composition being assessed.

(114) Absorbance of barium titanate particles over the wavelength range of 200-800 nm was measured for each concentration using a Cary 300 UV-Vis spectrophotometer with quartz cuvette (10 mm light pathway). A suspension of 2% (w/w) titanium dioxide was included as reference for comparative purposes. Results are presented in FIG. 4A.

(115) As seen in FIG. 4A, absorption in the 360-400 nm wavelength range was greater using higher concentrations of barium titanate in the range tested. At the same concentration, barium titanate (upper long dash line) displayed a higher absorbance than reference titanium dioxide (lower dotted line), as well as a prolonged UV attenuation.

(116) The density of BaTiO.sub.3 is about 6.0 g/cm.sup.3, while the density of TiO.sub.2 is about 4.2 g/cm.sup.3. Therefore, the number of particles in a TiO.sub.2 suspension is higher than the number of particles in a BaTiO.sub.3 suspension at the same concentration. Thus the physical absorption properties of barium titanate may be considered to be superior to those of titanium dioxide per same amount of particles. As the particle size distribution of the BaTiO.sub.3 particles is comparable to the distribution of the particles of the TiO.sub.2 reference (see FIG. 2A), such finding is believed to be significant.

(117) Absorbance of bismuth oxide particles over the wavelength range of 200-800 nm was measured for each concentration using a Cary 300 UV-Vis spectrophotometer with quartz cuvette (10 mm light pathway). Results are presented in FIG. 4B, from which it can be seen that absorption in the 360-400 nm wavelength range was greater using higher concentrations of bismuth oxide in the range tested.

(118) Absorbance of bismuth vanadate particles over the wavelength range of 200-800 nm was measured for each concentration using a Cary 300 UV-Vis spectrophotometer with quartz cuvette (10 mm light pathway). Results are presented in FIG. 4C, from which it can be seen that absorption in the 380-400 nm wavelength range was greater using higher concentrations of bismuth vanadate in the range tested.

(119) It must be emphasized that the absorption curve may be shifted to the left and down by further milling to reduce the particle size, preferably coupled with maintaining or reducing the PDI, as will be further elaborated hereinbelow.

(120) Absorbance of the 5% manganese-doped zinc oxide nanoparticles over the wavelength range of 200-800 nm was measured as described above for each concentration, and compared to that of undoped zinc oxide nanoparticles at the same concentrations. Results are presented in FIG. 4D-A, which shows that, at each of the tested concentrations, zinc oxide nanoparticles doped with 5% manganese showed significantly greater absorbance of UV radiation in the 380-400 nm wavelength range, as compared to the absorbance of undoped zinc oxide nanoparticles at the same concentrations. Absorbance in the 380-400 nm range was found to increase with zinc oxide concentration for the tested concentrations.

(121) Absorbance of the 5% copper-doped zinc oxide nanoparticles over the wavelength range of 200-800 nm was measured for each concentration using a Cary 300 UV-Vis spectrophotometer with quartz cuvette (10 mm light pathway). Suspensions of undoped zinc oxide at same concentrations served as references. Results are presented in FIG. 4D-B for the 200-800 nm range and in FIG. 4D-C for a close-up view in the 340-500 nm sub-range. As seen in FIG. 4D-B, and better shown in FIG. 4D-C, at each of the tested concentrations, zinc oxide nanoparticles doped with 5% copper showed significantly greater absorbance of UV radiation in the 380-400 nm wavelength range, as compared to the absorbance of undoped zinc oxide nanoparticles at the same concentrations. Absorbance in the 380-400 nm range was found to increase with zinc oxide concentration for the tested concentrations.

Example 4: Comparison of Absorbance of UV Radiation by Nanoparticles of Inorganic UV-Absorbing Agents to that of a Commercially Available Organic Sunscreen Composition

(122) Skingard sunscreen composition by Careline (Pharmagis, Israel) is a commercially available chemical sunscreen composition. The Skingard product was burned in a ceramic oven (Vulcan 3-1750) at 500 C. for 5 hours after which the weight percentage of residual solids was found to be very low (0.07%), suggesting that the Skingard product substantially comprises organic compounds.

(123) An aqueous suspension of 9% (w/w) bismuth oxide nanoparticles of median hydrodynamic diameter (D50 of the number of particles) of about 20 nm and having a D.sub.N95 of about 28 nm, a D.sub.N97.5 of about 31 nm and a D.sub.N99 of about 35 nm was prepared by milling, as described in Example 2. Absorbance over the wavelength range of 200-800 nm was measured for the 9% (w/w) bismuth oxide nanoparticles, for a 9% (w/w) undoped zinc oxide reference and for the Skingard comparative composition. Absorbance measurements were performed as previously described. Results are presented in FIG. 5A, which shows that absorbance of bismuth oxide in the 380-400 nm wavelength range was greater than that of zinc oxide, and at least equal to that of Skingard.

(124) An aqueous suspension of 2% (w/w) bismuth vanadate nanoparticles having a D.sub.N95 of about 36 nm, a D.sub.N97.5 of about 42 nm and a D.sub.N99 of about 65 nm, was prepared by milling, as described in Example 2. Absorbance over the wavelength range of 200-800 nm was measured for the 2% (w/w) bismuth vanadate nanoparticles, for a 2% (w/w) zinc oxide reference and for the Skingard comparative composition. Absorbance measurements were performed as previously described. Results are presented in FIG. 5B, which shows that absorbance of bismuth vanadate in the 380-400 nm wavelength range was greater than that of zinc oxide, and similar to that of Skingard.

(125) An aqueous suspension of 2% (w/w) zinc oxide nanoparticles doped with either 5% copper or 5% manganese was prepared by milling, as described in Example 2 above, to provide copper-doped zinc oxide nanoparticles having a D.sub.N95 of about 27 nm, a D.sub.N97.5 of about 31 nm and a D.sub.N99 of about 36 nm and manganese-doped zinc oxide nanoparticles having a D.sub.N95 of about 33 nm, a D.sub.N97.5 of about 37 nm and a D.sub.N99 of about 44 nm. Absorbance over the wavelength range of 200-800 nm was measured for the copper-doped and manganese-doped zinc oxide nanoparticles, for a 2% (w/w) undoped zinc oxide reference and for the Skingard comparative composition. Absorbance measurements were performed as previously described. Results are presented in FIG. 5C, which shows that absorbance of manganese-doped zinc oxide in the 380-400 nm wavelength range was greater than that of zinc oxide, and at least equal to that of Skingard.

Example 5: Composition Comprising Inorganic UV-Absorbing Agents and Metallic Silver Nanoparticles

(126) Silver nanoparticles having a cumulative particle size distribution of hydrodynamic diameter of about 14 nm at D90, about 15 nm at D97.5 and about 17 nm at D99 (in terms of number of particles) are added to a 1% (w/w) suspension in water of a doped or undoped inorganic UV-protective agent of the present teachings, prepared as described above, so that the concentration of silver nanoparticles is either 0.001% or 0.002% (w/w) of the final composition. The absorption of each of the silver particle-containing compositions is measured as described previously, and compared to that of each ingredient separately (i.e. an aqueous suspension of 1% (w/w) of the inorganic UV-protective agent and another of 0.001% silver nanoparticles (w/w)) and to commercially available Skingard sunscreen composition of Careline. Results for the experiments using mixtures of bismuth oxide nanoparticles and are presented in FIG. 6, addition of 0.002% silver nanoparticles to a suspension of bismuth oxide extended the wavelength at which maximum absorbance was seen from about 380 nm up to about 430 nm.

Example 6: Determination of Critical Wavelength

(127) Based on the absorbance spectra determined above, critical wavelength was calculated for Bi.sub.2O.sub.3 (D.sub.N95 28 nm) at concentrations 0.5%, 1%, 2% and 9% (w/w); for 1% (w/w) Bi.sub.2O.sub.3 with 0.001% or 0.002% (w/w) silver nanoparticles (D95 14 nm); for BiVO.sub.4 (D.sub.N95 36 nm) at concentrations 0.5%, 1%, and 2% (w/w); for zinc oxide at concentrations 0.5%, 1%, 2% and 9% (w/w), doped with 5% copper (D.sub.N95 27 nm) or 5% manganese (D.sub.N95 33 nm); for undoped ZnO (D.sub.N95 39 nm) as reference at concentrations 0.5%, 1%, 2% and 9% (w/w), only the two latter concentrations of the zinc oxide reference being illustrated in FIGS. 5A and 5B; and for the Skingard product.

(128) 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.

(129) The critical wavelength .sub.c was defined according to the following equation:

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

(131) .sub.c is the critical wavelength;

(132) T() is the mean transmittance for each wavelength; and

(133) D is the wavelength interval between measurements.

(134) Critical wavelengths as calculated are presented in Table 2 below.

(135) As seen in Table 2, according to the Critical Wavelength Method, Bi.sub.2O.sub.3 is classified as providing broad spectrum protection (i.e. has a critical wavelength of greater than 370 nm) at concentrations of from 2%, or at concentration of from 1% in the presence of 0.001% silver nanoparticles.

(136) The density of Bi.sub.2O.sub.3 is 8.9 g/cm.sup.3, while the density of ZnO is about 5.6 g/cm.sup.3. Therefore, the number of particles in each ZnO suspension (at concentrations of 0.5%, 1%, 2% and 9% w/w) is higher than the number of particles in each Bi.sub.2O.sub.3 suspension at the same concentration. As the critical wavelengths values of Bi.sub.2O.sub.3 were comparable to undoped zinc oxide reference, the physical absorption properties of Bi.sub.2O.sub.3 may be considered to be superior to those of ZnO per same amount of particles. As the particle size distribution of the Bi.sub.2O.sub.3 particles is comparable to the distribution of the particles of the ZnO reference (see FIG. 2B), such finding is believed to be significant.

(137) Also seen in Table 2, according to the Critical Wavelength Method, BiVO.sub.4 is classified as providing broad spectrum protection (i.e. has a critical wavelength of greater than 370 nm) at concentrations of from 0.5%.

(138) The density of BiVO.sub.4 is 6.1 g/cm.sup.3, while the density of ZnO is about 5.6 g/cm.sup.3. Therefore, the number of particles in each ZnO suspension (at concentrations of 0.5%, 1%, and 2% w/w) is higher than the number of particles in each BiVO.sub.4 suspension at the same concentration. As the critical wavelengths values of BiVO.sub.4 were greater than those of the undoped zinc oxide reference, the physical absorption properties of BiVO.sub.4 may be considered to be superior to those of ZnO per same amount of particles. As the particle size distribution of the BiVO.sub.4 particles is comparable to the distribution of the particles of the ZnO reference (see FIG. 2C), such finding is believed to be significant.

(139) Also as seen in Table 2, according to the Critical Wavelength Method, doped zinc oxide is classified as providing broad spectrum protection (i.e. has a critical wavelength of greater than 370 nm) at concentrations of from 0.5% (w/w) when the dopant is 5% manganese in molar percentage, or at concentration of from 2% (w/w) when the dopant is 5% copper in molar percentage.

(140) TABLE-US-00002 TABLE 2 Material name and concentration (w/w) Critical Wavelength (nm) 0.5% Bi.sub.2O.sub.3 349 1.0% Bi.sub.2O.sub.3 362 2.0% Bi.sub.2O.sub.3 371 9.0% Bi.sub.2O.sub.3 389 1% Bi.sub.2O.sub.3 + 0.001% silver nanoparticles 370 1% Bi.sub.2O.sub.3 + 0.002% silver nanoparticles 379 0.5% BiVO.sub.4 378 1.0% BiVO.sub.4 379 2.0% BiVO.sub.4 380 0.5% ZnO doped 5% Cu 358 1.0% ZnO doped 5% Cu 363 2.0% ZnO doped 5% Cu 370 9.0% ZnO doped 5% Cu 388 0.5% ZnO doped 5% Mn 372 1.0% ZnO doped 5% Mn 381 2.0% ZnO doped 5% Mn 391 0.5% ref ZnO 362 1.0% ref ZnO 366 2.0% ref ZnO 372 9.0% ref ZnO 384

Example 5: Non-Aqueous Compositions Comprising Bismuth Oxide or Bismuth Vanadate Nanoparticles

(141) Powders of bismuth oxide and bismuth vanadate having an average particle size of about 5 m were size-reduced as described above, subject to the following modifications. The water medium was replaced by an oil carrier, namely C.sub.12-C.sub.15 alkyl benzoate (commercially available from Phoenix Chemical as Pelemol 256), and the water-miscible PAA dispersant was replaced by a vegetable-derived polyester obtained from the homopolymerization of hydroxystearic acid (commercially available from Phoenix Chemicals as Pelemol PHS-8).

(142) The oil-based slurries were milled as described for the aqueous counterparts. The resulting product was a 10% (w/w) suspension of bismuth oxide or bismuth vanadate nanoparticles in oil, the inorganic solid content being assessed by oven burning as described above.

(143) The oil suspensions of bismuth oxide and bismuth vanadate nanoparticles were diluted in C.sub.12-C.sub.15 alkyl benzoate to obtain particle concentrations of 0.5%, 1.0% or 2.0% (w/w), then sonicated for 30 seconds using a Misonix Sonicator tip (Misonix, Inc.) at amplitude 100, 15 W.

(144) The hydrodynamic diameter of the oil-dispersed nanoparticles was determined by Dynamic Light Scattering, using a Zen 3600 Zetasizer from Malvern Instruments Ltd. (Malvern, UK) using the suspension containing 0.5 wt. % nanoparticles.

(145) Results showing the percentage of the number of bismuth oxide and bismuth vanadate particles having hydrodynamic diameters in the range of 10-1000 nm are presented in FIG. 7, which shows that the majority of bismuth oxide nanoparticles in oil suspension had hydrodynamic diameters in the size range of from about 30 nm and up to about 250 nm, mainly not exceeding 100 nm with a predominant peak around about 60 nm. Specifically, the cumulative particle size distributions for the hydrodynamic diameter of bismuth oxide particles at D95, D97.5 and D99 of the population, analyzed in terms of percentage of number of particles, were found to be about 134 nm, about 167 nm and about 199 nm, respectively.

(146) The majority of bismuth vanadate particles in suspension had hydrodynamic diameters in the size range of from about 18 nm and up to about 100 nm, with a predominant peak around about 34 nm. Specifically, the cumulative particle size distribution for the hydrodynamic diameter of titanium dioxide particles at D95, D97.5 and D99 of the population, analyzed in terms of percentage of number of particles were found to be about 59 nm, about 68 nm and about 82 nm, respectively.

(147) The bismuth oxide and bismuth vanadate nanoparticles oil-milled suspensions were also each 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 were sonicated for 30 seconds using a Misonix Sonicator tip (Misonix, Inc.) at amplitude 100, 15 W. The sonicated lacquer dispersions were applied upon a microscopic glass slide at an initial thickness of about 100 m (using 100 m thick spacers and a leveling rod). The lacquer-coated slides were 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 served as control. Absorbance of the dried layers of lacquer over the wavelength range of 200-800 nm was assessed using a Cary 300 UV-Vis spectrophotometer. Results are shown in FIG. 8, which shows that both bismuth oxide and bismuth vanadate nanoparticles improve the absorbance of the lacquer vehicle over the UV range of interest. The critical wavelength calculated for a 5 m dried layer of lacquer containing 1 wt. % of bismuth oxide was found to be about 380 nm, while for a similar sample containing 1 wt. % of bismuth vanadate displayed a critical wavelength of about 382 nm. For comparison, the plain lacquer control had a critical wavelength of about 360 nm. Such relatively high value is to be expected from such a product aimed, among other things, to protect wood products subjected to external conditions and weather exposures. This study supports the applicability of compounds according to the present teachings for use in non-aqueous carriers and/or on inert objects as well.

(148) FIG. 9 provides UV absorbance spectra for a composition based on barium titanate, in which the UV absorbance spectra for composition samples are characterized as a function of the milling time of the samples. The compositions were prepared substantially as described in Example 2, with samples being removed at various times, for characterization purposes. As milling time is increased (e.g., from 7 hours to 15 hours), it is manifest that the absorption curves are shifted down and to the left, in a monotonic fashion. Thus, for a given wavelength between about 320 nm and 700 nm, the absorbance (in absorbance units AU) exhibited by the sample milled for 15 hours is lower than the sample milled for 13 hours. This trend is exhibited for all samples (milling times of 7, 9, 11, 13, and 15 hours).

(149) Particle size distribution information, including PDI, are provided below as a function of milling time. The values are averaged based on 3 samples per milling time.

(150) TABLE-US-00003 Milling time D.sub.v(50) Avg. D.sub.n(50) Avg. PDI Avg. 2 hr 238.7 90.1 0.181 4 hr 175.3 81.4 0.189 5 hr 150.0 66.7 0.175 6 hr 137.3 69.7 0.162 7 hr 136.0 72.8 0.159 9 hr 103.6 42.8 0.182 11 hr 90.1 47.5 0.186 13 hr 80.4 43.5 0.247 15 hr 69.7 44.2 0.220

(151) It will be appreciated that further reduction in size, particularly of the large particles, may be achieved by further milling, using finer milling media, etc. The criticality of the weight ratio of dispersant to inorganic UV-absorbing agents is further elaborated hereinbelow.

(152) The area under curve (AUC) and UV absorbance selectivity data are provided below:

(153) TABLE-US-00004 UV absorbance AUC(280-400) AUC(280-700) selectivity 7 hr 469 643 72.9 9 hr 408 534 76.4 11 hr 358 451 79.5 13 hr 341 409 83.3 15 hr 311 365 85.4

(154) Calculation of both the critical wavelength and the UV absorption selectivity may be facilitated by the gridlines provided in the Figure.

(155) It is further observed that the absolute drop in absorbance within the UV range between about 320 and 400 nm is considerably larger than the absolute drop in absorbance within the visible range between about 400 and 700 nm. It would appear that the additional milling time disadvantageously reduces the UV absorbance, and disadvantageously reduces the critical wavelength.

(156) However, the inventors have found that the reduction in UV absorbance within the visible range is appreciable, such that the UV absorbance selectivity may be appreciably improved. Consequently, the formulations of the present invention may be significantly more transparent than identical formulations in which the inorganic UV-absorbing agents (barium titanate and bismuth vanadate) have a larger particle size.

(157) Without wishing to be limited by theory, the inventors believe that the measured UV absorbance within the visible range may actually include a major contribution due to scatter, which may be caused by particles at the high end of the particle size distribution.

(158) The inventors believe that for a given median particle size (D.sub.N50), improved efficacy, including a higher UV absorbance selectivity, may be obtained by operating the milling stage so as to obtain a relatively low PDI. This may be achieved by using an excess of dispersant with respect to the inorganic UV-absorbing agents, and by using a dispersant that is particularly efficacious in dispersing the inorganic UV-absorbing agents.

(159) To this end, the weight ratio of dispersant to inorganic UV-absorbing agents may be increased above and beyond the increase required by the additional surface area produced by the size reduction.

(160) All of the above may be coupled with size reduction to a suitably low characteristic particle size, so as to achieve an absorbance curve that provides superior UV absorbance (though not necessarily up to the 400 nm boundary) along with high UV absorbance selectivity, such that the formulation has excellent transparency properties (minute absorbance in the visible range, and relatively little scatter).

CONCLUSIONS

(161) Barium titanate was shown to provide at least equivalent absorbance of ultraviolet radiation in the 280-400 nm range and in particular at the higher end of the range i.e. about 380-400 nm range than that of the known inorganic sunscreen component titanium dioxide. Nanoparticles of barium titanate also provide excellent UV absorbance, while providing a composition which is substantially invisible when applied to the skin.

(162) Bismuth oxide was shown to provide at least equivalent absorbance of ultraviolet radiation in the 280-400 nm range, and in particular at the higher end of the range i.e. about 380-400 nm range than that of the known inorganic sunscreen component zinc oxide. Nanoparticles of bismuth oxide also provide excellent UV absorbance, while providing a composition which is substantially invisible when applied to the skin. Nanoparticles of bismuth oxide thus provide excellent absorption of both UVA and UVB radiation, providing broad-spectrum UV protection (i.e. a composition having a critical wavelength of greater than 370 nm), while providing a composition which is invisible when applied to the skin. Absorption of the UVA and UVB radiation was at least as great as that of the known commercial sunscreen composition.

(163) Bismuth vanadate was shown to provide better absorbance of ultraviolet radiation in the 280-400 nm range and in particular at the higher end of the range i.e. about 380-400 nm range than that of the known inorganic sunscreen component zinc oxide. Nanoparticles of bismuth vanadate also provide excellent absorption of both UVA and UVB radiation, providing broad-spectrum UV protection (i.e. a composition having a critical wavelength of greater than 370 nm), while providing a composition which is invisible when applied to the skin. Absorption of the UVA and UVB radiation was at least as great as that of the known commercial sunscreen composition.

(164) Doped zinc oxide was shown to provide at least equivalent absorbance of ultraviolet radiation in the 280-400 nm range and in particular at the higher end of the range i.e. about 380-400 nm range than that of undoped zinc oxide. Nanoparticles of doped zinc oxide thus provide excellent UV absorption, while providing a composition which is substantially invisible when applied to the skin or hair of a subject. Absorption of the UVA and UVB radiation was at least as great as that of the known commercial sunscreen composition.

(165) Although the invention 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.

(166) 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 invention.