FR2965719A1 - PARTICLE COMPRISING TWO PLASMONIC METALS - Google Patents

Abstract

The present invention relates to a cosmetic composition comprising: a cosmetically acceptable medium, and colored particles having a size of between 70 nm and 1 μm, comprising: in a first region, a first metal compound consisting of a first plasmonic metal or a of its alloys, and o in a second region distinct from the first, a second metal compound consisting of a second plasmonic metal or one of its alloys, the second metal compound being different from the first metal compound, the first and second regions each having a size or thickness greater than or equal to 2 nm and the first and second metal compounds together affecting the plasmonic resonance of the particles.

Description

The present invention relates to particles comprising at least two different plasmonic metals, compositions containing such particles and their use for the makeup of keratin materials, especially skin and hair.

Description of the Prior Art WO 2007/011103 discloses colored cosmetic compositions comprising a mixture of gold nanoparticles and silver nanoparticles. The synthesis of nanoparticles comprising a gold / silver alloy and producing an orange color is described.

JP 2008/024677 teaches colored powders having gold particles dispersed in a titanium dioxide matrix. JP 2005/068019 discloses cosmetic compositions comprising nanocylindrical plasmonic particles. JP 2008/088296 discloses plasmonic particles associated with polyamide particles. US 2009/0022766 discloses particles comprising a metal core and a coating layer comprising a fluorophore. US Pat. No. 7,147,687 describes particles having a silver core coated with a gold monolayer.

In addition, the publications are known: M. Schierhorn, L. M. Liz-Marzan. Synthesis of Bimetallic Colloids with Tailored Intermetallic Separation. Nano Lett. 2002, 2, 13-16; Rodriguez-Gonzalez, B .; Burrows, A .; Watanabe, M .; Kiely, C. J .; Liz-Marzan, M. Multishell Bimetallic AuAg Nanoparticles: Synthesis, Structure and Optical Properties. J Mater. Chem., 2005, 15, 1755-1759; Fan, F.-R .; Liu, D.-Y; Wu, Y.-F .; Duan, S .; Xie, Z.-X .; Jiang, Z.-Y .; Tian; Z.-Q. Epitaxial growth of heterogeneous metal nanocrystals: from gold nano-octahedra to palladium and silver nanocubes. J Am. Chem. Soc. 2008, 130, 6949-6951; Xue, C .; Millstone, J. E .; Lily.; Mirkin, C. A. Plasmon-Driven Synthesis of Triangular Core-Shell Nanoprisms from Gold Seeds. Angew. Chem. Int. Ed. 2007, 46, 8436-8439; Liu, M .; Guyot-Sionnest, P. Synthesis and Optical Characterization of Au / Ag Core / Shell Nanorods. J. Phys. Chem. B 2004, 108, 5882-5888; Ah, C. S .; Hong, S. D .; Jang, DA. Preparation of AucoreAgsheil Nanorods and Characterization of Their Surface Plasmon Resonances. J. Phys. Chem. B 2001, 105, 7871-7873; Gao, L .; Fan, L .; Zhang, J.

Selective Growth of Ag Nanodewdrops on Nanostructures: A New type of Bimetallic Heterostmcture. Langmuir, 2009, 25, 11844-11848; Rycenga, M .; Hou, K. K .; Cobley, C. M .; Schwartz, A. G .; Camargo, P. H. C .; Xia, Y. Probing the surface-enhanced Raman scattering properties of Au-Ag nanocages at two different excitation wavelengths. Phys.

Chem. Chem. Phys. 2009, 11, 5903-5908; Mandai, M., Jana, NR, Kundt ', S., Ghosh, SK, Panigrahi, M., Pal, T. Synthesis of Aucore-Agshell type Bimetallic nanoparticles for single meecule detection in solution by SERS method (2004) Journal of Nanoparticle Research, 6 (1), pp. 53-61. These publications describe bi-metallic particles. In order to obtain a satisfactory color and coverage, makeup products can use a large quantity of pigments, for example pigment pastes or iron oxides. In the case of iron oxides, this important amount can be explained by the need to combine a mixture of iron oxides (yellow, red and black) as well as a white base to obtain a brown opaque color. Compositions having a large amount of pigments may not be completely satisfactory in terms of texture and rheology. Significant quantities of pigments may further reduce the stability and reproducibility of compacts of foundation powders or eyeshadows. In addition, some applications require a deposit of small amounts of pigments. As an illustration of these applications, mention may be made of hair makeup or eyelashes where it may be necessary to deposit on the surface of the fibers; a restricted volume of composition so that the fibers retain satisfactory mechanical properties, especially in terms of flexibility. Compositions comprising conventional pigments are not suitable for these applications. Therefore, there is a need to decrease the amount of pigments incorporated into the cosmetic compositions while maintaining satisfactory color properties. In addition, there is a need for cosmetic compositions which make it possible to obtain a satisfactory makeup of human keratin materials, in particular of the skin, the eyelashes and the hair.

The present invention aims to meet all or part of these needs. SUMMARY According to a first of its aspects, the invention relates to a colored particle of size included (limits included) between 70 nm and 1 μm, preferably between 80 nm and 700 nm, better still between 90 nm and 300 nm, better still between 100 nm and 250 nm, comprising: - in a first region, a first metal compound consisting of a first plasmonic metal or one of its alloys, and in a second region distinct from the first, a second metal compound consisting of a second plasmonic metal or one of its alloys, the second metal compound being different from the first metal compound, the first and second regions each having a size or thickness greater than or equal to 2 nm and the first and second metal compounds together affecting the plasma resonance of the particle. Throughout the rest of the text, the term "visible spectrum" refers to the spectrum of wavelengths between 400 and 700 nm. By "colored particle" is meant a particle that reflects at least one wavelength of the visible spectrum. In other words, a colored particle has a reflectance spectrum that has at least one peak in the visible spectrum. By "size" we must understand the smallest dimension. It may, for example, be a diameter. By "plasmonic metal or one of its alloys", it is necessary to understand a metal or an alloy capable of producing a phenomenon of plasmon resonance in the visible spectrum. A material exhibits plasmon resonance in the visible spectrum as the conduction electrons of the material oscillate in response to the electric alternating field E of the electromagnetic radiation for a wavelength in the visible. The plasmon resonance itself generates an intense local electromagnetic field. By "the first and second metal compounds together affecting the particle plasmon resonance", it is to be understood that the particle plasmon resonance spectrum comprises at least one plasmonic resonance peak, different from the plasmonic resonance peaks of the plasmonic resonance. first and second pure metal compounds, whose spectral position is related to the presence of the first and second metal compounds.

Unless stated otherwise, "plasmonic resonance" means the surface plasmon resonance occurring at the interface between a conductor, for example a metal, and a dielectric. The inventors have found that the use of plasmonic particles having a size of between 70 nm and 1 μm, comprising two metal compounds that together have an effect on the plasmonic resonance of the particles, makes it possible to access an enlarged gamma-colonel as well as to obtain effects. improved dyes while reducing the amount of particles used in comparison with plasmonic particles having only one metal compound.

When the first and second metal compounds are both plasmonic metal alloys, they may differ by the nature of the first and second plasmonic metals and / or by the nature of the alloy compound (s) other (s). ) than the first and second plasmonic metals. In an exemplary embodiment, the first and second plasmonic metals may be different. The fact that each of the first and second regions has a size or a thickness as defined above can cause the particle, when irradiated with visible light, to produce a plasmon resonance phenomenon. The composition and structure of each of the first and second regions 20 modify their incidence on the plasmon resonance of the particle and thus the overall optical properties of the particle, when this particle is irradiated with visible light. Each of the first and second regions may, for example, have a size or a thickness greater than or equal to 2 nm, for example between 2 nm and 1 25 μm. Preferably, the first region may have a size of between 30 nm and 900 nm, better still between 40 nm and 800 nm and more preferably between 60 and 700 nm, preferably between 70 nm and 600 nm. Preferably, the second region may have a size of between 2 nm and 1 μm, in particular between 2 nm and 30 nm, even between 3 nm and 25 nm, and more preferably between 4 nm and 20 nm.

Sufficient size for the first and / or second regions of the particles may advantageously give the composition in which these particles are present a satisfactory opacity. The distance between the first and second regions may, for example, be less than or equal to 45 nm, especially at 30 nm, especially at 15 nm. The first and second regions may, for example, be in contact (zero distance). Advantageously, a small distance between the first and the second region may allow the first and second metal compounds to together have an impact on the plasmonic resonance of the particle. Thus, as explained above, the fact that the first and second regions of the particle are close together allows the particle to exhibit at least one plasmonic resonance peak distinct from the plasmonic resonance peaks of the first and second pure metal compounds. The inventors have found that the presence of such a plasmon resonance peak can allow improved coverage and colon properties to be obtained. Independently or in combination with the foregoing, the invention relates, according to another of its aspects, to a colored particle of size between 70 nm and 1 μm, preferably between 80 nm and 700 nm, better still between 90 nm and 300 nm, still more preferably between 100 nm and 250 nm, comprising: in a first region, a first metal compound consisting of a first plasmonic metal or one of its alloys, and in a second region, distinct from the first, a second metal compound comprising in a second plasmonic metal or one of its alloys, the second metal compound being different from the first metal compound, the first and second regions each having a size or thickness greater than or equal to 2 nm, the second region coating the first region and the first and second metal compounds together affecting the plasmon resonance of the particle. Thus, the invention may relate to particles of the "core-shell" type, also called "core-shell". The second region may be in contact with the first region.

When the particle is of "core-shell" type, it may be advantageous for the thickness of the second region to be less than 45 nm, for example between 2 and 45 minutes, in particular 2 and 30 minutes, better 3 and 25 nm more preferably 4 and 20 nm. When the particle is of the "core-shell" type, the size of the first region may preferably be between 30 and 800 nm, more preferably between 40 and 700 nm, more preferably between 50 and 600 nm. When the particle is of the "core-shell" type, the second region may preferably be in contact with the first region. Alternatively, the second region may be separated from the first region by one or more layers including, for example, a dielectric material as discussed below. Independently or in combination with the above, the invention relates, in another of its aspects, to a colored particle of size between 110 nm and 1 μm comprising: in a first region, a first metal compound consisting of a first plasmon metal or one of its alloys, and - in a second region distinct from the first, a second metal compound consisting of a second plasmonic metal or one of its alloys, the second metal compound being different from the first metal compound, the first and second regions each having a size or thickness greater than or equal to 2 nm and the first and second metal compounds together affecting the plasmonic resonance of the particle. Independently or in combination with the above, the invention relates, in another of its aspects, to a colored particle of size between 70 nm and 1 μm comprising: in a first region a first metal compound consisting of a first metal plasmonic or one of its alloys, and - in a second region coating the first and distinct region thereof, a second metal compound consisting of a second plasmonic metal or one of its alloys, the second metal compound being different from the first compound metal, the first and second regions each having a size or thickness greater than or equal to 2 nm, the first and second metal compounds together affecting the plasmonic resonance of the particle. Independently or in combination with the foregoing, the invention relates, in another of its aspects, to a cosmetic composition comprising: a cosmetically acceptable medium, and particles as defined above. When several particles according to the invention are present in a composition, the "size" corresponds to the statistical granulometric size at half of the so-called D (0.5) population. The cosmetic composition described above may, for example, be a hair composition intended for cosmetic treatment, in particular for make-up, especially for hair coloring. It can also be a makeup composition for eyelashes, nails, skin or lips.

The particles may be present in the composition in a content ranging from 0.00001% to 50% by volume, in particular from 0.0001% to 20% by volume, better still 0.01% to 15% by volume, and still more preferably 0, 1 to 10%, or even 1 to 8% by volume. The composition according to the invention may, in an exemplary embodiment, comprise a mixture of at least two types of plasmonic particles according to the invention.

In this case, the plasmonic particles can produce the same color or distinct colors when formulated in the composition. The composition according to the invention may comprise a mixture of at least three types of plasmonic particles according to the invention. Independently or in combination with the foregoing, the invention relates, according to another of its aspects, to a process for the cosmetic treatment, in particular of makeup or coloring of human keratin materials, comprising the step of applying to human keratin materials to treat a composition as defined above. Independently or in combination with the foregoing, another aspect of the invention relates to a method of making up the lips, skin of the body or face, nails, hair or eyelashes comprising the step of apply on the lips, skin, nails, hair or eyelashes a composition as defined above. The invention offers a particularly interesting solution to the makeup of hair, skin and lips.

Plasmonic particles Plasmonium metals The plasmonic metals that can be used in the context of the present invention are preferably chosen from tungsten (W), aluminum (Al), palladium (Pd), platinum (Pt), silver (Ag), copper (Cu), gold (Au), chromium (Cr), zinc (Zn), rhodium (Rh), nickel (Ni), tin (Sn). More preferably, the first and second plasmonic metals are selected from among gold, silver, platinum, nickel and copper, still better one of the metals is gold and the other is silver. In particular, when the second region coats the first region, the first and second plasmonic metals may advantageously be chosen from gold and silver. The first plasmonic metal may be gold and the second plasmonic metal may be silver or the first plasmonic metal may be silver and the second plasmonic metal may be gold. The first metal compound may be gold and the second metal compound may be silver or the first metal compound may be silver and the second metal compound may be gold. The particle according to the invention may comprise, in a third region, a third metal compound consisting of a third plasmonic metal or one of its alloys, the third metal compound being distinct from the first and second metal compounds. The third plasmonic metal may be selected from the plasmonic metals listed above. The third region may, for example, have a size or a thickness greater than or equal to 2 nm, especially at 3 nm, especially at 5 nm. The third region may be in contact with or separated from the second region by a layer of dielectric material as defined hereinafter.

It is possible, when the plasmonic particle has a third region, that the first, second and third metal compounds together have an effect on the plasmonic resonance of the particle. Alternatively, it is possible that only two of the first, second and third metal compounds together have an impact on the plasmonic resonance of the particle. A-layout of the rememe and second re-ion form and size of plasmonic articules Size and shape of the particles The particle size according to the invention is between 70 nm and 1 μm, for example between 0 nm and 700 nm, for example between 90 nm and 300 nm, for example between 100 nm and 250 nm, for example between 110 nm and 200 nm. The plasmonic particles may be of any shape, for example cylindrical, spherical, platelet, oval or polyhedral, in particular cubic, parallelepipedal or pyramidal. The plasmonic particles may, for example, have an aspect ratio of between 1 and 2, for example between 1 and 1.5, for example between 1 and 1.25, for example with an aspect ratio substantially equal to 1. By "aspect ratio" is meant the ratio of the largest dimension of the particle to the smallest dimension of the particle. In a preferred example, the plasmonic particles according to the invention have a substantially spherical shape. In one exemplary embodiment, the plasmonic particles according to the invention do not have a cylindrical shape. The particles can be further dispersed within a matrix. Dielectric Materials The plasmonic particles according to the invention may comprise a dielectric material in a region distinct from the first, second and possible third regions. No phenomenon of plasmonic resonance occurs in the mass of the dielectric material. However, plasmon resonance phenomena can occur at the interface between the dielectric and the first and / or second regions. The dielectric material may be located between the first and second regions or between the second and third regions.

Especially in the case where the second region coats the first region, it is possible that the dielectric material is located between the first and second regions. In this case, the dielectric material may be in contact with the first and second regions. In another embodiment, the dielectric material can coat the first and second regions. In particular, when the second region coats the first region, the dielectric material can coat the first and second regions. In this case, the dielectric material may be on the outer periphery of the plasmonic particle. In another embodiment, particularly when the second region coats the first region, it is possible for the dielectric material to be located so as to be coated by the first region. In this case, the dielectric material may be in contact with the first region. The size or thickness of the region where the dielectric material is present may be between 2 nm and 1000 nm.

When it is located between the first and second regions, the size or the thickness of the region where the dielectric material is present may advantageously be less than 45 nm, preferably less than 30 ions, better still less than 15 nm, and even better less than 5 nm. When located between the first and second regions, a small size or thickness of the region comprising the dielectric material may allow the first and second metal compounds to together affect the plasmonic resonance of the particle. The dielectric material may, for example, be chosen from: inorganic compounds, for example metal oxides, for example alumina, silica or titanium dioxide, polymers, for example polyurethane, polystyrene, polymethyl methacrylate, polymers of natural origin, and the possible solvent or dispersion phase of the particles. In an exemplary embodiment, the plasmonic particles according to the invention may comprise an empty region. This empty region may, for example, be coated by the first region, especially when the second region coats the first region. The particle according to the present invention may also be covered by an additional coating, in particular chosen from biodegradable or biocompatible materials, lipid materials such as surfactants or emulsifiers, polymers, polymers, and the like. oxides. When the additional coating comprises a biodegradable or biocompatible material, this coating may in particular comprise any natural or synthetic molecule chosen especially lipids, carbohydrates, polysaccharides, proteins, polymers, glycoproteins, glycolipids which may be used for make the combination physiologically acceptable. Preferably, the biodegradable or biocompatible materials are chosen from polymers made from D- or L-lactide type monomers, lactic acid, glycolic acid, hydroxybutyric acid or malic acid. When the additional coating comprises a lipid material, this coating may in particular comprise a lipid or a mixture of lipids, synthetic or natural, optionally modified by chemical or biological means. These lipids can be neutral or positively or negatively charged. When the additional coating comprises a polymer, this coating may in particular comprise at least one polymer chosen from polyesters, polyamides, polyethers, polythioethers, polyureas, polycarbonates, polycarbamides, proteins, polysaccharides and polyaryls, preferably with molar masses (Mw). ranging from 100g / mol to 100000 g / mol. When the additional coating comprises an oxide, this coating may in particular comprise an oxide of an element chosen from Ti, Fe, Cu, Zn, Y, Zr, Nb, Mo, In, Si, Sn, Sb, Ta, W, Pb, Bi and Ce, preferably the oxide is SiO2. The particles according to the invention may, in addition, comprise surface functionalization. Advantageously, a surface functionalization can make it possible to obtain: a high affinity for keratinous substrates (for example by residual or reversible grafting or else by adsorption, etc.), a better compatibility with the formulative supports commonly used in cosmetics, o a particular association or organization of the particles (networks). Advantageously, the particle is functionalized in order to improve its affinity for the substrate, in particular the skin or the hair. This functionalization consists in introducing reactive functions on the surface of the particle, which will make it possible to carry out covalent bonds between said particle and the keratinous substrate. By reactive function is meant a reactive group which allows the formation of a covalent bond (by reaction with nucleophilic functions, in this case sulfhydryl functions -SH) and which therefore comprises one or more X nucleofugues, or one or several carbons or activated bonds. The usual nucleofuges are F, Cl, Br, -OSO3M, -OSO2alkyl, -OSO2aryl, -OSO2N (alkyl) 2, -OR1, SR2, -SOR2, -SO2R2, -S + R2R3, -SCN, -SCOOR2, -NR2R3, N + R2R3R4,

± NN \\ N \ e ~ and M represents a hydrogen atom, an alkaline or alkaline earth metal or an ammonium residue, R1 represents a hydrogen atom, a C1-C4 alkyl radical, a phenyl radical , substituted or not, the radical PO3H2 and its salts or the acetyl radical. R2, R3 and R4, which may be identical or different, represent a hydrogen atom, a C1-C4 alkyl radical or a substituted or unsubstituted phenyl radical. Among the most well-known reactive groups, mention may be made in particular of: mono and dihalotriazines, dihalogenoquinoxalines, dihalogeno pyrimidines, vinylsulfones or their precursors (3-halo or [3-sulfatoethylsulfones, acrylates and methacrylates, acrylamides and methacrylamides , maleimides and halomaleimides, epoxides and aziridine derivatives, oxazolinium, imidazolium or thi: azolidinium groups, carboxylic or sulfonic acid halides, esters, carbamates, anhydrides, isothiocyanates and isocyanates, lactones, azalactones having the structure: N 0 in which R 15 and R 16, which may be identical or different, represent a hydrogen atom, a C 1 -C 12 alkyl radical, C 3 -C 12 cycloalkyl, C 5 -C 12 aryl or C 6 -C 26 arenyl radicals; having from 0 to 3 heteroatoms selected from S, N and O, or R15 and R16 together form a carbocycle containing from 4 to 12 atoms and n is an integer from 0 to 3. D Surface functionalizations which may be suitable for the particles according to the invention are described in the following publications: Michalet et al., Science 2005, 307, 538, T. Pellegrino et al., Nano Lett. 2004, 4, 703, J.-E. Jdnsson et al., Macromolecules 27, 1932 (1994), Y. Kobayashi et al., JCIS 2003, 264, 385, Liz-Marzan, et al., Chem. Common. 1996, 731, L. Zhang et al. Adv. Funct. Mater. 2008, 18, 3834, I. Pastoriza-Santos, et al., Chem. Mater 2006, 18, 2465. The surface functionalization of these particles can, for example, comprise: groups chosen from -C (O) -, thiol, hydroxyl or sulfo groups, -00OR groups where R is H or a C1-C18 alkyl group, -SiX groups and neutral or cationic amines, -hydrophilic or hydrophobic polymers belonging to the polyacrylic, polysiloxane, polyamide, polyurethane, polyolefin, POE, potycationic, polyanionic, -mother families. cosmetic active agents such as antioxidants, essential oils, emollients, moisturizers or vitamins, dielectric materials, in particular described in paragraphs [0036] to [0039] of the application US 2009/0022766, and metal coatings, chosen in particular from coatings chosen from gold and silver or their alloys, the coatings being distinct from the first and second regions. DESCRIPTION OF THE FIGURES - FIGS. 1 and 1A to ID schematically represent examples of plasmonic particles according to the invention, FIG. 2 represents a simulation of the colorimetric gammut in reflectance reachable by particles according to the invention in comparison with plasmonic particles comprising only gold, FIGS. 3 and 3A represent colorimetric reflectance ranges attained by bi-metallic plasmonic particles, FIG. 4 represents an electron microscopy analysis of particles according to the invention, FIG. Particle reflectance according to the invention, FIG. 6 represents a comparative comparison of a contrast map comparing a composition comprising particles according to the invention and a composition comprising plasmonic particles of gold; FIG. 7 is a spectrum; in comparative reflectance between particles according to the invention and FIG. 8 represents a comparison between the reflectance spectra of compositions according to the invention and compositions comprising conventional pigments; FIG. 9 represents the coloration obtained by particles according to the invention in a composition, FIG. 10 represents the coloration obtained by particles according to the invention formulated in a composition. FIG. 1 shows an exemplary embodiment of a particle 1 according to the invention. The particle 1 comprises, in a first region 2, a first plasmonic metal, the first region 2 is coated with a second plasmonic metal, different from the first, present within a second region 3. The first and second plasmonic metals have together affect the plasmon resonance of the particle.

The first and second plasmonic metals may, for example, be selected from the group of plasmonic metals listed above as being suitable for the invention. The first and second plasmonic metals are preferably selected from gold and silver. The particle 1 may comprise within the first and / or second region (s) 2 and / or 3 an optically active material. FIG. 1A illustrates a variant embodiment in which the particle 1 comprises a first region 2 comprising a first plasmonic metal coated by a second region 3 comprising a second plasmonic metal, which is coated by a third region 4 comprising a third plasmonic metal. The three plasmonic metals are distinct in pairs and at least two of them may be able to influence the plasmonic resonance of the particle.

FIG. 1B represents a variant embodiment in which the plasmonic particle 1 comprises within it a dielectric material. The particle 1 comprises a first region 2 comprising a first plasmonic metal, coated with a layer 5 of a dielectric material, which is coated by a second region 3 comprising a second plasmonic metal.

The dielectric material may, for example, be selected from the group of dielectric materials listed above. The thickness e of the dielectric layer 5 is chosen such that the first and second plasmonic metals together have an effect on the plasmon resonance of the particle.

In a variant not illustrated, the dielectric layer 5 is not interposed between the first and second regions 2 and 3 but is located at the outer periphery of the particle. The particle 1 may further comprise, as illustrated in FIG. 1D, a dielectric material within a region 5 situated in the middle of the particle 1. The first region 2 encapsulates the dielectric material.

There is shown in Figure 1C an alternative embodiment wherein the particle 1 comprises, in a first region 2, a first plasmonic metal. The first region 2 is coated with a second region 3 which is, itself, coated with a layer made of the first plasmonic metal.

Of course, the stacks of layers that have just been described above can be applied to other geometries of particles, in particular platelet, polyhedral or cylindrical particles. Furthermore, it is not beyond the scope of the present invention if the particles 1 described above are themselves coated with other coating layers.

It is also not within the scope of the present invention when the particle 1 comprises surface functionalization, as described above. FIG. 2 represents a simulation of the ranges attainable, on the one hand, by Au @ Ag particles (gold coated with silver) and Ag @ Au (silver coated gold) according to the invention, and on the other hand , by plasmoids particles of gold. The solid arrows indicate an increase in the thickness of the particle's court and the dashed arrows indicate an increase in the thickness of the particle's bark. It is found that the colorimetric gamma reachable by the particles according to the invention is much greater than that attainable by plasmonic particles of gold. Figures 3 and 3A represent the colorimetric gammut reflectance reachable by particles "heart-bark" gold / silver. The thicknesses of the bark are indicated on the graduation of the horizontal axis and the thicknesses of the core are indicated on the graduation of the vertical axis. It can be seen that the "court-bark" gold / silver systems make it possible to obtain a colorimetric gammut with a particularly wide reflectance. . Measurement of Coverage Liquid Compositions (at 25 ° C) By "liquid composition" is meant a composition whose viscosity can be measured. A liquid composition can flow under the effect of its own weight. It can in particular be liquid compositions to be applied to the lips, in particular liquid lipsticks, liquid lip glosses and liquid lip balms, for nail polishes, eyeshadow, liquid foundations, mascaras and other liquid make-up products not intended to be applied to the lips The coverage of the compositions is measured at a finite thickness of 50 μm.

The composition is spread on matt black and matt white contrast cards, for example LENETA Form WP1 for the matte black card and Leneta 1A for the matt white card. The application can be performed with an automatic spreader.

The measurements are carried out on the compositions thus spread. Solid Compositions (at 25 ° C) Solid compositions are those whose viscosity can not be measured. It may be compositions cast in a stick or powder form, in the form of free or compact powders. a) For powdery solid compositions, free or compacted, the composition is applied using the same contrast cards as above, covered with a transparent tape, slightly rough, for example brand BLENDERMe 3M company and reference 15025, glued by the adhesive side on the contrast cards.

The composition is deposited on the adhesive tape so as to obtain a homogeneous deposition of 0.5 mg / cm ± 0.02 mg / cm 2. It is possible to use for depositing a sponge loaded with the composition and mounted on a disintegrating device that makes predefined movements with the sponge. The sponge is for example a disposable sponge type "LANCÔME - Photogenic", used on the pink side. b) The stick compositions are melted, for example at 90 ° C, and then spread in the liquid state on matt black and matt white contrast cards, for example with the same references as above, not covered with BLENDERMe. The spreading bar is maintained at the same temperature as the composition, so as to avoid thermal shock.

The stick compositions are thus deposited once melted with a thickness of 50 gm. Measurements and calculations Reflectance spectra are acquired using a MINOLTA 3700-d spectrocolorimeter (diffuse / 8 ° measurement geometry and D65 / 10 ° observation, specular component excluded mode, small aperture (CREISS)) on the backgrounds black and white, the contrast cards being possibly covered with BLENDERMe as indicated above.

The spectra are expressed in colorimetric coordinates in C111.Lab76 space within the meaning of the International Commission on Illumination according to Recommendation 15: 2004. The contrast ratio, or coverage, is calculated by averaging Y on a black background, divided by the average value of Y on a white background, multiplied by 100. Measurement of * and C * The sample is deposited in a Spectroscopic quartz vessel of known thickness. The opacity of the tank is measured according to the protocol above. A broad spectrum white light source (250-780 nm) is collimated and oriented perpendicular to the surface of the vessel. A calibrated integral sphere allows the collection of the backscattered signal with the exception of specular reflection. The measurement geometry is called 0 ° / d specular excluded. The measured signal is independent of the angle and the spatial position of exit relative to the spectrosopic tank. The signal is then sent to a spectrometer which performs the measurement as a function of the wavelength, which is referenced with respect to the quantity of light of the source, taking into account the collection efficiency of the overall optical system. . The reflection spectrum thus acquired is then converted into colorimetric coordinates in CIELab76 space within the meaning of the International Commission on Illumination according to Recommendation 15: 2004. Cosmetic Composition The cosmetic compositions according to the invention further comprise a cosmetically acceptable medium, that is to say compatible with keratin materials such as the skin of the face or the body, the lips, the hair, the eyelashes. , eyebrows and nails. The composition may advantageously comprise a fatty phase, which may itself comprise oils and / or preferably lipophilic solvents, as well as solid fatty substances at ambient temperature such as waxes, pasty fatty substances, gums and their mixtures. Among the constituents of the fatty phase, mention may be made of volatile or non-volatile oils, which may be chosen from natural or synthetic, carbonaceous, hydrocarbon-based, fluorinated or optionally branched oils, alone or as a mixture. The term "non-volatile oil" means an oil capable of remaining on the skin at ambient temperature and atmospheric pressure for at least one hour and having in particular a vapor pressure at room temperature (25 ° C.) and atmospheric pressure, which is not zero, less than at 0.01 mmHg (1.33 Pa). Non-volatile carbonaceous oils, in particular hydrocarbon-based oils, of plant, mineral, animal or synthetic origin, such as liquid paraffin (or petrolatum), squalane, hydrogenated polyisobutene (Parleam), perhydrosqualene, may be mentioned in particular. mink oil, macadamia oil, turtle oil, soy oil, sweet almond oil, calophyllum oil, palm oil, grape seed oil, sesame oil, maize oil, arara oil, rapeseed oil, sunflower oil, cotton, apricot, castor oil, avocado, jojoba, olive or cereal sprouts, shea butter; linear, branched or cyclic esters having more than 6 carbon atoms, especially 6 to 30 carbon atoms, such as the lanolic acid, oleic acid, lauric acid and stearic acid esters; esters derived from acids or alcohols with a long chain (that is to say having from 6 to 20 carbon atoms), in particular esters of formula RCOOR 'in which R represents the residue of a higher fatty acid comprising 7 to 19 carbon atoms and R 'represents a hydrocarbon chain comprising from 3 to 20 carbon atoms, in particular the C 12 -C 36 esters, such as isopropyl myristate, isopropyl palmitate, stearate of butyl, hexyl Iaurate, diisopropyl adipate, isononyl isononanoate, 2-ethylhexyl palmitate, 2-hexyl-decyl laurate, 2-octyl decyl palmitate, myristate or 2-octyl-dodecyl lactate, di (2-ethyl hexyl) succinate, diisostearyl malate, glycerin or diglycerine triisostearate; higher fatty acids, especially C14-C22 fatty acids, such as myristic acid, palmitic acid, stearic acid, behenic acid, oleic acid, linoleic acid, linolenic acid or isostearic acid; higher fatty alcohols, especially C16-C22, such as cetanol, oleic alcohol, linoleic or linolenic alcohol, isostearyl alcohol or octyl dodecanol; and their mixtures. Mention may also be made of decanol, dodecanol, octadecanol, liquid triglycerides of fatty acids containing from 4 to 10 carbon atoms, for instance triglycerides of heptanoic or octanoic acids and triglycerides of caprylic / capric acids; linear or branched hydrocarbons of mineral or synthetic origin, such as liquid paraffins and derivatives thereof, petroleum jelly, polydecenes, hydrogenated polyisobutene such as parleam; esters and synthetic ethers, in particular of fatty acids, for example purcellin oil, isopropyl myristate, 2-ethylhexyl palmitate, octyl-2-dodecyl stearate, erucate octyl-2-dodecyl, isostearyl isostearate; hydroxylated esters such as isostearyl lactate, octyl hydroxystearate, octyldodecyl hydroxystearate, diisostearyl malate, triisocetyl citrate, heptanoates, octanoates, decanoates of fatty alcohols; polyol esters such as propylene glycol dioctanoate, neopentyl glycol diheptanoate, diethylene glycol diisononanoate; and pentaerythritol esters; fatty alcohols having 12 to 26 carbon atoms such as octyldodecanol, 2-butyloctanol, 2-hexyldecanol, 2-undecylpentadecanol. Mention may also be made of ketones which are liquid at ambient temperature, such as methyl ethyl ketone, methyl isobutyl ketone, diisobutyl ketone, isophorone, cyclohexanone and acetone; propylene glycol ethers which are liquid at room temperature, such as propylene glycol monomethyl ether, propylene glycol monomethyl ether acetate or dipropylene glycol mono-butyl ether; short chain esters (having from 3 to 8 carbon atoms in total) such as ethyl acetate, methyl acetate, propyl acetate, n-butyl acetate, isopentyl; ethers which are liquid at ambient temperature, such as diethyl ether, dimethyl ether or dichlorodiethyl ether; alkanes that are liquid at room temperature, such as decane, heptane, dodecane, isododecane, isohexadecane or cyclohexane; aromatic cyclic compounds which are liquid at room temperature, such as toluene and xylene; aldehydes which are liquid at room temperature, such as benzaldehyde and acetaldehyde, and mixtures thereof. Among the volatile compounds that may be mentioned are non-silicone volatile oils, especially C 8 -C 16 isoparaffins such as isododecane, isodecane and isohexadecane. More preferentially, mention may be made of alkanes which are liquid at room temperature, volatile or otherwise, and more particularly decane, heptane, dodecane, isododecane, isohexadecane, cyclohexane and isodecane, and mixtures thereof. The fatty phase may be present in a content ranging from 0.01 to 95%, preferably from 0.1 to 90%, more preferably from 10 to 85% by weight, relative to the total weight of the composition, and better from 30 to 80%. The composition may also comprise a hydrophilic phase comprising water or a mixture of water and hydrophilic organic solvent (s) such as alcohols and in particular linear or branched lower monoalcohols having from 2 to 5 carbon atoms such as ethanol, isopropanol or n-propanol, and polyols such as glycerine, diglycerine, propylene glycol, sorbitol, pentylene glycol, and polyethylene glycols, or alternatively C 2 ethers; and hydrophilic C2-C4 aldehydes. The water or the mixture of water and hydrophilic organic solvents may be present in the composition according to the invention in a content ranging from 0.1 to 80% by weight, relative to the total weight of the composition, and preferably from 1 to 70% by weight. The composition according to the invention may also comprise waxes and / or gums. For the purposes of the present invention, the term "wax" means a lipophilic compound, solid at room temperature (25 ° C.), with a reversible solid / liquid state change, having a melting point of greater than or equal to 30 ° C. at 120 ° C. By bringing the wax to the liquid state (melting), it is possible to render it miscible with the oils that may be present and to form a homogeneous mixture microscopically, but by bringing the temperature of the mixture to room temperature, recrystallization of the mixture is obtained. wax in the oils of the mixture. The melting point of the wax can be measured using a differential scanning calorimeter (D.S.C.), for example the calorimeter sold under the name DSC 30 by the company METLER. The waxes may be hydrocarbon-based, fluorinated and / or silicone-based and may be of vegetable, mineral, animal and / or synthetic origin. In particular, the waxes have a melting point greater than 25 ° C. and better still greater than 45 ° C. As waxes for use in the composition of the invention, there may be mentioned beeswax, carnauba wax or Cande111a wax, paraffin wax, microcrystalline waxes, ceresin or ozokerite; synthetic waxes such as polyethylene or Fischer Tropsch waxes, silicone waxes such as alkyl or alkoxy dimeticone containing from 16 to 45 carbon atoms. The gums are generally high molecular weight polydimethylsiloxanes (PDMS) or cellulose gums or polysaccharides and the pasty substances are generally hydrocarbon compounds such as lanolines and their derivatives or else PDMSs. The nature and quantity of the solid bodies depend on the mechanical properties and textures sought. As an indication, the composition may contain from 0.01 to 50% by weight of waxes, relative to the total weight of the composition and better still from 1 to 30% by weight. The composition according to the invention may further comprise one or more dyestuffs chosen from water-soluble dyes, liposoluble dyes, and pulverulent dyestuffs such as pigments, nacres, and flakes well known to those skilled in the art. The dyestuffs may be present in the composition in a content ranging from 0.01 to 50% by weight, relative to the weight of the composition, preferably from 0.01 to 30% by weight. By pigments, it is necessary to include particles of any shape, white or colored, mineral or organic, insoluble in the physiological medium, intended to color the composition. By nacres, it is necessary to understand particles of any iridescent background, especially produced by some shellfish in their shell or synthesized. The pigments may be white or colored, mineral and / or organic. Among the inorganic pigments, titanium dioxide, optionally surface-treated, zirconium oxide or cerium oxides, and oxides of zinc, iron (black, yellow or red) or chromium, the violet of manganese, ultramarine blue, chromium hydrate and ferric blue, metallic powders such as aluminum powder, copper powder. Among the organic pigments, mention may be made of carbon black, D & C type pigments, and lacquers based on cochineal carmine, barium, strontium, calcium, aluminum. The pearlescent pigments may be chosen from white pearlescent pigments such as mica coated with titanium, or bismuth oxychloride, colored pearlescent pigments such as titanium mica coated with iron oxides, titanium mica coated with, inter alia, blue. ferric oxide or chromium oxide, titanium mica coated with an organic pigment of the aforementioned type as well as pearlescent pigments based on bismuth oxychloride. Examples of water-soluble dyes that may be mentioned are the disodium salt of a culvert, the disodium salt of alizarin green, quinoline yellow, the trisodium salt of amaranth, the disodium salt of tartrazine, the monosodium salt of rhodamine and the disodium salt. fuchsin, xanthophyll, methylene blue. The composition according to the invention may also comprise one or more fillers, in particular in a content ranging from 0.01% to 50% by weight, relative to the total weight of the composition, preferably ranging from 0.01% to 30% by weight. % in weight. By fillers, it is necessary to include particles of any form, colorless or white, mineral or synthetic, insoluble in the medium of the composition regardless of the temperature at which the composition is manufactured. These fillers serve in particular to modify the rheology or the texture of the composition. The fillers can be mineral or organic of any form, platelet, spherical or oblong, irrespective of the crystallographic form (for example sheet, cubic, hexagonal, orthorhombic, etc.). Mention may be made of talc, mica, silica, kaolin, polyamide (Nylone) powders (Orgasol® from Atochem), poly-13-alanine and polyethylene, tetrafluoroethylene polymer powders (Tenor ™). , lauroyl-lysine, starch, boron nitride, polymeric hollow microspheres such as those of polyvinylidene chloride / acrylonitrile such as Expancel® (Nobel Industry), copolymers of acrylic acid (Polytrape Dow Coming) and silicone resin microbeads (Toshiba Tospearlse, for example), elastomeric polyorganosiloxane particles, precipitated calcium carbonate, magnesium carbonate and hydrocarbonate, hydroxyapatite, hollow silica microspheres (Silica Beadsc de Maprecos), glass or ceramic microcapsules, metal soaps derived from organic carboxylic acids having 8 to 22 carbon atoms, preferably 12 to 18 carbon atoms, for example st. arate zinc, magnesium or lithium, zinc laurate, magnesium myristate 15. The composition may further comprise an additional polymer such as a film-forming polymer. According to the present invention, the term "film-forming polymer" means a polymer capable of forming on its own or in the presence of an auxiliary film-forming agent, a continuous and adherent film on a support, in particular on keratin materials. Among the film-forming polymers that may be used in the composition of the present invention, mention may be made of synthetic polymers, of radical type or of polycondensate type, polymers of natural origin and mixtures thereof, in particular acrylic polymers, polyurethanes, polyesters, polyamides, polyureas, cellulosic polymers such as nitrocellulose. The composition according to the invention may also comprise ingredients commonly used in cosmetics, such as vitamins, thickeners, gelling agents, trace elements, softeners, sequestering agents, perfumes, alkalizing or acidifying agents, preservatives. sunscreens, surfactants, antioxidants, anti-hair loss agents, anti-dandruff agents, propellants, ceramides, or mixtures thereof. Of course, those skilled in the art will take care to choose this or these optional additional compounds, and / or their quantity, in such a way that the advantageous properties of the composition according to the invention are not, or not substantially, impaired by the addition envisaged. The composition according to the invention may be in particular in the form of a suspension, a dispersion, an especially organic solution, a gel or an emulsion, in particular an oil-in-water (O / W) or water-in-oil (E) emulsion. / H), or multiple (W / O / E or polyol / H / E or H / E / H), in the form of cream, paste, foam, dispersion of vesicles including ionic lipids or not, lotion biphase or multiphase, spray, powder, stick (stick). Those skilled in the art may choose the appropriate dosage form, as well as its method of preparation, on the basis of its general knowledge, taking into account, on the one hand, the nature of the constituents used, in particular their solubility in the support, and on the other hand, of the application envisaged for the composition. The composition according to the invention may be a makeup composition, especially a complexion product such as a foundation, a blush or an eyeshadow; a lip product such as lipstick, lip care, lip gloss; a concealer product; a blush, a mascara, an eyeliner; an eyebrow makeup product, a lip pencil or an eye pencil; nail product such as nail polish or nail care; a body make-up product. The composition according to the invention can also be a composition for protecting or caring for the skin of the face, neck, hands or body, in particular a composition that is anti-wrinkle, anti-fatigue and anti-fatigue that gives the skin a boost. a moisturizing or treating composition; an antisolar composition or an artificial tanning composition The composition according to the invention can also be a hair product, in particular for shaping, conditioning and / or making up the hair.

It may be a conditioner, a gel, a lotion, a fixing and styling composition such as a lacquer; or a mascara for hair. The composition according to the invention finds particular application as a make-up composition for keratin materials, in particular the skin of the face, lips, eyelashes, nails or hair.

The subject of the invention is also a process for the cosmetic treatment of keratin materials, in particular the skin of the body or of the face, the lips, the nails, the hair and / or the eyelashes, comprising the application on the said materials of a cosmetic composition as defined above. It is preferably a method of making said keratin materials.

Process for the cosmetic treatment of the hair When the process according to the invention consists of a process for the cosmetic treatment, in particular of makeup, in particular of coloring, of the hair, the application of the composition according to the invention can be carried out, for example, by spraying, dipping or shampooing. Any tool suitable for applying the composition to hair can be used. In particular, it is possible to use a brush or a brush. Alternatively, the composition according to the invention can be applied to the hair manually. In an exemplary embodiment, the hair may undergo a pretreatment step before application of the composition according to the invention. The pretreatment of the hair may in particular make it possible to improve the adhesion of the makeup composition, in particular of coloration, to the hair. EXAMPLES Example 1 Synthesis of a "Heart-Bark" Particle Having a 150-nm Golden Yard Coated with a Silver Bark having a Thickness of 5 nm All the experiments detailed in this example were conducted at 25 ° C. The synthesis of "bark-shell" particles has two stages. The first step consists of a synthesis of gold particles having a diameter of 150 nm using a slightly modified particle growth method compared to that developed by Liz-Marzan et al. (Langmuir, 2006, 22, 7007-7010). The second step consists in coating the gold particles, obtained at the end of the first stage, with a silver bark. Replenishment of Gold Particles having a Size of 15 nm HAuC14 was mixed in a flask with 0.5 L of water to obtain a final gold concentration of 0.5 mM. Then 25 ml of a hot aqueous solution containing 0.25 g of sodium citrate dihydrate (116C607Na2.2112O) is added to the boiling gold solution.

The resulting solution is then boiled for 30 minutes and then placed in the refrigerator. Synthesis of gold particles before a size of 60 nm It is possible to connect the size of the particles after growth (rf) to the size of the particles before growth (ri) by the following formula: I / 3 / Cs + C rf = YX C, where Cs is the concentration of gold salt and Ci is the concentration of gold particles before growth. In order to obtain particles with a final diameter of 60 nm, a final theoretical diameter rf of 68 nm was taken into account in the formula above. By taking rf = 68 nm and Cs = 0.25 mm, a concentration Ci equal to 2.7 × 10 -6 M is obtained. Gold particles having a size of 15 nm to one liter of water comprising 15 mmol of hexadecyltrimethylammonium bromide (CTAB) and 0.25 mmol of HAuCl4 are added at 35 ° C. in order to obtain the concentration Ci in gold particles.

Then, 5 mL of an aqueous solution of L-ascorbic acid (C6H806, formulated at C = 100 mM in 10 mL of water) is added giving a final concentration of 0.5 mM. After the reaction, the particles were centrifuged at 3500 rpm for thirty minutes. The supernatant was remixed with 0.1 M CTAB and the particles were again centrifuged. The grains obtained in the centrifuge tubes were then placed in a test tube which was placed in a hot water bath (substantially boiling, T = 95 ° C) for 5 minutes.

The test tube was then placed upright and the particles allowed to settle overnight.

The supernatant comprising the spherical particles has been preserved. Svnthesis of gold particles having a size of l 50 nm

The same growth method as described in the previous paragraph was used to change the gold particle diameter from 60 nm to 150 nm. However, the concentrations at the beginning of the growth reaction in HAuC14, CTAB and ascorbic acid used were 0.5, 30 and 1 mM, respectively. No purification was necessary because only spherical particles were used in this process. Silver Coating of Gold Particles Before a Size of 150 nm Two different approaches can be used depending on the stabilizing agent used with the gold particles. PEG-SH Stabilizing Agent The gold particles having a size of 150 nm, obtained previously, were centrifuged at 1500 rpm and the supernatant was discarded. The particles were redispersed in half of the initial volume of water and, depending on the nanoparticle concentrations, a certain volume of O- [2- (3-mercapiopropylamino) ethyl] -O'-methylpolyethylene glycol stock solution (PEG-thiol Mw = 5000, C = 0.5mM) was added to give a final concentration of 4 molecules / nm3. Then, in a flask, gold particles were dispersed in a phosphate buffer solution at a pH of 7.4. Hydroquinone (HQ) and silver ions (AgNO3) were added, with stirring, with a molar ratio of 1. For 5 nm silver bark the concentrations at the beginning of the coating reaction by silver, gold, phosphate ions, HQ and silver are respectively 0.25, 10, 0.05 and 0.05 mM. After reaction, 5 mg of polyethylenimine (PEI, Mw = 25,000) was added to prevent aggregation of the particles. The particles were then centrifuged at 1500 rpm for 30 minutes and washed with water. The purification step was repeated three times. CTAB stabilizing agent (hexadecyltrimethylammonium bromide) In this case, no modification of the stabilizing agent is necessary.

In a flask, gold particles were dispersed with stirring in a glycine buffer at pH 9. Then, after adjusting the CTAB concentration, silver ions and hydroquirione (HO) were added. For a silver bark of 5 nm, the concentrations at the beginning of the coating reaction with silver, gold, glycine, CTAB, HQ and silver were 0.25, 10 , 1, 0.05 and 0.05 mM respectively. The particles were centrifuged at 1500 rpm for 30 minutes and washed with 10 mM CTAB solution. The purification step was repeated three times.

EXAMPLE 2 Synthesis of a "core-shell" particle having a gold core of 150 nm in diameter coated with a silver bark having a thickness of 10 nm The procedure described in Example 1 for obtaining gold particles of 150 nm.

Then, in a 200 ml flask, gold particles were dispersed, with stirring, in a glycine buffer at a pH of 9. Then, after adjusting the CTAB concentration, silver ions and hydroquinone ( HO) have been added. The concentrations at the beginning of the silver coating reaction of gold, glycine, CTAB, HO and silver were 0.5, 10, 1, 0.05 and 0.05. mM respectively. The particles were centrifuged at 1500 rpm for 30 minutes and washed with 10 mM CTAB solution. The purification step was repeated three times.

FIG. 4 represents an electron microscopy analysis of the "core-shell" type particles synthesized in example 2. FIG. 5 represents the reflectance spectrum of the "core-shell" particles synthesized in example 2 and the spectrum corresponds to 3: Comparison of the colorimetric effects produced, on the one hand, by particles according to the invention and, on the other hand, by particles comprising a single plasmonic metal. a first tank, a first solution comprising an aqueous solution having a concentration of 10 mM CTAB and plasmonic particles of gold, having a diameter of 160 nm, prepared following the protocol described in step 1 of Example 2 ( for rf = 160 nm) formulated at 0.005% by volume. A second solution was placed in a second tank comprising the same aqueous solution having a concentration of 10 mM CTAB and Au @ Ag plasmonic particles, synthesized in Example 2, formulated at a rate of 0.0005% by volume. These first and second tanks are superimposed on a contrast map having a white area and a black area. The results are given in FIG. 6. It can be seen that, although they are formulated in a quantity ten times smaller, the plasmonic particles according to the invention give the solution a clearly improved brightness and a covering (visibility white / black background). ) about the same as that obtained with gold plasmonic particles. The benefit in terms of brightness is evaluated at 20% when the medium is opaque. When the medium is non-opaque and the same amount of material the colorimetric benefit is much higher.

Indeed, Figure 7 provides a comparison of the reflectance spectra of solutions each comprising one of two types of plasmonic particles formulated at the same concentration, namely 0.1% by weight. In this case, the systems are non-opaque but have the same mass fraction of material (corresponding to 0.005% by volume). The opacity is measured for a deposited film thickness of 500 μm. Brightness, saturation and opacity measurements are provided in Table 1 below. Example Brightness * Saturation * Gold Sphere Capacity 160 15 11 2.5 nm diameter 0.005% v in 500 μm Gold Sphere 150 45 42 37 nm diameter with a shell 10 nm thick silver 0.005% v in 500! lm * Measurements with a D65 illuminant and a 10 ° observer Table 1

EXAMPLE 4 Comparison of the Colorimetric Effects Produced, on the one hand, by Particles According to the Invention and, on the Other Hand, by Conventional Pigments The preparations are aqueous solutions consisting of 0.05% by volume of the plasmonic particles according to the invention and cationic surfactant CTAB at lOMM. Various measurements have been made for thicknesses deposited on dark background / white background contrast cards.

The reflectance spectra of FIG. 8 correspond to measurements on a black background, in other words to the energy returned by the pigments alone. The comparison between the reflectance spectra makes it possible to calculate the opacity of the system. The measurements are made on a black background so that the opacity and the reflected light come only from the pigments used in the examples of Table 2 below: Example Brightness * Saturation * Gold Sphere opacity of 150 nm diameter 53 59 100 with bark 10 nm thick silver 0.05% v in 500 am gold sphere 150 nm in diameter 51 54 75 with a bark 10 nm thick silver 0.05% v in 100 pm ~. Gold sphere 150 nm in diameter 32 29 11 with a bark 10 nm thick in silver 0.05% v in I0 am - ~ `Pigments Red? (17% v) in oil of 27 54 100 - Parleam + solsperse. Tank 500 μm. Iron oxides (0.5% v) in oil of 30 64 100 Fmμ `` - ~, ~ ® Parleam + solsperse. Vessel 500 microns * Measurements carried out with a D65 illuminant and an observer 10 ° Table 2 It is found that, compared to traditional pigments, a very small amount of plasmonic pigments according to the invention is sufficient to obtain a higher brightness. EXAMPLE 5 Cosmetic Composition According to the Invention Base of Foundation The contents indicated in the composition below are by weight.

Magnesium sulphate 0.7 eyclopentasiloxane and disteardimonium hectorite 5.8 dimethicone 2.9 cyclopentasiloxane 10.3 acetylated glycol stearate 0.5 propylene glycol 5.0 isododecane 1.9 preservative qs polyglyceryl-4 isostearate and eetyl peg / ppg- 10/1 dimethicone 6.55 and hexyl laurate 20 Water qs 100%

Comparative Trial A photograph between a foundation base with and without the plasmonic particles synthesized in Example 2 is provided in Figure 9. Example Brightness * Saturation * Foundation Base 40 0.5 Base Foundation 58 165 incorporating 0.0028% by volume of plasmonic particles Au @ Ag 150/10 nm Gain 47% * Measurements carried out with a D65 illuminant and a 10 ° observer. Thickness = 200 μm Table 3 The use of a very small amount of plasmonic particles according to the invention at 0.0028% by volume increased the brightness of the foundation base by 47%. In addition to the increase in brightness, there is a saturation of the color of the base. EXAMPLE 6 Cosmetic composition according to the invention Sheathing capillary composition: Resyn 28-2930 25% 12.5 g AMP neutralization 1.44 g EtOH, qs 100% 36.06 g Resyn 28-2930: terpolymer vinyl acetate / crotonic acid / neodecanoate vinyl (Tg = 39 ° C). This copolymer must be neutralized with 2-Amin 2-methyl-1-propanol (AMP) for solvation in absolute ethanol (EtOH)

Application of the formula: - 80% Au @ Ag 150/10 nm in the Resyn 28-2930 preparation described above; that is 5% MA of resin and 0.8% MA of plasmon. - Application of 0.8 g of formula on a 1 g BP wick. - spread flat and with the finger and drying with a hair dryer. When the alcoholic resin solution is introduced, no change in the color of the plasmons is observed; it is during the application made 2-3 minutes later that we detect on the hair at first and then in solution 2-3 minutes later an evolution of the color of the formula. The final result is a visibly colored wick (c £ Figure 10). Table 4 given, below, gives the colorimetric measurements made at D65, 10 °. L * a b C * h * Reference 48.2 3.4 9.8 10.4 70.9 Colored wick 41.0 11.8 13.8 18.1 49.6 Table 3

EXAMPLE 7 A liquid eye shadow comprising (in g) distearyl dimethyl ammonium modified hectorite 3.7 triglycerides of 6,6 lauric / palmitic / cetyl / stearic acid (50/20/10/10) protected refined paraffin 3 is prepared. 9 propylene carbonate 1.2 beeswax 7.8 protected shorea butter 1.7 liquid fraction of protected shea butter 0.85 talc 10.4 nylon powder 12 10.4 Particles of Example 1 4, Example 8 A powder eye shadow comprising (in g) white petrolatum 1.2 oleic alcohol 1.2 lanolin liquid 0.7 castor oil 1.3 vaseline oil 6.5 myristate isopropyl 0.8 mixture p-hydroxybenzoates of methyl, ethyl, propyl, 0.6 butyl isobutyl / 2-phenoxy ethanol talc 30 Particles of Example 1 0.5 magnesium stearate 4 Preservative qs Antioxidant qs The expression " with "must be understood as" comprising at least one ". The expression "understood between" must be understood as inclusive limits.

Claims (15)

REVENDICATIONS1. Cosmetic composition comprising: a medium CLAIMS1. Cosmetic composition comprising: a cosmetically acceptable medium, and colored particles of size between 70 nm and 1 μm comprising: in a first region, a first metal compound consisting of a first plasmonic metal or one of its alloys, and o in a second region distinct from the first, a second metal compound consisting of a second plasmonic metal or one of its alloys, the second metal compound being different from the first metal compound, the first and second regions each having a size or thickness greater than or equal to 2 nm and the first and second metal compounds together affecting the plasmonic resonance of the particles. 2. Composition according to claim 1, the particles having a distance between the first and second regions of less than or equal to 45 nm, in particular at 30 nm, in particular at 15 nm. 3. Composition according to any one of the preceding claims, the particles having a size between 80 nm and 700 nm, especially between 90 and 300 nm, especially between 100 and 250 nm, in particular between 110 nm and 200 nm. 4. Composition according to any one of the preceding claims, the second region of the particles encapsulating the first region of the particles. 5. Composition according to any one of the preceding claims, the second region having a size of between 2 nm and 1 μm, in particular between 2 nm and 30 nm, even between 3 nm and 25 nm, and even better between 4 nm. and 20 nm. 6. Composition according to any one of the preceding claims, the first region having a size between 30 nm and 900 nm, better between 40 nm and 800 nm, better between 60 nm and 700 nm, preferably between 70 nm and 600 nm. . 7. Composition according to any one of the preceding claims, the first and second regions of the particles being in contact with each other. 8. Composition according to any one of the preceding claims, the particles further comprising a dielectric material. 9. Composition according to any one of the preceding claims, the particles comprising, in a third region, a third metal compound consisting of a third plasmonic metal or one of its alloys, the third metal compound being different from the first and second metal compounds. 10. Composition according to any one of the preceding claims, the first and / or the second and / or the possible third plasmonic metal of the particles being chosen from tungsten (W), aluminum (Al), palladium (Pd), platinum (Pt), silver (Ag), copper (Cu), gold (Au), chromium (Cr), zinc (Zn), rhodium (Rh), nickel (Ni) and tin (Sn). 11. Composition according to the preceding claim, the first and second metal compounds of the particles being chosen from gold and silver, in particular the first metal compound being gold and the second metal compound being silver. 12. A process for the cosmetic treatment, especially of makeup or coloring, of human keratin materials, comprising the step of applying to the human keratin materials to be treated a composition according to any one of claims 1 to 11. 13. A method of making up the hair, skin and / or lips, comprising a step of applying to the hair, lips and / or skin of a composition according to any one of claims 1 to 11. 14. A colored particle of size between 110 nm and 1 μm comprising: in a first region, a first metal compound consisting of a first plasmonic metal or one of its alloys, and in a second region distinct from the first, a second compound 25 metal comprising a second plasmonic metal or one of its alloys, the second metal compound being different from the first metal compound, the first and second regions each having a size or a thickness greater than or equal to 2 nm and the first and second metal compounds having together affect the plasmon resonance of the particle. 30 15. A colored particle of size between 70 nm and 1 μm comprising: in a first region a first metal compound consisting of a first plasmonic metal or one of its alloys, and in a second region coating the first region and distinct from that a second metal compound consisting of a second plasmonic metal or one of its alloys, the second metal compound being different from the first metal compound, the first and second regions each having a size or a thickness greater than or equal to 2 nm, the first and second metal compounds together affecting the plasmon resonance of the particle.