Spheroidal composite particles and cosmetic composition containing the same

Abstract

The present invention aims to provide a composite particle that simultaneously blocks both ultraviolet light and infrared light with a single particle, has good dispersibility and photothermal effect, and is highly safe.The present invention relates to a prolate ellipsoidal composite particle that includes Au nanorods, a Pt nanoparticle coating layer containing Pt nanoparticles provided on the surface of the Au nanorods, and an Au nano outermost layer provided on the surface of the Pt nanoparticle coating layer.

Description

[Technical Field]

[0001] The present invention relates to prolate ellipsoidal composite particles and cosmetic compositions containing the same. [Background technology]

[0002] Skin aging is caused by various factors, one of which is photoaging caused by exposure to ultraviolet light. Skin aging caused by ultraviolet light has long been known, and various ultraviolet light blocking materials have been developed. In recent years, near-infrared light has also been considered a cause of skin aging, and accordingly, infrared light blocking materials have also been developed.

[0003] For example, Patent Document 1 discloses a cosmetic composition for simultaneously blocking ultraviolet and infrared rays, which contains an ultraviolet-blocking inorganic material, an infrared-blocking inorganic material, and a dispersant. Patent Document 2 discloses a cosmetic composition whose active ingredient is a composite powder comprising infrared-blocking particles and ultraviolet-blocking particles coated on one surface of the infrared-blocking particles. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japan Special Publication No. 2022-533797 [Patent Document 2] Japan Special Publication No. 2012-519166 Summary of the Invention [Problem to be solved by the invention]

[0005] The cosmetic composition for simultaneous blocking of ultraviolet and infrared rays described in Patent Document 1 contains an ultraviolet blocking material and an infrared blocking material, respectively, to simultaneously block ultraviolet light and infrared light. In such a cosmetic composition, it is necessary to adjust the content ratio of each inorganic blocking material and select the type of dispersant. Furthermore, when attempting to mix the composition with other active ingredients, the blocking materials tend to aggregate, resulting in a cloudy appearance.

[0006] Furthermore, in the composite powder described in Patent Document 2, titanium oxide (titanium dioxide) is used for the ultraviolet-blocking particles and infrared-blocking particles, but titanium oxide is classified as a group that may be carcinogenic to humans in the carcinogenicity classification established by the International Agency for Research on Cancer (IARC) (also abbreviated as IARC carcinogenicity classification), and there are concerns about its safety.

[0007] Therefore, an object of the present invention is to provide a composite particle that simultaneously blocks both ultraviolet light and infrared light with a single particle, has good dispersibility and photothermal effect, and is highly safe. [Means for solving the problem]

[0008] As a result of extensive research, the present inventors have discovered that the above-mentioned problems can be solved by using prolate ellipsoidal composite particles (hereinafter also abbreviated as "Au / Pt / Au prolate ellipsoidal nanoparticles") comprising Au nanorods, a Pt nanoparticle coating layer containing Pt nanoparticles provided on the surface of the Au nanorods, and an Au nano outermost layer provided on the surface of the Pt nanoparticle coating layer, and have thus completed the present invention.

[0009] That is, the present invention is as follows. 1. A prolate ellipsoidal composite particle comprising an Au nanorod, a Pt nanoparticle coating layer containing Pt nanoparticles provided on the surface of the Au nanorod, and an Au nano outermost layer provided on the surface of the Pt nanoparticle coating layer. 2. The oblong ellipsoidal composite particle according to 1 above, which has absorption maxima simultaneously in the wavelength range of 200 nm to 400 nm and in the wavelength range of 700 nm or more. 3. The oblong ellipsoidal composite particle according to 2 above, which further has an absorption maximum in the wavelength range of 500 nm to 700 nm. 4. The oblong ellipsoidal composite particle according to 1 above, having a major axis of 100 nm or more and 1000 nm or less and a minor axis of 50 nm or more and 300 nm or less. 5. The oblong ellipsoidal composite particle according to 1 above, wherein the Au nanorods have a minor axis diameter of 5 nm or more and 20 nm or less and a major axis diameter of 15 nm or more and 200 nm or less. 6. The oblong ellipsoidal composite particle according to 1 above, wherein the Au nanorods have an aspect ratio of 3 or more. 7. The oblong ellipsoidal composite particles according to 1 above, wherein the Pt nanoparticles have an aspect ratio of 1 to 2. 8. The oblong ellipsoidal composite particle according to 1 above, wherein the Pt nanoparticle coating layer has a thickness of 1 nm to 100 nm. 9. The oblong ellipsoidal composite particle according to 1 above, wherein the thickness of the outermost Au nanolayer is 1 nm to 200 nm. 10. A cosmetic composition containing the prolate ellipsoidal composite particles described in any one of 1 to 9 above. [Effects of the Invention]

[0010] The composite particles of the present disclosure use a single particle rather than multiple types of particles to simultaneously block both ultraviolet light and infrared light, which results in good dispersibility and can be easily mixed with other cosmetic ingredients.

[0011] Furthermore, in the composite particles of the present disclosure, the Pt nanoparticle coating layer, which is an intermediate layer, is coated on the outside with an Au nano outermost layer, which prevents the Pt from coming into direct contact with the skin and does not induce inflammatory reactions such as allergies, even when used in cosmetics, etc. Furthermore, the Au in the outermost layer of the composite particles of the present disclosure has a low ionization tendency and is unlikely to release metal ions that cause inflammatory reactions such as allergies, so that the particles are also unlikely to induce inflammatory reactions from this perspective.

[0012] Furthermore, in the composite particles of the present disclosure, the rod-shaped Au nanoparticles (Au nanorods) that serve as the core have a photothermal effect, absorbing light energy and generating heat. However, the Au nanorods are coated with a Pt nanoparticle coating layer at the outermost Au nanolayer, increasing their volume relative to the Au nanorods. This increases the scattering and absorption intensity depending on the particle's volume, further enhancing the photothermal effect. This leads to anti-aging effects, such as destroying melanin-producing cells (melanocytes) that cause age spots, promoting skin cell turnover, and suppressing the occurrence of age spots. Furthermore, because the composite particles of the present disclosure use Au and Pt, which are not classified as carcinogenic by the IARC, they can be used as highly safe cosmetic materials. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a schematic diagram of a cross section of an oblong ellipsoidal composite particle according to one embodiment of the present invention. [Figure 2] FIG. 2 shows the results of observing an example of an Au nanorod with an electron microscope. [Figure 3] FIG. 3 shows the results of observing an example of a Pt / Au nanorod with an electron microscope. [Figure 4] FIG. 4 is a diagram showing the results of observing, with an electron microscope, prolate spheroidal composite particles (Au / Pt / Au prolate spheroidal nanoparticles) according to one embodiment of the present invention. [Figure 5] FIG. 5 is a schematic diagram showing the shape of an oblong spheroidal composite particle (Au / Pt / Au oblong spheroidal nanoparticle) according to one embodiment of the present invention. [Figure 6] FIG. 6 shows the extinction spectrum of Example 1 (Au nanorods). [Figure 7] FIG. 7 shows the extinction spectrum of Example 2 (Pt / Au nanorods). [Figure 8] FIG. 8 shows the extinction spectrum of Example 3 (Pt / Au nanorods). [Figure 9] FIG. 9 shows the extinction spectrum of Example 4 (Au / Pt / Au prolate spheroidal nanoparticles). [Figure 10] FIG. 10 shows the extinction spectrum of Example 5 (Au / Pt / Au prolate spheroidal nanoparticles). [Figure 11] FIG. 11 shows the extinction spectrum of Example 6 (Au / Pt / Au prolate spheroidal nanoparticles). [Figure 12] FIG. 12 shows the results of evaluating the thermal properties of nanoparticles on a substrate. [Figure 13A] FIG. 13A shows the results of evaluating the photothermal effect of nanoparticles in simulated cosmetics. [Figure 13B] FIG. 13B shows the results of evaluating the photothermal effect of nanoparticles in simulated cosmetics. DETAILED DESCRIPTION OF THE INVENTION

[0014] The present invention will be described in detail below based on the embodiments, but the present invention is not limited to the following embodiments and can be implemented in any modified form within the scope of the gist of the present invention.

[0015] In this specification, the use of "to" to indicate a range of values ​​means that the values ​​before and after it are included as the lower and upper limits.

[0016] In this specification, "blocking light" does not necessarily mean blocking 100% of the light, but also means blocking a certain percentage of the light that is less than 100%.

[0017] [Spheroidal composite particles] The oblong composite particle of this embodiment (hereinafter also referred to as the present composite particle) is characterized by including an Au nanorod, a Pt nanoparticle coating layer containing Pt nanoparticles provided on the surface of the Au nanorod, and an Au nano outermost layer provided on the surface of the Pt nanoparticle coating layer.

[0018] The composite particles have a prolate ellipsoidal shape. FIG. 5 is a schematic diagram showing the shape of a prolate ellipsoidal composite particle (Au / Pt / Au prolate ellipsoidal nanoparticle) 50 according to one embodiment of the present invention. In this specification, the term "prolate ellipsoidal" refers to a curved surface that extends symmetrically along a central axis in three-dimensional space, and its cross section is elliptical, having a major axis and a minor axis. Depending on the ratio of the major axis to the minor axis, the prolate ellipsoidal shape can take on a more elongated or spherical shape. Specifically, as shown in FIG. 5, the prolate ellipsoidal shape can be defined by the ratio of the lengths along the two axes, the diameter of the major axis 51 and the diameter of the minor axis 52. Furthermore, the prolate ellipsoid has a radius of curvature.

[0019] The major axis of the composite particles is preferably 100 nm or more, more preferably 125 nm or more, and even more preferably 150 nm or more, and is preferably 1000 nm or less, more preferably 500 nm or less, and even more preferably 300 nm or less. When the major axis of the composite particles is 100 nm or more, the composite particles can be prevented from penetrating into the dermis, and when it is 1000 nm or less, the dispersibility of the particles can be sufficiently maintained.

[0020] The major axis of the composite particle is determined by measuring the major axis dimensions of rectangles circumscribing 50 composite particles of the present embodiment randomly selected from a TEM image and averaging the measurements.

[0021] The minor axis of the composite particles is preferably 50 nm or more, more preferably 75 nm or more, and even more preferably 100 nm or more, and is preferably 300 nm or less, more preferably 250 nm or less, and even more preferably 200 nm or less. When the minor axis of the composite particles is 50 nm or more, the Pt has a structure in which it is sufficiently coated with Au, and when it is 300 nm or less, the composite particles do not aggregate and can maintain sufficient dispersibility.

[0022] The minor axis of the composite particle is determined by measuring the minor axis dimensions of rectangles circumscribing 50 composite particles of the present embodiment randomly selected from a TEM image and averaging the measurements.

[0023] The present composite particles preferably have absorption maxima simultaneously in the wavelength range of 200 nm to 400 nm and in the wavelength range of 700 nm or more when dispersed in a solution. This allows them to simultaneously block ultraviolet light and infrared light. In the present composite particles, the absorption maxima in the wavelength range of 200 nm to 400 nm are thought to be derived from Pt nanoparticles, and the absorption maxima in the wavelength range of 700 nm or more are thought to be derived from the major axis of the prolate ellipsoid.

[0024] The present composite particles preferably also have an absorption maximum in the wavelength range of 500 nm to 700 nm when dispersed in a solution. In the present composite particles, the absorption maximum in the wavelength range of 500 nm to 700 nm is thought to be derived from the minor axis of the prolate ellipsoid.

[0025] As used herein, the term "absorption maximum" refers to the change in extinction from an increase to a decrease at a certain wavelength in the extinction spectrum of the combined absorption and scattering components of the composite particle. The presence or absence of an absorption maximum can be analyzed by the method described in the Examples.

[0026] A schematic diagram of the present composite particle is shown in Figure 1. As shown in Figure 1, the present composite particle 10 has a Pt nanoparticle coating layer 12 containing Pt nanoparticles provided on the surface of an Au nanorod 11, and an Au nano outermost layer 13 provided on the surface of the Pt nanoparticle coating layer 12. Each element will be described in detail below.

[0027] (Au nanorods) The composite particles include Au nanorods. In this specification, "Au nanorods" refers to rod-shaped Au nanoparticles. In this specification, "rod-shaped" refers to a one-dimensional rod-like shape, typically with a length greater than its diameter. An example of a rod-shaped shape is a cylindrical shape. Figure 2 is a microscopic image of an example of an Au nanorod.

[0028] The Au nanorods in this embodiment preferably have an aspect ratio of at least 3. In this specification, the "aspect ratio of the Au nanorods" refers to the ratio of the long axis to the short axis of the particle [long axis / short axis].

[0029] Au nanorods can absorb infrared light sufficiently when their aspect ratio is 3 or greater. The aspect ratio of Au nanorods is preferably 3 or greater, more preferably 4 or greater, even more preferably 5 or greater, particularly preferably 6 or greater, and is, for example, 10 or less.

[0030] The "nano" in Au nanorods means that both the long and short axes of the particles are on the order of nanometers, that is, 1 nm or more and less than 1 μm (less than 1000 nm).

[0031] The major axis of the Au nanorod is preferably 15 nm or more, more preferably 50 nm or more, even more preferably 100 nm or more, and is preferably 200 nm or less, more preferably 180 nm or less, and even more preferably 150 nm or less. By ensuring that the major axis diameter of the Au nanorod is 15 nm or more and 200 nm or less, the size required for the major axis of the prolate ellipsoid described below can be ensured in the composite particle.

[0032] The minor axis of the Au nanorod is preferably 5 nm or more, more preferably 10 nm or more, and is preferably 20 nm or less. By setting the minor axis of the Au nanorod to 5 nm or more and 20 nm or less, the size required for the minor axis of the oblong ellipsoid can be ensured.

[0033] The long and short axes of the Au nanorods were determined by measuring the long and short axes of 50 randomly selected particles from a transmission electron microscope (TEM) image and averaging them. Specifically, the long axis of the Au nanorod was determined as the long axis of the rectangle circumscribing the TEM image of the particle, and the short axis of the circumscribing rectangle was determined as the short axis. Each of these was measured for 50 particles and averaged.

[0034] The Au nanorods may be prepared by the method described below in the section on the method for producing rod-shaped composite particles, or may be commercially available products such as gold nanorods, 10 nm diameter (minor axis diameter (width)), λmax, 780 nm, dispersion in H2O, manufactured by Sigma-Aldrich (catalog number: 716812-25ML).

[0035] Au nanorods absorb infrared light and generate heat, which has a photothermal effect. In particular, in the present composite particles, the core Au nanorod is coated with an outermost Au nanolayer via a Pt nanoparticle coating layer (described later), which increases its volume and increases the scattering and absorption intensities depending on the volume, thereby further enhancing the photothermal effect.

[0036] (Pt nanoparticle coating layer) In this composite particle, a Pt nanoparticle coating layer containing Pt nanoparticles is provided on the surface of the Au nanorod. Figure 3 shows the results of a microscope observation of an example of a particle (also called a "Pt / Au nanorod") in which a Pt nanoparticle coating layer containing Pt nanoparticles is provided on the surface of an Au nanorod. The Pt nanoparticle coating layer has the effect of absorbing and scattering ultraviolet light.

[0037] In this specification, "Pt nanoparticles" refers to Pt particles having an average particle size on the order of nanometers, i.e., 1 nm or more and less than 1 μm (less than 1000 nm). The average particle size of Pt nanoparticles is determined by measuring the Feret diameters of 50 particles randomly selected from a TEM image and averaging them.

[0038] In this embodiment, the average particle size of the Pt nanoparticles is preferably 1 nm to 60 nm. Having an average particle size of 60 nm or less can enhance the ultraviolet light absorption effect. The average particle size of the Pt nanoparticles is preferably 60 nm or less, more preferably 40 nm or less, and even more preferably 20 nm or less. Having an average particle size of the Pt nanoparticles of 1 nm or more can further enhance the photothermal effect of the Au nanorods.

[0039] In this embodiment, the Pt nanoparticles preferably have an aspect ratio of 1 to 2, and most preferably have an aspect ratio of 1, i.e., are spherical. Here, the aspect ratio of the Pt nanoparticles refers to the major axis / minor axis of the particles.

[0040] In this embodiment, the Pt nanoparticle coating layer contains Pt nanoparticles in an amount of 2.5×10 6 Molar ~ 7 x 10 6 It is preferable that the amount of Pt contained is 2.5 × 10 6 The content of 7×10 moles or more has the effect of sufficiently absorbing ultraviolet light. 6 When the amount is less than 1 mole, the particles can be dispersed sufficiently without agglomeration.

[0041] The Pt nanoparticle coating layer is composed of Pt nanoparticles with a Pt mass of 3 × 10 per mole of composite particle. 6 It is more preferable that the content is 5×10 mol or more. 6 It is more preferable that the content is 6×10 mol or more. 6 It is more preferable that the content be less than 1 mole.

[0042] The Pt nanoparticle coating layer may contain components other than Pt nanoparticles, such as nanoparticles containing Ru, Rh, Pd, Ag, Os, and Ir. One or more of these components may be contained. The inclusion of these components provides the effect of absorbing and scattering ultraviolet light.

[0043] In this embodiment, the thickness of the Pt nanoparticle coating layer on the major axis side is preferably 1 nm to 100 nm so that the Pt nanoparticles coat the outer surfaces of the Au nanorod particles that are the cores. A thickness of 1 nm or more on the major axis side of the Pt nanoparticle coating layer ensures sufficient absorption of ultraviolet light, while a thickness of 100 nm or less allows the particles to be sufficiently dispersed without agglomerating.

[0044] In this composite particle, the surface of the Au nanorod is not completely covered with Pt nanoparticles without any gaps, but rather there are small gaps as shown in Figure 1. Therefore, the "thickness of the Pt nanoparticle coating layer on the major axis side" refers to the average thickness including the gaps.

[0045] In this embodiment, the thickness of the Pt nanoparticle coating layer on the major axis side is more preferably 5 nm or more, even more preferably 10 nm or more, and more preferably 90 nm or less, even more preferably 80 nm or less.

[0046] The thickness of the long axis diameter of the Pt nanoparticle coating layer was calculated by subtracting the average long axis value of the core Au nanorod from the average long axis value of 50 particles (Pt / Au nanorods) with a Pt nanoparticle coating layer on the surface of the Au nanorod randomly selected from the TEM image, and dividing the result by 2.

[0047] In order to coat the outer surface of the Au nanorod particle core with Pt nanoparticles, the thickness of the Pt nanoparticle coating layer on the minor axis side is preferably 1 nm to 100 nm. A thickness of 1 nm or more on the minor axis side of the Pt nanoparticle coating layer has the effect of sufficiently absorbing ultraviolet light, while a thickness of 100 nm or less allows the particles to be sufficiently dispersed without agglomerating.

[0048] The thickness of the Pt nanoparticle coating layer on the minor axis side is more preferably 5 nm or more, even more preferably 10 nm or more, and more preferably 90 nm or less, even more preferably 80 nm or less.

[0049] The thickness of the minor axis side of the Pt nanoparticle coating layer was calculated by subtracting the average minor axis diameter (width) of the core Au nanorod from the average minor axis diameter (width) of 50 particles (Pt / Au nanorods) with a Pt nanoparticle coating layer on the surface of the Au nanorods randomly selected from the TEM image, and dividing the result by 2.

[0050] (Au nano outermost layer) The composite particle has an Au nano-outermost layer provided on the surface of the Pt nanoparticle coating layer. In this specification, the "Au nano-outermost layer" refers to an Au film having a thickness on the order of nanometers, i.e., 1 nm or more but less than 1 μm (less than 1000 nm).

[0051] Figure 4 shows the results of microscopic observation of an example of a composite particle (Au / Pt / Au prolate ellipsoidal nanoparticle) in which a Pt nanoparticle coating layer containing Pt nanoparticles is provided on the surface of the Au nanorod core, and an Au nanoouter layer is provided on the surface of the Pt nanoparticle coating layer.

[0052] The present composite particles have an Au nano-outermost layer, so the Pt nanoparticle coating layer is not exposed on the surface of the composite particles. This prevents Pt from coming into direct contact with the skin when the present composite particles are used in cosmetics, etc., and can suppress the induction of inflammatory reactions such as allergies. Furthermore, the Au in the outermost layer of the present composite particles has a low ionization tendency, making it less likely to release metal ions that cause inflammatory reactions such as allergies, making them less likely to cause inflammatory reactions from this perspective as well.

[0053] In this embodiment, the Au nano-outermost layer contains Au in an amount of 5×10 6 ~400×10 6 It is preferable that the amount of Au contained is 5×10 moles per mole of the composite particles. 6 When the Au content is more than 400 × 10 moles, the Pt is coated and absorbs infrared light. 6 By containing the compound in an amount of less than 1 mole, the composite particles do not become spherical and infrared absorption can be maintained.

[0054] In this embodiment, the Au nano-outermost layer contains Au in an amount of 10×10 6 More preferably, it contains 50×10 moles or more. 6 It is more preferable that the content is 300×10 mol or more. 6 It is more preferable that the content is 200×10 moles or less. 6 It is more preferable that the content be less than 1 mole.

[0055] In this embodiment, the thickness of the Au nano-outermost layer is preferably 1 nm to 200 nm. When the Au nano-outermost layer is 1 nm or more, it can cover the Pt nanoparticle coating layer, and when it is 200 nm or less, the composite particle does not become spherical and infrared absorption can be maintained.

[0056] The thickness of the Au nano-outermost layer is more preferably 5 nm or more, even more preferably 10 nm or more, and is more preferably 180 nm or less, even more preferably 150 nm or less.

[0057] The thickness of the outermost Au nanolayer was calculated by subtracting the average major and minor axes of the Pt / Au nanorods from the average major and minor axes of 50 composite particles (Au / Pt / Au ellipsoidal nanoparticles) randomly selected from a transmission electron microscope (TEM) image, and dividing the result by 2.

[0058] [Method of manufacturing prolate ellipsoidal composite particles] One embodiment of the method for producing the composite particles preferably includes, for example, the following steps (1) to (3) in order: (1) preparing Au nanorods, (2) providing a Pt nanoparticle coating layer on the surface of the Au nanorods prepared in step (1) to prepare Pt / Au nanorods, and (3) providing an Au nano outermost layer on the surface of the Pt / Au nanorods prepared in step (2) to prepare Au / Pt / Au prolate ellipsoidal nanoparticles. Each step will be explained below.

[0059] (1) Process for producing Au nanorods In step (1), Au nanorods are produced by reducing a gold source with a reducing agent in the presence of a protective agent, using Au nanoclusters as nuclei. The Au clusters can be obtained, for example, by adding HAuCl4 solution and NaBH4 to a CTAB solution, stirring the mixture, and aging it at room temperature for at least one hour.

[0060] As used herein, "Au nanoclusters" refer to minute particles composed of gold atoms, typically having a diameter of several nanometers or less. Examples of the gold source include chloroauric acid, chloroaurate, potassium gold cyanide, and gold bromide. Examples of the reducing agent include inorganic compounds such as sodium borohydride and hydrazine, and organic acids or salts thereof such as hydroquinone, ascorbic acid, and citric acid.

[0061] Examples of the protective agent include surfactants such as hexadecyltrimethylammonium bromide and polyoxyethylene (20) sorbitan monolaurate, water-soluble polymers such as gelatin and BSA, and organic acid compounds such as citric acid.

[0062] The reduction conditions include, for example, standing or shaking preferably at 60° C. for 1 hour, or standing or shaking preferably at room temperature preferably overnight.

[0063] (2) A step of forming a Pt / Au nanorod by providing a Pt nanoparticle coating layer on the surface of the Au nanorod prepared in step (1). In step (2), the platinum source is reduced with a reducing agent in the presence of a protective agent using the Au nanorods prepared in step (1) as nuclei to prepare Pt / Au nanorods, which are particles with a Pt nanoparticle coating layer on the surface of the Au nanorods.

[0064] Examples of the platinum source include potassium chloroplatinate, platinum bromide, tetraammine platinum, etc. The protecting agent and the reduction conditions are the same as those in step (1).

[0065] (3) A process of forming an outermost Au nanolayer on the surface of the Pt / Au nanorods prepared in step (2) to prepare Au / Pt / Au ellipsoidal nanoparticles. In step (3), the gold source is reduced with a reducing agent in the presence of a protective agent, using the Pt / Au nanorods prepared in step (2) as cores to obtain the present composite particles, i.e., Au / Pt / Au prolate ellipsoidal nanoparticles. The gold source, protective agent, and reduction conditions are the same as those in step (1).

[0066] [Cosmetic composition] A cosmetic composition according to one embodiment of the present invention (hereinafter also referred to as the present cosmetic composition) contains the present composite particles described above.

[0067] The present cosmetic composition preferably contains 0.01 to 10% by mass of the present composite particles. When the present cosmetic composition contains 0.01% by mass or more of the present composite particles, it has the effect of simultaneously blocking ultraviolet light and infrared light. Furthermore, when the present cosmetic composition contains 10% by mass or less of the present composite particles, the particles do not aggregate and the cosmetic composition can be made to have good dispersibility.

[0068] The present cosmetic composition preferably contains the present composite particles in an amount of 0.05% by mass or more, even more preferably 0.07% by mass or more, and more preferably 5% by mass or less, even more preferably 2.5% by mass or less.

[0069] The cosmetic composition can be prepared in any formulation commonly used in the art, such as a water-in-oil or oil-in-water solution, suspension, emulsion, paste, gel, cream, lotion, powder, soap, surfactant-containing cleanser, oil, sunscreen, powder foundation, emulsion foundation, wax foundation, or spray formulation. Thus, the cosmetic composition can be prepared in a variety of formulations.

[0070] In addition to the present composite particles, the present cosmetic composition may contain components commonly used in cosmetic compositions, such as general adjuvants such as antioxidants, stabilizers, solubilizers, vitamins, pigments, and fragrances, and / or carriers. Carriers that can be used for each dosage form are described below.

[0071] When the cosmetic composition is in the form of a powder or spray, examples of the carrier component include lactose, talc, silica, aluminum hydroxide, calcium silicate, or polyamide powder. In particular, when the cosmetic composition is in the form of a spray, chlorofluorohydrocarbon, propane / butane, or dimethyl ether may be additionally used.

[0072] When the cosmetic composition is in the form of a solution or emulsion, the carrier component may be, for example, a solvent, a solubilizer, or an emulsifier, such as water, ethyl alcohol, isopropanol, ethyl carbonate, ethyl acetate, benzyl alcohol, benzyl benzoate, propylene glycol, 1,3-butyl glycol oil, aliphatic glycerol esters, polyethylene glycol, or fatty acid esters of sorbitan.

[0073] When the cosmetic composition is in the form of a suspension, examples of the carrier component include a liquid diluent such as water, ethyl alcohol, or propylene glycol, a suspending agent such as ethoxylated isostearyl alcohol, polyoxyethylene sorbitol ester, or polyoxyethylene sorbitan ester, microcrystalline cellulose, aluminum metahydroxide, bentonite, agar, or tragacanth.

[0074] When the cosmetic composition is in the form of a paste, cream, or gel, examples of the carrier component include animal oil, vegetable oil, wax, paraffin, starch, tragacanth, cellulose derivatives, polyethylene glycol, silicone, bentonite, silica, talc, and zinc oxide.

[0075] When the cosmetic composition is in the form of a surfactant-containing cleanser, examples of the carrier component include fatty alcohol sulfates, fatty alcohol ether sulfates, sulfosuccinic acid monoesters, isocyanates, imidazolium derivatives, methyl taurates, sarcosinates, fatty acid amide ether sulfates, alkylamido betaines, fatty alcohols, fatty acid glycerides, fatty acid diethanolamides, vegetable oils, lanolin derivatives, and ethoxylated glycerol fatty acid esters.

[0076] The present cosmetic composition contains the present composite particles, which are single particles, and therefore can simultaneously block both ultraviolet light and infrared light, and the particles are uniform in size, so they have good dispersibility.

[0077] Furthermore, since the intermediate Pt nanoparticle coating layer of the present composite particles is coated with an Au nano-outermost layer, even when the particles are contained in a cosmetic composition, direct contact of Pt with the skin can be prevented, thereby suppressing inflammatory reactions such as allergies. Furthermore, the Au in the outermost layer of the present composite particles has a low ionization tendency and is less likely to release metal ions that cause inflammatory reactions such as allergies, making the particles less likely to cause inflammatory reactions from this perspective as well.

[0078] Furthermore, since the Au nanorods in the present composite particles absorb light energy and generate heat, the core Au nanorods are coated with the outermost Au nanolayer via a Pt nanoparticle coating layer, which further enhances the photothermal effect. Therefore, by incorporating the present composite particles into a cosmetic composition, it is possible to achieve anti-aging effects such as destroying melanin-producing cells (melanocytes) that cause age spots, promoting skin cell turnover, and suppressing the occurrence of age spots.

[0079] As described above, the present specification discloses the following: [1] A prolate ellipsoidal composite particle comprising an Au nanorod, a Pt nanoparticle coating layer containing Pt nanoparticles provided on the surface of the Au nanorod, and an Au nano outermost layer provided on the surface of the Pt nanoparticle coating layer. [2] The prolate ellipsoidal composite particle according to [1], which has absorption maxima simultaneously in the wavelength range of 200 nm to 400 nm and in the wavelength range of 700 nm or more. [3] The prolate ellipsoidal composite particle according to [2], further having an absorption maximum in the wavelength range of 500 nm to 700 nm. [4] The oblong ellipsoidal composite particle according to any one of [1] to [3], having a major axis of 100 nm or more and 1000 nm or less and a minor axis of 50 nm or more and 300 nm or less. [5] The oblong ellipsoidal composite particle according to any one of [1] to [4], wherein the Au nanorod has a minor axis diameter of 5 nm or more and 20 nm or less and a major axis diameter of 15 nm or more and 200 nm or less. [6] The oblong ellipsoidal composite particle according to any one of [1] to [5], wherein the Au nanorods have an aspect ratio of 3 or more. [7] The oblong ellipsoidal composite particles according to any one of [1] to [6], wherein the Pt nanoparticles have an aspect ratio of 1 to 2. [8] The oblong ellipsoidal composite particle according to any one of [1] to [7], wherein the Pt nanoparticle coating layer has a thickness of 1 nm to 100 nm. [9] The oblong ellipsoidal composite particle according to any one of [1] to [8], wherein the thickness of the outermost Au nanolayer is 1 nm to 200 nm.

[10] A cosmetic composition containing the prolate ellipsoidal composite particles according to any one of [1] to [9].

[0080] Although the embodiments of the present invention have been described above, the present invention is not limited to the embodiments disclosed in this specification and can be appropriately modified and implemented without departing from the spirit of the invention. The embodiments disclosed in this specification can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. [Example]

[0081] The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to these examples.

[0082] <Test Example 1> (material) Hexadecyltrimethylammonium bromide (CTAB): Fujifilm Wako Pure Chemical Industries, Ltd. Hexadecyltrimethylammonium chloride (CTAC): Fujifilm Wako Pure Chemical Industries, Ltd. Sodium tetrahydroborate powder (NaBH4): Fujifilm Wako Pure Chemical Industries, Ltd. Hydroquinone: Fujifilm Wako Pure Chemical Industries, Ltd. L(+)-Ascorbic acid: Fujifilm Wako Pure Chemical Industries, Ltd. 30.0% by mass chloroauric acid solution: Tanaka Kikinzoku Kogyo Co., Ltd. Silver nitrate crystals: Tanaka Kikinzoku Kogyo Co., Ltd. Potassium hexachloroplatinate 47% by mass: Tanaka Kikinzoku Kogyo Co., Ltd.

[0083] (method) 1. Preparation of Au nanoclusters CTAB, NaBH4, and chloroauric acid were mixed to final concentrations of 100 mM, 0.6 mM, and 0.25 mM, respectively. The mixed solution was left to stand at room temperature for 1 hour, yielding brown gold nanoclusters.

[0084] 2. Fabrication of Au Nanorods CTAB, hydroquinone, chloroauric acid, and silver nitrate were mixed to final concentrations of 100 mM, 3 mM, 0.5 mM, and 0.4 mM, respectively. The gold nanoclusters prepared in step 1 above were added to the mixed solution so as to be diluted 100 times and mixed. The mixed solution was left to stand overnight at room temperature to obtain Au nanorods.

[0085] 3. Fabrication of Pt / Au Nanorods CTAC and L(+)-ascorbic acid were mixed with the Au nanorods obtained in step 2 above to a final concentration of 10 mM. Potassium hexachloroplatinate was added to the mixed solution to a final concentration of 1-60 mM. The mixed solution was left to stand at 60°C for 1 hour to obtain Au nanorods coated with a Pt nanoparticle layer (Pt / Au nanorods).

[0086] 4. Preparation of Au / Pt / Au ellipsoidal nanoparticles CTAC and L(+)-ascorbic acid were mixed with the Pt / Au nanorods obtained in step 3 above to a final concentration of 10 mM. Chloroauric acid was added to the mixed solution to a final concentration of 10-1000 mM. The mixed solution was left to stand at 60°C for 1 hour to obtain Au / Pt / Au prolate ellipsoidal nanoparticles.

[0087] 5. Analysis method for each particle (ultraviolet, visible, and near-infrared extinction spectrum) The Au nanorods, Pt / Au nanorods, and Au / Pt / Au prolate ellipsoidal nanoparticles prepared above were suspended in a 1 mM CTAB solution, and ultraviolet, visible, and near-infrared extinction spectra were obtained using a Spectrophotometer V-770 (Jusco Engineering Co., Ltd.). The results are shown in Figures 6 to 11. Figures 6 to 11 show the extinction spectra of Examples 1 to 6, respectively.

[0088] (particle size, thickness measurement) Each particle was suspended in water, and 1 μL of the suspension was dropped onto a collodion-coated mesh (Nissin EM Co., Ltd.) and dried in vacuum to prepare a sample. Images of more than 50 particles were taken using a JEM-2100PLUS electron microscope (JEOL Ltd.), and their sizes were measured using ImageJ.

[0089] The major axis diameter of each particle was determined by measuring the major axis dimensions of a rectangle circumscribing 50 particles randomly selected from the TEM image and averaging these measurements. The minor axis diameter of each particle was determined by measuring the minor axis dimensions of a rectangle circumscribing 50 particles randomly selected from the TEM image and averaging these measurements.

[0090] The long and short axes of the Au nanorods were determined by measuring the long axis of the rectangle circumscribing the TEM image of the particle, and the short axis of the rectangle circumscribing the particle, respectively, and averaging the measurements for 50 particles.

[0091] The thickness of the Pt nanoparticle coating layer on the major axis side was calculated by subtracting the average value of the major axis of the core Au nanorod from the average value of the major axes of 50 Pt / Au nanorods randomly selected from the TEM image, and dividing the result by 2.

[0092] The thickness of the Pt nanoparticle coating layer on the minor axis side was calculated by subtracting the average minor axis of the core Au nanorod from the average minor axis of 50 Pt / Au nanorods randomly selected from the TEM image, and dividing the result by 2.

[0093] The thickness of the outermost Au nanolayer was calculated by subtracting the average major and minor axes of the Pt / Au nanorods from the average major and minor axes of 50 Au / Pt / Au ellipsoidal nanoparticles randomly selected from a transmission electron microscope (TEM) image, and dividing the result by 2.

[0094] The results are shown in Table 1. In Table 1, Examples 1 to 3 are Reference Examples, and Examples 4 to 6 are Working Examples.

[0095] [Table 1]

[0096] Figure 6 shows the extinction spectrum of Example 1, Figure 7 shows that of Example 2, Figure 8 shows that of Example 3, Figure 9 shows that of Example 4, Figure 10 shows that of Example 5, and Figure 11 shows that of Example 6. Example 2 shows the lower limit of the Pt amount in the composite particles of the present invention, and Example 3 shows the upper limit of the Pt amount in the composite particles of the present invention. Furthermore, Example 4 shows the lower limit of the Au amount in the outermost Au nanolayer in the composite particles of the present invention, and Example 6 shows the upper limit of the Au amount in the outermost Au nanolayer in the composite particles of the present invention.

[0097] As shown in Figures 6 to 11, the Au / Pt / Au prolate ellipsoidal nanoparticles of Examples 4 to 6, which are working examples, have simultaneous absorption maxima in three wavelength ranges: 200 nm to 400 nm, 500 nm to 700 nm, and 700 nm or longer, and are therefore capable of blocking ultraviolet light, visible light, and infrared light simultaneously.

[0098] (Structural identification) The results of electron microscope observation of Au nanorods (Example 7), Pt / Au nanorods (Example 8), and Au / Pt / Au prolate ellipsoidal nanoparticles (Example 9) are shown in Figures 2 to 4, respectively. The results of measuring the average major axis diameter and average minor axis diameter of Examples 7 to 9 are shown in Table 2. Examples 7 and 8 are reference examples, and Example 9 is an embodiment.

[0099] [Table 2]

[0100] <Test Example 2> In this test example, Au / Pt / Au prolate ellipsoidal nanoparticles were coated onto a plastic substrate using a silane coupling agent, and then the thermal properties of the Au / Pt / Au prolate ellipsoidal nanoparticles were evaluated on the substrate by measuring the temperature change due to laser irradiation.

[0101] (material) Au / Pt / Au ellipsoidal nanoparticles 11-Mercaptoundecanoic acid (MUA) (Sigma 450561) 3-Aminopropyltrimethoxysilane (APTMS) (Fujifilm Wako Pure Chemical Industries, Ltd. 323-74352) Tris(hydroxymethyl)aminomethane (Nacalai Tesque 35409-45) 1N HCl (Fujifilm Wako Pure Chemical Industries, Ltd. 083-01095) Polyoxyethylene (20) sorbitan monooleate (Fujifilm Wako Pure Chemical Industries, Ltd. 163-21625) 1N NaOH (Kanto Chemical 37847-79) Small plasma device (Yamato Scientific PM100) 35mm dish for adherent cells (IWAKI 3000-035) 980nm laser (MDL-III-980-500mW FC31445) Radiation thermometer (Japan Sensor TMHX-CNE0500-0070E003)

[0102] (method) 1. Coating the substrate with silane coupling agent: A 35 mm plastic dish was plasma treated for 15 minutes using a small plasma device to hydrophilize the surface of the dish. 2 mL of 1% APTMS aqueous solution was added and left to stand at room temperature for 30 minutes. After standing, the dish was washed with purified water and air-dried.

[0103] 2. Protectant substitution of Au / Pt / Au prolate nanoparticles A 950 μL dispersion containing 2.5 nM Au / Pt / Au prolate nanoparticles was centrifuged, the supernatant removed, and then added to 950 μL of 10 mM NaOH solution containing 1 mM 11-mercaptoundecanoic acid (MUA) to disperse the particles. This dispersion was aged at room temperature for 1 hour by shaking at 500 rpm. After aging, the dispersion was centrifuged again and the supernatant removed. The nanoparticles were then dispersed in a 10 mM tris(hydroxymethyl)aminomethane (Tris-HCl) solution adjusted to pH 8.5 and containing 0.1% by mass of polyoxyethylene(20)sorbitan monooleate to a particle concentration of 2.5 nM.

[0104] 3. Coating of Au / Pt / Au spheroidal nanoparticles onto substrate: 950 μL of the Au / Pt / Au prolate ellipsoidal nanoparticle dispersion liquid in which the protective material had been replaced in Test Example 2 (Method) 2. was placed in a plastic dish coated with a silane coupling agent in Test Example 2 (Method) 1. and shaken overnight at 500 rpm. The supernatant was removed, and the dish was washed with purified water and air-dried.

[0105] 4. Laser irradiation of the substrate and temperature measurement The center of the final plastic dish coated with Au / Pt / Au prolate nanoparticles was irradiated with a 980 nm laser (MDL-III-980-500 mW FC31445). The temperature of the irradiated area was measured using a radiation thermometer (Japan Sensor TMHX-CNE0500-0070E003). After the start of laser irradiation, the point at which the measured value stabilized was set as time 0, and the temperature change over the next 5 minutes was recorded.

[0106] The results are shown in Figure 12. In Figure 12, the solid line shows the results without Au / Pt / Au prolate spheroidal nanoparticles, and the dashed line shows the results with Au / Pt / Au prolate spheroidal nanoparticles. Figure 12 shows that the dish temperature increased with infrared irradiation in the dish containing Au / Pt / Au prolate spheroidal nanoparticles, demonstrating that the Au / Pt / Au prolate spheroidal nanoparticles of the present disclosure have a photothermal effect, absorbing light energy and generating heat.

[0107] <Test Example 3> In this test, the photothermal effect of Au / Pt / Au spheroidal nanoparticles in simulated cosmetics was investigated. Specifically, Au / Pt / Au spheroidal nanoparticles were added to commercially available cosmetics (sunscreen or foundation), which were then coated onto a plastic substrate. The temperature change due to laser irradiation was measured to evaluate the photothermal properties of the Au / Pt / Au spheroidal nanoparticles.

[0108] (material) Au / Pt / Au ellipsoidal nanoparticles prepared by (Method) 2 of Test Example 2 Commercial cosmetics Sunscreen (Rohto Pharmaceutical Skin Aqua Tone Up UV) Foundation (Shiseido Maquillage Dramatic Essence Liquid, Ocher 10) 35mm dish for adherent cells (IWAKI 3000-035) 980nm laser (MDL-III-980-500mW FC31445) Radiation thermometer (Japan Sensor TMHX-CNE0500-0070E003)

[0109] (method) 1. Preparation of simulated cosmetics (mixture of commercial cosmetics and Au / Pt / Au ellipsoidal particles) 90 mg of a commercially available cosmetic product was weighed out, and 10 μL of a dispersion containing 25 nM Au / Pt / Au prolate ellipsoidal nanoparticles was added to it. After addition, the mixture was mixed with a medicine spoon until it was uniform.

[0110] 2. Coating on the substrate 18 mg of the simulant cosmetic or the commercially available cosmetic alone in (Method) 1 of Test Example 3 was weighed out into a 35 mm dish. The measured simulant cosmetic or the commercially available cosmetic was spread over the entire dish with a spatula.

[0111] 3. Laser irradiation of the substrate and temperature measurement A 980 nm laser was irradiated onto the center of the plastic dish of (Method) 2 of Test Example 3, and the temperature of the irradiated area was measured with a radiation thermometer. The time when the measured value stabilized after the start of laser irradiation was set as time 0, and the temperature change over 5 minutes from that point was measured.

[0112] The results are shown in Figures 13A and 13B. In Figure 13A, the solid line shows the results for sunscreen alone, and the dashed line shows the results for sunscreen with Au / Pt / Au prolate spheroidal nanoparticles added. In Figure 13B, the solid line shows the results for foundation alone, and the dashed line shows the results for foundation with Au / Pt / Au prolate spheroidal nanoparticles added. Figures 13A and 13B show that the temperature of the dish increased more with infrared irradiation when the Au / Pt / Au prolate spheroidal nanoparticles were present than when they were not present, demonstrating that the Au / Pt / Au prolate spheroidal nanoparticles of the present disclosure have a photothermal effect, absorbing light energy and generating heat, even when incorporated into cosmetics.

[0113] <Test Example 4> In this test example, the optical properties of Au / Pt / Au spheroidal nanoparticles in simulated cosmetics were investigated. Specifically, Au / Pt / Au spheroidal nanoparticles were added to commercially available cosmetics, and the transmittance properties of the Au / Pt / Au spheroidal nanoparticles were evaluated by measuring the ultraviolet and near-infrared absorbance of the resulting solution.

[0114] (material) Au / Pt / Au ellipsoidal nanoparticle dispersion prepared in Test Example 2 (Method) 2. Commercial cosmetics Sunscreen (Rohto Pharmaceutical Skin Aqua Tone Up UV) Foundation (Shiseido Maquillage Dramatic Essence Liquid, Ocher 10) Spectrophotometer V-770 (Jasco Engineering Co., Ltd.)

[0115] (method) 1. Mixing commercial cosmetics with Au / Pt / Au ellipsoidal nanoparticles A solution was prepared by adding 990 μL of purified water to 10 mg of a commercially available cosmetic product, and then adding 10 μL of a dispersion containing 25 nM Au / Pt / Au prolate ellipsoidal nanoparticles to 90 μL of this solution.

[0116] 2. Transmittance Measurement The ultraviolet and near-infrared absorbance of the solution prepared in 1 was measured using a Spectrophotometer V-770. The transmittance was calculated from the obtained absorbance.

[0117] The results are shown in Tables 3 and 4.

[0118] [Table 3]

[0119] [Table 4]

[0120] As shown in Tables 3 and 4, the transmittance of ultraviolet and infrared rays was reduced in the presence of Au / Pt / Au prolate ellipsoidal nanoparticles compared to the absence of Au / Pt / Au prolate ellipsoidal nanoparticles. This indicates that the Au / Pt / Au prolate ellipsoidal nanoparticles of the present disclosure can effectively block ultraviolet and infrared light simultaneously even when incorporated into cosmetics.

[0121] Although the present invention has been described in detail with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the present invention. This application is based on a Japanese patent application (Patent Application No. 2024-073904) filed on April 30, 2024, the entirety of which is incorporated by reference. All references cited herein are incorporated in their entirety. [Explanation of symbols]

[0122] 10, 50 Prolate ellipsoidal composite particles 11. Au nanorods 12 Pt nanoparticle coating layer 13 Au nano outermost layer 51 Long axis 52 Short axis

Claims

1. A composite particle having an oblong shape, comprising an Au nanorod, a Pt nanoparticle coating layer containing Pt nanoparticles provided on the surface of the Au nanorod, and an Au nano outermost layer provided on the surface of the Pt nanoparticle coating layer.

2. The oblong ellipsoidal composite particle according to claim 1, which has absorption maxima simultaneously in the wavelength range of 200 nm to 400 nm and in the wavelength range of 700 nm or more.

3. The prolate ellipsoidal composite particle according to claim 2, further having an absorption maximum in the wavelength range of 500 nm to 700 nm.

4. 2. The ellipsoidal composite particle according to claim 1, wherein the major axis is 100 nm or more and 1000 nm or less, and the minor axis is 50 nm or more and 300 nm or less.

5. The prolate ellipsoid composite particle according to claim 1 , wherein the Au nanorod has a minor axis diameter of 5 nm to 20 nm and a major axis diameter of 15 nm to 200 nm.

6. The prolate ellipsoidal composite particle according to claim 1 , wherein the Au nanorods have an aspect ratio of 3 or more.

7. The ellipsoidal composite particles according to claim 1, wherein the Pt nanoparticles have an aspect ratio of 1 to 2.

8. 2. The ellipsoidal composite particle according to claim 1, wherein the thickness of the Pt nanoparticle coating layer is 1 nm to 100 nm.

9. 2. The oblong ellipsoidal composite particle according to claim 1, wherein the thickness of the outermost Au nanolayer is 1 nm to 200 nm.

10. A cosmetic composition comprising the prolate ellipsoidal composite particles according to any one of claims 1 to 9.

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