Zinc oxide nanoparticle and use thereof

Abstract

Provided are a zinc oxide nanoparticle and the use thereof. The average hydrodynamic diameter of the zinc oxide nanoparticle is less than or equal to 90 nm, and the value of the average hydrodynamic diameter / (TEMa+TEMb) is less than or equal to 1. The zinc oxide nanoparticle can be uniformly dispersed in water, is not prone to aggregation, and has good stability, and can thus be easily formulated into a sunscreen cosmetic having an aqueous formulation and leaving no greasy feel after use; moreover, the zinc oxide nanoparticle produces few strongly oxidizing substances after the absorption of ultraviolet light.

Description

A zinc oxide nanoparticle and its application

[0001] This disclosure claims priority to Chinese Patent Application No. 202411851593.2, filed on December 16, 2024, entitled "A Zinc Oxide Nanoparticle and Its Application", the entire contents of which are incorporated herein by reference. Technical Field

[0002] This disclosure relates to the field of sun protection technology, and in particular to a zinc oxide nanoparticle and its application. Background Technology

[0003] Due to the effects of ultraviolet (UV) radiation from sunlight, the incidence of melanoma, a skin cancer, has increased significantly, making it the most common cancer among people aged 25 to 29. Sunscreen is recommended to prevent skin cancer, sunburn, photoaging, and wrinkles. It is generally known that ultraviolet radiation can be divided into several bands based on wavelength: UVA, UVB, UVC, and UVD. Among these, UVA and UVB are the two bands most relevant to human health.

[0004] UVA radiation has a wavelength of 320-400 nm. Such UVA radiation can burn the skin, and overexposure may lead to skin cancer. UVB radiation has a wavelength of 280-320 nm and may cause short-term or long-term skin damage, including the formation of deep wrinkles, collagen breakdown, and pigmentation. Publications from the 22nd World Federation of Societies of Cosmetic Chemists Symposium (Edinburgh 2002, Oral Papers, Vol. 2, Zastrow et al.) and other publications indicate that electron spin resonance (ESR) imaging has determined that UVA and UVB rays can penetrate to different depths in the skin. UVB rays can penetrate up to a depth of approximately 50 μm, while UVA radiation can reach the lower dermis, approximately 3 mm. Therefore, sunscreen plays a crucial role in daily UV protection.

[0005] Traditional sunscreens contain chemical agents that absorb and decompose ultraviolet (UV) rays to reduce their effectiveness. Therefore, their effectiveness diminishes with prolonged exposure, requiring repeated application. Furthermore, some of these chemicals or their decomposition products may irritate or damage the skin. Nano zinc oxide (ZnO), a broad-spectrum inorganic UV shielding agent, is increasingly widely used due to its physical method of blocking UV rays. Its principle of UV shielding is absorption and scattering. When exposed to UV radiation, electrons in the valence band absorb the UV rays and are excited to the conduction band, simultaneously creating electron-hole pairs, thus absorbing UV rays. However, nano ZnO scatters UV rays according to Rayleigh scattering. When the particle size is much smaller than the wavelength of UV light, the nanoparticles can scatter the UV rays acting on them in all directions, thereby reducing the intensity of UV rays in the direction of irradiation. This description is documented in CN105030571B.

[0006] To address this issue, Yan Chunyue et al., in their paper "Application and Testing of ZnO@SiO2 Sunscreen Agent," described the preparation of ZnO@SiO2 composite materials by coating the surface of nano-ZnO with SiO2. SiO2 is inert and can inhibit the photocatalytic activity of nano-ZnO, while the SiO2 shell can increase the transparency of ZnO in the visible light region. However, the article also pointed out that the shielding effect of the outer SiO2 shell on ZnO leads to a reduction in its sunscreen performance. CN116171146A (corresponding to the commercial product Pavise) discloses a nanoparticle with a nanodiamond core and a zinc oxide or titanium oxide shell. The nanodiamond core removes holes through an internal oxidation process or by capturing electrons in the conduction band of the shell. However, nanodiamonds are expensive and difficult to prepare. Summary of the Invention

[0007] This disclosure provides zinc oxide nanoparticles, wherein the outer layer of the nanoparticles is zinc oxide; when the nanoparticles are dispersed in water, the average hydrated particle size is ≤90 nm.

[0008] Average hydrated particle size / (TEM) a +TEM b )≤1, TEM a TEM b These represent the minimum and maximum TEM particle sizes, respectively;

[0009] Alternatively, the outer layer of the nanoparticles may be zinc oxide;

[0010] When the nanoparticles are dispersed in water, the average hydrated particle size is ≤90nm;

[0011] When the concentration of the nanoparticles dispersed in water is 0.2 mg / ml, the generation of singlet oxygen is no higher than 16% under ultraviolet light excitation for 10 s.

[0012] In some embodiments, the nanoparticles have a core-shell structure, with a core of silicon dioxide and a shell of zinc oxide. In some embodiments, the silicon dioxide is carboxylated modified silicon dioxide.

[0013] When the nanoparticles are dispersed in water, the average hydrated particle size of the zinc oxide nanoparticles is ≤90nm; in some embodiments, 50nm ≤ average hydrated particle size ≤90nm, or 60nm ≤ average hydrated particle size ≤90nm, or 70nm ≤ average hydrated particle size ≤90nm, or 60nm ≤ average hydrated particle size ≤85nm.

[0014] When the nanoparticles are dispersed in water, the PDI of the zinc oxide nanoparticles is ≤0.3. In some embodiments, the PDI is ≤0.2, or PDI is ≤0.19, or PDI is ≤0.18, or PDI is ≤0.17.

[0015] When the nanoparticles are dispersed in water, the Span of the zinc oxide nanoparticles is ≤1.5, or ≤1.4, or ≤1.3, or ≤1.2, or ≤1.1, or ≤1.0, or ≤0.9, or ≤0.8, or ≤0.7. In some embodiments, 0.1≤Span≤1.5, or 0.2≤Span≤1.4, or 0.3≤Span≤1.3, or 0.4≤Span≤1.2, or 0.5≤Span≤1.1, or 0.5≤Span≤1.0, or 0.5≤Span≤0.9, or 0.5≤Span≤0.8, or 0.5≤Span≤0.7.

[0016] When the nanoparticles are dispersed in water, the D10 of the zinc oxide nanoparticles is ≤60nm. In some embodiments, 20nm≤D10≤60nm, or 21nm≤D10≤60nm, or 22nm≤D10≤60nm, or 23nm≤D10≤60nm, or 24nm≤D10≤60nm, or 25nm≤D10≤60nm, or 30nm≤D10≤60nm, or 40nm≤D10≤60nm, or 45nm≤D10≤55nm.

[0017] When the nanoparticles are dispersed in water, the D50 of the zinc oxide nanoparticles is ≤80nm. In some embodiments, D50 is ≤79nm, or D50 is ≤78nm, or D50 is ≤77nm, or D50 is ≤76nm, or D50 is ≤75nm, or 30nm is ≤D50 is ≤80nm, or 35nm is ≤D50 is ≤80nm, or 40nm is ≤D50 is ≤80nm, or 45nm is ≤D50 is ≤80nm, or 50nm is ≤D50 is ≤80nm, or 55nm is ≤D50 is ≤80nm, or 60nm is ≤D50 is ≤80nm, or 65nm is ≤D50 is ≤80nm.

[0018] When the nanoparticles are dispersed in water, the D90 of the zinc oxide nanoparticles is ≤110nm. In some embodiments, D90 is ≤109nm, or D90 ≤108nm, or D90 ≤107nm, or D90 ≤106nm, or D90 ≤105nm, or D90 ≤104nm, or D90 ≤103nm, or D90 ≤102nm, or D90 ≤101nm, or D90 ≤100nm, or 50nm ≤ D90 ≤105nm, or 60nm ≤ D90 ≤105nm, or 70nm ≤ D90 ≤105nm, or 80nm ≤ D90 ≤105nm, or 80nm ≤ D90 ≤100nm, or 80nm ≤ D90 ≤90nm.

[0019] When the nanoparticles are dispersed in water, the absolute value of the Zeta potential of the zinc oxide nanoparticles is ≥15mV, or ≥16mV, or ≥17mV, or ≥18mV, or ≥19mV, or ≥20mV, or ≥21mV, or ≥22mV, or ≥23mV, or ≥24mV, or ≥25mV. In some embodiments, when the nanoparticles are dispersed in water, the Zeta potential is 18~40mV, or 19~40mV, or 18~35mV, or 19~35mV, or 18~34mV, or 19~34mV.

[0020] When the nanoparticles are dispersed in water, the TEM particle size of the zinc oxide nanoparticles is 30-70 nm. Alternatively, the TEM particle size is 30-80 nm.

[0021] When the nanoparticles are dispersed in water, the average hydrated particle size of the zinc oxide nanoparticles is (TEM). a +TEM b )≤1, TEM a TEM b These represent the minimum and maximum TEM particle size, respectively. In some embodiments, the average hydrated particle size / (TEM) a +TEM bThe average hydrated particle size of the zinc oxide nanoparticles is ≤0.9, ≤0.8, or ≤0.7. In some embodiments, the average hydrated particle size of the zinc oxide nanoparticles is ≤0.9, ≤0.8, or ≤0.7. a +TEM b )≤0.8, 60nm≤average hydrated particle size≤85nm.

[0022] The inventors of this disclosure unexpectedly discovered that while simple nano-ZnO materials provide sun protection, they also generate various reactive oxygen species (ROS) upon UV excitation, such as hydroxyl radicals and superoxide anions. These ROS can damage cells and are also associated with melanoma and photoaging of the skin. However, when zinc oxide nanoparticles meet the characteristics described in this disclosure, their ability to generate various ROS upon UV excitation is reduced.

[0023] Another aspect of this disclosure is to provide a zinc oxide nanoparticle having a core-shell structure consisting of a core and an outer shell, wherein the core comprises silicon dioxide nanoparticles and the shell is zinc oxide.

[0024] Furthermore, the silicon dioxide is carboxylated modified silicon dioxide.

[0025] Furthermore, when the zinc oxide nanoparticles of this disclosure are dispersed in water, under ultraviolet light excitation for 5 seconds, the generation of singlet oxygen is less than 10%, less than 8% in some embodiments, less than 7% in some embodiments, less than 6% in some embodiments, and less than 5% in some embodiments.

[0026] Furthermore, when the zinc oxide nanoparticles of this disclosure are dispersed in water, under ultraviolet light excitation for 10 s, the generation of singlet oxygen is less than 16%, less than 15% in some embodiments, less than 14% in some embodiments, less than 13% in some embodiments, and less than 12% in some embodiments.

[0027] Furthermore, zinc oxide nanoparticles were dispersed in water at a concentration of 0.2 mg / ml, and the percentage of singlet oxygen generated was measured.

[0028] The formula for calculating singlet oxygen is as follows:

[0029] Singlet oxygen production percentage = [Abs] （ 400 nm ，曝光 0s ） -Abs （ 400 nm ，曝光时长） ] / Abs ( 400 nm ，曝光 0s ) × 100%

[0030] Abs refers to the absorbance of the sample in the ultraviolet region, namely the UVA and UVB regions;

[0031] Furthermore, when zinc oxide nanoparticles are dispersed in water, the peak value (Abs) of the absorption peak in the wavelength range of 280-320 nm is greater than 0.2, in some embodiments greater than 0.3, in some embodiments greater than 0.4, in some embodiments greater than 0.5, in some embodiments greater than 0.6, in some embodiments greater than 0.7, in some embodiments greater than 0.8, in some embodiments greater than 0.9, in some embodiments greater than 1.0, in some embodiments greater than 1.1, in some embodiments greater than 1.2, in some embodiments greater than 1.3, in some embodiments greater than 1.4, and in some embodiments greater than 1.5.

[0032] Furthermore, zinc oxide nanoparticles were dispersed in water at a concentration of 0.2 mg / ml, and the spectrum was measured.

[0033] Furthermore, the zinc oxide nanoparticles described in this disclosure, by mass fraction, have a zinc oxide shell distribution relative to the silicon dioxide core of at least 100%, in some embodiments at least 110%, in some embodiments at least 120%, in some embodiments at least 130%, in some embodiments at least 140%, in some embodiments at least 150%, in some embodiments at least 200%, in some embodiments at least 300%, in some embodiments at least 400%, in some embodiments at least 500%, in some embodiments at least 600%, and in some embodiments at least 700%. The distribution has at least 800% in some embodiments, at least 900% in some embodiments, at least 1000% in some embodiments, at least 1100% in some embodiments, at least 1200% in some embodiments, at least 1300% in some embodiments, at least 1400% in some embodiments, at least 1500% in some embodiments, at least 1600% in some embodiments, at least 1700% in some embodiments, at least 1800% in some embodiments, at least 1900% in some embodiments, and at least 2000% in some embodiments.

[0034] Furthermore, when the nanoparticles are dispersed in water, they may optionally have an average hydrated particle size and / or PDI and / or D10 and / or D50 and / or D90 and / or Zeta potential and / or TEM particle size and / or average hydrated particle size / (TEM) as defined in this disclosure. a +TEM b ).

[0035] Another aspect of this disclosure is to provide a zinc oxide nanoparticle having a core-shell structure consisting of a core and an outer shell, wherein the core of the nanoparticle is prepared from carboxyl-modified silicon dioxide (SiO2-COOH);

[0036] Furthermore, the shell layer is zinc oxide;

[0037] Furthermore, in the nanoparticles, the mass ratio of zinc to silicon is 100:1~5000:1, or 200:1~5000:1, or 300:1~5000:1, or 400:1~5000:1, or 500:1~5000:1, or 500:1~4900:1, or 500:1~4800:1, or 500:1~4700:1, or 500:1~4600:1, or 500:1~ 4500:1, or 500:1~4400:1, or 500:1~4300:1, or 500:1~4200:1, or 500:1~4100:1, or 500:1~4000:1, or 500:1~3500:1, or 500:1~3000:1, or 500:1~2500:1, or 1000:1~3000:1, or 1500:1~3000:1, or 200 0:1~3000:1, or 2100:1~3000:1, or 2200:1~3000:1, or 2300:1~3000:1, or 2400:1~3000:1, or 2500:1~3000:1, or 600:1~5000:1, or 700:1~5000:1, or 800:1~5000:1, or 900:1~5000:1, or 1000:1~50000:1 0:1, or 1100:1~5000:1, or 1200:1~5000:1, or 1300:1~5000:1, or 1400:1~5000:1, or 1500:1~5000:1, or 1600:1~5000:1, or 1700:1~5000:1, or 1800:1~5000:1, or 1900:1~5000:1, or 2000:1~5000:1.

[0038] Furthermore, in the nanoparticles, the mass ratio of zinc to silicon is 100:1 to 1000:1, or 200:1 to 900:1, or 300:1 to 800:1, or 300:1 to 700:1, or 300:1 to 600:1, or 300:1 to 500:1, or 300:1 to 400:1.

[0039] Furthermore, the mass ratio of zinc to silicon in the nanoparticles was obtained by TEM / EDS.

[0040] Furthermore, when the nanoparticles are dispersed in water, they optionally have an average hydrated particle size and / or PDI and / or D10 and / or D50 and / or D90 and / or Zeta potential and / or TEM particle size and / or average hydrated particle size / (TEM) as defined above. a +TEM b ).

[0041] This disclosure also provides a use of the zinc oxide nanoparticles in the preparation of sunscreen cosmetics.

[0042] This disclosure also provides a dispersion comprising the aforementioned zinc oxide nanoparticles and cosmetically acceptable excipients. The zinc oxide nanoparticles have any of the characteristics defined above. Before being formulated into a cosmetic preparation, the nanoparticles can be stored in the form of a dispersion for ease of storage and sale. To prevent nanoparticle agglomeration during storage and / or to accelerate the dispersion of nanoparticles in the cosmetic during production, surfactants or other functional excipients can be added to the dispersion, such as functional excipients to prevent particle agglomeration and increase stability, or excipients for color adjustment.

[0043] This disclosure also provides a use of the dispersion to prepare sunscreen cosmetics.

[0044] This disclosure provides a cosmetic product comprising the zinc oxide nanoparticles or the dispersed material.

[0045] This disclosure provides a cosmetic product prepared from the dispersion to be dispersed.

[0046] This disclosure provides a method for preparing the zinc oxide nanoparticles, comprising the following steps:

[0047] Step 1: Add the zinc source to the solvent to form a uniform dispersion 1; uniformly disperse the nucleating agent in water to form a dispersion 2;

[0048] Step 2: Mix dispersion 1 and dispersion 2, and the mass ratio of nucleating agent to zinc source in the resulting mixture is 0.15:100~2000;

[0049] Step 3: Heat the mixture to 120-140°C and stir; in some embodiments, stirring is performed for at least 10 minutes.

[0050] Step 4: Continue heating to 140-200℃ until the reaction is complete; in some embodiments, the reaction time is not less than 90 minutes.

[0051] Step 5: After the reaction solution cools to room temperature, separate the solid and liquid phases, wash three times to obtain the solid;

[0052] Step 6: After the solid is dried, it is pulverized with a pulverizer to obtain zinc oxide nanoparticles;

[0053] The nucleating agent is carboxyl-modified silica nanoparticles.

[0054] In some embodiments, the concentration of the zinc source in dispersion 1 is 0.5~2 mol / L, or 0.6~1.9 mol / L, or 0.7~1.8 mol / L, or 0.8~1.7 mol / L, or 0.9~1.6 mol / L, or 1~1.5 mol / L, or 1~1.4 mol / L, or 1~1.3 mol / L, or 1~1.2 mol / L, or 1~1.1 mol / L, or 0.5~1.5 mol / L, or 0.6~1.4 mol / L, or 0.7~1.3 mol / L, or 0.8~1.2 mol / L, or 0.9~1.1 mol / L.

[0055] In some embodiments, the concentration of the nucleating agent in the dispersion 2 is 10%~20%, or 11%~20%, or 12%~20%, or 13%~20%, or 14%~20%, or 15%~20% by mass fraction.

[0056] In some embodiments, the mass ratio of nucleating agent to zinc source in the mixture is 0.15:100~2000; or 0.15:100~1000, or 0.15:100~800, or 0.15:200~800, or 0.15:300~800, or 0.15:400~800, or 0.15:500~800, or 0.15:500~700, or 0.15:500~600, or 0.15:100~700, or 0.15:100~600, or 0.15:100~500.

[0057] In some embodiments, the zinc source is added to the solvent to form a uniform dispersion with a concentration of 0.5~5 mol / L. In some embodiments, the concentration is 0.5~4 mol / L, in some embodiments it is 0.5~3 mol / L, in some embodiments it is 0.5~2 mol / L, and in some embodiments it is 1±0.5 mol / L.

[0058] In some embodiments, the zinc source is selected from one or more of zinc acetate, zinc nitrate, zinc chloride, zinc sulfate, and zinc ethylhexanoate.

[0059] In some embodiments, the zinc source is selected from zinc acetate.

[0060] In some embodiments, the solvent is selected from glycol solvents.

[0061] In some embodiments, the solvent is selected from one or more of ethylene glycol, diethylene glycol (DEG), tetraethylene triethylene glycol (TEG), polyethylene glycol 200 (PEG200), polyethylene glycol 300 (PEG300), and polyethylene glycol 400 (PEG400).

[0062] In some embodiments, the solvent is selected from tetraethylene glycol.

[0063] In some embodiments, in step 4, the temperature is raised to 160-200°C. In some embodiments, the temperature is raised to 170-190°C. In some embodiments, the temperature is raised to 180±5°C.

[0064] Another aspect of this disclosure is to provide a silica for preparing zinc oxide nanoparticles, specifically carboxyl-modified silica (SiO2-COOH) nanoparticles, wherein the average hydrated particle size of the carboxyl-modified silica nanoparticles ranges from 10 to 50 nm, the PDI is not greater than 0.05, and the zeta potential is greater than -40 mV. In some embodiments, the zeta potential is greater than -41 mV, or greater than -42 mV, or greater than -43 mV, or greater than -44 mV, or greater than -45 mV, or greater than -46 mV, or greater than -47 mV, or greater than -48 mV. In some embodiments, the PDI is not greater than 0.04; in some embodiments, the PDI is not greater than 0.03; and in some embodiments, the PDI is not greater than 0.02.

[0065] Another aspect of this disclosure is the use of carboxyl-modified silica (SiO2-COOH) nanoparticles for the preparation of zinc oxide nanoparticles.

[0066] Furthermore, the carboxyl-modified silica (SiO2-COOH) nanoparticles are used in the preparation of sunscreen nanoparticles, serving as nucleating agents for the nanoparticles.

[0067] Furthermore, the carboxyl-modified silica (SiO2-COOH) nanoparticles are used to prepare sunscreen nanoparticles. The prepared sunscreen nanoparticles have a core-shell structure consisting of a core and a shell. The core is prepared from carboxyl-modified silica nanoparticles (SiO2-COOH), and the shell is zinc oxide.

[0068] Furthermore, another aspect of this disclosure is to provide a method for preparing carboxyl-modified silica (SiO2-COOH):

[0069] Step 1: Disperse silica in water to form a suspension;

[0070] Step 2: Add 3-aminopropyltriethoxysilane (APTES) to the above SiO2 suspension and stir to react to obtain amino-modified silica (SiO2-NH2).

[0071] Step 3: Centrifuge the mixture obtained in Step 2, wash the separated precipitate and dry it;

[0072] Step 4: Disperse the solid obtained in Step 3 in DMF, add succinic anhydride and stir to react;

[0073] Step 5: Centrifuge the mixture obtained in Step 4, wash the separated precipitate and dry it to obtain carboxyl-modified silica (SiO2-COOH).

[0074] In some embodiments, the prepared SiO2-COOH has the characteristic range mentioned above.

[0075] In some embodiments, silica nanoparticles are prepared according to the following method:

[0076] Step 1: Dissolve arginine in water, then add cyclohexane and tetraethyl orthosilicate (TEOS) and mix well;

[0077] Step 2: The mixture is placed at a high temperature to react, and finally silica nanoparticles (SiO2) are obtained.

[0078] In some embodiments, the average hydrated particle size of the silica nanoparticles ranges from 10 to 50 nm, the PDI is not greater than 0.05, and the zeta potential is greater than -20 mV. For example, the zeta potential can be -25 mV, -30 mV, or -31 mV, etc.

[0079] In some embodiments, the average hydrated particle size of the silica nanoparticles ranges from 10 to 50 nm, the PDI is not greater than 0.05, and the zeta potential is greater than -31 mV. In some embodiments, the PDI is not greater than 0.04, in some embodiments, the PDI is not greater than 0.03, and in some embodiments, the PDI is not greater than 0.02.

[0080] Another aspect of this disclosure is to provide a method for preparing zinc oxide nanoparticles.

[0081] Includes the following steps:

[0082] Step 1: Add the zinc source to the solvent to form a uniform dispersion;

[0083] Step 2: Disperse the nucleating agent uniformly into the above dispersion; finally, the mass ratio of nucleating agent to zinc source in the resulting mixture is 0.15:100~2000;

[0084] Step 3: Heat the mixture to 120-140℃ and stir;

[0085] Step 4: Continue heating to 140-200℃ until the reaction is complete;

[0086] Step 5: After the reaction solution cools to room temperature, separate the solid and liquid, and wash to obtain the solid.

[0087] Step 6: After the solid is dried, it is pulverized with a pulverizer to obtain zinc oxide nanoparticles;

[0088] The nucleating agent is carboxyl-modified silica nanoparticles.

[0089] Furthermore, in the preparation method described above, the zinc source is selected from one or more of zinc acetate, zinc nitrate, zinc chloride, zinc sulfate, and zinc ethylhexanoate.

[0090] Furthermore, in the preparation method described above, the solvent is selected from glycol solvents.

[0091] Further, in the preparation method described above, in step 2, the mass ratio of the nucleating agent to the zinc source is 0.15:100~1000; or the mass ratio is 0.15:100~800; or the mass ratio is 0.15:200~800; or the mass ratio is 0.15:300~800; or the mass ratio is 0.15:400~800; or the mass ratio is 0.15:500~800.

[0092] Furthermore, in the preparation method described above, in step 4, the temperature is raised to 160-200℃; or to 170-190℃; or to 180±5℃.

[0093] Furthermore, the feeding ratio of the core (nucleating agent) to the shell (zinc source) material of the nanoparticles is 0.15:100~2000 by mass; or 0.15:100~1000, or 0.15:100~800, or 0.15:200~800, or 0.15:300~800, or 0.15:400~800, or 0.15:500~800, or 0.15:500~700, or 0.15:500~600, or 0.15:100~700, or 0.15:100~600, or 0.15:100~500.

[0094] Related terms:

[0095] Silica: The silica in the zinc oxide nanoparticles disclosed herein may be unmodified or modified with other functional groups. In some embodiments, these modifying groups can ionize in the reaction environment to generate a negative charge, such as carboxyl groups, to enhance zinc ion adsorption. Alternatively, they may be other non-ionizable but electronegative groups.

[0096] Hydrated particle size: refers to the diameter of a substance in fluid dynamics. The hydrated particle size of a substance can be measured using a dynamic light scattering instrument. The testing principle is based on the scattering of light by particles, a principle well known to those skilled in the art.

[0097] Average hydrated particle size: refers to the weighted average of the particle sizes of all particles. In this disclosure, the indexed average hydrated particle size is the average value obtained by weighting the number of particles corresponding to the hydrated particle size.

[0098] TEM particle size: TEM stands for Transmission Electron Microscope. The particle size calculated from the particles in the TEM image using ImageJ software is the TEM particle size.

[0099] TEM a : Indicates the minimum TEM particle size.

[0100] TEM b : Indicates the maximum TEM particle size.

[0101] PDI: Polydispersity Index is one of the important parameters characterizing the uniformity of particle distribution. PDI is usually obtained by dynamic light scattering.

[0102] Span: Particle size distribution width (Span) is another indicator that characterizes the width of particle distribution. Span is often used to characterize asymmetric particle systems, especially when the particle diameter distribution is significantly skewed. The formula for calculating Span is: Span = (D90 - D10) / D50.

[0103] D10: The particle size corresponding to a cumulative particle size distribution percentage of 10% in the test sample can be obtained by statistical analysis using a dynamic light scattering instrument.

[0104] D50: The particle size corresponding to a cumulative particle size distribution percentage of 50% in the test sample, which can be obtained by statistical analysis using a dynamic light scattering instrument.

[0105] D90: The particle size corresponding to the cumulative particle size distribution percentage of the test sample reaching 90%, which can be obtained by dynamic light scattering.

[0106] Zeta potential: Used as a measure of the strength of mutual repulsion or attraction between particles, it can be obtained statistically by dynamic light scattering. For potential values, the "-" before the value represents a negative potential. Therefore, when comparing potential magnitudes, only the absolute value is considered, and the influence of the "-" on the numerical value is ignored.

[0107] Any zinc oxide nanoparticle as defined above in this disclosure, when used in sunscreen products, has the following technical effects:

[0108] 1. Good dispersibility in water: For particles that easily aggregate, it is necessary to disperse them in cosmetic formulations with poor flowability to avoid clumping and causing undesirable effects such as a false white cast. Therefore, when water is used as the main dispersing carrier, thickeners are often added to reduce the flowability of the particles (increase viscosity) and prevent aggregation. However, adding too much thickener can cause problems such as a greasy feeling after use and poor breathability. The zinc oxide nanoparticles prepared in this disclosure disperse well in water, have low viscosity requirements for the cosmetic dispersing carrier, thus reducing the amount of such thickeners used, improving user comfort, and reducing the probability of a false white cast.

[0109] 2. Less generation of strong oxidizing substances: The nanoparticles disclosed herein and the sunscreen compositions prepared therefrom not only have stronger UV absorption capabilities, but also generate less of the strong oxidizing substances. For example, the proportion of singlet oxygen generated at 10s is less than 17% in some embodiments, less than 16% in some embodiments, less than 15% in some embodiments, less than 14% in some embodiments, less than 13% in some embodiments, less than 12% in some embodiments, and less than 11% in some embodiments. This means that to achieve the same sunscreen effect, the amount of zinc oxide nanoparticles disclosed herein used can be reduced, or even eliminated, the use of chemical sunscreen agents can be reduced. In addition, since less strong oxidizing agents are generated, the amount or types of reducing chemical agents used can also be reduced. Some users are sensitive to these chemical agents, and sometimes even experience discomfort. Reducing the amount or types of these chemical agents used makes it easier to obtain gentler formulations that are suitable for a wider range of people, and also simplifies the formulation of cosmetics.

[0110] 3. For smoother skin: Due to the good dispersion effect of this invention, agglomeration is reduced, the particles are smoother, and the comfort of use is improved.

[0111] 4. Excellent sun protection effect: The nanoparticles disclosed herein exhibit an ultraviolet absorbance (Abs) greater than 0.5, in some embodiments greater than 0.6, in some embodiments greater than 0.7, in some embodiments greater than 0.8, in some embodiments greater than 0.9, and in some embodiments greater than 1.0. This demonstrates stronger ultraviolet spectral absorption performance, greatly enhancing the sun protection effect.

[0112] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and are not intended to limit this disclosure. Attached Figure Description

[0113] The accompanying drawings, which are incorporated in and form a part of this specification, illustrate embodiments consistent with this disclosure and, together with the description, serve to explain the principles of this disclosure.

[0114] To more clearly illustrate the technical solutions in the embodiments of this disclosure or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0115] Figure 1 shows the particle size distribution of silica nanoparticles in Example 1;

[0116] Figure 2 is a TEM image of the silica nanoparticles in Example 1;

[0117] Figure 3 shows the particle size distribution of the carboxyl-modified silica nanoparticles in Example 1;

[0118] Figure 4 is a TEM image of the carboxyl-modified silica nanoparticles in Example 1;

[0119] Figure 5 is a TEM image of zinc oxide nanoparticles prepared in Comparative Example 1 dispersed in water.

[0120] Figure 6 is a TEM image of the zinc oxide nanoparticles prepared in Example 2 dispersed in water;

[0121] Figure 7 is a TEM image of zinc oxide nanoparticles prepared in Example 3 dispersed in water;

[0122] Figure 8 is a TEM image of the zinc oxide nanoparticles prepared in Example 4 dispersed in water;

[0123] Figure 9 is a TEM image of zinc oxide nanoparticles prepared in Comparative Example 2 dispersed in water;

[0124] Figure 10 is a TEM image of zinc oxide nanoparticles prepared in Comparative Example 3 dispersed in water.

[0125] Figure 11 is a TEM image of zinc oxide nanoparticles prepared in Example 5 dispersed in water;

[0126] Figure 12 is a TEM image of the zinc oxide nanoparticles prepared in Example 6 dispersed in water;

[0127] Figure 13 is a TEM image of zinc oxide nanoparticles separated from Pavise and dispersed in water in Comparative Example 4.

[0128] Figure 14 shows the absorption spectra obtained using a UV-Vis spectrophotometer (TU-1810). In the figure, "0.15-10-0.02%", "0.15-100-0.02%", "0.15-500-0.02%", "0.15-800-0.02%", and "0.15-2000-0.02%" represent samples prepared according to nucleating agent to zinc source mass ratios of 0.15:10 (Comparative Example 1), 0.15:100 (Example 2), 0.15:500 (Example 3), 0.15:800 (Example 4), and 0.15:2000 (Comparative Example 2), respectively, and uniformly dispersed in water at a concentration of 0.2 mg / ml. "Pavise-0.02%" represents zinc oxide nanoparticles separated from Pavise (Comparative Example 4), uniformly dispersed in water at a concentration of 0.2 mg / ml.

[0129] Figure 15 shows the absorption spectrum obtained using a UV-Vis spectrophotometer (TU-1810). In the figure, "140℃-0.02%", "160℃-0.02%", "180℃-0.02%", and "200℃-0.02%" indicate that the tested samples came from Comparative Example 3, Example 5, Example 3, and Example 6, respectively, and were uniformly dispersed in water at a concentration of 0.2 mg / ml. Embodiments of the present invention

[0130] To make the objectives, technical solutions, and advantages of the embodiments of this disclosure clearer, the technical solutions in the embodiments of this disclosure will be clearly and completely described below. Obviously, the described embodiments are only some, not all, of the embodiments of this disclosure. Based on the embodiments of this disclosure, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this disclosure.

[0131] Example 1

[0132] Preparation of carboxyl-modified silica nanoparticles (SiO2-COOH):

[0133] Step 1: Dissolve 9.1 mg of arginine in 6.9 mL of deionized water, then add 0.45 mL of cyclohexane and 0.55 mL of tetraethyl orthosilicate (TEOS) and mix well;

[0134] Step 2: Place the mixture at 60°C and stir continuously for 20 hours to obtain silica nanoparticles (SiO2).

[0135] Step 3: Add 0.5 mL of 3-aminopropyltriethoxysilane (APTES) to the above SiO2 suspension and stir overnight at room temperature to obtain amino-modified SiO2 (SiO2-NH2).

[0136] Step 4: Centrifuge the mixture and wash the resulting lower precipitate with ethanol and N,N-dimethylformamide (DMF), respectively.

[0137] Step 5: Take 60 mg of the precipitate, resuspend it in DMF, add 100 mg of succinic anhydride, and stir overnight at room temperature;

[0138] Step 6: Centrifuge the mixture, wash the lower precipitate with DMF and deionized water respectively, and dry the precipitate to obtain carboxyl-modified SiO2 (SiO2-COOH).

[0139] The zeta potential of silica nanoparticles was measured to be -31.2 mV, while that of carboxyl-modified silica nanoparticles was -47.9 mV. This indicates that the silica was successfully bonded with carboxyl groups, thereby enhancing its electronegativity. Furthermore, the modification did not affect the particle size distribution (as shown in Figures 1-4).

[0140] Example 2

[0141] This embodiment provides zinc oxide nanoparticles and a method for their preparation. The preparation method includes the following steps:

[0142] Step 1: Disperse zinc acetate (zinc source) evenly in tetraethylene glycol (solvent) to form mixture 1 (concentration of 1 mol / L).

[0143] Step 2: Carboxyl-modified silica nanoparticles (nucleating agent) are uniformly dispersed in water to form mixture 2 (mass fraction of 15%). Subsequently, mixture 1 and mixture 2 are mixed, and the mass ratio of nucleating agent to zinc source in the resulting mixture is 0.15:100.

[0144] Step 3: Heat the mixture to 120-140℃ and premix for 10-30 minutes.

[0145] Step 4: Continue heating to approximately 180°C and stop the reaction after 90-120 minutes.

[0146] Step 5: After the reaction solution cools to room temperature, perform solid-liquid separation and wash with water three times to obtain the solid.

[0147] Step 6: After the solid is dried, it is pulverized with a pulverizer to obtain zinc oxide nanoparticles.

[0148] Nanoparticles were dispersed in water to prepare a sample for testing at a concentration of approximately 0.16 mg / ml. The sample was obtained using a transmission electron microscope (Hitachi, HT7800) as shown in Figure 6. The TEM images were analyzed using ImageJ software, and the TEM particle size was found to be 30–70 nm.

[0149] Example 3

[0150] The implementation method is the same as in Example 2, except that the mass ratio of nucleating agent to zinc source in the mixture in step 2 is 0.15:500.

[0151] The TEM image is shown in Figure 7. The TEM particle size is 30~70 nm.

[0152] Example 4

[0153] The implementation method is the same as in Example 2, except that the mass ratio of nucleating agent to zinc source in the mixture in step 2 is 0.15:800.

[0154] The TEM image is shown in Figure 8. The TEM particle size is 30~60 nm.

[0155] Example 5

[0156] Same as Example 2, except that the temperature is raised to about 160°C in step 4.

[0157] The TEM image is shown in Figure 11. The TEM particle size is 25~55 nm.

[0158] Example 6

[0159] Same as Example 2, except that the temperature is raised to about 200°C in step 4.

[0160] The TEM image is shown in Figure 12. The TEM particle size is 30~80 nm.

[0161] Comparative Example 1

[0162] The implementation method is the same as in Example 2, except that the mass ratio of nucleating agent to zinc source in the mixture in step 2 is 0.15:10.

[0163] The TEM image is shown in Figure 5. The TEM particle size is 20~40 nm.

[0164] Comparative Example 2

[0165] The implementation method is the same as in Example 2, except that the mass ratio of nucleating agent to zinc source in the mixture in step 2 is 0.15:2000.

[0166] The TEM image is shown in Figure 9. The TEM particle size is 30~80 nm.

[0167] Comparative Example 3

[0168] Same as Example 2, except that the temperature is raised to about 140°C in step 4.

[0169] The TEM image is shown in Figure 10. The TEM particle size is 15~40 nm.

[0170] Comparative Example 4

[0171] We purchased a commercially available sunscreen product called Pavise and isolated zinc oxide nanoparticles from it.

[0172] The TEM image is shown in Figure 13. The TEM particle size is 40~60 nm.

[0173] Test Example 1

[0174] 1.1 Hydrated Particle Size Test

[0175] The particles prepared in the above embodiments and comparative examples were dispersed in water and tested using a dynamic light scattering instrument (Anton Paar, Litesizer 500), and the data are shown in Table 1 below.

[0176] Table 1

[0177]

[0178] The average hydrated particle size in Table 1 is the number-average hydrated particle size obtained by weighting the number of particles. PDI stands for Dispersion Index, which describes the range of particle size distribution. D10, D50, and D90 represent the particle size values ​​corresponding to the cumulative distribution percentages of 10%, 50%, and 90%, respectively, from smallest to largest.

[0179] 1.2 Dispersion (aggregation) test

[0180] TEM images can observe the particle size of individual particles in a dry state and can also indirectly reflect the aggregation when dispersed in water. To quantitatively characterize whether particles aggregate, the applicant used hydrated particle size data combined with TEM particle size to describe the dispersion of particles in water, and the results are shown in Table 2.

[0181] Table 2

[0182]

[0183] TEM a TEM b These represent the minimum and maximum TEM particle size, respectively.

[0184] Dispersion was assessed using TEM images. +++ indicates excellent dispersion with very little particle aggregation. ++ indicates good dispersion with some particle aggregation. + indicates poor uniformity of particle distribution in the TEM image, but without tight aggregation. This indicates that the particles are poorly distributed in the TEM image and have formed dense aggregates.

[0185] While existing technologies typically use Zeta potential to describe dispersion stability, this method cannot accurately reflect the severity of particle aggregation. A comparison of Figure 8 (Example 4) and Figure 10 (Comparative Example 3) reveals that the aggregation degree in Comparative Example 3 is significantly higher than that in Example 4, yet the Zeta potential for Example 4 is lower than that for Comparative Example 3. Therefore, the applicant calculated the following formula: "Average hydrated particle size / (TEM)..." a +TEM b "TEM" indicates the proportion of particles that have aggregated to form aggregates (particles exceeding the maximum individual particle size) within the particle structure, used to describe the severity of particle aggregation. a +TEM b This represents the particle size of the theoretical minimum aggregated state, that is, the particle size at which the largest and smallest particles are closely aggregated. When the particle size after aggregation exceeds the TEM value... a +TEM b The more particles there are, the more severe the aggregation. When the particle size after aggregation is smaller than TEM... a +TEM b If the particle size of the aggregate does not exceed the particle size of the largest and smallest tightly aggregated particles, it is considered to have a low degree of aggregation and is treated as a single particle.

[0186] Table 2 shows that the more densely aggregated the particles, the larger the average hydrated particle size. The more severe the aggregation, the larger the average hydrated particle size / (TEM) ratio. a +TEM b The value is greater than 1, and the larger the value, the better. When the particles are well dispersed, the average hydrated particle size / (TEM) a +TEM b )≤1.

[0187] Test Example 2

[0188] Characterization of singlet oxygen generation capacity

[0189] The nanoparticles from the above examples and comparative examples were uniformly dispersed in water to prepare a sample with a concentration of 0.2 mg / ml. The singlet oxygen generation capacity was tested using the ABDA method. 1 ml of 100 μM ABDA solution was mixed with each sample, and the ultraviolet absorption spectrum was measured. The sample was excited with a 365 nm UV lamp for 5 s, followed by another 5 s of excitation. The decrease in the characteristic absorption peak of ABDA at 400 nm was observed. The light source was 5 cm above the liquid surface.

[0190] Singlet oxygen production percentage = [Abs] （ 400 nm ，曝光 0s ） -Abs （ 400 nm ，曝光时长） ] / Abs ( 400 nm ，曝光 0s ) × 100%

[0191] Table 3 below shows the calculated percentage of singlet oxygen generated at exposure times of 5s and 10s. The smaller the percentage of singlet oxygen generated, the less strong oxidizing substances are produced.

[0192] Table 3

[0193]

[0194] Based on the above data, it can be seen that the nano-zinc oxide used in the commercial product Pavise utilizes a nanodiamond core to remove holes through an internal oxidation process or by capturing electrons in the conduction bands of the shell (as described in CN116171146A), resulting in a singlet oxygen generation ratio of 17.89% at 10 s. Meanwhile, Examples 2-6 of this disclosure (average hydrated particle size / (TEM)) a +TEM b Nanoparticles with a density ≤1 and an average hydrated particle size ≤90 nm exhibit a singlet oxygen generation rate of less than 14% over 10 s, with some even reaching less than 10%. This indicates that the nanoparticles provided in this disclosure generate fewer highly oxidizing substances. Based on the mechanism of reactive oxygen generation in ZnO, higher light absorbance should correspond to a greater generation of reactive oxygen species. To comprehensively evaluate the performance of the nanoparticles in this disclosure as sunscreens, the following spectral absorption performance characterization was performed.

[0195] Test Example 3

[0196] Spectral absorption performance

[0197] Those skilled in the art will understand that the peroxides are generated from the absorption of light energy by the nano-zinc oxide. Therefore, this test example performs spectral absorption tests on the nanoparticles of the above embodiments and comparative examples to comprehensively evaluate the spectral absorption performance and the corresponding peroxides generated.

[0198] The nanoparticles from the above examples and comparative examples were uniformly dispersed in water at a concentration of 0.2 mg / ml. Measurements were performed using a UV-Vis spectrophotometer (TU-1810) within the range of 290-800 nm. The test results are shown in Figures 14 and 15.

[0199] According to the test results, in the ultraviolet region, namely the UVA and UVB regions, particles with an absorbance (Abs) less than 1.0 include: Example 2, Comparative Example 1, Comparative Example 3, and Comparative Example 4; particles with an absorbance (Abs) greater than or equal to 1.0 include: Examples 3-6 and Comparative Example 2. Therefore, Examples 3-6 and Comparative Example 2 have strong sun protection capabilities. Especially Examples 3, Example 5, and Comparative Example 2.

[0200] Combining UV absorption data, it was unexpectedly discovered that in Examples 3-6, the average hydrated particle size exceeding 50 nm exhibited stronger absorption capacity in the UV spectrum. That is, when 50 nm ≤ average hydrated particle size ≤ 90 nm, and the particle dispersion is good (average hydrated particle size / (TEM)... a +TEM b While exhibiting stronger ultraviolet spectral absorption capacity, it also produces less of the strong oxidizing agents. In contrast, the nanoparticles used in Pavise have a much lower ultraviolet absorbance (Abs) than those in Examples 3-6.

[0201] Furthermore, by comparing Examples 3 to 6 (all with absorbance (Abs) greater than 1.0 in the ultraviolet region), it can be observed that when PDI decreases (particle size distribution is more uniform), the proportion of singlet oxygen generated at 10s also decreases accordingly. That is, compared with Examples 5 and 6, Examples 3 and 4 have smaller PDI (PDI≤20%), more uniform distribution, and less mass of strong oxidizing agents.

[0202] Having strong UV absorption capabilities while producing less strong oxidizing agents means that the amount of chemical sunscreen agents and reducing chemical agents can be reduced in sunscreen formulations. Because of the reduction in the content or ingredients of these chemical agents, it is easier to obtain a gentle formula that can be suitable for a wider range of people.

[0203] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0204] The above description is merely a specific embodiment of this disclosure, enabling those skilled in the art to understand or implement it. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this disclosure. Therefore, this disclosure is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein. Industrial applicability

[0205] The zinc oxide nanoparticles disclosed herein are uniformly dispersed in water, do not easily aggregate, and have good stability. They are easy to formulate into water-based sunscreen cosmetics, and do not feel greasy after use. Moreover, they produce few strong oxidizing substances after absorbing ultraviolet light, which can reduce the amount or types of reducing chemical reagents used. They show significant application value in the preparation of sunscreen products and have strong industrial applicability.

Claims

1. A zinc oxide nanoparticle, characterized in that: The outer layer of the nanoparticles is zinc oxide; When the nanoparticles are dispersed in water, the average hydrated particle size is ≤90nm. Average hydrated particle size / (TEM) a +TEM b )≤1, TEM a TEM b These represent the minimum and maximum TEM particle size, respectively.

2. The zinc oxide nanoparticles according to claim 1, characterized in that: The nanoparticles have a core-shell structure consisting of a core and an outer shell, wherein the core contains silicon dioxide and the shell is zinc oxide.

3. The zinc oxide nanoparticles according to claim 2, characterized in that: The silicon dioxide is carboxylated modified silicon dioxide.

4. The zinc oxide nanoparticles according to claim 1, characterized in that: 50nm≤average hydrated particle size≤90nm, or 60nm≤average hydrated particle size≤90nm, or 70nm≤average hydrated particle size≤90nm, or 60nm≤average hydrated particle size≤85nm.

5. The zinc oxide nanoparticles according to claim 1, characterized in that: When the nanoparticles are dispersed in water, D50 ≤ 80 nm, or D50 ≤ 79 nm, or D50 ≤ 78 nm, or D50 ≤ 77 nm, or D50 ≤ 76 nm, or D50 ≤ 75 nm.

6. The zinc oxide nanoparticles according to claim 1, characterized in that: D90≤110nm, or D90≤109nm, or D90≤108nm, or D90≤107nm, or D90≤106nm, or D90≤105nm.

7. The zinc oxide nanoparticles according to claim 1, characterized in that: The polydispersity index (PDI) of the zinc oxide nanoparticles is ≤0.3, ≤0.2, ≤0.19, ≤0.18, or ≤0.

17.

8. The zinc oxide nanoparticles according to claim 1, characterized in that: When the nanoparticles are dispersed in water, under 5s ultraviolet light excitation, the generation of singlet oxygen is less than 10%, or less than 8%, or less than 7%, or less than 6%, or less than 5%.

9. The zinc oxide nanoparticles according to claim 1, characterized in that: When the nanoparticles are dispersed in water, under 10s ultraviolet light excitation, the generation of singlet oxygen is less than 16%, or less than 15%, or less than 14%, or less than 13%, or less than 12%.

10. The zinc oxide nanoparticles according to claim 1, characterized in that: When the nanoparticles are dispersed in water, the peak value Abs of the absorption peak in the wavelength range of 280-320 nm is greater than 0.2, or greater than 0.3, or greater than 0.4, or greater than 0.5, or greater than 0.6, or greater than 0.7, or greater than 0.8, or greater than 0.9, or greater than 1.0, or greater than 1.1, or greater than 1.2, or greater than 1.3, or greater than 1.4, or greater than 1.

5.

11. The zinc oxide nanoparticles according to claim 2, characterized in that: Based on mass fractions, the zinc oxide in the shell has a distribution of at least 100%, or at least 110%, or at least 120%, or at least 130%, or at least 140%, or at least 150%, or at least 200%, or at least 300%, or at least 400%, or at least 500%, or at least 600%, or at least 700%, relative to the silicon dioxide in the core. It has a distribution of at least 800%, or at least 900%, or at least 1000%, or at least 1100%, or at least 1200%, or at least 1300%, or at least 1400%, or at least 1500%, or at least 1600%, or at least 1700%, or at least 1800%, or at least 1900%, or at least 2000%.

12. The zinc oxide nanoparticles according to claim 11, characterized in that: In the nanoparticles, the mass ratio of zinc to silicon is 100:1 to 5000:1, or 200:1 to 5000:1, or 300:1 to 5000:1, or 400:1 to 5000:1, or 500:1 to 5000:1, or 500:1 to 4900:1, or 500:1 to 4800:1, or 500:1 to 4700:1, or 500:1 to 4600:1, or 500:1 to 4500. :1, or 500:1~4400:1, or 500:1~4300:1, or 500:1~4200:1, or 500:1~4100:1, or 500:1~4000:1, or 500:1~3500:1, or 500:1~3000:1, or 500:1~2500:1, or 1000:1~3000:1, or 1500:1~3000:1, or 2000:1 ~3000:1, or 2100:1~3000:1, or 2200:1~3000:1, or 2300:1~3000:1, or 2400:1~3000:1, or 2500:1~3000:1, or 600:1~5000:1, or 700:1~5000:1, or 800:1~5000:1, or 900:1~5000:1, or 1000:1~5000: 1, or 1100:1~5000:1, or 1200:1~5000:1, or 1300:1~5000:1, or 1400:1~5000:1, or 1500:1~5000:1, or 1600:1~5000:1, or 1700:1~5000:1, or 1800:1~5000:1, or 1900:1~5000:1, or 2000:1~5000:

1.

13. The method for preparing zinc oxide nanoparticles according to any one of claims 1 to 12, characterized in that: include: Step 1: Add the zinc source to the solvent to form a uniform dispersion; Step 2: Disperse the nucleating agent uniformly into the above dispersion; finally, the mass ratio of nucleating agent to zinc source in the resulting mixture is 0.15:100~2000; Step 3: Heat the mixture to 120-140℃ and stir; Step 4: Continue heating to 140-200℃ until the reaction is complete; Step 5: After the reaction solution cools to room temperature, separate the solid and liquid, and wash to obtain the solid. Step 6: After the solid is dried, it is pulverized with a pulverizer to obtain zinc oxide nanoparticles.

14. Use of zinc oxide nanoparticles according to any one of claims 1 to 12 in the preparation of sunscreen cosmetics.

15. A dispersion, characterized in that: Includes zinc oxide nanoparticles as described in any one of claims 1 to 12 and cosmetic excipients.

16. Use of the dispersible material of claim 15 in the preparation of sunscreen cosmetics.

17. A cosmetic product, characterized in that: It includes the zinc oxide nanoparticles according to any one of claims 1 to 12 or the dispersion according to claim 15.

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