A zinc oxide nanoparticle and its applications

Abstract

The present invention relates to the field of sunscreen technology, and particularly relates to zinc oxide nanoparticles and their applications. The present invention successfully prepares zinc oxide nanoparticles with good dispersibility. The average hydrated particle size of the nanoparticles is ≤90 nm, and the average hydrated particle size / (TEM a + TEM b ) ≤ 1. They are evenly dispersed in water, not easily aggregated, and have good stability. They are easily formulated into water-based sunscreen cosmetics. After use, there is no greasy feeling. Moreover, the amount of strongly oxidizing substances generated after absorbing ultraviolet light is small, which means that in the sunscreen formula, the addition of chemical sunscreen reagents can be reduced, as well as reducing reducing chemical reagents. Since the content or composition of these chemical reagents is reduced, it is easier to obtain a mild formula and increase the applicable population.

Description

Technical Field

[0001] The present invention relates to the field of sunscreen technology, and particularly relates to a zinc oxide nanoparticle and its application. Background Art

[0002] Due to the action of ultraviolet (UV) rays in sunlight, the incidence of melanoma skin cancer has increased significantly, and it is the most common cancer among people aged 25 to 29. It is recommended to use sunscreen to prevent skin cancer, sunburn, photoaging and skin wrinkles. It is generally known that, according to different wavelengths, ultraviolet rays can be divided into several bands: UVA, UVB, UVC and UVD. Among them, UVA and UVB are the two bands most relevant to human health.

[0003] The wavelength of UVA radiation is 320 - 400 nm. Such UVA radiation can burn the skin, and excessive exposure may lead to skin cancer. The wavelength of UVB radiation is 280 - 320 nm, which may cause short-term or long-term skin damage, including the formation of deep wrinkles, collagen breakage and mottled pigmentation, etc. It can be known from the conference publications of the 22nd World Congress of the International Federation of Societies of Cosmetic Chemists (Edinburgh 2002, Oral Papers, Vol.2, Zastrow et al.) and other publications that: Through electron spin resonance (ESR) imaging, it has been determined that UVA and UVB rays can penetrate to different depths of the skin. UVB rays can penetrate up to a depth of about 50 μm, while UVA radiation can reach the underlying dermis, that is, about 3 mm. Therefore, sunscreen plays an important role in daily ultraviolet protection.

[0004] The traditional sunscreen contains sunscreen chemical reagents, which weaken the ultraviolet effect by decomposing after absorbing ultraviolet rays. Therefore, as the exposure time increases, the effect continuously weakens and needs to be used repeatedly. Moreover, some sunscreen chemical reagents or the chemical substances generated by decomposition may irritate or damage the skin. Nano-zinc oxide (ZnO) is a broad-spectrum inorganic ultraviolet shielding agent, and it has been increasingly widely used because it shields ultraviolet rays physically. Its principle of shielding ultraviolet rays is to absorb and scatter ultraviolet rays. When irradiated by ultraviolet rays, the electrons in the valence band can absorb ultraviolet rays and be excited to the conduction band, and at the same time, electron-hole pairs are generated, so it has the function of absorbing ultraviolet rays. However, the scattering of nano-ZnO to ultraviolet rays conforms to Rayleigh scattering. When the particle size is much smaller than the wavelength of ultraviolet rays, the nanoparticles can scatter the ultraviolet rays acting on them in all directions, thereby reducing the intensity of ultraviolet rays in the irradiation direction. Such descriptions are recorded in CN105030571B.

[0005] To solve this problem, Yan Chunyue et al. described in "Application and Testing of ZnO@SiO2 Sunscreen" that ZnO@SiO2 composite materials were prepared by coating SiO2 on the surface of nano-ZnO. SiO2 is inert and can inhibit the photocatalytic activity of nano-ZnO. The SiO2 shell can increase the transparency of ZnO in the visible light region. However, it was also pointed out in this article that due to the shielding effect of the outer SiO2 shell on ZnO, its sunscreen performance was reduced. CN116171146A (the corresponding commercial product is Pavise) discloses a kind of nanoparticle with a nanodiamond core and a zinc oxide or titanium oxide shell. The nanodiamond core scavenges holes through an internal oxidation process or by capturing electrons in the conduction band of the shell. However, nanodiamonds are costly and difficult to prepare. Summary of the Invention

[0006] The present invention provides a kind of zinc oxide nanoparticles, the outer layer of the nanoparticles is zinc oxide; when the nanoparticles are dispersed in water, the average hydrated particle size ≤ 90 nm,

[0007] the average hydrated particle size / (TEMa + TEMb) ≤ 1, where TEMa and TEMb respectively represent the minimum and maximum values of the TEM particle size;

[0008] or, the outer layer of the nanoparticles is zinc oxide;

[0009] when the nanoparticles are dispersed in water, the average hydrated particle size ≤ 90 nm;

[0010] when the concentration of the nanoparticles dispersed in water is 0.2 mg / ml, the generation of singlet oxygen under ultraviolet light excitation for 10 s is not higher than 16%.

[0011] Preferably, the nanoparticles are of core-shell structure, the core is silica, and the shell is zinc oxide. Preferably, the silica is carboxylated modified silica.

[0012] when the nanoparticles are dispersed in water, the average hydrated particle size of the zinc oxide nanoparticles ≤ 90 nm; preferably, 50 nm ≤ the average hydrated particle size ≤ 90 nm, or 60 nm ≤ the average hydrated particle size ≤ 90 nm, or 70 nm ≤ the average hydrated particle size ≤ 90 nm, or 60 nm ≤ the average hydrated particle size ≤ 85 nm.

[0013] when the nanoparticles are dispersed in water, the PDI of the zinc oxide nanoparticles ≤ 0.3, preferably, PDI ≤ 0.2, or PDI ≤ 0.19, or PDI ≤ 0.18, or PDI ≤ 0.17.

[0014] 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. Preferably, 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.

[0015] When the nanoparticles are dispersed in water, the D10 of the zinc oxide nanoparticles is ≤ 60 nm. Preferably, 20 nm ≤ D10 ≤ 60 nm, or 21 nm ≤ D10 ≤ 60 nm, or 22 nm ≤ D10 ≤ 60 nm, or 23 nm ≤ D10 ≤ 60 nm, or 24 nm ≤ D10 ≤ 60 nm, or 25 nm ≤ D10 ≤ 60 nm, or 30 nm ≤ D10 ≤ 60 nm, or 40 nm ≤ D10 ≤ 60 nm, or 45 nm ≤ D10 ≤ 55 nm.

[0016] When the nanoparticles are dispersed in water, the D50 of the zinc oxide nanoparticles is ≤ 80 nm. Preferably, D50 ≤ 79 nm, or D50 ≤ 78 nm, or D50 ≤ 77 nm, or D50 ≤ 76 nm, or D50 ≤ 75 nm, or 30 nm ≤ D50 ≤ 80 nm, or 35 nm ≤ D50 ≤ 80 nm, or 40 nm ≤ D50 ≤ 80 nm, or 45 nm ≤ D50 ≤ 80 nm, or 50 nm ≤ D50 ≤ 80 nm, or 55 nm ≤ D50 ≤ 80 nm, or 60 nm ≤ D50 ≤ 80 nm, or 65 nm ≤ D50 ≤ 80 nm.

[0017] When the nanoparticles are dispersed in water, the D90 of the zinc oxide nanoparticles is ≤ 110 nm. Preferably, D90 ≤ 109 nm, or D90 ≤ 108 nm, or D90 ≤ 107 nm, or D90 ≤ 106 nm, or D90 ≤ 105 nm, or D90 ≤ 104 nm, or D90 ≤ 103 nm, or D90 ≤ 102 nm, or D90 ≤ 101 nm, or D90 ≤ 100 nm, or 50 nm ≤ D90 ≤ 105 nm, or 60 nm ≤ D90 ≤ 105 nm, or 70 nm ≤ D90 ≤ 105 nm, or 80 nm ≤ D90 ≤ 105 nm, or 80 nm ≤ D90 ≤ 100 nm, or 80 nm ≤ D90 ≤ 90 nm.

[0018] When the nanoparticles are dispersed in water, the absolute value of the Zeta potential of the zinc oxide nanoparticles is ≥15 mV, or ≥16 mV, or ≥17 mV, or ≥18 mV, or ≥19 mV, or ≥20 mV, or ≥21 mV, or ≥22 mV, or ≥23 mV, or ≥24 mV, or ≥25 mV. When the nanoparticles are dispersed in water, preferably, the Zeta potential is 18 - 40 mV, or 19 - 40 mV, or 18 - 35 mV, or 19 - 35 mV, or 18 - 34 mV, or 19 - 34 mV.

[0019] When the nanoparticles are dispersed in water, the TEM particle size of the zinc oxide nanoparticles is 30 - 70 nm. Or, the TEM particle size is 30 - 80 nm.

[0020] When the nanoparticles are dispersed in water, the average hydrated particle size of the zinc oxide nanoparticles / (TEM a + TEM b ) ≤ 1, where TEMa and TEMb respectively represent the minimum and maximum values of the TEM particle size. Preferably, the average hydrated particle size / (TEM a + TEM b ) ≤ 0.9, or ≤ 0.8, or ≤ 0.7. Preferably, the average hydrated particle size of the zinc oxide nanoparticles / (TEM a + TEM b ) ≤ 0.8, and 60 nm ≤ average hydrated particle size ≤ 85 nm.

[0021] The inventors of the present invention unexpectedly found that while the pure nano-ZnO material has sunscreen properties, it can also be excited by ultraviolet light to generate various reactive oxygen species (ROS), such as hydroxyl radicals and superoxide anions. These reactive oxygen species can cause damage to cells and are also related to melanoma and skin photoaging. However, when the zinc oxide nanoparticles meet the characteristics described in the present invention, their ability to generate various reactive oxygen species under ultraviolet light excitation is weakened.

[0022] Another aspect of the present invention is to provide a zinc oxide nanoparticle, which has a core-shell structure composed of a core and a shell outside the core. The core contains silica nanoparticles, and the shell is zinc oxide.

[0023] Furthermore, the silica is carboxylated modified silica.

[0024] Furthermore, when the zinc oxide nanoparticles of the present invention are dispersed in water, under ultraviolet light excitation for 5 s, the generation of singlet oxygen is less than 10%, preferably less than 8%, more preferably less than 7%, more preferably less than 6%, and more preferably less than 5%.

[0025] Furthermore, when the zinc oxide nanoparticles of the present invention are dispersed in water, upon excitation by ultraviolet light for 10 s, the generation of singlet oxygen is less than 16%, preferably less than 15%, more preferably less than 14%, more preferably less than 13%, and more preferably less than 12%.

[0026] Furthermore, zinc oxide nanoparticles are dispersed in water at a concentration of 0.2 mg / ml, and the proportion of singlet oxygen generation is measured.

[0027] The calculation formula for the singlet oxygen is as follows:

[0028] Proportion of singlet oxygen generation = [Abs （400 nm，曝光0s） - Abs （400 nm，曝光时长） / Abs( 400 nm，曝光0s ) × 100%

[0029] Abs refers to the absorbance of the sample in the ultraviolet region, namely the UVA and UVB regions;

[0030] Furthermore, when the zinc oxide nanoparticles are dispersed in water, the peak value (Abs) of the absorption peak in the wavelength range of 280 - 320 nm of the spectrum is greater than 0.2, preferably greater than 0.3, preferably greater than 0.4, preferably greater than 0.5, preferably greater than 0.6, preferably greater than 0.7, preferably greater than 0.8, preferably greater than 0.9, preferably greater than 1.0, preferably greater than 1.1, preferably greater than 1.2, preferably greater than 1.3, preferably greater than 1.4, and preferably greater than 1.5.

[0031] Furthermore, zinc oxide nanoparticles are dispersed in water at a concentration of 0.2 mg / ml, and the spectrum is measured.

[0032] Furthermore, for the zinc oxide nanoparticles of the present invention, by mass fraction, the shell layer zinc oxide has a distribution of at least 100% or more relative to the core silica, preferably at least 110% or more, preferably at least 120% or more, preferably at least 130% or more, preferably at least 140% or more, preferably at least 150% or more, preferably at least 200% or more, preferably at least 300% or more, preferably at least 400% or more, preferably at least 500% or more, preferably at least 600% or more, preferably at least 700% or more, preferably at least 800% or more, preferably at least 900% or more, preferably at least 1000% or more, preferably at least 1100% or more, preferably at least 1200% or more, preferably at least 1300% or more, preferably at least 1400% or more, preferably at least 1500% or more, preferably at least 1600% or more, preferably at least 1700% or more, preferably at least 1800% or more, preferably at least 1900% or more, preferably at least 2000% or more.

[0033] Furthermore, when the nanoparticles are dispersed in water, they optionally have an average hydrated particle size or / and PDI or / and D10 or / and D50 or / and D90 or / and Zeta potential or / and TEM particle size or / and average hydrated particle size / (TEM a +TEM b ) as defined in any of the above in the present invention.

[0034] Another aspect of the present invention is to provide a zinc oxide nanoparticle, which has a core-shell structure composed of a core and a shell layer outside the core, and the core of the nanoparticle is prepared from carboxyl-modified silica (SiO2-COOH);

[0035] Furthermore, the shell layer is zinc oxide;

[0036] Further, 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 to 4400:1, or 500:1 to 4300:1, or 500:1 to 4200:1, or 500:1 to 4100:1, or 500:1 to 4000:1, or 500:1 to 3500:1, or 500:1 to 3000:1, or 500:1 to 2500:1, or 1000:1 to 3000:1, or 1500:1 to 3000:1, or 2000:1 to 3000:1, or 2100:1 to 3000:1, or 2200:1 to 3000:1, or 2300:1 to 3000:1, or 2400:1 to 3000:1, or 2500:1 to 3000:1, or 600:1 to 5000:1, or 700:1 to 5000:1, or 800:1 to 5000:1, or 900:1 to 5000:1, or 1000:1 to 5000:1, or 1100:1 to 5000:1, or 1200:1 to 5000:1, or 1300:1 to 5000:1, or 1400:1 to 5000:1, or 1500:1 to 5000:1, or 1600:1 to 5000:1, or 1700:1 to 5000:1, or 1800:1 to 5000:1, or 1900:1 to 5000:1, or 2000:1 to 5000:1.

[0037] Further, 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.

[0038] Further, the mass ratio of zinc to silicon in the nanoparticles is obtained by TEM / EDS.

[0039] Further, when the nanoparticles are dispersed in water, they optionally have any of the average hydrodynamic diameter or / and PDI or / and D10 or / and D50 or / and D90 or / and Zeta potential or / and TEM particle size or / and average hydrodynamic diameter / (TEM a +TEM b ) defined above.

[0040] The present invention also provides a use of the zinc oxide nanoparticles for preparing sunscreen cosmetics.

[0041] The present invention also provides a dispersion to be dispersed, comprising the zinc oxide nanoparticles and excipients acceptable in cosmetics. The zinc oxide nanoparticles have the characteristics defined above. Before being formulated into a cosmetic preparation, for the convenience of storage and sales, the nanoparticles can be stored in the form of a dispersion to be dispersed. In order to prevent the nanoparticles from agglomerating during storage or / and to accelerate the dispersion of the nanoparticles in the dispersion to be dispersed in the production of cosmetics, a surfactant or other functional excipients can be added to the dispersion to be dispersed, such as functional excipients for preventing particle agglomeration and increasing stability, or excipients for adjusting color, etc.

[0042] The present invention also provides a use of the dispersion to be dispersed for preparing sunscreen cosmetics.

[0043] The present invention provides a cosmetic, comprising the zinc oxide nanoparticles or the dispersion to be dispersed.

[0044] The present invention provides a cosmetic prepared from the dispersion to be dispersed.

[0045] The present invention provides a preparation method for preparing the zinc oxide nanoparticles, comprising the following steps:

[0046] Step 1: Add a zinc source to a solvent to form a uniform dispersion liquid 1; uniformly disperse a nucleating agent in water to form a dispersion liquid 2;

[0047] Step 2: Mix the dispersion liquid 1 and the dispersion liquid 2, and the mass ratio of the nucleating agent to the zinc source in the obtained mixture is 0.15:100 - 2000;

[0048] Step 3: Heat the mixture to 120 - 140 °C and stir; preferably, stir for not less than 10 min;

[0049] Step 4: Continue to raise the temperature to 140 - 200 °C until the reaction is completed; preferably, the reaction time is not less than 90 min;

[0050] Step 5: Wait for the reaction solution to cool to room temperature, perform solid-liquid separation, and wash three times to separate the solid;

[0051] Step 6: After the solid is dried, it is pulverized with a pulverizer to obtain zinc oxide nanoparticles;

[0052] The nucleating agent is a carboxyl-modified silica nanoparticle.

[0053] Preferably, the concentration of the zinc source in the dispersion liquid 1 is 0.5 to 2 mol / L, or 0.6 to 1.9 mol / L, or 0.7 to 1.8 mol / L, or 0.8 to 1.7 mol / L, or 0.9 to 1.6 mol / L, or 1 to 1.5 mol / L, or 1 to 1.4 mol / L, or 1 to 1.3 mol / L, or 1 to 1.2 mol / L, or 1 to 1.1 mol / L, or 0.5 to 1.5 mol / L, or 0.6 to 1.4 mol / L, or 0.7 to 1.3 mol / L, or 0.8 to 1.2 mol / L, or 0.9 to 1.1 mol / L.

[0054] Preferably, the concentration of the nucleating agent in the dispersion liquid 2 is 10% to 20% by mass fraction, or 11% to 20%, or 12% to 20%, or 13% to 20%, or 14% to 20%, or 15% to 20%.

[0055] Preferably, the mass ratio of the nucleating agent to the zinc source in the mixture is 0.15:100 to 2000; or 0.15:100 to 1000, or 0.15:100 to 800, or 0.15:200 to 800, or 0.15:300 to 800, or 0.15:400 to 800, or 0.15:500 to 800, or 0.15:500 to 700, or 0.15:500 to 600, or 0.15:100 to 700, or 0.15:100 to 600, or 0.15:100 to 500.

[0056] Preferably, the zinc source is added to the solvent to form a uniform dispersion liquid with a concentration of 0.5 to 5 mol / L. The preferred concentration is 0.5 to 4 mol / L, the preferred concentration is 0.5 to 3 mol / L, the preferred concentration is 0.5 to 2 mol / L, and the preferred concentration is 1 ± 0.5 mol / L.

[0057] Preferably, the zinc source is selected from one or more of zinc acetate, zinc nitrate, zinc chloride, zinc sulfate, and zinc ethylhexanoate.

[0058] Preferably, the zinc source is selected from zinc acetate.

[0059] Preferably, the solvent is selected from glycol solvents.

[0060] Preferably, the solvent is selected from one or more of ethylene glycol, diethylene glycol (DEG), tetraethylene glycol (TEG), polyethylene glycol 200 (PEG200), polyethylene glycol 300 (PEG300), and polyethylene glycol 400 (PEG400).

[0061] Preferably, the solvent is selected from tetraethylene glycol.

[0062] Preferably, in step 4, the temperature is raised to 160 - 200 °C. Preferably, the temperature is raised to 170 - 190 °C. Preferably, the temperature is raised to 180 ± 5 °C.

[0063] Another aspect of the present invention also lies in providing a silica for preparing zinc oxide nanoparticles, specifically carboxyl - modified silica (SiO₂ - COOH) nanoparticles. The average hydrated particle size range of the carboxyl - modified silica nanoparticles is 10 - 50 nm, the PDI is not greater than 0.05, and the zeta potential is greater than - 40 mV. Preferably, 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. Preferably, the PDI is not greater than 0.04, preferably, the PDI is not greater than 0.03, preferably, the PDI is not greater than 0.02.

[0064] Another aspect of the present invention also lies in providing the use of carboxyl - modified silica (SiO₂ - COOH) nanoparticles for preparing zinc oxide nanoparticles.

[0065] Furthermore, the use of the carboxyl - modified silica (SiO₂ - COOH) nanoparticles as a nucleating agent for preparing sunscreen nanoparticles.

[0066] Furthermore, the use of the carboxyl - modified silica (SiO₂ - COOH) nanoparticles for preparing sunscreen nanoparticles, and the prepared sunscreen nanoparticles have a core - shell structure composed of a core and a shell. The core is prepared from carboxyl - modified silica nanoparticles (SiO₂ - COOH), and the shell is zinc oxide.

[0067] Furthermore, another aspect of the present invention also lies in providing a preparation method of carboxyl - modified silica (SiO₂ - COOH):

[0068] Step 1: Disperse silica in water to form a suspension;

[0069] Step 2: Add 3 - aminopropyltriethoxysilane (APTES) to the above - mentioned SiO₂ suspension, and stir and react to obtain amino - modified silica (SiO₂ - NH₂);

[0070] Step 3: Centrifuge the mixture obtained in step 2, wash the separated precipitate and dry it;

[0071] Step 4: Disperse the solid obtained in Step 3 in DMF, add succinic anhydride and stir for reaction;

[0072] Step 5: Centrifuge the mixture obtained in Step 4, wash the separated precipitate and dry it to obtain carboxyl-modified silica (SiO2-COOH).

[0073] Preferably, the prepared SiO2-COOH has the characteristic range mentioned above.

[0074] Preferably, the silica nanoparticles are prepared according to the following method:

[0075] Step 1: Dissolve arginine in water, then add cyclohexane and tetraethyl orthosilicate (TEOS) and mix evenly;

[0076] Step 2: React the mixture at a high temperature to finally obtain silica nanoparticles (SiO2);

[0077] Preferably, the average hydrated particle size range of the silica nanoparticles is 10-50 nm, the PDI is not more 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.

[0078] Preferably, the average hydrated particle size range of the silica nanoparticles is 10-50 nm, the PDI is not more than 0.05, and the zeta potential is greater than -31 mV. Preferably, the PDI is not more than 0.04, preferably, the PDI is not more than 0.03, preferably, the PDI is not more than 0.02.

[0079] On the other hand, the present invention also lies in providing a preparation method of zinc oxide nanoparticles,

[0080] including the following steps:

[0081] Step 1: Add a zinc source to a solvent to form a uniform dispersion;

[0082] Step 2: Uniformly disperse a nucleating agent into the above dispersion; finally, the mass ratio of the nucleating agent to the zinc source in the obtained mixture is 0.15:100-2000;

[0083] Step 3: Heat the mixture to 120-140 °C and stir;

[0084] Step 4: Continue to raise the temperature to 140-200 °C until the reaction is completed;

[0085] Step 5: Wait for the reaction solution to cool to room temperature, perform solid-liquid separation, and wash the separated solid;

[0086] Step 6: After the solid is dried, it is pulverized by a pulverizer to obtain zinc oxide nanoparticles;

[0087] The nucleating agent is carboxyl-modified silica nanoparticles.

[0088] Further, in the preparation method as described above, the zinc source is selected from one or more of zinc acetate, zinc nitrate, zinc chloride, zinc sulfate, and zinc 2-ethylhexanoate.

[0089] Further, in the preparation method as described above, the solvent is selected from glycol solvents.

[0090] Further, in the preparation method as 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.

[0091] Further, in the preparation method as described above, in Step 4, the temperature is raised to 160 - 200 °C; or the temperature is raised to 170 - 190 °C; or the temperature is raised to 180 ± 5 °C.

[0092] Further, the feeding ratio of the core (nucleating agent) to the shell (zinc source) materials of the nanoparticles, calculated by mass ratio, is 0.15:100 - 2000; or is 0.15:100 - 1000, or is 0.15:100 - 800, or is 0.15:200 - 800, or is 0.15:300 - 800, or is 0.15:400 - 800, or is 0.15:500 - 800, or is 0.15:500 - 700, or is 0.15:500 - 600, or is 0.15:100 - 700, or is 0.15:100 - 600, or is 0.15:100 - 500.

[0093] Related terms:

[0094] Silica: The silica in the zinc oxide nanoparticles of the present invention can be unmodified or modified with other functional groups. Preferably, the modifying group can ionize to generate negative charges in the reaction environment, such as carboxyl groups, for enhancing zinc ion adsorption. Or other groups that cannot ionize but have electronegativity.

[0095] Hydrodynamic diameter: It refers to the diameter of a substance in hydrodynamic conditions. The hydrodynamic diameter of a substance can be measured by a dynamic light scattering instrument. The test principle is based on the scattering of light by particles, which is well-known to those skilled in the art.

[0096] Average hydrated particle size: It refers to the weighted average of the particle sizes of each particle. In the present invention, it refers to the number-average hydrated particle size, that is, the average value obtained by weighted averaging according to the number of particles corresponding to the hydrated particle size.

[0097] TEM particle size: TEM is a transmission electron microscope. The particle size calculated from the particles in the TEM image by Image J software is the TEM particle size.

[0098] TEMa: It represents the minimum value of the TEM particle size.

[0099] TEMb: It represents the maximum value of the TEM particle size.

[0100] PDI: The polydispersity index (PDI) is one of the important parameters characterizing the uniformity of particle distribution. PDI is usually obtained by statistical analysis with a dynamic light scattering instrument.

[0101] Span: The particle size distribution width (Span) is another index characterizing the particle distribution width. Span is usually used to characterize an asymmetric particle system, especially when the particle diameter distribution shows a large skew. The calculation formula for Span is: Span = (D90 - D10) / D50.

[0102] D10: The particle size corresponding to when the cumulative particle size distribution percentage of the test sample reaches 10%, which can be obtained by statistical analysis with a dynamic light scattering instrument.

[0103] D50: The particle size corresponding to when the cumulative particle size distribution percentage of the test sample reaches 50%, which can be obtained by statistical analysis with a dynamic light scattering instrument.

[0104] D90: The particle size corresponding to when the cumulative particle size distribution percentage of the test sample reaches 90%, which can be obtained by statistical analysis with a dynamic light scattering instrument.

[0105] Zeta potential: It is used as a measure of the strength of the mutual repulsion or attraction between particles, which can be obtained by statistical analysis with a dynamic light scattering instrument. For the potential value, the "-" before the value represents a negative potential. Therefore, when comparing the magnitudes of the potentials, only the absolute values are considered, and the influence of the "-" on the numerical magnitude is not considered.

[0106] Any zinc oxide nanoparticles as defined above in the present invention, when used in sunscreen products, have the following technical effects:

[0107] 1. Good dispersibility in water: For particles that are prone to aggregation, they need to be dispersed in a cosmetic formulation with poor fluidity to avoid aggregation and form lumps, which may cause adverse aesthetic effects such as a false whitening appearance. To this end, when water is used as the main dispersion carrier, thickeners are often added to reduce the fluidity of the particles (increase the viscosity) and prevent aggregation. However, adding too much thickener may cause problems such as a greasy feeling after use and poor breathability. The zinc oxide nanoparticles prepared by the present invention have good dispersion in water, have low requirements for the viscosity of the cosmetic dispersion carrier, thereby reducing the amount of such thickeners used, improving the comfort of users, and also reducing the probability of false whitening.

[0108] 2. Less generation of strong oxidizing substances: The nanoparticles of the present invention and the sunscreen compositions prepared therefrom not only have stronger ultraviolet absorption ability, but also generate less amount of strong oxidizing substances. For example, the singlet oxygen generation ratio at 10 s is preferably less than 17%, more preferably less than 16%, more preferably less than 15%, more preferably less than 14%, more preferably less than 13%, more preferably less than 12%, more preferably less than 11%. This means that when achieving the same sunscreen effect, if the zinc oxide nanoparticles of the present invention are used, the usage amount will be reduced, or chemical sunscreen reagents can be reduced or even not used. In addition, due to less generation of strong oxidants, the usage amount or types of reducing chemical reagents can also be reduced. Some users are sensitive or even uncomfortable with the use of these chemical reagents. Reducing the usage amount or types of these chemical reagents can more easily obtain a mild formulation, which can be suitable for more people and is also simpler for formulating cosmetics.

[0109] 3. The skin becomes more delicate: Due to the good dispersion effect of the present invention, the agglomeration phenomenon is reduced, the particle feeling is more delicate, and the comfort of use is improved.

[0110] 4. Good sunscreen effect: The absorbance (Abs) of the nanoparticles of the present invention to ultraviolet rays is preferably greater than 0.5, more preferably greater than 0.6, more preferably greater than 0.7, more preferably greater than 0.8, more preferably greater than 0.9, more preferably greater than 1.0. It shows stronger ultraviolet spectral absorption performance, greatly improving the sunscreen effect. Description of the Drawings

[0111] Figure 1 It is the particle size distribution diagram of the silica nanoparticles in Example 1;

[0112] Figure 2 It is the TEM diagram of the silica nanoparticles in Example 1;

[0113] Figure 3 It is the particle size distribution diagram of the carboxyl-modified silica nanoparticles in Example 1;

[0114] Figure 4TEM image of carboxyl-modified silica nanoparticles in Example 1;

[0115] Figure 5 TEM image of zinc oxide nanoparticles prepared in Comparative Example 1 dispersed in water;

[0116] Figure 6 TEM image of zinc oxide nanoparticles prepared in Example 2 dispersed in water;

[0117] Figure 7 TEM image of zinc oxide nanoparticles prepared in Example 3 dispersed in water;

[0118] Figure 8 TEM image of zinc oxide nanoparticles prepared in Example 4 dispersed in water;

[0119] Figure 9 TEM image of zinc oxide nanoparticles prepared in Comparative Example 2 dispersed in water;

[0120] Figure 10 TEM image of zinc oxide nanoparticles prepared in Comparative Example 3 dispersed in water;

[0121] Figure 11 TEM image of zinc oxide nanoparticles prepared in Example 5 dispersed in water;

[0122] Figure 12 TEM image of zinc oxide nanoparticles prepared in Example 6 dispersed in water;

[0123] Figure 13 TEM image of zinc oxide nanoparticles isolated from Pavise in Comparative Example 4 dispersed in water;

[0124] Figure 14 Absorption spectra obtained by testing with 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%", "0.15-2000-0.02%" respectively represent that the tested samples were prepared according to the mass ratio of nucleating agent to zinc source of 0.15:10 (Comparative Example 1), 0.15:100 (Example 2), 0.15:500 (Example 3), 0.15:800 (Example 4), 0.15:2000 (Comparative Example 2), and were uniformly dispersed in water at a concentration of 0.2 mg / ml. "Pavise-0.02%" represents zinc oxide nanoparticles isolated from Pavise (Comparative Example 4), which were uniformly dispersed in water at a concentration of 0.2 mg / ml;

[0125] Figure 15 The absorption spectra were measured using a UV-visible spectrophotometer (TU-1810). In the figure, "140°C - 0.02%", "160°C - 0.02%", "180°C - 0.02%", and "200°C - 0.02%" indicate that the tested samples were 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. Detailed implementation manners

[0126] Unless otherwise specified, the experimental methods used in the following examples are all conventional methods.

[0127] Unless otherwise specified, the materials, reagents, etc. used in the following examples are all ordinary commercially available products and can be purchased in the market.

[0128] The present invention will be further described below through examples, and these descriptions do not further limit the content of the present invention. Those skilled in the art should understand that equivalent substitutions or corresponding improvements made to the content of the present invention still fall within the protection scope of the present invention.

[0129] Example 1

[0130] Preparation of carboxyl-modified silica nanoparticles (SiO2-COOH):

[0131] 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 evenly;

[0132] Step 2: Place the mixed solution at 60°C and continuously stir. After reacting for 20 h, silica nanoparticles (SiO2) are obtained;

[0133] 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);

[0134] Step 4: Centrifuge the mixed solution, and wash the obtained lower-layer precipitate with ethanol and N,N N,N-dimethylformamide (DMF);

[0135] Step 5: Take 60 mg of the precipitate and redisperse it in DMF, add 100 mg of succinic anhydride and stir overnight at room temperature;

[0136] Step 6: Centrifuge the mixed solution, wash the obtained lower-layer precipitate with DMF and deionized water respectively, and dry the obtained precipitate to obtain carboxyl-modified SiO2 (SiO2-COOH).

[0137] After detection, the zeta potential of the silica nanoparticles was -31.2 mV, and that of the carboxyl-modified silica nanoparticles was -47.9 mV. It can be seen that the carboxyl group was successfully grafted onto the silica, resulting in an enhanced electronegativity. In addition, the modification did not affect the particle size distribution (as Figures 1 - 4 shown).

[0138] Example 2

[0139] This example provides a kind of zinc oxide nanoparticles and its preparation method. The preparation method includes the following steps:

[0140] Step 1: Zinc acetate (zinc source) was uniformly dispersed in triethylene glycol (solvent) to form mixture 1 (with a concentration of 1 mol / L).

[0141] Step 2: The carboxyl-modified silica nanoparticles (nucleating agent) were uniformly dispersed in water to form mixture 2 (with a mass fraction of 15%). Subsequently, mixture 1 and mixture 2 were mixed, and the mass ratio of the nucleating agent to the zinc source in the resulting mixture was 0.15:100.

[0142] Step 3: The mixture was heated to 120 - 140 °C and premixed for 10 - 30 min.

[0143] Step 4: The temperature was continuously raised to about 180 °C, and the reaction was stopped after 90 - 120 min.

[0144] Step 5: After the reaction solution was cooled to room temperature, solid-liquid separation was carried out, and the solid was separated and washed three times with water.

[0145] Step 6: After the solid was dried, it was pulverized with a pulverizer to obtain zinc oxide nanoparticles.

[0146] The nanoparticles were dispersed in water and made into a sample to be measured, with a concentration of about 0.16 mg / ml. The Figure 6 TEM image was obtained by a transmission electron microscope (Hitachi, HT7800). The TEM particle size was analyzed using Image J software to obtain a TEM particle size of 30 - 70 nm.

[0147] Example 3

[0148] The implementation method was the same as that of Example 2, except that the mass ratio of the nucleating agent to the zinc source in the mixture in Step 2 was 0.15:500.

[0149] The TEM image was as Figure 7 , and the TEM particle size was 30 - 70 nm.

[0150] Example 4

[0151] The implementation method is the same as that of Example 2, except that the mass ratio of the nucleating agent to the zinc source in the mixture in Step 2 is 0.15:800.

[0152] The TEM image is as follows Figure 8 , and the TEM particle size = 30 - 60 nm.

[0153] Example 5

[0154] The same as Example 2, except that in Step 4, the temperature is raised to about 160°C.

[0155] The TEM image is as follows Figure 11 , and the TEM particle size = 25 - 55 nm.

[0156] Example 6

[0157] The same as Example 2, except that in Step 4, the temperature is raised to about 200°C.

[0158] The TEM image is as follows Figure 12 , and the TEM particle size = 30 - 80 nm.

[0159] Comparative Example 1

[0160] The implementation method is the same as that of Example 2, except that the mass ratio of the nucleating agent to the zinc source in the mixture in Step 2 is 0.15:10.

[0161] The TEM image is as follows Figure 5 , and the TEM particle size = 20 - 40 nm.

[0162] Comparative Example 2

[0163] The implementation method is the same as that of Example 2, except that the mass ratio of the nucleating agent to the zinc source in the mixture in Step 2 is 0.15:2000.

[0164] The TEM image is as follows Figure 9 , and the TEM particle size = 30 - 80 nm.

[0165] Comparative Example 3

[0166] The same as Example 2, except that in Step 4, the temperature is raised to about 140°C.

[0167] The TEM image is as follows Figure 10 , and the TEM particle size = 15 - 40 nm.

[0168] Comparative Example 4

[0169] Purchase a commercially available sunscreen skin care product named Pavise, and isolate the zinc oxide nanoparticles therein.

[0170] The TEM image is as follows Figure 13 , and the TEM particle size = 40 - 60 nm.

[0171] Test Example 1

[0172] 1.1 Hydrated Particle Size Test

[0173] The particles prepared in the above examples and comparative examples were dispersed in water and tested using a dynamic light scattering instrument (Anton Paar, Litesizer 500), and the data in Table 1 below were obtained.

[0174] Table 1

[0175]

[0176] The number-average hydrated particle size in Table 1 was obtained by weighted averaging the average hydrated particle size with the number of particles. PDI represents the dispersion index and is used to describe the situation of the particle size distribution range. D10, D50, and D90 respectively represent the particle size values corresponding to when the cumulative distribution percentages from small to large reach 10%, 50%, and 90%.

[0177] 1.2 Dispersion (Degree of Aggregation) Test

[0178] The TEM images can observe the particle size of individual particles in the dry state and can also indirectly reflect the aggregation situation during dispersion in water. To quantitatively characterize whether the particles aggregate, the applicant described the dispersion situation of the particles in water by combining the hydrated particle size data with the TEM particle size, and the results are shown in Table 2.

[0179] Table 2

[0180]

[0181] TEMa and TEMb respectively represent the minimum and maximum values of the TEM particle size.

[0182] The degree of dispersion was evaluated through TEM images. +++ indicates excellent dispersion and extremely few particles aggregate. ++ indicates good dispersion and some particles aggregate. + indicates that the distribution uniformity of the particles in the TEM image is poor, but they are not tightly aggregated. indicates that the distribution uniformity of the particles in the TEM image is poor and tight aggregates are formed.

[0183] Although in the prior art, the dispersion stability is usually described by the Zeta potential, it cannot accurately reflect the severity of particle aggregation. By comparing Figure 8 (Example 4) and Figure 10 (Comparative Example 3), it can be found that the degree of aggregation of Comparative Example 3 is significantly higher than that of Example 4, but the Zeta potential corresponding to Example 4 is lower than that of Comparative Example 3. Therefore, the applicant used the calculation formula "average hydrated particle size / (TEM a + TEM b)” indicates the proportion of particles in the particles after aggregation to form aggregates (the particle size exceeds the maximum particle size of individual particles), which is used to describe the severity of particle aggregation. Among them, TEM a +TEM b represents the particle size of the smallest aggregation state in the theory, that is, the particle size of the closest aggregation of the largest and smallest particles. When the particle size after aggregation exceeds TEM a +TEM b more, the aggregation is more severe. When the particle size after aggregation is smaller than TEM a +TEM b , the particle size of the aggregate does not exceed the particle size of the closest aggregation of the largest and smallest particles, and it is considered to have a low degree of aggregation and is regarded as an individual particle.

[0184] According to Table 2, the more closely aggregated particles, the larger the average hydrated particle size. When the aggregation phenomenon is more severe, the average hydrated particle size / (TEM a +TEM b ) > 1, and the larger the value. When the particles are well dispersed, the average hydrated particle size / (TEM a +TEM b ) ≤ 1.

[0185] Test Example 2

[0186] Characterization of singlet oxygen generation ability

[0187] The above-mentioned nanoparticles in the examples and comparative examples were uniformly dispersed in water to prepare a test sample with a concentration of 0.2 mg / ml. The singlet oxygen generation ability was tested by the ABDA method. 1 ml of ABDA solution with a concentration of 100 μM was mixed with each test sample, and the ultraviolet absorption spectrum was measured. It was excited with a 365 nm ultraviolet lamp for 5 s for testing, and then excited for 5 s for testing. The decrease of the characteristic absorption peak of ABDA at 400 nm was observed, and the distance between the light source and the liquid surface was 5 cm.

[0188] Proportion of singlet oxygen generation = [Abs （400 nm，曝光0s） -Abs （400 nm，曝光时长） / Abs( 400 nm，曝光0s ) × 100%

[0189] The following Table 3 shows the calculation results of the proportion of singlet oxygen generation when the exposure times are 5 s and 10 s respectively. The smaller the value of the proportion of singlet oxygen generation, the fewer the strong oxidizing substances produced.

[0190] Table 3

[0191]

[0192] From the above data, it can be seen that the nano-zinc oxide used in the pavise commodity utilizes a nano-diamond core to scavenge holes through an internal oxidation process or by capturing electrons in the conduction band of the shell (as described in CN116171146A), enabling the singlet oxygen generation ratio at 10 s to reach 17.89%. In Examples 2 to 6 of the present invention (average hydrated particle size / (TEM a +TEM b ) ≤ 1, and the average hydrated particle size ≤ 90 nm), the singlet oxygen generation ratio of the nanoparticles at 10 s is below 14%, and some can even reach below 10%. This means that the strong oxidizing substances generated by the nanoparticles provided by the present invention are less. According to the mechanism of reactive oxygen generation by ZnO, the higher the light absorbance, the more reactive oxygen should be generated. To comprehensively evaluate the performance of the nanoparticles of the present invention as sunscreen, the following spectral absorption performance characterization is carried out.

[0193] Test Example 3

[0194] Spectral Absorption Performance

[0195] Those skilled in the art can understand that the generation of peroxides comes from the absorption of light energy by nano-zinc oxide. Therefore, in this test example, spectral absorption tests are carried out on the nanoparticles of the above examples and comparative examples to comprehensively evaluate the spectral absorption performance and the corresponding peroxides generated.

[0196] The nanoparticles of the above examples and comparative examples are uniformly dispersed in water at a concentration of 0.2 mg / ml. Tested using a UV-visible spectrophotometer (TU-1810), the test range is 290 - 800 nm. The test results are shown in Attachment Figure 14 and Attachment Figure 15 .

[0197] According to the test results, in the ultraviolet region, that is, the UVA and UVB regions, the particles with absorbance (Abs) less than 1.0 are: Example 2, Comparative Example 1, Comparative Example 3, Comparative Example 4, and the particles with absorbance (Abs) greater than or equal to 1.0 are: Examples 3 to 6, Comparative Example 2. Therefore, Examples 3 to 6 and Comparative Example 2 have strong sunscreen ability. Especially Examples 3, 5 and Comparative Example 2.

[0198] Combined with the ultraviolet absorption data, it is unexpectedly found that among Examples 2 to 6, Examples 3 to 6 with an average hydrated particle size exceeding 50 nm have a stronger absorption ability for the ultraviolet spectrum. That is, when 50 nm ≤ average hydrated particle size ≤ 90 nm, and the particles are well dispersed (average hydrated particle size / (TEM a +TEM b) ≤ 1), while having a stronger ultraviolet spectrum absorption ability, it also produces less amount of strongly oxidizing substances. In contrast, the nanoparticles used in pavise have far lower ultraviolet light absorbance (Abs) than those in Examples 3 to 6.

[0199] Furthermore, by comparing Examples 3 to 6 (the absorbance (Abs) in the ultraviolet region is greater than 1.0), it can be observed that when the PDI decreases (the particle size distribution is more uniform), the proportion of singlet oxygen generation at 10 s also decreases accordingly. That is, compared with Examples 5 and 6, Examples 3 and 4 have a smaller PDI (PDI ≤ 20%), a more uniform distribution, and produce less amount of strongly oxidizing substances.

[0200] Having a strong ultraviolet absorption ability while producing less amount of strongly oxidizing substances means that the content of chemical sunscreen reagents can be reduced in the sunscreen formulation, and reducing agents can also be reduced. Due to the reduction of the content or components of these chemical reagents, a milder formulation can be obtained more easily and can be suitable for more people.

Claims

1. A zinc oxide nanoparticle, characterized in that: The outer layer of the nanoparticle is zinc oxide; When the nanoparticle is dispersed in water, the average hydrated particle size ≤ 90 nm, Average hydrodynamic particle size / (TEM a + TEM b ) ≤ 1, where TEM a and TEM b represent the minimum and maximum TEM particle sizes, respectively; The TEM particle size is 30 - 80 nm; The preparation method of the zinc oxide nanoparticle includes the following steps: Step 1: Add a zinc source to a solvent to form a homogeneous dispersion; Step 2: Uniformly disperse a nucleating agent into the above dispersion; finally, the mass ratio of the nucleating agent to the zinc source in the obtained mixture is 0.15:100 - 800; Step 3: Heat the mixture to 120 - 140 °C and stir; Step 4: Continue to raise the temperature to 160 - 200 °C until the reaction is complete; Step 5: Wait for the reaction solution to cool to room temperature, perform solid-liquid separation, and wash and separate to obtain a solid; Step 6: After drying the solid, pulverize it with a pulverizer to obtain zinc oxide nanoparticles.

2. The zinc oxide nanoparticle according to claim 1, characterized in that: The nanoparticle has a core-shell structure composed of a core and a shell outside it, the core contains silica, and the shell is zinc oxide.

3. The zinc oxide nanoparticle according to claim 2, characterized in that: 50 nm ≤ average hydrated particle size ≤ 90 nm, or 60 nm ≤ average hydrated particle size ≤ 90 nm, or 70 nm ≤ average hydrated particle size ≤ 90 nm, or 60 nm ≤ average hydrated particle size ≤ 85 nm.

4. The zinc oxide nanoparticle according to claim 3, characterized in that: When the nanoparticle is 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.

5. The zinc oxide nanoparticle according to claim 4, characterized in that: D90 ≤ 110 nm, or D90 ≤ 109 nm, or D90 ≤ 108 nm, or D90 ≤ 107 nm, or D90 ≤ 106 nm, or D90 ≤ 105 nm.

6. The zinc oxide nanoparticle according to claim 5, characterized in that: The polydispersity index PDI of the zinc oxide nanoparticle ≤ 0.3, or PDI ≤ 0.2, or PDI ≤ 0.19, or PDI ≤ 0.18, or PDI ≤ 0.

17.

7. Use of the zinc oxide nanoparticle according to any one of claims 1 - 6 for preparing a sunscreen cosmetic.

8. A dispersion to be dispersed, characterized in that: It includes the zinc oxide nanoparticle according to any one of claims 1 - 6 and excipients acceptable in cosmetics.

9. Use of the dispersion to be dispersed according to claim 8 for preparing a sunscreen cosmetic.

10. A cosmetic, characterized in that: It includes the zinc oxide nanoparticle according to any one of claims 1 - 6 or the dispersion to be dispersed according to claim 8.

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