Preparation method of lignin-coated zinc oxide composite nanoparticles, product and application thereof

Abstract

The application discloses a preparation method of lignin-coated zinc oxide composite nanoparticles, a product and application thereof, and belongs to the technical field of chemical product preparation, and comprises the following steps: lignin powder is added into an alkali solution to obtain a lignin powder suspension, a zinc salt solution is slowly added dropwise, the pH is adjusted to 9.0-12.0, a hydrothermal reaction is carried out under a nitrogen atmosphere, and the precipitate is collected by centrifugation and washed to obtain raspberry-shaped lignin-coated zinc oxide composite nanoparticles. The composite nanoparticles exhibit a "raspberry"-shaped rough surface, increase the friction, have a certain rigidity, and improve the cleaning effect, have more excellent ultraviolet shielding performance and antioxidant performance, can effectively relieve scalp inflammation and prevent ultraviolet damage of hair, and simultaneously endow the composite nanoparticles with excellent antibacterial performance, which can effectively inhibit the growth of fungi such as malassezia, thereby reducing the generation of dandruff.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of chemical product preparation, and particularly relates to a preparation method of lignin-coated zinc oxide composite nanoparticles, a product thereof and application. BACKGROUND

[0002] Hair cleaning and scalp care are important issues in the field of public health. The health of the hair and the problem of dandruff significantly affect the daily life of individuals. The production of dandruff is mainly attributed to the following factors: excessive secretion of sebum: the excessive secretion of sebum on the scalp provides a suitable environment for the growth of fungi, thereby stimulating the generation of dandruff. Scalp inflammation: various scalp inflammatory diseases, such as scalp eczema and psoriasis, are associated with an increase in dandruff. These inflammatory reactions not only cause discomfort on the scalp, but also can lead to the destruction of the skin barrier function, thereby exacerbating the problem of dandruff. Bacterial and fungal infections: Malassezia globosa and Malassezia restricta are associated with dandruff and seborrheic dermatitis, and when their numbers are out of control, they can lead to an increase in dandruff. Currently, the most widely used anti-dandruff ingredients are zinc pyrithione, piroctone olamine, selenium disulfide, etc. However, these ingredients can irritate the scalp, and in severe cases, can cause contact dermatitis and cause the hair to become dry and frizzy.

[0003] Lignin is widely present in the cell walls of natural plants and is the second largest natural polymer after cellulose. It has excellent biocompatibility, broad-spectrum UV protection, antioxidant properties, and antibacterial properties. Its structure contains a large number of phenolic hydroxyl groups, carbonyl groups, unsaturated double bonds, and conjugated structures, which can interact with dirt through hydrogen bonds, van der Waals forces, and wetting effects, thereby achieving the effect of removing skin dirt. However, lignin also has problems such as poor dispersibility, heavy color, weak antibacterial activity, and insufficient rigidity, making it difficult to be directly used as a functional additive for scalp cleaning products.

[0004] Therefore, how to apply lignin to hair care products and improve its efficacy is a technical problem to be solved. SUMMARY

[0005] The purpose of the present application is to provide an antibacterial and anti-dandruff sunscreen ingredient, which is a composite particle composed of lignin and zinc oxide. The introduction of zinc oxide can effectively enhance the antibacterial properties of lignin, provide certain rigidity, and improve the friction of the composite particle, thereby effectively removing dirt. In addition, the composite particle as an additive for shampoo products can effectively inhibit the production of dandruff, clean the scalp, and relieve inflammation. The method is simple, fast, low-cost, and has mild reaction conditions, and has good application value.

[0006] As one of the aspects of the present application, the present application provides a preparation method of lignin-coated zinc oxide composite nanoparticles, which comprises the following steps,

[0007] The lignin powder is added into an alkali solution to obtain a lignin powder suspension, a zinc salt solution is slowly added dropwise, the pH is adjusted to 9.0-12.0, a hydrothermal reaction is carried out under a nitrogen atmosphere, the precipitate is collected by centrifugation, and washing is carried out to obtain raspberry-shaped lignin-coated zinc oxide composite nanoparticles.

[0008] As one of the preferred embodiments of the preparation method of the lignin-coated zinc oxide composite nanoparticles, the lignin comprises enzymatic hydrolysis lignin.

[0009] As one of the preferred embodiments of the preparation method of the lignin-coated zinc oxide composite nanoparticles, the zinc salt is at least one of zinc nitrate, zinc acetate, zinc sulfate, zinc chloride and zinc nitrite.

[0010] As one of the preferred embodiments of the preparation method of the lignin-coated zinc oxide composite nanoparticles, the mass ratio of the lignin to the zinc salt is 0.5-2.0:1.

[0011] As one of the preferred embodiments of the preparation method of the lignin-coated zinc oxide composite nanoparticles, the hydrothermal reaction temperature is 80-120℃, and the time is 6.0-12.0 h.

[0012] As one of the preferred embodiments of the preparation method of the lignin-coated zinc oxide composite nanoparticles, the concentration of the lignin powder suspension is 0.01-0.015 g / mL; and the concentration of the zinc salt solution is 0.1-0.2 g / mL.

[0013] As one of the preferred embodiments of the preparation method of the lignin-coated zinc oxide composite nanoparticles, the alkali solution comprises a sodium hydroxide solution.

[0014] The present application also provides the application of the lignin-coated zinc oxide composite nanoparticles prepared by the preparation method of the lignin-coated zinc oxide composite nanoparticles in the preparation of cosmetics.

[0015] The lignin-coated zinc oxide composite nanoparticles are used for the preparation of a scalp care agent, a hair conditioner, a scalp cleanser or a shampoo.

[0016] The scalp care agent comprises the following components in percentage by mass: lignin-coated zinc oxide composite nanoparticles 5-25%, surfactant 10-25%, conditioning agent 2-5%, emulsifier 0.05-0.15%, emollient 10-30%, preservative 0.01-0.3%, essence 0-0.8%, viscosity regulator 0.5-1%, chelating agent 0.05-0.2%, pH regulator 0.001-0.2%, humectant 10-25%, and the balance is water.

[0017] Preferably, the surfactant is at least one of sodium laureth sulfate, ammonium lauryl sulfate, sodium lauroamphoacetate, cocamide MEA, cocamidopropyl betaine, behenamidopropyl dimethylamine, trideceth-10, trideceth-3, polyethylene oxide lauryl acid, and sodium poly naphthalene sulfonate; and the component plays a role of cleaning.

[0018] Preferably, the conditioning agent is at least one of ethylene glycol distearate, maleic acid-modified castor oil, polyquaternium-10, dipalmitoyl oxy ethyl dimethyl ammonium chloride, oleamidopropyl PG-dimethyl ammonium chloride, guar hydroxypropyltrimonium chloride, amodimethicone, serine, and cocodimethylammonium hydroxypropyl hydrolyzed collagen; and the component plays a role of anti-dandruff and antistatic.

[0019] Preferably, the emulsifier is at least one of cetrimonium chloride, propylene glycol fatty acid ester, sucrose fatty acid ester, and polyglycerol fatty acid ester; and the component plays a role of stabilizing oil-soluble components.

[0020] Preferably, the emollient is at least one of shea butter, coconut oil, mango seed oil, serine, glycerin, propylene glycol, ethylene glycol distearate, and glyceryl stearate.

[0021] Preferably, the preservative is at least one of piroctone olamine, phenoxyethanol, cetrimonium chloride, phenoxyethanol, and p-hydroxybenzoic acid ester.

[0022] Preferably, the humectant is at least one of glycerin, propylene glycol, dipropylene glycol, and pentylene glycol.

[0023] Preferably, the chelating agent is disodium EDTA.

[0024] Preferably, the essence is vanillin.

[0025] Preferably, the viscosity regulator is sodium chloride.

[0026] The present application has the following advantages:

[0027] (1) The present application provides an antibacterial and anti-dandruff sunscreen ingredient, which is a composite particle prepared by hydrothermal method combining zinc oxide with lignin as a precursor; on the one hand, lignin has an amorphous three-dimensional structure and abundant surface groups, which can form stable particles with zinc oxide particles through hydrogen bonding and electrostatic interaction, so that the prepared composite particles have suitable particle size, uniform particle size distribution, resistance to migration and light color. On the other hand, the composite particles effectively adsorb dirt through hydrogen bonding, van der Waals force and wetting effect, at the same time, they exhibit a "raspberry" rough surface, increase the friction, have a certain rigidity, and improve the cleaning effect.

[0028] (2) The composite particles have more excellent ultraviolet shielding performance and antioxidant performance, which can effectively alleviate the inflammation of the scalp and prevent the ultraviolet damage of the hair, and at the same time, the composite particles have excellent antibacterial performance, which can effectively inhibit the growth of fungi such as Malassezia, thereby reducing the generation of dandruff.

[0029] (3) The present application selects natural biomass lignin as a precursor, which is widely available and cheap, and simply and quickly prepares composite nanoparticles with stable size, excellent antibacterial and ultraviolet resistance, and antioxidant (anti-inflammatory) performance, which improves the problems of poor utilization of lignin raw materials, difficulty in dispersion, deep color, toxic solvents, and difficulty in controlling the size and morphology of lignin-zinc oxide composite particles. At the same time, the solvent used for the lignin-coated zinc oxide composite particles prepared by this method is water and glycerol, which has the advantages of simple preparation, green and non-toxic product, high yield, etc. compared with traditional organic solvents for dissolving lignin, and is suitable for large-scale production.

[0030] (4) The antibacterial and anti-dandruff ingredient provided by the present application has a particle size of more than 100 nm and does not penetrate into the body tissue, and the particle has a certain rigidity and rough surface, which enhances the cleaning force without scratching the skin. The introduction of zinc oxide improves the antibacterial performance of the composite particles, thereby inhibiting the growth and reproduction of bacteria and effectively reducing the generation of dandruff. In addition, the lipophilicity, antioxidant property and ultraviolet shielding property of lignin are also beneficial to the removal of skin oil, the relief of scalp inflammation and the prevention of ultraviolet damage of hair. BRIEF DESCRIPTION OF DRAWINGS

[0031] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced as follows:

[0032] Figure 1 Figure 1 is a micro-morphology diagram of lignin-coated zinc oxide nanocomposite particles of Example 2.

[0033] Figure 2 Figure 2 is a SEM diagram of the product of Comparative Example 1.

[0034] Figure 3Particle size distribution histogram of the product of Example 3.

[0035] Figure 4 Thermogravimetric curve of the lignin-coated zinc oxide composite particles, in which the right mark is the zinc oxide loading rate of each sample.

[0036] Figure 5 Picture of the product of Example 4 being prepared into a water dispersion solution with a concentration of 15 wt%. DETAILED DESCRIPTION

[0037] In order to make the above objectives, features and advantages of the present application more obvious and easy to understand, the specific embodiments of the present application will be described in detail below.

[0038] Unless otherwise specified, various raw materials of the present application can be commercially available.

[0039] Ultraviolet shielding performance test: the sample is mixed with a polyvinyl alcohol (PVA) aqueous solution (10 % w / v), and a PVA composite film with a uniform thickness (the content of the lignin-coated zinc oxide composite particles in the PVA composite film is 1 wt%) is cast. The absorbance at 320 nm is tested using an ultraviolet spectrophotometer;

[0040] Radical self-scavenging assay: the lignin-coated zinc oxide composite particles are prepared into a water suspension (0.05 g / mL) using a ZnO dispersion (0.05 g / mL) as a blank control. The radical scavenging capacity is detected by DPPH radical.

[0041] Composite particle migration amount determination: water / ethanol (9:1 v / v) is configured as a simulation liquid. The above 1.0 g of PVA composite film is placed in 20 g of simulation liquid. After standing for 48 h, the film is taken out, and the migration amount (mg) of the lignin-coated zinc oxide composite particles in the PVA composite film is determined.

[0042] Antibacterial performance test: gram-positive bacteria (Staphylococcus aureus) and gram-negative bacteria (Escherichia coli) are selected as target bacteria, and bacterial colony counting method is used for characterization. Bacterial solution preparation: the activated bacterial solution is diluted by ten times gradient with sterile PBS to a concentration of 1×10 5 CFU / mL; sample treatment: the composite nanoparticles are configured into a dispersion solution of 50 mg / mL with PBS, and 1 mL of the dispersion solution is mixed with 1 mL of the bacterial solution under 37°C, 200 rpm shaking culture for 3 h; plate culture: 50 μL of the culture solution is uniformly coated on an LB agar plate, and the surviving colonies are counted after 37°C culture for 24 h; control group: an equal volume of PBS buffer (pH=7.4) is used instead of the sample solution; the antibacterial rate (A) is calculated by formula (3-1):

[0043]

[0044] N in the formula control and N sample represent the number of colonies of the control group and the sample group, respectively

[0045]

[0046] Sunscreen ability evaluation: the lignin-coated zinc oxide composite nanoparticles were mixed with the blank cream (baby water moisturizing cream) without sunscreen active ingredients at a mass ratio of 1:10 to prepare the sunscreen cream. The SPF value of the composite sunscreen cream was measured to evaluate the ability of the composite particles to prevent ultraviolet damage.

[0047] The test method is as follows: two regions are selected on the back of the person to be tested, one of which is coated with the sample, and the other is not protected. Then, the two regions are simultaneously exposed to ultraviolet radiation of the same intensity (since the intensity of the ultraviolet radiation received by the two regions is equal, the minimum erythema dose required to produce the minimum erythema is proportional to the irradiation time), and the time at which erythema is produced in the two regions is recorded. The SPF value of the sample is obtained by dividing the time at which erythema is produced in the two regions. The test results are shown in Table 1.

[0048] Example 1:

[0049] After grinding, the enzyme lignin is sieved through a screen with a mesh size of 140 mesh (pore size 106 μm) to obtain micron-sized enzyme lignin powder (LMP). 4 g of enzyme lignin powder is slowly added to 0.05 mol / L, 300 mL of NaOH solution under stirring to obtain an enzyme lignin powder (LMP) suspension. Under stirring, 4 g of zinc acetate (dissolved in 40 mL of water) is slowly added dropwise to the enzyme lignin powder (LMP) suspension, and the pH is adjusted to 12 with NaOH. The reaction mixture is transferred to a flask and reacted at 90°C under a nitrogen atmosphere for 6 h. After the reaction is completed, the precipitated product is collected by centrifugation at 9000 rpm for 30 min, and the supernatant is replaced with distilled water. The centrifugation operation is repeated three times to obtain "raspberry"-shaped lignin-coated zinc oxide composite nanoparticles. The enzyme lignin (LIG-I type) is purchased from Shandong Longli Biological Technology Co., Ltd.

[0050] Example 2:

[0051] Referring to Example 1, only the hydrothermal reaction time is changed to 9 h, and the other conditions remain unchanged.

[0052] Example 3:

[0053] Referring to Example 1, only the hydrothermal reaction time is changed to 12 h, and the other conditions remain unchanged.

[0054] Example 4:

[0055] Referring to Example 3, only the hydrothermal reaction temperature was changed to 120 °C, and the other conditions were not changed. Figure 5 A picture of the product obtained in Example 4 was prepared into a water dispersion liquid having a concentration of 15 wt%.

[0056] Example 5:

[0057] Referring to Example 3, only the hydrothermal reaction temperature was changed to 60 °C, and the other conditions were not changed.

[0058] Example 6:

[0059] Referring to Example 3, only the pH of the mixture of zinc acetate and the enzyme lignin powder (LMP) suspension was changed to 11, and the other conditions were not changed.

[0060] Example 7:

[0061] Referring to Example 3, only the pH of the mixture of zinc acetate and the enzyme lignin powder (LMP) suspension was changed to 13, and the other conditions were not changed.

[0062] Example 8:

[0063] Referring to Example 3, only the amount of zinc acetate added was changed to 8 g, and the other conditions were not changed.

[0064] Example 9:

[0065] Referring to Example 3, only the amount of zinc acetate added in the step was changed to 2 g, and the other conditions were not changed.

[0066] Comparative Example 1:

[0067] After the enzyme lignin was ground, the micron-sized enzyme lignin powder (LMP) was sieved through a screen having a mesh size of 140 mesh (pore size 106 μm). 4 g of the enzyme lignin powder was slowly added to 0.05 mol / L, 300 mL of a NaOH solution under stirring to be sufficiently dissolved to obtain an enzyme lignin powder (LMP) suspension. The pH was adjusted to 12 using NaOH, and the mixture was transferred to a flask and reacted at 90 °C for 12 h under a nitrogen atmosphere. After the reaction was completed, the precipitated product was collected by centrifugation at 9000 rpm for 30 min, and the centrifugation operation was repeated three times to obtain the product.

[0068] Comparative Example 2:

[0069] The enzymatic lignin was ground and sieved to micron-sized lignin powder with a mesh size of 140 mesh (pore size 106 μm). The lignin powder (4 g) was slowly added to a NaOH solution (0.05 mol / L, 300 mL) under stirring to fully dissolve. 4 g of zinc oxide nanoparticles (average particle size of 50 ± 10 nm) were slowly added to the lignin suspension under stirring, the pH was adjusted to 12 with NaOH, transferred to a flask, and reacted at 90 °C for 12 h under a nitrogen atmosphere. After the reaction was completed, the precipitated product was collected by centrifugation at 9000 rpm for 30 min, the supernatant was replaced with distilled water, and the centrifugation operation was repeated three times to obtain lignin-zinc oxide composite nanoparticles.

[0070] Comparative Example 3:

[0071] The alkali-extracted lignin was ground and sieved to micron-sized lignin powder (LMP) with a mesh size of 140 mesh (pore size 106 μm). 4 g of the alkali-extracted lignin powder was slowly added to a NaOH solution (0.05 mol / L, 300 mL) under stirring to fully dissolve. 4 g of zinc acetate (dissolved in 40 mL of water) was slowly added dropwise to the alkali-extracted lignin powder (LMP) suspension under stirring, the pH was adjusted to 12 with NaOH, transferred to a flask, and reacted at 90 °C for 12 h under a nitrogen atmosphere. After the reaction was completed, the precipitated product was collected by centrifugation at 9000 rpm for 30 min, the supernatant was replaced with distilled water, and the centrifugation operation was repeated three times to obtain lignin-zinc oxide composite nanoparticles.

[0072] Table 1 Performance comparison of lignin-coated zinc oxide composite nanoparticles prepared in the present application

[0073]

[0074] Figure 1 The micro-morphology and particle size distribution of the zinc oxide / lignin nanoparticles prepared by the method of the present application in Example 2 are shown in the figure. As can be seen from the figure, the lignin-coated zinc oxide composite nanoparticles as a whole present a multi-directional "raspberry" shape, the lignin nanoparticles are wrapped around the periphery of the zinc oxide, and the two are combined by hydrogen bonding and electrostatic interaction. When the force is greater than the destruction force of strong alkali or strong acid, lignin-coated zinc oxide composite nanoparticles can be formed, and the lignin-zinc oxide combination is uniform. As can be seen from the particle size statistical diagram, the lignin-coated zinc oxide composite particles have uniform particle sizes, more than 90% of the particles have a particle size greater than 200 nm, and the overall particle size distribution is uniform (D50 ≈ 372 nm). Figure 3The figure of particle size distribution of the lignin-coated zinc oxide composite nanoparticles in Example 3 is shown. By comparing Example 2 and Example 3, it can be seen that with the increase of the reaction time, the lignin is more fully combined with the zinc oxide, the shape of the lignin-coated zinc oxide composite nanoparticles is more full, the particle size is increased, the zinc oxide loading is improved, and the particle size distribution is more concentrated.

[0075] Examples 1-8 explore the influence of the morphology and properties of the composite nanoparticles by changing the reaction time, reaction temperature, zinc salt content and reaction pH value. The core is to regulate the hydrogen bond and electrostatic force between lignin and zinc salt. Lignin is soluble in alkaline environment, and zinc salt acts as a nucleating agent in the self-assembly process of lignin during the formation of crystals. Nano-lignin and nano-zinc oxide co-grow, so that lignin is effectively coated on the surface of zinc oxide and forms a raspberry-like structure. From the above results, it can be seen that because lignin and zinc oxide have antibacterial and anti-ultraviolet functions, the composite nanoparticles can effectively inhibit bacterial growth and exhibit excellent anti-ultraviolet function. The 320 nm ultraviolet light transmittance decreases with the increase of the ZnO content and reaches only 0.1%. At the same time, the migration amount of the composite particles is low, and the nano-toxicity is greatly reduced. In Comparative Example 2, nano-lignin and nano-zinc oxide are added respectively, and the hydrogen bond or electrostatic binding capacity of the two is weak. At the same time, lignin is in a dissolved state at pH 12, and nano-zinc oxide cannot become a nucleating agent in the self-assembly and growth process of lignin, so it is difficult to form effective coating on zinc oxide. In Comparative Example 3, the interaction between the dealkalized lignin and the zinc salt is weak, so it is also difficult to form effective coating on zinc oxide, resulting in uneven particle size distribution and easy migration of zinc oxide. Examples 6 and 7 explore the influence of different pH values on the morphology of nanoparticles. When the pH is 13, the lignin is fully dissolved, making it difficult for zinc oxide to precipitate while lignin is precipitating, resulting in small particle size and unsatisfactory morphology of the composite particles. Examples 8 and 9 explore the influence of different ratios of zinc salt and lignin on the performance of nanoparticles. When the zinc salt is 8 g, the content of zinc oxide formed is increased, and the combination sites of lignin and zinc oxide are increased, resulting in a large increase in the content of zinc oxide in the formed composite nanoparticles, reaching 80.2%. However, the efficiency of lignin in capturing active oxygen free radicals produced by ZnO under ultraviolet light stimulation is reduced.

[0076] The products prepared in Examples 3, 5, 7, 8 and Comparative Examples 1, 2 are used as antibacterial and anti-dandruff active ingredients, and are added to the scalp cleaning and care agents shown in the application examples according to the corresponding mass percentage. In each application example, the addition amount of each component in the scalp cleaning and care agent is shown in Table 2, and the preparation method is to mix the formula raw materials uniformly.

[0077] Table 2 Scalp cleaning and care agent prepared in the present application (wt%)

[0078]

[0079]

[0080]

[0081] The scalp cleansing and care agents prepared according to Examples 1-6 and Comparative Examples 1-2 were subjected to evaluation tests, 10 evaluators were selected, each index was scored from 0 to 10 according to the sensory intensity from low to high, 1 g ± 0.1 g of sample was taken each time and applied on the inner side of the forearm, after 20 circles of application, the sample was evaluated for easy spreading (0 for easy spreading, 10 for difficult spreading), and stinging (0 for almost no feeling of mechanical friction, 10 for feeling of stinging caused by friction). At the same time, male volunteers aged 18-60 with dandruff and scalp inflammation were selected, 5 people in each group. The volunteers in each group used the scalp care agents obtained according to Examples 1-6 or Comparative Examples 1-2, the frequency of use was twice a week, and the method of use was to take 3 g ± 0.5 g of the scalp care agent to the hair root position after wetting the hair, spread it with the palm, massage for 5 min, then wash it with clean water, and then wash the hair according to their personal daily washing habits. After continuous use for 1 month, the results were evaluated and counted (dandruff, scalp itching, hair tangles), and the results are shown in Table 3.

[0082] Table 3 Effect of scalp care agents with different proportions

[0083]

[0084] Note: Significant improvement means that dandruff is significantly reduced, and scalp itching and inflammation problems disappear; some improvement means that dandruff is partially reduced, the frequency of scalp itching is reduced, and the number of scalp acne is reduced; no effect means that dandruff and itching and inflammation problems have no change.

[0085] It should be noted that the above examples are only used to illustrate the technical solutions of the present application and not to limit it. Although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present application, which should be covered in the scope of the claims of the present application.

Claims

1. Use of lignin-coated zinc oxide composite nanoparticles in the preparation of a cosmetic product, characterized in that: The lignin-coated zinc oxide composite nanoparticles are used for preparing a scalp care agent, a hair conditioner, a scalp cleanser or a shampoo. The preparation method of the lignin-coated zinc oxide composite nanoparticles comprises the following steps. After the enzymatic hydrolysis lignin is ground, 4 g of the enzymatic hydrolysis lignin powder is slowly added into 0.05 mol / L, 300 mL of the NaOH solution under stirring to be fully dissolved to obtain an enzymatic hydrolysis lignin powder suspension; 4 g of zinc acetate is dissolved in 40 mL of water under stirring, slowly added into the enzymatic hydrolysis lignin powder suspension, and the pH is adjusted to 12 by using NaOH; then the mixture is transferred into a flask and reacted at 90 ℃ under a nitrogen atmosphere for 12 h; after the reaction is completed, the precipitated product is collected by centrifugation at 9000 rpm for 30 min, the supernatant is replaced with distilled water, and the centrifugation operation is repeated three times to obtain "raspberry"-shaped lignin-coated zinc oxide composite nanoparticles. The enzymatic hydrolysis lignin is LIG-I type enzymatic hydrolysis lignin.

2. Use according to claim 1, characterized in that: The scalp care agent comprises the following components in percentage by mass: 5-25% of the lignin-coated zinc oxide composite nanoparticles, 10-25% of a surfactant, 2-5% of a conditioning agent, 0.05-0.15% of an emulsifying agent, 10-30% of an emollient, 0.01-0.3% of a preservative, 0-0.8% of a fragrance, 0.5-1% of a viscosity regulator, 0.05-0.2% of a chelating agent, 0.001-0.2% of a pH regulator, 10-25% of a humectant, and the balance of water.

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