A coated and enhanced nano-silver powder and its preparation method

Abstract

This invention belongs to the field of antibacterial nanosilver materials and discloses a coated and reinforced nanosilver powder and its preparation method. The preparation method of the coated and reinforced nanosilver powder includes the following steps: preparing nanosilver sol by reducing silver nitrate with glycerol and sodium citrate; growing and coating zinc oxide on the surface of nanosilver by reacting zinc acetate and triethanolamine; modifying the surface of the zinc oxide layer with N-(2-aminoethyl)-3-aminopropyltrimethoxysilane; and coating the surface of the zinc oxide layer with a polyurethane layer by interfacial polymerization. The coated and reinforced nanosilver powder prepared by this method has the advantages of strong antibacterial properties, low cost, and stable bonding with the coating matrix.

Description

Technical Field

[0001] This invention belongs to the field of antibacterial nano-silver materials technology, specifically relating to a coated and reinforced nano-silver powder and its preparation method. Background Technology

[0002] Nano-silver, with its superior antibacterial properties, is widely used in various fields. Due to its large specific surface area and significant surface effect, nano-silver can continuously release silver ions, which can interact with bacterial cell walls, thereby effectively inhibiting bacterial growth and reproduction. Specifically, silver ions mainly cause bacterial death by disrupting the integrity of bacterial cell walls, interfering with their metabolic activities, and hindering DNA replication. Because the antibacterial mechanism of nano-silver is a multi-target synergistic attack, bacteria are unlikely to resist all mechanisms through a single mutation, greatly reducing the risk of drug-resistant bacteria. For this reason, nano-silver coatings play a crucial role in fields such as medicine and textiles.

[0003] Despite the excellent antibacterial properties of nano-silver coatings, several technical challenges remain in their application. Nano-silver particles are prone to agglomeration, resulting in uneven dispersion within the coating and weakening the antibacterial effect. Furthermore, the relatively high market price of nano-silver makes the development of a nano-silver coating filler that guarantees both high antibacterial efficacy and low cost with high bonding stability a pressing technical problem. Summary of the Invention

[0004] To address the shortcomings mentioned in the background section, the present invention aims to provide a coated and enhanced nano-silver powder and its preparation method.

[0005] The objective of this invention can be achieved through the following technical solutions: A method for preparing coated and enhanced silver nanopowder, characterized by comprising the following steps: S1: Add deionized water, glycerol and silver nitrate to a reaction flask, heat to 85-95℃, add sodium citrate, keep warm and stir for 1-2 hours, and cool to obtain nano silver sol. S2: Zinc acetate, triethanolamine, and nano silver sol are mixed and ultrasonically stirred at 60-65℃ and 20MHz for 2-3 hours. The precipitate is separated by centrifugation, washed multiple times with deionized water and anhydrous ethanol, and dried to obtain zinc oxide-coated nano silver powder. S3: Mix N-(2-aminoethyl)-3-aminopropyltrimethoxysilane and aqueous ethanol solution, add zinc oxide-coated silver nanoparticles and stir for 2-3 hours, then dry to obtain surface-modified zinc oxide-coated silver nanoparticles. S4. Isophorone diisocyanate, dibutyltin dilaurate, and sorbitol monooleate are dissolved in hexane and stirred evenly at room temperature to obtain oil phase A. Polypropylene glycol, polysorbate 80, and surface-modified zinc oxide-coated nano-silver powder are added to deionized water and stirred evenly at room temperature to obtain aqueous phase B. Aqueous phase B is slowly added to oil phase A and stirred at high speed at room temperature for 10-20 minutes. Then, it is heated to 40-45℃ and stirred at low speed for 8 hours to obtain a suspension. The suspension is centrifuged in a high-speed centrifuge for 5-10 minutes, washed multiple times with anhydrous ethanol and deionized water, and dried in a vacuum drying oven to obtain coated and reinforced nano-silver powder.

[0006] Preferably, the addition ratio of glycerol, silver nitrate and sodium citrate in S1 is 50-60mL: 2-5g: 0.13-0.2g.

[0007] Preferably, the addition ratio of zinc acetate, triethanolamine, and nano silver sol in S2 is 18-43g: 45-60mL: 65-81g.

[0008] Preferably, the concentration of the ethanol aqueous solution in S3 is 90 vol.

[0009] Preferably, the addition ratio of N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, aqueous ethanol solution, and zinc oxide-coated silver nanopowder in S3 is 4-10g:50mL:12-20g.

[0010] Preferably, in S4, the addition ratio of isophorone diisocyanate, dibutyltin dilaurate, sorbitol monooleate, and n-hexane in the oil phase A is 25-40g:0.4-0.6mL:5g:200g, and the addition ratio of polypropylene glycol, polysorbate 80, surface-modified zinc oxide-coated nano-silver powder, and deionized water in the aqueous phase B is 20-30g:15g:10-20g:200mL. The mixing ratio of oil phase A to aqueous phase B is 3:1.

[0011] A coated and enhanced nano-silver powder is prepared by any of the above methods.

[0012] The beneficial effects of this invention are: (1) In the preparation of nano-silver sol, this invention uses two reducing agents: glycerol and sodium citrate. In this step, sodium citrate acts as both a reducing agent and a surface modifier. Citrate ions contain three carboxyl groups and one hydroxyl group, which can chelate with silver ions in the solution. When silver ions are reduced, a large number of citrate ions are deposited on the surface of the nano-silver particles through chemical bonds and van der Waals forces, providing a certain amount of electrostatic repulsion and stabilizing the silver sol. At the same time, after sodium citrate is adsorbed onto the surface of the nano-silver particles, the hydroxyl groups are exposed, forming a vitreous surface, which provides favorable conditions for the coating of zinc oxide. The use of sodium citrate can reduce the aggregation of nano-silver, and the use of ultrasonic dispersion can significantly reduce the aggregation of nano-zinc oxide, thereby improving antibacterial properties.

[0013] (2) This invention uses nano-zinc oxide grown on the surface of nano-silver to coat the nano-silver and form a core-shell structure. Zinc ions can inhibit the replication of various RNA viruses. At the same time, zinc oxide is a photocatalytic material with a wide bandgap and high exciton binding energy. It can utilize water or oxygen in the photocatalytic environment to generate reactive oxygen species, which react chemically with bacterial membrane proteins to achieve an antibacterial effect. By coating nano-silver with nano-zinc oxide, the photoresponse region of zinc oxide can be extended to the visible light region, improving quantum efficiency and photocatalytic activity. The plasmonic resonance effect is used to achieve synergistic antibacterial action between nano-silver and zinc oxide, improving antibacterial properties and reducing the amount of silver raw material used, thus significantly reducing costs.

[0014] (3) In this invention, the surface of nano-silver coated with nano-zinc oxide is modified by the diaminosilane coupling agent N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, which reduces the surface energy of the nano-zinc oxide layer and introduces amino groups. Then, isophorone diisocyanate is reacted with polypropylene glycol to generate polyurethane, which is then coated on the zinc oxide layer by interfacial polymerization. Since isophorone diisocyanate can react with the amino groups of the nano-zinc oxide layer to generate urea groups, it forms a cross-linking network with various groups such as urethane groups generated during the polyurethane polymerization process, so that the coated and reinforced nano-silver powder can be stably bonded in the coating substrate.

[0015] Of course, any product implementing this invention does not necessarily need to achieve all of the advantages described above at the same time. Detailed Implementation

[0016] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0017] Example 1: A method for preparing coated and reinforced silver nanopowder includes the following steps: S1: Add 100mL of deionized water, 50mL of glycerol and 2g of silver nitrate to a reaction flask, heat to 85℃, add 0.13g of sodium citrate, keep warm and stir for 1h, and cool to obtain nano silver sol; S2: Mix 18g zinc acetate, 45mL triethanolamine and 65g nano silver sol, and react with ultrasonic stirring at 60℃ and 20MHz for 2h. Separate the precipitate by centrifugation, wash with deionized water and anhydrous ethanol multiple times, and dry to obtain zinc oxide coated nano silver powder. S3: Mix 4g of N-(2-aminoethyl)-3-aminopropyltrimethoxysilane and 50mL of 90vol% ethanol aqueous solution, add 12g of zinc oxide-coated silver nanoparticles and stir for 2h. Dry to obtain surface-modified zinc oxide-coated silver nanoparticles. S4. Dissolve 25g isophorone diisocyanate, 0.4mL dibutyltin dilaurate, and 5g sorbitol monooleate in 200g n-hexane and stir evenly at room temperature to obtain oil phase A. Add 20g polypropylene glycol, 15g polysorbate 80, and 10g surface-modified zinc oxide-coated silver nanoparticles to 200mL deionized water and stir evenly at room temperature to obtain aqueous phase B. Slowly add aqueous phase B to oil phase A at an oil-to-water ratio of 3:1 and stir at high speed at room temperature for 10min. Then heat to 40℃ and stir at low speed for 8h to obtain a suspension. Centrifuge the suspension in a high-speed centrifuge for 5min, wash repeatedly with anhydrous ethanol and deionized water, and dry in a vacuum drying oven to obtain coated and reinforced silver nanoparticles.

[0018] Example 2 A method for preparing coated and reinforced silver nanopowder includes the following steps: S1: Add 100 mL of deionized water, 55 mL of glycerol and 3.5 g of silver nitrate to a reaction flask, heat to 90 °C, add 0.17 g of sodium citrate, keep warm and stir for 1.5 h, and cool to obtain nano silver sol; S2: Mix 30g zinc acetate, 55mL triethanolamine and 73g nano silver sol, and react with ultrasonic stirring at 65℃ and 20MHz for 2.5h. Separate the precipitate by centrifugation, wash with deionized water and anhydrous ethanol multiple times, and dry to obtain zinc oxide coated nano silver powder. S3: Mix 7g of N-(2-aminoethyl)-3-aminopropyltrimethoxysilane and 50mL of 90vol% ethanol aqueous solution, add 16g of zinc oxide-coated silver nanoparticles and stir for 2.5h. Dry to obtain surface-modified zinc oxide-coated silver nanoparticles. S4. Dissolve 33g isophorone diisocyanate, 0.5mL dibutyltin dilaurate, and 5g sorbitol monooleate in 200g n-hexane and stir evenly at room temperature to obtain oil phase A. Add 25g polypropylene glycol, 15g polysorbate 80, and 15g surface-modified zinc oxide-coated silver nanoparticles to 200mL deionized water and stir evenly at room temperature to obtain aqueous phase B. Slowly add aqueous phase B to oil phase A at an oil-to-water ratio of 3:1 and stir at high speed at room temperature for 15min. Then heat to 40-45℃ and stir at low speed for 8h to obtain a suspension. Centrifuge the suspension in a high-speed centrifuge for 8min, wash it several times with anhydrous ethanol and deionized water, and dry it in a vacuum drying oven to obtain coated and reinforced silver nanoparticles.

[0019] Example 3 A method for preparing coated and reinforced silver nanopowder includes the following steps: S1: Add 100mL of deionized water, 60mL of glycerol and 5g of silver nitrate to a reaction flask, heat to 95℃, add 0.2g of sodium citrate, keep warm and stir for 2h, and cool to obtain nano silver sol; S2: Mix 43g zinc acetate, 60mL triethanolamine and 81g nano silver sol, and react with ultrasonic stirring at 65℃ and 20MHz for 3h. Separate the precipitate by centrifugation, wash with deionized water and anhydrous ethanol multiple times, and dry to obtain zinc oxide coated nano silver powder. S3: Mix 10g of N-(2-aminoethyl)-3-aminopropyltrimethoxysilane and 50mL of 90vol% ethanol aqueous solution, add 20g of zinc oxide-coated silver nanoparticles and stir for 3h, then dry to obtain surface-modified zinc oxide-coated silver nanoparticles. S4. Dissolve 40g isophorone diisocyanate, 0.6mL dibutyltin dilaurate, and 5g sorbitol monooleate in 200g n-hexane and stir evenly at room temperature to obtain oil phase A. Add 30g polypropylene glycol, 15g polysorbate 80, and 20g surface-modified zinc oxide-coated silver nanoparticles to 200mL deionized water and stir evenly at room temperature to obtain aqueous phase B. Slowly add aqueous phase B to oil phase A at an oil-to-water ratio of 3:1 and stir at high speed at room temperature for 20min. Then heat to 45℃ and stir at low speed for 8h to obtain a suspension. Centrifuge the suspension in a high-speed centrifuge for 10min, wash repeatedly with anhydrous ethanol and deionized water, and dry in a vacuum drying oven to obtain coated and reinforced silver nanoparticles.

[0020] Comparative Example 1: The preparation method of coated silver nanopowder includes the following steps: S1: Add 100 mL of deionized water, 62 mL of glycerol and 3.5 g of silver nitrate to a reaction flask, heat to 90 °C, stir and keep warm for 1.5 h, and cool to obtain nano silver sol; S2: Mix 30g zinc acetate, 55mL triethanolamine and 73g nano silver sol, stir and react at 65℃ for 2.5h, centrifuge to separate the precipitate, wash with deionized water and anhydrous ethanol several times, and dry to obtain zinc oxide coated nano silver powder. S3: Mix 7g of N-(2-aminoethyl)-3-aminopropyltrimethoxysilane and 50mL of 90vol% ethanol aqueous solution, add 16g of zinc oxide-coated silver nanoparticles and stir for 2.5h. Dry to obtain surface-modified zinc oxide-coated silver nanoparticles. S4. Dissolve 33g isophorone diisocyanate, 0.5mL dibutyltin dilaurate, and 5g sorbitol monooleate in 200g n-hexane and stir evenly at room temperature to obtain oil phase A. Add 25g polypropylene glycol, 15g polysorbate 80, and 15g surface-modified zinc oxide-coated silver nanoparticles to 200mL deionized water and stir evenly at room temperature to obtain aqueous phase B. Slowly add aqueous phase B to oil phase A at an oil-to-water ratio of 3:1 and stir at high speed at room temperature for 15min. Then heat to 40-45℃ and stir at low speed for 8h to obtain a suspension. Centrifuge the suspension in a high-speed centrifuge for 8min, wash it several times with anhydrous ethanol and deionized water, and dry it in a vacuum drying oven to obtain coated silver nanoparticles.

[0021] Comparative Example 2: The preparation method of coated silver nanopowder includes the following steps: S1: Add 100 mL of deionized water, 55 mL of glycerol and 3.5 g of silver nitrate to a reaction flask, heat to 90 °C, add 0.17 g of sodium citrate, keep warm and stir for 1.5 h, and cool to obtain nano silver sol; S2: Mix 30g zinc acetate, 55mL triethanolamine and 73g nano silver sol, and react with ultrasonic stirring at 65℃ and 20MHz for 2.5h. Separate the precipitate by centrifugation, wash with deionized water and anhydrous ethanol multiple times, and dry to obtain coated nano silver powder. S3: Mix 7g of N-(2-aminoethyl)-3-aminopropyltrimethoxysilane and 50mL of 90vol% ethanol aqueous solution, add 16g of zinc oxide-coated silver nanoparticles and stir for 2.5h. Dry to obtain coated silver nanoparticles.

[0022] Comparative Example 3: The preparation method of coated silver nanopowder includes the following steps: S1: Add 100 mL of deionized water, 55 mL of glycerol and 3.5 g of silver nitrate to a reaction flask, heat to 90 °C, add 0.17 g of sodium citrate, keep warm and stir for 1.5 h, and cool to obtain nano silver sol; S2: Mix 30g zinc acetate, 55mL triethanolamine and 73g nano silver sol, and react with ultrasonic stirring at 65℃ and 20MHz for 2.5h. Separate the precipitate by centrifugation, wash with deionized water and anhydrous ethanol multiple times, and dry to obtain zinc oxide coated nano silver powder. S3. Dissolve 33g isophorone diisocyanate, 0.5mL dibutyltin dilaurate, and 5g sorbitol monooleate in 200g n-hexane and stir evenly at room temperature to obtain oil phase A. Add 25g polypropylene glycol, 15g polysorbate 80, and 15g surface-modified zinc oxide-coated silver nanoparticles to 200mL deionized water and stir evenly at room temperature to obtain aqueous phase B. Slowly add aqueous phase B to oil phase A at an oil-to-water ratio of 3:1 and stir at high speed at room temperature for 15min. Then heat to 40-45℃ and stir at low speed for 8h to obtain a suspension. Centrifuge the suspension in a high-speed centrifuge for 8min, wash repeatedly with anhydrous ethanol and deionized water, and dry in a vacuum drying oven to obtain coated silver nanoparticles.

[0023] Comparative Example 4: The preparation method of coated silver nanopowder includes the following steps: S1: Add 100 mL of deionized water, 55 mL of glycerol and 3.5 g of silver nitrate to a reaction flask, heat to 90 °C, add 0.17 g of sodium citrate, keep warm and stir for 1.5 h, and cool to obtain nano silver sol; S2: Dry the nano-silver sol, mix 7g of N-(2-aminoethyl)-3-aminopropyltrimethoxysilane and 50mL of 90vol% ethanol aqueous solution, add 16g of nano-silver powder and stir for 2.5h, then dry to obtain surface-modified zinc oxide-coated nano-silver powder. S3. Dissolve 33g isophorone diisocyanate, 0.5mL dibutyltin dilaurate, and 5g sorbitol monooleate in 200g n-hexane and stir evenly at room temperature to obtain oil phase A. Add 25g polypropylene glycol, 15g polysorbate 80, and 15g surface-modified zinc oxide-coated silver nanoparticles to 200mL deionized water and stir evenly at room temperature to obtain aqueous phase B. Slowly add aqueous phase B to oil phase A at an oil-to-water ratio of 3:1 and stir at high speed at room temperature for 15min. Then heat to 40-45℃ and stir at low speed for 8h to obtain a suspension. Centrifuge the suspension in a high-speed centrifuge for 8min, wash repeatedly with anhydrous ethanol and deionized water, and dry in a vacuum drying oven to obtain coated silver nanoparticles.

[0024] Performance testing (1) Antibacterial performance: According to GB / T 21866-2008 "Determination of antibacterial properties and antibacterial effects of antibacterial coatings (films)", the test samples were obtained as follows: by weight, 10 parts of Examples 1-3 and Comparative Examples 1-3 were mixed with 30 parts of E-51 type epoxy resin, 50 parts of deionized water and 4 parts of reactive diluent, angle-ground for 1 hour and cured for 8 hours. The coatings were applied to polyethylene sheets twice, dried and cut into 50mm×50mm×5mm sizes, and sterilized with ultraviolet sterilization lamps. The samples were then exposed to cultured bacterial solutions at (37±1)℃ and relative humidity greater than 90%, and the antibacterial rate was calculated by counting viable bacteria. An antibacterial rate ≥90% was considered to have strong antibacterial effect, and ≥99% was considered to have excellent antibacterial performance. The results are shown in Table 1.

[0025] (2) Total silver content: According to GB / Z 43890-2024 "Guide to the test method of nanotechnology nano silver" and GB / T15337-2008 "General rules of atomic absorption spectrometry", Examples 1-3 and Comparative Examples 1-4 were digested into ionic solutions, and the silver content was detected by atomic absorption spectrometry. The total silver content was calculated, and the results are shown in Table 1.

[0026] (3) Bonding stability: According to GB 6753.3-1986 "Test method for storage stability of coatings", the test samples were obtained as follows: by weight, 10 parts of Examples 1-3 and Comparative Examples 1-3 were mixed with 30 parts of E-51 type epoxy resin, 50 parts of deionized water and 4 parts of reactive diluent, angle-ground for 1 hour and cured for 8 hours; the samples were sealed in a standard pressure-capped metal paint can with the sample amount 15 mm away from the top of the can, and stored in a constant temperature drying oven at (50±2)℃ under accelerated conditions for 30 days. The degree of sedimentation was checked by vertically inserting a cutting tool into the center of the sample. The evaluation was divided into 6 levels, with level 0 being unqualified.

[0027] Table 1. Statistical table of performance test data of samples prepared in Examples 1-3 and Comparative Examples 1-3

[0028] As shown in the table, Examples 1-3 exhibit high antibacterial properties with a small silver content, significantly reducing raw material costs due to the low silver content, and demonstrating stable bonding with epoxy resin. Comparative Example 1 did not add a surface modifier when preparing the nano-silver sol, nor did it undergo ultrasonic dispersion when preparing the zinc oxide-coated nano-silver powder, resulting in agglomeration of the nano-silver and nano-zinc oxide, leading to the lowest antibacterial rate among all examples and comparative examples. Comparative Example 2 did not perform surface modification on the nano-zinc oxide layer, and Comparative Example 3 did not coat the nano-zinc oxide layer with a polyurethane layer, resulting in high sedimentation of the coating and poor bonding stability between the coating and filler. Comparative Example 4 uses fluorinated polyurethane to coat pure nano-silver powder, exhibiting good antibacterial properties but at a higher cost. Furthermore, compared with Examples 2 and Comparative Examples 2 and 3, it can be found that the effect of polyurethane coating on nano-silver is not as good as that of coating on zinc oxide, and while the sedimentation performance is acceptable, it does not reach a high level.

[0029] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0030] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention.

Claims

1. A method for preparing coated and reinforced nano-silver powder, characterized in that, Includes the following steps: S1: Add deionized water, glycerol and silver nitrate to a reaction flask, heat to 85-95℃, add sodium citrate, keep warm and stir for 1-2 hours, and cool to obtain nano silver sol. S2: Zinc acetate, triethanolamine, and nano silver sol are mixed and ultrasonically stirred at 60-65℃ and 20MHz for 2-3 hours. The precipitate is separated by centrifugation, washed multiple times with deionized water and anhydrous ethanol, and dried to obtain zinc oxide-coated nano silver powder. S3: Mix N-(2-aminoethyl)-3-aminopropyltrimethoxysilane and aqueous ethanol solution, add zinc oxide-coated silver nanoparticles and stir for 2-3 hours, then dry to obtain surface-modified zinc oxide-coated silver nanoparticles. S4. Dissolve isophorone diisocyanate, dibutyltin dilaurate, and sorbitol monooleate in hexane and stir evenly at room temperature to obtain oil phase A. Add polypropylene glycol, polysorbate 80, and surface-modified zinc oxide-coated silver nanoparticles to deionized water and stir evenly at room temperature to obtain aqueous phase B. Slowly add aqueous phase B to oil phase A and stir at high speed at room temperature for 10-20 minutes. Then heat to 40-45℃ and stir at low speed for 8 hours to obtain a suspension. The suspension was centrifuged in a high-speed centrifuge for 5-10 minutes, washed repeatedly with anhydrous ethanol and deionized water, and then dried in a vacuum drying oven to obtain coated and enhanced nano-silver powder.

2. The method for preparing coated and reinforced nano-silver powder according to claim 1, characterized in that, The addition ratio of glycerol, silver nitrate, and sodium citrate in S1 is 50-60 mL: 2-5 g: 0.13-0.2 g.

3. The method for preparing coated and reinforced nano-silver powder according to claim 1, characterized in that, The addition ratio of zinc acetate, triethanolamine, and nano silver sol in S2 is 18-43g: 45-60mL: 65-81g.

4. The method for preparing coated and reinforced nano-silver powder according to claim 1, characterized in that, The concentration of the ethanol aqueous solution in S3 is 90 vol.

5. The method for preparing coated and reinforced nano-silver powder according to claim 1, characterized in that, The addition ratio of N-(2-aminoethyl)-3-aminopropyltrimethoxysilane and zinc oxide-coated silver nanopowder is 4-10g:12-20g.

6. The method for preparing coated and reinforced nano-silver powder according to claim 1, characterized in that, In S4, the addition ratio of isophorone diisocyanate, dibutyltin dilaurate, sorbitol monooleate, and n-hexane in oil phase A is 25-40g:0.4-0.6mL:5g:200g. The addition ratio of polypropylene glycol, polysorbate 80, surface-modified zinc oxide-coated nano-silver powder, and deionized water in aqueous phase B is 20-30g:15g:10-20g:200mL. The mixing ratio of oil phase A to aqueous phase B is 3:

1.

7. A coated and reinforced nano-silver powder, characterized in that, It is prepared by the preparation method according to any one of claims 1-6.

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