A three-layer core-shell structure nanocomposite antibacterial material and a preparation method and application thereof

Abstract

The application discloses a kind of three-layer core-shell structure nanocomposite antibacterial materials and its preparation method and application, with a core, the core is coated with an antibacterial polymer material layer, the antibacterial polymer material layer is coated with a prolamine layer.The core metal or metal oxide nanoparticle in the application provides long-lasting antibacterial properties, the intermediate layer polymer quaternary ammonium salt gradually dissolves and releases in the presence of water or water vapor to provide long-lasting direct contact type antibacterial properties, while the outermost layer of hydrophobic prolamine is compatible with resin, making the three-layer core-shell structure composite nanomaterials have good dispersibility.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of nanomaterials, and particularly relates to a three-layer core-shell structure nanocomposite antibacterial material and a preparation method and application thereof. BACKGROUND

[0002] With the progress of science and technology and the development of society, people's requirements for the quality of life are getting higher and higher, and green and healthy commodities are increasingly favored. The interaction between special materials and microorganisms such as bacteria can inhibit the growth of microorganisms, thereby reducing the harm of microorganisms in people's life. At present, the traditional antibacterial agent has low bactericidal efficiency due to drug resistance, and the natural antibacterial agent also has the disadvantages of short antibacterial time and complex processing technology, that is, the use of a single antibacterial material as an antibacterial agent will have various shortcomings. Compounding organic antibacterial agents with inorganic antibacterial agents can bring more comprehensive antibacterial effect, expand the application range and improve the antibacterial performance.

[0003] Common antibacterial nanoparticles include silver, copper, zinc and their oxides, which have broad-spectrum antibacterial properties and high antibacterial efficiency, but mainly have the problems of poor dispersibility and high cost. In order to enhance the dispersibility of nanoparticles, two methods can be adopted. One is to use physical methods such as ultrasonic, shearing, etc., but this method has poor stability and high energy consumption. In addition, using appropriate surface modifiers, such as surfactants, dispersants, etc., can improve the dispersibility of nanoparticles. For example, sodium dodecyl sulfate, polyvinylpyrrolidone, silane coupling agent, etc. (Materials Review, 2019, 33(z1): 16-21) can be used to modify the surface of titanium dioxide to improve its dispersibility in the medium, but because the active agent will wrap part of the nanoparticles, it will reduce the active site and affect its performance.

[0004] Chitosan has good antibacterial property, biocompatibility and biodegradability, and has been widely recognized as an important biomaterial. However, in neutral and alkaline aqueous solutions, chitosan is insoluble in water due to the linear aggregation of chain molecules and the formation of crystals. At the same time, chitosan contains rich active groups such as amino and hydroxyl groups, and has strong hydrophilicity and weak hydrophobicity, which is difficult to disperse uniformly in conventional hydrophobic resins (Polym.-Plast. Technol. Mater. 2023, 62, 2182-2220). These factors greatly limit the practical application of chitosan as an excellent antibacterial material.

[0005] The nanoparticles antibacterial material and the organic antibacterial material are directly compounded, and synergistic antibacterial effect can be effectively played. The most convenient method is to directly disperse some inorganic antibacterial ingredients such as silver antibacterial agents in the organic antibacterial raw materials, for example, directly composite multiple antibacterial agents by using a simple blending method (for example, CN116180489A, CN116477939A, CN116478613A and CN116333461A). Chemical methods can also be used, for example, Jun et al. (Carbohydr. Polym. 2019, 220, 22-29) disperse the prepared silver nanoparticles in the acetic acid dissolved chitosan solution, and use a crosslinking agent to fix the chitosan on the surface of the nanoparticles to form a core-shell structure. In addition, Nithya et al. (Int. J. Biol. Macromol. 2017, 104, 1774-1782) bond chitosan to the surface of copper nanoparticles without using a reducing agent. However, the composite antibacterial materials prepared by the methods of the prior art have complex process, low yield and high cost, and are difficult to be applied in industrialization. SUMMARY

[0006] The present application aims to overcome the inherent defects of the prior art of single metal or metal oxide nano-antibacterial agent, organic antibacterial agent and existing composite antibacterial material, improve the applicability, simplify the preparation and reduce the cost, and endow the nano-composite material with long-acting, persistent and high antibacterial performance, and provide a three-layer core-shell structure nano-composite antibacterial material.

[0007] Another object of the present application is to provide a preparation method of the three-layer core-shell structure nano-composite antibacterial material.

[0008] Still another object of the present application is to provide the application of the three-layer core-shell structure nano-composite antibacterial material.

[0009] The technical scheme of the present application is as follows:

[0010] A three-layer core-shell structure nano-composite antibacterial material has an inner core, an antibacterial polymer material layer is coated outside the inner core, and a prolamin layer is coated outside the antibacterial polymer material layer.

[0011] The inner core is a metal nanoparticle or a metal oxide nanoparticle with antibacterial performance, and the particle size is 20-400 nm.

[0012] The antibacterial polymer material layer is formed by self-assembly of the antibacterial polymer material on the inner core through electrostatic interaction, and the antibacterial polymer material is at least one of a high molecular quaternary ammonium salt, a high molecular quaternary phosphonium salt and a guanidine high molecule.

[0013] The prolamin layer is formed by self-assembly of the prolamin on the antibacterial polymer material layer through hydrogen bond and hydrophobic interaction.

[0014] In a preferred embodiment of the present application, the metal nanoparticles are at least one of silver nanoparticles, silver nanowires, copper nanoparticles and copper nanowires, and the metal oxide nanoparticles are at least one of zinc oxide nanoparticles, silver oxide nanoparticles and copper oxide nanoparticles.

[0015] In a preferred embodiment of the present application, the antibacterial macromolecular material is tetradecyl trimethyl ammonium chloride, hexadecyl trimethyl ammonium chloride, hydroxypropyl trimethyl ammonium chloride chitosan or polyhexamethylene biguanide hydrochloride.

[0016] In a preferred embodiment of the present application, the prolamine is zein and / or wheat gluten.

[0017] In a preferred embodiment of the present application, the content of the metal nanoparticles or metal oxide nanoparticles is 90-94wt%, the content of the antibacterial macromolecular material is 0.5-6wt%, and the content of the prolamine is 0.5-6wt%.

[0018] The preparation method of the three-layer core-shell structure nanocomposite antibacterial material comprises the following steps:

[0019] (1) mixing the metal nanoparticles or metal oxide nanoparticles with a strong alkali aqueous solution to prepare a stable dispersion A;

[0020] (2) adding the dispersion A into an aqueous solution of the antibacterial macromolecular material under stirring to prepare a dispersion B;

[0021] (3) centrifuging the dispersion B after standing at -18℃-30℃ for 0.5-4h to obtain a solid, and uniformly drying and grinding the solid to obtain a two-layer core-shell structure nanomaterial C;

[0022] (4) adding the two-layer core-shell structure nanomaterial C into an alcohol solution of the prolamine under stirring to prepare a dispersion D;

[0023] (5) centrifuging the dispersion D after stirring at room temperature for 10min to 4h to obtain a solid, and uniformly drying and grinding the solid to obtain the three-layer core-shell structure nanocomposite antibacterial material.

[0024] In a preferred embodiment of the present application, the solute in the strong alkali aqueous solution is at least one of lithium hydroxide, sodium hydroxide and potassium hydroxide, and the concentration of the strong alkali aqueous solution is 0.2-2wt%.

[0025] In a preferred embodiment of the present application, the concentration of the aqueous solution of the antibacterial macromolecular material is 0.2-2wt%.

[0026] In a preferred embodiment of the present invention, the alcohol solvent in the alcohol solution is at least one of methanol, ethanol, n-propanol, isopropanol, propylene glycol, butanol, n-pentanol, and isopentanol, and the concentration of the alcohol-soluble protein in the alcohol solution is 1-5 wt%.

[0027] The above-mentioned three-layer core-shell structured nanocomposite antibacterial material is used in the preparation of antibacterial plastic products.

[0028] The beneficial effects of this invention are:

[0029] 1. The core metal or metal oxide nanoparticles in the three-layer core-shell structured nanocomposite antibacterial material of the present invention provide long-lasting antibacterial properties, the middle layer of high molecular weight quaternary ammonium salt gradually dissolves and releases in the presence of water or water vapor to provide long-lasting direct contact antibacterial properties, and the outermost layer of hydrophobic alcohol-soluble protein has good compatibility with resin, which makes the three-layer core-shell structured composite nanomaterial have good dispersibility.

[0030] 2. This invention utilizes a strong alkali to negatively charge the surface of metal or metal oxide nanoparticles, and then prepares a two-layer core-shell composite nanomaterial through electrostatic interaction with a positively charged polymeric quaternary ammonium salt. Furthermore, a three-layer core-shell composite nanomaterial is formed through self-assembly of the polymeric quaternary ammonium salt and proteases via hydrophobic and hydrogen bonding interactions. In other words, this invention employs a simple, easy-to-implement, non-toxic chemical reagent-free, and low-energy-consumption process to prepare nanocomposite materials with synergistic and long-lasting antibacterial effects through a supramolecular self-assembly strategy, which has good scientific significance and practical prospects. Attached Figure Description

[0031] Figure 1 The thermogravimetric curves of the two-layer core-shell structured nanomaterials prepared under different strong alkalis in Example 1 of this invention are shown.

[0032] Figure 2 This is a scanning electron microscope image of the product prepared using nano-copper oxide and nano-silver particles in Example 2 of the present invention.

[0033] Figure 3 This is a transmission electron microscope (TEM) image of the product prepared using silver nanowires and copper nanowires in Example 2 of the present invention.

[0034] Figure 4 This is a digital photograph of the two-layer core-shell structured nanomaterials and silver nanoparticles (middle) prepared by tetradecyltrimethylammonium chloride (left) and polyhexamethylene biguanide hydrochloride (right) in Example 3 of the present invention, and the three dispersed in water.

[0035] Figure 5 This is a graph showing the relationship between the content of hydroxypropyltrimethylammonium chloride chitosan (HACC) prepared in Example 4 of the present invention and the concentration of NaOH used.

[0036] Figure 6 The graph shows the effect of the concentration of hydroxypropyltrimethylammonium chloride chitosan (HACC) on the adsorption capacity of HACC in Example 5 of this invention.

[0037] Figure 7 This is an adsorption kinetic curve of hydroxypropyltrimethylammonium chloride chitosan (HACC) on nano zinc oxide at room temperature in Example 6 of the present invention.

[0038] Figure 8 The figure shows the effect of temperature on the adsorption of hydroxypropyltrimethylammonium chloride chitosan (HACC) on nano zinc oxide in Example 6 of the present invention.

[0039] Figure 9 These are scanning electron microscope (SEM) images of the initial silver nanoparticles (A), the intermediate two-layer core-shell composite nanomaterial (B), and the final three-layer core-shell composite nanomaterials (C, D) in Example 8 of this invention.

[0040] Figure 10 This is a graph showing the effect of stirring time in alcohol-soluble corn protein on the adhesion amount on a two-layer core-shell composite nanomaterial in Example 10 of the present invention.

[0041] Figure 11 This is a graph showing the effect of alcohol-soluble corn protein concentration on the adhesion amount on a two-layer core-shell composite nanomaterial in Example 10 of the present invention.

[0042] Figure 12 The image shows the antibacterial performance of the three-layer core-shell composite nanomaterial prepared in Example 11 of this invention.

[0043] Figure 13 The images show actual photos of the linear low-density polyethylene film (left) and nylon film (right) prepared by adding a three-layer core-shell structured composite nanomaterial in Example 12 of this invention.

[0044] Figure 14 Scanning electron microscope (SEM) (left) and transmission electron microscope (TEM) images of the cross-section of a linear low-density polyethylene film prepared by adding a three-layer core-shell structured composite nanomaterial in Example 12 of this invention.

[0045] Figure 15 This is a photograph of a melamine resin-based cutting board prepared by adding a three-layer core-shell structured composite nanomaterial in Example 12 of the present invention. Detailed Implementation

[0046] The technical solution of the present invention will be further explained and described below with reference to specific embodiments and accompanying drawings.

[0047] Example 1 (Different types of strong bases)

[0048] LiOH, NaOH, KOH were dissolved in 100 mL deionized water respectively to prepare 0.1% solution, then 1 g of 50 nm zinc oxide was added to each solution and ultrasonic treated for 10 min and stirred for 10 min to form stable dispersion. 1 g of hydroxypropyltrimethylammonium chloride chitosan was weighed and added to 100 mL deionized water to prepare 1% HACC aqueous solution. The above prepared nano zinc oxide dispersion was added dropwise into the hydroxypropyltrimethylammonium chloride chitosan aqueous solution, and 200 rpm magnetic stirring was used during the dropwise addition. After the dropwise addition was completed, it was placed at 25°C for 4 h. Then, the mixture was centrifuged at 10000 rpm and the precipitate was washed with deionized water three times. The separated material was dried and ground into uniform particles. The obtained product was analyzed by thermogravimetric analysis Figure 1 ) and the mass percentage of HACC in the product was calculated to be 3.7% (LiOH), 4.1% (NaOH), and 3.9% (KOH) respectively. The results show that the surface of the nano zinc oxide treated with strong alkali solution can be negatively charged, so that the positively charged hydroxypropyltrimethylammonium chloride chitosan can be adsorbed on the surface of the nanoparticles.

[0049] Example 2 (different types of nanoparticles)

[0050] 1 g of 20 nm copper, 30-50 nm copper oxide, 30-50 nm / 400-600 nm copper nanowires, 80 nm silver oxide, 50 nm silver particles, and 80 nm / 1200 nm silver nanowires were respectively added to 0.5% NaOH aqueous solution to form stable dispersion by ultrasonic treatment for 10 min. The above dispersion was added dropwise into 1% cetyltrimethylammonium chloride aqueous solution, and 200 rpm magnetic stirring was used during the dropwise addition. After the dropwise addition was completed, it was placed at 25°C for 4 h. Then, the mixture was centrifuged at 10000 rpm and the precipitate was washed with deionized water three times. The separated material was dried and ground into uniform particles. Thermogravimetric analysis was performed on the obtained composite nanoparticles, and the mass percentage of cetyltrimethylammonium chloride in the composite nanoparticles was calculated to be 4.7% (nano copper), 4.0% (nano copper oxide), 4.2% (copper nanowires), 3.6% (nano silver oxide), 3.3% (nano silver), and 3.2% (silver nanowires) respectively. The results show that the surface of these metal or metal oxide nanoparticles or nanowires treated with NaOH solution can carry a certain amount of negative charge, so that the positively charged cetyltrimethylammonium chloride can be adsorbed. The scanning electron microscope photos of the products prepared from nano copper oxide and nano silver particles and the particle size distribution measured by dynamic light scattering are shown in Figure 2 The transmission electron microscope photos of the products prepared from silver nanowires and copper nanowires are shown in Figure 3 Thus, it is shown that the surface of the metal or metal oxide nanoparticles or nanowires is covered with a layer of amorphous polymer.

[0051] Example 3 (different high molecular quaternary ammonium salt types)

[0052] 2 g of 50 nm silver particles were dispersed into 200 mL of 0.5% NaOH solution by ultrasonic treatment for 10 min to form a stable dispersion. 100 mL of 1% tetradecyl trimethyl ammonium chloride, polyhexamethylene biguanide hydrochloride were prepared. 100 mL of the above silver nanoparticle dispersion was added dropwise into the two kinds of high molecular quaternary ammonium salt aqueous solutions respectively, and a magnetic stirring device was used for stirring at 200 rpm during the dropwise addition. After the dropwise addition was completed, the mixture was allowed to stand at 25°C for 4 h. Then, the mixture was centrifuged at 10000 rpm and the precipitate was washed with deionized water three times. The separated material was dried and ground into uniform particles. The initial silver nanoparticles and their dispersion in water, and the two prepared products and their dispersion in water were compared, and the results showed that the two-layer core-shell structure nanomaterials were still well dispersed in water. The content of the high molecular quaternary ammonium salt in the two different composite products was calculated by thermogravimetric analysis, and the content of tetradecyl trimethyl ammonium chloride was 3.8% and the content of polyhexamethylene biguanide hydrochloride was 3.5%. The results showed that the positively charged high molecular quaternary ammonium salt was well adsorbed on the silver nanoparticles treated with NaOH solution. Figure 4

[0053] Example 4 (NaOH concentration 0.1%-4%)

[0054] NaOH solutions with concentrations of 0.1%, 0.2%, 0.6%, 0.8%, 1%, 2%, 3%, and 4% were prepared, and 20 mL of each was taken. Then, 0.2 g of 40 nm copper oxide nanoparticles was added to each, and a stable aqueous dispersion was formed by ultrasonic treatment for 10 min. Eight 50 mL of 1% hydroxypropyl trimethyl ammonium chloride chitosan aqueous solutions were prepared. The above nanometer copper oxide dispersions treated with different concentrations of NaOH were added dropwise into the hydroxypropyl trimethyl ammonium chloride chitosan, and a magnetic stirring device was used for stirring at 200 rpm during the dropwise addition. After the dropwise addition was completed, the mixture was allowed to stand at 25°C for 4 h. Then, the mixture was centrifuged at 10000 rpm and the precipitate was washed with deionized water three times. The separated material was dried and ground into uniform particles. The relationship between the content of hydroxypropyl trimethyl ammonium chloride chitosan (HACC) in the composite product and the concentration of NaOH used was calculated by thermogravimetric analysis, as shown in Figure 5

[0055] Example 5 (high molecular quaternary ammonium salt concentration)

[0056] ​​Take 1 g of nano copper oxide with a particle size of 40 nm, disperse in 100 mL of 0.6% NaOH solution with a mass concentration of 0.6%, and form a stable water dispersion liquid after ultrasonic treatment for 10 min. Prepare 10 mL of hydroxypropyltrimethylammonium chloride chitosan aqueous solution with a mass concentration of 0.1%, 0.2%, 0.5%, 1%, 1.5%, 2%, and 3%, respectively. Take 10 mL of nano copper oxide dispersion liquid and add it dropwise into the above hydroxypropyltrimethylammonium chloride chitosan aqueous solution with different concentrations, and stir with a magnetic stirring device at 200 rpm during the dropwise addition. After the dropwise addition is completed, stand at 25°C for 4 h. Then, centrifuge the mixed solution at 10000 rpm and wash the precipitate with deionized water for three times. After drying, the separated material is ground into uniform particles. The content of hydroxypropyltrimethylammonium chloride chitosan (HACC) in the composite product is calculated by thermogravimetric analysis, and the change is shown in Figure 6 The above data show that HACC has a good adsorption effect on nano copper oxide when the concentration of HACC in the solution is greater than 1%.

[0057] Example 6 (different standing time)

[0058] Add 2 g of nano zinc oxide (50 nm) into 200 mL of 0.2% NaOH aqueous solution and form a stable dispersion liquid after ultrasonic treatment for 10 min. Add the above dispersion liquid dropwise into 200 mL of 1% hydroxypropyltrimethylammonium chloride chitosan (HACC) aqueous solution, and stir with a magnetic stirring device at 200 rpm during the dropwise addition. After the dropwise addition is completed, stand at 25°C, and after 10 min, 30 min, 1 h, 2 h, 3 h, and 4 h, respectively, take 20 mL and centrifuge at 10000 rpm. Wash the precipitate with deionized water for three times, dry, and grind into uniform particles. The change of the content of HACC in the product with the standing time is shown in Figure 7 The results show that under the above conditions, the adsorption of HACC on nano zinc oxide reaches equilibrium basically in 30 min, and therefore the standing time is preferably more than 30 min.

[0059] Take 10 mL of the mixed liquid after adding the above nano zinc oxide dispersion liquid into the hydroxypropyltrimethylammonium chloride chitosan (HACC) aqueous solution, and stand in -25°C, -18°C, 0°C, 12°C, 30°C, and 40°C for 4 h. After taking out, the frozen samples are naturally melted at room temperature, and then the obtained dispersion liquid is centrifuged at 10000 rpm and washed with deionized water for three times. After drying, the precipitate is ground into uniform particles. The change of the content of HACC in the product with the standing temperature is shown in Figure 8 The above results show that low temperature is conducive to the adsorption of HACC, and therefore the standing temperature is preferably -18°C to 30°C.

[0060] Example 7 (different standing temperature)

[0061] Similar to Example 6, but using nano copper oxide (40 nm) instead of nano zinc oxide, 10 mL of the mixture after adding nano copper oxide dispersion dropwise into hydroxypropyltrimethylammonium chloride chitosan (HACC) aqueous solution, and then placing the mixture in -25°C, -18°C, 0°C, 12°C, 30°C, and 40°C for 4 h, respectively. The frozen samples were then placed in a room temperature environment for natural thawing, and then the obtained dispersion was centrifuged at 10,000 rpm, and the precipitate was washed with deionized water three times, dried, and ground to obtain a uniform powder. The content of HACC in the product was determined by thermogravimetric analysis, and the results were 5.4% (-25°C), 5.5% (-18°C), 5.4% (0°C), 5.3% (12°C), 4.3% (25°C, data from Example 5), 3.7% (30°C), and 2.4% (40°C), respectively. The above results are similar to those of Example 6, and also indicate that low temperature is conducive to the adsorption of HACC, and thus -18°C to 30°C is preferred.

[0062] Example 8 (three-layer core-shell structure)

[0063] 1 g of nano silver particles (50 nm) was dispersed into 100 mL of 1.0% by mass NaOH solution, and a stable dispersion was formed after ultrasonic treatment for 10 min. 100 mL of 1.0% by mass hydroxypropyltrimethylammonium chloride chitosan (HACC) aqueous solution was prepared. The nano silver particle dispersion was added dropwise into the hydroxypropyltrimethylammonium chloride chitosan (HACC) aqueous solution, and 200 rpm magnetic stirring was used during the dropwise addition. After the dropwise addition was completed, the mixture was placed at -18°C for 4 h. Then, the sample was placed in a room temperature environment for natural thawing, and then centrifuged at 10,000 rpm and washed with deionized water three times. The precipitate was dried and ground to obtain a uniform powder, and the obtained composite nanomaterial with a two-layer core-shell structure was about 1.05 g.

[0064] Take the above 1 g of two-layer core-shell structure composite nanomaterials into 100 mL of ethanol, and continue to stir for 10 min after ultrasonic treatment for 10 min. Respectively prepare 50 mL of alcohol soluble corn protein and alcohol soluble wheat protein solution with a mass concentration of 1% dissolved in ethanol. Take 50 mL of the above two-layer core-shell structure composite nanomaterials in ethanol, and add them dropwise into the alcohol soluble corn protein and alcohol soluble wheat protein solution under stirring. After the addition is completed, continue to stir for 4 h, and then centrifuge at 10000 rpm. The separated solids are washed with ethanol for 3 times and centrifuged. The obtained solid separates are dried, and their mass is measured by weighing method, which is 0.59 g and 0.61 g respectively. The results show that the alcohol soluble corn protein and alcohol soluble wheat protein have been effectively attached, and the alcohol soluble wheat protein is more easily attached to the surface of the two-layer core-shell structure composite nanomaterials. The starting nanosilver particles, two-layer core-shell structure composite nanomaterials, and the finally obtained three-layer core-shell structure composite nanomaterials are observed by scanning electron microscope, as shown in Figs. 1-3, which shows that the alcohol soluble corn protein or alcohol soluble wheat protein increases the particle size of the nanomaterials, and the size of the final material is 100-800 nm; combined with the microstructure of the two-layer core-shell structure composite nanomaterials shown in Figs. 4 and 5, it can be concluded that the final material is a three-layer core-shell structure composite nanomaterial. Figure 9 Figure 2 3

[0065] Example 9 (three-layer core-shell structure)

[0066] Take 0.50 g of the two-layer core-shell structure composite nanomaterials of tetradecyl trimethyl ammonium chloride / Ag, polyhexamethylene biguanide hydrochloride / Ag prepared in Example 3, and prepare their ethanol dispersion liquid of 50 mL by the method of Example 8, and then add them dropwise into 50 mL of alcohol soluble corn protein ethanol solution with a mass concentration of 1% dissolved in ethanol, respectively. After the addition is completed, continue to stir for 4 h, and then centrifuge at 10000 rpm. The separated solids are washed with ethanol for 3 times and centrifuged. The obtained solid separates are dried, and their mass is measured by weighing method, which is 0.57 g and 0.54 g respectively. The mass increase shows that the alcohol soluble corn protein can be further attached to the nanometer particles coated with high molecular quaternary ammonium salt, thereby forming a three-layer core-shell structure composite nanomaterial.

[0067] Example 10 (standing time, protein concentration, alcohol)

[0068] ​​​Take 5 g of zinc oxide nanoparticles (50 nm) dispersed into 500 mL of 0.1% mass concentration NaOH solution, and form a stable dispersion liquid by ultrasonic treatment for 10 min. Prepare 500 mL of 0.5% mass concentration aqueous solution of tetradecyl trimethyl ammonium chloride. Add the zinc oxide nanoparticle dispersion liquid into the aqueous solution of tetradecyl trimethyl ammonium chloride under stirring at 200 rpm, and let it stand at -18°C for 4 h after the addition is completed. Then, let the sample stand at room temperature, and centrifuge at 10,000 rpm after natural thawing. Wash the precipitate with deionized water for three times, and centrifuge to separate. Grind the separated material to uniformity, and obtain about 5.21 g of two-layer core-shell structure composite nanomaterials.

[0069] Take 1.00 g of the two-layer core-shell structure composite nanomaterials above, and add into 100 mL of ethanol. Ultrasonic treatment for 10 min, and continue stirring for 10 min. Prepare 100 mL of 1% mass concentration alcohol-soluble zein solution dissolved in ethanol. Add the prepared 100 mL two-layer core-shell structure composite nanomaterials dispersion liquid into the alcohol-soluble zein solution under stirring, and continue stirring for 10 min, 20 min, 40 min, 1 h, 2 h, 3 h, 4 h, and 6 h. Centrifuge the mixture at 10,000 rpm, and wash the separated solid with ethanol for three times. Dry the obtained solid, and measure the mass by weighing method. Plot the stirring time, as shown in FIG. 2. The results show that the alcohol-soluble zein is significantly adsorbed at 10 min, and basically reaches adsorption equilibrium after 4 h. Figure 10

[0070] Take 1.00 g of the two-layer core-shell structure composite nanomaterials above, and add into 100 mL of ethanol. Ultrasonic treatment for 10 min, and continue stirring for 10 min. Prepare 10 mL of alcohol-soluble zein solution dissolved in ethanol, and the mass concentration is 0.2%, 0.5%, 2%, 5%, and 7%. Add the two-layer core-shell structure composite nanomaterials dispersion liquid into the alcohol-soluble zein solution of different concentrations under stirring, and continue stirring for 4 h after the addition is completed. Then, centrifuge the mixture at 10,000 rpm, and wash the separated solid with ethanol for three times. Dry the obtained solid, and measure the mass by weighing method. Plot the stirring time, as shown in FIG. 3. The results show that the alcohol-soluble zein concentration is significantly adsorbed when it is higher than 0.5%, and the adsorption amount increases with the increase of the concentration, but basically does not change when it is greater than 5%. Therefore, the preferred alcohol-soluble protein concentration is 1%-5%. Figure 11

[0071] ​​The two-layer core-shell structure composite nanomaterial 0.10 g was added into 10 mL of other types of alcohol solvents, and the alcohols were methanol, n-propanol, isopropanol, propylene glycol, butanol, n-pentanol, and isoamyl alcohol, respectively. Then, the mixture was ultrasonically treated for 10 min and continuously stirred for 10 min. 10 mL of an alcohol-soluble corn protein solution with a mass concentration of 1% was prepared by dissolving the corn protein in the above-mentioned various alcohols. The prepared 10 mL of the two-layer core-shell structure composite nanomaterial dispersion was added dropwise into the corresponding alcohol-soluble corn protein solution under stirring. After the dropwise addition was completed, the mixture was continuously stirred for 4 h, and then centrifuged at 10,000 rpm. The separated solid was washed with the corresponding alcohol for 3 times and centrifuged. After drying, the mass of the obtained solid was determined by weighing, and the results were 0.11 g, 0.13 g, 0.12 g, 0.12 g, 0.11 g, 0.11 g, and 0.11 g, respectively. The results show that the selected alcohol-soluble corn protein solvents have little effect on the attachment of the alcohol-soluble corn protein, and the three-layer core-shell structure composite nanomaterials can be formed.

[0072] Example 11 (antibacterial property)

[0073] The two-layer core-shell structure composite nanomaterial prepared in Example 2 was added into 50 mL of ethanol at 0.5 g, and the mixture was ultrasonically treated for 10 min and continuously stirred for 10 min. 50 mL of an alcohol-soluble corn protein solution with a mass concentration of 1% was prepared by dissolving the corn protein in ethanol. The prepared various two-layer core-shell structure composite nanomaterial dispersions were added dropwise into the alcohol-soluble corn protein solution under stirring. After the dropwise addition was completed, the mixture was continuously stirred for 4 h, and then centrifuged at 10,000 rpm. The separated solid was washed with the corresponding alcohol for 3 times and centrifuged. The samples were sent to the third-party Jin Da Microbial Antimicrobial Testing Center for detection of the 48 h antibacterial and bacteriostatic properties according to the “Disinfection Technology Standard-2002 Edition 2.1.1 Disinfectant Microorganism Killing Test”. The results, as shown in Table 1, show that the bactericidal rate of the three-layer core-shell structure nanomaterial is greater than 99.9%. Figure 12

[0074] Example 12 (application)

[0075] ​Take 300 g of 80 nm silver nanoparticles into 30 L of 1% mass concentration NaOH solution, after stirring, form a stable dispersion by ultrasonic treatment for 10 min. Prepare 30 L of 1% mass concentration hydroxypropyltrimethylammonium chloride chitosan aqueous solution. Drop the silver nanoparticle dispersion into the hydroxypropyltrimethylammonium chloride chitosan aqueous solution under mechanical stirring, and after the dropwise addition is completed, stand at -18°C for 4 h. Then, let the sample stand at room temperature and naturally thaw, and then centrifuge at 10,000 rpm, and grind the separated material into a uniform two-layer core-shell structure composite nanomaterial about 314 g. Take 300 g and add it to 30 L of ethanol, ultrasonic treatment for 10 min and continue stirring for 10 min, then slowly drop 30 L of 1% mass concentration alcohol soluble zein solution dissolved in ethanol into a dropping funnel, continue stirring for 4 h after the dropwise addition is completed, and centrifuge the mixture at 10,000 rpm. The obtained solid separated material is dried to obtain a three-layer core-shell structure nanocomposite antibacterial material about 317 g.

[0076] Take 100 g of the above three-layer core-shell structure nanocomposite antibacterial material, respectively, and mix with 20 kg of commercially available linear low density polyethylene (LDPE) and nylon (PA) plastic rice, then extrude and pelletize by a twin-screw extruder, and then prepare PE film and nylon film by the corresponding method. The prepared physical photos are shown in Figure 13 As can be seen, the addition of the three-layer core-shell structure nanocomposite antibacterial material does not affect the transparency and appearance of the film. After the PE film is brittle fractured in liquid nitrogen, the cross section is observed by scanning electron microscopy, and the ultrathin section is observed by transmission electron microscopy after embedding with epoxy resin, as shown in Figure 14 As can be seen, the three-layer core-shell structure nanocomposite antibacterial material is dispersed relatively uniformly and almost no agglomeration.

[0077] Take 100 g of the above three-layer core-shell structure nanocomposite antibacterial material, add it to 10 kg of melamine resin raw material before curing, and disperse uniformly by high-speed stirring, then add 2 kg of hull powder filler to prepare a melamine resin-based cutting board by hot pressing method. The prepared product physical photos are shown in Figure 15 The above prepared sample is sent to the third party Jin Da Microbial Antimicrobial Testing Center for testing, and its antibacterial and bacteriostatic performance is tested according to "Disinfection Technology Standard - 2002 Edition 2.1.1 Disinfectant Microorganism Killing Test", and the cutting board prepared by adding the same dose of nanosilver and without adding the above three-layer core-shell structure nanocomposite antibacterial material is used as a control group. The test results are shown in Table 1 below:

[0078] Table 1

[0079]

[0080] The above results show that the pure melamine resin-based cutting board has no antibacterial property, the cutting board added with nano-silver has better antibacterial property but the antibacterial property is continuously reduced, and the cutting board added with the three-layer core-shell nano-composite antibacterial material has higher antibacterial property and continuously maintains at a high level.

[0081] The above merely describes preferred embodiments of the present application, and therefore cannot limit the scope of the present application, i.e. equivalent changes and modifications made according to the patent scope and content of the present application should still fall within the scope of the present application.

Claims

1. A three-layer core-shell structure nanocomposite antibacterial material, characterized in that: The core is coated with an antibacterial polymer material layer, and the antibacterial polymer material layer is coated with a prolamine layer. The core is metal nanoparticles or metal oxide nanoparticles with antibacterial properties, and the particle size is 20-400 nm; the metal nanoparticles are at least one of silver nanoparticles, silver nanowires, copper nanoparticles and copper nanowires, and the metal oxide nanoparticles are at least one of zinc oxide nanoparticles, silver oxide nanoparticles and copper oxide nanoparticles. The antibacterial polymer material layer is formed by self-assembly of the antibacterial polymer material on the core through electrostatic interaction, and the antibacterial polymer material is tetradecyl trimethyl ammonium chloride, hexadecyl trimethyl ammonium chloride or polyhexamethylene biguanide hydrochloride. The prolamine layer is formed by self-assembly of the prolamine on the antibacterial polymer material layer through hydrogen bonding and hydrophobic interaction. The preparation method comprises the following steps: (1) mixing the metal nanoparticles or metal oxide nanoparticles with a strong alkali aqueous solution to prepare a stable dispersion A; (2) adding the dispersion A to an aqueous solution of the antibacterial polymer material under stirring to prepare a dispersion B; (3) centrifuging the dispersion B after standing at -18-30℃ for 0.5-4 h to obtain a solid, and uniformly drying and grinding the solid to obtain a two-layer core-shell structure nanomaterial C; (4) adding the two-layer core-shell structure nanomaterial C to an alcohol solution of the prolamine under stirring to prepare a dispersion D; (5) centrifuging the dispersion D after stirring at room temperature for 10 min to 4 h to obtain a solid, and uniformly drying and grinding the solid to obtain the three-layer core-shell structure nanocomposite antibacterial material.

2. The three-layer core-shell structure nanocomposite antibacterial material according to claim 1, characterized in that: The prolamine is alcohol-soluble corn protein and / or alcohol-soluble wheat protein.

3. The three-layer core-shell structure nanocomposite antibacterial material according to claim 1 or 2, characterized in that: The content of the metal nanoparticles or metal oxide nanoparticles is 90-94 wt%, the content of the antibacterial polymer material is 0.5-6 wt%, and the content of the prolamine is 0.5-6 wt%.

4. The three-layer core-shell structure nanocomposite antibacterial material according to claim 1, characterized in that: The solute in the strong alkali aqueous solution is at least one of lithium hydroxide, sodium hydroxide and potassium hydroxide, and the concentration of the strong alkali aqueous solution is 0.2-2 wt%.

5. The three-layer core-shell structure nanocomposite antibacterial material according to claim 1, characterized in that: The concentration of the aqueous solution of the antibacterial polymer material is 0.2-2 wt%.

6. The three-layer core-shell structure nanocomposite antibacterial material according to claim 1, characterized in that: The alcohol solvent in the alcohol solution is at least one of methanol, ethanol, n-propanol, isopropanol, propylene glycol, butanol, n-pentanol and isopentanol, and the concentration of the prolamine in the alcohol solution is 1-5 wt%.

7. Use of the three-layer core-shell structure nanocomposite antibacterial material in any one of claims 1-6 in the preparation of antibacterial plastic products.

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