Novel preparation method of copper-doped chitosan composite titanium dioxide microspheres

Abstract

The invention discloses a novel preparation method of copper-doped chitosan composite titanium dioxide microspheres, and relates to the technical field of chemical industry for preparing antibacterial agents, modified nano titanium dioxide with amino loaded on the surface, a copper-doped reagent and chitosan are subjected to a Schiff base reaction under the action of an aldehyde crosslinking agent, and the copper-doped chitosan composite titanium dioxide microspheres are prepared. And crosslinking and curing to form the copper-doped chitosan composite titanium dioxide microspheres. According to the method, a catalyst does not need to participate, the preparation process is simple, the prepared composite microspheres are fused with various antibacterial agents, copper ions and a nano photocatalytic synergistic antibacterial mechanism are provided, inorganic matter is enveloped in microspheres with chitosan as a matrix, the composite microspheres have wider-spectrum, efficient and long-acting antibacterial performance, and the application scene is widened.

Description

Technical Field

[0001] The invention relates to the technical field of chemical engineering for preparing antimicrobial agents, in particular to a novel method for preparing copper-doped chitosan composite titanium dioxide microspheres. Background Art

[0002] Different antimicrobial agents have different antimicrobial action mechanisms and effectiveness against the same pathogen, and the same antimicrobial agent can also have different antimicrobial action mechanisms and inhibition ranges against different pathogens. Therefore, the development of compound antimicrobial technology will be an important development direction for the future preparation of new antimicrobial agents. Compound antimicrobial agents are simply mixed or combined by different types of antimicrobial agents. Through synergistic effects and complementary advantages, the performance and application range of the antimicrobial agent can be greatly improved. Compound antimicrobial agents have the advantages of low price, low dosage, high antimicrobial performance, and good stability. They have great commercial value and are also a common method in practical antimicrobial applications.

[0003] Chitosan is an alkaline high-molecular-weight biopolysaccharide and a functional, renewable biomaterial. It is made from chitin through a deacetylation reaction and has good biocompatibility and degradability. Its chemical and physical properties are stable, and it is non-toxic, harmless, and odorless. It has good affinity with organisms and has health benefits for the human body. Since chitosan molecules contain amino and hydroxyl functional groups, they can undergo a variety of chemical reactions, such as acylation, etherification, Schiff base reaction, esterification, oxidation, and cross-linking reactions. They can also be combined with other materials to produce functional composite materials, but these combinations and products are under continuous research and development.

[0004] Titanium dioxide has a variety of crystal configurations, mainly rutile, anatase, and brookite, which belong to the tetragonal system. Among them, anatase titanium dioxide has lattice defects and a relatively open structure. When its particle size is reduced to the nanometer scale, it has super strong oxidizing properties and can adsorb and decompose pathogens it contacts, showing excellent antibacterial effects. However, compared with single titanium dioxide antibacterial agents, composite antibacterial agents have better antibacterial properties, but the cross-linking effect of unmodified titanium dioxide and chitosan is poor, and the titanium dioxide surface needs to be amino-modified for further compounding with chitosan. In addition, titanium dioxide photocatalyst is an N-type semiconductor with a relatively wide band gap energy (Eg) of 3.2eV. When exposed to light radiation, it mainly absorbs short-wavelength ultraviolet light and absorbs very little visible light in the long-wave direction. In addition, the photogenerated electron-hole pairs generated are easy to recombine, and the quantum efficiency is low, so its large-scale industrial application is affected.

[0005] In the prior art, catalysts are generally added to prepare chitosan / titanium dioxide composites. However, the difficulty in separating and recovering the catalyst after the reaction, as well as the difficulty in dispersing nano-titanium dioxide in polymer materials, limit the preparation, performance, and application of the composites. Summary of the Invention

[0006] In order to solve the problems of the prior art, the purpose of the present invention is to overcome the shortcomings of the existing technology and provide a method for preparing copper-doped chitosan composite titanium dioxide microspheres. The modified nano-titanium dioxide with surface-loaded amino groups is cross-linked and solidified with a copper-doping reagent and chitosan under the action of an aldehyde cross-linking agent through a Schiff base reaction to form composite microspheres. The prepared copper-doped chitosan composite titanium dioxide microspheres have excellent stability and antibacterial durability.

[0007] One of the purposes of the present invention is to provide a technical solution for the preparation of copper-doped chitosan composite titanium dioxide microspheres, specifically:

[0008] A method for preparing copper-doped chitosan composite titanium dioxide microspheres comprises the following steps:

[0009] Prepare the first solution and the second solution respectively,

[0010] The second solution is added dropwise to the first solution, stirred evenly, and then an aldehyde crosslinking agent is added and stirred continuously. After the Schiff base reaction is completed, the solid phase material is the copper-doped chitosan composite titanium dioxide microspheres.

[0011] in,

[0012] The first solution is prepared by mixing modified nano-titanium dioxide with amino groups loaded on its surface, a copper doping agent, chitosan, glacial acetic acid, and deionized water, and uniformly mixing them by ultrasonic dispersion to obtain the first solution;

[0013] The second solution is prepared by mixing liquid paraffin and an emulsifier and stirring the mixture until uniform.

[0014] Preferably, the preparation method of the copper-doped chitosan composite titanium dioxide microspheres includes any of the following technical features:

[0015] A, the copper doping agent is one or more of copper sulfate, copper chloride, and copper nitrate;

[0016] B, the emulsifier is one or more of Span20, Span40, Span60, and Span80;

[0017] C, the aldehyde cross-linking agent is an aqueous solution of one or more of glyoxal, glutaraldehyde, and adipaldehyde with a mass fraction of 22 to 28 wt.%;

[0018] D. The chitosan has a deacetylation degree greater than or equal to 95% and a viscosity of 200 mPa·s to 400 mPa·s.

[0019] Further preferably, the preparation method of the copper-doped chitosan composite titanium dioxide microspheres comprises any of the following technical features:

[0020] A, the mass volume ratio of the modified nano-titanium dioxide, the copper doping reagent, the chitosan, the glacial acetic acid, and the deionized water is: (0.3-1) g: (0.3-1) g: (1-3) g: 2 mL: 98 mL;

[0021] B, the mass volume ratio of the liquid paraffin and the emulsifier is: (500-1000) mL: (60-100) g;

[0022] C, the volume ratio of the aldehyde cross-linking agent to the deionized water is: (15-30):98.

[0023] Preferably, the solid-liquid mixture obtained after the Schiff base reaction is subjected to solid-liquid separation, washing, and drying to obtain the dried copper-doped chitosan composite titanium dioxide microspheres.

[0024] Preferably, the preparation method of the modified nano titanium dioxide is:

[0025] 0.25-1.50 g of nano titanium dioxide, (6-18) mL of an amino-containing treatment agent and (50-150) mL of anhydrous ethanol are mixed, and the modified nano titanium dioxide is obtained after reaction, centrifugation, washing, drying and grinding.

[0026] Further preferably, the amino-containing treating agent is one or more of γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, N-β (aminoethyl)-γ-aminopropyltrimethoxysilane, N-β (aminoethyl)-γ-aminopropylmethyldimethoxysilane, N-β (aminoethyl)-γ-aminopropyltriethoxysilane, N-β (aminoethyl)-γ-aminopropylmethyldiethoxysilane, and aminoethylaminoethylaminopropyltrimethoxysilane.

[0027] More preferably, the nano-titanium dioxide has an anatase crystal form and an average particle size of 2 nm to 10 nm.

[0028] The second object of the present invention is to provide copper-doped chitosan composite titanium dioxide microspheres, which are prepared by the above-mentioned preparation method of copper-doped chitosan composite titanium dioxide microspheres.

[0029] The third object of the present invention is to provide an application of copper-doped chitosan composite titanium dioxide microspheres, wherein the copper-doped chitosan composite titanium dioxide microspheres are used to prepare antibacterial materials.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] The present invention provides a method for preparing copper-doped chitosan composite titanium dioxide microspheres. By using modified nano-titanium dioxide with abundant amino groups on the surface, the dispersibility of the nanoparticles is improved and the uniform mixing with chitosan dissolved in water is more favorable, without the need to add an additional emulsifying dispersant. In addition, after the amino groups are introduced, a Schiff base reaction can occur between the titanium dioxide and the chitosan during the cross-linking stage, that is, the titanium dioxide is not simply encapsulated in the chitosan, but is connected together by a strong imine bond. At the same time, the copper-doping reagent is a hydrophilic material that can be evenly distributed in the aqueous phase and has particle attraction with the acetyl groups, hydroxyl groups, etc. on the chitosan, and can ultimately be encapsulated in the microspheres. For these reasons, the release of titanium dioxide can be delayed during actual application, thereby improving the antibacterial durability.

[0032] The present invention provides a copper-doped chitosan composite titanium dioxide microsphere, in which a large amount of copper ions are doped inside the microspheres, mainly based on ion adsorption and cross-linking coating. The copper ions have excellent antibacterial effects. After being doped with copper ions, the absorption wavelength range defects of titanium dioxide are supplemented. When used in combination with chitosan, it can show excellent antibacterial properties under visible light conditions and dark conditions indoors and outdoors. At the same time, the copper ions are gradually released during the actual antibacterial process, which is also beneficial to prolonging the antibacterial durability.

[0033] The copper-doped chitosan composite titanium dioxide microspheres provided by the present invention integrate multiple types of antibacterial agents: first, the inorganic antibacterial agent titanium dioxide, whose antibacterial mechanism is mainly photocatalytic; second, the natural antibacterial agent chitosan contains abundant amino groups on its surface, which provides positive charge and can effectively inhibit bacterial growth; third, there is a synergistic antibacterial mechanism of copper ions and nano-photocatalysis, in which inorganic substances are encapsulated in the chitosan-based microspheres, and nanoparticles and metal ion antibacterial agents are slowly released, thereby enhancing the antibacterial properties in different scenarios.

[0034] In summary, the antibacterial mechanism of the present invention is diversified, the resistance effect is excellent, the antibacterial durability is good, and it has a broader spectrum, high efficiency and long-lasting antibacterial performance, which broadens the antibacterial application scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is a scanning electron microscope image of the copper-doped chitosan composite titanium dioxide microspheres prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0036] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0037] This specific embodiment provides a method for preparing copper-doped chitosan composite titanium dioxide microspheres.

[0038] Example 1

[0039] S1. Preparation of modified nano-titanium dioxide:

[0040] Add 100 mL of ethanol and 1 g of nano-titanium dioxide into a flask and ultrasonically disperse at room temperature for 10 min to obtain a nano-titanium dioxide dispersion. Then, add 12 mL of γ-aminopropyltriethoxysilane (APTES) into the flask and mix well.

[0041] The flask was placed in a constant temperature magnetic stirrer and subjected to magnetic stirring and condensation reflux at 95°C oil bath conditions for 12 hours to obtain a milky white solution. After cooling to room temperature, the solution was separated into solid and liquid using a high-speed centrifuge and washed three times with anhydrous ethanol. The solution was then vacuum dried at 60°C for 24 hours. The obtained dry powder was uniformly ground in a mortar to obtain a white modified nano-titanium dioxide powder.

[0042] S2. Preparation of copper-doped chitosan composite titanium dioxide microspheres:

[0043] 0.5 g of modified nano-titanium dioxide powder, 0.5 g of copper sulfate, 1 g of chitosan, 2 mL of glacial acetic acid, and 98 mL of deionized water were added to a beaker and ultrasonically dispersed for 30 min to obtain a first solution;

[0044] 800 mL of liquid paraffin and 64 g of emulsifier Span80 were added to the reactor and stirred at a constant temperature for 0.5 h to obtain a second solution;

[0045] Use a microsyringe to slowly add the first solution to the second solution, stir for 30 minutes, add 16 mL of glutaraldehyde, and continue stirring and reacting for 4 hours. After the reaction, use a high-speed centrifuge to separate the solid and liquid, wash with petroleum ether 3 times, wash with anhydrous ethanol 3 times, and then vacuum dry at 60°C for 24 hours. The obtained dry powder is evenly ground in a mortar to obtain copper-doped chitosan composite titanium dioxide microspheres.

[0046] In this embodiment, glutaraldehyde is an aqueous solution with a mass fraction of 25 wt.%.

[0047] In this embodiment, the parameters for solid-liquid separation by centrifugation are: 10000 r / min, 5 min.

[0048] Example 2

[0049] S1. Preparation of modified nano-titanium dioxide:

[0050] Add 100 mL of ethanol and 1 g of nano-titanium dioxide into a flask and disperse them ultrasonically at room temperature for 10 min to obtain a nano-titanium dioxide dispersion. Then add 12 mL of APTES into the flask and mix well.

[0051] The flask was placed in a constant temperature magnetic stirrer and subjected to magnetic stirring and condensation reflux at 95°C oil bath conditions for 12 hours to obtain a milky white solution. After cooling to room temperature, the solution was separated into solid and liquid using a high-speed centrifuge and washed three times with anhydrous ethanol. The solution was then vacuum dried at 60°C for 24 hours. The obtained dry powder was uniformly ground in a mortar to obtain a white modified nano-titanium dioxide powder.

[0052] S2. Preparation of copper-doped chitosan composite titanium dioxide microspheres:

[0053] 1 g of modified nano-titanium dioxide powder, 0.5 g of copper sulfate, 1 g of chitosan, 2 mL of glacial acetic acid, and 98 mL of deionized water were added to a beaker and ultrasonically dispersed for 30 min to obtain a first solution;

[0054] 800 mL of liquid paraffin and 64 g of emulsifier Span80 were added to the reactor and stirred at a constant temperature for 0.5 h to obtain a second solution;

[0055] Use a microsyringe to slowly add the first solution to the second solution, stir for 30 minutes, add 16 mL of glutaraldehyde, and continue stirring and reacting for 4 hours. After the reaction, use a high-speed centrifuge to separate the solid and liquid, wash with petroleum ether 3 times, wash with anhydrous ethanol 3 times, and then vacuum dry at 60°C for 24 hours. The obtained dry powder is evenly ground in a mortar to obtain copper-doped chitosan composite titanium dioxide microspheres.

[0056] In this embodiment, glutaraldehyde is an aqueous solution with a mass fraction of 25 wt.%.

[0057] In this embodiment, the parameters for solid-liquid separation by centrifugation are: 10000 r / min, 5 min.

[0058] Example 3

[0059] S1. Preparation of modified nano-titanium dioxide:

[0060] Add 100 mL of ethanol and 1 g of nano-titanium dioxide into a flask and disperse them ultrasonically at room temperature for 10 min to obtain a nano-titanium dioxide dispersion. Then add 12 mL of APTES into the flask and mix well.

[0061] The flask was placed in a constant temperature magnetic stirrer and subjected to magnetic stirring and condensation reflux at 95°C oil bath conditions for 12 hours to obtain a milky white solution. After cooling to room temperature, the solution was separated into solid and liquid using a high-speed centrifuge and washed three times with anhydrous ethanol. The solution was then vacuum dried at 60°C for 24 hours. The obtained dry powder was uniformly ground in a mortar to obtain a white modified nano-titanium dioxide powder.

[0062] S2. Preparation of copper-doped chitosan composite titanium dioxide microspheres:

[0063] 1.5 g of modified nano-titanium dioxide powder, 0.5 g of copper sulfate, 1 g of chitosan, 2 mL of glacial acetic acid, and 98 mL of deionized water were added to a beaker and ultrasonically dispersed for 30 min to obtain a first solution;

[0064] 800 mL of liquid paraffin and 64 g of emulsifier Span80 were added to the reactor and stirred at a constant temperature for 0.5 h to obtain a second solution;

[0065] Use a microsyringe to slowly add the first solution to the second solution, stir for 30 minutes, add 16 mL of glutaraldehyde, and continue stirring and reacting for 4 hours. After the reaction, use a high-speed centrifuge to separate the solid and liquid, wash with petroleum ether 3 times, wash with anhydrous ethanol 3 times, and then vacuum dry at 60°C for 24 hours. The obtained dry powder is evenly ground in a mortar to obtain copper-doped chitosan composite titanium dioxide microspheres.

[0066] In this embodiment, glutaraldehyde is an aqueous solution with a mass fraction of 25 wt.%.

[0067] In this embodiment, the parameters for solid-liquid separation by centrifugation are: 10000 r / min, 5 min.

[0068] Example 4

[0069] S1. Preparation of modified nano-titanium dioxide:

[0070] Add 100 mL of ethanol and 1 g of nano-titanium dioxide into a flask and disperse them ultrasonically at room temperature for 10 min to obtain a nano-titanium dioxide dispersion. Then add 12 mL of APTES into the flask and mix well.

[0071] The flask was placed in a constant temperature magnetic stirrer and subjected to magnetic stirring and condensation reflux at 95°C oil bath conditions for 12 hours to obtain a milky white solution. After cooling to room temperature, the solution was separated into solid and liquid using a high-speed centrifuge and washed three times with anhydrous ethanol. The solution was then vacuum dried at 60°C for 24 hours. The obtained dry powder was uniformly ground in a mortar to obtain a white modified nano-titanium dioxide powder.

[0072] S2. Preparation of copper-doped chitosan composite titanium dioxide microspheres:

[0073] 0.5 g of modified nano-titanium dioxide powder, 0.5 g of copper sulfate, 1.5 g of chitosan, 2 mL of glacial acetic acid, and 98 mL of deionized water were added to a beaker and ultrasonically dispersed for 30 min to obtain a first solution;

[0074] 800 mL of liquid paraffin and 64 g of emulsifier Span80 were added to the reactor and stirred at a constant temperature for 0.5 h to obtain a second solution;

[0075] Use a microsyringe to slowly add the first solution to the second solution, stir for 30 minutes, add 16 mL of glutaraldehyde, and continue stirring and reacting for 4 hours. After the reaction, use a high-speed centrifuge to separate the solid and liquid, wash with petroleum ether 3 times, wash with anhydrous ethanol 3 times, and then vacuum dry at 60°C for 24 hours. The obtained dry powder is evenly ground in a mortar to obtain copper-doped chitosan composite titanium dioxide microspheres.

[0076] In this embodiment, glutaraldehyde is an aqueous solution with a mass fraction of 25 wt.%.

[0077] In this embodiment, the parameters for solid-liquid separation by centrifugation are: 10000 r / min, 5 min.

[0078] Example 5

[0079] S1. Preparation of modified nano-titanium dioxide:

[0080] Add 100 mL of ethanol and 1 g of nano-titanium dioxide into a flask and disperse them ultrasonically at room temperature for 10 min to obtain a nano-titanium dioxide dispersion. Then add 12 mL of APTES into the flask and mix well.

[0081] The flask was placed in a constant temperature magnetic stirrer and subjected to magnetic stirring and condensation reflux at 95°C oil bath conditions for 12 hours to obtain a milky white solution. After cooling to room temperature, the solution was separated into solid and liquid using a high-speed centrifuge and washed three times with anhydrous ethanol. The solution was then vacuum dried at 60°C for 24 hours. The obtained dry powder was uniformly ground in a mortar to obtain a white modified nano-titanium dioxide powder.

[0082] S2. Preparation of copper-doped chitosan composite titanium dioxide microspheres:

[0083] 0.5 g of modified nano-titanium dioxide powder, 0.5 g of copper sulfate, 0.5 g of chitosan, 2 mL of glacial acetic acid, and 98 mL of deionized water were added to a beaker and ultrasonically dispersed for 30 min to obtain a first solution;

[0084] 800 mL of liquid paraffin and 64 g of emulsifier Span80 were added to the reactor and stirred at a constant temperature for 0.5 h to obtain a second solution;

[0085] Use a microsyringe to slowly add the first solution to the second solution, stir for 30 minutes, add 16 mL of glutaraldehyde, and continue stirring and reacting for 4 hours. After the reaction, use a high-speed centrifuge to separate the solid and liquid, wash with petroleum ether 3 times, wash with anhydrous ethanol 3 times, and then vacuum dry at 60°C for 24 hours. The obtained dry powder is evenly ground in a mortar to obtain copper-doped chitosan composite titanium dioxide microspheres.

[0086] In this embodiment, glutaraldehyde is an aqueous solution with a mass fraction of 25 wt.%.

[0087] In this embodiment, the parameters for solid-liquid separation by centrifugation are: 10000 r / min, 5 min.

[0088] It should be noted that, in the above five embodiments,

[0089] The selected nano titanium dioxide has an anatase crystal form and an average particle size of 2nm to 10nm.

[0090] The selected APTES is an amino-containing treatment agent. In actual implementation, it can also be replaced by other amino-containing treatment agents, such as γ-aminopropyltrimethoxysilane, N-β (aminoethyl)-γ-aminopropyltrimethoxysilane, N-β (aminoethyl)-γ-aminopropylmethyldimethoxysilane, N-β (aminoethyl)-γ-aminopropyltriethoxysilane, N-β (aminoethyl)-γ-aminopropylmethyldiethoxysilane, aminoethylaminoethylaminopropyltrimethoxysilane, etc., or two or more amino-containing treatment agents can be used together;

[0091] The copper sulfate used is a copper doping agent. In actual implementation, it can also be replaced by copper chloride, copper nitrate, etc., or two or more copper doping agents can be used together.

[0092] The selected chitosan has a deacetylation degree greater than or equal to 95% and a viscosity of 200 mPa·s to 400 mPa·s;

[0093] The selected Span80 is an emulsifier. In actual implementation, it can also be replaced by: Span20, Span40, Span60, etc., or two or more emulsifiers can be used together;

[0094] The selected glutaraldehyde is an aldehyde cross-linking agent. In actual implementation, it can also be replaced by glyoxal, adipaldehyde, etc., or two or more aldehyde cross-linking agents can be used together with a mass fraction of 22 to 28 wt.%.

[0095] Furthermore, the copper-doped chitosan composite titanium dioxide microspheres prepared above are further coated, specifically as follows:

[0096] A 5000 r / min high-speed shearing machine was used to mechanically stir and mix the aqueous acrylic resin, deionized water, and the copper-doped chitosan composite titanium dioxide microsphere antibacterial agent prepared above to form a uniform mixture, and then passed through a 1000-mesh sieve to remove large particle agglomerates;

[0097] Then add a small amount of dispersant, defoamer and leveling agent and other additives to the mixed liquid and continue to stir and mix evenly to obtain a slurry;

[0098] Take an appropriate amount of slurry and add it to the spray pot. Use the air flow spraying method to spray on the tinplate substrate. Control the spray gun pressure to 0.22-0.24MPa, the spraying angle to 45°, and the distance between the nozzle and the sprayed surface to be 100mm. Spray evenly and quickly place the sprayed sample in a dry place at room temperature to naturally cure for 24 hours.

[0099] Comparative Example Coating Preparation:

[0100] Chitosan was used as an antibacterial agent to replace the copper-doped chitosan composite titanium dioxide microspheres, and the coating was prepared in the same manner.

[0101] The antibacterial performance of the coating was tested at different pH values, and the test results are shown in Table 1. It can be seen that the copper-doped chitosan composite titanium dioxide microsphere antibacterial agent prepared in the present invention has excellent antibacterial performance and a wider pH application range than chitosan.

[0102] Table 1 Antibacterial test results of coating at pH = 5 to 9

[0103]

[0104]

[0105] According to the test method for antimicrobial properties of products specified in the National Standard of the People's Republic of China GB / T 21866-2008, "Determination of Antimicrobial Activity and Antimicrobial Effect of Antimicrobial Coatings (Paint Films)," the test strains were Gram-positive Staphylococcus aureus AS1.89, Gram-negative Escherichia coli AS1.90, and fungi Candida albicans. The antimicrobial properties of the coating samples obtained above were tested (pH = 7.0-7.2). The test results are shown in Table 2 below. As can be seen, the antimicrobial agent exhibited excellent antimicrobial properties when applied to acrylic coatings and tested in antimicrobial testing.

[0106] Table 2 Antibacterial test results of coating at pH = 7.0 to 7.2

[0107]

[0108]

[0109] Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is limited by the accompanying embodiments and their equivalents.

Claims

1. A method for preparing copper-doped chitosan composite titanium dioxide microspheres, characterized in that: The following steps are involved: Prepare the first solution and the second solution respectively, The second solution is added dropwise to the first solution, stirred evenly, and then an aldehyde crosslinking agent is added and stirred continuously. After the Schiff base reaction is completed, the solid phase material is the copper-doped chitosan composite titanium dioxide microspheres. in, The first solution is prepared by mixing modified nano-titanium dioxide with amino groups loaded on its surface, a copper doping agent, chitosan, glacial acetic acid, and deionized water, and uniformly mixing them by ultrasonic dispersion to obtain the first solution; The second solution is prepared by mixing liquid paraffin and an emulsifier and stirring the mixture until uniform.

2. The method for preparing copper-doped chitosan composite titanium dioxide microspheres according to claim 1, characterized in that: The preparation method of the copper-doped chitosan composite titanium dioxide microspheres includes any of the following technical features: A, the copper doping agent is one or more of copper sulfate, copper chloride, and copper nitrate; B, the emulsifier is one or more of Span20, Span40, Span60, and Span80; C, the aldehyde cross-linking agent is an aqueous solution of one or more of glyoxal, glutaraldehyde, and adipaldehyde with a mass fraction of 22 to 28 wt.%; D. The chitosan has a deacetylation degree greater than or equal to 95% and a viscosity of 200 mPa·s to 400 mPa·s.

3. The method for preparing copper-doped chitosan composite titanium dioxide microspheres according to claim 2, characterized in that: The preparation method of the copper-doped chitosan composite titanium dioxide microspheres includes any of the following technical features: A, the mass volume ratio of the modified nano-titanium dioxide, the copper doping reagent, the chitosan, the glacial acetic acid, and the deionized water is: (0.3-1) g: (0.3-1) g: (1-3) g: 2 mL: 98 mL; B, the mass volume ratio of the liquid paraffin and the emulsifier is: (500-1000) mL: (60-100) g; C, the volume ratio of the aldehyde cross-linking agent to the deionized water is: (15-30):

98.

4. The method for preparing copper-doped chitosan composite titanium dioxide microspheres according to claim 1, characterized in that: The solid-liquid mixture obtained after the Schiff base reaction is subjected to solid-liquid separation, washing, and drying to obtain the dried copper-doped chitosan composite titanium dioxide microspheres.

5. The method for preparing copper-doped chitosan composite titanium dioxide microspheres according to claim 1, characterized in that: The preparation method of the modified nano titanium dioxide is: 0.25-1.50 g of nano titanium dioxide, (6-18) mL of an amino-containing treatment agent and (50-150) mL of anhydrous ethanol are mixed, and the modified nano titanium dioxide is obtained after reaction, centrifugation, washing, drying and grinding.

6. The method for preparing copper-doped chitosan composite titanium dioxide microspheres according to claim 5, characterized in that: The amino-containing treating agent is one or more of γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, N-β (aminoethyl)-γ-aminopropyltrimethoxysilane, N-β (aminoethyl)-γ-aminopropylmethyldimethoxysilane, N-β (aminoethyl)-γ-aminopropyltriethoxysilane, N-β (aminoethyl)-γ-aminopropylmethyldiethoxysilane, and aminoethylaminoethylaminopropyltrimethoxysilane.

7. The method for preparing copper-doped chitosan composite titanium dioxide microspheres according to claim 1, characterized in that: The nano titanium dioxide has an anatase crystal form and an average particle size of 2nm-10nm.

8. A copper-doped chitosan composite titanium dioxide microsphere, characterized in that: The microspheres are prepared by the method for preparing copper-doped chitosan composite titanium dioxide microspheres according to any one of claims 1 to 7.

9. An application of copper-doped chitosan composite titanium dioxide microspheres, characterized in that: The copper-doped chitosan composite titanium dioxide microspheres described in claim 8 are used to prepare antibacterial materials.

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