Preparation method of antibacterial agent with synergistic effect of photocatalysis and natural antibacterial mechanism and application of antibacterial agent in latex paint

Abstract

The invention belongs to the technical field of functional coatings, and discloses a preparation method of an antibacterial agent with a synergistic effect of photocatalysis and a natural antibacterial mechanism and application of the antibacterial agent in latex paint. Under the illumination condition, zinc oxide and graphite phase carbon nitride heterojunction components in the antibacterial agent generate active oxygen, so that the antibacterial purpose is achieved; and under the dark condition, the natural chitosan bacteriostatic agent plays an antibacterial role. The preparation process of the zinc oxide and graphite phase carbon nitride-chitosan antibacterial agent comprises the following steps: 1) preparing a zinc oxide / graphite phase carbon nitride photocatalyst by calcining urea and a zinc acetate dihydrate precursor at high temperature; and 2) stirring the chitosan solution and a photocatalyst under an alkaline condition, centrifuging, washing and freeze-drying to obtain the zinc oxide / graphite phase carbon nitride-chitosan composite antibacterial agent. The composite antibacterial agent disclosed by the invention has the advantages of environmental protection, broad-spectrum antibacterial property, long-acting stability and the like, and can be widely applied to various latex paint products.

Description

Technical Field

[0001] The present invention belongs to the technical field of functional coatings, and particularly relates to a preparation method of an antibacterial agent of zinc oxide-doped graphitic carbon nitride-chitosan with the synergistic effect of photocatalytic oxidation and natural antibacterial mechanism and its application in latex paint. Background Art

[0002] With the improvement of living standards, people's understanding and requirements for the living environment are constantly increasing, and higher requirements are also put forward for the quality of the living environment. Bacteria and fungi are likely to grow on the exterior walls of buildings; interior walls, floors and other surfaces, especially in humid environments, which will not only affect people's health, but may also lead to the damage and aging of building materials. In addition, public places such as hospitals, schools, shopping malls, etc., due to the dense population, are more likely to become places for the spread of germs.

[0003] At present, there are many types of antibacterial agents on the market, but there are still many deficiencies. Traditional antibacterial agents mainly rely on inorganic antibacterial agents, such as copper ions. Although they have good antibacterial effects in the short term, they may have toxicity problems, and harmful substances may be released during long-term use, posing potential threats to human health and the environment. Some highly efficient antibacterial agents (such as nano silver) are difficult to be popularized and applied on a large scale due to the complex preparation process and being precious metals, resulting in high costs. In addition, there are also some organic antibacterial agents, such as dichlorophenol, although they have good antibacterial ability, they are not easily degraded in the environment and may interfere with the human endocrine system, posing potential threats to human health and the environment. In contrast, some natural antibacterial agents (such as chitosan and its derivatives) have good biocompatibility and low toxicity, and can maintain stable antibacterial properties under various environmental conditions. However, their antibacterial efficiency is sometimes not as high as that of organic antibacterial agents, and their stability is poor in extreme environments. And existing photocatalytic antibacterial agents often can only exhibit antibacterial properties in specific environments and may lose their antibacterial effects under other conditions (such as a lightless environment), restricting their application scope.

[0004] The relevant patents and technologies currently on the market also have certain limitations. For example, CN107722819A proposes a photocatalytic antibacterial coating and a preparation method thereof. The antibacterial coating involved in this patent can only work under light, and the antibacterial effect is obviously insufficient under weak light conditions or no light conditions. Compared with the broad-spectrum long-lasting antibacterial water-based environmentally friendly coating disclosed in CN111423804A, although it can achieve good antibacterial effects through nanosilver and nanozinc oxide under different lighting conditions, it relies on precious metals and nanomaterials, has high costs, and has relatively poor biocompatibility, which limits its large-scale application. Therefore, in order to meet the needs of maintaining stable antibacterial properties under a variety of environments while being environmentally friendly and economically beneficial, it is necessary to develop an environmentally friendly antibacterial agent that combines photocatalysis with the synergistic effects of natural antibacterial mechanisms. Summary of the invention

[0005] Based on the technical problems existing in the background technology, the present invention proposes an environmentally friendly antibacterial agent with synergistic effects of photocatalysis and natural antibacterial mechanism.

[0006] The technical solution of the present invention:

[0007] A method for preparing an antibacterial agent with synergistic effects of photocatalysis and natural antibacterial mechanism, comprising the following steps:

[0008] Step (1), mixing zinc salt and deionized water in proportion until the zinc salt is completely dissolved, adding a nitrogen-rich precursor to the above solution, mixing completely in a water bath at 60° C.-80° C., transferring the mixture to a crucible and cooling to room temperature; wrapping the crucible with tin foil and placing it in a muffle furnace, heating it to a calcination temperature and calcining it for 2-4 hours, and grinding it after cooling to obtain zinc oxide-doped graphite phase carbon nitride with antibacterial properties;

[0009] Step (2), dispersing the zinc oxide-doped graphite phase carbon nitride obtained in step (1) in a sodium hydroxide solution to obtain a solution a; completely dispersing the natural antibacterial agent in a 1 vol% (v / v) acetic acid solution to obtain a solution b; slowly dripping solution b dropwise into solution a to fully mix the two until the pH is 8-12 to obtain a mixed solution;

[0010] Step (3), after reacting the mixed solution in step (2) in a 60° C. water bath for 3-4 hours, centrifuging, washing and freeze-drying for 12-24 hours, grinding to obtain a composite antibacterial agent zinc oxide doped with graphite phase carbon nitride-chitosan, which is an antibacterial agent with synergistic effects of photocatalysis and natural antibacterial mechanism.

[0011] Preferably, in step (1), the nitrogen-rich precursor includes but is not limited to one or more of urea, melamine, thiourea, cyanamide, and dicyandiamide.

[0012] Further preferably, the nitrogen-rich precursor in step (1) is urea.

[0013] Preferably, in step (1), the zinc salt includes but is not limited to one or more of zinc acetate dihydrate, zinc nitrate hexahydrate, anhydrous zinc acetate, zinc chloride, and zinc sulfate;

[0014] More preferably, the zinc salt in step (1) is zinc acetate dihydrate.

[0015] Preferably, in step (1), the mass ratio of the nitrogen-rich precursor to the zinc salt is (10 - 15)∶(0.01 - 0.5).

[0016] More preferably, in step (1), the mass ratio of the nitrogen-rich precursor to the zinc salt is 10∶0.05.

[0017] Preferably, in step (1), the mass ratio of the zinc salt to deionized water is (0.01 - 0.5)∶(2 - 10).

[0018] More preferably, in step (1), the mass ratio of the zinc salt to deionized water is 0.05∶6.

[0019] Preferably, in step (1), the calcination temperature is 300 - 650 °C, and the temperature increase of the muffle furnace is set at 2 - 10 °C / min.

[0020] More preferably, in step (1), the calcination temperature is 550 °C, and the temperature increase of the muffle furnace is set at 2 °C / min.

[0021] Preferably, in step (2), the natural antibacterial agent includes but is not limited to one or more of chitosan and its derivatives, capsaicin and its derivatives, indole derivatives, and allicin.

[0022] More preferably, in step (2), the natural antibacterial agent is chitosan with a degree of deacetylation of 85% - 95%.

[0023] Preferably, in step (2), the mass ratio of the natural antibacterial agent to the photocatalytic antibacterial agent zinc oxide-doped graphitic carbon nitride is (2 - 0.5)∶1.

[0024] More preferably, in step (2), the ratio of the natural antibacterial agent to the photocatalytic antibacterial agent zinc oxide-doped graphitic carbon nitride is 2∶1.

[0025] Preferably, in step (2), the concentration of the sodium hydroxide solution is 0.1 M - 1 M, and the volume is controlled to make the pH of the mixed solution 8 - 12.

[0026] The present invention also claims the application of the antibacterial agent prepared by this method with the synergistic effect of photocatalysis and natural antibacterial mechanism in latex paint.

[0027] Advantages of the present invention:

[0028] 1. The present invention selects nitrogen-rich precursors and zinc salts as raw materials, and synthesizes zinc oxide-doped graphitic carbon nitride by calcination under specific conditions. These raw materials are widely sourced and low-cost, avoiding the high-cost problem caused by the use of precious metals. In particular, the heterojunction structure formed between zinc oxide and graphitic carbon nitride significantly enhances the photocatalytic efficiency and stability of the material. This heterojunction not only promotes charge separation, reduces the recombination of electron-hole pairs, but also broadens the light absorption range, enabling the composite material to exhibit higher photocatalytic activity under light illumination conditions.

[0029] 2. The present invention combines natural antibacterial components such as chitosan with photocatalytic antibacterial agents, making up for the deficiencies of photocatalytic antibacterial agents under dark conditions, so that the final product can maintain stable antibacterial performance under various light conditions (including sunlight, illumination light, and dark conditions). Moreover, the natural antibacterial agent has good biocompatibility and low toxicity, ensuring the safety of the product and making it suitable for a wide range of industrial and domestic application scenarios.

[0030] 3. The present invention can be widely applied to various application scenarios such as interior and exterior wall coatings for buildings, transportation coatings, medical facility coatings, food processing and storage coatings, and industrial equipment coatings, meeting the needs of modern society for a healthy environment. Due to the use of low-cost and easily accessible raw materials, and the simple preparation process, this antibacterial agent has significant economic advantages, facilitating large-scale production and promotion, and promoting the development of related industries. Description of the Drawings

[0031] Figure 1 It is a part of the composite catalyst of the present invention, showing the degradation rate diagrams of RhB by the photocatalytic antibacterial agent zinc oxide-doped graphitic carbon nitride (Example 1), zinc oxide (Comparative Example 1), and graphitic carbon nitride (Comparative Example 2) under sunlight.

[0032] Figure 2 It is a part of the composite catalyst of the present invention, showing the degradation rate diagrams of RhB by the photocatalytic antibacterial agent zinc oxide-doped graphitic carbon nitride, zinc oxide, and graphitic carbon nitride under illumination light.

[0033] Figure 3 It is a part of the composite antibacterial agent of the present invention, showing the antibacterial rate diagrams of Escherichia coli after co-culturing for 18 hours under multiple conditions (sunlight, illumination light, dark) by zinc oxide-doped graphitic carbon nitride-chitosan (Examples 2-3), chitosan (Comparative Example 3), and zinc oxide-doped graphitic carbon nitride (Comparative Example 4).

[0034] Figure 4The antibacterial rate diagrams of the composite antibacterial agent zinc oxide doped graphitic carbon nitride-chitosan (Example 3) of the present invention co-cultured with Escherichia coli for 24 hours and 48 hours under light and dark conditions respectively with three different brands of latex paints, namely Dulux, Camel, and Nippon (abbreviated as latex paint A, latex paint B, and latex paint C). Detailed implementation manners

[0035] The following further describes the detailed implementation manners of the present invention in conjunction with the attached drawings and technical solutions.

[0036] Example 1

[0037] A preparation method of the photocatalytic antibacterial agent zinc oxide doped graphitic carbon nitride includes the following steps:

[0038] Step (1): Dissolve 0.05 g of zinc acetate dihydrate in 6 ml of deionized water, add 10 g of urea, water bath at 80 °C until completely mixed, and transfer to a crucible to cool to room temperature; wrap the crucible with tin foil and place it in a muffle furnace. Under an air atmosphere, heat it to 550 °C at a rate of 2 °C / min, calcine for 2 h, cool and grind to obtain the photocatalytic antibacterial agent zinc oxide doped graphitic carbon nitride.

[0039] Comparative example 1

[0040] Place 10 g of zinc acetate dihydrate in a crucible, heat it to 550 °C at a rate of 2 °C / min under an air atmosphere, calcine for 2 h, cool and grind to obtain zinc oxide, and compare the ability of the material of the present invention to generate reactive oxygen for antibacterial.

[0041] Comparative example 2

[0042] Place 10 g of urea in a crucible, heat it to 550 °C at a rate of 2 °C / min under an air atmosphere, calcine for 2 h, cool and grind to obtain graphitic carbon nitride, and compare the ability of the material of the present invention to generate reactive oxygen for antibacterial.

[0043] Example 2

[0044] A preparation method of a composite antibacterial agent zinc oxide doped graphitic carbon nitride-chitosan with the synergistic effect of photocatalysis and natural antibacterial mechanism includes the following steps:

[0045] Step (1): Dissolve 0.05 g of zinc acetate dihydrate in 6 ml of deionized water, add 10 g of urea, water bath at 80 °C until completely mixed, and transfer to a crucible to cool to room temperature; wrap the crucible with tin foil and place it in a muffle furnace. Under an air atmosphere, heat it to 550 °C at a rate of 2 °C / min, calcine for 2 h, cool and grind to obtain the photocatalytic antibacterial agent zinc oxide doped graphitic carbon nitride.

[0046] Step (2): Disperse 0.2 g of the photocatalytic antibacterial agent zinc oxide doped with graphitic carbon nitride obtained in step (1) in 20 ml of sodium hydroxide solution, and stir for 15 min to obtain solution a; completely dissolve 0.4 g of chitosan in 100 ml of 1% (v / v) acetic acid solution to obtain solution b, and slowly add solution b dropwise to solution a until the pH reaches 10, and continuously stir for 30 min until fully mixed;

[0047] Step (3): After stirring the mixed solution obtained in step (2) in a water bath at 60 °C for 3 hours, a suspension is obtained. The suspension is centrifuged at a speed of 8000 r / min for 7 min, washed 2 - 3 times until the pH is 7, the precipitate is freeze-dried for 12 h, and ground to obtain the composite antibacterial agent zinc oxide doped with graphitic carbon nitride - chitosan.

[0048] Example 3

[0049] A preparation method of a composite antibacterial agent zinc oxide doped with graphitic carbon nitride - chitosan with the synergistic effect of photocatalysis and natural antibacterial mechanism, comprising the following steps:

[0050] Step (1): Dissolve 0.05 g of zinc acetate dihydrate in 6 ml of deionized water, add 10 g of urea, and heat in a water bath at 80 °C until completely mixed, and transfer to a crucible and cool to room temperature; wrap the crucible with tin foil and place it in a muffle furnace. Under an air atmosphere, heat it to 550 °C at a rate of 2 °C / min, calcine for 2 h, cool and grind to obtain the photocatalytic antibacterial agent zinc oxide doped with graphitic carbon nitride.

[0051] Step (2): Disperse 0.3 g of the photocatalytic antibacterial agent zinc oxide doped with graphitic carbon nitride obtained in step (1) in 20 ml of sodium hydroxide solution, and stir for 15 min to obtain solution a; completely dissolve 0.3 g of chitosan in 100 ml of 1% (v / v) acetic acid solution to obtain solution b, and slowly add solution b dropwise to solution a until the pH reaches 10, and continuously stir for 30 min until fully mixed;

[0052] Step (3): After stirring the mixed solution obtained in step (2) in a water bath at 60 °C for 3 hours, a suspension is obtained. The suspension is centrifuged at a speed of 8000 r / min for 7 min, washed 2 - 3 times until the pH is 7, the precipitate is freeze-dried for 12 h, and ground to obtain the composite antibacterial agent zinc oxide doped with graphitic carbon nitride - chitosan.

[0053] 10 mg of the photocatalytic antibacterial agent zinc oxide-doped graphitic carbon nitride obtained in Example 1 (zinc oxide obtained in Comparative Example 1 and graphitic carbon nitride obtained in Comparative Example 2) was added to 50 ml of a RhB solution (20 mg / l), and continuously stirred in the dark for 30 min to reach the adsorption-desorption equilibrium. A 300 W xenon lamp was used as the light source for testing the degradation performance to simulate sunlight, and a filter with a cut-off wavelength of 400 nm was added to simulate visible light. Through detection and analysis, the degradation rate of the photocatalytic antibacterial agent zinc oxide-doped graphitic carbon nitride could reach 99.72% under sunlight for 60 minutes and 98.71% under visible light for 60 minutes. The results are as Figure 1 , Figure 2 .

[0054] Examples 2-3, chitosan and the photocatalytic antibacterial agent zinc oxide-doped graphitic carbon nitride were selected as Comparative Example 3 and Comparative Example 4, and the antibacterial performance against Escherichia coli was tested for the group without antibacterial materials. The test method is as follows:

[0055] The Escherichia coli broth in the logarithmic phase was diluted with physiological saline to a bacterial concentration of 10 6 CFU / ml, and 20 mg of the antibacterial material was taken and dispersed in 50 ml of the diluted Escherichia coli broth. Magnetically stirred for 1 hour under dark conditions to reach the adsorption-desorption equilibrium. 15 W LED lamps with different wavelengths were used to simulate sunlight and visible light. After irradiation for 18 hours, samples were taken and coated, and cultured for 24 h, and the antibacterial rate was calculated by counting the number of colony forming units (CFU). Among them, the best antibacterial performance of Example 3 could reach 93%, which was about 50% higher than that of the comparative example. The results are as Figure 3 .

[0056] The bacteriostatic agent obtained in Example 3 was selected for testing, and its antibacterial performance against Escherichia coli in latex paint was tested. The test method is as follows: The antibacterial agent in Example 3 was mixed with different brands of latex paint in a certain proportion, and the antibacterial rates of the latex paint incorporated with the antibacterial agent against Escherichia coli were tested under light conditions and dark conditions after 24 hours and 48 hours. As a result, the antibacterial agent could reach an antibacterial rate of more than 70% in different types of latex paint. The results are as Figure 4 .

[0057] From the above test data, it can be seen that the antibacterial agent with the synergistic effect of photocatalysis and natural antibacterial mechanism of the present invention has good antibacterial performance, and has good antibacterial effects in different latex paints, and is suitable for a variety of latex paints.

[0058] The above is only the preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, makes equivalent substitutions or changes, and should be covered within the protection scope of the present invention.

Claims

1. A method for preparing an antibacterial agent with synergistic effects of photocatalysis and natural antibacterial mechanism, characterized in that: Here are the steps: Step (1), mixing zinc salt and deionized water in proportion until the zinc salt is completely dissolved, adding a nitrogen-rich precursor to the above solution, mixing completely in a water bath at 60°C-80°C, transferring to a crucible and cooling to room temperature; wrapping the crucible with tin foil and placing it in a muffle furnace, heating to the calcination temperature and calcining for 2-4 hours, and grinding after cooling, Zinc oxide-doped graphite-phase carbon nitride with antibacterial properties is obtained; Step (2), dispersing the zinc oxide-doped graphite phase carbon nitride obtained in step (1) in a sodium hydroxide solution to obtain a solution a; The natural antibacterial agent is completely dispersed in a 1 vol% acetic acid solution to obtain a solution b; the solution b is slowly dripped into the solution a drop by drop to fully mix the two until the pH is 8-12 to obtain a mixed solution; Step (3), after reacting the mixed solution in step (2) in a 60° C. water bath for 3-4 hours, centrifuging, washing and freeze-drying for 12-24 hours, grinding to obtain a composite antibacterial agent zinc oxide doped with graphite phase carbon nitride-chitosan, which is an antibacterial agent with synergistic effects of photocatalysis and natural antibacterial mechanism.

2. The preparation method according to claim 1, characterized in that: In step (1), The nitrogen-rich precursor includes, but is not limited to, one or a mixture of two or more of urea, melamine, thiourea, cyanamide, and dicyandiamide; The nitrogen-rich precursor is urea; The zinc salt includes, but is not limited to, one or a mixture of two or more of zinc acetate dihydrate, zinc nitrate hexahydrate, anhydrous zinc acetate, zinc chloride, and zinc sulfate; The zinc salt is zinc acetate dihydrate.

3. The preparation method according to claim 2, characterized in that: In step (1), The mass ratio of nitrogen-rich precursor to zinc salt is (10-15): (0.01-0.5); The mass ratio of zinc salt to deionized water is (0.01-0.5):(2-10).

4. The preparation method according to claim 1, characterized in that: In step (1), The calcination temperature is 300-650°C, and the temperature rise of the muffle furnace is set at 2-10°C / min.

5. The preparation method according to claim 1, characterized in that: In step (2), The natural antibacterial agent includes but is not limited to one or a mixture of two or more of chitosan and its derivatives, capsaicin and its derivatives, indole derivatives, and allicin.

6. The preparation method according to claim 5, characterized in that: In step (2), The mass ratio of the natural antibacterial agent to the zinc oxide-doped graphite phase carbon nitride is (2-0.5):1; The concentration of the sodium hydroxide solution is 0.1M-1M.

7. Use of the antibacterial agent with synergistic photocatalytic and natural antibacterial mechanisms obtained by the preparation method according to any one of claims 1 to 6 in latex paint.

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