Preparation method of polyvinyl alcohol graphite phase carbon nitride nanosheet photosensitive antibacterial paper

Abstract

The invention provides a preparation method of polyvinyl alcohol graphite phase carbon nitride nanosheet photosensitive antibacterial paper. The preparation method of the polyvinyl alcohol graphite phase carbon nitride nanosheet photosensitive antibacterial paper comprises the following steps: S1, weighing a proper amount of urea, tightly wrapping the urea with aluminum-foil paper, placing the wrapped urea in a tubular furnace, calcining under the protection of nitrogen, and naturally cooling to obtain faint yellow powdery graphite phase carbon nitride; s2, performing ultrasonic dispersion on 500mg of graphite phase carbon nitride in 500ml of water, then adding water and potassium persulfate, adjusting the pH to 12 by using a KOH solution, performing water bath stirring at 85 DEG C for 6 hours, then washing by using deionized water to be neutral, and performing freeze drying to obtain the graphite phase carbon nitride nanosheet. The preparation method of the polyvinyl alcohol graphite phase carbon nitride nanosheet photosensitive antibacterial paper has the advantages of being simple and convenient in process, excellent in antibacterial performance, environmentally friendly and capable of effectively prolonging the shelf life of products.

Description

Technical Field

[0001] The invention belongs to the technical field of photosensitive antibacterial packaging paper, and in particular relates to a method for preparing polyvinyl alcohol graphite phase carbon nitride nanosheet photosensitive antibacterial paper. Background Art

[0002] The food people use daily may be contaminated by microorganisms during processing, transportation, storage and sales, which increases economic losses, reduces food safety and quality, and threatens human health. Paper is made of natural plant fibers and is the most ideal packaging material. Most paper-based packaging on the market does not have antibacterial properties. In recent years, more and more logistics and transportation industries have experienced packaging materials being contaminated by microorganisms, so it is urgent to study a truly green and environmentally friendly antibacterial packaging paper.

[0003] Common antimicrobial agents include inorganic metal antimicrobial agents, organic antimicrobial agents, natural antimicrobial agents and photocatalytic antimicrobial agents. Due to their physical and chemical properties, organic and inorganic antimicrobial agents will accumulate harmful substances in animals and soil after degradation, making it difficult to achieve complete degradation. They may also cause bacterial resistance, secondary pollution, and potential safety hazards after long-term use. Among photocatalytic antimicrobial materials, inorganic photocatalytic materials have the advantages of low cost, significant effect, long effective period, and no drug resistance. As a new type of non-metallic photocatalytic material, graphite phase carbon nitride has the advantages of being non-toxic, environmentally friendly, and simple to manufacture. Its antibacterial activity is mainly manifested in the superoxide free radicals (·O2 - ), hydroxyl radicals (·OH) and other active oxygen species, which destroy the bacterial cell membrane and interrupt cell respiration, thus having long-lasting and broad-spectrum antibacterial properties.

[0004] Graphite phase carbon nitride has not yet been widely used in the field of packaging and transportation. The loading method and antibacterial properties of graphite phase carbon nitride are key factors affecting its development.

[0005] Therefore, it is necessary to provide a new method for preparing polyvinyl alcohol graphite phase carbon nitride nanosheet photosensitive antibacterial paper to solve the above technical problems. Summary of the invention

[0006] The technical problem solved by the invention is to provide a method for preparing polyvinyl alcohol graphite phase carbon nitride nanosheet photosensitive antibacterial paper which has simple process, excellent antibacterial performance, is green and environmentally friendly, and can effectively extend the shelf life of the product.

[0007] In order to solve the above technical problems, the present invention provides a method for preparing polyvinyl alcohol graphite phase carbon nitride nanosheet photosensitive antibacterial paper, comprising the following steps:

[0008] S1. Weigh an appropriate amount of urea, wrap it tightly with aluminum foil, place it in a tube furnace, calcine it under nitrogen protection, and cool it naturally to obtain a pale yellow powdery graphite phase carbon nitride;

[0009] S2. 500 mg of graphite carbon nitride was ultrasonically dispersed in 500 ml of water, and then water and potassium persulfate were added, the pH was adjusted to 12 with KOH solution, stirred in a water bath at 85°C for 6 h, washed with deionized water until neutral, and freeze-dried to obtain graphite carbon nitride nanosheets;

[0010] S3. ultrasonically dispersing graphite carbon nitride nanosheets in water, adding polyvinyl alcohol and glycerol, stirring in a water bath at 95° C. for 60 min, and cooling to obtain a photosensitive antibacterial emulsion;

[0011] S4. The antibacterial emulsion prepared in step 3 is coated on the base paper, and then dried in an oven at 60° C. for 2 h to obtain polyvinyl alcohol / graphite phase carbon nitride nanosheet photosensitive antibacterial paper.

[0012] As a further solution of the present invention, in step S1, the heating rate is 5°C / min and the calcination temperature is 550°C.

[0013] As a further solution of the present invention, in step S2, the graphite phase carbon nitride used is a block-like lamellar porous structure with a diameter of 1.5 to 3 μm, and in step S2, 5.6 g of potassium persulfate is added.

[0014] As a further solution of the present invention, in step S3, the prepared photosensitive nano antibacterial emulsion has a mass fraction of 0.1% to 0.9% of graphite phase carbon nitride nanosheets, a mass fraction of 6% of polyvinyl alcohol, and a mass fraction of 1.5% of glycerol.

[0015] As a further solution of the present invention, in the step S3, the diameter of the graphite phase carbon nitride nanosheets used is 90-320 nm and the thickness is 5-10 nm. In the step S3, the alcoholysis degree of the polyvinyl alcohol is 87.0-89.0%.

[0016] As a further solution of the present invention, in step S4, the base paper includes but is not limited to kraft paper for food packaging, oil-proof paper, and fresh-keeping absorbent paper. In step S4, the coating thickness of the antibacterial emulsion is 30 μm.

[0017] As a further solution of the present invention, urea is used as a precursor in step S1, so that the graphite phase carbon nitride prepared by thermal polymerization is simple in process and low in cost, and large-scale production of graphite phase carbon nitride can be achieved.

[0018] As a further solution of the present invention, polyvinyl alcohol is used as a film-forming agent in step S4 to evenly disperse graphite phase carbon nitride nanosheets in the emulsion. After coating on the surface of paper, excellent antibacterial properties can be obtained and the physical properties of the paper can be enhanced.

[0019] As a further solution of the present invention, in step S2, graphite phase carbon nitride is used as an antibacterial agent of a metal-free photocatalytic material, so that it has the characteristics of being green, environmentally friendly, non-toxic and pollution-free. It can photocatalytically produce active oxygen species under visible light, improve the antibacterial performance, and can effectively and widely resist bacteria for a long time.

[0020] Compared with the related art, the preparation method of polyvinyl alcohol graphite phase carbon nitride nanosheet photosensitive antibacterial paper provided by the present invention has the following beneficial effects:

[0021] 1. The present invention uses graphite phase carbon nitride, a metal-free photocatalytic material, as an antibacterial agent, which is green, environmentally friendly, non-toxic and pollution-free. It can photocatalytically produce active oxygen species under visible light and can effectively and widely resist bacteria for a long time;

[0022] 2. The present invention uses urea as a precursor and a thermal polymerization method to prepare graphite phase carbon nitride, which has a simple process and low cost, and can realize large-scale production of graphite phase carbon nitride;

[0023] 3. The present invention uses polyvinyl alcohol as a film-forming agent, and evenly disperses graphite phase carbon nitride nanosheets into the emulsion. After coating on the surface of paper, it can not only obtain excellent antibacterial properties, but also enhance the physical properties of the paper;

[0024] 4. The present invention uses paper as the substrate, and the coating solution is green and pollution-free. It is a truly degradable and environmentally friendly food packaging material with simple process and significant antibacterial effect. It can effectively inhibit the growth and reproduction of food pathogens and has potential commercial value in the packaging of fresh meat, fruits and vegetables and other products;

[0025] 5. The present invention uses a thermal oxidation exfoliation method to exfoliate the porous bulk graphite phase carbon nitride into nanosheets, which increases the specific surface area of ​​the material, promotes the separation of electron-hole pairs, and thus enhances the photocatalytic antibacterial properties of the graphite phase carbon nitride. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to facilitate understanding by those skilled in the art, the present invention is further described below with reference to the accompanying drawings.

[0027] Figure 1 It is a schematic diagram of the antibacterial rate of the polyvinyl alcohol / graphite phase carbon nitride nanosheet photosensitive antibacterial paper of the present invention. DETAILED DESCRIPTION

[0028] A method for preparing polyvinyl alcohol graphite phase carbon nitride nanosheet photosensitive antibacterial paper comprises the following steps:

[0029] S1. Weigh an appropriate amount of urea, wrap it tightly with aluminum foil, place it in a tube furnace, calcine it under nitrogen protection, and cool it naturally to obtain a pale yellow powdery graphite phase carbon nitride;

[0030] S2. 500 mg of graphite carbon nitride was ultrasonically dispersed in 500 ml of water, and then water and potassium persulfate were added, the pH was adjusted to 12 with KOH solution, stirred in a water bath at 85°C for 6 h, washed with deionized water until neutral, and freeze-dried to obtain graphite carbon nitride nanosheets;

[0031] S3. ultrasonically dispersing graphite carbon nitride nanosheets in water, adding polyvinyl alcohol and glycerol, stirring in a water bath at 95° C. for 60 min, and cooling to obtain a photosensitive antibacterial emulsion;

[0032] S4. The antibacterial emulsion prepared in step 3 is coated on the base paper, and then dried in an oven at 60° C. for 2 h to obtain polyvinyl alcohol / graphite phase carbon nitride nanosheet photosensitive antibacterial paper.

[0033] In the step S1, the heating rate is 5°C / min and the calcination temperature is 550°C.

[0034] In the step S2, the graphite phase carbon nitride used is a block-shaped lamellar porous structure with a diameter of 1.5 to 3 μm. In the step S2, 5.6 g of potassium persulfate is added.

[0035] In the step S3, the prepared photosensitive nano antibacterial emulsion has a mass fraction of 0.1% to 0.9% of graphite phase carbon nitride nanosheets, a mass fraction of 6% of polyvinyl alcohol, and a mass fraction of 1.5% of glycerol.

[0036] In the step S3, the diameter of the graphite phase carbon nitride nanosheets used is 90-320 nm and the thickness is 5-10 nm. In the step S3, the alcoholysis degree of the polyvinyl alcohol is 87.0-89.0%.

[0037] In the step S4, the base paper includes but is not limited to kraft paper for food packaging, oil-proof paper, and fresh-keeping absorbent paper. In the step S4, the coating thickness of the antibacterial emulsion is 30 μm.

[0038] In the step S1, urea is used as a precursor, so that the graphite phase carbon nitride prepared by the thermal polymerization method has a simple process and low cost, and can realize the large-scale production of graphite phase carbon nitride.

[0039] In step S4, polyvinyl alcohol is used as a film-forming agent to evenly disperse graphite-phase carbon nitride nanosheets in the emulsion, and after coating on the surface of paper, excellent antibacterial properties can be obtained and the physical properties of the paper can be enhanced.

[0040] In step S2, graphite phase carbon nitride is used as an antibacterial agent of a metal-free photocatalytic material, so that it has the characteristics of being green, environmentally friendly, non-toxic and pollution-free. It can photocatalytically produce active oxygen species under visible light, improve the antibacterial performance, and can effectively and widely fight bacteria for a long time.

[0041] Embodiment 1, a method for preparing polyvinyl alcohol graphite phase carbon nitride nanosheet photosensitive antibacterial paper, comprising the following steps:

[0042] (1) Under room temperature, 0.1% by mass of graphite carbon nitride nanosheets were ultrasonically dispersed in deionized water. After 30 minutes, 6% by mass of polyvinyl alcohol was added and stirred continuously to fully disperse the polyvinyl alcohol in the water.

[0043] (2) Then, stir in a water bath at 95°C for 60 min to fully dissolve the polyvinyl alcohol, and then cool naturally to room temperature to obtain an antibacterial coating emulsion;

[0044] (3) According to the above step S4, polyvinyl alcohol / graphite phase carbon nitride nanosheet photosensitive antibacterial paper was prepared, wherein the paper coating thickness was 30 μm, and the paper was dried in a blast oven at 60°C for 2 h. The antibacterial rate was Figure 1 .

[0045] The method for preparing the polyvinyl alcohol graphite phase carbon nitride nanosheet photosensitive antibacterial paper described in Example 1 has the following advantages:

[0046] Photosensitive antibacterial paper with good antibacterial effect was prepared by utilizing the excellent photocatalytic and antibacterial properties of graphite phase carbon nitride nanosheets.

[0047] The graphite phase carbon nitride nanosheets are fully dispersed in deionized water by ultrasonic dispersion, thereby improving the dispersibility and antibacterial effect of the nanosheets.

[0048] Polyvinyl alcohol is added into a dispersion of graphite phase carbon nitride nanosheets to prepare an antibacterial coating emulsion, which is then coated on the surface of paper to form a uniform antibacterial coating.

[0049] The coating thickness is 30μm, which can ensure the antibacterial effect without affecting the performance and printing performance of the paper.

[0050] Drying in a forced air oven at 60°C for 2 h can effectively promote the curing of the coating and improve its antibacterial properties.

[0051] The obtained polyvinyl alcohol graphite phase carbon nitride nanosheet photosensitive antibacterial paper has a high antibacterial rate and can meet the antibacterial needs of various application scenarios.

[0052] Embodiment 2, a method for preparing polyvinyl alcohol graphite phase carbon nitride nanosheet photosensitive antibacterial paper, comprising the following steps:

[0053] (1) Under room temperature, 0.3% by mass of graphite carbon nitride nanosheets were ultrasonically dispersed in deionized water. After 30 minutes, 6% by mass of polyvinyl alcohol was added and stirred continuously to fully disperse the polyvinyl alcohol in the water.

[0054] (2) Then, stir in a water bath at 95°C for 60 min to fully dissolve the polyvinyl alcohol, and then cool naturally to room temperature to obtain an antibacterial coating emulsion;

[0055] (4) According to the above step S4, polyvinyl alcohol / graphite phase carbon nitride nanosheet photosensitive antibacterial paper was prepared, wherein the paper coating thickness was 30 μm, and the paper was dried in a blast oven at 60°C for 2 h. The antibacterial rate was Figure 1 .

[0056] The method for preparing the polyvinyl alcohol graphite phase carbon nitride nanosheet photosensitive antibacterial paper has the following advantages:

[0057] The antibacterial effect and coating performance of the antibacterial paper can be improved by adjusting the mass fraction of graphite phase carbon nitride nanosheets (0.3%) and the mass fraction of polyvinyl alcohol (6%).

[0058] During the same preparation steps, the coating thickness is maintained at 30 μm, which can ensure the antibacterial effect without affecting the performance and printing performance of the paper.

[0059] Drying in a forced air oven at 60°C for 2 h can effectively promote the curing of the coating and improve its antibacterial properties.

[0060] The obtained polyvinyl alcohol graphite phase carbon nitride nanosheet photosensitive antibacterial paper has a high antibacterial rate and can meet the antibacterial needs of various application scenarios.

[0061] The antibacterial paper prepared by this method has the advantages of low cost, simple operation and good antibacterial effect.

[0062] Embodiment 3, a method for preparing polyvinyl alcohol graphite phase carbon nitride nanosheet photosensitive antibacterial paper, comprising the following steps:

[0063] (1) Under room temperature, 0.5% by mass of graphite carbon nitride nanosheets were ultrasonically dispersed in deionized water. After 30 minutes, 6% by mass of polyvinyl alcohol was added and stirred continuously to fully disperse the polyvinyl alcohol in the water.

[0064] (2) Then, stir in a water bath at 95°C for 60 min to fully dissolve the polyvinyl alcohol, and then cool naturally to room temperature to obtain an antibacterial coating emulsion;

[0065] (3) Prepare polyvinyl alcohol / graphite phase carbon nitride nanosheet photosensitive antibacterial paper according to step 4 above, wherein the paper coating thickness is 30 μm, and the paper is dried in a blast oven at 60°C for 2 h. The antibacterial rate is shown in Figure 1 .

[0066] The method for preparing the polyvinyl alcohol graphite phase carbon nitride nanosheet photosensitive antibacterial paper has the following advantages:

[0067] The antibacterial effect and coating performance of the antibacterial paper can be improved by adjusting the mass fraction of graphite phase carbon nitride nanosheets (0.5%) and the mass fraction of polyvinyl alcohol (6%).

[0068] During the same preparation steps, the coating thickness is maintained at 30 μm, which can ensure the antibacterial effect without affecting the performance and printing performance of the paper.

[0069] Drying in a forced air oven at 60°C for 2 h can effectively promote the curing of the coating and improve its antibacterial properties.

[0070] The obtained polyvinyl alcohol graphite phase carbon nitride nanosheet photosensitive antibacterial paper has a high antibacterial rate and can meet the antibacterial needs of various application scenarios.

[0071] It should be noted that the mass fraction in this method may be adjusted according to specific application scenarios and requirements in order to obtain the best antibacterial effect and coating performance.

[0072] Embodiment 4, a method for preparing polyvinyl alcohol graphite phase carbon nitride nanosheet photosensitive antibacterial paper, comprising the following steps:

[0073] (1) Under room temperature, 0.7% by mass of graphite carbon nitride nanosheets were ultrasonically dispersed in deionized water. After 30 minutes, 6% by mass of polyvinyl alcohol was added and stirred continuously to fully disperse the polyvinyl alcohol in the water.

[0074] (2) Then, stir in a water bath at 95°C for 60 min to fully dissolve the polyvinyl alcohol, and then cool naturally to room temperature to obtain an antibacterial coating emulsion;

[0075] (3) Prepare polyvinyl alcohol / graphite phase carbon nitride nanosheet photosensitive antibacterial paper according to step 4 above, wherein the paper coating thickness is 30 μm, and the paper is dried in a blast oven at 60°C for 2 h. The antibacterial rate is shown in Figure 1

[0076] The method for preparing the polyvinyl alcohol graphite phase carbon nitride nanosheet photosensitive antibacterial paper has the following advantages:

[0077] The antibacterial effect and coating performance of the antibacterial paper can be improved by adjusting the mass fraction of graphite phase carbon nitride nanosheets (0.7%) and the mass fraction of polyvinyl alcohol (6%).

[0078] During the same preparation steps, the coating thickness is maintained at 30 μm, which can ensure the antibacterial effect without affecting the performance and printing performance of the paper.

[0079] Drying in a forced air oven at 60°C for 2 h can effectively promote the curing of the coating and improve its antibacterial properties.

[0080] The obtained polyvinyl alcohol graphite phase carbon nitride nanosheet photosensitive antibacterial paper has a high antibacterial rate and can meet the antibacterial needs of various application scenarios.

[0081] It should be noted that the mass fraction in this method may be adjusted according to specific application scenarios and requirements in order to obtain the best antibacterial effect and coating performance.

[0082] Example 5, a method for preparing polyvinyl alcohol graphite phase carbon nitride nanosheet photosensitive antibacterial paper, comprising the following steps:

[0083] (1) Under room temperature, 0.9% by mass of graphite carbon nitride nanosheets were ultrasonically dispersed in deionized water. After 30 minutes, 6% by mass of polyvinyl alcohol was added and stirred continuously to fully disperse the polyvinyl alcohol in the water.

[0084] (2) Then, stir in a water bath at 95°C for 60 min to fully dissolve the polyvinyl alcohol, and then cool naturally to room temperature to obtain an antibacterial coating emulsion;

[0085] (3) Prepare polyvinyl alcohol / graphite phase carbon nitride nanosheet photosensitive antibacterial paper according to step 4 above, wherein the paper coating thickness is 30 μm, and the paper is dried in a blast oven at 60°C for 2 h. The antibacterial rate is shown in Figure 1 .

[0086] The method for preparing the polyvinyl alcohol graphite phase carbon nitride nanosheet photosensitive antibacterial paper has the following advantages:

[0087] The antibacterial effect and coating performance of the antibacterial paper can be improved by adjusting the mass fraction of graphite phase carbon nitride nanosheets (0.9%) and the mass fraction of polyvinyl alcohol (6%).

[0088] During the same preparation steps, the coating thickness is maintained at 30 μm, which can ensure the antibacterial effect without affecting the performance and printing performance of the paper.

[0089] Drying in a forced air oven at 60°C for 2 h can effectively promote the curing of the coating and improve its antibacterial properties.

[0090] The obtained polyvinyl alcohol graphite phase carbon nitride nanosheet photosensitive antibacterial paper has a high antibacterial rate and can meet the antibacterial needs of various application scenarios.

[0091] It should be noted that the mass fraction in this method may be adjusted according to specific application scenarios and requirements in order to obtain the best antibacterial effect and coating performance.

[0092] The polyvinyl alcohol / graphite phase carbon nitride nanosheet photosensitive antibacterial paper in the above examples 1 to 5 was selected, and the number of colonies grown was calculated after 48 hours of cultivation by plate counting method. The antibacterial rate was shown in FIG. Figure 1 .from Figure 1 The data show that the antibacterial paper coated with different proportions of graphite phase carbon nitride nanosheets exhibits antibacterial effects against Escherichia coli and Staphylococcus aureus, and the antibacterial rate increases with the increase in the amount of graphite phase carbon nitride nanosheets added. However, when the mass fraction of graphite phase carbon nitride nanosheets is 0.7%, an antibacterial effect of 99% can be achieved.

[0093] Graphite phase carbon nitride nanosheets have good antibacterial properties, and coating them on polyvinyl alcohol paper can prepare paper with antibacterial function.

[0094] Benefits of this antibacterial paper include:

[0095] according to Figure 1 According to the data, antibacterial paper coated with different proportions of graphite phase carbon nitride nanosheets showed antibacterial effects on Escherichia coli and Staphylococcus aureus, and the antibacterial rate increased with the increase of the amount of graphite phase carbon nitride nanosheets added. When the mass fraction of graphite phase carbon nitride nanosheets is 0.7%, an antibacterial effect of 99% can be achieved. This antibacterial property can effectively inhibit the growth of bacteria and reduce the risk of cross infection.

[0096] Antibacterial paper can be used in the fields of medical treatment, food packaging, daily necessities, etc. In the medical field, antibacterial paper can be used to prepare oral care products, medical dressings, etc. to effectively prevent infection. In the field of food packaging, antibacterial paper can be used to package fresh food to extend the shelf life of food. In the field of daily necessities, antibacterial paper can be used to prepare antibacterial wipes, antibacterial paper towels, etc., to provide a more hygienic use experience.

[0097] Polyvinyl alcohol paper is a degradable material with better environmental performance than traditional plastic paper. The addition of graphite phase carbon nitride nanosheets can provide antibacterial function, reduce dependence on traditional antibacterial agents, and thus reduce the impact on the environment.

[0098] In addition to the benefits mentioned above, polyvinyl alcohol / graphite phase carbon nitride nanosheet photosensitive antibacterial paper has the following benefits:

[0099] Graphite-phase carbon nitride nanosheets have long-lasting antibacterial properties and can form an antibacterial layer on the surface of paper to continuously inhibit the growth of bacteria, thereby achieving a long-lasting antibacterial effect. Compared with traditional antibacterial agents, the antibacterial effect of graphite-phase carbon nitride nanosheets is more lasting and not easily washed off or worn away.

[0100] Graphite phase carbon nitride nanosheets have low toxicity and good biocompatibility, and are highly safe for the human body and the environment. Therefore, the use of polyvinyl alcohol / graphite phase carbon nitride nanosheet photosensitive antibacterial paper will not cause harm to human health or pollution to the environment.

[0101] By adjusting the amount of graphite carbon nitride nanosheets added, the antibacterial properties of the antibacterial paper can be flexibly controlled. According to experimental results, when the mass fraction of graphite carbon nitride nanosheets is 0.7%, an antibacterial effect of 99% can be achieved. This adjustability allows the antibacterial paper to be prepared with different antibacterial properties according to different needs.

[0102] Although the 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 or applied directly or indirectly without departing from the principles and spirit of the present invention. In other related technical fields, the scope of the present invention is defined by the appended claims and their equivalents, which are equally included in the scope of patent protection of the present invention.

[0103] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A method for preparing polyvinyl alcohol graphite phase carbon nitride nanosheet photosensitive antibacterial paper, characterized in that: The following steps are involved: S1. Weigh an appropriate amount of urea, wrap it tightly with aluminum foil, place it in a tube furnace, calcine it under nitrogen protection, and cool it naturally to obtain a pale yellow powdery graphite phase carbon nitride; S2. 500 mg of graphite carbon nitride was ultrasonically dispersed in 500 ml of water, and then water and potassium persulfate were added, the pH was adjusted to 12 with KOH solution, stirred in a water bath at 85°C for 6 h, washed with deionized water until neutral, and freeze-dried to obtain graphite carbon nitride nanosheets; S3. ultrasonically dispersing graphite carbon nitride nanosheets in water, adding polyvinyl alcohol and glycerol, stirring in a water bath at 95° C. for 60 min, and cooling to obtain a photosensitive antibacterial emulsion; S4. The antibacterial emulsion prepared in step 3 is coated on the base paper, and then dried in an oven at 60° C. for 2 h to obtain polyvinyl alcohol / graphite phase carbon nitride nanosheet photosensitive antibacterial paper.

2. The method for preparing the polyvinyl alcohol graphite phase carbon nitride nanosheet photosensitive antibacterial paper according to claim 1, characterized in that: In the step S1, the heating rate is 5°C / min and the calcination temperature is 550°C.

3. The method for preparing the polyvinyl alcohol graphite phase carbon nitride nanosheet photosensitive antibacterial paper according to claim 1, characterized in that: In the step S2, the graphite phase carbon nitride used is a block-shaped lamellar porous structure with a diameter of 1.5 to 3 μm. In the step S2, 5.6 g of potassium persulfate is added.

4. The method for preparing the polyvinyl alcohol graphite phase carbon nitride nanosheet photosensitive antibacterial paper according to claim 1, characterized in that: In the step S3, the prepared photosensitive nano antibacterial emulsion has a mass fraction of 0.1% to 0.9% of graphite phase carbon nitride nanosheets, a mass fraction of 6% of polyvinyl alcohol, and a mass fraction of 1.5% of glycerol.

5. The method for preparing the polyvinyl alcohol graphite phase carbon nitride nanosheet photosensitive antibacterial paper according to claim 1, characterized in that: In the step S3, the diameter of the graphite phase carbon nitride nanosheets used is 90-320 nm and the thickness is 5-10 nm. In the step S3, the alcoholysis degree of the polyvinyl alcohol is 87.0-89.0%.

6. The method for preparing the polyvinyl alcohol graphite phase carbon nitride nanosheet photosensitive antibacterial paper according to claim 1, characterized in that: In the step S4, the base paper includes but is not limited to kraft paper for food packaging, oil-proof paper, and fresh-keeping absorbent paper. In the step S4, the coating thickness of the antibacterial emulsion is 30 μm.

7. The method for preparing the polyvinyl alcohol graphite phase carbon nitride nanosheet photosensitive antibacterial paper according to claim 1, characterized in that: In the step S1, urea is used as a precursor, so that the graphite phase carbon nitride prepared by the thermal polymerization method has a simple process and low cost, and can realize the large-scale production of graphite phase carbon nitride.

8. The method for preparing the polyvinyl alcohol graphite phase carbon nitride nanosheet photosensitive antibacterial paper according to claim 1, characterized in that: In step S4, polyvinyl alcohol is used as a film-forming agent to evenly disperse graphite-phase carbon nitride nanosheets in the emulsion, and after coating on the surface of paper, excellent antibacterial properties can be obtained and the physical properties of the paper can be enhanced.

9. The method for preparing the polyvinyl alcohol graphite phase carbon nitride nanosheet photosensitive antibacterial paper according to claim 1, characterized in that: In step S2, graphite phase carbon nitride is used as an antibacterial agent of a metal-free photocatalytic material, so that it has the characteristics of being green, environmentally friendly, non-toxic and pollution-free. It can photocatalytically produce active oxygen species under visible light, improve the antibacterial performance, and can effectively and widely fight bacteria for a long time.

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