Self-cleaning food packaging film based on nano-photocatalyst, preparation method and application

Abstract

This invention discloses a self-cleaning food packaging film based on a nano-photocatalyst, its preparation method, and its application, belonging to the field of packaging films. The method first prepares m-WO3 containing mesopores and oxygen vacancies. 3‑x Then, using Nb2AlC as the raw material, selective etching was performed with hydrofluoric acid solution, followed by intercalation with tetramethylammonium hydroxide solution, resulting in monolayer or few-layer Nb2CT. x Amino functionalization yields N-Nb2CT x Finally, the ternary composite material NTW was prepared by hydrothermal synthesis. Under the catalysis of acetic acid, the aldehyde and amino groups underwent Schiff base condensation, allowing TpPa-1 to grow on N-Nb2CT. x On nanosheets, a multilayer self-cleaning antibacterial food packaging film was prepared using carboxymethyl chitosan, pullulan, and polyvinyl alcohol as the matrix, NTW photocatalyst as the antibacterial additive, and ferulic acid as the crosslinking agent, via a layer-by-layer casting method. The self-cleaning food packaging film based on the nanophotocatalyst prepared in this invention exhibits excellent antibacterial properties, providing a feasible solution for the research of biodegradable food packaging materials.

Description

Technical Field

[0001] This invention belongs to the field of packaging films, specifically relating to a method for preparing and applying a self-cleaning food packaging film based on a nano-photocatalyst. Background Technology

[0002] Food waste and food safety issues caused by foodborne pathogens cannot be ignored. Using packaging films is one of the effective ways to prevent food from being contaminated by foodborne pathogens. However, traditional petroleum-based plastic packaging materials have problems such as being non-degradable and non-renewable, having poor antibacterial properties, and releasing harmful components during production, posing a huge threat to the natural environment and human health. Therefore, developing a new type of biodegradable, renewable, and self-cleaning food packaging film has promising application prospects.

[0003] Carboxymethyl chitosan (CMCS) is an amphoteric derivative of chitosan, rich in COOH and NH2, COOH (or COO2) - ) and NH2 (or NH 3+ The hydrophilicity of the side groups and the hydrophobicity of the main chain in CMCS give it amphiphilic properties. CMCS is obtained by introducing carboxymethyl groups into the amino, primary, and secondary hydroxyl sites of the glucosamine unit. CMCS possesses excellent film-forming properties, biodegradability, and biocompatibility. However, its mechanical properties, water-blocking properties, and antibacterial properties are relatively poor, limiting its application in the food industry. To overcome the shortcomings of CMCS forming films alone and obtain better functional properties, introducing other biodegradable materials to form composite films with CMCS is a feasible method. Pullulan (PUL) is a colorless, tasteless, water-soluble extracellular polysaccharide produced by *Brachystomata buddingii*. It is formed by glucose linked by two α-1,4 glycosidic bonds to form maltotriose, which is then polymerized into a chain through α-1,6 glycosidic bonds to form polymaltotriose, thus forming the linear structure of PUL. The flexibility of the PUL structure comes from its unique linkage mode, and this structure can increase its water solubility, thereby giving PUL good film-forming properties. PUL film also has the advantages of being food safe, biodegradable, and having good gas barrier properties. Polyvinyl alcohol (PVA) is a water-soluble vinyl polymer prepared by the hydrolysis of polyvinyl acetate. It is non-toxic, transparent, biocompatible, and biodegradable, and has been widely used in food packaging and other fields.

[0004] Biodegradable materials have attracted much attention due to their wide availability, renewability, and biodegradability; however, their performance as packaging materials still needs improvement. Compared with traditional petroleum-based packaging materials, biodegradable materials have weaker mechanical properties and higher water vapor permeability, making them susceptible to lipid oxidation and microbial corrosion, thus reducing the performance of food packaging and affecting its shelf life. To address the drawbacks of biodegradable food packaging materials, physical, chemical, and biochemical modifications are applied during or after film formation. The addition of active substances such as crosslinking agents and antibacterial agents is a primary method. Crosslinking agents can overcome the inherent defects of biodegradable food packaging films in terms of mechanical properties, barrier properties, and thermal stability, while enhancing their hydrophobicity. This is related to the interaction between the crosslinking agent and different molecular chains, forming a stronger three-dimensional network. Ferulic acid (FA) is a low-toxicity phenolic acid widely found in the plant kingdom, possessing antioxidant, antibacterial, anticancer, cholesterol-lowering, and crosslinking functions. It can be absorbed by the intestines and excreted through urine, posing little threat to the human body. Furthermore, ferulic acid has a crosslinking effect on biomacromolecules such as polysaccharides and proteins. Therefore, ferulic acid can be used as a chemical crosslinking agent to improve the performance of food packaging films. Besides chemical crosslinking, physical crosslinking is also a commonly used method to improve film performance. Repeated freeze-thaw cycles of PVA aqueous solution can significantly improve some of its physical and mechanical properties without affecting the film's biocompatibility, biodegradability, and non-toxicity. Since microbial growth and metabolism can lead to food spoilage, adding antibacterial agents to the composite film matrix is ​​an effective way to improve the preservation performance of composite films. Since the 20th century, photocatalysis technology has developed rapidly, with nano-photocatalytic materials, represented by titanium dioxide, being widely used and achieving significant results. As a novel composite photocatalytic material, N-

[0005] Nb2CT x / TpPa-1 / m-WO 3-x (NTW) has a killing effect on foodborne pathogens under light conditions. Due to the small size of nanomaterials, they are difficult to recycle and reuse in practical applications, often resulting in resource waste. Summary of the Invention

[0006] The purpose of this invention is to address the problems existing in the prior art by providing a method for preparing and applying a self-cleaning food packaging film based on a nano-photocatalyst. A novel biodegradable and renewable self-cleaning food packaging film is prepared by introducing nano-photocatalyst materials onto a film substrate. Layer-by-layer assembly (LbL) is a method for manufacturing multilayer films and is considered a viable approach to achieve better film performance by utilizing the unique properties of the substrate. Using CMCS, PUL, and PVA as substrates, NTW nano-photocatalyst as an antibacterial additive, and FA as a crosslinking agent, we prepared a multilayer antibacterial food packaging film using a layer-by-layer casting method, aiming to achieve long-term food storage and promote the development of biodegradable food packaging films.

[0007] The complete technical solution of this invention includes:

[0008] A self-cleaning food packaging film based on a nano-photocatalyst, characterized in that,

[0009] The self-cleaning food packaging film has a multi-layer structure, including CMCS / FA film, PUL / NTW film and PVA film arranged in sequence;

[0010] The PUL / NTW membrane comprises PUL and NTW, wherein NTW is N-Nb2CT. x / TpPa-1 / m-WO 3-x Composite nano-photocatalytic materials;

[0011] In the XRD pattern, TpPa-1 shows a sharp peak at 5.1° and a broad peak at 26.6°, corresponding to (100) and (001) respectively;

[0012] In SEM tissue images, Nb2CT x The structure is an accordion shape composed of nanosheets, N-Nb2CT x TpPa-1 nanostructures were grown in situ on the surface of nanosheets. The TpPa-1 nanostructures were rod-shaped aggregates with an overall flower-like appearance.

[0013] WO 3-x It is shaped like a sea urchin composed of nanosheets, and TpPa-1 and m-WO 3-x A core-shell structure was formed, in which m-

[0014] WO 3-x It is the core, and TpPa-1 is the shell.

[0015] Furthermore, in the XRD pattern of the self-cleaning food packaging film, CMCS has a diffraction peak at 20.1°, PUL has an amorphous structure and a bun-shaped peak appears at around 19.6°, and PVA film has semi-crystalline properties and a sharp peak appears at around 19.5°.

[0016] Furthermore, in the self-cleaning food packaging film based on nano-photocatalysts, the loading content of 0 < NTW ≤ 0.2%.

[0017] Furthermore, intermolecular interactions exist between the NTW nanocomposite material and the film matrix, but no covalent bonds are formed between the CMCS / FA film, the PUL / NTW film, and the PVA film.

[0018] A method for preparing a self-cleaning food packaging film based on a nano-photocatalyst is disclosed. The method is a layer-by-layer assembly process. First, a nano-photocatalyst is prepared via hydrothermal synthesis as an antibacterial agent, and FA is used as a crosslinking agent. Using CMCS, PUL, and PVA as substrates, the packaging film is prepared by layer-by-layer casting. The specific preparation steps are as follows:

[0019] (1) Preparation of WO3 containing mesoporous structures and oxygen vacancies: First, a certain mass of tungsten hexachloride (WCl6) was added to a certain volume of anhydrous ethanol under ultrasonic conditions to form a clear yellow solution. Then, a certain volume of acetylacetone was added, and the yellow solution immediately turned deep blue. A certain mass of mesoporous silica (KIT-6) was slowly added, and after 2 hours of continuous ultrasonication, the solution was transferred to a high-pressure reactor. The reaction was carried out in a 150℃ oven for 24 hours. After cooling to room temperature, the product was washed sequentially with deionized water and ethanol, and then dried in a 60℃ oven. The resulting solid product was soaked in a 10% hydrofluoric acid solution for 6 hours to remove KIT-6, then separated and centrifuged, and washed with deionized water until the pH was neutral. The sample was washed 3-5 times with anhydrous methanol, centrifuged, and dried in a 70℃ oven for 18 hours to obtain WO3 (m-WO3) containing mesoporous structures and oxygen vacancies. 3-x );

[0020] Furthermore, in step (1), the mass of WCl6 is 0.4-1.2g, the volume of anhydrous ethanol is 50-150mL, the volume of acetylacetone is 0.6-1.8mL, and the mass of KIT-6 is 0.2-0.6g.

[0021] (2) Aminated Nb2CT x Preparation: A certain mass of Nb₂AlC was added to a certain volume of 40% hydrofluoric acid solution and stirred at 55°C. After the reaction was complete, the prepared solid was washed repeatedly with deionized water and centrifuged until the pH of the solution was nearly neutral. The precipitate after centrifugation was dried and the product was collected. Then, it was dispersed in a certain volume of 26% tetramethylammonium hydroxide solution at room temperature for a period of time to form a suspension. The suspension was centrifuged and washed with deionized water to remove residual tetramethylammonium hydroxide solution. The obtained solid was then redispersed in deionized water and sonicated for 1 hour. After sonication, it was centrifuged at low speed, washed, and dried to obtain a monolayer or few-layer Nb₂CT.x A certain mass of Nb2CT will be obtained. x Dissolve in deionized water and stir for 10 min. Then add a certain volume of ethanol and stir continuously. Next, add a certain volume of triethoxysilane and stir the mixture under a nitrogen atmosphere for 24 h. The resulting product is washed three times with ethanol to remove unreacted triethoxysilane and three times with deionized water to remove ethanol. The precipitate is freeze-dried to obtain aminated Nb2CT. x (N-Nb2CT x );

[0022] Furthermore, in step (2), the mass of Nb2AlC is 1-3g, the volume of hydrofluoric acid solution is 60-180mL, the volume of tetramethylammonium hydroxide solution is 5-15mL, and the mass of Nb2CT is... x The mass is 1-3g, the volume of ethanol is 3-9g, and the volume of triethoxysilane is 200-600μL.

[0023] (3) Preparation of composite photocatalyst NTW: A certain mass of N-Nb2CT was prepared. x and m-WO 3-x A mixture of N,N-dimethylformamide (DMF) and a certain volume of pyrogallol and p-phenylenediamine, a certain volume of mesitylene and 1,4-dioxane were added sequentially. An aqueous solution of acetic acid was then added as a catalyst. The mixture was sonicated for 30 min to ensure uniform dispersion, then transferred to a high-pressure reactor and bubbled with nitrogen for 10 min. The reactor was then placed in an oven at 120°C for 72 h. After cooling to room temperature, the mixture was washed three times with 1,4-dioxane and ethanol, centrifuged, and finally freeze-dried for 12 h to obtain NTW.

[0024] Furthermore, in step (3), N-Nb2CT x The mass is 27–81 g, m-WO 3-x The mass is 90–270 g, the volume of DMF is 3–9 mL, the mass of trialdehyde pyrogallol is 63–189 mg, the mass of p-phenylenediamine is 48–144 mg, the volumes of mesitylene and 1,4-dioxane are both 1.5–4.5 mL, the volume of acetic acid aqueous solution is 0.5–1.5 mL, and the volume concentration is 3 M.

[0025] (4) Preparation of film-forming solution: First, a certain mass of CMCS and glycerol were dispersed in a certain volume of deionized water and stirred continuously until the CMCS was completely dissolved. Then, a certain mass of FA was dissolved in the above solution to prepare the CMCS / FA solution. Next, a certain mass of PUL and glycerol were added to a certain volume of deionized water and stirred continuously at 50°C until the PUL was completely dissolved. Then, a certain mass of NTW was dissolved in the above solution to obtain the PUL / NTW solution. Finally, a certain mass of PVA and glycerol were dispersed in a certain volume of deionized water and stirred continuously at 95°C until the PVA was completely dissolved to obtain the PVA solution.

[0026] Furthermore, in step (4), the mass of CMCS is 2-6g, the mass of glycerol is 1-3g, the volume of deionized water is 100-300mL, the mass of FA is 0.5-1.5g, the mass of PUL is 2-6g, the masses of NTW are 0.05-0.15g, 0.1-0.3g, 0.15-0.45g and 0.2-0.6g respectively, and the mass of PVA is 2-6g.

[0027] (5) Preparation of multilayer food packaging film: A certain volume of CMCS / FA solution was poured into a circular mold with a diameter of 10 mm. After the film solution was evenly leveled, it was dried in an oven at 40°C until a firm but still tacky surface was obtained. Then, a certain volume of PUL / NTW solution was poured onto the top of the first layer to form the inner layer, and then dried in an oven at 40°C. Subsequently, a certain volume of PVA solution was poured into the circular mold again, and the film was repeatedly frozen and thawed 8 times in a freezer at -80°C. Then, the outer layer was formed using the same drying method, thus obtaining the multilayer food packaging film.

[0028] Furthermore, in step (5), the volume of the CMCS / FA solution is 15 mL, the volume of the PUL / NTW solution is 15 mL, and the volume of the PVA solution is 15 mL.

[0029] The self-cleaning food packaging film based on nano-photocatalysts consists of CMCS / PUL / PVA / FA loaded with different amounts of NTW, and is named LbL-CPP / FA, LbL-CPP / FA-0.05, LbL-CPP / FA-0.1, LbL-CPP / FA-0.15 and LbL-CPP / FA-0.2, respectively.

[0030] The antibacterial application of the self-cleaning food packaging film based on nano-photocatalyst in meat preservation.

[0031] The application of the self-cleaning food packaging film based on nano-photocatalysts, wherein the bacteria are Staphylococcus aureus, Listeria monocytogenes, Escherichia coli, and Salmonella.

[0032] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0033] (1) This invention uses nano-photocatalysts as novel bactericidal active substances, which can effectively utilize sunlight. The synthesis method is simple and easy to operate. It can promote carrier transfer and inhibit photogenerated electron-hole pair recombination, providing a new idea for the design of novel antibacterial agents.

[0034] (2) The present invention generates a stronger and more tightly bound three-dimensional network structure through the synergistic effect of chemical cross-linking and physical cross-linking, thereby enhancing the mechanical properties of packaging materials.

[0035] (3) This invention selects biodegradable CMCS, PUL, and PVA as matrix materials, and uses a layer-by-layer casting method.

[0036] A composite multilayer film was prepared using this method, providing a feasible solution for the research of biodegradable food packaging materials and contributing to food safety. Attached Figure Description

[0037] Figure 1 The image shows the XRD pattern of the NTW composite material prepared according to this invention.

[0038] Figure 2 This is a SEM image of the NTW composite material prepared according to the present invention.

[0039] Figure 3 (a) is the XRD pattern of the self-cleaning food packaging film prepared according to the present invention. Figure 3 (b) is the FTIR image of the self-cleaning food packaging film prepared according to the present invention.

[0040] Figure 4 This is a SEM image of the self-cleaning food packaging film prepared according to the present invention.

[0041] Figure 5 The image shows the photocatalytic bactericidal performance of the NTW composite material prepared in this invention. Figure 5 (a) is a graph showing the sterilization efficiency. Figure 5 (b) is a cell density map.

[0042] Figure 6 This is a photocatalytic sterilization diagram of the self-cleaning food packaging film prepared according to the present invention. Figure 6 (a) is a graph showing the sterilization efficiency. Figure 6 (b) is a cell density map. Detailed Implementation

[0043] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are merely illustrative and are not intended to limit this application.

[0044] The present invention will now be described in detail with reference to embodiments and accompanying drawings. However, it should be understood that the embodiments and drawings are for illustrative purposes only and do not constitute any limitation on the scope of protection of the present invention. All reasonable modifications and combinations included within the inventive spirit of the present invention fall within the scope of protection of the present invention.

[0045] Example 1

[0046] A method for preparing a nano-photocatalyst, comprising the following steps:

[0047] (1) First, a certain mass of WCl6 was added to 50 mL of anhydrous ethanol under ultrasonic conditions to form a clear yellow solution. Then, 0.6 mL of acetylacetone was added, and the yellow solution immediately turned deep blue. 0.2 g of KIT-6 was slowly added, and after 2 hours of continuous ultrasonication, the solution was transferred to a high-pressure reactor. The reaction was carried out in a 150°C oven for 24 hours. After cooling to room temperature, the product was washed sequentially with deionized water and ethanol, and then dried in a 60°C oven. The resulting solid product was soaked in a 10% hydrofluoric acid solution for 6 hours to remove KIT-6, then separated and centrifuged, and washed with deionized water until the pH was neutral. The sample was washed 3-5 times with anhydrous methanol, centrifuged, and dried in a 70°C oven for 18 hours to obtain m-WO3. 3-x .

[0048] (2) 1 g of Nb₂AlC powder was added to 120 mL of 40% hydrofluoric acid solution and stirred at 55 °C. After the reaction was complete, the prepared solid was washed and centrifuged repeatedly with deionized water until the pH of the solution was nearly neutral. The precipitate after centrifugation was dried and the product was collected. Then, it was dispersed in 5 mL of 26% tetramethylammonium hydroxide solution at room temperature for a period of time to form a suspension. The suspension was centrifuged and washed with deionized water to remove residual tetramethylammonium hydroxide solution. The obtained solid was then redispersed in deionized water and sonicated for 1 h. After sonication, it was centrifuged at low speed, washed, and dried to obtain a monolayer or few-layer Nb₂CT. x The resulting single-layer or few-layer Nb2CT x Dissolve in 12 g of deionized water and stir for 10 min. Then add 3 g of ethanol and stir continuously. Next, add 200 μL of triethoxysilane and stir the mixture under a nitrogen atmosphere for 24 h. The resulting product is washed three times with ethanol to remove unreacted triethoxysilane, and then washed three times with deionized water to remove ethanol. The precipitate is freeze-dried to obtain N-Nb2CT. x。

[0049] (3) 27mg N-Nb2CT x and 90mg m-WO 3-xAdd 63 mg of trialdehyde pyrogallol and 48 mg of p-phenylenediamine, 1.5 mL of mesitylene and 1.5 mL of 1,4-dioxane to a reaction vessel containing 3 mL of DMF, then add 0.5 mL of 3 M acetic acid aqueous solution as a catalyst. Sonicate the mixture for 30 min to ensure uniform dispersion, then transfer it to a high-pressure reactor and bubble it with nitrogen for 10 min. Place the reactor in an oven at 120 °C for 72 h. After the reactor cools to room temperature, wash three times with 1,4-dioxane and ethanol, centrifuge, and finally freeze-dry for 12 h to obtain NTW.

[0050] Figure 1 The image shows the XRD pattern of the NTW composite material prepared according to this invention. (Nb2CT) x The low-angle (002) peak in the XRD pattern is a characteristic peak of MXene, which confirms that Nb2CT... x Successful synthesis. TpPa-1 shows a sharp peak at 5.1° and a broad peak at 26.6°, corresponding to (100) and (001) respectively. In m-WO 3-x The XRD pattern is consistent with the standard XRD pattern (JCPDS No. 89-1287).

[0051] Figure 2 This is a SEM image of the NTW composite material prepared according to the present invention. (Nb2CT) x Structure such as Figure 2 As shown in figure a, the peeling of the Al layer transforms the dense layered structure into an accordion shape. Figure 2 b shows that TpPa-1 exhibits a rod-like aggregated morphology, with large clusters resembling a flower shape. For example... Figure 2 As shown in c, the KIT-6 sample exhibits spherical particles. m-WO 3-x The shape is like Figure 2 As shown in diagram d, it is composed of many nanosheets, forming a structure similar to a sea urchin. Figure 2 As shown in e, the morphology of NT is N-Nb2CT. x TpPa-1 nanoflowers were grown in situ on the surface of nanosheets. Figure 2 As can be seen from f, TpPa-1 and m-WO in the ternary composite material NTW 3-x A core-shell structure was formed, in which m-WO 3-x It is the core, and TpPa-1 is the shell.

[0052] Example 2

[0053] A method for preparing a self-cleaning food packaging film based on a nano-photocatalyst, comprising the following steps:

[0054] First, 2g of CMCS and 1g of glycerol were dispersed in 100mL of deionized water and stirred continuously until the CMCS was completely dissolved. Then, 0.5g of FA was dissolved in the above solution to prepare a CMCS / FA solution. Next, 2g of PUL and 1g of glycerol were added to 100mL of deionized water and stirred continuously at 50℃ until the PUL was completely dissolved. Then, different concentrations of NTW were dissolved in the above solution to obtain a PUL / NTW solution. Finally, 2g of PVA and 1g of glycerol were dispersed in 100mL of deionized water and stirred continuously at 95℃ until the PVA was completely dissolved to obtain a PVA solution. 15mL of the CMCS / FA solution was cast into a circular mold with a diameter of 10mm. After the film solution was evenly leveled, it was dried in an oven at 40℃ until a firm but still viscous surface was obtained. Then, 15mL of PUL / NTW solution was cast on top of the first layer to form the inner layer, and then dried in an oven at 40℃. Subsequently, 15 mL of PVA solution was poured into a circular mold again, and the mold was repeatedly frozen and thawed 8 times in a -80°C freezer. The outer layer was then formed using the same drying method, thus obtaining a multi-layer food packaging film.

[0055] Figure 3 (a) is the XRD pattern of the self-cleaning food packaging film prepared according to the present invention. CMCS shows a diffraction peak at 20.1°, mainly related to the crystalline region formed by strong physical forces between polymer chains. The PUL film shows a peak around 19.6°, indicating that PUL has an amorphous structure. The PVA film shows a sharp peak around 19.5°, indicating semi-crystalline properties. When the three film solutions are blended, the crystallinity of CPP decreases significantly compared to PVA. This is because the interweaving of CMCS, PUL, and PVA molecules disrupts the original arrangement pattern, leading to a decrease in crystallinity. The crystallinity of LbL-CPP film increases slightly, possibly because the PVA layer retains an independent crystalline structure. Furthermore, the crystallinity of the film increases significantly after adding FA as a crosslinking agent and repeatedly freezing and thawing the PVA layer eight times. This is related to the chemical crosslinking effect of FA and the physical crosslinking formed by repeated freeze-thaw cycles of PVA, which enhances the intermolecular interactions. The diffraction peak of LbL-CPP / FA-0.2 at around 20° increases slightly, indicating enhanced hydrogen bonding forces and suggesting good biocompatibility between the film and the NTW nanomaterial.

[0056] Figure 3 (b) is the FTIR image of the self-cleaning food packaging film prepared according to the present invention. The CMCS film at 3433 cm⁻¹... -1 The peak at 1611 cm⁻¹ is attributed to the stretching vibrations of -NH₂ and -OH. -1 and 1409cm -1 The peak at 1308 cm⁻¹ is attributed to the stretching vibrations of both the asymmetric and symmetric C=O groups. -1The absorption peak at 1118 cm⁻¹ is due to the stretching vibration of -CN-. -1 and 1047cm -1 The absorption peaks are all due to the stretching vibration of -CO-. For PUL membranes, the peak at 3430 cm⁻¹ is... -1 The broad absorption peaks around 1640 cm⁻¹ are due to the stretching vibration of -OH groups. -1 The peak observed at 3406 cm⁻¹ is due to the C=C vibration of the benzene skeleton. In the infrared spectrum of PVA, this peak is at 3406 cm⁻¹. -1 The frequency band at 1471 cm⁻¹ is attributed to the stretching vibration of -OH and the hydrogen bonds formed between -OH groups. -1 The peaks at 1112 and 1047 cm⁻¹ correspond to the bending vibration of -OH. -1 The absorption band at this point is attributed to the stretching vibration of C-OH. CPP films prepared by the blending method show an absorption band at 3436 cm⁻¹. -1 The absorption peak at this point is attributed to the stretching vibrations of -OH and -NH. Furthermore, PUL is located at 1640 cm⁻¹. -1 The peak shifted to 1629 cm. -1 The presence of this feature indicates an interaction between the three substances, but no covalent bonds are formed. The infrared spectrum of the LbL-CPP film is similar to that of the CPP film. After adding FA as a crosslinking agent, the 1648 cm⁻¹... -1 1404cm -1 and 1044cm -1 The absorption peak shifted to 1642 cm⁻¹ -1 1403cm -1 and 1041cm -1 This indicates that FA, as a crosslinking agent, may cause free amino and hydroxyl groups in the film to interact. With the addition of NTW, the structure of the composite film did not change, but the characteristic absorption band of the film shifted slightly to a lower wavenumber, indicating that there is an intermolecular interaction between the NTW nanocomposite material and the film matrix.

[0057] Figure 4 This is a SEM image of the self-cleaning food packaging film prepared according to the present invention. Figure 4 As shown in (a), a small number of aggregates are observed on the surface of the CMCS film. Figure 4 (bc) shows that the surfaces of PUL and PVA films are relatively smooth. Figure 4 (d) It can be seen that the CPP blend film exhibits an uneven and rough surface. This is due to the microphase separation between CMCS, PUL, and PVA, which retains the characteristics of these three components after mechanical blending. Figure 4 As shown in (e), the surface of the film prepared by the LbL method is smoother than that of the CPP film. Figure 4 (f) indicates that FA, as a crosslinking agent, increases the compatibility of the film. And... Figure 4As shown in (g), NTW, added as an antibacterial additive to the intermediate layer, did not affect the surface morphology of the film. Furthermore, the cross-sections of the different films also showed significant differences. Figure 4 (h) shows that the cross-section of the film prepared by the blending method is continuous and compact. For example... Figure 4 As shown in (i), the films prepared by the LbL method, similar to those prepared by the blending method, did not exhibit delamination. The difference lies in the presence of a boundary line at the junction of PVA and PUL, while no boundary line was observed at the junction of PUL and CMCS. This may be because both PUL and CMCS are polysaccharides and possess good compatibility. Figure 4 As can be seen from (j) and 4(k), after adding FA as a crosslinking agent and NTW as an antibacterial agent, the cross-section of the film did not change, only the thickness increased.

[0058] Application Example 1:

[0059] The nano-photocatalyst obtained in Example 1 above is applied to photocatalytic sterilization.

[0060] Staphylococcus aureus frozen at -80℃ was activated on LB agar using the streak method. Single colonies were picked and inoculated into LB broth at 37℃ and 120 rpm for 12 h. The suspension was then diluted with 0.85% physiological saline solution to obtain a bacterial suspension concentration of approximately 10. 7 CFU / mL. The sterilization test procedure is as follows: 50 mg of the nano-photocatalyst was placed in 50 mL of bacterial suspension, and then irradiated with a 300 W xenon lamp equipped with a UV cutoff filter (λ>420 nm) for 30 min, with samples taken every 5 min. 100 μL of each suspension from different irradiation times was spread onto freshly prepared LB agar plates and incubated at 37℃ for 24 h. Each group was tested in triplicate, and the bacterial suspension was diluted before plate counting. Simultaneously, a light control experiment (without photocatalyst under light conditions) and a dark control experiment (with photocatalyst in the dark) were also conducted. The sterilization efficiency of the nano-photocatalyst was calculated using Formula 1.

[0061] Sterilization rate (%) = (N0 - N) t ) / N0*100%(1)

[0062] Where N0 and N t These correspond to the number of colonies counted on the control and sample culture medium plates, respectively.

[0063] Figure 5 This image shows the photocatalytic bactericidal performance of the NTW composite material prepared in this invention. Oxygen vacancies are the most common and extensively studied ionic defects, possessing advantages such as simple structure, strong controllability, and significant improvement in photocatalytic performance. For example... Figure 5 As shown in (a), m-WO3 containing mesopores and oxygen vacancies 3-xIt exhibits excellent bactericidal effect, with a bactericidal efficiency of 67.12%. After 30 minutes of light exposure, Nb2CT... x The bactericidal efficiencies of TpPa-1 and NT were 44.64% and 45.86%, respectively, while the bactericidal efficiency of NT was significantly improved to 84.63%. Furthermore, the compound m-WO3... 3-x The sterilization efficiency of the ternary composite material NTW was 99.90%. Figure 5 (b) It can be seen that the corresponding cell concentration decreased from 7.15 to 4.11 log. 10 CFU / mL.

[0064] Application Example 2:

[0065] The self-cleaning food packaging film based on nano-photocatalyst obtained in Example 2 above is used for antibacterial purposes.

[0066] The application of self-cleaning food packaging film based on nano-photocatalysts is described in Example 1, except that 0.2g of the packaging film is placed in 50mL of bacterial suspension and then irradiated with a xenon lamp for 1h.

[0067] Figure 6 This image illustrates the photocatalytic sterilization process of the self-cleaning food packaging film prepared according to the present invention. Figure 6 As shown in (a), the bactericidal efficiency of the LbL-CPP membrane is approximately 20%. This is likely due to the interaction between the positive charge of CMCS and the negative charge on the surface of the microbial cell membrane, which alters the permeability of the cell membrane and leads to microbial cell death. Adding FA as a crosslinking agent slightly increases the bactericidal efficiency of the LbL-CPP / FA membrane, as FA itself has a certain antibacterial effect. When NTW is added as a bacteriostatic agent, the bactericidal efficiency of the composite membrane increases significantly, with the highest bactericidal efficiency of 99.95% achieved when the NTW loading is 0.2%. Figure 6 (b) It can be seen that the corresponding cell concentration decreased from 7.49 to 4.18 log. 10 CFU / mL.

[0068] The above description is merely a preferred embodiment of the present invention and does not constitute any limitation on the present invention. Any simple modifications, alterations, or equivalent structural changes made to the above embodiments based on the technical essence of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A self-cleaning food packaging film based on a nano-photocatalyst, characterized in that, The self-cleaning food packaging film has a multi-layer structure, including CMCS / FA film, PUL / NTW film and PVA film arranged in sequence; The PUL / NTW membrane comprises a PUL and NTW nanocomposite material, wherein the NTW nanocomposite material is N-Nb2CT. x / TpPa-1 / m-WO 3-x Composite nano-photocatalytic materials; In the XRD pattern, TpPa-1 shows a sharp peak at 5.1° and a broad peak at 26.6°, corresponding to crystal plane (100) and crystal plane (001), respectively. In SEM tissue images, N-Nb2CT x The structure is an accordion shape composed of nanosheets, N-Nb2CT x TpPa-1 nanostructures were grown in situ on the surface of nanosheets. The TpPa-1 nanostructures exhibited a flower-like morphology with rod-like aggregates. m-WO 3-x It is shaped like a sea urchin composed of nanosheets, and TpPa-1 and m-WO 3-x A core-shell structure was formed, in which m-WO 3-x It is the core, and TpPa-1 is the shell.

2. A self-cleaning food packaging film based on a nano-photocatalyst as described in claim 1, characterized in that, In the XRD pattern of the self-cleaning food packaging film, CMCS has a diffraction peak at 20.1°, PUL has an amorphous structure and a bun-shaped peak at 19.6°, and PVA film has a semi-crystalline structure and a sharp peak at 19.5°.

3. The self-cleaning food packaging film based on nano-photocatalyst as described in any one of claims 1-2, characterized in that, In the self-cleaning food packaging film based on nano-photocatalyst, the loading content of 0 < NTW nanocomposite material is ≤ 0.2%.

4. The self-cleaning food packaging film based on nano-photocatalyst as described in any one of claims 1-2, characterized in that, There are intermolecular interactions between NTW nanocomposites and the self-cleaning food packaging film matrix based on nanophotocatalysts.

5. A method for preparing an NTW nanocomposite photocatalyst, characterized in that, (1) Preparation of WO3 containing mesopores and oxygen vacancies: WO3 containing oxygen vacancies was prepared using tungsten hexachloride (WCl6) as raw material, and WO3 containing mesopores and oxygen vacancies, i.e., m-WO3, was obtained using mesoporous silica KIT-6 as a hard template. 3-x ; (2) Aminated Nb2CT x Preparation: Nb₂AlC is added to hydrofluoric acid solution, and the resulting reaction product is processed to obtain monolayer or few-layer Nb₂CT. x Subsequently, triethoxysilane was added to obtain aminated Nb2CT. x That is, N-Nb2CT x ; (3) N-Nb2CT x m-WO 3-x The reaction with trialdehyde pyrogallol, p-phenylenediamine, mesitylene, and 1,4-dioxane yields N-Nb2CT. x / TpPa-1 / m-WO 3-x That is, NTW nanocomposite photocatalyst; In the XRD pattern, TpPa-1 shows a sharp peak at 5.1° and a broad peak at 26.6°, corresponding to crystal planes (100) and (001), respectively. In SEM tissue images, N-Nb2CT x The structure is an accordion shape composed of nanosheets, N-Nb2CT x TpPa-1 nanostructures were grown in situ on the surface of nanosheets. The TpPa-1 nanostructures exhibited a flower-like morphology with rod-like aggregates. m-WO 3-x It is shaped like a sea urchin composed of nanosheets, and TpPa-1 and m-WO 3-x A core-shell structure was formed, in which m-WO 3-x It is the core, and TpPa-1 is the shell.

6. The NTW nanocomposite photocatalyst obtained by the method of claim 5.

7. A method for preparing a self-cleaning food packaging film based on a nano-photocatalyst as described in any one of claims 1-4, characterized in that, The preparation method is a layer-by-layer assembly method, using the NTW nanocomposite photocatalyst of claim 6 as an antibacterial agent, ferulic acid as a crosslinking agent, and carboxymethyl chitosan, pullulan polysaccharide and polyvinyl alcohol as the matrix, and preparing the packaging film by layer-by-layer casting.

8. The antibacterial application of the self-cleaning food packaging film based on nano-photocatalyst as described in any one of claims 1-4 in meat preservation.

9. The application according to claim 8, characterized in that, The bacteria mentioned are Staphylococcus aureus, Listeria monocytogenes, Escherichia coli, and Salmonella.

10. The application according to claim 9, characterized in that, After 30 minutes of light exposure, the sterilization efficiency of the self-cleaning food packaging film based on nano-photocatalyst is 99.90%.

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