Composite material for adsorbing and catalytically degrading food pathogenic bacteria and preparation method thereof

Abstract

This invention relates to a composite material and its preparation method for adsorbing and catalytically degrading foodborne pathogens, belonging to the field of composite material technology. The composite material for adsorbing and catalytically degrading foodborne pathogens comprises a porous nanocarrier, a photocatalytically active component loaded on the porous nanocarrier, and nano-silver modified on the surface of the photocatalytically active component; wherein the porous nanocarrier is graphene oxide; the photocatalytically active component is titanium dioxide and zinc oxide in a mass ratio of 2:1 to 1:2; and the mass ratio of the photocatalytically active component to the porous nanocarrier is 1:5 to 1:1. The composite material of this invention possesses both high-efficiency, broad-spectrum antibacterial properties and long-term stability, and can be widely used in the food antibacterial industry.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of composite materials, and particularly relates to a composite material for adsorbing and catalytically degrading food pathogenic bacteria and a preparation method thereof. BACKGROUND

[0002] With the increasing global concern about food safety, the pollution control of food pathogenic bacteria (such as Escherichia coli, Staphylococcus aureus, etc.) has become a key challenge faced by the food industry. Although traditional physical or chemical sterilization techniques (such as high-temperature sterilization, irradiation, chemical disinfectants) are effective, they generally have the risks of destroying food flavor and nutrients, producing harmful chemical residues, and secondary pollution, etc., and are difficult to meet the modern consumer demand for "fresh, natural, and safe" food.

[0003] Under this background, nano-antibacterial materials are considered as a potential solution for the new generation of food preservation and safety control due to their high efficiency and low dosage. Among them, semiconductor photocatalytic materials (such as titanium dioxide, zinc oxide) and metal nanoparticles are of great concern due to their broad-spectrum antibacterial activity and are tried to be applied in active packaging, processing equipment coating, etc. However, the existing technology still has significant defects if it is to truly meet the extremely harsh requirements of the food industry for broad-spectrum, long-acting, stable, and safe:

[0004] (1) Contradiction between the limitations of material performance and the adaptability to food environment: photocatalytic materials (such as titanium dioxide) usually need to be excited by ultraviolet light, and their activity decreases sharply in the visible or weak light environment commonly seen during food storage and transportation. Moreover, their nanoparticles are easy to aggregate and deactivate, and it is difficult to maintain high efficiency in complex food matrix (such as oil and protein surfaces) for a long time.

[0005] (2) Rough composite structure design and insufficient synergistic effect: many existing composite materials only physically mix or simply load the antibacterial components, resulting in uneven dispersion of each component and weak interface bonding. This not only causes high recombination rate of photo-generated electron-hole pairs and low catalytic efficiency, but also makes the material easy to fall off or lose activity under the mechanical stress, temperature and humidity changes of food processing or packaging, which cannot guarantee the durability and stability of the antibacterial performance.

[0006] (3) Carrier selection and structural defects: conventional carriers (such as silica, activated carbon) have limited specific surface area and uneven pore size distribution, making it difficult to simultaneously achieve efficient adsorption of pathogenic bacteria and high loading of active components. For example: macroporous carriers are beneficial for adsorption, but active components are easy to fall off; microporous carriers can fix nanoparticles, but hinder bacteria from contacting active sites.

[0007] Patent application CN120441795A discloses a porphyrin-based covalent organic framework nanomaterial, which is prepared by a Schiff base reaction of 5,10,15,20-tetra(4-aminophenyl)porphyrin and bis-(5-formylfurfuryl) ether. This porphyrin-based covalent organic framework nanomaterial exhibits high photothermal conversion efficiency as a photothermal agent and good bactericidal effect at relatively low concentrations. However, the nanomaterial has a single pore size, weak bacterial adsorption capacity, and a complex and inefficient preparation method. Summary of the Invention

[0008] To address the shortcomings of existing technologies, the present invention aims to provide a composite material for adsorbing and catalytically degrading food pathogens and a method for its preparation. The composite material possesses both high efficiency and broad-spectrum antibacterial properties as well as long-term stability, and can be widely used in the food antibacterial industry.

[0009] To achieve the above objectives, according to one aspect of the present invention, the object of the present invention is to provide a composite material for adsorbing and catalytically degrading foodborne pathogens, comprising a porous nanocarrier, a photocatalytically active component loaded on the porous nanocarrier, and nano-silver modified on the surface of the photocatalytically active component; wherein the porous nanocarrier is graphene oxide; the photocatalytically active component is titanium dioxide and zinc oxide in a mass ratio of 2:1 to 1:2; and the mass ratio of the photocatalytically active component to the porous nanocarrier is 1:5 to 1:1.

[0010] In this invention, the mass ratio of the photocatalytic active component to the porous nanocarrier is 1:5 to 1:1. It is understood that this mass ratio can be any specific value among 1:5, 1:4, 1:3, 1:2, and 1:1, or any value within the range of 1:5 to 1:1. This invention ensures high loading without clogging the carrier pores by controlling the specific mass ratio of the photocatalytic component to the carrier.

[0011] In this invention, the loading of silver nanoparticles accounts for 0.5-5% of the total mass of the composite material. This loading ensures sufficient metal sites for rapid contact sterilization while avoiding excessive metal clogging of the carrier pores or causing aggregation and inactivation.

[0012] In this invention, the photocatalytic active component is titanium dioxide and zinc oxide in a mass ratio of 2:1 to 1:2. It is understood that the mass ratio of titanium dioxide to zinc oxide can be any specific value among 2:1, 1:1, and 1:2, or any value within the range of 2:1 to 1:2. Preferably, the particle size range of the photocatalytic active component is 5-20 nm. When the particle size is less than 5 nm, the strong quantum size effect leads to a significant change in the band structure, causing instability in the photochemical properties of the material, making it prone to deactivation during long-term or cyclic use, thus severely impairing the activity retention rate. When the particle size is greater than 20 nm, the specific surface area of ​​the material will decrease sharply, resulting in insufficient exposed active sites, low photogenerated electron-hole pair separation efficiency, weakened photocatalytic oxidation reaction intensity, and decreased sterilization rate. Therefore, the 5-20nm particle size selected in this invention can provide a sufficiently high specific surface area to ensure a high density of surface reaction sites, thereby driving an efficient photocatalytic process to achieve a high sterilization rate; at the same time, it can avoid excessive quantum size effects, ensure the robustness of the heterojunction band structure, and enable it to maintain stable photocatalytic performance after multiple uses, that is, achieve excellent activity retention.

[0013] In this invention, the nano-silver has a particle size range of 2-20 nm. Using nano-silver within this particle size range ensures that the surface of the composite material per unit mass exposes the highest density of silver active sites, guaranteeing sufficient thermodynamic stability of the nano-silver particles. This allows for more secure anchoring on the surface of the titanium dioxide / ZnO nanoparticle heterojunction, reducing the aggregation and loss of nano-silver during use and ensuring that the material maintains a high activity retention rate after 5 cycles. If the particle size is too small, it is easily oxidized and deactivated; if the particle size is too large, the specific surface area drops sharply, leading to a decrease in antibacterial activity. If the particle size is less than 2 nm, the nano-silver is extremely unstable, with extremely high mobility and surface energy, making it very easy to detach from the carrier surface, resulting in rapid loss of active ingredients.

[0014] In this invention, the porous nanocarrier is graphene oxide; preferably, the pore size of the porous nanocarrier is in the range of 5-50 nm. The applicant has found that within this pore size range, the composite material exhibits optimal capture and antibacterial properties. This is because the suitable nanoscale pore structure can greatly increase the specific surface area of ​​the carrier, providing abundant and stable loading sites for the photocatalytically active components and nano-silver, effectively preventing their aggregation and detachment, and ensuring that a large number of highly active antibacterial sites are exposed on the material surface. Furthermore, the capture of bacteria (such as Staphylococcus aureus and Escherichia coli) by the composite material mainly occurs on the outer surface of the material and in its microscopic three-dimensional network structure. Through electrostatic interactions and hydrophobic interactions, bacteria are enriched and fixed, allowing them to fully contact the high-density antibacterial active components on the material surface, thereby achieving highly efficient photocatalytic synergistic sterilization.

[0015] According to another aspect of the present invention, a method for preparing the composite material for adsorbing and catalytically degrading food pathogens as described in any one of the above claims is also provided, comprising the following steps:

[0016] (1) Preparation of carrier dispersion: The porous nanocarrier is dispersed in a solvent to form a uniform dispersion;

[0017] (2) Photocatalytic component loading: Add titanium source, zinc source and structure directing agent to the dispersion obtained in step (1), and react by solvothermal method to generate and composite titanium dioxide and zinc oxide nanoparticles in situ, and load them together on the porous nanocarrier to form a primary composite material.

[0018] (3) Nano silver modification: After separating and washing the primary composite material obtained in step (2), it is redispersed in ultrapure water, silver nitrate solution is added, and sodium borohydride aqueous solution is added dropwise under light-protected conditions. The temperature is controlled at 2-5℃ for 1-3h reduction reaction.

[0019] (4) Post-processing: The product obtained in step (3) is separated, washed and dried to obtain the final composite material.

[0020] In this invention, in step (1), the carrier dispersion is prepared by dispersing the porous nanocarrier in a solvent to form a uniform dispersion. Preferably, the solvent is at least one of water, ethanol, methanol, or isopropanol; the concentration of the porous nanocarrier in the dispersion is 0.5-2 mg / mL; and the dispersion method is ultrasonic treatment for 10-60 min with an ultrasonic power of 200-400 W.

[0021] In this invention, in step (2), the photocatalytic component is loaded by adding a titanium source, a zinc source, and a structure-directing agent to the dispersion obtained in step (1), and reacting by a solvothermal method to generate and composite titanium dioxide and zinc oxide nanoparticles in situ, and load them together on the porous nanocarrier to form a primary composite material. The titanium source is tetrabutyl titanate, titanium tetrachloride, or titanium sulfate; the zinc source is zinc acetate, zinc nitrate, or zinc chloride; the reaction temperature of the solvothermal method is 150-180℃, and the reaction time is 12-24h; the structure-directing agent is hexadecyltrimethylammonium bromide or polyethylene glycol, and its addition amount is 1-5% of the total mass of the titanium source and zinc source.

[0022] In this invention, the molar ratio of the titanium source to the zinc source can be determined by chemometric calculation based on the mass ratio of titanium dioxide to zinc oxide in the target product. Theoretically, at complete conversion, the molar ratio of the titanium source to the zinc source is approximately (2.0-1.0):(1.0-2.0). In actual processes, considering slight differences in conversion efficiency, it can be controlled within the range of (2.2-1):(1-2.2).

[0023] This invention constructs a composite photocatalytic structure with strong interfacial bonding by simultaneously adding titanium and zinc sources to a carrier dispersion and, under the control of a structure-directing agent, simultaneously completing the in-situ generation and composite of titanium dioxide and ZnO nanoparticles through a single solvothermal reaction to form a type II heterojunction and the chemical bonding loading of the heterojunction on the carrier surface.

[0024] In this invention, in step (3), the nano-silver modification involves separating and washing the primary composite material obtained in step (2), redispersing it in ultrapure water, adding silver nitrate solution, stirring under light-protected conditions, and adding sodium borohydride aqueous solution dropwise, controlling the temperature at 0-25℃ for a reduction reaction of 1-3 hours. Preferably, the concentration of the silver nitrate solution is 0.01-0.1 mol / L; the concentration of the sodium borohydride aqueous solution is 0.05-0.2 mol / L, and the dropping rate is 0.44-1.92 mL / min.

[0025] This invention controls the concentration of the silver nitrate solution to 0.01-0.1 mol / L. This concentration range regulates the nucleation rate by controlling the initial concentration and diffusion driving force of silver ions in the reaction system. Too low a concentration leads to sparse nucleation sites and insufficient silver nanoparticle loading; too high a concentration easily induces homogeneous nucleation and rapid aggregation, forming large and unevenly distributed silver particles. This preferred range ensures that silver ions mainly undergo heterogeneous nucleation on the pre-loaded titanium dioxide / ZnO heterojunction surface, which is beneficial for forming uniformly dispersed silver nanoparticles with controllable particle size. By controlling the concentration of sodium borohydride aqueous solution to 0.05-0.2 mol / L and the dropping rate to 0.44-1.92 mL / min, the low reducing agent concentration and strictly slow dropping rate create a mild and controllable reduction kinetic environment. This ensures that the reduction reaction rate is much lower than the nucleation rate, effectively confining the growth of silver nanoparticles to a surface heterogeneous nucleation-dominated mode. This promotes the slow and orderly growth of silver atoms at active sites, thereby precisely limiting the size of silver nanoparticles to the 2-20 nm range. The low-temperature reduction process at 2-5℃ under light-shielded conditions ensures that newly reduced silver atoms are fixed in situ near the nucleation sites, thus suppressing their migration and aggregation to form large particles and ensuring the stability of the ultra-small silver nanoparticles. Simultaneously, the low temperature slows down the overall reaction rate, making the reduction and anchoring processes more compatible, which is beneficial for the formation of stronger chemical bonds between silver nanoparticles and the heterojunction surface, forming a photocatalytic-metal synergistic interface. The synergistic effect of the above parameters achieves high dispersion and strong anchoring of nano-silver on the titanium dioxide / ZnO surface, forming a stable interface. This not only endows the composite material with high overall stability, but also achieves slow-release behavior of silver ions by inhibiting the rapid dissolution and shedding of nano-silver, ensuring extremely low short-term silver release levels and long-term antibacterial activity.

[0026] In this invention, in step (4), the post-processing involves separating, washing, and drying the product obtained in step (3) to obtain the final composite material. Preferably, the drying is vacuum drying at a temperature of 40-60℃ for 12-24 hours.

[0027] Compared with the prior art, the beneficial effects of the present invention are:

[0028] (1) This invention creatively designs a ternary synergistic antibacterial composite material, using graphene oxide with adjustable pore size as a carrier. Its unique surface properties enable a high bacterial adsorption rate for food pathogens. The in-situ constructed titanium dioxide / zinc oxide heterojunction effectively broadens the light response range and can generate active oxygen species under visible light, significantly improving the photocatalytic sterilization rate of adsorbed bacteria. The ultra-small nano-silver with precise surface modification provides a third layer of protection for contact sterilization. The three mechanisms work closely together to achieve efficient and rapid killing of pathogens.

[0029] (2) This invention achieves stable and uniform composite of ternary components through a three-step synergistic preparation process of carrier pre-dispersion, in-situ solvothermal composite, and low-temperature directional reduction. This process ensures that the nano-silver is firmly anchored, enabling the composite material to exert highly efficient antibacterial properties while having an extremely low 24-hour release of silver ions, resulting in excellent safety. In addition, this integrated structure exhibits excellent stability and durability, maintaining a high activity retention rate after 5 cycles under simulated use conditions, proving that it has long-lasting and stable antibacterial properties, and the sustained-release characteristics of nano-silver are maintained, meeting the stringent requirements of the food industry for long-term material safety. Detailed Implementation

[0030] To enable those skilled in the art to understand the features and effects of the present invention, the terms and expressions used in the specification and claims are explained and defined in general below. Unless otherwise specified, all technical and scientific terms used herein have the ordinary meaning understood by those skilled in the art regarding the present invention, and in case of conflict, the definitions in this specification shall prevail.

[0031] The theories or mechanisms described and disclosed herein, whether right or wrong, should not in any way limit the scope of the invention, that is, the contents of the invention can be implemented without being limited by any particular theory or mechanism.

[0032] In this document, when describing embodiments or examples, it should be understood that it is not intended to limit the invention to those embodiments or examples. Rather, all alternatives, modifications, and equivalents of the methods and materials described herein are covered within the scope defined by the claims.

[0033] For the sake of brevity, not all possible combinations of the technical features in each implementation scheme or embodiment are described herein. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each implementation scheme or embodiment can be combined arbitrarily, and all possible combinations should be considered within the scope of this specification.

[0034] This invention provides a composite material for adsorbing and catalytically degrading foodborne pathogens, comprising a porous nanocarrier, a photocatalytically active component loaded on the porous nanocarrier, and nano-silver modified on the surface of the photocatalytically active component; wherein the porous nanocarrier is graphene oxide; the photocatalytically active component is titanium dioxide and zinc oxide in a mass ratio of 2:1 to 1:2; and the mass ratio of the photocatalytically active component to the porous nanocarrier is 1:5 to 1:1.

[0035] In some embodiments, the loading of the nanosilver accounts for 0.5-5% of the total mass of the composite material.

[0036] In some embodiments, the particle size range of the photocatalytic active component is 5-20 nm.

[0037] In some embodiments, the particle size of the silver nanoparticles ranges from 2 to 20 nm.

[0038] In some embodiments, the pore size of the porous nanocarrier ranges from 5 to 50 nm.

[0039] According to another aspect of the present invention, a method for adsorbing and catalytically degrading the composite material of any one of the above claims is also provided, comprising the following steps:

[0040] (1) Preparation of carrier dispersion: The porous nanocarrier is dispersed in a solvent to form a uniform dispersion;

[0041] (2) Photocatalytic component loading: Add titanium source, zinc source and structure directing agent to the dispersion obtained in step (1), and react by solvothermal method to generate and composite titanium dioxide and zinc oxide nanoparticles in situ, and load them together on the porous nanocarrier to form a primary composite material.

[0042] (3) Nano silver modification: After separating and washing the primary composite material obtained in step (2), it is redispersed in ultrapure water, silver nitrate solution is added, and sodium borohydride aqueous solution is added dropwise under light-protected conditions. The temperature is controlled at 2-5℃ for 1-3h reduction reaction.

[0043] (4) Post-processing: The product obtained in step (3) is separated, washed and dried to obtain the final composite material.

[0044] In some embodiments, in step (1), the solvent is at least one of water, ethanol, methanol or isopropanol; the concentration of the porous nanocarrier in the dispersion is 0.5-2 mg / mL; the dispersion method is ultrasonic treatment for 10-60 min, and the ultrasonic power is 200-400 W.

[0045] In some embodiments, in step (2), the titanium source is tetrabutyl titanate, titanium tetrachloride, or titanium sulfate; the zinc source is zinc acetate, zinc nitrate, or zinc chloride; the reaction temperature of the solvothermal method is 150-180℃, and the reaction time is 12-24h; the structure directing agent is hexadecyltrimethylammonium bromide or polyethylene glycol, and its addition amount is 1-5% of the total mass of the titanium source and the zinc source.

[0046] In some embodiments, in step (3), the concentration of the silver nitrate solution is 0.01-0.1 mol / L; the concentration of the sodium borohydride aqueous solution is 0.05-0.2 mol / L, and the dropping rate is 0.44-1.92 mL / min.

[0047] The present invention will be described in detail below through embodiments. It should be understood that the following embodiments are only used to further explain and illustrate the content of the present invention by way of example, and are not intended to limit the present invention.

[0048] Example 2 is the best embodiment.

[0049] The chemical additives used in the embodiments and comparative examples of this invention are all commercially available, and the specific information is as follows:

[0050] Staphylococcus aureus (ATCC6538) and Escherichia coli (ATCC25922): purchased from Qingdao Haibo Biotechnology; porous nanocarrier: graphene oxide with a pore size range of 5-50 nm, purchased from Jiangsu Xianfeng Nanomaterials Technology Co., Ltd.; anhydrous zinc acetate: purchased from Aladdin Reagent Co., Ltd.; other auxiliaries and solvents: purchased from Aladdin Reagent Co., Ltd.

[0051] Example 1

[0052] The composite material for adsorbing and catalytically degrading foodborne pathogens described in this embodiment consists of a porous nanocarrier, a photocatalytically active component loaded on the porous nanocarrier, and nano-silver modified on the surface of the photocatalytically active component; wherein, the porous nanocarrier is graphene oxide; and the photocatalytically active component is titanium dioxide and zinc oxide in a mass ratio of 1:1.

[0053] The method for using the composite material to adsorb and catalytically degrade food pathogens includes the following steps:

[0054] (1) Preparation of carrier dispersion: 1.0 g of graphene oxide was dispersed in 1.0 L of water / ethanol mixed solvent (volume ratio 1:1), and ultrasonically treated (power 300 W) for 40 min to form a uniform dispersion with a concentration of 1.0 mg / mL;

[0055] (2) Photocatalytic component loading: 0.520 g tetrabutyl titanate, 0.366 g anhydrous zinc acetate (molar ratio Ti:Zn = 2.2:1) and 12 mg cetyltrimethylammonium bromide (CTAB) were added to the above dispersion. The mixture was transferred to a high-pressure reactor and reacted at 160 °C for 20 h using a solvothermal method to generate and composite titanium dioxide and zinc oxide nanoparticles in situ, and load them onto a porous nanocarrier. After the reaction was completed, the mixture was centrifuged and washed three times each with deionized water and ethanol to obtain the primary composite material.

[0056] (3) Nano-silver modification: All the primary composite material obtained in step (2) (approximately 1.33 g) was redispersed in 133 mL of ultrapure water. 8.0 mL of 0.05 mol / L silver nitrate solution was added, and the mixture was stirred at 5 °C in the dark. 0.75 mL of 0.1 mol / L sodium borohydride aqueous solution was added dropwise at a rate of 0.5 mL / min. After the addition was complete, the reaction was continued at 5 °C for 1.5 h.

[0057] (4) Post-processing: The reaction product obtained in step (3) is centrifuged, washed three times with deionized water, and dried under vacuum at 60°C for 12 hours to obtain the final composite material.

[0058] Example 2

[0059] The composite material described in this embodiment for adsorbing and catalytically degrading foodborne pathogens consists of a porous nanocarrier, a photocatalytically active component loaded on the porous nanocarrier, and nano-silver modified on the surface of the photocatalytically active component; wherein, the porous nanocarrier is graphene oxide; and the photocatalytically active component is titanium dioxide and zinc oxide in a mass ratio of 2:1.

[0060] The method for using the composite material to adsorb and catalytically degrade food pathogens includes the following steps:

[0061] (1) Preparation of carrier dispersion: 1.0 g of graphene oxide was dispersed in 2.0 L of water / ethanol mixed solvent (volume ratio 1:1), and ultrasonically treated (power 200 W) for 60 min to form a uniform dispersion with a concentration of 0.5 mg / mL;

[0062] (2) Photocatalytic component loading: 0.415 g tetrabutyl titanate, 0.122 g anhydrous zinc acetate (molar ratio Ti:Zn = 4.1:1) and 5.4 mg cetyltrimethylammonium bromide (CTAB) were added to the dispersion. The mixture was transferred to a high-pressure reactor and reacted at 150 °C for 24 h to allow titanium dioxide and zinc oxide nanoparticles to be generated and composited in situ and co-loaded onto a porous nanocarrier. After the reaction was completed, the mixture was centrifuged and washed three times each with deionized water and ethanol to obtain the primary composite material.

[0063] (3) Nano-silver modification: The primary composite material (approximately 1.1 g) obtained in step (2) was redispersed in 110 mL of ultrapure water. 8.82 mL of 0.01 mol / L silver nitrate solution was added and stirred at 2 °C in the dark. 0.66 mL of 0.05 mol / L sodium borohydride aqueous solution was added dropwise, with the slowest dropping rate controlled at 0.44 mL / min. After the addition was complete, the reaction was continued at 2 °C for 3 h.

[0064] (4) Post-processing: The reaction product obtained in step (3) is centrifuged, washed three times with deionized water, and vacuum dried at 40°C for 24 hours to obtain the final composite material.

[0065] Example 3

[0066] The composite material for adsorbing and catalytically degrading foodborne pathogens described in this embodiment consists of a porous nanocarrier, a photocatalytically active component loaded on the porous nanocarrier, and nano-silver modified on the surface of the photocatalytically active component; wherein, the porous nanocarrier is graphene oxide; and the photocatalytically active component is titanium dioxide and zinc oxide in a mass ratio of 1:2.

[0067] The method for using the composite material to adsorb and catalytically degrade food pathogens includes the following steps:

[0068] (1) Preparation of carrier dispersion: 1.0 g of graphene oxide was dispersed in 0.5 L of water / ethanol mixed solvent (volume ratio 1:1), and ultrasonically treated (power 400 W) for 10 min to form a uniform dispersion with a concentration of 2.0 mg / mL;

[0069] (2) Photocatalytic component loading: 0.347 g tetrabutyl titanate, 0.732 g anhydrous zinc acetate (molar ratio Ti:Zn=1:2.7) and 54 mg cetyltrimethylammonium bromide (CTAB) were added to the dispersion. The mixture was transferred to a high-pressure reactor and reacted at 180 °C for 12 h to allow titanium dioxide and zinc oxide nanoparticles to be generated and composited in situ and co-loaded onto a porous nanocarrier. After the reaction was completed, the mixture was centrifuged and washed three times each with deionized water and ethanol to obtain the primary composite material.

[0070] (3) Nano-silver modification: The primary composite material (approximately 2.1 g) obtained in step (2) was redispersed in 210 mL of ultrapure water. 15.73 mL of 0.1 mol / L silver nitrate solution was added, and the mixture was stirred at 5 °C in the dark. 2.88 mL of 0.2 mol / L sodium borohydride aqueous solution was added dropwise at a rate of 1.92 mL / min. After the addition was complete, the reaction was continued at 5 °C for 1 h.

[0071] (4) Post-processing: The reaction product obtained in step (3) is centrifuged, washed three times with deionized water, and dried under vacuum at 60°C for 12 hours to obtain the final composite material.

[0072] Comparative Example 1

[0073] The preparation method of the composite material for adsorbing and catalytically degrading food pathogens described in this comparative example is exactly the same as that in Example 2, except that the photocatalytic active components are titanium dioxide and zinc oxide in a mass ratio of 3:1.

[0074] Comparative Example 2

[0075] The preparation method of the composite material for adsorbing and catalytically degrading food pathogens described in this comparative example is exactly the same as that in Example 2, except that the photocatalytic active components are titanium dioxide and zinc oxide in a mass ratio of 1:3.

[0076] Comparative Example 3

[0077] The preparation method of the composite material for adsorbing and catalytically degrading foodborne pathogens described in this comparative example is exactly the same as that in Example 2, except that step (3) is as follows: Nano-silver modification: The obtained primary composite material (about 1.1 g) is redispersed in 110 mL of ultrapure water. 8.82 mL of 0.01 mol / L silver nitrate solution is added and stirred at 25 °C in the dark. 2.0 mL of 0.2 mol / L sodium borohydride aqueous solution is added rapidly in one go, and the reaction is stirred vigorously at 25 °C for 0.5 h.

[0078] Comparative Example 4

[0079] The preparation method of the composite material for adsorbing and catalytically degrading foodborne pathogens described in this comparative example is exactly the same as that in Example 2, except that step (3) is as follows: Nano-silver modification: The obtained primary composite material (about 1.1 g) is redispersed in 110 mL of ultrapure water. 8.82 mL of 0.1 mol / L silver nitrate solution (concentration increased 10 times) is added and stirred at 25 °C in the dark. 0.66 mL of 0.05 mol / L sodium borohydride aqueous solution is added dropwise at a rate of 0.44 mL / min. After the addition is complete, the system temperature is raised to 60 °C and the reaction is continued to be stirred for 3 h.

[0080] Comparative Example 5

[0081] The preparation method of the composite material for adsorbing and catalytically degrading foodborne pathogens described in this comparative example is exactly the same as that in Example 2, except that step (3) is as follows: the obtained primary composite material (about 1.1 g) is redispersed in 110 mL of ultrapure water. 35.3 mL of 0.1 mol / L silver nitrate solution (4 times the amount used in Example 2) is added, and the mixture is stirred at 10 °C in the dark. To treat the high concentration of silver ions, 5.0 mL of 0.2 mol / L sodium borohydride aqueous solution is added dropwise at a rate of 1.0 mL / min. After the addition is complete, the reaction is continued at 10 °C for 2 h.

[0082] Comparative Example 6

[0083] The preparation method of the composite material for adsorbing and catalytically degrading food pathogens described in this comparative example is exactly the same as that in Example 1, except that the photocatalytic component is directly added externally. That is, steps (1) and (2) are as follows: 0.333g of titanium dioxide and 0.667g of ZnO are added to 200mL of ethanol and ball-milled (zirconia balls, 300rpm, 12h) to obtain a titanium dioxide / ZnO mixture; 1g of the titanium dioxide / ZnO and 1g of graphene oxide carrier are dispersed in 1L of water / ethanol mixed solvent (V:V=1:1) and ultrasonically dispersed for 40min to form a uniform dispersion; wherein, the ultrasonic power is 300W; centrifuged and washed, and vacuum dried at 60℃ for 12h to obtain the primary composite material.

[0084] Material characterization

[0085] The nano-silver and composite materials obtained using Examples 1-3 and Comparative Examples 1-6 were characterized and tested according to the following methods, and the specific results are shown in Table 1.

[0086] (1) Composition and Loading Determination: The absolute masses of Ti, Zn, and Ag elements in the composite material were determined using inductively coupled plasma atomic emission spectrometry (ICP-AES). 10.0 mg of the composite material sample was accurately weighed, completely digested with 5 mL of aqua regia at 150 °C using microwave, and then diluted to 50 mL before testing. The mass fractions of titanium dioxide and zinc oxide were calculated by converting the mass of Ti and Zn elements, and the mass ratio of titanium dioxide to zinc oxide was directly calculated from the converted mass. The loading of nano-silver (wt%) was expressed as the percentage of Ag element mass to the total sample mass. The mass ratio of the photocatalytically active component to the support was calculated as the mass ratio of the total mass of titanium dioxide and ZnO to the mass ratio of the graphene oxide support.

[0087] (2) Morphology and particle size analysis: The microstructure of the composite material was observed using transmission electron microscopy. The sample was ultrasonically dispersed in ethanol, dropped onto an ultrathin carbon film copper mesh, dried, and then observed. The size of no less than 200 particles was randomly selected using ImageJ software.

[0088] (3) Specific surface area and pore size analysis: The specific surface area and pore size distribution of the composite material were determined at 77 K using a nitrogen adsorption-desorption apparatus. Before testing, the samples were degassed at 150 °C for 6 hours. The specific surface area was calculated using the BET model, and the average pore size of the porous nanocarrier was calculated from the adsorption branch using the BJH model.

[0089] Table 1. Material characterization of Examples 1-3 and Comparative Examples 1-6

[0090] .

[0091] As shown in Table 1, Examples 1-3 successfully controlled the core parameters of the composite material, such as the mass ratio of titanium dioxide to ZnO, the mass ratio of photocatalytic components to the support, the loading of silver nanoparticles, the particle size of each component, and the pore size of the support, using the in-situ solvothermal-low-temperature controllable reduction method described in this invention, within the strictly defined optimization range of the claims. The comparative examples deviated from the technical solution of this invention, resulting in deviations in key parameters: the mass ratios of titanium dioxide to ZnO in Comparative Examples 1 and 2 (2.85:1 and 1:2.91, respectively) exceeded the upper and lower limits of the ratio defined in Claim 1; the particle sizes of silver nanoparticles in Comparative Examples 3 and 4 (1.5 nm and 35.2 nm, respectively) deviated from the 2-20 nm range defined in Claim 4; the loading of silver nanoparticles in Comparative Example 5 (7.8 wt%) was significantly higher than the 5 wt% upper limit specified in Claim 2; and Comparative Example 6, due to the use of a simple physical mixing method, resulted in severe agglomeration of the photocatalytic components, with a particle size far exceeding the limit of Claim 3 (>500 nm).

[0092] Performance testing

[0093] The composite materials obtained in Examples 1-3 and Comparative Examples 1-6 for adsorbing and catalytically degrading food pathogens were tested for performance according to the following methods, and the specific results are shown in Table 2.

[0094] (1) Bacterial adsorption rate test

[0095] Bacterial strains: Staphylococcus aureus (ATCC6538) and Escherichia coli (ATCC25922)

[0096] Steps: Add the composite material (10 mg) to 10 mL of bacterial solution (10... 6 Centrifuge at CFU / mL, and shake in the dark (150 rpm, 30 min, 25 ℃); collect the supernatant and determine the residual colony count using the plate count method.

[0097] Calculation formula: Adsorption rate = (1 - Residual bacteria count / Initial bacteria count) × 100%

[0098] (2) Photocatalytic sterilization rate test

[0099] Light source: 300W xenon lamp (simulating sunlight, intensity 100mW / cm²)

[0100] Steps: Add 10 mg of the composite material to 10 mL of bacterial solution (10... 6 (CFU / mL), after dark adsorption for 30 min, light was turned on for timed sampling (0 / 1 / 2 h), and the viable count was determined by plate counting.

[0101] Calculation formula: Sterilization rate = (1 - t-hour bacterial count / initial bacterial count) × 100%

[0102] (3) Ag⁺ sustained-release kinetics test

[0103] Instrument: Inductively Coupled Plasma Optical Emission Spectrometer (ICP-OES)

[0104] Procedure: The composite material (50 mg) was dispersed in 50 mL of PBS (pH=7.4), shaken at 37 °C (100 rpm), and samples were taken at regular intervals (1 / 3 / 6 / 12 / 24 h). After centrifugation and filtration, Ag was determined. + concentration.

[0105] (4) Cyclic stability test

[0106] Procedure: After each photocatalytic sterilization experiment, the material was centrifuged to recover the material, washed 3 times with sterile PBS, dried at 60℃, and the sterilization experiment was repeated 5 times.

[0107] Table 2 Performance data of Examples 1-3 and Comparative Examples 1-6

[0108] .

[0109] As shown in Table 2, the composite materials described in Examples 1-3 for adsorbing and catalytically degrading foodborne pathogens possess high bacterial adsorption rates (>90.5%), high photocatalytic sterilization rates (>99.5%), low silver release (<0.085 μg / mg), and high activity retention rates (>92.1%), making them particularly suitable for the food packaging field where safety and long-term effectiveness are critical. Example 3 has the largest pore size (35.6 nm), but its adsorption rate is not the highest. This indicates that adsorption is the result of the combined effect of surface properties (such as functional groups and charge) and pore structure, rather than being determined solely by pore size. Therefore, it can be seen that, through the in-situ solvothermal-low temperature controllable reduction process, the core parameters such as the titanium dioxide / ZnO mass ratio, the nano-silver particle size and loading, and the carrier pore size are synergistically controlled within the optimized range defined in the claims, thereby constructing a structurally stable and functionally complementary system. This ensures efficient photocatalytic oxidation capability, and the porous carrier achieves efficient bacterial adsorption and firm component anchoring. Meanwhile, the precisely controlled nano-silver provides contact sterilization while achieving safe and sustained release of silver ions. Ultimately, this synergistic approach achieves efficient, safe, and long-lasting food-grade antibacterial effects.

[0110] A comparison of Example 2 and Comparative Examples 1 and 2 reveals that the titanium dioxide / ZnO ratios in Comparative Examples 1 and 2 are imbalanced, resulting in significantly lower photocatalytic sterilization rates (85.2% and 88.7%, respectively) compared to Example 2. This imbalance in the titanium dioxide / ZnO mass ratio leads to a mismatch in the heterojunction band structure, inhibiting the effective separation and migration of photogenerated electron-hole pairs and weakening the photocatalytic oxidation function.

[0111] A comparison of Example 2 with Comparative Examples 3 and 4 reveals that: Comparative Example 3, due to its excessively small particle size (1.5 nm), experienced a burst release of silver ions (0.320 μg / mg) and a collapse in cycle stability (65.3%); Comparative Example 4, due to its excessively large particle size (35.2 nm), exhibited decreased adsorption rate, sterilization rate, and poor stability. This is because when the nano-silver particles are too small (<2 nm), they are extremely unstable, tending to dissolve and aggregate rapidly, leading to burst release and early inactivation; when the particle size is too large (>20 nm), the specific surface area decreases sharply, the number of active sites decreases, and the interfacial binding force with the carrier weakens, thus impairing its immediate and long-term performance.

[0112] A comparison between Example 2 and Comparative Example 5 shows that the excessive loading (7.8 wt%) in Comparative Example 5 resulted in the highest silver release (0.450 μg / mg) and poor cycle stability (70.1%). This is because the excessive loading far exceeded the capacity of the effective anchoring points on the carrier surface, causing a large amount of nano-silver to exist in an unstable form of physical adsorption or weak binding. This allows for rapid dissolution and release in the medium, followed by detachment under mechanical or chemical action, severely compromising the material's structural stability and safety.

[0113] A comparison between Example 2 and Comparative Example 6 reveals that Comparative Example 6, employing a physical mixing method, resulted in severe agglomeration of the photocatalytic components (>500nm), leading to the worst overall performance (e.g., sterilization rate of 70.5% and activity retention rate of 58.2%). This further demonstrates that the in-situ solvothermal-low-temperature controllable reduction process of this invention is indispensable for constructing nanoscale uniform composite structures with robust interfaces.

[0114] Therefore, this invention creatively designs a ternary synergistic antibacterial composite material. Using tunable-pore-size graphene oxide as a carrier, its unique surface properties enable a high bacterial adsorption rate for foodborne pathogens. The in-situ constructed titanium dioxide / zinc oxide heterostructure effectively broadens the light response range, generating reactive oxygen species even under visible light, significantly improving the photocatalytic sterilization rate of adsorbed bacteria. The precisely modified ultra-small silver nanoparticles provide a third layer of protection for contact sterilization. These three mechanisms work synergistically to achieve highly efficient and rapid killing of pathogens. Furthermore, this invention achieves stable and uniform composite of the ternary components through a three-step synergistic preparation process: carrier pre-dispersion, in-situ solvothermal composite, and low-temperature directional reduction. This process ensures that the silver nanoparticles are firmly anchored, enabling the composite material to exhibit highly efficient antibacterial properties while having an extremely low 24-hour silver ion release rate, resulting in excellent safety. Furthermore, the integrated structure exhibits excellent stability and durability, maintaining a high activity retention rate even after five cycles under simulated usage conditions, demonstrating its long-lasting and stable antibacterial properties. Moreover, the sustained-release characteristics of nano-silver are maintained, meeting the stringent requirements of the food industry for the long-term safety of materials.

[0115] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. For those skilled in the art, other variations or modifications can be made based on the above description. It is impossible to exhaustively list all the implementation methods here. All obvious variations or modifications derived from the technical solutions of the present invention are still within the protection scope of the present invention.

Claims

1. A composite material for adsorbing and catalytically degrading pathogenic bacteria in food, characterized in that, The composite material is composed of a porous nanocarrier, a photocatalytically active component supported on the porous nanocarrier, and silver nanoparticles modified on the surface of the photocatalytically active component. The porous nanocarrier is graphene oxide; the photocatalytically active component is titanium dioxide and zinc oxide in a mass ratio of 2:1 to 1:2; the mass ratio of the photocatalytically active component to the porous nanocarrier is 1:5 to 1:1; the loading of silver nanoparticles accounts for 0.5-5% of the total mass of the composite material; the particle size range of the photocatalytically active component is 5-20 nm; the particle size range of the silver nanoparticles is 2-20 nm; and the pore size range of the porous nanocarrier is 5-50 nm. The method for preparing the composite material for adsorbing and catalytically degrading food pathogens includes the following steps: (1) Preparation of carrier dispersion: The porous nanocarrier is dispersed in a solvent to form a uniform dispersion; (2) Photocatalytic component loading: Add titanium source, zinc source and structure directing agent to the dispersion obtained in step (1), and react by solvothermal method to generate and composite titanium dioxide and zinc oxide nanoparticles in situ, and load them together on the porous nanocarrier to form a primary composite material. (3) Nano silver modification: After separating and washing the primary composite material obtained in step (2), it is redispersed in ultrapure water, silver nitrate solution is added, and sodium borohydride aqueous solution is added dropwise under light-protected conditions. The temperature is controlled at 2-5℃ for 1-3h reduction reaction; the concentration of the silver nitrate solution is 0.01-0.1mol / L. (4) Post-processing: The product obtained in step (3) is separated, washed and dried to obtain the final composite material.

2. A method for preparing the composite material as described in claim 1 for adsorbing and catalytically degrading foodborne pathogens, characterized in that, Includes the following steps: (1) Preparation of carrier dispersion: The porous nanocarrier is dispersed in a solvent to form a uniform dispersion; (2) Photocatalytic component loading: Add titanium source, zinc source and structure directing agent to the dispersion obtained in step (1), and react by solvothermal method to generate and composite titanium dioxide and zinc oxide nanoparticles in situ, and load them together on the porous nanocarrier to form a primary composite material. (3) Nano silver modification: After separating and washing the primary composite material obtained in step (2), it is redispersed in ultrapure water, silver nitrate solution is added, and sodium borohydride aqueous solution is added dropwise under light-protected conditions. The temperature is controlled at 2-5℃ for 1-3h reduction reaction. (4) Post-processing: The product obtained in step (3) is separated, washed and dried to obtain the final composite material.

3. The method for preparing a composite material for adsorbing and catalytically degrading foodborne pathogens according to claim 2, characterized in that, In step (1), the solvent is at least one of water, ethanol, methanol or isopropanol; the concentration of the porous nanocarrier in the dispersion is 0.5-2 mg / mL; the dispersion method is ultrasonic treatment for 10-60 min, and the ultrasonic power is 200-400 W.

4. The method for preparing a composite material for adsorbing and catalytically degrading foodborne pathogens according to claim 2, characterized in that, In step (2), the titanium source is tetrabutyl titanate, titanium tetrachloride or titanium sulfate; the zinc source is zinc acetate, zinc nitrate or zinc chloride; the structure directing agent is hexadecyltrimethylammonium bromide or polyethylene glycol, and its addition amount is 1-5% of the total mass of the titanium source and zinc source.

5. The method for preparing a composite material for adsorbing and catalytically degrading foodborne pathogens according to claim 2, characterized in that, In step (2), the reaction temperature of the solvothermal method is 150-180℃ and the reaction time is 12-24h.

6. The method for preparing a composite material for adsorbing and catalytically degrading foodborne pathogens according to claim 2, characterized in that, In step (3), the concentration of the sodium borohydride aqueous solution is 0.05-0.2 mol / L, and the dropping rate is 0.44-1.92 mL / min.