Hunting-type fruit and vegetable fresh-keeping material, fresh-keeping film, and preparation method and application thereof

Abstract

The present invention discloses a method for preparing a hunting-type fruit and vegetable fresh-keeping material, comprising the following steps: (1) dispersing clay minerals in an organic solvent and stirring and mixing at high speed to obtain a clay mineral dispersion; (2) preparing carbon quantum dot-modified titanium dioxide nanosheets; (3) adding carbon quantum dot-modified titanium dioxide nanosheets to the clay mineral dispersion, and adding metal oxides, metal salts and dispersants and stirring and mixing at high speed, calcining, adding organic antibacterial agents, ball milling, and drying to obtain a dispersion. Also disclosed are a fruit and vegetable fresh-keeping material prepared by the above method, a hunting-type fruit and vegetable dormant fresh-keeping film prepared by the fruit and vegetable fresh-keeping material, and the use of the above fruit and vegetable fresh-keeping material and fresh-keeping film in fruit and vegetable preservation.

Description

Technical Field

[0001] The invention belongs to the technical field of food fresh-keeping materials, and in particular relates to a hunting-type fruit and vegetable fresh-keeping material, a fresh-keeping film, and a preparation method and application thereof. Background Art

[0002] Fresh fruits and vegetables are essential foods for people's lives because they are rich in minerals, vitamins, carbohydrates and other nutrients. The proportion of my country's fruit and vegetable industry has increased year by year, and it has become a pillar industry for agricultural efficiency, farmers' income and rural stability. It has become an important way to promote the development of agricultural industrialization, guide agricultural structural adjustment, and achieve sustainable development of my country's agriculture; and the import and export volume of cross-border fruit and vegetable agricultural products has maintained a steady growth.

[0003] Fresh fruits and vegetables are different from ordinary industrial products and have the following characteristics: (1) they still breathe after being picked; (2) the pH of the product is > 4.6; (3) the water activity aw > 0.85; (4) they have not been heat-treated or otherwise treated; (5) there are no other barrier factors such as preservatives, acidifiers, etc. These characteristics make them very easy to spoil or produce toxins in the absence of low temperatures. They are difficult to store at room temperature and it is not easy to maintain their original freshness and quality. After being left for a short period of time, they are very likely to lose their nutritional and edible value. At the same time, they are easy to rot and be contaminated, which not only causes huge waste, but also poses a hidden danger to food safety. The main reasons for the deterioration of fresh fruits and vegetables are ethylene gas, microorganisms (including pathogenic bacteria and spoilage bacteria) and mechanical damage.

[0004] Common methods of storing and preserving fruits and vegetables include: low-temperature controlled atmosphere storage, controlled atmosphere preservation, irradiation preservation, and chemical preservation. Overall, these preservation technologies are either too expensive or not commercially available; secondly, they have side effects and will leave harmful substances that are harmful to the human body. Fruits and vegetables have a short shelf life after harvest, coupled with improper commercial processing, low level of storage and transportation preservation technology, and insufficient storage and transportation hardware facilities, resulting in excessively high loss rates of fruits and vegetables, high cross-regional and cross-border transportation costs, and particularly limited large-scale production of fruits and vegetables. At present, although cold chain circulation is the best technology for preserving fruits and vegetables, due to the high surface humidity of fruits and vegetables and incomplete pre-cooling during cold chain transportation, fruits and vegetables will also have problems such as soft ripening and crown rot during circulation. Functional packaging preservation technology can be used to control or improve the microenvironment of fruit and vegetable storage, affect the respiration rate and metabolic activity of fruits and vegetables, inhibit the proliferation of microorganisms and the reaction activity of enzymes, thereby delaying the aging and corruption of fruits and vegetables and extending the shelf life of commodities. The application of packaging preservation technology has become an indispensable part of the fruit and vegetable industry and an important means to ensure product quality and safety. Common fruit and vegetable preservation packaging technologies mainly include film preservation technology, silicon window preservation technology and perforated preservation technology. Relevant research on new materials technology for fresh-keeping packaging at home and abroad is still in full swing. For example, CN202010402771.9 discloses a preparation and method of a photocatalyst fresh-keeping plastic film using a photocatalyst combined with functional components such as potassium permanganate to achieve coordination and removal of ethylene and cell disinfecting. The main disadvantages of this type of method are: first, it is more susceptible to the limitation of insufficient light source, resulting in the lack of protective effect of functional materials on fruits and vegetables in a dark environment; second, the potassium permanganate exposed on the surface of the film may affect some sensory properties and safety of the product. However, in this field, better combining functional components with materials in the form of loading and incorporating them into polymer films has become the research and development direction of new functional packaging. Currently, many such products have been recognized by the market.

[0005] Packaging preservation is safe, convenient and environmentally friendly. However, the preservation of fruits and vegetables varies greatly, and its effect is restricted by many factors. A packaging preservation technology that is effective for a single product and a few categories is often ineffective or has little preservation effect on other categories. This makes it extremely difficult to promote it on a large scale and commercialize it, resulting in no industry scale and influence. Therefore, it is of great significance to develop a universal preservation functional material from the perspective of materials science, especially in the de-refrigeration e-commerce storage and transportation environment. Summary of the invention

[0006] The first object of the present invention is to provide a method for preparing a hunting-type fruit and vegetable fresh-keeping material and the fruit and vegetable fresh-keeping material prepared by the method.

[0007] The present invention also aims to provide a hunting type dormant fresh-keeping film for fruits and vegetables, which is made from the above-mentioned fresh-keeping material for fruits and vegetables.

[0008] The last object of the present invention is to provide the use of the above-mentioned fruit and vegetable fresh-keeping material and the above-mentioned fruit and vegetable fresh-keeping film in the preservation of fruits and vegetables.

[0009] The first object of the present invention can be achieved by the following technical solution: A method for preparing a hunting-type fruit and vegetable fresh-keeping material comprises the following steps:

[0010] (1) dispersing clay minerals in an organic solvent and stirring at high speed to obtain a clay mineral dispersion;

[0011] (2) Preparation of carbon quantum dot modified titanium dioxide nanosheets:

[0012] (2.1) The biomass material is ultrafinely ground and heated in a muffle furnace at 290-310° C. for 2-4 hours, and then dispersed in deionized water to obtain a dispersion, and organic small molecules are dissolved in water to obtain an organic small molecule aqueous solution, and the dispersion and the organic small molecule aqueous solution are hydrothermally reacted at 180-200° C. for 6 hours, cooled, and centrifuged to obtain a carbon quantum dot solution;

[0013] (2.2) mixing a nano-titanium dioxide precursor and an acidic solution, subjecting the obtained mixture to high temperature treatment, naturally cooling the product after high temperature treatment, removing a layer of precipitate, washing, drying, and grinding to obtain titanium dioxide nanosheets;

[0014] (2.3) ultrasonically dispersing the titanium dioxide nanosheets obtained in step (2.2) in deionized water, and then mixing with the carbon quantum dot solution obtained in step (2.1) and ultrasonically treating at high temperature in an oil bath or oven at 120 to 150° C., centrifuging and washing the obtained product, collecting the precipitate, and drying to obtain carbon quantum dot-modified titanium dioxide nanosheets with antibacterial and ethylene decomposition functions;

[0015] (3) Add the carbon quantum dot-modified titanium dioxide nanosheets prepared in step (2) to the clay mineral dispersion of step (1), and add metal oxides, metal salts and dispersants, stir and mix at high speed, calcine at 200-250° C. and 100-150 kPa for 15-25 hours, then add an organic antibacterial agent, ball mill and dry, and the resulting dispersion is the hunting-type fruit and vegetable fresh-keeping material.

[0016] In the preparation method of the hunting-type fruit and vegetable fresh-keeping material:

[0017] Optionally, the clay mineral in step (1) is one or more of kaolinite, montmorillonite, vermiculite and diatomaceous earth.

[0018] The clay mineral used as a carrier in the present invention has the characteristics of large specific surface area, many pores and strong polarity. It is a hydrated aluminum silicate mineral with a layered structure. The layered structure of the clay mineral leads to weak bonding force between atoms. When the clay is dispersed in a solvent, the internal structure of the material is easily stratified, resulting in interlayer voids. The layered particles undergo new bonding and reconstruction, thereby obtaining a larger specific surface area, which is more conducive to compounding different materials, thereby obtaining new structures and functions.

[0019] Optionally, the biomass material in step (2.1) is litchi peel and / or sugarcane bagasse.

[0020] Optionally, the organic small molecule in step (2.1) is citric acid, citrate, glucose or ascorbic acid.

[0021] In step (2.1) of the present invention, the carbon source is preferably a composite of biomass and organic small molecules. The biomass carbon source is litchi peel, sugarcane bagasse or other straw-like materials; the organic small molecule carbon source is citric acid, citrate, glucose or ascorbic acid.

[0022] The present invention uses natural biomass waste such as litchi peel and organic small molecules as composite raw materials, and prepares carbon quantum dots (CQDs) below 10nm through carbonization combined with hydrothermal reaction. The carbon quantum dots (CQDs) prepared from natural biomass can simultaneously introduce rich heteroatom functional groups because they contain heteroatoms, provide active sites, optimize the energy level structure, and enhance the ability to utilize visible light.

[0023] Optionally, the nano titanium dioxide precursor in step (2.2) is butyl titanate, isopropyl titanate, titanyl sulfate, titanium tetrachloride, titanium trichloride and titanium dioxide P 25 One or more of the .

[0024] Optionally, the nano-titanium dioxide precursor in step (2.2) is butyl titanate.

[0025] The present invention uses butyl titanate as a titanium source to prepare TiO 2 Anatase TiO nanotubes and nanoparticles with large specific surface areas 2 Nanosheets (TNS), anatase TiO 2 Nanosheets can adsorb many oxygen atoms on the surface, and photogenerated carriers are not easy to recombine, making the obtained TiO 2 The nanosheets have higher photocatalytic activity.

[0026] Optionally, the acidic solution in step (2.2) is a strong acid, and the strong acid is concentrated hydrochloric acid, concentrated sulfuric acid or hydrofluoric acid.

[0027] More preferably, the acidic solution in step (2.2) is hydrofluoric acid.

[0028] Optionally, in step (2.2), the obtained mixture is subjected to high temperature treatment in a silicone oil bath at 175-200° C. for 23-25 ​​h.

[0029] More preferably, in step (2.2), the obtained mixture is subjected to high temperature treatment in a silicone oil bath at 180° C. for 24 h.

[0030] Optionally, in step (2.3), the dosage of the titanium dioxide nanosheets TNS and the biomass quantum dot solution is in the ratio of 0.1 g: 1 to 6 mL.

[0031] More preferably, in step (2.3), high temperature treatment is performed in a 150° C. oil bath for 2 to 4 h.

[0032] Optionally, in step (2.2) and step (2.3), washing is performed using ethanol and deionized water, and drying is performed in an oven at 60° C. for 12 h.

[0033] After the carbon quantum dots are compounded with titanium dioxide nanosheets, the modification of the carbon quantum dots is verified by a variety of characterization methods. Then, the analysis after detection by UV-visible near-infrared spectrophotometer shows that after the carbon quantum dots are modified into the nanosheets, the energy band gap thereof is significantly reduced, and the photocatalytic activity in the visible light region is significantly improved compared with that of the titanium dioxide nanosheets.

[0034] Optionally, the metal oxide in step (3) is one or more of zinc oxide, ferric oxide, aluminum oxide and magnesium oxide.

[0035] Optionally, the metal salt in step (3) is one or more of copper sulfate, silver nitrate, copper nitrate, copper acetylacetonate, copper chloride, copper acetate, amino acid copper, copper humate, copper rosinate, calcium carbonate, copper succinate and copper ammonia.

[0036] Optionally, the organic antibacterial agent in step (3) is one or more of benzyl ammonium bromide, benzyl ammonium chloride and chitosan quaternary ammonium salt.

[0037] Optionally, the mass ratio of clay mineral, carbon quantum dot modified titanium dioxide nanosheets, metal oxide and metal salt in the clay mineral dispersion in step (3) is: 45-80 clay mineral, 2-10 carbon quantum dot modified titanium dioxide nanosheets, 4-15 metal oxide and 2-25 metal salt.

[0038] Optionally, the organic antibacterial agent in step (3) is one or more of benzyl ammonium bromide, benzyl ammonium chloride and chitosan quaternary ammonium salt.

[0039] The present invention dopes carbon dot-modified titanium dioxide nanosheets, metal atoms, metal ions and organic metal antibacterial agents into clay minerals. After the clay minerals are compounded with titanium dioxide nanosheets modified with carbon quantum dots doped with metal atoms and organic antibacterial agents, the former can achieve continuous effects such as adsorption and the latter can decompose and kill bacteria.

[0040] Optionally, the rotation speed during high-speed stirring in step (1) and step (3) is 2000 to 4500 r / min.

[0041] Optionally, the chemical formula of the hunting-type fruit and vegetable preservation material in step (3) is: x (B) y [M z Ti 8-z ]O 16 (x≤2, y≤6, z≤5), where A=K + Mg 2+ , Ca 2+ 、Al 3+ or H + ; B=Si, C or N; M=Zn 2+ , Fe 3+ , Cu 2+ , Cu + or Ag + , A x (B) y The adsorption buffer waiting area constructed by the "card house" structure of the hunting-type fruit and vegetable preservation material, [M z Ti 8-z ] is the antibacterial decomposition zone and photocatalytic synergistic enhancement zone of the hunting-type fruit and vegetable preservation material.

[0042] In the present invention, the clay mineral can be used as an adsorption waiting buffer zone, the metal ion inorganic antibacterial agent and the organic antibacterial agent between the clay layers and on the surface can be used as an antibacterial decomposition zone, and the carbon quantum dot-modified titanium dioxide can be used as a synergistic enhancement zone (catalytic degradation of gases such as ethylene).

[0043] The invention also provides a hunting-type fruit and vegetable fresh-keeping material, which is prepared by adopting the above method.

[0044] The above second object of the present invention can be achieved by the following technical scheme: A fruit and vegetable fresh-keeping film is prepared by the following method: the hunting-type fruit and vegetable fresh-keeping material is granulated, blown, bagged and perforated to obtain the fruit and vegetable fresh-keeping film.

[0045] Furthermore, according to the breathing intensity of the packaged fresh-keeping agricultural products, inorganic small molecules are added to the fruit and vegetable fresh-keeping materials, and the air permeability and breathing intensity are adjusted through granulation, film blowing, bag making and perforation to obtain the hunting-type fruit and vegetable dormant fresh-keeping film.

[0046] Optionally, the inorganic small molecule is one or more of calcium chloride, sodium sulfate and silica gel.

[0047] The addition of inorganic small molecules and the setting of perforations can form a gas regulation zone, which can keep fruits and vegetables in a dormant state, even if the fruits and vegetables remain alive, but slow down their life metabolic activities.

[0048] Since the respiration intensity, water content and putrefactive bacteria of each kind of fruit and vegetable are different, the effect of packaging and preservation will produce large differences with different fruit and vegetable categories, so it is difficult for general packaging and preservation to have universal applicability. The hunting-type fruit and vegetable dormant fresh-keeping film in the present invention has various elements. By constructing new materials in four dimensions of adsorption waiting buffer zone, antibacterial decomposition zone, synergistic enhancement zone and gas adjustment zone, its preservation effect is not restricted and limited by the storage environment. It can also play a good preservation effect under weak light or even dark conditions or in a sealed system. The adsorption buffer zone and the gas adjustment zone can adjust the humidity and the concentration of carbon dioxide and oxygen in the surrounding environment during the fruit and vegetable preservation process, thereby reducing the respiration of fruits and vegetables. At the same time, the adsorption buffer zone and the synergistic enhancement zone can adsorb and degrade ethylene and other bad gases, reduce the ethylene concentration and bad odor in the surrounding environment, and the antibacterial decomposition zone has a good antibacterial effect, which can ensure the freshness of fruits and vegetables, making it universal for fruit and vegetable preservation.

[0049] The fruit and vegetable fresh-keeping film of the present invention is a combination of titanium composite oxide modified by carbon quantum dots doped with metal atoms and an organic antibacterial agent with clay mineral as a carrier, which has the characteristics of surface activity, antibacterial property and photocatalysis. The clay mineral is dispersed in an organic solvent by high-speed stirring, which can accelerate the thermal motion between molecules, thereby expanding the interlayer spacing of the clay carrier, making its structure more loose and increasing the specific surface area; it is convenient for metal ions and organic ion antibacterial functional components to be embedded in the inner and outer interlayers of the clay carrier; the carbon quantum dots modify the TiO 2 Nanosheets can adsorb many oxygen atoms on the surface, provide more active sites, optimize the energy level structure, improve the photocatalytic activity in the visible light region, and enhance the ability to utilize visible light. The synergy of inorganic and organic antimicrobial agents catalyzes the decomposition of decay-causing microorganisms, allowing them to exert better antibacterial and antibacterial effects, and have broad-spectrum antibacterial properties.

[0050] In addition, clay minerals have abundant positive and negative charges, and contain abundant amine, hydroxyl and carboxyl groups, which are conducive to the regular arrangement of metal ions and organic ions, and are more conducive to the synergistic effect of multiple antimicrobial active components, and better antibacterial and broad-spectrum properties. It is worth noting that after clay minerals react with titanium dioxide nanosheets modified with carbon quantum dots doped with metal atoms and are incorporated into functional films, they will not migrate and can be used in the packaging industry for food preservation.

[0051] The last object of the present invention can be achieved by the following technical solutions: application of the above-mentioned hunting-type fruit and vegetable fresh-keeping material in the preparation of fruit and vegetable fresh-keeping film and application of the above-mentioned hunting-type fruit and vegetable fresh-keeping material or the above-mentioned hunting-type fruit and vegetable dormant fresh-keeping film in fruit and vegetable fresh-keeping.

[0052] To verify the effect, the present invention granulates the obtained fruit and vegetable fresh-keeping material, blends it with polyolefin, and adopts a blow molding process to prepare a polyethylene-based fresh-keeping film with a thickness of 20nm. The fresh-keeping test objects are the fresh-keeping of lychees, the fresh-keeping of bayberries, and the yellowing of perfume lemons under the real logistics e-commerce normal temperature delivery environment. Lychees were delivered from Hainan to Yili, Xinjiang at room temperature for 9 days, and the flavor and taste were still retained, without a single rotten fruit; while the ordinary fresh-keeping film on the market was all moldy and rotten, without a single good fruit. From the performance of the taste of the origin of bayberry, the hardness, weight loss rate, spoilage rate, color, fragrance and other dimensions of the fresh-keeping packaging are significantly better than ordinary packaging, and the overall fresh-keeping period can be extended by at least 2 days. For perfume lemons, the yellowing time is extended by 19 days under refrigeration at 15 degrees, and the effect diagram is presented in the attached figure. The fresh-keeping effect will vary with the film making process, film thickness and film-forming substrate, and the fresh-keeping objects are not limited to watercress, lychees and perfume lemons.

[0053] The invention has found through experiments that the obtained fresh-keeping film has a significant antibacterial effect on Staphylococcus aureus, Escherichia coli, Aspergillus niger and Bacillus subtilis, and the adsorption and decomposition rate of ethylene and histamine is 50% to 80%.

[0054] Compared with the prior art, the present invention has the following advantages:

[0055] (1) The present invention composites carbon quantum dots (CQDs) prepared from natural biomass waste such as lychee peel and organic small molecules with titanium dioxide nanosheets, verifies the modification of carbon quantum dots by various characterization methods, and then analyzes the nanosheets after detection by ultraviolet-visible near-infrared spectrophotometer, indicating that the band gap of carbon quantum dots modified nanosheets is significantly reduced, and the photocatalytic activity in the visible light region is significantly improved compared with titanium dioxide nanosheets;

[0056] (2) Compared with the existing packaging preservation of fruits and vegetables, the hunting-type dormant fruit and vegetable cling film of the present invention has greater universality. The four-dimensional construction of the cling film of the present invention, namely, the adsorption waiting buffer zone, the antibacterial decomposition zone, the synergistic enhancement zone and the gas adjustment zone, has a preservation effect that is not restricted or limited by the storage environment. It can also play a good preservation effect under weak light or even dark conditions or in a sealed system. The adsorption buffer zone and the gas adjustment zone can adjust the humidity and the concentration of carbon dioxide and oxygen in the surrounding environment during the preservation of fruits and vegetables, thereby reducing the respiration of fruits and vegetables. At the same time, the adsorption buffer zone and the synergistic coordination zone can adsorb and degrade ethylene and other harmful gases, reducing the ethylene concentration and bad odor in the surrounding environment. The antibacterial decomposition zone has a good antibacterial effect, which can ensure the freshness of fruits and vegetables, and is particularly important in the e-commerce distribution of fruits and vegetables.

[0057] (3) Compared with the common methods of preserving fruits and vegetables by controlled atmosphere, irradiation and chemicals, the preservative factors in the present invention do not come into direct contact with the fruits and vegetables, nor diffuse into the fruits and vegetables through escaping. Instead, they create a clean microenvironment through functional packaging, slowing down the metabolism of fruits and vegetables and allowing the fruits and vegetables to reach dormancy;

[0058] (4) The preparation method of the fruit and vegetable fresh-keeping material of the present invention has a simple process and cheap raw materials, which meets the requirements of food contact materials. The application of the fruit and vegetable fresh-keeping material of the present invention can ensure the safety and freshness of fruits and vegetables to the greatest extent and extend the shelf life of food. The hunting-type fruit and vegetable dormant fresh-keeping material of the present invention meets the leading direction of reducing the amount of chemical preservatives, controlling harm, saving costs and increasing efficiency, and developing food safety and healthy agriculture. It also provides a new method for upgrading food preservation technology and has great economic and social benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] Figure 1 The TNS and CQDs@TiO in Examples 1-4 2 UV-Vis DRS spectra and calculation of TNS and CQDs@TiO based on UV-vis DRS data 2 Band gap, where (a) is TNS and CQDs@TiO 2 UV-Vis DRS spectrum of TNS and CQDs@TiO calculated based on UV-Vis DRS data. 2 Band gap;

[0060] Figure 2 The TNS and CQDs@TiO2 in Examples 1-4 under visible light and UV light 2 The removal rate of ethylene, where (a) shows TNS and CQDs@TiO under visible light 2 The removal rate of ethylene, (b) TNS and CQDs@TiO under UV light 2Ethylene removal rate;

[0061] Figure 3 is the antibacterial effect of the fruit and vegetable preservation material in Example 5;

[0062] Figure 4 This is the ethylene removal performance test result of the fruit and vegetable fresh-keeping material in Example 5;

[0063] Figure 5 This is a test of the preservation effect of the hunting-type fruit and vegetable dormant cling film in Example 5 on the lychee logistics e-commerce in Example 8, wherein (a) shows the packaging method before logistics, (b) shows the scene of receiving the express delivery 9 days later, and (c) shows the use of commercially available ordinary packaging;

[0064] Figure 6 In Example 9, the preservation effect of the hunting-type fruit and vegetable dormant cling film in Example 6 on bayberry was tested;

[0065] Figure 7 The test results of hardness, weight loss rate and spoilage rate of waxberry fresh-keeping packaging using the hunting-type fruit and vegetable dormant fresh-keeping film in Example 6 in Example 9;

[0066] Figure 8 This is the preservation effect of the perfume lemon obtained on the 6th day using different preservative films in Example 7 in Example 10, wherein the left picture is a common packaging film, and the right picture is the hunting-type fruit and vegetable dormant preservative film of the present invention;

[0067] Fig. 9 This is the test result of the preservation effect of the hunting-type fruit and vegetable dormant cling film on perfume lemon in Example 10 using Example 7. DETAILED DESCRIPTION

[0068] Example 1

[0069] The method for preparing carbon quantum dot-modified titanium dioxide nanosheets provided in this embodiment comprises the following steps:

[0070] (1) Ultrafinely crushing litchi peel, heating it in a muffle furnace at 300° C. for 3 h, and then dispersing it in deionized water to obtain a dispersion; dissolving anhydrous citric acid of small organic molecules in water to obtain an aqueous solution of small organic molecules citric acid; hydrothermally reacting the dispersion and the aqueous solution of small organic molecules citric acid at 200° C. for 6 h, cooling, and centrifuging to obtain a biomass carbon quantum dots (CQDs) solution;

[0071] (2) Preparation of TiO by hydrothermal method 2Nanosheets: 10 mL of butyl titanate was absorbed into the polytetrafluoroethylene liner, 1.2 mL of HF was slowly added into 10 mL of butyl titanate and mechanically stirred, butyl titanate and HF were stirred and mixed to make them uniform, and then the mixed solution was poured into the white inner liner of the high-pressure reactor. The top of the reactor was tightened with a stainless steel rod and placed in a 180°C silicone oil bath for 24 hours of hydrothermal reaction and then naturally cooled to room temperature. After the liner was taken out, the upper yellow oily liquid was poured out and the lower light blue viscous solid was left. It was washed twice with ethanol and then washed twice with deionized water. The final product was placed in a 60°C oven and dried for 12 hours. It was ground into powder with an agate mortar to obtain TiO 2 Nanosheets (TNS);

[0072] (3) Weigh 0.1 g of TNS powder, add 9 mL of deionized water to a beaker, ultrasonicate, then add 1 mL of CQDs solution to keep the total volume of the solution at 10 mL. Stir the mixed solution in the beaker mechanically for 30 min, then take it to an ultrasonic cleaner for 30 min of ultrasonication to obtain a uniform white suspension. Pour the suspension into the white inner tank of a high-pressure reactor, tighten the reactor, and then place it in a 150 °C oil bath for hydrothermal reaction for 3 h. After the reaction is completed, wait for the reactor and its inner tank to cool to room temperature and then pour out the upper white transparent liquid. Rinse the white product at the bottom with deionized water and pour it into a centrifuge tube. Place it in a high-speed desktop centrifuge (10000 rpm, 5 min) for centrifugal washing. Wash it 4 times in total. Finally, place the product in a 60 °C oven to dry for 12 h and grind it into powder to obtain carbon quantum dot modified titanium dioxide nanosheets CQDs@TiO 2 , denoted as CT-1.

[0073] Example 2

[0074] The difference from Example 1 is that in step (3), 0.1 g of TNS powder is weighed, 8 mL of deionized water is added to a beaker, ultrasonic treatment is performed, and then 2 mL of CQDs solution is added to keep the total volume of the solution at 10 mL. The mixed solution in the beaker is mechanically stirred for 30 min, and then ultrasonicated in an ultrasonic cleaner for 30 min to obtain a uniform white suspension. The suspension is poured into the white inner liner of the high-pressure reactor, the reactor is tightened, and then placed in a 150°C oil bath for hydrothermal reaction for 3 h. After the reaction is completed, the reactor and its inner liner are cooled to room temperature and then the upper white transparent liquid is poured out. The white product at the bottom is rinsed with deionized water and poured into a centrifuge tube, which is placed in a high-speed desktop centrifuge (10000 rpm, 5 min) for centrifugal washing. The washing is performed 4 times in total. Finally, the product is placed in a 60°C oven to dry for 12 h and ground into powder to obtain carbon quantum dot modified titanium dioxide nanosheets CQDs@TiO 2 , recorded as CT-2.

[0075] Example 3

[0076] The difference from Example 1 is that in step (3), 0.1 g of TNS powder is weighed, 6 mL of deionized water is added to a beaker, ultrasonic treatment is performed, and then 4 mL of CQDs solution is added to keep the total volume of the solution at 10 mL. The mixed solution in the beaker is mechanically stirred for 30 min, and then ultrasonicated in an ultrasonic cleaner for 30 min to obtain a uniform white suspension. The suspension is poured into the white inner liner of the high-pressure reactor, the reactor is tightened, and then placed in a 150°C oil bath for hydrothermal reaction for 3 h. After the reaction is completed, the reactor and its inner liner are cooled to room temperature and then the upper white transparent liquid is poured out. The white product at the bottom is rinsed with deionized water and poured into a centrifuge tube, which is placed in a high-speed desktop centrifuge (10000 rpm, 5 min) for centrifugal washing. The washing is performed 4 times in total. Finally, the product is placed in a 60°C oven to dry for 12 h and ground into powder to obtain carbon quantum dot modified titanium dioxide nanosheets CQDs@TiO 2 , recorded as CT-4.

[0077] Example 4

[0078] The difference from Example 1 is that in step (3), 0.1 g of TNS powder is weighed, 4 mL of deionized water is added to a beaker, ultrasonic treatment is performed, and then 6 mL of CQDs solution is added to keep the total volume of the solution at 10 mL. The mixed solution in the beaker is mechanically stirred for 30 min, and then ultrasonicated in an ultrasonic cleaner for 30 min to obtain a uniform white suspension. The suspension is poured into the white inner liner of the high-pressure reactor, the reactor is tightened, and then placed in a 150°C oil bath for hydrothermal reaction for 3 h. After the reaction is completed, the reactor and its inner liner are cooled to room temperature and then the upper white transparent liquid is poured out. The white product at the bottom is rinsed with deionized water and poured into a centrifuge tube, which is placed in a high-speed desktop centrifuge (10000 rpm, 5 min) for centrifugal washing. The washing is performed 4 times in total. Finally, the product is placed in a 60°C oven to dry for 12 h and ground into powder to obtain carbon quantum dot modified titanium dioxide nanosheets CQDs@TiO 2 , recorded as CT-6.

[0079] That is, in Examples 1-4, four portions of 0.1 g TNS powder were weighed, and different volumes of deionized water (9 mL, 8 mL, 6 mL, and 4 mL) were added to four beakers, and then different volumes of CQDs solution (1 mL, 2 mL, 4 mL, and 6 mL) were added to keep the total volume of the solution at 10 mL. After subsequent treatment, four CQDs@TiO 2 The composite materials are denoted as CT-1, CT-2, CT-4, and CT-6.

[0080] The carbon quantum dot modified titanium dioxide nanosheets in Examples 1-4 were subjected to the following performance tests:

[0081] 1. Ultraviolet-visible diffuse reflectance spectroscopy (UV-Vis DRS)

[0082] A UV-3600 ultraviolet-visible diffuse reflectometer was used to characterize the light absorption capacity of the prepared samples. The band gap of the samples was calculated through the test results and formula, and the light response range of the samples was determined based on the results.

[0083] Semiconductor bandgap calculation formula:

[0084] (αhv) n =K(hv-E g )

[0085] hv=1240 / λ

[0086] α is the absorption coefficient, h is the Planck constant, v is the frequency, K is the constant, Eg is the semiconductor bandgap width, and λ is the test wavelength. 2 is an indirect band gap, n=1 / 2; since the data measured by the UV-visible diffuse reflectance spectrum is the absorption value Abs, Abs is proportional to α and will not affect , the measured Abs data can be used instead of α for calculation.

[0087] Ultraviolet-visible diffuse reflectance spectroscopy (UV-Vis DRS) was used to study the properties of TNS, CQDs, and CQDs@TiO 2 The optical response wavelength and bandgap width of the composite material.

[0088] TNS and CQDs@TiO 2 UV-Vis DRS spectra and calculation of TNS and CQDs@TiO based on UV-vis DRS data 2 Band gap Figure 1 As shown, (a) is TNS and CQDs@TiO 2 UV-Vis DRS spectrum of (b) TNS and CQDs@TiO calculated based on UV-vis DRS data. 2 Band gap.

[0089] Depend on Figure 1As can be seen in Figure (a), after compounding with different concentrations of CQDs, the absorption intensity of the composite catalyst in the ultraviolet region of 350-400nm has been significantly improved, indicating that the unique optical properties of CQDs enable it to act as a photosensitizer to enhance the absorption of TNS for ultraviolet light, thereby improving its photocatalytic activity under ultraviolet light conditions. The absorption intensity of CT-4 in the visible light region of 400-500nm is better than that of TNS, indicating that the compounding of CQDs can enhance the absorption intensity of TNS for ultraviolet and visible light. At the same time, Figure 1 As shown in Figure (b), based on the UV-Vis DRS data, the band gap of TNS is calculated to be 3.03 eV, the band gap of CQDs is 2.42 eV, and the composite CQDs@TiO 2 The bandgap width is shortened due to the recombination of CQDs.

[0090] 2. NS, CQDs@TiO 2 Study on the photocatalytic ethylene removal performance

[0091] Place the samples in an acrylic box and illuminate them with a small visible light lamp or UV lamp. Set up an ethylene detector and place it in the box. Place TNS powder (0.2 g) and the four prepared CQDs@TiO 2 The composite materials (0.2 g) were placed in an acrylic box in turn, the acrylic box was closed, and ethylene gas was then filled into the hole with a syringe. The hole was then blocked with vaseline. The ethylene detector recorded data every hour, recording the ethylene concentration in the acrylic box under visible light and ultraviolet light respectively. The data was recorded for four hours and finally the data was collected to calculate the ethylene removal rate of the sample.

[0092] The photocatalytic performance of different samples was evaluated by photocatalytic removal of ethylene under simulated visible light and ultraviolet light. The results are as follows: Figure 2 As shown in Figures (a) and (b), the samples are TNS and CQDs@TiO composite modified with different concentrations of CQDs. 2 Composite materials.

[0093] from Figure 2 It can be seen that after 240 minutes of photocatalytic removal of the above five samples, the final removal rates of ethylene under visible light conditions were 21.25%, 22.00%, 22.58%, 48.84%, and 34.41%, respectively. Figure 2 As shown in Figure (a), the final ethylene removal rates under UV conditions were 30.90%, 32.09%, 32.81%, 53.93%, and 39.87%, respectively. Figure 2As shown in Figure (b), the photocatalytic performance of the five samples under visible light and ultraviolet light is in the order of CT-4>CT-6>CT-2>CT-1>TNS. It can be seen that the CQDs@TiO 2 The composite material has a significant improvement in the photocatalytic removal rate of ethylene under visible light and ultraviolet light conditions, indicating that the compounding of CQDs helps to improve the photocatalytic performance of TNS. When the addition amount of CQDs solution is 4mL, the photocatalytic removal rate of ethylene of the composite material CT-4 under visible light conditions reaches 48.84%, and the photocatalytic removal rate of ethylene under ultraviolet light conditions reaches 53.93%, which is the best sample among all composite samples. Further increasing the compounding amount of CQDs, when the added CQDs solution is 6mL, the photocatalytic performance of the composite material CT-6 decreases instead, indicating that excessive concentration of CQDs compounding will make CQDs.

[0094] From the comparison of the photocatalytic removal rates of ethylene under visible light and ultraviolet light conditions, the photocatalytic removal rates of ethylene of all samples under ultraviolet light conditions are higher than those under visible light conditions, and the effect is better. This is because ultraviolet light has a short wavelength and high energy, so the samples absorb more energy under ultraviolet light conditions than visible light, and therefore the photocatalytic removal rate of ethylene is also better.

[0095] Example 5

[0096] The method for preparing the hunting-type fruit and vegetable fresh-keeping material provided in this embodiment comprises the following steps:

[0097] (1) Disperse 50 g of diatomaceous earth in 164 mL of 50% (v / v) anhydrous ethanol and 2 mL of glacial acetic acid, and stir to obtain a diatomaceous earth dispersion;

[0098] (2) Add the carbon quantum dot modified titanium dioxide nanosheets CQDs@TiO2 prepared in Example 3 to the diatomaceous earth dispersion of step (1), and add the metal oxide zinc oxide, the metal salt copper sulfate and the dispersant vinyl acetate resin, calcine at 220°C and 120 kPa for 20 hours, then add the organic antibacterial agent benzyl ammonium bromide, ball mill for 12 hours, and dry at 65°C for 24 hours to obtain a dispersion with an average particle size of about 100 nm, thereby obtaining a hunting-type fruit and vegetable fresh-keeping material.

[0099] The mass proportions of clay mineral, carbon quantum dot modified titanium dioxide nanosheets, metal oxides and metal salts in the clay mineral dispersion are: 50% clay mineral, 5% carbon quantum dot modified titanium dioxide nanosheets, 10% metal oxides and 15% metal salts; the amount of organic antibacterial agent added accounts for 0.5% of the total mass of the material.

[0100] The hunting-type fruit and vegetable fresh-keeping material in this embodiment is used for antibacterial and ethylene removal tests, as shown below:

[0101] (1) Activation of bacterial strains: Use a sterilized inoculation loop to streak the second-generation slant bacterial strains stored at low temperature onto a plate medium that has solidified into a white solid, and place it in a 37°C bacterial incubator for 24 hours to allow it to grow.

[0102] (2) Preparation of bacterial liquid: A single colony was inoculated into 100 mL of liquid culture medium that had been sterilized by high pressure and cooled to about 40°C. The culture was incubated in a shaking incubator at 37°C and 150 rpm for 8 h. The bacterial liquid was stored at low temperature for later use.

[0103] (3) After sterilizing the culture medium, pour 15 mL of the culture medium into a plate when the conical flask is about 45°C. After the culture medium solidifies, take 0.1 mL of the bacterial solution and pour it onto the plate. Use a spreading rod to evenly spread the culture medium, and then use a 4 mm puncher to punch holes in the culture medium. After punching, pour 10 mg of the sample evenly into the holes of the solidified culture medium, and place it in a 37°C incubator and culture it for 24 hours under no light (darkness), visible light, and ultraviolet light. The antibacterial activity of the prepared sample is determined by the difference between the size of the inhibition zone and the size of the punch hole.

[0104] The antibacterial effects of the hunting-type fruit and vegetable preservation material in Example 5 on Staphylococcus aureus, Escherichia coli, Aspergillus niger and Bacillus subtilis under the conditions of no light (darkness), visible light and ultraviolet light are as follows: Figure 3 As shown, the larger the diameter of the inhibition zone, the better the antibacterial effect. The effect is very significant. It can also be clearly seen that the effect of ultraviolet light is better than that of visible light, and visible light is better than that of dark conditions.

[0105] (2) Ethylene determination experiment

[0106] The hunting-type fruit and vegetable preservation material of this embodiment is placed in an acrylic box, and the ethylene detector is also placed in the box after being set up. The lightless (darkness), visible light and ultraviolet light are turned on respectively, and the acrylic box is sealed. Then, ethylene gas is filled into the hole with a syringe, and then the hole is blocked with vaseline. The ethylene detector records data every hour, and records the ethylene concentration in the acrylic box under darkness, visible light and ultraviolet light respectively. The data is recorded for four hours, and finally the data is collected to calculate the ethylene removal rate of the sample. The results are as follows: Figure 4 shown.

[0107] The hunting-type fruit and vegetable preservation material has a photocatalytic removal rate of ethylene in the dark, visible light and ultraviolet light conditions of 30% to 80%. From a comparative point of view, the photocatalytic removal rate of ethylene of all samples under ultraviolet light conditions is higher than that under visible light conditions, and the effect is better. This is because the ultraviolet light has a short wavelength and high energy, so the sample absorbs more energy under ultraviolet light conditions than visible light, so the photocatalytic removal rate of ethylene is also better. Moreover, the photocatalytic removal rate of ethylene by the hunting-type fruit and vegetable preservation material in the present invention is also much higher than that of using carbon quantum dots to modify titanium dioxide nanosheets alone.

[0108] Therefore, the hunting-type fruit and vegetable fresh-keeping material prepared by the present invention has the effects of adsorbing and decomposing ethylene and antibacterial under dark, visible light and ultraviolet light conditions, and is used as a fresh-keeping packaging material, especially for fruit and vegetable preservation, and is suitable for preservation under different storage environments, such as e-commerce, shelves and static warehousing.

[0109] Example 6

[0110] The method for preparing the hunting-type fruit and vegetable fresh-keeping material provided in this embodiment comprises the following steps:

[0111] (1) Disperse 40 g of diatomaceous earth in 160 mL of 50% (v / v) anhydrous ethanol and 3 mL of glacial acetic acid, and stir to obtain a diatomaceous earth dispersion;

[0112] (2) Add the carbon quantum dot modified titanium dioxide nanosheets CQDs@TiO prepared in Example 3 to the diatomite dispersion of step (1) 2 , and add metal oxides zinc oxide, ferric oxide, metal salt copper humate and dispersant vinyl acetate resin, calcine at 240°C and 140kPa for 15 hours, then add organic antibacterial agent benzyl ammonium bromide, ball mill for 12 hours, and dry at 65°C for 24 hours to obtain a dispersion with an average particle size of about 100nm, thus obtaining a hunting-type fruit and vegetable preservation material.

[0113] The mass proportions of clay mineral, carbon quantum dot modified titanium dioxide nanosheets, metal oxides and metal salts in the clay mineral dispersion are: 45 clay minerals, 3 carbon quantum dot modified titanium dioxide nanosheets, 8 metal oxides and 20 metal salts; the amount of organic antibacterial agent added accounts for 0.3% of the total mass of the material.

[0114] Example 7

[0115] The method for preparing the hunting-type fruit and vegetable fresh-keeping material provided in this embodiment comprises the following steps:

[0116] (1) Disperse 60 g of kaolinite in 180 mL of 50% (v / v) anhydrous ethanol and 2 mL of glacial acetic acid, and stir to obtain a kaolinite dispersion;

[0117] (2) Adding the carbon quantum dot modified titanium dioxide nanosheets CQDs@TiO prepared in Example 3 to the kaolinite dispersion in step (1) 2 , and add metal oxides zinc oxide and ferric oxide, metal salt copper humate and dispersant vinyl acetate resin, calcine at 240°C and 140kPa for 15 hours, then add organic antibacterial agent benzyl ammonium bromide, ball mill for 12 hours, and dry at 65°C for 24 hours to obtain a dispersion with an average particle size of about 100nm, thus obtaining a hunting-type fruit and vegetable preservation material.

[0118] The mass proportions of clay mineral, carbon quantum dot modified titanium dioxide nanosheets, metal oxides and metal salts in the clay mineral dispersion are: 60% clay mineral, 8% carbon quantum dot modified titanium dioxide nanosheets, 12% metal oxides and 5% metal salts; the amount of organic antibacterial agent added accounts for 0.8% of the total mass of the material.

[0119] Example 8

[0120] The hunting-type fruit and vegetable fresh-keeping material prepared in step (2) of the above embodiment 5 was granulated by adding 0.5 g of calcium chloride with a particle size of 200 nm and 0.8 g of sodium sulfate. Then, the granulated material was blown with PE to form a film with a thickness of 20 μm and 4 micropores to obtain a hunting-type fruit and vegetable dormant fresh-keeping film.

[0121] Lychee has a high respiration rate, high sugar content, and rich water content, and is known as the most difficult fruit to keep fresh. To verify the effect, the prepared plastic wrap was used to wrap lychees and directly used the logistics e-commerce distribution model for the test. The lychees were delivered from Hainan to Yili, Xinjiang at room temperature for 9 days. The results are as follows: Figure 5 After 9 days, although the color of the lychees wrapped in the functional plastic wrap has decreased, the flavor and taste are still preserved, and there is not a single rotten fruit. However, all the lychees wrapped in the ordinary plastic wrap on the market have become moldy and rotten, and there is not a single good fruit.

[0122] Example 9

[0123] The hunting-type fruit and vegetable fresh-keeping material prepared in step (2) of the above Example 6 was granulated with 0.8 g of sodium sulfate to obtain a functional masterbatch, which was then blown into a film with a thickness of 20 μm and 1 micropore to obtain a hunting-type fruit and vegetable dormant fresh-keeping film.

[0124] Bayberry has a moderate sweet and sour taste and is rich in nutrients. It matures in the high temperature and high humidity rainy season. Without the protection of the outer skin, it is very easy to spoil and deteriorate, and it is very difficult to keep it fresh. To verify the effect, the prepared plastic wrap was used to package bayberry for preservation test and compared with ordinary packaging. The results are as follows Figure 6 shown.

[0125] From the perspective of maintaining the taste of the origin, the hardness, weight loss rate, spoilage rate, color, aroma and other dimensions of fresh-keeping packaging are significantly better than ordinary packaging, and the overall fresh-keeping period can be extended by at least 2 days. Figure 7 shown.

[0126] Example 10

[0127] The hunting-type fruit and vegetable fresh-keeping material prepared in step (2) of the above embodiment 7 is granulated to obtain a functional masterbatch, which is then blown with PE to form a film with a thickness of 20 μm to obtain a hunting-type fruit and vegetable dormant fresh-keeping film.

[0128] Compared with other fruits and vegetables, perfume lemon has low respiration intensity and is easier to preserve. However, its aroma and flavor vary greatly due to the change of color from green to yellow, which leads to considerable price differences. In order to verify the preservation effect, the perfume lemon was preserved by static storage at room temperature and refrigeration with functional packaging film and ordinary commercial packaging film. The preservation effect on the 6th day at room temperature is as follows: Figure 8 shown.

[0129] The test results of the preservation effect of the hunting-type fruit and vegetable dormant plastic wrap of this embodiment on perfume lemon are as follows: Fig. 9 As shown, from Fig. 9 It can be seen that at room temperature, ordinary commercially available packaging bags begin to turn yellow on the 6th day, while functional packaging only begins to turn yellow on the 14th day, extending the yellowing time by 8 days. Under refrigeration at 15 degrees, the yellowing time is extended by 19 days.

[0130] Embodiment 11

[0131] According to the national standard GB 31604.1-2015 General Rules for Migration Test of Food Contact Materials and Products, the selected food simulant liquid is 10% ethanol and 95% ethanol, 20°C, and the test days are 10 days. The substance migration test result of the hunting-style fruit and vegetable dormant cling film prepared in Example 8 is <2.0 mg / dm 2 , in line with national standards ≤10mg / dm 2 The results show that the hunting-type fruit and vegetable dormant fresh-keeping film of the present invention meets the requirements of the national standard "GB4806.7-2016 National Food Safety Standard Food Contact Plastic Materials and Products" after testing.

[0132] Table 1 Total migration amount of the hunting type fruit and vegetable dormant fresh-keeping film of the present invention

[0133] Test conditions <![CDATA[PPCP / PBAT-g-LAE-15kGymg / dm 2 ]]> 10% ethanol (volume fraction) <2.0 95% ethanol (volume fraction) <2.0

[0134] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be thought of by a person skilled in the art within the technical scope disclosed by the present invention without creative work should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope defined in the claims.

Claims

1. A method for preparing a hunting-type fruit and vegetable fresh-keeping material, characterized in that The following steps are involved: (1) dispersing clay minerals in an organic solvent and stirring at high speed to obtain a clay mineral dispersion; (2) Preparation of carbon quantum dot modified titanium dioxide nanosheets: (2.1) The biomass material is ultrafinely ground and heated in a muffle furnace at 290-310° C. for 2-4 hours, and then dispersed in deionized water to obtain a dispersion, and organic small molecules are dissolved in water to obtain an organic small molecule aqueous solution, and the dispersion and the organic small molecule aqueous solution are hydrothermally reacted at 180-200° C. for 6 hours, cooled, and centrifuged to obtain a carbon quantum dot solution; (2.2) mixing a nano-titanium dioxide precursor and an acidic solution, subjecting the obtained mixture to high temperature treatment, naturally cooling the product after high temperature treatment, removing a layer of precipitate, washing, drying, and grinding to obtain titanium dioxide nanosheets; (2.3) ultrasonically dispersing the titanium dioxide nanosheets obtained in step (2.2) in deionized water, and then mixing with the carbon quantum dot solution obtained in step (2.1) and ultrasonically treating at high temperature in an oil bath or oven at 120 to 150° C., centrifuging and washing the obtained product, collecting the precipitate, and drying to obtain carbon quantum dot-modified titanium dioxide nanosheets with antibacterial and ethylene decomposition functions; (3) Add the carbon quantum dot-modified titanium dioxide nanosheets prepared in step (2) to the clay mineral dispersion of step (1), and add metal oxides, metal salts and dispersants, stir and mix at high speed, calcine at 200-250° C. and 100-150 kPa for 15-25 hours, then add an organic antibacterial agent, ball mill and dry, and the resulting dispersion is the hunting-type fruit and vegetable fresh-keeping material.

2. The method for preparing the hunting-type fruit and vegetable fresh-keeping material according to claim 1, characterized in that: The clay mineral in step (1) is one or more of kaolinite, montmorillonite, vermiculite and diatomaceous earth.

3. The method for preparing the hunting-type fruit and vegetable fresh-keeping material according to claim 1, characterized in that: The biomass material in step (2.1) is litchi peel and / or sugarcane bagasse; the organic small molecule in step (2.1) is citric acid, citrate, glucose or ascorbic acid; the nano titanium dioxide precursor in step (2.2) is one or more of butyl titanate, isopropyl titanate, titanyl sulfate, titanium tetrachloride, titanium trichloride and titanium dioxide P25; the acidic solution in step (2.2) is a strong acid, and the strong acid is concentrated hydrochloric acid, concentrated sulfuric acid or hydrofluoric acid; In step (2.2), the obtained mixture is subjected to high temperature treatment in a silicone oil bath at 175-200°C for 23-25h; in step (2.3), the dosage of the titanium dioxide nanosheets TNS and the biomass quantum dot solution is in the ratio of 0.1g:1-6mL; in step (2.3), the high temperature treatment is carried out in an oil bath at 150°C for 2-4h; in steps (2.2) and (2.3), ethanol and deionized water are used for washing, and the mixture is dried in an oven at 60°C for 12h.

4. The method for preparing the hunting-type fruit and vegetable fresh-keeping material according to claim 1, characterized in that: The metal oxide in step (3) is one or more of zinc oxide, ferric oxide, aluminum oxide and magnesium oxide; the metal salt in step (3) is one or more of copper sulfate, silver nitrate, copper nitrate, copper acetylacetonate, copper chloride, copper acetate, amino acid copper, copper humate, copper rosinate, calcium carbonate, copper succinate and copper ammonia; the organic antibacterial agent in step (3) is one or more of benzyl ammonium bromide, benzyl ammonium chloride and chitosan quaternary ammonium salt.

5. The method for preparing the hunting-type fruit and vegetable fresh-keeping material according to claim 1, characterized in that: The mass proportions of clay mineral, carbon quantum dot modified titanium dioxide nanosheets, metal oxide and metal salt in the clay mineral dispersion in step (3) are: 45-80% clay mineral, 2-10% carbon quantum dot modified titanium dioxide nanosheets, 4-15% metal oxide and 2-25% metal salt.

6. A hunting-type fruit and vegetable preservation material, characterized in that: The method is prepared by any one of claims 1 to 5.

7. A hunting type dormant fresh-keeping film for fruits and vegetables, characterized in that The method is prepared by the following method: the hunting type fruit and vegetable fresh-keeping material according to claim 6 is granulated, film blown, bagged and perforated to obtain the hunting type fruit and vegetable dormant fresh-keeping film.

8. The hunting type dormant fruit and vegetable fresh-keeping film according to claim 7, characterized in that: According to the breathing intensity of the packaged fresh-keeping agricultural products, inorganic small molecules are added to the fruit and vegetable fresh-keeping materials, and the air permeability and breathing intensity are adjusted through granulation, film blowing, bag making and perforation to obtain the hunting-type fruit and vegetable dormant fresh-keeping film, wherein the inorganic small molecules are one or more of calcium chloride, sodium sulfate and silica gel.

9. Use of the hunting-type fruit and vegetable fresh-keeping material according to claim 6 in preparing fruit and vegetable fresh-keeping film.

10. Use of the hunting-type fruit and vegetable fresh-keeping material according to claim 6 or the hunting-type fruit and vegetable dormant fresh-keeping film according to claim 7 in the preservation of fruits and vegetables.

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