Ag-mofs modified fresh-keeping paper and preparation method and application thereof

Abstract

The application belongs to the technical field of packaging materials, and particularly relates to Ag-MOFs modified preservative paper and a preparation method and application thereof. The preparation method comprises the following steps: performing carboxymethylation treatment on filter paper to obtain carboxymethylated filter paper; soaking the carboxymethylated filter paper in a silver ion solution; and adding an organic ligand solution to obtain the Ag-MOFs modified preservative paper. The preparation method has the advantages of mild reaction conditions, green environmental protection and simple operation. The Ag-MOFs modified preservative paper has good water stability, antibacterial performance and fruit and vegetable preservation performance, and can be used as an agricultural product packaging material to prolong the fruit and vegetable preservation period, and has important application value.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of packaging materials, and particularly relates to an Ag-MOFs modified fresh-keeping paper and a preparation method and application thereof. TECHNICAL BACKGROUND

[0002] Among the food wasted in the world every year, more than half of the total amount of food waste is caused by the corruption of fruits and vegetables, and microbial infection is the main reason for the deterioration of fruits and vegetables. In order to prolong the shelf life of fruits and vegetables, it has become a research focus to develop fresh-keeping materials with good antibacterial performance.

[0003] Silver metal organic framework (Ag-MOFs) has good antibacterial performance and is an ideal antibacterial material. Modifying paper-based materials with Ag-MOFs to prepare fruit and vegetable fresh-keeping materials is a very promising technology. However, the Ag-MOFs modified fruit and vegetable fresh-keeping materials reported so far have problems such as harsh reaction conditions, complex preparation process and poor water stability, and toxic chemical reagents are used in the synthesis process, which seriously endangers human health and is difficult to realize large-scale application. Therefore, it is urgent to use green synthesis technology to prepare Ag-MOFs modified fruit and vegetable fresh-keeping paper with high stability. SUMMARY

[0004] In view of the problems existing in the prior art, a first object of the present application is to provide a preparation method of Ag-MOFs modified fresh-keeping paper, which has the advantages of mild reaction conditions, green environmental protection and simple operation.

[0005] A second object of the present application is to provide a fresh-keeping paper prepared by the above method, which has good water stability, antibacterial performance and fruit and vegetable fresh-keeping performance.

[0006] A third object of the present application is to provide an application of the fresh-keeping paper prepared by the above method, which can be used for fresh-keeping.

[0007] To achieve the above objects, the technical scheme adopted by the present application is as follows:

[0008] A preparation method of Ag-MOFs modified fresh-keeping paper, the preparation method comprises the following steps:

[0009] (1) Carrying out carboxymethylation treatment on filter paper to obtain carboxymethylated filter paper;

[0010] (2) Soaking the carboxymethylated filter paper obtained in step (1) in a silver ion solution;

[0011] (3) Adding an organic ligand solution to the solution obtained in step (2) to obtain the fresh-keeping paper.

[0012] Further, in step (1), the carboxymethylation treatment method is to immerse the filter paper in a sodium chloroacetate solution, stir, wash and dry.

[0013] Further, in step (2), the soaking time is 0.5-24 h; the silver ion solution is an aqueous silver nitrate solution; the silver nitrate solution is prepared by dissolving silver nitrate in deionized water;

[0014] The mass ratio of silver nitrate to carboxymethylated filter paper is 1: (2.12-2.83).

[0015] Further, in step (3), the organic ligand solution is an ethanol solution of 2-methylimidazole; the 2-methylimidazole solution is prepared by dissolving 2-methylimidazole in anhydrous ethanol;

[0016] The mass ratio of 2-methylimidazole to carboxymethylated filter paper is 1: (1.62-4.39).

[0017] Further, the concentration of the sodium chloroacetate solution is 1 mol / L; the sodium chloroacetate solution is prepared by dissolving sodium chloroacetate in an aqueous sodium hydroxide solution; the mass concentration ratio of the aqueous sodium hydroxide solution is 15-20%; the mass-volume ratio of the filter paper to the sodium chloroacetate solution is 1 g: (68.97-156.25) mL.

[0018] Further, the stirring rate is 400 rpm, and the stirring time is 1 h; the washing uses deionized water; the drying temperature is room temperature (20-30 ℃), and the drying time is 12-24 h.

[0019] Further, in step (3), after adding the organic ligand solution, stirring, standing, washing and drying are further required.

[0020] The stirring temperature is room temperature, the stirring rate is 400 rpm, the stirring time is 30 min, the standing time is 3 h, the washing method is to first wash 3 times with anhydrous ethanol and then wash 3 times with deionized water, the drying temperature is 45 ℃, and the drying time is 12-24 h.

[0021] The Ag-MOFs modified fresh-keeping paper prepared by the above method.

[0022] The above fresh-keeping paper can be used for fruit and vegetable preservation.

[0023] Further, the fruits and vegetables are tomatoes, bananas and strawberries. Beneficial effects

[0024] (1) The application provides an Ag-MOFs modified fresh-keeping paper and a preparation method and application thereof. The preparation method is an in-situ synthesis method. First, filter paper is subjected to carboxymethylation modification, and then the obtained carboxymethylated filter paper is immersed in a precursor solution for synthesizing Ag-MOFs, and the Ag-MOFs modified fresh-keeping paper is obtained. The in-situ synthesis method is that Ag-MOFs are uniformly in-situ grown on the surface of cellulose fibers under normal temperature and pressure through cross-linking. The preparation method has the advantages of mild reaction conditions and simple synthesis steps. Meanwhile, the solvent used is ethanol, which meets the green and environmental protection requirements. The Ag-MOFs modified fruit and vegetable fresh-keeping material prepared by the application has good water stability.

[0025] (2) The Ag-MOFs modified fresh-keeping paper provided by the application has good water stability, antibacterial performance and fresh-keeping performance, can be used as a fruit and vegetable packaging material, and can be used to prolong the fresh-keeping period of fruits and vegetables. In addition, the material has the characteristics of being renewable and good in flexibility, and is expected to replace part of petroleum-based materials in the future, so as to promote the development of a resource-saving and environment-friendly society. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 XRD spectrum of the fresh-keeping paper prepared in Example 2;

[0027] Figure 2 Antibacterial performance test diagram of the fresh-keeping paper prepared in Example 2;

[0028] Figure 3 Water stability test diagram of the fresh-keeping paper prepared in Example 2;

[0029] Figure 4 Fresh-keeping performance test diagram of the fresh-keeping paper prepared in Example 2. DETAILED DESCRIPTION

[0030] The technical solutions of the application will be described below in conjunction with the embodiments. Obviously, the described embodiments are part of the embodiments of the application, rather than all the embodiments. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the application. Example 1

[0031] Preparation of silver nitrate solution: 0.17 g of silver nitrate was dissolved in 30 mL of deionized water, stirred for 15 min, and ultrasonically treated for 2 min to obtain a solution;

[0032] Preparation of methyl imidazole solution: 0.082 g of 2-methyl imidazole was dissolved in 30 mL of anhydrous ethanol, stirred for 15 min, and ultrasonically treated for 2 min to obtain a solution;

[0033] Preparation of sodium chloroacetate solution: sodium chloroacetate was dissolved in 15% (w / v) aqueous sodium hydroxide solution to obtain;

[0034] The filter paper (0.32 g) was immersed in 50 mL of 1 mol / L sodium chloroacetate solution, stirred at 400 rpm for 1 h, washed with deionized water for 3 times, and dried at room temperature (20-30 ℃) for 12 h to obtain carboxymethylated filter paper; the carboxymethylated filter paper (0.36 g) was immersed in silver nitrate solution for 30 min; then 2-methylimidazole solution was added, and the mixture was stirred at 400 rpm for 30 min, stood for 3 h, washed with ethanol for 3 times, washed with deionized water for 3 times, and dried at 45 ℃ for 12 h. Example 2

[0035] Preparation of silver nitrate solution: 0.6 g of silver nitrate was dissolved in 90 mL of deionized water, stirred for 15 min, and ultrasonicated for 2 min to obtain;

[0036] Preparation of 2-methylimidazole solution: 1.05 g of 2-methylimidazole was dissolved in 90 mL of anhydrous ethanol, stirred for 15 min, and ultrasonicated for 2 min to obtain;

[0037] Preparation of sodium chloroacetate solution: sodium chloroacetate was dissolved in 20% (w / v) aqueous sodium hydroxide solution to obtain;

[0038] The filter paper (1.45 g) was immersed in 100 mL of 1 mol / L sodium chloroacetate solution, stirred at 400 rpm for 1 h, washed with deionized water for 3 times, and dried at room temperature (20-30 ℃) for 24 h to obtain carboxymethylated filter paper; the carboxymethylated filter paper (1.7 g) was immersed in silver nitrate solution for 24 h; then 2-methylimidazole solution was added, and the mixture was stirred at 400 rpm for 30 min, stood for 3 h, washed with ethanol for 3 times, washed with deionized water for 3 times, and dried at 45 ℃ for 24 h.

[0039] Performance test

[0040] XRD test

[0041] The material was subjected to XRD analysis by an X-ray diffractometer (Japan Smartlab SE, Cu Kα, 40 kV, 40 mA, 2θ=3-80°, 10°·min −1 ). The XRD spectrum is shown in Figure 1 The characteristic peaks of Ag-MOFs and cellulose in the carboxymethylated filter paper appeared in the XRD spectrum of the Ag-MOFs / carboxymethylated filter paper composite material, indicating that the Ag-MOFs particles successfully grew on the surface of the carboxymethylated filter paper.

[0042] Antibacterial performance

[0043] The antibacterial activity of the samples on E. coli and S. aureus was tested by the inhibition zone method. Filter paper, carboxymethylated filter paper and Ag-MOFs / carboxymethylated filter paper composite were cut into 12 mm diameter discs and sterilized with ultraviolet light for 1 h. Then 100 µL (10 7 cfu / mL) of bacterial solution was evenly distributed on the medium. Finally, all samples were placed in the medium containing the bacterial solution, incubated at 37 ℃ for 24 h, and the inhibition zone diameter was measured. The test results are shown in Figure 2 There was no inhibition zone found around the filter paper and carboxymethylated filter paper, indicating that they had no antibacterial activity. In contrast, there was a clear inhibition zone around the Ag-MOFs / carboxymethylated filter paper composite, indicating that it had good antibacterial activity.

[0044] Water stability performance

[0045] 0.1 g of Ag-MOFs / carboxymethylated filter paper composite was immersed in 100 mL of water and taken out periodically. Then the taken-out sample was dried at 45 ℃, and the structural changes of the sample were characterized by XRD. The test results are shown in Figure 3 The structure of the composite did not change significantly after immersion, indicating that it had good water stability.

[0046] Fresh-keeping performance

[0047] Fresh cherry tomatoes were used as an example for fruit and vegetable preservation testing. First, the cherry tomatoes were washed with deionized water, then placed in packaging boxes made of filter paper, carboxymethylated filter paper and Ag-MOFs / carboxymethylated filter paper composite, and stored at room temperature (25-28 ℃, 60-65% relative humidity), and the surface changes of the cherry tomatoes were recorded. The test results are shown in Figure 4 The surfaces of the control group and the cherry tomatoes packaged with filter paper and carboxymethylated filter paper all showed signs of rotting on the 6th day, while the surfaces of the cherry tomatoes packaged with Ag-MOFs / carboxymethylated filter paper still showed no signs of rotting on the 12th day, indicating that it can effectively extend the shelf life of fruits and vegetables and has good fresh-keeping performance.

[0048] The above only illustrates several embodiments of the present application and should not be construed as limiting the scope of the patent. It should be noted that other persons in the art can make modifications, substitutions and improvements without departing from the concept and scope of the present application, which are all within the scope of protection of the present application. Therefore, the patent protection scope of the present application should be subject to the description according to the claims.

Claims

1. A method for preparing Ag-MOFs-modified food preservation paper, characterized in that, The preparation method adopts the following steps: (1) Immerse the filter paper in sodium chloroacetate solution, stir, wash and dry to obtain carboxymethylated filter paper; (2) Immerse the carboxymethylated filter paper obtained in step (1) in a silver ion solution; (3) Add an organic ligand solution to the solution obtained in step (2) to obtain the preservation paper; In step (2), the soaking time is 0.5 to 24 hours. In step (3), the organic ligand solution is an ethanol solution of 2-methylimidazole.

2. The preparation method according to claim 1, characterized in that, In step (2), the silver ion solution is an aqueous solution of silver nitrate; the mass ratio of silver nitrate to carboxymethylated filter paper is 1:(2.12 ~ 2.83).

3. The preparation method according to claim 1, characterized in that, In step (3), the mass ratio of 2-methylimidazole to carboxymethylated filter paper is 1: (1.62 ~ 4.39).

4. The preparation method according to claim 2, characterized in that, The concentration of the sodium chloroacetate solution is 1 mol / L; the sodium chloroacetate solution is prepared by mixing sodium chloroacetate and sodium hydroxide aqueous solution; the concentration of the sodium hydroxide aqueous solution is 15 ~ 20 (w / v)%; the mass-to-volume ratio of the filter paper to the sodium chloroacetate solution is 1 g: (68.97 ~ 156.25) mL.

5. The preparation method according to claim 2, characterized in that, The stirring rate is 400 rpm, and the stirring time is 1 hour; the washing uses deionized water; the drying temperature is room temperature, and the time is 12 to 24 hours.

6. The preparation method according to claim 1, characterized in that, In step (3), after adding the organic ligand solution, it is necessary to stir, let stand, wash and dry; the stirring temperature is room temperature, the stirring speed is 400 rpm, the stirring time is 30 min; the standing time is 3 h; the washing method is to wash 3 times with anhydrous ethanol and then wash 3 times with deionized water; the drying temperature is 45℃, and the drying time is 12 ~ 24 h.

7. The Ag-MOFs-modified preservation paper prepared by the method according to any one of claims 1-6.

8. The application of the Ag-MOFs-modified preservative paper prepared by the method according to any one of claims 1-6 and / or the Ag-MOFs-modified preservative paper according to claim 7, characterized in that, The preservation paper is used for preserving fruits and vegetables.

9. The application according to claim 8, characterized in that, The fruits and vegetables mentioned are tomatoes, bananas, and strawberries.

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