Method for synthesizing nano-silver by using Chinese cabbage residue extracting solution and application of nano-silver

Abstract

The invention discloses a method for synthesizing nano-silver by using a Chinese cabbage residue extracting solution and application of the method. The method comprises the following steps: (1) drying Chinese cabbage residues, cutting the Chinese cabbage residues into pieces, soaking the Chinese cabbage residues in distilled water, and filtering and centrifuging the Chinese cabbage residues to obtain the Chinese cabbage residue extracting solution; and (2) the extracting solution and an AgNO3 solution are mixed to react, the reaction temperature is 60-90 DEG C, the reaction time is 30-80 min, nano-silver is synthesized, centrifugation is conducted to remove supernatant, then washing is conducted through distilled water, and a nano-silver solution is obtained. Compared with the prior art, the method has the advantages that (1) the cabbage residue extracting solution is used as a reducing agent and a stabilizing agent, so that the problem of environmental pollution caused by a traditional chemical reducing agent is avoided; (2) through process optimization, the synthesized nano-silver is uniform in particle size and excellent in antibacterial property, and particularly has a remarkable antibacterial effect on enterobacter hormaechei and staphylococcus sciuri; and (3) the method combines waste vegetable treatment and nano-silver green synthesis, and has a wide application prospect.

Description

Technical Field

[0001] The invention belongs to the technical field of green agriculture, relates to the resource utilization of agricultural wastes, and realizes the application of an extract in the preparation of nanosilver through a simple process, specifically a method for synthesizing nanosilver using a cabbage tail extract and the application thereof. Background Art

[0002] Waste vegetables are waste generated during the production, circulation and sales of vegetables. The amount is huge and improper handling can easily cause environmental pollution. Traditional methods of waste vegetable treatment include landfill and incineration, which has the disadvantage of easily causing waste of resources and causing environmental problems such as soil pollution and air pollution. Therefore, how to efficiently and greenly utilize waste vegetable resources is a research hotspot in the current field of agricultural waste treatment.

[0003] Nanosilver has attracted much attention from the scientific community due to its excellent antibacterial properties and potential application prospects. Nanosilver has been widely used in medicine, food packaging, environmental protection and other fields. It has broad-spectrum antibacterial properties and can effectively inhibit the growth of a variety of bacteria, fungi and viruses. However, traditional nanosilver synthesis methods, such as physical and chemical methods, have disadvantages such as high cost, complex process and serious environmental pollution. In particular, chemical synthesis of nanosilver usually requires the use of toxic chemical reducing agents and stabilizers. Although nanosilver particles can be obtained efficiently, they are easy to cause environmental pollution and remain in the product, which is harmful to users and ecosystems. In recent years, biosynthesis technology has become an emerging method for the preparation of nanosilver due to its advantages such as green environmental protection, simple operation and low cost. The biosynthesis of nanosilver usually uses plant extracts, microorganisms or enzymes as reducing agents and stabilizers, which not only reduces the use of harmful chemicals, but also better controls the morphology and particle size of nanosilver.

[0004] A Chinese patent with publication number CN113996801A discloses a method for preparing nanosilver based on red amaranth extract, wherein the red amaranth ethanol extract is mixed with a silver ion solution to react and generate nanosilver. The principle of this prior art is to use the red amaranth extract to reduce silver ions and prepare single-substance nanosilver with a particle size of 1-30nm. Specifically, the red amaranth leaf part is dried and crushed, and the red amaranth powder is refluxed and extracted with an ethanol aqueous solution, then subjected to ultrasound, and then filtered to obtain the red amaranth ethanol extract. In this prior art, ethanol is required for reflux, extraction, and ultrasound, and the raw material is the red amaranth leaf part, which is a daily edible part; therefore, the cost of the raw materials and process of the scheme is relatively high, and it is not suitable for large-scale industrial application.

[0005] The Chinese patent with publication number CN118080872A discloses a method and application of rapidly preparing nanosilver using gardenia extract in a green manner. The method uses gardenia extract as a reducing agent, alkyl glycoside as a surfactant and stabilizer, and prepares nanosilver hydrosol by microwave-assisted heating. Specifically, the gardenia fruit is crushed and sieved to obtain gardenia powder; then the gardenia powder is added to water, stirred and dissolved, and then placed in a microwave oven for heating, and then bathed in 50-70°C water for 20-40min; taken out, centrifuged to obtain a clarified gardenia extract and cooled to 15-25°C; the gardenia extract is taken, and APG diluent and silver nitrate solution are added respectively; after stirring, it is quickly placed in a microwave oven for heating for 50-70s to obtain a silver nanoparticle sol. The prior art additionally adds alkyl glycoside as a surfactant and stabilizer, which is inconsistent with the concept of green environmental protection; in addition, the microwave-assisted heating method can only be used in a laboratory environment, and the yield of the raw material gardenia fruit is not high, which is not conducive to industrialized production.

[0006] The cultivated area of ​​Chinese cabbage is very large in my country, with a sown area of ​​about 40 million mu, accounting for about 15% of the total sown area of ​​vegetables in China. Among them, cabbage tail is a kind of agricultural waste, rich in a variety of plant active ingredients, such as polyphenols, flavonoids, vitamins and minerals, etc. These ingredients have good reducibility and can reduce silver ions to nanosilver under appropriate conditions, thus providing a new idea for the green synthesis of nanosilver. Therefore, using cabbage tail extract as a reducing agent and stabilizer to develop a green and efficient nanosilver synthesis process can not only realize the high value utilization of tail resources, but also provide a new path for the sustainable preparation of nanosilver, which has important research significance and broad application prospects. In addition, the synthesized nanosilver has excellent antibacterial properties, especially for some common pathogens such as Escherichia coli and Staphylococcus aureus, which has a significant antibacterial effect, further broadening its application in the fields of medical treatment, food preservation and environmental protection. Summary of the invention

[0007] Technical problem to be solved: In order to overcome the shortcomings of the existing technology and realize the resource utilization of Chinese cabbage tail, its extract is used as a reducing agent and stabilizer to react with a silver nitrate solution to generate nanosilver, thereby realizing the green synthesis of nanosilver; in view of this, the present invention provides a method for synthesizing nanosilver using Chinese cabbage tail extract and its application.

[0008] Technical solution: A method for synthesizing nanosilver using Chinese cabbage tail extract comprises the following steps:

[0009] S1, drying the Chinese cabbage tail, cutting it into pieces, soaking it in distilled water, filtering it, and centrifuging it to obtain a Chinese cabbage tail extract;

[0010] S2, Chinese cabbage tail vegetable extract and AgNO3 solution are mixed, the reaction temperature is 60-90 ℃, the reaction time is 30-80min, nano silver is generated, and the supernatant is removed by centrifugation and washed with distilled water to obtain a nano silver solution; wherein, the volume ratio of the Chinese cabbage tail vegetable extract to the AgNO3 solution is 1:(0.5-2). During the reaction, the color of the solution gradually changes from light yellow to brown, indicating that nano silver has been generated. After the reaction is completed, centrifugation is performed, washed and resuspended to obtain a nano silver solution. Further, the characteristic absorption peak of nano silver is detected by ultraviolet-visible absorption spectroscopy, and the characteristic absorption peak is located at 438nm, indicating the generation of nano silver particles.

[0011] Preferably, the solid-liquid ratio of the dried cabbage tail to distilled water in S1 is 1:(10-30) g / mL.

[0012] Preferably, the cabbage tails in S1 are immersed in distilled water at a temperature of 60-90° C. for 20-40 minutes; and the centrifugal parameters are 6000-10000 r / min.

[0013] Preferably, the volume ratio of the Chinese cabbage tail extract to the AgNO3 solution in S2 is 1:2, and the concentration of the AgNO3 solution is 5-25 mmol / L.

[0014] Preferably, the concentration of AgNO3 solution in S2 is 25mmol / L, the reaction temperature is 74°C, and the reaction time is 62min.

[0015] Nanosilver prepared by any of the above methods.

[0016] Preferably, the nanosilver is in the form of uniform spherical particles with a particle size of about 1 μm.

[0017] The application of the above-mentioned nanosilver in the preparation of antibacterial agents.

[0018] The application of the above-mentioned nanosilver in inhibiting Enterobacter holmesii and Staphylococcus aureus.

[0019] Preferably, the antibacterial property of nanosilver is tested by the filter paper method, and the diameter of the inhibition zone of the nanosilver against Enterobacter holmesii is 8-12 mm, and the diameter of the inhibition zone against Staphylococcus sciuri is 7-9 mm. The test conditions are: incubate in a 37°C incubator for 48 hours, and then measure the diameter of the inhibition zone.

[0020] The principle of the method for synthesizing nanosilver by using the extract of Chinese cabbage tail is that the extract of Chinese cabbage tail is used as a reducing agent and a stabilizer to react with a silver nitrate solution under mild conditions to biosynthesize nanosilver. When the reaction temperature is controlled between 60-90°C and the reaction time is 30-80 minutes by process optimization, the particle size of the nanosilver can be ensured to be about 1 μm and evenly distributed.

[0021] Beneficial effects: (1) The method of synthesizing nanosilver using the extract of Chinese cabbage tail is used as a reducing agent and a stabilizer, thereby avoiding the environmental pollution problem caused by traditional chemical reducing agents; (2) The method is optimized by process, and the synthesized nanosilver has uniform particle size and excellent antibacterial properties, especially having a significant antibacterial effect on Enterobacter hallii and Staphylococcus sciuri. (3) The method not only solves the problem of waste of Chinese cabbage tail resources, but also provides a new way for the green synthesis of nanosilver, and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is the UV-visible absorption spectrum of the Chinese cabbage tail extract and the synthesized nanosilver;

[0023] Figure 2 This is a scanning electron microscope image of nanosilver synthesized using the extract of Chinese cabbage tail;

[0024] Figure 3 This is a diagram of the antibacterial effect of nanosilver synthesized using the extract of cabbage tail; the left picture shows Staphylococcus aureus, and the right picture shows Enterobacter hallii. DETAILED DESCRIPTION

[0025] The following examples further illustrate the content of the present invention, but should not be construed as limiting the present invention. Without departing from the spirit and essence of the present invention, modifications and substitutions made to the method, steps or conditions of the present invention all belong to the scope of the present invention. Unless otherwise specified, the technical means used in the examples are conventional means well known to those skilled in the art.

[0026] Example 1

[0027] 1. Material Preparation

[0028] Fresh Chinese cabbage tails were washed with clean water and then naturally air-dried. 5 g of dried Chinese cabbage tails were weighed, chopped and soaked in 100 mL of distilled water. Extraction was performed in a water bath at 80°C for 30 minutes. After cooling, vacuum filtration was performed with a fast filter paper, and then filtration was performed with a 0.45 μm microporous filter membrane to obtain a Chinese cabbage tail extract.

[0029] 2. Synthesis of Silver Nanoparticles

[0030] 10mL of Chinese cabbage tail extract and 20mL of 10mmol / L AgNO3 solution were placed in beakers, preheated to 60℃ and mixed, and reacted at 60℃ for 50 minutes on a constant temperature magnetic stirrer. During the process, the color of the solution gradually changed from light yellow to dark brown, indicating the formation of nanosilver. After the reaction, the solution was centrifuged at 10000r / min for 10 minutes, the supernatant was removed, and the solution was washed with distilled water to obtain a nanosilver solution.

[0031] 3. Characterization of Silver Nanoparticles

[0032] The absorbance of the nanosilver solution was measured by UV-visible spectrophotometer, and the results showed that there was an obvious absorption peak at 438nm, proving that the nanosilver particles were successfully synthesized ( Figure 1 ). Scanning electron microscope observation shows that the silver nanoparticles are spherical and have a diameter of about 1 μm ( Figure 2 ).

[0033] 4. Antibacterial performance test

[0034] The antibacterial test of the nanosilver solution was carried out using the filter paper method. Staphylococcus sciuri (G+) and Enterobacter hormaechei (G-) were inoculated on LB solid culture medium, and each strain was repeated three times. A sterile filter paper was soaked in the nanosilver solution and cabbage extract and placed on the culture medium. After incubation at 37°C for 48 hours, the diameter of the inhibition zone was measured. The experimental results showed that nanosilver had a significant inhibitory effect on both bacteria. The diameter of the inhibition zone of Staphylococcus sciuri was 8mm ( Figure 3 Left), the diameter of the inhibition zone of Enterobacter hallii is 10 mm ( Figure 3 Right), the left side of each culture medium is a blank control, that is, only the Chinese cabbage tail extract.

[0035] Example 2

[0036] 1. Material Preparation

[0037] Prepare the Chinese cabbage tail extract according to the method of Example 1.

[0038] 2. Optimized Synthesis of Silver Nanoparticles

[0039] According to the response surface optimization experiment, the best conditions are 25mmol / L AgNO3 solution concentration, 62 minutes reaction time, and 74°C reaction temperature. Under these conditions, 10mL of Chinese cabbage tail extract was mixed with 20mL of 25mmol / L AgNO3 solution, stirred, and reacted at 74°C. After the reaction was completed, the nanosilver solution was centrifuged, washed, and collected according to the method of Example 1.

[0040] 3. Characterization of Silver Nanoparticles

[0041] Nanosilver was characterized by UV-visible spectroscopy and scanning electron microscopy, and it was found that its particle size was uniform, about 1 μm, and there was a significant absorption peak at 438 nm.

[0042] 4. Antibacterial performance test

[0043] The antibacterial properties of nanosilver were tested using the same filter paper method as in Example 1. The test results showed that the diameter of the inhibition zone of the optimized nanosilver against Enterobacter hallii was 12 mm, and the diameter of the inhibition zone against Staphylococcus sciuri was 9 mm.

[0044] Example 3: Synthesis of Nanosilver from Low Concentration AgNO3 Solution and Testing of Its Antibacterial Properties

[0045] 1. Material Preparation

[0046] The Chinese cabbage tail extract was prepared according to the method of Example 1.

[0047] 2. Synthesis of Silver Nanoparticles

[0048] 10mL of cabbage extract was mixed with 20mL of 5mmol / L AgNO3 solution and stirred at 60℃ for 40 minutes. After the reaction, the nanosilver solution was centrifuged, washed and collected according to the above method. This process uses low-concentration AgNO3 solution to reduce the use of chemical reagents, reduce costs and environmental impact.

[0049] 3. Characterization of Silver Nanoparticles

[0050] The UV-visible spectrum analysis showed that the synthesized nanosilver had an absorption peak at 438nm, but the absorbance was low, indicating that the amount of nanosilver generated was relatively small. Scanning electron microscopy showed that the particles had uniform morphology and a large particle size of about 2μm.

[0051] 4. Antibacterial performance test

[0052] The nanosilver solution was used for antibacterial testing. The experimental results showed that the diameter of the inhibition zone for Enterobacter hallii was 8 mm, and the diameter of the inhibition zone for Staphylococcus aureus was 7 mm. The antibacterial effect was reduced, but still effective.

Claims

1. A method for synthesizing nanosilver using a Chinese cabbage tail extract, characterized in that: The following steps are involved: S1, drying the Chinese cabbage tail, cutting it into pieces, soaking it in distilled water, filtering it, and centrifuging it to obtain a Chinese cabbage tail extract; S2, the Chinese cabbage tail extract is mixed with the AgNO3 solution, the reaction temperature is 60-90°C, the reaction time is 30-80min, nanosilver is generated, the supernatant is removed by centrifugation and then washed with distilled water to obtain a nanosilver solution; wherein the volume ratio of the Chinese cabbage tail extract to the AgNO3 solution is 1:(0.5-2).

2. The method for synthesizing nanosilver using Chinese cabbage tail extract according to claim 1, characterized in that: The solid-liquid ratio of the dried cabbage tail to distilled water in S1 is 1:(10-30) g / mL.

3. The method for synthesizing nanosilver using Chinese cabbage tail extract according to claim 1, characterized in that: In S1, the cabbage tails are immersed in distilled water at a temperature of 60-90° C. for 20-40 minutes; and the centrifugal parameters are 6000-10000 r / min.

4. The method for synthesizing nanosilver using Chinese cabbage tail extract according to claim 1, characterized in that: The volume ratio of the Chinese cabbage tail extract to the AgNO3 solution in S2 is 1:2, and the concentration of the AgNO3 solution is 5-25mmol / L.

5. The method for synthesizing nanosilver using Chinese cabbage tail extract according to claim 1, characterized in that: The concentration of AgNO3 solution in S2 is 25mmol / L, the reaction temperature is 74℃, and the reaction time is 62min.

6. Nanosilver prepared by the method according to any one of claims 1 to 5.

7. The nanosilver according to claim 6, characterized in that: The nano silver is in the form of uniform spherical particles with a particle size of 1 μm.

8. Use of the nano silver according to claim 6 in the preparation of an antibacterial agent.

9. Use of the nanosilver according to claim 6 in inhibiting Enterobacter hallii and Staphylococcus sciuri.

10. The use according to claim 9, characterized in that: The diameter of the antibacterial zone of the nano-silver against Enterobacter holmesii is 8-12 mm, and the diameter of the antibacterial zone of the nano-silver against Staphylococcus australis is 7-9 mm.

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