Preparation method of carbon quantum dot composite material

Abstract

The invention discloses a preparation method of a carbon quantum dot composite material, which comprises the following steps: (1) firstly, weighing a proper amount of waste fruit peel, drying at high temperature, then crushing to form fine fragments, grinding into fine powder, and sieving with a 100-mesh sieve; dissolving a proper amount of powder in 10 mL of water, then adding 0.3 mL of an ethylenediamine solution, then carrying out ultrasonic treatment on the mixture for 10 min, putting the treated mixture into a microwave oven to react for 5 min, and taking out the mixture after the mixture is cooled to normal temperature; the preparation method comprises the following steps: adding 20 mL of distilled water to fully dissolve, centrifuging for 20 min at 15000 r / min to obtain a supernatant, filtering with a 0.22 [mu] m water system filter membrane, dialyzing for 24 h to obtain a pure carbon quantum dot solution, and placing at 4 DEG C for later use; (2) 1.5 g of chitosan is weighed and dissolved in 100 mL of 1% acetic acid solution, 100 mL of 1.5% chitosan solution is obtained after the solution is fully dissolved, and the 1.5% chitosan solution is stored at 4 DEG C for standby application; and (3) preparing chitosan-carbon quantum dot composite nano materials with different concentrations.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of composite materials, and particularly relates to a preparation method of a carbon quantum dot composite material. BACKGROUND

[0002] Carbon quantum dots, also known as carbon dots or carbon nanodots, are a new type of carbon nanofluorescent material, which is composed of a hybrid carbon core and surface functional groups. The presence of these hydrophilic functional groups not only increases the water solubility of carbon quantum dots, but also enables carbon quantum dots to coordinate with some ions or interact electrostatically, thereby promoting the fluorescence quenching of carbon quantum dots, and thus can be used for analysis and detection.

[0003] From the field of food preservation, carbon quantum dots can be easily compounded with other materials to form new composite materials, which can be used for food preservation. Carbon dots can not only effectively inhibit the growth of microorganisms in food and slow down food spoilage, but also can synergize with other mild sterilization methods such as radio frequency and microwave to reduce the adverse effects of heat sterilization on food quality, extend the shelf life, and reduce waste. At the same time, the raw materials for preparing carbon quantum dots can come from agricultural and forestry waste, which is low in cost, friendly to the environment, and conducive to the recycling of resources. SUMMARY

[0004] The purpose of the present application is to design a preparation method of a carbon quantum dot composite material.

[0005] In order to achieve the above purpose, the technical scheme adopted by the present application is as follows: A preparation method of a carbon quantum dot composite material, the method being as follows: (1) First, weigh an appropriate amount of discarded fruit peels, dry them at high temperature, then break them into small pieces, grind them into fine powder, and pass them through a 100-mesh sieve; take an appropriate amount of powder, dissolve it in 10 mL of water, then add 0.3 mL of ethylenediamine solution, then ultrasonicate the mixture for 10 min, and then take out the treated mixture after it has been cooled to room temperature; add 20 mL of distilled water to make it fully dissolved, then centrifuge it at 15000 r / min for 20 min to obtain the supernatant, then filter it through a 0.22 μm water system filter membrane, and then dialyze it for 24 h to obtain a pure carbon quantum dot solution, which is stored at 4 ℃ for standby use; (2) Weigh 1.5 g of chitosan and dissolve it in 100 mL of 1% acetic acid solution to obtain 100 mL of 1.5% chitosan solution, which is stored at 4 ℃ for standby use; (3) Prepare chitosan-carbon quantum dot composite nanomaterials with different concentrations Coating agent I: 50 mL of chitosan solution + 0.0 mL of carbon quantum dot solution; Coating agent II, 49.25 mL chitosan solution + 0.75 mL carbon quantum dot solution; Coating agent III, 48.5 mL chitosan solution + 1.5 mL carbon quantum dot solution; Coating agent IV, 47.75 mL chitosan solution + 2.25 mL carbon quantum dot solution; Coating agent V, 50 mL pure water, namely the control group.

[0006] Further, the carbon quantum dots are characterized, 50 mL carbon quantum dot solution is taken, vacuum drying is carried out at 45 DEG C for 12 h, carbon quantum dot powder is obtained, and infrared spectrum, particle size and scanning electron microscope analysis are carried out respectively.

[0007] The above technical scheme can obtain the following beneficial effects: The application obtains a novel composite material, which can be used for food preservation, the carbon dots can not only effectively inhibit the growth of microorganisms in food, slow down food corruption, but also can synergistically act with other mild sterilization methods such as radio frequency and microwave, reduce the adverse effects of heat sterilization on food quality, prolong the shelf life and reduce waste. Meanwhile, the raw material for preparing the carbon quantum dots can come from agricultural and forestry waste, the cost is low, the application is friendly to the environment, and the application is conducive to realizing the recycling of resources. BRIEF DESCRIPTION OF DRAWINGS

[0008] Figure 1 is the infrared spectrum of the carbon quantum dots.

[0009] Figure 2 is the particle size comparison diagram of the carbon quantum dots and the composite material.

[0010] Figure 3 is the scanning electron microscope diagram of the carbon quantum dots.

[0011] Figure 4 is the influence diagram of different concentrations of coating agents on the weight loss rate of agaricus bisporus.

[0012] Figure 5 is the influence diagram of different concentrations of coating agents on the hardness of agaricus bisporus.

[0013] Figure 6 is the influence diagram of different concentrations of coating agents on the sensory of agaricus bisporus. DETAILED DESCRIPTION

[0014] The following will be combined with the drawings Figures 1-6 The application is further explained as follows: A preparation method of a carbon quantum dot composite material, the method is as follows: I. Preparation of chitosan-carbon quantum dot composite nanomaterial (1) First, weigh an appropriate amount of discarded peel, dry it at high temperature, then break it into small pieces, grind it into fine powder, and pass it through a 100-mesh sieve. Take an appropriate amount of powder, dissolve it in 10 mL of water, add 0.3 mL of ethylenediamine solution, and then ultrasonicate the mixture for 10 minutes. Place the treated mixture in a microwave oven to react for 5 minutes, and then take it out after cooling to room temperature. Add 20 mL of distilled water to fully dissolve it, then centrifuge it at 15,000 r / min for 20 minutes to obtain the supernatant, filter it with a 0.22 μm water filter membrane, and then dialyze it for 24 hours to obtain a pure carbon quantum dot solution, which is stored at 4 °C for later use.

[0015] (2) Weigh 1.5 g of chitosan and dissolve it in 100 mL of 1% acetic acid solution. After the solution is fully dissolved, 100 mL of 1.5% chitosan solution is obtained and stored at 4 °C for later use.

[0016] (3) Preparation of chitosan-carbon quantum dot composite nanomaterials with different concentrations Coating agent I: 50 mL chitosan solution + 0.0 mL carbon quantum dot solution; Coating agent II, 49.25 mL chitosan solution + 0.75 mL carbon quantum dot solution; Coating agent III, 48.5 mL chitosan solution + 1.5 mL carbon quantum dot solution; Coating agent IV, 47.75 mL chitosan solution + 2.25 mL carbon quantum dot solution; Coating agent V, 50 mL pure water, was the control group.

[0017] 2. Characterization of Carbon Quantum Dots 50 mL of the carbon quantum dot solution was vacuum dried at 45°C for 12 h to obtain carbon quantum dot powder. The powder was analyzed by infrared spectroscopy, particle size, and scanning electron microscopy.

[0018] like Figure 1 As shown, at 3363 cm -1 The absorption peak at 3153 cm is the OH stretching vibration, which shows that the surface of carbon quantum dots is rich in hydroxyl groups. -1 The absorption peak at 2927 cm is NH stretching vibration, and the surface is rich in amino groups, which can provide active sites for subsequent biomarkers. -1 The absorption peak at is the CH stretching vibration, that is, sp 3 Hybridization may affect the hydrophobic interaction and requires purification to reduce the residue. -1 The absorption peak at 1592 cm is the stretching vibration of the C=C aromatic ring. -1 The absorption peak at is C=O stretching vibration, which reflects the sp 2 Hybrid. 1348 cm -1The absorption peak at 3500 cm-1 is C-O vibration or inorganic impurities; possible sulfur, nitrogen doping, which can mediate the electronic structure and enhance the fluorescence efficiency. The above expressions are consistent with the typical characteristics of biomass carbon quantum dots, in line with the structure and performance of carbon quantum dots, and these properties and structures make carbon quantum dots have certain stability and dispersibility, which can be used for biological preservation.

[0019] The average particle size of carbon quantum dots is 935.3 ± 21.3 nm, and the coefficient of variation is 2.28 %, indicating that the degree of dispersion is small. The average particle size of carbon quantum dot-chitosan composite material is 1132.7 ± 45.2 nm, and the coefficient of variation is 3.99 %. From the above data, it can be seen that the particle size of the composite material is increased by about 200 nm compared with the carbon quantum dots. Figure 2

[0020] The morphology of carbon quantum dots is shown in Figure 3 After microwave treatment, the peel part is converted into carbon quantum dots and attached to the surface. It can be seen that the surface of the carbon quantum dot sample presents irregular granular morphology and part of the spherical morphology, and obvious agglomeration phenomenon can be seen on the surface, forming a relatively uniform aggregate.

[0021] III. Preservation application of chitosan-carbon quantum dot composite nanomaterial Select double-spore mushrooms with similar shape and size, wash with tap water, dry with clear water, and then slice and group. The double-spore mushroom slices are coated with different concentrations of coating agents using a brush, so that the coating agent uniformly covers the surface of the fresh-cut double-spore mushrooms. After coating, place them in different preservation bags according to the concentration and seal. The control group is only coated with distilled water, and after completion, it is also placed in a preservation bag and sealed. Place all sealed samples in a 4 ℃ refrigerator for 10 days, and measure the physicochemical indicators every 1 day, with each sample repeated 3 times.

[0022] (1) Double-spore mushroom weight loss rate determination After slicing, the internal organization of double-spore mushrooms is damaged, and water is easily lost. Determining the weight loss rate of double-spore mushrooms can reflect the rate of water loss of double-spore mushrooms coated with different concentrations of carbon quantum dot composite materials, and compare the preservation effects of different concentrations of carbon quantum dot composite materials.

[0023] As shown in Figure 4 ​As can be seen, after 10 days of storage, the weight loss rate of the experimental group was significantly lower than that of the control group. The weight loss rate of Agaricus bisporus slices treated with coating agent I in the experimental group ranged from 3.5% to 4%, indicating that chitosan alone can delay the weight loss of mushrooms in a short period of time. The weight loss rate of Agaricus bisporus slices treated with coating agent II was approximately 2%. The weight loss rate of Agaricus bisporus slices treated with coating agents III and IV remained at 1%, indicating that the carbon quantum dots formed a dense film on the surface of the mushroom slices, reducing water loss and inhibiting mushroom respiration, thereby preserving the mushrooms. The weight loss rate of the Agaricus bisporus slices in the control group ranged from 6% to 6.5%. This demonstrates that the carbon quantum dot-chitosan composite material has a good preservation effect on Agaricus bisporus.

[0024] (2) Agaricus bisporus hardness test Depend on Figure 5 After 10 days of storage, the hardness of the experimental groups decreased more slowly than that of the control group. The hardness of the fresh-cut mushrooms in the control group was 6.5 N, while the hardness of the fresh-cut mushrooms treated with coatings I, II, III, and IV was 8 N, 7 N, 8.5 N, and 10.5 N, respectively, all higher than the control group. The hardness of the fresh-cut mushrooms treated with coatings III and IV showed less change than that of the other groups, indicating that the high-concentration composite film can reduce water evaporation, reduce enzymatic degradation and damage of cell walls by spoilage bacteria, and thus has a good preservation effect.

[0025] (3) Sensory evaluation of Agaricus bisporus As the storage time increases, the physiological indicators of Agaricus bisporus, such as color, smell, degree of corruption and performance status, will change to varying degrees. Carbon quantum dot composite films of different concentrations were used to preserve Agaricus bisporus, and the preservation effects were compared.

[0026] like Figure 6 As shown, after 10 days of storage, the sensory evaluation of all Agaricus bisporus samples declined. The control group, without composite film protection, experienced a sharp decline. Coatings I and II experienced a steady decline, while the high-concentration groups of Coatings III and IV experienced the slowest decline. This suggests that the combination of carbon quantum dots and chitosan, a highly film-forming chitosan, can effectively preserve Agaricus bisporus.

[0027] The effects of the carbon quantum dot-chitosan composite on Agaricus bisporus (Agaricus bisporus) were measured in terms of weight loss, hardness, and sensory evaluation. The results showed that a coating IV (47.75 mL of a 1.5% chitosan solution mixed with 2.25 mL of a carbon quantum dot solution) significantly inhibited water loss and enzyme activity, enhanced antioxidant activity, and slowed browning. Therefore, the carbon quantum dot-chitosan composite has demonstrated efficacy in mushroom preservation and generally complies with the green ecological concept of safety, environmental protection, and sustainable development.

[0028] The above are preferred embodiments of the present application, and modifications of various equivalent forms of the present application which do not depart from the spirit of the present application are intended to be within the scope of the appended claims.

Claims

1. A method for preparing a carbon quantum dot composite material, characterized in that: The method is as follows: (1) First, weigh an appropriate amount of discarded peel, dry it at high temperature, then break it into small fragments, grind it into fine powder, and pass it through a 100-mesh sieve; take an appropriate amount of powder, dissolve it in 10 mL of water, add 0.3 mL of ethylenediamine solution, and then ultrasonicate the mixture for 10 minutes. Place the treated mixture in a microwave oven to react for 5 minutes, wait for it to cool to room temperature and then take it out; add 20 mL of distilled water to fully dissolve it, then centrifuge it at 15,000 r / min for 20 minutes to obtain the supernatant, filter it with a 0.22 μm water filter membrane, and then dialyze it for 24 hours to obtain a pure carbon quantum dot solution, which is placed at 4°C for use; (2) Weigh 1.5 g of chitosan and dissolve it in 100 mL of 1% acetic acid solution. After the solution is fully dissolved, 100 mL of 1.5% chitosan solution is obtained and stored at 4 °C for later use. (3) Preparation of chitosan-carbon quantum dot composite nanomaterials with different concentrations Coating agent I: 50 mL chitosan solution + 0.0 mL carbon quantum dot solution; Coating agent II, 49.25 mL chitosan solution + 0.75 mL carbon quantum dot solution; Coating agent III, 48.5 mL chitosan solution + 1.5 mL carbon quantum dot solution; Coating agent IV, 47.75 mL chitosan solution + 2.25 mL carbon quantum dot solution; Coating agent V, 50 mL of pure water, was the control group.

2. The method for preparing a carbon quantum dot composite material according to claim 1, wherein: To characterize the carbon quantum dots, 50 mL of carbon quantum dot solution was taken and vacuum dried at 45 °C for 12 h to obtain carbon quantum dot powder, which was then analyzed by infrared spectroscopy, particle size and scanning electron microscopy.

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