Garlic carbon dots and preparation method and antibacterial application thereof

Abstract

The application discloses garlic carbon dots and a preparation method and antibacterial application thereof, and the preparation method of the garlic carbon dots is as follows: (1) garlic pulp is treated to obtain garlic powder, then the garlic powder is mixed uniformly in a mixed solution of water and ethanol to obtain a garlic suspension; (2) the garlic suspension is subjected to a mixed solvent thermal reaction, and supernatant is taken after the reaction to obtain a garlic carbon dot solution; and (3) the garlic carbon dot solution is dialyzed to remove impurities, and finally, drying is performed to remove the solvent to obtain powder-shaped garlic carbon dots. According to the application, ethanol and water are selected as the reaction solvents, the activity of the obtained garlic carbon dots is improved, and the sterilization capacity of the garlic carbon dots on escherichia coli and staphylococcus aureus is greater than 99%.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of nanomaterials, in particular to a garlic carbon dot, a preparation method thereof and antibacterial application thereof. BACKGROUND

[0002] Under the current social environment, bacterial infection has caused serious threat to human health. Long-term use of traditional antibacterial drugs can easily make bacteria resistant, leading to gradually weakened antibacterial effect. Therefore, it is urgent to develop new, efficient and safe antibacterial materials.

[0003] As a new type of carbon nanomaterial, carbon dots have excellent optical properties, good biocompatibility and low toxicity, and have wide application prospects in the fields of biomedicine, environmental monitoring and photocatalysis. At present, the preparation methods of carbon dots mainly include arc discharge method, laser ablation method, chemical oxidation method and hydrothermal method. However, these methods have problems such as complex preparation process, high cost and low product purity. Therefore, it is of great practical significance to develop a simple, efficient and low-cost carbon dot preparation method.

[0004] At present, most of the preparation methods of carbon dots need to use toxic and harmful chemical reagents, which not only has high cost, but also is not friendly to the environment. Garlic is a common seasoning and traditional Chinese medicinal material, which has various biological activities such as antibacterial, antiviral and antioxidant. In recent years, it has been found that garlic contains rich carbon sources and can be used as a raw material for preparing carbon dots. Although the traditional hydrothermal method for preparing garlic carbon dots has certain effect, it also has some deficiencies, such as low activity of carbon dots. SUMMARY

[0005] The first object of the present application is to provide a garlic carbon dot with improved activity; the second object of the present application is to provide a preparation method of the garlic carbon dot; and the third object of the present application is to provide an application of the garlic carbon dot in antibacterial.

[0006] Technical scheme: The preparation method of the garlic carbon dot provided by the present application comprises the following steps:

[0007] (1) treating garlic pulp to obtain garlic powder, then adding a mixed solution of water and ethanol to mix uniformly to obtain a garlic suspension;

[0008] (2) performing a mixed solvent thermal reaction on the garlic suspension, taking supernatant after the reaction to obtain a garlic carbon dot solution;

[0009] (3) dialyzing the garlic carbon dot solution to remove impurities, and finally drying to remove the solvent to obtain a powder-shaped garlic carbon dot.

[0010] Preferably, in step (1), the garlic pulp treatment is as follows: after peeling, the garlic pulp is washed and crushed.

[0011] Preferably, in step (1), the concentration of the garlic powder in water and ethanol is 1.0-2.0 g of garlic powder per 50-100 mL of mixed solvent.

[0012] Preferably, the water is deionized water.

[0013] Preferably, in step (2), the volume ratio of water to ethanol is 1:1-1.5.

[0014] Preferably, in step (2), the reaction temperature is 180-200°C.

[0015] Preferably, in step (2), the reaction time is 10-12 hours.

[0016] Under the conditions of mixed solvent thermal reaction, the organic components in garlic, such as polysaccharides and proteins, undergo complex chemical reactions in a high-temperature and high-pressure environment. These organic components gradually decompose and carbonize, forming carbon dot structures with nanoscale sizes. The mixed solvent thermal reaction provides a relatively closed environment, which is conducive to the progress of the reaction and the formation of products. At the same time, high temperature can promote the breaking and recombination of chemical bonds, while high pressure can help the diffusion of substances and increase the reaction rate.

[0017] Preferably, in step (3), the dialysis time is 36-48 hours.

[0018] The purpose of dialysis is to remove impurities from the reaction products. During dialysis, small molecules such as unreacted raw materials and by-products can pass through the semi-permeable membrane, while garlic carbon dots cannot pass through the semi-permeable membrane due to their relatively large size, thereby achieving the removal of impurities and obtaining a pure garlic carbon dot solution.

[0019] A garlic carbon dot prepared by the method described in the present application.

[0020] The application of the garlic carbon dot described in the present application in antibacterial applications.

[0021] The bacteria are Escherichia coli or Staphylococcus aureus.

[0022] The bacteria have a sterilization efficiency of greater than 99% on Escherichia coli or Staphylococcus aureus.

[0023] Inventive mechanism: In the preparation method of the present application, by selecting the solvent water and ethanol, the prepared garlic carbon dots have different polarity, activity and surface groups. This is determined by the characteristics of the raw materials. First, the characteristics of garlic, garlic contains a large amount of organic matter, such as carbohydrates, proteins, etc. These organic components are rich in carbon elements, which are the carbon source basis for the formation of carbon dots. At the same time, garlic itself also contains nitrogen, sulfur and other heteroatoms, which can be naturally doped into the carbon dot structure during pyrolysis and other processes, giving the carbon dots special properties, such as enhanced fluorescence characteristics, changed surface charge distribution, etc. As a natural biomass, it has a wide source, low cost and good biocompatibility, and the carbon dots prepared therefrom have a lower toxicity risk when applied in the field of biomedicine. Second, the characteristics of the mixed solvent of water and ethanol, water is a polar solvent that can dissolve many water-soluble components in garlic; ethanol is also a common organic solvent that has good solubility for some organic components in garlic. After mixing, it can more fully dissolve the various components in garlic, making the reaction system more uniform, which is conducive to the formation of carbon dots. The mixed solvent provides a suitable medium environment for the reaction, promoting the decomposition, polymerization and other reactions of the organic components in garlic under heating conditions. The mixing ratio of water and ethanol can adjust the reaction rate and the properties of the product, for example, appropriately increasing the proportion of ethanol can increase the solubility of some organic components, thereby affecting the size and surface properties of the carbon dots.

[0024] Reaction mechanism: Under certain temperature conditions, the organic components in garlic begin to undergo pyrolysis, and the macromolecular organic substances gradually decompose into small molecular compounds. As the temperature rises, these small molecules further undergo carbonization to form carbon nuclei. During the formation of carbon nuclei, a graphite-like microcrystalline structure is gradually formed, which is an important basis for the fluorescence properties of carbon dots. At the same time, the nitrogen, sulfur and other heteroatoms originally present in garlic will be doped into the carbon nuclei during the carbonization process, changing the electronic structure of the carbon dots and giving them special optical and electrical properties. Water and ethanol molecules will interact with the surface of the carbon dots during the reaction, passivating the surface of the carbon dots. The hydroxyl groups and other functional groups in the ethanol molecules can bind to the unsaturated bonds on the surface of the carbon dots, reducing surface defects and improving the stability and fluorescence quantum yield of the carbon dots. Water and ethanol in the reaction system also promote the formation of a variety of functional groups on the surface of the carbon dots, such as hydroxyl, carboxyl, amino, etc. These functional groups not only improve the water solubility of the carbon dots, but also provide more reactive sites for the carbon dots.

[0025] Antibacterial mechanism of garlic carbon dots:

[0026] (1) Destroying bacterial cell membrane

[0027] Garlic carbon dots may interact with bacterial cell membranes, disrupting the integrity of the cell membrane. The nanoscale size of carbon dots allows them to come into close contact with bacterial cell membranes, affecting the permeability of the cell membrane, leading to the leakage of intracellular substances, thereby inhibiting the growth of bacteria. It may be adsorbed on the surface of the bacterial cell membrane by electrostatic interaction, changing the potential of the cell membrane and interfering with the normal function of the cell membrane.

[0028] (2) Producing reactive oxygen species (ROS)

[0029] Garlic carbon dots may produce reactive oxygen species such as superoxide anions and hydroxyl radicals under certain conditions. These reactive oxygen species have strong oxidizing properties and can attack biological molecules such as proteins and nucleic acids within bacterial cells, disrupting the metabolic function of bacteria and thus playing an antibacterial role.

[0030] (3) Interfering with bacterial metabolic processes

[0031] Garlic carbon dots may enter bacterial cells and interfere with the metabolic processes of bacteria. For example, they can affect key metabolic pathways such as bacterial respiration, energy metabolism, and protein synthesis, thereby inhibiting the growth and reproduction of bacteria.

[0032] In summary, the present application prepares garlic carbon dots through a mixed solvent thermal reaction, and achieves good antibacterial effects by utilizing their unique physical and chemical properties. This green, environmentally friendly, and low-cost preparation method and antibacterial application provides a new way of thinking and method for solving the problem of bacterial infection.

[0033] Beneficial effects: Compared with the prior art, the present application has the following remarkable advantages: (1) By selecting ethanol and water as the reaction solvent, the activity of the garlic carbon dots obtained is improved; (2) The garlic carbon dots prepared have good stability and can maintain their antibacterial performance and physical and chemical properties under different environmental conditions (such as temperature and humidity), are not prone to aggregation, have good dispersibility, and are convenient for application in various materials; (3) The bactericidal ability of the garlic carbon dots prepared by the method to Escherichia coli and Staphylococcus aureus is greater than 99%; (4) The preparation method has a high yield, which can reach more than 50%, and is conducive to reducing production costs; (5) The application prospect is wide, and the garlic carbon dots can be applied to the field of medical dressings, can effectively prevent wound infection, and promote wound healing. In antibacterial coatings, the garlic carbon dots can improve the antibacterial performance of the coatings, prolong the service life of the coatings, and are suitable for places with high hygiene requirements such as hospitals and food processing plants. In food packaging materials, the garlic carbon dots can inhibit the growth of bacteria in food, prolong the shelf life of food, and ensure food safety; (6) Scientific research value: The present application provides a new idea and method for the preparation of carbon dots, and enriches the research field of carbon dot materials. The study on the antibacterial mechanism of garlic carbon dots helps to further understand the interaction between nanomaterials and bacteria, and provides a theoretical basis for the development of new antibacterial materials; (7) Environmentally friendly: The present application uses garlic as a raw material to prepare carbon dots, and garlic is a natural food material, which is widely available and renewable. Compared with the toxic and harmful chemical reagents used in traditional carbon dot preparation methods, the present application has little environmental pollution, and conforms to the development concept of green environmental protection. The entire preparation process does not produce a large amount of waste that is difficult to handle, reduces the burden on the environment, and is conducive to sustainable development. (8) Low cost: Garlic is relatively low in price, and is common in daily life and easy to obtain. This greatly reduces the cost of raw materials. The mixed solvent thermal reaction method used in the preparation process is relatively simple, and does not require expensive equipment and complex processes, further reducing production costs. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 Transmission electron microscope (TEM) image of the garlic carbon dots prepared by the mixed solvent thermal method of Example 1;

[0035] Figure 2 Ultraviolet spectrum of the garlic carbon dots and garlic juice prepared by the mixed solvent thermal method of Example 1;

[0036] Figure 3 Fluorescence spectrum of the garlic carbon dots prepared by the mixed solvent thermal method of Example 1;

[0037] Figure 4 Antibacterial kinetics plate of garlic juice (8 mg / mL) of Comparative Example 1 against Staphylococcus aureus;

[0038] Figure 5Antibacterial kinetic plate of garlic carbon dots (8 mg / mL) prepared by the mixed solvothermal method (1:1.5) of Example 2 against Staphylococcus aureus;

[0039] Figure 6 Antibacterial kinetic plate of garlic carbon dots (8 mg / mL) prepared by the mixed solvothermal method (1:1.5) of Example 2 against Staphylococcus aureus;

[0040] Figure 7 Antibacterial kinetic plate of garlic carbon dots (8 mg / mL) prepared by the mixed solvothermal method (1:1) of Example 1 against Staphylococcus aureus;

[0041] Figure 8 Antibacterial kinetic curve of garlic juice of Comparative Example 1, garlic carbon dots solution (8 mg / mL) prepared by the traditional hydrothermal method of Comparative Example 2, garlic carbon dots solution (8 mg / mL) prepared by the mixed solvothermal method of Example 2 and Example 1 against Staphylococcus aureus;

[0042] Figure 9 Antibacterial kinetic plate of garlic juice (8 mg / mL) of Comparative Example 1 against Escherichia coli;

[0043] Figure 10 Antibacterial kinetic plate of garlic carbon dots (8 mg / mL) prepared by the traditional hydrothermal method of Comparative Example 2 against Escherichia coli;

[0044] Figure 11 Antibacterial kinetic plate of garlic carbon dots (8 mg / mL) prepared by the mixed solvothermal method (1:1.5) of Example 2 against Escherichia coli;

[0045] Figure 12 Antibacterial kinetic plate of garlic carbon dots (8 mg / mL) prepared by the mixed solvothermal method (1:1) of Example 1 against Escherichia coli;

[0046] Figure 13 Antibacterial kinetic curve comparison of garlic juice of Comparative Example 1, garlic carbon dots solution (8 mg / mL) prepared by the traditional hydrothermal method of Comparative Example 2, garlic carbon dots solution (8 mg / mL) prepared by the mixed solvothermal method of Example 2 and Example 1 against Escherichia coli. DETAILED DESCRIPTION

[0047] The technical solutions of the present application are further described below in combination with examples.

[0048] Example 1

[0049] The garlic carbon dots of the present application, the preparation method thereof comprises the following steps:

[0050] (1) Peel garlic, wash and crush to obtain garlic powder;

[0051] (2) 1.0 g of garlic powder was weighed and added to 50 mL of deionized water and ethanol (volume ratio 1:1), stirred uniformly to obtain a garlic suspension;

[0052] (3) The garlic suspension was transferred to a reaction kettle and mixed solvothermal reaction was carried out at 200°C for 10 h.

[0053] (4) After the reaction was completed, it was naturally cooled to room temperature, the reaction liquid was centrifuged, and the supernatant was taken to obtain a garlic carbon dot solution;

[0054] (5) The garlic carbon dot solution was dialyzed for 48 h to remove impurities, and a pure garlic carbon dot solution was obtained;

[0055] (6) The pure garlic carbon dot solution was freeze-dried to obtain 692 mg of garlic carbon dot powder, with a yield of 69.2%.

[0056] Example 2

[0057] (1) The garlic was peeled, washed, and crushed to obtain garlic powder;

[0058] (2) 1.0 g of garlic powder was weighed and added to 50 mL of deionized water and ethanol (volume ratio 1:1.5), stirred uniformly to obtain a garlic suspension;

[0059] (3) The garlic suspension was transferred to a reaction kettle and mixed solvothermal reaction was carried out at 200°C for 10 h.

[0060] (4) After the reaction was completed, it was naturally cooled to room temperature, the reaction liquid was centrifuged, and the supernatant was taken to obtain a garlic carbon dot solution;

[0061] (5) The garlic carbon dot solution was dialyzed for 36-48 h to remove impurities, and a pure garlic carbon dot solution was obtained;

[0062] (6) The pure garlic carbon dot solution was freeze-dried to obtain 534 mg of garlic carbon dot powder, with a yield of 53.4%.

[0063] Comparative Example 1

[0064] After the fresh garlic was peeled, garlic juice was squeezed out using a juicer, and the solid residue was removed by filtration to obtain a relatively pure garlic juice solution.

[0065] Comparative Example 2

[0066] On the basis of Example 1, 50 mL of deionized water and ethanol (volume ratio 1:1) was changed to 50 mL of deionized water, and the rest of the conditions were unchanged, to obtain 322 mg of garlic carbon dot powder, with a yield of 32.2%.

[0067] Structural characterization

[0068] 1. The morphology of the garlic carbon dots prepared in Example 1 was observed by transmission electron microscopy (TEM), and the results are shown in Figure 1 .

[0069] It can be seen from Figure 1 that the garlic carbon dots are spherical, have good dispersity, and have a particle size distribution of 2-8 nm and a lattice spacing of 0.21 nm.

[0070] 2. The garlic carbon dots prepared in Example 1 were analyzed by ultraviolet-visible absorption spectrometry, and the results are shown in Figure 2 .

[0071] It can be seen from Figure 2 that there is an obvious absorption peak at 280 nm. The garlic juice of Comparative Example 1 and the garlic carbon dots prepared in Comparative Example 2 do not have strong absorption peaks at 280 nm. On the one hand, this indicates that the surface functional groups and defects of the carbon dots obtained by calcining garlic juice with different solvents are not the same; on the other hand, suitable ultraviolet-visible light absorption performance helps to maintain the stability and activity of the carbon dots in the antibacterial process. If the absorption performance is poor, the carbon dots may not be able to effectively produce active oxygen or undergo photodegradation under light, reducing the antibacterial effect.

[0072] 3. The garlic carbon dots prepared in Example 1 were analyzed by fluorescence spectrometry, and the results are shown in Figure 3 .

[0073] It can be seen from Figure 3 that the garlic carbon dots have the maximum fluorescence intensity under ultraviolet light excitation at 360 nm, and the emission wavelength is about 425 nm.

[0074] Performance characterization

[0075] 1. Antibacterial performance test: The antibacterial performance of the garlic carbon dots prepared in Example 1, the garlic juice prepared in Comparative Example 1, and the garlic carbon dots prepared in Comparative Example 2 using deionized water as the solvent against Escherichia coli and Staphylococcus aureus was tested by plate counting method. The test results are shown in Figures 4-7 and Figures 9-12 . The antibacterial activity of the material was measured by the bactericidal rate, which is the ratio of the number of bacteria killed after treatment to the original number of bacteria.

[0076] The experimental results are as follows:

[0077] The garlic carbon dots prepared in Example 1 had a bactericidal rate of 99.96% against Staphylococcus aureus within 4 hours at a concentration of 8 mg / mL, and a bactericidal rate of 99.997% against Escherichia coli within 4 hours at a concentration of 8 mg / mL.

[0078] Comparative Example 1 showed that garlic juice had a certain inhibitory effect on Escherichia coli at higher concentrations, but compared with garlic carbon dots, the concentration required for garlic juice to achieve the same inhibitory rate for the same volume was higher. For example, the inhibitory rate of garlic juice at a concentration of 5 mg / mL may be comparable to that of garlic carbon dots at 1.0 mg / mL. A similar situation was observed with Staphylococcus aureus.

[0079] Furthermore, the effective antibacterial components in garlic juice are easily volatilized or degraded in the environment, resulting in poor antibacterial stability and durability. In contrast, garlic carbon dots, due to their nanostructure and unique physicochemical properties, exhibit better stability and durability, maintaining their antibacterial effect for a longer period.

[0080] Garlic juice has a strong, pungent odor that may cause discomfort in practical applications, and its high fluidity makes it difficult to control the amount used and the scope of application. Garlic carbon dots, on the other hand, can be combined with various materials to achieve a wider range of applications, and they do not have a noticeable pungent odor during use.

[0081] Compared with the antibacterial application of garlic juice, the garlic carbon dots prepared by this invention have significant advantages in terms of antibacterial properties, stability, durability and ease of application, providing a better option for the development of antibacterial materials.

[0082] Comparative Example 2, prepared using deionized water as a solvent, showed a bactericidal rate of 86.7% against Staphylococcus aureus and 83.3% against Escherichia coli at a concentration of 8 mg / mL. This indicates that the antibacterial activity of the carbon dots in Comparative Example 2 is weaker than that of the carbon dots in Example 1.

[0083] 2. The antibacterial kinetic curves of the garlic carbon dot solution (8 mg / mL) prepared by mixed solvothermal method in Examples 1 and 2, the garlic juice in Comparative Example 1, and the garlic carbon dot solution (8 mg / mL) prepared by conventional hydrothermal method in Comparative Example 2 against Staphylococcus aureus and Escherichia coli were tested. The results are as follows: Figure 8 and Figure 13 As shown.

[0084] Depend on Figure 8 and Figure 13 It can be seen that the garlic carbon dots prepared by the mixed solvent method have a faster bactericidal rate than those obtained by garlic juice and the traditional hydrothermal method. In particular, the method in Example 1 can kill most bacteria within 2 hours.

Claims

1. A method for preparing garlic carbon dots, characterized in that, The method comprises the following steps: (1) treating garlic pulp to obtain garlic powder, and then adding a mixed solution of water and ethanol to mix uniformly to obtain a garlic suspension; (2) performing a mixed solvent hydrothermal reaction on the garlic suspension, taking supernatant after the reaction to obtain a garlic carbon dot solution; (3) dialyzing the garlic carbon dot solution to remove impurities, and finally drying to remove the solvent to obtain powder-shaped garlic carbon dots; The volume ratio of the water and the ethanol is 1:

1.

2. The method of claim 1, wherein the garlic carbon dots are prepared by the method comprising the steps of: In step (1), the concentration of the garlic powder in the water and the ethanol is 1.0-2.0 g of garlic powder per 50-100 mL of the mixed solvent.

3. The method for preparing garlic carbon dots according to claim 1, characterized in that, In step (2), the temperature of the reaction is 180-200 DEG C.

4. The method for preparing garlic carbon dots according to claim 1, characterized in that, In step (3), the dialysis time is 36-48 hours.

5. The method for preparing garlic carbon dots according to claim 1, characterized in that, In step (3), the drying is freeze-drying.

6. A garlic carbon dot, characterized by, The garlic carbon dots are prepared by the preparation method of any one of claims 1-5.

7. The garlic carbon dots of claim 6 are used in antibiosis.

8. Use according to claim 7, characterized in that, The bacteria are Escherichia coli or Staphylococcus aureus.

9. Use according to claim 8, characterized in that, The bactericidal efficiency of the garlic carbon dots on the Escherichia coli or Staphylococcus aureus is greater than 99%.

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