Garlic carbon dots as well as preparation method and antibacterial application thereof

Abstract

The invention discloses garlic carbon dots as well as a preparation method and antibacterial application thereof, the preparation method of the garlic carbon dots comprises the following steps: (1) treating garlic pulp to obtain garlic powder, then adding the garlic powder into a mixed solution of water and ethanol, and uniformly mixing to obtain a garlic suspension; (2) carrying out mixed solvent thermal reaction on the garlic suspension, and taking supernate after the reaction is ended, so as to obtain a garlic carbon dot solution; and (3) dialyzing the garlic carbon dot solution, removing impurities, and finally drying to remove the solvent, thereby obtaining the powdery garlic carbon dots. Ethanol and water are selected as reaction solvents, so that the activity of the obtained garlic carbon dots is improved, and the bactericidal ability on escherichia coli and staphylococcus aureus is greater than 99%.

Description

Technical Field

[0001] The invention relates to the technical field of nanomaterials, and in particular to garlic carbon dots and a preparation method and antibacterial application thereof. Background Art

[0002] In the current social environment, bacterial infections pose a serious threat to human health. Long-term use of traditional antibacterial drugs can easily lead to bacterial resistance, resulting in a gradual weakening of the antibacterial effect. Therefore, there is an urgent need 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 broad application prospects in biomedicine, environmental monitoring, photocatalysis and other fields. At present, the main methods for preparing carbon dots are arc discharge method, laser ablation method, chemical oxidation method, hydrothermal method, etc. 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 method for preparing carbon dots.

[0004] At present, most methods for preparing carbon dots require the use of toxic and harmful chemical reagents, which are not only costly but also environmentally unfriendly. Garlic is a common condiment and Chinese herbal medicine with multiple biological activities such as antibacterial, antiviral, and antioxidant. In recent years, studies have found that garlic contains a rich carbon source and can be used as a raw material for preparing carbon dots. Although the traditional hydrothermal method for preparing garlic carbon dots has achieved certain results, it also has some shortcomings, such as low carbon dot activity. Summary of the invention

[0005] Purpose of the invention: The first purpose of the present invention is to provide a garlic carbon dot that improves the activity of the garlic carbon dot; the second purpose of the present invention is to provide a method for preparing the garlic carbon dot; the third purpose of the present invention is to provide the application of the garlic carbon dot in antibacterial applications.

[0006] Technical solution: The method for preparing garlic carbon dots of the present invention comprises the following steps:

[0007] (1) processing garlic pulp to obtain garlic powder, then adding the powder into a mixed solution of water and ethanol and mixing the mixture evenly to obtain a garlic suspension;

[0008] (2) subjecting the garlic suspension to a mixed solvent thermal reaction, and after the reaction is completed, collecting the supernatant to obtain a garlic carbon dot solution;

[0009] (3) The garlic carbon dots solution is dialyzed to remove impurities, and finally dried to remove the solvent to obtain powdered garlic carbon dots.

[0010] Preferably, in step (1), the garlic pulp is processed by peeling the garlic to obtain the pulp, washing it, and crushing it.

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

[0012] Preferably, the water is deionized water.

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

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

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

[0016] Under the conditions of mixed solvent thermal reaction, 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 to form nano-sized carbon dot structures. Mixed solvent thermal reaction provides a relatively closed environment, which is conducive to 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 helps the diffusion of substances and the increase of reaction rate.

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

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

[0019] A garlic carbon dot is prepared by using the garlic carbon dot preparation method described herein.

[0020] The application of garlic carbon dots in antibacterial applications of the present invention.

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

[0022] The bactericidal efficiency of the bacteria on Escherichia coli or Staphylococcus aureus is greater than 99%.

[0023] Invention mechanism: In the preparation method of the present invention, the polarity, activity and surface groups of the prepared garlic carbon dots are different by selecting solvents water and ethanol. This is determined by the characteristics of the raw materials. First, garlic contains a large amount of organic substances, such as carbohydrates, proteins, etc. These organic components are rich in carbon elements and are the carbon source basis for the formation of carbon dots. At the same time, garlic itself also contains heteroatoms such as nitrogen and sulfur, 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 properties and changed surface charge distribution. As a natural biomass, it has a wide source, low cost, and good biocompatibility. The carbon dots prepared with it have a lower toxicity risk when used in biomedicine and other fields. Secondly, 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 the two are mixed, the various components in garlic can be more fully dissolved, 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 and polymerization of the organic components in garlic under heating and other 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 may increase the solubility of certain organic components, thereby affecting the size and surface properties of carbon dots.

[0024] Mechanism of the reaction process: Under certain temperature conditions, the organic components in garlic begin to undergo pyrolysis reactions, and the macromolecular organic substances gradually decompose into small molecular compounds. As the temperature rises, these small molecules further undergo carbonization reactions to form carbon cores. During the formation process, the carbon core will gradually form a microcrystalline structure similar to graphite, which is an important basis for the fluorescence characteristics of carbon dots. At the same time, heteroatoms such as nitrogen and sulfur originally present in garlic will be doped into the carbon core during the carbonization process, changing the electronic structure of carbon dots and giving them special optical and electrical properties. Water and ethanol molecules will interact with the surface of carbon dots during the reaction process to passivate the surface of carbon dots. Functional groups such as hydroxyl groups in ethanol molecules can combine with unsaturated bonds on the surface of carbon dots, reduce surface defects, and improve the stability and fluorescence quantum yield of carbon dots. Water and ethanol in the reaction system will also prompt some components in garlic to form rich functional groups on the surface of carbon dots, such as hydroxyl groups, carboxyl groups, amino groups, etc. These functional groups can not only improve the water solubility of carbon dots, but also provide more reactive sites for carbon dots.

[0025] Antibacterial mechanism of garlic carbon dots:

[0026] (1) Destroy bacterial cell membrane

[0027] Garlic carbon dots may interact with bacterial cell membranes and destroy the integrity of cell membranes. The nanometer size of carbon dots enables them to come into close contact with bacterial cell membranes, affecting the permeability of cell membranes and causing leakage of intracellular substances, thereby inhibiting bacterial growth. They may adsorb on the surface of bacterial cell membranes through electrostatic effects, changing the potential of cell membranes and interfering with the normal function of cell membranes.

[0028] (2) Generation of reactive oxygen species (ROS)

[0029] Garlic carbon dots may produce reactive oxygen species under certain conditions, such as superoxide anions, hydroxyl radicals, etc. These reactive oxygen species are highly oxidizing and can attack biological molecules in bacterial cells, such as proteins, nucleic acids, etc., destroying the metabolic function of bacteria, thereby playing an antibacterial role.

[0030] (3) Interfering with bacterial metabolic processes

[0031] Garlic carbon dots may enter bacterial cells and interfere with bacterial metabolic processes, for example, affecting key metabolic pathways such as bacterial respiration, energy metabolism, and protein synthesis, thereby inhibiting bacterial growth and reproduction.

[0032] In summary, the present invention prepares garlic carbon dots by mixed solvent thermal reaction, and uses its unique physical and chemical properties to achieve good antibacterial effect. This green, environmentally friendly, low-cost preparation method and antibacterial application provide new ideas and methods for solving bacterial infection problems.

[0033] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: (1) By selecting ethanol and water as reaction solvents, the activity of the obtained garlic carbon dots is improved; (2) The prepared garlic carbon dots have good stability, can maintain their antibacterial properties and physical and chemical properties under different environmental conditions (such as temperature, humidity, etc.), are not prone to agglomeration, have good dispersibility, and are easy to be used in various materials; (3) The garlic carbon dots prepared by this method have a bactericidal ability against Escherichia coli and Staphylococcus aureus greater than 99%; (4) The preparation method has a high yield, which can reach more than 50%, which is conducive to reducing production costs; (5) It has a wide range of application prospects and can be applied to the field of medical dressings, which can effectively prevent wound infection and promote wound healing. Using garlic carbon dots in antibacterial coatings can improve the antibacterial properties of coatings and extend the service life of coatings, and is suitable for places with high hygiene requirements such as hospitals and food processing plants. When used in food packaging materials, it can inhibit the growth of bacteria in food, extend the shelf life of food, and ensure food safety; (6) Scientific research value: It provides a new idea and method for the preparation of carbon dots and enriches the research field of carbon dot materials. The study of the antibacterial mechanism of garlic carbon dots helps to gain a deeper understanding of the interaction between nanomaterials and bacteria, and provides a theoretical basis for the development of new antibacterial materials; (7) Environmentally friendly: The present invention uses garlic as a raw material to prepare carbon dots. Garlic is a natural food material with a wide source and is renewable. Compared with the toxic and harmful chemical reagents used in traditional carbon dot preparation methods, this method has minimal pollution to the environment and is in line with the development concept of green environmental protection. The entire preparation process does not produce a large amount of difficult-to-treat waste, which reduces the burden on the environment and is conducive to sustainable development. (8) Low cost: Garlic is relatively cheap and is relatively common and easy to obtain in daily life. 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 THE DRAWINGS

[0034] Figure 1 The transmission electron microscope (TEM) image of garlic carbon dots prepared by mixed solvent thermal treatment in Example 1;

[0035] Figure 2 The ultraviolet spectra of garlic carbon dots and garlic juice prepared by mixed solvent thermal method in Example 1;

[0036] Figure 3 The fluorescence spectrum of garlic carbon dots prepared by mixed solvent thermal method in Example 1;

[0037] Figure 4 This is the antibacterial kinetic plate diagram of garlic juice (8 mg / mL) against Staphylococcus aureus in Comparative Example 1;

[0038] Figure 5This is the antibacterial kinetics plate diagram of garlic carbon dots (8 mg / mL) prepared by traditional hydrothermal method against Staphylococcus aureus in Comparative Example 2;

[0039] Figure 6 This is the antibacterial kinetics plate diagram of garlic carbon dots (8 mg / mL) prepared by mixed solvent thermal (1:1.5) in Example 2 against Staphylococcus aureus;

[0040] Figure 7 The antibacterial kinetics plate diagram of garlic carbon dots (8 mg / mL) prepared by mixed solvent thermal (1:1) in Example 1 against Staphylococcus aureus;

[0041] Figure 8 The antibacterial kinetic curves of garlic juice in comparative example 1, garlic carbon dot solution (8 mg / mL) prepared by conventional hydrothermal method in comparative example 2, and garlic carbon dot solution (8 mg / mL) prepared by mixed solvent hydrothermal method in example 2 and example 1 against Staphylococcus aureus;

[0042] Fig. 9 This is a plate photo of the antibacterial kinetics of garlic juice (8 mg / mL) against Escherichia coli in Comparative Example 1;

[0043] Fig.10 This is a plate photo of the antibacterial kinetics of garlic carbon dots (8 mg / mL) prepared by the traditional hydrothermal method against Escherichia coli in Comparative Example 2;

[0044] Fig.11 This is a plate photo of the antibacterial kinetics of garlic carbon dots (8 mg / mL) prepared by mixed solvent thermal (1:1.5) in Example 2 against Escherichia coli;

[0045] Fig.12 This is a plate photo of the antibacterial kinetics of garlic carbon dots (8 mg / mL) prepared by mixed solvent thermal (1:1) in Example 1 against Escherichia coli;

[0046] Fig.13 Comparison of the antibacterial kinetic curves of garlic juice in comparative example 1, garlic carbon dot solution (8 mg / mL) prepared by traditional hydrothermal method in comparative example 2, garlic carbon dot solution (8 mg / mL) prepared by mixed solvent hydrothermal method in example 2 and garlic carbon dot solution (8 mg / mL) prepared by mixed solvent hydrothermal method in example 1 against Escherichia coli. DETAILED DESCRIPTION

[0047] The technical solution of the present invention is further described below in conjunction with embodiments.

[0048] Example 1

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

[0050] (1) peeling, washing and crushing garlic to obtain garlic powder;

[0051] (2) Weigh 1.0 g of garlic powder, add it to 50 mL of deionized water and ethanol (volume ratio 1:1), stir evenly to obtain a garlic suspension;

[0052] (3) The garlic suspension was transferred to a reactor and subjected to a mixed solvent thermal reaction at 200° C. for 10 h.

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

[0054] (5) dialyzing the garlic carbon dot solution for 48 hours to remove impurities and obtain a pure garlic carbon dot solution;

[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) peeling, washing and crushing garlic to obtain garlic powder;

[0058] (2) Weigh 1.0 g of garlic powder, add it to 50 mL of deionized water and ethanol (volume ratio 1:1.5), stir evenly to obtain a garlic suspension;

[0059] (3) The garlic suspension was transferred to a reactor and subjected to a mixed solvent thermal reaction at 200° C. for 10 h.

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

[0061] (5) dialyzing the garlic carbon dot solution for 36 to 48 hours to remove impurities and obtain a pure garlic carbon dot solution;

[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 peeling the fresh garlic, use a juicer to extract the garlic juice, and remove the solid residue by filtering 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) were replaced with 50 mL of deionized water, and other conditions remained 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). Figure 1 shown.

[0069] Depend on Figure 1 It can be seen that garlic carbon dots are spherical, well dispersed, with a particle size distribution between 2 and 8 nm and a lattice spacing of 0.21 nm.

[0070] 2. The garlic carbon dots prepared in Example 1 were analyzed using a UV-visible absorption spectrometer. The results are as follows: Figure 2 shown.

[0071] Depend on Figure 2 It can be seen that there is an obvious absorption peak at 280nm. However, the garlic juice of comparative example 1 and comparative example 2 have no strong absorption peak at 280nm. On the one hand, it shows that the surface functional groups and defects of the carbon dots obtained after the garlic juice is calcined with different solvents are different; on the other hand, the appropriate 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 not good, the carbon dots may not be able to effectively produce active oxygen or photodegrade under light, thereby reducing the antibacterial effect.

[0072] 3. The garlic carbon dots prepared in Example 1 were analyzed using a fluorescence spectrometer. The results are as follows: Figure 3 shown.

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

[0074] Performance Characterization

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

[0076] The experimental results are as follows:

[0077] The garlic carbon dots prepared in Example 1 have a sterilization rate of 99.96% for Staphylococcus aureus within 4 hours when the concentration of the garlic carbon dots is 8 mg / mL; and a sterilization rate of 99.997% for Escherichia coli within 4 hours when the concentration of the garlic carbon dots is 8 mg / mL.

[0078] The garlic juice of Comparative Example 1 has a certain antibacterial effect on Escherichia coli at a higher concentration, but compared with garlic carbon dots, the concentration required for garlic juice to achieve the same antibacterial rate at the same volume is higher. For example, when the concentration of garlic juice is 5 mg / mL, the antibacterial rate may reach a level comparable to that of garlic carbon dots at 1.0 mg / mL. A similar situation is also seen for Staphylococcus aureus.

[0079] In addition, the effective antibacterial components in garlic juice are easily volatilized or degraded in the environment, and its antibacterial stability and durability are poor. In contrast, garlic carbon dots have better stability and durability due to their nanostructure and special physical and chemical properties, and can maintain their antibacterial effects for a longer period of time.

[0080] Garlic juice has a strong pungent smell, which may cause discomfort in practical applications. In addition, it has high fluidity and is difficult to control the amount and scope of application. However, garlic carbon dots can be combined with different materials to achieve a wider range of applications, and there is no obvious pungent smell during use.

[0081] Compared with the antibacterial application of garlic juice, the garlic carbon dots prepared by the present invention have obvious advantages in antibacterial performance, stability, durability and ease of application, providing a better choice for the development of antibacterial materials.

[0082] In Comparative Example 2, garlic carbon dots prepared using deionized water as solvent had a sterilization rate of 86.7% against Staphylococcus aureus and 83.3% against Escherichia coli at a concentration of 8 mg / mL. It can be concluded 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 garlic carbon dot solution (8 mg / mL) prepared by mixed solvent thermal treatment of Example 1 and Example 2, garlic juice of Comparative Example 1 and garlic carbon dot solution (8 mg / mL) prepared by conventional hydrothermal method of Comparative Example 2 were tested against Staphylococcus aureus and Escherichia coli. The results are as follows: Figure 8 and Fig.13 shown.

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

Claims

1. A method for preparing garlic carbon dots, characterized in that: The following steps are involved: (1) processing garlic pulp to obtain garlic powder, then adding the powder into a mixed solution of water and ethanol and mixing the mixture evenly to obtain a garlic suspension; (2) subjecting the garlic suspension to a mixed solvent thermal reaction, and after the reaction is completed, collecting the supernatant to obtain a garlic carbon dot solution; (3) The garlic carbon dots solution is dialyzed to remove impurities, and finally dried to remove the solvent to obtain powdered garlic carbon dots.

2. The method for preparing garlic carbon dots according to claim 1, characterized in that: In step (1), the volume ratio of water to ethanol is 1:1 to 1.

5.

3. The method for preparing garlic carbon dots according to claim 1, characterized in that: In step (1), the concentration of the garlic powder in water and ethanol is 1.0 to 2.0 g of garlic powder per 50 to 100 mL of the mixed solvent.

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

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

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

7. A garlic carbon dot, characterized in that: The garlic carbon dots are prepared by the preparation method of any one of claims 1 to 6.

8. An application of the garlic carbon dots according to claim 7 in antibacterial applications.

9. The use according to claim 8, characterized in that: The bacteria is Escherichia coli or Staphylococcus aureus.

10. The use according to claim 9, characterized in that: The bactericidal efficiency of the bacteria on Escherichia coli or Staphylococcus aureus is greater than 99%.

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