A nitrogen-doped biomass-based carbon material, a preparation method thereof and application thereof in antibiosis

Abstract

The application provides a nitrogen-doped biomass-based carbon material, a preparation method thereof and application thereof in antibiosis. The preparation method of the nitrogen-doped biomass-based carbon material comprises the following steps: dispersing biomass in deionized water; adding a zinc salt aqueous solution and uniformly mixing; aging, centrifugal separation and drying to obtain a supramolecular precursor; uniformly mixing the supramolecular precursor with a nitrogen source by grinding, and calcining to obtain the nitrogen-doped biomass-based carbon material. The preparation process is simple, low in cost and green and sustainable; the nitrogen-doped biomass-based carbon material has uniform nitrogen element distribution, good biocompatibility and great application and expansion potential in the field of antibiosis.

Description

A nitrogen-doped biomass-based carbon material, its preparation method, and its application in antibacterial applications. Technical Field

[0001] This invention relates to a nitrogen-doped biomass-based carbon material, its preparation method, and its application in antibacterial applications, belonging to the field of materials synthesis technology. Background Technology

[0002] Bacterial infections have long posed a serious threat to human health, especially the widespread spread of drug-resistant bacteria due to the long-term overuse of antibiotics, which has become a serious public health threat. Therefore, it is widely believed that there is an urgent need to develop novel, highly effective antibacterial agents that will not further induce drug resistance or cause biosafety problems. To date, nanozymes have been considered promising candidates for combating bacteria. Nanozymes combine the advantages of nanomaterials and natural enzymes, possessing characteristics such as low cost, good stability, controllable size, simple preparation, strong multifunctionality, and high catalytic activity. Inspired by natural enzymes, the basic design principle of nanozymes for antibacterial purposes is mainly based on the generation of reactive oxygen species by oxidase-like or peroxidase-like enzymes, thereby damaging bacterial cell membranes, DNA, and cellular proteins to produce an antibacterial effect. Among them, oxidase-like enzymes can activate molecular oxygen under mild conditions to generate reactive oxygen species for antibacterial purposes without any external energy input or chemical addition. From the perspective of green and sustainable development, molecular oxygen is the greenest, most abundant, and inexpensive oxidant. Therefore, exploring nanozyme materials with excellent oxidase-like activity for antibacterial applications is of great significance.

[0003] Compared to precious metal and transition metal-based materials, carbon materials have broad application prospects in the field of enzyme-like catalysis due to their advantages such as low cost, avoidance of metal ion leaching, good biocompatibility, strong acid and alkali resistance, and tunable electronic and physicochemical properties. Currently, the synthesis of carbon materials typically relies on traditional fossil resources. The world's over-reliance on fossil resources has led to climate change and environmental problems. Due to concerns about environmental issues and production costs, more and more researchers are focusing on using green biomass resources instead of fossil resources to produce carbon nanomaterials. Compared to fossil resources, biomass is renewable, low-pollution, and widely distributed, making it a very abundant resource. Using low-cost, readily available, environmentally friendly, and renewable biomass resources as sustainable precursors for carbon materials is of practical significance. However, carbon materials obtained directly from biomass pyrolysis usually do not possess oxidase-like activity, which poses a challenge to the application of biomass-derived carbon materials in the field of oxidase-like antibacterial agents.

[0004] Therefore, there is an urgent need to develop a carbon material with excellent oxidase-like activity and sustainable precursors from green biomass to achieve antibacterial properties while reducing the vicious cycle caused by antibiotic use in organisms. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a nitrogen-doped biomass-based carbon material, its preparation method, and its application in antibacterial applications. The preparation process of this invention is simple, low-cost, and environmentally sustainable; the resulting nitrogen-doped biomass-based carbon material exhibits uniform nitrogen distribution, good biocompatibility, and significant potential for expansion in the antibacterial field.

[0006] This invention is achieved through the following technical solution:

[0007] A nitrogen-doped biomass-based carbon material, wherein the microstructure of the nitrogen-doped biomass-based carbon material is a porous sheet-like structure with folds.

[0008] According to a preferred embodiment of the present invention, the nitrogen doping amount of the nitrogen-doped biomass-based carbon material is 6 at% to 9 at%. The nitrogen doping amount refers to the percentage of nitrogen atoms on the surface of the nitrogen-doped biomass-based carbon material relative to the total number of atoms on the surface.

[0009] According to a preferred embodiment of the present invention, nitrogen in the nitrogen-doped biomass-based carbon material exists in the forms of pyridine nitrogen, graphitic nitrogen, pyrrole nitrogen, and nitrogen oxides.

[0010] According to a preferred embodiment of the present invention, the pore size in the nitrogen-doped biomass-based carbon material is 2.2-150 nm.

[0011] The above-mentioned method for preparing nitrogen-doped biomass-based carbon materials includes the following steps:

[0012] (1) The biomass was fully dispersed in deionized water; zinc salt aqueous solution was added and mixed evenly; after aging, centrifugation and drying, supramolecular precursor was obtained.

[0013] (2) The supramolecular precursor and nitrogen source are ground and mixed evenly, and then calcined to obtain nitrogen-doped biomass-based carbon materials.

[0014] According to a preferred embodiment of the present invention, in step (1), the biomass is one or a combination of two or more of straw, rice husk, wood flour or lignocellulose.

[0015] According to a preferred embodiment of the present invention, in step (1), the mass ratio of biomass to deionized water is (0.05-5):(100-1500); more preferably, the mass ratio of biomass to deionized water is (2-3):(500-1000).

[0016] According to a preferred embodiment of the present invention, in step (1), the zinc salt is zinc acetate, zinc chloride, zinc citrate, zinc sulfate, or zinc nitrate; preferably, the zinc salt is zinc acetate.

[0017] According to a preferred embodiment of the present invention, in step (1), the molar concentration of the zinc salt aqueous solution is 0.05 to 5 mol / L; more preferably, the molar concentration of the zinc salt aqueous solution is 0.2 to 0.4 mol / L.

[0018] According to the present invention, in step (1), the mass ratio of zinc salt to biomass is (0.1-2.5):(0.1-5); preferably, the mass ratio of zinc salt to biomass is (0.5-1.5):(1-3).

[0019] According to a preferred embodiment of the present invention, in step (1), after adding the zinc salt aqueous solution, the mixture is stirred at room temperature for 0.1 to 5 hours to achieve uniform mixing; more preferably, the mixture is stirred at room temperature for 0.5 to 2 hours to achieve uniform mixing.

[0020] According to a preferred embodiment of the present invention, in step (1), the aging temperature is room temperature, the aging time is 6 to 24 hours, and the aging is carried out under static conditions; preferably, the aging time is 10 to 15 hours.

[0021] According to a preferred embodiment of the present invention, in step (1), the centrifugation speed is 2000-5000 r / min and the centrifugation time is 1-10 min; preferably, the centrifugation speed is 3000-4000 r / min and the centrifugation time is 2-5 min.

[0022] According to a preferred embodiment of the present invention, in step (1), the drying temperature is 50-90°C and the drying time is 10-24h; preferably, the drying temperature is 60-80°C and the drying time is 12-15h.

[0023] According to a preferred embodiment of the present invention, in step (2), the nitrogen source is one or a combination of two or more of 1,2,4,5-tetraaminobenzene, urea, p-phenylenediamine, 4,4'-bipyridine, cyanamide, polyethyleneimine, dicyandiamide or melamine; preferably, the nitrogen source is one or a combination of two or more of urea, cyanamide, polyethyleneimine, dicyandiamide or melamine.

[0024] According to the present invention, in step (2), the mass ratio of supramolecular precursor to nitrogen source is 1:(1-50); preferably, the mass ratio of supramolecular precursor to nitrogen source is 1:(5-30); most preferably, the mass ratio of supramolecular precursor to nitrogen source is 1:(10-25).

[0025] According to the present invention, in step (2), the grinding time is 5 to 60 minutes; preferably, the grinding time is 30 to 40 minutes.

[0026] According to a preferred embodiment of the present invention, in step (2), the calcination conditions are: gas protection, gas flow rate of 30-100 mL / min, calcination temperature of 800-1100℃, and calcination time of 1-6 h; preferably, the gas is nitrogen, argon or helium, gas flow rate of 60-80 mL / min, calcination temperature of 900-1000℃, and calcination time of 2-4 h.

[0027] The application of the above-mentioned nitrogen-doped biomass-based carbon materials in antibacterial applications.

[0028] According to a preferred embodiment of the present invention, the nitrogen-doped biomass-based carbon material is used for bactericidal or bacteriostatic purposes against Escherichia coli or Staphylococcus aureus.

[0029] The technical features and beneficial effects of this invention are as follows:

[0030] 1. This invention employs a mixture of biomass and zinc salts to form a supramolecular precursor. Zinc ions act as nodes, coordinating with phenolic hydroxyl groups in the biomass to form an insoluble supramolecular precursor. The supramolecular precursor is ground and mixed with a nitrogen source in a suitable ratio, then calcined at high temperature. A zinc salt-assisted pyrolysis strategy is used to complete the carbonization-nitridation-activation process in one step, achieving the synthesis of biomass-based nitrogen-rich porous carbon materials.

[0031] 2. In this invention, the phenolic hydroxyl groups of biomass can adsorb transition metal zinc ions through chelation, improving the dispersibility of zinc salts in biomass; during pyrolysis, the evaporation of zinc creates defects, facilitating the introduction of nitrogen into carbon materials; the gas generated by the pyrolysis of the nitrogen source facilitates the construction of pores. This preparation strategy allows for the simultaneous optimization of the surface functionality and porous structure of nitrogen-doped carbon.

[0032] 3. The nitrogen-doped biomass-based carbon material prepared by this invention has nitrogen in its carbon framework existing in different forms such as pyridine nitrogen, graphitic nitrogen, and pyrrole nitrogen, with a high nitrogen content. Furthermore, the doping of nitrogen facilitates the formation of the wrinkled, sheet-like structure of this invention. Carbon atoms and nitrogen atoms undergo sp2 hybridization, thereby forming a highly delocalized π-conjugated system, which is beneficial for electron transport on the ring and enhances electron transfer. In addition, the synergistic effect of the microporous-mesoporous layered porous system and nitrogen-containing groups gives the material high oxidase-like performance.

[0033] 4. The preparation process of this invention is simple and low-cost; the obtained material exhibits a wrinkled, sheet-like structure with abundant porosity and high nitrogen content. The nitrogen-doped biomass-based carbon material prepared by this invention fully utilizes the bactericidal properties enhanced by nitrogen atom doping, while avoiding the damage to organisms caused by transition metal loss, thus possessing great application potential in the field of antibacterial applications. It can continuously generate a large number of superoxide anion free radicals to damage bacterial cell membranes.

[0034] 5. Compared with existing doped carbon materials, the nitrogen-doped biomass-based carbon material of this invention has a higher nitrogen atom doping amount, stronger oxidase-like performance, stronger catalytic bactericidal and bacteriostatic activity, and lower toxicity to organisms, and has great potential for application expansion in the field of antibacterial.

[0035] 6. In the preparation method of nitrogen-doped biomass-based carbon materials of the present invention, biomass can coordinate with zinc ions to form a supramolecular precursor. The specific type and ratio of zinc salts in this invention facilitate the formation of the supramolecular precursor, thereby facilitating the acquisition of carbon materials with the structure and properties of the present invention. Without zinc salts, the properties of the obtained material will decrease. The reason for choosing zinc salts is that zinc has a low boiling point (907℃), allowing for evaporation at a lower temperature to obtain carbon materials; using other transition metal salts would only yield transition metal-doped carbon materials. The specific type of nitrogen source in this invention, combined with a specific ratio and specific calcination conditions, facilitates the acquisition of carbon materials with the structure and properties of the present invention. If the above conditions are not suitable, the properties of the obtained material will decrease. In summary, the method of the present invention, as a whole, achieves its excellent effects through the combined action of each step and condition. Attached Figure Description

[0036] Figure 1 is a transmission electron microscope (TEM) image of the nitrogen-doped biomass-based carbon material prepared in Example 1.

[0037] Figure 2 is a scanning electron microscope (SEM) image of the nitrogen-doped biomass-based carbon material prepared in Example 1.

[0038] Figure 3 shows the energy dispersive spectra (SEM-Mapping) of different elements in the nitrogen-doped biomass-based carbon material prepared in Example 1.

[0039] Figure 4 shows the full X-ray photoelectron spectroscopy (XPS) spectra of the carbon materials prepared in Example 1 and Comparative Example 1. The horizontal axis represents binding energy, and the vertical axis represents intensity.

[0040] Figure 5 shows the N-spectrum X-ray photoelectron spectroscopy (XPS) of the carbon materials prepared in Example 1 and Comparative Example 1. The horizontal axis represents binding energy, and the vertical axis represents intensity.

[0041] Figure 6 shows the N2 adsorption-desorption isotherm of the nitrogen-doped biomass-based carbon material prepared in Example 1. The horizontal axis represents relative pressure, and the vertical axis represents the adsorption amount.

[0042] Figure 7 is a pore size distribution diagram of the nitrogen-doped biomass-based carbon material prepared in Example 1.

[0043] Figure 8 shows the oxidase-like activity of the carbon materials prepared in Examples 1, 10, 18, 22 and Comparative Examples 1 and 2.

[0044] Figure 9 shows the transmission electron microscope (TEM) images of the biomass-based carbon material prepared in Comparative Example 1.

[0045] Figure 10 shows the transmission electron microscope (TEM) images of the biomass-based carbon material prepared in Comparative Example 1.

[0046] Figure 11 is a photograph of plate images showing the survival rate of Escherichia coli incubated under different conditions in Experiment Example 1.

[0047] Figure 12 is a comparison of the survival rates of Escherichia coli and Staphylococcus aureus incubated in Example 1 and Comparative Example 1. The vertical axis represents the survival rate.

[0048] Figure 13 is a plate photograph showing the survival rate of Staphylococcus aureus under different conditions in Experiment Example 2.

[0049] Figure 14 is a cytotoxicity test diagram of the nitrogen-doped biomass-based carbon material prepared in Example 1. The horizontal axis represents the concentration of the nitrogen-doped biomass-based carbon material, and the vertical axis represents the cell viability. Detailed Implementation

[0050] The present invention will be further described below through specific embodiments, but is not limited thereto.

[0051] All raw materials used in the following examples are commercially available products of analytical grade.

[0052] Example 1

[0053] A method for preparing nitrogen-doped biomass-based carbon materials, comprising the following steps:

[0054] 2.0 g of biomass lignocellulose was added to 500 ml of deionized water and mechanically stirred to ensure thorough dispersion. Zinc acetate was dissolved in 20 mL of water to obtain a 0.2 mol / L zinc salt aqueous solution. The zinc salt aqueous solution was added to the biomass solution and stirred at room temperature for 1 h. After aging at room temperature for 12 h, the mixture was centrifuged at 3500 r / min for 3 min and dried at 80 °C for 12 h to obtain a supramolecular precursor. The obtained supramolecular precursor was ground and mixed with dicyandiamide (mass ratio of supramolecular precursor to dicyandiamide was 1:20) for 35 min. The mixed powder was annealed in a tube furnace at 950 °C for 3 h under an argon atmosphere (flow rate of 70 mL / min). Finally, after cooling to room temperature, nitrogen-doped biomass-based carbon material (N / C-20) was obtained.

[0055] In the nitrogen-doped biomass-based carbon material prepared in this embodiment, the nitrogen doping amount is 8.3 at%.

[0056] The TEM image of the nitrogen-doped biomass-based carbon material prepared in this embodiment is shown in Figure 1, which shows a sheet-like structure with abundant pores. The SEM image is shown in Figure 2, which shows that the prepared nitrogen-doped biomass-based carbon material exhibits a wrinkled layered structure. The elemental mapping image is shown in Figure 3, which proves the successful loading of nitrogen and its uniform distribution in the carbon framework.

[0057] The overall X-ray photoelectron spectroscopy (XPS) spectrum (Figure 4) and N spectrum (Figure 5) of the nitrogen-doped biomass-based carbon material (N / C-20) prepared in this embodiment are shown, indicating that N was successfully incorporated into the carbon framework. The N 1s XPS peak consists of peaks at 398.2 eV (pyridine nitrogen), 399.4 eV (pyrrole nitrogen), 401.0 eV (graphite nitrogen), and 402.5 eV (nitric oxide).

[0058] The pore structure of the prepared material was characterized using an N2 adsorption-desorption isotherm at -196℃, as shown in Figure 6. According to the IUPAC classification, the isotherm is a combination of Type I and Type IV, typical characteristics of a layered porous structure consisting of micropores and mesopores. The small hysteresis loop under high pressure reflects the presence of mesopores, which facilitates O2 diffusion. Notably, in the low-pressure stage (P / P0 < 0.1), the N2 adsorption amount increases rapidly, indicating the presence of numerous micropores in the material. Within the relative pressure range of 0.4–0.9, the isotherm shows a narrow desorption hysteresis loop, indicating the presence of a certain number of narrow mesopores. The pore size distribution shown in Figure 7 also confirms these conclusions and indicates that nitrogen doping generated a large number of narrow mesopores (2.2 nm).

[0059] The oxidase-like activity of the carbon material was evaluated using TMB as a substrate. In a typical experiment, 120 μL of 1.0 mg / mL aqueous dispersion of the carbon material and 40 μL of 10 mM TMB aqueous solution were added to 3.6 mL of NaAc-HAc buffer at pH 5. After incubation at 25 °C for 10 min, the absorbance change at 652 nm was monitored using a UV-Vis spectrophotometer. As shown in Figure 8, the prepared material (N / C-20) exhibited excellent oxidase-like activity.

[0060] Example 2

[0061] A method for preparing nitrogen-doped biomass-based carbon materials, as described in Example 1, except that zinc chloride is used instead of zinc acetate; other steps and conditions are the same as in Example 1.

[0062] Example 3

[0063] A method for preparing nitrogen-doped biomass-based carbon materials, as described in Example 1, except that zinc citrate is used instead of zinc acetate; other steps and conditions are the same as in Example 1.

[0064] Example 4

[0065] A method for preparing nitrogen-doped biomass-based carbon materials, as described in Example 1, except that zinc sulfate is used instead of zinc acetate; other steps and conditions are the same as in Example 1.

[0066] Example 5

[0067] A method for preparing nitrogen-doped biomass-based carbon materials, as described in Example 1, except that zinc nitrate is used instead of zinc acetate; other steps and conditions are the same as in Example 1.

[0068] Example 6

[0069] A method for preparing nitrogen-doped biomass-based carbon material, as described in Example 1, except that the stirring time after adding the zinc salt aqueous solution to the biomass solution is 0.5 h; other steps and conditions are the same as in Example 1.

[0070] Example 7

[0071] A method for preparing nitrogen-doped biomass-based carbon material, as described in Example 1, except that the stirring time after adding the zinc salt aqueous solution to the biomass solution is 2 hours; other steps and conditions are the same as in Example 1.

[0072] Example 8

[0073] A method for preparing nitrogen-doped biomass-based carbon material, as described in Example 1, except that the drying temperature is 60°C; other steps and conditions are the same as in Example 1.

[0074] Example 9

[0075] A method for preparing nitrogen-doped biomass-based carbon material is as described in Example 1, except that the drying temperature is 70°C; other steps and conditions are the same as in Example 1.

[0076] Example 10

[0077] A method for preparing nitrogen-doped biomass-based carbon materials, as described in Example 1, except that 1,2,4,5-tetraaminobenzene is used instead of dicyandiamide; other steps and conditions are the same as in Example 1.

[0078] Example 11

[0079] A method for preparing nitrogen-doped biomass-based carbon material (N / C-20-urea) is as described in Example 1, except that urea is used instead of dicyandiamide; other steps and conditions are the same as in Example 1.

[0080] The oxidase-like activity of carbon materials was evaluated using TMB as a substrate, and the test method was as described in Example 1. The oxidase-like performance of the obtained material (N / C-20-urea) decreased compared to Example 1, as shown in Figure 8.

[0081] Example 12

[0082] A method for preparing nitrogen-doped biomass-based carbon materials, as described in Example 1, except that ammonium nitrate is used instead of dicyandiamide; other steps and conditions are the same as in Example 1.

[0083] Example 13

[0084] A method for preparing nitrogen-doped biomass-based carbon materials, as described in Example 1, except that p-phenylenediamine is used instead of dicyandiamide; other steps and conditions are the same as in Example 1.

[0085] Example 14

[0086] A method for preparing nitrogen-doped biomass-based carbon materials, as described in Example 1, except that 4,4'-bipyridine is used instead of dicyandiamide; other steps and conditions are the same as in Example 1.

[0087] Example 15

[0088] A method for preparing nitrogen-doped biomass-based carbon materials, as described in Example 1, except that cyanamide is used instead of dicyandiamide; other steps and conditions are the same as in Example 1.

[0089] Example 16

[0090] A method for preparing nitrogen-doped biomass-based carbon materials, as described in Example 1, except that melamine is used instead of dicyandiamide; other steps and conditions are the same as in Example 1.

[0091] Example 17

[0092] A method for preparing nitrogen-doped biomass-based carbon material, as described in Example 1, except that the grinding time is 30 min; other steps and conditions are the same as in Example 1.

[0093] Example 18

[0094] A method for preparing nitrogen-doped biomass-based carbon material, as described in Example 1, except that the grinding time is 40 min; other steps and conditions are the same as in Example 1.

[0095] Example 19

[0096] A method for preparing nitrogen-doped biomass-based carbon material, as described in Example 1, except that the gas flow rate is 60 mL / min; other steps and conditions are the same as in Example 1.

[0097] Example 20

[0098] A method for preparing nitrogen-doped biomass-based carbon material, as described in Example 1, except that the gas flow rate is 80 mL / min; other steps and conditions are the same as in Example 1.

[0099] Example 21

[0100] A method for preparing nitrogen-doped biomass-based carbon material, as described in Example 1, except that the calcination temperature is 900℃; other steps and conditions are the same as in Example 1.

[0101] Example 22

[0102] A method for preparing nitrogen-doped biomass-based carbon materials (N / C-20-1000℃) is as described in Example 1, except that the calcination temperature is 1000℃; other steps and conditions are the same as in Example 1.

[0103] The oxidase-like activity of carbon materials was evaluated using TMB as a substrate, and the test method was as described in Example 1. The oxidase-like activity of the obtained material (N / C -20 -1000℃) decreased compared to that of Example 1, as shown in Figure 8.

[0104] Example 23

[0105] A method for preparing nitrogen-doped biomass-based carbon material is as described in Example 1, except that the calcination time is 2 hours; other steps and conditions are the same as in Example 1.

[0106] Example 24

[0107] A method for preparing nitrogen-doped biomass-based carbon material is as described in Example 1, except that the calcination time is 4 hours; other steps and conditions are the same as in Example 1.

[0108] Example 25

[0109] A method for preparing nitrogen-doped biomass-based carbon materials, as described in Example 1, except that the weight of dicyandiamide is 5 times that of the supramolecular precursor; other steps and conditions are the same as in Example 1.

[0110] Example 26

[0111] A method for preparing nitrogen-doped biomass-based carbon material (N / C-10) is as described in Example 1, except that the weight of dicyandiamide is 10 times that of the supramolecular precursor; other steps and conditions are the same as in Example 1.

[0112] The oxidase-like activity of carbon materials was evaluated using TMB as a substrate, and the test method was as described in Example 1. The oxidase-like performance of the obtained material (N / C-10) decreased compared to Example 1, as shown in Figure 8.

[0113] Example 27

[0114] A method for preparing nitrogen-doped biomass-based carbon materials, as described in Example 1, except that the weight of dicyandiamide is 15 times that of the supramolecular precursor; other steps and conditions are the same as in Example 1.

[0115] Example 28

[0116] A method for preparing nitrogen-doped biomass-based carbon materials, as described in Example 1, except that the weight of dicyandiamide is 25 times that of the supramolecular precursor; other steps and conditions are the same as in Example 1.

[0117] Example 29

[0118] A method for preparing nitrogen-doped biomass-based carbon materials, as described in Example 1, except that the weight of dicyandiamide is 30 times that of the supramolecular precursor; other steps and conditions are the same as in Example 1.

[0119] Comparative Example 1

[0120] A method for preparing a biomass-based carbon material, as described in Example 1, except that dicyandiamide is not added; the other steps and conditions are the same as in Example 1.

[0121] The specific method is as follows:

[0122] 2.0 g of biomass lignocellulose was added to 500 ml of deionized water and mechanically stirred to ensure thorough dispersion. Zinc acetate was dissolved in 20 mL of water to obtain a 0.2 mol / L zinc salt aqueous solution. The zinc salt aqueous solution was added to the biomass solution and stirred at room temperature for 1 h. After aging at room temperature for 12 h, the mixture was centrifuged at 3500 r / min for 3 min and dried at 80 °C for 12 h to obtain a supramolecular precursor. The obtained supramolecular precursor was ground for 35 min. The powder was annealed in a tube furnace at 950 °C for 3 h under an argon atmosphere (flow rate of 70 mL / min). Finally, after cooling to room temperature, biomass-based carbon material (C) was obtained.

[0123] Figure 9 (transmission electron microscope) and Figure 10 (scanning electron microscope) show that the carbon material without nitrogen doping is a typical bulk biomass material.

[0124] The oxidase-like activity of carbon materials was evaluated using TMB as a substrate, and the test method was as described in Example 1. The oxidase-like performance of the obtained material (C) decreased, as shown in Figure 8.

[0125] Comparative Example 2

[0126] A method for preparing a biomass-based carbon material, as described in Example 1, except that: no zinc salt aqueous solution is added; other steps and conditions are the same as in Example 1.

[0127] The specific method is as follows:

[0128] Biomass lignocellulose and dicyandiamide (biomass to dicyandiamide mass ratio 1:20) were ground and mixed for 35 min. The mixed powder was annealed in a tube furnace at 950 °C for 3 h under an argon atmosphere (flow rate 70 mL / min). Finally, after cooling to room temperature, biomass carbon material (N / C-20-B) was obtained.

[0129] The oxidase-like activity of carbon materials was evaluated using TMB as a substrate, and the test method was as described in Example 1. The oxidase-like performance of the obtained material (N / C-20-B) decreased, as shown in Figure 8.

[0130] Experiment 1: Antibacterial Performance Test of Escherichia coli

[0131] Antibacterial performance tests were conducted on Escherichia coli.

[0132] (1) Escherichia coli was inoculated into LB medium and cultured on a shaker at 37°C and 200 r / min for 12 h. The bacterial suspension was then diluted to determine the concentration of the bacterial suspension as 10. 7 CFU / mL. Take 10 mL of diluted E. coli culture and add 100 μL of the nitrogen-doped biomass-based carbon material aqueous solution (100 μg / mL) prepared in Example 1. Incubate at 37 °C and 200 r / min for 4 h on a shaker. Spread 100 μL of the culture onto LB solid medium and incubate at 37 °C for 12 h. Perform plate colony counting. The above is set as N / C-20 group.

[0133] (2) The method described in (1) above is followed, except that the sample is replaced with 100 μL of an aqueous solution (100 μg / mL) of the biomass-based carbon material prepared in Comparative Example 1. The above is set as Group C.

[0134] (3) The method described in (1) above is the same, except that 100 μL of an aqueous solution without the sample is added. The above is set as the control group.

[0135] The survival rate of *E. coli* was calculated to evaluate its antibacterial performance; the colony count on the plate of the control group was recorded as A0, and the colony count on the plate of the sample was recorded as A... t The survival rate of E. coli is calculated using the following formula: Survival rate (%) = A t / A0×100%.

[0136] Figure 11 shows the survival rate of *E. coli* bacterial culture in the N / C-20 group, group C, and the control group. Figure 12 shows that the nitrogen-doped biomass-based carbon material has a bactericidal rate of >99% against *E. coli*.

[0137] Further testing revealed that the minimum inhibitory concentration of the nitrogen-doped biomass-based carbon material prepared in Example 1 against Escherichia coli was 50 μg / mL.

[0138] Experiment Example 2: Antibacterial Performance Test of Staphylococcus aureus

[0139] The test method for the antibacterial performance against Staphylococcus aureus is as described in Test Example 1.

[0140] Figure 13 is a plate plot showing the survival rate of Staphylococcus aureus bacterial suspension in the N / C-20 group, group C, and control group. Figure 12 shows that the bactericidal rate of nitrogen-doped biomass-based carbon material against Staphylococcus aureus is >99%.

[0141] Further testing revealed that the minimum inhibitory concentration (MIC) of the nitrogen-doped biomass-based carbon material prepared in Example 1 against Staphylococcus aureus was 50 μg / mL.

[0142] Experimental Example 3: Cytotoxicity Test

[0143] The nitrogen-doped biomass-based carbon material from Example 1 was used to test the cytotoxicity of HeLa cells.

[0144] HeLa cells were incubated with N / C-20 aqueous solutions prepared in Example 1 at concentrations ranging from 0 to 300 μg / mL at 37°C for 12 h. Then, 200 mL of fresh culture medium containing 20 mL of MTT (5 mg / mL in PBS) was added, and the cells were incubated at 37°C for 4 h. Finally, 150 mL of DMSO was added to dissolve the formed purple formazan crystals. The optical density was measured at 570 nm using a microplate reader, with pure DMSO used as a blank. Cytotoxicity after each treatment is expressed as the percentage of cell viability relative to untreated control cells.

[0145] As shown in Figure 14, the experiment found that the nitrogen-doped biomass-based carbon material prepared in Example 1 was almost non-toxic to HeLa cells.

Claims

1. A method for preparing nitrogen-doped biomass-based carbon materials for antibacterial purposes, characterized in that, Includes the following steps: (1) Fully disperse the biomass in deionized water; Add zinc salt aqueous solution and mix evenly; after aging, centrifugation and drying, supramolecular precursor is obtained; the molar concentration of zinc salt aqueous solution is 0.05~5mol / L; the mass ratio of zinc salt to biomass is (0.1~2.5):(0.1~5); (2) grind and mix supramolecular precursor with nitrogen source evenly, and calcine to obtain nitrogen-doped biomass-based carbon material; the mass ratio of supramolecular precursor to nitrogen source is 1:(1~50); the calcination temperature is 900~1000℃, and the calcination time is 2~4h.

2. The method for preparing nitrogen-doped biomass-based carbon materials according to claim 1, characterized in that, Step (1) includes one or more of the following conditions: i. The biomass is one or more of straw, rice husk, wood flour or lignocellulose; ii. The mass ratio of biomass to deionized water is (0.05-5):(100-1500); iii. The zinc salt is zinc acetate, zinc chloride, zinc citrate, zinc sulfate or zinc nitrate; iv. The molar concentration of the zinc salt aqueous solution is 0.2-0.4 mol / L; v. The mass ratio of zinc salt to biomass is (0.5-1.5):(1-3); vi. After adding the zinc salt aqueous solution, stir at room temperature for 0.1-5 hours to mix evenly; vii. The aging temperature is room temperature, the aging time is 6-24 hours, and the aging is carried out under static conditions; viiii. The centrifugation speed is 2000-5000 r / min, and the centrifugation time is 1-10 minutes; ix. The drying temperature is 50-90℃, and the drying time is 10-24 hours.

3. The method for preparing nitrogen-doped biomass-based carbon materials according to claim 2, characterized in that, Includes one or more of the following conditions: i. The mass ratio of biomass to deionized water is (2-3):(500-1000); ii. The zinc salt is zinc acetate; iii. The aging time is 10-15 h; iv. The centrifugation speed is 3000-4000 r / min and the centrifugation time is 2-5 min; v. The drying temperature is 60-80℃ and the drying time is 12-15 h.

4. The method for preparing nitrogen-doped biomass-based carbon materials according to claim 1, characterized in that, In step (2), the nitrogen source is one or a combination of two or more of 1,2,4,5-tetraaminobenzene, urea, p-phenylenediamine, 4,4'-bipyridine, cyanamide, polyethyleneimine, dicyandiamide or melamine.

5. The method for preparing nitrogen-doped biomass-based carbon materials according to claim 4, characterized in that... The nitrogen source is one or a combination of two or more of urea, cyanamide, polyethyleneimine, dicyandiamide or melamine.

6. The method for preparing nitrogen-doped biomass-based carbon materials according to claim 1, characterized in that, In step (2), the mass ratio of supramolecular precursor to nitrogen source is 1:(5-30).

7. The method for preparing nitrogen-doped biomass-based carbon materials according to claim 6, characterized in that, In step (2), the mass ratio of supramolecular precursor to nitrogen source is 1:(10-25).

8. The method for preparing nitrogen-doped biomass-based carbon materials according to claim 1, characterized in that, In step (2), the grinding time is 5 to 60 minutes.

9. The method for preparing nitrogen-doped biomass-based carbon materials according to claim 8, characterized in that, The grinding time is 30 to 40 minutes.

10. The method for preparing nitrogen-doped biomass-based carbon materials according to claim 1, characterized in that, In step (2), the calcination conditions are: gas protection, gas flow rate of 30-100 mL / min.

11. The method for preparing nitrogen-doped biomass-based carbon materials according to claim 10, characterized in that, The gas is nitrogen, argon, or helium, and the gas flow rate is 60-80 mL / min.

12. The nitrogen-doped biomass-based carbon material prepared by any one of claims 1-11, characterized in that, The nitrogen-doped biomass-based carbon material has a microstructure of a porous, folded sheet.

13. The nitrogen-doped biomass-based carbon material according to claim 12, characterized in that, The nitrogen doping amount of nitrogen-doped biomass-based carbon materials is 6 at% - 9 at%; nitrogen in nitrogen-doped biomass-based carbon materials exists in the form of pyridine nitrogen, graphitic nitrogen, pyrrole nitrogen and nitrogen oxides.

14. The nitrogen-doped biomass-based carbon material according to claim 12, characterized in that, The pore size in nitrogen-doped biomass-based carbon materials ranges from 2.2 to 150 nm.

15. The application of nitrogen-doped biomass-based carbon materials prepared by any one of claims 1-11 in antibacterial applications.

16. The application according to claim 15, characterized in that, The nitrogen-doped biomass-based carbon material is used for the sterilization or inhibition of Escherichia coli or Staphylococcus aureus.

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