Nitrogen-doped biomass-based fluorescent carbon quantum dot as well as preparation method and application thereof

Abstract

The invention provides a nitrogen-doped biomass-based fluorescent carbon quantum dot, a preparation method and application, and relates to the technical field of carbon nanomaterials, the method comprises the following steps: mixing a biomass material and deionized water under an ultrasonic condition, adding a nitrogen source, and carrying out ultrasonic dispersion to obtain a uniformly dispersed to-be-reacted solution; reacting the to-be-reacted solution at a preset temperature for a preset time to obtain a mixed product solution; and filtering and dialyzing the mixed product solution to obtain the nitrogen-doped biomass-based fluorescent carbon quantum dot solution. The nitrogen-doped biomass-based fluorescent carbon quantum dot prepared by the method shows a stable fluorescent effect and good water solubility, the free radical clearance rate can reach 90% or above, and the antibacterial rate can reach 99% or above. The method can be used in the fields of drug sustained release, bioimaging and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of carbon nanomaterials, and in particular to nitrogen-doped biomass-based fluorescent carbon quantum dots, a preparation method and uses thereof. Background Art

[0002] Carbon quantum dots have the advantages of high cost-effectiveness, green and simple preparation conditions, environmental friendliness, easy functionalization, and strong multi-photon excitation ability. They are considered to be the first choice for other luminescent nanomaterials with a particle size of less than 10 nm. In addition, quantum dots have excellent fluorescence properties based on quantum size effects and surface functional groups. However, semiconductor quantum dots contain heavy metals such as cadmium and chromium, which are seriously harmful to the environment and human body. At the same time, traditional phosphors need to be calcined at a temperature of about 1000°C, which leads to the consumption of rare earth elements. Natural biomass materials, especially cellulose, can be used as a carbon source to obtain low-toxicity and biocompatible carbon quantum dots. Based on these findings, biomass carbon quantum dots have gradually replaced traditional semiconductor quantum dots and are used in drug delivery and bioimaging.

[0003] At present, researchers have publicly used natural biomass materials such as coffee grounds and orange peels as raw materials, and prepared carbon quantum dots through steps such as plasma treatment, pyrolysis, and combustion. Although this method reduces the cost of raw materials, the process is relatively complicated and takes a long time. It also has certain toxicity and causes harm to the natural environment and human health. On the other hand, although biomass-based materials are widely available, the performance of carbon quantum dots obtained directly from raw materials without appropriate methods is often limited. Therefore, in order to maximize the advantages of biomass-based materials and obtain carbon quantum dots with stable performance, it has become an inevitable trend to design a simple, effective, and green and pollution-free preparation method for preparing carbon quantum dots. Summary of the Invention

[0004] The present invention aims to provide nitrogen-doped biomass-based fluorescent carbon quantum dots, a preparation method and uses thereof, in order to at least partially solve at least one of the above-mentioned technical problems.

[0005] In order to solve the above technical problems, the first aspect of the present invention provides a method for preparing nitrogen-doped biomass-based fluorescent carbon quantum dots, the method comprising:

[0006] After mixing the biomass material and deionized water under ultrasonic conditions, a nitrogen source is added and ultrasonically dispersed to obtain a uniformly dispersed solution to be reacted;

[0007] reacting the solution to be reacted at a preset temperature for a predetermined time to obtain a mixed product solution;

[0008] The mixed product solution is filtered and dialyzed to obtain a nitrogen-doped biomass-based fluorescent carbon quantum dot solution.

[0009] The method according to claim 1 is characterized in that the biomass material is one or more of bagasse, orange peel, straw, lignin, lychee shell, and peanut shell.

[0010] According to a preferred embodiment of the present invention, the nitrogen source is a small molecule reagent containing nitrogen element;

[0011] According to a preferred embodiment of the present invention, the nitrogen-containing small molecule reagent is one or more of melamine, urea, ammonia, dopamine, and ethylenediamine.

[0012] According to a preferred embodiment of the present invention, the mass volume ratio of the biomass material and deionized water is: 10mg-1000mg:60ml; the mass of the nitrogen source is: 10mg-1000mg.

[0013] According to a preferred embodiment of the present invention, the biomass material and deionized water are mixed under ultrasonic conditions for 0.5h-4h, and ultrasonically dispersed for 10-60 minutes. The preset temperature is 120-220°C, and the predetermined time is 5-24 hours.

[0014] According to a preferred embodiment of the present invention, the dialyzed solution is used for 1-4 days through a dialysis bag with a molecular weight cut-off of 1000 Da.

[0015] In order to solve the above technical problems, the second aspect of the present invention provides nitrogen-doped biomass-based fluorescent carbon quantum dots, which are prepared by any of the above-mentioned nitrogen-doped biomass-based fluorescent carbon quantum dots preparation methods.

[0016] In order to solve the above technical problems, the third aspect of the present invention provides a use of nitrogen-doped biomass-based fluorescent carbon quantum dots, wherein the nitrogen-doped biomass-based fluorescent carbon quantum dots are used for the release of curcumin drug.

[0017] In order to solve the above technical problems, the fourth aspect of the present invention provides a method for using nitrogen-doped biomass-based fluorescent carbon quantum dots, the method comprising:

[0018] Adding the curcumin drug to be loaded into the nitrogen-doped biomass-based fluorescent carbon quantum dot solution, stirring in the dark, centrifuging, and vacuum drying to obtain a nitrogen-doped biomass-based fluorescent carbon quantum dot sample loaded with curcumin to be tested;

[0019] The samples were placed in phosphate buffers of different pH values, and drug release was performed in a constant temperature dark place.

[0020] In summary, the present invention uses environmentally friendly biomass-based materials as raw materials, adds different small molecule nitrogen sources, and employs a simple one-step hydrothermal method to prepare small-sized nitrogen-doped biomass-based fluorescent carbon quantum dots. These nitrogen-doped biomass-based fluorescent carbon quantum dots exhibit stable fluorescence, good water solubility, a free radical scavenging rate exceeding 90%, and an antibacterial rate exceeding 99%. They can be used in areas such as drug sustained release and bioimaging. Compared to existing technologies, the present invention has at least the following beneficial effects:

[0021] (1) The present invention uses biomass materials as raw materials, which are low-cost, easy to obtain, environmentally friendly and sustainable;

[0022] (2) The present invention can prepare biomass-based carbon quantum dots with good stability, good water solubility and good biocompatibility through a green and pollution-free one-step hydrothermal method, and the preparation method is simple and easy to operate;

[0023] (3) The biomass-based carbon quantum dots prepared by the present invention do not contain heavy metal elements such as lead and cadmium, and are safe and have no toxic risks.

[0024] (4) The biomass carbon quantum dots prepared by the present invention have uniform particle size distribution and uniform size, with an average diameter of 1.5-4.5 nm.

[0025] (5) The biomass-based carbon quantum dots prepared by the present invention as a carrier of curcumin drugs have extremely high drug encapsulation efficiency and can effectively load curcumin through chemical reactions, with a drug encapsulation efficiency of 80%.

[0026] (6) The biomass-based carbon quantum dots prepared by the present invention have the characteristics of responding to the external environment, achieving efficient release of curcumin, and the cumulative drug release rate is as high as 95%.

[0027] Figures in the specification

[0028] Figure 1 This is a schematic flow chart of a method for preparing nitrogen-doped biomass-based fluorescent carbon quantum dots provided in Example 1 of the present invention;

[0029] Figure 2a This is a transmission electron microscope image of nitrogen-doped biomass-based fluorescent carbon quantum dots prepared in Example 1 of the present invention;

[0030] Figure 2b This is a particle size distribution diagram of nitrogen-doped biomass-based fluorescent carbon quantum dots prepared in Example 1 of the present invention;

[0031] Figure 3 This is the Zeta potential image of nitrogen-doped biomass-based fluorescent carbon quantum dots prepared in Example 1 of the present invention;

[0032] Figure 4This is an X-ray photoelectron spectrum of nitrogen-doped biomass-based fluorescent carbon quantum dots prepared in Example 1 of the present invention;

[0033] Figure 5 This is an anti-free radical image of nitrogen-doped biomass-based fluorescent carbon quantum dots prepared in Example 1 of the present invention;

[0034] Figure 6 This is an image of nitrogen-doped biomass-based fluorescent carbon quantum dots against Escherichia coli prepared in Example 1 of the present invention;

[0035] Figure 7a and 7b These are images of the cumulative release of curcumin at different pH values ​​by the nitrogen-doped biomass-based fluorescent carbon quantum dot drug carrier prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0036] The features and exemplary embodiments of various aspects of the present invention will be described in detail below. In order to make the objects, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below in conjunction with the accompanying drawings and Examples. It should be understood that the specific embodiments described herein are only configured to explain the present invention and are not configured to limit the present invention. For those skilled in the art, the present invention can be implemented without the need for some of these specific details. The following description of the embodiments is merely to provide a better understanding of the present invention by illustrating examples of the present invention.

[0037] It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article, or device comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or elements inherent to such process, method, article, or device. In the absence of further limitations, the elements defined by the phrase "comprising..." do not exclude the presence of other identical elements in the process, method, article, or device comprising the elements.

[0038] Example 1

[0039] The first embodiment of the present invention provides a method for preparing nitrogen-doped biomass-based fluorescent carbon quantum dots. Figure 1 As shown, the method includes:

[0040] S1. After mixing the biomass material and deionized water under ultrasonic conditions, a nitrogen source is added and ultrasonically dispersed to obtain a uniformly dispersed solution to be reacted;

[0041] Exemplarily, the biomass material is one or more of bagasse, orange peel, straw, lignin, lychee shell, and peanut shell.

[0042] The nitrogen source is a small molecule reagent containing nitrogen elements; preferably, the small molecule reagent containing nitrogen elements is one or more of melamine, urea, ammonia water, dopamine, and ethylenediamine.

[0043] Preferably, the mass volume ratio of the biomass material and deionized water is: 10mg-1000mg:60ml; the mass of the nitrogen source is: 10mg-1000mg.

[0044] In a preferred embodiment, the biomass material and deionized water are mixed under ultrasonic conditions for 0.5 h to 4 h, and ultrasonically dispersed for 10 to 60 minutes.

[0045] S2, reacting the solution to be reacted at a preset temperature for a predetermined time to obtain a mixed product solution;

[0046] This step uses a one-step hydrothermal method to react the solution to be reacted. The solution to be reacted can be transferred to a reactor and reacted at a preset temperature for a predetermined time. The preset temperature is 120-220°C, and the predetermined time is 5-24 hours.

[0047] S3. Filtering and dialyzing the mixed product solution to obtain a nitrogen-doped biomass-based fluorescent carbon quantum dot solution.

[0048] Optionally, the mixed product solution is filtered through a filter membrane having a pore size of less than 220 nm, and the filtered solution is transferred to a dialysis bag and dialyzed, preferably, for 1-4 days through a dialysis bag with a molecular weight cut-off of 1000 Da.

[0049] In a specific embodiment, the preparation method of the nitrogen-doped biomass-based fluorescent carbon quantum dots comprises: ultrasonically dispersing 5 mg of lychee shell in 60 mL of aqueous solution for 40 minutes to uniformly disperse it in the aqueous solution, then adding 200 mg of urea to the aqueous solution and ultrasonically dispersing it for 10 minutes. The uniform reaction solution obtained by ultrasonic dispersion is then transferred to a 100 mL polytetrafluoroethylene autoclave, reacted at 180 ° C for 10 hours, and taken out after cooling. Filtered with a 220 nm filter membrane, the filtered solution is transferred to a 1000 Da dialysis bag and dialyzed for 1 day to obtain a nitrogen-doped biomass-based fluorescent carbon quantum dot solution. The solution is vacuum dried at 60 ° C to obtain a black nitrogen-doped biomass-based fluorescent carbon quantum dot solution powder.

[0050] In another specific embodiment, the preparation method of the nitrogen-doped biomass-based fluorescent carbon quantum dots comprises: ultrasonically dispersing 5 mg of lychee shell in 60 mL of aqueous solution for 40 minutes to uniformly disperse it in the aqueous solution, then adding 200 mg of melamine to the aqueous solution and ultrasonically dispersing it for 20 minutes. The uniform reaction solution obtained by ultrasonic dispersion is then transferred to a 100 mL polytetrafluoroethylene autoclave and reacted at 180 ° C for 12 hours. After cooling, it is taken out and filtered with a 220 nm filter membrane. The filtered solution is transferred to a 1000 Da dialysis bag and dialyzed for 2 days to obtain a nitrogen-doped biomass-based fluorescent carbon quantum dot solution. The solution is vacuum dried at 60 ° C to obtain a black nitrogen-doped biomass-based fluorescent carbon quantum dot solution powder.

[0051] Figure 2a and 2b The transmission electron microscope images and particle size distribution diagrams of nitrogen-doped biomass-based fluorescent carbon quantum dots prepared by the present invention are shown respectively. Figure 2a and 2b It can be seen that the nitrogen-doped biomass carbon quantum dots prepared by the present invention have uniform particle size distribution and uniform size, with an average diameter of 1.5-4.5 nm.

[0052] Figure 3 This is the zeta potential image of nitrogen-doped biomass-based fluorescent carbon quantum dots prepared in Example 1 of the present invention. Figure 4 This is the X-ray photoelectron spectrum of nitrogen-doped biomass-based fluorescent carbon quantum dots prepared in Example 1 of the present invention. Figure 3 and 4 It can be seen that the nitrogen-doped biomass-based fluorescent carbon quantum dots prepared in the present invention exhibit a stable fluorescence effect.

[0053] Figure 5 and Figure 6 They are respectively the anti-free radical image and the anti-E. coli image of nitrogen-doped biomass-based fluorescent carbon quantum dots prepared in Example 1 of the present invention. Figure 5 and Figure 6 It can be seen that the nitrogen-doped biomass-based fluorescent carbon quantum dots prepared by the present invention have a free radical scavenging rate of more than 90% and an antibacterial rate of more than 99%.

[0054] Example 2

[0055] The second embodiment of the present invention provides nitrogen-doped biomass-based fluorescent carbon quantum dots, which can be prepared by any of the nitrogen-doped biomass-based fluorescent carbon quantum dots preparation methods described in the first embodiment.

[0056] Example 3

[0057] A third embodiment of the present invention provides a use of nitrogen-doped biomass-based fluorescent carbon quantum dots, wherein the nitrogen-doped biomass-based fluorescent carbon quantum dots are used for the release of curcumin drug.

[0058] Example 4

[0059] A fourth embodiment of the present invention provides a method for using nitrogen-doped biomass-based fluorescent carbon quantum dots, the method comprising:

[0060] S101, adding the curcumin drug to be loaded into the nitrogen-doped biomass-based fluorescent carbon quantum dot solution, stirring in the dark, centrifuging, and vacuum drying to obtain a nitrogen-doped biomass-based fluorescent carbon quantum dot sample loaded with curcumin to be tested;

[0061] S102, placing the samples in phosphate buffers of different pH values, respectively, and performing drug release in a dark place at a constant temperature;

[0062] Furthermore, the concentration of the buffer solution can be measured using an ultraviolet spectrophotometer to obtain the cumulative release amount of curcumin in the buffer solution.

[0063] Exemplary, the nitrogen-doped biomass-based fluorescent carbon quantum dots prepared in Example 1 are used as drug carrier materials to perform an accumulation release test of curcumin drugs. 5 mL of nitrogen-doped biomass-based fluorescent carbon quantum dot solution loaded with curcumin is placed in a dialysis bag with a molecular weight cut-off of 1000, 80 mL of phosphate buffer of pH=5.0 and pH=7.4 are added, and stirred in a dark place at a constant temperature of 37 ° C. At intervals of a certain time, 1 mL of solution (added to the same volume of PBS buffer) is taken and its concentration is determined using an ultraviolet spectrophotometer. Thus, information on the concentration of curcumin released from biomass carbon quantum dots in the solution is obtained. Figure 7a and 7b The images are respectively of the cumulative release of curcumin by the nitrogen-doped biomass-based fluorescent carbon quantum dot drug carrier prepared by the present invention at different pH values. Figure 7a and 7b It can be seen that the cumulative release of curcumin in phosphate buffer at pH = 5.0 reaches 95%; and the biomass-based carbon quantum dots prepared by the present invention as a carrier of curcumin drugs have extremely high drug encapsulation efficiency and can effectively load curcumin through chemical reactions, with a drug encapsulation efficiency of 80%.

[0064] It should be understood that the present invention is not limited to the specific structures and processes described above and illustrated in the figures. For the sake of simplicity, a detailed description of known methods is omitted here. In the above embodiments, several specific steps are described and illustrated as examples. However, the method process of the present invention is not limited to the specific steps described and illustrated. Those skilled in the art can make various changes, modifications, and additions, or change the order of the steps after understanding the spirit of the present invention.

[0065] It should also be noted that the exemplary embodiments described herein describe methods or systems based on a series of steps or devices. However, the present invention is not limited to the order of the steps described above. In other words, the steps may be performed in the order described in the embodiments, or in a different order, or several steps may be performed simultaneously.

[0066] The above description is only a specific embodiment of the present invention. Those skilled in the art will clearly understand that for the convenience and brevity of description, the specific working processes of the systems, modules and units described above can refer to the corresponding processes in the aforementioned method embodiments, and will not be repeated here. It should be understood that the protection scope of the present invention is not limited to this. Any person skilled in the art can easily think of various equivalent modifications or replacements within the technical scope disclosed by the present invention, and these modifications or replacements should be included in the protection scope of the present invention.

Claims

1. A method for preparing nitrogen-doped biomass-based fluorescent carbon quantum dots, characterized in that: The method comprises: After mixing the biomass material and deionized water under ultrasonic conditions, a nitrogen source is added and ultrasonically dispersed to obtain a uniformly dispersed solution to be reacted; reacting the solution to be reacted at a preset temperature for a predetermined time to obtain a mixed product solution; The mixed product solution is filtered and dialyzed to obtain a nitrogen-doped biomass-based fluorescent carbon quantum dot solution.

2. The method according to claim 1, characterized in that The biomass material is one or more of bagasse, orange peel, straw, lignin, litchi shell and peanut shell.

3. The method according to claim 1, characterized in that The nitrogen source is a small molecule reagent containing nitrogen element.

4. The method according to claim 3, characterized in that The nitrogen-containing small molecule reagent is one or more of melamine, urea, ammonia, dopamine, and ethylenediamine.

5. The method according to claim 1, wherein The mass volume ratio of the biomass material and deionized water is: 10mg-1000mg:60ml; the mass of the nitrogen source is: 10mg-1000mg.

6. The method according to claim 1, characterized in that The biomass material and deionized water are mixed under ultrasonic conditions for 0.5 h to 4 h, and ultrasonically dispersed for 10 to 60 minutes. The preset temperature is 120 to 220° C., and the predetermined time is 5 to 24 hours.

7. The preparation method according to claim 1, characterized in that The product was dialyzed for 1-4 days using a dialysis bag with a molecular weight cut-off of 1000 Da.

8. A nitrogen-doped biomass-based fluorescent carbon quantum dot, characterized in that: The carbon quantum dots are prepared by the method for preparing nitrogen-doped biomass-based fluorescent carbon quantum dots according to any one of claims 1 to 7.

9. Use of the nitrogen-doped biomass-based fluorescent carbon quantum dots according to claim 8, characterized in that: The nitrogen-doped biomass-based fluorescent carbon quantum dots are used in curcumin drug release.

10. A method for using nitrogen-doped biomass-based fluorescent carbon quantum dots, characterized in that: The nitrogen-doped biomass-based fluorescent carbon quantum dots are prepared by the method for preparing nitrogen-doped biomass-based fluorescent carbon quantum dots according to any one of claims 1 to 7, the method comprising: Adding the curcumin drug to be loaded into the nitrogen-doped biomass-based fluorescent carbon quantum dot solution, stirring in the dark, centrifuging, and vacuum drying to obtain a nitrogen-doped biomass-based fluorescent carbon quantum dot sample loaded with curcumin to be tested; The samples were placed in phosphate buffers of different pH values, and drug release was performed in a constant temperature dark place.

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