CN111807348A - Carbon quantum dot and preparation method thereof - Google Patents

Abstract

The application provides a carbon quantum dot and a preparation method thereof. The preparation method comprises the following steps: s1, mixing the precursor with an organic solvent to prepare precursor dispersion liquid; s2, performing ultrasonic treatment and/or microwave treatment on the precursor dispersion liquid at normal pressure to obtain a carbon quantum dot solution; s3, purifying the carbon quantum dot solution to obtain carbon quantum dots; wherein the precursor comprises a plant. The preparation method has short time, easy process control and good repeatability; compared with the conventional high-temperature heating method, the prepared carbon quantum dots have higher efficiency and narrower half-peak width.

Description

Carbon quantum dot and preparation method thereof

Technical Field

The application belongs to the field of nano materials, and particularly relates to a carbon quantum dot and a preparation method thereof.

Background

The carbon quantum dot is a carbon nano material with three-dimensional sizes within 10 nanometers, and the main constituent elements of the carbon quantum dot comprise carbon, hydrogen, oxygen and the like. The fluorescent material has attracted more and more attention due to its unique advantages of excellent luminescent properties, non-toxicity, excellent biocompatibility, etc. The carbon quantum dots are widely applied to the fields of photoelectricity, biological marking and the like.

The carbon quantum dots with high luminous efficiency and narrow half-peak wide emission have important significance in enhancing the contrast ratio of bioluminescence imaging, improving the color purity of a display device and serving as a laser emission material. However, there are still many challenges to produce carbon dots with high quantum yield and narrow half-peak width. At present, most of reported high-efficiency and narrow-half-peak-width carbon quantum dots are concentrated on blue light and green light, and the reported high-efficiency red light carbon quantum dots have less literature, however, in biological applications, the carbon quantum dots need excitation with larger wavelength (near infrared or even infrared), which means that the carbon dot markers are excited by adopting lower energy, so that the risk of damaging normal cells can be reduced, the identification degree of the carbon quantum dot marked cells can be enhanced, and a better cell tracing effect can be achieved. Therefore, the method for synthesizing the carbon quantum dots with high quantum efficiency and narrow half-peak width by the green and environment-friendly method with simple preparation process can promote the practical application of the carbon quantum dots in the aspects of biological imaging and photoelectric devices, and the development of the preparation method of the carbon quantum dots has important significance for the development of the carbon quantum dots.

Disclosure of Invention

In order to solve the technical problems, the application provides a preparation method of a carbon quantum dot, which comprises the following steps:

s1, mixing the precursor with an organic solvent to prepare precursor dispersion liquid;

s2, performing ultrasonic treatment and/or microwave treatment on the precursor dispersion liquid at normal pressure to obtain a carbon quantum dot stock solution;

s3, purifying the carbon quantum dot stock solution to obtain carbon quantum dots;

wherein the precursor comprises a plant.

Further, the precursor comprises at least one of plant leaves, plant rhizomes, plant branches, plant fruits and flowers;

preferably, the precursor comprises at least one of maple leaves, maple roots and rhizomes, Chinese yew leaves, Chinese yew roots and rhizomes, ginkgo leaves, ginkgo biloba roots and rhizomes, scindapsus aureus roots and rhizomes, chlorophytum comosum leaves and chlorophytum comosum roots.

Further, the mass-to-volume ratio of the precursor to the organic solvent in step S1 is 1g (20-500) mL, preferably 5g (100-400) mL;

preferably, the organic solvent includes at least one of ethanol, methanol, acetone, N-heptane, N-hexane, dimethyl sulfoxide, and N, N-dimethylformamide.

Further, when the precursor solution is subjected to ultrasonic treatment, the frequency of the ultrasonic treatment is 25-130 KHz, preferably 40-100 KHz.

Furthermore, the time of the ultrasonic treatment is between 5 and 60min, preferably between 10 and 30 min.

Further, when the precursor solution is subjected to microwave treatment, the power of the microwave treatment is 700-1000W, preferably 800-900W.

Furthermore, the microwave treatment time is between 1 and 60min, preferably between 1 and 10 min.

Further, S3 includes the steps of:

s31, adding the carbon quantum dot solution into a chromatographic column filled with silica gel;

s32, purifying the carbon quantum dot solution by using an eluent to separate carbon quantum dots;

preferably, the mesh number of the silica gel is 200-400 meshes, and the mesh number of the silica gel is gradually reduced from bottom to top.

Further, the eluent comprises a good solvent and a poor solvent of the carbon quantum dots;

preferably, the good solvent comprises at least one of n-heptane, n-hexane, dichloromethane, chloroform, petroleum ether and toluene;

preferably, the poor solvent includes at least one of ethanol, methanol, propanol, acetone, dimethyl sulfoxide, ethyl acetate, N-dimethylformamide;

preferably, the volume ratio of the poor solvent to the good solvent is 1/20-1/2.

The application also provides a carbon quantum dot prepared by the method;

preferably, the emission peak of the carbon quantum dot is located between 656nm and 800nm, and the half-peak width is not more than 18 nm.

Has the advantages that:

(1) the preparation method of the carbon quantum dots has the advantages of short time, easily controlled process, good repeatability, simple equipment, high yield, rich raw material sources, environmental friendliness, low cost and suitability for industrial production.

(2) Compared with the conventional high-temperature heating method, the prepared carbon quantum dots have higher efficiency and narrower half-peak width.

Drawings

FIG. 1 is an emission spectrum of carbon quantum dots in example 1;

FIG. 2 is an absorption spectrum of carbon quantum dots in example 1;

FIG. 3 is a diagram of silica gel column purification treatment of carbon quantum dots in example 2;

FIG. 4 is a transmission electron microscope photograph of carbon quantum dots in example 2;

FIG. 5 is an emission spectrum of carbon quantum dots in example 2;

FIG. 6 is an absorption spectrum of carbon quantum dots in example 2;

FIG. 7 is a comparison of emission spectra before and after purification of carbon quantum dots in example 2;

FIG. 8 is a spectrum of the absorption and fluorescence emission spectra of carbon quantum dots in example 3;

FIG. 9 is a spectrum of the absorption and fluorescence emission spectra of carbon quantum dots in example 4;

fig. 10 is an absorption and fluorescence emission spectrum of the carbon quantum dots in example 5.

In the drawings like parts are provided with the same reference numerals. The figures show embodiments of the application only schematically.

Detailed Description

The following describes technical solutions in the examples of the present application in detail with reference to the embodiments of the present application. It should be noted that the described embodiments are only some embodiments of the present application, and not all embodiments.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting. Unless otherwise defined, all terms (including technical and scientific terms) in the specification may be defined as commonly understood by one of ordinary skill in the art. Terms defined in commonly used dictionaries should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and the present disclosure, and may not be interpreted in an idealized or overly formal sense unless expressly so defined. Furthermore, unless expressly stated to the contrary, the terms "comprises" and "comprising," when used in this specification, specify the presence of stated features, regions, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, regions, integers, steps, operations, elements, components, and/or groups thereof. Thus, the above wording will be understood to mean that the stated elements are included, but not to exclude any other elements.

It will be understood that, although the terms first, second, third, etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or section from another element, component, region, layer or section. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the present embodiments.

The following definitions apply to aspects described in relation to some embodiments of the invention, and these definitions may be extended herein as well.

As used herein, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. Unless the context clearly dictates otherwise, reference to an object may include multiple objects.

As used herein, the term "adjacent" refers to being proximate or contiguous. The adjacent objects may be spaced apart from each other, or may be in actual or direct contact with each other. In some cases, adjacent objects may be connected to each other, or may be integrally formed with each other.

As used herein, the term "connected" refers to an operative coupling or link. The linked objects may be directly coupled to each other or may be indirectly coupled to each other via another set of objects.

As used herein, relative terms, such as "inside," "interior," "exterior," "top," "bottom," "front," "back," "upper," "lower," "vertical," "lateral," "above … …," and "below … …," refer to the orientation of a group of objects relative to one another as a matter of manufacture or use, for example, according to the drawings, but do not require the particular orientation of the objects during manufacture or use.

The application provides a preparation method of a carbon quantum dot, which is characterized by comprising the following steps:

s1, mixing the precursor with an organic solvent to prepare a precursor dispersion liquid

S2, performing ultrasonic treatment and/or microwave treatment on the precursor dispersion liquid at normal pressure to obtain a carbon quantum dot crude liquid;

s3, purifying the carbon quantum dot solution to obtain carbon quantum dots;

wherein the precursor comprises a plant.

The process of mixing the precursor is to uniformly disperse the precursor in the organic solvent so that the precursor and the organic solvent are fully mixed. The mixing process can be performed by means of operation modes such as ultrasonic, oscillation, stirring and the like, so as to accelerate the full mixing of the precursor and the organic solvent. The above process for preparing the precursor dispersion may be carried out in the following manner: and (3) crushing the precursor into powder, and adding an organic solvent to fully and uniformly mix the precursor and the organic solvent.

After the precursor dispersion liquid is prepared, the precursor dispersion liquid can be put into a microwave generating device, microwaves have certain energy, the temperature of the precursor dispersion liquid can be rapidly increased, and meanwhile, the reaction among molecules of a precursor is facilitated, so that the carbon quantum dots are prepared in a short time; or the precursor dispersion liquid can be put into an ultrasonic generator, and the energy generated by ultrasonic waves enables the precursor dispersion liquid to generate chemical reaction to obtain carbon quantum dot solution; the precursor dispersion may be subjected to microwave treatment and ultrasonic treatment at the same time, for example, the precursor dispersion may be subjected to a combination of microwave and ultrasonic treatment using a microwave-ultrasonic combination reaction system; of course, the precursor dispersion may be subjected to the microwave treatment and the ultrasonic treatment, or the precursor dispersion may be subjected to the ultrasonic treatment and the microwave treatment. The purification treatment aims at removing impurities, obtaining carbon quantum dots with higher purity and better optical performance, and purifying the carbon quantum dot solution by adopting modes such as centrifugal filtration, elution and the like.

The traditional synthesis method of carbon quantum dots generally adopts a high-temperature heating mode, for example: mainly utilize citric acid and urea as the carbon source, solvents such as distilled water, ethanol are as reaction medium, place high temperature heating reaction (certain reaction time, reaction temperature) behind polytetrafluoroethylene inside lining, after the reaction finishes, carbon quantum dot needs loaded down with trivial details purification step, including commonly used: the method has the characteristics of low yield of the obtained carbon quantum dots, complex components, wide half-height peak width of fluorescence spectra of the carbon quantum dots, low fluorescence efficiency, difficulty in realizing large-scale production and application and the like. Compared with the method for preparing the carbon quantum dots by adopting a high-temperature heating method, the method has the advantages that the process of carrying out normal-pressure treatment on the precursor dispersion liquid by adopting microwaves and/or ultrasonic waves is very simple, the requirement on the device is low, higher reaction temperature, complex equipment and the like are not needed. And the inventor finds that the carbon quantum dots prepared by microwave treatment and/or ultrasonic treatment have higher luminous efficiency and narrower half-peak width.

In the present application, the precursor includes at least one of plant leaves, plant roots, plant branches, plant fruits, and flowers. The precursor includes, but is not limited to, at least one of maple leaf, maple rhizome, yew leaf, yew rhizome, ginkgo leaf, ginkgo rhizome, scindapsus aureus leaf, scindapsus aureus rhizome, chlorophytum comosum leaf, and chlorophytum comosum rhizome. The precursors are used as raw materials, and the carbon quantum dots with high yield, narrow half-peak width and high luminous efficiency can be prepared.

In one embodiment of the present application, the mass-to-volume ratio of the precursor to the organic solvent in step S1 is 5g (20-500) mL, and the prepared carbon quantum dot has excellent performance, particularly, the mass-to-volume ratio of the precursor to the organic solvent is 5g (100-400) mL; the yield and the quantum efficiency of the carbon quantum dots are obviously improved, and the half-peak width is obviously narrowed.

In another embodiment of the present application, the organic solvent includes at least one of ethanol, methanol, acetone, N-heptane, N-hexane, dimethyl sulfoxide, and N, N-dimethylformamide, and the organic solvent can effectively disperse the precursor and accelerate the generation of the carbon quantum dots.

In another embodiment of the present application, when the precursor solution is subjected to ultrasonic treatment, the frequency of the ultrasonic treatment is between 25 to 130KHz, and the carbon quantum dots with high luminous efficiency and narrow half-peak width are prepared, and particularly, when the frequency of the ultrasonic treatment is between 40 to 100KHz, the optical properties of the carbon quantum dots are more excellent.

In a further specific embodiment of the application, the time of ultrasonic treatment is between 5 and 60min, so that the precursor dispersion liquid effectively reacts to form carbon quantum dots through ultrasonic treatment; the yield of the carbon quantum dots is high, and the yield of the carbon quantum dots is high when the ultrasonic treatment time is 10-30 min.

In another embodiment of the present application, when the precursor solution is subjected to microwave treatment, the power of the microwave treatment is between 700W and 1000W, so that the reaction speed of the precursor dispersion is high, the energy utilization rate in the preparation process of the carbon quantum dots is high, the temperature rise rate is high, the repeatability is good, the uniformity of the particle size of the obtained carbon quantum dots is stronger, the power of the microwave treatment can be 700W, 800W, 900W or 1000W, and the power of the microwave treatment is preferably between 800W and 900W.

In the specific embodiment of the present application, the microwave treatment time is between 1 to 60min, so that the carbon quantum dot yield and the production efficiency are maintained at a preferable level, and the microwave treatment time is preferably between 1 to 10 min.

In another embodiment of the present application, the method for preparing carbon quantum dots further comprises the steps of:

s3, adding the carbon quantum dot solution into a chromatographic column filled with silica gel;

s4, eluting the carbon quantum dot solution by using an eluent to separate carbon quantum dots;

the carbon quantum dots are separated in an elution mode, the obtained carbon quantum dots are high in purity, and meanwhile, the carbon quantum dots are higher in luminous efficiency, narrower in half-peak width and wider in application range.

Preferably, the chromatographic column is filled with silica gel;

preferably, the mesh number of the silica gel is 200-400 meshes, and the mesh number of the silica gel is gradually reduced from bottom to top.

In another embodiment of the present application, the elution solution comprises a good solvent for the carbon quantum dots and a poor solvent; the good solvent is used for dissolving the carbon quantum dots adsorbed on the silica gel and carrying out the carbon quantum dots out of the chromatographic column, the poor solvent is used for dissolving substances except the quantum dots and carrying out the substances out of the chromatographic column, and pure carbon quantum dot solutions are separated according to different elution times.

Preferably, the good solvent comprises at least one of n-heptane, n-hexane, dichloromethane, chloroform, petroleum ether and toluene.

Preferably, the poor solvent includes at least one of ethanol, methanol, propanol, acetone, dimethyl sulfoxide, ethyl acetate, and N, N-dimethylformamide

Preferably, the volume ratio of the poor solvent to the good solvent is 1/20-1/2.

In the present application, to further increase the water solubility or oil solubility of the carbon quantum dots, a molecule which has a hydrophilic segment or a hydrophobic segment and can participate in the reaction can be added into a precursor. For example, when the precursor contains polyethylene glycol, the prepared carbon quantum dots have very good dispersibility in water; when the precursor contains C8-C18 carboxylic acid, the prepared carbon quantum dots have very good dispersibility in oil. According to the application environment of the carbon quantum dots, polyethylene glycol or C8-C18 carboxylic acid can be added into a precursor, so that the water-soluble or oil-soluble carbon quantum dots are prepared without subsequent surface modification. The polyethylene glycol can be polyethylene glycol with various molecular weights such as polyethylene glycol 400, polyethylene glycol 600, polyethylene glycol 800 and the like, and the carboxylic acid of C8-C18 can be oleic acid, stearic acid, palmitic acid and the like.

In addition, the preparation method in the application is very suitable for preparing the carbon quantum dots emitting red light or even near infrared light, for example, the emission peak of the prepared carbon quantum dots is 656 nm-800 nm, specifically but not limited to 660nm, 670nm, 680nm, 690nm, 700nm, 720nm, 740nm, 750nm, 850nm and the like, wherein the optimal emission peak is about 672nm and 731 nm; the half-peak width of the carbon quantum dot is not more than 19nm, the half-peak width is 18nm and 19nm for example, the color purity of light emitted by the carbon quantum dot with narrow half-peak width is higher, and the carbon quantum dot has great application value in the fields of biological imaging, tracing, photoelectric display and the like.

A method of preparing a carbon quantum dot according to some exemplary embodiments of the present application will be described in detail below with reference to various examples; however, the exemplary embodiments of the present application are not limited thereto.

Example 1

Microwave treatment: taking 5g of dry maple leaves, crushing the dry maple leaves, placing the crushed maple leaves in a beaker, adding 50ml of ethanol, mixing and stirring the maple leaves uniformly, and then placing the beaker in a microwave oven with the power set to be 800W for 5 min. After the reaction was completed, the supernatant was taken out, centrifuged at 9000rpm for 5min to remove the precipitate, and the supernatant was retained after two times of centrifugation. The supernatant was then filtered through a 0.22 μ filter head. The resulting solution was placed in a flask and rotary evaporated. Finally, the volume of the carbon quantum dot solution was concentrated to 5mL for further purification.

And (3) purification treatment: about 200g of silica gel is added into n-heptane, the mixture is loaded into a packing column, 5mL of carbon quantum dot solution is added after the silica gel is filled, gradient elution is carried out by using a mixed solution (volume ratio is 1/20) of poor solvent and good solvent (such as ethanol and n-heptane) as eluent, purification is carried out step by step, the carbon quantum dots after purification are dispersed in the n-heptane, an emission spectrum of the carbon quantum dots is tested by an F4500 spectrometer and is shown in figure 1, an absorption spectrum is shown in figure 2, the yield is 80%, the half-peak width is 18nm, and the luminous efficiency is 51.8%.

Example 2

Ultrasonic treatment: taking 5g of dry ginkgo leaves, crushing the ginkgo leaves, placing the crushed ginkgo leaves in a beaker, adding 250mL of acetone, mixing and stirring the ginkgo leaves uniformly, and then placing the ginkgo leaves in an ultrasonic machine (the ultrasonic frequency is 50KHz) for 30 min. After the reaction is finished, taking out the supernatant, centrifuging for 10min at the rotating speed of 11000rpm, removing the substrate precipitate, and reserving the supernatant after centrifuging twice. Then, the supernatant was filtered through a 0.22-precipitate filter head, and the resulting solution was placed in a flask and rotary-distilled. Finally, the volume of the carbon quantum dot solution was concentrated to 2mL for further purification.

And (3) purification treatment: adding about 150g of silica gel into n-heptane, loading into a packing column, adding 2mL of carbon quantum dot solution after silica gel is completely filled, and performing gradient elution by using a mixed solution (with a volume ratio of 1/15) of a poor solvent and a good solvent (such as acetone and n-hexane) as an eluent, wherein the carbon quantum dots after the step-by-step purification are dispersed in the n-heptane, and a transmission electron microscope image of the carbon quantum dots is shown in FIG. 4, wherein the carbon quantum dots are granular, have uniform size distribution and have an average particle size of about 5 nm; the emission spectrum and the absorption spectrum of the carbon quantum dot tested by the F4500 spectrometer are shown in the figure 5 and the figure 6 respectively; comparing the fluorescence emission spectra of the carbon quantum dots before and after purification as shown in fig. 7, it can be seen that the half-peak width of the carbon quantum dots is significantly reduced from 29nm to 18nm after purification, the purification treatment of the present application significantly improves the luminescence performance of the carbon quantum dots, the yield is 75%, the half-peak width is 19nm, and the luminescence efficiency is 32%.

Example 3

And (3) jointly processing by ultrasonic waves and microwaves: taking 5g of dried rhizome of Metasequoia glyptostroboides, crushing the rhizome, placing the crushed rhizome into a beaker, adding 100mL of dimethyl sulfoxide, mixing and stirring the mixture evenly, then placing the mixture into an ultrasonic machine (the ultrasonic frequency is 40KHz), carrying out ultrasonic treatment for 10min, and then placing the mixture into a microwave oven (850W) for 4 min. After the reaction, the supernatant was taken out, centrifuged at 10000rpm for 7min to remove the precipitate, and the supernatant was retained after two times of centrifugation. The supernatant was then filtered through a 0.22-starch filter head. The resulting solution was placed in a flask and rotary evaporated. Finally, the volume of the carbon quantum dot solution was concentrated to 3mL for further purification.

And (3) purification treatment: about 180g of silica gel is added into n-heptane, the mixture is loaded into a packing column, 3mL of carbon quantum dot solution is added after the silica gel is filled, gradient elution is carried out by using a mixed solution (volume ratio is 1/10) of poor solvent and good solvent (such as dimethyl sulfoxide and n-heptane) as eluent, purification is carried out step by step, the carbon quantum dots after purification are dispersed in the n-heptane, an emission spectrum and an absorption spectrum of the carbon quantum dots are tested by an F4500 spectrometer, as shown in FIG. 8, the yield of the carbon quantum dots is 80%, the half-peak width is 18nm, and the luminous efficiency is 55%.

Example 4

And (3) jointly processing by ultrasonic waves and microwaves: taking 5g of fresh epipremnum aureum leaves, crushing the epipremnum aureum leaves, placing the crushed epipremnum aureum leaves into a beaker, adding 200mL of methanol, mixing and stirring the mixture evenly, placing the mixture into a microwave oven (900W) for 3min, and then placing the mixture into an ultrasonic machine (the ultrasonic frequency is 25KHz), wherein the ultrasonic time is 10 min. After the reaction, the supernatant was taken out, centrifuged at 10000rpm for 10min to remove the precipitate, and the supernatant was retained after two times of centrifugation. The supernatant was then filtered through a 0.22 μ filter head. The resulting solution was placed in a flask and rotary evaporated. Finally, the volume of the carbon quantum dot solution was concentrated to 4mL for further purification.

And (3) purification treatment: about 160g of silica gel is added into n-heptane, the mixture is loaded into a packing column, 4mL of carbon quantum dot solution is added after the silica gel is completely filled, gradient elution is carried out by using a mixed solution (volume ratio is 1/10) of poor solvent and good solvent (such as dimethyl sulfoxide and n-heptane) as eluent, purification is carried out step by step, the carbon quantum dots after purification are dispersed in the n-heptane, and an emission spectrum and an absorption spectrum of the carbon quantum dots are tested by an F4500 spectrometer, as shown in FIG. 9, the yield of the carbon quantum dots is 80%, the half-peak width is 18nm, and the luminous efficiency is 52%.

Example 5

Ultrasonic wave and microwave simultaneous treatment: taking 5g of fresh chlorophytum comosum leaves, crushing the leaves, putting the crushed leaves into a glass guide tube, adding 300mL of ethyl acetate, mixing and stirring the leaves uniformly, then placing the leaves into an ultrasonic microwave chemical reactor, controlling relevant parameters of the reactor, setting the frequency of ultrasonic waves to be 30KHz, setting the power of microwaves to be 850W, and setting the reaction time to be 15 min. After the reaction was completed, the supernatant was taken out, centrifuged at 11000rpm for 6min to remove the precipitate, the precipitate was removed, and the supernatant was retained after two times of centrifugation. The supernatant was then filtered through a 0.22 μm filter head. The resulting solution was placed in a flask and rotary evaporated. Finally, the volume of the carbon quantum dot solution was concentrated to 2mL for further purification.

And (3) purification treatment: about 260g of silica gel is added into n-heptane, the mixture is loaded into a packing column, 2mL of carbon quantum dot solution is added after the silica gel is completely filled, gradient elution is carried out by using a mixed solution (volume ratio is 1/18) of poor solvent and good solvent (such as dimethyl sulfoxide and n-heptane) as eluent, purification is carried out step by step, the carbon quantum dots after purification are dispersed in the n-heptane, and an emission spectrum and an absorption spectrum of the carbon quantum dots are tested by an F4500 spectrometer, as shown in FIG. 10, the yield of the carbon quantum dots is 95%, the half-peak width is 18nm, and the luminous efficiency is 58%.

This application is through ultrasonic treatment and/or microwave treatment's near-infrared carbon quantum dot, after centrifugation and filtration process again, purify it with poor solvent and good solvent, the best emission peak position of the carbon quantum dot who obtains is 672nm, the narrowest half peak width is 18nm, the highest efficiency is 58%, compare in prior art's carbon quantum dot preparation method, the carbon quantum dot preparation technology and equipment of this application are simple, the process is easily controlled, good reproducibility, be suitable for the industrial production.

Although the present disclosure has been described and illustrated in greater detail by the inventors, it should be understood that modifications and/or alterations to the above-described embodiments, or equivalent substitutions, will be apparent to those skilled in the art without departing from the spirit of the disclosure, and that no limitations to the present disclosure are intended or should be inferred therefrom.

Claims (10)

1. A method for preparing a carbon quantum dot is characterized by comprising the following steps:

s1, mixing the precursor with an organic solvent to prepare precursor dispersion liquid;

s2, performing ultrasonic treatment and/or microwave treatment on the precursor dispersion liquid at normal pressure to obtain a carbon quantum dot stock solution;

s3, purifying the carbon quantum dot stock solution to obtain carbon quantum dots;

wherein the precursor comprises a plant.

2. The method according to claim 1, wherein the precursor comprises at least one of a plant leaf, a plant rhizome, a plant branch, a plant fruit, and a flower;

preferably, the precursor comprises at least one of maple leaves, maple roots and rhizomes, Chinese yew leaves, Chinese yew roots and rhizomes, ginkgo leaves, ginkgo biloba roots and rhizomes, epipremnum aureum leaves, epipremnum aureum roots and rhizomes, chlorophytum comosum leaves and chlorophytum comosum roots.

3. The preparation method according to claim 1, wherein the mass-to-volume ratio of the precursor to the organic solvent in step S1 is 5g (20-500) mL, preferably 5g (100-400) mL;

preferably, the organic solvent includes at least one of ethanol, methanol, acetone, N-heptane, N-hexane, dimethyl sulfoxide, and N, N-dimethylformamide.

4. The method according to claim 1, wherein when the precursor solution is subjected to the ultrasonic treatment, the frequency of the ultrasonic treatment is 25 to 130KHz, preferably 40 to 100 KHz.

5. The method according to claim 4, wherein the ultrasonic treatment is performed for 5 to 60min, preferably 10 to 30 min.

6. The method according to claim 1, wherein the power of the microwave treatment is 700-1000W, preferably 800-900W, when the precursor solution is subjected to the microwave treatment.

7. The method according to claim 6, wherein the microwave treatment time is 1-60 min, preferably 1-10 min.

8. The method of claim 1, wherein S3 includes the steps of:

s31, adding the carbon quantum dot solution into a chromatographic column filled with silica gel;

s32, purifying the carbon quantum dot solution by using an eluent to separate carbon quantum dots;

preferably, the mesh number of the silica gel is 200-400 meshes, and the mesh number of the silica gel is gradually reduced from bottom to top.

9. The method according to claim 8, wherein the eluting solution includes a good solvent and a poor solvent for the carbon quantum dots;

preferably, the good solvent comprises at least one of n-heptane, n-hexane, dichloromethane, chloroform, petroleum ether and toluene;

preferably, the poor solvent includes at least one of ethanol, methanol, propanol, acetone, dimethyl sulfoxide, ethyl acetate, N-dimethylformamide;

preferably, the volume ratio of the poor solvent to the good solvent is 1/20-1/2.

10. A carbon quantum dot prepared by the method according to any one of claims 1 to 9;

preferably, the emission peak of the carbon quantum dot is located between 656nm and 800nm, and the half-peak width is not more than 19 nm.

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