CN111500285B - Method for synthesizing fluorescent carbon quantum dots by using citric acid and sodium ethylene diamine tetramethylene phosphate - Google Patents
Method for synthesizing fluorescent carbon quantum dots by using citric acid and sodium ethylene diamine tetramethylene phosphate Download PDFInfo
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Abstract
The invention relates to a method for synthesizing fluorescent carbon quantum dots by using citric acid and ethylenediamine tetramethylene sodium phosphate. The method comprises the following steps: citric acid and ethylene diamine tetramethylene sodium phosphate are mixed according to the mass ratio of 1-10: 1 is dissolved in water to obtain a solution with the mass concentration of 4-6%, then the hydrothermal reaction is carried out, and the carbon quantum dot solution is obtained by filtering. The carbon quantum dot aqueous solution prepared by the method is green fluorescence under ultraviolet light, and an emission peak with larger fluorescence intensity is 425-427nm under the excitation wavelength of 330-335 nm. The carbon quantum dot synthesis method provided by the invention is simple and pollution-free, has low raw material cost, and can realize large-scale mass production.
Description
Technical Field
The invention relates to the technical field of nano materials, in particular to a method for synthesizing fluorescent carbon quantum dots by using citric acid and ethylene diamine tetramethylene sodium phosphate.
Background
Carbon quantum dots, also called carbon dots, are a nanomaterial with excellent properties; meanwhile, carbon is also an important basic element constituting life on earth. Therefore, compared with other element nanomaterials, carbon nanomaterials have good dispersibility in water and special optical characteristics, and have attracted much attention in the fields of biomarkers, environmental detection and the like.
The fluorescence probe method has the advantages of wide linear dynamic range, less spectral interference, high sensitivity and multiple elementsThe detection function is strong; meanwhile, the sample is simple to prepare, and complex treatment is not needed, so that the method becomes an analysis method widely applied at present. At present, the preparation of carbon quantum dots has been developed more mature, but faces the difficulties of high raw material price, low fluorescence yield of synthesized carbon quantum dots and the like. Related literature reports that after citric acid, urea and L-cysteine are mixed according to a proper proportion, carbon quantum dots doped with nitrogen and sulfur are synthesized in one step by a microwave method, and the fluorescence quantum yield is 25%; see Wan X, li S, zhuang L, et al. Journal of Nanoparticle Research,2016,18 (7): 202. In addition, it is reported that the mass ratio m is used Citric acid ：m Urea The reaction conditions are that the raw material is =1 and ethanol is a solvent, and the fluorescence quantum yield of the fluorescent carbon quantum dots prepared by the microwave method is 36%; see Songnan Qu, xingyuan Liu, xiaoyang Guo, minghui Chu, ligong Zhang, D ezhen Shen.Adv.Funct.Mater.,2014,24 (18): 2689-2695.). The fluorescent carbon quantum dots prepared by the microwave method by taking citric acid and urea as raw materials reported in the literature at present have low fluorescence quantum yield and unsatisfactory stability, and the application range of the fluorescent carbon quantum dots is limited. Therefore, there is an urgent need to develop a synthetic method that can produce high fluorescence quantum yield.
Chinese patent document CN111100637A discloses a green fluorescent carbon quantum dot with high fluorescent quantum yield and a preparation method thereof, and the carbon quantum dot is prepared by taking m-phenylenediamine as a carbon source and a nitrogen source and L-cysteine as a nitrogen source and a sulfur source through hydrothermal reaction. The carbon quantum dot has good water solubility, emits green fluorescence under the irradiation of exciting light of 340-460 nm, and can be used as a cell imaging agent for cell imaging. Chinese patent document CN110562957A provides a green fluorescent carbon quantum dot and a preparation method thereof, wherein 2, 7-dihydroxy naphthalene is used as a carbon source, hydrogen peroxide is used as an oxidant, ethylenediamine is used as a nitrogen dopant, and absolute ethyl alcohol is used as a solvent, and the green fluorescent carbon quantum dot is prepared by a solvothermal method. The prepared green fluorescent carbon quantum dots can be used as fluorescent powder to be applied to preparation of warm white LEDs suitable for indoor illumination. However, the method uses an ethanol solvent, and has potential safety hazard in the reaction at 180 ℃.
Disclosure of Invention
In order to solve the technical problems of the existing carbon quantum dots, the invention provides a method for synthesizing fluorescent carbon quantum dots by using citric acid and ethylene diamine tetramethylene sodium phosphate. The fluorescent carbon quantum dot prepared by the invention has good stability and water solubility, has the characteristic of exciting independent fluorescence, has higher fluorescence intensity under the excitation wavelength of 330-335nm, and has the corresponding emission wavelength of 425-427nm.
The invention also provides application of the synthesized fluorescent carbon quantum dots.
The technical scheme of the invention is as follows:
a method for preparing a carbon quantum dot, comprising:
citric acid and ethylene diamine tetramethylene sodium phosphate are mixed according to the mass ratio of 1-10: 1 is dissolved in water to obtain a solution with the mass concentration of 4-6%; and carrying out hydrothermal reaction on the obtained solution at the temperature of 130-210 ℃ for 3-15 h, cooling to room temperature, and filtering to obtain the carbon quantum dot solution.
According to the invention, the mass ratio of the citric acid to the sodium ethylene diamine tetramethylidene phosphate is 1-4, and further preferably 1-2, wherein the optimal reaction mass ratio is 1.
According to the invention, the mass concentration of the reaction solution of the citric acid and the ethylene diamine tetraacetic acid sodium salt is preferably 5%.
According to the invention, the hydrothermal reaction temperature is preferably 180 to 190 ℃.
According to the invention, the reaction time is preferably 6 to 11 hours, more preferably 8 to 10 hours, and most preferably 9 hours.
According to the invention, the filtration is preferably carried out using a 0.05 to 0.22 μm membrane filter.
Preferably, according to the present invention, the water is deionized water or ultrapure water.
A preferred embodiment according to the invention is as follows:
dissolving citric acid and ethylene diamine tetraacetic acid sodium methylene phosphate into ultrapure water according to a mass ratio of 1-2, and uniformly mixing and stirring to obtain a mixed solution with a mass concentration of 5%; and moving the mixture into a stainless steel reaction kettle with a polytetrafluoroethylene lining. And (3) placing the reaction kettle in an oven at 180-190 ℃, reacting for 6-9 h, naturally cooling to room temperature, and filtering by using a filter membrane to obtain a pure carbon quantum dot solution.
The carbon quantum dot aqueous solution prepared by the invention is green under the irradiation of ultraviolet light; can be used for detecting the hypochlorous acid in the circulating water by using a fluorescent probe or cell imaging.
The emission peak of the carbon quantum dot obtained by the invention with larger fluorescence intensity is 425-427nm under the excitation wavelength of 330-335 nm; the optimal excitation/emission wavelength is 331nm/426nm.
The invention has the technical characteristics and beneficial effects that:
the carbon quantum dot aqueous solution synthesized by the method is green under ultraviolet light, obtains stronger fluorescence under the excitation wavelength of 330-335nm, has high sensitivity and good stability, is less interfered by other ions, and can be used for a hypochlorous acid detection fluorescent probe in water and cell imaging.
The method for synthesizing the fluorescent carbon quantum dots by using citric acid as a carbon source and using the sodium ethylene diamine tetramethylene phosphate as a nitrogen source under the hydrothermal reaction condition has the advantages of low raw material price and safe reaction by adopting a water solvent; the synthetic method of the invention is simple, has low toxicity and can not cause secondary pollution to the environment.
The carbon quantum dot synthesized by the method has stable fluorescence performance and is beneficial to expanding the application field of the carbon quantum dot.
Drawings
FIG. 1 is a graph of an ultraviolet absorption spectrum of a synthetic carbon quantum dot of example 1;
FIG. 2 is a graph of fluorescence spectra of different concentrations of the synthetic carbon quantum dots of example 1;
FIG. 3 is a graph of the fluorescence intensity spectra of carbon quantum dots synthesized by mass ratios of different raw materials in examples 1 to 6;
FIG. 4 is a graph of the fluorescence intensity of the synthesized carbon quantum dots versus different reaction temperatures for examples 7-10;
FIG. 5 is a fluorescence intensity spectrum of carbon quantum dots synthesized in example 11 at a mass ratio of 1 under different reaction times;
FIG. 6 is a graph showing the results of chlorine resistance measurement of the carbon quantum dots synthesized in example 1, with the abscissa representing the residual chlorine concentration and the ordinate representing the fluorescence intensity of the carbon quantum dots.
Fig. 7 is a graph showing the stability test results of the carbon quantum dots synthesized in example 1. The abscissa is the different ions and the ordinate is the relative fluorescence intensity.
Detailed Description
In order to further explain the meaning of the present invention, the following examples are given for the purpose of illustration of the present invention, but the present invention is not limited thereto. The filtration membrane used in the examples was a commercially available filtration membrane of 0.20 to 0.22. Mu.m. The citric acid used in the examples was citric acid monohydrate, sodium ethylene diamine tetra methylene phosphate used was purchased from Shandongtai and Water treatment technologies, inc., with a sodium ethylene diamine tetra methylene phosphate content of 25wt%; in the embodiment, the mass ratio of the citric acid to the sodium ethylene diamine tetra-methylene phosphate is calculated by converting the used raw materials into pure products of the citric acid and the sodium ethylene diamine tetra-methylene phosphate.
In the examples, "%" is a mass percentage unless otherwise specified.
The detection conditions of the fluorescence emission spectra in the examples are: the detection mode is set as emission spectrum, the excitation wavelength is 331nm, the slit width is 10nm multiplied by 10nm, and the wavelength scanning range is 200-600nm.
Example 1, preparation of fluorescent carbon quantum dots, the steps were as follows:
(a) Dissolving 1.367g of citric acid and 5g of sodium ethylene diamine tetramethylenephosphate into ultrapure water according to the mass ratio of the citric acid to the sodium ethylene diamine tetramethylenephosphate of 1;
(b) And (3) placing the hydrothermal reaction kettle in a 180 ℃ oven, reacting for 9h, naturally cooling to room temperature, and filtering by using a filter membrane to obtain a relatively pure carbon quantum dot solution.
Taking 2.0g of the carbon quantum dot solution prepared in the step, transferring the carbon quantum dot solution into a 100mL volumetric flask, and preparing 100mL of 1g/L solution; for the following tests:
measuring 5.0mL of 1g/L solution by using a pipette, transferring the solution into a 50mL colorimetric tube, performing constant volume to obtain 100ppm of carbon quantum dot dilute solution, and measuring the ultraviolet absorption spectrum of the carbon quantum dot dilute solution under the wavelength of 200-600nm to obtain the maximum absorption wavelength lambda =331; the fluorescence intensity was measured using the maximum absorption wavelength as the excitation wavelength, as shown in FIG. 1.
The prepared 1g/L solution was taken out, 2.0mL and 4.0mL, transferred into a 50mL volumetric flask, and diluted solutions of 40ppm and 80ppm carbon quantum dots were obtained, respectively, in constant volume, and the fluorescence intensity of the emission peak at EM =426nm was F =1103, respectively, at the optimum excitation wavelength EX =331nm, and 2092 is shown in fig. 2. As can be seen from FIG. 2, the fluorescence intensity of the carbon quantum dots synthesized by the method increases with the increase of the concentration.
Example 2, preparation of fluorescent carbon quantum dots, the steps were as follows:
(a) According to a mass ratio of citric acid to sodium ethylene diamine tetramethylene phosphate of 2. Stirring uniformly, and transferring into a stainless steel reaction kettle with a 100mL polytetrafluoroethylene lining;
(b) And (3) placing the hydrothermal reaction kettle in a 180 ℃ oven, reacting for 9h, naturally cooling to room temperature, and filtering by using a 0.22um filter membrane to obtain a relatively pure carbon quantum dot solution.
2.0g of the carbon quantum dot prepared in the above step was taken and transferred to a 100mL volumetric flask to prepare 100mL of a 1g/L solution.
Measuring 4.0mL of 1g/L solution by using a pipette, transferring the solution into a 50mL colorimetric tube, carrying out constant volume to obtain 80ppm carbon quantum dot diluted solution, and testing the fluorescence intensity of the diluted solution. At the optimal excitation wavelength EX =331nm, the emission peak has a fluorescence intensity F =1875 at EM =426nm, as shown in fig. 3.
Example 3 preparation of fluorescent carbon quantum dots, the steps were as follows:
(a) Dissolving 2.051g of citric acid and 2.5g of ethylene diamine tetramethylene sodium phosphate in ultrapure water according to the mass ratio of the citric acid to the ethylene diamine tetramethylene sodium phosphate of 3;
(b) And (3) placing the hydrothermal reaction kettle in a drying oven at 180 ℃, reacting for 9 hours, naturally cooling to room temperature, and filtering with a filtering membrane to obtain a relatively pure carbon quantum dot solution.
2.0g of the carbon quantum dot prepared in the above step was taken and transferred to a 100mL volumetric flask to prepare 100mL of a 1g/L solution.
Measuring 4.0mL of 1g/L solution by using a pipette, transferring the solution into a 50mL colorimetric tube, carrying out constant volume to obtain 80ppm carbon quantum dot diluted solution, and testing the fluorescence intensity of the diluted solution. At the optimal excitation wavelength EX =331nm, the emission peak has fluorescence intensity F =1638 at EM =426nm, as shown in fig. 3.
Example 4, preparation of fluorescent carbon quantum dots, the steps were as follows:
(a) Dissolving 2.187g of citric acid and 2.0g of ethylene diamine tetramethylene sodium phosphate in ultrapure water according to a mass ratio of 4;
(b) And (3) placing the hydrothermal reaction kettle in a 180 ℃ oven, reacting for 9h, naturally cooling to room temperature, and filtering by using a filter membrane to obtain a relatively pure carbon quantum dot solution.
2.0g of the carbon quantum dot prepared in the above step was taken and transferred to a 100mL volumetric flask to prepare 100mL of a 1g/L solution.
Measuring 4.0mL of 1g/L solution by using a pipette, transferring the solution into a 50mL colorimetric tube, carrying out constant volume to obtain 80ppm of carbon quantum dot dilute solution, and testing the fluorescence intensity of the solution. At an optimal excitation wavelength EX =331nm, the emission peak has a fluorescence intensity F =1496 at EM =426nm, as shown in fig. 3.
Example 5, preparation of fluorescent carbon quantum dots, the steps were as follows:
(a) Dissolving 2.279g of citric acid and 1.668g of sodium ethylene diamine tetra-methylene phosphate into ultrapure water according to the mass ratio of the citric acid to the sodium ethylene diamine tetra-methylene phosphate of 5;
(b) And (3) placing the hydrothermal reaction kettle in a 180 ℃ oven, reacting for 9h, naturally cooling to room temperature, and filtering by using a filter membrane to obtain a relatively pure carbon quantum dot solution.
2.0g of the carbon quantum dot prepared in the above step was taken and transferred to a 100mL volumetric flask to prepare 100mL of a 1g/L solution.
Measuring 4.0mL of 1g/L solution by using a pipette, transferring the solution into a 50mL colorimetric tube, carrying out constant volume to obtain 80ppm carbon quantum dot diluted solution, and testing the fluorescence intensity of the diluted solution. At the optimal excitation wavelength EX =331nm, the emission peak has fluorescence intensity F =998 at EM =426nm, as shown in fig. 3.
Example 6 preparation of fluorescent carbon quantum dots, the steps were as follows:
(a) 2.486g of citric acid and 0.909g of sodium ethylenediamine tetramethylene phosphate were dissolved in 46.605g of ultrapure water in a mass ratio of citric acid to sodium ethylenediamine tetramethylene phosphate of 10. Stirring uniformly, and transferring into a stainless steel reaction kettle with a 100mL polytetrafluoroethylene lining;
(b) And (3) placing the hydrothermal reaction kettle in a 180 ℃ oven, reacting for 9h, naturally cooling to room temperature, and filtering by using a filter membrane to obtain a relatively pure carbon quantum dot solution.
2.0g of the carbon quantum dot prepared in the above step was taken and transferred to a 100mL volumetric flask to prepare 100mL of a 1g/L solution.
Measuring 4.0mL of 1g/L solution by using a pipette, transferring the solution into a 50mL colorimetric tube, carrying out constant volume to obtain 80ppm carbon quantum dot diluted solution, and testing the fluorescence intensity of the diluted solution. At the optimal excitation wavelength EX =331nm, the emission peak has fluorescence intensity F =500 at EM =426nm, as shown in fig. 3.
Example 7 preparation of fluorescent carbon quantum dots, the procedure was as follows:
(a) Dissolving 1.367g of citric acid and 5g of sodium ethylene diamine tetra-methylene phosphate in ultrapure water according to the mass ratio of the citric acid to the sodium ethylene diamine tetra-methylene phosphate of 1. After being stirred evenly, the mixture is moved into a stainless steel reaction kettle with a 100mL polytetrafluoroethylene lining;
(b) And (3) respectively placing the hydrothermal reaction kettle in an oven with the temperature of 130 ℃, 160 ℃, 180 ℃ and 210 ℃, reacting for 9 hours, naturally cooling to room temperature, and filtering by using a filtering membrane to obtain a relatively pure carbon quantum dot solution.
2.0g of the carbon quantum dot prepared in the above step was taken and transferred to a 100mL volumetric flask to prepare 100mL of a 1g/L solution.
Measuring 4.0mL of 1g/L solution by using a pipette, transferring the solution into a 50mL colorimetric tube, carrying out constant volume to obtain 80ppm carbon quantum dot diluted solution, and testing the fluorescence intensity of the diluted solution. At the optimal excitation wavelength EX =331nm, the fluorescence intensity of the emission peak at EM =426nm is F =1003, 1650, 2092, 1873, respectively, as shown in fig. 4.
Example 8, preparation of fluorescent carbon quantum dots, the steps were as follows:
(a) According to a mass ratio of citric acid to sodium ethylene diamine tetramethylene phosphate of 2. After being stirred evenly, the mixture is moved into a stainless steel reaction kettle with a 100mL polytetrafluoroethylene lining;
(b) And (3) respectively placing the hydrothermal reaction kettle in an oven with the temperature of 130 ℃, 160 ℃, 180 ℃ and 210 ℃, reacting for 9 hours, naturally cooling to room temperature, and filtering by using a filtering membrane to obtain a relatively pure carbon quantum dot solution.
2.0g of the carbon quantum dot prepared in the above step was taken and transferred to a 100mL volumetric flask to prepare 100mL of a 1g/L solution.
Measuring 4.0mL of 1g/L solution by using a pipette, transferring the solution into a 50mL colorimetric tube, carrying out constant volume to obtain 80ppm carbon quantum dot diluted solution, and testing the fluorescence intensity of the diluted solution. At the optimal excitation wavelength EX =331nm, the emission peak has fluorescence intensities F =876, 1540, 1900, 1630 at EM =426nm, respectively, as shown in fig. 4.
Example 9 preparation of fluorescent carbon quantum dots, the procedure was as follows:
(a) Dissolving 2.051g of citric acid and 2.50g of sodium ethylene diamine tetracarboxylate into ultrapure water according to the mass ratio of the citric acid to the sodium ethylene diamine tetracarboxylate of 3;
(b) And (3) placing the hydrothermal reaction kettle in a baking oven with the temperature of 130 ℃, 160 ℃, 180 ℃ and 210 ℃ respectively, reacting for 9 hours, naturally cooling to room temperature, and filtering by using a filter membrane to obtain a relatively pure carbon quantum dot solution.
2.0g of the carbon quantum dot prepared in the above step was taken and transferred to a 100mL volumetric flask to prepare 100mL of a 1g/L solution.
Measuring 4.0mL of 1g/L solution by using a pipette, transferring the solution into a 50mL colorimetric tube, carrying out constant volume to obtain 80ppm carbon quantum dot diluted solution, and testing the fluorescence intensity of the diluted solution. At the optimal excitation wavelength EX =331nm, the fluorescence intensity of the emission peak at EM =426nm is F =657, 1320, 1530, 1425, respectively, as shown in fig. 4.
Example 10, preparation of fluorescent carbon quantum dots, the steps were as follows:
(a) According to a mass ratio of citric acid to sodium ethylene diamine tetramethylene phosphate of 4. Stirring uniformly, and transferring into a stainless steel reaction kettle with a 100mL polytetrafluoroethylene lining;
(b) And (3) placing the hydrothermal reaction kettle in a baking oven with the temperature of 130 ℃, 160 ℃, 180 ℃ and 210 ℃ respectively, reacting for 9 hours, naturally cooling to room temperature, and filtering by using a filter membrane to obtain a relatively pure carbon quantum dot solution.
2.0g of the carbon quantum dot prepared in the above step was taken and transferred to a 100mL volumetric flask to prepare 100mL of a 1g/L solution.
Measuring 4.0mL of 1g/L solution by using a pipette, transferring the solution into a 50mL colorimetric tube, carrying out constant volume to obtain 80ppm of carbon quantum dot dilute solution, and testing the fluorescence intensity of the solution. At the optimal excitation wavelength EX =331nm, the fluorescence intensity of the emission peak at EM =426nm is F =498, 1000, 1420, 1321, respectively, as shown in fig. 4.
Example 11, preparation of fluorescent carbon quantum dots, the procedure was as follows:
(a) 1, dissolving 1.367g of citric acid and 5g of sodium ethylene diamine tetramethylenephosphate in 43.63g of ultrapure water according to the mass ratio of the citric acid to the sodium ethylene diamine tetramethylenephosphate of 1. After being stirred evenly, the mixture is moved into a stainless steel reaction kettle with a 100mL polytetrafluoroethylene lining;
(b) And (3) placing the hydrothermal reaction kettle in an oven at 180 ℃, reacting for 3h, 6h, 9h, 12h and 15h respectively, naturally cooling to room temperature, and filtering with a filtering membrane to obtain a relatively pure carbon quantum dot solution.
2.0g of the carbon quantum dots prepared in the step (b) with different reaction times are respectively taken and transferred into a 100mL volumetric flask to prepare 100mL of 1g/L solution.
Measuring 4.0mL of 1g/L solution by using a pipette, transferring the solution into a 50mL colorimetric tube, carrying out constant volume to obtain 80ppm carbon quantum dot diluted solution, and testing the fluorescence intensity of the diluted solution. At the optimal excitation wavelength EX =331nm, the fluorescence intensities of the emission peaks at EM =426nm were F =1005, 1654, 2092, 2010, 2027, respectively, as shown in fig. 5.
Experimental example: detection experiment of chlorine resistance and complex organic matter of carbon quantum dots
(a) 2.0g of the carbon quantum dot solution prepared in example 1 was taken out and transferred to a 100mL volumetric flask to prepare 100mL of a 1g/L solution.
(b) And (b) transferring 100mL of the 1g/L solution prepared in the step (a) to a 1L volumetric flask, and performing constant volume to obtain a 100ppm carbon quantum dot dilute solution.
(c) Fixing the prepared solution in the step (b) to 5 colorimetric tubes of 50mL, and respectively adding (0-0.4 mL of NaClO + NaBr (calculated by chloride ions) into the solution;
(d) The prepared solution in step (b) was metered into 5 colorimetric tubes of 50mL, and NaClO + NaBr +20ppm of H-2000 was added to the solution (0-0.4 mL) to measure the fluorescence intensity at 700V, as shown in FIG. 6.
The bactericide NaClO + NaBr has stronger fluorescence quenching performance on the synthesized carbon quantum dots, and the scale and corrosion inhibitor TH-2000 has little influence on the fluorescence thereof. As can be seen from FIG. 7, the synthesized carbon quantum dots have strong anti-interference ability to other factors and strong fluorescence stability. The synthesized carbon quantum dots only respond to the bactericide and can be used as a fluorescent probe for detecting hypochlorous acid.
The above-mentioned embodiments are merely preferred embodiments for fully illustrating the present invention, and the scope of protection is not limited thereto. The equivalent substitutions or changes of the present invention by those skilled in the art are all within the protection scope of the present invention, and the protection scope of the present invention is subject to the claims.
Claims (11)
1. A preparation method of a carbon quantum dot comprises the following steps:
mixing citric acid and ethylene diamine tetramethylene sodium phosphate according to a mass ratio of 1 to 10:1, dissolving in water to obtain a solution with the mass concentration of 4-6%; and carrying out hydrothermal reaction on the obtained solution at the temperature of 130-210 ℃ for 3-15 h, cooling to room temperature, and filtering to obtain the carbon quantum dot solution.
2. The method for preparing the carbon quantum dot according to claim 1, wherein the mass ratio of the citric acid to the sodium ethylene diamine tetramethylene phosphate is 1 to 4.
3. The method for preparing the carbon quantum dot according to claim 1, wherein the mass ratio of the citric acid to the sodium ethylene diamine tetramethylene phosphate is 1 to 2.
4. The method for preparing the carbon quantum dot according to claim 1, wherein the mass concentration of the reaction solution of citric acid and sodium ethylene diamine-tetra-methylene-phosphate is 5%.
5. The method for preparing a carbon quantum dot according to claim 1, wherein the hydrothermal reaction temperature is 180 to 190 ℃.
6. The method for producing a carbon quantum dot according to claim 1, wherein the reaction time is 6 to 11 hours.
7. The method for producing a carbon quantum dot according to claim 1, wherein the reaction time is 8 to 10 hours.
8. The method for producing a carbon quantum dot according to claim 1, wherein the filtration is performed with a filtration membrane of 0.05 to 0.22 μm.
9. The method for preparing the carbon quantum dot according to claim 1, wherein the prepared carbon quantum dot aqueous solution is green under ultraviolet irradiation; the emission peak with larger fluorescence intensity is 425-427nm at the excitation wavelength of 330-335 nm.
10. The method for producing the carbon quantum dot according to claim 1, characterized by comprising the steps of:
dissolving citric acid and ethylene diamine tetramethylene sodium phosphate in ultrapure water according to the mass ratio of 1-2, and uniformly mixing and stirring to obtain a mixed solution with the mass concentration of 5%; transferring the mixture into a stainless steel reaction kettle with a polytetrafluoroethylene lining, putting the reaction kettle into an oven at the temperature of 180-190 ℃, reacting for 6-9 h, naturally cooling to room temperature, and filtering by using a filter membrane to obtain the carbon quantum dot solution.
11. Use of the carbon quantum dots prepared by the method of any one of claims 1 to 10 for fluorescent probes or cellular imaging for the detection of hypochlorous acid in circulating water.
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