A chelating ligand functionalized carbon dot and its high-yield synthesis method and application

Abstract

A chelating ligand functionalized carbon dot and a high-yield synthesis method and application thereof. The present invention belongs to the technical field of synthesis and application of functional carbon materials. The purpose of the present invention is to solve the technical problems that the existing carbon dots have poor recognition ability for metal ions and the low synthesis yield of the existing carbon dots. The carbon dots of the present invention are synthesized by simultaneous reaction of free radical polymerization and hydrothermal carbonization under the action of an initiator using a small molecule compound containing an unsaturated carbon-carbon double bond and a metal ion chelating agent as precursors. Method: The small molecule compound containing an unsaturated carbon-carbon double bond, the metal ion chelating agent and the free radical initiator are dissolved in water or an organic solvent respectively, and then the above solutions are mixed and placed in a hydrothermal reactor of polytetrafluoroethylene, heated from room temperature to the hydrothermal carbonization reaction temperature and kept warm to synthesize the chelating ligand functionalized carbon dots. The carbon dots of the present invention are used as fluorescent probes for specific recognition of metal ions. The present invention realizes the functionalization of the chelating ligands and high-yield synthesis of carbon dots.

Description

Technical Field

[0001] The invention belongs to the technical field of synthesis and application of functional carbon materials, and specifically relates to a chelated ligand functionalized carbon dot and a high-yield synthesis method and application thereof. Background Art

[0002] As a new type of fluorescent probe, carbon dots have the advantages of strong fluorescence stability, high biocompatibility and low biotoxicity, and have wide application potential in metal ion detection, sensors and bioimaging (ACS Applied Bio Materials, 2019, 2(6): 2317-2338). Carbon dots are usually synthesized by hydrothermal carbonization of precursors, but this method has the problem of low synthesis yield of carbon dots (less than 30%).

[0003] In addition, the surface of carbon dots contains abundant functional groups (hydroxyl, carboxyl and amino), which causes carbon dots to respond to multiple metal ions simultaneously, that is, the selectivity of carbon dots to different metal ions is poor, so carbon dots do not have the ability to specifically recognize metal ions. 2+ and Fe 3+ The carbon dots with -COOH and -NH2 functional groups on the surface have the ability to detect Cu 2+ The carbon dots with -NH2 on the surface have the ability to detect a variety of metal ions, such as Co 2+ Cr 3+ and Fe 3+ (Talanta 205 (2019) 120121, Chem. Eng. J. 384 (2020) 123260). Therefore, the relationship between which metal ions the carbon dots with different functional groups on their surfaces have the ability to detect is still unclear, which makes it impossible for carbon dots to achieve specific recognition and detection of metal ions.

[0004] It can be seen that although the existing technology has solved the technical problem of poor selectivity of carbon dots for metal ions, the process method of synthesizing carbon dots using metal ion chelators as precursors has a low synthesis yield, which restricts the industrial production of chelated functionalized carbon dots. Therefore, it is particularly important to develop a chelated functionalized carbon dot suitable for industrial production. Summary of the invention

[0005] The purpose of the present invention is to solve the technical problems that the existing carbon dot synthesis method has low yield and the existing carbon dot does not have the specific recognition ability of metal ions, and to provide a chelating ligand functionalized carbon dot and its high-yield synthesis method and application.

[0006] The chelated ligand functionalized carbon dots of the present invention are synthesized by using small molecule compounds containing unsaturated carbon-carbon double bonds and metal ion chelating agents as precursors and by simultaneous reactions of free radical polymerization and hydrothermal carbonization under the action of an initiator.

[0007] It is further defined that the small molecule compound containing an unsaturated carbon-carbon double bond is a small molecule carboxylic acid compound, a small molecule amide compound or a small molecule ester compound containing an unsaturated carbon-carbon double bond.

[0008] It is further defined that the small molecule carboxylic acid compound containing unsaturated carbon-carbon double bonds is acrylic acid, methacrylic acid or crotonic acid, the small molecule amide compound containing unsaturated carbon-carbon double bonds is N,N-dimethylacrylamide, isopropylacrylamide or acrylamide, and the small molecule ester compound containing unsaturated carbon-carbon double bonds is methyl acrylate, ethyl acrylate, methyl 2-methacrylate or ethyl 2-methacrylate.

[0009] It is further defined that the metal ion chelating agent is an amino-containing carboxylic acid compound or an organic polyphosphonic acid compound.

[0010] It is further limited that the amino-containing carboxylic acid compound is one of ethylenediaminetetraacetic acid, disodium ethylenediaminetetraacetate, aminotriacetic acid, diethylenetriaminepentaacetic acid, and ethylene glycol bis(2-aminoethyl ether)tetraacetic acid, and the organic polyphosphonic acid compound is one of hydroxyethylidene diphosphonic acid, tetrasodium hydroxyethylidene diphosphonic acid, and ethylenediaminetetramethylenephosphonic acid.

[0011] It is further defined that the free radical initiator is an azo, persulfate or peroxide free radical initiator.

[0012] It is further specified that the azo free radical initiator is one of azobisisobutyronitrile, azobisisoheptanenitrile, and dimethyl azobisisobutyrate, the persulfate free radical initiator is ammonium persulfate or potassium persulfate, and the peroxide free radical initiator is one of benzoyl peroxide, tert-butyl benzoyl peroxide, and methyl ethyl ketone peroxide.

[0013] It is further defined that the molar ratio of the small molecule compound containing unsaturated carbon-carbon double bonds, the metal ion chelating agent and the free radical initiator is 1:(0.035-0.07):(0.001-0.003).

[0014] The high-yield synthesis method of a chelating ligand functionalized carbon dot of the present invention is carried out by the following steps:

[0015] A small molecule compound containing an unsaturated carbon-carbon double bond, a metal ion chelating agent and a free radical initiator are dissolved in water or an organic solvent, and then placed in a polytetrafluoroethylene hydrothermal reactor, heated from room temperature to a hydrothermal carbonization reaction temperature, and kept warm at the hydrothermal carbonization reaction temperature, and then sequentially separated, dialyzed and dried to obtain chelated ligand functionalized carbon dots.

[0016] It is further defined that the concentration of the small molecule compound solution containing unsaturated carbon-carbon double bonds is 0.5-1.2 mol / L, and the concentration of the metal ion chelating agent solution is 1.7×10 -2 -8.4×10 -2 mol / L, the concentration of the free radical initiator solution is 0.5×10 -3 -3.6×10 -3 mol / L.

[0017] It is further defined that the hydrothermal carbonization reaction temperature is 180-250°C and the insulation time is 6-24h.

[0018] It is further specified that the hydrothermal carbonization reaction temperature is 220°C and the insulation time is 12h.

[0019] The chelated ligand functionalized carbon dots of the present invention are used as fluorescent probes for specific identification of metal ions.

[0020] Further defined, the metal ion is Fe 3+ , Cu 2+ or Ca 2+ .

[0021] Compared with the prior art, the present invention has the following significant effects:

[0022] In order to achieve the chelation functionalization and high synthesis yield of carbon dots, the present invention innovatively proposes a two-component system with a small molecule containing an unsaturated carbon-carbon double bond as a carrier and a metal ion chelating agent as a chelating ligand, and realizes the chelation functionalization and high-yield synthesis of carbon dots through the simultaneous reaction of free radical polymerization and hydrothermal carbonization. The specific advantages are as follows:

[0023] 1) The present invention achieves the completion of the free radical polymerization and hydrothermal carbonization of the precursor in one step in a hydrothermal reactor by directional control of the reaction process of the carbon dots and providing functional groups (such as carboxyl and amino groups, bisphosphonate groups) that can selectively chelate metal ions with metal ion chelators. The free radical initiator is used to control the small molecule precursor containing unsaturated carbon-carbon double bonds as a carrier. The initiator acts on the C=C bond and opens the C=C through free radical polymerization, so that the precursor is directional converted, thereby avoiding the problem of low carbon dot synthesis yield due to the side reactions of the precursor. This technology significantly improves the synthesis yield of chelated ligand functionalized carbon dots, which provides a large-scale preparation technology for the industrial synthesis of chelated ligand functionalized carbon dots and their applications.

[0024] 2) The reaction mechanism of the present invention is: at a relatively low heating temperature, a small molecule precursor containing an unsaturated carbon-carbon double bond undergoes free radical polymerization under the action of a trace amount of free radical initiator to generate a polymer precursor of carbon dots. Using this as a carrier, the formed polymer precursor and the metal ion chelator undergo a hydrothermal carbonization reaction at high temperature to thereby be directionally converted into chelated functionalized carbon dots. The precursor raw materials are simple and easy to obtain, and the synthesis technology is simple and convenient, which greatly reduces the production cost of the carbon dots, and the chelated ligand functionalized carbon dots that can specifically recognize metal ions are synthesized in high yield, giving the carbon dots the ability to recognize metal ions, thereby enhancing the selectivity of the carbon dots in detecting metal ions and improving the detection sensitivity. Changing the type of metal ion chelator in the precursor can achieve specific recognition of different metal ions. For example: ethylenediaminetetraacetic acid for Fe 3+ The chelation constant of Fe is relatively large (lgk = 25.1). The chelating ligand functionalized carbon dots prepared with EDTA as precursor can achieve the chelation of Fe 3+ Specific recognition of hydroxyethylidene diphosphonic acid for Cu 2+ The chelation constant of Cu is relatively large (lgk = 12.5). The chelating ligand functionalized carbon dots prepared with hydroxyethylidene diphosphonic acid as a precursor can achieve Cu 2+ Specific recognition of ethylene glycol bis(2-aminoethyl ether)tetraacetic acid for Ca 2+ The chelation constant of the carbon dots is relatively large (lgk = 11.0). The chelating ligand functionalized carbon dots prepared with ethylene glycol bis(2-aminoethyl ether) tetraacetic acid as the precursor can achieve Ca 2+ specific identification.

[0025] 3) The synthesis yield of the chelating ligand functionalized carbon dots in the method of the present invention is up to 86.7%, which is three times the synthesis yield of the carbon dots synthesized with ethylenediaminetetraacetic acid as a precursor. The ethylenediaminetetraacetic acid functionalized carbon dots synthesized with ethylenediaminetetraacetic acid as a functional precursor of the metal ion chelator can achieve Fe 3+ The specific sensitive detection of hydroxyethylidene diphosphonic acid was performed, and the linear detection range and detection limit were 0-50 μM and 33.8 nM, respectively. The synthesis yield of hydroxyethylidene diphosphonic acid functionalized carbon dots synthesized with hydroxyethylidene diphosphonic acid as the functional precursor of metal ion chelator was 72.5%, which is 7 times the synthesis yield of carbon dots synthesized with hydroxyethylidene diphosphonic acid as the precursor. The carbon dots can achieve Cu 2+ The linear detection range and detection limit were 0-50 μM and 88.7 nM, respectively. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 A bar chart comparing the synthesis yields of the chelated ligand functionalized carbon dots of Example 1-2 and the non-chelated functionalized carbon dots of Comparative Example 1-2;

[0027] Figure 2 A bar graph comparing the fluorescence quenching degree of the chelated functionalized carbon dots of Example 1 and the non-chelated functionalized carbon dots solution of Comparative Example 1;

[0028] Figure 3 This is a bar graph comparing the fluorescence quenching degrees of the chelated functionalized carbon dots of Example 2 and the non-chelated functionalized carbon dots solution of Comparative Example 2. DETAILED DESCRIPTION

[0029] Specific implementation method 1: A chelated ligand functionalized carbon dot in this implementation method is synthesized by using a small molecule compound containing an unsaturated carbon-carbon double bond and a metal ion chelating agent as precursors, and by the simultaneous reaction of free radical polymerization and hydrothermal carbonization under the action of an initiator.

[0030] Specific implementation method two: The difference between this implementation method and specific implementation method one is that the small molecule compound containing unsaturated carbon-carbon double bonds is a small molecule carboxylic acid compound containing unsaturated carbon-carbon double bonds, a small molecule amide compound containing unsaturated carbon-carbon double bonds, or a small molecule ester compound containing unsaturated carbon-carbon double bonds. The other steps and parameters are the same as those in specific implementation method one.

[0031] Specific embodiment 3: This embodiment is different from specific embodiment 2 in that: the small molecule carboxylic acid compound containing unsaturated carbon-carbon double bonds is acrylic acid, methacrylic acid or crotonic acid, the small molecule amide compound containing unsaturated carbon-carbon double bonds is N,N-dimethylacrylamide, isopropylacrylamide or acrylamide, and the small molecule ester compound containing unsaturated carbon-carbon double bonds is methyl acrylate, ethyl acrylate, 2-methyl methacrylate or 2-ethyl methacrylate. Other steps and parameters are the same as those in specific embodiment 2.

[0032] Specific embodiment 4: This embodiment differs from specific embodiment 1 in that the metal ion chelating agent is a carboxylic acid compound containing an amino group or an organic polyphosphonic acid compound. Other steps and parameters are the same as those of specific embodiment 1.

[0033] Specific embodiment 5: This embodiment is different from specific embodiment 4 in that: the amino-containing carboxylic acid compound is one of ethylenediaminetetraacetic acid, disodium ethylenediaminetetraacetate, aminotriacetic acid, diethylenetriaminepentaacetic acid, and ethylene glycol bis(2-aminoethyl ether)tetraacetic acid, and the organic polyphosphonic acid compound is one of hydroxyethylidene diphosphonic acid, tetrasodium hydroxyethylidene diphosphonic acid, and ethylenediaminetetramethylenephosphonic acid. Other steps and parameters are the same as those of specific embodiment 4.

[0034] Specific embodiment 6: This embodiment is different from the specific embodiment 1 in that the free radical initiator is an azo, persulfate or peroxide free radical initiator. The other steps and parameters are the same as those of the specific embodiment 1.

[0035] Specific embodiment 7: This embodiment is different from specific embodiment 6 in that the azo free radical initiator is one of azobisisobutyronitrile, azobisisoheptanenitrile, and dimethyl azobisisobutyrate, the persulfate free radical initiator is ammonium persulfate or potassium persulfate, and the peroxide free radical initiator is one of benzoyl peroxide, tert-butyl benzoyl peroxide, and methyl ethyl ketone peroxide. The other steps and parameters are the same as those of specific embodiment 6.

[0036] Specific embodiment eight: This embodiment differs from specific embodiment one in that the molar ratio of the small molecule compound containing unsaturated carbon-carbon double bonds, the metal ion chelating agent and the free radical initiator is 1: (0.035-0.07): (0.001-0.003). Other steps and parameters are the same as those of specific embodiment one.

[0037] Specific embodiment 9: A high-yield synthesis method of chelating ligand functionalized carbon dots in this embodiment is carried out by the following steps:

[0038] A small molecule compound containing an unsaturated carbon-carbon double bond, a metal ion chelating agent and a free radical initiator are dissolved in water or an organic solvent, and then placed in a polytetrafluoroethylene hydrothermal reactor, heated from room temperature to a hydrothermal carbonization reaction temperature, and kept warm at the hydrothermal carbonization reaction temperature, and then sequentially separated, dialyzed and dried to obtain chelated ligand functionalized carbon dots.

[0039] Specific embodiment 10: This embodiment differs from specific embodiment 9 in that the concentration of the small molecule compound solution containing unsaturated carbon-carbon double bonds is 0.5-1.2 mol / L, and the concentration of the metal ion chelating agent solution is 1.7×10 -2 -8.4×10 -2 mol / L, the concentration of the free radical initiator solution is 0.5×10 -3 -3.6×10 -3 mol / L. Other steps and parameters are the same as those in the ninth embodiment.

[0040] Specific embodiment 11: This embodiment differs from specific embodiment 9 in that: the hydrothermal carbonization reaction temperature is 180-250°C, and the heat preservation time is 6-24h. The other steps and parameters are the same as those of specific embodiment 9.

[0041] Specific embodiment 12: This embodiment differs from specific embodiment 9 in that the hydrothermal carbonization reaction temperature is 220°C and the heat preservation time is 12 hours. The other steps and parameters are the same as those of specific embodiment 9.

[0042] Specific implementation thirteen: This implementation differs from specific implementation nine in that: the separation step is centrifugation at a rotation speed of 16000 r / min for 20 min. Other steps and parameters are the same as those of specific implementation nine.

[0043] Specific embodiment 14: This embodiment differs from specific embodiment 9 in that the dialysis step is to use a dialysis bag with a molecular weight cut-off of 500D to perform dialysis in anhydrous ethanol and deionized water for 12 hours respectively. Other steps and parameters are the same as those of specific embodiment 9.

[0044] Specific embodiment 15: This embodiment differs from specific embodiment 9 in that the drying is freeze-drying. Other steps and parameters are the same as those of specific embodiment 9.

[0045] Specific embodiment 16: In this embodiment, a chelated ligand functionalized carbon dot is used as a fluorescent probe for specific detection of metal ions.

[0046] Specific embodiment 17: This embodiment differs from specific embodiment 16 in that the metal ion is Fe 3+ , Cu 2+ or Ca 2+ The other steps and parameters are the same as those in the sixteenth embodiment.

[0047] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0048] The experimental methods used in the following examples are conventional methods unless otherwise specified. The materials, reagents, methods and instruments used are conventional materials, reagents, methods and instruments in the art unless otherwise specified, and can be obtained through commercial channels by those skilled in the art.

[0049] The terms "comprising," "including," "having," "containing," or any other variations thereof, as used in the following examples, are intended to cover a non-exclusive inclusion. For example, a composition, step, method, article, or apparatus comprising the listed elements is not necessarily limited to only those elements, but may include other elements not expressly listed or inherent to such composition, step, method, article, or apparatus.

[0050] When equivalent, concentration or other value or parameter is represented by the range limited by range, preferred range or a series of upper preferred value and lower preferred value, this should be understood as specifically disclosing all ranges formed by any pairing of any upper range limit or preferred value and any lower range limit or preferred value, regardless of whether the scope is disclosed separately. For example, when disclosing range "1 to 5", described range should be interpreted as including range "1 to 4", "1 to 3", "1 to 2", "1 to 2 and 4 to 5", "1 to 3 and 5" etc. When numerical range is described in this article, unless otherwise stated, the scope is intended to include its end value and all integers and fractions within the scope. In the present application specification and claims, range limitation can be combined and / or interchanged, if these ranges are not otherwise stated, include all sub-ranges contained therein.

[0051] The indefinite articles "a" and "an" before the elements or components of the present invention do not limit the quantity requirements (i.e. the number of occurrences) of the elements or components. Therefore, "a" or "an" should be interpreted as including one or at least one, and the elements or components in the singular form also include the plural form, unless the quantity clearly refers to only the singular form.

[0052] Example 1: A high-yield synthesis method of chelating ligand functionalized carbon dots in this example is carried out by the following steps:

[0053] 28 mmol of acrylamide, 1 mmol of an aqueous solution of hydroxyethylidene diphosphonic acid and 0.04 mmol of ammonium persulfate were dissolved in 30 mL of deionized water, and then placed in a polytetrafluoroethylene hydrothermal reactor, heated from room temperature to 220°C, and reacted at 220°C for 12 hours to obtain a dark yellow mixed solution, which was then centrifuged in a high-speed centrifuge at a speed of 16000 r / min for 20 minutes. The clarified solution after removing the precipitate was dialyzed in anhydrous ethanol and deionized water for 12 hours respectively using a dialysis bag with a molecular weight cutoff of 500D, and finally freeze-dried to obtain carbon dot powder, i.e., chelated ligand functionalized carbon dots.

[0054] Example 2: A high-yield synthesis method of chelating ligand functionalized carbon dots in this example is carried out by the following steps:

[0055] 28mmol of acrylamide, 1mmol of ethylenediaminetetraacetic acid and 0.04mmol of ammonium persulfate were dissolved in 30mL of deionized water, then placed in a polytetrafluoroethylene hydrothermal reactor, heated from room temperature to 220°C, and reacted at 220°C for 12h to obtain a dark yellow mixed solution, which was then centrifuged at 16000r / min for 20min in a high-speed centrifuge. The clarified solution after removing the precipitate was dialyzed in anhydrous ethanol and deionized water for 12h respectively using a dialysis bag with a molecular weight cutoff of 500D, and finally freeze-dried to obtain carbon dot powder, i.e., chelated ligand functionalized carbon dots.

[0056] Comparative Example 1: The carbon dot synthesis method of this embodiment is carried out according to the following steps:

[0057] 1mmol of hydroxyethylidene diphosphonic acid and 0.04mmol of ammonium persulfate were dissolved in 30mL of deionized water, then placed in a polytetrafluoroethylene hydrothermal reactor, heated from room temperature to 220°C, and reacted at 220°C for 12h to obtain a dark yellow mixed solution, which was then centrifuged in a high-speed centrifuge at 16000r / min for 20min. The clarified solution after removing the precipitate was dialyzed in anhydrous ethanol and deionized water for 12h respectively using a dialysis bag with a molecular weight cutoff of 500D, and finally freeze-dried to obtain carbon dot powder.

[0058] Comparative Example 2: The carbon dot synthesis method of this embodiment is carried out according to the following steps:

[0059] 1mmol ethylenediaminetetraacetic acid and 0.04mmol ammonium persulfate were dissolved in 30mL deionized water, then placed in a polytetrafluoroethylene hydrothermal reactor, heated from room temperature to 220°C, and reacted at 220°C for 12h to obtain a dark yellow mixed solution, which was then centrifuged in a high-speed centrifuge at 16000r / min for 20min. The clarified solution after removing the precipitate was dialyzed in anhydrous ethanol and deionized water for 12h respectively using a dialysis bag with a molecular weight cutoff of 500D, and finally freeze-dried to obtain carbon dot powder.

[0060] Figure 1 The synthetic yields of four kinds of carbon dots synthesized in Example 1, Example 2, Comparative Example 1, and Comparative Example 2 are shown. It can be seen that in Comparative Example 1 and Comparative Example 2, carbon dots are synthesized using hydroxyethylidene diphosphonic acid and ethylenediamine tetraacetic acid as precursors, respectively, and the synthetic yields of carbon dots in the comparative examples are relatively low, 10.6% and 28.9%, respectively. In Example 1 and Example 2 of the present invention, carbon dots are synthesized using acrylamide and hydroxyethylidene diphosphonic acid or acrylamide and ethylenediamine tetraacetic acid as precursors, and the addition of carbon-carbon double bonds in acrylamide can significantly improve the synthetic yields of carbon dots, and the synthetic yields of the two carbon dots are respectively improved to 72.5% and 86.7%, which is because the initiator can act on the small molecule precursor containing C=C bond, promote free radical polymerization, open C=C through addition polymerization, and make the precursor directional conversion, thereby avoiding the problem of low synthetic yield caused by side reactions, and then significantly improving the synthetic yield.

[0061] The chelated functionalized carbon dots of Example 1 and the non-chelated functionalized carbon dots of Comparative Example 1 were mixed with Pb 2+ 、Ag + Sn 4+ , Mn 2+ Mg 2+ , Ca 2+ , Fe 2+ 、Zn2+ , Cu 2+ The fluorescence spectra of each group of carbon dots and metal ion mixed solutions at the optimal excitation wavelength were measured by fluorescence spectrometer and compared. Figure 2 As shown in the figure, it can be seen that metal ions have no obvious effect on the fluorescence intensity of unchelated functionalized carbon dots, which indicates that unchelated functionalized carbon dots have no ability to recognize metal ions. 2+ The fluorescence quenching degree of the chelated functionalized carbon dots exceeded 50%, and other ions did not have obvious fluorescence quenching. The results showed that the chelated ligand functionalized carbon dots of Example 1 can specifically recognize Cu 2+ .

[0062] The chelated functionalized carbon dots of Example 2 and the non-chelated functionalized carbon dots of Comparative Example 2 were mixed with Ca 2+ 、Ag + Mg 2+ , Pb 2+ 、Nd 3+ 、Al 3+ , Cu 2+ Sn 4+ 、Cd 2+ 、Co 2+ , Fe 3+ The fluorescence spectra of each group of carbon dots and metal ion mixed solutions at the optimal excitation wavelength were measured by fluorescence spectrometer. Figure 3 As shown in the figure, it can be seen that metal ions have no obvious effect on the fluorescence intensity of unchelated functionalized carbon dots, which indicates that unchelated functionalized carbon dots have no ability to recognize metal ions. 3+ The fluorescence quenching degree of the chelated functionalized carbon dots reached nearly 65%, and there was no obvious fluorescence quenching of other ions. The results showed that the chelated ligand functionalized carbon dots can specifically recognize Fe 3+ .

[0063] The above are only preferred specific embodiments of the present invention, which are all different implementations based on the overall concept of the present invention, and the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A chelating ligand functionalized carbon dot, characterized in that: The carbon dots are synthesized by using a small molecule compound containing an unsaturated carbon-carbon double bond and a metal ion chelating agent as precursors, and by simultaneous reactions of free radical polymerization and hydrothermal carbonization under the action of an initiator; the small molecule compound containing an unsaturated carbon-carbon double bond is acrylamide, the metal ion chelating agent is ethylenediaminetetraacetic acid or hydroxyethylidene diphosphonic acid, the initiator is an azo, persulfate or peroxide free radical initiator, the molar ratio of the small molecule compound containing an unsaturated carbon-carbon double bond, the metal ion chelating agent and the free radical initiator is 1: (0.035-0.07): (0.001-0.003), and the hydrothermal carbonization reaction temperature is 180-250°C.

2. The chelating ligand functionalized carbon dots according to claim 1, characterized in that: The azo free radical initiator is one of azobisisobutyronitrile, azobisisoheptanenitrile, and dimethyl azobisisobutyrate; the persulfate free radical initiator is ammonium persulfate or potassium persulfate; and the peroxide free radical initiator is one of benzoyl peroxide, tert-butyl benzoyl peroxide, and methyl ethyl ketone peroxide.

3. A high-yield synthesis method of chelating ligand functionalized carbon dots according to any one of claims 1 to 2, characterized in that: The method proceeds as follows: A small molecule compound containing an unsaturated carbon-carbon double bond, a metal ion chelating agent and a free radical initiator are dissolved in water or an organic solvent, and then placed in a polytetrafluoroethylene hydrothermal reactor, heated from room temperature to a hydrothermal carbonization reaction temperature, and kept warm at the hydrothermal carbonization reaction temperature, and then sequentially separated, dialyzed and dried to obtain chelated ligand functionalized carbon dots.

4. The method according to claim 3, characterized in that The concentration of the small molecule compound solution containing unsaturated carbon-carbon double bonds is 0.5-1.2 mol / L, and the concentration of the metal ion chelating agent solution is 1.7×10 -2 -8.4×10 -2 mol / L, the concentration of the free radical initiator solution is 0.5×10 -3 -3.6×10 -3 mol / L.

5. The method according to claim 3, characterized in that: The holding time of the hydrothermal carbonization reaction is 6-24 h.

6. The method according to claim 5, characterized in that The hydrothermal carbonization reaction temperature is 220°C and the insulation time is 12h.

7. The use of a chelating ligand functionalized carbon dot according to any one of claims 1 to 2, characterized in that: Metal ion chelator ethylenediaminetetraacetic acid carbon dots as fluorescent probes for Fe 3+ The specific recognition of Cu by using the metal ion chelator hydroxyethylidene diphosphonic acid as a fluorescent probe 2+ The above applications are not used for the diagnosis and treatment of diseases.

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