Iron-doped carbon dots and their preparation method and application

Abstract

The present invention discloses iron-doped carbon dots, a preparation method, and applications thereof. The preparation method comprises the following steps: dissolving serine, sodium citrate, and an iron salt in a solvent and performing a hydrothermal reaction to obtain the iron-doped carbon dots. The carbon dots are synthesized using a hydrothermal method and exhibit advantages such as good stability, excellent water solubility, and high sensitivity. Due to the iron doping, the iron-doped carbon dots of the present invention can be used for the precise detection of H2O2, glucose, and GSH / Cys / HomoCys.

Description

Technical Field

[0001] The present invention relates to the technical field of carbon dots, and in particular to iron-doped carbon dots and a preparation method and application thereof. Background Art

[0002] Carbon dots (CDs) are ultra-small nanomaterials, less than 10 nm in size, with excellent optical and catalytic properties, especially good biocompatibility, and possess great potential for application. Importantly, CDs can be produced in large quantities using simple, environmentally friendly, and high-yield methods. Since 2007, the development of various stable and economical natural enzyme-mimicking nanozymes has revealed their unique properties and shown great potential in fields such as chemical sensing, biomedicine, food safety, and environmental monitoring.

[0003] However, the poor electron transfer efficiency within the CDs structure leads to limited catalytic efficiency, hindering its further application.

[0004] Therefore, the existing technology still needs to be improved and developed. Summary of the Invention

[0005] In view of the above-mentioned deficiencies in the prior art, the present invention provides an iron-doped carbon dot and a preparation method and application thereof, so as to solve the problem that the internal electron transfer efficiency of the existing carbon dots is poor, resulting in their limited catalytic efficiency.

[0006] The technical solutions adopted by the present invention to solve the above technical problems are as follows:

[0007] A first aspect of the present invention provides a method for preparing iron-doped carbon dots, the method comprising the following steps:

[0008] Serine, sodium citrate and iron salt are dissolved in a solvent and subjected to a hydrothermal reaction to obtain the iron-doped carbon dots.

[0009] Preferably, the mass ratio of serine to sodium citrate is 1:1;

[0010] The mass ratio of the total mass of the serine and sodium citrate to the iron salt is 0.5-2:1.

[0011] Preferably, the iron salt is selected from one or both of ferric chloride and ferrous sulfate.

[0012] Preferably, the solvent is selected from ultrapure water or anhydrous ethanol.

[0013] Preferably, the temperature of the hydrothermal reaction is 140-200° C., and the time is 8-16 hours.

[0014] Preferably, after dissolving serine, sodium citrate and iron salt in a solvent and performing a hydrothermal reaction, the method further comprises the step of purifying the product after the hydrothermal reaction.

[0015] The second aspect of the present invention provides iron-doped carbon dots prepared by the above preparation method.

[0016] A third aspect of the present invention provides the use of the above-mentioned iron-doped carbon dots in hydrogen peroxide detection.

[0017] A fourth aspect of the present invention provides the use of the above-mentioned iron-doped carbon dots in glucose detection.

[0018] A fifth aspect of the present invention provides the use of the above-mentioned iron-doped carbon dots in the detection of glutathione, cysteine ​​or homocysteine.

[0019] Beneficial effects:

[0020] The present invention discloses iron-doped carbon dots, their preparation method, and applications. The carbon dots are synthesized using a hydrothermal method and exhibit advantages such as good stability, excellent water solubility, and high sensitivity. Due to the iron doping, the iron-doped carbon dots can be used for the precise detection of H2O2, glucose, and GSH / Cys / HomoCys. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Characterization of the Fe-CDs material prepared in Example 1 of the present invention: (a) high-resolution transmission electron microscopy (HR-TEM) image and particle size distribution; (b) X-ray photoelectron spectroscopy (XPS) spectrum; (c) X-ray diffraction (XRD) pattern; (d) Fourier transform infrared (FTIR) spectrum.

[0022] Figure 2 UV-visible spectra of (a) TMB, TMB+H2O2, TMB+CDs, TMB+Fe-CDs, TMB+CDs+H2O2, and TMB+Fe-CDs+H2O2 in the present invention; (b) hydrogen peroxide; (c) steady-state kinetic analysis of TMB Fe-CDs.

[0023] Figure 3 The optimal conditions for Fe-CDs to participate in the reaction in the present invention are: (a) Fe-CDs optimal concentration test; (b) optimal reaction pH test; (c) optimal reaction temperature test; (d) optimal reaction time test.

[0024] Figure 4(a) The UV-visible absorption changes of Fe-CDs (0.1 mg / mL) under different H2O2 concentrations in the present invention and the corresponding photos; (b) its line graph and its calibration curve when the H2O2 concentration is 10-60 μM.

[0025] Figure 5 (a) Description of the colorimetric determination of glucose based on the hybrid cascade system (Fe-CDs / GOx) in the present invention; (b) Changes in UV-visible absorption of the Fe-CDs / GOx system (0.1 / 0.05 mg / mL) with different concentrations of glucose and corresponding photographs; (c) its line graph and its calibration curve when the glucose concentration is 1-60 μM.

[0026] Figure 6 Figure 2 shows the selectivity of the Fe-CDs / GOx system for glucose detection (5 mM fructose, maltose, sucrose, and lactose, respectively, and 0.5 mM glucose) and its time response curve in the present invention (a); the UV-visible absorption changes of the reaction in different concentrations of (b) human serum and (c) plasma.

[0027] Figure 7 (a) Parameters (R, G, and B) and OD values ​​of different glucose concentrations (1-10 mM); (b) calibration curve between analytical signal (RB-RS) (R blank-R sample) and glucose concentration and its corresponding captured images in the present invention.

[0028] Figure 8 In the present invention, (a) GSH, (b) Cys, and (c) HomoCys show that as the concentration increases, the peak value of the UV-visible absorption curve of ox-TMB becomes lower and lower; (d) GSH, (e) Cys, and (f) HomoCys show that the time response curve of the inhibition of ox-TMB by adding different concentrations of GSH, (e) Cys, and (f) HomoCys.

[0029] Figure 9 (a) Cell phone photos of the reaction after adding different concentrations of GSH / Cys / HomoCys (the blue color becomes lighter as the concentration increases); (b) Calibration curves for GSH, (c) Cys, and (d) HomoCys at concentrations ranging from 1 to 60 μM, with LODs of 0.54 μM, 0.29 μM, and 1.41 μM, respectively.

[0030] Figure 10 Corresponding detection strips for (a) GSH, (b) Cys, and (c) HomoCys based on Fe-CDs in the present invention. DETAILED DESCRIPTION

[0031] The present invention provides iron-doped carbon dots, their preparation methods, and applications. To clarify the objectives, technical solutions, and effects of the present invention, the present invention is described in further detail below. It should be understood that the specific embodiments described herein are intended only to illustrate the present invention and are not intended to limit the present invention.

[0032] Since the first demonstration of peroxidase (POD)-like activity in ferroferric oxide magnetic nanoparticles (MNPs) in 2007, various nanozymes have attracted widespread attention due to their stable and economical mimicry of natural enzymes, as well as their ability to be efficiently mass-produced, enhance stability, simplify purification, adjust size and surface modification, and optimize catalytic performance. Encouragingly, CDs (CDs) have great potential for application due to their excellent optical and catalytic properties, especially their good biocompatibility. More importantly, CDs can be produced in large quantities using simple, environmentally friendly, and high-yield methods. However, the poor internal electron transfer efficiency of CDs limits their catalytic efficiency, hindering their further application.

[0033] Based on this, an embodiment of the present invention provides a method for preparing iron-doped carbon dots, the preparation method comprising the following steps:

[0034] Serine, sodium citrate and iron salt are dissolved in a solvent and subjected to a hydrothermal reaction to obtain the iron-doped carbon dots (Fe-CDs).

[0035] The iron-doped probe synthesized by the hydrothermal method of the embodiment of the present invention has the advantages of good stability, excellent water solubility, and high sensitivity. In addition, the iron-doped carbon dots prepared by the present invention can be used to detect H2O2, glucose, and GSH / Cys / HomoCys with high sensitivity and selectivity. Specifically, heteroatom doping is widely used to improve the internal electronic environment. Among them, Fe doping has a higher utilization rate of active sites in the entire POD catalytic process. This heteroatom doping can not only change the internal electronic environment, but also provide active sites, giving CDs new functions.

[0036] In some embodiments, the mass ratio of serine to sodium citrate is 1:1;

[0037] The mass ratio of the total mass of the serine and sodium citrate to the iron salt is 0.5-2:1.

[0038] In the embodiment of the present invention, the mass ratio of the total mass of serine and sodium citrate to the mass ratio of iron salt is controlled at 0.5-2:1. The doping of iron within this range enables the iron-doped carbon dots to simulate peroxidase as much as possible. Serine and sodium citrate provide -NH2 and -COO. The nitrogen and oxygen elements enhance the peroxidase activity of the iron-doped carbon dots. Too much or too little iron will affect its peroxidase activity.

[0039] In some preferred embodiments, the mass ratio of serine to sodium citrate is 1:1;

[0040] The mass ratio of the total mass of the serine and sodium citrate to the iron salt is 2:1.

[0041] In some embodiments, the iron salt is selected from one or both of ferric chloride and ferrous sulfate.

[0042] In some embodiments, the solvent is selected from ultrapure water or anhydrous ethanol.

[0043] In some embodiments, the hydrothermal reaction temperature is 140-200° C., and the time is 8-16 hours.

[0044] In some preferred embodiments, the hydrothermal reaction temperature is 140° C. and the time is 16 hours.

[0045] In some embodiments, after dissolving serine, sodium citrate and iron salt in a solvent and performing a hydrothermal reaction, the method further comprises the step of purifying the product after the hydrothermal reaction.

[0046] An embodiment of the present invention further provides iron-doped carbon dots prepared by the above preparation method.

[0047] The embodiment of the present invention provides the application of the above-mentioned iron-doped carbon dots in hydrogen peroxide detection.

[0048] In the experiment of detecting Fe-CDs simulating POD activity:

[0049] 3',3',5',5'-tetramethylbenzidine (TMB) was used to test the POD-mimicking activity of Fe-CDs. Fe-CDs exhibit excellent POD-mimicking activity under acidic conditions. Consequently, Fe-CDs catalyze H2O2 to produce reactive oxygen species, which oxidize the colorless, transparent TMB to its blue, oxidized form (ox-TMB). The effectiveness of this reaction is demonstrated by measuring the OD value of the solution at 562 nm using a microplate reader (where the peak increases).

[0050] The embodiment of the present invention provides the application of the above-mentioned iron-doped carbon dots in glucose detection.

[0051] In the glucose test:

[0052] Glucose reacts with glucose oxidase (GOx) to produce H2O2 and gluconic acid, thereby combining Fe-CDs and GOx to form a Fe-CDs / GOx system. Since the H2O2 generated in the above reaction process is catalyzed by Fe-CDs into active oxygen, that is, TMB is oxidized to ox-TMB, and the reaction shows a significant color change (from colorless to blue);

[0053] As glucose concentration increases, the color depth of the reaction solution changes accordingly. Reaction solutions containing varying glucose concentrations were photographed and color analyzed using RGB software (R: red; G: green; B: blue). Since the reaction solution ultimately appears blue, and R is a contrasting color to blue, significant changes in R are detected, reflecting the degree of color change in the reaction solution and indirectly reflecting changes in glucose concentration.

[0054] The embodiments of the present invention provide the use of the above-mentioned iron-doped carbon dots in the detection of glutathione, cysteine ​​or homocysteine ​​(GSH / Cys / HomoCys).

[0055] GSH / Cys / HomoCys can effectively inhibit the absorbance response of ox-TMB through redox reactions. As its concentration increases, the color of the reaction solution also changes (the blue becomes lighter and lighter). Similarly, by photographing and monitoring the reaction solution and analyzing its color using RGB software, changes in the R signal can also reflect changes in GSH / Cys / HomoCys concentration.

[0056] Cut laboratory filter paper into 6mm diameter discs and immerse them in the original solution without GSH / Cys / HomoCys for 2 hours. Remove the discs, blot the excess water onto the filter paper, and then drip different concentrations of GSH / Cys / HomoCys onto the discs. Let them react at room temperature for 1.5 hours. Remove the remaining solution onto the filter paper and photograph the discs. The color of the discs can be directly observed to change from dark to light as the concentration of the target solution increases.

[0057] Compared to other iron-doped carbon dots, the iron-doped carbon dots in this embodiment accurately detect hydrogen peroxide (H2O2), glucose, and glutathione / cysteine / homocysteine ​​(GSH / Cys / HomoCys). These iron-doped carbon dots are compact and highly water-soluble, and the iron doping allows them to mimic peroxidase activity.

[0058] In an embodiment of the present invention, 3',3',5',5'-tetramethylbenzidine (TMB) is used to test the peroxidase-like activity of iron-doped carbon dots: under acidic conditions, TMB can react with hydrogen peroxide through peroxidase catalysis, and the colorless TMB will turn into blue oxidized TMB. Its absorbance is detected at 562nm, and the peak value there is recorded. Through this principle, the function of detecting the iron-doped carbon dots to simulate peroxidase is achieved. At the same time, this principle can also be used to detect hydrogen peroxide; and since glucose reacts with glucose oxidase to produce gluconic acid and hydrogen peroxide, hydrogen peroxide and iron-doped carbon dots with simulated peroxidase activity catalyze the colorless TMB into blue oxidized TMB under acidic conditions, which can indirectly detect glucose; finally, GSH / Cys / HomoCys can inhibit the oxidation of TMB, causing the blue oxidized TMB to become lighter or even fade to colorless. Therefore, it can play the role of detecting GSH / Cys / HomoCys. More importantly, the color change test paper method developed can be applied to many of the above detection examples.

[0059] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them, and are intended only to illustrate the present invention and in no way limit the present invention. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort shall fall within the scope of protection of the present invention.

[0060] Example 1

[0061] The invention discloses a method for preparing iron-doped carbon dots, comprising the following steps: mixing 400 mg of serine, 400 mg of sodium citrate, and 400 mg of FeCl3·H2O in 25 ml of anhydrous ethanol; heating the mixed solution in a high-pressure reactor at a temperature of 140°C for 16 hours; and performing purification after the reaction to obtain iron-doped carbon dots.

[0062] Performance testing experiment

[0063] Experiment 1

[0064] The Fe-CDs prepared in Example 1 were characterized.

[0065] Experiment 2

[0066] The Fe-CDs prepared in Example 1 were tested for their POD-like activity. Different control groups were set up and the experiments were conducted simultaneously to more accurately confirm the POD-like activity of Fe-CDs. The experimental groups were TMB, TMB+H2O2, TMB+CDs, TMB+Fe-CDs, TMB+CDs+H2O2, and TMB+Fe-CDs+H2O2. The concentrations of Fe-CDs, H2O2, and TMB were 0.1 mg / ml, 0.1 mM, and 0.25 mM, respectively. 700 μl of acetic acid / sodium acetate buffer (HAc / NaAc) (pH = 3.5, 0.1 M) was added to promote the reaction. After 10 minutes of reaction, the absorbance at 652 nm was measured using a microplate reader.

[0067] The present invention also tested the affinity of Fe-CDs for H2O2 and TMB. The present invention conducted a kinetic analysis of the reaction by keeping one substrate constant while varying the concentration of the other substrate (1. TMB: 0.25 mM, H2O2: 0, 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5 mM; 2. TMB: 0, 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5 mM, H2O2: 0.1 mM).

[0068] Experiment 3

[0069] To detect the optimal reaction conditions of the Fe-CDs prepared in Example 1, the present invention regulated the concentration of Fe-CDs (0, 0.001, 0.01, 0.05, 0.1, 0.2, 0.25 mg / ml); pH (3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8); temperature (25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80°C) and time (0-60 min).

[0070] Experiment 4

[0071] The Fe-CDs prepared in Example 1 were tested for different H₂O₂ concentrations (0, 5, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, and 200 μM), using 0.1 mg / ml Fe-CDs, 0.1 M HAc / NaAc at pH 3.5, and 0.25 mM TMB. A calibration curve and LOD values ​​were also tested for H₂O₂ concentrations ranging from 10 to 60 μM.

[0072] Experiment 5

[0073] The Fe-CDs / GOx system was tested for glucose at various concentrations (0, 5, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 200, 300, 400, and 500 μM) using 50 μg / ml GOx, 0.1 mg / ml Fe-CDs, 0.1 M HAc / NaAc at pH 3.5, and 0.25 mM TMB. Calibration curves and LOD values ​​were also tested for glucose concentrations ranging from 1 to 60 μM.

[0074] In subsequent tests, the concentrations of GOx, Fe-CDs, HAc / NaAc, H2O2 and TMB were set to 50 μg / ml, 0.1 mg / ml, pH = 3.5, 0.1 M, 0.1 mM and 0.25 mM, respectively.

[0075] Experiment 6

[0076] The selectivity of the Fe-CDs / GOx system was tested, and the present invention selected sucrose, fructose, maltose, lactose, and glucose for comparison. The concentrations of sucrose, fructose, maltose, and lactose were all set to 5 mM, while the concentration of glucose was 0.5 mM.

[0077] At the same time, the ability of the Fe-CDs / GOx system to detect glucose in serum and plasma was also tested. The serum and plasma were diluted 100 times to remove the glucose in the serum and plasma. Then 0, 10, 20, and 30 μM glucose were added to simulate blood glucose for detection.

[0078] Experiment 7

[0079] It is well known that the fasting blood glucose concentration of a healthy individual is between 3.9 and 6.0 mmol / L, while that of a diabetic individual is ≥7.0 mmol / L, and the blood glucose concentration during random sampling is ≥11.1 mmol / L. Therefore, the present invention adjusts the glucose concentration to 1, 2, 3, 4, 5, 6, 7, 8, 9, and 10 mM, takes a photo with a smartphone, and analyzes the color signal using RGB software, achieving the intelligent and convenient blood glucose concentration detection effect using the Fe-CDs / GOx system.

[0080] Experiment 8

[0081] Since GSH / Cys / HomoCys can inhibit the color reaction of ox-TMB through redox reaction, the present invention sets different concentrations of GSH / Cys / HomoCys (0, 0.5, 1, 5, 10, 20, 30, 40, 50, 60 μM) to interfere with the color reaction of ox-TMB, thereby achieving the effect of detecting GSH / Cys / HomoCys.

[0082] Experiment 9

[0083] The reaction solutions containing different concentrations of GSH / Cys / HomoCys were photographed using a smartphone and the color signals were analyzed using RGB software. The calibration curves and LOD values ​​were also analyzed.

[0084] Experiment 10

[0085] Laboratory filter paper was cut into 6 mm diameter discs and immersed in the original solution without GSH / Cys / HomoCys for 2 h. The discs were removed and excess water was blotted off on filter paper. Different concentrations of GSH / Cys / HomoCys (0, 10, 50, 80, 100, 200, 300, and 400 μM) were then dripped onto the discs. The reaction was allowed to proceed at room temperature for 1.5 h. The remaining target solution was blotted off on the filter paper, and the color change was recorded and photographed.

[0086] Experiment 11

[0087] Prepare two different brands of commercial wine (pre-treated with a decolorizer) and filter each through a 0.22μm filter membrane. Prepare the aforementioned disc test paper and place a drop of wine sample onto the test paper as the experimental group. Simultaneously, place a drop of ultrapure water onto the test paper as the control group. Allow the reaction to stand at room temperature for 1.5 hours. Remove the excess solution and observe the color change of the test paper, comparing it to the control group.

[0088] The test results are as follows:

[0089] The Fe-CDs prepared in Example 1 were characterized using HR-TEM, XPS, XRD, and FTIR. HR-TEM imaging showed that the Fe-CDs were spherical with an average diameter of 2.5 nm ( Figure 1 a); XPS spectrum shows that Fe-CDs have high O and C contents ( Figure 1 b), FTIR spectrum ( Figure 1 d) at 3366cm -1 There is a broad peak at 3146-3041 cm, indicating the presence of OH or NH bonds; -1 The characteristic bands observed at can also be attributed to the presence of CH.

[0090] To evaluate the POD-like activity of Fe-CDs, the changes of TMB (in the presence and absence of H2O2) and the steady-state kinetic analysis of Fe-CDs with hydrogen peroxide and TMB were monitored by UV-visible absorption at 652 nm. Figure 2 ).

[0091] To investigate the various factors that influence the POD-like activity of Fe-CDs, the present invention systematically evaluated the effects of Fe-CDs (0.001-1 mg / mL), pH (3.0-8.0), temperature (25-8°C), and reaction time (0-60 min) on the reaction. Similar to most nanozymes, Fe-CDs exhibit significant catalytic activity in acidic environments and very weak activity in neutral and alkaline environments. Figure 3 The optimal reaction conditions of Fe-CDs are: concentration (100 μg / mL); pH (3.5); temperature (40℃); reaction time (30 min).

[0092] In the experiment of visual detection of H2O2 and Glucose, Figure 4 Figure a shows a typical concentration-absorbance curve of H2O2, where an increase in H2O2 concentration corresponds to a higher absorbance peak at 652nm. In addition, the color of the mixture changes significantly, indicating that visual detection of H2O2 can be completed by the naked eye ( Figure 4 : The color changes from transparent to blue-green). In order to accurately detect glucose, the present invention adopts a cascade reaction involving GOx and Fe-CDs to generate H2O2 in situ and then participate in the reaction. Figure 5 Figure a shows the reaction principle. Figure 5 Figure b shows a positive correlation between glucose concentration and the absorbance peak at 652 nm. Utilizing the unique POD-like activity and strong affinity of Fe-CDs for H2O2, this method can be used to indirectly detect glucose when combined with the catalytic properties of GOx and Fe-CDs.

[0093] The selectivity of the Fe-CDs / GOx system for glucose detection was analyzed. Figure 6 The results in Figure a show that the absorbance of glucose is significantly higher than that of other sugars, while the absorbance of fructose, maltose, sucrose, and lactose is not significant (even though the glucose concentration is 1 / 10 of that of other sugars). Next, real human serum samples were evaluated. To minimize the effect of intrinsic glucose in serum, the serum was diluted 100-fold. It was found that even with only a trace amount of glucose added, the Fe-CDs / GOx system could effectively detect ( Figure 6 Similar results were also found in plasma using the same method ( Figure 6Through the smartphone RGB software, the intensity changes of red (R), green (G), and blue (B) can be used to analyze and easily detect the glucose concentration ( Figure 7 ).

[0094] Since GSH / Cys / HomoCys can inhibit the color reaction of ox-TMB through redox reaction, the present invention sets different concentrations of GSH / Cys / HomoCys to interfere with the color reaction of ox-TMB, thereby achieving the effect of detecting GSH / Cys / HomoCys. Experiments have shown that with the increase of GSH / Cys / HomoCys concentration, the peak value of the reaction at 652nm becomes lower and lower ( Figure 8 The present invention also conducted an experiment to easily detect the concentration of GSH / Cys / HomoCys based on a smartphone. The three substrates inhibit the color change of ox-TMB as shown in the following figure: Figure 9 Finally, the present invention designs a test paper that can detect GSH / Cys / HomoCys intuitively and simply. Figure 10 As shown in the figure, it can be seen with the naked eye that the color of the test paper changes from blue to light green or even loses its color as the concentration of the target solution increases. Therefore, the above results show that combining the colorimetric sensing system with the cheap and available smartphone / paper device can provide a promising tool for antioxidant detection.

[0095] It should be understood that the application of the present invention is not limited to the above examples. For those skilled in the art, improvements or changes can be made based on the above description. All these improvements and changes should fall within the scope of protection of the claims attached to the present invention.

Claims

1. A method for preparing iron-doped carbon dots, characterized in that: The preparation method comprises the following steps: Serine, sodium citrate and iron salt are dissolved in anhydrous ethanol and subjected to a solvothermal reaction to obtain the iron-doped carbon dots.

2. The method for preparing iron-doped carbon dots according to claim 1, wherein: The mass ratio of serine to sodium citrate is 1:1; The mass ratio of the total mass of the serine and sodium citrate to the iron salt is 0.5-2:

1.

3. The method for preparing iron-doped carbon dots according to claim 1, wherein: The iron salt is selected from one or both of ferric chloride and ferrous sulfate.

4. The method for preparing iron-doped carbon dots according to claim 1, wherein: The temperature of the solvent thermal reaction is 140-200° C., and the time is 8-16 hours.

5. The method for preparing iron-doped carbon dots according to claim 1, wherein: After dissolving serine, sodium citrate and iron salt in a solvent and performing a solvent thermal reaction, the method further comprises the step of purifying the product after the solvent thermal reaction.

6. Iron-doped carbon dots prepared by the preparation method according to any one of claims 1 to 5.

7. Use of the iron-doped carbon dots according to claim 6 in hydrogen peroxide detection.

8. Use of the iron-doped carbon dots according to claim 6 in glucose detection.

9. Use of the iron-doped carbon dots according to claim 6 in the detection of glutathione, cysteine ​​or homocysteine.

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