Microwave-assisted synthesis method and application of nitrogen-iron-manganese co-doped carbon dots

Abstract

The application discloses a microwave-assisted synthesis method of nitrogen-iron-manganese co-doped carbon dots and application, and belongs to the technical field of fluorescent nanometer materials. The microwave-assisted synthesis method of nitrogen-iron-manganese co-doped carbon dots comprises the following specific steps: sequentially adding iron chloride hexahydrate, manganese sulfate monohydrate, sodium citrate, ethylenediamine and ultrapure water into a polytetrafluoroethylene reaction kettle, and performing ultrasonic dissolution; moving the mixed solution into a microwave digestion instrument reaction kettle to perform a digestion reaction; performing centrifugal treatment, removing impurities through filtration, and obtaining N, Fe, Mn-CDs products. The application takes sodium citrate as a carbon source, takes iron chloride hexahydrate, manganese sulfate monohydrate and ethylenediamine as doping agents, is low in raw material cost, easy to obtain, simple in operation, short in reaction time, high in synthesis yield, good in water solubility of the prepared nitrogen-iron-manganese co-doped carbon dots, and high in stability, and can be applied to H2O2 detection as a fluorescent probe, is high in detection sensitivity, good in selectivity, fast in response speed, does not need to introduce a complex enzyme catalytic reaction or a color reaction, and can realize rapid and high-sensitivity detection of H2O2.

Description

Technical Field

[0001] The present invention belongs to the technical field of fluorescent nanomaterials, and in particular relates to a microwave-assisted synthesis method and application of nitrogen, iron and manganese co-doped carbon dots. Background Art

[0002] Carbon dots (Cdots) are zero-dimensional, carbon-based fluorescent nanomaterials with sizes below 10 nm. They offer advantages such as broad raw material availability, simple preparation, excellent optical properties, resistance to photobleaching, low toxicity, easy surface modification, and good biocompatibility. As an emerging fluorescent nanomaterial, Cdots are widely used in biosensing, bioimaging, photocatalysis, environmental monitoring, and other fields.

[0003] There are numerous methods for preparing carbon dots (CDs). These can be categorized into "top-down" and "bottom-up" approaches, depending on the relationship between the carbon source and the product. The "bottom-up" approach involves pyrolysis or carbonization of a precursor to produce CDs, with the most commonly used methods being hydrothermal and solvothermal. Microwave-assisted synthesis, as an emerging method for synthesizing CDs, offers ease of use and uniform heating, shortening reaction times and increasing the yield and purity of CDs. The incorporation of heteroatoms during CD synthesis can alter the electron density distribution and energy gap, thereby adjusting the fluorescence and physicochemical properties of the CDs and broadening their application.

[0004] Currently, hydrogen peroxide (H2O2) is detected primarily using titration, spectrophotometry, chemiluminescence, electrochemical analysis, chromatography, and fluorescence spectroscopy. Fluorescence spectroscopy has attracted considerable attention due to its rapidity, sensitivity, and visualization of detection results. It is necessary to explore heteroatom-codoped carbon dots and their preparation methods, resulting in highly selective carbon dots for H2O2, for application in fluorescence detection of H2O2. Summary of the Invention

[0005] To overcome the technical problems existing in the background technology, the present invention proposes a microwave-assisted synthesis method and application of nitrogen-iron-manganese co-doped carbon dots, using sodium citrate as the carbon source and ferric chloride hexahydrate, manganese sulfate monohydrate, and ethylenediamine as dopants. The raw materials are cheap and easily available, the operation is simple, the reaction time is short, and the synthesis yield is high. The prepared nitrogen-iron-manganese co-doped carbon dots have good water solubility and high stability. They can be used as fluorescent probes for H2O2 detection with high detection sensitivity and fast response speed. No complex enzyme-catalyzed reactions or color development reactions are required, and rapid and highly sensitive detection of H2O2 can be achieved.

[0006] To achieve the above object, the present invention is implemented through the following technical solutions:

[0007] A microwave-assisted synthesis method of nitrogen, iron and manganese co-doped carbon dots, the specific steps are as follows:

[0008] 1) Add ferric chloride hexahydrate, manganese sulfate monohydrate, sodium citrate, ethylenediamine, and ultrapure water to a polytetrafluoroethylene reactor in sequence and perform ultrasonication for 3-10 minutes until they are completely dissolved;

[0009] 2) transferring the mixed solution in step 1) into a microwave digestion apparatus reactor for digestion reaction;

[0010] 3) The product obtained in step 2) was centrifuged, and the supernatant was filtered through a 0.22 μm filter membrane to remove impurities, thereby obtaining the N, Fe, Mn-CDs product.

[0011] Preferably, in step 1), the molar ratio of ferric chloride hexahydrate to manganese sulfate monohydrate is 0.2-5:1, the amount of ethylenediamine used is 0.4-0.8 mL, and the amounts of sodium citrate and ultrapure water are 0.2000 g and 10 mL, respectively.

[0012] Preferably, in step 2), the digestion temperature is 160-180° C., and the reaction time is 1-2 hours.

[0013] Preferably, in step 3), the centrifugal treatment speed is 7000 r / min and the time is 5 min.

[0014] The nitrogen, iron and manganese co-doped carbon dots prepared by the above method were used as fluorescent probes in the detection of hydrogen peroxide.

[0015] Furthermore, the specific detection steps are: 1) mixing the detection solution containing N, Fe, and Mn-CDs with the solution to be tested; 2) allowing the mixed solution to stand for 5 to 10 minutes and then performing fluorescence detection.

[0016] Preferably, the detection solution in step 1) is prepared by diluting N, Fe, Mn-CDs 200-1000 times with a HAc-NaAc buffer solution with a pH of 3.0-5.0.

[0017] Beneficial effects of the present invention:

[0018] (1) The present invention uses sodium citrate as a carbon source, ferric chloride hexahydrate, manganese sulfate monohydrate, and ethylenediamine as dopants. The synthetic raw materials are cheap and easily available, the reaction operation is simple, the reaction time is short, the synthetic yield is high, the reproducibility is good, and the production cost is low.

[0019] (2) The carbon dots prepared in the present invention have good water solubility, good stability, low toxicity, and good biocompatibility, and can be used for H2O2 detection without further modification.

[0020] (3) The prepared N, Fe, Mn-CDs were used as fluorescent probes for the fluorescence detection of H2O2. This fluorescence detection method is simple to operate, has good selectivity, high sensitivity, and fast response speed. It does not require the introduction of complex enzyme-catalyzed reactions or color development reactions, simplifies the operation method and operation process, and can achieve rapid and highly sensitive detection of H2O2. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Transmission electron microscopy images of N, Fe, Mn-CDs prepared in Example 1;

[0022] Figure 2 The XPS graph of N, Fe, Mn-CDs prepared in Example 1;

[0023] Figure 3 The infrared spectra of N, Fe, Mn-CDs prepared in Example 1;

[0024] Figure 4 UV-visible absorption spectra, fluorescence excitation and emission spectra of the aqueous solution of N, Fe, Mn-CDs prepared in Example 1;

[0025] Figure 5 Comparison of fluorescence properties of carbon dots prepared with different ratios of metal ions (446 nm) in Experiment 1;

[0026] Figure 6 Comparison of fluorescence properties of carbon dots prepared with different volumes of ethylenediamine (446 nm);

[0027] Figure 7 Comparison of fluorescence properties of carbon dots prepared at different temperatures (446 nm);

[0028] Figure 8 The fluorescence intensity of N,Fe,Mn-CD prepared in Example 1 at 446nm changes with the carbon dot concentration;

[0029] Figure 9 This is a bar graph showing the change in fluorescence intensity at 446 nm of the N,Fe,Mn-CD prepared in Example 1 as a function of solution pH;

[0030] Figure 10 This is the time response diagram of the N, Fe, Mn-CD prepared in Example 1 when detecting H2O2;

[0031] Figure 11 The fluorescence response bar graphs of N, Fe, and Mn-CDs prepared in Example 1 to different substances are shown;

[0032] Figure 12 Linearity graph for H2O2 detection. DETAILED DESCRIPTION

[0033] The present invention will be further described in detail below with reference to specific embodiments, but the protection scope of the present invention is not limited to the contents described above.

[0034] Example 1

[0035] A preparation method of nitrogen, iron and manganese co-doped carbon dots (N,Fe,Mn-CDs) is as follows:

[0036] Weigh 0.0270g of ferric chloride hexahydrate and 0.0338g of manganese sulfate monohydrate, i.e. The mixture was prepared by dissolving 0.7 mL of ethylenediamine in an ultrasonic cleaner after complete dissolution and continuing ultrasonication for 3 min to obtain a mixed solution. The mixed solution was transferred to a microwave digester reactor and reacted at 170°C for 1.5 h. The obtained product was centrifuged at 7000 r / min for 5 min, and the supernatant was filtered with a 0.22 μm filter membrane to remove impurities to obtain N,Fe,Mn-CDs product, which was stored at 4°C for future use.

[0037] The transmission electron microscopy images of N, Fe, Mn-CDs prepared in this example are shown in Figure 1 The N, Fe, Mn-CDs are spherical, well dispersed, with an average particle size of about 4 nm and a lattice spacing of about 0.20 nm, which proves that they are mainly graphitic carbon structures. The X-ray electron spectrum (XPS) of the N, Fe, Mn-CDs prepared in this example is shown in FIG. Figure 2 From the XPS full spectrum ( Figure 2 A) shows that N, Fe, Mn-CDs have five characteristic energy level peaks, corresponding to C1s, N1s, O1s, Fe2p and Mn2p respectively. This proves that the carbon dots contain C, N, O, Fe, Mn and other elements at the same time. The C1s peak spectrum of N, Fe, Mn-CDs ( Figure 2 B) It can be seen that there are groups such as C═C (284.80eV), CN\CO (286.27eV) and C═O (288.34eV) in the carbon dot structure. Figure 2 As shown in C, O1s can be divided into two peaks at 530.14eV and 531.33eV, corresponding to C═O and CO groups, respectively. N1s spectrum ( Figure 2 D) shows three peaks with binding energies of 398.93 eV, 399.87 eV, and 399.94 eV, corresponding to pyridinic N, amino N, and pyrrolic N, respectively. Figure 2 E, The binding energy at the satellite peaks of 710.68 eV and 724.42 eV confirms the presence of Fe. Figure 2 The F and Mn2p spectra showed the presence of Mn-O coordination. The above results indicate that N, Fe, and Mn co-doped carbon dots were successfully prepared.

[0038] The infrared spectra of N, Fe, Mn-CDs prepared in this example are shown in Figure 3 , 3404cm -1 The absorption peak at 1397 cm is due to the stretching vibration of OH or NH; –1 The absorption peak at 1659cm is related to the stretching vibration of the C–N bond; –1 and 1072cm –1 The absorption peak at 619 cm indicates the presence of C═N / C═O on the surface; –1 、484cm –1 The peaks at 3 and 4 correspond to Fe–O and Mn–O, respectively. In summary, N, Fe, and Mn co-doped carbon dots have been successfully prepared.

[0039] The UV-visible absorption spectra, fluorescence excitation and emission spectra of N, Fe, Mn-CDs prepared in this example are shown in Figure 4 , n-π of C═O * The transition results in a clear absorption peak of N,Fe,Mn-CDs at 324nm. The maximum excitation and emission wavelengths of N,Fe,Mn-CDs are 360nm and 446nm, respectively.

[0040] Example 2

[0041] A preparation method of nitrogen, iron and manganese co-doped carbon dots (N,Fe,Mn-CDs) is as follows:

[0042] Weigh 0.0270g of ferric chloride hexahydrate and 0.0169g of manganese sulfate monohydrate, i.e. The mixture was prepared by dissolving 0.7 mL of ethylenediamine in an ultrasonic cleaner after complete dissolution and continuing ultrasonication for 3 min to obtain a mixed solution. The mixed solution was transferred to a microwave digester reactor and reacted at 170°C for 1.5 h. The obtained product was centrifuged at 7000 r / min for 5 min, and the supernatant was filtered with a 0.22 μm filter membrane to remove impurities to obtain N,Fe,Mn-CDs product, which was stored at 4°C for future use.

[0043] Example 3

[0044] A preparation of nitrogen, iron and manganese co-doped carbon dots (N,Fe,Mn-CDs) was conducted with the other steps and parameters remaining unchanged, and only the amounts of ferric chloride hexahydrate and manganese sulfate monohydrate were adjusted, wherein the amount of ferric chloride hexahydrate was 0.0540 g and the amount of manganese sulfate monohydrate was 0.0169 g, i.e.

[0045] Example 4

[0046] A preparation of nitrogen, iron and manganese co-doped carbon dots (N,Fe,Mn-CDs) was conducted. The other steps and parameters remained unchanged, and only the amounts of ferric chloride hexahydrate and manganese sulfate monohydrate were adjusted. The amount of ferric chloride hexahydrate was 0.1350 g, and the amount of manganese sulfate monohydrate was 0.0169 g.

[0047] Example 5

[0048] A preparation of nitrogen, iron and manganese co-doped carbon dots (N,Fe,Mn-CDs) was conducted with the other steps and parameters remaining unchanged, and only the amounts of ferric chloride hexahydrate and manganese sulfate monohydrate were adjusted, wherein the amount of ferric chloride hexahydrate was 0.0270 g and the amount of manganese sulfate monohydrate was 0.0845 g, i.e.

[0049] Example 6

[0050] A preparation method of nitrogen, iron and manganese co-doped carbon dots (N,Fe,Mn-CDs) is as follows:

[0051] Weigh 0.0270g of ferric chloride hexahydrate and 0.0338g of manganese sulfate monohydrate, i.e. The mixture was prepared by dissolving 0.6 mL of ethylenediamine in an ultrasonic cleaner after complete dissolution, and continuing ultrasonication for 3 min to obtain a mixed solution. The mixed solution was transferred to a microwave digester reactor and reacted at 170°C for 1.5 h. The obtained product was centrifuged at 7000 r / min for 5 min, and the supernatant was filtered with a 0.22 μm filter membrane to remove impurities to obtain N,Fe,Mn-CDs product, which was stored at 4°C for future use.

[0052] Example 7

[0053] A preparation method of nitrogen, iron and manganese co-doped carbon dots (N,Fe,Mn-CDs) is as follows:

[0054] 0.0270 g of ferric chloride hexahydrate, 0.0338 g of manganese sulfate monohydrate, and 0.2000 g of sodium citrate were weighed and dissolved in 10 mL of ultrapure water. The mixture was ultrasonically treated in an ultrasonic cleaner. After complete dissolution, 0.7 mL of ethylenediamine was added and ultrasonic treatment was continued for 3 min to obtain a mixed solution. The mixed solution was transferred to a microwave digester reactor and reacted at 160°C for 1.5 h. The obtained product was centrifuged at 7000 r / min for 5 min, and the supernatant was filtered with a 0.22 μm filter membrane to remove impurities to obtain the N,Fe,Mn-CDs product, which was refrigerated and stored at 4°C for later use.

[0055] Experimental Analysis Experiment 1: Effects of Different Addition Amounts of Ferric Chloride Hexahydrate and Manganese Sulfate Monohydrate on N,Fe,Mn-CDs Products

[0056] The excitation wavelength was fixed at 360 nm, and the N, Fe, and Mn-CDs products prepared in different ratios in Examples 1-5 were subjected to fluorescence detection at room temperature to compare the fluorescence intensity at the maximum emission wavelength of 446 nm. The results are as follows: Figure 5 As shown, the fluorescence intensity of carbon dots is the highest when the molar ratio of ferric chloride hexahydrate to manganese sulfate monohydrate is 1:2, and the molar ratio of ferric chloride hexahydrate to manganese sulfate monohydrate is 1:2, which is the optimal ratio.

[0057] Experiment 2: Effects of different ethylenediamine addition amounts on N,Fe,Mn-CDs products

[0058] Based on the preparation method of Example 1, only the amount of ethylenediamine was adjusted, and 0.4 mL, 0.5 mL, 0.6 mL, 0.7 mL, and 0.8 mL of ethylenediamine were added, respectively, to prepare 5 groups of N, Fe, and Mn-CDs products.

[0059] The excitation wavelength was fixed at 360 nm, and the carbon dots prepared with different amounts of ethylenediamine were subjected to fluorescence detection at room temperature. The fluorescence intensity at the maximum emission wavelength of 446 nm was compared. The results are as follows: Figure 6 As shown in the figure, the fluorescence intensity of carbon dots is the highest when the amount of ethylenediamine added is 0.7 mL, and the optimal volume of ethylenediamine is 0.7 mL.

[0060] Experiment 3: Effects of different digestion temperatures on N, Fe, and Mn-CDs products

[0061] Based on the preparation method of Example 1, only the digestion temperature was adjusted, and the reactions were carried out at 140°C, 150°C, 160°C, 170°C, and 180°C, respectively, to prepare 5 groups of N, Fe, and Mn-CDs products.

[0062] The excitation wavelength was fixed at 360 nm, and the carbon dots prepared at different temperatures were subjected to fluorescence detection at room temperature. The fluorescence intensity at the maximum emission wavelength of 446 nm was compared. The results are shown in Figure 2. Figure 7 As shown in Figure 3, the fluorescence intensity of carbon dots is the highest when the reaction temperature is 170℃, and the optimal reaction temperature is 170℃.

[0063] Experiment 4: Study on the Luminescence Properties of N, Fe, and Mn-CDs at Different Concentrations

[0064] The N, Fe, Mn-CDs solution prepared in Example 1 was used as a raw material, and 1.0 μL, 2.0 μL, 3.0 μL, 4.0 μL, 5.0 μL, 6.0 μL, 7.0 μL, 8.0 μL, 9.0 μL, and 10.0 μL were taken and diluted to 1 mL, respectively; 100 μL of the above N, Fe, and Mn-CDs of different concentrations were added to 900 μL of 0.1 M acetic acid-sodium acetate (HAc-NaAc) buffer solution with a pH of 4.0, mixed evenly, fixed the excitation wavelength to 360 nm, and performed fluorescence detection at room temperature to compare the fluorescence intensity at the maximum emission wavelength of 446 nm.

[0065] Test results such as Figure 8 As shown in the figure, as the concentration of carbon dots increases, the fluorescence intensity in the solution first increases and then decreases. When the concentration of carbon dots is 4.0 μL / mL, the fluorescence intensity is the highest. It can be concluded that the optimal concentration of N, Fe, Mn-CDs is 4.0 μL / mL. Experiment 5: Study on the effect of pH on N, Fe, Mn-CDs (4.0 μL / mL)

[0066] Using the N, Fe, and Mn-CDs solutions prepared in Example 1 as starting materials, 100 μL of each solution was added to 900 μL of 0.1 M HAc-NaAc buffer solutions at different pH values ​​(1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, and 9.0). The mixture was then mixed thoroughly, and the fluorescence intensity was measured at room temperature. The excitation wavelength was fixed at 360 nm, and the fluorescence intensity at the maximum emission wavelength of 446 nm was compared.

[0067] Test results such as Figure 9 As shown in the figure, with the increase of pH value, the fluorescence intensity of the solution first increases and then decreases. When the pH is 4.0, the fluorescence intensity is the largest. It can be concluded that pH has an effect on the N,Fe,Mn-CDs with a concentration of 4.0 μL / mL, and the optimal pH is 4.0.

[0068] Experiment 6: Time response experiment of detecting H2O2 with N,Fe,Mn-CDs (4.0μL / mL)

[0069] Take 100 μL of the N,Fe,Mn-CDs solution (4.0 μL / mL) prepared in Example 1, take 800 μL of 0.1MHAc-NaAc buffer solution with a pH of 4.0, take 100 μL of 5 mM H2O2, mix them evenly, and immediately detect their fluorescence properties. The excitation wavelength is fixed at 360 nm, and the fluorescence is measured once at different times (0 min, 1.5 min, 3 min, 4.5 min, 6 min, 7.5 min, 9 min, 10.5 min, 15 min, 20 min), and the fluorescence intensity at the maximum emission wavelength of 446 nm is recorded.

[0070] like Figure 10 As shown, with time as the horizontal axis and the fluorescence intensity at 466 nm as the vertical axis, the fluorescence intensity of H2O2 detected by N,Fe,Mn-CDs (4.0 μL / mL) at 466 nm remained basically unchanged after 4.5 minutes, that is, the reaction between N,Fe,Mn-CDs and H2O2 was completed in 4.5 minutes.

[0071] Experiment 7: Selectivity of N,Fe,Mn-CDs (4.0 μL / mL) for H2O2

[0072] A 5 mM solution was prepared using a 0.1 M HAc-NaAc buffer solution at pH 4.0, along with substances (KCl, KH2PO4, CaCl2, Pb(NO3)2, MgSO4, Al2(SO4)3, ZnSO4·7H2O, CuCl2, NaCl, K2S2O8, and Na2O2) that may interfere with fluorescence intensity in a real sample (a commercially available milk). 100 μL of each solution was added to 100 μL of the N,Fe,Mn-CDs solution (4.0 μL / mL) prepared in Example 1 and 800 μL of a 0.1 M HAc-NaAc buffer solution at pH 4.0. The mixture was then incubated at room temperature for 5 minutes to ensure a full reaction. The excitation wavelength was fixed at 360 nm, and the fluorescence intensity at the maximum emission wavelength of 446 nm was compared to achieve selective detection of H2O2.

[0073] like Figure 11 As shown in the figure, the maximum emission fluorescence intensity before adding interfering substances and analytes is F0, and the maximum emission fluorescence intensity after adding interfering substances and analytes is F. The interfering substances and analytes are used as the horizontal axis. The results show that the fluorescence of N, Fe, and Mn-CDs can be enhanced only in the presence of H2O2, which proves that the use of N, Fe, and Mn-CDs to detect H2O2 has good selectivity.

[0074] Experiment 8: Linearity test of the analytical detection method of N, Fe, Mn-CDs (4.0 μL / mL) as a H2O2 probe

[0075] To 100 μL of the N,Fe,Mn-CDs solution (4.0 μL / mL) prepared in Example 1, add 800 μL of 0.1 M HAc-NaAc buffer (pH 4.0) and 100 μL of H₂O₂ at various concentrations (0 μM, 50 μM, 100 μM, 500 μM, 1000 μM, 1500 μM, and 2000 μM). Incubate at room temperature for 5 minutes to ensure a full reaction. The excitation wavelength was fixed at 360 nm, and the fluorescence intensity at the maximum emission wavelength of 446 nm was recorded.

[0076] like Figure 12 As shown, with H2O2 concentration as the horizontal axis and lg(F) as the vertical axis, lg(F) and H2O2 concentration show a good linear relationship in the range of 1.0 to 2000.0 μM.

[0077] The present invention uses sodium citrate as a carbon source and ferric chloride hexahydrate, manganese sulfate monohydrate, and ethylenediamine as dopants. The raw materials are cheap and easily available, the operation is simple, the reaction time is short, and the synthesis yield is high (this effect can be achieved through Example 1 of this patent). The prepared nitrogen, iron, and manganese co-doped carbon dots have good water solubility and high stability. They can be used as fluorescent probes for H2O2 detection with high detection sensitivity and fast response speed. There is no need to introduce complex enzyme-catalyzed reactions or color development reactions, and real-time detection of H2O2 can be achieved.

[0078] Finally, it should be noted that the above preferred embodiments are only used to illustrate the technical solutions of the present invention and are not limiting. Although the present invention has been described in detail through the above preferred embodiments, those skilled in the art should understand that various changes can be made in form and details without departing from the scope of the present invention as defined in the claims.

Claims

1. A microwave-assisted synthesis method of nitrogen, iron and manganese co-doped carbon dots, characterized by: The specific steps are as follows: 1) Ferric chloride hexahydrate, manganese sulfate monohydrate, sodium citrate, ethylenediamine, and ultrapure water were sequentially added to a polytetrafluoroethylene reactor and sonicated for 3-10 minutes until completely dissolved. The molar ratio of ferric chloride hexahydrate to manganese sulfate monohydrate was 0.2-5:1, the amount of ethylenediamine was 0.4-0.8 mL, and the amounts of sodium citrate and ultrapure water were 0.2000 g and 10 mL, respectively. 2) transferring the mixed solution in step 1) into a microwave digestion apparatus reactor for digestion reaction; 3) The product obtained in step 2) was centrifuged, and the supernatant was filtered through a 0.22 μm filter membrane to remove impurities, thereby obtaining the N,Fe,Mn-CDs product.

2. The microwave-assisted synthesis method of nitrogen-iron-manganese co-doped carbon dots according to claim 1, characterized in that: In step 2), the digestion temperature is 160-180° C., and the reaction time is 1-2 hours.

3. The microwave-assisted synthesis method of nitrogen-iron-manganese co-doped carbon dots according to claim 1, characterized in that: In step 3), the centrifugal treatment speed is 7000 r / min and the time is 5 min.

4. Use of the nitrogen, iron and manganese co-doped carbon dots prepared according to any one of claims 1 to 3 as a fluorescent probe in the detection of hydrogen peroxide.

5. The use according to claim 4, characterized in that: The specific detection steps are: 1) Mixing the detection solution containing N, Fe, and Mn-CDs with the solution to be tested; 2) The mixed solution was allowed to stand for 5 to 10 minutes before fluorescence detection.

6. The use according to claim 5, characterized in that: The detection solution is prepared by diluting N, Fe, Mn-CDs 200-1000 times with HAc-NaAc buffer solution with a pH of 3.0-5.0.

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