Preparation method of metal-doped carbon dots and application thereof

Abstract

The application provides a preparation method of metal-doped carbon dots, comprising the following steps: drying an aqueous solution of reactants containing ethylenediaminetetraacetate, Cu 2+ and Fe 3+ , high-temperature pyrolysis, acid washing, water washing, methanol purification and filtering, and drying at 60 DEG C to obtain the metal-doped carbon dots. The phenol measurement steps provided by the application are as follows: mixing a sample solution with a buffer solution, a 4-aminoantipyrine solution and a carbon dot solution, incubating to obtain a solution A, and measuring the absorbance of the solution A at 509 nm for quantitative analysis. The measurement steps of dimethoate provided by the application are as follows: mixing a sample solution with a acetylcholinesterase solution, incubating for half an hour, adding a acetylthiocholine chloride solution and incubating for another half an hour, adding a solution A, and incubating for half an hour before fluorescence measurement. The synthesis method provided by the application is simple, the detection method has high sensitivity and small interference, and is suitable for simultaneous detection of phenol and dimethoate in actual samples.

Description

Technical Field

[0001] This invention relates to the preparation and application of metal-doped carbon nanodots, belonging to the field of nanomaterials technology. Background Technology

[0002] Phenolic compounds are a common class of toxic substances with wide-ranging sources, including coal chemical, plastics, textile, and dye industries. Even low concentrations of phenol in water can damage the lungs and kidneys in humans. Dimethoate is an important organophosphate pesticide commonly used to control pests on crops. Dimethoate residues in water and food can cause serious health problems in humans, including memory loss, anxiety, and depression. Studies have shown that high levels of exposure to dimethoate can lead to cancer and death. Due to highly developed human industrial and agricultural activities, and the environmental persistence of phenols and organophosphate pesticides, their remediation and degradation in the environment are difficult, increasing the risk of their long-term coexistence in contaminated sites. Therefore, simultaneous detection of both pollutants is crucial for assessing the pollution levels of the environment and water bodies.

[0003] However, since phenol and dimethoate are different types of pollutants, they are usually detected separately (Journal of Separation Science.2018,41(15):3097; Journal of Colloid and Interface Science.2019,554:603; Chempluschem.2023,88(7):202300247; Sensors and Actuators B-Chemical.2020,303:127225), and there are few reports in the literature on the simultaneous detection of the two pollutants. Therefore, it is very important to develop a rapid, convenient, and sensitive method for the simultaneous detection of phenol and dimethoate. Summary of the Invention

[0004] The technical problem solved by this invention is to provide a method for preparing and applying metal-doped carbon dots, enabling convenient and rapid simultaneous detection of phenol and dimethoate. The specific technical solution is as follows:

[0005] A method for preparing metal-doped carbon dots includes the following steps:

[0006] (1) Obtain an aqueous solution of reactants, wherein the aqueous solution of reactants contains ethylenediaminetetraacetic acid ions and Cu. 2+ and Fe 3+ ;

[0007] (2) The aqueous solution of the reactants is dried at 70°C and then placed in a high-temperature tube furnace. The temperature is raised to the pyrolysis temperature at 5°C / min in a N2 atmosphere and maintained at the pyrolysis temperature for 2 hours.

[0008] (3) The product was transferred to a 0.5M H2SO4 solution and stirred at 60℃ for 8 hours. After centrifugation at 10000rpm, the lower solid particles were collected, washed with three distilled water until neutral, and dried at 60℃ to collect the crude product.

[0009] (4) The crude product was dispersed in anhydrous methanol and stirred for 15 minutes. After centrifugation at 10,000 rpm twice, it was filtered through a 0.22 μm membrane. The filtrate was dried at 60 °C to obtain metal-doped carbon dots.

[0010] Preferably, the concentration of ethylenediaminetetraacetic acid (EDTA) is 0.5-1.0 M.

[0011] Preferably, the ethylenediaminetetraacetic acid ion and the Cu 2+ The molar ratio is 1:(0.3~0.7).

[0012] Preferably, the ethylenediaminetetraacetic acid ion and the Fe 3+ The molar ratio is 1:(0.3~0.7).

[0013] Preferably, the pyrolysis temperature is 250℃~350℃.

[0014] A method for measuring phenol, comprising the following steps:

[0015] (1) Mix 200 μL of sample with 50 μL of 0.2 M tris(hydroxymethyl)aminomethane-hydrochloric acid buffer and 20 μL of 2 mM 4-aminoantipyrine solution and shake well.

[0016] (2) Add 50 μL of metal-doped carbon dot solution;

[0017] (3) Incubate the above mixed solution at 70°C for 30 minutes to obtain solution A;

[0018] (4) Measure the UV-Vis spectrum of solution A and perform quantitative analysis based on the absorbance at 509 nm.

[0019] Preferably, the concentration of carbon dots in the metal-doped carbon dot solution is 0.2–0.5 mg / mL.

[0020] A method for measuring dimethoate includes the following steps:

[0021] (1) Mix 10 μL of sample with 50 μL of 0.2 M tris(hydroxymethyl)aminomethane-hydrochloric acid buffer and 50 μL of 50 mU / mL acetylcholinesterase solution and shake well.

[0022] (2) After incubating the above solution at 37°C for 30 minutes, add 50 μL of acetylthiocholine chloride solution and incubate at 37°C for 30 minutes.

[0023] (3) Add solution A and incubate at 37°C for 30 minutes to obtain solution B;

[0024] (4) Fluorescence spectroscopy analysis was performed on solution B. The excitation wavelength was 350 nm, and the emission intensity at 440 nm was used for quantitative analysis.

[0025] Preferably, the concentration of acetylthiocholine chloride in the acetylthiocholine chloride solution is 50–100 μM.

[0026] The iron-copper doped carbon dots synthesized using the method of this invention possess oxidase properties, catalyzing the reaction of phenol with 4-aminoantipyrine for colorimetric detection. Furthermore, these carbon dots can bind to mercaptocholine, a product of acetylthiocholine chloride enzymatic hydrolysis, causing a significant change in fluorescence emission intensity, thus enabling the detection of dimethoate. Although both phenol and mercaptocholine are reducing compounds, the carbon dots synthesized using the method of this invention do not interfere with each other in detection. The method provided by this invention offers short sample processing time, simple operation, and can be used for the detection of contaminants in complex samples. Attached Figure Description

[0027] Figure 1 TEM characterization of Fe / Cu-CDs. HRTEM image (A); particle size distribution map (B)

[0028] Figure 2 XPS analysis of Fe / Cu-CDs. XPS measurement spectra of Fe / Cu-CDs (A); N1s (B); high-resolution XPS spectra of Cu2p (C) and Fe2p (D).

[0029] Figure 3 UV-Vis absorption spectra of phenol at different concentrations (A); Standard curve of phenol (B)

[0030] Figure 4 Fluorescence spectra of the probe at different concentrations of dimethoate (A); Standard curve of dimethoate (B)

[0031] Figure 5 Selectivity of phenol detection

[0032] Figure 6 Selectivity of dimethoate detection. No dimethoate added (A); Dimethoate added (B) Detailed Implementation

[0033] The inventors discovered in their research that, during the synthesis of iron-copper metal-doped carbon dots (Fe / Cu-CDs), adjusting the molar ratio of [Fe(EDTA)(H2O)]Na·H2O to Na2[Cu(EDTA)] in the initial solution, the Fe / Cu-CDs generated after high-temperature pyrolysis not only possess the characteristics of oxidases but also strongly bind to thiol compounds, with these two effects not interfering with each other. Based on this, the present invention provides a method for the preparation and application of metal-doped carbon dots, enabling convenient and rapid simultaneous detection of phenol and dimethoate. The specific scheme is as follows:

[0034] A method for preparing metal-doped carbon dots includes the following steps:

[0035] (1) Obtain an aqueous solution of reactants, wherein the aqueous solution of reactants contains ethylenediaminetetraacetic acid ions and Cu. 2+ and Fe 3+ ;

[0036] (2) The aqueous solution of the reactants is dried at 70°C and then placed in a high-temperature tube furnace. The temperature is raised to the pyrolysis temperature at 5°C / min in a N2 atmosphere and maintained at the pyrolysis temperature for 2 hours.

[0037] (3) The product was transferred to a 0.5M H2SO4 solution and stirred at 60℃ for 8 hours. After centrifugation at 10000rpm, the lower solid particles were collected, washed with three distilled water until neutral, and dried at 60℃ to collect the crude product.

[0038] (4) The crude product was dispersed in anhydrous methanol and stirred for 15 minutes. After centrifugation at 10,000 rpm twice, it was filtered through a 0.22 μm membrane. The filtrate was dried at 60 °C to obtain metal-doped carbon dots.

[0039] The concentration of the ethylenediaminetetraacetic acid (EDTA) ion is 0.5-1.0 M; the EDTA ion and the Cu 2+ The molar ratio is 1:(0.3-0.7); the ethylenediaminetetraacetic acid ion and the Fe 3+ The molar ratio is 1:(0.3~0.7); the pyrolysis temperature is 250℃~350℃.

[0040] A method for measuring phenol, comprising the following steps:

[0041] (1) Mix 200 μL of sample with 50 μL of 0.2 M tris(hydroxymethyl)aminomethane-hydrochloric acid buffer and 20 μL of 2 mM 4-aminoantipyrine solution and shake well.

[0042] (2) Add 50 μL of metal-doped carbon dot solution;

[0043] (3) Incubate the above mixed solution at 70°C for 30 minutes to obtain solution A;

[0044] (4) Measure the UV-Vis spectrum of solution A and perform quantitative analysis based on the absorbance at 509 nm.

[0045] The concentration of carbon dots in the metal-doped carbon dot solution is 0.2–0.5 mg / mL.

[0046] A method for measuring dimethoate includes the following steps:

[0047] (1) Mix 10 μL of sample with 50 μL of 0.2 M tris(hydroxymethyl)aminomethane-hydrochloric acid buffer and 50 μL of 50 mU / mL acetylcholinesterase solution and shake well.

[0048] (2) After incubating the above solution at 37°C for 30 minutes, add 50 μL of acetylthiocholine chloride solution and incubate at 37°C for 30 minutes.

[0049] (3) Add solution A and incubate at 37°C for 30 minutes to obtain solution B;

[0050] (4) Fluorescence spectroscopy analysis was performed on solution B. The excitation wavelength was 350 nm, and the emission intensity at 440 nm was used for quantitative analysis.

[0051] The concentration of acetylthiocholine chloride in the acetylthiocholine chloride solution is 50–100 μM.

[0052] To further understand the present invention, the synthesis and measurement methods provided by the present invention will be described in detail below with reference to the embodiments. The scope of protection of the present invention is not limited by the following embodiments.

[0053] Unless otherwise specified, the experimental methods described in the following examples are conventional methods; unless otherwise specified, the reagents and materials are commercially available.

[0054] Example 1: Synthesis and Characterization of Metal-Doped Carbon Dots

[0055] 1.1 Synthesis of Metal-Doped Carbon Dots

[0056] Prepare a 10 mL solution containing 0.15 M [Fe(EDTA)(H2O)]Na·H2O and 0.35 M Na2[Cu(EDTA)]. After sonication for 1 h, dry at 70 °C. Place the powder in a quartz boat in a high-temperature tube furnace. Before the reaction, purge with nitrogen for 30 min. Then, in a N2 atmosphere, heat to 250 °C at 5 °C / min and maintain this temperature for 2 h for pyrolysis. Transfer the collected black product to 10 mL of 0.5 M H2SO4 solution and stir at 60 °C for 8 h to remove Fe particles. Wash with water until neutral, dry at 60 °C, and collect the sample. Disperse the sample in 80 mL of anhydrous methanol to remove insoluble iron, copper, and sodium salts. Stir the dark suspension for 15 min, centrifuge twice at high speed (10000 rpm, 20 min), and filter through a 0.22 μm membrane to remove carbon fragments. Finally, dry the filtrate at 60 °C to obtain iron-copper doped carbon dots (Fe / Cu-CDs).

[0057] 1.2 Characterization of Fe / Cu-CDs

[0058] 1.2.1 Transmission Electron Microscopy Characterization

[0059] The morphology of Fe / Cu-CDs was characterized by high-resolution transmission microscopy (HRTEM). Figure 1 As shown in Figure A, these carbon dots are uniformly dispersed, with no obvious aggregation observed. Morphologically, Fe / Cu-CDs mainly exhibit a spherical structure. Figure 1 B. Particle size statistical analysis showed that the particle size of Fe / Cu-CDs was mainly concentrated in the range of 2 to 6 nm, with an average particle size of 4.0 nm.

[0060] 1.2.2 X-ray photoelectron spectroscopy characterization

[0061] The presence of elements such as C, O, N, Fe, and Cu was detected by X-ray photoelectron spectroscopy (XPS). Figure 2 A). The atomic percentages of Cu and Fe are 2.39% and 2.33%, respectively, which indicates that the two elements have been successfully doped into the carbon matrix.

[0062] For Fe, high-resolution Fe2p XPS analysis showed the presence of Fe. 3+ and Fe 2+ Two valence states, just as Figure 2 As shown in D, Fe2p 3 / 2 Fe in the orbital close to 711 eV 2+ The signal can be attributed to the presence of Fe-Nx sites. In the obtained Fe / Cu-CDs, Fe2p 3 / 2 Fe 2+The peak position shifted slightly because O also participated in the coordination process, indicating that the single atom center exists in the form of Fe-O / N.

[0063] For Cu, XPS spectral analysis mainly focused on the 930-935 and 940-945 μm values ​​(Cu2p). 3 / 2 ), 950-960 (Cu2p) 1 / 2 Three signals were observed at 938-943 (satellite peak) eV. Figure 2 C). The peaks for Cu2p3 / 2 and Cu2p1 / 2 are at 933.3 and 953.3 eV, respectively, attributed to CuO; while the peaks at 943.2 and 961.5 eV are attributed to CuO. 2+ .

[0064] Furthermore, the N1s XPS spectrum of Fe / Cu-CD shows that the N element can be divided into three peaks at 398.4, 399.1, and 400.9 eV. Figure 2 (B) Among them, the peak at 398.4 eV is from pyridine N, and the peak at 399.1 eV is attributed to pyrrole N. Both of these N species contribute to the formation of a π-conjugated system to anchor Fe and Cu sites.

[0065] Example 2: Establishment of standard curves for phenol and dimethoate

[0066] 2.1 Synthesis of Fe / Cu-CDs

[0067] Prepare a 10 mL solution containing 0.7 M [Fe(EDTA)(H2O)]Na·H2O and 0.3 M Na2[Cu(EDTA)], sonicate for 1 h, and dry at 70 °C. Then, place the powder in a quartz boat in a high-temperature tube furnace. Before the reaction, purge with nitrogen for 30 min, then heat to 350 °C at 5 °C / min in a N2 atmosphere and maintain the temperature for pyrolysis for 2 h. Transfer the collected black product to 10 mL of 0.5 M H2SO4 solution and stir at 60 °C for 8 h to remove Fe particles. Wash with water until neutral, dry at 60 °C, and collect the sample. Disperse the sample in 80 mL of anhydrous methanol to remove insoluble iron, copper, and sodium salts. Stir the dark suspension for 15 min, centrifuge twice at high speed (10000 rpm, 20 min), and filter through a 0.22 μm membrane to remove carbon fragments. Finally, dry the filtrate at 60 °C to obtain iron-copper doped carbon dots (Fe / Cu-CDs).

[0068] 2.2 Establishment of the phenol standard curve

[0069] 200 μL of phenol standard solution was mixed with 50 μL of 0.2 M Tris-HCl buffer and 20 μL of 2 mM 4-aminoantipyrine (4-AAP) solution and shaken well. Then, 50 μL of 0.2 mg / mL Fe / Cu-CDs solution was added. The mixture was incubated at 70 °C for 30 minutes to obtain solution A. The UV-Vis spectrum of solution A was measured, and quantitative analysis was performed based on the net absorbance at 509 nm (ΔA, peak height minus baseline).

[0070] like Figure 3 As shown, the UV-Vis absorption gradually increases with increasing phenol concentration; within the concentration range of 0.5-100 μM, there is a good linear relationship between the phenol concentration and the UV absorption response signal ΔA at 502 nm, with the linear equation being ΔA = 0.00284C. 苯酚 -0.00339(R 2 =0.9973), and the detection limit was calculated to be 0.103 μM.

[0071] 2.3 Establishment of the standard curve for dimethoate

[0072] 10 μL of dimethoate standard solution was mixed with 50 μL of 0.2 M Tris-HCl buffer and 50 μL of 50 mU / mL acetylcholinesterase solution and shaken well. The mixture was incubated at 37 °C for 30 minutes. Then, 50 μL of 50 μM acetylthiocholine chloride solution was added and incubated at 37 °C for 30 minutes. Solution A was then added and incubated at 37 °C for 30 minutes to obtain solution B. Fluorescence spectroscopy analysis was performed on solution B with an excitation wavelength of 350 nm. Quantitative analysis was performed using the emission intensity increment (ΔF, with the emission intensity at a dimethoate concentration of 0 as a reference) at 440 nm.

[0073] like Figure 4 As shown in Figure A, the fluorescence intensity gradually decreases with increasing pesticide concentration. To quantitatively describe this relationship, the logarithm of pesticide concentration was plotted against the fluorescence intensity increment ΔF at 440 nm. Linear regression analysis revealed that the fluorescence intensity at a pesticide concentration of 10... -4 A good linear relationship was observed between the concentration and ΔF in the range up to 5 μg / mL. Figure 4 B). The linear equation is ΔF = 869.3lgC. 乐果 +5037.7(R 2 =0.9907). The calculated limit of detection is 1.94 × 10⁻⁶. -5 μg / mL.

[0074] Example 3: Comparison with existing methods

[0075] 3.1 Detection of Phenol

[0076] Table 1 lists the methods for phenol detection using different materials in recent years and their corresponding detection limits. The data in the table show that the detection limit for Fe / Cu-CDs is 0.1030 μM, which is better than other reported colorimetric methods, indicating that Fe / Cu-CDs is a material with excellent phenol detection capabilities.

[0077] Table 1 Comparison of different detection methods for phenol

[0078]

[0079] 3.2 Detection of Dimethoate

[0080] Numerous reports have been published on the detection of the pesticide dimethoate. Table 2 lists the methods for dimethoate detection using different materials and their corresponding limits of detection in recent years. The data shows that the limit of detection for Fe / Cu-CDs is 0.0194 ng / mL, which demonstrates better performance compared to other reported methods, indicating that Fe / Cu-CDs is a material with excellent pesticide detection capabilities.

[0081] Table 2 Comparison of different detection methods for dimethoate

[0082]

[0083]

[0084] References in the table

[0085] [1]Darabdhara G,Das MR.Dual responsive magnetic Au@Ni nanostructuresloaded reduced graphene oxide sheets for colorimetric detection and photocatalytic degradation of toxic phenolic compounds[J].Journal ofHazardous Materials.2019,368:365.

[0086] [2]Wang J,Zhou Y,Zeng M,et al.Zr(IV)-based metal-organic frameworknanocomposites with enhanced peroxidase-like activity as a colorimetricsensing platform for sensitive detection of hydrogen peroxide and phenol[J].Environmental Research.2022,203:111818.

[0087] [3]Wu S,Guo D,Xu X,et al.Colorimetric quantification anddiscrimination of phenolic pollutants based peroxidase-like Fe3O4nanoparticles[J].Sensors and Actuators B-Chemical.2020,303:127225.

[0088] [4]Luo M,Wan D,Chang F.Two-dimensional Ni / Co bimetal pyrophosphatenanosheets for sensitive electrochemical detection of phenol[J].InternationalJournal of Electrochemical Science.2024,19(1):100453.

[0089] [5]Hu C,Huang H,Yan Y,et al.Simple Synthesis of CeO2 NanoparticleComposites In Situ Grown on Carbon Nanotubes for Phenol Detection[J].Frontiers in Chemistry.2022,10:907777.

[0090] [6]Yin HY,Zheng YF,Wang L.Au / CeO2 / g-C3N4 Nanocomposite ModifiedElectrode as Electrochemical Sensor for the Determination of Phenol[J].Journal of Nanoscience and Nanotechnology.2020,20(9):5539.

[0091] [7]Patel S,Shrivas K,Sinha D,et al.Smartphone-integrated printed-paper sensor designed for on-site determination of dimethoate pesticide infood samples[J].Food Chemistry.2022,383:132449.

[0092] [8]Amirzehni M,Hassanzadeh J,Vahid B.Surface imprinted CoZn-bimetalicMOFs as selective colorimetric probe:Application for detection of dimethoate[J].Sensors and Actuators B-Chemical.2020,325:128768.

[0093] [9]He J,Song L,Chen S,et al.Novel restricted access materialscombined to molecularly imprinted polymers for selective solid-phaseextraction of organophosphorus pesticides from honey[J].Food Chemistry.2015,187:331.

[0094]

[10] Du D,Chen S,Cai J,et al.Recognition of dimethoate carried by bi-layerposition electrode of silver nanoparticles and imprinted poly-o-phenylenediamine[J].Electrochimica Acta.2008,53(22):6589.

[0095]

[11] Vahid B.Specific Fluorescence Probe for Direct Recognition ofDimethoate Using Molecularly Imprinting Polymer on ZnO Quantum Dots[J].Journal of Fluorescence.2017,27(4):1339.

[0096]

[12] Lu TT, Wang JL, Zhan XQ, et al. Carbon Dots-based Fluorescent Aptasensor for Detection of Dimethoate Pesticide[J]. Chinese Journal of Analytical Chemistry. 2020, 48(1):74. Example 4, Method Selectivity

[0097] 4.1 Synthesis of Fe / Cu-CDs

[0098] Similar to 1.1 in Example 1, except that the initial reaction solution is 10 mL of a solution containing 0.35 M [Fe(EDTA)(H2O)]Na·H2O and 0.15 M Na2[Cu(EDTA)].

[0099] 4.2 Selectivity of phenol detection

[0100] To verify the selectivity of Fe / Cu-CDs as nanozymes for phenol detection, NaCl, Na2SO4, NaNO3, Na2CO3, acetone, cyclohexane, ethanol, and acetonitrile at concentrations of 3 mM were selected as potential interfering substances, and a 30 μM phenol solution was prepared as the test solution.

[0101] 200 μL of the above solution was added to 50 μL of 0.2 M Tris-HCl buffer (pH = 7.8), followed by 20 μL of 4-AAP (2 mM), and finally 50 μL of 0.5 mg / mL Fe / Cu-CDs. The solution was incubated at 70 °C for 30 minutes to obtain solution A, and the UV-Vis spectrum of solution A was measured.

[0102] Experimental results are as follows Figure 5 As shown, the presence of these interfering substances has almost no significant impact on the detection of phenol. This indicates that the method of the present invention has good selectivity and can achieve specific detection of phenol in complex environmental samples.

[0103] 4.3 Selectivity of Dimethoate Detection

[0104] To investigate the selectivity of the Fe / Cu-CDs probe for the detection of dimethoate, 10 mM NaCl, MgCl2, KCl, CaCl2, glycine, sarcosine, cysteine, and methionine were selected as potential interfering substances. At the same time, a 0.1 μg / mL (0.43 μM) dimethoate solution was prepared as the analyte.

[0105] Add 10 μL of the above solution to 50 μL of 0.2 M Tris-HCl buffer (pH = 7.8), then add 50 μL of 50 mU / mL acetylcholinesterase, and incubate at 37 °C for 30 minutes. Next, add 50 μL of 100 μM acetylthiocholine chloride and incubate at 37 °C for 30 minutes. Then add solution A from step 4.2, mix well, and incubate at 37 °C for 30 minutes to obtain solution B. Measure the fluorescence intensity of solution B at 440 nm.

[0106] 10 μL of triple-distilled water was used as a blank sample (with a dimethoate concentration of 0). After treatment under the same conditions as the previous experiment, the fluorescence intensity at 440 nm was measured. Finally, dimethoate was added to different interfering substances, and incubation and fluorescence detection were performed under the same conditions.

[0107] from Figure 6 As can be seen, the value of ΔF is much smaller when dimethoate is not added than when dimethoate is added. This indicates that the detection system has a weaker response in the absence of the target pesticide, effectively eliminating interference from other non-target substances.

[0108] When dimethoate was added to these substances, the ΔF value was close to that when dimethoate was added alone. This result indicates that the detection system can produce a strong response as long as the target pesticide dimethoate is present, regardless of the presence of other substances. The above results demonstrate that the detection method has high selectivity for pesticides and can accurately identify target pesticides in complex environments. Example 5: Detection of environmental pollutants in actual samples

[0109] 5.1 Synthesis of Fe / Cu-CDs

[0110] Similar to 2.1 in Example 2, except that the initial reaction solution is 10 mL of a solution containing 0.3 M [Fe(EDTA)(H2O)]Na·H2O and 0.7 M Na2[Cu(EDTA)].

[0111] 5.2 Sample Preparation

[0112] 5.2.1 Treatment of Phenol-Containing Samples

[0113] Tap water and river water (North Moat, Beijing) from the laboratory were selected as samples for testing. First, both water samples were filtered through a 0.45 μM filter membrane to remove impurities. Then, three different concentrations of phenol (final detection concentrations of 5, 25, and 50 μM) were added to the two treated water samples.

[0114] 5.2.2 Treatment of samples containing dimethoate

[0115] The experiment selected tap water, river water, chives, and cabbage as actual samples for the detection of dimethoate.

[0116] First, the samples were pretreated. Water samples (tap water and river water) were filtered through a 0.45 μM filter membrane to remove impurities. Vegetable samples (1 g each of chives and cabbage) were chopped and crushed. Then, 15 mL of acetonitrile was added to a beaker containing the two vegetables, and the mixture was stirred vigorously for 30 minutes. Next, 5 mL of 1 M sodium chloride aqueous solution was added to facilitate the separation of water and acetonitrile. The separated acetonitrile solution was centrifuged at 12000 rpm for 30 minutes. The supernatant was then filtered and diluted 10-fold for subsequent experiments.

[0117] Next, the four prepared solutions were added with different concentrations of dimethoate, resulting in spiked concentrations of 0.05, 0.1, and 0.15 μg / mL.

[0118] 5.3 Detection of phenol in samples

[0119] The steps are the same as in 2.2.

[0120] Table 3 lists the detection results and recovery rates of phenol at different concentrations in laboratory tap water and river water. Whether it is tap water or river water samples, the Fe / Cu-CDs catalyzed colorimetric method can accurately detect spiked phenol, and the recovery rates are all between 89.6% and 112%. This shows that the method has good accuracy and reliability in practical applications.

[0121] Table 3. Detection of phenol in actual samples (n=3)

[0122]

[0123] 5.4 Detection of dimethoate in samples

[0124] The steps are the same as in 2.3.

[0125] The experimental results in Table 4 show that the recovery rate and relative standard deviation of each concentration are within the allowable error range. These results indicate that the detection method can be used to detect dimethoate in actual samples.

[0126] Table 4. Detection of pesticides in actual samples (n=3)

[0127]

[0128]

[0129] The above embodiments are merely illustrative of the method and core ideas of this invention. It should be noted that those skilled in the art can make various improvements and modifications to this invention without departing from its principles, and these improvements and modifications also fall within the scope of protection of the claims of this invention.

Claims

1. A method for measuring phenol, comprising the following steps: (1) Mix 200 µL of sample with 50 µL of 0.2 M tris(hydroxymethyl)aminomethane-hydrochloric acid buffer and 20 µL of 2 mM 4-aminoantipyrine solution and shake well; (2) Add 50 µL of metal-doped carbon dot solution; (3) Incubate the above mixed solution at 70°C for 30 minutes to obtain solution A; (4) Measure the UV-Vis spectrum of solution A and perform quantitative analysis based on the absorbance at 509 nm; The method for preparing the metal-doped carbon dots includes the following steps: (a) Obtaining an aqueous solution of reactants, said aqueous solution containing ethylenediaminetetraacetic acid (EDTA) and Cu. 2+ and Fe 3+ ; (b) The aqueous solution of the reactants was dried at 70°C and then placed in a high-temperature tube furnace and heated to 350°C at 5°C / min in a N2 atmosphere and held for 2 hours. (c) The product was transferred to a 0.5 M H2SO4 solution, stirred at 60 °C for 8 h, centrifuged at 10000 rpm, and the lower solid particles were collected. The product was washed with triple-distilled water until neutral, dried at 60 °C, and the crude product was collected. (d) The crude product was dispersed in anhydrous methanol, stirred for 15 minutes, centrifuged twice at 10,000 rpm, filtered through a 0.22 μm membrane, and the filtrate was dried at 60 °C to obtain metal-doped carbon dots.

2. The measurement method according to claim 1, characterized in that, In the method for preparing metal-doped carbon dots, the concentration of ethylenediaminetetraacetic acid (EDTA) is 0.5-1.0 M.

3. The measurement method according to claim 1, characterized in that, In the method for preparing the metal-doped carbon dots, ethylenediaminetetraacetic acid (EDTA) and Cu 2+ The molar ratio is 1:(0.3~0.7).

4. The measurement method according to claim 1, characterized in that, In the method for preparing the metal-doped carbon dots, ethylenediaminetetraacetic acid (EDTA) and Fe... 3+ The molar ratio is 1:(0.3~0.7).

5. The measurement method according to claim 1, characterized in that, The concentration of metal-doped carbon dots in the solution is 0.2~0.5 mg / mL.

6. A method for measuring dimethoate, comprising the following steps: (1) Mix 10 µL of sample with 50 µL of 0.2 M tris(hydroxymethyl)aminomethane-hydrochloric acid buffer and 50 µL of 50 mU / mL acetylcholinesterase solution and shake well. (2) After incubating the above solution at 37°C for 30 minutes, add 50 µL of acetylthiocholine chloride solution and incubate at 37°C for 30 minutes. (3) Add the solution A described in claim 1, and incubate at 37°C for 30 minutes to obtain solution B; (4) Fluorescence spectroscopy analysis was performed on solution B. The excitation wavelength was 350 nm, and the emission intensity at 440 nm was used for quantitative analysis.

7. The measurement method according to claim 6, characterized in that, The concentration of acetylthiocholine chloride in the acetylthiocholine chloride solution is 50~100 µM.

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