Single-atom / nitrogen-doped carbon sphere material and preparation method and application thereof

Abstract

The application discloses a kind of single-atom / nitrogen doped carbon sphere materials and preparation method and application thereof, it is related to electrochemical detection technical field, the preparation method includes the following steps: glucose and cetyltrimethylammonium bromide are added in deionized water and carry out hydrothermal reaction, and carbon sphere is obtained;Carbon sphere is mixed with urea and grinds, calcination, and nitrogen-doped carbon sphere is obtained;Metal salt solution is added to nitrogen-doped carbon sphere suspension and is stirred, then after filtration, washing and drying, finally, under nitrogen atmosphere, calcination, and single-atom / nitrogen doped carbon sphere material is obtained.The application also discloses the single-atom / nitrogen doped carbon sphere material prepared by the method and its application in electrochemical detection of organic pesticide.The single metal atom is anchored on the vacancy on the nitrogen-doped carbon sphere in the application, and the sensitivity, detection limit, selectivity, stability and anti-interference ability when it is used for electrochemical detection of organic pesticide are significantly optimized, which has important practical application value.

Description

Technical Field

[0001] This invention relates to the field of electrochemical detection technology, specifically to a single-atom / nitrogen-doped carbon sphere material, its preparation method, and its application. Background Technology

[0002] Carbendazim, a broad-spectrum benzimidazole organic pesticide, is widely used for disease control in vegetables, fruits, grains, and other crops. However, carbendazim easily leaves residues in the environment and, after entering the human body through the food chain, can interfere with the endocrine system and damage organs such as the liver and kidneys. Therefore, establishing a highly sensitive and rapid detection method for carbendazim is of great significance.

[0003] Currently, the main detection methods for carbendazim include high-performance liquid chromatography (HPLC), gas chromatography-mass spectrometry (GC-MS), and enzyme-linked immunosorbent assay (ELISA). While HPLC and GC-MS offer high accuracy, they require complex sample pretreatment processes, are costly to operate, and are time-consuming, making rapid on-site detection difficult. Although ELISA is simple to operate, the antibodies are susceptible to environmental factors, exhibiting poor stability and a narrow detection range.

[0004] Electrochemical detection methods have gained widespread attention in pesticide residue detection due to their advantages such as ease of operation, rapid response, low cost, and easy miniaturization. Their detection performance mainly depends on the sensitive material on the working electrode surface. Traditional sensitive materials, such as carbon nanotubes and graphene, suffer from problems such as few active sites and low electron conduction efficiency, resulting in insufficient sensitivity and selectivity for the detection of carbendazim.

[0005] Single-atom materials exhibit excellent catalytic performance in electrochemistry due to their atomically dispersed active sites, extremely high atomic utilization, and unique electronic structure. However, single-atom metals are prone to aggregation, requiring the selection of suitable supports to achieve stable dispersion. Nitrogen-doped carbon materials, with their good electronic conductivity, large specific surface area, and abundant nitrogen coordination sites, can anchor single-atom metals through metal-nitrogen coordination interactions, effectively inhibiting aggregation and enhancing the electrochemical activity of the material. However, existing nitrogen-doped carbon-supported single-atom metal materials still suffer from low active site utilization, high detection limits, and poor anti-interference capabilities in the detection of carbendazim, making it difficult to meet practical detection requirements. Summary of the Invention

[0006] To address the aforementioned technical problems, the present invention aims to provide a single-atom / nitrogen-doped carbon sphere material, its preparation method, and its application. By anchoring single metal atoms on the vacancies of nitrogen-doped carbon spheres, the present invention significantly optimizes the sensitivity, detection limit, selectivity, stability, and anti-interference ability when used for the electrochemical detection of organic pesticides, and has significant practical application value.

[0007] The technical solution of this invention to solve the above-mentioned technical problems is as follows: A method for preparing single-atom / nitrogen-doped carbon sphere materials is provided, comprising the following steps: (1) Add glucose and hexadecyltrimethylammonium bromide to deionized water and mix well. Then carry out a hydrothermal reaction, and then filter, wash and dry to obtain carbon spheres. (2) The carbon balls obtained in step (1) are mixed with urea and then ground, and then calcined under a nitrogen atmosphere to obtain nitrogen-doped carbon balls; (3) Add the nitrogen-doped carbon spheres obtained in step (2) to deionized water and mix evenly to obtain a nitrogen-doped carbon sphere suspension. Then add a metal salt solution and stir. After filtration, washing and drying, calcination is carried out under a nitrogen atmosphere to obtain a single-atom / nitrogen-doped carbon sphere material.

[0008] Furthermore, the mass-to-volume ratio of glucose, hexadecyltrimethylammonium bromide, and deionized water is 1.5-2.5 g: 0.15-0.2 g: 30 mL.

[0009] Furthermore, in step (1), the hydrothermal reaction is carried out at a temperature of 170-190℃ for 4-6 h.

[0010] Furthermore, in step (2), the mass ratio of carbon spheres to urea is 1.5-2.5:1.

[0011] Furthermore, in steps (2) and (3), the sample is calcined at 850-950℃ for 1-3 h.

[0012] Furthermore, in step (3), the metal salt solution is one of ferric chloride solution, cobalt chloride solution and nickel chloride solution.

[0013] Furthermore, the concentration of the nitrogen-doped carbon sphere suspension was 4-6 mg / mL; the concentration of the metal salt solution was 0.04-0.06 mM; and the volume ratio of the nitrogen-doped carbon sphere suspension to the metal salt solution was 1:1.

[0014] The present invention also provides a single-atom / nitrogen-doped carbon sphere material prepared by the above-mentioned method for preparing single-atom / nitrogen-doped carbon sphere material.

[0015] The present invention also provides the application of the above-mentioned single-atom / nitrogen-doped carbon sphere material in the electrochemical detection of organic pesticides.

[0016] Furthermore, the aforementioned organic pesticide is carbendazim.

[0017] The present invention also provides an electrode for detecting organic pesticides, which is made of the above-mentioned single-atom / nitrogen-doped carbon sphere material.

[0018] Furthermore, the electrode used for detecting organic pesticides is prepared by dropping a suspension of single-atom / nitrogen-doped carbon spheres onto a glassy carbon electrode and then drying it.

[0019] The present invention has the following beneficial effects: 1. The single-atom / nitrogen-doped carbon sphere material provided by the present invention significantly reduces the detection limit for electrochemical detection of organic pesticides, significantly improves sensitivity, repeatability and anti-interference ability, and has high storage stability.

[0020] 2. When the electrode prepared using the single-atom / nitrogen-doped carbon sphere material of the present invention is used for the detection of carbendazim, the linearity is 0.001-20 μmol / L, the detection limit is as low as 0.2 nmol / L, and the sensitivity can reach 4.61 μA / (μmol / L). Attached Figure Description

[0021] Figure 1 SEM images of different single-atom / nitrogen-doped carbon sphere materials; Figure 2 TEM, HRTEM, and EDS images of Fe single-atom / nitrogen-doped carbon spheres (Fe SAs / N-CSs); Figure 3 TEM, HRTEM, and EDS images of Co single-atom / nitrogen-doped carbon spheres (Co SAs / N-CSs); Figure 4 TEM, HRTEM, and EDS images of Ni single-atom / nitrogen-doped carbon sphere materials (Ni SAs / N-CSs); Figure 5 XRD patterns of different single-atom / nitrogen-doped carbon sphere materials; Figure 6 XPS images of different single-atom / nitrogen-doped carbon sphere materials; Figure 7 Differential pulse voltammetric curves for detecting carbendazim using different electrodes, along with a comparison of electrode sensitivity and detection limit; Figure 8 The image shows the results of detecting carbendazim using the electrode in Example 4 in an interfering solution containing diuron; Figure 9 The image shows the results of detecting carbendazim using the electrode in Example 4 in an interfering solution containing diphenylamine. Figure 10 The image shows the results of detecting carbendazim using the electrode in Example 4 in a bisphenol A-interfering solution; Figure 11 The image shows the results of detecting carbendazim using the electrode in Example 4 in an ascorbic acid-interfering solution; Figure 12 The image shows the results of detecting carbendazim using the electrode in Example 4 in an interfering solution containing urea. Figure 13 The image shows the results of detecting carbendazim using the electrode in Example 4 in an interfering solution containing glucose. Figure 14 The image shows the results of detecting carbendazim using the electrode in Example 4 in an interference solution containing magnesium ions; Figure 15 The image shows the results of detecting carbendazim using the electrode in Example 4 in an interference solution containing copper ions; Figure 16 The image shows the results of detecting carbendazim using the electrode in Example 4 in an interference solution containing potassium ions; Figure 17 This is a graph showing the results of the stability verification of carbendazim by electrode detection in Example 4. Detailed Implementation

[0022] The principles and features of this invention are described below. The examples given are for illustrative purposes only and are not intended to limit the scope of the invention. Unless otherwise specified in the examples, conventional conditions or conditions recommended by the manufacturer should be followed. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0023] Example 1 A single-atom / nitrogen-doped carbon sphere material, the preparation method of which includes the following steps: (1) Add glucose and hexadecyltrimethylammonium bromide to deionized water, stir for 60 min to mix evenly, then hydrothermally react at 180℃ for 5 h, filter, wash alternately with deionized water and ethanol, dry to obtain carbon spheres; the mass-volume ratio of glucose, hexadecyltrimethylammonium bromide and deionized water is 1.95 g: 0.18 g: 30 mL; (2) Mix the carbon balls obtained in step (1) with urea at a mass ratio of 2:1 and grind them. Then calcine them at 900°C for 2 h under a nitrogen atmosphere to obtain nitrogen-doped carbon balls (denoted as N-CSs or N-Doped CSs). (3) Add the nitrogen-doped carbon spheres obtained in step (2) to deionized water and mix well to obtain a 5 mg / mL nitrogen-doped carbon sphere suspension. Then add an equal volume of 0.05 mM ferric chloride solution and stir. Filter, wash successively with DMF, deionized water and ethanol, and vacuum dry at 60℃ (to obtain Fe). 3+ The adsorbed nitrogen-doped carbon spheres are denoted as Fe. 3+ The carbon spheres were calcined at 900℃ for 2 h under a nitrogen atmosphere to obtain single-atom / nitrogen-doped carbon spheres (denoted as Fe SAs / N-CSs).

[0024] Example 2 A single-atom / nitrogen-doped carbon sphere material, the preparation method of which includes the following steps: (1) Add glucose and hexadecyltrimethylammonium bromide to deionized water and mix well. Then, perform hydrothermal reaction at 170°C for 4 h. After filtration, washing and drying, carbon spheres are obtained. The mass-volume ratio of glucose, hexadecyltrimethylammonium bromide and deionized water is 1.5 g: 0.15 g: 30 mL. (2) The carbon balls obtained in step (1) are mixed with urea at a mass ratio of 1.5:1 and then ground. The mixture is then calcined at 850°C for 1 h under a nitrogen atmosphere to obtain nitrogen-doped carbon balls. (3) Add the nitrogen-doped carbon spheres obtained in step (2) to deionized water and mix evenly to obtain a 4 mg / mL nitrogen-doped carbon sphere suspension. Then add an equal volume of 0.04 mM cobalt chloride solution and stir. After filtration, washing and drying, calcine at 850℃ for 1 h under nitrogen atmosphere to obtain single-atom / nitrogen-doped carbon sphere material.

[0025] Example 3 A single-atom / nitrogen-doped carbon sphere material, the preparation method of which includes the following steps: (1) Add glucose and hexadecyltrimethylammonium bromide to deionized water and mix well. Then, perform hydrothermal reaction at 190℃ for 6 h. After filtration, washing and drying, carbon spheres are obtained. The mass-volume ratio of glucose, hexadecyltrimethylammonium bromide and deionized water is 2.5 g: 0.2 g: 30 mL. (2) The carbon balls obtained in step (1) are mixed with urea at a mass ratio of 2.5:1 and then ground. The mixture is then calcined at 950°C for 3 h under a nitrogen atmosphere to obtain nitrogen-doped carbon balls. (3) Add the nitrogen-doped carbon spheres obtained in step (2) to deionized water and mix evenly to obtain a 6 mg / mL nitrogen-doped carbon sphere suspension. Then add an equal volume of 0.06 mM nickel chloride solution and stir. After filtration, washing and drying, calcine at 950℃ for 3 h under nitrogen atmosphere to obtain single-atom / nitrogen-doped carbon sphere material.

[0026] Example 4 An electrode for detecting organic pesticides is prepared from the single-atom / nitrogen-doped carbon sphere material of Example 1; the specific steps are as follows: A glassy carbon electrode (GCE) with a diameter of 3 mm was first polished sequentially with alumina powders of 1.0 µm, 0.3 µm, and 0.05 µm, and sonicated in deionized water for 1 min after each polishing stage. Then, the polished electrode was characterized by cyclic voltammetry (CV) at a scan rate of 100 mV / s in a 0.1 M KCl solution containing 0.5 mM K3[Fe(CN)6] until a quasi-reversible redox reaction was observed. Then, 7 μL of an ethanol suspension containing Fe SAs / N-CSs (2 mg / mL) was dropped onto the pretreated GCE, dried at room temperature, and the modified electrode was stored in air for 6 h before use.

[0027] Experimental Example 1 Following the method of Example 1, but with the metal salt solution replaced, Co was obtained. 2+ / N-CSs, Co SAs / N-CSs, Ni 2+ / N-CSs and Ni SAs / N-CSs were studied and characterized.

[0028] (1) SEM images of the above materials are as follows Figure 1 As shown, (a) is Fe 3+ / N-CSs, (b) is Co 2+ / N-CSs, (c) is Ni 2+ / N-CSs, (d) is Fe SAs / N-CSs, (e) is Co SAs / N-CSs, and (f) is Ni SAs / N-CSs.

[0029] SEM results showed that the adsorbed metal cations retained the spherical shape, and the surface remained unchanged. SEM results for the single-atom / nitrogen-doped carbon spheres indicated that the spheres were well preserved, although the size decreased slightly due to high-temperature annealing.

[0030] (2) TEM, HRTEM, and EDS images of Fe single-atom / nitrogen-doped carbon spheres (Fe SAs / N-CSs) are shown below. Figure 2 As shown, (a) is a TEM image, (b) and (c) are HRTEM images at different magnifications, and (d), (e) and (f) are EDS images of C, N and Fe elements, respectively.

[0031] TEM images showed that no Fe agglomeration occurred throughout the carbon matrix during pyrolysis, and HRTEM images also showed no lattice fringes of related metallic iron, indicating the absence of any iron-related metallic phases. Corresponding elemental mapping confirmed the uniform distribution of C, N, and Fe elements.

[0032] (3) TEM, HRTEM, and EDS images of Co single-atom / nitrogen-doped carbon spheres (Co SAs / N-CSs) are shown below. Figure 3 As shown, (a) is a TEM image, (b) and (c) are HRTEM images at different magnifications, and (d), (e) and (f) are EDS images of C, N and Co elements, respectively.

[0033] TEM images show that no Ni agglomeration occurred on the entire carbon matrix during pyrolysis, and HRTEM images also show no cobalt lattice fringes, indicating the absence of cobalt-related metallic phases. Corresponding elemental mapping confirms the uniform distribution of C, N, and Co elements.

[0034] (4) TEM, HRTEM, and EDS images of Ni single-atom / nitrogen-doped carbon spheres (Ni SAs / N-CSs) are shown below. Figure 4 As shown, (a) is a TEM image, (b) and (c) are HRTEM images at different magnifications, and (d), (e) and (f) are EDS images of C, N and Ni elements, respectively.

[0035] TEM images show that no Ni agglomeration occurred on the entire carbon matrix during pyrolysis, and HRTEM images also show no nickel lattice fringes, indicating the absence of any nickel-related metallic phases. Corresponding elemental mapping confirms the uniform distribution of C, N, and Ni elements.

[0036] (5) The X-ray diffraction (XRD) patterns of the above single-atom / nitrogen-doped carbon sphere materials are as follows: Figure 5 As shown.

[0037] The results show that characteristic peaks of nitrogen-doped carbon spheres can be observed, and the XRD patterns of single-atom / nitrogen-doped carbon sphere materials are consistent with those of nitrogen-doped carbon spheres. Single-atom metallic materials show no obvious metallic elemental peaks and do not exist in the form of oxides or particles, proving that the metal is dispersed at the atomic level.

[0038] (6) The full X-ray photoelectron emission (XPS) spectrum of the above single-atom / nitrogen-doped carbon sphere material is as follows: Figure 6 As shown.

[0039] The results showed that the Fe SAs / N-CSs, Co SAs / N-CSs, and Ni SAs / N-CSs samples were composed of C, N, and Fe / Co / Ni atoms. Specifically, the Fe atom content of Fe SAs / N-CSs was 2.08 wt%, the Co atom content of Co SAs / N-CSs was 1.58 wt%, and the Ni atom content of Ni SAs / N-CSs was 2.37 wt%.

[0040] Experimental Example 2 Electrodes were prepared using N-CSs, Co SAs / N-CSs, and Ni SAs / N-CSs, as described in Example 4. These electrodes were used as working electrodes, with Pt wire and Ag / AgCl serving as the counter and reference electrodes, respectively. The three-electrode system was placed in a phosphate buffer solution (containing different concentrations of carbendazim, 0.001-20 μmol / L) at pH 7.0. Electrochemical measurements were performed using differential pulse voltammetry (DPV) with the following parameters: incremental potential 4 mV, amplitude 100 mV, pulse width 0.05 s, and pulse period 0.5 s.

[0041] (1) Differential pulse voltammetric curves for detecting different concentrations of carbendazim with different electrodes, and comparisons of electrode sensitivity and detection limit, for example. Figure 7 As shown, (a)-(e) are the differential pulse voltammetry curves for detecting different concentrations of carbendazim using the bare GCE electrode, N-CSs, Fe SAs / N-CSs, Co SAs / N-CSs and Ni SAs / N-CSs, respectively, with the inset showing the linear relationship between the oxidation peak current and the carbendazim concentration; (f) is a bar chart comparing the sensitivity and detection limit of different electrodes.

[0042] The results showed that when detecting carbendazim with different electrodes, the oxidation peak current gradually increased with the increase of carbendazim concentration, showing a good linear relationship with concentration; the electrode prepared with single-atom / nitrogen-doped carbon sphere material had significantly increased sensitivity and lower detection limit.

[0043] Experimental Example 3 Referring to the detection method in Example 2, the carbendazim was tested in interference solutions containing 5 times the concentration of organic matter (diphenylamine, bisphenol A, ascorbic acid, urea, and glucose) and 50 times the concentration of magnesium, copper, and potassium ions, respectively. The results are as follows: Figure 8-16 As shown.

[0044] The results showed that the current signal for detecting carbendazim in the interfering solution did not change significantly, indicating that the material has a specific recognition ability for carbendazim and can still accurately detect carbendazim in the presence of common interfering substances.

[0045] Test Example 4 Using the electrode prepared in Example 4, the stability of this electrode for detecting carbendazim (15 µM carbendazim in 0.1 M PBS) was tested according to the detection method in Example 2. The results are as follows: Figure 17 As shown, (a) is the differential pulse voltammetry curve of carbendazim detected 18 times consecutively, (b) is the repeatability analysis result of 18 consecutive detections, (c) is the differential pulse voltammetry curve of carbendazim detected for 30 consecutive days, and (d) is the storage stability analysis result of 30 consecutive days.

[0046] The results showed that the relative deviation from the standard was only 2.85% in 18 consecutive carbendazim tests, indicating good repeatability; and the relative deviation from the standard was only 1.51% over 30 consecutive days, demonstrating good storage stability of the material.

[0047] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions or improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a single-atom / nitrogen-doped carbon sphere material, characterized in that, Includes the following steps: (1) Add glucose and hexadecyltrimethylammonium bromide to deionized water and mix well. Then carry out a hydrothermal reaction, and then filter, wash and dry to obtain carbon spheres. (2) The carbon balls obtained in step (1) are mixed with urea and then ground, and then calcined under a nitrogen atmosphere to obtain nitrogen-doped carbon balls; the mass ratio of carbon balls to urea is 1.5-2.5:1; (3) Add the nitrogen-doped carbon spheres obtained in step (2) to deionized water and mix evenly to obtain a nitrogen-doped carbon sphere suspension. Then add a metal salt solution and stir. After filtration, washing and drying, calcination is carried out under a nitrogen atmosphere to obtain a single-atom / nitrogen-doped carbon sphere material. The metal salt solution is one of ferric chloride solution, cobalt chloride solution, and nickel chloride solution.

2. The method for preparing single-atom / nitrogen-doped carbon sphere material as described in claim 1, characterized in that, In step (1), the mass-volume ratio of glucose, hexadecyltrimethylammonium bromide and deionized water is 1.5-2.5 g: 0.15-0.2 g: 30 mL.

3. The method for preparing single-atom / nitrogen-doped carbon sphere material as described in claim 1, characterized in that, In step (1), the hydrothermal reaction is carried out at a temperature of 170-190℃ for 4-6 hours.

4. The method for preparing single-atom / nitrogen-doped carbon sphere material as described in claim 1, characterized in that, In steps (2) and (3), the calcination is carried out at 850-950℃ for 1-3 h.

5. The method for preparing single-atom / nitrogen-doped carbon sphere material as described in claim 1, characterized in that, The concentration of the nitrogen-doped carbon sphere suspension is 4-6 mg / mL; the concentration of the metal salt solution is 0.04-0.06 mM; and the volume ratio of the nitrogen-doped carbon sphere suspension to the metal salt solution is 1:

1.

6. The single-atom / nitrogen-doped carbon sphere material prepared by the method of any one of claims 1-5.

7. The application of the single-atom / nitrogen-doped carbon sphere material according to claim 6 in the electrochemical detection of organic pesticides.

8. An electrode for detecting organic pesticides, characterized in that, It is prepared from the single-atom / nitrogen-doped carbon sphere material as described in claim 6.

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