Transition metal doped zinc-based phosphide, preparation method thereof and application of transition metal doped zinc-based phosphide in electrochemical sensor

Abstract

The invention provides a transition metal doped zinc-based phosphide, a preparation method thereof and application of the transition metal doped zinc-based phosphide in an electrochemical sensor. Transition metal (M) doped ZnxPy is prepared by mainly utilizing a Kirkendall effect, and organophosphorus is used as a phosphorus source and a carbon source to control the structural form and promote the formation of an MZnP2 phase in MZnP2 / C doped microspheres, so that the transition metal doped zinc-based phosphide MZnP2 / C is prepared by adjusting electronic structures and bonding states of surrounding P, M and Zn atoms. The MZnP2 / C has large electrode surface area and conductivity, and can increase electrochemical signals to neonicotinoid insecticides as an electrocatalyst. The content of a detected target object is electrochemically reflected by utilizing the gain and loss of electrons on nitrite generated by the neonicotinoid insecticide in a buffer solution with the pH value of 4-7, and a signal-increased electrochemical sensor for on-site detection of the neonicotinoid insecticide is obtained. The method can provide a detection basis for food safety risk monitoring.

Description

Technical Field

[0001] The present invention relates to a neonicotinoid insecticide detection technology, and specifically relates to a transition metal-doped zinc-based phosphide, a preparation method thereof, and an application thereof in an electrochemical sensor. Background Art

[0002] Neonicotinoid insecticides, such as clothianidin, cycloheximidine, thiamethoxam, and acetamiprid, are a class of systemic insecticides with a nitroolefin oxygen bridge structure. They have the advantages of broad spectrum, high efficiency, high water solubility, and strong systemic properties, and are widely used in pest control of crops. However, the use of neonicotinoid insecticides will pollute the environment, thereby affecting the ecosystem, and human health will also be indirectly threatened through the food chain. my country's GB 2763-2021 "Maximum Residue Limits of Pesticides in Food" stipulates the temporary maximum residue limits of various pesticides in food. For example, the maximum residue limit of cycloheximidine in rice, brown rice, wheat, and cabbage is 0.1 mg / kg, and there are no relevant testing standards at home and abroad. Therefore, timely and accurate detection of pesticides is crucial to human health and ecological safety.

[0003] The detection methods for neonicotinoid pesticides mainly include liquid chromatography (HPLC), high performance liquid chromatography-tandem mass spectrometry (HPLC-MS / MS), electrochemical detection, etc. Among them, HPLC and HPLC-MS / MS are commonly used detection methods. For example, Zhang Yan et al. used ultra-high performance liquid chromatography-tandem mass spectrometry to establish a detection method for residues of cycloheximide and other substances in vegetables (Zhang Yan, Qu Liangjiao, Ling Li. Modern Preventive Medicine, 2024, 51(4):722); Wang Xia et al. used dispersed solid phase extraction combined with ultra-high performance liquid chromatography-tandem mass spectrometry to establish a detection method for 10 neonicotinoid pesticide residues such as cycloheximide in vegetables (Wang Xia, Zhang Weiyi, Wang Min. Analytical Laboratory, 2023, 42(7):897). However, HPLC and HPLC-MS / MS detection require expensive equipment and professional operators, and are time-consuming. Although they can meet the requirements of sensitivity and high accuracy, they are not always suitable for real-time detection. Electrochemical sensors have attracted great interest from researchers due to their advantages of simple sample preparation, easy analysis, low cost and high precision.The performance of the sensor depends largely on the electrocatalytic materials used to design the modified electrodes.

[0004] In terms of electrode materials, transition metal phosphides (TMPs) have become effective materials for detecting target analytes due to their unique physical and chemical properties, such as non-toxicity, low cost, good chemical stability, high conductivity, and abundant reserves. In the periodic table, most transition metals can react with phosphorus to form TMPs. Among them, zinc has a high yield, low cost, and high conductivity (1.69× 10 7 S m -1), has become an element that has attracted much attention recently, and its corresponding phosphide Zn x P y The system exhibits excellent semiconductor properties and has high chemical and thermal stability. However, the activity of these materials is often inferior to that of commonly used Pt-based electrocatalysts, mainly due to their limited active sites and restricted electron / ion transfer, which limits their application in electrochemical sensing. Therefore, by optimizing the Zn x P y electronic structure and catalytic activity of Zn x P y The charge transfer ability and electrochemical stability of Zn-based bimetallic TMPs are relatively few studies, especially the M-doped Zn-based bimetallic TMPs. x P y Research, M represents Fe, Co, Cu and Ni.

[0005] Therefore, how to provide a zinc-based bimetallic TMPs modified electrode suitable for electrochemical sensors to improve the stability and sensitivity of electrochemical detection of neonicotinoid insecticides is one of the important research directions of neonicotinoid insecticide detection technology. Summary of the Invention

[0006] In view of this, an object of the present invention is to provide a method for preparing transition metal-doped zinc-based phosphide, which mainly utilizes the Kirkendall effect to prepare transition metal M-doped Zn x P y , and using organic phosphorus as a phosphorus and carbon source to control the structural morphology and promote the formation of the MZnP2 phase in the doped MZnP2 / C microspheres. This opens up a new path for designing efficient and highly conductive phosphorus-rich metal phosphating catalysts by regulating the electronic structure and bonding state of the surrounding P, M, and Zn atoms. The transition metal M can be Co, Fe, Cu, Mo, or Ni. To achieve this goal, the present invention provides the following technical solutions: A method for preparing a transition metal-doped zinc-based phosphide comprises the following steps: Preparation of the precursor: Using zinc nitrate, transition metal nitrate, and organophosphorus as raw materials, a transition metal-doped zinc-based phosphide precursor is prepared by ball milling, wherein the molar ratio of zinc nitrate, transition metal nitrate, and organophosphorus is 0.1-2:0.1-2:100-110, and the transition metal nitrate is cobalt nitrate, iron nitrate, copper nitrate, molybdenum nitrate, or nickel nitrate; Preparation of target phosphide: The precursor is carbonized at 700-1000° C. by a calcination method to obtain transition metal-doped zinc-based phosphide: MZnP2 / C.

[0007] Based on the above, in the preparation step of the precursor, the process parameters of the ball milling method are: ball milling time 8 to 14 h, ball to powder weight ratio of 25:1 to 10:1, and rotation speed of 200 to 600 rpm.

[0008] Based on the above, the calcination method includes: transferring the precursor into a tube furnace, and performing high-temperature carbonization at 700-1000° C. for 1-4 h in a flowing inert gas to obtain the transition metal-doped zinc-based phosphide.

[0009] Based on the above, the preparation step of the target phosphide further includes: acid washing and vacuum drying the product after high-temperature carbonization, so as to obtain a purified transition metal-doped zinc-based phosphide.

[0010] Another object of the present invention is to provide a transition metal-doped zinc-based phosphide prepared by the above-mentioned preparation method, namely, transition metal-doped MZnP2 / C microspheres, which are used as a high-efficiency, highly conductive phosphorus-rich metal phosphide catalyst and have excellent electrochemical adsorption performance for neonicotinoid insecticides.

[0011] A third objective of the present invention is to provide a transition metal-doped zinc-phosphide-modified electrode with a large surface area and conductivity, which, as an electrocatalyst, can enhance the electrochemical signal of neonicotinoid insecticides. To achieve this objective, the present invention provides the following technical solutions: A transition metal-doped zinc-based phosphide modified electrode comprises a bare electrode and the transition metal-doped zinc-based phosphide uniformly dispersed on the bare electrode.

[0012] A fourth object of the present invention is to provide a method for preparing the above-mentioned transition metal-doped zinc-based phosphide modified electrode. To achieve this object, the present invention provides the following technical solutions: A method for preparing the above-mentioned transition metal-doped zinc-based phosphide modified electrode comprises: uniformly dispersing the transition metal-doped zinc-based phosphide in water to prepare a transition metal-doped zinc-based phosphide dispersion, wherein the solid-liquid ratio of the transition metal-doped zinc-based phosphide is 0.5-2:0.5-2 mg / mL; dropwise adding the transition metal-doped zinc-based phosphide dispersion onto the surface of the bare electrode and drying to obtain the zinc-based phosphide modified electrode.

[0013] A fifth objective of the present invention is to prepare an electrochemical sensor using the aforementioned transition metal-doped zinc-phosphide modified electrode. This electrochemical sensor has the advantages of high sensitivity, good repeatability, high accuracy, and good stability for detecting neonicotinoid insecticides. To achieve this objective, the present invention provides the following technical solutions: An electrochemical sensor comprises a working electrode comprising the aforementioned transition-metal-doped zinc-phosphide-modified electrode and an aqueous dispersion of a neonicotinoid insecticide dripped onto the transition-metal-doped zinc-phosphide-modified electrode. A sixth object of the present invention is to provide a use of the aforementioned transition-metal-doped zinc-phosphide, transition-metal-doped zinc-phosphide-modified electrode, or electrochemical sensor for electrochemical detection of neonicotinoid insecticides, thereby amplifying the electrochemical signal of neonicotinoid insecticides and exhibiting good detection stability and sensitivity.

[0014] Furthermore, the detection object is a 0.08-486 μmol / L neonicotinoid insecticide aqueous dispersion, and the neonicotinoid insecticide aqueous dispersion is dropped onto the surface of the working electrode to achieve the purpose of detection.

[0015] By utilizing the electron gain and loss on nitrite generated by neonicotinoid insecticides in a pH 4-7 buffer solution to electrochemically reflect the content of the detection target, a signal-amplified electrochemical sensor for on-site detection of neonicotinoid insecticides was obtained; this method can provide a detection basis for food safety risk monitoring. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 Schematic diagram of the synthesis process of CoZnP2 / C under optimal process conditions provided in an embodiment of the present invention; Figure 2 SEM images of precursors with different PA:total metal ion molar ratios: a) 106: 0, b) 106: 1, c)106: 3, d) 106: 30, e) 106: 106, f) 106: 210; Figure 3 SEM images of precursors with different Zn: Co molar ratios: a) 2:0, b) 2:0.67, c) 2:2, d)2:6; SEM images of precursors with different ball milling times and rotation speeds: e) 8 h, f) 12 h, g) 200 rpm, h) 600 rpm; Figure 4 SEM images of ZnM phosphate in the precursors: a) ZnFe, b) ZnNi, c) ZnMo, d) ZnCu, e) ZnCo, f, g) CoZn phosphate elemental mapping characterization and h) EDX spectrum; Figure 5 a) TEM image, b, c) high-resolution transmission electron microscopy images, d-h) elemental mapping of cobalt zinc phosphate in the precursor; Figure 6 TEM elemental composition and EDX spectrum of cobalt zinc phosphate in the precursor; Figure 7 a) XRD spectra, b) FTIR spectra, c) Raman analysis, d) XPS spectra, e) deconvolution spectra of P 2p spectra, and f) nitrogen adsorption-desorption isotherms of CoZnP2 / C-700, CoZnP2 / C-800, and CoZnP2 / C-900; Figure 8 CoZnP4O 11 , CoZnP2 / C-700, CoZnP2 / C-800 and CoZnP2 / C-900: a) C 1s, b) O1s, c) Co2p and d) Zn 2p XPS spectra; Figure 9 The pore size distribution diagrams of CoZnP2 / C-700, CoZnP2 / C-800 and CoZnP2 / C-900; Figure 10 CoZnP4O in the precursor 11 TGA curve under argon conditions at 30~1100℃; Figure 11 a) XRD spectrum, b) XPS spectrum of ZnP / C: c) C 1s, d) O 1s, e) P 2p, f) Zn2p spectrum; Figure 12 SEM images of a) CoZnP2 / C-700, b) CoZnP2 / C-800, c) CoZnP2 / C-900; Figure 13 TEM elemental composition characterization and EDX spectrum of CoZnP2 / C; Figure 14 TEM images of a) CoZnP2 / C-700, c) CoZnP2 / C-900, b, d) corresponding elemental mapping characterization images; Figure 15 a) TEM image, b) HRTEM image, c) HAADF-STEM image, d) line scan spectrum, and e) elemental mapping of CoZnP2 / C; Figure 16 Schematic diagram of the CLD process detected by electrochemical sensor and the possible electrocatalytic reduction mechanism of CLD; Figure 17 CV curves of a) different PA:total metal ion molar ratios and b) different transition metal-doped zinc phosphate precursors; Figure 18 a) ZnCoP4O 11 and ZnCoP2 / C in 5 mM Fe(CN)6 at different calcination temperatures3− / 4− b) CV graphs of AuE, ZnCoP2 / C / AuE and CLD / ZnCoP2 / C / AuE containing 100 μmol / L CLD in 0.01 mol / L PBS (pH 6.0); Figure 19 a) AuE, ZnP / C / AuE and CLD / ZnP / C / AuE, b) AuE, CoZnP4O 11 / C / AuE、 CLD / CoZnP4O 11 / AuE、CLD / CoZnP4O 11 CV graph of α / AuE in 100 μmol / L CLD, 50 mV / s, 0.01 mol / L PBS (pH 6.0); c) Comparison of the DPV response of the sensor in the presence and absence of CLD; Figure 20 a) DPV curves of ZnCoP2 / C / AuE with different concentrations of CLD in 0.01 mol / L PBS (pH 6.0); b) linear relationship between peak current response and CLD concentration. DETAILED DESCRIPTION

[0017] In order to make the purpose, technical solutions and advantages of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention.

[0018] The endpoints of the ranges and any values disclosed herein are not limited to the precise ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values can be combined with each other to form one or more new numerical ranges, and these numerical ranges should be considered to be specifically disclosed in the present invention.

[0019] Unless otherwise specified, the terms used in the present invention are commonly used terms in the relevant field. The preparation processes, testing methods, etc. used in each embodiment are conventional means well known to those skilled in the art unless otherwise specified. The raw materials and equipment used can be obtained from public commercial channels.

[0020] The present invention mainly combines ball milling and calcination to prepare transition metal (M) doped zinc-based phosphide based on Kirkendall effect. x P y / C, and use organic phosphorus as phosphorus source and carbon source to control the structural morphology; by adjusting the content of P and M doping, promote the MZn x P yMZn / C microspheres x P y The formation of the phase, thereby opening up a new way to design efficient and highly conductive phosphorus-rich metal phosphide catalysts by regulating the electronic structure and bonding state of the surrounding P, M, and Zn atoms. In addition, density functional theory (DFT) shows that neonicotinoids have a great influence on the MZn x P y / C has excellent electrochemical adsorption performance and has been successfully applied to the electrochemical detection of neonicotinoid insecticides.

[0021] The specific implementation scheme of the present invention is as follows: A method for preparing MZnP2 / C comprises the steps of preparing a precursor and preparing a target phosphide.

[0022] Preparation of precursor: The precursor of MZnP2 / C is prepared by ball milling. Specifically, zinc nitrate, transition metal nitrate and organophosphorus are mixed, and the mixture is mechanically ball milled for 8 to 14 hours using a stainless steel tank and stainless steel grinding balls under inert gas, with a ball-to-powder weight ratio of 25:1 to 10:1 and a rotation speed of 200 to 600 rpm to obtain the precursor of MZnP2 / C. The precursor of MZnP2 / C includes transition metal-doped zinc-based phosphate MZnP4O 11 .

[0023] In the process of preparing the precursor, the phosphorus element in the organic phosphorus is complexed with the zinc ions in the zinc nitrate and the transition metal ions in the transition metal nitrate to form the organic phosphate precursor of MZnP2 / C.

[0024] The transition metal nitrate described herein is cobalt nitrate, iron nitrate, copper nitrate, molybdenum nitrate, or nickel nitrate. That is, M in MZnP2 / C can be Co, Fe, Cu, Mo, or Ni. The organophosphorus described herein is one or more of phytic acid (C6H6(H2PO4)6, abbreviated as PA, an organic compound with a high phosphorus content (six phosphate groups)), yeast, spirulina, and DNA. The inert gas described herein is one or more of nitrogen, helium, and argon. The molar ratio of zinc ion to transition metal ion is preferably 0.1-2:0.1-2. The molar ratio of organophosphorus to total metal ions is preferably 106:0.2-4; the total metal ions are composed of zinc ion and transition metal ions. The molar ratio of zinc nitrate to transition metal nitrate to organophosphorus is 0.1-2:0.1-2:100-110, preferably 0.2-2:0.5-2:104-108. In the ball milling method, the length of the ball milling time affects the material's particle size distribution, surface area, and purity. Therefore, the ball milling time is limited to 8 to 14 hours, such as 8, 9, 10, 11, 12, 13, and 14 hours, with 8 to 12 hours being more preferred. The ball-to-powder weight ratio affects the material's particle size distribution, grain size, and defect density, so it is limited to 25:1, 20:1, 15:1, and 10:1, among others. The rotational speed affects the material's average particle size, lattice distortion, specific surface area, and contamination risk. Therefore, it is limited to 200 to 600 rpm, such as 200, 300, 400, 500, and 600 rpm.

[0025] Preparation of target phosphide: MZnP2 / C is prepared by calcination. Specifically, the precursor is transferred to a tube furnace and carbonized at high temperature in a flowing inert gas. First, it is heated from room temperature to 700-1000°C at a heating rate of 1-10°C / min and maintained for 1-4 hours. Then, the temperature is further lowered to room temperature at the same rate. The resulting product is etched with a 1-5 mol / L strong acid solution, washed with water 2-5 times, and dried in a vacuum at 40-90°C overnight to obtain MZnP2 / C. The strong acid solution described in the present invention is one or more of hydrochloric acid, sulfuric acid, nitric acid, and phosphoric acid.

[0026] During the calcination process, the precursor organic phosphate decomposes at high temperature, the oxygen in it is gasified and discharged with the inert gas, the atoms between the metal elements and phosphorus are rearranged, and the organic matter is carbonized to form a carbon framework, which enhances the conductivity of MZnP2 / C.

[0027] The high-temperature carbonization temperature and carbonization time are related to the decomposition temperatures of nitrates and organophosphorus. Preferably, the high-temperature carbonization temperature is 700-1000°C, such as 700°C, 800°C, 900°C, 1000°C, etc.; the high-temperature carbonization time is 1-4 hours, such as 1, 2, 3, 4 hours, etc. The heating rate and cooling rate of the tube furnace affect the crystal structure, phase transition and material properties respectively. Therefore, the heating rate and cooling rate are the same, respectively, 1-10°C / min, such as 1, 2, 3, 4, 5, 6, 7, 8, 9, 10°C / min, etc.

[0028] The second aspect of the present invention provides MZnP2 / C prepared by the above preparation method.

[0029] The third aspect of the present invention provides a transition metal doped zinc phosphide modified electrode, namely MZnP2 / C uniformly dispersed on the surface of the bare electrode. The bare electrode can be made of gold, glassy carbon, nickel foam, etc., and the bare electrode is preferably a screen-printed electrode.

[0030] The fourth aspect of the present invention provides a method for preparing the above-mentioned transition metal-doped zinc-based phosphide modified electrode, comprising: firstly dispersing the above-mentioned MZnP2 / C uniformly in water at a solid-liquid ratio of 0.5-2:0.2-2 mg / mL to form a MZnP2 / C dispersion; then using a pipette to remove the MZn x P y The Zn / C dispersion is dropped onto the surface of the bare electrode and dried under an infrared lamp for 6 to 10 minutes to finally obtain a transition metal-doped zinc-based phosphide modified electrode.

[0031] The fifth aspect of the present invention provides an electrochemical sensor comprising a working electrode, wherein the working electrode comprises the above-mentioned transition metal-doped zinc-based phosphide modified electrode and an aqueous dispersion of a neonicotinoid insecticide dripped onto the modified electrode. Preferably, the aqueous dispersion of the neonicotinoid insecticide has a concentration of 0.08 to 486 μmol / L. The electrochemical sensor further comprises an electrolyte having a pH of 4 to 7 and a concentration of 0.005 to 0.05 mol / L. The neonicotinoid insecticides described in the present invention may be cycloheximide, clothianidin, thiamethoxam, dinotefuran and imidacloprid, etc. The buffer solution described in the present invention is one or more of a phosphate buffered saline solution, a Tris-HCl buffer solution, and triethanolamine.

[0032] The rest of the electrochemical sensor's structure is conventional. For example, the electrochemical sensor also includes a counter electrode and a reference electrode. The counter electrode can be made of a metal such as platinum, gold, or silver; the reference electrode can be a saturated calomel electrode (SCE) or a silver / silver chloride electrode (Ag / AgCl).

[0033] A sixth aspect of the present invention provides the above-mentioned transition metal-doped zinc-based phosphide, a transition metal-doped zinc-based phosphide modified electrode, and their use in electrochemical detection of neonicotinoid insecticides.

[0034] A working electrode was prepared by adding a 0.08-486 μmol / L aqueous dispersion of a neonicotinoid insecticide dropwise to the surface of a transition metal-doped zinc phosphide-modified electrode. Detection was achieved through this working electrode. The gain and loss of electrons on the nitrite ions generated by the neonicotinoid insecticide in a pH 4-7 buffer solution reflected the concentration of the target neonicotinoid insecticide solution on a portable electrochemical workstation, resulting in a signal-amplified electrochemical sensor for on-site neonicotinoid insecticide detection. This electrochemical sensor exhibits high sensitivity, good repeatability, and high accuracy in detecting neonicotinoid insecticides.

[0035] The technical solution of the present invention is further explained below by taking cobalt nitrate, zinc nitrate and phytic acid (PA) as raw materials to prepare CoZnP2 / C and its related applications as an example.

[0036] 1. Synthesis of CoZnP2 / C See also Figure 1 The present invention provides a method for preparing CoZnP2 / C microspheres, which specifically includes the following steps: Preparation of precursor: Phytic acid (PA) and metal nitrate were mixed by ball milling through a self-assembly process to form the precursor metal phosphate-CoZnP4O 11 : Zinc nitrate hexahydrate, cobalt nitrate hexahydrate and PA are mixed; the mixture is mechanically ball milled in a stainless steel pot and stainless steel grinding balls under an argon atmosphere for 8 to 12 hours, with a ball-to-powder weight ratio of 20:1 and a rotation speed of 200 to 600 rpm to obtain a cobalt-doped zinc-based phosphide precursor: zinc cobalt phosphate - CoZnP4O 11 , wherein the molar ratio of PA to total metal ions is 106: 1 to 3, wherein the total metal ions are Zn 2+ and Co 2+ Composition; Zn 2+ and Co 2+ The molar ratio is 1:0.3~2; Preparation of CoZnP2 / C: Cobalt-doped zinc-based phosphide was prepared by calcination: the synthesized precursor zinc cobalt phosphate-CoZnP4O 11The product was transferred to a tube furnace and calcined and carbonized under flowing argon. The temperature was first increased from room temperature to 700-1000°C at a rate of 2°C / min and held for 2 hours. The temperature was then further decreased to room temperature at the same rate. The resulting product was cleaned of impurities with 3 mol / L hydrochloric acid and washed three times with water. The product was then dried overnight in a vacuum at 60°C to obtain cobalt-doped zinc-based phosphide CoZnP2 / C, which exhibited the same microspherical morphology as the precursor.

[0037] (1) Effect of the amount of each raw material on the CoZnP2 / C precursor In terms of precursors, PA plays a vital role in the formation of precursors of different forms. The experimental process parameters of the molar ratio of PA to total metal ions are: PA and total metal ions (including Zn 2+ and Co 2+ ) were 106:0, 106:1, 106:3, 106:30, 106:106, 106:210, Zn 2+ and Co 2+ The molar ratio of 1:1, the mechanical ball milling time was 10 h, the ball-to-powder weight ratio was 20:1, and the rotation speed was 400 rpm.

[0038] Scanning electron microscope (SEM) images of the precursor are shown in Figure 2. Figure 2 As shown in the figure, under different molar ratios of PA: M, with the increase of metal amount, except for the molar ratio of 106:1 ( Figure 2 b) The morphology of the cobalt zinc phosphate precursor is becoming more and more uneven. Figure 2 In Figure a, the precursor containing only phytic acid (106:0) exhibits uniform nanoparticles (≈600 nm) and is viscous. This suggests that PA provides an organic framework, while the addition of an appropriate amount of metal facilitates particle growth and the formation of microspherical precursor metal phosphates.

[0039] The size of the precursor microspheres can be further optimized by controlling the molar ratio of Co and Zn doping, different ball milling time and rotation speed. The specific process parameters are as follows: 1) The molar ratio of Co and Zn doping affects the experimental parameters: the molar ratio of PA to total metal ions is 106:1, Zn 2+ and Co 2+ The molar ratios were 2: 0, 2: 0.67, 2: 2, and 2: 6, respectively. The mechanical ball milling time was 10 h, the ball-to-powder weight ratio was 20:1, and the rotation speed was 400 rpm. 2) Ball milling time affects the experimental parameters: the molar ratio of PA to total metal ions is 106:1, Zn 2+ and Co 2+The molar ratio of 1:1, the mechanical ball milling time was 8 h and 12 h, the ball-to-powder weight ratio was 20:1, and the rotation speed was 400 rpm; 3) Rotational speed affects test parameters: the molar ratio of PA to total metal ions is 106:1, Zn 2+ and Co 2+ The molar ratio of 1:1, the mechanical ball milling time was 10 h, the ball-to-powder weight ratio was 20:1, and the rotation speeds were 200 rpm and 600 rpm, respectively.

[0040] exist Figure 3 In the Zn: Co = 2:0 zinc phosphate, the diameter of the microspheres was 500 nm to 1.9 μmol / L, which was not conducive to the formation of a stable structure. When the Co element was doped into the zinc phosphate at a molar ratio of Zn: Co = 1:1 ( Figure 3 c) We obtained uniform microspheres with rough surface and diameter of 1.2 μmol / L. Under different ball milling times and rotation speeds, we observed irregular spherical morphology of the precursor. 2+ and Co 2+ The cobalt zinc phosphate precursor with uniform size can only be successfully synthesized under the conditions of a molar ratio of 1:1, a molar ratio of PA to total metal ions of 106:1, a ball milling time of 10 h, and a ball milling speed of 400 rpm.

[0041] Different transition metal nitrates have an important influence on transition metal doped zinc-based phosphides. The specific influencing test parameters are: the molar ratio of PA to total metal ions is 106:1, Zn 2+ and M 2+ The molar ratio of is 1:1, M is Fe, Ni, Cu and Mo respectively, the mechanical ball milling time is 10 h, the ball powder weight ratio is 20:1, the rotation speed is 400 rpm, and the structural characterization is as follows Figure 4 shown.

[0042] from Figure 4 It can be found in ae that Fe-, Ni-, Cu- and Mo-doped Zn-based phosphates have serious size differences and aggregation phenomena compared with Co-doped Zn-based phosphates, which further proves that the morphology of Co-doped zinc phosphides is more stable.

[0043] In summary, P has an important influence on the morphology of the catalyst, and Co doping induces the phase composition of phosphide. Figure 4 Elemental mapping of the cobalt zinc phosphate in Figures f and 4g shows the uniform distribution of P, C, O, Zn, and Co in the material. In addition, the corresponding energy-dispersive X-ray (EDX) spectra indicate the presence of C, P, O, and Zn, with only a small amount of Co being detected, likely due to its low concentration, making it difficult to accurately capture in the spectrum.

[0044] Figure 5 The TEM image shown in a shows the solid microsphere structure of cobalt zinc phosphate. Figure 5 Lattice fringes in high-resolution transmission electron microscopy (HRTEM) images (b) and (c) distinguish the composition of cobalt zinc phosphate. However, the absence of lattice fringes indicates that the material, cobalt-doped zinc phosphide, is amorphous. Figure 5 The elemental mapping images in dh show the presence and uniformity of C, P, O, and Zn components in the material.

[0045] exist Figure 6 In the corresponding EDS spectrum, Figure 4 Compared to the results of (h), only the atomic percentage of C increased, while the contents of the remaining elements decreased, indicating that the metal phosphate occupied more of the outer surface, leaving more of the carbon skeleton in the center of the sphere. The corresponding inductively coupled plasma optical emission spectroscopy (ICP-OES) test results are shown in Table 1. Table 1 shows that the P, Co, and Zn contents in the microspheres are only 0.0964%, 0.0007%, and 0.0013%, respectively, confirming the presence of Co in the catalyst.

[0046] Table 1 CoZnP4O 11 and ICP-OES analysis results of CoZnP2 / C

[0047] (2) Effect of calcination temperature on CoZnP2 / C The process parameters are: the precursor zinc cobalt phosphate - CoZnP4O synthesized under the above optimal process conditions 11 The calcination temperatures were 700, 800 and 900 °C, the calcination time was 2 h, and the inert gas used was argon. The structural characterization results of the prepared CoZnP2 / C-700, CoZnP2 / C-800 and CoZnP2 / C-900 are shown in Figure 2. Figure 7 shown.

[0048] The crystal structure and phase of the catalytic materials were analyzed by X-ray diffraction (XRD). Figure 7 As shown in a, the main peak of the material is consistent with the ZnP4O 11 or PDF#97-004-3334 corresponding to ZnP2, confirming that the metal phosphate CoZnP4O 11 Successfully synthesized. In order to further study the bonding structure, Figure 7 b shows CoZnP4O 11 Fourier transform infrared spectroscopy (FT-IR). At about 1617 cm -1 The C=C group appears at 1000-1400 cm-1 PO4 appeared 2− peak, which is due to Zn-PO4 2− and Co-PO4 2− The coordination of the bonds indicates the presence of graphite C and phosphate, which is consistent with the XRD results.

[0049] Raman spectroscopy is widely used to study the crystal structure of carbon-based materials. Figure 7 As shown in c, CoZnP4O 11 There are two distinct carbon-related peaks: one at approximately 1370 cm -1 (corresponding to the D band), and another at approximately 1580 cm -1 (corresponding to the G band). The D band peak is caused by the local defects at the edge of graphite carbon and the sp 3 The G band peak indicates graphite carbon (sp 2 ) in-plane CC bond stretching vibration, indicating that graphite carbon has a crystalline intensity ratio (ID / IG), reflecting the disorder of the carbon structure. 11 The relative ID / IG is 0.37, indicating that its graphitization degree is high, but there are defects in the carbon matrix.

[0050] To further explore the CoZnP4O 11 The surface chemical composition and chemical bonds of the precursors are investigated in this work. 11 X-ray photoelectron spectroscopy (XPS) tests were performed, and the results are shown in Table 2.

[0051] Table 2 CoZnP4O 11 , ZnP / C and CoZnP2 / Cx XPS peak table

[0052] Table 2 confirms the presence of Co, Zn, P, C and O. Figure 7 As shown in d, the XPS survey spectrum shows that CoZnP4O 11 The high oxygen content indicates that the surface of the material is rich in PO4 2− .exist Figure 7 In the P 2p spectrum shown in e, a small peak at 133.7 eV (P-C) is assigned to the phosphate environment, corresponding to metal phosphate. Figure 8 In the O 1s spectrum shown in a, two types of characteristic peaks, -P=O (532.9 eV) and metallic O (531.3 eV), appeared, proving the presence of phosphate. In addition, Figure 8 The weak Zn 2p and Co 2p signals in bc indicate the presence of trace amounts of Zn and Co elements. Figure 8 In the C 1s spectrum shown in d, the characteristic peaks at 284.8, 286.2, and 288.6 eV belong to the CC, CP, and O=CO bonds, respectively, which originate from the PA-derived carbon skeleton.

[0053] The N2 adsorption-desorption curves were used to study the 11 The specific surface area, porosity and average pore size of the composite are shown in Table 3.

[0054] Table 3 CoZnP4O 11 , ZnP / C and CoZnP2 / Cx nitrogen adsorption and desorption characteristics table sample <![CDATA[S BET (m² / g)]]> <![CDATA[Pore volume (cm 3 / g)]]> Average pore size (nm) <![CDATA[CoZnP4O 11 ]]> 4.9431 0.019521 15.7969 <![CDATA[CoZnP2 / C-700]]> 638.9659 0.271635 1.7005 <![CDATA[CoZnP2 / C-800]]> 655.0492 0.276417 1.6879 <![CDATA[CoZnP2 / C-900]]> 835.1510 0.352941 1.6904 CoZnP4O 11 The BET specific surface area is relatively small, which is 4.9431 m 2 g -1 ,like Figure 7 f. Figure 9 The pore size distribution curve shows that most of the pores are approximately 15.7 nm in size, confirming the microporous nature of the precursor shown in Table 3. This indicates that the outer surface of the microspheres is oxidized to phosphate, while the internal carbon framework is wrapped with metal Co and Zn, which can effectively improve the electrical conductivity and synergistic catalytic ability. Thermogravimetric analysis (TGA) evaluated the calcination temperature range of the material and determined the thermal behavior of the precursor in an inert gas. The results are shown in Figure 3. Figure 10 shown. Figure 10 It shows that with the increase of temperature, CoZnP4O 11 The total mass of the precursors gradually decreased and stabilized at about 43% at 800 °C. Therefore, the calcination temperatures of the precursors were set at 700 °C, 800 °C, and 900 °C, respectively.

[0055] CoZnP4O 11 Subsequently, CoZnP2 / C-700, CoZnP2 / C-800 and CoZnP2 / C-900 were obtained by calcination in an argon atmosphere. The physical properties of the obtained materials were studied as follows: Figure 7 The XRD patterns shown in a show the presence of amorphous carbon and similar peaks in all annealed samples, and the intensity of these peaks gradually decreases as the phosphating temperature increases from 700°C to 900°C. They include two broad diffraction peaks of ZnC2O4 at ≈23.9° and 43.3° (PDF#97-010-9665) and a characteristic peak of graphite C of CoZnP2 / C-800 at 6.1° (PDF#97-02-8419), confirming the formation of CoZnP2 phase and carbon layer. These results are due to the reaction of PA with Zn during the thermal reduction process. 2+ and Co 2+Strong interactions between the ions resulted in the formation of P vapor, which subsequently produced CoZnP2, which was then incorporated into the carbon matrix. Thus, through this simple one-step process, a CoZnP2 phase embedded in a carbon framework was synthesized in situ to obtain the electrocatalytic material CoZnP2 / C. This phosphating strategy not only simplifies existing methods but also uses phytic acid as a P source instead of the conventional NaH2PO2 or NH4H2PO2, which prevents the generation of toxic PH3.

[0056] No Co diffraction peaks were observed in CoZnP2 / C-700, CoZnP2 / C-800, and CoZnP2 / C-900 samples, indicating that Co may have partially evaporated during the calcination process. No other impurity peaks appeared in the material, indicating the successful incorporation of Co species and the high purity of the product. For comparison, the XRD spectrum of single zinc phosphide (ZnP / C) is shown in Figure 2. Figure 11 As shown in Figure a, the two peaks at 29.7° and 43.1° belong to Zn2P2O7 (PDF#00-050-1370). Compared with CoZnP2 / C, the peak at 29.7° shows a certain degree of positive shift, while the peak at 43.1° does not shift, indicating that the introduction of Co can promote the formation of graphitization and induce phase transformation. Figure 7 The FTIR spectrum shown in b shows the presence of coordination bonds in CoZnP2 / C. Compared with the precursor, the peaks at 1500-1750 cm -1 C=C band and 3000~3500 cm -1 The position and intensity of the -OH band in the range remain basically unchanged, but the peak is slightly lower after calcination, which is due to the reduction of the content of hydrophilic groups and aromatic groups after calcination. 2− Peak at 500~-1400 cm -1 There is a significant change at 2− and Co-PO4 2− Bond formation. Figure 7 c The ordered graphitization degree and carbon content of CoZnP2 / C-700, CoZnP2 / C-800 and CoZnP2 / C-900 were studied by Raman spectroscopy. Their ID / IG ratios were 0.85, 0.96 and 1.01, respectively, indicating that sp 2 The degree of graphitization of the bonds and disordered carbon decreases with increasing temperature. Thus, the distortion of the graphene-like structure leads to an increase in the concentration of defects within the carbon skeleton, thereby improving the electrocatalytic performance by reducing the surface energy and increasing the accessibility of active sites. However, in the CoZnP2 / C samples, the peak at approximately 1024 cm -1 A new band appeared at the peak, which originated from PO4 3−The symmetrical stretching of CoZnP2 / C-700 is similar to that of CoZnP4O 11 The corresponding peaks have obvious overlap. As the temperature increases, the intensity of the peak decreases, which is mainly due to the 11 The decomposition of CoZnP2 / C-800 at 1480 cm -1 There is an A2 band nearby, indicating that the carbon structure is amorphous. This is consistent with the FTIR results, indicating that the calcination process has little effect on the composition and crystal structure of CoZnP2 / C.

[0057] Figure 11 The XPS spectrum of non-Co-doped ZnP / C shown in b and the peak table shown in Table 2 confirm the presence of Zn, P, O and C. Figure 11 The C 1s spectrum in c confirms the sp 2 The presence of carbon (284.0 eV) and graphite C-C bonds (284.8 eV). In addition, there is a small peak at 289.0 eV corresponding to C=O. In the O 1s spectrum, there is only one peak at 532.0 eV ( Figure 11 d) belongs to CO. There is a PO (133.3 eV) characteristic peak in the P 2p spectrum, which corresponds to metal phosphate. The weak signal of the Zn 2p spectrum ( Figure 11 f) indicates the presence of trace amounts of zinc. After Co doping, the XPS spectrum of CoZnP2 / C is shown in 7d, confirming that O and P are added to the carbon matrix, while no obvious Zn and Co peaks are observed. This may be because at higher temperatures, P and O are mainly present on the surface, and a carbon layer is formed around the Zn and Co particles, preventing the XPS electron beam from detecting these metals. In addition, the peak intensity of O after calcination is much smaller than that before calcination, which may be because high temperature is conducive to the formation of surface PO4 3− The reduction to phosphide or the redox reaction of O with Zn and Co in the sample may be caused by the high-resolution P 2p shows the presence of PO (only for CoZnP2 / C-700) and PC bonds ( Figure 7 e), indicating that 700℃ is not the optimal calcination temperature. As the temperature increases, the PC peak shifts toward the positive charge (133.6), indicating that P has more negative charge. P doping in the carbon skeleton improves the conductivity and helps maintain the integrity of the electrode material. Combined with the C 1s spectrum ( Figure 8 a) It can be seen that most of the phosphorus is doped into the carbon structure, and the rest exists in an oxidized state. Compared with ZnP / C, the doped CoZnP2 / C shows PC bonds, proving that Co doping can promote C to carry more positive charges and adjust the lattice structure to form the final product. In addition, the negative shift of O 1s ( Figure 8b) and the positive shift of P 2p indicates that the electronic interaction involves charge transfer from P atoms to O atoms. This leads to a large reduction in the electrocatalytically active phosphides on the microsphere surface, driving them to move inward. From the weak Zn 2p and Co 2p spectra ( Figure 8 a, d) It can be seen that with the increase of temperature, the relative peak intensity of the metal decreases significantly, which further proves that the gradual increase of temperature is not conducive to the formation of phosphide. The peak table of CoZnP2 / C shown in Table 2 shows that compared with the precursor CoZnP4O 11 In comparison, the carbon content of CoZnP2 / C increases while the contents of other elements decrease, indicating that calcination favors the formation of the carbon framework and that other components evaporate with the argon flow. The zinc content decreases with increasing temperature, indicating that elevated temperatures are detrimental to the synthesis of zinc-based phosphides. Therefore, 800°C is the optimal calcination temperature for the catalytic materials. XPS results for CoZnP2 / C and ZnP / C reveal the following: 1) The positive P 2p shift indicates that electron interactions involve transfer from P atoms to other atoms; 2) Cobalt doping effectively optimizes the electronic structure of the phosphide, promoting the bonding of P with carbon and catalyzing carbon graphitization; and 3) The elemental distribution of the microspherical carbon framework is characterized by oxygen in the second layer, P in the third layer, and Co and Zn in the innermost layer.

[0058] Nitrogen adsorption isotherm results ( Figure 7 f) shows that CoZnP2 / C has a type I isotherm, proving its microporous nature. Figure 9 The corresponding pore size distribution curves show that their pore sizes are between 1 and 5 nm, indicating that the material has formed micropores and small mesopores. In addition, among CoZnP2 / C, only CoZnP2 / C-800 has the smallest pores, which is conducive to the adsorption of small molecule targets to be tested and is expected to facilitate the reactants to reach the active sites while enhancing mass transfer. This further proves the rationality of using 800 ° C as the calcination temperature of the final material, which is subsequently abbreviated as CoZnP2 / C. As can be seen from Table 3, the specific surface areas of CoZnP2 / C-700, CoZnP2 / C-800, and CoZnP2 / C-900 are 638.9659 m 2 / g, 655.0492 m 2 / g、835.1510m 2 / g (larger than most TMPs-based catalysts reported so far), indicating that the specific surface area increases with increasing temperature, which may be due to the increase in micropores leading to more pores for the phosphate groups attached to PA, which prompts the material to produce more active sites for electrocatalytic reactions.

[0059] The scanning electron microscopy images of CoZnP2 / C-700, CoZnP2 / C-800 and CoZnP2 / C-900 are as follows: Figure 12 As shown, from Figure 12 In Figure b, CoZnP2 / C-800 is uniformly distributed, with few impurities and consistent size. The identical morphology of the cobalt zinc phosphide and the precursor is due to the increased carbon content on the surface after calcination, which protects the inherent morphology of the material and improves its conductivity and specific surface area. Figure 15 a TEM of CoZnP2 / C was observed. The microspheres have a diameter of 1.1 μmol / L, slightly smaller than the precursor, and their surface is smooth and evenly distributed. It is possible that the phosphate is distributed on the surface of the microspheres, and the oxygen in them is desorbed at high temperature, forming phosphides that migrate into the microspheres, thereby changing the morphology of the crystals and reducing their size. In addition, no obvious lattice fringes were observed in the HR-TEM image ( Figure 15 b), which may be due to the low content of metal elements. The convex contours showing fluctuations of C, P, Zn, Co, and O in the energy spectrum line scan element distribution further confirm the carbon sphere structure of the metal phosphide shell with a thickness of about 100 nm ( Figure 15 cd). Notably, this spherical structure enhances the accessibility of the phosphide active sites, making it easier for electrolytes and ions to penetrate when electrochemical reactions occur on the catalyst surface. Figure 15 The elemental mapping of CoZnP2 / C in e verifies the uniform distribution of elements. Figure 13 The corresponding EDS spectrum shows an increase in the content of all elements, except O, compared to the precursor. This phenomenon can be attributed to the Kirkendall effect, which causes different diffusion rates of metal atoms in the phosphide. Metal atoms migrate from the surface to the interior of the sphere, reacting with P to form a phosphide layer. This is because the diffusion rate of metal atoms on the surface is significantly faster than that inside. As a result, oxygen remaining on the surface is carried away by the argon gas as vapor. The Co content is also low. This is likely due to the lower formation energy of the Co site (-1433.9708 eV) compared to the Zn site (-1433.9413 eV) in CoZnP2 / C. As shown in Table 4, this preferential phosphating of Co slows the migration of Co on the surface. During calcination, Co is first released from the tube furnace as vapor at high temperatures with the argon flow.

[0060] Table 4 DFT calculated CoZnP4O 11 , the formation energies of CoZnP2 / C and ZnP / C, and the adsorption energies of clothianidin on Co and Zn sites

[0061] The TEM-EDX results of the P, Co, and Zn contents in CoZnP2 / C are consistent with the ICP-OES results in Table 1.

[0062] Figure 14TEM images of CoZnP2 / C-700 and CoZnP2 / C-900 were also examined. They were microspheres of varying sizes and contained a significant amount of impurities. Therefore, CoZnP2 / C-800 was selected for subsequent electrochemical performance studies.

[0063] 2. CoZnP2 / C modified electrode and electrochemical sensor See also Figure 16 The present invention provides a method for constructing an electrochemical sensor based on CoZnP2 / C, which specifically includes the following steps: Preparation of CoZnP2 / C modified electrode: First, 1 mg of CoZnP2 / C was evenly dispersed in 1 mL of water. 6 μL of the CoZnP2 / C dispersion was pipetted onto the surface of the screen-printed electrode and dried under an infrared lamp for about 8 minutes to obtain the CoZnP2 / C modified electrode. Preparation of electrochemical sensor: A platinum wire was used as the counter electrode, a saturated calomel electrode (SCE) was used as the reference electrode, and a 100 μmol / L clothianidin (CLD) aqueous solution was added dropwise onto the CoZnP2 / C modified electrode to prepare the working electrode. The three electrodes were inserted into a pH 6, 0.01 mol / L phosphate buffer (PBS).

[0064] The specific electrochemical test method is as follows: 1) Cyclic voltammetry (CV): using 5 mM Fe(CN)6 3- / 4- As a redox probe, the potential range of -0.2 V to 0.6 V was 0.05 V s -1 The electrochemical properties of the materials and their potential applicability as electrode materials for electrochemical sensing of CLD were evaluated by CV method at a scan rate of 1.5 Å.

[0065] 2) Differential pulse voltammetry (DPV): DPV was performed using a potential ranging from -0.4 V to -1.4 V in 0.01 mol / L PBS (pH 6.0).

[0066] For the precursor CoZnP4O 11 , respectively according to Figure 17 a and Figure 17 b, Comparison of electroactivity with different molar ratios of PA:total metal ions and doping with different transition metal ions. The results show that when the molar ratio of PA:total metal ions = 106:1 and Co doping is used, the oxidation peak current (I pa ) is the largest, which is consistent with the SEM results. Figure 18 a shows that after calcination, except for CoZnP2 / C-800, the I paThe results show that calcination promotes the formation of microspheres through the Kirkendall effect, providing abundant active sites and good charge transfer ability, thereby improving the electrocatalytic performance.

[0067] When the electrochemical performance of CLD detection was evaluated with CoZnP2 / C, bare AuE, CoZnP2 / C / AuE, and CLD / CoZnP2 / C / AuE were tested by CV in 100 μmol / L CLD. Figure 18 b, Cathodic peak current of bare Au electrode (I pc ) and cathode peak potential (E pc ) are - 466 µA and - 1.25 V, respectively. After loading CoZnP2 / C on the Au electrode, the peak current increases significantly to -612 µA. Figure 19 a I of non-C-doped ZnP / C / AuE pc It is 0.8 times smaller than that of CoZnP2 / C / AuE. This may be due to the fact that the doping of Co makes CoZnP2 / C have a higher specific surface area and better electrocatalytic activity. When CLD exists, the I pc This improvement can be explained by the formation of hydrogen bonds between the functional groups in CoZnP2 / C / AuE and CLD, which leads to an increase in the accumulation of CLD on the electrode surface. In addition, when using ZnP / C to detect CLD, the I pc The value of the ZnP / C sensor is −437 μA, which indicates that the ZnP / C sensor cannot achieve electrochemical detection of CLD. This is because the adsorption energy of CoZnP2 / C for CLD is −1.52 eV, which is lower than that of ZnP / C, which is −1.09 eV.

[0068] In addition, CoZnP4O 11 It is also used to detect CLD, such as Figure 19 As shown in b, I pc decreased, indicating that the precursor could not detect CLD. Figure 19 The DPV test in c further confirmed the feasibility of the sensor based on CoZnP2 / C. In the presence of 100 μmol / L CLD, I pc The change (∆I) = 280 μA proves that the sensor is successfully constructed.

[0069] Electrochemical detection In 0.01 mol / L PBS at pH 6.0, the electrochemical behavior of CoZnP2 / C / AuE at different CLD concentrations of 0.08 μmol / L, 0.5 μmol / L, 3 μmol / L, 18 μmol / L, 54 μmol / L, 162 μmol / L, and 486 μmol / L was systematically investigated using the DPV method. Figure 20 As shown in a, the peak current increases significantly with the increase of CLD concentration. Figure 20 b, within the range of 0.08 to 486 μmol / L, I pc There is a strong linear relationship between I pc (µA) = - 13.1520x- 217.1570 (R 2 = 0.9967). The limit of detection (LOD) was determined using the formula 3: s / m, where s is the standard deviation and m is the slope of the calibration curve. The calculated LOD value was 0.016 μmol / L. Therefore, the CoZnP2 / C material provided by the present embodiment shows potential for fabricating effective CLD electrochemical sensors.

[0070] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to preferred embodiments, ordinary technicians in the field should understand that the specific implementation methods of the present invention can still be modified or some technical features can be replaced by equivalents without departing from the spirit of the technical solutions of the present invention. They should all be included in the scope of the technical solutions claimed for protection by the present invention.

Claims

1. A method for preparing a transition metal-doped zinc-based phosphide, comprising the steps of: Preparation of precursor: Using zinc nitrate, transition metal nitrate and organic phosphorus as raw materials, the precursor of transition metal-doped zinc-based phosphide is prepared by ball milling, wherein: The molar ratio of zinc nitrate, the transition metal nitrate and the organic phosphorus is 0.1-2:0.1-2:100-110, and the transition metal nitrate is cobalt nitrate, iron nitrate, copper nitrate, molybdenum nitrate or nickel nitrate; Preparation of the target phosphide: The precursor is carbonized at 700-1000° C. by a calcination method to obtain a transition metal-doped zinc-based phosphide: MZnP2 / C, wherein M is Co, Fe, Cu, Mo or Ni.

2. The preparation method according to claim 1, characterized in that In the step of preparing the precursor, the process parameters of the ball milling method are: ball milling time 8 to 14 hours, ball-to-powder weight ratio of 25:1 to 10:1, and rotation speed of 200 to 600 rpm.

3. The preparation method according to claim 1 or 2, characterized in that The calcination method comprises: transferring the precursor into a tube furnace, and performing high-temperature carbonization at 700-1000° C. for 1-4 hours in a flowing inert gas to obtain the transition metal-doped zinc-based phosphide.

4. The preparation method according to claim 3, characterized in that The preparation step of the target phosphide further includes: acid washing and vacuum drying the product after high-temperature carbonization to obtain purified transition metal-doped zinc-based phosphide.

5. A transition metal-doped zinc-based phosphide prepared by the preparation method according to any one of claims 1 to 4.

6. A transition metal-doped zinc-based phosphide modified electrode, characterized in that: The invention comprises a bare electrode and the transition metal-doped zinc-based phosphide according to claim 5 uniformly dispersed on the bare electrode.

7. A method for preparing the transition metal-doped zinc-based phosphide modified electrode according to claim 6, comprising: The transition metal-doped zinc-based phosphide is uniformly dispersed in water to prepare a transition metal-doped zinc-based phosphide dispersion, and the solid-liquid ratio of the two is 0.5-2:0.5-2 mg / mL; the transition metal-doped zinc-based phosphide dispersion is dropwise added to the surface of the bare electrode and dried to obtain a zinc-based phosphide modified electrode.

8. An electrochemical sensor comprising a working electrode, characterized in that The working electrode comprises the transition metal-doped zinc-based phosphide modified electrode according to claim 6 and a neonicotinoid insecticide aqueous dispersion dripped onto the transition metal-doped zinc-based phosphide modified electrode.

9. The electrochemical sensor according to claim 8, characterized in that It also includes an electrolyte, which is a buffer solution with a pH of 4 to 7; the concentration of the neonicotinoid insecticide aqueous dispersion is 0.08 to 486 μmol / L.

10. Use of the transition metal-doped zinc-based phosphide according to claim 5, the transition metal-doped zinc-based phosphide modified electrode according to claim 6, or the electrochemical sensor according to claim 8 in electrochemical detection of neonicotinoid insecticides.

Images