Fe monatomic nano-enzyme as well as preparation method and application thereof

Abstract

The invention relates to a Fe monatomic nano-enzyme as well as a preparation method and application thereof. The preparation method of the Fe monatomic nano-enzyme comprises the following steps: dispersing poly-polyphenol spheres in water, adding ferric trichloride, stirring for 10-14 hours, centrifuging, drying, carbonizing, and pickling to obtain the Fe monatomic nano-enzyme. According to the Fe monatomic nano-enzyme as well as the preparation method and the application thereof, the poly polyphenol spheres and the ferric trichloride are taken as raw materials, the Fe monatomic nano-enzyme with different distances between adjacent active centers can be prepared, the preparation method is simple, the cost is low, and the reaction conditions are mild.

Description

Technical Field

[0001] The present invention belongs to the technical field of single-atom nanozymes, and specifically relates to a Fe single-atom nanozyme and a preparation method and application thereof. Background Art

[0002] Since Fe3O4 nanoparticles were found to have peroxidase-like activity similar to that of natural enzymes, nanozymes have attracted great attention as substitutes for natural enzymes. With the development of nanotechnology, many nanomaterials have been found to exhibit excellent enzyme-like activity and perform enzyme-like catalytic reactions. Nanozymes have been applied in anti-tumor, biomedical, wound healing, antibacterial, antioxidant, pesticide detection, environmental protection and other fields. Although nanozymes have been widely designed, they still have low catalytic activity and poor selectivity, which seriously limits their application. Therefore, it is crucial to design nanozymes with high catalytic activity to broaden the application range of nanozymes. Inspired by horseradish peroxidase (HRP), single-atom nanozymes with porphyrin structures with peroxidase-like catalytic activity were designed with Fe, Cu, Ir, Zn, Ru and Mn as active centers, thereby improving peroxidase-like catalytic activity and selectivity. Single-atom nanozymes have the characteristics of high atomic utilization, clear active centers and good stability. The peroxidase-like catalytic activity of single-atom nanozymes is enhanced by adjusting the valence state, metal spin state and coordination environment. However, due to the low selectivity and activity, feasible design strategies should be adopted to improve the enzyme-like catalytic activity and efficiency. The cooperative catalysis of diatomic nanozymes has been shown to regulate the chemical environment and change the electron transfer pathway to improve the activity of single-atom nanozymes. However, the contingency of atom pair formation leads to a relatively low proportion of diatomic sites, which weakens the cooperative effect of heterokaryotic di-single-atom nanozymes in peroxidase-like catalytic activity. Homokaryotic di-single-atom nanozymes can also regulate peroxidase-like catalytic activity by adjusting the coordination environment of metal sites.

[0003] Pesticides are indispensable in agriculture and are used to control pests and diseases and improve crop quality. According to FAO data, global pesticide use has increased, reaching 1.77 million tons in 2019. Increasing pesticides can increase yields, but residues may harm the environment and health, cause diseases, pollute soil, water and atmosphere, and disrupt ecological balance. Therefore, pesticide detection is crucial to food safety and health. With the improvement of living standards, people are paying more and more attention to food safety, and the requirements for pesticide detection technology are also increasing. Spectroscopy, chromatography, mass spectrometry and enzyme inhibition are commonly used techniques for detecting pesticide residues. Spectroscopy performs preliminary screening through color changes of chemical reactions. It is simple to operate but has low sensitivity. Gas chromatography (GC) and high-performance liquid chromatography (HPLC) are suitable for volatile and polar pesticides, respectively, with high sensitivity and efficiency. Mass spectrometry has high accuracy, but requires professional equipment and operation. Enzyme inhibition uses pesticides to inhibit enzyme activity. It is fast and simple, but has limited sensitivity and specificity.

[0004] In recent years, single-atom nanozymes have gradually become a research hotspot due to their advantages such as clear active centers, high atom utilization and adjustable active centers, but they still have limitations such as low enzyme-like activity and selectivity.

[0005] In view of this, the present invention proposes a new Fe single-atom nanozyme and a preparation method and application, which can prepare Fe single-atom nanozymes with different distances between adjacent atoms. Summary of the invention

[0006] The object of the present invention is to provide a method for preparing a Fe single-atom nanozyme. The preparation method is simple. A Fe single-atom nanozyme with adjacent active centers is prepared through reasonable design, and the purpose of regulating the activity of the Fe single-atom nanozyme is achieved by regulating the distance between adjacent active centers.

[0007] In order to achieve the above purpose, the technical solution adopted is:

[0008] A method for preparing a Fe single-atom nanozyme comprises the following steps: dispersing polyphenol balls in water, adding ferric chloride, stirring for 10-14 hours, centrifuging, drying, carbonizing, and acid-washing to obtain the Fe single-atom nanozyme.

[0009] Furthermore, the preparation method of the polyphenol spheres is as follows: P123, F127, phloroglucinol, 1,3,5-trimethylbenzene, ethylenediamine and ethanol solution are uniformly mixed, stirred for reaction, and after the reaction is completed, centrifuged and dried to obtain solid powder polyphenol spheres.

[0010] Furthermore, the mass volume ratio of the P123, F127, phloroglucinol, 1,3,5-trimethylbenzene, ethylenediamine, and ethanol solution is 0.70-0.80 g: 0.22-0.28 g: 0.55-0.65 g: 1.8-2.2 mL: 270-330 μL: 100 mL;

[0011] The volume ratio of ethanol to ethanol solution in the ethanol solution is 2-3:10.

[0012] Furthermore, the mass volume ratio of P123, F127, phloroglucinol, 1,3,5-trimethylbenzene, and ethylenediamine is 0.75 g: 0.25 g: 0.6 g: 2 mL: 300 μL;

[0013] The volume ratio of ethanol to water in the ethanol solution is 3:7.

[0014] Furthermore, the mass molar ratio of the polyphenol balls to ferric chloride is 1g:10-80mmol.

[0015] Furthermore, the mass molar ratio of the polyphenol balls to ferric chloride is 1g:10mmol, or 1g:20mmol, or 1g:40mmol, or 1g:80mmol.

[0016] Furthermore, the carbonization is: calcining at 700-900° C. in a nitrogen atmosphere.

[0017] Furthermore, the pickling is performed using a 2-3 mol / L hydrochloric acid solution.

[0018] Another object of the present invention is to provide a Fe single-atom nanozyme prepared by the above-mentioned preparation method.

[0019] Another object of the present invention is to provide an application of the above-mentioned Fe single-atom nanozyme. A pesticide detection platform is constructed based on the Fe single-atom nanozyme as a sensing unit for pesticide detection at lower concentrations to meet the requirements of on-site rapid detection of pesticides.

[0020] In order to achieve the above purpose, the technical solution adopted is:

[0021] Application of the above-mentioned Fe single-atom nanozyme in pesticide detection.

[0022] Furthermore, the above-mentioned Fe single-atom nanozyme was used to detect pesticides by colorimetry.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] 1. In the technical solution of the present invention, by adjusting the amount of ferric chloride added, the distance between adjacent Fe atoms can be adjusted, thereby adjusting the activity of the Fe single-atom nanozyme.

[0025] 2. In the technical solution of the present invention, the prepared Fe single-atom nanozyme is a peroxidase mimetic with peroxidase-like activity, which can catalyze the substrate (H2O2) to produce active oxygen (·OH), and ·OH can react with TMB to generate oxTMB, producing a blue reaction. By testing the absorbance of the system with different concentrations of pesticides added at the maximum absorption wavelength of the developer, a standard working curve of pesticide concentration-absorbance change value is drawn, which can be used for pesticide detection.

[0026] 3. In the technical solution of the present invention, the prepared Fe single-atom nanozyme is used for pesticide detection. The detection method is simple to operate, low-cost, mild reaction conditions, and does not require the addition of other reagents, thereby meeting the requirements of rapid detection of pesticides. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 SEM images of Fe single-atom nanozymes prepared for the examples. (a) FeN4 single-atom nanozyme, (b) Fe2N8 single-atom nanozyme, (c) Fe2N7 single-atom nanozyme, (d) Fe2N6 single-atom nanozyme.

[0028] Figure 2 AC HAADF-STEM images of Fe single-atom nanozymes prepared as examples. (ac) Atomic phase diagram of FeN4 single-atom nanozymes, (df) Atomic phase diagram of Fe2N8 single-atom nanozymes, (gi) Atomic phase diagram of Fe2N7 single-atom nanozymes, (jl) Atomic phase diagram of Fe2N6 single-atom nanozymes.

[0029] Figure 3 Steady-state kinetics diagram of the Fe single-atom nanozyme prepared as an example.

[0030] Figure 4 The standard curves of the Fe single-atom nanozyme prepared in Example 4 for the detection of different types of pesticides. (a) Malathion (MA), (b) Paraquat (PQ), (c) Carbaryl (CBL), (d) Cypermethrin (CMT), (e) 1,2-Dibromo-3-chloropropane (DBCP), (f) Thiamethoxam (TAT).

[0031] Figure 5 This is the scoring chart of the Fe single-atom nanozyme prepared in Example 4 for different types of pesticides.

[0032] Figure 6 Fe NPs SEM image of nanozyme. DETAILED DESCRIPTION

[0033] In order to further illustrate the Fe single-atom nanozyme of the present invention and its preparation method and application, and to achieve the intended purpose of the invention, the following is a detailed description of the Fe single-atom nanozyme and its preparation method and application, its specific implementation method, structure, characteristics and efficacy proposed in accordance with the present invention in combination with the preferred embodiments. In the following description, different "one embodiment" or "embodiment" does not necessarily refer to the same embodiment. In addition, specific features, structures or characteristics in one or more embodiments may be combined in any suitable form.

[0034] The following will further introduce the Fe single-atom nanozyme and its preparation method and application in detail in combination with specific embodiments:

[0035] The present invention discloses an Fe single-atom nanozyme and a preparation method and application thereof, and relates to the design, synthesis and application fields of single-atom nanozymes. The adjacent atoms of the Fe single-atom nanozyme prepared by the present invention have different distances, which can regulate the peroxidase-like activity of the Fe single-atom nanozyme, and the prepared Fe single-atom nanozyme can be used to perform sensitive detection of pesticides. The technical solution of the present invention is:

[0036] A method for preparing a Fe single-atom nanozyme comprises the following steps: dispersing polyphenol balls in water, adding ferric chloride, stirring for 10-14 hours, centrifuging, drying, carbonizing, and acid-washing to obtain the Fe single-atom nanozyme.

[0037] The polyphenol sphere is obtained by self-assembly of phloroglucinol, has a multi-level pore structure, a large specific surface area, and has the characteristics of rich functional groups of polyphenol substances and easy complexation with metals. It can be chelated with a variety of metals to prepare single-atom nanozyme precursors. At the same time, the polyphenol sphere has a strong reducing ability and can reduce a variety of metals to form nanoparticles. In the above technical scheme, hexahydrate ferric chloride is used to complex with the polyphenol sphere, and the ratio of the two is controlled to prepare Fe single-atom nanozymes with different metal loadings, and the distance between adjacent metal active centers is regulated.

[0038] Preferably, the preparation method of the polyphenol spheres is: P123, F127, phloroglucinol, 1,3,5-trimethylbenzene, ethylenediamine and ethanol solution are uniformly mixed, stirred for reaction, and after the reaction is completed, centrifuged and dried to obtain solid powder polyphenol spheres.

[0039] Further preferably, the mass volume ratio of the P123, F127, phloroglucinol, 1,3,5-trimethylbenzene, ethylenediamine, and ethanol solution is 0.70-0.80 g: 0.22-0.28 g: 0.55-0.65 g: 1.8-2.2 mL: 270-330 μL: 100 mL;

[0040] The volume ratio of ethanol to ethanol solution in the ethanol solution is 2-3:10.

[0041] Further preferably, the mass volume ratio of P123, F127, phloroglucinol, 1,3,5-trimethylbenzene, and ethylenediamine is 0.75 g: 0.25 g: 0.6 g: 2 mL: 300 μL;

[0042] The volume ratio of ethanol to water in the ethanol solution is 3:7.

[0043] Preferably, the mass molar ratio of the polyphenol spheres to ferric chloride is 1 g: 10-80 mmol.

[0044] Further preferably, the mass molar ratio of the polyphenol spheres to ferric chloride is 1 g:1 mmol, or 1 g:20 mmol, or 1 g:40 mmol, or 1 g:80 mmol.

[0045] Preferably, the carbonization is carried out by calcining at 700-900° C. in a nitrogen atmosphere.

[0046] In the above technical solution, a Fe single-atom nanozyme with a stable structure can be obtained at this temperature.

[0047] Preferably, the pickling is performed using a 2-3 mol / L hydrochloric acid solution.

[0048] An Fe single-atom nanozyme is prepared using the above-mentioned preparation method.

[0049] Application of the above-mentioned Fe single-atom nanozyme in pesticide detection.

[0050] Preferably, the above-mentioned Fe single-atom nanozyme is used to detect pesticides by colorimetry.

[0051] Example 1.

[0052] This example provides the preparation of FeN4 single-atom nanozyme (FeN4-SAzyme) and its peroxidase-like activity test, and the specific operation steps are as follows:

[0053] (1) Accurately weigh 0.75 g P123, 0.25 g F127 and 0.6 g phloroglucinol respectively and dissolve them in 100 mL ethanol solution (the volume ratio of water to anhydrous ethanol is 7:3), and ultrasonicate until fully dissolved. After magnetic stirring for 30 min, 2 mL of 1,3,5-trimethylbenzene was added, and stirring was continued for 30 min. After that, 300 μL of ethylenediamine was added, and the reaction was continued for 24 h. After centrifugation, the precipitated product was collected and vacuum dried for 24 h to obtain a solid product 1.

[0054] (2) Accurately weigh 0.1 g of solid product 1, disperse it in 100 mL of deionized water, add 0.027 g of ferric chloride hexahydrate, stir for 12 h, centrifuge, collect the precipitated product, and vacuum dry it for 24 h to obtain solid product 2.

[0055] (3) The solid product 2 was placed in a tubular furnace, calcined and carbonized at 800 °C under a nitrogen atmosphere, and then acid-washed with a 2 mol / L hydrochloric acid solution to obtain FeN4 single-atom nanozyme.

[0056] Example 2.

[0057] This example provides the preparation of Fe2N8 single-atom nanozyme (Fe2N8-SAzyme) and its peroxidase-like activity test, and the specific operation steps are as follows:

[0058] (1) Accurately weigh 0.75 g P123, 0.25 g F127 and 0.6 g phloroglucinol respectively and dissolve them in 100 mL ethanol solution (the volume ratio of water to anhydrous ethanol is 7:3), and ultrasonicate until fully dissolved. After magnetic stirring for 30 min, 2 mL of 1,3,5-trimethylbenzene was added, and stirring was continued for 30 min. After that, 300 μL of ethylenediamine was added, and the reaction was continued for 24 h. After centrifugation, the precipitated product was collected and vacuum dried for 24 h to obtain a solid product 1.

[0059] (2) Accurately weigh 0.1 g of solid product 1, disperse it in 100 mL of deionized water, add 0.054 g of ferric chloride hexahydrate, stir for 12 h, centrifuge, collect the precipitated product, and vacuum dry it for 24 h to obtain solid product 2.

[0060] (3) The solid product 2 was placed in a tubular furnace, calcined and carbonized at 800 °C under a nitrogen atmosphere, and then acid-washed with a 2 mol / L hydrochloric acid solution to obtain Fe2N8 single-atom nanozyme.

[0061] Example 3.

[0062] This example provides the preparation of Fe2N6 single-atom nanozyme (Fe2N6-SAzyme) and its peroxidase-like activity test, and the specific operation steps are as follows:

[0063] (1) Accurately weigh 0.75 g P123, 0.25 g F127 and 0.6 g phloroglucinol respectively and dissolve them in 100 mL ethanol solution (the volume ratio of water to anhydrous ethanol is 7:3), and ultrasonicate until fully dissolved. After magnetic stirring for 30 min, 2 mL of 1,3,5-trimethylbenzene was added, and stirring was continued for 30 min. After that, 300 μL of ethylenediamine was added, and the reaction was continued for 24 h. After centrifugation, the precipitated product was collected and vacuum dried for 24 h to obtain a solid product 1.

[0064] (2) Accurately weigh 0.1 g of solid product 1, disperse it in 100 mL of deionized water, add 0.216 g of ferric chloride hexahydrate, stir for 12 h, centrifuge, collect the precipitated product, and vacuum dry it for 24 h to obtain solid product 2.

[0065] (3) The solid product 2 was placed in a tubular furnace, calcined and carbonized at 800 °C under a nitrogen atmosphere, and then acid-washed with a 2 mol / L hydrochloric acid solution to obtain Fe2N6 single-atom nanozyme.

[0066] Example 4.

[0067] This example provides the preparation of Fe2N7 single-atom nanozyme (Fe2N7-SAzyme), the test of its peroxidase-like activity, and a method for detecting pesticides based on Fe2N7 single-atom nanozyme colorimetry. The specific steps are as follows:

[0068] (1) Accurately weigh 0.75 g P123, 0.25 g F127 and 0.6 g phloroglucinol respectively and dissolve them in 100 mL ethanol solution (the volume ratio of water to anhydrous ethanol is 7:3), and ultrasonicate until fully dissolved. After magnetic stirring for 30 min, 2 mL of 1,3,5-trimethylbenzene was added, and stirring was continued for 30 min. After that, 300 μL of ethylenediamine was added, and the reaction was continued for 24 h. After centrifugation, the precipitated product was collected and vacuum dried for 24 h to obtain a solid product 1.

[0069] (2) Accurately weigh 0.1 g of solid product 1, disperse it in 100 mL of deionized water, add 0.108 g of ferric chloride hexahydrate, stir for 12 h, centrifuge, collect the precipitated product, and vacuum dry it for 24 h to obtain solid product 2.

[0070] (3) The solid product 2 was placed in a tubular furnace, calcined and carbonized at 800 °C under a nitrogen atmosphere, and then acid-washed with a 2 mol / L hydrochloric acid solution to obtain Fe2N7 single-atom nanozyme.

[0071] (2) Method for detecting pesticides based on Fe2N7 single-atom nanozyme colorimetric method

[0072] ①Material preparation:

[0073] The Fe2N7 single-atom nanozyme was prepared into a 0.198 mg / mL solution for later use.

[0074] Prepare a 10 mM solution of 3,3',5,5'-tetramethylbenzidine (TMB) powder with anhydrous ethanol for later use.

[0075] Acetic acid and sodium acetate were prepared into a 0.1 mol / L buffer solution (pH 4) and set aside for later use.

[0076] Pesticides (malathion (MA), paraquat (PQ), carbaryl (CBL), cypermethrin (CMT), thiamethoxam (TAT), 1,2-dibromo-3-chloropropane (DBCP)) were prepared into a 3.3 mg / mL solution for use.

[0077] ②Method

[0078] 5 μL of 0.198 mg / mL Fe2N7 single-atom nanozyme solution was evenly dispersed in 0.1 mol / L acetic acid-sodium acetate buffer solution to obtain a Fe2N7 single-atom nanozyme buffer solution with a concentration of 0.3 μg / mL. Hydrogen peroxide and TMB were added to make the concentrations of the two in the Fe2N7 single-atom nanozyme buffer solution 20 mM and 0.3 mM, respectively. Pesticides (malathion (MA), paraquat (PQ), carbaryl (CBL), cypermethrin (CMT), 1,2-dibromo-3-chloropropane (DBCP), thiamethoxam (TAT)) of different concentrations (0, 2, 4, 6, 8, 10 ppm) were added. After incubation at 25°C for 20 minutes, the absorbance value (A) was tested at a wavelength of 652 nm. The absorbance value without pesticide addition (A0) was compared to obtain the absorbance change value (ΔA=A0-A), and a standard curve for pesticide detection was obtained.

[0079] result Figure 4-5 As shown in the figure, within the tested pesticide concentration range, the six pesticides all showed good linear relationships. Therefore, based on the colorimetric method, the Fe2N7 single-atom nanozyme showed good detection effect on low-concentration pesticide detection. Based on the above pesticide detection results, principal component analysis was performed, and the principal component analysis diagram ( Figure 5 ), it can be seen that the Fe2N7 single-atom nanozyme has good discrimination in the pesticide detection process and can distinguish six different types of pesticides.

[0080] Example 5.

[0081] (1) SEM image of Fe single-atom nanozyme

[0082] The Fe single-atom nanozymes prepared in Examples 1-4 were subjected to SEM. Figure 1 As shown, it can be seen that the prepared Fe single-atom nanozyme has a porous structure and a size of about 500nm.

[0083] (2) AC HAADF-STEM image of Fe single-atom nanozyme

[0084] AC HAADF-STEM was performed on the Fe single-atom nanozymes prepared in Example 1-4. Figure 2 As shown, it can be seen Figure 2(ac) show that the FeN4 single-atom nanozyme has isolated Fe atoms and does not form atomic pairs with adjacent atoms; Figure 2 (de) indicates that the Fe2N8 single-atom nanozyme has adjacent Fe atoms, and Figure 2 The distance between adjacent Fe atoms marked by f indicates that the distance between two Fe atoms is Figure 2 (gh) indicates that the Fe2N7 single-atom nanozyme has adjacent Fe atoms, and Figure 2 The distance between adjacent Fe atoms marked by i indicates that the distance between two Fe atoms is Figure 2 (jk) shows that the Fe2N6 single-atom nanozyme has adjacent Fe atoms, and Figure 2 The distance between the adjacent Fe atoms marked on the left shows that the distance between the two Fe atoms is

[0085] (3) Peroxidase-like activity test

[0086] The Fe single-atom nanozyme prepared by the present invention has peroxidase-like activity and is a peroxidase mimetic that can catalyze a substrate (H2O2) to produce reactive oxygen (·OH), and ·OH can react with a color developer (3,3',5,5'-tetramethylbenzidine) to generate oxidized TMB (oxTMB), producing a blue reaction. The absorbance test is performed at 652nm using a UV-visible spectrophotometer to obtain the concentration of oxTMB, and then the peroxidase-like activity of the Fe single-atom nanozyme is subjected to a steady-state kinetic test to obtain the peroxidase-like performance of the Fe single-atom nanozyme.

[0087] The FeN4, Fe2N8, Fe2N7 and Fe2N6 single-atom nanozymes prepared in Examples 1-4 were used as samples, and the specific method was as follows:

[0088] 1.98 mg of Fe single-atom nanozyme sample was accurately weighed and diluted to 10 mL with deionized water. 5 μL of the diluted solution was then dispersed in acetic acid-sodium acetate buffer solution (0.1 mol / L, pH 4) to obtain a Fe single-atom nanozyme solution with a concentration of 0.3 μg / mL. The peroxidase-like steady-state kinetic test of the Fe single-atom nanozyme was carried out under different hydrogen peroxide concentrations. Based on this, different volumes of hydrogen peroxide solution were added to the 0.3 μg / mL Fe single-atom nanozyme solution, so that the concentrations of hydrogen peroxide were 0, 5, 10, 15, 20, 25, 30, 35 and 40 mM, respectively, and then TMB solution (10 mM) was added to make the TMB concentration 0.3 mM. After shaking evenly, it can be observed that the solution gradually turns blue with time. After incubation at 25°C for 20 minutes, the absorbance values ​​were tested at a wavelength of 652 nm, and the recorded data were plotted to obtain the peroxidase activity curve of the Fe single-atom nanozyme.

[0089] The results are as follows Figure 3 As shown, under the same test conditions, Fe2N7 single-atom nanozymes have the best peroxidase-like activity. It was calculated that the Michaelis constants of FeN4, Fe2N8, Fe2N7 and Fe2N6 single-atom nanozymes for hydrogen peroxide were 3.36, 5.31, 6.56 and 5.14 mM, respectively, showing good substrate binding ability, demonstrating excellent peroxidase-like activity and selectivity.

[0090] Example 6.

[0091] The specific steps are as follows:

[0092] (1) Accurately weigh 0.70 g P123, 0.22 g F127 and 0.55 g phloroglucinol respectively and dissolve them in 100 mL ethanol solution (the volume ratio of water to anhydrous ethanol is 8:2), and ultrasonicate until fully dissolved. After magnetic stirring for 30 min, 1.8 mL of 1,3,5-trimethylbenzene was added, and stirring was continued for 30 min. After that, 270 μL of ethylenediamine was added, and the reaction was continued for 24 h. After centrifugation, the precipitated product was collected and vacuum dried for 24 h to obtain a solid product 1.

[0093] (2) Accurately weigh 0.1 g of solid product 1, disperse it in 100 mL of deionized water, add 0.027 g of ferric chloride hexahydrate, stir for 10 h, centrifuge, collect the precipitated product, and vacuum dry it for 24 h to obtain solid product 2.

[0094] (3) The solid product 2 was placed in a tubular furnace, calcined and carbonized at 700 °C under a nitrogen atmosphere, and then acid-washed with a 2.5 mol / L hydrochloric acid solution to obtain FeN4 single-atom nanozyme.

[0095] Example 7.

[0096] The specific steps are as follows:

[0097] (1) Accurately weigh 0.80 g P123, 0.28 g F127 and 0.65 g phloroglucinol respectively and dissolve them in 100 mL ethanol solution (the volume ratio of water to anhydrous ethanol is 7.5:2.5), and ultrasonicate until fully dissolved. After magnetic stirring for 40 min, 2.2 mL of 1,3,5-trimethylbenzene was added, and stirring was continued for 40 min. After that, 330 μL of ethylenediamine was added, and the reaction was continued for 24 h. After centrifugation, the precipitated product was collected and vacuum dried for 24 h to obtain a solid product 1.

[0098] (2) Accurately weigh 0.1 g of solid product 1, disperse it in 100 mL of deionized water, add 0.027 g of ferric chloride hexahydrate, stir for 14 h, centrifuge, collect the precipitated product, and vacuum dry it for 24 h to obtain solid product 2.

[0099] (3) The solid product 2 was placed in a tubular furnace, calcined and carbonized at 900 °C under a nitrogen atmosphere, and then acid-washed with a 3 mol / L hydrochloric acid solution to obtain FeN4 single-atom nanozyme.

[0100] Comparative Example 1.

[0101] The operation steps of Comparative Example 1 are the same as those of Example 1, except that the amount of ferric chloride hexahydrate is used. The amount of ferric chloride hexahydrate and the results are specifically shown in Table 1.

[0102] Table 1

[0103]

[0104] Figure 6 Fe prepared in Comparative Example 5 NPs Nanozymes, obvious metal agglomeration and metal lattice can be observed, and uniform Fe single-atom nanozymes cannot be formed.

[0105] The above is only a preferred embodiment of the embodiment of the present invention, and does not impose any form of limitation on the embodiment of the present invention. Any simple modification, equivalent changes and modifications made to the above embodiment based on the technical essence of the embodiment of the present invention are still within the scope of the technical solution of the embodiment of the present invention.

Claims

1. A method for preparing a Fe single-atom nanozyme, characterized in that: The preparation method is as follows: after dispersing the polyphenol balls in water, adding ferric chloride, stirring for 10-14 hours, centrifuging, drying, carbonizing, and acid washing to obtain the Fe single-atom nanozyme.

2. The preparation method according to claim 1, characterized in that: The preparation method of the polyphenol spheres comprises the following steps: uniformly mixing P123, F127, phloroglucinol, 1,3,5-trimethylbenzene, ethylenediamine and ethanol solution, stirring for reaction, and after the reaction is completed, centrifuging and drying to obtain the polyphenol spheres in solid powder form.

3. The preparation method according to claim 2, characterized in that: The mass volume ratio of P123, F127, phloroglucinol, 1,3,5-trimethylbenzene, ethylenediamine, and ethanol solution is 0.70-0.80 g: 0.22-0.28 g: 0.55-0.65 g: 1.8-2.2 mL: 270-330 μL: 100 mL; The volume ratio of ethanol to ethanol solution in the ethanol solution is 2-3:

10.

4. The preparation method according to claim 3, characterized in that: The mass volume ratio of P123, F127, phloroglucinol, 1,3,5-trimethylbenzene, and ethylenediamine is 0.75 g: 0.25 g: 0.6 g: 2 mL: 300 μL; The volume ratio of ethanol to water in the ethanol solution is 3:

7.

5. The preparation method according to claim 1, characterized in that: The mass molar ratio of the polyphenol balls to ferric chloride is 1g:10-80mmol.

6. The preparation method according to claim 5, characterized in that: The mass molar ratio of the polyphenol balls to ferric chloride is 1g:10mmol, or 1g:20mmol, or 1g:40mmol, or 1g:80mmol.

7. The preparation method according to claim 1, characterized in that: The carbonization is as follows: calcining at 700-900° C. in a nitrogen atmosphere; The pickling is performed using a 2-3 mol / L hydrochloric acid solution.

8. An Fe single-atom nanozyme, characterized in that: The method is prepared by any one of claims 1 to 7.

9. Application of the Fe single-atom nanozyme according to claim 8 in pesticide detection.

10. The use according to claim 9, characterized in that: The Fe single-atom nanozyme described in claim 8 is used to detect pesticides by colorimetry.

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