Preparation method of iridium-doped graphene oxide nanozyme and application of its product in pesticide residue detection of samples to be tested

Abstract

The present invention discloses a preparation method of iridium-doped graphene oxide nanozyme and its product and application in the detection of pesticide residues in samples to be tested. The present invention obtains graphene nanozymes with enzyme-like activity by a doping method. The pesticide molecules remaining in crops belong to aromatic compounds, which can produce π-π adsorption with graphene-based nanozymes, shield the active sites of graphene-based nanozymes, and cause the activity of peroxidase-like enzymes to decrease. According to the enzyme-like activity, the efficiency is reduced and the pesticide residues are evaluated. The invention is environmentally friendly and low-cost, which is conducive to reducing the cost of pesticide residue detection and improving detection efficiency.

Description

Technical Field

[0001] The present invention belongs to the intersecting field involving materials science and biochemical analysis and detection, and specifically relates to a preparation method of iridium-doped graphene oxide nanozyme and the application of the product in the detection of pesticide residues in samples to be tested. Background Art

[0002] Pesticides are chemical agents widely used in the production of crops, mainly used to control weeds, pests and diseases, and pathogenic bacteria of crops, and to increase crop yields. However, with the increasing demand and use of pesticides, long-term and high-dose pesticide control will not only cause pesticide resistance, but also cause pesticide residues in crops and the environment. Pesticide residues in the soil will cause soil compaction, affecting the subsequent growth of plants and crops; pesticides flow into lakes through surface water, destroying the aquatic environment and threatening the health of aquatic organisms; pesticides diffuse into the air through spray, causing acute and chronic toxicity to birds, bees and other organisms; pesticide residues on animals and plants will indirectly cause pesticide poisoning in humans, thereby threatening human life and health. The World Health Organization estimates that there are 3 million cases of pesticide poisoning each year, causing as many as 220,000 deaths, especially in developing countries. Pesticide poisoning may lead to a series of neurological health problems, such as amnesia, visual impairment, loss of coordination, etc. It may also induce asthma, allergies and hypersensitivity reactions. In severe cases, it may also lead to cancer and hormone disorders, affecting human reproductive health and fetal development. Therefore, pesticide testing is necessary, especially low-cost and efficient pesticide testing.

[0003] Traditional pesticide detection technologies include gas chromatography, liquid chromatography, high-performance liquid chromatography, enzyme-linked immunosorbent assay, capillary electrophoresis, etc. In order to improve the convenience of detection, biosensors are also commonly used in pesticide detection, including electrochemical sensors, optical sensors, piezoelectric sensors, etc. At present, there are many types of pesticide residue detection technologies, which can be roughly divided into two categories according to the principle: one is chromatographic detection, including gas chromatography, liquid chromatography and high-performance liquid chromatography, etc. This type of detection technology not only relies on expensive detection instruments, but also requires complex pre-treatment of samples; the second type is biochemical detection, which detects pesticide residues based on enzyme inhibition rate and is also the mainstream technology advocated by national standards (GB / T5009.199-2003) and agricultural standard methods (NY / T 448-2001). However, this type of technology requires the use of expensive natural enzymes and antibodies, and the detection system has a low reuse rate. Based on the specificity of natural enzymes, only one pesticide can be detected at a time.

[0004] Nanozymes are a type of nanomaterials with enzyme-like catalytic activity. They have become a new generation of natural enzyme substitutes due to their advantages such as easy preparation, low price, good stability and long storage time. They have broad application prospects in biological analysis, imaging, treatment, environmental protection, etc. Carbon-based nanozymes have become a hot research object in the field of nanozymes due to their abundant sources, low cost and low biological toxicity, especially carbon nanozymes that obtain specific activity after doping. Based on this, the development of doped carbon nanozymes for the detection of pesticides will greatly reduce the detection cost and achieve efficient detection.

[0005] Chemical pesticide molecules such as lactofen, clofopyralid, benzylsulfuron-methyl, fomesafen and buthenyl sulfamethoxam are all aromatic compounds, and these aromatic hydrocarbon compounds produce π-π adsorption with graphene nanozymes, which in turn shield the active sites of graphene-based nanozymes, resulting in reduced enzyme activity. The pesticide residue content can be determined based on the degree of reduction in the enzyme activity of graphene-based nanozymes, and no expensive instruments are required, so low-cost rapid detection of pesticides can be achieved.

[0006] Based on the above research background analysis, there are the following difficulties in developing suitable nanozymes and using them for the detection of pesticide residues: (1) Developing and preparing nanozymes with stable enzyme-like activity; (2) The linear detection of enzyme-like activity needs to be within a certain range to meet the needs of quantitative detection of pesticide residues; (3) At present, there are no doped graphene nanozymes for the rapid detection of pesticide residues.

[0007] In view of the above background analysis and the importance of pesticide detection, developing a class of graphene nanozymes for rapid and low-cost detection of pesticide residues has important application value. Summary of the invention

[0008] Purpose of the invention: In view of the shortcomings of the prior art, the present invention endows the graphene material with enzyme-like activity, especially peroxidase-like activity, by doping the graphene material with elements. Since most pesticide molecules belong to aromatic hydrocarbon compounds, they can produce π-π adsorption with graphene nanozymes, shielding the active sites of graphene-based nanozymes, resulting in reduced enzyme-like activity; the degree of reduction in the enzyme-like activity of graphene-based nanozymes is used to determine the pesticide residue content, and no expensive instruments and equipment are required, so low-cost rapid detection of pesticides can be achieved.

[0009] Technical solution: In order to solve the above technical problems, the present invention provides a preparation method based on iridium-doped graphene oxide nanozyme, comprising the following steps:

[0010] (1) dissolving di-μ-chlorotetra[3,5-difluoro-2-(2-pyridyl-κN)phenyl-κC]diiridium and graphene oxide in ethylene glycol, and obtaining a precursor solution after ultrasonic dispersion;

[0011] (2) introducing the precursor solution obtained in step (1) into a flask, stirring and refluxing at 140° C.-180° C. for 12 h-16 h under nitrogen protection, and then cooling to room temperature to obtain a liquid;

[0012] (3) The liquid obtained in step (2) is divided into centrifuge tubes, and the supernatant is removed by centrifugation. Methanol is added to each centrifuge tube for rinsing, and the washing liquid is removed by centrifugation. This step is repeated multiple times; water is added to each centrifuge tube for rinsing, and the washing liquid is removed by centrifugation. This step is repeated multiple times, and then, iridium-doped graphene oxide nanozyme is obtained.

[0013] Wherein, the mass ratio of di-μ-chlorotetrakis[3,5-difluoro-2-(2-pyridyl-κN)phenyl-κC]diiridium to graphene oxide in step (1) is 5:7.

[0014] Wherein, the centrifugal speed described in step (3) is 8000~10000g.

[0015] The present invention also includes the iridium-doped graphene oxide nanozyme obtained by the preparation method.

[0016] The present invention also includes the application of the iridium-doped graphene oxide nanozyme in the detection of pesticide residues.

[0017] Wherein, the pesticide is an aromatic compound, including one or more of lactofen-butyl, clofopyralid, benzylsulfuron-methyl, fomesafen-butyl or diafenthiuron.

[0018] Wherein, the concentration of the pesticide is 1 to 80 μg / mL.

[0019] The present invention also includes a method for detecting pesticide residues in a sample to be tested, comprising the following steps: adding acetic acid-sodium acetate buffer, the iridium-doped graphene oxide nanozyme according to claim 4 and the sample to be tested into the wells of a porous plate, incubating at room temperature, then adding H2O2, and finally adding TMB, mixing and reacting, and evaluating the pesticide residue content by reading the spectral absorption value at 652nm with an enzyme reader.

[0020] Wherein, the concentration of the iridium-doped graphene oxide nanozyme is 1 to 80 μg / mL.

[0021] Wherein, the volume ratio of the iridium-doped graphene oxide nanozyme to the sample to be detected is 1:1-1:5.

[0022] The samples to be tested in the present invention include but are not limited to samples containing pesticides such as crops or agricultural products.

[0023] The present invention is based on the development of doped graphene nanozymes and their application in the detection of pesticide residues in samples to be tested. The doped graphene refers to a nanomaterial formed by the accumulation of carbon atoms, which has high stability and strong modifiability. The doped graphene refers to a new type of graphene carbon nanomaterial obtained by doping graphene carbon nanomaterials with different elements. The nanozyme refers to a nanomaterial with enzyme-like activity, and the enzyme-like activity includes peroxidase (POD), oxidase (OXD), etc. The doped graphene nanozyme refers to a graphene carbon nanomaterial with enzyme-like activity after graphene carbon nanomaterials are doped with different chemical elements. The pesticide residue refers to the use of chemical drugs in the process of crop planting to suppress the influence of weeds, pests and diseases, and plant pathogens, causing some pesticides to be retained in crops. The present invention utilizes a doping method to obtain graphene nanozymes with enzyme-like activity. The pesticide molecules remaining in crops are aromatic compounds, which can produce π-π adsorption with graphene-based nanozymes, shielding the active sites of graphene-based nanozymes, resulting in reduced peroxidase-like activity. The pesticide residues are evaluated based on the efficiency of the enzyme-like activity reduction.

[0024] Among them, the detection of pesticide residues by the iridium-doped graphene nanozyme is based on the fact that the pesticide molecules retained in the crops have aromatic hydrocarbon rings, which can produce π-π adsorption with the graphene-based nanozymes, masking the active sites of the graphene-based nanozymes, resulting in a decrease in peroxidase-like activity. The efficiency is reduced based on the enzyme-like activity, and is used for the detection of pesticide residues.

[0025] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages:

[0026] 1. Convenient detection method: The present invention obtains nanozymes with enzyme-like activity by doping graphene nanomaterials with iridium, which are used for the detection of pesticide molecules. Compared with the traditional enzymatic detection of pesticide molecules, the nanozyme detection method has wider application conditions, does not require expensive experimental instruments, and has low investment.

[0027] 2. Simple preparation process: The present invention develops iridium-doped graphene nanozymes, which are graphene nanomaterials doped with iridium to obtain nanomaterials with enzyme-like activity. Compared with biological enzymes, the preparation process is simple and controllable, with good repeatability, low raw material cost, and convenient for industrial production and market transformation.

[0028] 3. Rapid detection effect of pesticide molecule residues: The pesticide molecules remaining in crops are aromatic compounds, which can produce π-π adsorption with graphene-based nanozymes, shielding the active sites of graphene-based nanozymes, resulting in reduced peroxidase-like activity. The pesticide residues are detected based on the reduced efficiency of enzyme-like activity. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 TEM images of graphene and iridium-doped graphene oxide according to Example 1 of the present invention;

[0030] Figure 2 High resolution TEM (HRTEM) and element distribution map of iridium-doped graphene oxide according to Example 1 of the present invention;

[0031] Figure 3 X-ray photoelectron spectroscopy (XPS) of iridium-doped graphene oxide according to Example 1 of the present invention;

[0032] Figure 4 X-ray diffraction (XRD) of iridium-doped graphene oxide according to Example 1 of the present invention;

[0033] Figure 5 The oxidase-like activity of iridium-doped graphene oxide in Example 2 of the present invention;

[0034] Figure 6 The peroxidase-like activity of iridium-doped graphene oxide in Example 2 of the present invention;

[0035] Figure 7 Kinetic test of TMB by the peroxidase-like enzyme of iridium-doped graphene oxide in Example 2 of the present invention;

[0036] Figure 8 Kinetic test of the peroxidase-like enzyme of iridium-doped graphene oxide on H2O2 in Example 2 of the present invention;

[0037] Fig. 9 In Example 3 of the present invention, iridium-doped graphene oxide is used for the detection and analysis of the pesticide molecule lactofop-butyl;

[0038] Fig.10 In Example 4 of the present invention, iridium-doped graphene oxide is used for the detection and analysis of the pesticide molecule fomesafen;

[0039] Fig.11 In Example 4 of the present invention, iridium-doped graphene oxide is used for the detection and analysis of the pesticide molecule fluazifop-pyralid. DETAILED DESCRIPTION

[0040] The technical solution of the present invention is described in detail below with reference to examples.

[0041] Example 1

[0042] A method for preparing nanozymes having multi-enzyme activity by synthesizing nanomaterial precursors and doping them with elements:

[0043] ① Take 100 mg of di-μ-chlorotetra[3,5-difluoro-2-(2-pyridyl-κN)phenyl-κC]diiridium (CAS No.: 391611-77-1) and 140 mg of graphene oxide and dissolve them in 15 mL of ethylene glycol. After ultrasonic dispersion, a precursor solution is obtained for use.

[0044] ② The precursor solution obtained in ① was introduced into a 50 mL flask, stirred and refluxed at 140°C for 12 h under nitrogen protection, and then cooled to room temperature.

[0045] ③ The liquid obtained in ② was divided into 10 mL centrifuge tubes, centrifuged at 8000 g to remove the supernatant, 5 mL of methanol was added to each centrifuge tube for rinsing, and the washing liquid was removed by centrifugation at 10000 g. This step was repeated 3 times; 5 mL of water was added to each centrifuge tube for rinsing, and the washing liquid was removed by centrifugation at 10000 g. This step was repeated 3 times. Subsequently, iridium-doped graphene oxide nanozyme (Ir-GO) was obtained.

[0046] In this example, iridium-doped graphene oxide nanozyme was prepared by single element doping. Figure 1 The TEM image shows that iridium-doped graphene oxide retains a two-dimensional structure similar to graphene, proving that the synthesis process does not damage the graphene structure; Figure 2 HRTEM images and elemental analysis images of Figure 3 The XPS graph shows the successful doping of iridium, and ICP shows that the iridium doping amount is about 0.62wt%; Figure 4 The XRD pattern shows that iridium-doped graphene oxide has a broad peak at (20-30)° and no obvious peak after 40°, proving that the doped iridium has no obvious crystallization.

[0047] Example 2

[0048] The iridium-doped graphene oxide nanozyme prepared in Example 1 was tested and verified for enzyme-like activity. The enzyme activity substrate was 3,3',5,5'-tetramethylbenzidine (TMB) (CAS No.: 54827-17-7, purchased from Sigma-Aldrich (Shanghai) Trading Co., Ltd.).

[0049] Oxidase-like detection: 3,3',5,5'-tetramethylbenzidine (TMB) was used to detect the peroxidase-like activity of iridium-doped graphene oxide nanozyme. The specific method is: add 160μL of acetic acid-sodium acetate buffer (0.2M, pH=4.66) and 20μL of iridium-doped graphene oxide nanozyme (final concentration 25μg / mL) to the wells of a 96-well plate, and finally use a spray gun to add 20μL of TMB (final concentration 0.25mM), mix and react for 10 minutes, and then use an enzyme reader to read the (350-750)nm ultraviolet spectrum.

[0050] Peroxidase-like detection: 3,3',5,5'-tetramethylbenzidine (TMB) was used to detect the peroxidase-like activity of iridium-doped graphene oxide nanozyme. The specific method is: 140 μL of acetic acid-sodium acetate buffer (0.2M, pH = 4.66) and 20 μL of iridium-doped graphene oxide nanozyme (final concentration 25 μg / mL) were added to the wells of a 96-well plate, and finally 20 μL of TMB (final concentration 0.25 mM) and 20 μL of H2O2 (final concentration 0.25 mM) were added using a spray gun. After mixing and reacting for 10 minutes, the (350-750) nm ultraviolet spectrum was read using an enzyme reader.

[0051] Steady-state kinetics of peroxidase-like activity of iridium-doped graphene oxide nanozyme: 140 μL of acetic acid-sodium acetate buffer (0.2 M, pH = 4), 20 μL of iridium-doped graphene oxide nanozyme (Ir-GO) (final concentration 25 μg / mL) and 20 μL of H2O2 (see concentration below) were added to the wells of a 96-well plate. Finally, TMB was added using a spray gun. After mixing, the change in ultraviolet absorbance at 652 nm was immediately read using an ELISA reader within 1 min. For comparison, the following groups were set: (1) The H2O2 concentration was kept at 2.5 mM, and the TMB concentrations were 0.01 mM, 0.02 mM, 0.05 mM, 0.1 mM, 0.2 mM, 0.5 mM, and 1 mM, respectively. (2) The TMB concentration was kept at 1 mM, and the H2O2 concentration was changed to 0 mM, 0.1 mM, 0.2 mM, 0.5 mM, 1 mM, and 2.5 mM. The quotient of the concentration and time was taken as the average reaction rate. The two sets of data were fitted with Michaelis–Menten and double reciprocal fitting to obtain the Michaelis constant K of the iridium-doped graphene oxide nanozyme. m and maximum reaction speed V max .

[0052] In this example, the enzyme-like activity of iridium-doped graphene oxide nanozymes was measured, including oxidase-like activity ( Figure 5 ), peroxidase-like activity ( Figure 6 ) and the steady-state kinetics of peroxidase-like activity ( Figure 7 and Figure 8 ), indicating that the iridium-doped graphene oxide nanozyme has oxidase-like and peroxidase-like activities, especially the absorbance of the peroxidase-like activity at 652nm increased significantly, indicating that the iridium-doped graphene oxide nanozyme has a higher peroxidase-like activity; the enzymatic reaction kinetics test found that the maximum reaction rate of the iridium-doped graphene oxide nanozyme to TMB was 0.388mM / min, and the Michaelis constant K m The value is 0.382mM; the maximum reaction rate to H2O2 is 0.440mM / min, and the Michaelis constant K mThe value is 0.363mM; the above enzyme activity analysis shows that the synthesized iridium-doped graphene oxide nanozyme can be used for subsequent detection of pesticide molecules.

[0053] Example 3

[0054] The preferred iridium-doped graphene oxide nanozyme and enzyme-like activity test conditions in Example 1 and Example 2 were used for the detection of pesticide molecules, with lactofensulfuron (purchased from Hubei Wonder Chemical Co., Ltd.) being an example of the pesticide molecule.

[0055] Detection of lactofenze by the Ir-GO nanozyme prepared in Example 1: 120 μL of acetic acid-sodium acetate buffer (0.2M, pH=3-8), 20 μL of iridium-doped graphene oxide nanozyme (final concentration 25 μg / mL), and 20 μL of lactofenzeze at different concentrations (specific concentrations refer to the following) were added to a 96-well plate, and incubated at room temperature for 10 min. Subsequently, 20 μL of H2O2 (final concentration 0.25 mM) was added, and finally 20 μL of TMB (final concentration 0.25 mM) was added using a spray gun. After mixing and reacting for 10 min, the (350-750) nm ultraviolet spectrum was read using an enzyme reader. The concentrations of lactofenzeze were set to: 20 μg / mL, 10 μg / mL, 4 μg / mL, 2 μg / mL, 1 μg / mL, and 0 μg / mL. After detection and calculation, the results are as follows. Fig. 9 The detection limit of Ir-GO nanozyme for lactofensulfuron was 0.2441 μg / mL.

[0056] Example 4

[0057] The preferred iridium-doped graphene oxide nanozyme and enzyme-like activity test conditions in Example 1 and Example 2 were used to detect the pesticide molecule fomesafen (purchased from Wuhan Lvjing Fenghua Biotechnology Co., Ltd.).

[0058] The detection steps of fomesafen by the Ir-GO nanozyme prepared in Example 1 are as follows: 120 μL of acetic acid-sodium acetate buffer (0.2M, pH=3-8), 20 μL of iridium-doped graphene oxide nanozyme (final concentration 25 μg / mL), and 20 μL of fomesafen of different concentrations (specific concentrations refer to the following) were added to the wells of a 96-well plate, and incubated at room temperature for 10 minutes. Subsequently, 20 μL of H2O2 (final concentration 0.25 mM) was added, and finally 20 μL of TMB (final concentration 0.25 mM) was added using a spray gun. After mixing and reacting for 10 minutes, the (350-750) nm ultraviolet spectrum was read using an enzyme reader. The concentrations of fomesafen were set to: 40 μg / mL, 20 μg / mL, 10 μg / mL, 5 μg / mL, 2.5 μg / mL, and 0 μg / mL. After detection and calculation, the results are as follows. Fig.10The detection limit of Ir-GO nanozyme for fomesafen was 0.2775 μg / mL.

[0059] Example 5

[0060] The preferred iridium-doped graphene oxide nanozyme and enzyme-like activity test conditions in Example 1 and Example 2 were used to detect the pesticide molecule fluazifop-pyralid (purchased from Wuhan Lvjing Fenghua Biotechnology Co., Ltd.).

[0061] The detection steps of fluazifop-butyl by the Ir-GO nanozyme prepared in Example 1 are as follows: 120 μL of acetic acid-sodium acetate buffer (0.2M, pH=3-8), 20 μL of iridium-doped graphene oxide nanozyme (final concentration 25 μg / mL), and 20 μL of fluazifop-butyl of different concentrations (specific concentrations refer to the following) were added to the wells of a 96-well plate, and incubated at room temperature for 10 minutes. Subsequently, 20 μL of H2O2 (final concentration 0.25 mM) was added, and finally 20 μL of TMB (final concentration 0.25 mM) was added using a spray gun. After mixing and reacting for 10 minutes, the (350-750) nm ultraviolet spectrum was read using an enzyme reader. The concentrations of fluazifop-butyl were set to: 20 μg / mL, 10 μg / mL, 5 μg / mL, 2.5 μg / mL, 1 μg / mL, 0.5 μg / mL, 0.1 μg / mL, and 0 μg / mL. After detection and calculation, the results are as follows. Fig.11 The detection limit of Ir-GO nanozyme for fluazifop-butyl was 0.0513 μg / mL.

[0062] Example 3, Example 4 and Example 5 respectively demonstrate the detection of pesticide molecules such as lactofenzein, fomesafen and fluazifop-butyl by the doped nanozyme represented by iridium-doped graphene oxide in the present invention, showing a lower detection limit; based on the π-π adsorption effect between pesticide molecules and graphene nanozymes, the active sites of graphene-based nanozymes are shielded, resulting in reduced peroxidase-like activity, and no additional auxiliary detection reagents such as enzyme molecules are required; the detection of various pesticide molecules can be realized, and it has good universality.

[0063] In summary, the present invention prepares a doped graphene nanozyme, aiming to improve the nanozyme activity of graphene materials; based on the π-π adsorption effect of pesticide molecules and graphene nanozymes, the active sites of graphene-based nanozymes are shielded, resulting in a decrease in peroxidase-like activity, and the pesticide residues are evaluated based on the efficiency of enzyme-like activity reduction, which can be used for the detection and analysis of pesticide residues; based on the importance of pesticide residue detection, the present invention has certain universality and market conversion value.

Claims

1. Application of iridium-doped graphene oxide nanozyme in pesticide residue detection, characterized in that: The preparation method based on iridium-doped graphene oxide nanozyme comprises the following steps: (1) dissolving di-μ-chlorotetra[3,5-difluoro-2-(2-pyridyl-κN)phenyl-κC]diiridium and graphene oxide in ethylene glycol, and obtaining a precursor solution after ultrasonic dispersion; (2) introducing the precursor solution obtained in step (1) into a flask, stirring and refluxing at 140°C-180°C for 12 h-16 h under nitrogen protection, and then cooling to room temperature to obtain a liquid; (3) The liquid obtained in step (2) is divided into centrifuge tubes, and the supernatant is removed by centrifugation. Each centrifuge tube is rinsed with methanol, and the washing liquid is removed by centrifugation. This step is repeated multiple times; each centrifuge tube is rinsed with water, and the washing liquid is removed by centrifugation. This step is repeated multiple times, and then, iridium-doped graphene oxide nanozyme is obtained; The mass ratio of di-μ-chlorotetra[3,5-difluoro-2-(2-pyridyl-κN)phenyl-κC]diiridium to graphene oxide in step (1) is 5:

7.

2. The use according to claim 1, characterized in that: The centrifugal speed in step (3) is 8000~10000g.

3. The use according to claim 1, characterized in that: The pesticide is an aromatic compound, including one or more of lactofen-butyl, clofopyralid, benzylsulfuron-methyl, fomesafen-butyl or diafenthiuron.

4. The use according to claim 1, characterized in that: The concentration of the pesticide is 1-80 μg / mL.

5. A method for detecting pesticide residues in a sample to be tested, characterized in that: The following steps are involved: Add acetic acid-sodium acetate buffer, iridium-doped graphene oxide nanozyme and the sample to be tested into the wells of the multi-well plate, incubate at room temperature, then add H2O2, and finally add TMB, mix and react, and read the spectral absorption value at 652 nm by a microplate reader to evaluate the pesticide residue content; the preparation method based on iridium-doped graphene oxide nanozyme comprises the following steps: (1) dissolving di-μ-chlorotetrakis[3,5-difluoro-2-(2-pyridyl-κN)phenyl-κC]diiridium and graphene oxide in ethylene glycol, and obtaining a precursor solution after ultrasonic dispersion, wherein the mass ratio of di-μ-chlorotetrakis[3,5-difluoro-2-(2-pyridyl-κN)phenyl-κC]diiridium to graphene oxide is 5:7; (2) introducing the precursor solution obtained in step (1) into a flask, stirring and refluxing at 140°C-180°C for 12 h-16 h under nitrogen protection, and then cooling to room temperature to obtain a liquid; (3) The liquid obtained in step (2) is divided into centrifuge tubes, centrifuged to remove the supernatant, methanol is added to each centrifuge tube for washing, centrifuged to remove the washing solution, and this step is repeated multiple times; Each centrifuge tube is rinsed with water and centrifuged to remove the washing solution. This step is repeated multiple times to obtain iridium-doped graphene oxide nanozyme.

6. The method for detecting pesticide residues in a sample to be tested according to claim 5, characterized in that: The concentration of the iridium-doped graphene oxide nanozyme is 1-80 μg / mL.

7. The method for detecting pesticide residues in a sample to be tested according to claim 5, characterized in that: The volume ratio of the iridium-doped graphene oxide nanozyme to the sample to be detected is 1:1-1:5.

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