A PS@AuNPs composite microsphere and preparation and application thereof

Abstract

The present application relates to the technical field of pesticide molecule detection, and particularly relates to a PS@AuNPs composite microsphere and preparation and application thereof. The present application designs a carboxyl and amino modified polystyrene microsphere, and synthesizes PS@AuNPs-COOH and PS@AuNPs-NH2 composite microspheres through an interface assembly method; the composite microspheres are placed into a pesticide molecule storage solution, and through electrostatic interaction, the pesticide molecules are adsorbed to the surface of the composite microspheres; an SPE@GO@GNRs screen-printed electrode is prepared through an electrochemical deposition method, and an electrochemical enrichment method is adopted to adsorb pesticide molecules with positive and negative charges in the solution on the SPE@GO@GNRs screen-printed electrode; the Raman spectrum signal of the substance on the surface of the SPE@GO@GNRs screen-printed electrode is detected, so as to qualitatively and quantitatively analyze and detect the pesticide molecules. The present application has excellent selectivity, does not need to be labeled and separated and purified, can simultaneously analyze and detect multiple pesticide molecules, has a low detection limit, and guarantees the stability and accuracy of the analysis result.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of pesticide molecule detection, and in particular to PS@AuNPs composite microspheres and a preparation and application thereof. BACKGROUND

[0002] Graphene oxide (GO) is defined as an oxidized single layer of carbon atoms, which is produced by the oxidation process of graphene. GO has outstanding and unique characteristics such as large surface area, easy functionalization, photoluminescence, strong hydrophilicity, good dispersibility in various solvents, etc., and is a significant biocompatible material that can enhance electrochemical activity and adapt to charge transfer in molecules. Surface-enhanced Raman scattering (SERS) refers to the phenomenon that when some molecules are adsorbed to the surface of some rough metal (Au, Ag, Cu, etc.), the Raman scattering intensity of the molecules will be increased by 10 4 ~ 10 6 times. Due to the fast and sensitive characteristics of SERS technology, it is widely used in food safety, biological detection and other aspects. Gold nanorod modified reduced graphene can be used as a surface-enhanced Raman substrate material. Polyvinyl alcohol microgel (PVA) has many attractive properties such as excellent adhesion, availability of chemical modification, non-toxicity, strong mechanical strength, operation feasibility and easy handling. Microgels with local surface plasmon resonance (LSPR) can adsorb and enrich trace analytes in water, and have excellent SERS activity and conductivity.

[0003] Lasso is a non-selective herbicide, which has strong destructive effect on the environment. Organophosphorus pesticide methyl parathion (MeP) is widely used as an agricultural insecticide due to its low persistence and high insecticidal activity. However, it has caused serious pollution to the environment and ecological system due to leaving toxic residues in organisms, water and soil. In recent years, gold nanoparticles are often used as SERS substrates for pesticide analysis and detection, but there are few reports on simultaneous analysis and detection of Ami and MeP. Therefore, sensitive and convenient detection methods are needed to quickly and reliably detect the two pesticides, and it is of important practical significance to develop an analysis method for simultaneous detection of multiple pesticide molecules. SUMMARY

[0004] In order to solve the above problems, the purpose of the present application is to provide a PS@AuNPs composite microsphere and its preparation and application. The present application designs a carboxyl and amino modified polystyrene microsphere, and synthesizes PS@AuNPs-COOH and PS@AuNPs-NH2 composite microspheres by an interfacial assembly method; the composite microspheres are placed in a pesticide molecule stock solution, and through electrostatic interaction, the pesticide molecules are adsorbed to the surface of the composite microspheres; an SPE@GO@GNRs screen-printed electrode is prepared by an electrochemical deposition method, and an electrochemical enrichment method is used to adsorb the pesticide molecules with positive and negative charges in the solution on the SPE@GO@GNRs screen-printed electrode; the Raman spectrum signal of the substance on the surface of the SPE@GO@GNRs screen-printed electrode is detected, so that the pesticide molecules are qualitatively and quantitatively analyzed and detected. The present application has excellent selectivity, does not need to be labeled and separated and purified, realizes rapid and sensitive detection of Ami and MeP, has a low detection limit, and ensures the stability and accuracy of the analysis results.

[0005] Ami has a positive charge and MeP has a negative charge in an aqueous solution, and the PS@AuNPs-COOH composite microspheres and the PS@AuNPs-NH2 composite microspheres have negative charges and positive charges respectively, so that through electrostatic interaction, the pesticide molecules are adsorbed to the surface of the composite microspheres (Ami is adsorbed to the surface of the PS@AuNPs-COOH composite microspheres, and MeP is adsorbed to the surface of the PS@AuNPs-NH2 composite microspheres). Subsequently, an electrochemical in-situ enrichment method can be used to selectively adsorb Ami and MeP, so that on-site rapid detection of the pesticide molecules is realized. The electrochemical enrichment-SERS technology has the characteristics of fast analysis speed, high detection sensitivity and good selectivity, and the technology is expected to be further applied to the fields of environmental and food analysis and detection.

[0006] The purpose of the present application can be achieved by the following technical solutions:

[0007] The first purpose of the present application is to provide a preparation method of a PS@AuNPs composite microsphere, comprising the following steps:

[0008] (1) heating and boiling H2O and chloroauric acid, adding trisodium citrate to reduce gold nanoparticles to obtain a gold nanoparticle solution;

[0009] (2) adding PS microspheres to the gold nanoparticle solution obtained in step (1) and uniformly mixing with a reducing agent to obtain PS@AuNPs composite microspheres;

[0010] The PS@AuNPs composite microspheres are PS@AuNPs-NH2 composite microspheres or PS@AuNPs-COOH composite microspheres; wherein PS is a core, AuNPs is a shell layer, and carboxyl or amino is modified on the surface of AuNPs

[0011] In one embodiment of the present application, in step (1), the H2O, chloroauric acid and trisodium citrate are used in a ratio of 100 ml: 1 ml: 1-2.5 ml.

[0012] In one embodiment of the present application, in step (2), the PS microspheres are added in an amount of 0.02-0.05 g.

[0013] In one embodiment of the present application, the reducing agent is selected from one or more of sodium borate and trisodium citrate.

[0014] In one embodiment of the present application, during centrifugation, the centrifugal speed is 2000-6000 rpm and the centrifugation time is 10-30 min; during washing, the washing is repeated three times with deionized water.

[0015] In one embodiment of the present application, the PS microspheres are PS-NH2 microspheres or PS-COOH microspheres, and the PS@AuNPs composite microspheres correspond to PS@AuNPs-NH2 composite microspheres or PS@AuNPs-COOH composite microspheres.

[0016] A second object of the present application is to provide a PS@AuNPs composite microsphere prepared by the above method.

[0017] A third object of the present application is to provide an application of the PS@AuNPs composite microsphere, which is used for detecting the pesticide molecules MeP or Ami.

[0018] When the PS@AuNPs composite microspheres are used for detecting MeP, the PS@AuNPs composite microspheres are PS@AuNPs-NH2 composite microspheres.

[0019] When the PS@AuNPs composite microspheres are used for detecting Ami, the PS@AuNPs composite microspheres are PS@AuNPs-COOH composite microspheres.

[0020] In one embodiment of the present application, the detection of Ami by the PS@AuNPs-COOH composite microspheres specifically comprises the following steps:

[0021] (1) mixing the PS@AuNPs-COOH composite microspheres, sodium chloride and Ami to obtain a series of reaction solutions with different Ami concentrations;

[0022] (2) mixing the PS@AuNPs-COOH composite microspheres, sodium chloride and the sample to be detected to obtain a reaction solution to be detected;

[0023] (3) using the electrochemical workstation, adopting the i-t method, immersing the SPE@GO@GNRs screen-printed electrode into the reaction solution prepared in step (1) to perform enrichment treatment, after the enrichment treatment, using the portable Raman spectrometer to perform Raman signal detection of Ami, obtaining a standard curve with the Raman signal intensity as the vertical coordinate and the Log value of the Ami concentration as the horizontal coordinate;

[0024] (4) using the electrochemical workstation, adopting the i-t method, immersing the SPE@GO@GNRs screen-printed electrode into the reaction solution prepared in step (2) to perform enrichment treatment, after the enrichment treatment, using the portable Raman spectrometer to perform Raman signal detection of Ami, obtaining the Ami concentration in the sample to be detected by substituting the detected Raman signal intensity into the standard curve obtained in step (3).

[0025] In an embodiment of the present application, in step (1), the concentration of Ami in the reaction solution is 1.0*10 -7 M, 1.0*10 -6 M, 1.0*10 -5 M, 1.0*10 -4 M, and 1.0*10 -3 M.

[0026] In step (3), during the enrichment treatment, the enrichment potential is 0.01-0.25V, and the enrichment time is 5min; during the detection, the excitation wavelength is 785nm, and the excitation time is 1-60s.

[0027] In step (3), during the enrichment treatment, the enrichment potential is 0.01-0.25V, and the enrichment time is 5min; during the detection, the excitation wavelength is 785nm, and the excitation time is 1-60s.

[0028] The CTAB, chloroauric acid and NaBH4 are mixed to obtain a gold seed solution; then the CTAB, chloroauric acid, silver nitrate, hydrochloric acid, ascorbic acid and the gold seed solution are mixed and added dropwise to the surface of the SPE@GO electrode, and the SPE@GO@GNRs screen-printed electrode is obtained after post-processing.

[0029] In an embodiment of the present application, the detection of MeP by the PS@AuNPs-NH2 composite microspheres specifically includes the following steps:

[0030] (1) mixing the PS@AuNPs-NH2 composite microspheres, sodium chloride and MeP to obtain a series of reaction solutions with different MeP concentrations;

[0031] (2) mixing the PS@AuNPs-NH2 composite microspheres, sodium chloride and the sample to be detected to obtain a reaction solution to be detected;

[0032] (3) using the electrochemical workstation, adopting the i-t method, the SPE@GO@GNRs screen-printed electrode is immersed into the reaction solution prepared in step (1) to carry out enrichment treatment, after the enrichment treatment, the portable Raman spectrometer is adopted to detect the Raman signal of MeP, and a standard curve with the Raman signal intensity as the longitudinal coordinate and the Log value of the MeP concentration as the transverse coordinate is obtained;

[0033] (4) using the electrochemical workstation, adopting the i-t method, the SPE@GO@GNRs screen-printed electrode is immersed into the reaction solution prepared in step (2) to carry out enrichment treatment, after the enrichment treatment, the portable Raman spectrometer is adopted to detect the Raman signal of MeP, and the Raman signal intensity detected is substituted into the standard curve obtained in step (3), so that the MeP concentration in the sample to be detected is obtained.

[0034] In an embodiment of the application, in step (1), the concentration of MeP in the reaction solution is 1.0*10 -7 M, 1.0*10 -6 M, 1.0*10 -5 M, 1.0*10 -4 M and 1.0*10 -3 M.

[0035] In step (3), during the enrichment treatment, the enrichment potential is-0.25 to-0.01 V, and the enrichment time is 5 min; during the detection, the excitation wavelength is 785 nm, and the excitation time is 1-60 s.

[0036] The SPE@GO@GNRs screen-printed electrode is specifically as follows:

[0037] The CTAB, chloroauric acid and NaBH4 are uniformly mixed to obtain a gold seed solution; then the CTAB, chloroauric acid, silver nitrate, hydrochloric acid, ascorbic acid and the gold seed solution are uniformly mixed and then added dropwise to the surface of the SPE@GO electrode, and the SPE@GO@GNRs screen-printed electrode is obtained after post-processing.

[0038] Compared with the prior art, the application has the following beneficial effects:

[0039] (1) The PS@AuNPs-COOH composite microspheres constructed in the application have negative charges, and the PS@AuNPs-NH2 composite microspheres have positive charges, the composite microspheres pre-enrich the pesticide molecules with opposite charges through electrostatic interaction, improve the electron transfer rate, expand the specific surface area, and can pre-capture more pesticide molecules;

[0040] (2) The PS@AuNPs composite microspheres have excellent SERS activity, can be expanded by absorbing water, and can adsorb and enrich trace analytes, and when an enrichment potential is applied to the pesticide molecules on the SPE@GO@GNRs electrode, the structure and morphology of the PS@AuNPs composite microspheres are not damaged, the PS@AuNPs composite microspheres have good stability and electrochemical-SERS high sensitivity, and are easy to carry;

[0041] (3) The electrochemical enrichment method and the SERS technology are combined to realize the selective enrichment and detection of Ami and MeP in the sample to be detected, the method can eliminate the interference of other substances, and the detection sensitivity of Ami and MeP can be improved:

[0042] (4) The electrochemical workstation and the portable Raman spectrometer are combined to realize on-site rapid qualitative and quantitative detection of Ami and MeP in products, according to the linear relationship between the concentration of Ami and MeP and the Raman signal intensity, the detection limit (DL) is calculated according to the ratio of 3 times of the determination blank standard deviation (delta) and the linear curve slope (k), that is, DL = 3delta / k, and the detection limits of Ami and MeP are 1nM and 0.003nM respectively. BRIEF DESCRIPTION OF DRAWINGS

[0043] Figure 1 The SEM diagram of the PS@AuNPs-NH2 composite microspheres prepared in Example 1 of the application is shown in the figure.

[0044] Figure 2 The SEM diagram of the PS@AuNPs-COOH composite microspheres prepared in Example 2 of the application is shown in the figure.

[0045] Figure 3 The SERS spectrum change diagram of MeP before and after pre-enrichment of the AuNPs@PS-NH2 composite microspheres is shown in the figure.

[0046] Figure 4 The SERS spectrum diagram of the PS@AuNPs-NH2 composite microspheres after incubation with MeP of different concentrations is shown in the figure, and the spectrum characteristic peak of MeP is indicated by a pentagram in the figure.

[0047] Figure 5 The standard curve diagram of the PS@AuNPs-NH2 composite microspheres for detecting MeP is shown in the figure.

[0048] Figure 6 The SERS spectrum change diagram of Ami before and after pre-enrichment of the AuNPs@PS-COOH composite microspheres is shown in the figure.

[0049] Figure 7SERS spectrum of PS@AuNPs-COOH composite microspheres after incubation with different concentrations of Ami, the mark (pentagram) shown in the figure is the spectrum characteristic peak of Ami;

[0050] Figure 8 Standard curve of PS@AuNPs-COOH composite microspheres for detecting Ami; DETAILED DESCRIPTION

[0051] The application provides a preparation method of PS@AuNPs composite microspheres, comprising the following steps:

[0052] (1) heating and boiling H2O and chloroauric acid, adding trisodium citrate to obtain a gold nanoparticle solution;

[0053] (2) adding PS microspheres to the gold nanoparticle solution obtained in step (1) and uniformly mixing with a reducing agent to obtain PS@AuNPs composite microspheres;

[0054] The PS@AuNPs composite microspheres are PS@AuNPs-NH2 composite microspheres or PS@AuNPs-COOH composite microspheres; wherein PS is a core, AuNPs is a shell layer, and carboxyl or amino is modified on the surface of AuNPs

[0055] In an embodiment of the application, in step (1), the amount ratio of H2O, chloroauric acid and trisodium citrate is 100ml:1ml:1-2.5ml.

[0056] In an embodiment of the application, in step (2), the addition amount of PS microspheres is 0.02-0.05g.

[0057] In an embodiment of the application, the reducing agent is selected from one or more of sodium borate and trisodium citrate.

[0058] In an embodiment of the application, in the centrifugation process, the centrifugal speed is 2000-6000rpm, and the centrifugation time is 10-30min; in the washing process, the washing is repeated three times with deionized water.

[0059] In an embodiment of the application, the PS microspheres are PS-NH2 microspheres or PS-COOH microspheres, and the PS@AuNPs composite microspheres correspond to the PS@AuNPs-NH2 composite microspheres or PS@AuNPs-COOH composite microspheres of the PS microspheres.

[0060] The application provides a PS@AuNPs composite microsphere, which is prepared by the above method.

[0061] This invention provides an application of PS@AuNPs composite microspheres, which are used to detect pesticide molecules MeP or Ami;

[0062] When PS@AuNPs composite microspheres are used to detect MeP, the PS@AuNPs composite microspheres are PS@AuNPs-NH2 composite microspheres;

[0063] When PS@AuNPs composite microspheres detect Ami, the PS@AuNPs composite microspheres are PS@AuNPs-COOH composite microspheres.

[0064] In one embodiment of the present invention, the detection of Ami by PS@AuNPs-COOH composite microspheres specifically includes the following steps:

[0065] (1) PS@AuNPs-COOH composite microspheres, sodium chloride and Ami were mixed to obtain a series of reaction solutions with different Ami concentrations;

[0066] (2) Mix the PS@AuNPs-COOH composite microspheres, sodium chloride and the sample to be tested to obtain the reaction solution to be tested;

[0067] (3) Using an electrochemical workstation, the SPE@GO@GNRs screen-printed electrode was immersed in the reaction solution prepared in step (1) for enrichment treatment using the it method. After enrichment treatment, the Raman signal of Ami was detected by a portable Raman spectrometer, and a standard curve was obtained with the Raman signal intensity as the vertical axis and the Log value of Ami concentration as the horizontal axis.

[0068] (4) Using an electrochemical workstation, the SPE@GO@GNRs screen-printed electrode was immersed in the reaction solution prepared in step (2) for enrichment treatment using the it method. After enrichment treatment, the Raman signal of Ami was detected using a portable Raman spectrometer. The intensity of the detected Raman signal was substituted into the standard curve obtained in step (3) to obtain the concentration of Ami in the sample to be tested.

[0069] In one embodiment of the present invention, in step (1), the concentration of Ami in the reaction solution is 1.0 × 10⁻⁶. -7 M, 1.0×10 -6 M, 1.0×10 -5 M, 1.0×10 -4 M and 1.0×10 -3 M;

[0070] In step (3), during the enrichment process, the enrichment potential is 0.01 to 0.25 V and the enrichment time is 5 min; during the detection process, the excitation wavelength is 785 nm and the excitation time is 1 to 60 s.

[0071] The specific screen-printed electrodes for SPE@GO@GNRs are as follows:

[0072] CTAB, chloroauric acid, and NaBH4 were mixed to obtain a gold seed solution. Then, CTAB, chloroauric acid, silver nitrate, hydrochloric acid, ascorbic acid, and the gold seed solution were mixed and added dropwise to the surface of the SPE@GO electrode. After post-treatment, the SPE@GO@GNRs screen-printed electrode was obtained.

[0073] In one embodiment of the present invention, the detection of MeP by PS@AuNPs-NH2 composite microspheres specifically includes the following steps:

[0074] (1) PS@AuNPs-NH2 composite microspheres, sodium chloride and MeP were mixed to obtain a series of reaction solutions with different MeP concentrations;

[0075] (2) Mix the PS@AuNPs-NH2 composite microspheres, sodium chloride and the sample to be tested to obtain the reaction solution to be tested;

[0076] (3) Using an electrochemical workstation, the SPE@GO@GNRs screen-printed electrode was immersed in the reaction solution prepared in step (1) for enrichment treatment using the it method. After enrichment treatment, the Raman signal of MeP was detected by a portable Raman spectrometer, and a standard curve was obtained with the Raman signal intensity as the vertical axis and the Log value of MeP concentration as the horizontal axis.

[0077] (4) Using an electrochemical workstation, the SPE@GO@GNRs screen-printed electrode was immersed in the reaction solution prepared in step (2) for enrichment treatment using the it method. After enrichment treatment, the Raman signal of MeP was detected using a portable Raman spectrometer. The intensity of the detected Raman signal was substituted into the standard curve obtained in step (3) to obtain the concentration of MeP in the sample to be tested.

[0078] In one embodiment of the present invention, in step (1), the concentration of MeP in the reaction solution is 1.0 × 10⁻⁶. -7 M, 1.0×10 -6 M, 1.0×10 -5 M, 1.0×10 -4 M and 1.0×10 -3 M;

[0079] In step (3), during the enrichment process, the enrichment potential is -0.25 to -0.01V and the enrichment time is 5min; during the detection process, the excitation wavelength is 785nm and the excitation time is 1 to 60s.

[0080] The specific screen-printed electrodes for SPE@GO@GNRs are as follows:

[0081] The CTAB, chloroauric acid and NaBH4 are mixed to obtain a gold seed solution; then the CTAB, chloroauric acid, silver nitrate, hydrochloric acid, ascorbic acid and the gold seed solution are mixed and added dropwise to the surface of the SPE@GO electrode, and post-processing is performed to obtain the SPE@GO@GNRs screen-printed electrode.

[0082] The application will be described in detail below with reference to the drawings and specific embodiments.

[0083] In the following examples, if not specifically stated, the reagents used are commercially available reagents, and the detection means and methods used are conventional detection means and methods in the art.

[0084] Example 1

[0085] The present embodiment provides a PS@AuNPs-NH2 composite microsphere and a preparation method thereof, comprising the following steps:

[0086] (1) 100 mL of H2O and 1 mL of 0.01% HAuCl4 solution are heated to boiling, then 2.5 mL of 1% trisodium citrate is added, the solution is kept boiling for 10 minutes, and then cooled to room temperature to obtain a gold nanoparticle (AuNPs) solution;

[0087] (2) 0.02 g of dried PS microspheres is added to the above AuNPs solution, followed by gentle stirring for 16 h to adsorb AuNPs on the PS microspheres to obtain PS@AuNPs; the PS@AuNPs is functionalized with SH-PEG-NH2 to obtain a PS@AuNPs-NH2 composite microsphere; finally, the PS@AuNPs-NH2 composite microsphere is obtained by centrifugation twice (2000 rpm, 20 min) (PS@AuNPs-NH2 composite microspheres are dispersed in 10 mL of deionized water for standby. Figure 1

[0088] Example 2

[0089] The present embodiment provides a PS@AuNPs-COOH composite microsphere and a preparation method thereof, comprising the following steps:

[0090] (1) 100 mL of H2O and 1 mL of 0.01% HAuCl4 solution are heated to boiling, then 2.5 mL of 1% trisodium citrate is added, the solution is kept boiling for 10 minutes, and then cooled to room temperature to obtain a gold nanoparticle (AuNPs) solution;

[0091] ​(2) 0.02 g of dried PS microspheres was added to the above AuNPs solution, followed by gentle stirring for 16 h to adsorb AuNPs on the PS microspheres to obtain PS@AuNPs; the PS@AuNPs was functionalized with SH-PEG-COOH to obtain PS@AuNPs-COOH composite microspheres; finally, the PS@AuNPs-COOH composite microspheres were obtained by twice centrifugation (2000 rpm, 20 min) Figure 2 ), and the obtained PS@AuNPs-COOH composite microspheres were dispersed in 10 mL of deionized water.

[0092] Example 3

[0093] The present embodiment provides a SPE@GO@GNRs screen-printed electrode and a preparation method thereof, comprising the following steps:

[0094] (1) 2 mg of graphene oxide (GO) was added to anhydrous ethanol to prepare a 2 mg / mL GO alcohol solution, the GO alcohol solution was uniformly dispersed by ultrasonic, then 10 μL of the GO solution was added dropwise to the dark part of the surface of the SPE electrode, and the SPE@GO electrode was prepared after air drying;

[0095] (2) At room temperature, 9.75 mL of 0.1 mol / L cetyltrimethylammonium bromide (CTAB) aqueous solution was prepared, and was uniformly stirred until transparent, 0.25 mL of 0.01 mol / L chloroauric acid aqueous solution was added dropwise into the CTAB aqueous solution, and after it was uniformly dispersed in the solution, 0.6 mL of freshly prepared 0.01 mol / L sodium borohydride (NaBH4) solution (ice water bath) was quickly added, the solution changed from light yellow to brown yellow, and was uniformly stirred for 3 min to obtain a gold seed solution, which was reserved after standing at room temperature for 2 h;

[0096] (3) At room temperature, 10 mL of 0.1 mol / L CTAB aqueous solution was prepared, 0.5 mL of 0.01 mol / L chloroauric acid aqueous solution was added, and after being mixed uniformly, 0.1 mL of 0.01 mol / L silver nitrate (AgNO3) and 0.2 mL of 1 mol / L hydrochloric acid were added, and was fully stirred, 80 μL of 0.1 mol / L ascorbic acid was added, the solution changed from deep yellow to colorless, 12 uL of the gold seed solution prepared in step (2) was added, and was uniformly stirred for 3 min, and was reserved after standing at room temperature for 6 h, to obtain GNRs with a concentration of 1.8 nM, the GNRs were centrifuged at 8000 rpm for 5 min, and were washed three times, and were reserved after removing the excess CTAB;

[0097] (4) Take 20 uL of the GNRs prepared in step (3) and dilute 10 times. Ultrasonically disperse the diluted GNRs solution, then take 10 uL of the GNRs solution and drop it onto the dark part of the surface of the SPE@GO electrode prepared in step (1). After drying, the SPE@GO@GNRs screen-printed electrode is prepared.

[0098] Example 4

[0099] This example provides the determination of the oxidation-reduction potential of paraquat and methyl parathion, including the following steps:

[0100] An electrochemical workstation is used, the electrodes used are screen-printed electrodes, the working electrode and the auxiliary electrode are carbon electrodes, and the counter electrode is a silver-silver chloride electrode. The cyclic voltammetry (CV) method is used.

[0101] a. Oxidation-reduction potential of Ami: 5 mL of 1×10 -4 mol / L Ami and PBS mixed solution as electrolyte, the scanning voltage is -1-0.2V, and the scanning rate is 50mV / s, to obtain the oxidation-reduction potential of Ami;

[0102] b. Oxidation-reduction potential of MeP: 5 mL of 1×10 -4 mol / L MeP and PBS mixed solution as electrolyte, the scanning voltage is 0.05-0.9V, and the scanning rate is 50mV / s, to obtain the oxidation-reduction potential of MeP;

[0103] According to the oxidation-reduction potentials of the two pesticide molecules, the optimal enrichment potential of Ami is 0.2V, and the optimal enrichment potential of MeP is -0.2V.

[0104] Example 5

[0105] This example provides the detection of MeP by the PS@AuNPs-NH2 composite microspheres prepared in Example 1, including the following steps:

[0106] (1) Mix 6 mL of MeP and 6 mL of PS@AuNPs-NH2 composite microspheres mixed solution and 100 uL of 0.1 mol / L sodium chloride solution to obtain a reaction solution with MeP concentrations of 1.0×10 -7 M, 1.0×10 -6 M, 1.0×10 -5 M, 1.0×10 -4 M, and 1.0×10 -3 M,

[0107] (2) Using the electrochemical workstation, the SPE@GO@GNRs screen-printed electrode prepared in Example 3 was placed in the reaction solution prepared in step (1) for enrichment, the enrichment potential was controlled at-0.2 V, and the enrichment time was 5 min; after the enrichment, the Raman signal was detected by using the portable Raman spectrometer, the excitation wavelength was 785 nm, the excitation time was 10 s, the SERS spectrum of the sample was obtained, and thus the detection of MeP was realized; as shown in Figure 6 , the signal of MeP was obviously enhanced before and after the electrochemical enrichment.

[0108] The Raman spectrum peak 1110 cm -1 and 1346 cm -1 were taken as the characteristic peaks for judging MeP, with the gradual increase of the concentration of MeP (1.0×10 -7 M~1.0×10 -3 M), the characteristic peak intensity of 1110 cm -1 and 1346 cm -1 in the Raman spectrum gradually increased Figure 7 , and 1110 cm -1 and 1346 cm -1 were selected as the corresponding peak intensity combined with the linear curve Figure 8 , so that the content of MeP could be calculated, according to the linear relationship between the concentration of MeP and the Raman signal intensity y=0.663x+0.208, R 2 =0.998; the detection limit (DL) was calculated according to the ratio of 3 times the determination blank standard deviation (δ) to the slope (k) of the linear curve, i.e. DL=3δ / k, and the detection limit of MeP was 0.003 nM.

[0109] Example 6

[0110] This example provides the detection of Ami by using the PS@AuNPs-COOH composite microspheres prepared in Example 2, which comprises the following steps:

[0111] (1) 6 mL of Ami and 6 mL of PS@AuNPs-COOH composite microspheres mixed solution and 100 μL of 0.1 mol / L sodium chloride solution were uniformly mixed to obtain a reaction solution with Ami concentrations of 1.0×10 -7 M, 1.0×10 -6 M, 1.0×10 -5 M, 1.0×10 -4 M and 1.0×10 - 3 M,

[0112] (2) Using the electrochemical workstation, the SPE@GO@GNRs screen-printed electrode prepared in Example 3 was placed in the reaction solution prepared in step (1) for enrichment by the i-t method, the enrichment potential was controlled at 0.2 V, and the enrichment time was 5 min; after enrichment, the Raman signal was detected by a portable Raman spectrometer, the excitation wavelength was 785 nm, and the excitation time was 10 s, and the SERS spectrum of the sample was obtained, thereby realizing the detection of Ami; as shown in Figure 3 , the signal of Ami was obviously enhanced before and after electrochemical enrichment.

[0113] The Raman spectrum peak 1211 cm -1 and 1283 cm -1 were taken as the characteristic peaks for judging Ami, and as the concentration of Ami gradually increased (1.0×10 -7 M~1.0×10 -3 M), the characteristic peak intensity at 1211 cm -1 and 1283 cm -1 in the Raman spectrum gradually increased Figure 4 , and the content of Ami was calculated by selecting the peak intensity at 1211 cm -1 and 1283 cm -1 in combination with the linear curve Figure 5 , according to the linear relationship between the concentration of Ami and the Raman signal intensity y=0.586x+0.215, R 2 =0.995; the detection limit (DL) was calculated according to the ratio of 3 times the determination of blank standard deviation (δ) to the slope (k) of the linear curve, i.e. DL=3δ / k, and the detection limit of Ami was 1 nM.

[0114] Example 7

[0115] This example provides the application of PS@AuNPs composite microspheres for detecting MeP and Ami in the water sample to be tested, in this example, the PS@AuNPs-NH2 composite microspheres prepared in Example 1 were used to detect MeP, the PS@AuNPs-COOH composite microspheres prepared in Example 2 were used to detect Ami, and the SPE@GO@GNRs screen-printed electrode prepared in Example 3 was used as the enrichment electrode; the water sample to be tested was lake water from a school.

[0116] (1) 2 mL of lake water was mixed with 2 mL of 5×10 -4M Ami mixed, followed by mixing with 2 mL PS@AuNPs-COOH composite microspheres, 100 μL 0.1 mol / L sodium chloride solution to obtain a first reaction solution; using an electrochemical workstation, an i-t method was used, and the SPE@GO@GNRs screen-printed electrode was placed in the first reaction solution for enrichment, and the enrichment potential was controlled at 0.2 V, and the enrichment time was 5 min.

[0117] (2) 2 mL of lake water was mixed with 2 mL of 5×10 -5 M MeP mixed, followed by mixing with 2 mL PS@AuNPs-NH2 composite microspheres, 100 μL 0.1 mol / L sodium chloride solution to obtain a second reaction solution; using an electrochemical workstation, an i-t method was used, and the SPE@GO@GNRs screen-printed electrode was placed in the second reaction solution for enrichment, and the enrichment potential was controlled at -0.2 V, and the enrichment time was 5 min.

[0118] Meanwhile, the MeP and Ami in the lake water were detected by high performance liquid chromatography, and the detection results were compared with those of the embodiment, and the specific detection results are shown in Table 1. As shown in Table 1, the electrochemical-SERS combined analysis results of the embodiment are well matched with the results of the high performance liquid chromatography, indicating that the method has good detection accuracy, and is expected to be used as a rapid analysis and detection method for detecting various pesticide molecules.

[0119] Table 1 Comparison of detection results of the detection method of the application and high performance liquid chromatography

[0120]

[0121] The above description of the embodiments is for the purpose of facilitating understanding and use of the application by those of ordinary skill in the art. Those skilled in the art can easily make various modifications to the embodiments, and apply the general principles described herein to other embodiments without creative labor. Therefore, the application is not limited to the above embodiments, and improvements and modifications made by those skilled in the art without departing from the scope of the application should be within the scope of protection of the application.

Claims

1. A method for preparing PS@AuNPs composite microspheres, characterized in that, Includes the following steps: (1) Heat H2O and chloroauric acid to boiling, then add trisodium citrate to reduce and obtain a solution of gold nanoparticles; (2) Add PS microspheres to the gold nanoparticle solution obtained in step (1), mix well to obtain PS@AuNPs, functionalize them to obtain PS@AuNPs composite microspheres; The PS@AuNPs composite microspheres are either PS@AuNPs-NH2 composite microspheres or PS@AuNPs-COOH composite microspheres; wherein PS is the core, AuNPs is the shell, and carboxyl or amino groups are modified on the surface of AuNPs. By combining electrochemical enrichment and SERS technology, the detection limits of PS@AuNPs composite microspheres for Ami and MeP were 1 nM and 0.003 nM, respectively.

2. The method for preparing PS@AuNPs composite microspheres according to claim 1, characterized in that, In step (1), the ratio of H2O, chloroauric acid and trisodium citrate is 100ml:1ml:1~2.5ml.

3. The method for preparing PS@AuNPs composite microspheres according to claim 1, characterized in that, In step (2), the amount of PS microspheres added is 0.02~0.05g.

4. A PS@AuNPs composite microsphere, characterized in that, The PS@AuNPs composite microspheres were prepared by any one of the methods described in claims 1 to 3.

5. An application of the PS@AuNPs composite microspheres as described in claim 4, characterized in that, The PS@AuNPs composite microspheres are used to detect pesticide molecules MeP or Ami. When PS@AuNPs composite microspheres are used to detect MeP, the PS@AuNPs composite microspheres are PS@AuNPs-NH2 composite microspheres; When PS@AuNPs composite microspheres detect Ami, the PS@AuNPs composite microspheres are PS@AuNPs-COOH composite microspheres.

6. The application of the PS@AuNPs composite microspheres according to claim 5, characterized in that, The detection of Ami using PS@AuNPs-COOH composite microspheres specifically includes the following steps: (1) PS@AuNPs-COOH composite microspheres, sodium chloride and Ami were mixed to obtain a series of reaction solutions with different Ami concentrations; (2) Mix the PS@AuNPs-COOH composite microspheres, sodium chloride and the sample to be tested to obtain the reaction solution to be tested; (3) Using an electrochemical workstation, the SPE@GO@GNRs screen-printed electrode was immersed in the reaction solution prepared in step (1) for enrichment treatment using the it method. After enrichment treatment, the Raman signal of Ami was detected by a portable Raman spectrometer, and a standard curve was obtained with the Raman signal intensity as the vertical axis and the Log value of Ami concentration as the horizontal axis. (4) Using an electrochemical workstation, the SPE@GO@GNRs screen-printed electrode was immersed in the reaction solution prepared in step (2) for enrichment treatment using the it method. After enrichment treatment, the Raman signal of Ami was detected using a portable Raman spectrometer. The intensity of the detected Raman signal was substituted into the standard curve obtained in step (3) to obtain the concentration of Ami in the sample to be tested.

7. The application of the PS@AuNPs composite microspheres according to claim 6, characterized in that, In step (1), the concentration of Ami in the reaction solution is 1.0 × 10⁻⁶. -7 M, 1.0×10 -6 M, 1.0×10 -5 M, 1.0×10 -4 M and 1.0×10 -3 M; In step (3), during the enrichment process, the enrichment potential is 0.01~0.25V and the enrichment time is 5min; during the detection process, the excitation wavelength is 785nm and the excitation time is 1~60s. The specific screen-printed electrodes for SPE@GO@GNRs are as follows: CTAB, chloroauric acid, and NaBH4 were mixed to obtain a gold seed solution. Then, CTAB, chloroauric acid, silver nitrate, hydrochloric acid, ascorbic acid, and the gold seed solution were mixed and added dropwise to the surface of the SPE@GO electrode. After post-treatment, the SPE@GO@GNRs screen-printed electrode was obtained.

8. The application of the PS@AuNPs composite microspheres according to claim 5, characterized in that, The detection of MeP by PS@AuNPs-NH2 composite microspheres specifically includes the following steps: (1) PS@AuNPs-NH2 composite microspheres, sodium chloride and MeP were mixed to obtain a series of reaction solutions with different MeP concentrations; (2) Mix the PS@AuNPs-NH2 composite microspheres, sodium chloride and the sample to be tested to obtain the reaction solution to be tested; (3) Using an electrochemical workstation, the SPE@GO@GNRs screen-printed electrode was immersed in the reaction solution prepared in step (1) for enrichment treatment using the it method. After enrichment treatment, the Raman signal of MeP was detected by a portable Raman spectrometer, and a standard curve was obtained with the Raman signal intensity as the vertical axis and the Log value of MeP concentration as the horizontal axis. (4) Using an electrochemical workstation, the SPE@GO@GNRs screen-printed electrode was immersed in the reaction solution prepared in step (2) for enrichment treatment using the it method. After enrichment treatment, the Raman signal of MeP was detected using a portable Raman spectrometer. The intensity of the detected Raman signal was substituted into the standard curve obtained in step (3) to obtain the concentration of MeP in the sample to be tested.

9. The application of the PS@AuNPs composite microspheres according to claim 8, characterized in that, In step (1), the concentration of MeP in the reaction solution is 1.0 × 10⁻⁶. -7 M, 1.0×10 -6 M, 1.0×10 -5 M, 1.0×10 -4 M and 1.0×10 -3 M; In step (3), during the enrichment process, the enrichment potential is -0.25 to -0.01V and the enrichment time is 5 min; during the detection process, the excitation wavelength is 785 nm and the excitation time is 1 to 60 s. The specific screen-printed electrodes for SPE@GO@GNRs are as follows: CTAB, chloroauric acid, and NaBH4 were mixed to obtain a gold seed solution. Then, CTAB, chloroauric acid, silver nitrate, hydrochloric acid, ascorbic acid, and the gold seed solution were mixed and added dropwise to the surface of the SPE@GO electrode. After post-treatment, the SPE@GO@GNRs screen-printed electrode was obtained.

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