Preparation method and application of a composite material for detecting multiple neonicotinoid pesticides

Abstract

The application discloses a preparation method and application of a composite material for detecting various neonicotinoid pesticides. The composite material is prepared by combining the up-conversion fluorescence of UCNPs and the high enrichment of metal organic framework material ZIF-67, and can be used for sensing various neonicotinoid pesticides, and has high hydrophilic characteristics and wide application prospect.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of high polymer materials, and relates to a preparation method and application of a composite material for detecting various neonicotinoid pesticides. BACKGROUND

[0002] Neonicotinoid pesticides have the advantages of high efficiency, broad spectrum, low toxicity, etc., and are widely used in the world. Since 2010, the sales of neonicotinoid pesticides have increased year by year, and neonicotinoid pesticides have become the most widely used type of pesticides in the world. China is a big country in the production and use of neonicotinoid pesticides. Research has found that neonicotinoid pesticide residues are widely present in fruits and vegetables. Various neonicotinoid pesticides have also been detected in the environment such as atmosphere, surface water, tap water and drinking water. The acute symptoms caused by neonicotinoid pesticides are related to the physical condition of pesticide exposure persons, exposure dose and route, etc. Mild symptoms are nausea, vomiting, headache and diarrhea, etc., and severe symptoms can cause death. Long-term overuse or even misuse of this type of pesticide makes a large number of animals more likely to be exposed to neonicotinoid pesticides, which poses a threat to human health and seriously affects the development of the agricultural product industry. However, the existing rapid detection technology mainly targets a single pesticide, and it is difficult to meet the current demand for rapid screening by category.

[0003] With the development of fluorescent nanomaterials, fluorescent sensing detection technology has attracted widespread attention. Upconversion nanoparticles (UCNPs) are a kind of fluorescent nanomaterials emerging in recent years, which are composed of inorganic matrix and rare earth doped ions embedded in the matrix. UCNPs can convert longer wavelength radiation into shorter wavelength fluorescence through a two-photon or multi-photon mechanism. Compared with traditional organic dyes and quantum dots, UCNPs have the advantages of low toxicity, high fluorescence quantum yield, stable chemical properties, etc. Most importantly, UCNPs can convert lower energy near-infrared light into higher energy ultraviolet or visible light. Due to these excellent optical properties, UCNPs have great application value in the fields of biological imaging, medical treatment, food detection, etc.

[0004] Metal-Organic Frameworks (MOFs) are a kind of porous crystalline material derived from inorganic metal nodes and organic ligand frameworks, and are also a kind of low-density, high-void, chemically and structurally adjustable carrier material. MOFs have a large specific surface area and can accumulate and store many molecules in the pores, and have strong adsorption performance. Among them, ZIF-67 is a regular dodecahedron structure material with Co 2+ , which has high stability, high porosity, high stability in aqueous solution and high adsorption capacity, and has been widely studied in the removal of pollutants. At the same time, Co 2+ contains multiple energy levels, which can meet the energy exchange requirements with rare earth ions. SUMMARY

[0005] Therefore, the present application aims to provide a preparation method and application of a composite material for detecting multiple neonicotinoid pesticides, and provide a new material for the fields of detection and sensing.

[0006] To achieve the above-mentioned purpose, the present application provides the following technical scheme:

[0007] 1. The present application provides a preparation method of a composite material for detecting multiple neonicotinoid pesticides, comprising the following steps:

[0008] 1) First, ZIF-67 is prepared by using cobalt nitrate hexahydrate and 2-methylimidazole as raw materials;

[0009] 2) Then, a premix solution is prepared by mixing PAA-UCNPs, ZIF-67 and deionized water;

[0010] 3) Finally, polyvinylpyrrolidone (PVP) ethanol solution is added to the premix solution, and the reaction is stirred at room temperature (25℃), and then the composite material is obtained after post-processing.

[0011] Among them, the PAA-UCNPs are first prepared by using yttrium chloride, ytterbium chloride and erbium chloride as raw materials to form oil-soluble UCNPs, and then the UCNPs are mixed with polyacrylic acid (PAA) to obtain the PAA-UCNPs.

[0012] Preferably, the specific method of step 1) is as follows: first, dissolve cobalt nitrate hexahydrate in the first part of anhydrous methanol to obtain a cobalt nitrate solution, and dissolve 2-methylimidazole in the second part of anhydrous methanol to obtain a 2-methylimidazole solution; then, while stirring, add the 2-methylimidazole solution to the cobalt nitrate solution, and stir at a rate of 300 r / min at room temperature for 12 hours, and then perform post-processing.

[0013] Further preferably, the amount ratio of cobalt nitrate hexahydrate, 2-methylimidazole, the first part of anhydrous methanol and the second part of anhydrous methanol is 6-10 mmol: 12-20 mmol: 40-60 mL: 40-60 mL, and more preferably 8 mmol: 16 mmol: 50 mL: 50 mL.

[0014] Further preferably, the post-processing includes: centrifugation, taking the purple precipitate, washing with anhydrous methanol 5 times to remove excess cobalt nitrate hexahydrate and 2-methylimidazole, vacuum drying at 120℃, and fully activating for 12 hours to remove the solvent molecules in the pores.

[0015] Preferably, the specific method of step 2) is as follows: first, disperse the PAA-UCNPs in deionized water by ultrasonic dispersion, then add ZIF-67, and stir to mix evenly.

[0016] Further preferably, the stirring and mixing process conditions are 300 r / min stirring for 0.5 hours.

[0017] Preferably, in step 2), the amount ratio of PAA-UCNPs, deionized water and ZIF-67 is 20-50 mg: 10-15 mL: 50-100 mg.

[0018] Preferably, in step 3), the volume ratio of polyvinylpyrrolidone (PVP) ethanol solution to the pre-mixed solution is 2:1, and the concentration of the polyvinylpyrrolidone (PVP) ethanol solution is 0.005 g / mL.

[0019] Preferably, in step 3), the process conditions for stirring the reaction at room temperature are 300 r / min stirring for 10-15 hours.

[0020] Preferably, in step 3), the post-processing includes: 12000 r·min -1 centrifugation for 10 minutes, taking the precipitate, washing with anhydrous ethanol and deionized water respectively for multiple times to remove excess PVP molecules, and vacuum freeze-drying.

[0021] Further preferably, the specific method of vacuum freeze-drying is: pre-cooling at -80℃ for 1 hour, drying at a cold trap temperature of -40 to -60℃ for 5-10 hours after vacuumizing, and more preferably for 6 hours.

[0022] Preferably, the preparation method of the PAA-UCNPs is as follows:

[0023] A) First, dissolve yttrium chloride, ytterbium chloride and erbium chloride in oleic acid and octadecene, heat to 150-170℃, form a yellow transparent solution, and naturally cool to room temperature; then add NaOH and NH4F methanol solution drop by drop, stir at room temperature for 30-60 min; then gradually heat to remove methanol, heat to 80-100℃ for 30-60 min, heat to 290-310℃ under argon protection, heat for 50-70 min, naturally cool to room temperature, centrifuge to take the precipitate, wash with a volume ratio of 1:1 of ethanol-methanol mixture, and obtain oil-soluble UCNPs, i.e. OA-UCNPs;

[0024] B) Then, disperse the OA-UCNPs in toluene to obtain an OA-UCNPs toluene solution; dissolve polyacrylic acid (PAA) in diethylene glycol (DEG), heat to 100-120℃, continue to add the OA-UCNPs toluene solution, heat to 105-115℃ under argon protection for 50-70 min, heat to 230-250℃ for 50-70 min, naturally cool to room temperature, add excess hydrochloric acid solution, and centrifuge to obtain PAA-UCNPs.

[0025] Further preferably, in step A), the amount ratio of yttrium chloride, ytterbium chloride, erbium chloride, oleic acid, octadecene, the methanol solution of NaOH and NH4F, the ethanol-methanol mixture is 0.78 mmol: 0.2 mmol: 0.02 mmol: 6 mL: 17 mL: 10 mL: 10-15 mL, wherein the methanol solution of NaOH and NH4F is obtained by dissolving 2.5 mmol of NaOH and 4 mmol of NH4F in 10 mL of methanol.

[0026] Further preferably, in step A), the specific method for removing methanol is: first slowly heated to 80 DEG C, and kept for 45 minutes to remove most of the methanol, then heated to 100 DEG C, and degassed for 10 minutes to completely remove the methanol.

[0027] Further preferably, in step B), the amount ratio of PAA, DEG, the toluene solution of OA-UCNPs, the hydrochloric acid solution is 250-350 mg: 25-35 mL: 2-4 mL: 15-20 mL, wherein the concentration of OA-UCNPs contained in the toluene solution of OA-UCNPs is 25-50 mg / mL, and the pH of the hydrochloric acid is 4.6.

[0028] 2. The application also provides a composite material for detecting a plurality of neonicotinoid pesticides, which is prepared by the preparation method.

[0029] 3. The application also provides application of the composite material in preparing a sensor for detecting a plurality of neonicotinoid pesticides.

[0030] Preferably, the neonicotinoid pesticides include but are not limited to imidacloprid, acetamiprid, thiacloprid and thiamethoxam.

[0031] The application has the following beneficial effects:

[0032] The application combines the high enrichment of UCNPs with the high enrichment of metal-organic framework material ZIF-67, and the prepared composite material can be used for sensing a plurality of neonicotinoid pesticides, and has high hydrophilic properties, and has wide application prospects.

[0033] Specifically as follows:

[0034] 1. The application combines UCNPs with high fluorescence properties and nanomaterial ZIF-67 with high enrichment properties, so that the composite material has sensing and hydrophilic properties, and has wide application prospects.

[0035] 2、The application has sensing performance for various neonicotinoid pesticides, and can achieve specific identification of neonicotinoid pesticides. Among them, imidacloprid is the strongest, followed by thiacloprid, and the six-membered conjugated aromatic structure similar to benzene ring and S, N five-membered conjugated ring exist in the structure, which can effectively enhance the interaction with the composite material. The structure of acetamiprid only contains a six-membered conjugated aromatic structure similar to benzene ring, and thiamethoxam only contains S, N five-membered conjugated ring and N-containing six-membered ring structure, so the π-π interaction with the composite material is slightly weaker. Although pyrethroid pesticides and carbamate pesticides also cause a certain degree of reduction of the fluorescence of the composite material, because pyrethroid pesticides and carbamate pesticides also contain some aromatic structures, but because they are fat-soluble or contain other groups on the aromatic structure, the quenching degree is smaller. In summary, the composite material can specifically identify neonicotinoid pesticides. BRIEF DESCRIPTION OF DRAWINGS

[0036] In order to make the purpose, technical scheme and beneficial effects of the present application clearer, the present application provides the following drawings for illustration.

[0037] Figure 1 The response curve of the composite material of the present application to various neonicotinoid pesticides, wherein A is imidacloprid, B is acetamiprid, C is thiacloprid, and D is thiamethoxam;

[0038] Figure 2 The specificity of the composite material of the present application. DETAILED DESCRIPTION

[0039] The preferred embodiments of the present application will be described in detail below with reference to the accompanying drawings.

[0040] Example 1

[0041] A composite material for detecting various neonicotinoid pesticides is prepared, comprising the following steps:

[0042] (1) Preparation of PAA-UCNPs

[0043] A) 0.745 mmol YCl3-6H2O, 0.25 mmol YbCl3-6H2O and 0.005 mmol TmCl3-6H2O were placed in a 100 mL three-neck flask, 8 mL OA and 17 mL ODE were added, mixed well on a magnetic stirrer and heated to 160 °C for 1 h, at which time a yellow transparent solution was formed. After the reaction was cooled to room temperature, 10.0 mL of a methanol solution containing NaOH and NH4F (2.5 mmol NaOH and 4 mmol NH4F were dissolved in 10 mL methanol) was slowly added dropwise, and continuously stirred at room temperature for 1 h to ensure that the NH4F was fully reacted. The solution was then slowly heated to 80 °C for 45 min to remove the methanol, and then warmed to 100 °C and degassed for 10 min to completely remove the methanol. Argon was introduced, the reaction was rapidly warmed to 300 °C and held for 1 h. The resulting solution was naturally cooled to room temperature, the precipitate was centrifuged, and washed 4 times with a 1:1 volume ratio of ethanol-methanol mixture to obtain oil-soluble UCNPs.

[0044] B) 300 mg of PAA (MW = 1800) was weighed into a 100 mL three-neck flask, 30 mL DEG was added, heated to 110 °C for 15 min to form a transparent solution. Then 3 mL of a toluene solution containing 100 mg of OA-UCNPs was slowly added, and held at 110 °C for 1 h. Then heated to 240 °C for 1 h. The resulting solution was cooled to room temperature, and an excess of dilute hydrochloric acid solution (pH = 4.6) was added. PAA-UCNPs were obtained by centrifugation (12000 rpm, 15 min) and washed 3 times with water.

[0045] (2) Preparation of ZIF-67

[0046] 8 mmol of cobalt nitrate hexahydrate and 16 mmol of 2-methylimidazole were dissolved in 50 mL of anhydrous methanol, respectively, the cobalt nitrate hexahydrate methanol solution was placed in a 100 mL conical flask, stirred on a magnetic stirrer, and then the 2-methylimidazole methanol solution was added to the cobalt nitrate methanol solution, which was stirred at a rate of 300 r·min -1 for 12 h at room temperature. The resulting purple precipitate was washed 5 times with anhydrous methanol to remove excess cobalt nitrate hexahydrate and 2-methylimidazole. The resulting ZIF-67 was placed in a vacuum drying oven and vacuum dried at 120 °C for 12 h to remove solvent molecules in the pores.

[0047] (3) Preparation of the premix solution

[0048] A certain amount of PAA-UCNPs was ultrasonically dispersed in deionized water, ZIF-67 material was added, and the mixture was stirred uniformly on a magnetic stirrer to obtain a premix. The amount ratio of PAA-UCNPs, deionized water and ZIF-67 was 30 mg: 10 mL: 70 mg.

[0049] (4) Under continuous stirring, 20 mL of an ethanol solution containing 0.1 g of PVP was added to 10 mL of the premix, and the mixture was stirred at room temperature for 12 h at 12000 r·min -1 The mixture was centrifuged for 10 min, washed with ethanol and deionized water several times to remove excess PVP molecules, and vacuum dried for 6 h to obtain the ZIF-67@UCNPs multifunctional composite material.

[0050] In step (4), the specific method of vacuum freeze drying is: pre-cooling at -80°C for 1 h, drying at a cold trap temperature of -50°C for 6 h after vacuumizing.

[0051] Example 2

[0052] Pyrethroid pesticides (deltamethrin, cypermethrin, flucythrinate, cypermethrin), organophosphorus pesticides (dichlorvos, omethoate), carbamate pesticides (carbaryl, carbofuran) were selected as competitors to study the specificity of the composite material prepared in Example 1. The concentration of neonicotinoid pesticides was 5 mg / L, and the concentration of competitors was prepared. The composite material was used to identify the competing pesticides, and the fluorescence value was measured by a fluorescence spectrophotometer equipped with a 980 nm laser.

[0053] As shown in Figure 2 imidacloprid, acetamiprid, thiacloprid and thiamethoxam can strongly quench the fluorescence of the composite material. The competing pesticides have less effect on the fluorescence. This method has specificity for imidacloprid, acetamiprid, thiacloprid and thiamethoxam.

[0054] Finally, it should be pointed out that the above preferred embodiments are only used to illustrate the technical solutions of the present application and are not limiting. Although the present application has been described in detail through the above preferred embodiments, those skilled in the art should understand that various changes can be made in form and detail without departing from the scope defined by the claims of the present application.

Claims

1. Use of a composite material for the preparation of a sensor for the detection of a plurality of neonicotinoid pesticides, characterized in that, The neonicotinoid pesticide is imidacloprid, thiacloprid or thiamethoxam; The preparation method of the composite material comprises the following steps: 1) ZIF-67 is prepared by using cobalt nitrate hexahydrate and 2-methyl imidazole as raw materials; 2) PAA-UCNPs, ZIF-67 and deionized water are mixed to prepare a premix solution; 3) polyvinylpyrrolidone ethanol solution is added to the premix solution, and the reaction is stirred at room temperature, and then post-processing is performed to obtain the composite material; The PAA-UCNPs are prepared by using yttrium chloride, ytterbium chloride and erbium chloride as raw materials to prepare oil-soluble UCNPs, and then mixing and reacting the UCNPs with polyacrylic acid; The specific method of step 2) is that the PAA-UCNPs are ultrasonically dispersed in deionized water, then ZIF-67 is added, and stirring is performed until the mixture is uniformly mixed; the amount ratio of PAA-UCNPs, deionized water and ZIF-67 is 20-50 mg: 10-15 mL: 50-100 mg; In step 3), the volume ratio of the polyvinylpyrrolidone ethanol solution to the premix solution is 2:1, the concentration of the polyvinylpyrrolidone ethanol solution is 0.005 g / mL, and the process conditions of the reaction stirred at room temperature are 300 r / min for 10-15 hours; The specific method of step 1) is that cobalt nitrate hexahydrate is dissolved in a first part of anhydrous methanol to obtain a cobalt nitrate solution, 2-methyl imidazole is dissolved in a second part of anhydrous methanol to obtain a 2-methyl imidazole solution, then the 2-methyl imidazole solution is added to the cobalt nitrate solution while stirring, and the reaction is stirred at a speed of 300 r / min at room temperature for 12 hours, and then post-processing is performed; In step 3), the post-treatment includes: 12000 r·min -1 The precipitate was collected and washed with ethanol and deionized water to remove excess PVP molecules, and then vacuum freeze-dried. The preparation method of the PAA-UCNPs is as follows: A) yttrium chloride, ytterbium chloride and erbium chloride are dissolved in oleic acid and octadecene, heated to 150-170 DEG C, a yellow transparent solution is formed, and then naturally cooled to room temperature; then NaOH and NH4F methanol solution are added dropwise, stirred at room temperature for 30-60 min; then methanol is removed by gradually heating, and the solution is kept at 80-100 DEG C for 30-60 min, heated to 290-310 DEG C under argon protection, kept at 80-100 DEG C for 50-70 min, naturally cooled to room temperature, centrifuged to obtain the precipitate, and then washed with an ethanol-methanol mixture with a volume ratio of 1:1 to obtain the oil-soluble UCNPs, namely OA-UCNPs; B) then the OA-UCNPs are dispersed in toluene to obtain an OA-UCNPs toluene solution; polyacrylic acid is dissolved in diethylene glycol, heated to 100-120 DEG C, and then the OA-UCNPs toluene solution is added, kept at 105-115 DEG C under argon protection for 50-70 min, heated to 230-250 DEG C, kept at 230-250 DEG C for 50-70 min, naturally cooled to room temperature, added with excess hydrochloric acid solution, and then centrifuged to obtain the PAA-UCNPs.

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