CN108801990B - CsPbBr-based3Omethoate detection method of perovskite quantum dot-molecular imprinting fluorescence sensor - Google Patents

CsPbBr-based3Omethoate detection method of perovskite quantum dot-molecular imprinting fluorescence sensor Download PDF

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CN108801990B
CN108801990B CN201810358931.7A CN201810358931A CN108801990B CN 108801990 B CN108801990 B CN 108801990B CN 201810358931 A CN201810358931 A CN 201810358931A CN 108801990 B CN108801990 B CN 108801990B
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梁勇
郭慢丽
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South China Normal University
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Abstract

The invention provides a CsPbBr-based method3The method for detecting omethoate of the perovskite quantum dot-molecular imprinting fluorescence sensor comprises the following steps: s1: CsPbBr3Perovskite quantum dot-molecular imprintingPreparing a fluorescence sensor; s2: drawing a standard working curve of fluorescence quenching intensity-omethoate concentration, and calculating a working equation; s3: and measuring the content of omethoate in the sample. The detection method utilizes the CsPbBr terminated by APTES3The quantum dots are signal elements, and the molecular imprinting polymer layer is wrapped by the CsPbBr with the sensitive recognition function on the omethoate3The perovskite quantum dot-molecular imprinting fluorescence sensor realizes the detection of omethoate with high selectivity and high sensitivity. The detection method disclosed by the invention has the advantages that the linear detection range of omethoate is 50-400ng/mL, the linear correlation coefficient is 0.997, the detection limit is 18.8ng/mL, and the detection precision is 1.7% (RSD).

Description

CsPbBr-based3Omethoate detection method of perovskite quantum dot-molecular imprinting fluorescence sensor
Technical Field
The invention belongs to the field of analytical chemistry, and particularly relates to a CsPbBr-based sample3A method for detecting omethoate of a perovskite quantum dot-molecular imprinting fluorescence sensor.
Background
Omethoate detection is a hot spot in research and development of food safety fields at home and abroad, and at present, methods such as gas chromatography, liquid chromatography, immunoassay, gas chromatography-mass spectrometry (GC-MS), liquid chromatography-mass spectrometry (LC-MS) and the like are mainly adopted. Chromatography-mass spectrometry has high detection sensitivity but is expensive. Chromatographic detection has high limit, and can not meet the actual requirements of trace pesticide residue and export trade detection, so enrichment is usually required before analysis. The pretreatment methods adopted at present mainly comprise solid phase extraction, liquid-liquid extraction, matrix dispersion solid phase extraction, solid phase micro-extraction, supercritical fluid extraction, column chromatography and the like. Since matrix solid phase dispersion extraction has the advantages of less sample consumption, less consumption of organic solvent and the like, the matrix solid phase dispersion extraction is widely applied to analysis of drugs, organic pollutants and natural products in environment, biology and food. However, the solid phase dispersion extraction adsorbent based on commercial matrix is often poor in selectivity, the acting force between the target and the adsorbent is nonspecific, the efficiency of extraction and purification is not high, the interference of the matrix is difficult to completely remove, and the cost is also high. Therefore, the synthesis of adsorption functional materials with specific recognition ability to omethoate by using molecular imprinting technology is a trend.
Over the past two decades, photoluminescent semiconductor Quantum Dots (QDs) have attracted considerable attention due to their excellent photostability, broad absorption spectrum, narrow symmetric emission and adjustable size. They have wide application prospects in the fields of bio-imaging, Light Emitting Diodes (LEDs), solar cells, and particularly sensors. Therefore, in order to improve the selectivity of QD-based sensors, Molecularly Imprinted Polymers (MIPs) were introduced to synthesize MIP @ QDs fluorescence sensors to selectively detect analytes. The molecular imprinting technology is a mature technology for establishing a customized binding site and memorizing the shape, size and functional group of a template. MIPs have the characteristics of strong affinity, high selectivity, easy preparation, low cost and the like, so the MIPs are increasingly applied to some important application fields of biomimetic sensors, chromatographic separation, solid-phase extraction, controlled release of drug delivery, catalysis and the like. To date, a number of MIP-terminated QDs fluorescence sensors have been developed that combine MIP selectivity with QDs sensitivity to detect various compounds, such as cytochrome c, 4-nitrophenol, pyrethroids, melamine and ractopamine. Currently, common quantum dots used as luminescent elements of fluorescent sensors are composed of group IV, II-VI, IV-VI or III-V elements, such as CdSe, CdTe, CdS, Si, C, ZnS quantum dots, and the like. However, these quantum dots as the sensing element have a disadvantage of low sensitivity of the sensor due to their low quantum yield. Therefore, there is a great need to develop novel semiconductor quantum dots having excellent photoluminescence properties and high fluorescence quantum yield.
More recently, having the formula ABX3(wherein A = Cs)+、CH3NH3 +；B = Pb、Sn、Ge；X = Br-、I-、Cl-) Due to their tunable optical band gap, high emission efficiency and excellent charge transport properties, perovskites of have attracted considerable attention and have shown great potential in many areas of solar cells, photovoltaic cells, light emitting diodes and lasers. All Inorganic Metal Halide (IMH) perovskite quantum dots (CsBX)3，B = Pb、Sn、Ge；X = Br-、I-、Cl-) While having the advantages of both QDs and halide perovskites. All inorganic metal halides (OMH) in contrast to organic-inorganic metal halide (OMH) perovskitesIMH) perovskite has higher stability. In addition, such inorganic perovskite quantum dots have high Photoluminescence (PL) Quantum Yield (QYs). Wherein CsPbBr3The photoluminescence quantum yield of the perovskite quantum dot is more than 90%, and the perovskite quantum dot is a novel quantum dot material with growth potential. Although CsPbBr3The perovskite quantum dot has higher Photoluminescence (PL) Quantum Yield (QYs), CsPbBr3The stability of perovskite quantum dots in water and oxygen remains a significant challenge.
Therefore, the invention synthesizes APTES-terminated CsPbBr in one step3Quantum dot, APTES as functional monomer to synthesize CsPbBr3A perovskite quantum dot-molecular imprinting fluorescence sensor is used for establishing a detection method with high selectivity and high sensitivity to omethoate.
Disclosure of Invention
The technical problem to be solved by the invention is to provide a CsPbBr-based method aiming at the defects of the prior art3The method for detecting omethoate of the perovskite quantum dot-molecular imprinting fluorescence sensor is simple in steps, and can be used for quickly, sensitively and specifically detecting the content of omethoate in a sample.
In order to achieve the purpose, the invention adopts the following technical scheme:
CsPbBr-based3The method for detecting omethoate of the perovskite quantum dot-molecular imprinting fluorescence sensor comprises the following steps:
S1：CsPbBr3preparation of perovskite quantum dot-molecular imprinting fluorescence sensor
Firstly, adding cesium carbonate, octadecene and PbBr into 3-Aminopropyltriethoxysilane (APTES)2APTES blocked CsPbBr formed by oleic acid and oleylamine3Perovskite quantum dots; then, oxidizing dimethoate, octadecene, APTES-terminated CsPbBr by template molecules3Formation of CsPbBr by perovskite quantum dots and 3-Aminopropyltriethoxysilane (APTES)3Perovskite quantum dots-molecularly imprinted polymers; finally, CsPbBr was added3Template molecular oxygen in perovskite quantum dot-molecularly imprinted polymerEluting the omethoate to obtain CsPbBr3Perovskite quantum dots-molecularly imprinted fluorescent sensors;
s2: drawing a standard working curve of 'fluorescence quenching intensity-omethoate concentration' and calculating a working equation
CsPbBr prepared in step S13The perovskite quantum dot-molecular imprinting fluorescence sensor is dispersed in dichloromethane, then is respectively mixed with a series of omethoate solutions with concentration gradient, reacts for at least 30 minutes at the temperature of 15-30 ℃, and the fluorescence intensity of the mixture at 510nm is tested; drawing a standard working curve of 'fluorescence quenching intensity-omethoate concentration' according to omethoate concentration and fluorescence intensity at 510nm, and calculating a working equation;
s3: determining the content of omethoate in a sample
CsPbBr prepared in step S13Dispersing the perovskite quantum dot-molecular imprinting fluorescence sensor in dichloromethane, mixing sample solutions, reacting for at least 30 minutes at the temperature of 15-30 ℃, and testing the fluorescence intensity of the sensor at 510 nm; and substituting the obtained fluorescence intensity numerical value into a working equation to obtain the content of omethoate in the sample.
Preferably, the step S1 includes the steps of:
(1) preparation of APTES-capped CsPbBr3Perovskite quantum dots
Adding 3-Aminopropyltriethoxysilane (APTES) into cesium carbonate, octadecene, and PbBr2Stirring in the mixture of oleic acid and oleylamine for 3 hours at 20 ℃ and 40% humidity in the presence of air, hydrolyzing, and purifying to obtain the APTES-terminated CsPbBr3Perovskite quantum dots;
(2) preparation of CsPbBr3Perovskite quantum dot-molecularly imprinted polymer
Oxidizing the template molecule with dimethoate, octadecene and APTES-terminated CsPbBr obtained in the step (1)3Mixing and stirring the perovskite quantum dots and the residual 3-Aminopropyltriethoxysilane (APTES) reacted in the step (1) for 30 minutes, adding a cross-linking agent, and stirring for 12 hours to obtain CsPbBr3Perovskite quantum dot-molecular imprinting polymerizationAn agent;
(3) elution template molecular oxidation dimethoate
The CsPbBr obtained in the step (2) is added3Centrifuging the perovskite quantum dot-molecularly imprinted polymer, removing supernatant, removing template molecule with eluent to oxidize dimethoate, and obtaining CsPbBr3Perovskite quantum dot-molecularly imprinted fluorescence sensor.
Preferably, the step (1) comprises the steps of:
1) mixing cesium carbonate, oleic acid and octadecene, degassing for 10 minutes in vacuum, heating to 120 ℃ under the vacuum condition, keeping the temperature constant for 1 hour, heating to 150 ℃ under the condition of introducing nitrogen, keeping the temperature constant for 2 hours until the solution is clear, and preparing a cesium oleate solution;
2) octadecene and PbBr2Mixing, vacuum degassing for 10 min, vacuum drying at 120 deg.C for 1 hr, introducing nitrogen gas, adding oleic acid, oleylamine and 3-Aminopropyltriethoxysilane (APTES), clarifying, and heating to 160 deg.C;
3) preheating the cesium oleate solution prepared in the step 1) to 100 ℃, quickly injecting the preheated cesium oleate solution into the solution in the step 2), cooling the solution to room temperature by using an ice water bath after 5 seconds, stirring for 3 hours under the conditions of temperature of 20 ℃, humidity of 40% and air, and hydrolyzing;
4) centrifuging at 5000rpm for 10 min, washing with hexane for 2 times to obtain APTES-capped CsPbBr3Perovskite quantum dots.
Particularly preferably, in the step 1), the molar volume ratio of the cesium carbonate to the oleic acid and octadecene is 1mmol (1.0-1.1) ml: (12.0-12.3) ml.
Particularly preferably, in step 2), the PbBr is2And octadecene, oleic acid, oleylamine, 3-Aminopropyltriethoxysilane (APTES) in a molar volume ratio of 0.376 mmol: 10 ml: 0.1 ml: 0.1 ml:1 ml.
Particularly preferably, in step 3), the cesium oleate solution and PbBr2The molar volume ratio of (2-3) ml to 1 mmol.
Preferably, in the step (2), the molar volume ratio of the template molecule omethoate to the octadecene is 1 mol: (8-12) L.
Particularly preferably, in the step (2), the molar volume ratio of the template molecule omethoate to the octadecene is 1 mol: 10L.
Preferably, in step (2), the template molecule omethoate and APTES-capped CsPbBr3The molar ratio of the perovskite quantum dots is 1: (1X 10)-6-3×10-6）。
Particularly preferably, in step S2, the template molecule omethoate and APTES-capped CsPbBr3The molar ratio of the perovskite quantum dots is 1: (1.88X 10)-6）。
Preferably, in the step (2), the molar ratio of the template molecule omethoate to the residual 3-Aminopropyltriethoxysilane (APTES) in the reaction is 1 (3-5).
Particularly preferably, the molar ratio of the template molecule omethoate to the residual 3-Aminopropyltriethoxysilane (APTES) in the reaction is 1: 3.
Preferably, in the step (2), the cross-linking agent is tetramethyl orthosilicate, and the molar volume ratio of the template molecule omethoate to the tetramethyl orthosilicate is 1 mol: (75-125) ml.
Particularly preferably, the molar volume ratio of the template molecule omethoate to the tetramethyl orthosilicate is 1 mol: 100 ml.
Preferably, in the step (3), the eluent is a mixture of hexane and ethyl acetate, and the volume ratio of the hexane to the ethyl acetate is 1: 3.
Preferably, the step S2 includes the steps of:
CsPbBr prepared in step S13Dispersing the perovskite quantum dot-molecularly imprinted fluorescent sensor in dichloromethane, mixing with a series of omethoate solutions with concentration gradients respectively, oscillating for 30 minutes at the temperature of 25 ℃, and testing the fluorescence intensity of the omethoate solutions at 510 nm; drawing a standard worker of 'fluorescence quenching intensity-omethoate concentration' according to omethoate concentration and fluorescence intensity at 510nmDrawing a curve and calculating a working equation.
Preferably, in step S2, the aptamer-molecularly imprinted fluorescent sensor prepared in step S1 is dispersed in dichloromethane so as to have a mass concentration of 5 × 10-6g/mL solution, wherein the omethoate solutions with a series of concentration gradients are omethoate solutions with mass concentrations of 0ng/mL, 50ng/mL, 100ng/mL, 150ng/mL, 200ng/mL, 250ng/mL, 300ng/mL, 350ng/mL and 400ng/mL respectively.
Preferably, the step S3 includes the steps of:
CsPbBr prepared in step S13The perovskite quantum dot-molecular imprinting fluorescence sensor is dispersed in dichloromethane and is configured to have the mass concentration of 5 multiplied by 10-6Mixing the g/ml solution with the sample solution, shaking for 30 minutes at the temperature of 25 ℃, and testing the fluorescence intensity of the mixture at 510 nm; and substituting the obtained fluorescence intensity numerical value into a working equation to obtain the content of omethoate in the sample.
Preferably, in steps S2 and S3, the fluorescence intensity is measured under the conditions of using 365 nm as the excitation wavelength, 5nm for the excitation light slit width, 10nm for the emission light slit width, and 400V for the photomultiplier tube voltage; the measurements used a quartz cell with a 1cm path length.
Preferably, the linear detection range of the detection method for omethoate is 50-400ng/mL, the linear correlation coefficient is 0.997, and the detection limit is 18.8 ng/mL.
The invention has the beneficial effects that:
1. the detection method utilizes the CsPbBr terminated by APTES3The quantum dots are signal elements, and the molecular imprinting polymer layer is wrapped by the CsPbBr with the sensitive recognition function on the omethoate3The perovskite quantum dot-molecular imprinting fluorescence sensor realizes the detection of omethoate with high selectivity and high sensitivity.
2. The detection method disclosed by the invention has the advantages that the linear detection range of omethoate is 50-400ng/mL, the linear correlation coefficient is 0.997, the detection limit is 18.8ng/mL, and the detection precision is 1.7% (RSD).
3. The detection method is applied to the labeling detection of omethoate in an actual sample and the direct detection of ultra-trace omethoate residues in agricultural products, the recovery rate is 96.7-101% in the surface labeling detection, and the relative standard deviation is less than 4.21%; the test results show that the detection method has practical detection value and significance for omethoate.
4. A selectivity test is carried out, and the detection method provided by the invention is proved to have good selectivity on omethoate.
Drawings
FIG. 1 is a graph showing the results of an experiment for measuring the effect of time on omethoate in the detection method of the present invention;
FIG. 2 is a graph showing the results of an experiment for measuring the effect of temperature on omethoate in the detection method of the present invention;
FIG. 3 is a graph showing the results of an experiment for determining the effect of solvents of organic solutions of different polarities on omethoate in the detection method of the present invention; wherein, FIG. 3a shows the different polarity organic solvent pair MIP @ CsPbBr3Graphs of the results of the effects of QDs optical properties; FIG. 3bMIP @ CsPbBr3QDs is the fluorescence spectrum in different polar organic solutions;
FIG. 4 is CsPbBr3A fluorescence response test result graph of the perovskite quantum dot-molecular imprinting fluorescence sensor to omethoate with different concentrations;
FIG. 5 is CsPbBr3A fluorescence response test result graph of the perovskite quantum dot-molecular non-imprinted fluorescence sensor to omethoate with different concentrations;
FIG. 6 is a standard working curve of "fluorescence quenching intensity-omethoate concentration" obtained by the detection method of example 1;
FIG. 7 is a standard working curve of "fluorescence quenching intensity-omethoate concentration" obtained by the detection method of comparative example 1;
FIG. 8 is a graph showing the results of the selectivity test of the detection methods of example 1 and comparative example 1 for omethoate and its structural analogs.
Detailed Description
The various test devices and reagents are commercially available and commercially available.
The technical solution of the present invention is further described below by using specific preferred embodiments in combination with preparation process test examples, structure characterization test examples, detection condition test examples, and effect test examples, but the present invention is not limited to the following embodiments.
Example 1:
CsPbBr-based3The method for detecting omethoate of the perovskite quantum dot-molecular imprinting fluorescence sensor comprises the following steps:
S1：CsPbBr3preparation of perovskite quantum dot-molecular imprinting fluorescence sensor
(1) Preparation of APTES-capped CsPbBr3Perovskite quantum dots
1) Adding 0.32g of cesium carbonate, 1ml of oleic acid (90%, OA) and 12ml of octadecene (90%, ODE) into a 50ml three-neck round-bottom flask, carrying out vacuum degassing on a Schlenk line for 10 minutes, heating to 120 ℃ under a vacuum condition, keeping the temperature constant for 1 hour, then heating to 150 ℃ under a nitrogen-introduced condition, keeping the temperature constant for 2 hours until the solution is clear, and thus obtaining a cesium oleate solution;
2) 10ml of octadecene (90%, ODE) and 0.376mmol of PbBr2Loading into a 50ml three-necked round bottom flask, degassing for 10 minutes under vacuum, and vacuum drying at 120 ℃ for 1 hour, then switching the flask to nitrogen atmosphere, slowly adding 100. mu.l oleic acid (90%, OA), 100. mu.l oleylamine (80% -90%, OAm), and 1ml 3-Aminopropyltriethoxysilane (APTES) to the flask, and heating to 160 ℃ until the solution is clear;
3) preheating the cesium oleate solution prepared in the step 1) to 100 ℃, quickly injecting 1ml of the preheated cesium oleate solution into the solution in the step 2), cooling the solution to room temperature by using an ice water bath after 5 seconds, then opening a flask, stirring for 3 hours under the conditions of temperature of 20 ℃, humidity of 40% and air, hydrolyzing, and forming an organic silicon substrate through silanization;
4) centrifuging at 5000rpm for 10 min, washing with hexane for 2 times to obtain APTES-capped CsPbBr3Perovskite quantum dots; the prepared APTES-terminated CsPbBr3Perovskite quantum dots are dispersed in n-hexylThe molar concentration of the product in the alkane is 0.376 multiplied by 10-4mol/L。
(2) Preparation of CsPbBr3Perovskite quantum dot-molecularly imprinted polymer
A25 mL flask was charged with 1mmol of the template molecule Omethoate (OMT), 10mL octadecene (90%, ODE), 50. mu.L of APTES-capped CsPbBr obtained in step (1)3The perovskite quantum dot is prepared by taking the residual 3-Aminopropyltriethoxysilane (APTES) reacted in the step (1) as a functional monomer, mixing and stirring for 30 minutes, adding 100 mu l of tetramethyl orthosilicate (TMOS) into the mixture, and stirring for 12 hours to prepare CsPbBr3Perovskite quantum dots-molecularly imprinted polymers;
(3) elution template molecular oxidation dimethoate
The CsPbBr obtained in the step (2) is added3Centrifuging the perovskite quantum dot-molecularly imprinted polymer at a rotating speed, removing supernatant, washing with hexane/ethyl acetate mixed solution (the volume ratio of hexane to ethyl acetate is 1: 3) for 10 times, removing template molecular Omethoate (OMT), and obtaining CsPbBr3Perovskite quantum dot-molecular imprinting fluorescence sensor (MIP @ CsPbBr)3QDs）。
S2: drawing a standard working curve of 'fluorescence quenching intensity-omethoate concentration' and calculating a working equation
The aptamer-molecularly imprinted fluorescent sensor prepared in step S1 was dispersed in methylene chloride so as to be at a mass concentration of 5X 10-6g/mL solution, mixing with omethoate solution with mass concentration of 0ng/mL, 50ng/mL, 100ng/mL, 150ng/mL, 200ng/mL, 250ng/mL, 300ng/mL, 350ng/mL and 400ng/mL respectively, reacting for 30 minutes at 25 ℃, and testing the fluorescence intensity at 510 nm; and drawing a standard working curve of 'fluorescence quenching intensity-omethoate concentration' according to the omethoate concentration and the fluorescence intensity at 510nm, and calculating a working equation.
S3: determining the content of omethoate in a sample
CsPbBr prepared in step S13The perovskite quantum dot-molecular imprinting fluorescence sensor is dispersed in dichloromethane and is configured to have the mass concentration of 5 multiplied by 10-6g/ml solution, mixing the sample solution, reacting for 30 minutes at 25 ℃, and testing the fluorescence intensity at 510 nm; and substituting the obtained fluorescence intensity numerical value into a working equation to obtain the content of omethoate in the sample.
Wherein, in steps S2 and S3, the conditions for measuring the fluorescence intensity are that 365 nm is adopted as the excitation wavelength, the excitation light slit width is 5nm, the emission light slit width is 10nm, and the photomultiplier voltage is 400V; the measurements used a quartz cell with a 1cm path length.
The detection results are as followsEffect test example 1 and Effect test example 2As shown.
Comparative example 1:
CsPbBr-based3The method for detecting omethoate of the perovskite quantum dot-molecular non-imprinted fluorescent sensor comprises the following steps:
S1：CsPbBr3preparation of perovskite quantum dot-molecular non-imprinted fluorescent sensor
(1) Preparation of APTES-capped CsPbBr3Perovskite quantum dots
In this comparative example, the above-mentioned APTES-capped CsPbBr was used3The perovskite quantum dots are prepared by the same method as in example 1.
(2) Preparation of CsPbBr3Perovskite quantum dot-molecular non-imprinted polymer
A25 mL flask was charged with 10mL octadecene (90%, ODE), 50. mu.L of APTES-capped CsPbBr obtained in step (1)3The perovskite quantum dot is prepared by taking the residual 3-Aminopropyltriethoxysilane (APTES) reacted in the step (1) as a functional monomer, mixing and stirring for 30 minutes, adding 100 mu l of tetramethyl orthosilicate (TMOS) into the mixture, and stirring for 12 hours to prepare CsPbBr3Perovskite quantum dots-molecularly non-imprinted polymers;
(3) elution is carried out
The CsPbBr obtained in the step (2) is added3Centrifuging the perovskite quantum dot-molecular non-imprinted polymer at a rotating speed, removing supernatant, and washing with hexane/ethyl acetate mixed solution (the volume ratio of hexane to ethyl acetate is 1: 3) for 10 times to obtain CsPbBr3Perovskite quantumPoint-molecule non-imprinting fluorescence sensor (NIP @ CsPbBr)3QDs）。
S2: drawing a standard working curve of 'fluorescence quenching intensity-omethoate concentration' and calculating a working equation
The aptamer-molecularly imprinted fluorescent sensor prepared in step S1 was dispersed in methylene chloride so as to be at a mass concentration of 5X 10-6g/mL solution, mixing with omethoate solution with mass concentration of 0ng/mL, 50ng/mL, 100ng/mL, 150ng/mL, 200ng/mL, 250ng/mL, 300ng/mL, 350ng/mL and 400ng/mL respectively, reacting for 30 minutes at 25 ℃, and testing the fluorescence intensity at 510 nm; and drawing a standard working curve of 'fluorescence quenching intensity-omethoate concentration' according to the omethoate concentration and the fluorescence intensity at 510nm, and calculating a working equation.
S3: determining the content of omethoate in a sample
CsPbBr prepared in step S13The perovskite quantum dot-molecular imprinting fluorescence sensor is dispersed in dichloromethane and is configured to have the mass concentration of 5 multiplied by 10-6g/ml solution, mixing the sample solution, reacting for 30 minutes at 25 ℃, and testing the fluorescence intensity at 510 nm; and substituting the obtained fluorescence intensity numerical value into a working equation to obtain the content of omethoate in the sample.
Wherein, in steps S2 and S3, the conditions for measuring the fluorescence intensity are that 365 nm is adopted as the excitation wavelength, the excitation light slit width is 5nm, the emission light slit width is 10nm, and the photomultiplier voltage is 400V; the measurements used a quartz cell with a 1cm path length.
Test conditions test example 1:reaction time
The test method comprises the following steps: the MIP @ CsPbBr prepared in step S1 of example 1 was taken3QDs and NIP @ CsPbBr prepared in step S1 of comparative example 13QDs are respectively dispersed in dichloromethane to be prepared into a mass concentration of 5 × 10-6Mixing the g/mL solution with Omethoate (OMT) 300ng/mL respectively, water bathing at 25 deg.C, and testing for different time (0, 5, 10, 15, 20, 25, 30, 40, 50, 60 min), MIP @ CsPbBr3QDs and NIP @ CsPbBr3QDs are inFluorescence intensity at 510 nm. The adsorption kinetics of both complexes were explored and the results are shown in figure 1.
Fluorescence test conditions: 365 nm is adopted as an excitation wavelength, the width of an excitation light slit is 5nm, the width of an emission light slit is 10nm, and the voltage of a photomultiplier is 400V; the measurements were performed using a quartz cell (1 cm path length).
As can be seen from FIG. 1, the value at NIP @ CsPbBr3After omethoate was added to the QDs, the fluorescence intensity remained constant after 15 minutes, indicating omethoate and NIP @ CsPbBr3Lack of specific binding between QDs. In contrast, MIP @ CsPbBr3The intensity of QDs decreases at a faster rate and reaches a constant value after 30 minutes. The constant intensity value indicates an equilibrium state when the adsorption and desorption rates are equal. Therefore, a preferred incubation time is 30 minutes. MIP @ CsPbBr3QDs and NIP @ CsPbBr3The different absorption kinetics of QDs for omethoate can be attributed to the blotting process.
Test conditions test example 2:reaction temperature
The test method comprises the following steps: the MIP @ CsPbBr prepared in step S1 of example 1 was taken3QDs and NIP @ CsPbBr prepared in step S1 of comparative example 13QDs are respectively dispersed in dichloromethane to be prepared into a mass concentration of 5 × 10-6g/ml solution, separately taking MIP @ CsPbBr prepared in example 13QDs are dispersed in methylene chloride to a mass concentration of 5X 10-6Mixing the solution of g/mlg/mL with Omethoate (OMT) of 300ng/mL, sequentially placing into water bath at 15 deg.C, 20 deg.C, 25 deg.C, 30 deg.C, 35 deg.C, 40 deg.C, 45 deg.C, 50 deg.C, 55 deg.C and 60 deg.C, reacting for 30min, and testing MIP @ CsPbBr3QDs、NIP@ CsPbBr3QDs and Omethoate (OMT) -binding MIP @ CsPbBr3Fluorescence intensity of QDs at 510 nm. The test results are shown in FIG. 2.
Fluorescence test conditions: the same conditions as those of the fluorescence test in test example 1 were used.
As can be seen from FIG. 2, NIP @ CsPbBr3QDs and MIP @ CsPbBr3The change of fluorescence intensity of QDs after adsorption of Omethoate (OMT) with temperature. NIP @ CsPbBr3QDs and MIP @ CsPbBr3QDs show stronger fluorescence intensity at lower temperature and have more stable fluorescence quenching rate within the range of 15-30 ℃. In order to obtain stable fluorescence intensity and high sensitivity, the temperature condition is easier to realize when the temperature is 25 ℃ and is normal temperature. Therefore, the preferred detection temperature is 25 ℃.
Test conditions test example 3:solvent conditions for the reaction
The test method comprises the following steps: the MIP @ CsPbBr prepared in step S1 of example 1 was taken3QDs are dispersed in different solvents to be configured into 5 × 10 mass concentration-6g/ml solution. Test MIP @ CsPbBr3Fluorescence intensity at 510nm for QDs. The test results are shown in FIG. 3.
Different solvents: hexane, toluene, dichloromethane, ethyl acetate, chloroform, acetonitrile, N-dimethyl formamide (DMF) and ethanol.
Fluorescence test conditions: the same conditions as those of the fluorescence test in test example 1 were used.
FIG. 3a is a graph of the solvent pair MIP @ CsPbBr for different polar organic solutions3A result graph of the influence of the optical properties of the quantum dot composite material; FIG. 3b MIP @ CsPbBr3QDs is the fluorescence spectrum in different polar organic solutions. As can be seen from FIG. 3, MIP @ CsPbBr3Bright solutions of QDs in low polarity solvents (i.e., hexane, toluene and dichloromethane) exhibit characteristic absorption and emission peaks resulting from localization; however, compared to chalcogenide quantum dots, MIP @ CsPbBr3QDs are unstable in many common solvents, particularly in polar solvents (i.e., DMF and ethanol), because they are fully ionic crystals. The preferred detection solvent is methylene chloride, taking into account the toxicity of toluene and the subsequent sample extraction process.
Effect test example 1：
MIP @ CsPbBr was obtained at different omethoate concentrations according to example 1 steps S1, S2 and comparative example 1 steps S1, S2, respectively3QDs and NIP @ CsPbBr3The fluorescence spectra of QDs (as shown in FIGS. 4-5) and the standard working curve of "fluorescence quenching intensity-omethoate concentration" (as shown in FIGS. 6-7) is plotted.
As can be seen from FIGS. 4-5, MIP @ CsPbBr3QDs and NIP @ CsPbBr3QDs all exhibit a spectral response to the template molecule. However, with MIP @ CsPbBr3More pronounced fluorescence quenching was NIP @ CsPbBr compared to QDs3QDs；MIP@CsPbBr3Quenching efficiency or sensitivity of QDs is higher due to MIP @ CsPbBr3The imprinting cavities are present in QDs and have a specific binding affinity for omethoate.
The fluorescence quenching system conforms to the Stern-Volmer equation in a certain concentration range, namely (F)0-F)/F= Ksvcq，cqIs the concentration of the quencher, KsvAre constants of the Stern-Volmer equation. As can be seen from FIGS. 6-7, (F)0/F-1) and MIP @ CsPbBr3QDs and NIP @ CsPbBr3Concentration of quencher for QDs (c)q) All have good linear relationship. Calculated to obtain MIP @ CsPbBr3The quenching equation for QDs is a linear equation: (F)0-F)/F = 0.0016c -0.0082（R2= 0.997) at Omethoate (OMT) concentrations in the range of 50 to 400 ng/mL; NIP @ CsPbBr3The quenching equation for QDs is a linear equation: (F)0-F)/F = 0.0005c -0.0082（R2=0.991）
The assay also calculates the detection limit according to the 3 σ IUPAC criterion (3 σ/S), where σ is the standard deviation of the blank signal and S is the slope of the linear calibration, calculating MIP @ CsPbBr3The Omethoate (OMT) detection limit of QDs is 18.8 ng/mL. In addition, 300ng/mL-1The precision of 9 replicates of Omethoate (OMT) was 1.7% (RSD). Under the optimal condition, the IF is 3.2, which shows that the imprinting process can greatly improve MIP @ CsPbBr3Quenching efficiency of QDs for fluorescence of template molecules.
Effect test example 2:actual sample testing
In order to examine whether the detection method of the present invention can be used in an actual sample, the amount of omethoate remaining in a commercially available cabbage was examined. No target analyte was found in the sample after the sample extraction procedure. Therefore, the recovery test using the spiked samples was used for the evaluation. In addition, the utility of the detection method depends largely on the direct detection of ultra-trace OMT residues in agricultural products.
The test method comprises the following steps:
1. adding Omethoate (OMT) with mass concentration of 50ng/mL, 150ng/mL and 300ng/mL into the extract to obtain samples with low, medium and high addition concentration; the detection method of example 1 was further employed. Recovery corresponding to low, medium and high addition concentrations was carried out three times respectively. The test results are shown in Table 1.
2. The 40% Omethoate (OMT) pesticide was diluted 1000 times and then sprayed on the cabbage with an atomizer. After the sample extraction procedure, the sprayed cabbage was tested for omethoate residue after 1 day, 7 days and 15 days using the test method of example 1. The test results are shown in Table 2.
Fluorescence test conditions: 365 nm is adopted as an excitation wavelength, the width of an excitation light slit is 5nm, the width of an emission light slit is 10nm, and the voltage of a photomultiplier is 400V; the measurements were performed using a quartz cell (1 cm path length).
Table 1 recovery and RSD values for the spiked vegetable samples (n = 3)
Figure 562492DEST_PATH_IMAGE001
As can be seen from Table 1, the recovery of the spiked vegetable samples ranged from 96.7 to 101% with a relative standard deviation of less than 4.21%. The result shows that the detection method has reliability and practicability for analyzing the pesticide in the standard sample, and has higher accuracy and repeatability.
Table 2 OMT remains in sprayed cabbage
Figure 811071DEST_PATH_IMAGE002
As can be seen from Table 2, the OMT residues after 1 day, 7 days and 15 days of spraying were 0.30,0.05 and 0.012 mg/kg, respectively, with a Relative Standard Deviation (RSD) of 3.35% to 4.81%. The OMT residue after 15 days is lower than the Maximum Residue Limit (MRL) of vegetables allowed by GB 2763-2016 (national food safety standard, "maximum residue limit in pesticide food") by 0.02 mg/kg. Therefore, the sensitivity of the detection method can meet the requirement of directly detecting the OMT residues in agricultural products.
Effect test example 3: selective investigation
Organophosphorus insecticides, such as dimethoate, dichlorvos and phoxim, were selected as analogs of the template molecule Omethoate (OMT) to examine the selectivity of the detection method of the present invention.
The test method comprises the following steps: the omethoate, the dimethoate, the dichlorvos and the phoxim which are 0.3 mu g/mL are selected as samples, and the detection method of the example 1 and the detection method of the comparative example 1 are respectively adopted. The experiment also evaluated the selectivity of the composite using a selectivity factor (γ) calculated from the formula: γ = Δ Ftemplate/Δ Fanalog, where Δ Ftemplate and Δ Fanalog are MIP @ CsPbBr3QDs or NIP @ CsPbBr3In the QDs complexed analyte, the more the gamma value is close to 1.00, the higher the selectivity of the material to the template. The test results are shown in FIG. 8 and Table 2.
Fluorescence test conditions: 365 nm is adopted as an excitation wavelength, the width of an excitation light slit is 5nm, the width of an emission light slit is 10nm, and the voltage of a photomultiplier is 400V; a practical quartz cell (1 cm path length) was measured.
TABLE 3 Selectivity factors for MIP @ CspbBr3 QDs and NIP @ CspbBr3 QDs
△Fanalytes(MIP) γMIP △Fanalytes(NIP) γNIP
Omethoate 490 1.00 197 1.00
Leguo (fruit of musical instruments) 422 1.16 180 1.09
Dichlorvos 205 2.39 189 1.04
Phoxim 200 2.46 196 1.01
As can be seen from FIG. 8 and Table 3, MIP @ CsPbBr was observed among all the selected organophosphorus pesticides3QDs respond most strongly to OMT. This result indicates that the detection method of the invention has a higher specificity for OMT, since the custom imprinted cavity is complementary to OMT in terms of size, shape and chemical set. Since the structure of the dimethoate is closest to the template in the templates, dimethoate exhibits an excellent selectivity factor of 1.16 in the analogues, closest to 1.00, indicating that part of the dimethoate can enter the imprinting cavity of the OMT. In addition, the detection method of example 1 of the present invention and the detection method of comparative example 1 were weak in the reaction to dichlorvos and phoxim. Compared with OMT, other pesticides have different structures and cannot enter MIP @ CsPbBr3Identification cavities of QDs. Thus, the relatively weak reaction is due to non-specific adsorption. In addition, the selectivity factor of the assay of comparative example 1 for the template and all analogues was close to 1.00, indicating no selectivity for the analogue and template. The results show that the detection method of the invention has specificity to Omethoate (OMT).
Effect test example 4:detection limit compared with the prior art
The detection limit is compared with other methods for detecting omethoate in the prior art, and the result is shown in a table 4.
TABLE 4 detection limit comparison
Method of producing a composite material Reference to Detection limits Detection range
Surface enhanced Raman Scattering Pang, S.; Labuza, T. P.; He, L. L. Analyst. 2014, 139, 1895−1901. 24μM 24–500μM
Laser induced fluorescence capillary electrophoresis (CE-LIF) 36. Tang, T. T.; Deng, J. J.; Zhang, M.; Shi, G. Y.; Zhou, T. S. Talanta. 2016, 146, 55-61. 0.23μM 0.70–10.0μ M
Chemiluminescence-molecular imprinting (CL-MI) Ge,S.G.; Zhao, P. N.; Yan, M.; Zang, D. J.; Yu, J. H. Anal. Methods. 2012, 4, 3150-3156. 42ng/mL 0.20μM 100-9× 103ng/mL
Aptamer of chroma/Au 37. Wang, P. J.; Wan, Y.; Ali, A.; Deng, S. Y.; Su, Y.; Fan, C. H.; Yang, S. L. Sci China Chem. 2016, 59, 237-242. 0.1μM 0.1–10μM
CsPbBr3 perovskite-based quantum dot-molecular imprinting Omethoate detection method of fluorescent sensor The invention 18.8ng/mL （0.088μM） 50–400ng/ mL
As can be seen from Table 4, the detection method of the present invention has the advantages of the lowest detection limit, high sensitivity and good selectivity.
The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention in any way, so that any simple modification, equivalent change and modification made to the above embodiment according to the technical spirit of the present invention will still fall within the scope of the technical solution of the present invention without departing from the content of the technical solution of the present invention.

Claims (6)

1. CsPbBr-based3The method for detecting omethoate of the perovskite quantum dot-molecular imprinting fluorescence sensor is characterized by comprising the following steps of:
S1：CsPbBr3preparation of perovskite quantum dot-molecular imprinting fluorescence sensor
Firstly, adding cesium carbonate, octadecene and PbBr into 3-aminopropyltriethoxysilane2APTES blocked CsPbBr formed by oleic acid and oleylamine3Perovskite quantum dots; then, oxidizing dimethoate, octadecene, APTES-terminated CsPbBr by template molecules3Formation of CsPbBr from perovskite quantum dots and 3-aminopropyltriethoxysilane3Perovskite quantum dots-molecularly imprinted polymers; finally, CsPbBr was added3Carrying out omethoate elution on template molecules in the perovskite quantum dot-molecularly imprinted polymer to obtain CsPbBr3Perovskite quantum dots-molecularly imprinted fluorescent sensors;
s2: drawing a standard working curve of 'fluorescence quenching intensity-omethoate concentration' and calculating a working equation
CsPbBr prepared in step S13The perovskite quantum dot-molecular imprinting fluorescence sensor is dispersed in dichloromethane, then is respectively mixed with a series of omethoate solutions with concentration gradient, reacts for at least 30 minutes at the temperature of 15-30 ℃, and the fluorescence intensity of the mixture at 510nm is tested; drawing a standard working curve of 'fluorescence quenching intensity-omethoate concentration' according to omethoate concentration and fluorescence intensity at 510nm, and calculating a working equation;
s3: determining the content of omethoate in a sample
CsPbBr prepared in step S13Dispersing the perovskite quantum dot-molecular imprinting fluorescence sensor in dichloromethane, mixing sample solutions, oscillating for at least 30 minutes at the temperature of 15-30 ℃, and testing the fluorescence intensity of the sensor at 510 nm; the obtained fluorescence intensity value is substituted into a working equation to obtainTo the content of omethoate in the sample;
the step S1 includes the steps of:
(1) preparation of APTES-capped CsPbBr3Perovskite quantum dots
Adding 3-aminopropyltriethoxysilane into cesium carbonate, octadecene and PbBr2Stirring in the mixture of oleic acid and oleylamine for 3 hours at 20 ℃ and 40% humidity in the presence of air, hydrolyzing, and purifying to obtain the APTES-terminated CsPbBr3Perovskite quantum dots;
(2) preparation of CsPbBr3Perovskite quantum dot-molecularly imprinted polymer
Oxidizing the template molecule with dimethoate, octadecene and APTES-terminated CsPbBr obtained in the step (1)3Mixing and stirring the perovskite quantum dots and the residual 3-aminopropyltriethoxysilane in the step (1) for 30 minutes, adding a cross-linking agent, and stirring for 12 hours to obtain CsPbBr3Perovskite quantum dots-molecularly imprinted polymers;
(3) elution template molecular oxidation dimethoate
The CsPbBr obtained in the step (2) is added3Centrifuging the perovskite quantum dot-molecularly imprinted polymer, removing supernatant, removing template molecule with eluent to oxidize dimethoate, and obtaining CsPbBr3Perovskite quantum dots-molecularly imprinted fluorescent sensors;
in steps S2 and S3, the fluorescence intensity is measured under the conditions that 365 nm is used as the excitation wavelength, the excitation light slit width is 5nm, the emission light slit width is 10nm, and the photomultiplier voltage is 400V; the measurements used a quartz cell with a 1cm path length;
the step (1) comprises the following steps:
1) mixing cesium carbonate, oleic acid and octadecene, degassing for 10 minutes in vacuum, heating to 120 ℃ under the vacuum condition, keeping the temperature constant for 1 hour, heating to 150 ℃ under the condition of introducing nitrogen, keeping the temperature constant for 2 hours until the solution is clear, and preparing a cesium oleate solution;
2) octadecene and PbBr2Mixing, vacuum degassing for 10 min, vacuum drying at 120 deg.C for 1 hr, and introducing nitrogen into the stripAdding oleic acid, oleylamine and 3-aminopropyltriethoxysilane, heating to 160 ℃ after the solution is clarified;
3) preheating the cesium oleate solution prepared in the step 1) to 100 ℃, quickly injecting the preheated cesium oleate solution into the solution in the step 2), cooling the solution to room temperature by using an ice water bath after 5 seconds, stirring for 3 hours under the conditions of temperature of 20 ℃, humidity of 40% and air, and hydrolyzing;
4) centrifuging at 5000rpm for 10 min, washing with hexane for 2 times to obtain APTES-capped CsPbBr3Perovskite quantum dots;
in the step 1), the molar volume ratio of the cesium carbonate to the oleic acid and the octadecene is 1mmol (1.0-1.1) ml: (12.0-12.3) ml;
in step 2), the PbBr is2And octadecene, oleic acid, oleylamine, 3-aminopropyltriethoxysilane in a molar volume ratio of 0.376 mmol: 10 ml: 0.1 ml: 0.1 ml:1 ml;
in step 3), the cesium oleate solution and PbBr2The molar volume ratio of (2-3) ml to 1 mmol.
2. The detection method according to claim 1, characterized in that: in the step (2), the molar volume ratio of the template molecule omethoate to the octadecene is 1 mol: (8-12) L; the template molecule omethoate and APTES capped CsPbBr3The molar ratio of the perovskite quantum dots is 1: (1X 10)-6-3×10-6) (ii) a The molar ratio of the template molecule omethoate to the residual 3-aminopropyltriethoxysilane in the reaction is 1 (3-5).
3. The detection method according to claim 1, characterized in that: in the step (2), the cross-linking agent is tetramethyl orthosilicate, and the molar volume ratio of the template molecule omethoate to the tetramethyl orthosilicate is 1 mol: (75-125) ml.
4. The detection method according to claim 1, characterized in that: in the step (3), the eluent is a mixed solution of hexane and ethyl acetate, and the volume ratio of the hexane to the ethyl acetate is 1: 3.
5. The detection method according to claim 1, characterized in that: in step S2, the molecularly imprinted fluorescent sensor prepared in step S1 is dispersed in dichloromethane so as to be disposed at a mass concentration of 5 × 10-6g/mL solution, wherein the omethoate solutions with a series of concentration gradients are omethoate solutions with mass concentrations of 0ng/mL, 50ng/mL, 100ng/mL, 150ng/mL, 200ng/mL, 250ng/mL, 300ng/mL, 350ng/mL and 400ng/mL respectively.
6. The detection method according to claim 1, characterized in that: the linear detection range of the detection method for omethoate is 50-400ng/mL, the linear correlation coefficient is 0.997, and the detection limit is 18.8 ng/mL.
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