CN113686838A - Preparation of superfine mixed-valence Ce-MOF nanowire and application of superfine mixed-valence Ce-MOF nanowire in electrochemiluminescence sensing - Google Patents
Preparation of superfine mixed-valence Ce-MOF nanowire and application of superfine mixed-valence Ce-MOF nanowire in electrochemiluminescence sensing Download PDFInfo
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Abstract
The invention discloses a preparation method of an ultrafine mixed-valence Ce-MOF nanowire and application of the ultrafine mixed-valence Ce-MOF nanowire in electrochemical luminescence sensing, wherein the preparation method of the ultrafine mixed-valence Ce-MOF nanowire comprises the following steps: cationic CTAB and SDS surfactant are mixed to form a positive and negative ion micelle system, and a stable single crystal superfine Ce-MOF nanowire colloidal solution is generated in water. The size of the prepared Ce-MOF mixed valence state nanowire is about 50nM, and the prepared Ce-MOF mixed valence state nanowire has good water stability and conductivity, on the basis, the nanowire is introduced into a luminol hydrogen peroxide luminescent system, a novel two-channel self-circulation Electrochemiluminescence (ECL) catalytic amplification mechanism is provided, and finally, the ECL sensor based on the mixed valence state ultrafine Ce-MOF is developed by combining a molecular imprinting technology and is used for detecting trace imidacloprid in plant source food, the linear range of the sensor is 2-120 nM, and the detection limit is 0.34 nM.
Description
Technical Field
The invention relates to the field of preparation and application of nano materials, in particular to preparation of an ultrafine mixed-valence Ce-MOF nanowire and application of the ultrafine mixed-valence Ce-MOF nanowire in electrochemiluminescence sensing.
Background
Neonicotinoid insecticides are the most widely used botanical insecticides at present due to their high efficiency and broad spectrum, and they block the normal conduction of the central nervous system by controlling nicotinic acetylcholinesterase receptors, thus leading to paralysis and death of pests. However, studies have shown that neonicotinoids not only have a great potential hazard to bees, but also have a negative impact on human health, with imidacloprid (IMI) being the typical representative of neonicotinoid insecticides. Due to the long term widespread use, IMI residues have become a ubiquitous pesticide contaminant in agricultural products, and therefore, reliable quantitative analysis of IMI on samples of plant products is essential. Heretofore, methods for measuring IMI mainly include High Performance Liquid Chromatography (HPLC), liquid chromatography-tandem mass spectrometry (LC-MS/MS), gas chromatography-tandem mass spectrometry (GC-MS/MS), and an immunoassay method. However, these analytical methods are expensive and time consuming to use. Therefore, the development of an economic, convenient and high-sensitivity IMI determination method has wide application potential. Under such a background, electrochemical luminescence (ECL) sensors are receiving more and more attention from researchers due to their low background noise and inherently high sensitivity, and it is an important issue to improve the ECL response of a luminescence probe and to improve the sensor sensitivity in the ECL sensor construction process.
Metal Organic Framework (MOF) is a porous material formed by organic ligands and inorganic Metal ions through coordination bonds, and has excellent physicochemical properties such as large surface area, high permanent porosity, easy functionalization and the like. MOFs have found wide application in the fields of gas storage, biomedicine, catalysis, sensing, separation, etc. due to their unique properties, MOFs are commonly used to immobilize chromophores or provide catalytically active centers in MOF-based ECL sensors. For example, Wang et al prepared Co/Ni-based MOF nanosheets loaded with luminol-functionalized AgNPs, and constructed an immunosensor for detecting AFP; yang et al reported functionalization of a reticulated metal-organic framework to enhance ECL strength through encapsulation and surface modification; shao et al reported that MOF/Au/G quadruplexes were used as quenchers and enhancers for making target-triggered ratiometric ECL sensors for sensitive detection of prostate-specific antigens; huang et al prepared aggregation-inducing Hf-MOF of the ECL (AIECL) type by introducing tetraphenylvinyl ligands. Therefore, most of the previously reported MOF-based ECL sensors have focused on increasing the loading of chromophores or doping other catalytic materials.
Despite these advances, MOF-based ECL sensors still face several problems. For example, traditional methods of synthesizing MOFs typically have particle sizes on the order of micrometers, which presents a significant challenge to the immobilization of MOFs on electrodes. In fact MOF adhesion and post-functionalization are major problems facing MOF-based ECL sensors, and the large size of the MOF structure also limits its conductivity. In addition, most MOFs are unstable in water, which can lead to leakage of the supported chromophoric groups. These factors greatly limit the stability and reproducibility of MOF-based ECL sensors, and it is therefore of particular importance to develop a new technology to design and prepare high performance MOFs with ultra-fine size, good stability in water and high conductivity.
Disclosure of Invention
The invention aims to solve the technical problems of overlarge grain diameter of MOFs synthesized by the traditional method, poor stability in water and low conductivity, and provides a preparation method of an ultrafine mixed-valence Ce-MOF nanowire.
The preparation method of the superfine mixed-valence Ce-MOF nanowire comprises the following steps: cationic CTAB (cetyl trimethyl ammonium bromide) and SDS (sodium dodecyl sulfate) surfactant are mixed to form a positive and negative ion micelle system, and a stable single crystal superfine Ce-MOF nanowire colloidal solution is generated in water.
The preparation method specifically comprises the following steps: 40mg of NaOH (sodium hydroxide) and 70mg of H3BTC (trimesic acid) is dissolved in 3mL of water, 60mL of 0.1mol/L SDS solution and 2mL of 0.1mol/L CTAB solution are added, and the mixture is vortexed for 30 seconds to obtain an organic ligand micelle solution; 140mg of Ce (NO)3)3·6H2O(Cerous nitrate hexahydrate) is dissolved in 2mL of water, 40mL of 0.1mol/L SDS solution and 1mL of 0.1mol/L CTAB solution are respectively added, and ultrasonic treatment is carried out for 2min to obtain a metal ion micelle solution; slowly adding the organic ligand micelle solution into the metal ion micelle solution, and carrying out water bath reaction for 3 hours at the temperature of 40 ℃; then 1mL of 30 wt% H was added at room temperature2O2(hydrogen peroxide) reacting for 1h until the milky reaction mixture turns yellow, then centrifuging the obtained product, washing with deionized water and ethanol, and vacuum drying at 50 ℃ overnight to obtain the superfine mixed-valence Ce-MOF nanowire.
On the basis of the superfine mixed valence Ce-MOF, the invention also provides a preparation method of IMI-MIECS (imidacloprid molecularly imprinted electrochemical luminescence sensor) based on the superfine mixed valence Ce-MOF, which comprises the following steps: GCE (glassy carbon electrode) was polished to a mirror surface with 1.0, 0.3 and 0.05 μm alumina slurries in sequence, water, ethanol and 0.5mol/L H2SO4(sulfuric acid) rinsing in sequence; ultrasonically dispersing 15mg of Ce-MOF in 5mL of deionized water; then, 10 mu L of Ce-MOF dispersed liquid is dripped on the surface of the GCE electrode, and the Ce-MOF/GCE electrode is obtained after drying at 25 ℃; preparing an IMI molecularly imprinted membrane by electropolymerization of Ce-MOF/GCE serving as a working electrode in PBS (phosphate buffer solution) with the pH of 6.8 and containing 0.5mmol/L IMI and 3.0mmol/L o-PD (o-phenylenediamine), and performing 20 times of cyclic voltammetric scanning at the scanning rate of 50mV/s to prepare an IMI-MIP membrane; and finally, preparing the prepared IMI-MIP modified electrode in a volume ratio of 8: 1 for 7 minutes to remove the template, and obtaining IMI-MIECS.
Further, the IMI-MIECS is applied to detection of trace IMI in plant source food, and the detection method comprises the following steps: immersing the eluted MIECS into sample solutions with different concentrations for 10 minutes, and re-adsorbing imidacloprid in the solution to be detected; placing the sensor after the completion of the reabsorption into 0.1mmol/L luminol and 0.2mmol/L H2O2And 0.02mol/LpH 8.5.5 borate buffer luminescence solution, measuring ECL response; as the concentration of imidacloprid in the sample is increased, the molecular imprinting holes are occupied, the electron transfer of the probe on the surface of the electrode is blocked, so that the ECL response of the sensor is reduced, and a gate-controlled IMI-MIECS is constructed.
Furthermore, the action mechanism of IMI-MIECS on the luminol hydrogen peroxide catalytic luminescent system comprises two paths, in the path 1, dissolved oxygen in the solution generates superoxide anion
In the path 2, Ce (III) in Ce-MOF catalyzes the formation of superoxide anion, so that
Finally luminol radical and a large number of superoxide anions generate luminophore AP2-·Resulting in an enhancement of the ECL system of luminol in Ce-MOF/GCE.
The embodiment of the invention has the following beneficial effects:
the invention discloses a construction of an electrochemical luminescence (ECL) sensor based on a superfine mixed-valence cerium metal-organic framework (Ce-MOF); in order to prepare the sensor, the micelle is used as a nano reaction chamber to generate a stable superfine mixed-valence Ce-MOF crystal colloidal solution in water; the prepared superfine mixed valence Ce-MOF is successfully introduced into a luminol ECL system for the first time, and a double-path self-circulation catalytic luminescence strategy is provided; by combining with a molecular imprinting technology, a novel ECL sensor based on MOF is constructed and applied to trace IMI detection of plant source food; the method has a special significance in the field of pesticide detection, and provides a simple and reliable route for the design of the MOF-based molecular imprinting ECL sensor.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
FIG. 1 is an SEM, TEM image of an ultrafine mixed-valence Ce-MOF and its corresponding Fast Fourier Transform (FFT);
FIG. 2 is a PXRD pattern of ultrafine mixed-valence Ce-MOF;
FIG. 3 is a schematic diagram of the crystal planes of ultrafine mixed-valence Ce-MOF and {021} phases thereof;
FIG. 4 is a Ce-MOF colloidal solution in H2O2Photographic images in the presence and absence and partially oxidized samples showed tyndall effect images under 630nm laser irradiation;
FIG. 5 is a XPS measurement spectrum (A), a high-resolution Ce three-dimensional spectrum (B), and a FT-IR spectrum (C) of ultrafine mixed-valence Ce-MOF, and a stability measurement diagram (D) of UMV-Ce-MOF;
FIG. 6 shows MOF/GCE at 5mmol/L Fe (CN) in 0.1mol/L KCl6 3-/4-Cv plots at different scan rates in solution;
FIG. 7 is a graph showing the results of leaching test strength of Ce-MOF/GCE;
FIG. 8 is Ce-MOF catalyzed luminol/H2O2ECL mechanism schematic of the process;
FIG. 9 is a schematic diagram of the formation of IMI-MIP (A) and nMOP (B) on Ce-MOF/GCE;
FIG. 10 is a schematic diagram of electropolymerization o-PD/IMI molar ratio optimization;
FIG. 11 is a schematic diagram of the optimization of elution (a) and resorption (b) times;
FIG. 12 is pH and buffer media versus luminol/H2O2Schematic representation of the impact of the light emitting system;
FIG. 13 is H2O2An optimization schematic diagram of the addition amount;
FIG. 14 shows Δ ECL for MIECS (a) and non-MIECS (b)Re-a schematic diagram of t;
FIG. 15 is the electrochemiluminescence response performance of IMI-MIECS to imidacloprid and its working curve;
FIG. 16 is a schematic of an assessment of the stability of the ECL response;
FIG. 17 is a graph showing the results of a cross-reactivity study of ECL sensors.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the present application, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The invention provides a preparation method of superfine mixed-valence Ce-MOF nanowires, which comprises the following steps: cationic CTAB (cetyl trimethyl ammonium bromide) and SDS (sodium dodecyl sulfate) surfactant are mixed to form a positive and negative ion micelle system, and a stable single crystal superfine Ce-MOF nanowire colloidal solution is generated in water.
In this example, the preparation comprises the following specific steps: 40mg of NaOH (sodium hydroxide) and 70mg of H3BTC (trimesic acid) is dissolved in 3mL of water, 60mL of 0.1mol/L SDS solution and 2mL of 0.1mol/L CTAB solution are added, and the mixture is vortexed for 30 seconds to obtain an organic ligand micelle solution; 140mg of Ce (NO)3)3·6H2Dissolving O (cerous nitrate hexahydrate) in 2mL of water, respectively adding 40mL of 0.1mol/L SDS solution and 1mL of 0.1mol/L CTAB solution, and carrying out ultrasonic treatment for 2min to obtain a metal ion micelle solution; slowly adding the organic ligand micelle solution into the metal ion micelle solution, and carrying out water bath reaction for 3 hours at the temperature of 40 ℃; then 1mL of 30 wt% H was added at room temperature2O2(hydrogen peroxide) reacting for 1h until the milky reaction mixture turns yellow, then centrifuging the obtained product, washing with deionized water and ethanol, and vacuum drying at 50 ℃ overnight to obtain the superfine mixed-valence Ce-MOF nanowire.
Referring to FIG. 1, FIG. 1 is an SEM and TEM image of the ultrafine mixed-valence Ce-MOF and its corresponding Fast Fourier Transform (FFT), and it can be seen that the ultrafine mixed-valence Ce-MOF prepared by using the positive and negative ion micelle system exhibits a one-dimensional nanowire morphology with a diameter of about 50 nm. This is because the micelles provide stable compartments for the crystal nano-growth reaction, improving the growth continuity of Ce-MOF. Where FIG. 1e is an HRTEM image of ultrafine mixed-valence Ce-MOF and its corresponding Fast Fourier Transform (FFT). Referring to FIGS. 2 and 3, FIG. 2 is a PXRD pattern of ultrafine mixed-valence Ce-MOF; FIG. 3 is a schematic diagram of the crystal planes of ultrafine mixed-valence Ce-MOF and {021} phase thereof, in FIG. 1, an HRTEM imageThe images show that the prepared Ce-MOF maintains a good crystal structure, and the interlayer spacing is calculated to be about 0.35nm, which corresponds well to the {021} plane of the Ce-MOF in FIG. 3. Referring to FIG. 4, in FIG. 4, the Ce-MOF colloidal solution is in H sequence2O2Photographic images in the absence and presence and partially oxidized samples show the tyndall effect under 630nm laser irradiation, in the absence of H2O2The colloidal solution of Ce-MOF is milky white in the presence of H2O2The Ce-MOF colloidal solution of (A) is yellow and shows a Tyndall effect under the irradiation of 630nm laser.
Please refer to fig. 5, fig. 5 is an XPS measurement spectrum (a), a high resolution Ce three-dimensional spectrum (B), a FT-IR spectrum (C) of the ultrafine mixed-valence Ce-MOF, and a stability measurement diagram (D) of the ultrafine mixed-valence Ce-MOF. The element composition and the chemical state of the superfine mixed valence Ce-MOF are analyzed by XPS; as shown in fig. 5A, characteristic peaks of Ce 3d, C1 s and O1s regions were clearly observed in Ce-MOF full scan XPS; the high resolution XPS spectrum of Ce showed 10 deconvolution peaks, as shown in figure 5B; marked v0、v'、u0The peaks marked as v, v ', u ', and u ' are defined as characteristic peaks of Ce (IV), and the peaks correspond to two different valence states of Ce, so that the luminol/hydrogen peroxide dual-channel catalytic luminescence route taking the metal with the mixed valence state as an active center is supported, and the catalytic efficiency is finally improved; successful formation of Ce-MOF was confirmed by FT-IR spectroscopy in FIG. 5C at 1612--1The characteristic peaks of the ion source belong to upsilony and upsilosym stretching vibration and Ce-O stretching vibration of carboxylic acid ions respectively. For the MOF-based ECL sensor, since long-term soaking in an electrolytic cell is required, stability is the key to ensure good MOF performance, and thus the stability of Ce-MOF in water or methanol is tested, as shown in fig. 5D, it is found that the PXRD spectrum of Ce-MOF is not substantially changed when it is soaked in water for 24 or 48h, and similar results are obtained in the methanol soaking test. The analysis results prove that the Ce-MOF is successfully prepared, has mixed valence, superfine size and excellent stability, and importantly, the properties meet the requirements of hydrogen peroxide mimic enzyme, thereby indicating that the system has high-efficiency catalysis of luminol/H2O2Of ECLCapability.
On the basis of the superfine mixed valence Ce-MOF, the invention also provides a preparation method of IMI-MIECS based on the superfine mixed valence Ce-MOF, which comprises the following steps: GCE electrodes were polished to a mirror surface using 1.0, 0.3 and 0.05 μm alumina cement slurries in sequence, water, ethanol and 0.5mol/L H2SO4(sulfuric acid) rinsing in sequence; ultrasonically dispersing 15mg of Ce-MOF in 5mL of deionized water; then transferring 10 mu L of Ce-MOF dispersion liquid to an electrode, and drying at 25 ℃ to obtain a Ce-MOF/GCE electrode; the IMI molecularly imprinted membrane is prepared by electropolymerization of Ce-MOF/GCE serving as a working electrode in PBS buffer solution with pH of 6.8 and containing 0.5mmol/L IMI and 3.0mmol/L o-PD (o-phenylenediamine), and the IMI-MIP membrane is prepared by 20 times of cyclic voltammetry scanning at the scanning rate of 50 mV/s. And finally, preparing the prepared IMI-MIP modified electrode in a volume ratio of 8: 1 for 7 minutes to remove the template, and obtaining IMI-MIECS. (comparative example: non-MIP (nMOP) films were prepared from a polymerization solution without IMI under otherwise identical conditions, and non-MIECS was finally prepared).
The electrochemical performance of the prepared Ce-MOF/GCE is confirmed: with 5mmol/L Fe (CN) containing 0.1mol/L KCl6 3-/4-The solution is used as a probe, and the effective electrode area of the modified electrode is preliminarily researched by CV under different scanning rates. Referring to FIG. 6, FIG. 6 shows MOF/GCE at 0.1mol/LKCl in 5mmol/L Fe (CN)6 3-/4-CV plots at different scan rates in solution; the results show that Ip and V are in the range of 0.01-0.1V/s1/2The linear relationship indicates the existence of a diffusion control process. According to Randles-Sevcik equation (Ip ═ 2.69X 10)5n3/2AeffD1/2ν1/2C)，Ip-ν1/2Slope ip (A) of the curve is 2.68 × 10-4ν1/2-4.28×10-6，R20.991), the effective area of Ce-MOF/GCE was calculated to be 7.22mm2. Wherein n is 1 and D is 7.6 × 10-6cm2，Ip、AeffC and v are respectively the peak current (A) and the effective area (cm) of a probe of 5mmol/L2) Probe concentration (mol/cm)-3) And a scanning rate (v/s). With bare electrode (4.02 mm)2) Compared with the Ce-MOF/GCE, the effective electrode area of the Ce-MOF/GCE is increased by about 1.80 times, which is because the effective contact area of the electrode is increased due to the staggered network structure formed by the Ce-MOF nanowires. In addition, the stability of the Ce-MOF modified electrode was investigated by leaching experiments, see FIG. 7, FIG. 7 is a graph showing the results of the leaching experiments of Ce-MOF/GCE, placing the modified electrode containing 0.1mmol/L luminol and 0.2mmol/L H2O2The leaching test is carried out in borate buffer solution (pH 8.5,0.02mol/L), and electrochemiluminescence is measured every 20min, so that the result shows that the Ce-MOF/GCE still maintains good stability in long-term soaking.
The action mechanism of IMI-MIECS on the luminol hydrogen peroxide catalytic luminescent system comprises two paths, in the path 1, dissolved oxygen in a solution generates superoxide anion
In the path 2, Ce (III) in Ce-MOF catalyzes the formation of superoxide anion, so that
Finally luminol radical and a large number of superoxide anions generate luminophore AP2-·Resulting in an enhancement of the ECL system of luminol in Ce-MOF/GCE. Please refer to FIG. 8, FIG. 8 shows Ce-MOF catalyzed luminol/H2O2ECL mechanism schematic of the process.
MIP films and nMOP films are prepared by an electro-polymerization method, please refer to FIG. 9, and FIG. 9 is a schematic diagram of the formation of IMI-MIPs (A) and nMOP (B) on Ce-MOF/GCE. As can be seen from fig. 9A, the peak current of o-PD gradually decreased as the polymerization proceeded, reaching a minimum after 20 cycles due to the formation of a non-conductive molecularly imprinted film. nMIP membranes were prepared under the same conditions, and no significant difference was observed for CV except that the buffer did not contain IMI, indicating that the IMI did not participate in the polymerization reaction of the blotting membrane, but was embedded in the blotting membrane by van der waals forces or hydrogen bonding.
In order to improve the sensing performance of IMI-MIECS, key factors such as the molar ratio of the monomer to the template, elution time, adsorption time, probe solution composition and the like are optimized.
Referring to FIG. 10, FIG. 10 is a schematic diagram of electropolymerization o-PD/IMI molar ratio optimization. As the o-PD/IMI ratio increases, the ECL intensity increases, favoring the formation of more imprinted cavities, but at a monomer to template molar ratio of 6:1, the ECL signal intensity is highest and decreases with further increase in molar ratio. This is because excess monomer causes self-polymerization of o-PD, reducing the effectiveness of MIP membranes. Therefore, a monomer to template molar ratio of 6:1 is the best condition for preparing IMI-MIECS.
Referring to FIG. 11, FIG. 11 is a schematic diagram of the optimization of elution (a) and resorption (b) times; ECL intensity increased with increasing elution time, reaching a steady value after 7 min. Furthermore, as the heavy adsorption proceeds, the ECL signal gradually decreases due to the occupancy of the blot pores, reaching kinetic equilibrium after 10 min. The optimal elution time is 7min, and the reabsorption time is 10 min.
Referring to FIGS. 12-13, FIG. 12 shows pH and buffer media versus luminol/H2O2FIG. 13 is a schematic diagram showing the effect of the light-emitting system2O2Optimization of the addition amount, H2O2The concentration and the optimal selection of the buffer medium can further reduce the background of the sensor and improve the sensitivity. Therefore, ECL condition optimization experiments were carried out on the sensor with a re-adsorbed IMI of 100nmol/L as a working electrode, and the results showed borax borate buffer solution with pH 8.5 and 0.2mmol/L H2O2Most suitably ECL measurements are performed. For the adsorption kinetics research of IMI in MIECS and non-MIECS, the adsorption kinetics process conforms to a Langmuir adsorption model, and the fitting equation is as follows:
in the formula,. DELTA.ECLRe(a，u)And Δ ECLSa(a，u)The response of ECL intensity changes to different reabsorption times and saturation capacities, respectively. Referring to FIG. 14, FIG. 14 shows Δ ECL for MIECS (a) and non-MIECS (b)Re-a schematic diagram of t; and their kinetic parameters were calculated and are listed in table 1. Constant movementMechanical Rate (k; s)-1) Is widely used for evaluating the adsorption rate, so the rate can be used for evaluating the specific adsorption performance of MIECS and non-MIECS, and the k values of the two are calculated to be 209.7s respectively-1And 53.5s-1. The result is attributed to the modification of the ultrafine MOF, the effective electrode area is increased, the number of recognition sites in the MIECS is increased, and the molecular imprinting recognition efficiency is finally improved.
TABLE 1 MIECS and non-MIECS adsorption kinetics parameters
ECL sensor performance analysis of Ce-MOF, see fig. 15, according to the fit equation: Δ ECL ═ 48.50C (nmol/L) +452.09 (R)20.992), fig. 15 shows the electrochemiluminescence response performance of IMI-MIECS to imidacloprid and its working curve, and the ECL intensity was found to decrease linearly with increasing IMI concentration in the range of IMI concentration from 2 to 120nmol/L, calculated as 0.34nmol/L (3 δ/K, n 11) of the sensor inspection line. The response stability of the proposed sensor in 12 consecutive cyclic voltammetric scans was further confirmed, where the ECL intensity was found to remain stable throughout the 12 luminescence tests, with a calculated Relative Standard Deviation (RSD) of 5.6%, see fig. 16, fig. 16 for an evaluation of ECL response stability. Thus, this result confirms the successful construction of MOF-based ECL sensors with good response stability.
The prepared ECL sensor is subjected to cross-reaction performance study of common interferents, including insecticides (clothianidin, acetamiprid, thiamethoxam and cymazine) and ions (K)+、Ca2+、Na+、Mg2+、Fe3+) The concentration of all interfering substances was controlled at a level of 10. mu. mol/L and the Δ ECL intensity of the interfering substances in the presence and absence of IMI was recorded. Referring to fig. 17, fig. 16 is a graph showing the results of cross-reactivity studies of ECL sensors. As can be seen in fig. 17, the sensor has good anti-interference performance against other structural pesticides and ions. In addition, parallel studies of cross-reactivity were carried forwardThe method has the advantages that the sensor has good selective recognition capability on IMI, so that the good application potential of the sensor in actual sample detection is confirmed.
The application of IMI-MIECS in the detection of trace IMI in plant-derived food comprises the following steps:
preparation of a sample: randomly selecting plant source food, and extracting IMI from the sample by adopting a solvent extraction method. The method comprises the following specific steps: adding methanol (10mL) into cleaned and chopped plant source food (5g), stirring for 2min, then ultrasonically extracting for 10min, filtering the obtained extract through filter paper, centrifuging the filtrate at 5000rpm for 15min, taking supernatant, and diluting to 10mL with 0.02mol/LPBS to obtain sample solution.
And (3) detection: soaking the eluted MIECS in a sample solution for 10 minutes, and re-adsorbing IMI in the solution to be detected; placing the sensor after the adsorption is finished at the position containing 0.1mmol/L luminol and 0.2mmol/L H2O2And 0.02mol/LpH 8.5.5 of borate buffer solution in a luminous solution, then measuring the reaction of ECL by using a photomultiplier with the voltage of 600V, and scanning the potential range of 0-0.8V.
Taking apple, banana and tomato as examples in plant source food, 3 concentrations of IMI are added in the apple, banana and tomato respectively. Please refer to table 2, table 2 shows the IMI detection results of the plant-derived samples (ND is no detection); the standard recovery amount of IMI is 88.5-114.3%, the standard deviation is less than 6.4%, and the sensor prepared by the method is consistent with the detection result of liquid chromatography, which indicates that the MIECS based on Ce-MOF has potential applicability in the detection of IMI of actual samples.
Table 2 shows IMI test results of plant-derived samples
The application adopts a positive and negative ion micelle system to generate stable superfine Ce-MOF colloidal solution in water, and adopts micelles as an in-situ partial oxidation synthesis route of a nano reaction chamber to synthesize superfine mixed valence Ce-MOFs at 40 ℃. After preparation, a mixed valence MOF is introduced into a luminol hydrogen peroxide ECL system as a mimic enzyme for the first time, a double-path self-circulation catalytic luminescence strategy is provided, and an electrochemical luminescence sensor based on an ultrafine mixed valence cerium metal-organic framework is constructed by utilizing a molecular imprinting technology and is used for detecting trace IMI in plant source food. The technical scheme of the application provides a simple, convenient and reliable manufacturing method of the MOF-based molecular imprinting ECL sensor, and has extremely important significance to the field of pesticide detection.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.
Claims (5)
1. A preparation method of superfine mixed-valence Ce-MOF nanowires is characterized by comprising the following steps: cationic CTAB and SDS surfactant are mixed to form a positive and negative ion micelle system, and a stable superfine Ce-MOF nanowire colloidal solution is generated in water.
2. The method for preparing ultrafine mixed-valence Ce-MOF nanowires according to claim 1, wherein the preparation steps specifically comprise: 40mg of NaOH and 70mg of H3BTC is dissolved in 3mL of water, 60mL of 0.1mol/L SDS solution and 2mL of 0.1mol/L CTAB solution are added, and the mixture is vortexed for 30 seconds to obtain an organic ligand micelle solution; 140mg of Ce (NO)3)3·6H2Dissolving O in 2mL of water, respectively adding 40mL of 0.1mol/L SDS solution and 1mL of 0.1mol/L CTAB solution, and carrying out ultrasonic treatment for 2min to obtain a metal ion micelle solution; slowly adding the organic ligand micelle solution into the metal ion micelle solution, and carrying out water bath reaction for 3 hours at the temperature of 40 ℃; then 1mL of 30 wt% H was added at room temperature2O2And reacting for 1h until the milky reaction mixture turns yellow, then centrifuging the obtained product, washing with deionized water and ethanol, and drying in vacuum at 50 ℃ overnight to obtain the superfine mixed-valence Ce-MOF nanowire.
3. A preparation method of IMI-MIECS based on superfine mixed valence Ce-MOF is characterized by comprising the following steps: GCE was polished to a mirror surface with 1.0, 0.3 and 0.05 μm aqueous aluminum oxide slurries in sequence, water, ethanol and 0.5mol/L H2SO4Rinsing in sequence; ultrasonically dispersing 15mg of Ce-MOF in 5mL of deionized water; then, 10 mu L of Ce-MOF dispersed liquid is dripped on the surface of the electrode, and the Ce-MOF/GCE electrode is obtained after drying at 25 ℃; preparing an IMI molecularly imprinted membrane by electropolymerization of Ce-MOF/GCE serving as a working electrode in PBS (phosphate buffer solution) with the pH of 6.8 and containing 0.5mmol/L IMI and 3.0mmol/L o-PD, and performing 20 times of cyclic voltammetry scanning at the scanning rate of 50mV/s to prepare an IMI-MIP membrane; and finally, preparing the prepared IMI-MIP modified electrode in a volume ratio of 8: 1 for 7 minutes to remove the template, and obtaining IMI-MIECS.
4. The preparation method of the ultrafine mixed-valence Ce-MOF based IMI-MIECS according to claim 3, wherein the IMI-MIECS is applied to detection of trace IMI in plant-derived food, and the detection method is as follows: immersing the eluted MIECS into sample solutions with different concentrations for 10 minutes, and re-adsorbing imidacloprid in the solution to be detected; placing the sensor after the completion of the reabsorption into 0.1mmol/L luminol and 0.2mmol/L H2O2And 0.02mol/LpH 8.5.5 borate buffer luminescence solution, measuring ECL response; as the concentration of imidacloprid in a sample increases, a molecular imprinting hole is occupied, electron transfer on the surface of an electrode is blocked, the ECL response of the sensor is reduced, and a gate-controlled IMI-MIECS is constructed.
5. The method for preparing IMI-MIECS based on superfine mixed-valence Ce-MOF according to claim 4, wherein the mechanism of action of IMI-MIECS on luminol hydrogen peroxide catalytic luminescent system includes two paths, in path 1, dissolved oxygen in solution generates superoxide anion O2 ·-In the path 2, Ce (III) in Ce-MOF catalyzes the formation of superoxide anion to improve O2 ·-Finally luminol radical and a large number of superoxide anions generate luminophore AP2-·Resulting in an enhancement of the ECL system of luminol in Ce-MOF/GCE.
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