Molecularly imprinted electrochemical sensor based on β-FeOOH nanoparticles and preparation method thereof

Abstract

The present application relates to the technical field of electrochemical sensor, in particular to a kind of molecularly imprinted electrochemical sensor based on β-FeOOH nanoparticle and preparation method thereof.The preparation of the molecularly imprinted electrochemical sensor based on β-FeOOH nanoparticle includes the following steps: step one, preparation of modified electrode: β-FeOOH nanoparticles are grown in situ on carbon cloth using hydrothermal method;Step two, add RC and CBD;Step three, molecularly imprinted polymer (MIP) is polymerized using cyclic voltammetry, and the sensor MIP / β-FeOOH / CC is prepared.The electrode selected in the present application is carbon cloth electrode, which can provide more active sites for molecular imprinting;It is easy to obtain and low in price, and at the same time, it does not need to be polished, which simplifies the preparation process;When preparing, simple one-step hydrothermal method is used, and in repeatability and stability test, the relative standard deviation is less than 5%;The minimum detection limit is 0.025 nM, which can well meet the trace quantitative detection of carbendazim.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electrochemical sensors, in particular to a molecular imprinting electrochemical sensor based on beta-FeOOH nanoparticles and a preparation method thereof. BACKGROUND

[0002] Carbendazim (CBD), chemical name N-(2-benzimidazolyl) methyl carbamate, belongs to benzimidazole, is a disease control fungicide, which is widely used in crops, but the residue of CBD can cause dizziness, nausea, vomiting, convulsions and a series of poisoning symptoms, which seriously threatens the health of humans and animals. The residue of CBD in food belongs to trace (10 -8 M) range, which has a higher requirement for detection sensitivity.

[0003] The traditional methods currently applied to CBD detection include high performance liquid chromatography, gas chromatography and nuclear magnetic resonance spectroscopy, etc. In subsequent studies, it is found that the molecular imprinting electrochemical sensor can convert the content of the detected substance into current signals, which has higher sensitivity, and the molecular imprinting (MIP) contained therein has the advantage of higher specificity, so the molecular imprinting electrochemical sensor is widely used in the detection of pesticides (such as carbendazim).

[0004] In order to realize higher detection sensitivity of the molecular imprinting electrochemical sensor, obtain larger sensing area and better conductivity, the research on the modification of the working electrode surface becomes a continuous hotspot. Among them, the electrode with large electrochemical active area can provide more active sites for molecular imprinting, and the electrode which is simple, low-cost and easy to process is more conducive to the subsequent sensor. The electrode surface modification refers to modifying the electrode with materials having larger specific surface area and better conductivity.

[0005] When modifying the electrode surface, the method of modifying material will also affect the performance of the sensor. At present, the most common method is drop coating. In the document with the application number "CN202211307387.6", a technical solution named "an electrochemical sensor for high-sensitivity detection of carbendazim and a preparation method thereof" is disclosed. The problems of this solution are: 1. The electrode is a glassy carbon electrode (GCE), which needs to be polished before each test. If it is not polished clean, it will affect the electrochemical performance, and the single electrode is expensive, which increases the material cost; 2. The drop coating layer formed by the drop coating material Super P Li / ZIF-8 (conductive carbon black and zinc metal organic framework material) is easy to fall off, which makes the repeatability and stability of the final sensor poor, the sensitivity is poor, and the material is expensive, which increases the preparation cost. SUMMARY

[0006] The application provides a molecular imprinting electrochemical sensor based on beta-FeOOH nanoparticles and a preparation method thereof.

[0007] To achieve the object of the application, the application provides a preparation method of a molecular imprinting electrochemical sensor based on beta-FeOOH nanoparticles, which comprises the following steps

[0008] Step one, preparation of a modified electrode: beta-FeOOH nanoparticles are in-situ grown on carbon cloth by using a hydrothermal method;

[0009] Step two, addition of a functional monomer resorcinol (RC) and a template molecule carbendazim (CBD):

[0010] Carbendazim is configured into a carbendazim standard solution by using DMF, and the solution is diluted to a CBD concentration of 1-10 mmol / L by using a 0.1M PBS buffer solution with a pH value of 5.0-10.0, and then resorcinol is added into the above solution, and the RC concentration is 1-10 mmol / L;

[0011] Step three, polymerization of a molecular imprinting polymer (MIP) by using a cyclic voltammetry method, so that the sensor MIP / beta-FeOOH / CC is prepared.

[0012] Further, the specific process of step one is as follows: 2.5-5.4g FeCl3·6H2O and 0.1-0.4g [CPAM (polyacrylamide), PEI (polyethyleneimine), PAH (polyacrylamide), PBAE (polyamino ester), chitosan (CS), SDS (sodium dodecyl sulfonate) and PEG (polyethylene glycol)] are added into 40-50ml water and ultrasonically treated for 20-30min, then a piece of hydrophilic carbon cloth is added into a reaction kettle, and the reaction is carried out at 100-120℃ for 2-5h, the carbon cloth is taken out after the reaction kettle is naturally cooled, the carbon cloth is cleaned several times by using ethanol and ultrapure water alternately, and the modified electrode beta-FeOOH / CC is obtained by drying at 60℃.

[0013] Further preferably, in step one, 5.4g FeCl3·6H2O and 0.2g PAH are added into 40ml water and ultrasonically treated for 30min, then a piece of hydrophilic carbon cloth is added into a reaction kettle, and the reaction is carried out at 120℃ for 4h, the carbon cloth is taken out after the reaction kettle is naturally cooled, the carbon cloth is cleaned three times by using ethanol and ultrapure water alternately, and the modified electrode beta-FeOOH / CC is obtained by drying at 60℃.

[0014] Further, the specific process of the above step one is: after 0.1-0.5g FeCl3·6H2O and 0.01-0.02g [CPAM (polyacrylamide), PEI (polyethyleneimine), PAH (polyacrylamide), PBAE (polyamino ester), chitosan (CS), SDS (sodium dodecyl sulfonate) and PEG (polyethylene glycol)] are added into 20-40ml water and ultrasonic treatment is conducted for 20-40min, the reaction kettle is transferred and a piece of hydrophilic carbon cloth is added, reaction is conducted at 80-100℃ for 5-8h, the carbon cloth is taken out after the reaction kettle is naturally cooled, and the carbon cloth is cleaned several times alternately using ethanol and ultrapure water, and is dried at 60℃, so that the modified electrode β-FeOOH NRs / CC is obtained.

[0015] Further preferably, the specific process of the above step one is: after 0.35g FeCl3·6H2O and 0.01g PAH are added into 30ml water and ultrasonic treatment is conducted for 30min, the reaction kettle is transferred and a piece of hydrophilic carbon cloth is added, reaction is conducted at 100℃ for 3h, the carbon cloth is taken out after the reaction kettle is naturally cooled, and the carbon cloth is cleaned three times alternately using ethanol and ultrapure water, and is dried at 60℃, so that the modified electrode β-FeOOH NRs / CC is obtained.

[0016] Further, the specific process of the above step three is: in a three-electrode system, in 0.1M PBS buffer solution containing 1-10mmol / L RC and 1-10mmol / L CBD, a molecularly imprinted polymer (MIP) is obtained by conducting cyclic voltammetry for 5-60 cycles at a scanning rate of 0.025-0.25V / s in a potential window of 0-0.8V (vs.SCE).

[0017] Further preferably, in the above PBS buffer solution, pH is 7, and 7mmol / L RC and 2mmol / L CBD are contained, and a molecularly imprinted polymer (MIP) is obtained by conducting cyclic voltammetry for 40 cycles at a scanning rate of 0.1V / s in a potential window of 0-0.8V (vs.SCE).

[0018] Further, the molecularly imprinted electrochemical sensor based on β-FeOOH nanoparticles is prepared by the above preparation method.

[0019] Compared with the prior art, the application has the following advantages:

[0020] 1、The electrode selected in the application is a carbon cloth electrode, compared with commonly used working electrodes such as glassy carbon electrodes (GCE) and carbon paste electrodes, the carbon cloth electrode has a larger electrochemical active area (the electrochemical active area of the carbon cloth electrode is 1.618cm 2 , the maximum electrochemical active area of the glassy carbon electrode GCE is 0.196cm 2), can provide more active sites for molecular imprinting; a glassy carbon electrode is the cheapest at 550 yuan and needs to be equipped with polished Al2O3 powder, and the polishing process is relatively cumbersome, while a piece of 20*20cm carbon cloth is 235 yuan, can be used for 200 experiments and each small piece of carbon cloth is new, so it is easy to obtain and low in price, and does not need to be polished, simplifying the preparation process.

[0021] 2、The present application adopts a simple one-step hydrothermal method to in-situ grow two kinds of morphology of beta-FeOOH nanoparticles, the first kind of morphology of beta-FeOOH nanoparticles has a lower charge transfer resistance (R ct 2Ω), has better conductivity, and the in-situ growth method can make the interaction between the modified material and the substrate stronger and not easy to fall off, so that the sensor has excellent repeatability and stability, and in the repeatability and stability test, the relative standard deviation is less than 5%.

[0022] 3、In the current detection standard, the maximum residue amount of carbendazim is 0.5mg / kg, the minimum detection limit of the sensor of the present application is 0.025nM (4.78*10 -6 mg / kg), which can well meet the trace quantitative detection of carbendazim. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 is a schematic diagram of the preparation of the molecular imprinting electrochemical sensor based on beta-FeOOH nanoparticles.

[0024] Figure 2 A, B and C in the figure are SEM images of CC, beta-FeOOH / CC and beta-FeOOH NRs / CC.

[0025] Figure 3 is an XPS image of beta-FeOOH / CC.

[0026] Figure 4 is an EIS image of beta-FeOOH / CC and beta-FeOOH NRs / CC.

[0027] Figure 5 is a DPV image of the principle of detecting carbendazim. DETAILED DESCRIPTION

[0028] The method of the present application will be described below by specific examples and drawings, but the present application is not limited thereto. In the following examples, the experimental methods described are conventional methods, and the reagents and materials described are commercially available unless otherwise specified.

[0029] Embodiment 1, the application provides a preparation method of a molecular imprinting electrochemical sensor (MIP / β-FeOOH / CC sensor) based on β-FeOOH nanoparticles, which comprises the following steps:

[0030] Step one, preparation of a modified electrode:

[0031] The treatment method of the hydrophilic carbon cloth is as follows: 1*2 cm of the carbon cloth is soaked in a mixed solution of 10% nitric acid and 10% concentrated sulfuric acid (3:1, v:v) for three days, and then cleaned with ultrapure water for multiple times to remove the residual acid.

[0032] After 5.4 g of FeCl3*6H2O and 0.2 g of PAH are ultrasonically treated in 40 ml of water for 30 min, a piece of the hydrophilic carbon cloth is added into a reaction kettle, and the reaction is carried out at 120 DEG C for 4 h; after the reaction kettle is naturally cooled, the carbon cloth is taken out, cleaned with ethanol and ultrapure water alternately for three times, and dried at 60 DEG C to obtain the modified electrode β-FeOOH nanoparticles (abbreviated as modified electrode β-FeOOH / CC).

[0033] Step two, addition of a functional monomer resorcinol (RC) and a template molecule carbendazim (CBD):

[0034] The carbendazim is configured into a carbendazim standard solution with a concentration of 2 mg / mL by using DMF, 9.6 mL of which is taken and diluted with 0.1M PBS buffer solution with pH=7.0 to 50 mL, so that the CBD concentration is 2 mmol / L; then 0.0385 g of resorcinol is added into the above solution, so that the RC concentration is 7 mmol / L.

[0035] Step three, polymerization of a molecular imprinting polymer (MIP) by using a cyclic voltammetry method:

[0036] In a three-electrode system (working electrode-polymerized carbon cloth, counter electrode-platinum sheet electrode and reference electrode-saturated calomel electrode), in 0.1M PBS buffer solution (pH=7) (7 mmol / L of RC and 2 mmol / L of CBD), by using a cyclic voltammetry method, the MIP is obtained after 40 cycles of electrochemical polymerization in a potential window of 0-0.8V at a scanning rate of 0.1V / s, and finally the sensor MIP / β-FeOOH / CC is prepared.

[0037] Embodiment 2, the application provides a preparation method of a molecular imprinting electrochemical sensor (MIP / β-FeOOH / CC sensor) based on β-FeOOH nanoparticles, which comprises the following steps:

[0038] Step one, preparation of a modified electrode:

[0039] The treatment method of the hydrophilic carbon cloth: 2*2 cm carbon cloth was soaked in 10% nitric acid: 10% concentrated sulfuric acid (3:1, v:v) mixed solution for 80 h, and then washed with ultrapure water for multiple times to wash away the residual acid.

[0040] After 4 g of FeCl3·6H2O and 0.1 g of PAH were added in 50 ml of water and ultrasonicated for 30 min, the mixture was transferred into a reaction kettle and a piece of hydrophilic carbon cloth was added, and the reaction was carried out at 120°C for 5 h. After the reaction kettle was naturally cooled, the carbon cloth was taken out, washed with ethanol and ultrapure water alternately for three times, and dried at 60°C to obtain a modified electrode β-FeOOH nanoparticle (abbreviated as modified electrode β-FeOOH / CC).

[0041] Step two, adding a functional monomer resorcinol (RC) and a template molecule carbendazim (CBD):

[0042] Carbendazim was configured into a carbendazim standard solution of 2 mg / mL by using DMF, and during polymerization, the solution was diluted with 0.1 M PBS buffer solution with pH=10.0 to a CBD concentration of 5 mmol / L, and then resorcinol was added to the above solution, and the RC concentration was 5 mmol / L.

[0043] Step three, polymerizing a molecularly imprinted polymer (MIP) by cyclic voltammetry:

[0044] In a three-electrode system (working electrode-polymer coated carbon cloth, counter electrode-platinum sheet electrode, and reference electrode-saturated calomel electrode), in 0.1 M PBS buffer solution (5 mmol / L of RC and 5 mmol / L of CBD) with a scanning rate of 0.25 V / s in a potential window of 0-0.8 V, a MIP was obtained by cyclic voltammetry electrochemical polymerization for 50 cycles, and finally a sensor MIP / β-FeOOH / CC was prepared.

[0045] Example 3, a preparation method of a molecularly imprinted electrochemical sensor (MIP / β-FeOOH / CC sensor) based on β-FeOOH nanoparticles provided by the application, comprising the following steps:

[0046] Step one, preparing a modified electrode:

[0047] The treatment method of the hydrophilic carbon cloth is the same as that in Example 1.

[0048] After 0.4 g of FeCl3·6H2O and 0.015 g of PAH were added in 30 ml of water and ultrasonicated for 30 min, the mixture was transferred into a reaction kettle and a piece of hydrophilic carbon cloth was added, and the reaction was carried out at 100°C for 3 h. After the reaction kettle was naturally cooled, the carbon cloth was taken out, washed with ethanol and ultrapure water alternately for three times, and dried at 60°C to obtain a modified electrode β-FeOOH–rod / CC, which is abbreviated as β-FeOOH NRs / CC.

[0049] Step two, adding functional monomer resorcinol (RC) and template molecule carbendazim (CBD):

[0050] Carbendazim was configured into a 2mg / mL standard solution of carbendazim using DMF, and 4.8mL of the standard solution was taken and diluted to 50mL with 0.1M PBS buffer (pH=6) (the concentration of CBD was 1mmol / L at this time), and then 0.022g of resorcinol (RC) was added to the above solution (the concentration of RC was 4mmol / L at this time).

[0051] Step three, polymerizing the molecularly imprinted polymer (MIP) using cyclic voltammetry:

[0052] In a three-electrode system (working electrode-polymer coated carbon cloth, counter electrode-platinum sheet electrode, and reference electrode-saturated calomel electrode), in 0.1M PBS buffer (pH=7) (4mmol / L of RC and 1mmol / L of CBD), a MIP was obtained after 20 cycles of cyclic voltammetry electrochemical polymerization at a scan rate of 0.1V / s in a potential window of 0-0.8V, and finally a sensor MIP / β-FeOOH / CC was prepared.

[0053] Example 4, a preparation method of a molecularly imprinted electrochemical sensor (MIP / β-FeOOH / CC sensor) based on β-FeOOH nanoparticles provided by the application, comprising the following steps:

[0054] Step one, preparing a modified electrode:

[0055] The treatment method of the hydrophilic carbon cloth is the same as that in Example 2.

[0056] After 0.35g of FeCl3·6H2O and 0.01g of PAH were added to 30ml of water and ultrasonically treated for 40min, the mixture was transferred into a reaction kettle and a piece of hydrophilic carbon cloth was added, and the mixture was reacted at 100℃ for 3h. After the reaction kettle was naturally cooled, the carbon cloth was taken out, washed with ethanol and ultrapure water alternately for three times, and dried at 60℃ to obtain a modified electrode β-FeOOH–nanorod / CC, which is abbreviated as β-FeOOH NRs / CC.

[0057] Step two, adding functional monomer resorcinol (RC) and template molecule carbendazim (CBD):

[0058] Carbendazim was configured into a 2mg / mL standard solution of carbendazim using DMF, and 4.8mL of the standard solution was taken and diluted to 50mL with 0.1M PBS buffer (pH=6) (the concentration of CBD was 1mmol / L at this time), and then 0.022g of resorcinol (RC) was added to the above solution (the concentration of RC was 4mmol / L at this time).

[0059] Step three, the molecularly imprinted polymer (MIP) was prepared by cyclic voltammetry:

[0060] In a three-electrode system (working electrode-patch platinum electrode sandwich + carbon cloth, counter electrode-patch platinum electrode and reference electrode-saturated calomel electrode), the MIP was prepared by cyclic voltammetry electrochemical polymerization for 40 cycles in 0.1 M PBS buffer (pH = 8.0) (3 mmol / L RC and 3 mmol / L CBD) at a scan rate of 0.2 V / s in a potential window of 0-0.8 V, and finally the sensor MIP / β-FeOOH / CC was prepared.

[0061] Examples 1 and 4 are the best examples, wherein the process of detecting the sensor MIP / β-FeOOH / CC prepared in Example 1 is as follows:

[0062] First, elute the template molecule CBD: insert the MIP / β-FeOOH / CC electrode into a mixture of methanol: acetic acid (9:1, v:v) and stir for 12 min to elute the template molecule CBD.

[0063] Then adsorb CBD (detection): after eluting CBD, insert the electrode into a solution containing CBD and adsorb for 8 min, then wash the electrode surface with ultrapure water to remove the unadsorbed CBD.

[0064] In the preparation of non-imprinted-β-FeOOH modified carbon cloth (NIP / β-FeOOH / CC), no template molecule CBD is added, and the remaining steps are consistent with the preparation of MIP / β-FeOOH / CC.

[0065] The results of comparative detection of the molecularly imprinted electrochemical sensor MIP / β-FeOOH / CC based on β-FeOOH nanoparticles prepared in Example 1 and NIP / β-FeOOH / CC are as follows:

[0066] Figure 1 is the schematic diagram of the preparation of the molecularly imprinted electrochemical sensor based on β-FeOOH nanoparticles.

[0067] Figure 2 In the middle, A-B, C-D and E-F are SEM images of CC, β-FeOOH / CC and β-FeOOH NRs / CC, and from the images it can be seen that the β-FeOOH nanoparticles prepared by the two schemes are successfully modified on the carbon cloth; β-FeOOH / CC is a short rod structure arranged in a flat and random manner, and β-FeOOH NRs / CC is a rod structure arranged uniformly and neatly.

[0068] Figure 3XPS chart of β-FeOOH / CC, which further determines the elements contained in the material on the surface of carbon cloth. As can be seen from the chart, the surface of carbon cloth modified by β-FeOOH nanoparticles contains N, O and Fe elements, and the N element is derived from PAH.

[0069] Figure 4 EIS chart of β-FeOOH / CC and β-FeOOH NRs / CC. As can be seen from the chart, the charge transfer resistance of β-FeOOH / CC is smaller, so the β-FeOOH prepared on carbon cloth according to scheme one is selected for the subsequent sensor.

[0070] Figure 5 DPV chart of the principle of detecting carbofuran. As can be seen from the chart, the difference between the DPV peak current before and after elution and adsorption represents the amount of adsorbed carbofuran.

[0071] Table 1 is the recovery rate experiment for evaluating the feasibility of the sensor in practical application by adding a certain amount of CBD to fresh apple juice. As can be seen from the table, the recovery rate of MIP / β-FeOOH / CC sensor for CBD in apple juice is 92.5-99.4%, and the maximum RSD is 4.57. Table 2 is the detection of pesticide residues on the surface of two kinds of apple peels. The data in the table show that there is residual CBD on the surface of apple, but the residual amount is small, which meets the national residual standard of CBD. The data of actual sample detection show that the MIP / β-FeOOH / CC sensor can be applied to the detection of CBD in actual samples.

[0072] Table 1

[0073]

[0074] Table 2

[0075]

[0076] The above examples are only the preferred technical solutions of the present application, and are not regarded as limiting the present application. The protection scope of the present application should be the technical solutions recited in the claims, including the equivalent replacement solutions of the technical features recited in the claims, i.e. the equivalent replacement improvements within this range are also within the protection scope of the present application.

Claims

1. A method for preparing a molecularly imprinted electrochemical sensor based on β-FeOOH nanoparticles, characterized in that: Includes the following steps Step 1: Preparation of modified electrode: β-FeOOH nanoparticles are grown in situ on carbon cloth using a hydrothermal method; Step 2: Add the functional monomer resorcinol (RC) and the template molecule carbendazim (CBD): Carbendazim was prepared into a standard solution using DMF. During polymerization, the solution was adjusted to a CBD concentration of 1-10 mmol / L using 0.1 M PBS buffer (pH 5.0-10.0). Then, resorcinol was added to the solution to a concentration of 1-10 mmol / L. Step 3: Molecularly imprinted polymer (MIP) was polymerized using cyclic voltammetry to prepare the sensor MIP / β-FeOOH / CC; The specific process of step one is as follows: 2.5-8.4 g FeCl3·6H2O and 0.1-0.4 g polyacrylamide (PAH) are added to 40-50 ml of water and sonicated for 20-30 min. Then, the mixture is transferred to a reaction vessel and a piece of hydrophilic carbon cloth is added. The reaction is carried out at 100-120℃ for 2-5 h. After the reaction vessel cools naturally, the carbon cloth is removed and washed several times with alternating ethanol and ultrapure water. The mixture is then dried at 60℃ to obtain the modified electrode β-FeOOH / CC.

2. The method for preparing the molecularly imprinted electrochemical sensor based on β-FeOOH nanoparticles according to claim 1, characterized in that: In step one, 5.4 g FeCl3·6H2O and 0.2 g PAH were added to 40 ml of water and sonicated for 30 min. The mixture was then transferred to a reaction vessel and a piece of hydrophilic carbon cloth was added. The reaction was carried out at 120 °C for 4 h. After the reaction vessel cooled naturally, the carbon cloth was removed and washed three times with alternating ethanol and ultrapure water. The mixture was then dried at 60 °C to obtain the modified electrode β-FeOOH / CC.

3. The method for preparing a molecularly imprinted electrochemical sensor based on β-FeOOH nanoparticles according to claim 2, characterized in that: The specific steps of step three are as follows: In a three-electrode system, in a 0.1M PBS buffer containing 1-10 mmol / L LRC and 1-10 mmol / L CBD, the molecularly imprinted polymer (MIP) is obtained by electrochemical polymerization using cyclic voltammetry for 5-60 cycles at a scan rate of 0.025-0.25V / s within a potential window of 0-0.8V; the pH of the PBS buffer is 5.0-10.

0.

4. The method for preparing the molecularly imprinted electrochemical sensor based on β-FeOOH nanoparticles according to claim 3, characterized in that: The PBS buffer, pH=7, containing 7 mmol / L LRC and 2 mmol / L CBD, was electrochemically polymerized for 40 cycles using cyclic voltammetry within a potential window of 0-0.8 V at a scan rate of 0.1 V / s to obtain the molecularly imprinted polymer (MIP).

5. A molecularly imprinted electrochemical sensor based on β-FeOOH nanoparticles prepared by the method according to claim 1.

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