Preparation method of Ce-MOF / CNHs-coated NBA / GCE electrode, electrochemical sensor and application of electrochemical sensor in detection of parathion-methyl

Abstract

The invention discloses a preparation method of a Ce-MOF / CNHs (at) NBA / GCE electrode, an electrochemical sensor and application of the electrochemical sensor in detection of parathion-methyl. The preparation method comprises the following steps: sequentially polishing a glassy carbon electrode GCE to be smooth by using aluminum oxide powder with different particle sizes, sequentially carrying out ultrasonic treatment in ethanol and pure water to remove surface residues, and airing at room temperature; the preparation method comprises the following steps: adding single-walled carbon nanohorns (CNHs) powder and Nile blue A (NBA) powder into an aqueous solution, uniformly stirring at room temperature, centrifuging, washing and drying to obtain CNHs (at) NBA powder, preparing a mixed solution containing benzenetricarboxylic acid H3BTC and CNHs (at) NBA, adding cerous nitrate hexahydrate Ce (NO3) 3.6 H2O powder, stirring again, centrifuging, washing and drying to obtain a Ce-MOF / CNHs (at) NBA compound; the Ce-MOF / CNHs (at) NBA compound is dispersed in pure water, and a Ce-MOF / CNHs (at) NBA solution with the concentration being 0.2 mg / mL to 1 mg / mL is obtained; and dropwise adding a Ce-MOF / CNHs (at) NBA solution to the glassy carbon electrode GCE treated in the step (1), and airing at room temperature to obtain the Ce-MOF / CNHs (at) NBA / GCE electrode.

Description

TECHNICAL FIELD

[0001] The application relates to a preparation method of a Ce-MOF / CNHs@NBA / GCE electrode, an electrochemical sensor and application of the electrochemical sensor in detection of methyl parathion. BACKGROUND

[0002] Methyl parathion, as a typical nitroaromatic organophosphorus insecticide, has been widely used in the prevention and control of pests in fruits and vegetables by inhibiting the activity of cholinesterase in insects, inducing excessive excitement of the nervous system and even death, and plays an important role in improving agricultural productivity. However, long-term exposure to low-dose methyl parathion may cause nervous system symptoms, gastrointestinal discomfort, and even fatal risks. Therefore, it is of important practical significance to develop a sensitive, rapid and reliable detection method for methyl parathion residues to ensure food quality and safety and human health.

[0003] At present, the detection technologies for methyl parathion mainly include gas chromatography, high performance liquid chromatography-mass spectrometry, surface enhanced Raman scattering technology and the like. However, these technologies generally have limitations such as expensive instruments, long detection time and complex operation process, and are difficult to meet the needs of on-site rapid detection, which brings many inconveniences to the food supervision departments in carrying out agricultural product detection work. In comparison, electrochemical technology has the advantages of low cost, high sensitivity and fast response speed, and has shown excellent analysis performance in the detection of various pesticide residues.

[0004] Traditional electrochemical sensors usually only rely on the response change of single signal output to quantitatively analyze the content of the analyte, and the single signal is easily disturbed by internal and external factors such as differences in electrode modification methods and fluctuations in environmental conditions. These disturbances will cause slight differences in the background signal of the electrode, thereby reducing the accuracy of the detection results, and this problem is particularly prominent in trace detection. In order to solve this problem, an electrochemical ratio sensing strategy with a built-in calibration function emerges as the times require. Unlike the traditional sensor mode which relies on a single signal, the ratio sensor has double response signals, and the ratio of the two signals is used as the output, which can effectively eliminate potential interference and significantly improve the reliability of the detection results. Therefore, it is of important research value to develop a high-performance ratio-type electrochemical sensor which can realize double signal output for efficient and high-precision detection of methyl parathion. SUMMARY

[0005] The application is to solve the problems existing in the prior art, and provides a preparation method of a Ce-MOF / CNHs@NBA / GCE electrode, an electrochemical sensor and application of the electrochemical sensor in detection of methyl parathion.

[0006] The technical scheme adopted by the application is as follows:

[0007] A preparation method of a Ce-MOF / CNHs@NBA / GCE electrode, comprising the following steps:

[0008] (1) A glassy carbon electrode GCE is polished to be smooth by using aluminum oxide powders with different particle sizes in sequence, and is ultrasonically cleaned in ethanol and pure water in sequence, and is dried at room temperature;

[0009] (2) Single-walled carbon nanohorn (CNHs) powder and nile blue A (NBA) powder are added into an aqueous solution, and are stirred uniformly at room temperature, and are centrifuged, washed and dried to obtain CNHs@NBA powder, and then a mixed solution containing benzenetricarboxylic acid H3BTC and CNHs@NBA is prepared, and then cerium nitrate hexahydrate Ce(NO3)3·6H2O powder is added, and is stirred, centrifuged, washed and dried again to obtain a Ce-MOF / CNHs@NBA composite;

[0010] (3) The Ce-MOF / CNHs@NBA composite is dispersed in pure water to obtain a Ce-MOF / CNHs@NBA solution with a concentration of 0.2-1 mg / mL;

[0011] (4) The Ce-MOF / CNHs@NBA solution is added dropwise to the glassy carbon electrode GCE treated in step (1), and is dried at room temperature to obtain a Ce-MOF / CNHs@NBA / GCE electrode.

[0012] 2. The preparation method of the Ce-MOF / CNHs@NBA / GCE electrode according to claim 1, wherein in step (1), the diameter of the glassy carbon electrode is 3 mm; and the particle sizes of the aluminum oxide powders used are 0.3 μm and 0.05 μm in sequence.

[0013] 3. The preparation method of the Ce-MOF / CNHs@NBA / GCE electrode according to claim 1, wherein in step (2), the mass ratio of the single-walled carbon nanohorn (CNHs) powder to the nile blue A (NBA) powder is 2:1 (the former is 20-40 mg, and the latter is 10-20 mg).

[0014] 4. The preparation method of the Ce-MOF / CNHs@NBA / GCE electrode according to claim 1, wherein in step (4), the amount of the Ce-MOF / CNHs@NBA solution used is 4-8 μL.

[0015] 5. The preparation method of the Ce-MOF / CNHs@NBA / GCE electrode according to claim 1, wherein in step (2), the preparation process of the CNHs@NBA powder is as follows:

[0016] Take 20-40 mg of single-walled carbon nanohorn (CNHs) powder and disperse it in 120 mL of water, and take 10-20 mg of nile blue A (NBA) powder and dissolve it in 30 mL of water, and ultrasonic them respectively; mix the two solutions, continuously stir at room temperature for 10-14 hours, and finally centrifuge, wash and dry the obtained solution with pure water to obtain CNHs@NBA powder.

[0017] 6. The preparation method of the Ce-MOF / CNHs@NBA / GCE electrode according to claim 1, wherein in step (2), the preparation process of the Ce-MOF / CNHs@NBA composite is as follows:

[0018] Dissolve 4-5 mg of benzene tricarboxylic acid H3BTC in 40 mL of ethanol and water to obtain a mixed solution with a volume ratio of 1:1, and obtain solution A after ultrasonic treatment;

[0019] Add 8-12 mg of CNHs@NBA powder to solution A, and obtain solution B after ultrasonic treatment;

[0020] Add 7-9 mg of cerium nitrate hexahydrate Ce(NO3)3·6H2O powder to solution B, stir, and centrifuge, wash and dry with pure water to obtain a Ce-MOF / CNHs@NBA composite.

[0021] The application further discloses an electrochemical sensor with the Ce-MOF / CNHs@NBA / GCE electrode prepared by the preparation method.

[0022] Further, the detection limit of the electrochemical sensor is 16.67 ng / mL, and the concentration range of methyl parathion is 5×10 -8 ~ 5×10 -5 g / mL.

[0023] The application further discloses an application of the electrochemical sensor in detection of methyl parathion, including the following steps:

[0024] (1) Dilute methyl parathion into standard solutions with different concentrations by using PBS buffer solution, and place a plurality of electrochemical sensors in the standard solutions with different concentrations, each of which corresponds to one concentration;

[0025] In a three-electrode system, the Ce-MOF / CNHs@NBA / GCE electrode is used as a working electrode, the Ag / AgCl electrode is used as a reference electrode, and the platinum wire is used as a counter electrode, differential pulse voltammetry (DPV) is used for detection, and the current peak I MP and I NBA of methyl parathion (MP) and nile blue A are measured.

[0026] (2) Taking the concentration of methyl parathion as the abscissa, the ratio of the current peak value of methyl parathion and Nile blue A measured by DPV as the ordinate, a standard curve of the concentration of methyl parathion corresponding to the ratio of the current peak value is established; MP NBA MP NBA

[0027] (3) The electrochemical sensor is placed in the solution to be measured, and detection is carried out by using DPV in a three-electrode system, and the DPV current peak value of the sample solution is recorded; the concentration of methyl parathion in the sample to be measured is obtained by comparing the standard curve of the concentration of methyl parathion corresponding to the current peak value.

[0028] Further, the standard linear curve between the ratio of the current peak value I MP / I NBA and the concentration C MP of methyl parathion is I MP / I NBA =0.0014+0.0481C MP (R 2 =0.994);When the solution to be measured is detected, the pH value of the solution to be measured is adjusted to 4.5-7.

[0029] The present application has the following beneficial effects:

[0030] (1) In the preparation method of the present application, Ce-MOF is used as a carrier, CNHs and Nile blue A (NBA) are combined to form CNHs@NBA which is covered on the surface of Ce-MOF, and the two form a stable composite material through the synergistic effect of physical adsorption and chemical bonding, which provides a stable internal standard output signal for the sensor. Then, the Ce-MOF / CNHs@NBA composite material is modified on the surface of a glassy carbon working electrode, which significantly enhances the conductivity and adsorption performance of the electrode. In this system, Ce-MOF is not only an ideal carrier for assembling nanomaterials, but also has high porosity, large specific surface area, and the valence state conversion characteristics of Ce 3+ / Ce 4+ , which enables it to act as an electron transfer accelerator and helps to enhance the adsorption, enrichment and catalytic capacity of methyl parathion; NBA embedded in Ce-MOF serves as an internal electroactive probe and can be used for ratio electrochemical sensing strategy to ensure the reliability of the detection results. The further introduction of CNHs effectively improves the conductivity and catalytic activity of the composite material. Experimental results show that the prepared Ce-MOF / CNHs@NBA composite material exhibits excellent electrochemical catalytic performance for methyl parathion.

[0031] ​​​​(2) The ratio type electrochemical sensor for detecting methyl parathion has the advantages of fast detection speed, high sensitivity, wide linear range, high precision, low detection limit, excellent anti-interference and repeatability, and good potential application prospect in the field of agricultural product quality detection.

[0032] (3) The ratio type electrochemical sensor can realize high-sensitivity detection of methyl parathion, and has a wide linear range of 50-50000 ng / mL and a very low detection limit of 16.67 ng / mL. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 It is a schematic diagram of the construction and detection process of the ratio type electrochemical sensor of the present application.

[0034] Figure 2 (A) is the DPV response corresponding to different concentrations of MP, wherein the concentrations of MP are 5×10 -8 , 5×10 -7 , 1×10 -6 , 3×10 -6 , 5×10 -6 , 1×10 -5 , 2×10 -5 , 3×10 -5 and 5×10 -5 g / mL; (B) is a standard linear curve between the ratio of DPV current peak (I MP / I NBA ) and the concentration of MP.

[0035] Figure 3 It is a comparison diagram of DPV current response of GCE, Ce-MOF / GCE, Ce-MOF / NBA / GCE, CNHs@NBA / GCE and Ce-MOF / CNHs@NBA / GCE in 0.1 M PBS (pH 6.0) containing 30 μg mL -1 MP.

[0036] Figure 4 It is an influence diagram of changing the complex ratio of CNHs and NBA on the DPV current response in 0.1 M PBS (pH 6.0) containing 30 μg mL -1 MP. DETAILED DESCRIPTION

[0037] The present application will be further described below in combination with the drawings.

[0038] Example 1

[0039] The construction and detection process of the electrochemical sensor is shown in the followingFigure 1 as shown;

[0040] The preparation method of the Ce-MOF / CNHs@NBA / GCE electrode specifically includes the following steps:

[0041] (1) Preparation of CNHs@NBA:

[0042] Take 30 mg of single-walled carbon nanohorn (CNHs) powder and disperse it in 120 mL of water. Take another 15 mg of nile blue A (NBA) powder and dissolve it in 30 mL of water, and ultrasonic them for 5 minutes respectively. Mix the two solutions and continuously stir at room temperature for 12 hours. Finally, centrifuge and wash the resulting solution with pure water 3 times, and dry it at 60°C for 8 hours to obtain CNHs@NBA powder.

[0043] (2) Preparation of Ce-MOF / CNHs@NBA solution:

[0044] Dissolve 4.2 mg of benzene tricarboxylic acid H3BTC in 40 mL of ethanol and water mixed solution with a volume ratio of 1:1, ultrasonic for 5 minutes to obtain solution A;

[0045] Add 10 mg of CNHs@NBA powder to solution A and ultrasonic for 5 minutes to obtain solution B;

[0046] Add 8.69 mg of Ce(NO3)3·6H2O powder to solution B and stir quickly for 30 minutes. Centrifuge and wash with pure water 3 times, and dry it at 60°C for 8 hours to obtain Ce-MOF / CNHs@NBA powder.

[0047] Disperse 1 mg of Ce-MOF / CNHs@NBA powder in 5 mL of pure water to obtain a Ce-MOF / CNHs@NBA solution.

[0048] (3) A glassy carbon electrode GCE with a diameter of 3 mm is polished smooth with different particle sizes of aluminum oxide powder (0.3 μm and 0.05 μm in sequence), and ultrasonic in ethanol and pure water in sequence to remove surface residues, and air dry at room temperature.

[0049] (4) Add 6 μL of Ce-MOF / CNHs@NBA solution with a concentration of 0.2 mg / mL to the treated glassy carbon electrode GCE, and air dry at room temperature to obtain a Ce-MOF / CNHs@NBA / GCE electrode.

[0050] Example 2

[0051] This embodiment discloses an electrochemical sensor having a Ce-MOF / CNHs@NBA / GCE electrode prepared by the method of Example 1. This electrochemical sensor is used to detect methyl parathion, specifically as follows:

[0052] Methyl parathion (MP) was diluted with PBS buffer to prepare standard solutions of different concentrations. The electrochemical sensor used for detecting methyl parathion was then sequentially added with these standard solutions, with MP concentrations of 5 × 10⁻⁶ each time. -8 0.5×10 -7 1×10 -6 3×10 -6 5×10 -6 1×10 -5 , 2×10 -5 3×10 -5 and 5×10 -5 g / mL;

[0053] In the three-electrode system, the Ce-MOF / CNHs@NBA / GCE electrode was used as the working electrode, the Ag / AgCl (saturated KCl) electrode was used as the reference electrode, and the platinum wire was used as the counter electrode. The oxidation peak currents of methyl parathion and Nile Blue A were measured by scanning differential pulse voltammetry (DPV).

[0054] Plotting the concentration of methyl parathion on the x-axis, the ratio of the peak current of methyl parathion measured by DPV to that of Nile Blue A was calculated. MP / I NBA Using methyl parathion concentration as the ordinate, establish the ratio I of peak current corresponding to methyl parathion concentration. MP / I NBA The standard curve;

[0055] from Figure 2 As can be seen from (A), as the MP concentration increases, the peak current of MP gradually increases, while the peak current of NBA remains unchanged.

[0056] from Figure 2 From (B), it can be seen that the ratio of peak currents I MP / I NBA The standard linear curve between MP concentration and I is MP / I NBA =0.0014+0.0481C MP (R 2 =0.994), the linear range was 50 ng / mL to 50 μg / mL, and the limit of detection was 16.67 ng / mL.

[0057] The electrochemical sensor was applied to detect methyl parathion in different concentrations in the spiked detection of actual sample cabbage, and the detection process was as follows:

[0058] First, the cabbage bought from the local market was washed with pure water, and a certain amount of MP standard solution was added dropwise on the leaves. After drying at room temperature, the leaves were cut into pieces. 10 mL of methanol-water mixture (volume ratio 6:4) was added to the above leaf samples, shaken for 2 hours, and then centrifuged at 8000 rpm for 10 minutes. The supernatant was filtered with a 0.2 μm filter, then diluted 100 times with 0.1 MPBS solution, and 5 mL of the obtained solution was used for detection. In a three-electrode system, the modified electrode Ce-MOF / CNHs@NBA / GCE was used as the working electrode, Ag / AgCl (saturated KCl) electrode as the reference electrode, and platinum wire as the counter electrode. The three electrodes were placed in the above sample treated solution, and the differential pulse voltammetry (DPV) was scanned to measure the current peak I MP and I NBA , and the standard linear curve I MP / I NBA =0.0014+0.0481C MP was substituted, and the concentration information of methyl parathion in cabbage was calculated.

[0059] Table 1: Detection results of MP in cabbage sample detected by the constructed electrochemical sensor

[0060] “-”: indicates not detected.

[0061] The results in Table 1 show that the constructed electrochemical sensor can realize high sensitivity and high precision detection of methyl parathion, with a relative standard deviation controlled within 5%.

[0062] Figure 3 The DPV current response comparison chart of GCE, Ce-MOF / GCE, Ce-MOF / NBA / GCE, CNHs@NBA / GCE and Ce-MOF / CNHs@NBA / GCE in 0.1 M PBS (pH 6.0) containing 30 μg mL -1 MP. GCE, Ce-MOF / GCE, Ce-MOF / NBA / GCE, CNHs@NBA / GCE and Ce-MOF / CNHs@NBA / GCE represent glassy carbon electrode, Ce-MOF modified glassy carbon electrode, Ce-MOF / NBA composite material modified glassy carbon electrode, CNHs@NBA composite material modified glassy carbon electrode and Ce-MOF / CNHs@NBA composite material modified glassy carbon electrode, respectively, and the corresponding electrochemical sensor prepared. From Figure 3As can be seen, after the CNHs@NBA and Ce-MOF are compounded, the current response of methyl parathion is much higher than that of the current response detected by using Ce-MOF, Ce-MOF / NBA and CNHs@NBA, and the detection effect is significantly improved.

[0063] Example 3

[0064] In this embodiment, the volume ratio of CNHs to NBA is changed, such as 0.5:1, 1:1, 2:1, 3:1, 4:1, and a methyl parathion ratio type electrochemical sensor based on Ce-MOF / CNHs@NBA is prepared in the manner of Example 1, such as Figure 4 As shown in the figure, when the volume ratio of CNHs to NBA is 2:1, the DPV response is the highest, and at this time, the detection effect is the best.

[0065] The above only describes the preferred embodiments of the present application, and it should be pointed out that for ordinary skilled in the art, without departing from the principles of the present application, a number of improvements can also be made, and these improvements should be considered as the protection scope of the present application.

Claims

1. A method for preparing a Ce-MOF / CNHs@NBA / GCE electrode, characterized in that: Includes the following steps: (1) The glassy carbon electrode GCE was polished to smoothness with aluminum oxide powder of different particle sizes in turn, and then ultrasonicated in ethanol and pure water in turn to remove surface residues. It was then dried at room temperature. (2) Add single-walled carbon nanoparticles (CNHs) powder and Nile Blue A (NBA) powder to an aqueous solution, stir evenly at room temperature, and obtain CNHs@NBA powder after centrifugation, washing and drying. Prepare a mixed solution containing benzoic acid H3BTC and CNHs@NBA, and then add cerium nitrate hexahydrate Ce(NO3)3·6H2O powder. Stir, centrifuge, wash and dry again to obtain Ce-MOF / CNHs@NBA complex. (3) The Ce-MOF / CNHs@NBA complex was dispersed in pure water to obtain a Ce-MOF / CNHs@NBA solution with a concentration of 0.2 to 1 mg / mL; (4) The Ce-MOF / CNHs@NBA solution was added dropwise to the glassy carbon electrode GCE treated in step (1), and dried at room temperature to obtain the Ce-MOF / CNHs@NBA / GCE electrode.

2. The method for preparing the Ce-MOF / CNHs@NBA / GCE electrode as described in claim 1, characterized in that: In step (1), the diameter of the glassy carbon electrode is 3 mm; the particle size of the aluminum oxide powder used is 0.3 μm and 0.05 μm respectively.

3. The method for preparing the Ce-MOF / CNHs@NBA / GCE electrode as described in claim 1, characterized in that: In step (2), the mass ratio of single-walled carbon nanotubes (CNHs) powder to Nile Blue A (NBA) powder is 2:

1.

4. The method for preparing the Ce-MOF / CNHs@NBA / GCE electrode as described in claim 1, characterized in that: In step (4), the amount of Ce-MOF / CNHs@NBA solution used is 4 to 8 µL.

5. The method for preparing the Ce-MOF / CNHs@NBA / GCE electrode as described in claim 1, characterized in that: In step (2), the preparation process of CNHs@NBA powder is as follows: Disperse 20-40 mg of single-walled carbon nanotubes (CNHs) powder in 120 mL of water, and dissolve 10-20 mg of Nile Blue A (NBA) powder in 30 mL of water. Sonicate both solutions separately. Mix the two solutions and stir continuously at room temperature for 10-14 hours. Finally, centrifuge, wash and dry the resulting solution with pure water to obtain CNHs@NBA powder.

6. The method for preparing the Ce-MOF / CNHs@NBA / GCE electrode as described in claim 1, characterized in that: In step (2), the preparation process of the Ce-MOF / CNHs@NBA complex is as follows: Dissolve 4-5 mg of benzotricarboxylic acid (H3BTC) in 40 mL of ethanol and water at a volume ratio of 1:1 to prepare a mixed solution, and then sonicate to obtain solution A. Add 8-12 mg of CNHs@NBA powder to solution A, and then sonicate to obtain solution B; Add 7-9 mg of cerium nitrate hexahydrate Ce(NO3)3·6H2O powder to solution B, stir, centrifuge with pure water, wash and dry to obtain Ce-MOF / CNHs@NBA complex.

7. An electrochemical sensor, characterized in that: The electrochemical sensor has a Ce-MOF / CNHs@NBA / GCE electrode obtained by any of the preparation methods described in claims 1-6.

8. The application of the electrochemical sensor according to claim 7 in the detection of methyl parathion, characterized in that: Includes the following steps: (1) Methyl parathion was diluted with PBS buffer to prepare standard solutions of different concentrations, and multiple electrochemical sensors were placed in the standard solutions of different concentrations, with each electrochemical sensor corresponding to a certain concentration; In a three-electrode system, the Ce-MOF / CNHs@NBA / GCE electrode was used as the working electrode, the Ag / AgCl electrode as the reference electrode, and the platinum wire as the counter electrode. The differential pulse voltammetry (DPV) was used for detection, and the current peak value I of methyl parathion (MP) and Nile blue A was measured MP and I NBA ; (2) With methyl parathion concentration as the abscissa, the current peak value ratio I MP / I NBA of methyl parathion and Nile blue A measured by DPV as the ordinate, a standard curve of methyl parathion concentration corresponding to the peak current ratio I MP / I NBA was established; (3) Place the electrochemical sensor in the test solution and use DPV to detect it in the three electrodes. Record the peak value of the DPV current of the sample solution and obtain the concentration of methyl parathion in the test sample by referring to the standard curve of the peak value of the current corresponding to the concentration of methyl parathion.

9. The application of the electrochemical sensor as described in claim 8 in the detection of methyl parathion, characterized in that: Ratio of peak current I MP / I NBA With methyl parathion concentration C MP The standard linear curve between them is I MP / I NBA =0.0014+0.0481C MP (R 2 =0.994); When testing the solution to be tested, adjust the pH value of the solution to 4.5-7.

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