Preparation method of AgNPs (at) ZIF-8 / CNHs / GCE electrode, electrochemical sensor and application of electrochemical sensor in detection of bisphenol A

Abstract

The invention discloses a preparation method of an AgNPs (at) ZIF-8 / CNHs / GCE electrode, an electrochemical sensor and application of the electrochemical sensor in bisphenol A. 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: respectively dissolving zinc acetate dihydrate and 2-methylimidazole in a methanol solution to respectively obtain a clear solution A and a clear solution B, pouring the solution B into the stirred solution A, and then centrifuging, washing and drying to obtain ZIF-8 powder; the preparation method comprises the following steps: dissolving AgNO3 in a mixed solution of water and ethanol, stirring, then adding ZIF-8 powder and CNHs powder into the AgNO3 solution, continuously stirring, and then centrifuging, washing and drying to obtain AgNPs (at) ZIF-8 / CNHs powder; agNPs (at) ZIF-8 / CNHs powder is dispersed in pure water, and an AgNPs (at) ZIF-8 / CNHs solution is obtained; and dropwise adding the AgNPs (at) ZIF-8 / CNHs solution onto a glassy carbon electrode GCE, and airing to obtain the AgNPs (at) ZIF-8 / CNHs / GCE electrode.

Description

TECHNICAL FIELD

[0001] The application relates to a preparation method of an AgNPs@ZIF-8 / CNHs / GCE electrode, an electrochemical sensor and application of the electrochemical sensor in detection of bisphenol A. BACKGROUND

[0002] Bisphenol A (BPA) is a typical phenolic chemical, which is widely used in industrial production due to its stable properties, difficulty in degradation and long half-life. In addition to common food packaging materials and disposable tableware, BPA is also widely used in polycarbonate plastics (such as baby bottles and drinking water bottles), epoxy resins (such as the inner wall coating of canned food and beverage can sealing glue) and other products. However, under storage or heating conditions, BPA is easy to migrate into beverages, water and food. Due to its endocrine disrupting effect, excessive intake can cause early sexual maturity, growth and development retardation and other problems in infants and young children, and can also cause damage to the reproductive system of adults. More importantly, long-term low-dose exposure to BPA may induce abnormal proliferation of breast cells and prostate cells, which is potentially related to the incidence of cancer. Therefore, developing a sensitive and reliable BPA detection method is of great practical significance for ensuring food safety.

[0003] At present, the detection techniques for BPA mainly include gas chromatography, high performance liquid chromatography-mass spectrometry and surface enhanced Raman scattering. However, these techniques have limitations such as expensive instruments, long time consumption and complex operation, which cannot meet the needs of rapid screening in food production sites, market supervision and sampling inspection, and therefore it is urgent to develop simple, fast and efficient detection methods. In comparison, electrochemical sensing technology provides a feasible path for realizing rapid, low-cost and high-sensitivity detection of BPA in food due to its low cost, fast response and simple operation.

[0004] Most of the existing electrochemical sensors rely on single signal change to detect BPA, which is easily disturbed by external factors such as electrode modification difference, instrument performance fluctuation and environmental condition change, resulting in slight deviation of peak current of different electrodes and thus reducing the reliability of BPA detection. Unlike traditional single signal sensing, ratio electrochemical sensors have double signal response characteristics for target substances. Since the disturbance caused by external factors will simultaneously act on the double signals, the ratio strategy of measuring the double signal ratio to quantify the concentration of BPA can effectively improve the detection accuracy. Therefore, developing a high-performance ratio electrochemical sensor capable of realizing double signal response has important research significance for efficient and accurate detection of BPA. SUMMARY

[0005] The application is provided to solve the problems existing in the prior art, and relates to a preparation method of an AgNPs@ZIF-8 / CNHs / GCE electrode, an electrochemical sensor and application of the electrochemical sensor in detection of bisphenol A.

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

[0007] A preparation method of an AgNPs@ZIF-8 / CNHs / GCE electrode comprises 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 then ultrasonically treated in ethanol and pure water in sequence to remove surface residues, and is dried at room temperature;

[0009] (2) Zinc acetate dihydrate and 2-methylimidazole are respectively dissolved in a methanol solution to obtain clear solutions A and B, respectively, solution B is poured into stirring solution A, and then ZIF-8 powder is obtained after centrifugation, washing and drying;

[0010] (3) AgNO3 is dissolved in a mixed solution of water and ethanol and stirred, then ZIF-8 powder and CNHs powder are added to the AgNO3 solution, and continue to stir, then AgNPs@ZIF-8 / CNHs powder is obtained after centrifugation, washing and drying;

[0011] (4) The AgNPs@ZIF-8 / CNHs powder is dispersed in pure water to obtain an AgNPs@ZIF-8 / CNHs solution;

[0012] (5) The AgNPs@ZIF-8 / CNHs solution is added dropwise to the glassy carbon electrode GCE treated in step (1), and is dried at room temperature to obtain an AgNPs@ZIF-8 / CNHs / GCE electrode.

[0013] Further, in step (1), the diameter of the glassy carbon electrode is 3 mm; the particle sizes of the aluminum oxide powders used are 0.3 μm and 0.05 μm in sequence;

[0014] Further, in step (2),

[0015] 0.2933-2.933 g of zinc acetate dihydrate is dissolved in 10-100 mL of methanol, and solution A is obtained after ultrasonic treatment;

[0016] 0.6491-6.491 g of 2-methylimidazole is dissolved in 100-200 mL of methanol, and solution B is obtained after ultrasonic treatment;

[0017] Solution B is poured into stirring solution A, and continue to stir at room temperature for 10-48 hours, then the precipitate is dried after centrifugation and washing with methanol 3 times to obtain ZIF-8 powder.

[0018] Further, in step (3),

[0019] 10–20 mg of AgNO3 was dispersed in 10–20 mL of water and ethanol at a volume ratio of 1:6 to obtain a mixed solution, which was then sonicated to obtain solution C.

[0020] Add 100–150 mg of ZIF-8 powder and 15–20 mg of CNHs powder to solution C. After ultrasonic treatment, stir at room temperature for 2–5 hours, centrifuge with pure water, wash 2–5 times, and dry the precipitate to obtain AgNPs@ZIF-8 / CNHs powder.

[0021] Further, in step (4), 1~10 mg of Ag@ZIF-8 / CNHs powder is dispersed in 0.5~10 mL of pure water to obtain an Ag@ZIF-8 / CNHs solution of 0.1~2.0 mg / mL.

[0022] Further, in step (5), the amount of AgNPs@ZIF-8 / CNHs solution used is 4 to 8 µL.

[0023] The present invention also discloses an electrochemical sensor having an AgNPs@ZIF-8 / CNHs / GCE electrode obtained by the above preparation method.

[0024] This invention also discloses the application of an electrochemical sensor in the detection of bisphenol A, comprising the following steps:

[0025] (1) Dilute bisphenol A with PBS buffer to prepare standard solutions of different concentrations, and place multiple electrochemical sensors in the standard solutions of different concentrations, with each electrochemical sensor corresponding to a certain concentration;

[0026] In the three-electrode system, the AgNPs@ZIF-8 / CNHs / GCE electrode was used as the working electrode, the Ag / AgCl electrode as the reference electrode, and the platinum wire as the counter electrode. Differential pulse voltammetry (DPV) was used for detection, and the peak oxidation currents of bisphenol A and silver nanoparticles were measured to be I0 and I1, respectively. BPA and I AgNPs ;

[0027] (2) With bisphenol A concentration as the abscissa, the ratio of the peak current of bisphenol A measured by DPV to that of silver nanoparticles was calculated. BPA / I AgNPs Using bisphenol A concentration as the ordinate, establish the ratio I of the peak current of bisphenol A to that of silver nanoparticles corresponding to the bisphenol A concentration. BPA / I AgNPs The standard curve;

[0028] (3) Put the electrochemical sensor into the solution to be measured, detect by DPV in a three-electrode system, record the DPV current peak value of the sample solution, and obtain the concentration of bisphenol A in the sample to be measured by comparing with the standard curve of the bisphenol A concentration corresponding to the current peak value.

[0029] Further, the ratio of the current peak values I BPA / I AgNPs and the bisphenol A concentration C BPA is a standard linear curve I BPA / I AgNPs =0.0592+0.049C BPA (R 2 =0.995);When the solution to be measured is detected, the pH value of the solution to be measured is adjusted to 5-7.

[0030] The present application has the following beneficial effects:

[0031] (1) In the preparation method of the present application, ZIF-8 is used as a carrier, CNHs and AgNPs are loaded on the surface of the carrier by physical adsorption and chemical bonding to form a stable AgNPs@ZIF-8 / CNHs composite material. ZIF-8 is an ideal carrier for assembling nanomaterials, and its high porosity and large specific surface area provide abundant loading sites for CNHs and AgNPs, and its regular pore structure is conducive to the enrichment and mass transfer of target molecules. The introduction of CNHs further increases the specific surface area and conductivity of the composite material. AgNPs provide a stable internal standard signal, which does not interfere with the response signal of bisphenol A, can effectively resist external environmental disturbance, realize high-precision ratio electrochemical detection, and make up for the shortcomings of traditional single-signal electrodes. The synergistic effect of the three significantly improves the detection sensitivity and accuracy of the sensor for bisphenol A.

[0032] (2) The electrochemical sensor for detecting bisphenol A has the advantages of fast detection speed, high sensitivity, wide linear range, low detection limit, high precision, good anti-interference performance and stability, and has potential application prospects in the field of food safety detection.

[0033] The electrochemical sensor described in the present application can realize high-sensitivity detection of bisphenol A, and the sensor has a wide linear range of 500-40000 ng / mL and an extremely low detection limit of 166.7 ng / mL. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 It is a schematic diagram of the construction and detection process of the electrochemical sensor of the present application.

[0035] Figure 2 (A) is the DPV response corresponding to different concentrations of BPA, wherein the concentration of BPA is 5x10-7 , 1×10 -6 , 3×10 -6 , 5×10 -6 , 1×10 -5 , 2×10 -5 , 3×10 -5 and 4×10 -5 g / mL; (B) is the standard linear curve between the ratio of DPV current peak (I BPA / I AgNPS ) and BPA concentration (C BPA ).

[0036] Figure 3 is the DPV current response of GCE, ZIF-8 / GCE, AgNPs@ZIF-8 / GCE and AgNPs@ZIF-8 / CNHs / GCE respectively in 0.1 M PBS (pH 6.0) containing 40.0 μg mL -1 BPA. DETAILED DESCRIPTION

[0037] The application will be further described below with reference to the accompanying drawings.

[0038] Example 1

[0039] The construction of the electrochemical sensor and the detection process are shown in the accompanying drawings. Figure 1

[0040] The preparation method of the AgNPs@ZIF-8 / CNHs / GCE electrode comprises the following steps:

[0041] (1) A glassy carbon electrode GCE with a diameter of 3 mm is polished to be smooth by using alumina powder with different particle sizes of 0.3 μm and 0.05 μm in sequence, and is ultrasonically cleaned in ethanol and pure water in sequence, and is dried at room temperature;

[0042] (2) 1.756 g of zinc acetate dihydrate is dissolved in 40 mL of methanol, and is ultrasonically treated for 5 minutes to obtain solution A;

[0043] (3) 2.627 g of 2-methylimidazole is dissolved in 160 mL of methanol, and is ultrasonically treated for 5 minutes to obtain solution B;

[0044] (4) Solution B is slowly poured into the stirring solution A, and is continuously stirred at room temperature for 24 hours, and after being centrifuged and washed with methanol for 3 times, the precipitate is dried at 60°C for 8 hours to obtain ZIF-8 powder;

[0045] ​(5) 11 mg of AgNO3 was dispersed in 10 mL of a mixed solution of water and ethanol (volume ratio of water to ethanol was 1:6) and ultrasonicated for 5 minutes to obtain solution C;

[0046] (6) 100 mg of ZIF-8 powder and 15 mg of CNHs powder were added to solution C and ultrasonicated for 10 minutes. After stirring at room temperature for 3 hours, the precipitate was centrifuged and washed with pure water for 3 times. The precipitate was dried at 70°C for 12 hours to obtain Ag@ZIF-8 / CNHs powder;

[0047] (7) 1 mg of Ag@ZIF-8 / CNHs powder was dispersed in 1 mL of pure water to obtain a 1.0 mg / mL Ag@ZIF-8 / CNHs solution.

[0048] (8) A glassy carbon electrode GCE was polished with aluminum oxide powder of different particle sizes in sequence until smooth, and then ultrasonicated in ethanol and pure water in sequence to remove surface residues and air dried at room temperature.

[0049] (9) 6 μL of a 1.0 mg / mL AgNPs@ZIF-8 / CNHs solution was added dropwise to the glassy carbon electrode GCE treated in step (8) and air dried at room temperature to obtain an AgNPs@ZIF-8 / CNHs / GCE electrode.

[0050] Example 2

[0051] This example discloses an electrochemical sensor having an AgNPs@ZIF-8 / CNHs / GCE electrode prepared by the method of Example 1, which is used to detect bisphenol A. Specifically,

[0052] (1) Bisphenol A (BPA) was diluted with PBS buffer to obtain standard solutions of different concentrations. The electrochemical sensor for detecting bisphenol A was added dropwise with bisphenol A standard solutions of different concentrations in sequence, wherein the concentrations of BPA were 5×10 -7 , 1×10 -6 , 3×10 -6 , 5×10 -6 , 1×10 -5 , 2×10 -5 , 3×10 -5 and 4×10 -5 g / mL, respectively.

[0053] In a three-electrode system, the AgNPs@ZIF-8 / CNHs / GCE working 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 differential pulse voltammetry (DPV) was used to measure the oxidation peak current of bisphenol A and silver nanoparticles.

[0054] (2) The ratio of the peak current of bisphenol A to that of silver nanoparticles obtained by DPV measurement, with the concentration of bisphenol A as the abscissa (I). BPA / I AgNPS Using bisphenol A concentration as the ordinate, establish the ratio I of peak current corresponding to bisphenol A concentration. BPA / I AgNPS The standard curve.

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

[0056] from Figure 2 From (B), it can be seen that the ratio of peak currents I BPA / I AgNPS The standard linear curve between BPA concentration and I is shown in Figure I. BPA / I AgNPs =0.0592+0.049C BPA (R 2 =0.995), the linear range was 500–40000 ng / mL, and the limit of detection was 166.7 ng / mL.

[0057] (3) The electrochemical sensor was applied to the spiked detection of different concentrations of bisphenol A in milk. The detection process was as follows: A certain amount of standard bisphenol A solution was added to commercially available milk and shaken for 10 minutes. The mixture was then filtered through a filter with a membrane pore diameter of 0.45 micrometers. 1 mL of the filtrate was diluted 20 times with 0.1 M PBS solution (pH 6.0), and 5 mL of the resulting solution was used for detection. In the three-electrode system, the modified electrode AgNPs@ZIF-8 / CNHs / GCE 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 three electrodes were placed in the solution after the above sample treatment, and the differential pulse voltammetry (DPV) was used to measure the peak current I of bisphenol A and silver nanoparticles. BPA and I AgNPS Substitute into the standard linear curve I BPA / I AgNPs =0.0592+0.049C BPA The concentration of bisphenol A in the sample was calculated.

[0058] Table 1: Detection results of BPA in milk using the constructed electrochemical sensor

[0059] The results in Table 1 demonstrate that the constructed electrochemical sensor can achieve sensitive and accurate detection of bisphenol A.

[0060] Figure 3 The DPV current response of BPA in 0.1 M PBS (pH 6.0) for GCE, ZIF-8 / GCE, AgNPs@ZIF-8 / GCE and AgNPs@ZIF-8 / CNHs / GCE is shown in the following table. -1 The DPV current response of BPA in 0.1 M PBS (pH 6.0) for GCE, ZIF-8 / GCE, AgNPs@ZIF-8 / GCE and AgNPs@ZIF-8 / CNHs / GCE is shown in the following table. Figure 3 As can be seen from the above table, after ZIF-8 and AgNPS are compounded, the current response of bisphenol A is obviously reduced, but it provides an internal standard output signal for the sensor. After AgNPs@ZIF-8 and CNHs are compounded, the current response of bisphenol A is much higher than that of ZIF-8 and AgNPS@ZIF-8, which significantly improves the detection effect.

[0061] The above only describes the preferred embodiments of the present application, and it should be noted that those skilled in the art can make several improvements without departing from the principles of the present application, and these improvements should also be considered as the protection scope of the present application.

Claims

1. A method for preparing an AgNPs@ZIF-8 / CNHs / GCE electrode, characterized in that: Comprising the following steps: (1) polishing the glassy carbon electrode GCE with aluminum oxide powder of different particle sizes in sequence to smoothness, and then ultrasonicating in ethanol and pure water in sequence to remove surface residues, and drying at room temperature; (2) dissolving zinc acetate dihydrate and 2-methylimidazole in methanol solution respectively to obtain clear solutions A and B respectively, pouring solution B into solution A under stirring, and then obtaining ZIF-8 powder after centrifugation, washing and drying; (3) dissolving AgNO3 in a mixed solution of water and ethanol under stirring, then adding ZIF-8 powder and CNHs powder into the AgNO3 solution, continuing to stir, and then obtaining AgNPs@ZIF-8 / CNHs powder after centrifugation, washing and drying; (4) dispersing AgNPs@ZIF-8 / CNHs powder in pure water to obtain AgNPs@ZIF-8 / CNHs solution; (5) dropping AgNPs@ZIF-8 / CNHs solution onto the glassy carbon electrode GCE treated in step (1) and drying at room temperature to obtain AgNPs@ZIF-8 / CNHs / GCE electrode.

2. The preparation method of the AgNPs@ZIF-8 / CNHs / GCE electrode according to claim 1, characterized in that: In step (1), the diameter of the glassy carbon electrode is 3 mm; the particle sizes of the aluminum oxide powder used are 0.3 μm and 0.05 μm in sequence.

3. The preparation method of AgNPs@ZIF-8 / CNHs / GCE electrode according to claim 1, characterized in that: In step (2), 0.2933-2.933 g of zinc acetate dihydrate is dissolved in 10-100 mL of methanol, and solution A is obtained after ultrasonic treatment; 0.6491-6.491 g of 2-methylimidazole is dissolved in 100-200 mL of methanol, and solution B is obtained after ultrasonic treatment; solution B is poured into solution A under stirring, and the mixture is continuously stirred at room temperature for 10-48 hours; after centrifugation and washing with methanol for 3 times, the precipitate is dried to obtain ZIF-8 powder.

4. The preparation method of the AgNPs@ZIF-8 / CNHs / GCE electrode according to claim 1, characterized in that: In step (3), 10-20 mg of AgNO3 is dispersed in 10-20 mL of mixed solution prepared by mixing water and ethanol in a volume ratio of 1:6, and solution C is obtained after ultrasonic treatment; 100-150 mg of ZIF-8 powder and 15-20 mg of CNHs powder are added to solution C after ultrasonic treatment, and the mixture is stirred at room temperature for 2-5 hours; after centrifugation and washing with pure water for 2-5 times, the precipitate is dried to obtain AgNPs@ZIF-8 / CNHs powder.

5. The preparation method of AgNPs@ZIF-8 / CNHs / GCE electrode according to claim 1, characterized in that: In step (4), 1-10 mg of AgNPs@ZIF-8 / CNHs powder is dispersed in 0.5-10 mL of pure water to obtain Ag@ZIF-8 / CNHs solution with a concentration of 0.1-2.0 mg / mL.

6. The preparation method of AgNPs@ZIF-8 / CNHs / GCE electrode according to claim 1, characterized in that: In step (5), the amount of AgNPs@ZIF-8 / CNHs solution used is 4-8 μL.

7. An electrochemical sensor characterized by: The electrochemical sensor has an AgNPs@ZIF-8 / CNHs / GCE electrode obtained by the preparation method of any one of claims 1-6.

8. Use of the electrochemical sensor according to claim 7 for the detection of bisphenol A, characterized in that: Comprising the following steps: (1) diluting bisphenol A into standard solutions of different concentrations with PBS buffer, and placing a plurality of electrochemical sensors in the standard solutions of different concentrations, each electrochemical sensor corresponding to one concentration; In a three-electrode system, the AgNPs@ZIF-8 / CNHs / GCE electrode was used as the working electrode, the Ag / AgCl electrode was used as the reference electrode, and the platinum wire was used as the counter electrode. The differential pulse voltammetry (DPV) was used for detection. The oxidation current peak values of bisphenol A and silver nanoparticles were I BPA and I AgNPs , respectively. (2) Bisphenol A concentration as the abscissa, the current peak of bisphenol A and silver nanoparticles measured by DPV as the ordinate, to establish the standard curve of bisphenol A concentration corresponding to the current peak ratio I BPA / I AgNPs of bisphenol A and silver nanoparticles; BPA / I AgNPs ; (3) The electrochemical sensor is placed in the solution to be measured, and the DPV is used for detection in a three-electrode system; the DPV current peak value of the sample solution is recorded, and the concentration of bisphenol A in the sample to be measured is obtained by comparing with the standard curve of the bisphenol A concentration corresponding to the current peak value.

9. Use of an electrochemical sensor according to claim 8 for the detection of bisphenol A, characterized in that: The ratio of the current peak value I BPA / I AgNPs The standard linear curve between the bisphenol A concentration C BPA and the current I BPA / I AgNPs =0.0592+0.049C BPA (R 2 =0.995) is obtained. When the test solution is detected, the pH value of the test solution is adjusted to 5-7.

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