Photoelectrochemical Sensor Based on MWCNTsNiCo3-MOFCdS Composite Film, Preparation Method and Application

Abstract

The present invention discloses a photoelectrochemical sensor based on MWCNTsNiCo3-MOFCdS composite film, a preparation method and an application thereof, which relates to the technical field of analytical chemistry. The key technical points are as follows: The photoelectrochemical sensor based on the composite film includes a glassy carbon electrode and a composite film drop-coated on the surface of the glassy carbon electrode. The present invention also provides a preparation method for the sensor, and successfully prepares a photoelectrochemical sensor; the present invention applies the photoelectrochemical sensor to the detection of glyphosate in water samples. The sensor of the present invention has the effects of a wider detection range, a lower detection limit, better selectivity and stability, and also shows excellent application value in the detection of actual water samples.

Description

Technical Field

[0001] The present invention relates to the technical field of analytical chemistry, and more specifically, it relates to a photoelectrochemical sensor based on MWCNTs / NiCo3-MOF / CdS composite film, a preparation method thereof, and an application thereof. Background Art

[0002] As an important branch of organophosphorus pesticides (OPs), glyphosate has functions such as insecticidal, bactericidal, and herbicidal, and thus is widely used in agricultural production. At the same time, the extensive use of glyphosate will bring many problems, such as residue problems in water sources, food fruits and vegetables, and processing, which will seriously threaten the food and life safety of various non-target organisms such as birds, fish, and humans.

[0003] Meanwhile, although there are relatively rich detection means for glyphosate today, there are also certain defects and deficiencies. For example, methods such as high performance liquid chromatography (HPLC), gas chromatography (GC), fluorescence detection, and (enzyme-linked immunosorbent assay) can all detect glyphosate, and their detection performance and sensitivity are very reliable, but the analysis process is long, the sample preparation is cumbersome, and the cost is high. In contrast, developing an analytical method with simple operation and high credibility for detecting glyphosate has far-reaching implications. At the same time, according to research, the photoelectrochemical sensing technology not only has simple operation and low cost, but also has advantages such as low detection sensitivity, which well meets the requirements for the real-time detection of glyphosate.

[0004] Therefore, the present invention constructs a photoelectrochemical sensing platform based on MWCNTs / NiCo3-MOF / CdS composite film for the detection of glyphosate in water samples. This photoelectrochemical sensor has a wider detection range, a lower detection limit, better selectivity and stability, and also shows excellent application value in the detection of actual water samples. Summary of the Invention

[0005] The purpose of the present invention is to solve the above problems, and to provide a photoelectrochemical sensor based on MWCNTs / NiCo3-MOF / CdS composite film, a preparation method thereof, and an application thereof. The photoelectrochemical sensor of the present invention has a wider detection range, with the detection range being 1 nM - 10 μM, a lower detection limit, and the lowest detection limit can reach 0.3 nM, better selectivity and stability, and also shows excellent application value in the detection of actual water samples.

[0006] The above technical objectives of the present invention are achieved through the following technical solutions: a photoelectrochemical sensor based on a MWCNTsNiCo3-MOFCdS composite film, including a glassy carbon electrode and a MWCNTsNiCo3-MOFCdS composite film attached to the surface of the glassy carbon electrode. The MWCNTsNiCo3-MOFCdS composite film is made by drop-coating a MWCNTs / NiCo3-MOF / CdS suspension on the polished glassy carbon electrode and then drying it.

[0007] The present invention also provides a preparation method for a photoelectrochemical sensor based on a MWCNTsNiCo3-MOFCdS composite film, including the following steps:

[0008] S1. Synthesis of NiCo3-MOF;

[0009] S2. Synthesis of NiCo3-MOF / CdS;

[0010] S3. Acidification of MWCNTs;

[0011] S4. Take the NiCo3-MOF / CdS suspension synthesized in step S2 and the MWCNTs dispersion in step S3, ultrasonically mix them for 20-30 minutes to obtain a MWCNTs / NiCo3-MOF / CdS suspension. Drop the MWCNTs / NiCo3-MOF / CdS suspension on the polished glassy carbon electrode and dry it to prepare the photoelectrochemical sensor.

[0012] The present invention is further set as: the specific method for synthesizing NiCo3-MOF in step S1 is as follows:

[0013] Dissolve trimesic acid, polyvinylpyrrolidone, cobalt nitrate hexahydrate, and nickel nitrate hexahydrate in a mixed solution composed of ethanol, DMF, and H2O with a volume ratio of 1:1:1. Stir at room temperature for 30-40 minutes, then transfer it to a high-temperature-resistant polytetrafluoroethylene inner lining. React at 150-180 °C for 10-12 hours. After cooling to room temperature, filter the precipitate with a polytetrafluoroethylene microfiltration membrane and wash it with ultrapure water and ethanol multiple times. Finally, dry NiCo3-MOF in a vacuum drying oven at 50-60 °C overnight and collect it.

[0014] The present invention is further set as: the specific method for synthesizing NiCo3-MOF / CdS in step S2 is as follows:

[0015] Dissolve 120 - 150 mg of NiCo3 - MOF into 100 mL of a mixed aqueous solution containing sodium citrate, cadmium chloride, ammonia water solution, and thiourea, and stir for 60 - 80 minutes. Then transfer the homogeneous solution to an oil bath for condensation reflux for 3 - 4 hours, and cool it to room temperature. Filter the precipitate with a polytetrafluoroethylene microfiltration membrane, and wash it multiple times with ultrapure water and ethanol. Finally, dry NiCo3 - MOF / CdS overnight in a vacuum drying oven at 50 - 60 °C and collect it.

[0016] The present invention is further configured as follows: The specific method for acidifying MWCNTs in step S3 is:

[0017] Take a mixed acid solution of concentrated sulfuric acid and concentrated nitric acid, then add 200 mg of multi - walled carbon nanotubes to the mixed acid, ultrasonically disperse for 1 - 2 hours, reflux the dispersion and cool it to room temperature. Dilute the dispersion with secondary water, filter it using a polytetrafluoroethylene microfiltration membrane, repeat the washing, and then collect the MWCNTs and dry them in a vacuum environment.

[0018] The present invention is further configured as follows: The concentrations of both the NiCo3 - MOF / CdS suspension and the MWCNTs - COOH dispersion are 2 mg / mL, the ultrasonic mixing time is 20 - 30 min, and the volume of the MWCNTs - COOH / NiCo3 - MOF / CdS suspension droplet dropped on the polished glassy carbon electrode is 6 μL.

[0019] The present invention also provides a method for detecting glyphosate in water samples using a photoelectrochemical sensor based on an MWCNTsNiCo3 - MOFCdS composite film: Take the glyphosate solution to be detected, and 3- Detect the glyphosate solution to be detected with the photoelectrochemical sensor based on the MWCNTsNiCo3 - MOFCdS composite film in a PBS solution, and measure the change value of the photocurrent. The PBS buffer solution is a 0.1 mol buffer solution with a pH value of 3.5.

[0020] In summary, the present invention has the following beneficial effects: The present invention uses a one - pot method to load CdS onto the surface of NiCo3 - MOF, thereby obtaining a composite material NiCo3 - MOF / CdS with catalytic and optoelectronic properties. At the same time, after ultrasonically mixing MWCNTs with excellent electrical conductivity and catalytic properties with NiCo3 - MOF / CdS and dropping it on the electrode surface, a photoelectrochemical sensing platform based on an MWCNTsNiCo3 - MOFCdS composite film is successfully prepared for detecting glyphosate in water samples. This sensor has a wider detection range and a lower detection limit. The detection range can reach 1 nM - 10 μM, the lowest detection limit can reach 0.3 nM, has good selectivity and stability, and also shows excellent application value in the detection of actual water samples. Description of the Drawings

[0021] Figure 1 These are the impedance spectrograms of NiCo3-MOF, Ni-MOF / CdS, NiCo3-MOF / CdS, NiCo5-MOF / CdS, and MWCNTs / NiCo3-MOF / CdS in a solution of 5 mM [Fe(CN)6](1:1) containing 0.1 M KCl according to the present invention; 3- / 4- (1:1) solution, NiCo3-MOF, Ni-MOF / CdS, NiCo3-MOF / CdS, NiCo5-MOF / CdS, and MWCNTs / NiCo3-MOF / CdS impedance spectrograms;

[0022] Figure 2 These are the schematic diagrams of the i-t response photocurrent of MWCNTs / NiCo3-MOF / CdS / GCE of the present invention at different glyphosate concentrations (1 nM - 10 μM) under 0.1 M PBS (pH = 3.5);

[0023] Figure 3 These are the calibration diagrams of the measured photocurrent values and the Lg values of glyphosate concentrations according to the present invention;

[0024] Figure 4 These are the schematic diagrams of the results of detecting glyphosate by the sensor prepared by modifying five different glassy carbon electrodes with MWCNTs / NiCo3-MOF / CdS / GCE according to the present invention;

[0025] Figure 5 Schematic diagram of the anti-interference test results. Detailed implementation manners

[0026] Example: An optoelectrochemical sensor based on an MWCNTsNiCo3-MOFCdS composite film, an optoelectrochemical sensor based on an MWCNTsNiCo3-MOFCdS composite film, including a glassy carbon electrode and an MWCNTsNiCo3-MOFCdS composite film attached to the surface of the glassy carbon electrode, and the MWCNTsNiCo3-MOFCdS composite film is made by drop-coating an MWCNTs / NiCo3-MOF / CdS suspension on a polished glassy carbon electrode and then drying.

[0027] Preparation method of an optoelectrochemical sensor based on an MWCNTsNiCo3-MOFCdS composite film: S1, synthesis of NiCo3-MOF;

[0028] S2, synthesis of NiCo3-MOF / CdS;

[0029] S3, acidification of MWCNTs;

[0030] S4. Take the NiCo₃-MOF / CdS suspension synthesized in step S2 and the MWCNTs dispersion in step S3, ultrasonically mix them for 20 - 30 min to obtain the MWCNTs / NiCo₃-MOF / CdS suspension. Drop the MWCNTs / NiCo₃-MOF / CdS suspension onto the polished glassy carbon electrode, and dry it to prepare the photoelectrochemical sensor.

[0031] The specific method for synthesizing NiCo₃-MOF in step S1 is as follows: Dissolve 157.61 mg of trimesic acid, 2.0 g of polyvinylpyrrolidone, 121.26 mg of cobalt(II) nitrate hexahydrate, and 363.49 mg of nickel(II) nitrate hexahydrate in a mixed solution. The mixed solution is synthesized by mixing ethanol, DMF, and H₂O with a volume ratio of 1:1:1. Take 10 mL of each of ethanol, DMF, and H₂O, stir at room temperature for 30 - 40 minutes, and then transfer it to a high-temperature-resistant polytetrafluoroethylene inner liner. React at 150 - 180 °C for 10 - 12 hours. After cooling to room temperature, filter the precipitate with a polytetrafluoroethylene microfiltration membrane, and wash it multiple times with ultrapure water and ethanol. Finally, dry NiCo₃-MOF in a vacuum drying oven at 50 - 60 °C overnight and collect it.

[0032] The specific method for synthesizing NiCo₃-MOF / CdS in step S2 is as follows: Dissolve 120 - 150 mg of NiCo₃-MOF in 100 mL of a mixed aqueous solution containing 1.0 mL of 1.0 mol / L sodium citrate solution, 0.5 mL of 1.0 mol / L cadmium chloride solution, 2.0 mL of 28% ammonia water solution, and 2.0 mL of 1.0 mol / L thiourea solution. After stirring for 60 - 80 minutes, transfer the homogeneous solution to an oil bath for condensation reflux for 3 - 4 hours, and then cool to room temperature. Filter the precipitate with a polytetrafluoroethylene microfiltration membrane, and wash it multiple times with ultrapure water and ethanol. Finally, dry NiCo₃-MOF / CdS in a vacuum drying oven at 50 - 60 °C overnight and collect it.

[0033] The specific method for acidifying MWCNTs in step S3 is as follows: Take a mixed acid solution of 15 mL of concentrated sulfuric acid and 15 mL of concentrated nitric acid, add 200 mg of multi-walled carbon nanotubes to the mixed acid, ultrasonically disperse for 1 - 2 hours, reflux the dispersion and cool to room temperature. Dilute the dispersion with secondary water, filter it using a polytetrafluoroethylene microfiltration membrane, repeat the washing, and then collect the MWCNTs and dry them in a vacuum environment.

[0034] In step S4, the concentrations of the NiCo₃-MOF / CdS suspension and the MWCNTs-COOH dispersion are both 2 mg / mL, the ultrasonic mixing time is 20 - 30 min, and the volume of the MWCNTs-COOH / NiCo₃-MOF / CdS suspension droplet dropped on the polished glassy carbon electrode is 6 μL.

[0035] The method for detecting glyphosate in water samples by using a photoelectrochemical sensor based on MWCNTsNiCo3-MOFCdS composite film is as follows: Take the glyphosate solution to be detected, and use the photoelectrochemical sensor based on MWCNTsNiCo3-MOFCdS composite film to detect the glyphosate solution to be detected in PBS solution, and measure the change value of the photocurrent. The PBS buffer solution is a buffer solution with 0.1 mol and a pH value of 3.5.

[0036] Using the photoelectrochemical sensor based on MWCNTsNiCo3-MOFCdS composite film obtained according to the above experimental steps, the experimental data obtained by repeatedly measuring multiple groups of glyphosate solutions are as follows:

[0037]

[0038] It can be seen from the above experimental data that when the photoelectrochemical sensor prepared by the present invention measures the glyphosate content in the solution, the error is small and the reproducibility is good, indicating that the stability of the present photoelectrochemical sensor is relatively high.

[0039] In addition, in order to measure the influence of other substances on the measurement data of the photoelectrochemical sensor prepared by the present invention, we measured its photocurrent data using a glyphosate solution containing interfering substances. The specific experimental data are as follows:

[0040]

[0041] It can be seen from the above experimental data that when measuring in glyphosate solutions containing different interfering substances using the photoelectrochemical sensor prepared by the present invention, the influence of the interfering substances on the measurement results is small, and the deviation caused by the experimental data is small, which also indicates that the selectivity of the present photoelectrochemical sensor is good.

[0042] Using the experimental data obtained by measuring multiple groups of glyphosate solutions with the photoelectrochemical sensor prepared by the present invention, and then linearly fitting the experimental data to obtain a linear fitting curve. Subsequently, continuously measure glyphosate solutions with lower and higher concentrations until the experimental results deviate from the linear curve, so as to obtain the detection range of the photoelectrochemical sensor as 1 nM - 10 μM. The detection range of the photoelectrochemical sensor of the present invention is wider than that in the prior art. The linear fitting curve fits the original data as follows:

[0043]

[0044] The lowest detection limit of this photoelectrochemical sensor also needs to be obtained from the slope of the above linear fitting curve. We used glyphosate solutions at the lowest concentration within the detection range for 10 sets of measurements. By calculating the relative standard deviation of the 10 sets of measurement data and the slope of the linear fitting curve, the lowest detection limit of this photoelectrochemical sensor was found to be 0.3 nM. The 10 sets of measurement data are shown below:

[0045]

[0046] Note: The unit of photocurrent value in all the above tables is nA.

[0047] This specific embodiment is only an interpretation of the present invention and not a limitation thereof. After reading this specification, those skilled in the art can make modifications to this embodiment that do not contribute creatively as needed, but as long as it is within the scope of the claims of the present invention, it is protected by the patent law.

Claims

1. Preparation method of a photoelectrochemical sensor based on an MWCNTsNiCo3-MOFCdS composite film, characterized by: It includes the following steps: S1. Synthesis of NiCo3-MOF: Dissolve trimesic acid, polyvinylpyrrolidone, cobalt nitrate hexahydrate and nickel nitrate hexahydrate in a mixed solution composed of ethanol, DMF, and H2O with a volume ratio of 1:1:

1. Stir at room temperature for 30 - 40 minutes, then transfer it to a high-temperature-resistant polytetrafluoroethylene inner liner. React at 150 - 180 °C for 10 - 12 hours. After cooling to room temperature, filter the precipitate with a polytetrafluoroethylene microfiltration membrane and wash it multiple times with ultrapure water and ethanol. Finally, dry NiCo3-MOF in a vacuum drying oven at 50 - 60 °C overnight and collect it; S2. Synthesis of NiCo3-MOF / CdS: Dissolve 120 - 150 mg of NiCo3-MOF in 100 mL of a mixed aqueous solution containing sodium citrate, cadmium chloride, ammonia water solution and thiourea. Stir for 60 - 80 minutes, then transfer the homogeneous solution to an oil bath pot for condensation reflux for 3 - 4 hours and cool to room temperature. Filter the precipitate with a polytetrafluoroethylene microfiltration membrane and wash it multiple times with ultrapure water and ethanol. Finally, dry NiCo3-MOF / CdS in a vacuum drying oven at 50 - 60 °C overnight and collect it; S3. Acidification of MWCNTs; S4. Take the NiCo3-MOF / CdS suspension synthesized in step S2 and the MWCNTs dispersion in step S3, ultrasonically mix them for 20 - 30 min to obtain the MWCNTs / NiCo3-MOF / CdS suspension. Drop the MWCNTs / NiCo3-MOF / CdS suspension on a polished glassy carbon electrode, dry it, and prepare a photoelectrochemical sensor.

2. The preparation method of the photoelectrochemical sensor based on the MWCNTsNiCo3-MOFCdS composite film according to claim 1, characterized in that: The specific method for acidification of MWCNTs in step S3 is as follows: Take a mixed acid solution of concentrated sulfuric acid and concentrated nitric acid, add 200 mg of multi-walled carbon nanotubes to the mixed acid, ultrasonically disperse for 1 - 2 hours, reflux the dispersion and cool to room temperature. Dilute the dispersion with secondary water, filter it using a polytetrafluoroethylene microfiltration membrane, repeat the washing, and then collect the MWCNTs and dry them in a vacuum environment.

3. The preparation method of the photoelectrochemical sensor based on the MWCNTsNiCo3-MOFCdS composite film according to claim 1, characterized in that: The concentrations of the NiCo3-MOF / CdS suspension and the MWCNTs-COOH dispersion are both 2 mg / mL, the ultrasonic mixing time is 20 - 30 min, and the volume of the MWCNTs-COOH / NiCo3-MOF / CdS suspension droplet dropped on the polished glassy carbon electrode is 6 μL.

4. The photoelectrochemical sensor based on MWCNTsNiCo3-MOFCdS composite film prepared by the method according to any one of claims 1-3, characterized in that: The photoelectrochemical sensor includes a glassy carbon electrode and a MWCNTsNiCo3-MOFCdS composite film attached to the surface of the glassy carbon electrode. The MWCNTsNiCo3-MOFCdS composite film is made by dropping the MWCNTs / NiCo3-MOF / CdS suspension on a polished glassy carbon electrode and then drying it.

5. Use of the photoelectrochemical sensor based on the MWCNTsNiCo3-MOFCdS composite film according to claim 4, characterized in that: Apply the photoelectrochemical sensor to the detection of glyphosate in water samples.

6. The application of the photoelectrochemical sensor based on the MWCNTsNiCo3-MOFCdS composite film according to claim 4, characterized in that: The method for the application of a photoelectrochemical sensor to the detection of glyphosate in a water sample is as follows: Take the glyphosate solution to be detected, and use the photoelectrochemical sensor based on the MWCNTsNiCo3-MOFCdS composite film to detect the glyphosate solution to be detected in a PBS solution, and measure the change value of the photocurrent. The PBS solution is a buffer solution with a concentration of 0.1 mol and a pH value of 3.5.

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