Electrochemical sensor based on bismuth molybdate / cnt heterojunction and preparation method thereof

Abstract

The application provides a kind of electrochemical sensor based on bismuth molybdate / CNT heterojunction and a preparation method thereof, and belongs to the field of electrochemical sensing materials and detection technology.The molybdenum source, bismuth source and first solvent are mixed uniformly to obtain a first solution; carbon nanotubes are uniformly dispersed in a second solvent to obtain a second solution; the first solution and the second solution are mixed uniformly and then reacted to obtain the bismuth molybdate / CNT heterojunction. The heterojunction material has high electrocatalytic activity. The sensor based on the heterojunction material shows high sensitivity, high selectivity and strong anti-interference ability in detecting diuron in water. The sensor has an ultra-wide linear detection range (0.05-40.0 μmol / L) and an extremely low detection limit (17 nmol / L), and has excellent reproducibility and stability, which can realize rapid and direct determination of trace diuron in environmental water samples, and meet the needs of on-site rapid detection.

Description

Technical Field

[0001] This invention relates to the field of electrochemical sensing materials and detection technology, and in particular to an electrochemical sensor based on a bismuth molybdate / CNT heterojunction and its preparation method. Background Technology

[0002] Diuron is a widely used herbicide. It has systemic activity, meaning it can be absorbed through roots or leaves and spread within the plant. This property allows diuron to effectively control a variety of weeds. However, studies have found that diuron can disrupt the human endocrine system, causing vomiting, loss of appetite, and potentially affecting metabolism and even causing cancer. Therefore, establishing rapid, accurate, and reliable pesticide residue detection technologies is of paramount importance for environmental health risk prevention and control.

[0003] To date, numerous techniques exist for detecting diuron, including fluorescence spectrophotometry, high-performance liquid chromatography (HPLC), and gas chromatography-mass spectrometry (GC-MS). However, these methods suffer from drawbacks such as operational complexity, time consumption, and high cost. Compared to these traditional detection techniques, electrochemical analysis techniques offer several advantages, including higher sensitivity, better stability, simpler operation, and relatively lower cost.

[0004] Bismuth molybdate (Bi₂MoO₆), a typical Aurivillius phase semiconductor, has attracted widespread attention in the field of catalysts due to its high catalytic activity, non-toxicity, and excellent chemical stability. Carbon nanotubes (CNTs) possess a network aggregate structure, and their unique structure increases the effective area of ​​the electrode, thus exhibiting excellent electrical conductivity. Furthermore, numerous studies have shown that when carbon nanotubes are combined with other materials, there may be synergistic effects, resulting in electrode materials with even better electrochemical performance. Therefore, using doping techniques to combine bismuth molybdate with carbon nanotubes to prepare heterojunction materials aims to improve the surface polarity of the material, accelerate electron transport speed, reduce energy barriers in ion adsorption or desorption processes, and adjust the surface electronic structure, thereby effectively optimizing the physicochemical properties of the material. Summary of the Invention

[0005] Based on the above, the purpose of this invention is to provide an electrochemical sensor based on a bismuth molybdate / CNT heterojunction and its preparation method. This invention uses a bismuth molybdate / CNT heterojunction as an electrode modification material to construct an electrochemical sensor for detecting diuron, which has advantages such as simple operation, fast response speed, high sensitivity, and wide linear range.

[0006] To achieve the above objectives, the present invention provides the following technical solution: One of the technical solutions of this invention is a method for preparing a bismuth molybdate / CNT heterojunction, comprising the following steps: The molybdenum source, bismuth source, and first solvent are mixed evenly to obtain the first solution; Carbon nanotubes are uniformly dispersed in a second solvent to obtain a second solution; The first and second solutions are mixed evenly and then reacted to obtain the bismuth molybdate / CNT heterojunction.

[0007] The second technical solution of the present invention is a bismuth molybdate / CNT heterojunction prepared by the above preparation method.

[0008] The third technical solution of the present invention is a bismuth molybdate / CNT heterojunction modified electrode, comprising a substrate electrode and an electrode modification material; wherein the electrode modification material is the aforementioned bismuth molybdate / CNT heterojunction.

[0009] The fourth technical solution of the present invention is an electrochemical sensor, comprising the above-mentioned bismuth molybdate / CNT heterojunction modified electrode.

[0010] The fifth technical solution of the present invention is the application of the above-mentioned bismuth molybdate / CNT heterojunction or the above-mentioned bismuth molybdate / CNT heterojunction modified electrode or the above-mentioned electrochemical sensor in the detection of diuron in water.

[0011] The present invention discloses the following technical effects: This invention provides an electrochemical sensor based on a bismuth molybdate / carbon nanotube (Bi₂MoO₆ / CNT) heterostructure. This heterostructure material exhibits high electrocatalytic activity, and the constructed sensor demonstrates high sensitivity, high selectivity, and strong anti-interference capability for the detection of diuron in water. The sensor possesses an ultra-wide linear detection range (0.05-40.0 μmol / L) and an extremely low detection limit (17 nmol / L), while also exhibiting excellent reproducibility and stability. It enables rapid and direct determination of trace amounts of diuron in environmental water samples, meeting the needs of rapid on-site detection. Attached Figure Description

[0012] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0013] Figure 1 Here is a SEM image of Bi2MoO6 in this invention; Figure 2 This is a SEM image of the Bi2MoO6 / carbon nanotube heterostructure in this invention; Figure 3 The image shows the XRD pattern of the Bi2MoO6 / carbon nanotube heterostructure of this invention. Figure 4 The CV response diagram A and EIS diagram B of the Bi2MoO6 / carbon nanotube heterostructure of the present invention to diuron are shown. Figure 5 The results of the electrochemical sensor of the present invention for detecting diuron are shown in the figure. In the figure, A is the DPV (differential pulse voltammetry) response of diuron at different concentrations, and B is the graph of the relevant linear fitting equation. Figure 6 Figure B shows the reproducibility and anti-interference performance of the Bi2MoO6 / carbon nanotube composite film modified electrode prepared in the embodiments of the present invention in diuron solution. Detailed Implementation

[0014] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0015] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0016] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0017] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0018] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0019] The first aspect of this invention provides a method for preparing a bismuth molybdate / CNT heterojunction, comprising the following steps: The molybdenum source, bismuth source, and first solvent are mixed evenly to obtain the first solution; Carbon nanotubes are uniformly dispersed in a second solvent to obtain a second solution; The first and second solutions are mixed evenly and then reacted to obtain the bismuth molybdate / CNT heterojunction.

[0020] In a preferred embodiment of the present invention, the first solvent is ethylene glycol and the second solvent is ethanol. The present invention does not impose any particular limitation on the amount of the first and second solvents used, as long as the amount is sufficient to fully disperse / dissolve the solute. For example, the ratio of bismuth source to first solvent is 1.5 mmol:50 mL, and the ratio of carbon nanotubes to second solvent is 200 mg:30 mL.

[0021] In a preferred embodiment of the present invention, the molybdenum source is sodium molybdate and the bismuth source is bismuth nitrate.

[0022] In a preferred embodiment of the present invention, the molar ratio of molybdenum in the molybdenum source to bismuth in the bismuth source is 1:(1~3); the ratio of molybdenum to carbon nanotubes in the molybdenum source is 0.5~1 mmol:100~300 mg.

[0023] More preferably, the molar ratio of molybdenum in the molybdenum source to bismuth in the bismuth source is 1:1, 1:2, or 1:3; the ratio of molybdenum to carbon nanotubes in the molybdenum source is 0.5 mmol:100 mg, 0.5 mmol:200 mg, 0.75 mmol:200 mg, 1 mmol:200 mg, 1 mmol:300 mg, 0.75 mmol:250 mg, or 1 mmol:250 mg.

[0024] In a preferred embodiment of the present invention, the temperature of the solvothermal reaction is 140~160 ℃ and the time is 18~36 h.

[0025] More preferably, the temperature of the solvothermal reaction is 140 ℃, 150 ℃ or 160 ℃, and the time is 18 h, 20 h, 24 h, 28 h, 32 h or 36 h.

[0026] In a preferred embodiment of the present invention, after the solvothermal reaction is completed, the method further includes washing and drying the resulting solid product.

[0027] This invention does not impose any special limitations on the method of uniform mixing; conventional techniques used by those skilled in the art can be selected, such as ultrasonic or magnetic stirring.

[0028] A second aspect of the present invention provides a bismuth molybdate / CNT heterojunction prepared by the above preparation method.

[0029] A third aspect of the present invention provides a bismuth molybdate / CNT heterojunction modified electrode, comprising a substrate electrode and an electrode modification material; wherein the electrode modification material is the aforementioned bismuth molybdate / CNT heterojunction.

[0030] In a preferred embodiment of the present invention, the method for preparing the bismuth molybdate / CNT heterojunction modified electrode includes the following steps: A bismuth molybdate / CNT heterojunction was prepared by dispersing it in an aqueous ethanol solution, which was then coated onto the surface of a substrate electrode and dried to obtain the bismuth molybdate / CNT heterojunction modified electrode. The ethanol-water solution has a mass concentration of 50 wt%; the bismuth molybdate / CNT heterojunction concentration in the dispersion is 2 mg / mL. The substrate electrode is a glassy carbon electrode (GCE).

[0031] A fourth aspect of the present invention provides an electrochemical sensor comprising the above-described bismuth molybdate / CNT heterojunction modified electrode.

[0032] The fifth aspect of the present invention provides an application of the above-described bismuth molybdate / CNT heterojunction or the above-described bismuth molybdate / CNT heterojunction modified electrode or the above-described electrochemical sensor in the detection of diuron in water.

[0033] Unless otherwise specified, the technical solutions described in this invention are all conventional solutions in the field, and the reagents or raw materials used are all purchased from commercial channels or are publicly available unless otherwise specified.

[0034] To better understand the present invention, the following embodiments further illustrate the content of the present invention, but the content of the present invention is not limited to the following embodiments.

[0035] Example 1 This embodiment provides a bismuth molybdate / CNT heterojunction, and the preparation steps are as follows: S1: Add Bi(NO3)3·5H2O (1.50 mmol) and Na2MoO4·2H2O (0.75 mmol) to 50 mL of ethylene glycol, and sonicate for 30 min to mix the solution evenly to obtain the first solution; S2: Add 200 mg of carbon nanotubes to 30 mL of ethanol and sonicate for 30 min to mix the solution evenly, thus obtaining the second solution.

[0036] S3: Mix the first and second solutions, stir magnetically for 30 min to make the solution uniform, then transfer it into a 100 mL polytetrafluoroethylene-lined autoclave and maintain it at 160℃ for 24 h. After the reaction is complete, collect the solid product, wash the solid product three times with deionized water and ethanol respectively, and dry it in a 60℃ drying oven for 12 h to obtain bismuth molybdate / carbon nanotube (Bi2MoO6 / carbon nanotube) heterostructure.

[0037] Figure 1 The image shows a SEM image of pure Bi2MoO6. It can be seen from the image that the microsphere structure of Bi2MoO6 is composed of a series of mutually perpendicular or parallel nanosheets. The thickness of the nanosheets is about 10 nm, and they are uniform.

[0038] Figure 2 The image shows a SEM image of the Bi₂MoO₆ / carbon nanotube heterostructure. It can be seen that a large number of Bi₂MoO₆ nanosheets are attached to the surface of the carbon nanotubes, indicating that the Bi₂MoO₆ / carbon nanotube heterostructure has been successfully obtained.

[0039] Figure 3 XRD was used to investigate the crystal structures of Bi₂MoO₆, carbon nanotubes, and Bi₂MoO₆ / carbon nanotube heterostructures. For Bi₂MoO₆, sharp and distinct diffraction peaks were observed at 2θ = 10.7°, 25.5°, 28.2°, 32.4°, 46.8°, 55.4°, and 58.4°, indicating good crystallinity. These typical peaks can be indexed to the (020), (111), (131), (200), (260), (331), and (191) crystal planes. For carbon nanotubes, a diffraction peak at 2θ = 25.7° was observed, indexed to the (111) crystal plane. The XRD patterns of the Bi₂MoO₆ / carbon nanotube heterostructures were almost identical to those of pure Bi₂MoO₆ and carbon nanotubes.

[0040] Example 2 This embodiment provides a bismuth molybdate / CNT heterojunction modified electrode, and the preparation steps are as follows: (1) The Bi2MoO6 / carbon nanotube heterojunction prepared in Example 1 was added to a 50wt% ethanol solution and ultrasonically dispersed for 30 min to obtain a Bi2MoO6 / carbon nanotube dispersion with a concentration of 2 mg / mL. Then, it was dropped onto a clean and dry GCE surface prepared in advance, spread evenly, dried, and the solvent was evaporated to form a film without any delamination. The Bi2MoO6 / carbon nanotube heterojunction modified electrode was thus obtained.

[0041] Example 3 The Bi₂MoO₆ / carbon nanotube heterojunction modified electrode from Example 2 was used as the working electrode in the electrochemical determination of diuron in environmental water. The procedure included the following steps: Step 1: Connect one end of the working electrode, counter electrode (platinum electrode), and reference electrode (mercury / mercuric oxide electrode) to the electrochemical workstation. Place the other ends of the working electrode, counter electrode, and reference electrode in an electrolyte solution containing pesticide residues of known concentration in the electrolytic cell. Use electrochemical anodic stripping voltammetry for detection. Set the enrichment potential to -1.1V. Stir the solution while enriching. After the set enrichment time is reached, stop stirring and let it stand for the set time. Apply a positive scanning voltage with a voltage scan range of -1V to 0.3V to the three-electrode system. Record the changes in current and voltage using the electrochemical workstation to obtain a current-voltage curve. Plot a standard curve corresponding to the pesticide residue with pesticide residue concentration as the abscissa and peak current as the ordinate to obtain the regression equation and determine the linear or nonlinear relationship between pesticide residue concentration and peak current. Step 2: Place the environmental water sample to be tested into the electrolytic cell and repeat Step 1. Use an electrochemical workstation to detect the peak current corresponding to pesticide residues in the sample, substitute it into the regression equation, and calculate the concentration of pesticide residues in the sample.

[0042] Figure 4 This is the CV response diagram of the Bi2MoO6 / carbon nanotube heterostructure of the present invention to diuron ( Figure 4 (A) and EIS diagram ( Figure 4 Research on (B) in China. Figure 4 The A / C CV curves show that the redox peaks for GCE, Bi₂MoO₆, carbon nanotubes, and Bi₂MoO₆ / carbon nanotubes are 5.69 × 10⁻⁶. -5 5.98×10 -5 7.24×10 -5 and 8.25×10 -5 A. It can be seen that Bi2MoO6 / carbon nanotubes have higher electrical conductivity than pure Bi2MoO6 and carbon nanotubes. Figure 4 Figure B shows the electrochemical impedance spectroscopy (EIS) of the Bi₂MoO₆ / carbon nanotube heterostructure. The electrochemical performance of GCE, carbon nanotubes, Bi₂MoO₆, and Bi₂MoO₆ / carbon nanotube was examined. The larger semicircle represents the response of GCE and Bi₂MoO₆, and the smaller semicircle represents the response of carbon nanotubes and Bi₂MoO₆ / carbon nanotube. The impedances of Bi₂MoO₆ / carbon nanotube, carbon nanotube, Bi₂MoO₆, and GCE are 35 Ω, 64 Ω, 399 Ω, and 470 Ω, respectively. This indicates that Bi₂MoO₆ / carbon nanotube significantly enhances electron transport capability and accelerates charge transfer between the working electrode and the electrolyte solution.

[0043] Figure 5 This is a graph showing the detection results of diuron using the electrochemical sensor prepared according to the present invention. Figure 5 Figure A shows the DPV (differential pulse voltammetry) response of different concentrations of diuron. Figure 5 In the diagram, B represents the relevant linear fitting equation. (Example:) Figure 5 As shown in Figure A, when the concentration of diuron gradually increases within the range of 0.05-40.0 μmol / L, the current signal also exhibits a linear increase. The rapid increase in current signal is due to the abundant diuron adsorption active sites on the surface of Bi₂MoO₆ / carbon nanotubes in the diuron solution, which promotes the rapid increase in current. Figure 5 As shown in Figure B, the equation obtained by linearly fitting the current signal of diuron concentration within the diuron concentration range to the diuron concentration is expressed as: I pc = 0.01 + 0.20 C, the linear correlation coefficient is R 2 = 0.9910, and the detection limit is 17 nmol / L. This indicates that the Bi2MoO6 / carbon nanotube heterojunction modified electrode has high sensitivity, wide detection range, and low detection limit for detecting diuron solution.

[0044] Figure 6 Reproducibility of the Bi2MoO6 / carbon nanotube composite film modified electrode prepared in the embodiments of the present invention in diuron solution ( Figure 6 (A) and anti-interference ( Figure 6 (B) Research. For example... Figure 6 As shown in Figure A, the results of 11 repeated tests on the same electrode show a current value of 1.74 × 10⁻⁶. -6 -1.85×10 -6 Between A and B. Although the response to diuron standard solution decreased with increasing number of cycles, it remained within an acceptable range, with a relative standard deviation of 1.98%. The study indicates that the sensor has a highly repeatable response across multiple cycles. From Figure 6 In Figure B, the response to diuron can be observed when interfering substances are added. Notably, after the addition of interfering substances, the peak current value of the blank control (diuron standard solution) did not change significantly compared to the peak current values ​​with different interfering substances added, with a relative standard deviation of 4.1%. The experiment demonstrates that the Bi2MoO6 / carbon nanotube heterojunction modified electrode has good anti-interference performance in detecting diuron solution.

[0045] In summary, the bismuth molybdate / carbon nanotube heterostructure electrochemical sensor constructed in this invention has the characteristics of high sensitivity, rapid detection, and good anti-interference ability, and can detect diuron rapidly and efficiently.

[0046] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a bismuth molybdate / CNT heterojunction, characterized in that, Includes the following steps: The molybdenum source, bismuth source, and first solvent are mixed evenly to obtain the first solution; Carbon nanotubes are uniformly dispersed in a second solvent to obtain a second solution; After the first solution and the second solution are mixed evenly, a solvothermal reaction is carried out to obtain the bismuth molybdate / CNT heterojunction.

2. The preparation method according to claim 1, characterized in that, The first solvent is ethylene glycol, and the second solvent is ethanol.

3. The preparation method according to claim 1, characterized in that, The molybdenum source is sodium molybdate, and the bismuth source is bismuth nitrate.

4. The preparation method according to claim 1 or 3, characterized in that, The molar ratio of molybdenum in the molybdenum source to bismuth in the bismuth source is 1:(1~3); the ratio of molybdenum to carbon nanotubes in the molybdenum source is 0.5~1 mmol:100~300 mg.

5. The preparation method according to claim 1, characterized in that, The solvothermal reaction is carried out at a temperature of 140~160℃ for a time of 18~36 h.

6. The bismuth molybdate / CNT heterojunction prepared by the method described in claim 1.

7. A bismuth molybdate / CNT heterojunction modified electrode, characterized in that, It includes a base electrode and an electrode modification material; the electrode modification material is the bismuth molybdate / CNT heterojunction as described in claim 6.

8. An electrochemical sensor, characterized in that, Includes the bismuth molybdate / CNT heterojunction modified electrode as described in claim 7.

9. The application of the bismuth molybdate / CNT heterojunction of claim 6, the bismuth molybdate / CNT heterojunction modified electrode of claim 7, or the electrochemical sensor of claim 8 in the detection of diuron in water.

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