An electrochemical sensor for detecting uranyl ions, and a preparation method and application thereof

Abstract

The application relates to the field of detection of uranyl ions, in particular to an electrochemical sensor for detecting uranyl ions and a preparation method and application thereof, which comprises a three-electrode system composed of a working electrode, a reference electrode and a counter electrode; the working electrode comprises a substrate electrode, a cobalt trioxide tetrahydrate nanoparticle modification layer and a silver nanoparticle layer arranged in sequence; the electrochemical sensor can be used for detecting uranyl ions, has a wide detection range and a low detection limit, and has stable performance and good application prospect.

Description

Technical Field

[0001] This invention relates to the field of uranyl ion detection technology, and in particular to an electrochemical sensor for detecting uranyl ions, its preparation method, and its application. Background Technology

[0002] Uranium, as a naturally occurring metal, can spontaneously decay, releasing invisible radiation and exhibiting a certain degree of radioactivity, which can harm the human body. Uranium-containing wastewater and materials can severely impact daily life; high doses of exposure can cause death; while low doses may not cause obvious symptoms, they can disrupt the immune, circulatory, and reproductive systems, increasing the risk of cancer. Furthermore, uranium possesses strong heavy metal toxicity, leading to cancer, chronic poisoning, and other health problems. Therefore, researching and developing methods for detecting heavy metal pollutants like lead and improving the detection of trace amounts of uranium is of great significance.

[0003] Electrochemical sensors, with their excellent characteristics such as fast response time, high sensitivity, high speed, and low cost, have become a research hotspot in detection. Currently, bare working electrodes (such as glassy carbon electrodes) or electrodes modified with only one material suffer from poor conductivity and slow electron transfer, leading to unsatisfactory electrochemical detection performance for uranyl ions. Although modifying the electrode with multiple improvement materials can improve the sensor's detection performance to some extent, the use of composite materials undoubtedly increases the cost and difficulty of fabrication.

[0004] The increasingly mature development of electrochemical detection technology has provided various feasible technical means for the rapid detection of uranyl ions in environmental samples, such as potentiometric titration, electrophoresis, and voltammetry. Using electrochemical sensors to detect uranyl ions offers advantages such as high sensitivity, ease of operation, small reagent usage, and low cost, thus becoming a research hotspot in environmental protection work.

[0005] Therefore, an electrochemical sensor for detecting uranyl ions is proposed, along with its preparation method and application. Summary of the Invention

[0006] The purpose of this invention is to provide an electrochemical sensor for detecting uranyl ions, its preparation method, and its application in order to solve the above-mentioned problems.

[0007] In a first aspect, the present invention provides an electrochemical sensor comprising a three-electrode system consisting of a working electrode, a reference electrode, and a counter electrode; wherein the working electrode comprises a substrate electrode, a cobalt tetroxide nanoparticle modification layer, and a silver nanoparticle layer arranged sequentially.

[0008] Preferably, the substrate electrode is selected from one of glassy carbon electrode, metal oxide electrode, and metal electrode.

[0009] More preferably, the substrate electrode is a glassy carbon electrode.

[0010] Preferably, the reference electrode is one of a calomel electrode, a silver chloride electrode, a mercurous sulfate electrode, and a mercuric oxide electrode.

[0011] More preferably, the reference electrode is a calomel electrode, and the calomel electrode is a saturated calomel electrode.

[0012] Preferably, the counter electrode is one of a platinum electrode and a titanium electrode.

[0013] More preferably, the counter electrode is a platinum electrode.

[0014] Preferably, the platinum electrode is a platinum wire electrode.

[0015] Preferably, the cobalt tetroxide nanoparticles in the cobalt tetroxide nanoparticle modification layer are made from ZIF-67 through high-temperature sintering.

[0016] More preferably, the cobalt tetroxide nanoparticles in the cobalt tetroxide nanoparticle modification layer are prepared by the following method: ZIF-67 is loaded into a porcelain crucible, heated to 500°C in a muffle furnace for 2 hours, the heating rate is 1°C / min, and then cooled to obtain black cobalt tetroxide nanoparticles.

[0017] Preferably, ZIF-67 is prepared by the following method: cobalt nitrate hexahydrate and 2-methylimidazole are dissolved in methanol solution, and then the 2-methylimidazole alcohol solution is slowly added to the cobalt nitrate hexahydrate alcohol solution while stirring. After stirring, the mixture is allowed to stand for 24 hours. The mixture is collected by centrifugation, washed with methanol, and finally dried to obtain ZIF-67.

[0018] Preferably, the drying is carried out at 60°C for 12 hours.

[0019] Secondly, the present invention provides a method for preparing the electrochemical sensor described in the first aspect, comprising the following steps:

[0020] The base electrode is sequentially modified with a cobalt tetroxide nanoparticle layer and a silver nanoparticle layer to obtain a silver / cobalt tetroxide working electrode.

[0021] Preferably, the method for preparing the electrochemical sensor includes the following steps:

[0022] 1) Cobalt tetroxide nanoparticle dispersion is coated onto the surface of the substrate electrode and dried to form a cobalt tetroxide nanoparticle modification layer on the surface of the substrate electrode.

[0023] 2) The substrate electrode treated in step 1) is immersed in an electrolyte containing silver nitrate for electrodeposition to form a silver nanoparticle layer on the surface of the cobalt tetroxide nanoparticle modified layer, thus obtaining the working electrode.

[0024] 3) The working electrode, reference electrode and counter electrode from step 2) are combined to form a three-electrode system, thus obtaining the electrochemical sensor.

[0025] Preferably, the substrate electrode in step 1) has undergone surface pretreatment and activation treatment.

[0026] Preferably, the specific process of the surface pretreatment is as follows: the surface of the substrate electrode is polished into a mirror surface by Al2O3 powder with diameters of 0.3 and 0.05 μm in sequence, then rinsed with water and ultrasonically cleaned in anhydrous ethanol and water in sequence, then taken out and washed with water and air-dried at room temperature.

[0027] Preferably, the specific process of the activation treatment is as follows: the substrate electrode is immersed in sulfuric acid solution until the curve is stable when scanned by cyclic voltammetry at a potential of -1.0V to 1.0V.

[0028] Preferably, the silver nitrate-containing electrolyte in step 2) is a mixture of silver nitrate and potassium nitrate solution.

[0029] Preferably, the silver nitrate content of the electrolyte containing silver nitrate in step 2) is 0.005 mmol / L.

[0030] More preferably, the potassium nitrate content of the silver nitrate electrolyte in step 2) is 0.1 mmol / L.

[0031] Preferably, the electrodeposition method used in step 2) is the constant potential method, with a deposition potential of -0.3V and a deposition time of 300s.

[0032] Thirdly, the present invention provides a method for detecting uranyl ions, comprising the following steps:

[0033] Using the electrochemical sensor described in the first aspect, differential pulse voltammetry was performed on the sample to be tested to measure the current value of the reduction peak. Then, the concentration of uranium ions in the sample to be tested was quantitatively analyzed according to the uranium ion standard curve.

[0034] Preferably, the method for detecting uranyl ions includes the following steps:

[0035] 1) Plotting the standard curve: The working electrode in the electrochemical sensor described in the first or second aspect is placed in uranyl ion solutions of different concentrations, and the differential pulse voltammetry is used for scanning. The current magnitude of the reduction peak and the concentration of uranyl ion solution are used as the raw data to analyze and plot the standard curve.

[0036] 2) Sample detection: Place the working electrode from step 1) on the liquid sample to be tested and scan it using differential pulse voltammetry to measure the current magnitude of the reduction peak. Calculate the uranyl ion content in the liquid sample to be tested based on the standard curve from step 1).

[0037] Preferably, the differential pulse voltammetry method has the following parameter settings: initial potential: 0.2V, termination potential: -0.4V, potential increment: 4mV, pulse amplitude: 50mV, pulse width: 50, sampling width: 16.7ms, and pulse period: 200ms.

[0038] Preferably, the uranyl ion solutions of different concentrations in step 1) are prepared by mixing uranyl nitrate and 0.5 mol / L sulfuric acid solution.

[0039] Preferably, the concentration of the uranyl ion solution in step 1) is 1×10⁻⁶. -5 mol / L~1.0×10 -2 mo1 / L.

[0040] Preferably, the linear correlation coefficient of the standard curve in step 1) is R. 2 =0.9982.

[0041] The beneficial effects of this invention are:

[0042] The electrochemical sensor of this invention can be used for the detection of uranyl ions, has a wide detection range and a low detection limit, the reaction is carried out at room temperature, the performance is stable, and it has good application prospects.

[0043] Specifically:

[0044] 1) The electrochemical sensor of the present invention has good electron transfer properties, which can effectively transfer electrons generated by the reaction, enabling the detection of uranyl ions and a fast reaction rate;

[0045] 2) The electrochemical sensor of the present invention has good reproducibility and stability, can accurately detect uranyl ions, and has strong anti-interference ability;

[0046] 3) The electrochemical sensor of this invention can be used for the detection of uranyl ions in acidic aqueous solutions, exhibiting high specificity at a concentration of 1×10⁻⁶. -5 mol / L~1.0×10 -2 Within the range of mol / L, the response current exhibits a linear relationship with the change in uranyl ion concentration, with the following linear relationships: I(μA) = -7.22601c - 15.58742, and a correlation coefficient R. 2=0.9982; the detection limit is 0.01 mmol / L (S / N=3). The reaction is carried out at room temperature, the performance is stable, and it has good application prospects. Attached Figure Description

[0047] Figure 1 Differential pulse voltammetry plots of the electrochemical sensors of Examples 1-2 with the same concentration of uranyl ions added to a 0.5 mol / L sulfuric acid solution;

[0048] Figure 2 The differential pulse voltammetry diagrams of the electrochemical sensor in Example 3 after adding different concentrations of uranyl ions to a 0.5 mol / L sulfuric acid solution are shown.

[0049] Figure 3 The graph shows the linear relationship between the response current generated by the electrochemical sensor in Example 3 after adding different concentrations of uranyl ions to a 0.5 mol / L sulfuric acid solution and the different concentrations of uranyl ions. Detailed Implementation

[0050] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0051] The present invention will be further explained and described below with reference to specific embodiments.

[0052] The preparation of the potassium ferricyanide standard solution used in this invention includes the following steps: under the condition of 20-25℃ (room temperature), accurately weigh 0.1645g of potassium ferricyanide and 7.4500g of potassium chloride, then dissolve them in ultrapure water and make up to 100mL to obtain potassium ferricyanide standard solution (5mM K3Fe(CN)6+1M KCl).

[0053] The preparation of the silver nitrate electrolyte used in this invention includes the following steps: under the condition of 20-25℃ (room temperature), accurately weigh 1.01g KNO3 and 0.085g AgNO3, then dissolve them in ultrapure water and make up to 100mL to obtain a 0.1mol / L KNO3 + 0.005mol / L AgNO3 solution.

[0054] Examples 1-3 show that cobalt tetroxide nanoparticles were prepared by the following method: Cobalt nitrate hexahydrate and 2-methylimidazole were dissolved separately in methanol solution. Then, the 2-methylimidazole alcohol solution was slowly added to the cobalt nitrate hexahydrate alcohol solution under stirring. After stirring, the mixture was allowed to stand for 24 hours. The mixture was collected by centrifugation, washed with methanol, and finally dried to obtain ZIF-67. ZIF-67 was placed in a porcelain crucible and sintered in a muffle furnace at 500°C for 2 hours at a heating rate of 1°C / min. After cooling, black cobalt tetroxide nanoparticles were obtained.

[0055] Examples 1-3: Cobalt tetroxide nanoparticle dispersions were prepared by the following method: Under conditions of 20-25°C (room temperature), 1 mg of cobalt tetroxide nanoparticles were accurately weighed into a clean and dry glass bottle, 1 mL of distilled water and 2 mL of ethanol were added, and the mixture was stirred evenly with the aid of ultrasound; then 20 μL of 5 wt% Nafion solution was added, and the mixture was stirred evenly again with ultrasound to obtain the cobalt tetroxide nanoparticle dispersion.

[0056] Unless otherwise specified, the electrochemical workstation used in this invention is manufactured by Shanghai Chenhua Instrument Co., Ltd., model CHI660E; the platinum electrode used in this invention is a platinum wire electrode manufactured by Wuhan Gaoshi Ruilian Technology Co., Ltd.; the glassy carbon electrode, platinum electrode, and saturated calomel electrode used in this invention are all commercially available products.

[0057] In the accompanying drawings of this invention, the signs of current and potential only indicate direction, and the absolute values ​​of current and potential represent the current value or magnitude and the potential value or magnitude, respectively. Unless otherwise specified, current and potential in this article refer to the magnitude of current and the magnitude of potential, respectively.

[0058] Example 1

[0059] This embodiment provides a method for preparing a cobalt tetroxide nanoparticle-glassy carbon electrode, including the following steps:

[0060] 1) At room temperature (20-25℃), the glassy carbon electrode (3mm in diameter) was polished to a mirror finish with Al2O3 powder with diameters of 0.3µm and 0.05µm, then rinsed with distilled water and ultrasonically cleaned for 2 minutes each in anhydrous ethanol and distilled water. The glassy carbon electrode was then placed in a 0.5 mol / L sulfuric acid solution and activated by cyclic voltammetry at -1.0V to 1.0V until stable. The electrode surface was then washed with distilled water and placed in 15 mL of potassium ferricyanide solution and detected by cyclic voltammetry at 0V to 0.8V for one cycle. The electrode was then removed, rinsed with distilled water, and air-dried at room temperature to obtain the pretreated glassy carbon electrode.

[0061] 2) At room temperature (20-25°C), the cobalt tetroxide nanoparticle dispersion is coated onto the glassy carbon electrode surface treated in step 1), and dried to form a cobalt tetroxide nanoparticle modification layer on the glassy carbon electrode surface.

[0062] 3) At room temperature (20-25°C), the working electrode and platinum electrode from step 2) are used as the counter electrode and the saturated calomel electrode is used as the reference electrode to form a three-electrode system, thus obtaining the electrochemical sensor.

[0063] Example 2

[0064] This embodiment provides a method for preparing a silver nanoparticle-cobalt tetroxide nanoparticle-glassy carbon electrode, including the following steps:

[0065] 1) At room temperature (20-25℃), the glassy carbon electrode (3mm in diameter) was polished to a mirror finish with Al2O3 powder with diameters of 0.3µm and 0.05µm, then rinsed with distilled water and ultrasonically cleaned for 2 minutes each in anhydrous ethanol and distilled water. The glassy carbon electrode was then placed in a 0.5 mol / L sulfuric acid solution and activated by cyclic voltammetry at -1.0V to 1.0V until stable. The electrode surface was then washed with distilled water and placed in 15 mL of potassium ferricyanide solution and detected by cyclic voltammetry at 0V to 0.8V for one cycle. The electrode was then removed, rinsed with distilled water, and air-dried at room temperature to obtain the pretreated glassy carbon electrode.

[0066] 2) At room temperature (20-25°C), the cobalt tetroxide nanoparticle dispersion is coated onto the glassy carbon electrode surface treated in step 1), and dried to form a cobalt tetroxide nanoparticle modification layer on the glassy carbon electrode surface.

[0067] 3) Immerse the glassy carbon electrode treated in step 2) in 15 ml of electrolyte containing silver nitrate, and use a constant potential method to electrodeposit for 300 s at -0.3 V to form a silver nanoparticle layer on the surface of the cobalt tetroxide nanoparticle modified layer, thus obtaining the working electrode.

[0068] 4) At room temperature (20-25°C), the working electrode and platinum electrode from step 3) are used as the counter electrode and the saturated calomel electrode is used as the reference electrode to form a three-electrode system, thus obtaining the electrochemical sensor.

[0069] The electrochemical performance of these two electrochemical sensors was tested, and the specific process is as follows:

[0070] Electrochemical experiments were conducted at room temperature by immersing the two three-electrode systems described above in 10 mL of a 0.5 mol / L sulfuric acid solution with a uranyl ion concentration of 1 mmol / L. Differential pulse voltammetry was used during the tests, with an unmodified glassy carbon electrode serving as the blank control. Figure 1As shown. (The differential pulse voltammetry method has the following parameter settings: initial potential: 0.2V, termination potential: -0.4V, potential increment: 4mV, pulse amplitude: 50mV, pulse width: 50, sampling width: 16.7ms, and pulse period: 200ms.) Figure 1 It can be seen that the unmodified glassy carbon electrode did not show a significant reduction peak, while the cobalt tetroxide nanoparticle-glassy carbon electrode showed a reduction peak near -0.12V. This may be because the cobalt tetroxide nanoparticles have a porous structure and a large specific surface area, which allows them to adsorb more uranyl ions, thus promoting uranyl ion enrichment. The reduction peak potential of uranyl ions on the silver nanoparticle-cobalt tetroxide nanoparticle-glassy carbon electrode appeared near -0.15V, and the peak current was enhanced compared to the cobalt tetroxide nanoparticle-glassy carbon electrode. This may be because the silver nanoparticle-cobalt tetroxide nanoparticle-glassy carbon electrode has a better catalytic ability for uranyl ions, indicating that the silver nanoparticle-cobalt tetroxide nanoparticle-glassy carbon electrode holds promise for the detection of uranyl ions.

[0071] Example 3

[0072] This embodiment provides a method for preparing a silver nanoparticle-cobalt tetroxide nanoparticle-glassy carbon electrode, including the following steps:

[0073] 1) At room temperature (20-25℃), the glassy carbon electrode (3mm in diameter) was polished to a mirror finish with Al2O3 powder with diameters of 0.3µm and 0.05µm, then rinsed with distilled water and ultrasonically cleaned for 2 minutes each in anhydrous ethanol and distilled water. The glassy carbon electrode was then placed in a 0.5 mol / L sulfuric acid solution and activated by cyclic voltammetry at -1.0V to 1.0V until stable. The electrode surface was then washed with distilled water and placed in 15 mL of potassium ferricyanide solution and detected by cyclic voltammetry at 0V to 0.8V for one cycle. The electrode was then removed, rinsed with distilled water, and air-dried at room temperature to obtain the pretreated glassy carbon electrode.

[0074] 2) At room temperature (20-25°C), the cobalt tetroxide nanoparticle dispersion is coated onto the glassy carbon electrode surface treated in step 1), and dried to form a cobalt tetroxide nanoparticle modification layer on the glassy carbon electrode surface.

[0075] 3) Immerse the glassy carbon electrode treated in step 2) in 15 ml of electrolyte containing silver nitrate, and use a constant potential method to electrodeposit for 300 s at -0.3 V to form a silver nanoparticle layer on the surface of the cobalt tetroxide nanoparticle modified layer, thus obtaining the working electrode.

[0076] 4) At room temperature (20-25°C), the working electrode and platinum electrode from step 3) are used as the counter electrode and the saturated calomel electrode is used as the reference electrode to form a three-electrode system, thus obtaining the electrochemical sensor.

[0077] This embodiment provides an analysis and testing method, including the following steps:

[0078] 1) At room temperature, a three-electrode system was constructed using a silver nanoparticle-cobalt tetroxide nanoparticle-glassy carbon electrode as the working electrode, a saturated calomel electrode as the reference electrode, and a platinum wire electrode as the counter electrode. This system was then inserted into a 0.5 mol / L sulfuric acid solution containing uranyl ions and connected to an electrochemical workstation. 2) Construction of the standard curve: (20–25 °C) At room temperature, a 1 mol / L uranyl ion standard solution was diluted with 0.5 mol / L sulfuric acid to prepare standard solutions with concentrations of 0.01 mmol / L, 0.05 mmol / L, 0.1 mmol / L, 0.2 mmol / L, 0.4 mmol / L, 0.8 mmol / L, 1 mmol / L, 2 mmol / L, 3 mmol / L, 4 mmol / L, 5 mmol / L, 6 mmol / L, 8 mmol / L, and 10 mmol / L.

[0079] The test was conducted using the differential pulse voltammetry test conditions and methods described in Examples 1 and 2, and the raw data obtained by scanning the differential pulse voltammetry was used to plot the magnitude of the reduction peak current (i.e., the absolute value of the reduction peak current) at approximately -0.15V against the concentration of uranyl ions in the standard solution to form a standard curve.

[0080] The differential pulse voltammetry plots of the electrochemical sensor in Example 3 after adding different concentrations of uranyl ions to a 0.5 mol / L sulfuric acid solution are shown below. Figure 2 As shown.

[0081] Depend on Figure 2 It can be seen that by utilizing the conductivity and high specific surface area of ​​cobalt tetroxide nanoparticles and silver nanoparticles, effective catalysis of the substrate can be achieved, and the reduction peak current generated on the electrode increases with the increase of concentration.

[0082] The linear relationship between the response current of the electrochemical sensor in Example 3 after adding different concentrations of uranyl ions to a 0.5 mol / L sulfuric acid solution and the different uranyl ion concentrations is shown in the graph below. Figure 3 As shown.

[0083] Depend on Figure 3 It can be seen that the electrochemical sensor in Example 3 has a substrate detection range of 1×10⁻⁶. -5 mol / L~1.0×10 - 2The response current of the catalytic reduction reaction, measured in mol / L, showed a linear relationship with the change in uranyl ion concentration. The relationship between the response current and the uranyl ion concentration was: I(μA) = -7.22601c - 15.58742, with a linear correlation coefficient R0. 2 The value was 0.9982, and the detection limit was 0.1 mmol / L.

[0084] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. An application of an electrochemical sensor in uranyl ion detection, wherein the electrochemical sensor is a three-electrode system consisting of a working electrode, a reference electrode, and a counter electrode, characterized in that, The working electrode comprises a base electrode, a cobalt tetroxide nanoparticle modification layer, and a silver nanoparticle layer arranged sequentially. The fabrication steps of the electrochemical sensor are as follows: 1) Cobalt tetroxide nanoparticle dispersion is coated on the surface of the substrate electrode and dried to form a cobalt tetroxide nanoparticle modification layer on the surface of the substrate electrode. The cobalt tetroxide nanoparticles in the cobalt tetroxide nanoparticle modification layer are made by high-temperature sintering of ZIF-67. 2) The substrate electrode treated in step 1) is immersed in silver nitrate solution for electrodeposition to form a silver nanoparticle layer on the surface of the cobalt tetroxide nanoparticle modified layer, thus obtaining the working electrode; 3) The working electrode, reference electrode and counter electrode from step 2) are combined to form a three-electrode system, thus obtaining the electrochemical sensor.

2. The application of the electrochemical sensor according to claim 1 in uranyl ion detection, characterized in that: The base electrode is selected from glassy carbon electrode, metal oxide electrode, and metal electrode; the reference electrode is selected from calomel electrode, silver chloride electrode, mercurous sulfate electrode, and mercuric oxide electrode; and the counter electrode is selected from platinum electrode and titanium electrode.

3. The application of the electrochemical sensor according to claim 2 in uranyl ion detection, characterized in that: The base electrode is a glassy carbon electrode, the reference electrode is a calomel electrode, and the counter electrode is a platinum electrode.

4. The application of the electrochemical sensor according to claim 2 in the detection of uranyl ions, characterized in that: The calomel electrode is a saturated calomel electrode, and the platinum electrode is a platinum wire electrode.

5. The application of the electrochemical sensor according to claim 1 in uranyl ion detection, characterized in that: The preparation method of the cobalt tetroxide nanoparticle dispersion in step 1) is as follows: 1 mg of cobalt tetroxide nanoparticles are placed in a clean and dry glass bottle, 1 mL of distilled water and 2 mL of ethanol are added, and the mixture is stirred evenly under ultrasonic assistance; then 20 μL of 5 wt% Nafion solution is added, and the mixture is stirred evenly again under ultrasonic assistance; the electrodeposition method in step 2) is the constant potential method, the deposition potential is -0.3 V, and the deposition time is 300 s.

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