Electrochemical sensor as well as preparation method and application thereof

Abstract

The invention discloses an electrochemical sensor as well as a preparation method and application thereof, and relates to the technical field of sensors. The electrochemical sensor comprises a working electrode, a reference electrode and a counter electrode, wherein the surface of the working electrode of the electrochemical sensor contains a nano composite material; the nano composite material comprises a nitrogen-doped carbon-coated ferric oxide material and conductive nano particles. The electrochemical sensor disclosed by the invention has high sensitivity and high stability, has strong adsorption capacity on a target object when being applied to the field of detection, is small in relative standard deviation of test results obtained after being placed for different days, is particularly suitable for detection of 2, 4-dichlorophenol, and has the advantages of wide detection linear range, high sensitivity and the like.

Description

Technical Field

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

[0002] Chlorination disinfection is the most common treatment process for aquaculture water to eliminate pathogens. However, chlorine disinfectants can react with natural organic matter (chlorophenols, phenols, lignin, and humic acid, etc.) and antibiotics to form disinfection byproducts (DBPs). 2,4-Dichlorophenol (2,4-DCP) is a common DBP, detected in aquaculture water, wastewater, and tap water at levels in the ng / L range. 2,4-Dichlorophenol is toxic to aquatic organisms, has high permeability and the potential to cause tissue damage, and also has mutagenic and carcinogenic effects, posing a significant threat to the aquatic environment. Therefore, accurate detection of 2,4-dichlorophenol in aquaculture water and aquatic products is of great significance for food and biosafety monitoring.

[0003] Electrochemical sensors possess advantages such as high sensitivity, speed, and efficiency, enabling real-time rapid detection in the field and finding wide applications in biomedicine, food testing, and environmental analysis. However, in practical applications, complex sample matrices can interfere with detection signals and lead to the deactivation of electrochemically modified materials. Therefore, developing highly selective and interference-resistant electrochemically modified materials, along with rapid sample pretreatment techniques suitable for electrochemical sensing analysis, is crucial for improving the accuracy of point electrochemical analysis. However, traditional electrochemically modified materials for electrochemical sensors are mostly prepared from traditional solid materials such as noble metals and pure metal oxides, which suffer from insufficient adsorption capacity, poor interference resistance, and difficulty in simultaneously achieving both material conductivity and active sites, thus weakening the sensor's electrochemical response signal and reducing sensitivity. Therefore, there is an urgent need to develop a composite electrochemically modified material that combines high adsorption capacity, rapid electron transfer, and anti-contamination capabilities to improve the performance of electrochemical sensors. Summary of the Invention

[0004] The present invention aims to at least solve one of the aforementioned technical problems existing in the prior art. Therefore, one objective of the present invention is to provide an electrochemical sensor that, by designing a special nanocomposite material on the surface of the working electrode, enables the electrochemical sensor to possess high adsorption capacity, rapid electron transfer, and anti-fouling capabilities.

[0005] A second aspect of the present invention is to provide a method for preparing an electrochemical sensor.

[0006] A third aspect of the present invention is to provide an application of an electrochemical sensor.

[0007] A fourth aspect of the present invention is to provide a method for detecting 2,4-dichlorophenol.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A first aspect of the present invention provides an electrochemical sensor, including a working electrode, a reference electrode, and a counter electrode, wherein the surface of the working electrode of the electrochemical sensor contains a nanocomposite material; the nanocomposite material includes nitrogen-doped carbon-coated ferric oxide material and conductive nanoparticles.

[0009] Generally, bare electrodes (such as glassy carbon electrodes) have poor catalytic ability for the redox reactions of organic compounds, resulting in low redox signals during the electroanalysis of organic compounds. This invention modifies the electrode using nanocomposite materials, significantly improving the electrochemical response signal. Furthermore, in addition to good catalytic activity, this nanocomposite material also exhibits high adsorption capacity. When used in detection applications, it can improve the interaction between the analyte (e.g., 2,4-dichlorophenol) and the nanocomposite material, thereby enhancing detection sensitivity and other detection effects.

[0010] Specifically, the nanocomposite material on the surface of the working electrode of this invention includes conductive nanoparticles, which not only improve electron transport efficiency and active site density, but also provide a good adhesion interface for nitrogen-doped carbon-coated ferric oxide material, enhancing overall structural stability. The large specific surface area of ​​nitrogen-doped carbon-coated ferric oxide material provides abundant active sites, its hollow structure shortens the diffusion path and accommodates volume changes, and its excellent conductivity promotes electron transport. Furthermore, nitrogen doping not only further improves the conductivity of carbon, but also enhances its catalytic activity and affinity for specific analytes by regulating the surface electronic structure. Therefore, the nanocomposite material of this invention, as an electrode sensitizing material, possesses high specific surface area, good conductivity, electrocatalytic activity, and excellent stability. By synergistically constructing a high-performance electrochemical sensing interface, the resulting electrochemical sensor can achieve highly sensitive detection of 2,4-dichlorophenol.

[0011] In some embodiments, the reference electrode is at least one of a calomel electrode, an Ag / AgCl electrode, a mercurous sulfate electrode, and a mercury oxide electrode; the counter electrode is a platinum electrode, specifically at least one of a platinum wire electrode, a platinum sheet electrode, and a platinum mesh electrode.

[0012] In some embodiments, the conductive nanoparticles include at least one nanoparticle selected from gold, silver, platinum, palladium, and copper.

[0013] In some embodiments, the nitrogen-doped carbon-coated ferric oxide material is spherical; the particle size of the nitrogen-doped carbon-coated ferric oxide material is 100~300 nm.

[0014] In some preferred embodiments, the particle size of the nitrogen-doped carbon-coated ferric oxide material is 150~250 nm.

[0015] In some other preferred embodiments, the particle size of the nitrogen-doped carbon-coated ferric oxide material is 180~220 nm.

[0016] In some embodiments, the nitrogen-doped carbon-coated ferric oxide material is obtained by sequentially coating polydopamine layer and FeOOH layer onto polystyrene microspheres as templates, followed by calcination.

[0017] In some preferred embodiments, the calcination temperature is 300~500°C.

[0018] In some other preferred embodiments, the calcination temperature is 350~450°C.

[0019] In some other preferred embodiments, the calcination temperature is 380~420°C.

[0020] In some preferred embodiments, the calcination is carried out in a nitrogen atmosphere.

[0021] In some preferred embodiments, the calcination time is 1 to 3 hours.

[0022] In some preferred embodiments, the heating rate during calcination is 1~3 °C / min.

[0023] In some preferred embodiments, the polydopamine layer is formed by in-situ polymerization of dopamine hydrochloride; the mass ratio of dopamine hydrochloride to polystyrene microspheres is (0.5~0.7):1.

[0024] In some preferred embodiments, the FeOOH layer is obtained by reacting with a ferric chloride solution; the concentration of the ferric chloride solution is 0.005~0.015 mmol / mL. In other preferred embodiments, the concentration of the ferric chloride solution is 0.008~0.012 mmol / mL.

[0025] In some preferred embodiments, the polydopamine coating layer yields PS@PDA, and the mass ratio of ferric chloride to PS@PDA is (0.7~0.9):1. Specifically, the ferric chloride can be ferric chloride hexahydrate. When the mass ratio of ferric chloride to PS@PDA is (0.7~0.9):1, it refers to the mass ratio of ferric chloride hexahydrate to PS@PDA. It should be understood that, based on this mass ratio, the mass ratio of ferric chloride to PS@PDA in ferric chloride hexahydrate can be calculated as (0.4~0.6):1.

[0026] In some embodiments, the preparation method of the nitrogen-doped carbon-coated ferric oxide material includes the following steps: Dopamine hydrochloride was added to a suspension containing PS (polystyrene) microspheres to obtain PS@PDA; the PS@PDA was dispersed in an aqueous solution of ferric chloride to obtain PS@PDA@FeOOH; the PS@PDA@FeOOH was calcined under a nitrogen atmosphere to obtain the nitrogen-doped carbon-coated ferric oxide material.

[0027] Specifically, during the calcination process, the PS microspheres thermally decompose and escape, the PDA layer (polydopamine layer) is transformed into a nitrogen-doped carbon shell, and the FeOOH layer dehydrates to form Fe2O3, ultimately yielding a nitrogen-doped carbon-coated ferric oxide material.

[0028] In some preferred embodiments, the reaction temperature between the PS@PDA and the ferric chloride is 70~80°C; the reaction time is 4~6 hours.

[0029] In some embodiments, the electrochemical sensor further includes an electrolyte; the electrolyte includes a phosphate buffer solution (PBS buffer solution) and acetic acid. At least one of sodium acetate buffer solution and ammonia-ammonium chloride buffer solution.

[0030] A second aspect of the present invention provides a method for preparing the electrochemical sensor described in the first aspect of the present invention, the method comprising the following steps: An electrochemical sensor that assembles a working electrode, a reference electrode, and a counter electrode to form a three-electrode system; The method for preparing the working electrode includes the following steps: depositing conductive nanoparticles on the electrode surface by electrochemical deposition to obtain a modified electrode; coating the surface of the modified electrode with a dispersion of nitrogen-doped carbon-coated ferric oxide material to obtain the working electrode.

[0031] In some embodiments, the deposition potential of the electrochemical deposition is -1.0 to -0.1 V.

[0032] In some preferred embodiments, the deposition potential of the electrochemical deposition is -0.8 to -0.3 V.

[0033] In some other preferred embodiments, the deposition potential of the electrochemical deposition is -0.6 to -0.4 V.

[0034] In some embodiments, the deposition time of the electrochemical deposition is 1 to 15 seconds.

[0035] In some preferred embodiments, the deposition time for the electrochemical deposition is 3 to 7 seconds.

[0036] In some other preferred embodiments, the deposition time for the electrochemical deposition is 4 to 6 seconds.

[0037] In some embodiments, the electrochemical deposition is performed by placing the electrode in a solution of a soluble metal salt; the soluble metal salt includes at least one of HAuCl4, AgNO3, H2PtCl6, PdCl2, CuSO4, or their complexes.

[0038] In some preferred embodiments, the concentration of the soluble metal salt solution is 0.01~1 mmol / L.

[0039] In some other preferred embodiments, the concentration of the soluble metal salt solution is 0.4~0.6 mmol / L.

[0040] In some embodiments, the dispersion of the nitrogen-doped carbon-coated ferric oxide material is obtained by dispersing the nitrogen-doped carbon-coated ferric oxide material in an aqueous ethanol solution.

[0041] In some embodiments, the concentration of the nitrogen-doped carbon-coated ferric oxide material in the dispersion is 1~6 mg / mL.

[0042] In some embodiments, the coating volume of the dispersion is 5 to 10 μL.

[0043] In some embodiments, after the dispersion is coated, a drying step is further included; the drying temperature is 50~70°C.

[0044] A third aspect of the present invention provides an application of the electrochemical sensor described in the first aspect of the present invention or the electrochemical sensor prepared by the preparation method described in the second aspect of the present invention in the field of detection.

[0045] In the electrochemical sensor of the present invention, the working electrode contains a nanocomposite material, which can selectively enrich 2,4-dichlorophenol and can be used for electrochemical sensing analysis to determine the content of 2,4-dichlorophenol (2,4-DCP) in animal-derived foods. It has the advantages of good selectivity, high reproducibility and simple operation, and has high practical application value.

[0046] A fourth aspect of the present invention provides a method for detecting 2,4-dichlorophenol, using the electrochemical sensor described in the first aspect of the present invention, or the electrochemical sensor prepared by the preparation method described in the second aspect of the present invention.

[0047] In some embodiments, the detection involves detecting a test solution containing 2,4-dichlorophenol. Specifically, the test solution is obtained by diluting the target substance containing 2,4-dichlorophenol with an electrolyte solution.

[0048] In some preferred embodiments, the test solution further includes 2-CP, 2-C-4-NP, catechol, 2,5-DCP, 2,4,6-TCP, 2,5-DBP, 2,4,5-TCP, histidine, glucose, vitamin B12, and Cl. - SO4 2- CO3 2- Fe 3+ Ca 2+ The present invention contains one or more interfering substances, each with a concentration below 300 μmol / L. The electrochemical sensor of this invention exhibits excellent anti-interference capability and its sensitivity and accuracy are not affected by interfering substances in the analyte.

[0049] In some preferred embodiments, the pH of the test solution is 5-8. Detection sensitivity and accuracy are higher within this pH range.

[0050] In some preferred embodiments, the working electrode contacts the test liquid for 60-180 seconds during the detection process. The electrochemical sensor of the present invention has a fast detection speed, requires no excessive enrichment time, and can quickly obtain detection results.

[0051] In some preferred embodiments, the voltage during the detection process is -0.6 to 0.4 V.

[0052] In some implementations, the target substance is derived from animal-derived food.

[0053] In some preferred embodiments, the extraction of the target object includes the following steps: Animal-derived food is crushed and homogenized. Anhydrous magnesium sulfate and extraction solvent are added sequentially to the homogenized meat sample, and the mixture is vortexed to obtain a mixture. The mixture is extracted by ultrasonication, centrifugation, and the acetonitrile phase in the supernatant is collected as the extract. The above extraction process is repeated 1 to 2 times. The collected extracts are combined, filtered through a 0.22 µm filter membrane, purged with nitrogen until dry, and then the extract is redissolved. The resulting desorbed liquid is the target substance.

[0054] In some preferred embodiments, the ratio of the meat sample, anhydrous magnesium sulfate, and extraction solvent is 5 g: (1~3) g: (10~20) mL.

[0055] In some preferred embodiments, the extraction solvent comprises acetonitrile and / or n-hexane. For example, the extraction solvent is acetonitrile and n-hexane, wherein the volume ratio of acetonitrile to n-hexane is 1:(0.8~1.2).

[0056] In some preferred embodiments, the vortex oscillation time is 3-8 min; the ultrasonic extraction time is 15-25 min.

[0057] In some embodiments, the detection method includes the following steps: After mixing the 2,4-dichlorophenol standard solution with PBS buffer, electrochemical detection was performed using an electrochemical sensor. The DPV response values ​​of 2,4-dichlorophenol at different concentrations were recorded, and a curve showing the relationship between concentration and DPV intensity was plotted. The target analyte was diluted with PBS buffer to obtain the test solution, and electrochemical detection was performed using an electrochemical sensor. The DPV response value of the test solution was recorded, and the content of 2,4-dichlorophenol was calculated based on the relationship curve.

[0058] Compared with the prior art, the beneficial effects of the present invention are: This invention provides an electrochemical sensor whose working electrode surface is coated with a nanocomposite material. This nanocomposite material contains nitrogen-doped carbon-coated ferric oxide and conductive nanoparticles. Using this material as an electrode sensitizer, it exhibits high specific surface area, good conductivity, excellent electrocatalytic activity, and outstanding stability. Therefore, the electrochemical sensor of this invention possesses high sensitivity and high stability. When applied in detection fields, it exhibits strong adsorption capacity for target analytes, and the relative standard deviation of test results obtained after different number of days of storage is small. It is particularly suitable for the detection of 2,4-dichlorophenol, possessing advantages such as a wide detection linear range and high sensitivity. Attached Figure Description

[0059] Figure 1 This is a scanning electron microscope image of NC@Fe2O3 from Example 1.

[0060] Figure 2 This is a high-resolution spectrum of NC@Fe2O3 from Example 1; wherein, Figure 2 Figures (a) to (d) correspond to (a) Fe 2p spectrum, (b) C 1s spectrum, (c) O 1s spectrum, and (d) N 1s XPS spectrum, respectively.

[0061] Figure 3 This is a schematic diagram of the preparation process of the electrochemical sensor in Example 1 and its electrochemical detection of 2,4-DCP.

[0062] Figure 4 The spectrum is obtained from the reproducibility test of the electrochemical sensor in Test Example 1.

[0063] Figure 5 The DPV spectrum is obtained from the stability test of the electrochemical sensor in Test Example 1.

[0064] Figure 6 The results show the selectivity test results of the electrochemical sensor in Test Example 1; where, Figure 6 Figure (a) shows a comparison of the response currents of the working electrode of the electrochemical sensor to the target analyte and other coexisting substances; Figure 6 Figure (b) shows the change in response current of the working electrode of the electrochemical sensor in the presence of common interfering substances.

[0065] Figure 7 The results of the electrochemical sensor in Test Example 2 detecting 2,4-DCP under different conditions are shown; among them, Figure 7 Figure (a) shows the CV curves for PBS buffer containing 2,4-DCP at different pH values; Figure 7 Figure (b) shows the relationship between the oxidation peak current and the solution pH. Figure 7 Figure (c) shows the relationship between the oxidation peak current and the enrichment voltage. Figure 7 Figure (d) shows the relationship between the oxidation peak current and the enrichment time.

[0066] Figure 8 The CV curves of bare GCE, AuNPs / GCE and NC@Fe2O3 / AuNPs / GCE as working electrodes in KCl solution containing K3Fe(CN)6 are shown in Example 3.

[0067] Figure 9 This is a comparison graph showing the electrochemical response of the electrochemical sensor in Comparative Example 1 to 2,4-DCP.

[0068] Figure 10 This is a comparison graph showing the electrochemical response of the electrochemical sensor in Comparative Example 2 to 2,4-DCP.

[0069] Figure 11 The graphs show the response current relationships of the electrochemical sensors in Comparative Examples 3 and 4; where, Figure 11 Figures (a) and (b) in the figure respectively show the relationship between the concentration of soluble metal salt and the response current, and the relationship between the concentration of NC@Fe2O3 dispersion and the response current. Detailed Implementation

[0070] The present invention will be further described in detail below through specific embodiments. Unless otherwise specified, the raw materials, reagents, or apparatus used in the embodiments and comparative examples are all available from conventional commercial sources or can be obtained by existing technical methods. Unless otherwise specified, the experimental or testing methods are conventional methods in the art.

[0071] Example 1 An electrochemical sensor has a working electrode surface containing a nanocomposite material comprising nitrogen-doped carbon-coated ferric oxide (NC@Fe2O3) and gold nanoparticles (AuNPs).

[0072] The preparation method of the nitrogen-doped carbon-coated ferric oxide material in this embodiment is as follows: 1) Preparation of PS (polystyrene) by emulsion polymerization: 150 mL of deionized water was mixed with surfactant SDS (sodium dodecyl sulfate), preheated at 70 °C and deoxygenated by nitrogen gas; 1.5 g of styrene monomer was slowly added dropwise, and the mixture was stirred at high speed to form a fine emulsion. Then, dissolved potassium persulfate (0.3 g / 5 mL) was added to start polymerization. The reaction was carried out at 70 °C, stirring speed of 600 rpm and nitrogen gas gas for 26 h; the suspension after the reaction was completed was purified by centrifugation at 8000 rpm to obtain PS microspheres. 2) Preparation of PS@PDA: 100 mg of PS microspheres were dispersed in 30 mL of Tris buffer and sonicated for 30 min to obtain a suspension; then, 60 mg of dopamine hydrochloride (DA) was added to the suspension and stirred at room temperature for 12 h; after the reaction was completed, the product was centrifuged at 8000 rpm, washed three times with distilled water, and then dried overnight at 60 °C in a vacuum oven to obtain PS@PDA; 3) In-situ growth of PS@PDA@FeOOH: 100 mg PS@PDA was dispersed in 30 mL of aqueous solution containing 0.3 mmol FeCl3·6H2O and sonicated for 40 min. The resulting suspension was kept in a water bath at 75 °C with stirring for 5 h. The final product was collected by centrifugation, washed three times with water and dried overnight to obtain PS@PDA@FeOOH. 4) Calcination and transformation of NC@Fe2O3: PS@PDA@FeOOH was placed in a tube furnace and heated to 400°C at a rate of 2 °C / min under a N2 atmosphere, and held for 2 h. During this process, the PS core thermally decomposed and escaped, the PDA layer was transformed into a nitrogen-doped carbon shell (NC), and FeOOH was dehydrated into Fe2O3, ultimately forming a core-shell structure of NC-coated Fe2O3, i.e., nitrogen-doped carbon-coated ferric oxide material (NC@Fe2O3). The sample was collected and characterized after cooling to room temperature in the furnace.

[0073] The preparation method of the electrochemical sensor in this embodiment is as follows: After polishing, the glassy carbon electrode (GCE) was immersed in a 0.5 mmol / L chloroauric acid (HAuCl4) solution and electrodeposited for 5 s at a constant voltage of -0.5 V to deposit AuNPs on the GCE surface, resulting in AuNPs / GCE. After deposition, the electrode surface was carefully rinsed with ultrapure water to remove any undeposited HAuCl4 solution, ensuring the electrode surface was clean and uncontaminated. 8 μL of the above NC@Fe2O3 aqueous ethanol (water to ethanol volume ratio of 1:1) dispersion (3 mg / mL) was added dropwise to the electrode surface on which AuNPs were deposited, and the electrode was dried in an oven at 60 °C to allow NC@Fe2O3 to uniformly adhere to the electrode surface, finally obtaining NC@Fe2O3 / AuNPs / GCE, which served as the working electrode of the electrochemical sensor. The above working electrode was assembled with a saturated KCl-type Ag / AgCl electrode (reference electrode) and a platinum wire electrode (counter electrode) to form an electrochemical sensor. The electrolyte solution was PBS solution (0.1 mol / L, pH=6.5).

[0074] Test Example 1 This test example characterizes or tests the performance of the nitrogen-doped carbon-coated ferric oxide material and electrochemical sensor in Example 1 above.

[0075] 1) Morphology characterization of nitrogen-doped carbon-coated ferric oxide (NC@Fe2O3): The scanning electron microscope image of NC@Fe2O3 prepared in Example 1 is shown below. Figure 1 As shown, by Figure 1 The material can be seen to be spherical with a rough surface and a particle size of approximately 200 nm. Figure 2 This is a high-resolution XPS spectrum of NC@Fe2O3 from Example 1.

[0076] Using the NC@Fe2O3 / AuNPs / GCE from Example 1 as the working electrode, the content of 2,4-DCP (2,4-dichlorophenol) in meat samples was detected. The preparation process of the electrochemical sensor and the electrochemical detection process are as follows: Figure 3 As shown.

[0077] 2) Reproducibility test: The reproducibility of the electrochemical sensors was evaluated by assembling five NC@Fe2O3 / AuNPs / GCE-based electrochemical sensors in parallel and performing five repeated measurements on each sensor. The reproducibility test results for the five electrochemical sensors are shown below. Figure 4As shown, the current signals of the five electrochemical sensors used for the analysis of 2,4-DCP (3 μmol / L, 2,4-DCP is added directly to the electrolyte solution) are very close, with a low relative standard deviation (RSD) of 2.50%. The current signals of each electrochemical sensor measured five times are also very close, with an RSD of 1.78%. This result indicates that the electrochemical sensor developed in this invention has excellent reproducibility.

[0078] 3) Stability testing: To further explore the stability of the electrochemical sensor of this invention, its stability was evaluated by measuring the change in electrochemical response intensity caused by 2,4-DCP (3 μmol / L, 2,4-DCP directly added to the electrolyte solution) using the electrochemical sensor at the same time period for 5 consecutive weeks. The stability test results are as follows: Figure 5 As shown. From Figure 5 The results show that the current signal is still 93% after 28 days, which indicates that the electrochemical sensor developed in this invention has good and stable sensing performance and stability.

[0079] 4) Selective testing: The selectivity of the electrochemical sensor constructed in Example 1 of this invention is another important indicator for the effective detection of 2,4-DCP in real samples. To test the selectivity of the electrochemical sensor of this invention, homologues and structural analogs of 2,4-DCP were used as interfering substances, including 2-CP (2-chlorophenol), 2-C-4-NP (2-chloro-4-nitrophenol), catechol, 2,5-DCP (2,5-dichlorophenol), 2,4,6-TCP (2,4,6-trichlorophenol), 2,5-DBP (2,5-dibromophenol), and 2,4,5-TCP (2,4,5-trichlorophenol). The electrochemical sensor was used to test PBS solutions (0.1 mol / L, pH=6.5, as the electrolyte solution) containing 2,4-DCP (3 μmol / L) and coexisting interfering substances, with the concentration of the interfering substances being 3 μmol / L. By comparing the changes in current response of 2,4-DCP under different coexisting structural analogs, the selectivity performance of the electrochemical sensor in the presence of multiple similar compounds was evaluated.

[0080] Selective test results as follows Figure 6As shown in Figure (a), the electrochemical sensor of the present invention was used to detect interfering substances, namely 2-CP, 2-C-4-NP, catechol, 2,5-DCP, 2,4,6-TCP, 2,5-DBP, and 2,4,5-TCP. These substances only caused small changes in the current response, which were significantly smaller than the detection of 2,4-DCP. This shows that the electrochemical sensor developed in this invention still has superior selectivity when detecting 2,4-DCP in complex environments containing multiple interfering substances.

[0081] Figure 6 Figure (b) shows the anti-interference data of the electrochemical sensor in Example 1. Histidine, glucose, vitamin B12, and Cl... - SO4 2- CO3 2- Fe 3+ Ca 2+ As interfering substances, an electrochemical sensor was used to test a PBS solution (0.1 mol / L, pH=6.5, as the electrolyte solution) containing 2,4-DCP (3 μmol / L) and the coexisting interfering substance. The concentration of the interfering substance was 300 μmol / L. Here, "mixture" refers to a mixture of 2,4-DCP and the aforementioned interfering substance. The results in the figure show that the presence of the interfering substance does not affect the electrochemical signal of 2,4-DCP, demonstrating that the constructed electrochemical sensor has good anti-interference capability.

[0082] In summary, the electrochemical sensor provided by this invention has excellent selectivity, good reproducibility, and excellent stability.

[0083] Test Example 2 In this test case, the electrochemical sensor from Example 1 above was used to detect 2,4-DCP, and its detection conditions were optimized.

[0084] This test case investigated the effects of pH value, enrichment voltage, and enrichment time of the detection solution on the detection performance.

[0085] The effect of varying the pH of the detection solution (pH = 5.0, 6.0, 6.5, 7.0, 7.5, 8.0) on the detection performance of the electrochemical sensor was tested. The detection solution was a PBS solution containing 2,4-DCP (0.1 mol / L, pH = 6.5), with a 2,4-DCP concentration of 3 μmol / L. The detection solution served as the electrolyte solution. Figure 7As shown in Figures (a) and (b), the catalytic peak current (Ipa) for 2,4-DCP oxidation reaches its maximum at pH 6.5 when the solution pH changes from 5.0 to 6.5. The oxidation current decreases as the pH decreases or increases. Furthermore, the oxidation peak potential shifts positively with decreasing pH and negatively with increasing pH. Therefore, a PBS solution at pH 6.5 is selected as the optimal condition for 2,4-DCP determination.

[0086] Figure 7 In Figure (c), the concentration of 2,4-DCP was 3 μmol / L, the pH of the PBS solution was 6.5, and the oxidation current increased with increasing enrichment voltage from -0.6 V to -0.2 V, then decreased at 0.4 V. Therefore, -0.2 V was chosen as the preferred enrichment voltage for linear detection. In the electrochemical detection of organic compounds, the response current typically increases with increasing enrichment time, such as... Figure 7 In Figure (d), considering a single detection cycle, 120 s is selected as the preferred enrichment time.

[0087] Test Example 3 To evaluate the electrochemical performance of the electrochemical sensor of the present invention, this test example uses the electrochemical sensor of Example 1 to perform electrochemical detection.

[0088] The bare GCE, AuNPs / GCE, and NC@Fe2O3 / AuNPs / GCE from Example 1 were used as the working electrodes of the electrochemical sensor, and cyclic voltammetry (CV) was used for detection. Figure 8 The CV curves of different electrodes in a potassium chloride (KCl, 0.1 mol / L) solution containing potassium ferricyanide (K3Fe(CN)6, 5 mmol / L) are presented. For the unmodified bare GCE, the peak current is the smallest and ΔEp is the largest, indicating a slow electron transfer process. After modification with AuNPs, the peak current increases and ΔEp decreases slightly, indicating that AuNPs promote charge transfer. NC@Fe2O3 / AuNPs / GCE exhibits the highest redox peak current and the lowest impedance, indicating its excellent electrochemical activity. This result is attributed to the synergistic effect of AuNPs and NC@Fe2O3 on the electrode surface, which significantly improves the interfacial conductivity, expands the effective electrochemical surface area, and accelerates the reaction of the redox probe at the electrode interface.

[0089] Because the electrochemical sensor of this invention has enhanced sensing capabilities, it can be better used for the quantitative detection of 2,4-DCP. The limit of detection (LOD) of the electrochemical sensor constructed in Example 1 of this invention was evaluated by measuring a series of 2,4-DCP concentrations. Specifically, the electrode of the electrochemical sensor of Example 1 was immersed in 2,4-DCP target solutions of different concentrations (0.003 μmol / L, 0.03 μmol / L, 0.5 μmol / L, 2.0 μmol / L, 4.0 μmol / L, 6.0 μmol / L, 8.0 μmol / L, 10.0 μmol / L), and the corresponding currents were recorded. The target solution was a PBS solution containing 2,4-DCP (0.1 mol / L, pH=6.5), which served as the electrolyte solution during detection.

[0090] The obtained linear relationship is a linear regression equation of I(μA) = 3.01C(μmol / L) + 0.32 (correlation coefficient R). 2 =0.9986, n=3), the linear range is 0.003-10.0 μmol / L. According to LOD=3SD / k (SD is the standard deviation of the blank sample, k is the slope of the standard curve), the obtained LOD is 1.2 nmol / L.

[0091] Test Example 4 To evaluate the practicality of the electrochemical sensor of the present invention, this test example uses the electrochemical sensor of Example 1 to detect 2,4-DCP in animal-derived food.

[0092] Shrimp, clams, frozen shrimp meat, frozen chicken thigh meat, and canned shrimp were purchased through conventional commercial channels for 2,4-DCP content detection. Under the optimized conditions of Test Example 2, the electrochemical sensor prepared in Example 1 was used to perform sensing analysis on the animal-derived food. The obtained current signal was substituted into a linear equation to obtain the 2,4-DCP content.

[0093] Before detection, the animal-derived food samples need to be processed. The processing process of the samples is as follows: The samples are crushed and homogenized with a meat grinder. Exactly 5.00 g of the homogenized sample is weighed and placed in a centrifuge tube. 2.00 g of anhydrous magnesium sulfate is added, and then 15 mL of a mixed solvent of acetonitrile / n-hexane (1:1, V / V) is added. The mixture is vigorously vortexed for 5 min, then ultrasonically extracted for 20 min, centrifuged, and the acetonitrile phase in the supernatant is collected. The above extraction process is repeated once, and the two collected extracts are combined in a centrifuge tube, filtered through a 0.22 µm nylon-66 membrane, and then purged with nitrogen until dry. Then, the extract is redissolved with 10 mL of PBS solution (0.1 mol / L, pH = 6.5) to obtain an electrolyte solution, which is analyzed with the electrochemical sensor of Example 1. According to the actual content of 2,4-DCP in the animal-derived food samples, the standard addition method is used for the recovery experiment. The sample determination results are shown in Table 1. Each sample is determined in parallel 3 times. As can be seen from Table 1, the recovery rate of 2,4-DCP is between 9 S.7% and 115%, indicating that this method meets the requirements of trace analysis.

[0094] Table 1 Determination results of 2,4-DCP in animal-derived food samples <°

[0095] In Table 1, "<LOQ" means below the limit of quantification, and "ND" means not detected.

[0096] Comparative Example 1 The electrochemical sensor provided in this comparative example is different from that of Example 1 in that the type of soluble metal salt in the preparation process of the electrochemical sensor is changed. The HAuCl4 solution is replaced with an AgNO3 solution, a H2PtCl6 solution, a PdCl2 solution, and a Cu(NO3)2 solution with the same concentration, respectively, and the other conditions are the same as those in Example 1, obtaining an electrochemical sensor containing different conductive nanoparticles.

[0097] The obtained electrochemical sensor is tested for the DPV response of 2,4-DCP (3 μmol / L) in PBS solution (0.1 mol / L, pH = 6.5), and the results are as Figure 9 shown. It can be seen that there are differences in the DPV responses of different conductive nanoparticles, that is, the sensitivities of the electrochemical sensors are different, and when gold nanoparticles are used as the conductive nanoparticles, the response is the highest and the sensitivity of the electrochemical sensor is the best.

[0098] Comparative Example 2 The electrochemical sensor provided in this comparative example uses Fe2O3 and nitrogen-doped carbon materials as controls, that is, Fe2O3 and nitrogen-doped carbon materials are used to replace the nitrogen-doped carbon-coated iron oxide material in Example 1, respectively, to obtain different electrochemical sensors. The preparation process is the same as that in Example 1, and the difference is only that: 1) Fe2O3: PS@FeOOH was prepared by following the preparation method in Example 1 without introducing dopamine hydrochloride, and Fe2O3 was obtained by calcination; the resulting working electrode is denoted as Fe2O3 / AuNPs / GCE; 2) NC (without Fe source): Following the preparation method in Example 1, dopamine hydrochloride was introduced to form polydopamine coating on the PS surface. No ferric chloride solution was added, i.e., no FeOOH was adsorbed. Subsequently, N-doped carbon material was obtained by calcination under N2 atmosphere. The resulting working electrode is denoted as NC / AuNPs / GCE.

[0099] The electrochemical sensors in this comparative example and Example 1 were used to perform electrochemical tests on 2,4-DCP (3 μmol / L) under the same conditions (0.1 mol / L PBS solution, pH=6.5). The results are shown in [Figure Number]. Figure 10 . Figure 10 In the diagram, the " / GCE" marking is omitted for each curve corresponding to its respective electrochemical sensor. The test results show that, compared to a single component, NC@Fe2O3 achieves superior response performance by modulating the surface electronic structure and active site distribution.

[0100] Comparative Example 3 The electrochemical sensor provided in this comparative example differs from that in Example 1 in that the concentration of the HAuCl4 solution was changed, and the concentrations were set to 0.1 mmol / L, 0.3 mmol / L, 0.5 mmol / L, 0.7 mmol / L, and 1.0 mmol / L, respectively; otherwise, it is the same as in Example 1.

[0101] The electrochemical sensor used in this comparative example was used to detect 2,4-DCP (3 μmol / L) in PBS solution (0.1 mol / L, pH=6.5), and the DPV peak current of 2,4-DCP was recorded. Figure 11 Figure (a) shows that the current response increases with increasing concentration, reaching a maximum at a concentration of 0.5 mmol / L, with no significant increase observed with further increases.

[0102] Comparative Example 4 The electrochemical sensor provided in this comparative example differs from that in Example 1 in that the concentration of the NC@Fe2O3 dispersion was changed to 1 mg / mL, 2 mg / mL, 3 mg / mL, 4 mg / mL, 5 mg / mL, and 6 mg / mL; otherwise, it is the same as in Example 1.

[0103] The electrochemical sensor used in this comparative example was used to detect 2,4-DCP (3 μmol / L) in PBS solution (0.1 mol / L, pH=6.5), and the DPV peak current of 2,4-DCP was recorded. The results are as follows: Figure 11 As shown in Figure (b), the current is the largest when the dispersion concentration is 3 mg / mL.

[0104] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. An electrochemical sensor, comprising a working electrode, a reference electrode, and a counter electrode, characterized in that, The working electrode surface of the electrochemical sensor contains a nanocomposite material; the nanocomposite material includes nitrogen-doped carbon-coated ferric oxide and conductive nanoparticles.

2. The electrochemical sensor according to claim 1, characterized in that, The conductive nanoparticles include at least one nanoparticle selected from gold, silver, platinum, palladium, and copper. And / or, the nitrogen-doped carbon-coated ferric oxide material is spherical; the particle size of the nitrogen-doped carbon-coated ferric oxide material is 100~300 nm.

3. The electrochemical sensor according to claim 1, characterized in that, The nitrogen-doped carbon-coated ferric oxide material is obtained by coating polystyrene microspheres with a polydopamine layer and an FeOOH layer in sequence, followed by calcination.

4. The electrochemical sensor according to claim 3, characterized in that, The calcination temperature is 300~500℃; And / or, the calcination is carried out in a nitrogen atmosphere.

5. The electrochemical sensor according to any one of claims 1 to 4, characterized in that, The electrochemical sensor further includes an electrolyte; the electrolyte includes a phosphate buffer solution and acetic acid. At least one of sodium acetate buffer solution and ammonia-ammonium chloride buffer solution.

6. A method for preparing an electrochemical sensor according to any one of claims 1 to 5, characterized in that, The method for preparing the electrochemical sensor includes the following steps: An electrochemical sensor that assembles a working electrode, a reference electrode, and a counter electrode to form a three-electrode system; The method for preparing the working electrode includes the following steps: depositing conductive nanoparticles on the electrode surface by electrochemical deposition to obtain a modified electrode; coating the surface of the modified electrode with a dispersion of nitrogen-doped carbon-coated ferric oxide material to obtain the working electrode.

7. The preparation method according to claim 6, characterized in that, The deposition potential of the electrochemical deposition is -1.0 to -0.1 V; And / or, the deposition time of the electrochemical deposition is 1~15 s; And / or, the electrochemical deposition is performed by placing the electrode in a soluble metal salt solution for electrochemical deposition; the soluble metal salt includes at least one of HAuCl4, AgNO3, H2PtCl6, PdCl2, CuSO4, or their complexes.

8. The preparation method according to claim 6, characterized in that, The dispersion of the nitrogen-doped carbon-coated ferric oxide material is obtained by dispersing the nitrogen-doped carbon-coated ferric oxide material in an aqueous ethanol solution; And / or, the concentration of the nitrogen-doped carbon-coated ferric oxide material in the dispersion is 1~6 mg / mL; And / or, the coating volume of the dispersion is 5~10 μL.

9. The application of an electrochemical sensor according to any one of claims 1 to 5 or an electrochemical sensor prepared by the preparation method according to any one of claims 6 to 8 in the field of detection.

10. A method for detecting 2,4-dichlorophenol, characterized in that, The detection is performed using the electrochemical sensor according to any one of claims 1 to 5 of the present invention, or the electrochemical sensor prepared by the preparation method according to any one of claims 6 to 8.

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