A highly sensitive electrochemical sensor for detecting triclosan and its preparation method

Abstract

This invention discloses a highly sensitive electrochemical sensor for detecting triclosan and its preparation method, belonging to the field of electrochemical sensors. The preparation method includes: (1) synthesizing ZIF-67 powder using Co(NO3)2·6H2O and 2-methylimidazole as raw materials; (2) mixing ZIF-67 and iron salt solution by stirring and hydrothermal reaction to obtain CoFe MOF; (3) carbonizing CoFe MOF at high temperature to obtain CoFe@C; (4) drop-coating the suspension of CoFe@C onto a clean glassy carbon electrode surface, drying it, and naturally cooling it to room temperature. This sensor has good anti-interference ability against more than a dozen common types of interfering substances and exhibits good stability in long-term testing. In the applicability analysis of actual samples, the recovery rate of triclosan spiked is 97% to 104%, showing good application potential.

Description

Technical Field

[0001] This invention belongs to the field of electrochemical sensors and relates to a highly sensitive electrochemical sensor for detecting triclosan and its preparation method. Background Technology

[0002] Triclosan, scientifically known as 5-chloro-2-(2,4-dichlorophenoxy)phenol (TCS), is a broad-spectrum antibacterial agent widely used in daily chemicals and medical fields due to its low cost and broad antibacterial spectrum. Statistics show that global TCS usage exceeds 750,000 tons annually, making it one of the most commonly used antibacterial additives in recent decades. However, the large-scale use of TCS has led to increased concentrations in the environment, and the problems caused by TCS are becoming increasingly significant. For example, TCS is not only toxic to aquatic organisms, but studies have also shown that it may interfere with human endocrine and thyroid function, and its potential carcinogenic effects are attracting increasing attention. Therefore, many countries have issued relevant regulations to restrict the addition of TCS. Thus, developing a rapid and sensitive TCS detection method is essential.

[0003] Over the past few decades, various methods have been developed for the detection of TCS, including gas chromatography, high-performance liquid chromatography, liquid chromatography-mass spectrometry (LC-MS), gas chromatography-mass spectrometry (GC-MS), and electrochemical methods. Among these detection techniques, electrochemical methods have demonstrated significant advantages. Compared to traditional detection methods, which are expensive, time-consuming, and complex to operate, electrochemical detection methods, with their advantages of fast response, high sensitivity, low cost, and good selectivity, have gradually become a research hotspot for rapid and sensitive TCS detection.

[0004] Metal-organic frameworks (MOFs) have attracted widespread attention in the field of electrochemistry due to their high specific surface area, tunable pore structure, and ease of functionalization. However, their poor conductivity, insufficient structural stability, and tendency to collapse in electrolytes limit their applications. In recent years, metal-doped carbon-based nanocomposites prepared by high-temperature pyrolysis of MOFs have overcome the inherent defects of traditional MOFs, becoming an effective approach for constructing high-performance electrochemical sensors. ZIF-67 is a Co... 2+ MOF materials with zeolite topology constructed with imidazole organic linkers, wherein Co 2+ With a moderate radius and good coordination compatibility, it readily combines with Fe. 3+ In-situ doping or composite formation of bimetallic MOF materials with synergistic effects was achieved. Based on this, high-temperature carbonization successfully prepared cobalt-iron bimetallic doped carbon-based composite materials. These materials achieved a synergistic improvement in conductivity, stability, and catalytic activity, providing a new approach for electrochemical detection in TCS. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of traditional triclosan detection methods, such as reliance on large instruments which result in expensive equipment and inability to perform rapid analysis, as well as the narrow linear range, high detection limit, and poor anti-interference performance of conventional electrochemical sensors. This invention proposes an electrochemical sensor using CoFe@C as the electrode material to achieve highly sensitive detection of triclosan.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] An electrochemical sensor based on cobalt-iron bimetallic doped carbon-based composite material is designed for TCS detection. The sensor includes a glassy carbon electrode (GCE) and a CoFe@C modification layer coated on the surface of the GCE.

[0008] Firstly, a method for preparing a highly sensitive electrochemical sensor for detecting triclosan is as follows:

[0009] (1) Synthesis of ZIF-67: Cobalt salt and ligand were dissolved in an organic solvent, mixed evenly and aged. The reaction product was washed and dried to obtain ZIF-67 purple powder.

[0010] (2) Synthesis of CoFe MOF: ZIF-67 powder was uniformly dispersed in ethanol to obtain solution A, and iron salt was uniformly dissolved in deionized water to obtain solution B. Solution B was added to solution A and stirred until well mixed. The mixed solution was then transferred to a hydrothermal reactor for hydrothermal reaction. The product was washed, centrifuged, and dried to obtain CoFe MOF.

[0011] (3) Synthesis of CoFe@C: The CoFe MOF obtained in step (2) is transferred to a tube furnace and then subjected to high-temperature carbonization. After cooling, the black powder is collected, which is CoFe@C.

[0012] (4) Preparation of CoFe@C-based electrochemical sensor: CoFe@C suspension was drop-coated onto a pre-polished clean electrode, dried with an infrared lamp, and naturally cooled to room temperature.

[0013] In step (1), the cobalt salt used is Co(NO3)2·6H2O, the ligand is 2-methylimidazole, and the organic solvent is methanol. The aging time is 12 h to 24 h.

[0014] In step (2), the iron salt is K3[Fe(CN)6]. The reactor temperature is set to 150℃~180℃, and the reaction time is 12 h~15 h.

[0015] In step (3), the gas selected in the tubular furnace is argon or nitrogen, the temperature is set to 600℃, and the holding time is 2 h to 3 h.

[0016] In step (4), the amount of CoFe@C suspension dropped is 4 μL to 8 μL.

[0017] Secondly, the application of the electrochemical sensor described in this invention in the detection of triclosan includes:

[0018] The electrolytic cell used was a standard three-electrode system. Electrochemical tests were performed in phosphate-buffered saline (PBS) solution with a pH of 5.0–9.0. Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) were used to detect TCS-containing test solutions. The linear range of detection was 0.5 μM–500 μM.

[0019] Compared with existing technologies, this invention synthesizes CoFe@C, Fe through multiple steps. 3+ The introduction of [a specific ingredient] has a synergistic effect with cobalt in ZIF-67, thereby regulating the structure and properties of the material. High-temperature pyrolysis treatment overcomes the inherent shortcomings of MOFs, enhances conductivity and catalytic activity, and significantly improves the current response to triclosan.

[0020] The beneficial effects of this invention are:

[0021] 1. High sensitivity: CoFe@C provides abundant active sites for the electrochemical reaction of triclosan and accelerates electron transport, achieving a synergistic improvement in conductivity, stability and catalytic activity, and significantly enhancing the electrochemical response to TCS.

[0022] 2. Low detection limit: The lowest detection limit can reach 0.05 μM.

[0023] 3. Wide linear range: It exhibits good linearity within the concentration range of 0.5 μM to 500 μM.

[0024] 4. Strong anti-interference capability: It can maintain stable test results even against more than a dozen different types of interference.

[0025] 5. Good stability. When the prepared suspension is left to stand for a period of time, and the stability is measured every 5 days, the change in the TCS oxidation peak current does not exceed 5%.

[0026] 6. Highly practical: In actual sample testing, such as toothpaste and tap water, the recovery rate is between 97% and 104%. Attached Figure Description

[0027] Figure 1These are scanning electron microscope (SEM) images of the composite materials in the embodiments of the present invention; where (a) is ZIF-67, (b) is CoFe MOF, and (c) is CoFe@C;

[0028] Figure 2 The XRD pattern of CoFe@C in this embodiment of the invention;

[0029] Figure 3 The images show the Raman spectrum and fitting curve of CoFe@C in this embodiment of the invention; where (a) is the original Raman spectrum of CoFe@C and (b) is the fitting curve of the Raman spectrum.

[0030] Figure 4 This is a bar chart showing the effect of the amount of CoFe@C suspension dropped onto the 20 μM TCS response in this embodiment of the invention.

[0031] Figure 5 The following is a comparison of the electrochemical performance under different pH conditions in the embodiments of the present invention; where (a) is the cyclic voltammetry curve of 20 μM TCS under different pH conditions, and (b) is the peak oxidation current bar chart corresponding to different pH conditions.

[0032] Figure 6 This is a cyclic voltammetry curve of CoFe@C / GCE under optimized conditions for 20 μMTCS at different scan rates in an embodiment of the present invention;

[0033] Figure 7 The following are DPV response curves of different concentrations of TCS in the embodiments of the present invention; wherein (a) is the DPV curve of TCS concentration in the range of 0.5 μM to 500 μM, and (b) is the piecewise linear fitting curve of oxidation peak current and TCS concentration.

[0034] Figure 8 The above are the DPV curves of CoFe@C / GCE against different interfering substances tested in 20 μM TCS in this embodiment of the invention.

[0035] Figure 9 This is a bar chart showing the stability test results of CoFe@C / GCE in an embodiment of the present invention. Detailed Implementation

[0036] To illustrate the present invention in more detail, the technical solution of the present invention will be specifically described below with reference to preferred embodiments and accompanying drawings.

[0037] This invention discloses a method for preparing an electrochemical sensor based on CoFe@C composite material, and uses the sensor to sensitively detect triclosan.

[0038] Example 1

[0039] Preparation and structural morphology characterization of CoFe@C:

[0040] 1. Preparation of CoFe@C:

[0041] 0.728 g of Co(NO3)2·6H2O and 0.656 g of 2-methylimidazole were dissolved in 100 mL of methanol, ultrasonically mixed, and allowed to stand for 24 h. The product was centrifuged, washed three times alternately with methanol and ethanol, and then dried at 70 °C for 10 h, and the purple ZIF-67 powder was collected. 0.25 g of ZIF-67 was dispersed in 10 mL of ethanol and ultrasonically mixed, and this was recorded as solution A. 0.66 g of K3[Fe(CN)6] was dissolved in 20 mL of deionized water and ultrasonically mixed, and this was recorded as solution B. Under vigorous stirring of solution A, solution B was slowly added to solution A and stirred continuously for 10 min. The mixed solution was then transferred to a 50 mL hydrothermal reactor and reacted at 150 °C for 12 h. After the reactor cooled naturally to room temperature, the product was washed three times alternately with ethanol and water and dried at 70 °C for 10 h to obtain CoFe MOF. CoFe MOF was evenly spread in a quartz boat and transferred to a tube furnace. Under an argon atmosphere, the temperature was increased to 600℃ at a rate of 3℃ / min, and calcined at this temperature for 120 min to complete the carbonization treatment. After cooling, the black powder was collected and named CoFe@C.

[0042] 2. Structural and morphological characterization:

[0043] (1) SEM characterization: The surface morphology of ZIF-67, CoFe MOF, and CoFe@C was observed using field emission scanning electron microscopy (SEM). The results are as follows: Figure 1 As shown, ZIF-67 has a regular dodecahedral structure, CoFe MOF exhibits a cubic structure, and CoFe@C maintains a cubic morphology with a large number of nanoscale particles agglomerated inside the carbon skeleton, presenting a densely packed state. There are a large number of nanoscale gaps between the particles, which provide fast diffusion channels and ensure efficient electron transport.

[0044] (2) XRD characterization: The crystal structure of the CoFe@C composite material was analyzed by X-ray diffraction (XRD). The results are as follows: Figure 2 As shown, the XRD pattern of CoFe@C shows characteristic diffraction peaks of CoFe alloy. The strongest characteristic peak at 44.50° corresponds to the 110 crystal plane of CoFe alloy, and the peaks at 64.90° and 82.50° correspond to the 200 and 211 crystal planes of CoFe, respectively, confirming the successful synthesis of CoFe@C.

[0045] (3) Raman spectroscopy characterization: Raman spectroscopy was used to analyze the graphitization degree, order, and carbon structure of the CoFe@C composite material. The results are as follows: Figure 3 As shown, the Raman spectrum contains two core characteristic peaks of carbon materials, namely the D band and the G band, and their intensity ratio (I) is... D / I G The ratio (I0) is typically used to represent the degree of disorder and graphitization in carbon materials. A higher ratio indicates a higher degree of disorder and a lower degree of graphitization. The I0 of the material is calculated from this ratio. D / I G A value close to 1 indicates that the material has a moderate degree of graphitization and a moderate defect density, belonging to a typical semi-ordered and semi-disordered carbon structure, which can meet the electron transport requirements of electrochemical detection.

[0046] Example 2

[0047] Preparation of modified electrodes:

[0048] The GCE electrode was polished with alumina powder, and the powder on the surface was removed by ultrasonication with water and ethanol. The electrode was then placed in a mixed solution of potassium ferrocyanide and potassium ferrocyanide for testing. After passing the test, the electrode surface was ultrasonically cleaned to remove any remaining substances, and the water droplets on the electrode surface were dried with N2. 6 μL of CoFe@C suspension (mass concentration: 1 mg / mL) was accurately pipetted onto the clean electrode surface, dried with an infrared lamp, and allowed to cool naturally before testing.

[0049] Example 3

[0050] An electrochemical testing system was established, and the amount of CoFe@C modified material was optimized to determine the optimal modification conditions and improve the sensor's electrochemical response performance to TCS.

[0051] 1. Electrochemical testing system:

[0052] A standard three-electrode system, including an Ag / AgCl reference electrode, a platinum wire electrode, and a GCE, was used. The tests were conducted in a 0.1 M phosphate buffer solution at pH 7, and the test methods employed were CV and DPV.

[0053] 2. Experiment on optimizing the amount of modifying materials:

[0054] (1) Experimental design: The concentration of the modified material (CoFe@C) dispersion was fixed at 1 mg / mL, and the amount of the material was varied on the clean GCE surface, ranging from 4 μL to 8 μL. The peak current of the modified electrode at different amounts of material in response to the electrochemical response of 20 μM TCS was determined by CV. Each amount of material was measured in triplicate, and the average value was taken.

[0055] (2) Experimental results: The results are as follows Figure 4As shown, when the coating amount increased from 4 μL to 6 μL, the increase in electrode area led to an increase in the oxidation peak current. However, when the coating amount gradually increased from 6 μL to 8 μL, the excessive accumulation of material hindered electron transport, resulting in a decrease in the oxidation peak current. 6 μL was selected as the optimal coating amount, and this coating amount was used to prepare the modified electrode (CoFe@C / GCE) in subsequent experiments.

[0056] Example 4

[0057] Based on the optimal drop-coating amount determined in Example 3, the electrolyte pH value and scanning rate were further optimized to clarify the electrochemical reaction characteristics of TCS on the CoFe@C / GCE surface and determine the optimal test conditions.

[0058] 1. pH optimization experiment:

[0059] (1) Experimental design: pH 5-9 buffer solutions were prepared using a pH meter. CoFe@C / GCE was used as the working electrode, and PBS with different pH values ​​was used as the supporting electrolyte. The electrochemical response of 20 μM TCS was measured by CV, and the changes in peak current and peak potential were recorded.

[0060] (2) Experimental results: The results are as follows Figure 5 As shown, the peak current exhibits a parabolic curve with pH, ​​reaching its highest value at pH=7. It can also be observed that the peak potential shifts with pH; as pH increases, the oxidation peak gradually shifts to the left, indicating that not only electron transfer occurs in the TCS electrochemical reaction, but protons also participate in the reaction. Taking all factors into consideration, a buffer solution with pH=7 was chosen as the supporting electrolyte.

[0061] 2. Scan rate optimization experiment:

[0062] (1) Experimental design: In order to determine the kinetic characteristics of the electrochemical reaction of TCS on the electrode surface, 20 μMTCS was used as the detection object. The scanning rate of TCS was investigated by CV, with the scanning rate range being 0.05 V / s to 0.6 V / s. The relationship between the scanning rate and the oxidation peak current and peak potential was analyzed.

[0063] (2) Experimental results: The results are as follows Figure 6 As shown, with the increase of scan speed, the current intensity gradually increases, and the potential also shows a significant positive shift. There is a good linear relationship between the square root of the scan speed and the oxidation peak current of TCS. Subsequent experiments can select an appropriate scan rate according to actual needs.

[0064] Example 5

[0065] In this embodiment, under the above-mentioned optimal experimental conditions, the linear response range and detection limit of the CoFe@C / GCE sensor to TCS are tested, and the detection sensitivity of the sensor is evaluated.

[0066] (1) Experimental method: Under optimal conditions, the test curve of the blank solution was first scanned to a stable state using DPV. Then, TCS was added from the nanomolar level until the oxidation peak appeared. Three sets of data were tested until they stabilized and their peak current was recorded. A series of TCS solutions of different concentrations were added until the peak current value no longer increased or showed a decline, indicating that the concentration of TCS tested by CoFe@C / GCE reached the highest value. At this point, the addition of the test solution was stopped, and the data were sorted out and linear fitting was performed.

[0067] (2) Experimental results: The results are as follows Figure 7 As shown, the oxidation peak current gradually increases with increasing TCS concentration, exhibiting a good linear relationship in the two intervals of 0.5 μM~100 μM and 100 μM~500 μM. The fitting equation is I. pa (μA) = 0.054c(μM) + 0.66(R) 2 =0.9923), I pa (μA) = 0.011c (μM) + 4.82(R) 2 =0.9979). The detection limit (LOD) of the sensor is calculated using the following formula: LOD = 3S D / S (S D S represents the standard deviation of ten blank solution response values, and S is the slope of the linear equation. Using the above equation, the limit of detection (LOD) for TCS was calculated to be 0.05 μM. The results indicate that this sensor has high sensitivity and a low limit of detection for TCS.

[0068] Example 6

[0069] This embodiment tests the anti-interference and stability of the CoFe@C / GCE sensor, and verifies the reliability of its detection results and long-term performance.

[0070] 1. Anti-interference research:

[0071] Interference immunity experiments are a crucial step in verifying the selectivity and reliability of electrochemical sensors. Using the DPV method, potential interfering substances were added to a buffer solution containing 20 μM TCS at concentrations greater than ten times the normal level. The changes in the TCS oxidation peak current before and after the addition of the interfering substances were compared. The standards for interfering substances included small molecules, large molecules, substances with the same electrochemical response groups, and substances that might coexist during application, including inorganic salts, melamine, citric acid, hydroquinone, and L-menthol. The results are as follows: Figure 8As shown, after adding more than ten times the concentration of interfering substances, the curve obtained by DPV detection of TCS was not significantly different from that without the addition of interfering substances. The change in the TCS oxidation peak current was within 5%, indicating that the sensor has good anti-interference and selectivity and can effectively avoid the influence of common interfering substances on TCS detection.

[0072] 2. Stability test:

[0073] Stability testing is crucial for evaluating the long-term reliable detection capability of electrochemical sensors and ensuring reproducibility in practical applications. A fresh 1 mg / mL CoFe@C suspension was prepared. Under optimal experimental conditions, the material was used to prepare modified electrodes every 5 days, and DPV was used to detect 20 μM TCS for 20 consecutive days, recording changes in the oxidation peak current. The results are as follows: Figure 9 As shown, the variation range of the TCS oxidation peak current detected by CoFe@C / GCEs within 20 days does not exceed 5%, confirming that the sensor has good stability and can meet the requirements for long-term reliable detection.

[0074] Example 7

[0075] This embodiment uses the CoFe@C / GCE sensor to detect TCS residues in real samples, evaluating its applicability and feasibility in complex sample environments.

[0076] Toothpaste, lake water, and tap water were selected for spiked analysis. Lake water and tap water were sourced locally, while toothpaste was purchased from a supermarket. The toothpaste sample was prepared according to the following procedure: First, 0.5 g of toothpaste solid was weighed and added to 70% ethanol, and sonicated for 30 min. It was then filtered twice through filter paper, followed by two filtrations through a 0.45 μm pore size membrane. Finally, it was diluted with PBS (pH=7) to a total volume of 50 mL to maintain pH stability. Tap water and lake water samples were diluted five-fold with PBS at pH=7. All real samples were refrigerated at 4°C for later use.

[0077] Using the standard addition method, a certain amount of TCS was added to the pre-treated actual samples within the linear range, and then detected by DPV. Each sample was measured in triplicate, and the recovery rates are shown in Table 1. The sensor's TCS recovery rate ranged from 97% to 104%, with a relative standard deviation within 5%. This indicates that the sensor still has high selectivity and reliability in complex sample environments and has good application potential in practical TCS detection.

[0078] Table 1: Actual Sample Test Results

[0079]

[0080] The results of the above embodiments demonstrate that the CoFe@C-based sensor prepared by the method of the present invention exhibits excellent performance in TCS detection. Material characterization results show that the CoFe@C composite material possesses excellent structure and properties, and the sensor constructed based on this exhibits good catalytic performance, demonstrating high sensitivity, a wide linear response range, and a low detection limit in TCS detection. Furthermore, the sensor also exhibits good anti-interference ability and stability, and when used for the detection of actual samples, the recovery rate is close to 100%, verifying its application potential in real-world sample detection.

Claims

1. A method for preparing a highly sensitive electrochemical sensor for detecting triclosan, characterized in that, Includes the following steps: (1) Co(NO3)2·6H2O and 2-methylimidazole were dissolved in an organic solvent, mixed evenly, and then aged. The reaction product was washed and dried to obtain ZIF-67 powder. (2) ZIF-67 powder was uniformly dispersed in ethanol to obtain solution A, K3[Fe(CN)6] was uniformly dissolved in deionized water to obtain solution B, solution B was added to solution A and stirred and mixed, and then the mixed solution was subjected to hydrothermal reaction. The product was washed, centrifuged and dried to obtain CoFe MOF; (3) The CoFe MOF was subjected to high-temperature carbonization treatment. After cooling, the black powder was collected to obtain CoFe@C; (4) Drop the suspension of CoFe@C onto the pre-polished clean glassy carbon electrode, bake it dry, and let it cool naturally to room temperature.

2. The method for preparing a highly sensitive electrochemical sensor for detecting triclosan according to claim 1, characterized in that, In step (1), the organic solvent is methanol; the aging time is 12 h to 24 h.

3. The method for preparing a highly sensitive electrochemical sensor for detecting triclosan according to claim 1, characterized in that, In step (2), the temperature of the reactor is set to 150℃~180℃ and the reaction time is 12 h~15 h.

4. The method for preparing a highly sensitive electrochemical sensor for detecting triclosan according to claim 1, characterized in that, In step (3), the gas selected in the tubular furnace is argon or nitrogen, the temperature is set to 600℃, and the holding time is 2 h to 3 h.

5. The method for preparing a highly sensitive electrochemical sensor for detecting triclosan according to claim 1, characterized in that, In step (4), the amount of CoFe@C suspension dropped is 4 μL to 8 μL.

6. An electrochemical sensor for detecting triclosan, characterized in that, The high-sensitivity electrochemical sensor for detecting triclosan was prepared using the method described in any one of claims 1-5.

7. The electrochemical sensor for detecting triclosan according to claim 6, characterized in that, The steps for detecting triclosan include: using a standard three-electrode system, electrochemical testing is performed in a phosphate buffer solution with a pH of 5.0–9.0, and cyclic voltammetry and differential pulse voltammetry are used to detect the test solution containing triclosan. The linear range of the detection is 0.5 μM–500 μM.

Images