Dual-signal molecularly imprinted electrochemical sensor based on Cu / Fe-MOF and AuNPs and its preparation method

Abstract

This invention provides a dual-signal molecularly imprinted electrochemical sensor based on Cu / Fe-MOF and AuNPs, and its preparation method. Using carbon cloth as a substrate, Cu / Fe-MOF is grown in situ and AuNPs are electrodeposited to modify the electrode, constructing a dual-signal system. A molecularly imprinted polymer film is prepared by electropolymerization using aminourea as a template. This sensor achieves highly sensitive detection of aminourea through dual-signal variations, with a linear range of 0.005–100 nM and a detection limit of 0.0039 nM. This invention combines large specific surface area materials and molecular imprinting technology, improving detection sensitivity and specificity; the dual-signal mode enhances detection stability and accuracy; the preparation method is simple and low-cost, suitable for quantitative analysis of trace substances, and has broad application prospects.

Description

Technical Field

[0001] This invention relates to the field of electrochemical sensor technology, specifically to a dual-signal molecularly imprinted electrochemical sensor based on Cu / Fe-MOF and AuNPs and its preparation method. Background Technology

[0002] Furazolidone (NFZ), a widely used antibacterial drug in animal husbandry and aquaculture, plays a vital role in preventing and controlling various animal diseases. However, NFZ metabolism produces saminoglycans (SEM), which can stably bind to proteins, forming potentially carcinogenic and teratogenic food residues that pose a threat to human health. Given that SEM remains relatively stable in animal bodies, its usage and distribution are typically monitored indirectly, rather than NFZ itself, by detecting SEM levels to ensure the safety of animal food products.

[0003] Currently, traditional methods for SEM analysis include ultra-high performance liquid chromatography-tandem mass spectrometry, fluorescence methods, and surface-enhanced Raman scattering. While these methods offer certain analytical capabilities under specific conditions, they are often limited by high operating costs or insufficient sensitivity, significantly restricting their practical application. In contrast, electrochemical methods, due to their high precision, high sensitivity, ease of operation, and low cost, have become a more promising analytical approach. Voltammetry, in particular, as an electrochemical and electroanalytical technique based on the relationship between measured current and applied potential, can efficiently analyze trace substances, possessing a wide linear range of analytical concentrations, short analysis time, and selectivity for various solvents and electrolytes. Furthermore, it can simultaneously determine multiple analytes without prior separation. Among these, differential pulse voltammetry (DPV) has become one of the most widely used voltammetric methods due to its high efficiency, sensitivity, stability, and accuracy in detecting low-concentration analytes.

[0004] In the field of electrochemical sensors, molecularly imprinted layers can provide high selectivity, as demonstrated in application number "202210043233.4," which describes a molecularly imprinted electrochemical sensor based on a CoMOF-IL sensitive film-modified electrode, along with its preparation and detection methods. However, this method still has some limitations, such as insufficient stability of single-signal electrochemical sensors. To overcome this deficiency, a dual-signal mode is introduced. This mode can reduce interference from external factors such as environment and temperature by generating two electrochemical signals from different sources, thereby improving the stability and accuracy of detection.

[0005] While molecularly imprinted layers can improve selectivity, surface-modified molecularly imprinted polymer (MIP) layers often hinder electron transport, leading to decreased sensor sensitivity. Therefore, it is necessary to introduce materials with large specific surface areas and excellent charge transfer properties onto the electrode surface to increase active sites, reduce charge transfer resistance, and thus improve detection sensitivity. Cu / Fe-MOF, as an electrode material, provides abundant coordination sites, enabling electrode functionalization and electrochemical reactions. Furthermore, gold nanoparticles (AuNPs) not only exhibit good biocompatibility but also demonstrate excellent stability and reliable electrocatalytic performance, providing an effective electron transport interface for the electrode and further enhancing sensor performance.

[0006] In summary, although existing technologies can achieve SEM detection to a certain extent, they still suffer from insufficient stability and limited sensitivity. Therefore, developing a novel electrochemical sensor that combines molecular imprinting technology, efficient charge transfer materials, and a dual-signal readout mode is of great significance for improving the stability, sensitivity, and accuracy of detection, and is also an urgent need for current technological development. Summary of the Invention

[0007] This invention provides a dual-signal molecularly imprinted electrochemical sensor based on Cu / Fe-MOF and AuNPs and its preparation method, which solves the problems of poor specificity and high cost in the prior art.

[0008] To achieve the objectives of this invention, the technical solution provided by this invention is as follows:

[0009] A method for preparing a dual-signal molecularly imprinted electrochemical sensor based on Cu / Fe-MOF and AuNPs, characterized by comprising the following steps:

[0010] Step 1: Preparation of modified electrodes: AuNPs and Cu / Fe-MOF modified carbon cloth electrodes AuNPs / Cu / Fe-MOF / CC are prepared using hydrothermal and electrodeposition methods.

[0011] Step 2: Preparation of molecularly imprinted polymers: Add functional monomers and template molecule aminourea, and use AuNPs / Cu / Fe-MOF / CC as the working electrode to electropolymerize MIP using cyclic voltammetry: Polymerize in PBS solution containing SEM and monomers. After polymerization, immerse the working electrode in eluent to remove the template.

[0012] Step 3: The prepared molecularly imprinted sensor was used to re-identify targets at different concentrations. The testing method was electrochemical, with the CV test potential range being -0.2–0.6V and -0.2–0.85V, the DPV test range being -0.2–0.85V, and the EIS test frequency being 0.1Hz–100KHz with an amplitude of 5mV.

[0013] In step one, 1.0-1.5g of Cu(NO3)·3H2O and 0.05-0.30g of FeCl3·6H2O are dissolved in 22.5ml of ultrapure water and stirred until fully dissolved; aromatic acid is dissolved in 7.5ml of ethanol and 7.5ml of DMF and sonicated for 1h until fully dissolved; then the two solutions are mixed, and a water-soluble polymer is added for surface shaping, and sonication is continued for 1h. A piece of carbon cloth is added and placed in a reaction vessel, and the reaction is carried out at 100℃ for 6-18h; after the reaction is completed, the carbon cloth is taken out, washed alternately with ethanol and ultrapure water, and dried in an oven at 40℃ for 12h; Cu / Fe-MOF / CC is prepared.

[0014] The aromatic acid is one or more of benzoic acid, phthalic acid, triphthalic acid, and terephthalic acid.

[0015] In step one, 5-20 ml of HAuCl4 solution is used as the electrolyte, Cu / Fe-MOF / CC is used as the working electrode, a platinum sheet is used as the counter electrode, and a saturated calomel electrode is used as the reference electrode. The potential is set to -0.2–0.3 V, and electrodeposition is performed for 200-900 s. The electrode surface is rinsed with ethanol and ultrapure water and placed in a 40℃ oven for 12 h for later use; thus, AuNPs / Cu / Fe-MOF / CC electrode is prepared.

[0016] The specific steps of step two are as follows: in a three-electrode system, MIP is electropolymerized using cyclic voltammetry; in a PBS solution containing SEM and monomer, the voltage range is set between 0 and 1.2V, the rate is 20-200mV / s, and the number of polymerization cycles is 10-30; the working electrode is immersed in a weakly acidic elution solution to elute the template.

[0017] The specific steps of step three are as follows: electrochemical testing is performed in a three-electrode system, using AuNPs / Cu / Fe-MOF / CC as the working electrode. The tests include CV, DPV, and EIS measurements. The CV test potential ranges are -0.2–0.6V and -0.2–0.85V, the DPV test range is -0.2–0.85V, and the EIS test frequency is 0.1Hz–100kHz with an amplitude of 5mV. The electrolyte used in the tests contains 5mM [Fe(CN)6]. 3- / 4- And a probe solution of 0.1M potassium chloride.

[0018] The dual-signal molecularly imprinted electrochemical sensor based on Cu / Fe-MOF and AuNPs was prepared using the method described above.

[0019] Compared with the prior art, the advantages of the present invention are:

[0020] 1. High Sensitivity and Specificity Detection: This invention introduces electrode modification materials with large specific surface area and excellent charge transfer properties to increase the active sites on the electrode surface, thereby reducing the electrode charge transfer resistance and improving detection sensitivity. Specifically, this invention constructs a dual-signal detection system by modifying the electrode, and combined with the high selectivity of molecularly imprinted polymers (MIPs), successfully prepares a high-sensitivity electrochemical sensor, particularly suitable for the detection of urea (SEM). Under optimal conditions, the sensor's linear range reaches 0.005-100 nM, and the detection limit is as low as 0.0039 nM, demonstrating extremely high detection sensitivity and specificity.

[0021] 2. Construction of a dual-signal detection system: A copper-iron based metal-organic framework (Cu / Fe-MOF) was grown in situ using carbon cloth as the substrate electrode, and an inducing electrolyte [Fe(CN)6] was used. 3- / 4- A peak current is generated at a specific potential of 0.67V. Simultaneously, gold nanoparticles (AuNPs) are reduced in situ on the electrode, further increasing the electrochemical area of ​​the electrode, reducing the charge transfer resistance, and enhancing the current signal at a potential of 0.18V, thereby constructing a dual-signal detection system and improving the reliability and accuracy of detection.

[0022] 3. Innovations in Material Synthesis and Electrode Modification: Modified electrodes were prepared using hydrothermal and electrodeposition methods, ensuring uniform coverage and tight bonding of Cu / Fe-MOF and AuNPs on the carbon cloth surface. This method is not only simple to operate but also low in cost and easy to mass-produce.

[0023] 4. Application of Molecularly Imprinted Polymers (MIPs): Using SEM as a template molecule, MIP films are prepared by electropolymerization on modified electrodes. The MIP films can specifically recognize SEM molecules, resulting in a decrease in the intensity of the dual signal peaks after SEM adsorption and an increase in peak intensity after SEM elution, thus achieving specific detection of SEM.

[0024] 5. Significant Improvement in Electrochemical Performance: Electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and differential pulse voltammetry (DPV) were used to verify the significant improvement in electrochemical performance of the modified electrode. In particular, the introduction of AuNPs significantly reduced the charge transfer resistance of the electrode, enhanced the current signal, and improved the response speed and sensitivity of the sensor.

[0025] 6. Broad Application Prospects: The electrochemical sensor prepared in this invention is not only suitable for the detection of aminourea, but can also be extended to the quantitative analysis of other trace substances. Due to its advantages such as high sensitivity, specificity, and low cost, it has broad application prospects in environmental monitoring, food safety, and pharmaceutical analysis.

[0026] In summary, the advantages of this invention are mainly reflected in high sensitivity and specificity detection, the construction of a dual-signal detection system, innovations in material synthesis and electrode modification, the application of molecularly imprinted polymers, significant improvement in electrochemical performance, and broad application prospects. These advantages collectively constitute the core competitiveness of this invention, providing new ideas and methods for the development of electrochemical sensors. Attached Figure Description

[0027] Figure 1 In the image, A and B are SEM images of Cu / Fe-MOF / CC and AuNPs / Cu / Fe-MOF / CC, respectively.

[0028] Figure 2 The figures below show the XRD test results for CC, Cu / Fe-MOF / CC, and AuNPs / Cu / Fe-MOF / CC.

[0029] Figure 3 This is an XPS plot of AuNPs / Cu / Fe-MOF / CC.

[0030] Figure 4 EIS testing of CC, Cu / Fe-MOF / CC and AuNPs / Cu / Fe-MOF / CC.

[0031] Figure 5 The CV tests and linear equations for CC, Cu / Fe-MOF / CC, and AuNPs / Cu / Fe-MOF / CC at different scan rates are presented.

[0032] Figure 6 The stability of AuNPs / Cu / Fe-MOF / CC is tested using electrochemical methods.

[0033] Figure 7 It is an EIS test during the working process of MIP / AuNPs / Cu / Fe-MOF / CC.

[0034] Figure 8 It is the DPV test during the working process of MIP / AuNPs / Cu / Fe-MOF / CC.

[0035] Figure 9 It is a sensor for detecting DPV and linear range of different concentrations of aminourea. Detailed Implementation

[0036] The method of the present invention will be described below with reference to specific embodiments and accompanying drawings, but the present invention is not limited thereto. Unless otherwise specified, the experimental methods described in the following embodiments are conventional methods, and the reagents and materials described are commercially available.

[0037] Example 1

[0038] A method for preparing a dual-signal molecularly imprinted electrochemical sensor based on Cu / Fe-MOF and AuNPs includes the following steps:

[0039] Step 1: Preparation of modified electrode:

[0040] Hydrophilic treatment of carbon cloth: Immerse 1×2cm CC in a mixed solution containing 10% nitric acid and sulfuric acid (v / v=3 / 1) for 3 days, then wash with water and ethanol alternately before use.

[0041] Preparation of Cu / Fe-MOF / CC: 1.033 g of Cu(NO3)·3H2O and 0.25 g of FeCl3·6H2O were dissolved in 22.5 ml of ultrapure water and stirred until fully dissolved. 0.1 g of tricresylbenzene was dissolved in 7.5 ml of ethanol and 7.5 ml of DMF and sonicated for 1 h until fully dissolved. Then, the two solutions were mixed, and 1 ml (1 g / L) of PEI (a polymer compound used for surface shaping) was added. The mixture was sonicated for another 1 h, and a piece of carbon cloth was added. The mixture was placed in a reaction vessel and reacted at 100 °C for 12 h. After the reaction was complete, the carbon cloth was removed, washed alternately with ethanol and ultrapure water, and dried in an oven at 40 °C for 12 h.

[0042] Preparation of AuNPs / Cu / Fe-MOF / CC: 10 ml HAuCl4 (10 mM) solution was used as the electrolyte, Cu / Fe-MOF / CC was used as the working electrode, a platinum sheet was used as the counter electrode, and a saturated calomel electrode was used as the reference electrode. The potential was set to 0.15 V, and electrodeposition was carried out for 600 s. The electrode surface was rinsed with ethanol and ultrapure water and then placed in a 40 ℃ oven for 12 h before use.

[0043] Step 2: Prepare molecularly imprinted polymers (MIPs) using resorcinol and template molecule aminourea (SEM):

[0044] MIP was electropolymerized using cyclic voltammetry. Polymerization was performed in PBS (0.1 M, pH 6) solution containing SEM (1.5 mM) and phenolic monomers at a voltage of 0–0.8 V for 20 cycles at 50 mV / s. The working electrode was immersed in eluent (v / v = 9 / 1) to elute the template.

[0045] Step 3: Performance analysis of the molecularly imprinted electrochemical sensor using electrochemical methods:

[0046] The operation of the molecularly imprinted electrochemical sensor was characterized using electrochemical methods. The CV testing potential range was -0.2–0.6 V and -0.2–0.85 V, the DPV testing range was -0.2–0.85 V, and the EIS testing frequency was 0.1 Hz–100 kHz with an amplitude of 5 mV. All electrolytes used in the tests contained 5 mM [Fe(CN)6]. 3- / 4- A probe solution of 0.1M potassium chloride was used. After adsorbing template molecules onto the MIP / AuNPs / Cu / Fe-MOF / CC electrode, the concentration of the analyte was indirectly reflected by the total difference between the pre- and post-adsorption values ​​measured using DPV. To test the electrocatalytic activity of different electrodes, a 5mM [Fe(CN)6] solution was used. 3- / 4- EIS testing was performed using 0.1 M potassium chloride as the electrolyte.

[0047] Comparison Example

[0048] Preparation of non-imprinted polymers: The above experimental steps were repeated without adding a template molecule to the polymerization solution using SEM. The non-imprinted polymer served as a control group, reflecting the difference between monomer-imprinted and molecularly imprinted polymers.

[0049] Example 2

[0050] A method for preparing a dual-signal molecularly imprinted electrochemical sensor based on Cu / Fe-MOF and AuNPs includes the following steps:

[0051] Step 1: Preparation of modified electrode:

[0052] Hydrophilic treatment of carbon cloth: Immerse 1×2cm CC in a mixed solution containing 10% nitric acid and sulfuric acid (v / v=3 / 1) for 3 days, then wash with water and ethanol alternately before use.

[0053] Preparation of Cu / Fe-MOF / CC: 1.0 g of Cu(NO3)3H2O and 0.05 g of FeCl3·6H2O were dissolved in 22.5 ml of ultrapure water and stirred until fully dissolved. 0.1 g of benzoic acid was dissolved in 7.5 ml of ethanol and 7.5 ml of DMF and sonicated for 1 h until fully dissolved. Then, the two solutions were mixed, and 0.5 ml of polyvinyl alcohol (1 g / L) was added, followed by sonication for another 1 h. A piece of carbon cloth was then added, and the mixture was placed in a reaction vessel and reacted at 100 °C for 12 h. After the reaction was complete, the carbon cloth was removed, washed alternately with ethanol and ultrapure water, and dried in an oven at 40 °C for 12 h.

[0054] Preparation of AuNPs / Cu / Fe-MOF / CC: 5 ml HAuCl4 (10 mM) solution was used as the electrolyte, Cu / Fe-MOF / CC was used as the working electrode, a platinum sheet was used as the counter electrode, and a saturated calomel electrode was used as the reference electrode. The potential was set to -0.2 V, and electrodeposition was carried out for 900 s. The electrode surface was rinsed with ethanol and ultrapure water and then placed in a 40 ℃ oven for 12 h before use.

[0055] Step 2: Prepare molecularly imprinted polymers (MIPs) using o-phenylenediamine and the template molecule aminourea (SEM):

[0056] MIP was electropolymerized using cyclic voltammetry. Polymerization was performed in PBS (0.1 M, pH 6) solution containing SEM (0.5 mM) and monomer at a voltage of 0–1.0 V for 10 cycles at 200 mV / s. The working electrode was immersed in eluent (v / v = 9 / 1) to elute the template.

[0057] Step 3: Performance analysis of the molecularly imprinted electrochemical sensor using electrochemical methods:

[0058] The operation of the molecularly imprinted electrochemical sensor was characterized using electrochemical methods. The CV testing potential range was -0.2–0.6 V and -0.2–0.85 V, the DPV testing range was -0.2–0.85 V, and the EIS testing frequency was 0.1 Hz–100 kHz with an amplitude of 5 mV. All electrolytes used in the tests contained 5 mM [Fe(CN)6]. 3- / 4- A probe solution of 0.1M potassium chloride was used. After adsorbing template molecules onto the MIP / AuNPs / Cu / Fe-MOF / CC electrode, the concentration of the analyte was indirectly reflected by the total difference between the pre- and post-adsorption values ​​measured using DPV. To test the electrocatalytic activity of different electrodes, a 5mM [Fe(CN)6] solution was used. 3- / 4- EIS testing was performed using 0.1 M potassium chloride as the electrolyte.

[0059] Example 3

[0060] A method for preparing a dual-signal molecularly imprinted electrochemical sensor based on Cu / Fe-MOF and AuNPs includes the following steps:

[0061] Step 1: Preparation of modified electrode:

[0062] Hydrophilic treatment of carbon cloth: Immerse 1×2cm CC in a mixed solution containing 10% nitric acid and sulfuric acid (v / v=3 / 1) for 3 days, then wash with water and ethanol alternately before use.

[0063] Preparation of Cu / Fe-MOF / CC: 1.5 g of Cu(NO3)3H2O and 0.30 g of FeCl3·6H2O were dissolved in 22.5 ml of ultrapure water and stirred until fully dissolved. 0.1 g of benzoic acid was dissolved in 7.5 ml of ethanol and 7.5 ml of DMF and sonicated for 1 h until fully dissolved. Then, the two solutions were mixed, and 3.0 ml of polyvinyl alcohol (1 g / L) was added, followed by sonication for another 1 h. A piece of carbon cloth was then added, and the mixture was placed in a reaction vessel and reacted at 100 °C for 12 h. After the reaction was complete, the carbon cloth was removed, washed alternately with ethanol and ultrapure water, and dried in an oven at 40 °C for 12 h.

[0064] Preparation of AuNPs / Cu / Fe-MOF / CC: 20 ml HAuCl4 (10 mM) solution was used as the electrolyte, Cu / Fe-MOF / CC was used as the working electrode, a platinum sheet was used as the counter electrode, and a saturated calomel electrode was used as the reference electrode. The potential was set to 3.0 V, and electrodeposition was carried out for 200 s. The electrode surface was rinsed with ethanol and ultrapure water and then placed in a 40 ℃ oven for 12 h before use.

[0065] Step 2: Prepare molecularly imprinted polymers (MIPs) using o-phenylenediamine and the template molecule aminourea (SEM):

[0066] MIP was electropolymerized using cyclic voltammetry. Polymerization was performed in PBS (0.1 M, pH 6) solution containing SEM (2.5 mM) and monomer at a voltage of 0–1.2 V for 30 cycles at 20 mV / s. The working electrode was immersed in eluent (v / v = 9 / 1) to elute the template.

[0067] Step 3: Performance analysis of the molecularly imprinted electrochemical sensor using electrochemical methods:

[0068] The operation of the molecularly imprinted electrochemical sensor was characterized using electrochemical methods. The CV testing potential range was -0.2–0.6 V and -0.2–0.85 V, the DPV testing range was -0.2–0.85 V, and the EIS testing frequency was 0.1 Hz–100 kHz with an amplitude of 5 mV. All electrolytes used in the tests contained 5 mM [Fe(CN)6]. 3- / 4- A probe solution of 0.1 M potassium chloride was used. After adsorbing template molecules onto the MIP / AuNPs / Cu / Fe-MOF / CC electrode, the concentration of the analyte was indirectly reflected by the total difference between the pre- and post-adsorption values ​​measured using DPV. To test the electrocatalytic activity of different electrodes, a 5 mM [Fe(CN)6] solution was used. 3- / 4- EIS testing was performed using 0.1 M potassium chloride as the electrolyte.

[0069] The performance of the electrochemical sensor prepared in Example 1 was analyzed using the following methods.

[0070] The optimal parameters were selected to fabricate the sensing platform, and the DPV method was used in [Fe(CN)6]. 3- / 4- The performance of the MIP / AuNPs / Cu / Fe-MOF / CC electrochemical sensor was analyzed in probe solution. With increasing SEM concentration, the metal continuously occupied the imprinted cavity, hindering electron transfer on the sensing platform, leading to a decrease in the first pair of current peaks. Simultaneously, the metal-provided active centers in the MIP / AuNPs / Cu / Fe-MOF / CC were occupied, resulting in a decrease in the second pair of current peaks. The performance was analyzed using ΔI0. D (ΔI) D =ΔI1+ΔI2) reflects the concentration of the adsorbed template molecules. Analysis of test results at different concentrations shows that the concentration range of MIP / AuNPs / Cu / Fe-MOF / CC adsorbed on SEM is 5×10⁻⁶. -12 - 1×10 -7 M, the dual-signal current response is linearly related to concentration, and the linear equation is ΔI D = 0.0842 log C + 1.0290 (R) 2 =0.9979), detection limit is 3.9 × 10⁻⁶. -12 M (S / N = 3).

[0071] The performance of the dual-signal molecularly imprinted electrochemical sensor based on AuNPs and Cu / Fe-MOF obtained in the examples for testing aminourea is as follows:

[0072] Figure 1 In the figures, A and B are SEM images of Cu / Fe-MOF / CC and AuNPs / Cu / Fe-MOF / CC, respectively. SEM analysis was used to analyze the structural composition during electrode fabrication. Tests showed that AuNPs and Cu / Fe-MOF were uniformly coated on the carbon cloth surface, increasing the electrode's specific surface area. The modification with these two materials provided more electron transfer channels for the electrode. The formation of a dense material layer on the carbon cloth surface through hydrothermal growth of Cu / Fe-MOF / CC and electrodeposition of AuNPs demonstrates the successful synthesis of both materials.

[0073] Figure 2 The image shows the XRD results for CC, Cu / Fe-MOF / CC, and AuNPs / Cu / Fe-MOF / CC. The simulated diffraction peaks of Cu / Fe-MOF grown via hydrothermal method are similar to those of Cu-MOF, confirming the successful synthesis of Cu / Fe-MOF on the carbon cloth surface. AuNPs / Cu / Fe-MOF / CC prepared via electrodeposition showed results consistent with the standard simulated peak information for Au. No other impurity peaks were detected in the test results, demonstrating the successful synthesis of the target material on the electrode.

[0074] Figure 3 This is the XPS full spectrum information of AuNPs / Cu / Fe-MOF / CC. The expected elements can be observed; the nitrogen element originates from PEI generated during electrode fabrication, and the oxygen element originates from aromatic acid ligands.

[0075] Figure 4 EIS tests were performed on CC, Cu / Fe-MOF / CC, and AuNPs / Cu / Fe-MOF / CC. EIS tests were conducted in the probe solution to investigate the change in charge transfer resistance at the electrode interface during electrode modification. The results showed that the charge transfer resistance of the electrode gradually decreased during the stepwise modification of the material on the carbon cloth. This is attributed to the excellent electrocatalytic performance of AuNPs and Cu / Fe-MOF, which catalyzes the reaction of the probe solution at the electrode interface, gradually increasing the conductivity of the electrode material.

[0076] Figure 5 The results show the CV tests and linear equations for CC, Cu / Fe-MOF / CC, and AuNPs / Cu / Fe-MOF / CC at different scan rates. The test results for the three electrodes show a linear relationship between the electrode peak current and the square root of the scan rate, indicating that the electrolyte reaction on the electrode surface is diffusion-controlled. During the modification of the carbon cloth surface, the redox peak current continuously increases at the same scan rate, indicating a continuous increase in the electrochemical active area.

[0077] Figure 6 The stability of AuNPs / Cu / Fe-MOF / CC was tested by electrochemical methods. To ensure the stability of the sensor, the sensing material must be able to be repeatedly tested. The test process involved continuous treatment in the eluent several times, followed by DPV testing. The test results showed that the prepared AuNPs / Cu / Fe-MOF / CC electrode had strong stability. After 20 consecutive treatments and tests, the electrochemical response remained almost unchanged.

[0078] Figure 7 This study presents EIS measurements of the MIP / AuNPs / Cu / Fe-MOF / CC sensor during its operation. EIS characterizes the changes in charge transfer resistance during sensor fabrication and operation. The results show that the charge transfer resistance continuously decreases during material preparation. After polymerizing the molecularly imprinted polymer, a layered structure is formed at the electrode interface, hindering charge transfer in the electrolyte during the electrochemical reaction, leading to an increase in charge transfer resistance. The resistance decreases after eluting the template molecules.

[0079] Figure 8This is a DPV test during the operation of the MIP / AuNPs / Cu / Fe-MOF / CC electrode. The results show that the electrode catalytic performance continuously increases and the current response of the probe solution continuously strengthens during the material modification process. After modifying Cu / Fe-MOF, a new current response emerges, forming a dual-signal electrochemical sensing system. After preparing the molecularly imprinted polymer on the AuNPs / Cu / Fe-MOF / CC electrode, both current signals decrease simultaneously. After removing the template molecules, the current peak values ​​increase simultaneously. The sensor signal readout is the sum of the differences between the two current signals.

[0080] Figure 9 The test results (Fig. 6.B) show that the concentration range of aminourea adsorbed by the MIP / AuNPs / Cu / Fe-MOF / CC sensor is 5 × 10⁻⁶. -12 -1×10 -7 M, the dual-signal current response is linearly related to concentration, and the linear equation is ΔI D =0.0842logC+1.0290(R) 2 =0.9979), detection limit is 3.9×10 -12 M.

[0081] The detailed results illustrated in the accompanying figures clearly demonstrate the successful synthesis, defined structural features, and significant improvement in electrochemical performance of the dual-signal molecularly imprinted electrochemical sensor based on Cu / Fe-MOF and AuNPs. SEM images show the uniform coverage of the modified material on the carbon cloth surface, forming a dense morphology. XRD and XPS analyses verify the successful synthesis of the target material and the presence of the expected elements. EIS, CV, and stability tests indicate that the electrode material possesses excellent electrocatalytic performance and stability. Electrochemical behavior tests during operation reveal a significant change in the dual-signal response and a wide linear detection range, fully demonstrating its advantages in high sensitivity and specificity. These figures collectively demonstrate the significant beneficial effects of this patented technology in the field of electrochemical sensors.

[0082] The above embodiments are merely preferred technical solutions of the present invention and should not be regarded as limitations on the present invention. The scope of protection of the present invention should be the technical solution described in the claims, including equivalent substitutions of the technical features described in the claims. That is, equivalent substitutions and improvements within this scope are also within the scope of protection of the present invention.

Claims

1. A method for preparing a dual-signal molecularly imprinted electrochemical sensor based on Cu / Fe-MOF and AuNPs, characterized in that, Includes the following steps: Step 1: Preparation of modified electrodes: AuNPs and Cu / Fe-MOF modified carbon cloth electrodes AuNPs / Cu / Fe-MOF / CC are prepared using hydrothermal and electrodeposition methods. Step 2: Preparation of molecularly imprinted polymer: Add functional monomers and template molecule aminourea, and use AuNPs / Cu / Fe-MOF / CC as the working electrode to electropolymerize MIP using cyclic voltammetry: Polymerize in PBS solution containing aminourea and monomers. After polymerization, immerse the working electrode in eluent to remove the template. Step 3: The prepared molecularly imprinted sensor was used to re-identify different concentrations of aminourea. The test method was electrochemical, with a CV test potential range of -0.2–0.6V, a DPV test range of -0.2–0.85V, and an EIS test frequency of 0.1Hz–100KHz with an amplitude of 5mV.

2. The method for preparing a dual-signal molecularly imprinted electrochemical sensor based on Cu / Fe-MOF and AuNPs according to claim 1, characterized in that: In step one, 1.0-1.5g of Cu(NO3)2·3H2O and 0.05-0.30g of FeCl3·6H2O are dissolved in 22.5ml of ultrapure water and stirred until fully dissolved; aromatic acid is dissolved in 7.5ml of ethanol and 7.5ml of DMF and sonicated for 1h until fully dissolved; then the two solutions are mixed, and a water-soluble polymer is added for surface shaping, and sonication is continued for 1h. A piece of carbon cloth is added and placed in a reaction vessel, and the reaction is carried out at 100℃ for 6-18h; after the reaction is completed, the carbon cloth is taken out, washed alternately with ethanol and ultrapure water, and dried in an oven at 40℃ for 12h; Cu / Fe-MOF / CC is prepared.

3. The method for preparing a dual-signal molecularly imprinted electrochemical sensor based on Cu / Fe-MOF and AuNPs according to claim 2, characterized in that: The aromatic acid is one or more of benzoic acid, phthalic acid, and tribenzoic acid.

4. The method for preparing a dual-signal molecularly imprinted electrochemical sensor based on Cu / Fe-MOF and AuNPs according to claim 1, characterized in that: In step one, 5-20 ml of HAuCl4 solution is used as the electrolyte, Cu / Fe-MOF / CC is used as the working electrode, a platinum sheet is used as the counter electrode, and a saturated calomel electrode is used as the reference electrode. The potential is set to -0.2–0.3 V, and electrodeposition is performed for 200-900 s. The electrode surface is rinsed with ethanol and ultrapure water and placed in a 40℃ oven for 12 h for later use; thus, AuNPs / Cu / Fe-MOF / CC electrode is prepared.

5. The method for preparing a dual-signal molecularly imprinted electrochemical sensor based on Cu / Fe-MOF and AuNPs according to claim 1, characterized in that: The specific steps of step two are as follows: in a three-electrode system, MIP is electropolymerized using cyclic voltammetry; in a PBS solution containing aminourea and monomer, the voltage range is set between 0 and 1.2V, the rate is 20-200mV / s, and the number of polymerization cycles is 10-30; the working electrode is immersed in a weakly acidic elution solution to elute the template.

6. The method for preparing a dual-signal molecularly imprinted electrochemical sensor based on Cu / Fe-MOF and AuNPs according to claim 1, characterized in that: The specific steps of step three are as follows: electrochemical testing is performed in a three-electrode system, using AuNPs / Cu / Fe-MOF / CC as the working electrode. The tests include CV, DPV, and EIS measurements. The CV test potential range is -0.2–0.6V, the DPV test range is -0.2–0.85V, and the EIS test frequency is 0.1Hz–100kHz with an amplitude of 5mV. The electrolyte used in all tests contains 5mM [Fe(CN)6]. 3- / 4- And a probe solution of 0.1M potassium chloride.

7. A dual-signal molecularly imprinted electrochemical sensor based on Cu / Fe-MOF and AuNPs prepared by the method according to claim 1.

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