A method for preparing an electrochemical sensor for dopamine detection

Abstract

This invention provides a method for preparing an electrochemical sensor for dopamine detection, comprising: chelating Co(II) ions with polydopamine and thiourea-ethylenediamine-formaldehyde resin under room temperature stirring to form a polymer precursor; the polymer precursor material includes: deionized water, added polyether F127, thiourea, cobalt nitrate hexahydrate, dopamine hydrochloride powder, ethylenediamine, and formaldehyde; high-temperature carbonization of the polymer precursor to obtain a porous modification material, wherein the modification material is N / S@Co-CNSs; and modifying the working electrode of the electrochemical sensor to be modified using the porous modification material to obtain an electrochemical sensor for dopamine detection. This invention solves the problem of excessively high preparation costs of electrochemical sensors due to the high cost and scarcity of modification materials in the prior art.

Description

Technical Field

[0001] This invention relates to the field of conductive material preparation technology, and in particular to a method for preparing an electrochemical sensor for dopamine detection. Background Technology

[0002] Dopamine (DA) is an important catecholamine neurotransmitter with a unique distribution pattern throughout the brain, plasma, and other tissues in the body. DA transmits signals via DA receptors, exerting various effects on cells. Abnormal levels of DA can lead to neurological disorders such as Parkinson's disease, attention deficit hyperactivity disorder, addiction, and schizophrenia. In clinical practice, DA is used as a DA receptor agonist to treat shock and neurological disorders. Because DA is a high-risk adrenergic receptor agonist, its presence in animal feed and drinking water has been banned in several countries. Consuming meat from animals containing excessive amounts of this drug can cause various side effects such as vomiting, hypertension, and arrhythmias. Therefore, establishing an effective method for detecting DA residues in biological samples is crucial.

[0003] Currently, methods for quantitative analysis of dopamine (DA) include high-performance liquid chromatography (HPLC), liquid chromatography-mass spectrometry (LC-MS), colorimetry, and chemiluminescence. These techniques offer high selectivity and sufficient sensitivity, but suffer from drawbacks such as time consumption and high cost. Electrochemical sensors, as an emerging detection method, offer advantages such as speed, sensitivity, and convenience. Electrochemical sensors for DA detection typically use glassy carbon electrodes (GCE) as the working electrode, but these electrodes have limitations in electron transfer capability, sensitivity, and selectivity. A common strategy to improve sensor performance is to modify the working electrode with conductive materials to accelerate the electrochemical reaction at the interface.

[0004] Conventional materials used to modify electrochemical sensors include metal nanomaterials, carbon materials, polymer nanomaterials, and other potential modifiers. Metal nanomaterials are widely used in electrochemical detection due to their high specific surface area, high electronic conductivity, and excellent catalytic properties. For example, Saeb et al. used gold nanoparticles to improve the conductivity of a core-shell ZIF-8@ZIF-67 modified electrode, enabling the oxidation of nitrite at a lower potential and a higher current response, thus achieving easy detection of nitrite in samples such as sausages, cooked meat, and drinking water in a shorter time. However, the high cost and scarcity of precious metals severely hinder their widespread application. Summary of the Invention

[0005] In order to overcome the shortcomings of the prior art, the purpose of this invention is to provide a method for preparing an electrochemical sensor for dopamine detection. This invention solves the problem that the high cost of preparing electrochemical sensors is caused by the high cost and scarcity of the modifying materials in the prior art.

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

[0007] A method for preparing an electrochemical sensor for dopamine detection, comprising:

[0008] Co(II) ions are self-assembled with polydopamine and thiourea-ethylenediamine-formaldehyde resin under stirring at room temperature through chelation to form a polymer precursor. The polymer precursor materials include: deionized water, polyether F127, thiourea, cobalt nitrate hexahydrate, dopamine hydrochloride powder, ethylenediamine, and formaldehyde.

[0009] The polymer precursor is subjected to high-temperature carbonization to obtain a porous modified material, wherein the modified material is N / S@Co-CNSs;

[0010] The porous modification material is used to modify the working electrode of the electrochemical sensor to be modified in order to obtain an electrochemical sensor for dopamine detection.

[0011] Preferably, the process for forming the polymer precursor includes:

[0012] Deionized water was poured into the reaction vessel, and polyether F127, thiourea and cobalt nitrate hexahydrate were added in sequence to obtain the first mixed preparation solution;

[0013] The first mixed preparation solution is stirred until the materials in the first mixed preparation solution are completely dissolved to obtain the second mixed preparation solution;

[0014] Add dopamine hydrochloride powder to the second mixed preparation solution and wait for 5 minutes. Then, use a pipette to add ethylenediamine dropwise to the second mixed preparation solution at a rate of 15 seconds / drop to obtain the third mixed preparation solution.

[0015] Formaldehyde was added to the third mixed preparation solution at 5-minute intervals to obtain the fourth mixed preparation solution;

[0016] The fourth mixed preparation solution was continuously stirred for 24 hours to obtain the centrifuged product;

[0017] The polymer product was obtained from the centrifuged product.

[0018] Preferably, the polymer product obtained from the centrifuged product comprises:

[0019] The impurities in the centrifuged product precipitate were washed in the order of water-ethanol-water to obtain the washed centrifuged product.

[0020] The washed and centrifuged product was precipitated in an environment with a temperature of 80°C and vacuum drying to obtain a polymer precursor.

[0021] Preferably, the high-temperature carbonization of the polymer precursor to obtain the porous modified material comprises:

[0022] Construct a nitrogen atmosphere environment;

[0023] The polymer precursor was placed in a nitrogen atmosphere and heated to 5°C for 1 minute. -1 up to 800℃min -1 The polymer precursor was heated at a certain rate and held for 2 hours to obtain a porous modified material.

[0024] Preferably, the amounts of materials required to form the polymer precursor include:

[0025] 0.3g dopamine powder, 0.3mL ethylenediamine, 60mL deionized water, 0.3g polyether F127, 0.375g thiourea, 0.15g cobalt nitrate hexahydrate and 0.65mL formaldehyde.

[0026] Preferably, the stirring speed for the first mixed preparation solution is 1000 rpm.

[0027] Preferably, the stirring time for the first mixed preparation solution is 15 minutes.

[0028] Preferably, the porous modification material is used to modify the working electrode of the electrochemical sensor to be modified to obtain an electrochemical sensor for dopamine detection, comprising:

[0029] The surface of a 3mm diameter working electrode was polished on a wet chamois using 0.3μm alumina polishing powder and 0.05μm alumina polishing powder in sequence to obtain the polished working electrode.

[0030] The polished working electrode is rinsed with deionized water to obtain the rinsed working electrode.

[0031] The rinsed working electrode was placed vertically in deionized water and ultrasonically cleaned three times until no aluminum oxide polishing powder residue remained on the surface of the rinsed working electrode, thus obtaining a residue-free working electrode.

[0032] At a concentration of 0.5 mol L -1 The activated working electrode was obtained by activating the electrode without residue in a dilute sulfuric acid solution using cyclic voltammetry.

[0033] 3 mg N / S@Co-CNSs was dispersed by ultrasound in a mixture of 30 μL of 5 wt.% Nafion solution, 475 μL of deionized water and 475 μL of anhydrous ethanol for 20 min to obtain a dispersion of porous modified material.

[0034] An electrochemical sensor for dopamine detection was obtained by transferring 5 μL of the dispersion to the surface of the activated working electrode using a pipette and drying it at room temperature for 1 h.

[0035] Preferably, the time range for each ultrasonic cleaning in the three ultrasonic cleaning sessions is 2-3 minutes.

[0036] Preferably, the process of activating the working electrode is as follows:

[0037] Repeatedly scan the residual working electrode within the range of -1.0 to 1.0 V until a stable CV curve is obtained;

[0038] Set the scan rate to 50 mVs. -1 The scan range was set to -0.1 to 0.6 V, the peak potential difference was set to less than 80 mV, and the sample contained K3[Fe(CN)6], 1.0 mM K4[Fe(CN)6], and 0.1 mol L... -1 CV curves were recorded in a mixed solution of KCl until the working electrode was activated.

[0039] According to specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0040] This invention provides a method for preparing an electrochemical sensor for dopamine detection. The invention efficiently and conveniently prepares nanomaterials using solution self-assembly technology. The prepared N / S-doped carbon-based nanomaterials exhibit excellent sensing performance, including high specific surface area and enhanced electrocatalytic activity. The working electrode of the electrochemical sensor is modified using the nanostructure. This modified electrode (N / S@Co-CNSs / GCE) has a low detection limit, a wide linear range, good selectivity for dopamine (DA), and high sensitivity and accuracy, while also reducing the preparation cost. Attached Figure Description

[0041] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0042] Figure 1 A flowchart illustrating a method for preparing an electrochemical sensor for dopamine detection, provided in an embodiment of the present invention;

[0043] Figure 2 This is a schematic diagram showing the details of the fabrication of the modified electrode provided in an embodiment of the present invention;

[0044] Figure 3A flowchart illustrating the synthesis of N / S@Co-CNSs based on solution self-assembly technology provided in this embodiment of the invention;

[0045] Figure 4 This is a schematic diagram of the XRD pattern of N / S@Co-CNSs provided in an embodiment of the present invention;

[0046] Figure 5 The XPS analysis provided for embodiments of the present invention provides schematic diagrams of the surface chemical composition, valence state, and molecular structure of N / S@Co-CNSs, wherein (a) is an XPS spectrum, (b) is a high-resolution C1s spectrum, (c) is a high-resolution N1s spectrum, (d) is a high-resolution O1s spectrum, (e) is a high-resolution S2p spectrum, and (f) is a high-resolution Co2p spectrum.

[0047] Figure 6 This is a schematic diagram of the EDS spectrum of N / S@Co-CNSs provided in an embodiment of the present invention;

[0048] Figure 7 A schematic diagram of the FTIR spectrum of N / S@Co-CNSs provided in an embodiment of the present invention;

[0049] Figure 8 This is a schematic diagram of electrochemical characterization provided in an embodiment of the present invention, wherein (a) shows the modified electrode at 0.1 mol / L... -1 Schematic diagram of CV response in citric acid-sodium citrate buffer solution (pH=4), (b) shows the modified electrode in a solution containing 50 μmol L... -1 0.1 mol L of DA -1 A schematic diagram of the CV response at different scan rates in a citric acid-sodium citrate buffer solution (pH=4). (c) is a schematic diagram of the calibration curves of the peak current of the anode and cathode as a function of the scan rate, where the upper line represents the cathode.

[0050] Figure 9 The embodiment of the present invention provides a solution containing 50 μmol L -1 0.1 mol L of DA -1 Schematic diagram evaluating the DPV response of the modified electrode in citric acid-sodium citrate buffer solution (at different pH values), where the pH values ​​of the solution are: a, pH=6; b, pH=5; c, pH=4; d, pH=3;

[0051] Figure 10 This is a schematic diagram of the detection results of the DA-modified electrode using the DPV technology provided in this embodiment of the invention, wherein (a) shows the modified electrode in 0.1 mol L of water containing different concentrations of DA. -1A schematic diagram of the DPV response curve in citric acid-sodium citrate buffer solution, (b) is a schematic diagram of the linear fitting between the oxidation peak current and the DA concentration;

[0052] Figure 11 This is a schematic diagram of the current change response of an interfering object provided in an embodiment of the present invention;

[0053] Figure 12 The diagram below illustrates the performance evaluation of the modified electrode according to an embodiment of the present invention, wherein (a) is a diagram illustrating the reproducibility evaluation of the modified electrode; (b) is a diagram illustrating the stability evaluation of the modified electrode; and (c) is a diagram illustrating the repeatability evaluation of the modified electrode. Detailed Implementation

[0054] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0055] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0056] The terms "first," "second," "third," and "fourth," etc., used in the specification, claims, and accompanying drawings of this application are used to distinguish different objects, not to describe a specific order. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion. For example, including a series of steps, processes, methods, etc., is not limited to the steps listed, but may optionally include steps not listed, or may optionally include other steps inherent to these processes, methods, products, or devices.

[0057] The purpose of this invention is to provide a method for preparing an electrochemical sensor for dopamine detection. This invention solves the problem of excessively high preparation costs of electrochemical sensors due to the high cost and scarcity of modifying materials in the prior art.

[0058] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0059] like Figure 1As shown, the present invention provides a method for preparing an electrochemical sensor for dopamine detection, comprising:

[0060] Step 100: Co(II) ions are self-assembled with polydopamine and thiourea-ethylenediamine-formaldehyde resin under stirring at room temperature through chelation to form a polymer precursor; the polymer precursor materials include: deionized water, polyether F127, thiourea, cobalt nitrate hexahydrate, dopamine hydrochloride powder, ethylenediamine and formaldehyde;

[0061] Step 200: The polymer precursor is subjected to high-temperature carbonization to obtain a porous modified material, wherein the modified material is N / S@Co-CNSs;

[0062] Step 300: Modify the working electrode of the electrochemical sensor to be modified using the porous modification material to obtain an electrochemical sensor for dopamine detection.

[0063] Specifically, this self-assembly process for forming polymer precursors occurs at room temperature and requires no special conditions, templates, or pore-forming agents, such as... Figure 2 As shown.

[0064] Specifically, the materials used in the preparation and experimental process in this embodiment include: polyether F127, citric acid, sodium citrate, cobalt nitrate hexahydrate, dopamine hydrochloride, 5 wt.% Nafion, thiourea, ethylenediamine, formaldehyde, anhydrous ethanol, potassium ferrocyanide, potassium ferrocyanide, and a concentration of 1×10 -3 mol L -1 K3[Fe(CN)6] / K4[Fe(CN)6] solution (containing 0.1 mol L) -1 All reagents (KCl) are analytical grade unless otherwise specified. Ultrapure water was used in the experiments.

[0065] Specifically, the instruments used in the preparation and experimental processes in this embodiment include:

[0066] X-ray energy-dispersive spectroscopy (EDS) was performed using a field emission scanning electron microscope (SEM; Carl Zeiss AG, Germany) equipped with an Oxford Instruments X-ray energy dispersive spectrometer. Transmission electron microscopy (TEM; Philips FEI, Netherlands) was used to identify the internal structure of the material. Powder X-ray diffraction (XRD) patterns were obtained using a polycrystalline X-ray diffractometer (Ultima IV; Rigaku Co., Ltd., Japan). Fourier transform infrared spectroscopy (FTIR; Shimadzu, Japan) was used to identify the functional groups of the material. X-ray photoelectron spectroscopy (XPS; Thermo Fisher Scientific, USA) was used to determine the surface elements and their chemical states.

[0067] Furthermore, the process for forming the polymer precursor includes:

[0068] Deionized water was poured into the reaction vessel, and polyether F127, thiourea and cobalt nitrate hexahydrate were added in sequence to obtain the first mixed preparation solution;

[0069] The first mixed preparation solution is stirred until the materials in the first mixed preparation solution are completely dissolved to obtain the second mixed preparation solution;

[0070] Add dopamine hydrochloride powder to the second mixed preparation solution and wait for 5 minutes. Then, use a pipette to add ethylenediamine dropwise to the second mixed preparation solution at a rate of 15 seconds / drop to obtain the third mixed preparation solution.

[0071] Formaldehyde was added to the third mixed preparation solution at 5-minute intervals to obtain the fourth mixed preparation solution;

[0072] The fourth mixed preparation solution was continuously stirred for 24 hours to obtain the centrifuged product;

[0073] The polymer product was obtained from the centrifuged product.

[0074] Further, the polymer product obtained from the centrifuged product includes:

[0075] The impurities in the centrifuged product precipitate were washed in the order of water-ethanol-water to obtain the washed centrifuged product.

[0076] The washed and centrifuged product was precipitated in an environment with a temperature of 80°C and vacuum drying to obtain a polymer precursor, such as... Figure 3 As shown.

[0077] Furthermore, the high-temperature carbonization of the polymer precursor to obtain a porous modified material includes:

[0078] Construct a nitrogen atmosphere environment;

[0079] The polymer precursor was placed in a nitrogen atmosphere and heated to 5°C for 1 minute. -1 up to 800℃min -1 The polymer precursor was heated at a certain rate and held for 2 hours to obtain a porous modified material.

[0080] Specifically, the amounts of materials required to form the polymer precursor include:

[0081] 0.3g dopamine powder, 0.3mL ethylenediamine, 60ml deionized water, 0.3g polyether F127, 0.375g thiourea, 0.15g cobalt nitrate hexahydrate and 0.65mL formaldehyde.

[0082] Specifically, the first mixed preparation solution is stirred at a speed of 1000 rpm.

[0083] Specifically, the first mixed preparation solution is stirred for 15 minutes.

[0084] Furthermore, the porous modification material is used to modify the working electrode of the electrochemical sensor to be modified to obtain an electrochemical sensor for dopamine detection, including:

[0085] The surface of a 3mm diameter working electrode was polished on a wet chamois using 0.3μm alumina polishing powder and 0.05μm alumina polishing powder in sequence to obtain the polished working electrode.

[0086] The polished working electrode is rinsed with deionized water to obtain the rinsed working electrode.

[0087] The rinsed working electrode was placed vertically in deionized water and ultrasonically cleaned three times until no aluminum oxide polishing powder residue remained on the surface of the rinsed working electrode, thus obtaining a residue-free working electrode.

[0088] At a concentration of 0.5 mol L -1 The activated working electrode was obtained by activating the electrode without residue in a dilute sulfuric acid solution using cyclic voltammetry.

[0089] Repeat the scan within the range of -1.0 to 1.0 V until a stable CV curve is obtained. Finally, the scan was performed using K3[Fe(CN)6], 1.0 mM K4[Fe(CN)6], and 0.1 mol L... -1 CV curves were recorded in a mixed KCl solution at a scan rate of 50 mV / s. -1 The scanning range is -0.1 to 0.6V, and the peak potential difference should be less than 80mV.

[0090] 3 mg N / S@Co-CNSs were dispersed by ultrasound in a mixture of 30 μL of 5 wt.% Nafion solution, 475 μL of deionized water and 475 μL of anhydrous ethanol for 20 min to obtain a dispersion of porous modified material.

[0091] An electrochemical sensor for dopamine detection was obtained by transferring 5 μL of the dispersion to the surface of the activated working electrode using a pipette and drying it at room temperature for 1 h.

[0092] Specifically, the time range for each of the three ultrasonic cleaning sessions was 2-3 minutes.

[0093] Specifically, the process of activating the working electrode is as follows:

[0094] Repeatedly scan the residual working electrode within the range of -1.0 to 1.0 V until a stable CV curve is obtained;

[0095] Set the scan rate to 50 mVs. -1 The scan range was set to -0.1 to 0.6 V, the peak potential difference was set to less than 80 mV, and the sample contained K3[Fe(CN)6], 1.0 mM K4[Fe(CN)6], and 0.1 mol L... -1 CV curves were recorded in a mixed solution of KCl until the working electrode was activated.

[0096] This implementation also includes performing electrochemical experiments on the modified electrode after modifying the working electrode:

[0097] All electrochemical tests were performed on a CHI660E electrochemical workstation using a standard three-electrode system. The working electrode was a GCE (3 mm in diameter) loaded with N / S@Co-CNSs, and the reference electrode was an Ag / AgCl electrode (saturated with KCl). A citric acid-sodium citrate solution (pH 4) was used as the buffer solution, and a platinum wire was used as the counter electrode. Unless otherwise specified, the CV test range was 0–0.8 V, and the scan rate was 100 mV s. -1 The differential pulse voltammetry (DPV) test range is 0-0.8V. Electrochemical experiments were conducted at room temperature (25±1℃) without stirring.

[0098] Furthermore, this embodiment also discloses the morphology characterization of the synthesized N / S@Co-CNSs using SEM:

[0099] Due to the pore-forming effect of the synthesized polydopamine, high-temperature carbonization forms a porous structure on the surface of nanoparticles, further increasing the specific surface area.

[0100] TEM observations were used to accurately describe the microstructure of the material. C and N were uniformly distributed, while S and O were more concentrated at the Co sites, indicating the possible presence of Co and CoO. x CoS x Other species.

[0101] Furthermore, the obtained N / S@Co-CNSs were further characterized using powder XRD. Figure 4In the sample, a series of characteristic diffraction peaks were observed at 2θ = 44.2°, 51.5°, and 75.8°, which were attributed to the (111), (200), and (220) planes of face-centered cubic (fcc) Co (PDF#15-0806), respectively. Other diffraction peaks were attributed to Co9S8 (PDF#86-2273). This indicates that Co was successfully introduced into the nanoparticles and combined with S. Notably, the distribution characteristics of O observed in HAADF-STEM indicate the presence of CoO. x However, no corresponding characteristic diffraction peaks were observed in the XRD pattern, indicating that the formed CoO x It is in an amorphous state.

[0102] Furthermore, XPS analysis was used to determine the surface chemical composition, valence state, and molecular structure of N / S@Co-CNSs. Additionally, the elemental composition of the sample surface was determined by peak intensities. The presence of Co, O, C, N, and S was observed. Figure 5 Clearly visible in (a), this is consistent with the results observed in the HAADF-STEM elemental distribution map. The high-resolution C1s spectrum can be fitted to five peaks corresponding to C=O (289.5 eV), CO (286.3 eV), CN (285.3 eV), C=CC (284.7 eV), and CS (284.5 eV), indicating that N and S elements were successfully doped into N / S@Co-CNSs, as shown in (a). Figure 5 As shown in (b), the high-resolution N1s spectrum can be fitted to two peaks at 401.2 and 398.6 eV, corresponding to graphitic nitrogen and pyridine nitrogen, respectively, as shown in (b). Figure 5 As shown in (c), a high content of graphitic nitrogen can improve electron transfer capability. Therefore, N / S@Co-CNSs exhibit good electrical conductivity. The high-resolution O1s spectrum can be fitted with four peaks: C-OH (533.6 eV), CO (532.6 eV), C=O (531.7 eV), and Co-O (530.1 eV), as shown in (c). Figure 5 As shown in (d), the oxygen in the material mainly comes from DA. DA itself contains C-OH, which chelates with Co to form Co-O. CO and C=O are products of thermal decomposition and oxidation on the material surface. The S2p high-resolution spectrum can be fitted with three peaks: C=S (165.3 eV) is assigned to the functional group of thiourea itself, CS (164.1 eV) indicates that the S element was successfully retained in the carbon matrix during thermal decomposition, and Co-S (161.8 eV) was formed through the chelation of S with metallic cobalt. Figure 5 As shown in (e). These S peaks further indicate that S was successfully doped and formed metal sulfides during thermal decomposition. The high-resolution Co2p spectrum can be fitted with three pairs of peaks: the peaks at 804.2 and 785.8 eV are satellite peaks, and the peaks at 796.7 and 780.8 eV are Co in Co9S8. 2+The peaks at 795.2 and 779.6 eV represent Co in Co9S8. 3+ Peak, like Figure 5 As shown in (f).

[0103] Furthermore, the EDS spectra of N / S@Co-CNSs revealed the presence of key elements Co, N, O, and S. This result is consistent with elemental mapping and XPS spectroscopy results, further demonstrating that the proposed method using thiourea as the N and S source achieves simultaneous N / S doping via high-temperature pyrolysis. Figure 6 As shown.

[0104] Furthermore, the functional groups of the material were characterized using FTIR. For example... Figure 7 As shown, the characteristic peaks are located at 695, 1022, and 3450 cm⁻¹. -1 The positions correspond to the vibrations of CS, CO, C=C, and OH, respectively. The CS functional group corresponds to thiourea, while CO, C=C, and OH correspond to polydopamine, indicating that the raw materials were successfully assembled.

[0105] Furthermore, Figure 8 (a) records the levels of GCE and modified GCE in and without 50 mol L. -1 Three CV curves were obtained in the DA buffer solution. No redox signal was observed in curve c, indicating that the bare GCE did not undergo a redox reaction in the DA-containing buffer solution. No signal was also observed in curve b, indicating that no redox reaction occurred between the modified electrode and the DA-free buffer solution. However, curve a showed a significant redox signal, indicating that N / S@Co-CNSs can promote electron transfer of DA in trisodium citrate-citric acid buffer solution. This confirms the effectiveness and feasibility of using the modified electrode for the electrochemical detection of DA. The enhanced electrochemical response of DA can be attributed to several factors. First, N / S@Co-CNSs possesses a porous structure with a large specific surface area. This increased surface area results in more available electron transfer sites, thereby enabling efficient electron transfer during the redox reaction of DA. Furthermore, the porous structure of the modified material facilitates the permeation of DA molecules, allowing for better interaction with the electrode surface and enhanced electrocatalytic activity. In addition, the presence of N / S@Co-CNSs creates a favorable environment for the electrochemical detection of DA, and the unique composition of the modified electrode promotes the adsorption and oxidation of DA molecules. N / S@Co-CNSs act as active catalysts, promoting the electro-oxidation of DA and providing additional electron transfer pathways. In summary, the porous structure and increased specific surface area of ​​N / S@Co-CNSs contribute to the enhanced electrochemical response of DA, confirming the effectiveness and feasibility of the modified electrode for sensitive DA detection. Therefore, the current response during DA oxidation and reduction is significantly amplified. The possible reactions during DA oxidation and reduction are shown in equation (1):

[0106]

[0107] In a solution containing 50 mol L -1 0.1 mol L of DA -1 In a citric acid-sodium citrate buffer solution (pH=4), we further used CV to evaluate the effect of scan rate on the electrochemical behavior of the modified electrode. The response curves are shown below. Figure 8 As shown in (b). When the scan rate is from 10 mV / s -1 Increased to 150mVs -1 (From the inside to the outside) The oxidation and reduction peaks increase significantly. Furthermore, with increasing scan rate, the peak potential shifts towards both positive and negative directions, indicating rapid electron transfer between the DA and the modified electrode. Experiments demonstrate that the mechanism influencing the redox reaction on the electrode surface can be derived from the relationship between peak current and scan rate. Figure 8 (c) Displaying the calibration curves of peak oxidation and reduction currents versus scan rate. Y = 0.3199x + 1.3879(R) 2 =0.9965) and Y = -0.3117x + 1.2070(R) 2 =0.9991), the peak current increases linearly with the scan rate, indicating that the electrochemical redox reaction rate is controlled by adsorption kinetics.

[0108] Furthermore, the buffer range of the sodium citrate solution is 3.0–6.6. The pH of the buffer solution affects the potential and response current of the DA detection sensor. In this study, we recorded the DPV response curves of the modified electrode used for DA detection in citrate-sodium citrate buffer solutions with pH values ​​ranging from 3.0 to 6.0, as shown below. Figure 9 As shown, the peak potential shifts positively as the pH decreases, and the potential is negatively correlated with pH, ​​indicating that protons participate in the electrode reaction. The peak current reaches its maximum at pH = 4.0, indicating that detecting DA within the buffer range of the buffer solution is reasonable. Therefore, a citrate-sodium citrate buffer solution with a pH of 4.0 was chosen as the electrolyte. The pH values ​​of the solutions are: curve a: pH = 6; curve b: pH = 5; curve c: pH = 4; curve d: pH = 3.

[0109] Furthermore, compared with other voltammetry methods (SWV, LSV), DPV has advantages such as high sensitivity, negative redox peak potential, and fast response speed. Therefore, under optimized experimental conditions, DPV technology was chosen for the detection of DA modified electrodes. Figure 10 (a) shows the DPV response of the modified electrode to different DA concentrations. As the DA concentration increases from 3.0 × 10⁻⁶, the response decreases. -7 Gradually increase to 7×10 -4 mol L-1 The oxidation peak current (A) also increases accordingly. Figure 10 (b) shows two linear ranges. The first linear range (at low concentrations) is 3.0 × 10⁻⁶. -7 ~1×10 -5 mol L -1 The linear fitting equation is Y = 1.0955x - 6.0764 (R² = 0.9940); the second linear range (at high concentrations) is 2.0 × 10⁻⁶. -5 ~7.0×10 -4 mol L -1 The linear fitting equation is Y = 0.4617x - 5.3104 (R²). 2 =0.9905). The limit of detection (LOD) is calculated by the following formula: LOD = 3σ / S, where σ is the standard deviation of the blank solution, S is the slope of the calibration line, and 3 represents the signal-to-noise ratio. In the low concentration range, the detection limit of the sensor is approximately 4.0 × 10⁻⁶. -8 mol L -1 .

[0110] We compared the sensor's linear range and LOD with data reported in the literature (Table S1). N / S@Co-CNSs / GCE exhibited a wide linear range and a low detection limit. This can be attributed to the porous structure formed on the surface of N / S@Co-CNSs after carbonization modification. The modified electrode, when used in the electrochemical sensor, has a high specific surface area, significantly improving the electrode's adsorption capacity for dopamine during testing. The electron transport properties of carbonized N / S@Co-CNSs are significantly improved. This facilitates rapid electron transfer between the electrode and dopamine, accelerating the oxidation or reduction reaction of dopamine, thereby increasing the reaction rate and amplifying the current signal intensity. Table 1 shows a comparison of the sensor's linear range and LOD with data reported in the literature.

[0111] Table 1. Comparison of analytical performance with other electrochemical methods for determining DA

[0112]

[0113]

[0114]

[0115] Furthermore, considering the complexity of actual aquatic environments, we added various interfering substances (500 μmol L) to the DA solution. -1 This is used to evaluate the selectivity and anti-interference ability of the sensor. Figure 11 It showed that at 50 μmol L -1The current response within the DA range is shown with and without interfering compounds. The value varies within a reasonable range, indicating that these compounds have no effect on the oxidation peak current of the modified electrode. This demonstrates that the electrochemical sensor based on the modified electrode exhibits good anti-interference capability. Figure 11 In the table, a represents roxithromycin, b represents chloramphenicol, c represents lincomycin, d represents tetracycline, e represents enrofloxacin, f represents ciprofloxacin, g represents serine, h represents tyrosine, i represents norfloxacin, j represents norepinephrine, and k represents 4-methylcatechol.

[0116] Furthermore, to evaluate the reproducibility of the sensor, five modified electrodes were prepared under the same conditions and used to detect the same concentration of DA. Their DPV curves are shown below. Figure 12 As shown in (a), the five electrodes exhibit similar response currents with a relative standard deviation (RSD) of 4.95%, indicating acceptable reproducibility. Sensor stability is another important factor affecting its practical application. The prepared modified electrodes were placed in a dry, dark environment at room temperature (25°C) for DA determination. Figure 12 As shown in (b), the results indicate that after 10 days of storage, the current response remains at 92.58% of its initial value, demonstrating the sensor's good stability. Next, the same electrodes were used to measure the same DA-containing buffer solution, as shown... Figure 12 As shown in (c), after 13 tests, the signal remained at 91.29% of the initial value, with an RSD of 3.38%, indicating that the sensor has good repeatability.

[0117] This embodiment also provides actual biological sample testing:

[0118] Beef and pork samples (2.5 g each) were placed in 50 mL centrifuge tubes, and 10 mL of acetonitrile aqueous solution was added to each at an 8:2 ratio. The mixtures were sonicated for 10 min and then centrifuged at 10000 rpm for 5 min. The supernatant was collected and transferred to clean centrifuge tubes, and after fat removal, it was stored in the dark at 4 °C for 4 h. The supernatant was mixed with an equal volume of citrate-sodium citrate buffer and stored at 4 °C for further use. The content of added DA in the selected model was determined using the standard addition method. DA was not detected in the actual samples by HPLC. Different concentrations of DA (2 × 10⁻⁶) were added to the selected samples (n = 5). -5 mol L -1 5×10 -5 mol L -1 The method's recovery rate was between 93.6% and 102.1%, with an RSD less than 6.0%, meeting the requirements. Table 2 compares the sample test results with the standard method test results, as shown below:

[0119] Table 2 Comparison of Sample Detection Results

[0120]

[0121] The beneficial effects of this invention are as follows:

[0122] This study presents a method for fabricating an electrochemical sensor for dopamine detection. First, covalent bonds between polydopamine and thiourea-ethylenediamine-formaldehyde resin and cobalt ions can form spherical polymer nanomaterials. This unique structure provides enhanced stability and facilitates efficient charge transfer, contributing to the observation of excellent electrocatalytic activity for dopamine (DA) in the constructed electrochemical sensor. Second, the employed characterization techniques enable a comprehensive analysis of the structure and properties of the obtained nanomaterials. This thorough understanding helps optimize its performance and paves the way for further improvements. Furthermore, the modified glassy carbon electrode exhibits excellent selectivity for DA, ensuring accurate detection of DA in complex samples. The sensor also demonstrates significant anti-interference capability, effectively reducing the influence of other substances. This high selectivity and anti-interference capability are crucial for practical applications. The repeatability and stability of the sensor are also noteworthy. The nanomaterials used for electrode modification exhibit good reproducibility, ensuring consistent and reliable results. Moreover, they maintain their sensing performance, stability, and low cost across multiple applications, enhancing their long-term usability.

[0123] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. Specific examples have been used to illustrate the principles and implementation methods of the invention. The descriptions of the embodiments above are only for the purpose of helping to understand the method and core ideas of the invention; furthermore, those skilled in the art will recognize that, based on the ideas of the invention, there will be changes in specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the invention.

Claims

1. A method for preparing an electrochemical sensor for dopamine detection, characterized in that, include: Co(II) ions are self-assembled with polydopamine and thiourea-ethylenediamine-formaldehyde resin under stirring at room temperature through chelation to form a polymer precursor. The polymer precursor materials include: deionized water, polyether F127, thiourea, cobalt nitrate hexahydrate, dopamine hydrochloride powder, ethylenediamine, and formaldehyde. The polymer precursor is subjected to high-temperature carbonization to obtain a porous modified material, wherein the modified material is N / S@Co-CNSs; The porous modification material was used to modify the working electrode of the electrochemical sensor to be modified in order to obtain an electrochemical sensor for dopamine detection; The process for forming polymer precursors includes: Deionized water was poured into the reaction vessel, and polyether F127, thiourea and cobalt nitrate hexahydrate were added in sequence to obtain the first mixed preparation solution; The first mixed preparation solution is stirred until the materials in the first mixed preparation solution are completely dissolved to obtain the second mixed preparation solution; Add dopamine hydrochloride powder to the second mixed preparation solution and wait for 5 minutes. Then, use a pipette to add ethylenediamine dropwise to the second mixed preparation solution at a rate of 15 seconds / drop to obtain the third mixed preparation solution. Formaldehyde was added to the third mixed preparation solution at 5-minute intervals to obtain the fourth mixed preparation solution; The fourth mixed preparation solution was continuously stirred for 24 hours to obtain the centrifuged product; The polymer precursor was obtained from the centrifuged product.

2. The method for preparing an electrochemical sensor for dopamine detection according to claim 1, characterized in that, The polymer product obtained from the centrifuged product includes: The impurities in the centrifuged product precipitate were washed in the order of water-ethanol-water to obtain the washed centrifuged product. The washed and centrifuged product was precipitated in an environment with a temperature of 80°C and vacuum drying to obtain a polymer precursor.

3. The method for preparing an electrochemical sensor for dopamine detection according to claim 1, characterized in that, The process of obtaining a porous modified material by high-temperature carbonization of the polymer precursor includes: Construct a nitrogen atmosphere environment; The polymer precursor was placed in a nitrogen atmosphere and heated to 800°C at a temperature rise rate of 5°C / min, and held at 800°C for 2 hours to obtain a porous modified material.

4. The method for preparing an electrochemical sensor for dopamine detection according to claim 1, characterized in that, The amounts of materials required to form the polymer precursor include: 0.3 g dopamine hydrochloride powder, 0.3 mL ethylenediamine, 60 mL deionized water, 0.3 g polyether F127, 0.375 g thiourea, 0.15 g cobalt nitrate hexahydrate and 0.65 mL formaldehyde.

5. The method for preparing an electrochemical sensor for dopamine detection according to claim 1, characterized in that, The first mixed preparation solution was stirred at a speed of 1000 rpm.

6. The method for preparing an electrochemical sensor for dopamine detection according to claim 1, characterized in that, The first mixed preparation solution was stirred for 15 minutes.

7. The method for preparing an electrochemical sensor for dopamine detection according to claim 1, characterized in that, The porous modification material is used to modify the working electrode of the electrochemical sensor to be modified in order to obtain an electrochemical sensor for dopamine detection, comprising: The surface of a 3mm diameter working electrode was polished on a wet chamois using 0.3μm alumina polishing powder and 0.05μm alumina polishing powder in sequence to obtain the polished working electrode. The polished working electrode is rinsed with deionized water to obtain the rinsed working electrode. The rinsed working electrode was placed vertically in deionized water and ultrasonically cleaned three times until no aluminum oxide polishing powder residue remained on the surface of the rinsed working electrode, thus obtaining a residue-free working electrode. The residual-free working electrode was activated in a 0.5 mol L -1 of dilute sulfuric acid solution using cyclic voltammetry to obtain an activated working electrode; 3 mg N / S@Co-CNSs were dispersed by ultrasound in a mixture of 30 μL of 5 wt.% Nafion solution, 475 μL of deionized water and 475 μL of anhydrous ethanol for 20 min to obtain a dispersion of porous modified material. 5 μL of the dispersion was transferred to the surface of the activated working electrode using a pipette and dried at room temperature for 1 h to obtain an electrochemical sensor for dopamine detection.

8. The method for preparing an electrochemical sensor for dopamine detection according to claim 7, characterized in that, The time range for each of the three ultrasonic cleaning sessions was 2-3 minutes.

9. The method for preparing an electrochemical sensor for dopamine detection according to claim 7, characterized in that, The process of activating the working electrode is as follows: Repeatedly scan the residual working electrode within the range of -1.0 to 1.0 V until a stable CV curve is obtained; The scan rate was set to 50 mV s⁻¹, the scan range to -0.1 to 0.6 V, and the peak potential difference to less than 80 mV. The scan was performed in an atmosphere containing K₃[Fe(CN)₆], 1.0 mM K₄[Fe(CN)₆], and 0.1 mol L⁻¹. -1 CV curves were recorded in a mixed solution of KCl until the working electrode was activated.

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