Preparation and application of manganese oxide doped graphene flexible electrochemical sensor

Abstract

The invention discloses preparation and application of a manganese oxide doped graphene flexible electrochemical sensor, and belongs to the technical field of electrochemical sensing. The preparation method comprises the following steps: firstly, preparing a manganese oxide doped graphene electrode through one-step laser induction, then preparing a manganese oxide doped graphene flexible electrochemical sensor by using the manganese oxide doped graphene electrode, and then detecting fenitrothion through the flexible electrochemical sensor. The detection result shows that the flexible electrochemical sensor has excellent detection effect and detection stability on fenitrothion.

Description

Technical Field

[0001] This invention belongs to the field of electrochemical sensing technology, and more specifically relates to the preparation and application of a manganese oxide-doped graphene flexible electrochemical sensor. Background Technology

[0002] Fenitrothion (FT), also known as O,O-dimethylO-(3-methyl-4-nitrophenyl), is a widely used insecticide effective against lepidopteran larvae, as well as pests in the orders Hemiptera and Coleoptera. Its insecticidal action is primarily achieved by inhibiting acetylcholinesterase, and it can also interfere with other metabolic functions, such as blocking esterases and phosphodiesterases, thereby further enhancing its insecticidal effect. In recent years, with the increasing use of pesticides in agricultural production, fenitrothion has been widely applied to the control of pests and diseases in grain crops due to its high efficiency and broad spectrum. However, fenitrothion has certain toxicity and persistence, easily remaining in soil, water bodies, and agricultural products. Long-term ingestion may damage the human nervous system. Therefore, establishing a sensitive, rapid, and portable detection method for fenitrothion has become a research hotspot in the fields of agricultural environmental monitoring and food safety assurance.

[0003] Currently, the main methods for detecting fenitrothion include high-performance liquid chromatography (HPLC), gas chromatography (GC), colorimetric detection, enzyme-linked immunosorbent assay (ELISA), and molecular imprinting. While these methods offer high sensitivity, they generally suffer from drawbacks such as expensive equipment, complex detection procedures, high operator skill requirements, and unsuitability for rapid on-site detection. Therefore, developing a sensitive, rapid, and portable sensor for fenitrothion detection is of significant importance. Summary of the Invention

[0004] The purpose of this invention is to provide a preparation and application of a manganese oxide-doped graphene flexible electrochemical sensor to solve the problems existing in the prior art and to establish a sensitive, rapid, and portable method for detecting fenitrothion.

[0005] To achieve the above objectives, the present invention provides the following solution:

[0006] One of the technical solutions of this invention is to provide a one-step laser-induced preparation method for manganese oxide-doped graphene electrodes, comprising the following steps:

[0007] A manganese chloride solution was placed in polyamic acid to obtain a manganese chloride-doped polyamic acid solution.

[0008] The polyamic acid solution doped with manganese chloride was coated onto the substrate, dried twice, and the film was removed to obtain a manganese chloride-doped polyimide film.

[0009] The manganese chloride-doped polyimide film was laser-etched to obtain the manganese oxide-doped graphene electrode.

[0010] Preferably, the manganese chloride solution comprises an ethanol solution of manganese chloride; the concentration of the manganese chloride solution is 0.1–0.5 mol / L.

[0011] Preferably, the ratio of manganese chloride solution to polyamic acid is 0.1-0.3 mL: 4 g.

[0012] Preferably, the substrate comprises a glass plate.

[0013] Preferably, the thickness of the polyamic acid solution doped with manganese chloride is 25–35 μm.

[0014] Preferably, in the two drying processes, the temperature of the first drying is 90-110℃ and the time is 25-45 min, and the temperature of the second drying is 150-170℃ and the time is 8-15 min.

[0015] First drying (90-110℃): Gently removes residual solvent; prevents rapid evaporation of solvent at high temperatures, which could cause blistering, cracking, or peeling of the film; ensures a uniform and dense film.

[0016] The second drying process (150–170°C) further removes residual solvent from deeper layers; promotes partial imidization (cyclization) of PAA (polyamic acid) to PI (polyimide); enhances the mechanical stability and heat resistance of the film, facilitating subsequent laser etching; and provides a suitable pre-carbonization structural state, resulting in higher and more uniform carbonization efficiency during laser printing. Direct high-temperature rapid heating causes rapid evaporation of the internal solvent, leading to blistering and cracking of the film; uneven surface carbonization increases defects in the laser-induced graphene (LIG) pattern formed during laser printing. Therefore, this invention employs a two-stage drying process.

[0017] Preferably, the laser power of the laser etching is 1.1 to 2.75 W.

[0018] The second technical solution of the present invention is to provide a manganese oxide-doped graphene electrode prepared by the above method.

[0019] The third technical solution of the present invention provides the application of the above-mentioned manganese oxide-doped graphene electrode in the preparation of electrochemical sensors.

[0020] The fourth technical solution of the present invention provides an electrochemical sensor comprising the above-mentioned manganese oxide-doped graphene electrode.

[0021] Preferably, the electrochemical sensor uses the aforementioned manganese oxide-doped graphene electrode as the working electrode and a silver electrode as the reference electrode.

[0022] Fifth technical solution of the present invention: to provide the application of the above-mentioned electrochemical sensor in the detection of fenitrothion.

[0023] Compared to traditional carbonization methods, laser etching offers significant advantages such as low cost, high precision, template-free operation, and rapid in-situ generation. During laser-induced processing, the instantaneous high temperature and rapid cooling of the laser can introduce abundant microscopic defects and active sites on the material surface, significantly improving the specific surface area and electrochemical activity of the electrode.

[0024] MnO X It possesses advantages such as reversible multivalent state transitions, abundant electrochemical active sites, and high specific surface area, effectively promoting charge transport and ion diffusion, and enhancing the electrochemical performance of the electrode. MnO... x Modifying electrodes can enhance their catalytic activity and selectivity for metal ions, organic pollutants, and biomolecules.

[0025] This invention utilizes a highly efficient and convenient one-step laser-induced technique to prepare manganese oxide (MnO) in situ on a polyimide (PI) substrate pre-doped with a manganese precursor solution. X The method involves combining LIG with a flexible electrode. This method is simple to operate, requires no complex processes, and offers advantages such as rapid and low-cost preparation. LIG possesses a three-dimensional porous structure, excellent conductivity, and abundant microscopic defect sites, which facilitates rapid electron transport and effective adsorption of target molecules; MnO... X These materials possess multiple valence states, high electrochemical activity, and excellent catalytic performance, which can significantly improve the reaction rate and selectivity of the electrode. Through the synergistic effect of these two factors, the prepared flexible electrode not only exhibits good mechanical flexibility and adaptability to various bending deformation conditions, but also demonstrates high sensitivity and stability in electrochemical detection, providing a novel, efficient, and environmentally friendly functional electrode material for portable sensors.

[0026] The MnOx-LIGE flexible electrode of this invention achieves simultaneous generation of MnOx and porous graphene on a PI substrate via a laser-induced one-step method. The preparation process is simple and low-cost, avoiding the drawbacks of existing detection methods that require expensive instruments and complex pretreatment. Furthermore, it is easy to operate and suitable for rapid detection by non-professionals. Simultaneously, MnOx provides abundant electrocatalytic active sites, while LIG provides high conductivity and a large specific surface area, enabling sensitive and rapid detection of fenitrothion. It can be integrated into portable devices for rapid on-site analysis, solving the problems of expensive equipment, complex processes, high technical requirements, and unsuitability for rapid on-site detection in existing fenitrothion detection methods. Therefore, it has significant potential for widespread application.

[0027] The present invention discloses the following technical effects:

[0028] The manganese oxide-doped graphene electrode provided by this invention integrates material modification and electrode preparation, making it simple and convenient. Results show that the flexible portable electrochemical sensor based on the manganese oxide-doped graphene electrode provided by this invention has a detection limit of 13.66 nmol / L for fenitrothion (FT) and a linear range of 100 nmol / L to 250 mol / L. The spiked recoveries for determining the content of fenitrothion in actual samples ranged from 102.4 to 104.2.

[0029] The electrode preparation method provided by this invention is simple and easy to operate. When connected to a portable sensor and a mobile phone, a flexible portable electrochemical sensor can be obtained, which has excellent detection performance and good stability. Attached Figure Description

[0030] Figure 1 MnO prepared in Example 1 X - SEM image of LIG;

[0031] Figure 2 MnO prepared in Example 1 X -LIG transmission electron microscopy images at different magnifications;

[0032] Figure 3 MnO prepared in Example 1 X - Elemental mapping image of carbon (C), oxygen (O), and manganese (Mn) in LIG, where A is carbon (C), B is oxygen (O), and C is manganese (Mn);

[0033] Figure 4 Laser-induced graphene (LIG) and MnO prepared in Example 1 X -LIG X-ray diffraction pattern;

[0034] Figure 5 MnO prepared in Example 1 X X-ray photoelectron spectra of -LIG, where A is the full spectrum, B is the C1s spectrum, C is the O1s spectrum, and D is the Mn 2p spectrum;

[0035] Figure 6 The results of the detection of fenitrothion (FT) by the electrochemical sensor assembled with the electrodes prepared in Examples 1 to 8 are shown. Among them, A is the detection result of fenitrothion (FT) by the electrochemical sensor assembled with the electrodes prepared in Examples 1 to 5, and B is the detection result of fenitrothion (FT) by the electrochemical sensor assembled with the electrodes prepared in Examples 1 and 6 to 8.

[0036] Figure 7The effects of different buffer solution types and pH values ​​on the electrochemical reaction of FT are shown in Figure 1. In Figure 2, A represents the effect of different buffer solution types on the electrochemical reaction of FT, B represents the effect of different pH values ​​on the electrochemical reaction of FT, and C represents the relationship between the reduction peak current and potential of FT and pH value.

[0037] Figure 8 The results (A) and working curve (B) of the electrochemical sensor assembled from the electrodes prepared in Example 1 detecting different concentrations of FT;

[0038] Figure 9 The selectivity (A) and stability (B) of the electrochemical sensor assembled from the electrodes prepared in Example 1;

[0039] Figure 10 The effective area of ​​the electrode prepared in Example 1 is shown, where a represents LIGE and b represents MnOx-LIGE.

[0040] Figure 11 The electrochemical behavior of the electrode prepared in Example 1 for FT is shown in Figure 1. A represents the CV curves of (a) LIGE and (b) MnOx-LIGE in 0.1 mol / L BR solution; B represents the CV curves of (a) LIGE and (b) MnOx-LIGE in 0.1 mol / L BR containing 250 μmol / L FT; C represents the CV curves of MnOx-LIGE in 250 μmol / L FT at different scan rates (a to f are 0.02, 0.04, 0.06, 0.08, 0.1, and 0.15 V / s, respectively); D represents the linear relationship between the reduction peak current and the scan rate; and E represents the electrochemical reaction equation for FT. Detailed Implementation

[0041] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0042] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0043] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0044] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be readily apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0045] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0046] It should be noted that any aspects not described in detail in this invention are conventional practices in the field and are not the focus of this invention.

[0047] Unless otherwise specified, all raw materials used in this invention are commercially available products, and the source of these commercially available products does not affect the technical effect of this invention.

[0048] Example 1

[0049] This embodiment provides a one-step laser-induced preparation method for manganese oxide-doped graphene electrodes, the steps of which are as follows:

[0050] Manganese chloride was prepared into an ethanol dispersion with a concentration of 0.4 mol / L;

[0051] 0.2 mL of manganese chloride ethanol dispersion was placed in 4 g of polyamic acid to obtain a manganese chloride-doped polyamic acid solution;

[0052] A polyamic acid solution doped with manganese chloride was coated onto a glass plate (coating thickness of 30 μm), first placed in a vacuum drying oven at 100 °C for 30 min, and then placed in an oven at 166 °C for 10 min to obtain a manganese chloride doped polyimide film (MnCl2-PI).

[0053] Manganese chloride-doped polyimide films were laser-etched using a laser direct-writing instrument with an output power of 2.2 W to prepare manganese oxide (MnO) in situ. X Using laser-induced graphene (LIG) and other materials, a working electrode is formed on a glass plate. The working electrode is then removed from the glass plate to obtain a manganese oxide-doped graphene electrode material (MnO).X -LIG) is used to uniformly coat the desired area on the surface of the material with silver paste, with a coating thickness of approximately 30 μm, forming a reference electrode pattern. This is then cured at 140 °C for 20 min to obtain a manganese oxide-doped graphene electrode (MnO). X -LIGE).

[0054] Figure 1 MnO prepared in Example 1 X - SEM image of LIG.

[0055] from Figure 1 The prepared MnO can be clearly seen X -LIG possesses a three-dimensional porous structure for supporting particles.

[0056] Figure 2 MnO prepared in Example 1 X -LIG transmission electron microscopy images at different magnifications.

[0057] from Figure 2 The prepared MnO can be clearly seen in the image. X - The LIG surface contains particles with a diameter of less than 20 nm.

[0058] Figure 3 MnO prepared in Example 1 X - An elemental mapping image of carbon (C), oxygen (O), and manganese (Mn) in LIG, where A represents carbon (C), B represents oxygen (O), and C represents manganese (Mn).

[0059] Depend on Figure 3 It can be seen that the three elements are evenly distributed in MnO X -LIG's entire material further confirms MnO X Successful preparation of -LIG.

[0060] Figure 4 Laser-induced graphene (LIG) and MnO prepared in Example 1 X X-ray diffraction pattern of LIG.

[0061] Depend on Figure 4 It can be seen that in LIG and MnO x A peak of approximately 26.0° was observed in both MnO and LIG, corresponding to the (002) crystal plane of graphene (JCPDF#41-1487), confirming the presence of MnO. X The presence of graphite structures in LIG. Combined with... Figure 1The honeycomb porous structure shown in the scanning electron microscope image, along with the background indicating that the material was prepared by laser inscription on a PI substrate, confirms that the structure is LIG. Multiple characteristic diffraction peaks at 32.1°, 38.1°, and 69.8° correspond to the (103), (200), and (305) crystal planes of Mn3O4 (JCPDF#80-0382), the diffraction peaks at 35.0° and 40.6° are consistent with the (111) and (200) crystal planes of MnO (JCPDF#78-0424), and the diffraction peaks at 20.2° and 28.7° are related to the (100) and (110) crystal planes of MnO2 (JCPDF#71-0071). This indicates that Mn3O4... 2+ In an oxygen-containing environment, it is laser-induced to transform into MnO, an oxide containing Mn. X This proves that the particles loaded on the electrode surface are manganese oxides.

[0062] Figure 5 MnO prepared in Example 1 X X-ray photoelectron spectra of -LIG, where A is the full spectrum, B is the C1s spectrum, C is the O1s spectrum, and D is the Mn 2p spectrum.

[0063] Depend on Figure 5 It can be seen that, Figure 5 A shows the presence of elements such as O, C, and Mn. In the high-resolution spectrum of C 1s ( Figure 5 (B) The peak centered at 284.80 eV corresponds to the presence of graphitic carbon. Additional peaks at 285.8 eV, 287.2 eV, and 289.7 eV belong to the functional groups CO, C=O, and OC=O, respectively. Additionally... Figure 5 The C in the figure shows the O 1s spectrum, with binding energies of 530.8 eV, 532.3 eV, and 533.5 eV corresponding to Mn-O bonds, CO, and C=O, respectively. Figure 5 The fitting of the Mn 2p spectrum in D reveals that Mn 2+ Mn 3+ Mn 4+ The presence of cations, Mn 2p 3 / 2 It can be classified as 642.9 eV (Mn 3+ ) and 641.4 eV (Mn 2+ The combination of Mn 2p 1 / 2 It can be classified as 654.2 eV (Mn 3+ ) and 652.6eV (Mn 2+ The combination of 646.7 eV indicates that Mn 4+ The existence of.

[0064] Example 2

[0065] The difference from Example 1 is that the concentration of the manganese chloride ethanol dispersion was adjusted to 0.1 mol / L, while the rest is the same as in Example 1.

[0066] Example 3

[0067] The difference from Example 1 is that the concentration of the manganese chloride ethanol dispersion was adjusted to 0.2 mol / L, while the rest is the same as in Example 1.

[0068] Example 4

[0069] The difference from Example 1 is that the concentration of the manganese chloride ethanol dispersion was adjusted to 0.3 mol / L, while the rest is the same as in Example 1.

[0070] Example 5

[0071] The difference from Example 1 is that the concentration of the manganese chloride ethanol dispersion was adjusted to 0.5 mol / L, while the rest is the same as in Example 1.

[0072] Example 6

[0073] The difference from Example 1 is that the output power of the laser direct writing instrument is adjusted to 1.10W, while the rest is the same as in Example 1.

[0074] Example 7

[0075] The difference from Example 1 is that the output power of the laser direct writing instrument is adjusted to 1.65W, while the rest is the same as in Example 1.

[0076] Example 8

[0077] The difference from Example 1 is that the output power of the laser direct writing instrument is adjusted to 2.75W, while the rest is the same as in Example 1.

[0078] Electrochemical sensors were assembled from the electrodes prepared in Examples 1-8. The specific assembly process was as follows: using the electrodes prepared in Examples 1-8 as working electrodes, a reference electrode was formed by coating the electrode with silver paste (coating thickness 30 μm) and curing at 140°C for 20 min. The resulting electrochemical sensors were then used for fenitrothion (FT) detection. The specific detection process was as follows: to study the effect of MnCl2 concentration on the sensor's detection performance, MnCl2 solutions with concentrations of 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, and 0.5 mol / L were prepared and used to prepare electrodes, which were then assembled into electrochemical sensors for FT detection. By comparing the peak current changes during FT detection at different MnCl2 concentrations, the optimal MnCl2 doping concentration was selected. Furthermore, to optimize the laser output power during the laser direct-write electrode fabrication process, the laser power was set to 1.1W, 1.65W, 2.2W, and 2.75W. The peak current changes of the electrochemical sensor assembled from the electrodes prepared under different laser power conditions during FT detection were compared to determine the optimal laser output power.

[0079] The results are as follows Figure 6 As shown.

[0080] Figure 6 The results of the detection of fenitrothion (FT) by the electrochemical sensor assembled with the electrodes prepared in Examples 1 to 8 are shown. Among them, A is the detection result of fenitrothion (FT) by the electrochemical sensor assembled with the electrodes prepared in Examples 1 to 5, and B is the detection result of fenitrothion (FT) by the electrochemical sensor assembled with the electrodes prepared in Examples 1 and 6 to 8.

[0081] Depend on Figure 6 It can be seen that when the MnCl2 concentration increases from 0.1 mol / L to 0.4 mol / L, the peak current of the Fourier transform factor (FT) gradually increases, indicating that MnO2... X Increased concentrations favor the FT reaction at the electrode surface. When the MnCl2 concentration reaches 0.5 mol / L, the peak current of the FT decreases, which may be due to excess MnO. X The porous structure of LIG was disrupted, hindering the transport channels for Fourier transform (FT) diffusion. The peak current of FT was highest when the MnCl2 concentration was 0.4 mol / L; therefore, 0.4 mol / L was chosen as the optimal doping concentration for MnCl2. Further optimization of the output power of the laser direct writing instrument was performed, such as... Figure 6As shown in Figure B, when the laser power increases from 1.10W to 2.20W, the peak current of the Fourier transform (FT) gradually increases. When the laser power increases to 2.75W, the peak current of the FT decreases, and the peak current of the FT is at its maximum at 2.20W. This is because the degree of graphitization of PI increases with increasing power. When the laser power is too high, it destroys part of the structure and chemical bonds of the LIG carbon layer, leading to a decrease in current value. Therefore, 2.20W was chosen as the optimal output power of the laser.

[0082] The effects of different buffer solution types and pH values ​​on the electrochemical reaction of FT were analyzed in a 250.0 μmol / L FT solution. The electrochemical sensor used for the test was an electrochemical sensor assembled from the electrodes prepared in Example 1. The results are as follows: Figure 7 As shown.

[0083] Figure 7 The effects of different buffer solution types and pH values ​​on the electrochemical reaction of FT are shown, where A represents the effect of different buffer solution types on the electrochemical reaction of FT, B represents the effect of different pH values ​​on the electrochemical reaction of FT, and C represents the relationship between the reduction peak current and potential of FT and pH. Figure 7 In A, a, b, c, and d represent BR solution, citric acid-sodium citrate solution, HAc-NaAc solution, and Tris-HCl solution, respectively. Figure 7 In B, a, b, c, d, and e represent pH values ​​of 4.0, 5.0, 6.0, 7.0, and 8.0, respectively.

[0084] Depend on Figure 7 It was found that among BR buffer solution, citrate-sodium citrate solution, HAc-NaAc solution, and Tris-HCl solution, BR buffer solution had the highest current value and was used as the supporting electrolyte in the experiment. Simultaneously, the CV curves of BR buffer solution at different pH values ​​were recorded, as shown below. Figure 7 As shown in Figure B, the results indicate that the peak current increases with increasing pH until the solution pH reaches 7.0, and then decreases above pH 7.0. Furthermore, the FT peak potential shifts negatively with increasing solution pH, confirming the involvement of protons. Therefore, pH 7.0 was chosen as the optimal pH for further investigation. pc It exhibits a good linear relationship with pH: E pc (V) = -0.054pH - 0.53 (γ = 0.991) (e.g.) Figure 7 (As shown in C). The slope of -54 mV / pH is very close to the theoretical value of Nernst (-59 mV / pH), which indicates that electrons and protons are transferred in equal amounts in the FT reaction.

[0085] The optimal conditions (i.e., Example 1) were determined through the above tests, and the electrochemical sensor prepared under the optimal conditions was used to detect different concentrations of FT using linear sweep voltammetry (LSV). At the same time, the working curve of the electrochemical sensor prepared under the optimal conditions was determined.

[0086] The detection method was as follows: Under optimized experimental conditions, the electrochemical detection performance of the MnOx-LIGE flexible electrode in methamidophos (FT) solutions of different concentrations was tested using linear sweep voltammetry (LSV).

[0087] The specific method is as follows: Electrolyte solution detection: 0.1 mol / L phosphate buffer solution (PBS, pH 7.0) was used as the supporting electrolyte; Detection method: The prepared MnOx-LIG was used as the working electrode and the Ag electrode was used as the reference electrode to assemble a three-electrode system, and detection was performed at room temperature; Scanning conditions: The scanning voltage range was set to -1.15V to -0.75V, and the scanning rate was 0.1V / s; Test steps: 30 μL FT solutions of 100 nmol / L, 500 nmol / L, 12.5 μmol / L, 25 μmol / L, 50 μmol / L, 100 μmol / L, 125 μmol / L, 150 μmol / L, 175 μmol / L, 200 μmol / L, 225 μmol / L, and 250 μmol / L were respectively dropped onto the three-electrode system, and linear sweep voltammetry (LSV) was used for testing. The reduction peak current value under the corresponding LSV curve was recorded at the same time.

[0088] The results are as follows Figure 8 As shown.

[0089] Figure 8 The results (A) and working curve (B) of the electrochemical sensor assembled from the electrodes prepared in Example 1 detecting different concentrations of FT.

[0090] Depend on Figure 8 It can be seen that as the FT concentration increases, the reduction peak current increases. Within the concentration range of 100 nmol / L to 250 μmol / L, the corresponding regression equation is: I pc (μA)=0.68C(μmol / L)-0.11(γ=0.991), and the detection limit is 13.66nmol / L(3σ).

[0091] The selectivity and stability of the electrochemical sensor assembled from the electrodes prepared in Example 1 were tested.

[0092] The test method is as follows: Selective test: At room temperature, GLY and Na were added to a 250 μmol / L FT solution respectively. +Common interfering substances such as Cl-, DCP, and GLU were used. The concentration of the interfering substances was 2500 μmol / L. The electrochemical sensor assembled using the electrode prepared in Example 1 was used to record the current response values ​​under different conditions, and the influence of the interfering substances on the detection FT current response was analyzed.

[0093] Stability test: The electrochemical sensor assembled from the electrodes prepared in Example 1 was sealed and stored at room temperature. Every 3 days, it was taken out and the linear sweep voltammetry curve was measured in 250 μmol / LFT solution. The reduction peak current value was recorded. The test was carried out continuously for 15 days to evaluate the stability of the sensor.

[0094] The results are as follows Figure 9 As shown.

[0095] Figure 9 The selectivity (A) and stability (B) of the electrochemical sensor assembled from the electrodes prepared in Example 1.

[0096] To investigate the selectivity of the electrochemical sensor assembled from the electrodes prepared in Example 1 for FT, GLY and Na were tested respectively. + Cl - The effects of common ions and small molecules such as DCP and GLU on FT detection were investigated. The current response of the electrochemical sensor assembled from the electrodes prepared in Example 1 to 250 μmol / L FT was recorded under 10-fold interference ion conditions. The results showed that these substances had minimal impact on FT detection, indicating that the sensor has good selectivity for FT. The electrochemical sensor assembled from the electrodes prepared in Example 1 was stored in a sealed bag at room temperature, and the current value of the LSV curve was recorded every three days in a 250 μmol / L FT solution. Figure 9 As shown in Figure B), it can be observed that after 15 days of continuous storage, the reduction peak current detected by the electrode still maintains 86.4% of the initial value, indicating that the sensor has excellent stability.

[0097] Furthermore, the effective area of ​​the electrode prepared in Example 1 was tested by coulometric method in a mixed solution of 1 mmol / L K3[Fe(CN)6] and 0.5 mol / L KCl. The results are as follows... Figure 10 As shown.

[0098] Figure 10 The effective area of ​​the electrode prepared in Example 1 is denoted as a, where a represents LIGE and b represents MnOx-LIGE.

[0099] Depend on Figure 10 It can be seen that the Q and t of LIGE and MnOx-LIGE 1 / 2 There is a good linear relationship. The linear regression equations are Q(μC) = 129.81t. 1 / 2 (s 1 / 2)-5.52(γ=0.997) and Q(μC)=243.47t 1 / 2 (s 1 / 2 -15.98 (γ=0.999). According to the above formula, the effective areas of LIGE and MnOx-LIGE are 0.432 cm². 2 and 0.811cm 2 The effective area of ​​MnOx-LIGE is approximately twice that of LIG.

[0100] The electrochemical behavior of the electrode prepared in Example 1 with FT was studied using CV analysis, and the results are as follows: Figure 11 As shown.

[0101] Figure 11 The electrochemical behavior of the electrode prepared in Example 1 for FT is shown in Figure 1. A represents the CV curves of (a) LIGE and (b) MnOx-LIGE in 0.1 mol / L BR solution; B represents the CV curves of (a) LIGE and (b) MnOx-LIGE in 0.1 mol / L BR containing 250 μmol / L FT; C represents the CV curves of MnOx-LIGE in 250 μmol / L FT at different scan rates (a to f are 0.02, 0.04, 0.06, 0.08, 0.1, and 0.15 V / s, respectively); D represents the linear relationship between the reduction peak current and the scan rate; and E represents the electrochemical reaction equation for FT.

[0102] like Figure 11 As shown in Figure A, under a stable background current, LIGE and MnOx-LIGE do not exhibit any electrochemical response in the blank buffer solution. However, in the 250.0 μmol / L FT solution ( Figure 11 As shown in Figure B), on LIGE (curve a), at a potential of -0.17V (I pa ), -0.89V(I pc1 ) and -0.28V (I pc2 A distinct oxidation peak and two reduction peaks were observed at a potential of -0.29V on the MnOx-LIGE curve (curve b). pa ), -0.89V(I pc1 ) and -0.33V(I pc2 Similar redox peaks were also observed at the FT position, with a significant increase in peak current. This is because the -NO2 group, which has redox activity, can undergo multi-step, multi-electron electrochemical reactions. During the CV process, the -NO2 group on MnOx-LIGE is reduced to -NHOH at a negative reduction potential of -0.89V, and no peak was observed during the anodic scan, indicating the irreversible nature of this reduction process. The -NHOH and -NO groups undergo quasi-reversible redox reactions at potentials of -0.29V and -0.33V, respectively, with ΔEp At 0.04V, the oxidized and reduced forms of FT were generated, respectively. red and FT ox ,like Figure 11 As shown in E). MnOx-LIGE exhibits a higher current response than LIGE, further revealing that MnOx-LIGE has a higher electrocatalytic behavior for FT. Due to the irreversible reduction peak (I pc1 It exhibits a stronger current response and was therefore selected as the electrochemical detection peak for the Fourier transform (FT). For example... Figure 11 As shown in C and D, the reduction current (I) of FT on MnOx-LIGE pc1 The value increases with increasing scan rate, and is related to the square root of the scan rate (υ). 1 / 2 The linear relationship is shown, and the resulting linear equation is as follows: I pc (μA)=-297.47υ 1 / 2 (V / s) 1 / 2 +24.81 (γ=0.994). Therefore, the electroreduction reaction of FT on MnOx-LIGE is a diffusion-controlled process.

[0103] The preparation steps of the LIGE involved in the above detection process are as follows: 4g of polyamic acid solution is uniformly coated onto a clean glass plate surface, controlling the coating thickness to be approximately 30μm, forming a precursor film. The coating film is then subjected to the following heat treatments: dried in a vacuum drying oven at 100℃ for 30min to remove the solvent; then transferred to a constant temperature oven and further heated at 166℃ for 10min to achieve partial imidization reaction, obtaining a polyimide (PI) film. The surface of the PI film is patterned using a laser engraving device, with the laser power set to 2.2W. A conductive porous graphene structure is formed on the PI film surface by laser irradiation, thereby obtaining a laser-induced graphene electrode (LIGE). Silver paste is uniformly coated onto the desired area on the surface of the obtained LIGE electrode, with a coating thickness of approximately 30μm, forming a reference electrode pattern. Subsequently, it is cured at 140℃ for 20min.

[0104] Figure 10 and Figure 11 This study reveals the principle underlying the excellent detection performance and stability of the electrode prepared in Example 1 during the detection of fenitrothion.

[0105] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0106] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for one-step laser-induced fabrication of manganese oxide-doped graphene electrodes, characterized in that, Includes the following steps: A manganese chloride solution was placed in polyamic acid to obtain a manganese chloride-doped polyamic acid solution. The polyamic acid solution doped with manganese chloride was coated onto the substrate, dried twice, and the film was removed to obtain a manganese chloride-doped polyimide film. The manganese chloride-doped polyimide film was laser-etched to obtain the manganese oxide-doped graphene electrode.

2. The method according to claim 1, characterized in that, The manganese chloride solution includes an ethanol solution of manganese chloride; the concentration of the manganese chloride solution is 0.1–0.5 mol / L.

3. The method according to claim 1, characterized in that, The ratio of manganese chloride solution to polyamic acid is 0.1-0.3 mL: 4 g.

4. The method according to claim 1, characterized in that, The substrate includes a glass plate; and / or the thickness of the polyamic acid solution doped with manganese chloride is 25–35 μm.

5. The method according to claim 1, characterized in that, In the two drying processes, the temperature of the first drying is 90–110°C and the time is 25–45 min, and the temperature of the second drying is 150–170°C and the time is 8–15 min; and / or, the laser power of the laser etching is 1.1–2.75 W.

6. The manganese oxide-doped graphene electrode prepared by the method according to any one of claims 1 to 5.

7. The application of the manganese oxide-doped graphene electrode according to claim 6 in the preparation of electrochemical sensors.

8. An electrochemical sensor, characterized in that, It includes the manganese oxide-doped graphene electrode as described in claim 6.

9. The electrochemical sensor according to claim 8, characterized in that, The manganese oxide-doped graphene electrode as described in claim 6 is used as the working electrode, and the silver electrode is used as the reference electrode.

10. The application of the electrochemical sensor according to claim 8 or 9 in the detection of fenitrothion.

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