Self-supporting MnOx-LIG composite material as well as preparation method and application thereof

Abstract

The invention provides a self-supporting MnOx-LIG composite material as well as a preparation method and application thereof, and belongs to the technical field of electrochemical sensors. The preparation method comprises the following steps: uniformly mixing a manganese salt solution and a polyimide solution, coating the surface of a substrate material with the mixture, and drying to obtain an Mn salt doped polyimide film; and carrying out laser etching on the Mn salt doped polyimide film to obtain the self-supporting MnOx-LIG composite material. The composite material is further used for portable electrochemical detection of fenitrothion (FT). The MnOx-LIG composite material on the surface of the electrode shows obvious catalytic performance on the electrochemical reaction of FT, the detection limit is 13.66 nmol / L, and the linear range is 100.0 nmol / L to 250.0 mol / L. In addition, the developed sensor has good selectivity and stability. The developed sensor is used for detecting FT in a mango sample, and the good recovery rate is achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electrochemical sensors, and particularly relates to a self-supporting MnOx-LIG composite material and a preparation method and application thereof. BACKGROUND

[0002] Fenitrothion (FT), also known as O,O-dimethyl O-(3-methyl-4-nitrophenyl), is a widely used insecticide that has a killing effect on Lepidoptera larvae and pests such as Hemiptera and Coleoptera. The insecticidal effect of fenitrothion is mainly achieved by inhibiting acetylcholinesterase, and it can also interfere with other metabolic functions, such as blocking esterase and phosphodiesterase, thereby further enhancing its insecticidal effect. However, excessive use of FT can pollute land and rivers, and residues in crops can be harmful to the human nervous system. Therefore, it is of great significance to develop a rapid and accurate method for detecting FT for its safe use. At present, a series of methods have been used to detect FT, such as high-performance liquid chromatography, gas chromatography, colorimetric detection, enzyme-linked immunosorbent assay, and molecular imprinting method. Although these methods can produce accurate and reliable results, they usually require complex instruments, skilled operation and time-consuming sample preparation procedures. In addition to these methods, electrochemical sensors have become a research hotspot in the field of analytical detection due to their low cost, fast response, high sensitivity and high selectivity. Given the poor stability of enzymes and other problems, FT detection strategies based on non-enzymatic principles have also received increasing attention in the field of electrochemical sensing.

[0003] It is well known that the performance of electrochemical sensors depends on the properties of electrode materials. In recent years, laser-induced technology has become an advanced material design and synthesis technology, and LIG can be prepared by irradiating a carbon-containing substrate with a high-energy light beam. Compared with traditional methods, this method has the advantages of fast production speed, strong image capability, environmental friendliness, controllable micro-morphology and composition, etc. Therefore, it promotes the miniaturization of electrochemical devices and is increasingly recognized in the field of electrochemistry. For example, Sharma et al. used LIGE for hydrazine electrochemical sensing, which had good reproducibility and selectivity. Sain et al. applied LIGE for effective square wave voltammetry detection of paraquat with a detection limit as low as 0.54 μmol / L. However, the lower catalytic performance of carbon materials is still a bottleneck restricting the further application of LIG-based electrodes. SUMMARY

[0004] In view of the above, the present application aims to provide a self-supporting MnOx-LIG composite material and a preparation method and application thereof.

[0005] In order to achieve the above-mentioned purpose, the present application provides the following technical solutions:

[0006] One of the technical solutions of the present application is a preparation method of a self-supporting MnOx-LIG composite material, comprising the following steps:

[0007] After the manganese salt solution and the polyimide solution are uniformly mixed, the mixture is coated on the surface of a base material, dried to obtain a Mn salt doped polyimide film;

[0008] The Mn salt doped polyimide film is laser etched to obtain the self-supporting MnOx-LIG composite material.

[0009] The second technical solution of the present application is a self-supporting MnOx-LIG composite material prepared by the above preparation method.

[0010] The third technical solution of the present application is a modified electrode, comprising a base electrode and an electrode modification material; the electrode modification material is the above self-supporting MnOx-LIG composite material.

[0011] The fourth technical solution of the present application is an electrochemical sensor comprising the above modified electrode (denoted as a self-supporting MnOx-LIGE composite material modified electrode).

[0012] The fifth technical solution of the present application is an application of the above self-supporting MnOx-LIG composite material or the above modified electrode or the above electrochemical sensor in detecting fenitrothion.

[0013] The present application discloses the following technical effects:

[0014] The present application synthesizes a self-supporting MnO x -LIGE by laser etching and doping Mn salt PI film, and further uses it for portable electrochemical detection of FT. The MnO x -LIG composite material on the electrode surface shows obvious catalytic performance for the electrochemical reaction of FT, with a detection limit of 13.66 nmol / L and a linear range of 100.0 nmol / L-250.0 mu mol / L. In addition, the developed sensor has good selectivity and stability. The developed sensor is used to detect FT in a mango sample, and has a good recovery rate, providing a new effective way for portable detection and analysis of FT in food samples. It provides a new method and new material for the medical and health field, drug detection and food safety field. BRIEF DESCRIPTION OF DRAWINGS

[0015] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application, and those skilled in the art can also obtain other drawings according to these drawings without creative labor.

[0016] Figure 1 MnO x The preparation and FT detection process of LIG;

[0017] Figure 2 MnO x SEM of LIG;

[0018] Figure 3 MnO x TEM of LIG;

[0019] Figure 4 MnO x Elemental mapping of C, O and Mn in LIG;

[0020] Figure 5 MnO x XRD spectra of LIG and LIG;

[0021] Figure 6 MnO x XPS full spectrum of LIG;

[0022] Figure 7 MnO x High-resolution XPS spectra of C, O and Mn in LIG;

[0023] Figure 8 CV curves of different electrode modification materials in 1.0 mmol / L K3[Fe(CN)6] and 0.5 mol / L KCl mixed solution;

[0024] Figure 9 Q-t curve;

[0025] Figure 10 Linear relationship diagram of Q and t of LIGE and MnOx-LIGE; 1 / 2

[0026] Figure 11 CV curves of LIGE and MnO x -LIGE in 0.1 mol / L BR solution A and containing 250.0 μmol / L FT B;

[0027] Figure 12 MnO x CV curves of LIGE at different scan rates in 250.0 μmol / L FT;

[0028] Figure 13 Linear relationship of reduction peak current and scan rate;

[0029] Figure 14 FT electrochemical reaction equation;​

[0030] Figure 15 CV curves of MnO2 for 250.0 μmol / L FT x CV curves of LIGE (different MnCl2concentration);

[0031] Figure 16 CV curves of LIGE for FT prepared at different laser power x CV curves of LIGE;

[0032] Figure 17 CV curves of LIGE for MnO2 x CV curves of LIGE in different buffer solution;

[0033] Figure 18 CV curves of LIGE for MnO2 x CV curves of LIGE in different pH 0.1 mol / L BR solution;

[0034] Figure 19 Relationship of FT reduction peak current and potential with pH;

[0035] Figure 20 LSV response of LIGE for FT at different concentration x LSV response of LIGE;

[0036] Figure 21 Current vs. FT concentration curve

[0037] Figure 22 Current response of LIGE for MnO2 x Current response of LIGE in 250.0 μmol / L FT

[0038] Figure 23 Stability test of LIGE x Stability test of LIGE DETAILED DESCRIPTION

[0039] The following detailed description is presented to describe certain exemplary embodiments of the application. It should be appreciated that the detailed description is presented for the purpose of describing the application and is not intended to limit the application. Moreover, the detailed description is presented in terms of specific exemplary embodiments, which should not be construed as limiting the application. Rather, the detailed description is presented as a description of certain aspects, features, and embodiments of the application.

[0040] It should be understood that the terms used herein are for the purpose of describing particular embodiments and are not intended to limit the application. Additionally, for numerical ranges that are expressed in terms of "about" one limitation and "up to" another limitation, it is contemplated that any numerical value that falls within the range can be specifically recited. For example, if a range is stated as "about 5 up to 10," it is specifically contemplated that a numerical value recited as 6.2, 3.8, 9.9, 5.1, 10.0, 5.5, 8.5, etc. is within the scope of the range. Moreover, it should be understood that the numerical ranges explicitly recited are inclusive of the endpoints.

[0041] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present application, the preferred methods and materials are described. All documents mentioned herein are incorporated by reference to disclose and describe in full the methods and / or materials which are described therein. In case of conflict, the content of the present specification will control.

[0042] Many modifications and variations of the present application described in the specification are possible without departing from the scope or spirit of the application. Other implementations of the application will be apparent to those skilled in the art from consideration of the specification and practice of the application disclosed herein. The specification and examples given are exemplary only.

[0043] As used herein, the terms "comprises", "comprising", "includes", "including", "has", "having", and the like are open-ended terms that are intended to permit but not limit the inclusion of elements or the number of elements, as well as the possibility that one or more other elements can be added or otherwise included.

[0044] The first aspect of the present application provides a preparation method of a self-supporting MnOx-LIG composite material, comprising the following steps:

[0045] After the manganese salt solution and the polyimide solution are uniformly mixed, the mixture is coated on the surface of the base material, and then dried to obtain a Mn salt doped polyimide film;

[0046] The Mn salt doped polyimide film is laser etched to obtain the self-supporting MnOx-LIG composite material.

[0047] The selection of the base material is not limited in the present application, and the conventional technical means of those skilled in the art can be used, for example, a glass plate.

[0048] In the preferred embodiment of the present application, the concentration of the manganese salt solution is 0.1-0.5 mol / L; specifically, the concentration of the manganese salt is 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L or 0.5 mol / L; the solvent of the manganese salt solution is ethanol, and the solute is MnCl2·4H2O.

[0049] In the preferred embodiment of the present application, the volume-to-mass ratio of the manganese salt solution to the polyimide solution is 200 μL:4 g. In the present application, the polyimide solution is commercially available (solid content 20 wt%, Nantong Suyuan Plastic Industry Co., Ltd.).

[0050] In the preferred embodiment of the present application, the drying is performed at 80-100 ℃ for 20-30 minutes, and then at 140-160 ℃ for 10-20 minutes.

[0051] In a preferred embodiment of the present application, the power of the laser etching is 1.10-2.75 W. Specifically, the power of the laser etching is 1.10 W, 1.65 W, 2.20 W or 2.75 W.

[0052] The second aspect of the present application provides a self-supporting MnOx-LIG composite material prepared by the above preparation method.

[0053] The third aspect of the present application provides a modified electrode, comprising a base electrode and an electrode modification material; the electrode modification material is the self-supporting MnOx-LIG composite material described above.

[0054] The fourth aspect of the present application provides an electrochemical sensor, comprising the modified electrode described above.

[0055] The fifth aspect of the present application provides an application of the self-supporting MnOx-LIGE composite material described above, or the modified electrode described above, or the electrochemical sensor described above in detecting fenitrothion.

[0056] The technical solutions of the present application are conventional solutions in the art if not specifically stated, and the reagents or raw materials used are purchased from commercial channels or have been disclosed if not specifically stated.

[0057] In the examples, the electrochemical test conditions are as follows:

[0058] On a handheld electrochemical workstation, the electrochemical behavior of FT was studied by CV, LSV, CC and other electrochemical methods. CV measurement was carried out in a potential window range of-1.2 V to 0 V, LSV measurement was carried out in a range of-1.2 V to-0.6 V, and 0.1 mol / L Britton-Robinson (BR, pH=7.0) solution was used as a supporting electrolyte. CC method was used to calculate the effective area of the electrode, and the potential range was-0.2 to 0.6 V, and the pulse width was 0.25 s. All electrochemical measurements were carried out under ambient conditions.

[0059] The actual mango sample was pretreated as follows:

[0060] Mango samples were purchased from the Guilinyang market in Haikou City. 5 g of mango was weighed, cut into small pieces and ground, soaked in an ethanol solution for half an hour, then centrifuged for 10 min to collect the supernatant solution, filtered with a 0.22 μm injection filter, and then diluted 100 times with 0.1 mol / L BR solution. The MnO x The content of FT was determined by a standard calibration curve, and the standard solution was added to the mango extraction solution to detect the recovery rate.

[0061] In the examples, the polyimide solution was obtained commercially (solid content 20 wt%, Nantong Suyuan Plastic Industry Co., Ltd.).

[0062] In order to better understand the present application, the content of the present application is further illustrated below in combination with examples, but the content of the present application is not limited to the examples below.

[0063] Example 1

[0064] Self-supporting MnO x The preparation steps of the LIGE composite modified electrode are as follows:

[0065] 200 μL of MnCl2·4H2O solution with a concentration of 0.4 mol / L prepared with ethanol was added into 4.0 g of PI solution, and after stirring for 2 min to mix uniformly, the mixed solution was uniformly coated on a cleaned glass plate (10.0 cm x 15.0 cm x 1.0 mm) by using a coater. Then the glass plate was placed in a vacuum drying box and dried at 100°C for 30 min, and then dried in an oven at 166°C for 10 min to obtain a MnCl2-doped polyimide (MnCl2-PI) film. According to the designed electrode pattern, laser etching was performed on the surface of the film by using a laser engraving machine (the power of laser etching was 2.20 W), and silver paste was coated on one of the electrode surfaces, and baked at 140°C for 30 min to obtain a self-supporting MnO x LIGE composite modified electrode, wherein the modified material is MnO x LIG composite, and the electrode substrate is a cured PI film.

[0066] For comparison, LIGE was synthesized by using a PI solution (without MnCl2·4H2O) in a similar manner. The specific steps are as follows: the PI solution was uniformly coated on a cleaned glass plate (10.0 cm x 15.0 cm x 1.0 mm) by using a coater. Then the glass plate was placed in a vacuum drying box and dried at 100°C for 30 min, and then dried in an oven at 166°C for 10 min to obtain a PI film. According to the designed electrode pattern, laser etching was performed on the surface of the film by using a laser engraving machine (the power of laser etching was 2.20 W), and silver paste was coated on one of the electrode surfaces, and baked at 140°C for 30 min to obtain LIGE.

[0067] Characterization and effect verification:

[0068] Figure 1 MnO x Preparation of LIGE composite modified electrode and schematic diagram of FT detection process.

[0069] Figure 2 MnO x SEM image of LIG; from Figure 2 It can be seen that MnO x-LIG reveals a three-dimensional porous structure of loaded particles. When the carbon-containing precursor is irradiated by a laser, the laser energy is absorbed by the substrate material, triggering a thermal effect or photochemical reaction.

[0070] Figure 3 MnO at different magnifications x - TEM image of LIG; by Figure 3 It can be clearly seen that there are solid particles with a diameter of less than 20 nm on the surface of the composite material.

[0071] Figure 4 MnO x - Elemental mapping of C, O, and Mn in LIG; by Figure 4 It can be seen that the three elements are evenly distributed throughout the material.

[0072] Figure 5 MnO x -XRD spectra of LIG and LIG; by Figure 5 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 structure in -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), while 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 Mn 2+ In an oxygen-containing environment, it is laser-induced to transform into MnO, an oxide containing Mn. x .

[0073] Figure 6 MnO x -LIG's XPS full spectrum; by Figure 6 This indicates the presence of elements such as O, C, and Mn.

[0074] Figure 7 High-resolution XPS spectra of C, O, and Mn; by Figure 7 It can be seen that in the high-resolution C1s spectrum, the peak centered at 284.80 eV corresponds to the presence of graphitic carbon. The additional peaks at 285.8 eV, 287.2 eV, and 289.7 eV are attributed to the CO, C=O, and OC=O functional groups, respectively. Furthermore... Figure 7The O 1s spectrum is shown, with binding energies of 530.8 eV, 532.3 eV and 533.5 eV corresponding to Mn-O bond, C-O and C=O, respectively. Figure 7 The Mn 2p spectrum fitting in the range of 650-700 eV reveals the presence of Mn 2+ , Mn 3+ , Mn 4+ cations, Mn 2p3 / 2 can be assigned to a combination of 642.9 eV (Mn 3+ ) and 641.4 eV (Mn 2+ ), while Mn 2p1 / 2 can be assigned to a combination of 654.2 eV (Mn 3+ ) and 652.6 eV (Mn 2+ ), and 646.7 eV indicates the presence of Mn 4+ . These results indicate that MnO x -LIG has been successfully synthesized under laser induction.

[0075] Figure 8 CV curves of different electrodes LIGE and MnO x -LIGE in 1.0 mmol / L K3[Fe(CN)6] and 0.5 mol / L KCl mixed solution; it can be seen from the figure that the CV curves of LIGE (curve a) and MnO x -LIGE (curve b) both show a pair of characteristic redox peaks of [Fe(CN)6] 3- / 4- . The peak potential difference (ΔE x ) of LIGE and MnO p -LIGE is 0.16 V and 0.08 V, respectively. Compared with LIGE, the peak current of MnO x -LIGE is enhanced, and ΔE p is lower, which indicates that the surface of MnO x -LIGE has a larger electroactive area and faster electron transfer.

[0076] Figure 9 Q-t curves; Figure 10 Linear relationship diagram of Q and t 1 / 2 of LIGE (a) and MnOx-LIGE (b); it can be seen from Figure 9 and Figure 10 together that 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), respectively. According to the formula Q = 2nFAcD 1 / 2 t1 / 2 / π 1 / 2 +Q dl +Q ads where (cm 2 ) is the effective area of the electrode, F is the Faraday constant, c (mol cm -3 ) is the solution concentration, n is the number of electrons transferred, D is the diffusion coefficient of [Fe(CN)6] 3- / 4- (7.6 x 10 -6 cm 2 s -1 , 25 °C), Q dl is the double-layer charge, Q ads is the Faraday charge, the active area of the working electrode can be calculated. The effective areas of LIGE and MnO x -LIGE are 0.432 cm 2 and 0.811 cm 2 , respectively. The effective area of MnO x -LIGE is about 2 times that of LIGE, which indicates that the doping of MnO x significantly increases the effective area of the electrode, and MnO x -LIGE can effectively improve the electron transfer rate of the electrode and enhance its electrochemical performance.

[0077] Figure 11 CV curves of LIGE and MnO x -LIGE in 0.1 mol / L BR solution and 250.0 μmol / L FT; from the figure, it can be seen that under the stable background current, LIGE and MnO x -LIGE do not exhibit any electrochemical response in the blank buffer solution. In the 250.0 μmol / L FT solution, an obvious oxidation peak and two reduction peaks are observed on LIGE (curve a) at potentials of -0.17 V (I pa ), -0.89 V (I pc1 ) and -0.28 V (I pc2 ), respectively, and similar redox peaks are also observed on MnO x -LIGE (curve b) at potentials of -0.29 V (I pa ), -0.89 V (I pc1 ) and -0.33 V (I pc2 ), respectively, and the peak current is obviously increased. This is because FT has a redox-active -NO2 group, which can undergo a multi-step multi-electron electrochemical reaction. During the CV process, MnO xThe -NO2 group on LIGE is reduced to -NHOH at a negative reduction potential of -0.89 V, and no peak is observed during the anodic scan, indicating the irreversible nature of the reduction process.

[0078] Figure 12 MnO x CV curves of LIGE at different scan rates (0.02, 0.04, 0.06, 0.08, 0.1, 0.15 V / s, respectively) in 250.0 μmol / L FT; it can be seen from the figure that FT is reduced on MnO x The reduction current (I pc1 ) on LIGE increases with the increase of scan rate.

[0079] Figure 13 MnO x The reduction current (I pc1 ) on LIGE has a linear relationship with the square root of scan rate (υ 1 / 2 ), and the linear equation obtained is as follows: I pc (μA) = -297.47υ 1 / 2 (V / s) 1 / 2 + 24.81 (γ = 0.994). FT is reduced on MnO x The electroreduction reaction of LIGE is a diffusion-controlled process.

[0080] Figure 14 MnO x The electroreduction reaction of LIGE is a diffusion-controlled process.

[0081] Figure 15 CV curves of 250.0 μmol / L FT on MnO x LIGE (different MnCl2 concentrations); it can be seen from the figure that when the concentration of MnCl2 increases from 0.1 mol / L to 0.4 mol / L, the peak current of FT gradually increases, indicating that the increase of MnO x facilitates the reaction of FT on the electrode surface. When the concentration of MnCl2 reaches 0.5 mol / L, the peak current of FT decreases, which may be due to the fact that the excess MnO x destroys the porous structure of LIGE, hindering the transport channels for FT diffusion. When the concentration of MnCl2 is 0.4 mol / L, the peak current of FT is the largest, so 0.4 mol / L is selected as the optimal doping concentration of MnCl2.

[0082] Figure 16 MnO xCV curves of LIGE. From the figure, it can be seen that the peak current of FT gradually increases when the laser power increases from 1.10 W to 2.20 W, and the peak current of FT decreases when the laser power increases to 2.75 W. The peak current of FT is the largest at 2.20 W. This is because the degree of PI graphitization increases with the increase of power, and when the laser power is too high, it destroys the structure and chemical bonds of the carbon layer of LIGE, resulting in a decrease in current value. Therefore, 2.20 W is selected as the best output power of the laser.

[0083] Figure 17 MnO x CV curves of LIGE in different buffer solutions (a~d: BR solution, citric acid-sodium citrate solution, HAc-NaAc solution, Tris-HCl solution). From the figure, it can be seen that the current value of BR buffer solution is the highest in BR solution, citric acid-sodium citrate solution, HAc-NaAc solution and Tris-HCl solution, which is the supporting electrolyte for the experiment.

[0084] Figure 18 MnO x CV curves of LIGE in different pH 0.1 mol / L BR solutions (pH=4.0, 5.0, 6.0, 7.0, 8.0). From the figure, it can be seen that the peak current increases with the increase of pH, until the pH value of the solution reaches 7.0, and decreases above pH 7.0. In addition, with the increase of the pH value of the solution, the FT peak potential moves to the negative direction, thereby confirming the participation of protons.

[0085] Figure 19 FT reduction peak current and potential vs. pH; from the figure, pH 7.0 is selected as the best pH for further study. pc There is a good linear relationship with pH: E pc (V)=-0.054pH-0.53 (γ=0.991). The slope of-54 mV / pH is very close to the Nernst theoretical value (-59 mV / pH), which indicates that electrons and protons are transferred in equal amounts in the FT reaction.

[0086] Figure 20 FT in different concentrations of MnO x LSV response of LIGE, scan rate 0.1 V / s; from the figure, it can be seen that the reduction peak current increases with the increase of FT concentration.

[0087] Figure 21 Current vs. FT concentration curve; from the figure, it can be seen that in the concentration range of 100.0 nmol / L-250.0 μmol / L, the corresponding regression equation is: I pc(μA) = 0.68C(μmol / L)-0.11(γ = 0.991), the detection limit was 13.66 nmol / L (3σ). It can be seen that the prepared MnO x The LIGE electrochemical sensor showed good analytical performance with a wide linear response range and low detection limit.

[0088] Figure 22 The MnO x The current response of LIGE in 250.0 μmol / L FT (10 times the concentration of interfering ions); it can be seen from the figure that these substances have little effect on the detection of FT, indicating that the sensor has good selectivity for FT.

[0089] Figure 23 The stability test; it can be seen from the figure that the reduction peak current detected by the electrode still maintains 86.4% of the initial value after continuous storage for 15 days, indicating that the modified electrode MnO x The LIGE has good storage stability.

[0090] Table 1 is the detection result of FT in mango samples; it can be seen from the table that no FT is detected in the purchased mango samples, the recovery rate is 102.4% to 104.2%, and the relative standard deviation (RSD) is less than 5%. These findings confirm that the MnO x The LIGE has important prospects in quantitatively determining FT in actual mangoes.

[0091] Table 1

[0092]

[0093] In summary, the MnO x The LIGE composite material modified electrode shows obvious catalytic performance for the electrochemical reaction of FT, the detection limit is 13.66 nmol / L, and the linear range is 100.0 nmol / L to 250.0 μmol / L. In addition, the developed sensor has good selectivity and stability. The excellent sensing performance can be attributed to the MnO x The LIG composite material has fast electron transport rate, high conductivity, large effective area and three-dimensional porous nanostructure. The developed sensor is used to detect FT in mango samples, and has good recovery rate. The prepared electrochemical sensor shows good analytical performance with a wide linear response range and low detection limit. In addition, the MnO x The LIG nanocomposite material has the advantages of low cost and easy preparation, and therefore has good competitiveness compared with other electrochemical sensing materials.

[0094] The above merely describes the preferred embodiments of the present application, and it should be pointed out that, for those skilled in the art, several improvements and refinements can be made without departing from the principles of the present application, and these improvements and refinements should also be considered as falling within the protection scope of the present application.

Claims

1. A method for preparing a self-supporting MnOx-LIG composite material, characterized in that, Includes the following steps: After the manganese salt solution and the polyimide solution are mixed evenly, the mixture is coated onto the surface of the substrate material and dried to obtain a Mn salt-doped polyimide film. The Mn salt-doped polyimide film was laser-etched to obtain the self-supporting MnOx-LIG composite material.

2. The preparation method according to claim 1, characterized in that, The concentration of the manganese salt solution is 0.1-0.5 mol / L; the solvent of the manganese salt solution is ethanol, and the solute is MnCl2·4H2O.

3. The preparation method according to claim 2, characterized in that, The volume-to-mass ratio of the manganese salt solution to the polyimide solution is 200 μL: 4 g.

4. The preparation method according to claim 1, characterized in that, The drying process involves first drying at 80-100℃ for 20-30 minutes, and then drying at 140-160℃ for 10-20 minutes.

5. The preparation method according to claim 1, characterized in that, The power of the laser etching is 1.10-2.75W.

6. A self-supporting MnOx-LIG composite material prepared by the preparation method according to any one of claims 1-5.

7. A modified electrode, characterized in that, It includes a base electrode and an electrode modification material; the electrode modification material is the self-supporting MnOx-LIG composite material as described in claim 6.

8. An electrochemical sensor, characterized in that, Includes the modified electrode as described in claim 7.

9. The application of the self-supporting MnOx-LIG composite material of claim 6, the modified electrode of claim 7, or the electrochemical sensor of claim 8 in the detection of fenitrothion.

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