Amino-functionalized multi-walled carbon nanotube / nickel / nickel oxide-graphene electrode, and preparation method and application thereof

Abstract

The application provides an aminated multi-walled carbon nanotube / nickel / nickel oxide-graphene electrode and a preparation method and application thereof, and belongs to the technical field of electrochemical sensing. The aminated multi-walled carbon nanotube / nickel / nickel oxide-graphene electrode is prepared by mixing a nickel-containing compound solution and a polyamide acid solution to obtain a doped polyamide acid solution, coating the doped polyamide acid solution on a substrate and performing drying treatment to obtain a doped polyamide acid film; after coating silver paste, laser etching is performed, and an aminated multi-walled carbon nanotube dispersion solution is drop-coated to obtain the electrode. The electrode provided by the application integrates material modification and electrode preparation, is simple and convenient, and has a detection limit of 12.74 nmol / L for bisphenol A when the electrode is prepared into a sensor. The preparation method is simple and easy to operate, and the flexible portable electrochemical sensor can be obtained by connecting the electrode with a portable sensor and a mobile phone, and the flexible portable electrochemical sensor has excellent detection performance and good stability.

Description

Technical Field

[0001] This invention belongs to the field of electrochemical sensing technology, and particularly relates to an aminated multi-walled carbon nanotube / nickel / nickel oxide-graphene electrode, its preparation method and application. Background Technology

[0002] Bisphenol A (BPA) is an important organic chemical raw material, mainly used in the synthesis of polycarbonate plastics and epoxy resins. It is widely found in everyday items such as plastic water bottles, food storage containers, beverage can coatings, and thermal paper receipts. However, BPA is a typical endocrine disruptor, capable of mimicking the physiological effects of estrogen and interfering with the normal regulatory functions of the body's endocrine system. Long-term exposure to BPA may lead to reproductive system disorders, fetal developmental abnormalities, weakened immune function, and metabolic imbalances, and increase the risk of hormone-dependent diseases such as breast cancer and prostate cancer. Given its potential hazards, the European Chemicals Agency has listed BPA as a Substance of Very High Concern. This regulatory measure highlights the necessity of establishing efficient, sensitive, and reliable analytical methods to accurately monitor BPA in environmental and food samples.

[0003] Currently, BPA detection mainly relies on analytical techniques such as high-performance liquid chromatography (HPLC), gas chromatography-mass spectrometry (GC-MS), and HPLC-MS. While these methods offer excellent sensitivity and selectivity, their dependence on large-scale instruments and complex sample pretreatment processes limit their application in rapid on-site detection. Electrochemical sensing technology, due to its ease of operation, rapid response, low cost, and suitability for on-site detection, has broad application prospects in the field of pollutant detection. However, the performance of electrochemical sensing largely depends on the structure and properties of the electrode interface materials; therefore, developing high-performance electrode materials is crucial for improving sensing performance.

[0004] Laser-induced graphene (LIG) technology can rapidly prepare three-dimensional porous graphene structures by directly irradiating polymer substrates with lasers, offering significant advantages such as low precursor cost, simple preparation process, and patternable fabrication. LIGs, due to their high specific surface area and excellent conductivity, have been widely used in electrochemical sensing. However, the limited number of active sites in single-component LIGs restricts their application in trace analysis. In recent years, metal doping has been shown to significantly improve the sensing capabilities of LIGs. Existing research has reported methods such as plasma treatment of polyimide films to introduce hydrophilic groups for metal ion adsorption, followed by CO2 laser irradiation to achieve atomic-level metal doping; other studies have employed a two-step method to first prepare LIG electrodes and then modify them with nickel oxide nanoparticles. However, traditional doping methods are often limited by cumbersome pretreatment procedures or weak metal-graphene interfacial interactions. Furthermore, introducing conductive carbon nanomaterials or transition metal active components to functionalize the electrodes is considered an effective strategy for improving electrochemical performance. Aminated multi-walled carbon nanotubes (NH2-MWCNTs) possess excellent electrical conductivity and a large specific surface area. The abundant amino functional groups on their surface can not only improve the material's dispersibility but also enhance its interfacial bonding with the electrode substrate through hydrogen bonding or electrostatic interactions, thereby effectively improving electron transport efficiency and active site density.

[0005] Therefore, developing a doped graphene flexible electrochemical sensor with simple fabrication process and excellent electrode performance is of great practical significance. Summary of the Invention

[0006] To address the problems of limited active sites, cumbersome metal doping processes, and insufficient electrochemical detection sensitivity in existing laser-induced graphene electrodes, this invention proposes an aminated multi-walled carbon nanotube / nickel / nickel oxide-graphene electrode, its preparation method, and its application. This aims to solve the aforementioned problems in existing technologies and establish a sensitive, rapid, and portable method for detecting bisphenol A.

[0007] To achieve the above objectives, the present invention provides the following technical solution: This invention provides a method for preparing an aminated multi-walled carbon nanotube / nickel / nickel oxide-graphene electrode, comprising the following steps: A nickel-containing compound solution is mixed with a polyamic acid solution to obtain a doped polyamic acid solution; The doped polyamic acid solution is coated onto a substrate and then dried to obtain a doped polyamic acid film. The doped polyamic acid film was laser-etched to obtain nickel / nickel oxide-doped graphene material; Silver paste was coated onto the surface of the nickel / nickel oxide-doped graphene material and then heated to cure, resulting in a nickel / nickel oxide-doped graphene electrode. Aminated multi-walled carbon nanotubes (NH2-MWCNTs) dispersion was drop-coated onto the surface of the nickel / nickel oxide-doped graphene electrode, and after curing, the aminated multi-walled carbon nanotube / nickel / nickel oxide-graphene electrode (NH2-MWCNTs / Ni-LIGE) was obtained.

[0008] Furthermore, the nickel-containing compound solution is a nickel chloride solution.

[0009] Furthermore, the ratio of the nickel-containing compound solution to the polyamic acid solution is 50 μL: 1 g, the concentration of the nickel-containing compound solution is 60 mg / mL, and the mass concentration of the polyamic acid solution is 20%.

[0010] Furthermore, the substrate includes a glass plate; the thickness of the coating of the doped polyamic acid solution is 25~35 μm.

[0011] Furthermore, the drying process includes a first drying and a second drying; the temperature of the first drying is 90~110℃ and the time is 25~45 min; the temperature of the second drying is 150~170℃ and the time is 8~15 min.

[0012] 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.

[0013] Second drying (150~170℃): Further removes residual solvent from deeper layers; promotes partial imidization (cyclization) of PAA (polyamic acid) to PI (polyimide); improves the mechanical stability and heat resistance of the film, facilitating subsequent laser etching; 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.

[0014] Furthermore, the laser power of the laser etching is 2.20~2.75 W, and the etching depth is 30%.

[0015] 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.

[0016] Furthermore, the modification volume of the aminated multi-walled carbon nanotube dispersion is 2-6 μL, and the area of ​​the nickel / nickel oxide-doped graphene electrode is 12.57 mm². 2 .

[0017] The present invention also provides an aminated multi-walled carbon nanotube / nickel / nickel oxide-graphene electrode prepared according to the above preparation method.

[0018] The present invention also provides an electrochemical sensor comprising the above-mentioned aminated multi-walled carbon nanotube / nickel / nickel oxide-graphene electrode as a working electrode, and the electrochemical sensor further comprising a reference electrode; the reference electrode is a silver electrode.

[0019] The present invention also provides an application of the above-mentioned electrochemical sensor in the detection of bisphenol A (BPA).

[0020] Currently, BPA detection mainly relies on analytical techniques such as high-performance liquid chromatography (HPLC), gas chromatography-mass spectrometry (GC-MS), and HPLC-MS. While these methods offer excellent sensitivity and selectivity, their dependence on large-scale instruments and complex sample pretreatment processes limit their application in rapid on-site detection. Electrochemical sensing technology, due to its ease of operation, rapid response, low cost, and suitability for on-site detection, has broad application prospects in pollutant detection. However, electrochemical sensing performance largely depends on the structure and properties of the electrode interface materials. Therefore, developing high-performance electrode materials is crucial for improving sensing performance. Ligated Inductively Coupled Gas (LIG) has been widely used in electrochemical sensing due to its high specific surface area and excellent conductivity. However, the limited number of active sites in a single-component LIG limits its application in trace analysis. Therefore, it is necessary to improve its electrochemical performance through interface modulation using composite functional materials. Against this backdrop, introducing conductive carbon nanomaterials or transition metal active components to functionalize electrodes is considered an effective strategy for enhancing electrochemical performance. Aminated multi-walled carbon nanotubes (NH2-MWCNTs) possess excellent electrical conductivity and a large specific surface area. The abundant amino functional groups on their surface can not only improve the material's dispersibility but also enhance its interfacial bonding with the electrode substrate through hydrogen bonding or electrostatic interactions, thereby effectively improving electron transport efficiency and active site density.

[0021] The NH2-MWCNTs / Ni-LIGE composite electrode obtained in this invention achieves simultaneous generation of Ni / NiO and porous graphene on a PI substrate via a laser-induced one-step method. Subsequently, NH2-MWCNTs are introduced onto the electrode surface using a drop-coating method to obtain the NH2-MWCNTs / Ni-LIGE composite electrode. The interaction between Ni / NiO and NH2-MWCNTs not only enhances the adsorption of BPA molecules, but also, under laser irradiation, PAA undergoes in-situ carbonization to form highly conductive three-dimensional porous graphene. Simultaneously, nickel chloride is converted to Ni / NiO, which is uniformly anchored on the carbon framework surface. The interaction between Ni / NiO and NH2-MWCNTs not only enhances the adsorption energy of BPA molecules but also causes them to exhibit a higher distribution probability and shorter interaction distance near amino and nickel sites, thereby facilitating the interfacial charge transfer process and improving electrochemical detection sensitivity. Based on NH2-MWCNTs / Ni-LIGE as the working electrode material interface and combined with a portable electrochemical workstation, a bisphenol A electrochemical sensor was constructed.

[0022] Compared with the prior art, the present invention has the following advantages and technical effects: (1) The NH2-MWCNTs / Ni-LIGE composite electrode provided by this invention integrates material modification and electrode preparation, which is simple and convenient. Results show that the flexible portable electrochemical sensor based on NH2-MWCNTs / Ni-LIGE provided by this invention has a detection limit of 12.74 nmol / L for bisphenol A and a linear range of 5.0 × 10⁻⁶. -5 -0.35 mmol / L. The recoveries of spiking bisphenol A in actual samples ranged from 96.40% to 103.20%.

[0023] (2) The method for preparing the NH2-MWCNTs / Ni-LIGE composite electrode provided by the present invention is simple and easy to operate. It can be connected to a portable sensor and a mobile phone to obtain a flexible portable electrochemical sensor with excellent detection performance and good stability. Attached Figure Description

[0024] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 TEM images of the Ni / NiO-LIG (AC) and NH2-MWCNTs / Ni-LIGE composite electrodes (DF) prepared in Example 1 at different magnifications; Figure 2SEM images of the Ni / NiO-LIG (A and B) and NH2-MWCNTs / Ni-LIGE composite electrode (C) prepared in Example 1 at different magnifications; Figure 3 The XRD pattern (A), XPS total spectrum (B), and high-resolution XPS spectrum (C) of Ni / NiO-LIG prepared in Example 1 and LIG prepared in Comparative Example 2 are shown. Figure 4 The peak current variation test results are shown for (A) under different laser etching powers in Examples 1-3 and (B) under different NH2-MWCNTs dispersion modification volumes in Examples 1, 4-5, and Comparative Example 1. Figure 5 In Figure A, the CV curves of the NH2-MWCNTs / Ni-LIGE composite electrode prepared in Example 1 are shown in different buffer solutions. In Figure B, the peak current is shown. In Figure C, the CV curves are shown in PBS at different pH values. In Figure D, the peak current and peak potential are shown as changes in pH value. Figure 6 In Figure A, the CV curves of the electrochemical sensor based on the NH2-MWCNTs / Ni-LIGE composite electrode in Example 1 are shown in BPA solutions of different concentrations. In Figure B, the linear relationship between oxidation current and concentration is shown. In Figure C, the anti-interference test results of the electrochemical sensor based on the NH2-MWCNTs / Ni-LIGE composite electrode in Example 1 are shown. In Figure D, the stability test results are shown. Detailed Implementation

[0025] 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.

[0026] 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. Every smaller range between any stated value or intermediate value within a stated range, and 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.

[0027] 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.

[0028] 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 apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0029] 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.

[0030] This invention provides a method for preparing an aminated multi-walled carbon nanotube / nickel / nickel oxide-graphene electrode, comprising the following steps: A nickel-containing compound solution is mixed with a polyamic acid solution to obtain a doped polyamic acid solution; A polyamic acid solution was coated onto a substrate and then dried to obtain a polyamic acid film. Laser etching was performed on the doped polyamic acid film to obtain nickel / nickel oxide doped graphene material (Ni / NiO-LIG). Silver paste was coated onto the surface of nickel / nickel oxide-doped graphene material and then cured by heating to obtain a nickel / nickel oxide-doped graphene electrode (Ni / NiO-LIGE). Aminated multi-walled carbon nanotubes (NH2-MWCNTs) dispersion was drop-coated onto the surface of a nickel / nickel oxide-doped graphene electrode, and after curing, an aminated multi-walled carbon nanotube / nickel / nickel oxide-graphene electrode (NH2-MWCNTs / Ni-LIGE composite electrode) was obtained.

[0031] In a preferred embodiment of the present invention, the nickel-containing compound solution is a nickel chloride solution, more specifically an ethanol solution of NiCl2·4H2O.

[0032] In a preferred embodiment of the present invention, the ratio of nickel-containing compound solution to polyamic acid solution is 50 μL: 1 g, the concentration of nickel-containing compound solution is 60 mg / mL, and the mass concentration of polyamic acid solution is 20%.

[0033] In a preferred embodiment of the present invention, the substrate includes a glass plate; the thickness of the polyamic acid solution coating is 25~35μm.

[0034] In a preferred embodiment of the present invention, the drying process includes a first drying and a second drying; the temperature of the first drying is 90~110℃ and the time is 25~45 min; the temperature of the second drying is 150~170℃ and the time is 8~15 min.

[0035] In a preferred embodiment of the present invention, the laser power of the laser etching is 2.20~2.75 W, and the etching depth is 30%.

[0036] In a preferred embodiment of the present invention, the modification volume of the aminated multi-walled carbon nanotube dispersion is 2-6 μL, and the area of ​​the nickel / nickel oxide-doped graphene electrode is 12.57 mm². 2 .

[0037] Exemplary, the preparation method of the aminated multi-walled carbon nanotube / nickel / nickel oxide-graphene electrode (NH2-MWCNTs / Ni-LIGE composite electrode) of the present invention includes the following steps: 200 µL of ethanol solution of NiCl2·4H2O with a concentration of 60 mg / mL was added to 4.0 g of PAA solution (mass concentration of 20%), and ultrasonic treatment was performed for 10 min to achieve full and uniform dispersion, thus obtaining a doped polyamic acid solution. The doped polyamic acid solution was coated onto a glass plate (coating thickness of 25~35 μm), first placed in a vacuum drying oven at 90~110℃ for 25~45 min, and then placed in an oven at 150~170℃ for 8~15 min to obtain a doped polyamic acid film. Laser etching was performed on the doped polyamic acid film. The output power of the laser direct writing instrument was set to 2.20~2.75W and the etching depth was 30%. A graphene electrode pattern was formed on the glass plate. The pattern was then removed from the glass plate to obtain Ni / NiO doped graphene material (Ni / NiO-LIG). Silver paste was applied onto Ni / NiO-LIG and cured at 60 °C for 30 min to prepare a Ni / NiO-doped graphene electrode (Ni / NiO-LIGE). It should be noted that there are no special limitations on the coating thickness of the silver paste in this invention, and the coating can be done once with a brush during the preparation process. 2.0 mg of aminated multi-walled carbon nanotubes (NH2-MWCNTs) were dispersed in 1 mL of ethanol and mixed thoroughly to obtain an NH2-MWCNTs dispersion. This NH2-MWCNTs dispersion was then drop-coated onto a Ni / NiO-doped graphene electrode (Ni / NiO-LIGE, with an area of ​​12.57 mm²). 2 The surface of the working electrode region of the electrode was modified with a volume of 2~6 μL to obtain an aminated multi-walled carbon nanotube / nickel / nickel oxide-graphene electrode (NH2-MWCNTs / Ni-LIGE composite electrode).

[0038] The present invention also provides an aminated multi-walled carbon nanotube / nickel / nickel oxide-graphene electrode prepared according to the above preparation method.

[0039] This invention also provides an electrochemical sensor comprising the above-mentioned aminated multi-walled carbon nanotube / nickel / nickel oxide-graphene electrode as a working electrode, and the electrochemical sensor further comprising a reference electrode; the reference electrode is a silver electrode, and the prepared electrochemical sensor is used for the detection of bisphenol A (BPA).

[0040] 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.

[0041] The technical solution of the present invention will be further illustrated by the following embodiments.

[0042] Example 1 A composite electrode of NH2-MWCNTs / Ni-LIGE is prepared by the following steps: 4.0 g of PAA solution (20% by mass) was added to 200 µL of ethanol solution of NiCl2·4H2O with a concentration of 60 mg / mL, and ultrasonic treatment was performed for 10 min to achieve full and uniform dispersion, thus obtaining a polyamic acid doped solution. The doped polyamic acid solution was coated onto a glass plate (coating thickness of 30 μm), first placed in a vacuum drying oven at 100℃ for 30 min, and then placed in an oven at 166℃ for 10 min to obtain a doped polyamic acid film. Laser etching was performed on the doped polyamic acid film. The output power of the laser direct writing instrument was set to 2.75 W and the etching depth to 30%. A graphene electrode pattern was formed on the glass plate. The pattern was then removed from the glass plate to obtain Ni / NiO-LIG. Ni / NiO-LIG was prepared by coating silver paste onto Ni / NiO-LIG and curing it at 60 °C for 30 min. 2 mg of NH2-MWCNTs were dispersed in 1 mL of ethanol and mixed thoroughly to obtain an NH2-MWCNTs dispersion. The NH2-MWCNTs dispersion was then drop-coated onto Ni / NiO-LIG (working area 12.57 mm²). 2 The surface was modified with a volume of 6 μL and dried at room temperature to obtain the NH2-MWCNTs / Ni-LIGE composite electrode.

[0043] Example 2 Same as Example 1, except that the output power of the laser direct writing instrument is adjusted to 2.20W.

[0044] Example 3 Same as Example 1, except that the output power of the laser direct writing instrument is adjusted to 2.48W.

[0045] Example 4 Same as Example 1, except that the NH2-MWCNTs dispersion was drop-coated onto the Ni / NiO-LIG surface, with a modification volume of 2 μL.

[0046] Example 5 Same as Example 1, except that the NH2-MWCNTs dispersion was drop-coated onto the Ni / NiO-LIG surface, with a modification volume of 4 μL.

[0047] Comparative Example 1 Same as Example 1, except that the NH2-MWCNTs dispersion was drop-coated onto the Ni / NiO-LIG surface, with a modification volume of 8 μL.

[0048] Comparative Example 2 Undoped graphene electrodes (LIGs) were obtained by laser etching of pure polyamic acid (PAA) films without adding nickel chloride during the preparation of the precursor solution. Specifically: Add 4.0 g of PAA solution (20% by mass) to 200 µL of ethanol solution and sonicate for 10 min to achieve full and uniform dispersion to obtain a polyamic acid doped solution. The doped polyamic acid solution was coated onto a glass plate (coating thickness of 30 μm), first placed in a vacuum drying oven at 100℃ for 30 min, and then placed in an oven at 166℃ for 10 min to obtain a doped polyamic acid film. Laser etching was performed on the doped polyamic acid film. The output power of the laser direct writing instrument was set to 2.75 W and the etching depth to 30%. A graphene electrode pattern was formed on the glass plate. The pattern was then removed from the glass plate to obtain an undoped graphene electrode (LIG).

[0049] I. Material Characterization Figure 1 TEM images of the Ni / NiO-LIG (AC) and NH2-MWCNTs / Ni-LIGE composite electrodes (DF) prepared in Example 1 at different magnifications; the TEM images of Ni / NiO-LIG (A, B) show that Ni / NiO nanoparticles are uniformly distributed on the graphene surface. Figure 1 In the sample, the lattice fringe spacings are observed to be 0.204 nm and 0.186 nm, corresponding to the (111) and (200) crystal planes of Ni; the lattice fringe spacing is 0.209 nm, corresponding to the (020) crystal plane of NiO, indicating that Ni and NiO crystal phases coexist in the sample. Figure 1 The DE image presents TEM images of NH2-MWCNTs / Ni-LIGE, clearly showing the carbon nanotube structure. Figure 1 In the middle F, 0.331 nm lattice stripes can be observed, corresponding to the (002) crystal plane of graphite carbon, indicating that the composite material has a complete graphite carbon crystal phase structure.

[0050] Figure 2 The images show SEM images of the Ni / NiO-LIG (A and B) and NH2-MWCNTs / Ni-LIGE composite electrode (C) prepared in Example 1 at different magnifications. It can be seen that Ni / NiO-LIG exhibits a typical three-dimensional honeycomb porous structure. NH2-MWCNTs exhibit a tangled tubular network structure with uniform diameter and good dispersibility.

[0051] Figure 3The XRD patterns (A), XPS total spectra (B), and high-resolution XPS spectra (C) of Ni / NiO-LIG prepared in Example 1 and LIG prepared in Comparative Example 2 are shown. It can be seen that both LIG and Ni / NiO-LIG XRD patterns show a diffraction peak at 25.90°, corresponding to the (002) crystal plane of graphitic carbon (PDF#41-1487), indicating that the laser-induced process promoted the graphitization of the carbon material. Meanwhile, the diffraction peaks at 44.3° and 51.6° in the Ni-LIG XRD pattern belong to the (111) and (200) crystal planes of metallic Ni (PDF#04-0850), respectively, indicating the formation of metallic Ni. Furthermore, the weak diffraction peak at approximately 43.2° can be attributed to the (020) crystal plane of NiO (PDF#96-101-0096), indicating the formation of NiO. The XPS spectra clearly show characteristic peaks for C 1s, O 1s, N 1s, and Ni 2p, indicating the presence of C, O, N, and Ni elements in the material. The Ni 2p spectrum of Ni / NiO-LIG exhibits distinct characteristic peaks at 855.6 eV, 860.1 eV, 873.6 eV, and 879.2 eV. Among these, 855.6 eV and 873.6 eV represent Ni 2p peaks. 2+ Ni 2p 3 / 2 and Ni 2p 1 / 2 The spin-orbit double peaks correspond to its typical satellite peaks at 860.1 eV and 879.2 eV. Furthermore, the characteristic peaks observed at 852.9 eV and 862.1 eV can be attributed to metallic Ni. 0 .

[0052] II. Electrochemical Performance Testing Electrochemical sensors were assembled from the electrodes prepared in Examples 1-5 and Comparative Example 1, respectively. The specific assembly process was as follows: using the prepared electrodes as working electrodes, a reference electrode was formed by coating a substrate with silver paste (coating thickness of 30 μm). The electrodes were then cured at 140 °C for 20 min. BPA detection was then performed on the resulting electrochemical sensors. The peak current changes during BPA detection were compared between the electrochemical sensors assembled from electrodes prepared under different laser powers and different NH2-MWCNTs dispersion modification volumes to determine the optimal laser output power.

[0053] Figure 4 The results show the peak current changes (A) under different laser etching powers in Examples 1-3 and (B) under different NH2-MWCNTs dispersion modification volumes in Examples 1, 4-5, and Comparative Example 1; (from...) Figure 4As shown in section A, when the laser power increases from 2.2W to 2.75W, the peak current of BPA gradually increases, reaching its maximum at 2.75W. However, when the laser power reaches 2.75W, the excessively high power damages the LIG carbon layer structure, making it impossible to fabricate a complete LIGE. Therefore, 2.75W is chosen as the optimal laser output power. Figure 4 As shown in Figure B, when the NH2-MWCNTs dispersion modification volume is in the range of 2-6 µL, the oxidation peak current of BPA increases with the increase of the dispersion modification volume; however, when the NH2-MWCNTs dispersion modification volume reaches 8 µL, the oxidation peak current of BPA begins to decrease. This may be because excessive NH2-MWCNTs dispersion leads to the formation of a thicker modification layer on the electrode surface, prolonging the electron transport path and resulting in a decrease in current response.

[0054] In a 0.25 mmol / L BPA solution, the effects of different buffer solutions (BR solution, PBS solution, HAc-NaAc solution, and Tris-HCl solution) and pH values ​​(PBS buffer solutions with pH values ​​of 3.5, 4.5, 5.5, 6.5, and 7.5) on the electrochemical reaction of BPA were analyzed. 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 5 As shown.

[0055] Figure 5 The CV curves (A) and corresponding peak currents (B) of the NH2-MWCNTs / Ni-LIGE composite electrode prepared in Example 1 in different buffer solutions are shown below; the CV curves (C) and peak currents and peak potentials (D) of the NH2-MWCNTs / Ni-LIGE composite electrode prepared in Example 1 in PBS at different pH values ​​are shown below; Figure 5 As shown in section A, among BR buffer solution, PBS solution, HAc-NaAc solution, and Tris-HCl solution, PBS buffer solution exhibits the highest current value, thus serving as the supporting electrolyte in the experiment. Simultaneously, the CV curves for PBS buffer solution at different pH values ​​were recorded, as follows: Figure 5 As shown in Figure C, the results indicate that the peak current increases with increasing pH, but decreases when the solution pH reaches 7.5. Furthermore, the BPA peak potential shifts negatively with increasing solution pH, confirming the involvement of protons. Therefore, pH = 6.5 was chosen as the optimal pH for further investigation. Epc exhibits a good linear relationship with pH: Ep(V) = -0.049 pH + 0.862 (R² = 0.988). Figure 5(As shown in D). The slope of 0.049 V / pH is close to the theoretical 0.059 V / pH, indicating that the reaction can be classified as a proton-coupled electron transfer process.

[0056] Under optimized experimental conditions, the electrochemical detection performance of the NH2-MWCNTs / Ni-LIGE composite electrode prepared in Example 1 in BPA solutions of different concentrations was tested using cyclic voltammetry (CV). The specific methods are as follows: Electrolyte solution: 0.1 mol / L PBS buffer solution was used as the supporting electrolyte; Detection method: The prepared NH2-MWCNTs / Ni-LIGE 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 scan voltage range was set to 0 V~1.0 V, and the scan rate was 0.1 V / s; Test steps: 5.0 × 10⁻⁶... -5 25 μL of bisphenol A solution within the concentration range of -0.35 mmol / L was added to the three-electrode system, and the oxidation peak current value under the corresponding CV curve was recorded using CV testing.

[0057] Figure 6 Figure A shows the CV curves of the electrochemical sensor based on the NH2-MWCNTs / Ni-LIGE composite electrode in Example 1 in BPA solutions of different concentrations. Figure B shows the linear relationship between oxidation current and concentration. It can be seen that the oxidation peak current increases with increasing BPA concentration, reaching a peak at 5.0 × 10⁻⁶. -5 Within the concentration range of -0.35 mmol / L, the corresponding regression equation is: I (μA) = 283.836 C (mmol / L) + 20.168 (n = 3, R0). 2 = 0.988), and the detection limit is 12.74 nmol / L (3S / N).

[0058] The selectivity and stability of the electrochemical sensor assembled from the electrodes prepared in Example 1 were tested using the following method: Interference resistance test: The performance of NH2-MWCNTs / Ni-LIGE was recorded in the presence of the same concentration of interfering substances (catechol, hydroquinone) and twice the concentration of interfering substances (Mg). 2+ Na + Cl - CV curves were obtained in 0.25 mmol / L BPA solution. Stability testing: Five NH2-MWCNTs / Ni-LIGE composite electrodes were prepared under the same conditions as in Example 1 and stored in air at room temperature. Subsequently, one electrode was taken out daily and CV tests were recorded in 0.25 mmol / L BPA solution.

[0059] Figure 6In Figure C, the anti-interference test results of the electrochemical sensor based on the NH2-MWCNTs / Ni-LIGE composite electrode in Example 1 are shown, and in Figure D, the stability test results are shown. It can be seen that after the addition of the interfering agent, the CV curve did not change significantly, and the relative standard deviations were all less than 5.00%, indicating that the electrode has good anti-interference ability. The stability of NH2-MWCNTs / Ni-LIGE was further investigated, and the results are as follows... Figure 6 As shown in Figure D, all electrodes exhibit similar current responses, with relative standard deviations all less than 2.00%, indicating that the sensor has good stability.

[0060] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing an aminated multi-walled carbon nanotube / nickel / nickel oxide-graphene electrode, characterized in that, Includes the following steps: A nickel-containing compound solution is mixed with a polyamic acid solution to obtain a doped polyamic acid solution; The doped polyamic acid solution is coated onto a substrate and then dried to obtain a doped polyamic acid film. The doped polyamic acid film was laser-etched to obtain nickel / nickel oxide-doped graphene material; Silver paste was coated onto the surface of the nickel / nickel oxide-doped graphene material and then cured by heating to obtain a nickel / nickel oxide-doped graphene electrode. Aminated multi-walled carbon nanotube dispersions were drop-coated onto the surface of the nickel / nickel oxide-doped graphene electrode, and the aminated multi-walled carbon nanotube / nickel / nickel oxide-graphene electrode was obtained after curing.

2. The method for preparing the aminated multi-walled carbon nanotube / nickel / nickel oxide-graphene electrode according to claim 1, characterized in that, The nickel-containing compound solution is a nickel chloride solution.

3. The method for preparing the aminated multi-walled carbon nanotube / nickel / nickel oxide-graphene electrode according to claim 1, characterized in that, The ratio of the nickel-containing compound solution to the polyamic acid solution is 50 μL: 1 g, the concentration of the nickel-containing compound solution is 60 mg / mL, and the mass concentration of the polyamic acid solution is 20%.

4. The method for preparing the aminated multi-walled carbon nanotube / nickel / nickel oxide-graphene electrode according to claim 1, characterized in that, The substrate includes a glass plate; the thickness of the coating of the doped polyamic acid solution is 25~35 μm.

5. The method for preparing the aminated multi-walled carbon nanotube / nickel / nickel oxide-graphene electrode according to claim 1, characterized in that, The drying process includes a first drying and a second drying; the temperature of the first drying is 90~110℃ and the time is 25~45 min; the temperature of the second drying is 150~170℃ and the time is 8~15 min.

6. The method for preparing the aminated multi-walled carbon nanotube / nickel / nickel oxide-graphene electrode according to claim 1, characterized in that, The laser etching uses a laser power of 2.20~2.75 W and an etching depth of 30%.

7. The method for preparing the aminated multi-walled carbon nanotube / nickel / nickel oxide-graphene electrode according to claim 1, characterized in that, The modification volume of the aminated multi-walled carbon nanotube dispersion is 2-6 μL, and the area of ​​the nickel / nickel oxide-doped graphene electrode is 12.57 mm². 2 .

8. An aminated multi-walled carbon nanotube / nickel / nickel oxide-graphene electrode prepared by the preparation method according to any one of claims 1 to 7.

9. An electrochemical sensor, characterized in that, The electrochemical sensor includes the aminated multi-walled carbon nanotube / nickel / nickel oxide-graphene electrode of claim 8 as the working electrode, and further includes a reference electrode; the reference electrode is a silver electrode.

10. The application of the electrochemical sensor as described in claim 9 in the detection of bisphenol A.

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