Integrated monolithic electrode adhered by functional membrane, preparation method and application of integrated monolithic electrode in metal ion detection

Abstract

The invention belongs to the field of electrochemical detection, and particularly relates to an integrated monolithic electrode adhered by a functional membrane, a preparation method and application of the integrated monolithic electrode in metal ion detection. The integrated monolithic electrode is characterized in that a working electrode, an auxiliary electrode and a reference electrode are integrated on a chip, the working electrode is the integrated monolithic electrode bonded by the functional membrane, the surface of a matrix electrode is modified, and the surface of the matrix electrode is coated with a coating; the modification material is one or more of carbon nanoflowers with a porous cage-shaped structure, metal nanoparticles and an enhanced electron conduction film. According to the invention, a working electrode in an integrated monolithic electrode is used as a substrate electrode, and the surface of the working electrode is cooperated with carbon nanoparticles and gold nanoparticles with porous cage structures through a functional film, so that a sensing system with excellent interface characteristics is constructed, and the sensor has the advantages of high sensitivity and high stability.

Description

Technical Field

[0001] The present invention belongs to the field of electrochemical detection, and in particular relates to a functional membrane-adhesive integrated monolithic electrode, a preparation method thereof, and an application thereof in metal ion detection. Background Art

[0002] Trace metals play a vital role in regulating biogeochemical processes, promoting phytoplankton growth, and ultimately, the entire marine ecosystem. However, copper concentration has a significant dual effect on algae: low concentrations can promote algal growth, while excessive concentrations can be toxic. Therefore, rapid and accurate detection of copper in water is crucial for accurately assessing its bioavailability and ecological risks, enabling the implementation of effective control measures. This has become a key area of ​​analytical chemistry research in recent years.

[0003] Currently, the main methods for detecting metal elements, including copper, include atomic absorption spectrometry, inductively coupled plasma atomic emission spectrometry, inductively coupled plasma mass spectrometry, and electrochemical analysis. Atomic absorption spectrometry requires pre-enrichment, solvent extraction, desalination, and other treatments before analysis. The process is cumbersome, time-consuming, and costly. Inductively coupled plasma atomic emission spectrometry and inductively coupled plasma mass spectrometry require expensive instruments and are complex to operate. In contrast, electrochemical methods have significant advantages in trace metal detection. They have the characteristics of high sensitivity, low cost, strong portability, and simple operation, making them very suitable for on-site detection and large-scale environmental monitoring applications.

[0004] However, as a traditional electrode for electrochemical detection, mercury electrode has a wide potential window and high hydrogen overpotential, but due to its inherent toxicity and special storage conditions, it has significant limitations in practical applications. The development of environmentally friendly chemically modified electrodes can effectively improve the sensitivity of detection and avoid the use of mercury, which has become an important research direction. Conventional electrodes such as glassy carbon electrodes and gold electrodes have low surface chemical inertness, resulting in low efficiency of nano-modified material immobilization and weak interfacial bonding, which makes the modified material easy to fall off, affecting the stability of the electrode and poor reproducibility of detection results. For this reason, further research is needed in the construction of chemically modified electrodes. At the same time, on the basis of improving detection sensitivity, focusing on improving its stability has become a key research direction to provide technical solutions for the detection sensitivity and stability problems of metal elements. Summary of the Invention

[0005] The purpose of the present invention is to provide a functional membrane-adhesive integrated monolithic electrode and a preparation method thereof and application in metal ion detection.

[0006] To achieve the above object, the technical solution adopted by the present invention is: A functional membrane-adhered integrated monolithic electrode, wherein the working electrode, auxiliary electrode and reference electrode are integrated on a single chip. The working electrode is a functional membrane-adhered integrated monolithic electrode, which is a substrate electrode surface modified with one or more of porous cage-structured carbon nanoflowers, metal nanoparticles and enhanced electron conduction films.

[0007] The porous cage-structured carbon nanoflowers are prepared by an organic polymerization method, wherein acrylonitrile monomer and azobisisobutyronitrile initiator are added to an acetone solvent, and a free radical polymerization reaction is initiated at 30-120°C for 0.5-8 hours. The azobisisobutyronitrile is thermally decomposed to generate free radicals to initiate polymerization. After the reaction is completed, polyacrylonitrile (PACN) is obtained through precipitation, separation, and drying. The obtained polyacrylonitrile (PACN) is placed in a vacuum drying oven at 30-120°C for 0.5-8 hours for continuous drying and stabilization. Subsequently, the powder sample is spun in air at 0.1°C·min -1 The temperature is raised to 150~300℃ at a heating rate and stabilized for 0.5~8h. After stabilization, the product is carbonized in nitrogen at 700~1100℃ for 0.5~8h to obtain the carbonized product. The carbonized product is washed, separated and dried to obtain carbon nanoflower particles with a porous cage structure.

[0008] The acetone, acrylonitrile monomer and azobisisobutyronitrile initiator are mixed in a mass ratio of 791:810:1.

[0009] A method for preparing an integrated monolithic electrode adhered with a functional membrane, wherein the integrated monolithic electrode is a working electrode, an auxiliary electrode, and a reference electrode integrated on a single chip; wherein the working electrode is modified on the surface of a substrate electrode, and the modification material is one or more of carbon nanoflowers with a porous cage structure, metal nanoparticles, and an enhanced electron conduction film.

[0010] The working electrode is a pretreated substrate electrode surface that is sequentially modified with porous cage-like carbon nanoflowers, metal nanoparticles and an enhanced electron conduction film to obtain an integrated monolithic electrode with functional membrane adhesion.

[0011] The working electrode is a pretreated substrate electrode surface modified with an enhanced electron conduction film, a porous cage-like carbon nanoflower and metal nanoparticles in sequence, thereby obtaining an integrated monolithic electrode with functional membrane adhesion.

[0012] The metal nanoparticles are one or more of gold nanoparticles, platinum nanoparticles, and palladium nanoparticles.

[0013] The substrate electrode is a single micro-gold sheet or glassy carbon sheet with a diameter of 2 mm.

[0014] The enhanced electron conduction membrane is a cation exchange membrane (such as Nafion), a conductive polymer membrane (such as polyaniline, PEDOT-PSS), or a carrier membrane (such as polydopamine). The coating method used is a drop coating method. Specifically, the components of the enhanced electron conduction membrane are prepared into a solution with a concentration of 1-5% by weight. 1-5 mL is dripped onto the surface of an integrated monolithic electrode modified with caged carbon nanoflowers or caged carbon nanoflowers loaded with metal particles, and cured at room temperature. The conductive polymer membrane can also be coated by electrodeposition, and the carrier membrane, such as polydopamine, can also be coated by self-assembly.

[0015] The monolithic working electrode material is integrated with a printed carbon electrode (auxiliary electrode) and a silver / silver chloride electrode (reference electrode) on a single chip.

[0016] An application of the functional membrane-adhered integrated monolithic electrode, and an application of the functional membrane-adhered integrated monolithic electrode in detecting metal ions in the environment.

[0017] The functional membrane-adhered, gold-loaded caged carbon nanoflower-modified integrated monolithic electrode exhibits both high sensitivity and high stability for copper ion detection, and can be applied to the precise and stable detection of low concentrations of various metal ions in complex matrices such as river water and seawater. Preferably, the functional membrane-adhered, gold-loaded caged carbon nanoflower-modified integrated monolithic electrode is used for highly sensitive and stable detection of copper ions.

[0018] The advantages of the present invention are: This invention utilizes an integrated monolithic electrode as the base electrode, with a functionalized membrane layered on the surface in conjunction with carbon nanoparticles and gold nanoparticles with porous cage structures. This creates a sensing system with excellent interfacial properties, combining high sensitivity and stability. This preparation method is characterized by simplicity, environmental friendliness, and significant cost-effectiveness. The resulting modified electrode exhibits excellent electrocatalytic activity and detection sensitivity, and more significantly, improves its stability, enabling the highly sensitive and stable detection of trace copper and other metal ions in complex matrix samples such as river water and seawater.

[0019] Specifically, the present invention uses a single, 2mm-diameter micro-gold or glassy carbon sheet as the working electrode material and integrates it with a printed carbon electrode (auxiliary electrode) and a silver / silver chloride electrode (reference electrode) on a single chip to form an integrated monolithic electrode. By modifying its surface with carbon nanoparticles having a unique porous cage-like structure, further loading metal nanoparticles, and coating it with a functional membrane, a functionalized sensing interface is constructed. The porous cage-like carbon nanoflowers provide more binding sites for metal nanoparticles, which promote electron conduction and have a very good catalytic effect on the electrochemical detection of metal ions, greatly improving the sensitivity of metal ion detection. The functional membrane has an adhesive effect, entwining and bonding the cage-like carbon nanoflowers and metal nanoparticles together, providing protection and preventing them from falling off, thereby improving the stability of the modified electrode. As a result, the modified electrode forms a sensing structure with both high sensitivity and high stability. It can be applied to the precise and stable detection of low-concentration metal ions, especially copper ions, in complex matrices such as river water and seawater. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Schematic diagram of the preparation process of the working electrode of the integrated monolithic electrode modified with gold-loaded caged carbon nanoflowers adhered to the Nafion membrane provided in an embodiment of the present invention.

[0021] Figure 2 These are scanning electron microscope characterization images of the cage-like carbon nanoflowers prepared in an embodiment of the present invention and the gold-loaded cage-like carbon nanoflowers adhered to the Nafion membrane, wherein (a) is a morphological characterization image of the cage-like carbon nanoflowers at a 5 μm scale, (b) is a morphological characterization image of the gold-loaded cage-like carbon nanoflowers adhered to the Nafion membrane at a 5 μm scale, (c) is a morphological characterization image of the cage-like carbon nanoflowers at a 1 μm scale, and (d) is a morphological characterization image of the gold-loaded cage-like carbon nanoflowers adhered to the Nafion membrane at a 1 μm scale.

[0022] Figure 3 The cyclic voltammetric characterization diagrams of the working electrodes of the different integrated monolithic electrodes prepared according to the embodiments of the present invention in acetic acid buffer solution at pH 4.5, wherein a is an integrated monolithic electrode (P-tlE), b is an integrated monolithic electrode modified with caged carbon nanoflowers (CNFs / P-tIE), c is an integrated monolithic electrode modified with gold-loaded caged carbon nanoflowers (AuNPs / CNFs / P-tIE), and d is an integrated monolithic electrode modified with gold-loaded caged carbon nanoflowers (Nafion / AuNPs / CNFs / P-tIE) adhered to a functional membrane with Nafion as the functional membrane.

[0023] Figure 4The cyclic voltammetry characterization diagrams of different integrated monolithic electrodes prepared in an embodiment of the present invention in a 0.1M KCl solution containing 5mM K3[Fe(CN)6] are provided, wherein a is an integrated monolithic electrode (P-tlE), b is an integrated monolithic electrode modified with caged carbon nanoflowers (CNFs / P-tIE), c is an integrated monolithic electrode modified with gold-loaded caged carbon nanoflowers (AuNPs / CNFs / P-tIE), and d is an integrated monolithic electrode modified with gold-loaded caged carbon nanoflowers (Nafion / AuNPs / CNFs / P-tIE) adhered to a functional membrane with Nafion as the functional membrane.

[0024] Figure 5 The stripping voltammogram and corresponding working curve of the working electrode of the functional membrane-adhered gold-loaded cage-shaped carbon nanoflower modified integrated monolithic electrode provided by the embodiment of the present invention to different concentrations of heavy metal copper ions. DETAILED DESCRIPTION

[0025] The specific embodiments of the present invention are further described below with reference to examples. It should be noted that the specific embodiments described here are only for illustrating and explaining the present invention, and are not intended to limit the present invention.

[0026] The present invention obtains an integrated monolithic electrode in which the working electrode uses a carbon nanoflower with a porous cage structure as a carrier material, and the surface is loaded with metal nanoparticles. The porous cage-like carbon nanoflower has the advantages of good conductivity and large specific surface area, which can load more metal nanoparticles. The metal nanoparticles have the ability to promote electron conduction and catalytic performance in electrochemical detection of copper ions. Therefore, before and after the metal nanoparticles are loaded, a functional film is coated. The functional film is combined with hydroxyl groups, carboxyl groups, and other groups on the surface of the carbon nanoflower through hydrogen bonds and van der Waals forces, thereby having an adhesion effect, which can entangle and adhere the cage-like carbon nanoflower and the metal nanoparticles together, play a protective role, prevent them from falling off, and improve the stability of the modified electrode. At the same time, the functional film can further improve the conductivity, cation enrichment efficiency, and electrochemical detection performance, so that the modified electrode forms a sensing structure with both high sensitivity and high stability.

[0027] Finally, the functional membrane-bound gold-loaded caged carbon nanoflowers of the present invention were modified on the working electrode of an integrated monolithic electrode. This modified electrode exhibits high sensitivity, excellent selectivity, and stability for copper ion detection, enabling accurate and stable detection of low-concentration copper ions in complex matrices. In addition to copper ions, highly sensitive and stable detection of other metal ions can be achieved by varying the enrichment potential.

[0028] Further: The integrated monolithic electrode with functional membrane adhesion of the present invention has the following characteristics: (a) The integrated monolithic electrode uses carbon nanoflowers with a porous cage structure as the carrier material, and metal nanoparticles are loaded on the surface. The porous cage-like carbon nanoflowers have the advantages of good conductivity and large specific surface area, which can load more metal nanoparticles. Metal nanoparticles have the ability to promote electron conduction and catalytic performance in the electrochemical detection of copper ions.

[0029] (b) During the fabrication process, the integrated monolithic electrode is coated with a functional membrane before and after metal nanoparticle loading. The functional membrane binds to hydroxyl and carboxyl groups on the carbon nanoflower surface through hydrogen bonds and van der Waals forces, creating an adhesive bond. This membrane entangles and binds the caged carbon nanoflowers and metal nanoparticles together, protecting them from detachment and improving the stability of the modified electrode. Furthermore, the functional membrane further enhances conductivity, cation enrichment efficiency, and electrochemical detection performance, resulting in a highly sensitive and stable sensing structure.

[0030] (c) Functional membrane-adhesive gold-loaded caged carbon nanoflowers modified on an integrated monolithic electrode demonstrate high sensitivity, excellent selectivity, and stability for copper ion detection. This modified electrode can be used for the precise and stable detection of low-concentration copper ions in complex matrices. In addition to copper ions, it can also be used for the highly sensitive and stable detection of other metal ions. Example 1

[0031] Preparation of working electrode in integrated monolithic electrode modified by gold cage-like carbon nanoflowers bonded to Nafion membrane, such as Figure 1 As shown, the steps are as follows: (1) Electrode pretreatment: A single glassy carbon sheet with a diameter of 2 mm was selected as the integrated single-piece electrode substrate for the working electrode material. Sulfuric acid was added to the surface of the electrode for activation to remove impurities on the electrode surface. The electrode was then washed with ethanol and ultrapure water, dried with nitrogen, and set aside.

[0032] (2) Working electrode in integrated monolithic electrode modified with porous cage-like carbon nanoflowers: ① Preparation of porous cage-like carbon nanoflowers: Add acrylonitrile monomer (10 mL) and azobisisobutyronitrile initiator (10 mg) to acetone solvent (10 mL), and initiate free radical polymerization at 70°C for 2 h under nitrogen. After the reaction, separate the reaction by precipitation, filtration, and drying to obtain polyacrylonitrile (PACN). The obtained polyacrylonitrile (PACN) was placed in a vacuum drying oven at 60°C for 2 h to be continuously dried for stabilization. Subsequently, the powder sample was air-dried at 0.1°C·min -1The temperature was raised to 230°C at a heating rate and stabilized for 2 hours. Finally, the stabilized material was carbonized in nitrogen at 1000°C for 2 hours to obtain the carbonized product. After washing (three times with ethanol and three times with ultrapure water), separation, and drying, the porous cage-like carbon nanoflower particles were finally obtained.

[0033] ② Working electrode in the integrated monolithic electrode modified with porous cage-like carbon nanoflowers: The porous cage-like carbon nanoflower particles obtained above are uniformly dispersed in a DMF solution (the particle concentration in the dispersion is 1 mg / mL), 3 μL of the solution (corresponding to a carbon nanoflower loading of 3 μg) is drop-coated on the surface of the working electrode pretreated in step (1) above, and dried at room temperature to obtain the working electrode in the integrated monolithic electrode modified with the modified porous cage-like carbon nanoflowers. The scanning electron microscope characterization of the porous cage-like carbon nanoflowers is shown in FIG. Figure 2 (a), (c) in the figure.

[0034] (3) Working electrode in integrated monolithic electrode modified with gold-loaded caged carbon nanoflowers: The electroplating solution containing the gold nanoparticle precursor used in this embodiment is a 2 mmol / L HAuCl4 solution prepared by mixing gold nanoparticles with 0.5 mol / L H2SO4; wherein, the gold nanoparticles are electroplated onto the surface of the carbon nanoflower by HAuCl4 using a constant potential method according to a conventional method, and the average particle size of the obtained Au NPs is 80-200 nm; and then the prepared electroplating solution containing the gold nanoparticle precursor is electroplated on the surface of the integrated monolithic electrode modified with the porous cage-like carbon nanoflower obtained in step (2), that is, the metal nanoparticles are uniformly modified on the surface of the porous cage-like carbon nanoflower, and the modified electrode is rinsed with ultrapure water (18.2 MΩ·cm) and dried with a nitrogen flow to obtain the working electrode in the integrated monolithic electrode modified with the gold-loaded cage-like carbon nanoflower.

[0035] The electrodeposition conditions are as follows: the electroplating solution is dripped onto the electrode surface and a constant potential of -0.3 V is applied for 180 seconds. The AuNPs uniformly deposited on the surface of the carbon nanoflowers not only significantly improves the conductivity of the electrode, but also enhances the electrode performance due to its excellent electrocatalytic activity.

[0036] (4) Preparation of the working electrode in the integrated monolithic electrode modified with gold-loaded cage-like carbon nanoflowers adhered to the functional membrane: 2.5% wt Nafion solution (diluted by ethanol) was drop-coated on the surface of the integrated monolithic electrode modified with gold-loaded cage-like carbon nanoflowers obtained in the above step (3), and waited for solidification at room temperature, so that the Nafion membrane and the hydroxyl, carboxyl and other groups on the surface of the carbon nanoflowers were combined through hydrogen bonds and van der Waals forces, and at the same time, the adjacent gold-loaded carbon nanoflowers were interconnected and adhered by the polymer chains of the Nafion membrane to form a stable three-dimensional network structure, thus obtaining the working electrode of the gold-loaded cage-like carbon nanoflowers adhered to the Nafion membrane and modified on the integrated monolithic electrode (see Figure 2 (b), (d) in the figure.

[0037] Depend on Figure 2 Electron microscopy showed that Figure 2 (a) and (c) show the SEM images of CNFs / P-tIE. The flower-like appearance with three-dimensional structure can be clearly observed. Figure 2 The 1 μm-scale SEM image in (c) reveals the fine flower-like structural details of CNFs, and the diameter of CNFs is approximately 600 nm. Figure 2 (b) and (d) show the scanning electron microscopy characterization of Nafion-adhered gold-loaded caged carbon nanoflowers (Nafion / AuNPs / CNFs / P-tIE). It can be seen that gold nanoparticles with diameters of about 80 to 200 nm are uniformly loaded on CNFs.

[0038] Cyclic voltammetry tests were performed on different electrodes in pH 4.5 acetate buffer solution. The experimental parameters were as follows: starting potential: 0V; maximum potential: 1.2V; minimum potential: 0V; end potential: 1.2V; initial scanning polarity: scanning from positive potential to negative potential; scanning rate: 0.05V / s; waiting time: 2s. Figure 3 It can be seen that there is no obvious redox peak in the cyclic voltammetry curve of the integrated monolithic electrode. When the surface of the integrated monolithic electrode is modified with caged carbon nanoflowers, the cyclic voltammetric response of the electrode is enhanced to a certain extent, but the effect is relatively small. After modification with gold nanoparticles, the response current is greatly increased, and a large characteristic reduction peak of gold nanoparticles appears at 0.42V, which shows that the catalytic effect of gold nanoparticles is very obvious. And the experimental results show that the unmodified integrated monolithic electrode has a strong effect on Cu 2+ There is almost no current response, while AuNPs / P-tIE shows an obvious oxidation current signal at about -0.1 V. This phenomenon indicates that the presence of AuNPs significantly enhances the electrode's resistance to Cu 2+The electrocatalytic activity of the gold nanoparticles was enhanced, resulting in a significant increase in the current response during voltammetry. Further modification of the electrode surface with Nafion resulted in a slight decrease in the characteristic reduction peak of the gold nanoparticles, and a shift in the peak potential to 0.48 V. This indicates that the Nafion modification has a certain inhibitory effect on the electrode's response current. Example 2

[0039] The preparation of the working electrode in the integrated monolithic electrode modified with gold-loaded caged carbon nanoflowers adhered to Nafion membrane is different from that in Example 1 in that the modification order, i.e., the covering order of Nafion, is changed. The preparation method is as follows: Electrode pretreatment: A single glassy carbon sheet with a diameter of 2 mm was selected as the working electrode material for an integrated monolithic electrode. Sulfuric acid was added to the surface of the electrode for activation to remove impurities on the electrode surface. The electrode was then washed with ethanol and ultrapure water, dried with nitrogen, and set aside.

[0040] Nafion membrane modification: A 2.5% wt Nafion solution (diluted with ethanol) was drop-coated on the pretreated electrode surface and initially solidified at room temperature to form a working electrode in the Nafion membrane-modified integrated monolithic electrode.

[0041] Electrode modified with porous cage-like carbon nanoflowers: Porous cage-like carbon nanoflower particles were prepared according to step (2) of Example 1. After being dispersed in a DMF solution, the particles were drop-coated onto the surface of the pre-modified Nafion electrode. The initial adhesion of the materials was achieved through the interaction between the sulfonic acid groups on the Nafion membrane surface and the oxygen-containing functional groups of the carbon nanoflowers.

[0042] Modification of gold nanoparticles: Using the same electrodeposition conditions as step (3) in Example 1 (-0.3 V, 180 s), gold nanoparticles were deposited on the porous cage-like carbon nanoflower / Nafion composite interface on the electrode. The presence of the Nafion membrane can regulate the distribution of the metal particles and prevent excessive aggregation.

[0043] like Figure 4As shown, the cyclic voltammetry characterization diagrams of integrated monolithic electrodes with different modifications were performed in a 0.1M KCl solution containing 5mM K3[Fe(CN)6], and CV scans were performed in the range of -0.3~0.5V. a is the integrated monolithic electrode (P-tlE), and the redox peak current is weak; b is the integrated monolithic electrode modified with caged carbon nanoflowers (CNFs / P-tIE), and the redox peak is reduced after modification, which may be due to the semiconductor properties of the carbon nanoflowers themselves, resulting in a decrease in electron transfer efficiency; c is the integrated monolithic electrode modified with gold-loaded caged carbon nanoflowers (AuNPs / CNFs / P-tIE), which shows the largest redox peak current, indicating that the composite modification of gold nanoparticles and carbon nanoflowers significantly enhances the conductivity and electrocatalytic activity of the electrode; d is the gold-loaded caged carbon nanoflower electrode modified with Nafion membrane (Nafion / AuNPs / CNFs / P-tIE), and its redox peak current is slightly lower than that of c, which may be due to the partial obstruction of electron transfer by the Nafion membrane. The experimental results show that the AuNPs / CNFs / P-tIE electrode has the best electrochemical performance, which is mainly attributed to the synergistic effect of gold nanoparticles and carbon nanoflowers and the abundant active sites provided by the composite structure. Example 3

[0044] The preparation steps of the working electrode in the Nafion membrane-adhered platinum-loaded caged carbon nanoflower-modified integrated monolithic electrode are as follows: The difference from Example 1 is that the metal nanoparticles are platinum nanoparticles.

[0045] Preparation of platinum nanoparticles: This embodiment uses a 2mmol / L H2PtCl6 solution prepared with 0.5mol / L H2SO4 containing a platinum nanoparticle precursor as an electroplating solution, wherein the platinum nanoparticles are electroplated onto the surface of the carbon nanoflower by a constant potential method to deposit H2PtCl6; and then the prepared electroplating solution containing the platinum nanoparticle precursor is electroplated onto the surface of the integrated monolithic electrode modified with the porous cage-like carbon nanoflowers in step (2) of Example 1, i.e., platinum nanoparticles are uniformly modified on the surface of the porous cage-like carbon nanoflowers. The modified electrode is rinsed with ultrapure water (18.2MΩ·cm) and dried with a nitrogen flow to obtain a working electrode in the integrated monolithic electrode modified with the platinum-loaded cage-like carbon nanoflowers.

[0046] The electrodeposition conditions are as follows: immersing the electrode in the electroplating solution and applying a constant potential of -0.3 V for 180 seconds.

[0047] The other steps were carried out according to steps (1), (2), and (4) of Example 1. Example 4

[0048] The steps for preparing the working electrode in the integrated monolithic electrode modified with palladium-loaded caged carbon nanoflowers bonded to Nafion membrane are as follows: The difference from Example 1 is that the metal nanoparticles are palladium nanoparticles.

[0049] Preparation of palladium nanoparticles: This embodiment uses a 2mmol / L PdCl2 solution prepared with 0.5mol / L H2SO4 containing a palladium nanoparticle precursor as an electroplating solution, wherein the palladium nanoparticles are electroplated onto the surface of the carbon nanoflower by a constant potential method to deposit PdCl2; and then the prepared electroplating solution containing the palladium nanoparticle precursor is electroplated on the surface of the integrated monolithic electrode modified with the porous cage-like carbon nanoflower in step (2) of Example 1, that is, palladium nanoparticles are uniformly modified on the surface of the porous cage-like carbon nanoflower. The modified electrode is rinsed with ultrapure water (18.2MΩ·cm) and dried with a nitrogen flow to obtain a working electrode in the integrated monolithic electrode modified with the palladium-loaded cage-like carbon nanoflower.

[0050] The conditions for the electrodeposition are as follows: the electroplating solution is dropped onto the electrode surface, and a constant potential of -0.3 V is applied for deposition for 180 seconds.

[0051] The other steps were carried out according to steps (1), (2), and (4) of Example 1. Example 5

[0052] The steps for preparing the working electrode in the integrated monolithic electrode modified with gold-loaded caged carbon nanoflowers adhered to the EDOT-PSS film are as follows: The difference from Example 1 is that the functional membrane is changed from Nafion to EDOT-PSS.

[0053] Preparation of an integrated monolithic electrode modified with gold-loaded caged carbon nanoflowers with functional membrane adhesion: By cyclic voltammetry electrochemical polymerization, the potential was cycled between -0.8 and 1.3 V at a scan rate of 50 mV / s for 60 cycles in an aqueous solution containing 0.01 mol / L EDOT and PSS (the molar ratio of EDOT to PSS in the aqueous solution was 1:2.5). During the process, a dark blue PEDOT-PSS film gradually formed on the surface of the integrated monolithic electrode modified with gold-loaded caged carbon nanoflowers obtained in step (3) of Example 1. The electrode surface was rinsed with ultrapure water to remove unreacted monomers, dried with nitrogen, and allowed to stand at room temperature for 12 hours to stabilize the film structure. Surface modification of the gold-loaded caged carbon nanoflower-modified electrode with PEDOT-PSS was achieved.

[0054] The other steps were carried out according to steps (1), (2) and (3) of Example 1. Example 6

[0055] The steps for preparing the working electrode in the integrated monolithic electrode modified with gold-loaded caged carbon nanoflowers adhered to the polydopamine film are as follows: The difference from Example 1 is that the functional membrane is changed from Nafion to polydopamine, and the modification step sequence is replaced. The electrode pretreatment and the working electrode steps in the integrated monolithic electrode modified with porous cage-like carbon nanoflowers are carried out according to Example 1.

[0056] (3) Functional membrane coating: Modify the polydopamine adhesion layer. Dissolve dopamine in Tris-HCl buffer (pH 8.5). Then, drop 1-2 μL of the dopamine solution onto the surface of the integrated monolithic electrode modified with porous cage-like carbon nanoflowers. Subsequently, place the electrode in a sealed container (humidity > 80%) and let it stand at room temperature for 1-5 hours to complete the dopamine self-polymerization. Finally, gently rinse with ultrapure water three times to remove unreacted monomers and blow dry with nitrogen.

[0057] (4) Preparation of functional membrane-adhered gold-loaded caged carbon nanoflowers modified on an integrated monolithic electrode: The plating solution containing the gold nanoparticle precursor is a 2 mmol / L HAuCl4 solution prepared from 0.5 mol / L H2SO4; wherein, the gold nanoparticles are electro-deposited onto the surface of the carbon nanoflowers by HAuCl4 using a constant potential method, and the average particle size of the obtained AuNPs is 80-200 nm. These AuNPs are uniformly deposited on the surface of the carbon nanoflowers, which not only significantly improves the conductivity of the electrode, but also enhances the electrode performance due to its excellent electrocatalytic activity; then the prepared plating solution containing the gold nanoparticle precursor is electro-deposited on the surface of the integrated monolithic electrode modified with the porous caged carbon nanoflowers and polydopamine obtained above, that is, the metal nanoparticles are uniformly modified on the surface of the porous caged carbon nanoflowers. The modified electrode is rinsed with ultrapure water (18.2 MΩ·cm) and dried with a nitrogen flow to obtain a working electrode of functional membrane-adhered gold-loaded caged carbon nanoflowers modified on an integrated monolithic electrode.

[0058] The conditions for the electrodeposition are as follows: the electroplating solution is dropped onto the electrode surface, and a constant potential of -0.3 V is applied for deposition for 180 seconds. Application Examples

[0059] The working electrode of the gold-loaded caged carbon nanoflower-modified integrated monolithic electrode bonded with the Nafion membrane described in Example 1 was integrated with a printed carbon electrode (auxiliary electrode) and a silver / silver chloride electrode (reference electrode) on a single chip to form an integrated monolithic electrode, and then copper ions were detected: The gold-loaded caged carbon nanoflower-modified integrated monolithic electrode bonded to the Nafion membrane described in Example 1 was used as the working electrode. 100 μL of a copper ion standard solution prepared with HAc-NaAc buffer solution (pH = 4.5) was added dropwise to the surface of the working electrode. The solution was concentrated at -0.2 V for 180 s, and a square wave stripping voltammetry scan was performed in the range of -0.4 V to 0.2 V to obtain the electrochemical response signal of copper ions.

[0060] Conduct stripping voltammetry on copper ions at different concentrations and draw the working curve of the response of the stripping peak current to the copper ion concentration (see Figure 5 ). Among them: the concentration of copper ions from bottom to top is 0, 0.7, 1, 2, 5, 7, 10, 20, 50, 70, 100, 200, 500, 700, 1000, 2000, 5000, 7000, 10000nmol / L. Figure 5 It can be seen that the Nafion membrane-adhered gold-loaded caged carbon nanoflower-modified integrated monolithic electrode of the present invention has a good linear relationship for copper ions in the concentration range of 0.7-10000 nmol / L, high detection sensitivity, and a detection limit as low as 0.1 nmol / L.

[0061] Then, the copper ions can be replaced with other metal ions in the above manner, so that the electrode obtained by the present invention can be used to detect other ions.

Claims

1. A functional membrane-adhesive integrated monolithic electrode, wherein the working electrode, auxiliary electrode, and reference electrode are integrated on a single chip, characterized in that: The working electrode is an integrated monolithic electrode adhered with a functional membrane, which is a substrate electrode surface modified with one or more of porous cage-structured carbon nanoflowers, metal nanoparticles and enhanced electron conduction films.

2. The functional membrane-adhered integrated monolithic electrode according to claim 1, characterized in that: The porous cage-like carbon nanoflowers are prepared by an organic polymerization method, wherein acrylonitrile monomer and azobisisobutyronitrile initiator are added to an acetone solvent, and a free radical polymerization reaction is initiated at 30-120°C for 0.5-8 hours. The azobisisobutyronitrile is thermally decomposed to generate free radicals to initiate polymerization. After the reaction is completed, polyacrylonitrile is obtained through precipitation, separation, and drying. The obtained polyacrylonitrile is placed in a vacuum drying oven at 30-120°C for 0.5-8 hours for continuous drying and stabilization. Subsequently, the powder sample is spun in air at 0.1°C·min -1 The temperature is raised to 150~300℃ at a heating rate and stabilized for 0.5~8h. After stabilization, it is carbonized in nitrogen at 700~1100℃ for 0.5~8h to obtain the carbonized product. After washing, separation and drying, carbon nanoflower particles with porous cage structure are obtained.

3. The functional membrane-adhered integrated monolithic electrode according to claim 2, characterized in that: The acetone, acrylonitrile monomer and azobisisobutyronitrile initiator are mixed in a mass ratio of 791:810:

1.

4. A method for preparing the functional membrane-adhered integrated monolithic electrode according to claim 1, characterized in that: The integrated single-chip electrode is a working electrode, an auxiliary electrode and a reference electrode integrated on one chip; wherein, the working electrode is modified on the surface of the substrate electrode, and the modification material is one or more of carbon nanoflowers with porous cage structures, metal nanoparticles and enhanced electron conduction films.

5. The method for preparing a functional membrane-adhered integrated monolithic electrode according to claim 4, characterized in that: The working electrode is a pretreated substrate electrode surface that is sequentially modified with porous cage-like carbon nanoflowers, metal nanoparticles and an enhanced electron conduction film to obtain an integrated monolithic electrode with functional membrane adhesion.

6. The method for preparing a functional membrane-adhered integrated monolithic electrode according to claim 4, characterized in that: The working electrode is a pretreated substrate electrode surface modified with an enhanced electron conduction film, a porous cage-like carbon nanoflower and metal nanoparticles in sequence, thereby obtaining an integrated monolithic electrode with functional membrane adhesion.

7. The method for preparing a functional membrane-adhered integrated monolithic electrode according to claim 5 or 6, characterized in that: The metal nanoparticles are one or more of gold nanoparticles, platinum nanoparticles, and palladium nanoparticles.

8. The method for preparing a functional membrane-adhered integrated monolithic electrode according to any one of claims 4 to 6, characterized in that: The substrate electrode is a single micro-gold sheet or glassy carbon sheet with a diameter of 2 mm.

9. An application of the functional membrane-adhered integrated monolithic electrode according to claim 1, characterized in that: The functional membrane-adhered integrated monolithic electrode is used in detecting metal ions in the environment.

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