Integrated monolithic functional membrane-adhered electrodes, methods of making, and applications in metal ion detection

Abstract

The application belongs to the field of electrochemical detection, and particularly relates to a functional membrane adhesion integrated monolithic electrode, a preparation method and application in metal ion detection. The functional membrane adhesion integrated monolithic electrode is an integrated monolithic electrode in which a working electrode, an auxiliary electrode and a reference electrode are integrated on a chip. The working electrode is a functional membrane adhesion integrated monolithic electrode, which is modified on the surface of a base electrode. The modification material is one or more of carbon nanoflower with a porous cage structure, metal nanoparticles and an enhanced electron conduction film. In the integrated monolithic electrode, the working electrode is a base electrode, and the surface is modified by a functional film in cooperation with carbon nanoflower with a porous cage structure and gold nanoparticles, so that a sensing system with excellent interface characteristics is constructed, and the advantages of high sensitivity and high stability are achieved.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of electrochemical detection, and particularly relates to a functional membrane adhesion integrated monolithic electrode, a preparation method thereof and application thereof in metal ion detection. BACKGROUND

[0002] Micro metal elements play an important role in regulating biogeochemical processes, promoting phytoplankton growth, and even the entire marine ecosystem. However, the concentration of copper has a significant dual effect on algae, low concentration of copper can promote the growth of algae, while too high concentration of copper can have a toxic effect on algae. Therefore, it is of great significance to quickly and accurately detect copper in water to accurately assess the biological availability and ecological risk of copper and to take effective control measures. It has become an important content in the research of analytical chemistry in recent years.

[0003] Currently, the detection methods of metal elements including copper mainly include atomic absorption spectrometry, inductively coupled plasma atomic emission spectrometry, inductively coupled plasma mass spectrometry, and electrochemical analysis method. Atomic absorption spectrometry needs pre-concentration, solvent extraction, desalting and other treatments before analysis, which is relatively complicated and time-consuming, and has high cost. Inductively coupled plasma atomic emission spectrometry and inductively coupled plasma mass spectrometry have expensive instruments and complex operation. In comparison, electrochemical methods have significant advantages in trace metal detection, and have high sensitivity, low cost, strong portability, and simple operation, which are very suitable for on-site detection and large-scale environmental monitoring applications.

[0004] However, as a traditional electrode for electrochemical detection, the mercury electrode has a wide potential window and high hydrogen overpotential, but due to its inherent toxicity problem and special storage conditions, it has significant limitations in practical application. Developing environmentally friendly chemical modified electrodes can effectively improve the detection sensitivity and avoid the use of mercury, which has become an important direction of current research. Conventional electrodes such as glassy carbon electrodes and gold electrodes have low nanomaterial immobilization efficiency and weak interface bonding due to their chemical inertness, which leads to easy shedding of the modified materials and affects the stability of the electrode and the reproducibility of the detection results. Therefore, further research is needed when constructing a chemical modified electrode, and on the basis of improving the detection sensitivity, the stability should be improved, which is an important research direction, and provides a technical solution for the sensitivity and stability of metal element detection. SUMMARY

[0005] The application aims to provide a functional membrane adhesion integrated monolithic electrode, a preparation method thereof and application thereof in metal ion detection.

[0006] To achieve the above-mentioned purpose, the technical scheme adopted by the application is:

[0007] An integrated monolithic electrode of functional membrane adhesion, the integrated monolithic electrode is an integrated electrode of working electrode, auxiliary electrode and reference electrode on a chip, the working electrode is an integrated monolithic electrode of functional membrane adhesion, which is modified on the surface of the base electrode, and the modification material is one or more of carbon nanoflower with porous cage structure, metal nanoparticles and enhanced electron conducting film.

[0008] The carbon nanoflower with porous cage structure is obtained by organic polymerization method, acetonitrile monomer and azobisisobutyronitrile initiator are added in acetone solvent, radical polymerization is initiated under nitrogen environment at 30-120℃ for 0.5-8h, azobisisobutyronitrile is decomposed to generate free radicals to initiate polymerization, after the reaction is completed, the polyacrylonitrile (PACN) is obtained by precipitation, separation and drying, the obtained polyacrylonitrile (PACN) is continuously dried in a vacuum drying oven at 30-120℃ for 0.5-8h for stabilization treatment, then the powder sample is heated to 150-300℃ at a heating rate of 0.1℃·min -1 -1 in air and stabilized for 0.5-8h, and then carbonized at 700-1100℃ in nitrogen for 0.5-8h to obtain the carbonized product, and the carbon nanoflower with porous cage structure is obtained by washing, separation and drying.

[0009] The acetone, acetonitrile monomer and azobisisobutyronitrile initiator are mixed in a mass ratio of 791:810:1.

[0010] A preparation method of the integrated monolithic electrode of functional membrane adhesion, the integrated monolithic electrode is an integrated electrode of working electrode, auxiliary electrode and reference electrode on a chip, and the working electrode is modified on the surface of the base electrode, and the modification material is one or more of carbon nanoflower with porous cage structure, metal nanoparticles and enhanced electron conducting film.

[0011] The working electrode is a pretreated base electrode surface modified with carbon nanoflower with porous cage structure, metal nanoparticles and enhanced electron conducting film in sequence to obtain the integrated monolithic electrode of functional membrane adhesion.

[0012] The working electrode is a pretreated base electrode surface modified with enhanced electron conducting film, carbon nanoflower with porous cage structure and metal nanoparticles in sequence to obtain the integrated monolithic electrode of functional membrane adhesion.

[0013] The metal nanoparticles are one or more of gold nanoparticles, platinum nanoparticles and palladium nanoparticles.

[0014] The base electrode is a single monolithic micro gold sheet or glassy carbon sheet with a diameter of 2mm.

[0015] The enhanced electron-conducting film is one of a cation exchange membrane (such as Nafion), a conductive polymer film (such as polyaniline, PEDOT-PSS) or a carrier film (such as polydopamine), and the adopted coating method is drop coating, specifically, the components of the enhanced electron-conducting film are configured into a solution with a concentration of 1-5% wt, 1-5 mL of which is dropped on the surface of the integrated monolithic electrode modified by the cage-like carbon nanoflower or the cage-like carbon nanoflower loaded with metal particles, and solidified at room temperature. The conductive polymer film can also be coated by electrodeposition, and the carrier film such as polydopamine can also be coated by self-assembly.

[0016] The monolithic working electrode material is integrated with a printed carbon electrode (auxiliary electrode) and a silver / silver chloride electrode (reference electrode) on a chip.

[0017] 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.

[0018] The functional membrane-adhered gold-loaded cage-like carbon nanoflower modified integrated monolithic electrode has the advantages of high sensitivity and high stability in copper ion detection, and can be applied to the accurate and stable detection of different metal ions with low concentration in complex matrices such as river water and seawater. Preferably, the functional membrane-adhered gold-loaded cage-like carbon nanoflower modified integrated monolithic electrode is used for high-sensitivity and high-stability detection of copper ions.

[0019] The advantages of the present application are:

[0020] The present application uses the working electrode as a base electrode in the integrated monolithic electrode, and the surface is modified by the functional film and the carbon nanometer and gold nanoparticles with porous cage-like structure, to construct a sensing system with excellent interface characteristics, which has the advantages of high sensitivity and high stability. The preparation method has the characteristics of simple process, environmental friendliness and significant cost-effectiveness, and the obtained modified electrode not only exhibits excellent electrocatalytic activity and detection sensitivity, but also significantly improves the stability, which can meet the high-sensitivity and high-stability detection requirements of trace copper ions and other metal ions in complex matrix samples such as river water and seawater.

[0021] Specifically, the application adopts a single piece of micro gold sheet or glassy carbon sheet with a diameter of 2 mm as a working electrode material, and integrates the printed carbon electrode (auxiliary electrode) and silver / silver chloride electrode (reference electrode) on a chip to form an integrated single piece electrode. By modifying the carbon nanometer with a unique porous cage structure on the surface, further loading metal nanoparticles, and coating a functional film, a functional sensing interface is constructed. The porous cage structure of carbon nanometer flower can provide more binding sites for metal nanoparticles, while the metal nanoparticles promote electron conduction and have very good catalytic effect on electrochemical detection of metal ions, greatly improving the sensitivity of metal ion detection. The functional film has a binding effect, which can wrap and bind the cage-shaped carbon nanometer flower and metal nanoparticles together, play a protective role, prevent it from falling off, and improve the stability of the modified electrode. Therefore, the modified electrode forms a sensing structure with high sensitivity and high stability. It can be applied to precise and stable detection of low concentration metal ions, especially copper ions, in complex matrices such as river water and seawater. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 The schematic diagram of the preparation process of the working electrode of the Nafion film-bound gold-loaded cage-shaped carbon nanometer flower modified integrated single piece electrode provided by the embodiment of the application.

[0023] Figure 2 The scanning electron microscope characterization diagram of the cage-shaped carbon nanometer flower and the Nafion film-bound gold-loaded cage-shaped carbon nanometer flower prepared by the embodiment of the application, wherein (a) is a morphology characterization diagram of the cage-shaped carbon nanometer flower under a scale of 5 μm, (b) is a morphology characterization diagram of the Nafion film-bound gold-loaded cage-shaped carbon nanometer flower under a scale of 5 μm, (c) is a morphology characterization diagram of the cage-shaped carbon nanometer flower under a scale of 1 μm, and (d) is a morphology characterization diagram of the Nafion film-bound gold-loaded cage-shaped carbon nanometer flower under a scale of 1 μm.

[0024] Figure 3 The cyclic voltammetry characterization diagram of the working electrode of the integrated single piece electrode prepared by the embodiment of the application in an acetic acid buffer solution with pH 4.5, wherein a is an integrated single piece electrode (P-tlE), b is a cage-shaped carbon nanometer flower modified integrated single piece electrode (CNFs / P-tIE), c is a gold-loaded cage-shaped carbon nanometer flower modified integrated single piece electrode (AuNPs / CNFs / P-tIE), and d is a Nafion film-bound gold-loaded cage-shaped carbon nanometer flower modified integrated single piece electrode (Nafion / AuNPs / CNFs / P-tIE) with Nafion as a functional film.

[0025] Figure 4The cyclic voltammetry characterization figures of different integrated monolithic electrodes prepared by the embodiment of the present application in 0.1M KCl solution containing 5mM K3[Fe(CN)6] are provided, wherein a is an integrated monolithic electrode (P-tlE), b is a cage-shaped carbon nanoflower modified integrated monolithic electrode (CNFs / P-tIE), c is a gold-loaded cage-shaped carbon nanoflower modified integrated monolithic electrode (AuNPs / CNFs / P-tIE), and d is a functional membrane adhesion gold-loaded cage-shaped carbon nanoflower modified integrated monolithic electrode (Nafion / AuNPs / CNFs / P-tIE) with Nafion as a functional membrane.

[0026] Figure 5 The stripping voltammograms of different concentrations of heavy metal copper ions on the working electrode of the functional membrane adhesion gold-loaded cage-shaped carbon nanoflower modified integrated monolithic electrode provided by the embodiment of the present application and the corresponding working curve figures are provided. DETAILED DESCRIPTION

[0027] The specific embodiments of the present application are further described below in conjunction with examples, and it should be pointed out that the specific embodiments described herein are only for the purpose of illustrating and explaining the present application, and are not limited to the present application.

[0028] In the present application, the working electrode of the integrated monolithic electrode is provided with carbon nanoflowers with a porous cage structure as a carrier material, and the surface of the carbon nanoflowers is loaded with metal nanoparticles. The carbon nanoflowers with a porous cage structure have the advantages of good electrical conductivity and large specific surface area, and can load more metal nanoparticles. The metal nanoparticles have the ability to promote electron conduction and catalytic performance for copper ion electrochemical detection. Therefore, before and after loading the metal nanoparticles, the functional membrane is coated, and the functional groups on the surface of the carbon nanoflowers, such as hydroxyl groups and carboxyl groups, are combined through hydrogen bonds and van der Waals forces, thereby having an adhesion effect. The cage-shaped carbon nanoflowers and metal nanoparticles can be wound and adhered together, thereby playing a protective role and preventing them from falling off, and improving the stability of the modified electrode. At the same time, the functional membrane can further improve the electrical conductivity, cation enrichment efficiency and electrochemical detection performance, so that the modified electrode forms a sensing structure with high sensitivity and high stability.

[0029] Finally, the functional membrane adhesion gold-loaded cage-shaped carbon nanoflower modified working electrode of the integrated monolithic electrode has the advantages of high sensitivity, excellent selectivity and stability for copper ion detection, and can be applied to the accurate and stable detection of low-concentration copper ions in a complex matrix. In addition to copper ions, by changing the enrichment potential, high-sensitivity and high-stability detection of other metal ions can be realized.

[0030] Further:

[0031] The integrated monolithic electrode with a functional membrane adhesion in the present application has the following characteristics:

[0032] (a) The integrated monolithic electrode has carbon nanoflower with a porous cage structure as a carrier material, and metal nanoparticles are loaded on the surface; wherein the carbon nanoflower with a porous cage structure has the advantages of good electrical conductivity and large specific surface area, and can load more metal nanoparticles; the metal nanoparticles have the ability to promote electron conduction and catalytic performance for copper ion electrochemical detection.

[0033] (b) The integrated monolithic electrode is coated with a functional film before and after loading of the metal nanoparticles in the preparation process, and the functional film is combined with the hydroxyl, carboxyl and other groups on the surface of the carbon nanoflower through hydrogen bonds and van der Waals forces, thereby having a cohesive effect, which can wrap and adhere the cage-shaped carbon nanoflower and metal nanoparticles together, and play a protective role to prevent them from falling off, thereby improving the stability of the modified electrode. At the same time, the functional film can further improve the electrical conductivity, cation enrichment efficiency and electrochemical detection performance, so that the modified electrode forms a sensing structure with high sensitivity and high stability.

[0034] (c) The cage-shaped carbon nanoflower loaded with metal and modified by the functional film is modified on the integrated monolithic electrode, and the modified electrode has the advantages of high sensitivity, excellent selectivity and stability for copper ion detection, and can be applied to precise and stable detection of low-concentration copper ions in complex matrix. In addition to copper ions, it can also be used for high-sensitivity and high-stability detection of other metal ions. Example 1

[0035] Preparation of the working electrode of the integrated monolithic electrode modified by the cage-shaped carbon nanoflower loaded with metal and adhered by a Nafion film, as shown in Figure 1 , the steps are as follows:

[0036] (1) Electrode pretreatment: select a monolithic glassy carbon sheet with a diameter of 2 mm as the integrated monolithic electrode substrate of the working electrode material, drop sulfuric acid on the electrode surface for activation to remove impurities on the electrode surface, and then clean with ethanol and ultrapure water, and dry with nitrogen for standby.

[0037] (2) Working electrode of the integrated monolithic electrode modified by the cage-shaped carbon nanoflower:

[0038] ① Preparation of the cage-shaped carbon nanoflower: add acrylonitrile monomer (10 mL) and azobisisobutyronitrile initiator (10 mg) to acetone solvent (10 mL), and initiate the free radical polymerization reaction at 70°C for 2 h under a nitrogen environment. After the reaction is completed, separate by precipitation and filtration, and dry to obtain polyacrylonitrile (PACN). Place the obtained polyacrylonitrile (PACN) in a 60°C vacuum drying oven for 2 h for continuous drying and stabilization treatment, and then wrap the powder sample in air at a rate of 0.1°C·min -1The temperature of the material was raised to 230°C at a rate of 5°C / min and stabilized for 2h. Finally, the stabilized material was carbonized in nitrogen at 1000°C for 2h to obtain the carbonized product, which was washed (washed with ethanol three times and then with ultrapure water three times), separated, dried, and finally obtained as the product of porous cage-shaped carbon nanoflower particles.

[0039] The working electrode in the integrated monolithic electrode modified with porous cage-shaped carbon nanoflowers was obtained by uniformly dispersing the porous cage-shaped carbon nanoflower particles obtained above in a DMF solution (the concentration of the particles in the dispersion was 1 mg / mL), taking 3 μL of the solution (corresponding to a carbon nanoflower loading of 3 μg), and dropping the solution onto the surface of the working electrode pretreated in step (1) above, and drying at room temperature to obtain the working electrode in the integrated monolithic electrode modified with porous cage-shaped carbon nanoflowers. The scanning electron microscope characterization images of the porous cage-shaped carbon nanoflowers are shown in (a) and (c) in Figure 2

[0040] (3) The working electrode in the integrated monolithic electrode modified with gold-loaded cage-shaped carbon nanoflowers:

[0041] The electroplating solution containing gold nanoparticle precursors used in this example was prepared by dissolving gold nanoparticles in 0.5 mol / L H2SO4 to obtain a 2 mmol / L HAuCl4 solution. The gold nanoparticles were obtained by electrodeposition of HAuCl4 onto the surface of carbon nanoflowers by the conventional constant potential method, and the average particle size of the Au NPs obtained was 80-200 nm. The electroplating solution containing gold nanoparticle precursors prepared as above was then electrodeposited onto the surface of the integrated monolithic electrode modified with porous cage-shaped carbon nanoflowers obtained in step (2) above, i.e., metal nanoparticles were uniformly modified onto the surface of the porous cage-shaped carbon nanoflowers. The modified electrode was washed with ultrapure water (18.2 MΩ·cm) and dried with a nitrogen stream to obtain the working electrode in the integrated monolithic electrode modified with gold-loaded cage-shaped carbon nanoflowers.

[0042] The electrodeposition conditions were as follows: the electroplating solution was dropped onto the surface of the electrode, and a constant potential of -0.3 V was applied for 180 seconds. The Au NPs obtained were uniformly deposited on the surface of the carbon nanoflowers, which not only significantly improved the conductivity of the electrode, but also enhanced the performance of the electrode due to the excellent electrocatalytic activity of the Au NPs.

[0043] ​(4) Preparation of the working electrode of the integrated monolithic electrode modified by functional membrane-adhered gold-loaded cage-like carbon nanoflowers: 2.5%wt Nafion solution (diluted by ethanol) was drop-coated on the surface of the integrated monolithic electrode modified by gold-loaded cage-like carbon nanoflowers obtained in step (3) above, and allowed to solidify at room temperature, so that the Nafion membrane was combined with the hydroxyl, carboxyl and other groups on the surface of the carbon nanoflowers through hydrogen bonding and van der Waals force, and meanwhile, the adjacent gold-loaded carbon nanoflowers were interconnected and adhered through the entanglement of the polymer chains of the Nafion membrane, forming a stable three-dimensional network structure, i.e. the working electrode of the integrated monolithic electrode modified by Nafion-adhered gold-loaded cage-like carbon nanoflowers (see Figs. 1 (b) and (d) in the specification). Figure 2

[0044] As can be seen from the TEM characterization in the specification, Figure 2 Figure 2 Figs. 1 (a) and (c) in the specification show SEM images of CNFs / P-tIE. The flower-like appearance with a three-dimensional structure can be clearly observed. Figure 2 The SEM image in Fig. 1 (c) at a scale of 1 μm reveals the fine flower-like structural details of the CNFs, and the diameter of the CNFs is about 600 nm. Figure 2 Figs. 1 (b) and (d) in the specification show scanning electron microscope characterization images of Nafion-adhered gold-loaded cage-like carbon nanoflowers (Nafion / AuNPs / CNFs / P-tIE). It can be seen that gold nanoparticles with a diameter of about 80 to 200 nm are uniformly loaded on the CNFs.

[0045] The cyclic voltammetry tests were performed on different electrodes in an acetic acid buffer solution at pH 4.5. The experimental setup parameters were as follows: starting potential: 0 V; highest potential: 1.2 V; lowest potential: 0 V; terminal potential: 1.2 V; initial scanning polarity: positive potential to negative potential scanning; scanning rate: 0.05 V / s; waiting time: 2 s. As can be seen from Fig. 2 in the specification, Figure 3 The cyclic voltammogram of the integrated monolithic electrode has no obvious redox peak. After the surface of the integrated monolithic electrode was modified by cage-like carbon nanoflowers, the cyclic voltammetry response of the electrode was enhanced to a certain extent, but the effect was relatively small. After the modification of gold nanoparticles, the response current was greatly increased, and a large characteristic reduction peak of gold nanoparticles appeared at 0.42 V, which indicated that the catalytic effect of gold nanoparticles was very obvious. The experimental results showed that the unmodified integrated monolithic electrode had almost no current response to Cu 2+ , while AuNPs / P-tIE exhibited an obvious oxidation current signal at about -0.1 V. This phenomenon indicated that the presence of AuNPs significantly enhanced the current response of the electrode to Cu 2+ ​​The electrocatalytic activity of the electrode was enhanced, which resulted in an obvious increase in the current response in the voltammetry detection. After the Nafion was continuously modified on the electrode surface, the characteristic reduction peak of the gold nanoparticles was slightly decreased, and the peak potential was shifted, and the response current of the electrode was hindered at 0.48 V. Example 2

[0046] The preparation of the working electrode in the Nafion film-adhered gold-loaded cage-like carbon nanoflower modified integrated monolithic electrode, which was different from Example 1, was that the modification order, i.e. the covering order of Nafion, was changed, and the preparation method was as follows:

[0047] Electrode pretreatment: The integrated monolithic electrode with a diameter of 2 mm was selected as the working electrode material, sulfuric acid was added dropwise on the electrode surface for activation to remove impurities on the electrode surface, and the electrode was cleaned with ethanol and ultrapure water, and then dried with nitrogen for standby.

[0048] Nafion film modification: 2.5%wt Nafion solution (diluted by ethanol) was drop-casted on the surface of the pretreated electrode, and the Nafion film modified integrated monolithic electrode was formed after preliminary curing at room temperature.

[0049] Porous cage-like carbon nanoflower modified electrode: The porous cage-like carbon nanoflower particles were prepared according to the method of step (2) in Example 1, and then dispersed in DMF solution and drop-casted on the surface of the Nafion pre-modified electrode. The preliminary adhesion of the materials was realized through the interaction between the sulfonic acid groups on the surface of the Nafion film and the oxygen-containing functional groups of the carbon nanoflowers.

[0050] Gold nanoparticle modification: The same electrodeposition conditions (-0.3 V, 180 s) in step (3) of Example 1 were used to deposit gold nanoparticles on the porous cage-like carbon nanoflower / Nafion composite interface of the electrode. At this time, the distribution of metal particles was controlled by the presence of the Nafion film to avoid excessive aggregation.

[0051] As Figure 4As shown in the cyclic voltammograms of different modified integrated monolithic electrodes, the CV scan was performed in 0.1M KCl solution containing 5mM K3[Fe(CN)6] at-0.3~0.5V, a is the integrated monolithic electrode (P-tlE), the redox peak current is weak; b is the cage-like carbon nanoflower modified integrated monolithic electrode (CNFs / P-tIE), the redox peak of the modified electrode is reduced, which may be due to the semiconductor properties of carbon nanoflower itself leading to the reduction of electron transfer efficiency; c is the gold-loaded cage-like carbon nanoflower modified integrated monolithic electrode (AuNPs / CNFs / P-tIE), which shows the largest redox peak current, indicating that the composite modification of gold nanoparticles and carbon nanoflower significantly enhances the conductivity and electrocatalytic activity of the electrode; d is the Nafion film modified gold-loaded cage-like carbon nanoflower electrode (Nafion / AuNPs / CNFs / P-tIE), and the redox peak current is slightly lower than that of c, which may be due to the partial hindering of electron transmission by the Nafion film. The experimental results show that the AuNPs / CNFs / P-tIE electrode has the most excellent electrochemical performance, which is mainly due to the synergistic effect of gold nanoparticles and carbon nanoflower and the rich active sites provided by the composite structure. Example 3

[0052] The preparation steps of the working electrode in the Nafion film-adhered platinum-loaded cage-like carbon nanoflower modified integrated monolithic electrode are as follows:

[0053] The difference from Example 1 is that the metal nanoparticles are platinum nanoparticles.

[0054] Preparation of platinum nanoparticles: In this embodiment, a 2mmol / L H2PtCl6 solution prepared by using 0.5mol / L H2SO4 containing a platinum nanoparticle precursor as an electroplating solution is used, in which the platinum nanoparticles are electrodeposited on the surface of the carbon nanoflower by constant potential method; then the prepared electroplating solution containing the platinum nanoparticle precursor is electrodeposited on the surface of the porous cage-like carbon nanoflower modified integrated monolithic electrode obtained in step (2) of Example 1, i.e. platinum nanoparticles are uniformly modified on the surface of the porous cage-like carbon nanoflower, and the modified electrode is washed with ultrapure water (18.2MΩ·cm) and dried with a nitrogen stream to obtain the working electrode in the platinum-loaded cage-like carbon nanoflower modified integrated monolithic electrode.

[0055] The electrodeposition conditions are that the electrode is immersed in the electroplating solution and a constant potential of-0.3V is applied for 180 seconds.

[0056] The other steps are performed according to steps (1), (2) and (4) of Example 1, respectively. Example 4

[0057] The working electrode of the palladium-loaded cage-like carbon nanoflower modified integrated monolithic electrode with Nafion film adhesion was prepared as follows:

[0058] The difference from Example 1 is that the metal nanoparticles are palladium nanoparticles.

[0059] Preparation of palladium nanoparticles: In this example, a 2 mmol / L PdCl2 solution prepared with 0.5 mol / L H2SO4 containing palladium nanoparticle precursors was used as the electroplating solution, in which the palladium nanoparticles were electrodeposited on the surface of the carbon nanoflower by the constant potential method. Then, the prepared electroplating solution containing palladium nanoparticle precursors was electrodeposited on the surface of the porous cage-like carbon nanoflower modified integrated monolithic electrode obtained in step (2) of Example 1, that is, the surface of the porous cage-like carbon nanoflower was uniformly modified with palladium nanoparticles. The modified electrode was washed with ultrapure water (18.2 MΩ·cm) and dried with a nitrogen stream to obtain the working electrode of the palladium-loaded cage-like carbon nanoflower modified integrated monolithic electrode.

[0060] The electrodeposition conditions were that the electroplating solution was added dropwise on the electrode surface, and a constant potential of -0.3 V was applied for 180 seconds.

[0061] The other steps were performed according to steps (1), (2) and (4) of Example 1, respectively. Example 5

[0062] The working electrode of the gold-loaded cage-like carbon nanoflower modified integrated monolithic electrode with EDOT-PSS film adhesion was prepared as follows:

[0063] The difference from Example 1 is that the functional film is changed from Nafion to EDOT-PSS.

[0064] Preparation of the gold-loaded cage-like carbon nanoflower modified integrated monolithic electrode with functional film adhesion: The cyclic voltammetric electrochemical polymerization method was used to form a deep blue PEDOT-PSS film on the surface of the gold-loaded cage-like carbon nanoflower modified integrated monolithic electrode obtained in step (3) of Example 1 in an aqueous solution containing 0.01 mol / L of EDOT and PSS (the molar ratio of EDOT to PSS in the aqueous solution was 1:2.5) by cycling the potential between -0.8 and 1.3 V at a scan rate of 50 mV / s for 60 cycles. The electrode surface was washed with ultrapure water to remove the unreacted monomers, and dried with nitrogen. The film structure was stabilized by standing at room temperature for 12 hours. Thus, the surface modification of the gold-loaded cage-like carbon nanoflower modified electrode with PEDOT-PSS was achieved.

[0065] The other steps were performed according to steps (1), (2) and (3) of Example 1, respectively. Example 6

[0066] The working electrode of the gold-loaded cage-like carbon nanoflower modified integrated monolithic electrode with polydopamine film adhesion was prepared as follows:

[0067] The difference from Example 1 is that the functional film is changed from Nafion to polydopamine, and the modification step sequence is replaced, and the electrode pretreatment and the working electrode of the porous cage-like carbon nanoflower modified integrated monolithic electrode are carried out according to Example 1.

[0068] (3) Functional film coating: polydopamine adhesion layer modification was carried out, dopamine was dissolved in Tris-HCl buffer (pH 8.5), then 1-2 μL of dopamine solution was dropped on the surface of the porous cage-like carbon nanoflower modified integrated monolithic electrode. Then, the electrode was placed in a closed container (humidity > 80%) and left at room temperature for 1-5 hours to complete the self-polymerization of dopamine. Finally, it was gently washed with ultrapure water for 3 times to remove the unreacted monomer, and dried with nitrogen.

[0069] (4) Preparation of gold-loaded cage-like carbon nanoflower modified integrated monolithic electrode with functional film adhesion: the electroplating solution containing gold nanoparticle precursors was prepared by dissolving 2 mmol / L HAuCl4 in 0.5 mol / L H2SO4; the gold nanoparticles were obtained by electrodeposition of HAuCl4 onto the surface of the carbon nanoflower by constant potential method, and the average particle size of the obtained AuNPs was 80-200 nm. These AuNPs were uniformly deposited on the surface of the carbon nanoflower, which not only significantly improved the conductivity of the electrode, but also enhanced the performance of the electrode due to its excellent electrocatalytic activity; then the prepared electroplating solution containing gold nanoparticle precursors was electrodeposited on the surface of the above-mentioned porous cage-like carbon nanoflower and polydopamine modified integrated monolithic electrode, i.e. the metal nanoparticles were uniformly modified on the surface of the porous cage-like carbon nanoflower, and the modified electrode was washed with ultrapure water (18.2 MΩ·cm) and dried with nitrogen flow to obtain the working electrode of the gold-loaded cage-like carbon nanoflower modified integrated monolithic electrode with functional film adhesion.

[0070] The electrodeposition conditions are as follows: the electroplating solution is dropped on the surface of the electrode, and a constant potential of -0.3 V is applied for 180 seconds.

[0071] Application Example

[0072] The working electrode of the gold-loaded cage-like carbon nanoflower modified integrated monolithic electrode with Nafion film adhesion described in Example 1 was integrated with a printed carbon electrode (auxiliary electrode) and a silver / silver chloride electrode (reference electrode) on a chip to form an integrated monolithic electrode, and then the copper ion was detected:

[0073] The Nafion film-adhered gold-loaded cage-like carbon nanoflower modified integrated monolithic electrode described in embodiment 1 is used as a working electrode, 100 μL of a copper ion standard solution prepared by HAc-NaAc buffer solution (pH=4.5) is added dropwise on the surface of the working electrode, the working electrode is enriched at-0.2 V for 180 s, and square wave stripping voltammetry is performed in the range of-0.4 V to 0.2 V to obtain the electrochemical response signal of the copper ion.

[0074] The stripping voltammetry is performed on different concentrations of copper ions respectively, and a working curve of the stripping peak current size responding to different concentrations of copper ions is drawn (see Figure 5 ). In the working curve, the concentrations of the copper ions from bottom to top are 0, 0.7, 1, 2, 5, 7, 10, 20, 50, 70, 100, 200, 500, 700, 1000, 2000, 5000, 7000, 10000 nmol / L. Figure 5 It can be known that the Nafion film-adhered gold-loaded cage-like carbon nanoflower modified integrated monolithic electrode has a good linear relationship with the copper ion in the concentration range of 0.7-10000 nmol / L, has high detection sensitivity, and has a low detection limit of 0.1 nmol / L.

[0075] Then, the copper ion can be replaced by other metal ions in the above manner, and thus the electrode obtained by the present application can be used to detect other ions.

Claims

1. A functional membrane-bonded 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 a functional membrane-bonded monolithic electrode, which is a substrate electrode surface modified by a modification material consisting of porous cage-like carbon nanoflowers, metal nanoparticles, and an enhanced electron conduction membrane. The working electrode uses carbon nanoflowers with porous cage-like structures as a carrier material, and metal nanoparticles are loaded on the surface; the enhanced electron conduction membrane entangles and binds the cage-like carbon nanoflowers and metal nanoparticles together. The porous cage-like carbon nanoflowers were prepared via organic polymerization. Acrylonitrile monomer and azobisisobutyronitrile (AIBN) initiator were added to acetone solvent, and a free radical polymerization reaction was initiated at 30–120 °C for 0.5–8 h under nitrogen atmosphere. The AIBN decomposed thermally to generate free radicals that initiated the polymerization. After the reaction, polyacrylonitrile was obtained through precipitation, separation, and drying. The obtained polyacrylonitrile was then placed in a vacuum drying oven at 30–120 °C for 0.5–8 h for continuous drying to stabilize it. Subsequently, the powder sample was air-dried at 0.1 °C·min. -1 The temperature was raised to 150~300℃ and stabilized for 0.5~8h. After stabilization, the carbonized product was carbonized in nitrogen at 700~1100℃ for 0.5~8h to obtain the carbonized product. After washing, separation and drying, porous cage-like carbon nanoflower particles were obtained. The metal nanoparticles are gold nanoparticles, platinum nanoparticles, or palladium nanoparticles. The enhanced electron conduction membrane is Nafion, PEDOT-PSS, or polydopamine.

2. The integrated monolithic electrode with functional membrane adhesion according to claim 1, characterized in that: The acetone, acrylonitrile monomer, and azobisisobutyronitrile initiator are mixed in a mass ratio of 791:810:

1.

3. A method for preparing an integrated monolithic electrode with functional membrane adhesion as described in claim 1, characterized in that: An integrated monolithic electrode is obtained by integrating a working electrode, an auxiliary electrode, and a reference electrode on a single chip; wherein, the working electrode is a substrate electrode surface modified with a modified material consisting of porous cage-like carbon nanoflowers, metal nanoparticles, and an enhanced electron conduction membrane.

4. The method for preparing an integrated monolithic electrode with functional membrane adhesion according to claim 3, 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 membrane to obtain a functional membrane adhesion monolithic electrode.

5. The method for preparing an integrated monolithic electrode with functional membrane adhesion according to claim 3, characterized in that: The working electrode is a pretreated substrate electrode surface that is sequentially modified with an enhanced electron conduction membrane, porous cage-like carbon nanoflowers, and metal nanoparticles to obtain a functional membrane-adhesive monolithic electrode.

6. The method for preparing an integrated monolithic electrode with functional membrane adhesion according to any one of claims 3-5, characterized in that: The substrate electrode is a single micro gold sheet or glassy carbon sheet with a diameter of 2 mm.

7. An application of the integrated monolithic electrode with functional membrane adhesion as described in claim 1, characterized in that: Application of the functional membrane-bonded integrated monolithic electrode in detecting metal ions in the environment.

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