CN111982994A - All-solid-state ion selective electrode for ion detection and application thereof - Google Patents
All-solid-state ion selective electrode for ion detection and application thereof Download PDFInfo
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Abstract
The invention provides an ion selective electrode, which comprises a glassy carbon electrode; the multi-walled carbon nanotube/nitrogen-doped carbon composite material film layer is compounded on the surface of the glassy carbon electrode; and the ion selective film layer to be detected is compounded on the surface of the multi-wall carbon nano tube/nitrogen-doped carbon composite material film layer. The invention firstly uses the multi-wall carbon nano tube/nitrogen-doped carbon composite material with a specific structure to construct the all-solid-state ion selective electrode, ensures that the constructed MWCNT/NPC-ISE has high reliability and reproducibility, can realize in-situ and real-time monitoring of all-solid-state ions, and further realizes real-time detection of all-solid-state ions under the high-pressure deep water environment. And the preparation method of the composite material has simple synthesis steps and mild conditions, is suitable for large-scale production, popularization and application, and has good practical prospect.
Description
Technical Field
The invention belongs to the technical field of ion selective electrodes, relates to an ion selective electrode and application thereof, and particularly relates to an all-solid-state ion selective electrode for ion detection and application thereof.
Background
Ion Selective Electrode (ISE) is a potentiometric sensor that selectively measures ion activity, and is widely used by virtue of high selectivity, no need to separate samples, and the ability to achieve real-time in situ detection and analysis. However, conventional liquid-contact ion-selective electrodes have drawbacks that it cannot overcome, such as: the reference liquid is required to be filled in, the device cannot be used for a long time, and regular maintenance is required; the electrodes must be in a vertical position when in use, and the electrode is easily influenced by temperature and has the limitation of difficult miniaturization and the like. The all-solid-state ion selective electrode (SC-ISE) uses a solid-state transfer layer to replace an internal reference electrode and an internal reference solution, and overcomes the defects. Cattrall et al first proposed the concept of an all-solid-state ion-selective electrode, using a platinum wire instead of an internal reference system and called a wire-coated electrode, but because of the small electrode contact area and capacitance, the ion-electron conversion efficiency is low, and thus the potential stability of such electrodes is poor. Furthermore, the creation of a water layer between the solid-state transition layer and the ion-selective membrane also affects the stability of the electrode potential and the lifetime of the electrode. In order to overcome these problems, researchers have attempted to use a material having good conductivity, large capacitance or capable of undergoing a redox reaction with a target ion to perform signal conversion between ions and electrons, and excellent hydrophobicity as a solid state transition layer.
Currently, a large number of solid-state ion selective electrode designs are being used with a large number of solid-state materials, such as conductive polymers, redox monolayer self-assembled active films, silver ion epoxy-based materials, prussian blue, and carbon-based materials. Although the all-solid-state ion selective electrode with the solid-state ion sensitive membrane structure can realize high-efficiency and reversible ion-electron conversion in principle, the fixed connection material is complex in preparation and time-consuming, and the mass production of the material is limited; the problem of stacking and the like easily occurs, and the characteristics such as the specific surface area of the electrode interface, the electric double layer capacitance, the conductivity and the like are affected. These problems make miniaturization, in situ, real-time, continuous monitoring, etc. of all-solid-state ion-selective electrodes challenging. The development of high-quality fixedly connected conversion layer materials, the miniaturization of all-solid-state ion selective electrodes with high selectivity, high stability and high response speed, the improvement of measurement precision and the service life of the electrodes are realized, and researchers are still required to continuously explore and innovate.
In recent years, carbon-based materials have been used as a solid material because of their strong adsorption ability, large specific surface area, wide material selection, good machinability, and high electron conductivityThe body contact layer is used for improving the stability of the all-solid-state ion selective electrode, and particularly shows wide application potential in the aspect of real-time ion monitoring in a high-pressure deep water environment. Others aquatic research institute Andrea Brand and university of Japanese Watt 2015
The crespo group used carbon nanotubes as solid ion selective electrodes of the transition layer to measure ammonium ions in the eutrophic red lake in situ. The experimental results show that: the in situ test results were consistent with those obtained from conventional lake sampling and subsequent laboratory analysis. However, the electrode has poor long-term stability, the carbon nano tube solid ion selective electrode is less than 1mV/h, the polymethyl acrylate solid ion selective electrode is less than 3.6mV/h, long-term measurement cannot be realized, and the measurement depth is very limited. In 2017, Samuel P.Kounaves group of the university of Hedera helix adopts a microporous graphite electrode to manufacture an all-solid ion selective electrode to measure the content of potassium ions in high-pressure water. In the group, polished graphite with holes is used as a working electrode substrate, a modified ion selective membrane is used as a working electrode, a gold electrode is used as a reference electrode, a high-pressure electrolytic cell is designed to be filled with high-pressure gas to simulate a seawater environment with a certain depth to measure potassium ions in water, but the used solution is a standard solution to simulate the underwater pressure of about 100m, and the difference is formed from the practical application condition.
Therefore, how to obtain a suitable all-solid-state ion-selective electrode, which solves the problems of the existing all-solid-state ion-selective electrode, and further broadens the depth and the breadth of the application thereof, has become one of the focuses of great concern of many prospective researchers in the field.
Disclosure of Invention
In view of the above, the technical problem to be solved by the present invention is to provide an ion selective electrode and an application thereof, and in particular, to an all-solid-state ion selective electrode for ion detection, which contains a multi-walled carbon nanotube/nitrogen-doped carbon composite (MWCNT/NPC) having a specific structure, and is used as a material for a fixed conversion layer to construct the all-solid-state ion selective electrode, so as to implement real-time detection of all-solid-state ions in a high-pressure deep water environment. And the preparation method has simple synthesis steps and mild conditions, is suitable for large-scale production popularization and application, and has good practical prospect.
The invention provides an ion selective electrode, which comprises a glassy carbon electrode;
the multi-walled carbon nanotube/nitrogen-doped carbon composite material film layer is compounded on the surface of the glassy carbon electrode;
and the ion selective film layer to be detected is compounded on the surface of the multi-wall carbon nano tube/nitrogen-doped carbon composite material film layer.
Preferably, the thickness of the multi-walled carbon nanotube/nitrogen-doped carbon composite material film layer is 1-100 μm;
the thickness of the ion selective film layer to be detected is 20-100 mu m;
the ion selective electrode is specifically an ion selective electrode for ion detection in a water body;
the ions to be tested comprise cations and/or anions.
Preferably, the cation comprises one or more of potassium ion, ammonium ion, sodium ion, magnesium ion and calcium ion;
the anion comprises one or more of nitrate ion, nitrite ion, sulfate ion and phosphate ion;
the ion selective electrode is specifically an ion selective electrode for ion detection in a high-pressure water body;
the pressure of the high-pressure water body is 101.3-1000 kPa;
the high pressure body of water comprises seawater.
Preferably, the multi-walled carbon nanotube/nitrogen-doped carbon composite material comprises nitrogen-doped carbon particles and multi-walled carbon nanotubes connected among the nitrogen-doped carbon particles;
the particle size of the nitrogen-doped carbon particles is 50-400 nm;
the diameter of the multi-walled carbon nanotube is 5-25 nm;
the length of the multi-walled carbon nanotube is 1-5 mu m.
Preferably, the multi-walled carbon nanotubes are connected and/or wrapped around nitrogen-doped carbon particles;
the multi-walled carbon nanotube/nitrogen-doped carbon composite material has a necklace structure;
in the nitrogen-doped carbon particles, the atomic ratio of nitrogen to carbon is 1: (10-50);
the nitrogen-doped carbon particles have a cubic morphology.
Preferably, the nitrogen-doped carbon particles can be compounded with each other;
the nitrogen-doped carbon particles are nitrogen-doped carbon particles with porous structures;
the porosity of the nitrogen-doped carbon particles is 0.5-1.2 cm3/g；
The specific surface area of the nitrogen-doped carbon particles is 600-1000 m2/g；
The mass ratio of the nitrogen-doped carbon particles to the multi-walled carbon nanotubes is 1: (1-5).
Preferably, the ion-selective electrode comprises an all-solid-state ion-selective electrode;
the ion selective electrode is used as a working electrode during ion detection;
the multi-walled carbon nanotubes comprise functionalized multi-walled carbon nanotubes;
the functionalization comprises acid functionalization modification.
Preferably, the preparation of the multi-walled carbon nanotube/nitrogen-doped carbon composite material comprises the following steps:
1) mixing the functionalized multi-walled carbon nanotube, hydrated cobalt nitrate, polyvinylpyrrolidone and a solution, and adding 2-methylimidazole for reaction to obtain an intermediate;
2) and carbonizing the intermediate obtained in the step under a protective atmosphere to obtain the multi-wall carbon nanotube/nitrogen-doped carbon composite material.
Preferably, the mass ratio of the functionalized multi-walled carbon nanotubes to the hydrated cobalt nitrate is 1: (10-50);
the mass ratio of the functionalized multi-walled carbon nanotube to the polyvinylpyrrolidone is 1: (1-20);
the mass ratio of the functionalized multi-walled carbon nanotube to the 2-methylimidazole is 1: (20-100);
the reaction time is 20-30 h;
the carbonization temperature is 500-1000 ℃;
the carbonization time is 1-5 h.
The invention also provides application of the ion selective electrode in the technical scheme in the field of ion detection in water.
The invention provides an ion selective electrode, which comprises a glassy carbon electrode; the multi-walled carbon nanotube/nitrogen-doped carbon composite material film layer is compounded on the surface of the glassy carbon electrode; and the ion selective film layer to be detected is compounded on the surface of the multi-wall carbon nano tube/nitrogen-doped carbon composite material film layer. Compared with the prior art, the invention aims at the problems that the existing fixing material for the all-solid-state ion selective electrode is complex and time-consuming in preparation, limits the large-scale production of the material, is easy to generate agglomeration and lamination and the like, and influences the defects of the specific surface area of an electrode interface, the electric double layer capacitance, the conductivity and the like; in particular, the carbon-based material has the defects of poor long-term stability, limitation to practical application conditions, poor measurement precision and poor service life.
The invention is based on the research that the solid switching layer material of the all-solid-state ion selective electrode must meet the following conditions: conversion with reversible ion signaling (ion sensitive membrane) and electron conduction (conductive substrate); has ideal non-polarizable interface (high self-switching current density); the solid-state transfer layer material should also have excellent chemical stability. In order to meet the above criteria, the solid-state transition layer material must have mixed electrochemical redox and ion self-exchange capabilities. The solid switching layer material has sufficient electrochemical redox capacity, can ensure the potential stability on the interface between the protective conductive substrate and the solid switching layer material when the measuring current flows, and the ion exchange capacity of the solid switching layer material can provide a stable equilibrium potential on the interface between the solid switching layer and the ion sensitive membrane.
The invention designs an ion selective electrode, which is a multi-walled carbon nanotube/nitrogen-doped carbon composite material with a specific structure and consists of nitrogen-doped carbon particles and multi-walled carbon nanotubes connected among the nitrogen-doped carbon particles. The MWCNT/NPC composite material is based on specific composition and internal composition structure, has the characteristics of high porosity, large specific surface area, high capacitance, good hydrophobicity and the like, is creatively used for constructing an all-solid-state ion selective electrode for the first time, ensures that the constructed MWCNT/NPC-ISE has high reliability and reproducibility, can realize in-situ and real-time monitoring of all-solid-state ions, and further realizes real-time detection of all-solid-state ions in a high-pressure deep water environment. And the preparation method of the composite material has simple synthesis steps and mild conditions, is suitable for large-scale production, popularization and application, and has good practical prospect.
Experimental results show that the all-solid-state ion selective electrode prepared on the basis of the multi-walled carbon nanotube/nitrogen-doped carbon composite material has excellent performance, and can detect various cations and anions in simulated seawater with the pressure of more than 100m and the depth of water, wherein K is+Selective electrode at 1.0 x 10-1～1.0×10-6.5The response is linear in the range of M, and the response slope is 57.4 mV/decade. NH (NH)4 +Selective electrode at 1.0 x 10-1～1.0×10-6.8The response is linear in the range of M, and the response slope is 56.2 mV/decade. NO3 -Selective electrode at 1.0 x 10-1～1.0×10-6.4M has linear response in a linear range, and the response slope is 56.9 mV/decade.
Drawings
FIG. 1 is an SEM scanning electron microscope of a multi-walled carbon nanotube/N-doped carbon composite material prepared by the present invention;
FIG. 2 is a linear graph of the dynamic response of the ion selective electrode prepared in example 1 of the present invention;
FIG. 3 is a linear comparison of the long-term dynamic response of ion-selective electrodes prepared in example 1 of the present invention;
FIG. 4 is a linear graph of the dynamic response of an ion selective electrode prepared in example 2 of the present invention;
FIG. 5 is a linear comparison of the long-term dynamic response of ion-selective electrodes prepared in example 2 of the present invention;
FIG. 6 is a linear graph of the dynamic response of an ion selective electrode prepared in example 3 of the present invention;
FIG. 7 is a linear comparison of the long-term dynamic response of ion-selective electrodes prepared in example 3 of the present invention.
Detailed Description
For a further understanding of the invention, reference will now be made to the preferred embodiments of the invention by way of example, and it is to be understood that the description is intended to further illustrate features and advantages of the invention, and not to limit the scope of the claims.
All of the starting materials of the present invention, without particular limitation as to their source, may be purchased commercially or prepared according to conventional methods well known to those skilled in the art.
The raw material used in the present invention is not particularly limited in purity, and the present invention is preferably analytical pure or pure in purity which is conventional in the field of ion selective electrode production.
All the raw materials, the marks and the acronyms thereof belong to the conventional marks and acronyms in the field, each mark and acronym is clear and definite in the field of related application, and the raw materials can be purchased from the market or prepared by a conventional method by the technical staff in the field according to the marks, the acronyms and the corresponding application.
All the processes of the invention, the abbreviations thereof belong to the common abbreviations in the art, each abbreviation is clear and definite in the field of its associated use, and the ordinary process steps thereof can be understood by those skilled in the art from the abbreviations.
The invention provides a multi-walled carbon nanotube/nitrogen-doped carbon composite material for ion detection, which comprises nitrogen-doped carbon particles and multi-walled carbon nanotubes connected among the nitrogen-doped carbon particles.
The particle size of the nitrogen-doped carbon particles is not particularly limited in principle, and can be selected and adjusted by a person skilled in the art according to actual application conditions, product requirements and specific purposes, the structure of the composite material is better guaranteed, the porosity, the specific surface area, the capacitance value, the hydrophobicity and the like are improved, the reliability and the reproducibility of the subsequent ion-selective electrode are improved, the measurement precision is improved, the service life is prolonged, and further real-time detection under a high-pressure deep water environment is realized, and the particle size of the nitrogen-doped carbon particles is preferably 50-400 nm, more preferably 100-350 nm, more preferably 150-300 nm, and more preferably 200-250 nm.
In the nitrogen-doped carbon particles, the atomic ratio of nitrogen to carbon is not particularly limited in principle, and a person skilled in the art can select and adjust the atomic ratio according to actual application conditions, product requirements and specific purposes, so that the structure of the composite material is better ensured, the porosity, the specific surface area, the capacitance value, the hydrophobicity and the like are improved, the reliability and the reproducibility of a subsequent ion selective electrode are improved, the measurement precision and the service life are prolonged, and further real-time detection in a high-pressure deep water environment is realized, wherein the atomic ratio of nitrogen to carbon in the nitrogen-doped carbon particles is preferably 1: (10 to 50), more preferably 1: (15-45), more preferably 1: (20-40), more preferably 1: (25-35), specifically may be 1: 20.
the invention has no particular limitation on the specific morphology of the nitrogen-doped carbon particles in principle, and a person skilled in the art can select and adjust the specific morphology according to the actual application condition, the product requirements and the specific application.
The invention has no particular limitation on the specific structure of the nitrogen-doped carbon particles in principle, and a person skilled in the art can select and adjust the structure according to the actual application condition, the product requirement and the specific application.
The invention has no special limitation on the connection relation among the nitrogen-doped carbon particles in principle, and a person skilled in the art can select and adjust the nitrogen-doped carbon particles according to the actual application condition, the product requirement and the specific application.
The porosity of the nitrogen-doped carbon particles is not particularly limited in principle, and can be selected and adjusted by a person skilled in the art according to actual application conditions, product requirements and specific purposes, the structure of the composite material is better ensured, the porosity, the specific surface area, the capacitance value, the hydrophobicity and the like are improved, the reliability and the reproducibility of the subsequent ion selective electrode are improved, the measurement precision and the service life are prolonged, and further the real-time detection under the high-pressure deep water environment is realized, and the porosity of the nitrogen-doped carbon particles is preferably 0.5-1.2 cm3A concentration of 0.6 to 1.1cm3A concentration of 0.7 to 1.0cm3A concentration of 0.8 to 0.9cm3/g。
The specific surface area of the nitrogen-doped carbon particles is not particularly limited in principle, and can be selected and adjusted by a person skilled in the art according to actual application conditions, product requirements and specific purposes, the structure of the composite material is better ensured, the porosity, the specific surface area, the capacitance value, the hydrophobicity and the like are improved, the reliability and the reproducibility of the subsequent ion selective electrode are improved, the measurement precision and the service life are prolonged, and further the real-time detection under the high-pressure deep water environment is realized, and the specific surface area of the nitrogen-doped carbon particles is preferably 600-1000 m2(iv)/g, more preferably 650 to 950m2(iv)/g, more preferably 700～900m2(ii)/g, more preferably 750 to 850m2/g。
The diameter of the multi-walled carbon nanotube is not particularly limited in principle, and a person skilled in the art can select and adjust the diameter according to actual application conditions, product requirements and specific purposes, so that the structure of the composite material is better guaranteed, the porosity, the specific surface area, the capacitance value, the hydrophobicity and the like are improved, the reliability and the reproducibility of the subsequent ion selective electrode are improved, the measurement precision is improved, the service life is prolonged, and further real-time detection in a high-pressure deep water environment is realized, wherein the diameter of the multi-walled carbon nanotube is preferably 5-25 nm, more preferably 9-21 nm, and more preferably 13-17 nm.
The length of the multi-walled carbon nanotube is not particularly limited in principle, and a person skilled in the art can select and adjust the length according to actual application conditions, product requirements and specific purposes, so that the structure of the composite material is better guaranteed, the porosity, the specific surface area, the capacitance value, the hydrophobicity and the like are improved, the reliability and the reproducibility of the subsequent ion selective electrode are improved, the measurement precision is improved, the service life is prolonged, and further real-time detection under a high-pressure deep water environment is realized, wherein the length of the multi-walled carbon nanotube is preferably 1-5 micrometers, more preferably 1.5-4.5 micrometers, more preferably 2-4 micrometers, and more preferably 2.5-3.5 micrometers.
The invention has no particular limitation on the selection of the multi-walled carbon nanotube in principle, and a person skilled in the art can select and adjust the multi-walled carbon nanotube according to the actual application condition, the product requirement and the specific application.
The invention has no special limitation on the combination mode of the multi-walled carbon nanotube and the nitrogen-doped carbon particle in principle, and a person skilled in the art can select and adjust the combination mode according to the actual application condition, the product requirement and the specific application.
In the invention, the mass ratio of the nitrogen-doped carbon particles to the multi-walled carbon nanotubes is not particularly limited in principle, and a person skilled in the art can select and adjust the mass ratio according to actual application conditions, product requirements and specific applications, and in order to better ensure the structure of the composite material, improve the porosity, the specific surface area, the capacitance value, the hydrophobicity and the like, improve the reliability and reproducibility of a subsequent ion-selective electrode, prolong the measurement precision and the service life, and further realize real-time detection in a high-pressure deep water environment, the mass ratio of the nitrogen-doped carbon particles to the multi-walled carbon nanotubes is preferably 1: (1-5), more preferably 1: (1.5 to 4.5), more preferably 1: (2-4), more preferably 1: (2.5-3.5).
The invention has no special limitation on the structure of the multi-walled carbon nanotube/nitrogen-doped carbon composite material in principle, and a person skilled in the art can select and adjust the structure according to the actual application condition, the product requirement and the specific application.
The invention has no particular limitation on the specific type of the ion detection in principle, and a person skilled in the art can select and adjust the ion detection according to the actual application condition, the product requirement and the specific application. More particularly, the ion detection preferably comprises ion detection in a high pressure body of water.
The pressure of the high-pressure water body is not particularly limited in principle, and a person skilled in the art can select and adjust the pressure according to the actual application condition, the product requirement and the specific application, in order to better ensure the structure of the composite material, improve the porosity, the specific surface area, the capacitance value, the hydrophobicity and the like, improve the reliability and the reproducibility of the subsequent ion selective electrode, prolong the measurement precision and the service life, and further realize the real-time detection in the high-pressure deep water environment, wherein the pressure of the high-pressure water body is preferably 101.3-1000 kPa, more preferably 300-800 kPa, and more preferably 500-600 kPa.
The invention has no special limitation on the specific type of the high-pressure water body in principle, and a person skilled in the art can select and adjust the high-pressure water body according to the actual application condition, the product requirement and the specific application.
The invention has no particular limitation on the specific selection of the ions in principle, and a person skilled in the art can select and adjust the ions according to the actual application condition, the product requirements and the specific application.
The specific selection of the cation is not particularly limited in principle, and a person skilled in the art can select and adjust the cation according to the actual application condition, the product requirement and the specific application, so that the structure of the composite material is better ensured, the porosity, the specific surface area, the capacitance value, the hydrophobicity and the like are improved, the reliability and the reproducibility of the subsequent ion selective electrode are improved, the measurement precision is improved, the service life is prolonged, and the real-time detection under the high-pressure deep water environment is further realized.
The specific selection of the anions is not particularly limited in principle, and can be selected and adjusted by a person skilled in the art according to actual application conditions, product requirements and specific applications, the structure of the composite material is better ensured, the porosity, the specific surface area, the capacitance value, the hydrophobicity and the like are improved, the reliability and the reproducibility of a subsequent ion selective electrode are improved, the measurement precision is improved, the service life is prolonged, and further real-time detection under a high-pressure deep water environment is realized.
Referring to fig. 1, fig. 1 is an SEM scanning electron microscope image of the multi-walled carbon nanotube/nitrogen-doped carbon composite material prepared by the present invention.
The invention provides a multi-walled carbon nanotube/nitrogen-doped carbon composite material, and the preparation of the multi-walled carbon nanotube/nitrogen-doped carbon composite material comprises the following steps:
1) mixing the functionalized multi-walled carbon nanotube, hydrated cobalt nitrate, polyvinylpyrrolidone and a solution, and adding 2-methylimidazole for reaction to obtain an intermediate;
2) and carbonizing the intermediate obtained in the step under a protective atmosphere to obtain the multi-wall carbon nanotube/nitrogen-doped carbon composite material.
The selection, composition and structure of the materials in the preparation method of the multi-walled carbon nanotube/nitrogen-doped carbon composite material and the corresponding preferred principle of the invention can preferably correspond to the selection, composition and structure of the materials in the multi-walled carbon nanotube/nitrogen-doped carbon composite material and the corresponding preferred principle, and are not described in detail herein.
The method comprises the steps of firstly mixing a functionalized multi-walled carbon nanotube, hydrated cobalt nitrate, polyvinylpyrrolidone and a solution, and then adding 2-methylimidazole for reaction to obtain an intermediate.
The invention has no special restriction on the mass ratio of the functionalized multi-walled carbon nanotube to the cobalt nitrate hydrate in principle, and a person skilled in the art can select and adjust the mass ratio according to the actual application condition, the product requirement and the specific application, in order to better ensure the structure of the composite material, improve the porosity, the specific surface area, the capacitance value, the hydrophobicity and the like, improve the reliability and the reproducibility of the subsequent ion selective electrode, prolong the measurement precision and the service life and further realize the real-time detection in the high-pressure deep water environment, the mass ratio of the functionalized multi-walled carbon nanotube to the cobalt nitrate hydrate is preferably 1: (10 to 50), more preferably 1: (15-45), more preferably 1: (20-40), more preferably 1: (25-35), specifically may be 1: 15.
the invention has no special restriction on the mass ratio of the functionalized multi-walled carbon nanotube to the polyvinylpyrrolidone in principle, and a person skilled in the art can select and adjust the functionalized multi-walled carbon nanotube and the polyvinylpyrrolidone according to the actual application condition, the product requirement and the specific application, and in order to better ensure the structure of the composite material, improve the porosity, the specific surface area, the capacitance value, the hydrophobicity and the like, improve the reliability and the reproducibility of the subsequent ion selective electrode, prolong the measurement precision and the service life and further realize the real-time detection in the high-pressure deep water environment, the mass ratio of the functionalized multi-walled carbon nanotube to the polyvinylpyrrolidone is preferably 1: (1-20), more preferably 1: (3-17), more preferably 1: (5-15), more preferably 1: (7-13), specifically may be 1: 8.
in the invention, the mass ratio of the functionalized multi-walled carbon nanotube to the 2-methylimidazole is not particularly limited in principle, and a person skilled in the art can select and adjust the mass ratio according to actual application conditions, product requirements and specific application, in order to better ensure the structure of the composite material, improve the porosity, the specific surface area, the capacitance value, the hydrophobicity and the like, improve the reliability and the reproducibility of a subsequent ion selective electrode, prolong the measurement precision and the service life and further realize real-time detection in a high-pressure deep water environment, the mass ratio of the functionalized multi-walled carbon nanotube to the 2-methylimidazole is preferably 1: (20 to 100), more preferably 1: (30-90), more preferably 1: (40-80), more preferably 1: (50-70), specifically, the ratio of 1: 40.
the source and the type of the functionalized multi-walled carbon nanotube are not particularly limited in principle, and the functionalized multi-walled carbon nanotube can be prepared by a modification method well known by a person skilled in the art, and the person skilled in the art can select and adjust the functionalized multi-walled carbon nanotube according to the actual application condition, the product requirement and the specific application.
The invention is a complete and detailed integral technical scheme, better ensures the structure of the composite material, improves the porosity, the specific surface area, the capacitance value, the hydrophobicity and the like, improves the reliability and the reproducibility of the subsequent ion selective electrode, prolongs the measurement precision and the service life, and further realizes the real-time detection in the high-pressure deep water environment, and the acidic functionalized modified multi-walled carbon nanotube can be prepared by the following method:
adding a multi-walled carbon nanotube (MWCNTs) material into a sulfuric acid/nitric acid mixed solution, heating for reaction, and naturally cooling to room temperature; washing to neutrality and drying.
The reaction time is not particularly limited in principle, and can be selected and adjusted by a person skilled in the art according to actual application conditions, product requirements and specific purposes, the structure of the composite material is better ensured, the porosity, the specific surface area, the capacitance value, the hydrophobicity and the like are improved, the reliability and the reproducibility of the subsequent ion selective electrode are improved, the measurement precision is prolonged, the service life is prolonged, and further real-time detection under a high-pressure deep water environment is realized, wherein the reaction time is preferably 20-30 h, more preferably 22-28 h, and more preferably 24-26 h.
The invention is a complete and refined integral preparation process, and in order to better ensure the structure of a composite material, improve the porosity, the specific surface area, the capacitance value, the hydrophobicity and the like, improve the reliability and the reproducibility of a subsequent ion selective electrode, prolong the measurement precision and the service life, and further realize the real-time detection in a high-pressure deep water environment, the step 1) is preferably as follows:
firstly, ultrasonically mixing a functionalized multi-walled carbon nanotube solution and polyvinylpyrrolidone, then adding hydrated cobalt nitrate, continuously stirring and mixing, then slowly adding a 2-methylimidazole/methanol solution, stirring again, standing for reaction, and drying to obtain an intermediate.
The specific parameters of the steps are not particularly limited in principle, and a person skilled in the art can select and adjust the specific parameters according to actual application conditions, product requirements and specific purposes, so that the structure of the composite material is better ensured, the porosity, the specific surface area, the capacitance value, the hydrophobicity and the like are improved, the reliability and the reproducibility of the subsequent ion selective electrode are improved, the measurement precision is improved, the service life is prolonged, and further the real-time detection in a high-pressure deep water environment is realized, wherein the time for the ultrasonic treatment of the multi-walled carbon nanotube and the PVP is preferably 0.5-1.5 h, more preferably 0.7-1.3 h, and more preferably 0.9-1.1 h. The time for continuously stirring and mixing is preferably 15-40 min, more preferably 19-36 min, more preferably 23-32 min, and more preferably 27-28 min. The re-stirring time is preferably 10-30 min, more preferably 14-26 min, and more preferably 18-22 min. The time of the static reaction is preferably 20-30 h, more preferably 22-28 h, and more preferably 24-26 h.
Finally, under a protective atmosphere, carbonizing the intermediate obtained in the step to obtain the multi-walled carbon nanotube/nitrogen-doped carbon composite material.
The specific selection of the protective atmosphere is not particularly limited in principle, and a person skilled in the art can select and adjust the protective atmosphere according to the actual application condition, the product requirement and the specific application.
The carbonization temperature is not particularly limited in principle, and can be selected and adjusted by a person skilled in the art according to actual application conditions, product requirements and specific application, the structure of the composite material is better ensured, the porosity, the specific surface area, the capacitance value, the hydrophobicity and the like are improved, the reliability and the reproducibility of the subsequent ion selective electrode are improved, the measurement precision is prolonged, the service life is prolonged, and further real-time detection under a high-pressure deep water environment is realized, wherein the carbonization temperature is preferably 500-1000 ℃, more preferably 600-900 ℃, and more preferably 700-800 ℃.
The carbonization time is not particularly limited in principle, and can be selected and adjusted by a person skilled in the art according to actual application conditions, product requirements and specific purposes, the structure of the composite material is better ensured, the porosity, the specific surface area, the capacitance value, the hydrophobicity and the like are improved, the reliability and the reproducibility of the subsequent ion selective electrode are improved, the measurement precision is prolonged, the service life is prolonged, and further real-time detection under a high-pressure deep water environment is realized, wherein the carbonization time is preferably 1-5 h, more preferably 1.5-4.5 h, more preferably 2-4 h, and more preferably 2.5-3.5 h.
The preparation method of the multi-walled carbon nanotube/nitrogen-doped carbon composite material for ion detection is a complete and refined integral preparation process, can preferably comprise the following steps of:
preparation of functionalized MWCNTs:
adding the MWCNTs intrinsic material into a sulfuric acid/nitric acid mixed solution for reaction, and naturally cooling to room temperature; washing to be neutral; oven dry overnight.
Preparation of multiwall carbon nanotube/nitrogen-doped carbon composite (MWCNT/NPC): sequentially adding functional MWCNTs and PVP into methanol, and carrying out ultrasonic treatment; adding Co (NO)3)2·6H2O, stirring; slowly adding 2-methylimidazole/methanol solution, stirring, standing for a period of time, and drying; under the protection of nitrogen atmosphere, after carbonization, the product is dispersed in hydrochloric acid solution, and Co and other impurities in the product are removed, so that the MWCNT/NPC composite material with the necklace structure is obtained.
The invention provides an ion selective electrode, which comprises a glassy carbon electrode;
the multi-walled carbon nanotube/nitrogen-doped carbon composite material film layer is compounded on the surface of the glassy carbon electrode;
and the ion selective film layer to be detected is compounded on the surface of the multi-wall carbon nano tube/nitrogen-doped carbon composite material film layer.
The selection, composition and structure of the materials in the multi-walled carbon nanotube/nitrogen-doped carbon composite material in the ion selective electrode and the corresponding preferred principles of the invention preferably correspond to the selection, composition and structure of the materials in the multi-walled carbon nanotube/nitrogen-doped carbon composite material or the preparation method thereof and the corresponding preferred principles, and are not described in detail herein.
The thickness of the multi-walled carbon nanotube/nitrogen-doped carbon composite material film layer is not particularly limited in principle, and can be selected and adjusted by a person skilled in the art according to actual application conditions, product requirements and specific purposes, the structure of the composite material is better ensured, the porosity, the specific surface area, the capacitance value, the hydrophobicity and the like are improved, the reliability and the reproducibility of the composite material used for the ion selective electrode are improved, the measurement precision is prolonged, the service life is prolonged, and then real-time detection under a high-pressure deep water environment is realized, and the thickness of the multi-walled carbon nanotube/nitrogen-doped carbon composite material film layer is preferably 1-100 micrometers, more preferably 20-80 micrometers, and more preferably 40-60 micrometers.
The thickness of the ion selective membrane layer to be detected is not particularly limited in principle, and can be selected and adjusted by a person skilled in the art according to actual application conditions, product requirements and specific purposes, the structure of the composite material is better guaranteed, the porosity, the specific surface area, the capacitance value, the hydrophobicity and the like are improved, the reliability and the reproducibility of the ion selective electrode are improved, the measurement precision is improved, the service life is prolonged, and further real-time detection under a high-pressure deep water environment is realized, and the thickness of the ion selective membrane layer to be detected is preferably 20-100 micrometers, more preferably 35-85 micrometers, and more preferably 50-70 micrometers.
The invention has no special limitation on the specific types of the ion selective electrode in principle, and a person skilled in the art can select and adjust the ion selective electrode according to the actual application condition, the product requirement and the specific application.
The invention has no special limitation on the specific selection of the ion selective electrode in principle, and a person skilled in the art can select and adjust the ion selective electrode according to the actual application condition, the product requirement and the specific application.
The specific application of the ion selective electrode is not particularly limited in principle, and a person skilled in the art can select and adjust the ion selective electrode according to the actual application condition, the product requirement and the specific application.
The invention has no special limitation on the specific selection of the ions to be detected in principle, and a person skilled in the art can select and adjust the ions according to the actual application condition, the product requirement and the specific application.
The invention has no particular limitation on the specific selection of cations in the ion selective electrode in principle, and a person skilled in the art can select and adjust the cations according to the actual application condition, the product requirement and the specific application.
The invention has no particular limitation on the specific selection of anions in the ion selective electrode in principle, and a person skilled in the art can select and adjust the anions according to the actual application condition, the product requirement and the specific application.
The invention has no particular limitation on the specific selection of the ion selective electrode in principle, and a person skilled in the art can select and adjust the ion selective electrode according to the actual application condition, the product requirement and the specific application.
The pressure of the high-pressure water body is not particularly limited in principle, and a person skilled in the art can select and adjust the pressure according to the actual application condition, the product requirement and the specific application, in order to better ensure the structure of the composite material, improve the porosity, the specific surface area, the capacitance value, the hydrophobicity and the like, improve the reliability and the reproducibility of the ion selective electrode, prolong the measurement precision and the service life, and further realize real-time detection in a high-pressure deep water environment, wherein the pressure of the high-pressure water body is preferably 101.3-1000 kPa, more preferably 300-800 kPa, and more preferably 500-600 kPa.
The invention has no particular limitation on the specific selection of the high-pressure water body in principle, and a person skilled in the art can select and adjust the high-pressure water body according to the actual application condition, the product requirement and the specific application.
The specific preparation of the ion selective electrode is not particularly limited in principle, and the conventional preparation process of the ion selective electrode known to those skilled in the art can be used, and those skilled in the art can select and adjust the ion selective electrode according to the actual application condition, the product requirements and the specific application, and the ion selective electrode can be prepared by the following specific preparation process of the ion selective electrode, wherein the specific preparation process of the ion selective electrode comprises the following steps:
preparation of MWCNT/NPC — ion selective electrode: polishing, cleaning and drying the glassy carbon electrode, sequentially dripping the MWCNT/NPC and the ion selective membrane to be detected on the surface of the glassy carbon electrode, and airing to prepare the MWCNT/NPC-ion selective electrode to be detected.
The invention provides an application of the multi-walled carbon nanotube/nitrogen-doped carbon composite material in any one of the technical schemes or the ion selective electrode in any one of the technical schemes in the field of ion detection in water.
The selection, composition and structure of the material or the ion selective electrode in the multiwall carbon nanotube/nitrogen-doped carbon composite material in the above application and the corresponding preferred principle of the invention can preferably correspond to the selection, composition and structure of the multiwall carbon nanotube/nitrogen-doped carbon composite material or the preparation method thereof, or the selection, composition and structure of the material in the ion selective electrode and the corresponding preferred principle, and are not described in detail herein.
The water body is not particularly limited in principle, and can be selected and adjusted by a person skilled in the art according to actual application conditions, product requirements and specific purposes, the structure of the composite material is better guaranteed, the porosity, the specific surface area, the capacitance value, the hydrophobicity and the like are improved, the reliability and the reproducibility of the electrode for ion selectivity are improved, the measurement precision is prolonged, the service life is prolonged, and then real-time detection in a high-pressure deep water environment is realized, the water body preferably comprises a high-pressure water body, and the pressure of the high-pressure water body is preferably 101.3-1000 kPa, more preferably 300-800 kPa, and more preferably 500-600 kPa. The water body may be specifically seawater.
The steps of the invention provide an all-solid-state ion selective electrode for ion detection and application of the all-solid-state ion selective electrode in detection of ionic salts in seawater. The all-solid-state ion selective electrode provided by the invention contains a multi-walled carbon nanotube/nitrogen-doped carbon composite material with a specific structure, and consists of nitrogen-doped carbon particles and multi-walled carbon nanotubes connected among the nitrogen-doped carbon particles. The MWCNT/NPC composite material is based on specific composition and internal composition structure, has the characteristics of high porosity, large specific surface area, high capacitance, good hydrophobicity and the like, is used for constructing an all-solid-state ion selective electrode as a fixedly connected conversion layer material for the first time, ensures that the constructed MWCNT/NPC-ISE has high reliability and reproducibility, can realize in-situ and real-time monitoring of all-solid-state ions, and further realizes real-time detection of all-solid-state ions in a high-pressure deep water environment. The MWCNT/NPC provided by the invention has high porosity and large specific surface area, can obviously increase the contact area between the transducer and the ion selective exchange layer, effectively reduces the interface resistance and promotes the electron transmission; the high capacitance ensures the stability of the phase connection potential; the good hydrophobicity effectively prevents the occurrence of a water layer, and ensures that the developed SC-ISE has good repeatability. Based on the high charge conversion principle, the SC-ISE constructed based on MWCNT/NPC has potential feasibility of in-situ analysis. And the preparation method of the composite material has simple synthesis steps and mild conditions, is suitable for large-scale production, popularization and application, and has good practical prospect.
Experimental results show that the all-solid-state ion selective electrode prepared on the basis of the multi-walled carbon nanotube/nitrogen-doped carbon composite material has excellent performance, and can detect various cations and anions in simulated seawater with the pressure of more than 100m and the depth of water, wherein K is+Selective electrode at 1.0 x 10-1～1.0×10-6.5The response is linear in the range of M, and the response slope is 57.4 mV/decade. NH (NH)4 +Selective electrode in 1.010-1～1.0×10-6.8The response is linear in the range of M, and the response slope is 56.2 mV/decade. NO3 -Selective electrode at 1.0 x 10-1～1.0×10-6.4M has linear response in a linear range, and the response slope is 56.9 mV/decade.
To further illustrate the present invention, an ion selective electrode and its application are described in detail below with reference to examples, but it should be understood that these examples are carried out on the premise of the technical solution of the present invention, and the detailed embodiments and specific operation procedures are given, which are only for further illustrating the features and advantages of the present invention, but not for limiting the claims of the present invention, and the scope of the present invention is not limited to the following examples.
Example 1
Preparation of functionalized MWCNTs:
adding the MWCNTs intrinsic material into a sulfuric acid/nitric acid (3:1) mixed solution, reacting for 3h at 75 ℃, and naturally cooling to room temperature; washing to be neutral; oven-dried at 60 ℃ overnight.
Preparation of MWCNT/NPC composite material:
adding 35mg of functionalized MWCNTs and 200mg of PVP into 25ml of methanol in sequence, and carrying out ultrasonic treatment for 30 min; adding 500mg Co (NO)3)2·6H2O, stirring for 1 h; slowly adding 25mL of 2-methylimidazole (1.232 g)/methanol solution, stirring for 30min, standing for 12h, and drying; carbonizing at 800 ℃ for 2h under the protection of nitrogen atmosphere; dispersing in 3M hydrochloric acid solution, removing Co and other impurities in the product, and obtaining the MWCNT/NPC composite material with necklace structure.
MWCNT/NPC-K+Preparation of ion-selective electrode:
polishing, cleaning and drying the glassy carbon electrode, and sequentially adding 1mg/mL MWCNT/NPC and K+Dropping the ion selective membrane on the surface of the glassy carbon electrode, airing, and preparing MWCNT/NPC-K+An ion selective electrode.
MWCNT/NPC-K prepared in inventive example 1+And carrying out performance detection on the ion selective electrode.
And (3) testing conditions are as follows:
open circuit potential measurements were performed using the us CHI660A electrochemical workstation. The reference electrode was a 3mm Ag | AgCl electrode (3M KCl) used after polishing, the inside of which was filled with a double external reference electrode of an electrolyte salt bridge of 1M LiAcO (lithium acetate), the parameter current was set to 0.1nA by a constant current chronopotentiometry analysis method, and the electromotive force was measured in a standing solution at room temperature (22 ± 2 ℃). Using quantitative dripping method in simulated seawater to prepare 1.0X 10-1～1.0×10-7The KCl solution of M and the low-concentration solution are both prepared by diluting the high-concentration solution by 10 times, and the test is carried out on a simulated deep sea system under the pressure of 3 MPa.
Referring to fig. 2, fig. 2 is a linear graph of the dynamic response of the ion selective electrode prepared in example 1 of the present invention.
Referring to fig. 3, fig. 3 is a linear comparison of the long-term dynamic response of the ion-selective electrode prepared in example 1 of the present invention.
As can be seen from FIGS. 2 and 3, K prepared by the present invention+Selective electrode at 1.0 x 10-1～1.0×10-6.5The response is linear in the range, and the response slope is 57.4 mV/decade. During the test period of 7 weeks, the detection limit is gradually increased, and a small amount of water layer is inevitably formed when the response slope is gradually decreased, but the detection limit is still 10-6About M. The result shows that the all-solid-state ion selective electrode based on the multi-walled carbon nanotube/nitrogen-doped carbon composite material has excellent detection performance, and can be used for detecting K in simulated seawater with the pressure of more than 100m and the water depth+The detection is carried out, and the long-term stability is better.
Example 2
Preparation of functionalized MWCNTs:
adding the MWCNTs intrinsic material into a sulfuric acid/nitric acid (3:1) mixed solution, reacting for 3h at 75 ℃, and naturally cooling to room temperature; washing to be neutral; oven-dried at 60 ℃ overnight.
Preparation of MWCNT/NPC composite material:
adding 35mg of functionalized MWCNTs and 200mg of PVP into 25ml of methanol in sequence, and carrying out ultrasonic treatment for 30 min; adding 500mg Co (NO)3)2·6H2O, stirringStirring for 1 h; slowly adding 25mL of 2-methylimidazole (1.232 g)/methanol solution, stirring for 30min, standing for 12h, and drying; carbonizing at 800 ℃ for 2h under the protection of nitrogen atmosphere; dispersing in 3M hydrochloric acid solution, removing Co and other impurities in the product, and obtaining the MWCNT/NPC composite material with necklace structure.
MWCNT/NPC-NH4 +Preparation of ion-selective electrode: polishing, cleaning and drying the glassy carbon electrode, and sequentially adding 1mg/mL MWCNT/NPC and NH4 +Dropping the ion selective membrane on the surface of the glassy carbon electrode, airing, and preparing MWCNT/NPC-NH4 +An ion selective electrode.
MWCNT/NPC-NH prepared for example 2 of the present invention4 +And carrying out performance detection on the ion selective electrode.
And (3) testing conditions are as follows:
open circuit potential measurements were performed using the us CHI660A electrochemical workstation. The reference electrode was a 3mm Ag | AgCl electrode (3M KCl) used after polishing, the inside of which was filled with a double external reference electrode of an electrolyte salt bridge of 1M LiAcO (lithium acetate), the parameter current was set to 0.1nA by a constant current chronopotentiometry analysis method, and the electromotive force was measured in a standing solution at room temperature (22 ± 2 ℃). Using quantitative dripping method in simulated seawater to prepare 1.0X 10-1～1.0×10-7NH of M4The Cl solution and the low-concentration solution are both prepared by diluting the high-concentration solution by 10 times, and the test is carried out on a simulated deep sea system under the pressure of 3 MPa.
Referring to fig. 4, fig. 4 is a linear graph of the dynamic response of the ion selective electrode prepared in example 2 of the present invention.
Referring to fig. 5, fig. 5 is a linear comparison of the long-term dynamic response of the ion-selective electrode prepared in example 2 of the present invention.
As can be seen from FIGS. 4 and 5, NH prepared according to the present invention4 +Selective electrode at 1.0 x 10-1～1.0×10-6.8The response is linear in the range of M, and the response slope is 56.2 mV/decade. Occurrence of AND K in a test period of 7 weeks+Selective electrodes are similar. This shows that the multi-wall carbon nanotube/N-doped carbon composite prepared by the inventionThe all-solid-state ion selective electrode made of the composite material has excellent detection performance, and can be used for detecting NH in simulated seawater with the pressure of more than 100m and the water depth4 +The detection is carried out, and the long-term stability is better.
Example 3
Preparation of functionalized MWCNTs:
adding the MWCNTs intrinsic material into a sulfuric acid/nitric acid (3:1) mixed solution, reacting for 3h at 75 ℃, and naturally cooling to room temperature; washing to be neutral; oven-dried at 60 ℃ overnight.
Preparation of MWCNT/NPC composite material:
adding 35mg of functionalized MWCNTs and 200mg of PVP into 25ml of methanol in sequence, and carrying out ultrasonic treatment for 30 min; adding 500mg Co (NO)3)2·6H2O, stirring for 1 h; slowly adding 25mL of 2-methylimidazole (1.232 g)/methanol solution, stirring for 30min, standing for 12h, and drying; carbonizing at 800 ℃ for 2h under the protection of nitrogen atmosphere; dispersing in 3M hydrochloric acid solution, removing Co and other impurities in the product, and obtaining the MWCNT/NPC composite material with necklace structure.
MWCNT/NPC-NO3 -Preparation of ion-selective electrode:
polishing, cleaning and drying the glassy carbon electrode, and sequentially adding 1mg/mL MWCNT/NPC and NO3 -Dropping the ion selective membrane on the surface of the glassy carbon electrode, airing and preparing MWCNT/NPC-NO3 -An ion selective electrode.
MWCNT/NPC-NO prepared for example 3 of the present invention3 -And carrying out performance detection on the ion selective electrode.
And (3) testing conditions are as follows:
open circuit potential measurements were performed using the us CHI660A electrochemical workstation. The reference electrode was a 3mm Ag | AgCl electrode (3M KCl) used after polishing, the inside of which was filled with a double external reference electrode of an electrolyte salt bridge of 1M LiAcO (lithium acetate), the parameter current was set to 0.1nA by a constant current chronopotentiometry analysis method, and the electromotive force was measured in a standing solution at room temperature (22 ± 2 ℃). Using quantitative dripping method in simulated seawater to prepare 1.0X 10-1～1.0×10-7NaNO of M3The solution and the low-concentration solution are both prepared by diluting the high-concentration solution by 10 times, and the test is carried out on a simulated deep sea system under the pressure of 3 MPa.
Referring to fig. 6, fig. 6 is a linear graph of the dynamic response of the ion selective electrode prepared in example 3 of the present invention.
Referring to fig. 7, fig. 7 is a linear comparison of the long-term dynamic response of the ion-selective electrode prepared in example 3 of the present invention.
As can be seen from FIGS. 6 and 7, NO produced by the present invention3 -Selective electrode at 1.0 x 10-1～1.0×10-6.4M has linear response in a linear range, and the response slope is 56.9 mV/decade. Response slope decline and K in 7 weeks of test time+Selective electrode and NH4 +The decrease amplitude is slightly larger than that of the selective electrode, and is related to the membrane composition of the anion selective membrane. The result shows that the all-solid-state ion selective electrode based on the multi-walled carbon nanotube/nitrogen-doped carbon composite material has excellent detection performance, and can be used for detecting NO in simulated seawater with the pressure of more than 100m and the water depth3 -The detection is carried out, and the long-term stability is better.
Having thus described in detail an all-solid-state ion-selective electrode for ion detection and applications thereof, which is in accordance with the present invention, the principles and embodiments of the present invention are explained with the aid of specific examples, which are included to assist in understanding the method and its core concepts, including the best mode, and to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. It should be noted that, for those skilled in the art, it is possible to make various improvements and modifications to the present invention without departing from the principle of the present invention, and those improvements and modifications also fall within the scope of the claims of the present invention. The scope of the invention is defined by the claims and may include other embodiments that occur to those skilled in the art. Such other embodiments are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.
Claims (10)
1. An ion selective electrode comprising a glassy carbon electrode;
the multi-walled carbon nanotube/nitrogen-doped carbon composite material film layer is compounded on the surface of the glassy carbon electrode;
and the ion selective film layer to be detected is compounded on the surface of the multi-wall carbon nano tube/nitrogen-doped carbon composite material film layer.
2. The ion-selective electrode of claim 1, wherein the multi-walled carbon nanotube/nitrogen-doped carbon composite film has a thickness of 1-100 μm;
the thickness of the ion selective film layer to be detected is 20-100 mu m;
the ion selective electrode is specifically an ion selective electrode for ion detection in a water body;
the ions to be tested comprise cations and/or anions.
3. The ion-selective electrode of claim 2, wherein the cations comprise one or more of potassium ions, ammonium ions, sodium ions, magnesium ions, and calcium ions;
the anion comprises one or more of nitrate ion, nitrite ion, sulfate ion and phosphate ion;
the ion selective electrode is specifically an ion selective electrode for ion detection in a high-pressure water body;
the pressure of the high-pressure water body is 101.3-1000 kPa;
the high pressure body of water comprises seawater.
4. The ion-selective electrode of claim 1, wherein the multi-walled carbon nanotube/nitrogen-doped carbon composite comprises nitrogen-doped carbon particles and multi-walled carbon nanotubes connected between the nitrogen-doped carbon particles;
the particle size of the nitrogen-doped carbon particles is 50-400 nm;
the diameter of the multi-walled carbon nanotube is 5-25 nm;
the length of the multi-walled carbon nanotube is 1-5 mu m.
5. The ion-selective electrode of claim 4, wherein the multi-walled carbon nanotubes are connected to and/or wrapped around nitrogen-doped carbon particles;
the multi-walled carbon nanotube/nitrogen-doped carbon composite material has a necklace structure;
in the nitrogen-doped carbon particles, the atomic ratio of nitrogen to carbon is 1: (10-50);
the nitrogen-doped carbon particles have a cubic morphology.
6. The ion-selective electrode of claim 4, wherein the nitrogen-doped carbon particles are mutually recombinable;
the nitrogen-doped carbon particles are nitrogen-doped carbon particles with porous structures;
the porosity of the nitrogen-doped carbon particles is 0.5-1.2 cm3/g；
The specific surface area of the nitrogen-doped carbon particles is 600-1000 m2/g；
The mass ratio of the nitrogen-doped carbon particles to the multi-walled carbon nanotubes is 1: (1-5).
7. The ion-selective electrode of claim 1, wherein the ion-selective electrode comprises an all-solid-state ion-selective electrode;
the ion selective electrode is used as a working electrode during ion detection;
the multi-walled carbon nanotubes comprise functionalized multi-walled carbon nanotubes;
the functionalization comprises acid functionalization modification.
8. The ion-selective electrode of claim 1, wherein the preparation of the multi-walled carbon nanotube/nitrogen-doped carbon composite comprises the steps of:
1) mixing the functionalized multi-walled carbon nanotube, hydrated cobalt nitrate, polyvinylpyrrolidone and a solution, and adding 2-methylimidazole for reaction to obtain an intermediate;
2) and carbonizing the intermediate obtained in the step under a protective atmosphere to obtain the multi-wall carbon nanotube/nitrogen-doped carbon composite material.
9. The ion-selective electrode of claim 8, wherein the mass ratio of the functionalized multi-walled carbon nanotubes to the hydrated cobalt nitrate is 1: (10-50);
the mass ratio of the functionalized multi-walled carbon nanotube to the polyvinylpyrrolidone is 1: (1-20);
the mass ratio of the functionalized multi-walled carbon nanotube to the 2-methylimidazole is 1: (20-100);
the reaction time is 20-30 h;
the carbonization temperature is 500-1000 ℃;
the carbonization time is 1-5 h.
10. Use of the ion selective electrode of any one of claims 1 to 9 in the field of ion detection in a body of water.
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