CN115389589B

CN115389589B - Solid calcium ion selective electrode and preparation method thereof

Info

Publication number: CN115389589B
Application number: CN202211065706.7A
Authority: CN
Inventors: 甘世宇; 张依容; 牛利; 钟丽杰
Original assignee: Guangzhou University
Current assignee: Guangzhou University
Priority date: 2022-09-01
Filing date: 2022-09-01
Publication date: 2025-02-21
Anticipated expiration: 2042-09-01
Also published as: CN115389589A

Abstract

The invention relates to the field of ion analysis sensors and discloses a preparation method of a solid calcium ion selective electrode, which comprises the following steps of dispersing silicon dioxide in water by ultrasonic waves, adding 4-aminoantipyrine into a silicon dioxide solution for mixing, adding ferric nitrate, carrying out ultrasonic treatment, drying and heat treatment to obtain a substance I, etching a product of the substance I in an HF solution, removing iron particles and silicon dioxide to form NMC, dispersing NMC and Nafion in an ethanol solution, carrying out ultrasonic dispersion to obtain a solution A, taking the solution A, dripping the solution A on a treated glassy carbon electrode, carrying out electrode loading of an active material by about 1mg cm ^‑2, drying to obtain an NMC-SC layer, coating Ca ²⁺ -ISM solution on the NMC-SC layer, drying to obtain the solid calcium ion selective electrode, and testing the content of Ca ²⁺ in 5 mineral water and 5 soil leaching solutions.

Description

Solid calcium ion selective electrode and preparation method thereof

Technical Field

The invention relates to the field of ion analysis sensors, in particular to a solid calcium ion selective electrode and a preparation method thereof.

Background

Ca ²⁺ is an important ion for the growth and development of organisms, and can be used as a signal molecule to regulate the absorption of ions by cells and the function of carbohydrate metabolism in organisms. Through real-time, accurate and durable monitoring of Ca ²⁺ in water quality, people can monitor whether the water quality reaches the calcium ion content required by organisms in real time. However, conventional analytical methods (such as spectroscopic analysis) measure the concentration of Ca ²⁺ off-site, which is extremely time consuming and expensive in equipment. In the last 20 years, potential sensors based on Ion Selective Membranes (ISM) have been the main means of measuring Ca ²⁺ in water due to their simple structure, small size, portability, etc., which rely mainly on Solid Contact (SC) materials for ion-to-electrode transitions.

Currently, a variety of SC materials have been developed, including Conductive Polymers (CPs), carbon-based materials, metal oxides (MO _x), molecular redox conjugates, and noble metals. Where the redox capacitance of CPs is large but is subject to interference from gases, light or pH. In recent years, noble metals have been used at high cost, and metal oxides (MO _x) have been used to replace expensive noble metal materials, but suffer from poor electrical conductivity. Carbon-based materials are the most widely used superconducting materials due to their high Electrical Double Layer (EDL) capacitance and hydrophobicity. For example, heteroatom doping and pore-forming engineering are effective methods of increasing the EDL capacitance of carbon materials, particularly in the energy storage field. Some typical carbon materials, such as porous carbon, graphene, carbon nanotubes have been used as SC materials for SC-ISEs (solid contact-ion selective electrodes). However, in the field of SC-ISEs, a guideline for improving interfacial capacitance of carbon-based SC materials is lacking, and for this reason we propose a solid-state calcium ion selective electrode and a preparation method thereof.

Disclosure of Invention

(One) solving the technical problems

Aiming at the defects of the prior art, the invention provides a solid calcium ion selective electrode and a preparation method thereof, which solve the problems.

(II) technical scheme

In order to achieve the purpose, the invention provides a technical scheme that the solid calcium ion selective electrode comprises a glassy carbon electrode with the diameter of 5mm, a solution A with the concentration of 10mg/ml and a Ca ²⁺ -ISM (calcium ion selective membrane) solution.

Solution A included 10mgNMC (nitrogen doped mesoporous carbon), 250. Mu.L Nafion, and 750. Mu.L ethanol;

The Ca ²⁺ -ISM solution included 3mL THF (tetrahydrofuran, solvent), 117.72mg PVC (polyvinyl chloride, solute ratio 32.7 wt%), 235.44mg NPOE (o-nitrophenyl octyl ether, solute ratio 65.4 wt%), 4.68mg calcium ionophore IV (solute ratio 1.3 wt%), and 2.16mg KTPFB potassium tetrakis (pentafluorophenyl) borate, solute ratio 0.6 wt%).

Preferably, the NMC comprises silica, water, 4-aminoantipyrine, and ferric nitrate.

A preparation method of a solid calcium ion selective electrode comprises the following steps:

Firstly, dispersing silicon dioxide in water by using ultrasonic waves, adding 4-aminoantipyrine into a silicon dioxide solution for mixing, adding ferric nitrate, performing ultrasonic treatment, drying and performing heat treatment to obtain a substance I;

Etching the product of the first substance in an HF solution to remove iron particles and silicon dioxide and form NMC;

Dispersing NMC and PVDF in THF solution, performing ultrasonic dispersion to obtain solution A, dripping the solution A on a treated glassy carbon electrode, wherein the electrode load of an active material is about 1mg cm ^-2, and drying to obtain an NMC-SC layer (nitrogen doped mesoporous carbon-solid contact layer);

Fourthly, coating Ca ²⁺ -ISM solution on the NMC-SC layer, and drying to obtain a solid calcium ion selective electrode;

And fifthly, testing the content of Ca ²⁺ in 5 mineral water and 5 soil leaching solutions.

Preferably, the ultrasonic treatment time in the first step is 3 hours, and the drying temperature is 85 ℃;

the heat treatment conditions were heat treatment under an argon atmosphere at 800 ℃ for 3 hours.

Preferably, the ultrasonic dispersion in the third step is carried out for 2 hours, and the drying condition is that the materials are placed in a 60 ℃ oven for drying for half an hour.

Preferably, the glassy carbon electrode treatment process in the third step is to polish the glassy carbon electrode on nylon cloth with 0.3 mu m Al ₂O₃ polishing powder, polish the glassy carbon electrode with 0.05 mu m Al ₂O₃ polishing powder after cleaning, and finally wash the glassy carbon electrode with clean water and ethanol.

Preferably, the drying time in the fourth step is 3 hours.

(III) beneficial effects

Compared with the prior art, the invention provides a solid calcium ion selective electrode and a preparation method thereof, which comprises the following steps of

The beneficial effects are that:

1. The solid-state calcium ion selective electrode taking the carbon material under the synergistic effect of the mesoporous structure and the doped nitrogen as the substrate has low water layer effect and excellent stability, and the sensor is used for detecting calcium ions in mineral water and soil leaching liquid, has the advantages of low cost, high sensitivity, high selectivity and the like, and has great application potential and commercial prospect.

2. The solid calcium ion selective electrode and the preparation method thereof construct the solid calcium ion selective electrode for the first time by adopting a carbon-based material under the synergistic effect of a mesoporous structure and N doping, and verify the concentration of calcium ions in mineral water and soil leacheate.

3. According to the solid calcium ion selective electrode and the preparation method thereof, due to the influences of a mesoporous structure and N doping, NMC has a high EDL capacitance, meanwhile, high hydrophobicity is maintained, no obvious water layer effect is observed, and high potential stability is achieved, so that guidance is provided for developing carbon-based SC-ISEs based on a synergistic effect of mesoporous and nitrogen doping.

Drawings

FIG. 1 is an X-ray diffraction diagram of NMC;

fig. 2 (a) is a schematic diagram of a scanning electron microscope of NMC;

FIG. 3 (a) is a schematic diagram of the potential response of NMC-ISEs to Ca ²⁺;

FIG. 4 (a) is a schematic diagram showing the potential contrast of NMC-ISEs electrode to target ions Ca ²⁺ and interfering ions thereof, and (b) is a schematic diagram showing the selectivity coefficient of NMC-ISEs electrode to interfering ions;

FIG. 5 (a) is a schematic diagram of water layer test of NMC-ISEs and (b) is a schematic diagram of long-term potential stability of NMC-ISEs electrode;

Fig. 6 (a) is a schematic diagram of a charge-discharge test of NMC at a current density of 0.25A g ^-1, (b) is a schematic diagram of a chronopotentiometric test based on NMC solid-state calcium ion-selective electrodes;

Fig. 7 (a) is a schematic diagram showing the comparison between the test of the calcium ion sensor constructed based on NMC electrode for mineral water and the test result of ion chromatography, and (b) is a schematic diagram showing the comparison between the test of the calcium ion sensor constructed based on NMC electrode for soil leaching liquid and the test result of ion chromatography.

Detailed Description

The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.

Referring to fig. 1-7, a method for preparing a solid calcium ion selective electrode comprises the following steps:

0.5g of silica was first dispersed in water using ultrasound. Then 0.5g of 4-aminoantipyrine was added to the silicon solution and mixed. 0.5g of ferric nitrate is added as a polymerization inducer, treated by ultrasonic for about 3 hours and dried overnight in an oven at 85 ℃. The powder was heat treated under an argon atmosphere at 800 ℃ for 3h. Finally, the product is etched in HF solution to remove iron particles and silica, forming NMC.

The microscopic morphology of NMC was a surface porous irregular lamellar structure (fig. 2 a) using Scanning Electron Microscopy (SEM) testing (fig. 2). Elemental imaging analysis indicated the presence of C and N elements and a uniform distribution (fig. 2 b).

Before using, the glassy carbon electrode is polished on nylon cloth by using 0.3 mu m Al ₂O₃ polishing powder, then polished by using 0.05 mu m Al ₂O₃ polishing powder after cleaning, and finally washed by using clear water and ethanol for several times.

All electrochemical tests were completed by Gamry electrochemical workstation and EMF6 multichannel potentiometer test.

Preparation of solid calcium ion-selective electrode by dispersing 10mgNMC and 250 μl of Nafion in 750 μl of ethanol solution, and ultrasonic dispersing for 2h at concentration of 10mg/ml. Finally, 20 mu L of the dispersion liquid is dripped on the treated glassy carbon electrode, and the electrode load of the active material is about 1mg cm ^-2. The electrode was dried in an oven at 60℃for half an hour and designated NMC-SC layer.

3ML of THF, 117.72mg of PVC (32.7 wt%), 235.44mg of NPOE (65.4 wt%), 4.68mg of calcium ionophore IV (1.3 wt%), 2.16. 2.16mg KTPFB (0.6 wt%) were prepared as Ca ²⁺ -ISM solutions. The NMC-SC layer was coated with 50. Mu.L and dried at room temperature for 3 hours.

The charge-discharge performance of NMC electrodes was tested electrochemically using a three electrode system, and the chronopotentiometric test of NMC-based calcium ion selective electrodes was shown in fig. 6. According to the calculation formula of specific capacitance C _s =i×Δt/Δv, I is the applied current density (0.25A g ^-1), Δt is the average time of charge and discharge, Δv is the potential window, and the specific capacitance is calculated to be 106.6F g ^-1. And when a current of + -1 nA is applied to the NMC-based calcium ion selective electrode, the potential drift amount is only 0.8mV, which indicates that the NMC-based calcium ion selective electrode has strong polarization resistance.

The potential response of NMC-ISEs to Ca ²⁺ was tested using an electrochemical open circuit potential test method. As shown in FIG. 3, it can be seen that the sensitivity of NMC-ISEs to Ca ²⁺ is 26.25mV dec ^-1, limit of detection 10 ^-5.5 M. The test requirement of the actual sample is met.

NMC-ISEs were tested for selectivity in response to Ca ²⁺. Using the electrochemical open circuit potential test method, the potential values in interfering ions (Na ⁺,K⁺,NH₄ ⁺ and Mg ²⁺) at 0.1M concentration were tested for the target electrode, and then the respective selectivity coefficients were calculated: (wherein E _j and E _i,Z_j and Z _i,a_j and a _i represent the potential, charge number, and ion activity of interfering ions and target ions, respectively; F is Faraday constant, R is ideal gas constant, and T is temperature). The potentials of the NMC-ISEs electrode at 0.1M interfering ions and target ions are shown in FIG. 4a, and all the potentials of the interfering ions can be seen to be below the potential of the target ions Ca ²⁺, so that the NMC-ISEs have certain selectivity to Ca ²⁺. The selectivity coefficient for each interfering ion is calculated by the selectivity coefficient formula as shown in fig. 4 b. The selectivity coefficient of Na ⁺,K⁺,NH₄ ⁺ and Mg ²⁺ is calculated to obtain logK _ij which is less than or equal to-3. This is comparable to the selectivity coefficient reported in the literature.

The hydrophobicity of the NMC electrode was tested by testing its contact angle in the inset of fig. 5a, which is up to 127.3 °, indicating good hydrophobicity. The electrodes were analyzed for aqueous layer effects and long term stability in 0.1M CaCl ₂ solution using an electrochemical open circuit potential test. The NMC-ISEs in FIG. 5a were stable in potential in 0.1M MgCl ₂ and 0.1M CaCl ₂ after two changes of solution, demonstrating good capacitance and hydrophobicity, avoiding the water layer effect. As can be seen from FIG. 5b, NMC-ISEs have a potential drift of only 66.95 + -14.54 μ V h ^-1 over a measurement period of more than 7 days, indicating that the electrode potential is stable and can be used for a long period of time.

The content of Ca ²⁺ in 5 mineral waters and 5 soil leaches was tested using NMC-based calcium ion selective electrodes. Each sample was tested by 3 individuals Ca ²⁺ -SC-ISEs. The detection results were compared with the ion chromatography test results, and the results are shown in fig. 7a and 7 b. It can be seen that the two measurements are substantially identical. The detection accuracy of the sensor to Ca ²⁺ is over 85%, which proves that the ion selective electrode has good analysis performance.

Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made therein without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.

Claims

1. The preparation method of the solid calcium ion selective electrode is characterized in that the solid calcium ion selective electrode comprises a glassy carbon electrode with the diameter of 5mm, a solution A with the concentration of 10mg/ml and a calcium ion selective membrane Ca ²⁺ -ISM solution;

solution A included 10mg of nitrogen doped mesoporous carbon NMC, 250. Mu.L of Nafion, and 750. Mu.L of ethanol;

Ca ²⁺ -ISM solution comprised 3mL tetrahydrofuran THF, 117.72mg polyvinyl chloride PVC, 235.44mg o-nitrophenyl octyl ether NPOE, 4.68mg calcium ionophore IV, and 2.16mg potassium tetrakis (pentafluorophenyl) borate KTPFB;

The NMC comprises silicon dioxide, water, 4-aminoantipyrine and ferric nitrate;

The preparation method comprises the following steps:

Dispersing NMC and Nafion in an ethanol solution, performing ultrasonic dispersion to obtain a solution A, dripping the solution A on a treated glassy carbon electrode, wherein the electrode load of an active material is 1mg cm ^-2, and drying to obtain a nitrogen-doped mesoporous carbon-solid contact layer NMC-SC layer;

and fourthly, coating Ca ²⁺ -ISM solution on the NMC-SC layer, and drying to obtain the solid calcium ion selective electrode.

2. The method for preparing a solid calcium ion selective electrode according to claim 1, wherein the ultrasonic treatment time in the first step is 3 hours, and the drying temperature is 85 ℃;

3. The method for preparing a solid calcium ion selective electrode according to claim 1, wherein the ultrasonic dispersion in the third step is carried out for 2 hours, and the drying condition is that the solid calcium ion selective electrode is placed in a 60 ℃ oven for drying for half an hour.

4. The method of claim 1, wherein the third step comprises polishing the glass carbon electrode with 0.3 μm Al ₂O₃ polishing powder on nylon cloth, cleaning, polishing with 0.05 μm Al ₂O₃ polishing powder, and washing with clear water and ethanol.

5. The method of claim 1, wherein the drying time in the fourth step is 3 hours.