Electrochemical sensor electrode for chloride ion detection and preparation method thereof

Abstract

The invention provides an electrochemical sensor electrode for detecting chloride ions in water and a preparation method of the electrochemical sensor electrode, and belongs to the technical field of electrochemical sensors. According to the electrochemical sensor electrode for detecting the chloride ions in the water, silver is plated on conductive boron-doped diamond through a magnetron sputtering method or a thermal evaporation method, then high-temperature treatment is carried out in a vacuum or inert atmosphere, and the silver nanoparticle modified boron-doped diamond electrode is obtained. The electrode has electrochemical reaction high activity and multi-site characteristics, and is beneficial to obtaining high detection sensitivity of chloride ions. The electrochemical sensor electrode provided by the invention is used as a working electrode, has good linearity in a concentration detection range of 10 mg L <-1 > to 1500 mg L <-1 >, and can realize a low detection limit of 3.6 mg L <-1 > of chloride ions. The silver nanoparticle / boron doped diamond working electrode has good stability and repeatability, and the preparation method is simple.

Description

Technical Field

[0002] The invention belongs to the technical field of electrochemical sensors, and in particular relates to a method for preparing a diamond film electrode capable of detecting chloride ions and an application of the diamond film electrode as a high-sensitivity electrochemical electrode. Background Art

[0003] Chloride ions are common ions in water environments. They are one of the effective methods for disinfecting water pollution and are used in industrial production. Chloride ions are easily polarized, which can significantly accelerate the occurrence of corrosion reactions. When the concentration is too high, it will cause great harm to human health or production equipment. High concentrations of chlorine in drinking water can cause harm to human health; excessive concentrations of chlorine in swimming pool water are harmful to human skin. Chlorine in river water can corrode bridge structures and have a negative impact on the organisms and ecological environment in the water. Chloride ions in manufacturing wastewater are highly corrosive ions that can destroy the passivation film on the surface of metals and alloys such as carbon steel, stainless steel and aluminum in pipelines, causing pitting, crevice corrosion and stress corrosion cracking of metals, which will seriously affect production and greatly increase maintenance and repair costs. Controlling the concentration of chloride ions in circulating water is of great significance for protecting equipment, extending equipment service life and saving water resources. Chloride ion concentration is an important indicator for water quality monitoring, and accurate detection of chloride ion content in water has important practical significance.

[0004] Chloride ion detection methods include colorimetry, titration, spectrophotometry, ion chromatography and electrochemical detection, among which the electrochemical method has the advantages of convenient operation, low price, high sensitivity, and real-time in-situ detection, making it an important detection method. The preparation of the working electrode in the electrochemical detection method is a very important part, but the working electrode material.

[0005] The invention patent (authorization announcement number CN109828010B) is named "Preparation method of electrochemical sensor for detecting chloride ions and its detection method". The preparation method is to ultrasonically disperse graphene oxide in deionized water as a precursor solution, and hydrothermally heat it in a reactor. After the reaction, it is placed in a low-temperature refrigerator for pre-freezing, and then dried in a freeze dryer to obtain a three-dimensional porous graphene aerogel, which is mixed with liquid paraffin to prepare an electrochemical detection working electrode. The electrode has a chloride ion detection limit of 0.2 mM and a linear range of 0.5-1000 mM, but this preparation method has the problems of long preparation time and complex process, and the structure is relatively complex and the reusability is not high.

[0006] The invention patent (publication number CN118126371A) is named "A method for preparing an electrochemical sensor membrane for online chloride ion composite sensitive detection". The disclosed preparation method is to add polyvinyl chloride, cis-1,4 polybutadiene, 2-nitrophenyl octyl ether, dioctyl phthalate, and a crosslinking agent into a stoppered flask, add tetrahydrofuran, and heat up under nitrogen protection for crosslinking reaction. Then, 3,6-di-docosanyloxy-4,5-dimethyl-o-phenylene-bis-trimethylammonium chloride is added, stirred and allowed to stand for 24 hours, and then poured into a glass sheet mold to obtain an electrochemical sensor electrode. This electrode has problems such as complex composition, poor specificity, low sensitivity, and not suitable for multiple use.

[0007] The invention patent (authorization announcement number CN112858429B) is named "Electrochemical sensor electrode for detecting chloride ions and its preparation method and application". The preparation method is to disperse multilayer graphene oxide in potassium hydroxide solution, stir it twice, freeze it, dry it, add toluene and 3-aminopropyltriethoxysilane; add silver nitrate, deionized water and NaBH 4 The nano silver amino modified reduced graphene oxide framework material is prepared, and then the dispersed liquid is dropped on the surface of the glass electrode. The electrode has the problems of complex preparation process, complex composition and poor electrode repeatability.

[0008] Conductive diamond electrodes have a wide potential window, low background current, good electrochemical stability and biocompatibility, and have been widely used in electrochemical detection and analysis of pollutants. However, diamond electrodes have a low sensitivity when detecting chloride ions in water, which affects their application in detecting chloride ions in water. It is necessary to make composite diamond electrodes to improve the detection ability of chloride ions. Summary of the invention

[0009] In order to solve the above problems, the present invention combines diamond electrodes with silver nanoparticles to improve electrode sensitivity. Silver nanoparticles have the characteristics of large specific surface area, good stability and high electrochemical activity, which can further improve electrode sensitivity and electrode stability.

[0010] The present invention proposes an electrochemical sensor electrode for chloride ion detection, which has a silver nanoparticle / boron-doped diamond (Ag / BDD) structure. The silver nanoparticles are first coated on boron-doped diamond by magnetron sputtering or thermal evaporation, and then subjected to high-temperature treatment in a vacuum or inert atmosphere to obtain an Ag / BDD structure electrode.

[0011] The technical solution adopted by the present invention is specifically as follows: 1. Preparation of boron-doped diamond (BDD); Second, the boron-doped diamond is plated with metallic silver by magnetron sputtering or thermal evaporation; 3. The sample prepared in step 2 is placed in a tube furnace in a vacuum, nitrogen or argon atmosphere at 500-800° C. for 5-20 minutes. At high temperature, the silver becomes nanoparticles to form a silver nanoparticle / boron-doped diamond structure, i.e., the electrochemical sensor electrode for chloride ion detection in water; wherein the size of the silver nanoparticles is between 100 and 500 nm, which is controlled by magnetron sputtering time, sputtering thickness, high temperature treatment temperature and time, etc.

[0012] Preferably, in step 1, the boron-doped diamond is prepared by microwave plasma chemical vapor deposition (MPCVD) or hot filament chemical vapor deposition (HFCVD); Further preferably, the specific steps of preparing the boron-doped diamond electrode by MPCVD method in step 1 are: Boron-doped diamond was grown by MPCVD method with n-type conductive silicon as substrate. The growth gases were hydrogen, methane and boron source. The boron source was liquid trimethyl borate, which was loaded into the growth chamber by hydrogen. During the growth, the gas ratio displayed by the gas flowmeter was hydrogen: methane: boron = 300:6:6 sccm. The growth pressure was 7~8 kPa, the microwave power was 350 W, and the growth time was 8~10 hours.

[0013] The specific steps of plating metallic silver on boron-doped diamond by magnetron sputtering in step 2 are as follows: Place the boron-doped diamond prepared in step 1 into a magnetron sputtering device and evacuate to 10 -4 Pa, turn on the DC sputtering power supply, the sputtering pressure is 1~2 Pa, the sputtering time is 10~20 s, and the sputtering atmosphere is argon with a flow rate of 20~50 sccm to form a silver / boron doped diamond structure.

[0014] Preferably, in step 1, before growing boron-doped diamond by MPCVD, the substrate is sanded for 5 minutes and then placed in nano-diamond powder for ultrasonic treatment for 30 minutes to increase the diamond nucleation density.

[0015] Beneficial effects of the present invention: 1. The silver nanoparticle / boron-doped diamond structure prepared by the present invention has good electrochemical activity. The large specific surface area provides more active sites for the detection of chloride ions. -1 ~1000 mg L -1 The concentration range showed good linearity, and the detection limit was 3.6 mg L -1 , and has good stability and repeatability.

[0016] 2. The electrode proposed in the present invention has low preparation cost, simple operation, wide detection linear range, low detection limit, and can be reused many times. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 (a) is the scanning electron microscope morphology of the boron-doped diamond film, and (b) is the scanning electron microscope morphology of the silver nanoparticle / boron-doped diamond structure.

[0018] Figure 2 20 mg L -1 ~1000 mg L -1 This is the conventional differential pulse voltammetry diagram of chloride ions in a concentration range.

[0019] Figure 3 This is the linear relationship curve between different concentrations of chloride ions and oxidation peak potential.

[0020] Figure 4 Evaluation of electrode stability for chloride ion solution by measuring chloride ion concentration once a day for 7 days.

[0021] Figure 5 Evaluation of electrode stability for repeated tests of 30 consecutive chloride ion measurements in chloride ion solution.

[0022] Figure 6 The electrode was rinsed 10 times with deionized water to evaluate electrode stability and repeatability. DETAILED DESCRIPTION

[0024] The technical solution adopted by the present invention is further described in detail in the form of specific embodiments in conjunction with the accompanying drawings. It should be pointed out that the embodiments given below are only preferred embodiments intended to facilitate the understanding of the technical solution and do not have any limiting effect on it.

[0025] Example 1: Preparation of BDD film 1×1cm 2 The n-type silicon was used as the substrate, and the boron-doped diamond was grown by MPCVD. Before growth, the silicon wafer was polished on sandpaper for 5 minutes, then placed in diamond powder for ultrasonic treatment for 30 minutes, and finally cleaned with acetone, alcohol and deionized water in sequence. During growth, the pressure was controlled at 7~8kPa, the microwave power was 350W, the growth time was 10 hours, the gas flow rate was 300 sccm of hydrogen, 6 sccm of methane, and 6 sccm of trimethyl borate. Boron doping was produced by hydrogen as a carrier gas carrying liquid boron source trimethyl borate. The prepared BDD film has dense grains, and the exposed surfaces are mostly (111) and (100) planes (see Figure 1 (a)).

[0026] Example 2: Preparation of silver / boron doped diamond film The boron-doped diamond film prepared in Example 1 was placed in a DC magnetron sputtering device and evacuated to 10 - 4Pa, fill with 40 sccm of argon, maintain the sputtering pressure at 2 Pa, start the sputtering and prepare for sputtering. The sputtering time is 20 s to obtain a silver film of a certain thickness.

[0027] Example 3: Preparation of Ag / BDD structure electrode The silver nanoparticle / boron-doped diamond film prepared in Example 2 was placed in a tube furnace, argon or nitrogen was introduced into the tube furnace, and the annealing temperature was 800°C for 10 minutes. After high temperature treatment, the metal silver film formed silver nanoparticles with an average size of 250 nm (see Figure 1 (b) ) to obtain an electrochemical sensor electrode for chloride ion detection in water.

[0028] Example 4: The prepared electrode was used for chloride ion electrochemical testing.

[0029] Conventional differential pulse voltammetry was used to detect chloride ions. The working electrode was the silver nanoparticle / boron-doped diamond structure prepared in Example 3, the counter electrode was a platinum electrode, and the reference electrode was Ag / AgCl. 0.1 mol L -1 Phosphate buffer solution with pH=6.0 was used as the electrolyte solution in electrochemical detection to detect chloride ions of different concentrations (see Figure 2 In the potential window of -0.1 to 0.4 V, Ag nanoparticles are electrochemically oxidized to Ag + , in Cl - AgCl is formed when the concentration of ions increases. The oxidation peak potential moves toward the negative potential as the concentration increases. Figure 3 The linear relationship between chloride ion concentration and peak potential was fitted. -1 ~1000 mg L -1 Within the linear range of concentration, the detection limit of chloride ion was calculated to be 3.6 mg L based on the three-fold signal-to-noise ratio. -1 .

[0030] For comparison, the present invention also selected a BDD electrode without silver plating to perform the same test. Within the above chloride ion detection range, no oxidation peak was observed, and it was difficult to detect chloride ions in the solution.

[0031] Example 5: Repeatability and stability test of silver nanoparticles / / boron-doped diamond structure for detecting chloride ions Silver nanoparticle / boron-doped diamond structure electrode detects concentration of 100 mg L -1 The electrode was tested once a day in a chloride ion aqueous solution for 1 week (7 days). After each measurement and before the next measurement, it was rinsed with deionized water. The stability of the electrode was evaluated by recording the conventional differential pulse peak signal of the electrode. The peak potential response ranged from 100% to 93.4%, indicating that the electrode has good stability (see Figure 4We used a concentration of 100 mg L -1 The silver nanoparticle / boron-doped diamond electrode has good stability in electrochemical detection. The results show that the composite electrode Ag / BDD has a good stability in the 30th and 1st tests for chloride ion detection. - The response was within 96.7% (see Figure 5 The same electrode was rinsed with deionized water 10 times and then measured with aqueous chloride ion solution. The peak potential response of the electrode after each rinse was between 95.8% and 101.6% (see Figure 6 ), further demonstrating the stability and repeatability of the electrode.

[0032] Example 6: Sampling of actual chloride-containing industrial water from an industrial plant was used to detect the chloride ion concentration therein. The results detected by the electrode and method of the present invention were similar to the concentration value detected by the factory using the titration method, with a deviation within 5%, indicating the accuracy and practicality of the electrode and method of the present invention.

Claims

1. An electrochemical sensor electrode for chloride ion detection, characterized in that: The electrode is a silver nanoparticle / boron-doped diamond structure. The silver nanoparticles are first coated on boron-doped diamond by magnetron sputtering or thermal evaporation, and then treated at high temperature in vacuum or inert atmosphere to obtain the silver nanoparticle / boron-doped diamond structure electrode.

2. The method for preparing an electrochemical sensor electrode for chloride ion detection according to claim 1, characterized in that: The specific steps of this method are as follows:

1. Preparation of boron-doped diamond; 2. Plating metallic silver on boron-doped diamond by magnetron sputtering or thermal evaporation; 3. The sample prepared in step 2 is placed in a tube furnace in a vacuum, nitrogen or argon atmosphere, and subjected to high temperature treatment at 500-800°C for 5-20 minutes. At high temperature, the silver becomes nanoparticles to form a silver nanoparticle / boron-doped diamond structure, i.e., the working electrode of the electrochemical sensor for detecting chloride ions in water; wherein the size of the silver nanoparticles is between 100 and 500 nm, and is controlled by the magnetron sputtering time, sputtering thickness, high temperature treatment temperature and time.

3. The method for preparing an electrochemical sensor electrode for chloride ion detection according to claim 2, characterized in that: Step 1: Prepare boron-doped diamond by microwave plasma chemical vapor deposition or hot wire chemical vapor deposition.

4. The method for preparing an electrochemical sensor electrode for chloride ion detection according to claim 3, characterized in that: The specific steps of preparing the boron-doped diamond electrode by microwave plasma chemical vapor deposition in step 1 are as follows: Boron-doped diamond was grown using microwave plasma chemical vapor deposition with n-type silicon as substrate. The growth gases were hydrogen, methane and a boron source. The boron source was liquid trimethyl borate, which was loaded into the growth chamber by hydrogen. During the growth, the gas ratio displayed by the gas flow meter was hydrogen: methane: boron = 300:6:6 sccm. The growth pressure was 7-8 kPa, the microwave power was 350 W, and the growth time was 8-10 hours.

5. The method for preparing an electrochemical sensor electrode for chloride ion detection according to claim 4, characterized in that: In step 1, before growing boron-doped diamond by microwave plasma chemical vapor deposition, the substrate was polished with sandpaper for 5 minutes and then placed in nano-diamond powder for ultrasonic treatment for 30 minutes.

6. The method for preparing an electrochemical sensor electrode for chloride ion detection according to claim 2, characterized in that: The specific steps of plating metallic silver on boron-doped diamond by magnetron sputtering in step 2 are as follows: Place the boron-doped diamond prepared in step 1 into a magnetron sputtering device and evacuate to 10 -4 Pa, turn on the DC sputtering power supply, the sputtering pressure is 1~2 Pa, the sputtering time is 10~20 s, the sputtering atmosphere is argon with a flow rate of 20~50 sccm, and a silver film is formed on the surface of boron-doped diamond.

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