A sensitive electrode for direct electrochemical detection of copper ions in water and a preparation method thereof

Abstract

A sensitive electrode for direct electrochemical detection of copper ions in water and a preparation method thereof belong to the field of electrochemical sensing technology. The present invention first cleans the stainless steel mesh, then uses a mixed solution of sodium tungstate, perchloric acid and hydrogen peroxide as a deposition liquid, uses the stainless steel mesh as a working electrode, a platinum sheet as a counter electrode, and an Ag / AgCl electrode as a reference electrode to perform electrochemical deposition; after the deposition is completed, tungsten oxide is obtained on the surface of the working electrode, and after cleaning, the sensitive electrode for direct electrochemical detection of copper ions in water described in the present invention is obtained, and then the sensitive electrode is used as a copper ion sensitive electrode to perform a sensitive performance test on copper ions in water. The present invention successfully prepares a sensitive electrode for electrochemical detection of copper ions through electrochemical technology, which has the characteristics of direct and high efficiency, and has good electrochemical detection ability, high sensitivity, a wide linear detection range and a low detection limit, and also has the advantages of good stability and good repeatability.

Description

Technical Field

[0001] The invention belongs to the technical field of electrochemical sensing, and in particular relates to a sensitive electrode for direct electrochemical detection of copper ions in water and a preparation method thereof. Background Art

[0002] Copper ion (Cu 2+ ) is an indispensable trace element for the human body. It plays an important role in the physiological process of biological organisms and is beneficial to the growth, development and metabolism of the human body. However, copper ions are non-biodegradable and can be enriched thousands of times under the biomagnification of the food chain and finally enter the human body. Excessive accumulation of copper ions can cause overactivity of adrenal cortex hormones, allergies, anemia, hair loss, arthritis, autism, cystic fibrosis, diabetes, bleeding and kidney disease. Therefore, it is very important to achieve rapid, trace, accurate and highly selective on-site detection of copper ions in water.

[0003] Currently, there are many methods for copper ion detection, which can be divided into two types. One is the traditional laboratory method, such as atomic absorption spectroscopy, ICP-MS, etc. This method can provide higher detection sensitivity, better selectivity and accurate detection results, but the instrument is expensive, large in size, long in detection time and complicated in operation; the other is on-site rapid analysis, such as colorimetry and electrochemical methods. Among them, the colorimetry method is cheap and has a fast detection speed, but the detection sensitivity, selectivity and accuracy are relatively poor. Summary of the invention

[0004] The object of the present invention is to provide a sensitive electrode for direct electrochemical detection of copper ions in water and a preparation method thereof.

[0005] The present invention grows tungsten oxide on a stainless steel mesh current collector by an in-situ growth method through an electrochemical deposition method, prepares a tungsten oxide sensitive electrode supported by a stainless steel mesh, and uses it for rapid and direct electrochemical detection of copper ions in water. The electrode has the advantages of simple preparation process, good stability, strong detection ability, and environmental friendliness.

[0006] The method for preparing a sensitive electrode for direct electrochemical detection of copper ions in water according to the present invention comprises the following steps:

[0007] (1) Clean the stainless steel mesh;

[0008] (2) electrochemical deposition is performed using the stainless steel mesh obtained in step (1) as a working electrode, a platinum sheet as a counter electrode, and an Ag / AgCl electrode as a reference electrode; the deposition liquid is a mixture of an aqueous sodium tungstate solution, an aqueous perchloric acid solution, and an aqueous hydrogen peroxide solution; after the deposition is completed, tungsten oxide is obtained on the surface of the stainless steel mesh, and after cleaning, a sensitive electrode (WO 20 ) for direct electrochemical detection of copper ions in water according to the present invention is obtained.3 -SSM).

[0009] (3) Using an electrochemical workstation, WO 3 -SSM was used as the working electrode, platinum sheet (1.0 cm × 1.0 cm) was used as the counter electrode, and saturated calomel electrode (SCE) was used as the reference electrode. 2+ Phosphate buffered saline solution was used as the electrolyte (hereinafter referred to as Cu 2+ solution), using differential pulse stripping voltammetry (DPASV), using the sensitive electrode obtained in step (2) to detect copper ions in water, and obtaining the sensitive electrode in Cu 2+ The differential pulse voltammetry test curve (DPV) in the solution and the dissolution peak current intensity of the test curve are calculated according to the Cu 2+ The standard curve was drawn by comparing the concentration and the corresponding dissolution peak current intensity.

[0010] Preferably, the stainless steel selected in step (1) is 400-1000 mesh;

[0011] Preferably, in the step (1) of cleaning the stainless steel mesh, the reagent used is one or more of toluene, acetone and ethanol;

[0012] Preferably, in the step (1) of cleaning the stainless steel mesh, the cleaning time of each reagent is 10 to 15 minutes, and finally the cleaning process is terminated by rinsing with deionized water;

[0013] Preferably, the concentration of the sodium tungstate aqueous solution used in the deposition liquid in step (2) is 0.04-0.06M, the mass fraction of the perchloric acid aqueous solution is 70%-72%, the mass fraction of the hydrogen peroxide aqueous solution is 30%, and the volume ratio of the three solutions is 80-120:2-4:1-2.

[0014] Preferably, the electrochemical deposition in step (2) can be constant potential deposition, with a potential of -0.6 to -0.8 V (vs. SCE) and a deposition time of 120 to 960 s.

[0015] Preferably, the electrochemical deposition in step (2) can be pulsed electrochemical deposition. In one deposition cycle, the maintenance time of the -0.6 to -0.8 V square wave pulse is 0.1 to 0.3 s, and the maintenance time of the 0 V square wave is 0.1 to 0.3 s; 1200 to 9600 deposition cycles are required.

[0016] Preferably, the electrochemical deposition in step (2) can be pulsed electrochemical deposition. In one deposition cycle, the maintenance time of the -0.6 to -0.8 V square wave pulse is 0.1 to 0.3 s, the maintenance time of the 0 V square wave is 0.1 to 0.3 s, and the open circuit voltage is maintained for 0.2 to 1.4 s; 1200 to 7200 cycles are required; wherein the open circuit voltage is measured in advance by the OCPT test of the electrochemical workstation.

[0017] Preferably, the electrolyte in step (3) is a 0.1-0.3M phosphate buffered saline solution and a Cu 2+ A mixture of aqueous solutions; wherein the pH value of the phosphate buffered saline solution is 4.5-5.5.

[0018] The sensitive electrode for direct electrochemical detection of copper ions in water described in the present invention is prepared by the above method.

[0019] The sensitive electrode for direct electrochemical detection of copper ions in water prepared by the present invention has the following advantages:

[0020] 1) The stainless steel mesh used in the present invention has the advantages of acid and alkali resistance, and can meet the test of copper ions in solutions under different pH conditions; 2) A self-supporting electrode is constructed in the present invention, which eliminates the spraying / coating process of sensitive materials and makes the electrode have better stability; 3) The present invention adopts pulse electrodeposition to grow tungsten oxide in situ, forming a porous nano-interconnected structure, which increases the contact area between the electrode and the electrolyte and can adsorb more copper ions. The present invention successfully prepares a sensitive electrode for electrochemical detection of copper ions through electrochemical technology, which has the characteristics of direct and high efficiency, and has good electrochemical detection ability, high sensitivity, wide linear detection range and low detection limit, and also has the advantages of good stability and good repeatability. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 : Stainless steel mesh, tungsten oxide (WO) supported by stainless steel mesh prepared in Example 1, Example 2 and Example 3 3 -SSM) scanning electron microscope photos of sensitive electrodes: (a) stainless steel mesh, (b) WO deposited at constant potential 3 -SSM sensitive electrode, (c) WO deposited by pulse potential without open circuit voltage 3 -SSM sensitive electrode, (d) WO deposited by pulse potential with open circuit voltage 3 -SSM sensitive electrode; a 2 , b 2 、c 2 d 2 They are respectively a 1 , b 1 、c 1 d1 A magnified version of Fig.

[0022] Figure 2 : Tungsten oxide (WO) supported by stainless steel mesh prepared in Example 1, Example 2 and Example 3 3 -SSM) sensitive electrode at 5 μM Cu 2+ Differential pulse voltammetry test curve (DPV) in solution; the horizontal axis is the dissolution potential and the vertical axis is the response current.

[0023] Figure 3 : Tungsten oxide (WO) supported by stainless steel mesh prepared in Example 1, Example 4, Example 5, Example 6 and Example 7 3 SEM images of the sensitive electrode: (a) WO deposited by a pulse potential with an open circuit voltage maintained for 0.2 s 3 -SSM sensitive electrode, (b) WO deposited by pulse potential with open circuit voltage maintained for 0.5s 3 -SSM sensitive electrode, (c) WO deposited by pulse potential with open circuit voltage maintained for 0.8s 3 -SSM sensitive electrode, (d) WO deposited by pulse potential with open circuit voltage maintained for 1.1s 3 -SSM sensitive electrode, (e) WO deposited by pulse potential with open circuit voltage maintained for 1.4s 3 -SSM sensitive electrode; a 2 、b 2 、c 2 d 2 、e 2 They are respectively 1 、b 1 、c 1 d 1 、e 1 A magnified version of Fig.

[0024] Figure 4 WO prepared in Example 1, Example 4, Example 5, Example 6 and Example 7 3 -SSM electrode at 5 μM Cu 2+ Differential pulse voltammetry test curve (DPV) in solution; the horizontal axis is the dissolution potential and the vertical axis is the response current.

[0025] Figure 5 :(a) WO prepared in Example 1 3 -SSM sensitive electrode in different concentrations (100nM~20μM) of Cu 2+ Differential pulse voltammetry test curve (DPV) in solution; (b) is the test curve (DPV) dissolution peak current with Cu 2+ Two-segment linear standard curve of concentration changes.

[0026] Figure 6 :(a) WO prepared in Example 1 3 -Anti-interference test diagram of SSM sensitive electrode; (b) the same WO 3 -SSM sensitive electrode at 5 μM Cu 2+ Comparison of the results of 7 consecutive DPASV tests in solution; (c) the same WO 3 -SSM sensitive electrode in 5μM Cu at different days within 14 days 2+ Comparison of DPASV test results in solution. The vertical axis is the peak current of dissolution.

[0027] like Figure 1 As shown in the figure, the stainless steel mesh has a relatively smooth surface (a); after constant potential deposition, a dense tungsten oxide layer grows on the SSM surface (b); WO prepared by pulse electrodeposition 3 -SSM sensitive electrode can clearly see 80-100nm thick flake tungsten oxide loosely distributed on the SSM (c); after the introduction of open circuit voltage, it can be seen that the tungsten oxide is rod-like in shape and staggered to form a nanoscale interconnected grid structure (b).

[0028] like Figure 2 As shown, WO prepared in Example 1, Example 2 and Example 3 3 -SSM sensitive electrode to 5μM Cu 2+ All of them responded to the pulse potential deposited by the open circuit voltage. 3 - SSM responded best (Example 1).

[0029] like Figure 3 As shown in the figure, it can be seen that the interval time of maintaining the open circuit voltage has an effect on WO 3 -SSM sensitive electrode morphology. As the interval time increases, the number of flake tungsten oxide gradually decreases. When the interval time is 1.1s, there is no large-sized flake tungsten oxide; when the interval time is 1.4s, WO 3 Aggregation occurs and clusters are formed.

[0030] like Figure 4 As shown, WO prepared in Example 1, Example 4, Example 5, Example 6 and Example 7 3 -SSM electrode for 5 μM Cu 2+ All of them responded, and the open circuit voltage was maintained for 1.1s of pulse potential deposition of WO 3 -SSM has the best response (Example 1). Example 4 has a better response than Example 2, and Examples 5, 6 and 7 have better responses than Examples 2 and 3.

[0031] like Figure 5As shown in the DPV curve, it can be seen that the peak current of the dissolution between -0.30V and 0.20V increases with the Cu 2+ The peak current of DPV curve increases with the increase of Cu concentration (a); 2+ The concentration increases and presents a two-stage linear change relationship (b). 2+ When the solution is tested, the peak current of the DPV curve can be obtained under the same test conditions. Using this linear change relationship, the Cu 2+ concentration.

[0032] like Figure 6 As shown, common cations have a strong affinity for Cu 2+ The current effect during the detection process is small (at 5μM Cu 2+ When other cations with a concentration of 5 μM were added to the solution, the peak current of the dissolution was kept above 80% of that of the blank group (a); 3 -SSM sensitive electrode was tested 7 times, and the relative standard deviation of the peak current was 3.90% (b); the same WO 3 -The test results of the SSM sensitive electrode placed in deionized water at room temperature for different days within 2 weeks show that the relative standard deviation of the dissolution peak current is 3.26% (c). DETAILED DESCRIPTION

[0033] Example 1

[0034] The preparation method of the sensitive electrode suitable for electrochemical copper ion detection is as follows:

[0035] a) Cut the stainless steel mesh (SSM, 500 mesh) into 1.0 cm × 2.0 cm size, and ultrasonically clean it with toluene, acetone and ethanol respectively, and finally with deionized water. Each ultrasonic cleaning time is 10 minutes;

[0036] b) Add 1.6 mL of 70% by mass perchloric acid aqueous solution and 0.52 mL of 30% by mass hydrogen peroxide aqueous solution to 50 mL of 0.05 M sodium tungstate aqueous solution as a deposition solution;

[0037] c) A three-electrode system was used, with the stainless steel mesh treated in step a) as the working electrode, the platinum sheet (1.0 cm×1.0 cm) as the counter electrode, and the Ag / AgCl electrode as the reference electrode; pulse electrodeposition was used to deposit tungsten oxide. In one deposition cycle, the -0.7V square wave pulse was maintained for 0.1s, the 0V square wave was maintained for 0.3s, and the open circuit voltage was maintained for 1.1s. The complete material preparation required 2400 cycles, and the total deposition time was 3600s. The obtained tungsten oxide (WO ) supported by the stainless steel mesh was deposited. 3-SSM) sensitive electrode was rinsed with deionized water and then used.

[0038] d) You will get WO 3 -SSM sensitive electrode for electrochemical copper ion detection test, similarly, a three-electrode system, namely WO 3 -SSM was used as the working electrode, platinum sheet (1.0 cm × 1.0 cm) was used as the counter electrode, and saturated calomel electrode (SCE) was used as the reference electrode. 2+ The electrolyte was 0.1 M phosphate buffered saline with a pH of 5.0, and the test was performed by differential pulse voltammetric stripping (DPASV). The potential range was -0.3 V to 0.2 V (vs. SCE). Before the DPV test, the electrode was activated by cyclic voltammetry in 0.1 M phosphate buffered saline with a pH of 5.0, and the potential range was -1 V to 0 V (vs. SCE). The number of cycles was 30, and the scan rate was 50 mv s -1 The experimental results show that the electrode prepared by the method of the present invention has good conductivity for 100nM to 10μM Cu 2+ The sensitivity of detection (sensitivity is based on Cu 2+ The linearity of the standard curve drawn from the concentration and the corresponding peak current intensity is 14.113 μA μM -1 cm -2 , for 10μM~20μM Cu 2+ The detection sensitivity is 4.7356μA μM -1 cm -2 , when signal / noise = 3 (S / N = 3), the detection limit (LOD = 3σ / S, σ is the standard deviation, S is the sensitivity) is 27.48 nM (such as Figure 5 In addition, the sensitive electrode prepared in this embodiment has good selectivity, repeatability and stability (as shown in Figure 6 The DPV curve dissolution peak of the sensitive electrode prepared in this embodiment for detecting 5 μM copper ions is 110.71 μA cm -2 (like Figure 2 shown).

[0039] Example 2

[0040] a) The cleaning process of the stainless steel mesh is the same as in Example 1;

[0041] b) the deposition liquid is configured as in Example 1;

[0042] c) A three-electrode system was used, with the stainless steel mesh treated in process a) as the working electrode, the platinum sheet (1.0 cm × 1.0 cm) as the counter electrode, and the saturated silver-silver chloride electrode as the reference electrode. The tungsten oxide was deposited by constant potential deposition, with a potential of -0.7 V (vs. SCE) and a deposition time of 240 s. 3 -The SSM sensitive electrode was rinsed with deionized water and then used.

[0043] d) The test process is the same as in Example 1. The test results show that: 3 The dissolution peak of the SSM sensitive electrode for 5 μM copper ions is 43.16 μA cm -2 (like Figure 2 shown).

[0044] Example 3

[0045] a) The cleaning process of the stainless steel mesh is the same as in Example 1;

[0046] b) the deposition liquid is configured as in Example 1;

[0047] c) A three-electrode system was used, with the stainless steel mesh treated in process a) as the working electrode, the platinum sheet (1.0 cm × 1.0 cm) as the counter electrode, and the saturated silver-silver chloride electrode as the reference electrode. The pulse electrodeposition method was used to deposit tungsten oxide. In one deposition cycle, the -0.7V square wave pulse was maintained for 0.1s, and the 0V square wave was maintained for 0.3s. The complete material preparation required 2400 cycles, and the total deposition time was 960s. The obtained WO 3 -The SSM sensitive electrode was rinsed with deionized water and then used.

[0048] d) The test process is the same as in Example 1. The test results show that: 3 -The dissolution peak of the SSM sensitive electrode for 5 μM copper ions is 66.08 μA cm -2 (like Figure 2 shown).

[0049] Example 4

[0050] a) The cleaning process of the stainless steel mesh is the same as in Example 1;

[0051] b) the deposition liquid is configured as in Example 1;

[0052] c) A three-electrode system was used, with the stainless steel mesh treated in process a) as the working electrode, the platinum sheet (1.0 cm × 1.0 cm) as the counter electrode, and the saturated silver-silver chloride electrode as the reference electrode. The pulse electrodeposition method was used to deposit tungsten oxide. In one deposition cycle, the -0.7V square wave pulse was maintained for 0.1s, the 0V square wave was maintained for 0.3s, and the open circuit voltage was maintained for 0.2s. The complete material preparation required 2400 cycles, and the total deposition time was 1440s. The obtained WO 3 -The SSM sensitive electrode was rinsed with deionized water and then used.

[0053] d) The test process is the same as in Example 1. The test results show that: 3 -The dissolution peak of the SSM sensitive electrode for 5 μM copper ions is 50.01 μA cm -2 (like Figure 4 shown).

[0054] Example 5

[0055] a) The cleaning process of the stainless steel mesh is the same as in Example 1;

[0056] b) the deposition liquid is configured as in Example 1;

[0057] c) A three-electrode system was used, with the stainless steel mesh treated in process a) as the working electrode, the platinum sheet (1.0 cm × 1.0 cm) as the counter electrode, and the saturated silver-silver chloride electrode as the reference electrode. The pulse electrodeposition method was used to deposit tungsten oxide. In one deposition cycle, the -0.7V square wave pulse was maintained for 0.1s, the 0V square wave was maintained for 0.3s, and the open circuit voltage was maintained for 0.5s. The complete material preparation required 2400 cycles, and the total deposition time was 2160s. The obtained WO 3 -The SSM sensitive electrode was rinsed with deionized water and then used.

[0058] d) The test process is the same as in Example 1. The test results show that: 3 -The dissolution peak of the SSM sensitive electrode for 5 μM copper ions is 72.49 μA cm -2 (like Figure 4 shown).

[0059] Example 6

[0060] a) The cleaning process of the stainless steel mesh is the same as in Example 1;

[0061] b) the deposition liquid is configured as in Example 1;

[0062] c) A three-electrode system was used, with the stainless steel mesh treated in process a) as the working electrode, the platinum sheet (1.0 cm × 1.0 cm) as the counter electrode, and the saturated silver-silver chloride electrode as the reference electrode. The pulse electrodeposition method was used to deposit tungsten oxide. In one deposition cycle, the -0.7V square wave pulse was maintained for 0.1s, the 0V square wave was maintained for 0.3s, and the open circuit voltage was maintained for 0.8s. The complete material preparation required 2400 cycles, and the total deposition time was 2880s. The obtained WO 3 -The SSM sensitive electrode was rinsed with deionized water and then used.

[0063] d) The test process is the same as in Example 1. The test results show that: 3 -The dissolution peak of the SSM sensitive electrode for 5 μM copper ions is 100.90 μA cm -2 (like Figure 4 shown).

[0064] Example 7

[0065] a) The cleaning process of the stainless steel mesh is the same as in Example 1;

[0066] b) the deposition liquid is configured as in Example 1;

[0067] c) A three-electrode system was used, with the stainless steel mesh treated in process a) as the working electrode, the platinum sheet (1.0 cm × 1.0 cm) as the counter electrode, and the saturated silver-silver chloride electrode as the reference electrode. The pulse electrodeposition method was used to deposit tungsten oxide. In one deposition cycle, the -0.7V square wave pulse was maintained for 0.1s, the 0V square wave was maintained for 0.3s, and the open circuit voltage was maintained for 1.4s. The complete material preparation required 2400 cycles, and the total deposition time was 4320s. The obtained WO 3 -The SSM sensitive electrode was rinsed with deionized water and then used.

[0068] d) The test process is the same as in Example 1. The test results show that: 3 The dissolution peak of the SSM sensitive electrode for 5 μM copper ions is 96.39 μA cm -2 (like Figure 4 shown).

Claims

1. A method for preparing a sensitive electrode for direct electrochemical detection of copper ions in water, the steps of which are as follows: (1) Clean the stainless steel mesh; (2) electrochemical deposition is performed using the stainless steel mesh obtained in step (1) as a working electrode, a platinum sheet as a counter electrode, and an Ag / AgCl electrode as a reference electrode; the deposition liquid is a mixture of an aqueous sodium tungstate solution, an aqueous perchloric acid solution, and an aqueous hydrogen peroxide solution; after the deposition is completed, tungsten oxide is obtained on the surface of the stainless steel mesh, and after cleaning, the sensitive electrode WO for direct electrochemical detection of copper ions in water is obtained. 3 -SSM.

2. A method for preparing a sensitive electrode for direct electrochemical detection of copper ions in water as claimed in claim 1, Features: In step (1), the stainless steel mesh has a mesh size of 400 to 1000.

3. A method for preparing a sensitive electrode for direct electrochemical detection of copper ions in water as claimed in claim 1, Features: In the step (1) of cleaning the stainless steel mesh, the reagent used is one or more of toluene, acetone and ethanol.

4. A method for preparing a sensitive electrode for direct electrochemical detection of copper ions in water as claimed in claim 1, Features: During the cleaning process of step (1) the stainless steel mesh, the cleaning time of each reagent is 10 to 15 minutes, and finally the cleaning process is terminated by rinsing with deionized water.

5. A method for preparing a sensitive electrode for direct electrochemical detection of copper ions in water as claimed in claim 1, Features: The concentration of the sodium tungstate aqueous solution used in the deposition liquid in step (2) is 0.04-0.06M, the mass fraction of the perchloric acid aqueous solution is 70%-72%, the mass fraction of the hydrogen peroxide aqueous solution is 30%, and the volume ratio of the three solutions is 80-120:2-4:1-2.

6. A method for preparing a sensitive electrode for direct electrochemical detection of copper ions in water as claimed in claim 1, Features: The electrochemical deposition in step (2) is constant potential deposition, the potential is -0.6 to -0.8 V (vs. SCE), and the deposition time is 120 to 960 s.

7. A method for preparing a sensitive electrode for direct electrochemical detection of copper ions in water as claimed in claim 1, Features: The electrochemical deposition in step (2) is pulsed electrochemical deposition. In one deposition cycle, the holding time of the -0.6 to -0.8 V square wave pulse is 0.1 to 0.3 s, and the holding time of the 0 V square wave is 0.1 to 0.3 s, with a total of 1200 to 9600 deposition cycles.

8. A method for preparing a sensitive electrode for direct electrochemical detection of copper ions in water as claimed in claim 1, Features: The electrochemical deposition in step (2) is pulsed electrochemical deposition. In one deposition cycle, the maintenance time of the -0.6 to -0.8 V square wave pulse is 0.1 to 0.3 s, the maintenance time of the 0 V square wave is 0.1 to 0.3 s, and the open circuit voltage is maintained for 0.2 to 1.4 s, for a total of 1200 to 7200 cycles.

9. A sensitive electrode for direct electrochemical detection of copper ions in water. Features: The method is prepared by any one of claims 1 to 8.

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