Heavy metal ion detection method by coating cobalt oxide on screen-printed electrode
By coating cobalt oxide on the screen-printed electrode and constructing the Co3O4/C@SPE electrode, combined with the anode dissolution square wave voltammetry, the complex and cost-effective detection of detection methods in the prior art is solved, and high sensitivity heavy metal ion detection is achieved, which is suitable for the detection of water bodies and biological samples.
Patent Information
- Application Number
- CN202510915794.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-03
- Publication Date
- 2025-08-12
AI Technical Summary
Existing heavy metal ion detection methods such as atomic absorption spectroscopy and inductively coupled plasma mass spectroscopy are complex and costly, making it difficult to meet the needs of efficient and sensitive water quality monitoring.
The method of coating cobalt oxide with screen printing electrodes was adopted to construct Co3O4/C@SPE electrodes, combined with the anode dissolution square wave voltammetry for electrochemical detection, and the high specific surface area and good conductivity of porous cobalt tetroxide derived from zeolite imidazole framework were used to achieve high sensitivity detection of heavy metal ions.
It realizes heavy metal ion detection with simple operation, low cost and high sensitivity, and is suitable for the detection of water bodies and other biological samples, and complies with the World Health Organization's drinking water safety standards.
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Figure CN120468244A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of heavy metal ion detection, and in particular to a heavy metal ion detection method comprising coating cobalt oxide on a screen-printed electrode. Background Art
[0002] With the acceleration of industrialization, water pollution is becoming increasingly serious, especially pollution from heavy metal ions (such as mercury ions), which poses a serious threat to the environment and human health. Mercury ions are not only highly toxic but also difficult to degrade in the environment. Due to their high toxicity and bioaccumulation effects, they have become an important detection target in environmental monitoring. Traditional mercury ion detection methods, such as atomic absorption spectrometry (AAS) and inductively coupled plasma mass spectrometry (ICP-MS), although highly sensitive, are complex to operate and costly. Therefore, the development of efficient and sensitive detection methods is crucial for water quality monitoring and environmental protection. Summary of the Invention
[0003] In order to solve the above problems, the present invention provides a method for detecting heavy metal ions in cobalt oxide using a screen-printed electrode (SPE), which specifically comprises the following steps:
[0004] Step 1: Cobalt nitrate hexahydrate is thoroughly mixed with methanol to obtain solution A. 2-Methylimidazole is thoroughly mixed with methanol to obtain solution B. Solution B is slowly added to solution A and stirred for 45 minutes to obtain a purple mixture. The mixture is reacted at 120°C for 10 hours, cooled, washed until clear, and finally dried in vacuo at 60°C to obtain dimethylimidazole cobalt (ZIF-67).
[0005] Preferably, the ratio of the cobalt nitrate hexahydrate to methanol is 0.546 g:15 mL.
[0006] Preferably, the ratio of 2-methylimidazole to methanol is 0.616 g:1 mL.
[0007] Step 2: Take 40 mg of ZIF-67 sample and heat it to 250°C in air at a heating rate of 2°C / min and maintain it for 8 hours. After cooling to room temperature, cobalt trioxide / carbon (Co3O4 / C) is obtained.
[0008] Step 3: Disperse 4 mg of Co3O4 / C powder in 1 mL of water to obtain a Co3O4 / C suspension. Take 10 μL of the Co3O4 / C suspension and drop it onto the newly polished SPE surface. Evaporate the solvent at room temperature to obtain a Co3O4 / C-modified screen-printed electrode (Co3O4 / C@SPE).
[0009] In step three, a traditional three-electrode system was constructed using Co3O4 / C@SPE as the working electrode, platinum wire as the counter electrode, and Ag / AgCl as the reference electrode. The three electrodes were immersed in a buffer solution containing the analyte, and electrochemical detection was performed by anodic stripping square wave voltammetry (SWASV). The specific parameters were: enrichment potential +0.6 V, enrichment time 150 s; the working potential window was set to -0.1 V to -0.8 V; the step voltage and amplitude were 4 mV and 50 mV, respectively.
[0010] The present invention has the following advantages:
[0011] (1) High sensitivity: The electrode material based on the zeolite imidazole framework-derived porous cobalt tetroxide on the screen-printed electrode has a large specific surface area and good conductivity, which can effectively improve the electrochemical signal of mercury ions, thereby achieving high-sensitivity detection.
[0012] (2) Easy to operate: low detection cost, fast processing, high sensitivity, and easy to use, providing a more effective alternative method for detecting mercury ions to electrochemical analysis.
[0013] (3) Easy to produce: Screen printing technology makes the electrode preparation process simple and fast, suitable for large-scale production.
[0014] (4) Wide application: This method is not only applicable to the detection of mercury ions in water, but can also be extended to the detection of heavy metal ions in other animals and plants. BRIEF DESCRIPTION OF THE DRAWINGS
[0015] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are merely embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.
[0016] Figure 1 The results of cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) show that the modified electrode affects the electron transfer. (a) In the presence of 5 mmol / L ferricyanide ([Fe(CN)6] 3- / 4- ) solution, cyclic voltammetric responses of SPE, ZIF-67@SPE and Co3O4 / C@SPE at a scanning rate of 50 mV / s; (b) Nyquist plots of SPE, ZIF-67@SPE and Co3O4 / C@SPE at open circuit potential.
[0017] Figure 2Sensitivity analysis of Co3O4 / C@SPE for mercury ion measurement. (a) SWASV results of Co3O4 / C@SPE at different mercury ion concentrations (0.6-2.0 μM); (b) Corresponding linear current versus mercury(II) concentration; (c) SWASV results of Co3O4 / C@SPE in the presence of interfering compounds in PBS (pH 7); (d) Current response at different interfering concentrations. DETAILED DESCRIPTION
[0018] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.
[0019] Example 1
[0020] This embodiment provides a method for detecting heavy metal ions by coating cobalt oxide on a screen-printed electrode, which specifically includes the following steps:
[0021] Step 1: 0.546 g of cobalt nitrate hexahydrate is thoroughly mixed with 15 mL of methanol to obtain solution A. 0.616 g of 2-methylimidazole is thoroughly mixed with 15 mL of methanol to obtain solution B. Solution B is slowly added to solution A and stirred for 45 minutes to obtain a purple mixture. The mixture is reacted at 120°C for 10 hours, cooled, washed until clear, and finally dried in vacuo at 60°C to obtain ZIF-67.
[0022] Step 2: Take 40 mg of ZIF-67 sample and heat it to 250°C in air at a heating rate of 2°C / min and maintain it for 8 hours. After cooling to room temperature, cobalt trioxide / carbon (Co3O4 / C) is obtained.
[0023] Step 3: Disperse 4 mg of Co3O4 / C powder in 1 mL of water to obtain a Co3O4 / C suspension. Take 10 μL of the Co3O4 / C suspension and drop it onto the newly polished SPE surface. Evaporate the solvent at room temperature to obtain a Co3O4 / C-modified screen-printed electrode (Co3O4 / C@SPE).
[0024] In step three, a traditional three-electrode system was constructed using Co3O4 / C@SPE as the working electrode, platinum wire as the counter electrode, and Ag / AgCl as the reference electrode. The three electrodes were immersed in a buffer solution containing the analyte, and electrochemical detection was performed by anodic stripping square wave voltammetry (SWASV). The specific parameters were: enrichment potential +0.6 V, enrichment time 150 s; the working potential window was set to -0.1 V to -0.8 V; the step voltage and amplitude were 4 mV and 50 mV, respectively.
[0025] Test Example 1
[0026] According to the method of step 3 of Example 1, the electrochemical workstation was used to perform AC impedance spectroscopy (EIS) tests on SPE, ZIF-67@SPE and Co3O4 / C@SPE respectively. In the high-frequency region, the electron transfer resistance (Rct) corresponding to the semicircular part was recorded; in the low-frequency region, the diffusion process corresponding to the linear part was recorded. At different scan rates, the electrochemical workstation was used to record the cyclic voltammetry curve of the Co3O4 / C screen-printed electrode, observe the changes in its oxygen reduction peak, and record the changes in peak current (ipa and ipc). The results are shown in Figure 2. Figure 1 .
[0027] Depend on Figure 1 As shown in a, the electrochemical response of each electrode and the redox reaction of ferricyanide showed that [Fe(CN)6] 4- Oxidation and [Fe(CN)6] 3- The SPE and Co3O4 / C@SPE both showed a peak potential (ΔEp) separation of 95 mV, while the ZIF-67@SPE separation was significantly higher, approximately 200 mV. The ZIF-67@SPE curve showed that the electron transfer efficiency was reduced due to its poor conductivity, thus hindering the [Fe(CN)6] 3- / 4- Electron transfer of substances on the SPE surface. Figure 1 b shows the Nyquist plots of SPE, ZIF-67@SPE, and Co3O4 / C@SPE. The semicircular portion of the high-frequency part corresponds to the electron transfer resistance process or electron transfer resistance, while the straight line portion of the low-frequency part shows the diffusion process. In the Nyquist plot of the electrode impedance spectrum, Co3O4 / C@SPE has the smallest semicircle radius, which indicates that the lower the surface resistance value of the material, the higher the conductivity. The lowest Rct of Co3O4 / C@SPE indicates a faster reaction rate and stronger catalytic kinetics. This improved conductivity is attributed to the carbon layer, which creates a small energy gap, and the intrinsic conductivity of Co3O4, which facilitates interfacial charge transfer.
[0028] Test Example 2
[0029] A traditional three-electrode system was constructed with Co3O4 / C@SPE as the working electrode, platinum wire as the counter electrode, and Ag / AgCl as the reference electrode. The three electrodes were immersed in Hg 2+ Electrochemical detection was carried out by anodic stripping square wave voltammetry (SWASV) in ammonia-ammonium chloride buffer (0.1 M NH4Cl-NH3·H2O solution, pH = 7) with concentrations of 0.6, 0.8, 1.0, 1.2, 1.6, 1.8, and 2.0 μM, respectively. The specific parameters were: accumulation potential +0.6 V, accumulation time 150 s; the working potential window was set to -0.1 V to -0.8 V; the step voltage and amplitude were 4 mV and 50 mV, respectively.
[0030] Figure 2 a shows the effects of Co3O4 / C@SPE on Hg 2+ The SWASV response of the ion, along with the Hg 2+ The concentration changes in the range of 0.6-2.0 μM ( Figure 2 a), Hg 2+ The peak current increases proportionally. Figure 2 The corresponding Hg in b 2+ The calibration curve regression equation is Ipa / μA=2.05C / (μM)+0.96(R2=0.999), and the detection limit is 1.04nM(σ=3). The sensitivity of Co3O4 / C@SPE is better than other Co3O4-based sensors, and the detection limit (LOD) also meets the World Health Organization drinking water safety standard (0.03μM), indicating that Co3O4 / C@SPE is a suitable sensor for detecting low concentrations of Hg. 2+ An ideal electrode for ions. Figure 2 c Demonstrates the simultaneous detection of Hg using Co3O4 / C@SPE under optimal conditions. 2+ and Pb 2+ When Hg 2+ The concentration was kept constant at 1.0 μM while Pb 2+ The concentrations were 0, 1.0, 1.5, 2.0, 2.5, and 3.0 μM, respectively. 2+ As the concentration increases, its response increases linearly, while Hg 2+ The peak current increases only slightly ( Figure 2 c), indicating that Co3O4 / C@SPE can simultaneously detect Pb in the linear range. 2+ and Hg 2+ There is no significant mutual interference. The slight increase in the interfering ion response may be due to the formation of a Pb-Hg alloy film, which may slightly enhance the sensitivity to heavy metals. 2+ The relative standard deviation (RSD) was calculated to be 2.15%, indicating excellent reproducibility ( Figure 2 d).
[0031] The above description of the disclosed embodiments is intended to enable one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to the embodiments shown herein but is intended to conform to the widest scope consistent with the principles and novel features disclosed herein.
Claims
1. A method for detecting heavy metal ions by coating cobalt oxide on a screen printed electrode (SPE), characterized in that: The following steps are involved: Step 1: Apply a cobalt trioxide / carbon (Co3O4 / C) suspension to the surface of a screen-printed working electrode, and after the solvent dries, obtain a Co3O4 / C-modified screen-printed working electrode; Step 2: Construct a three-electrode system consisting of a working electrode, a counter electrode, and a reference electrode, immerse the three electrodes in the solution to be tested, and perform electrochemical detection of heavy metal ions by anodic stripping square wave voltammetry.
2. The method for detecting heavy metal ions by coating cobalt oxide on a screen-printed electrode according to claim 1, characterized in that: The Co3O4 / C suspension in step 1 includes Co3O4 / C powder and water in a mass ratio of 4:
1.
3. The method for detecting heavy metal ions by coating cobalt oxide on a screen-printed electrode according to claim 2, wherein: The preparation method of Co3O4 / C is as follows: heating dimethyl imidazolyl cobalt (ZIF-67) to 250°C in air, keeping the temperature for 8 hours, and cooling to room temperature to obtain Co3O4 / C.
4. The method for detecting heavy metal ions by coating cobalt oxide on a screen-printed electrode according to claim 3, wherein: The preparation method of ZIF-67 is as follows: cobalt nitrate hexahydrate is mixed with methanol to obtain solution A, 2-methylimidazole is mixed with methanol to obtain solution B, solution A and solution B are mixed and stirred, reacted at 120° C. for 10 hours, and dried to obtain ZIF-67.
5. The method for detecting heavy metal ions by coating cobalt oxide on a screen-printed electrode according to claim 4, characterized in that: The ratio of cobalt nitrate hexahydrate to methanol was 0.546 g:15 mL.
6. The method for detecting heavy metal ions by coating cobalt oxide on a screen-printed electrode according to claim 4, characterized in that: The ratio of 2-methylimidazole to methanol was 0.616 g:15 mL.
7. The method for detecting heavy metal ions by coating cobalt oxide on a screen-printed electrode according to claim 1, characterized in that: The heavy metal is mercury ion.