Modified electrode for detecting Ni < 2 + > in water environment and detection method

Abstract

The invention discloses a modified electrode for detecting Ni < 2 + > in a water environment and a detection method, and belongs to the technical field of water quality detection. The laser-induced graphene integrated electrode is used for replacing a traditional three-electrode system, M-CMC / Mus / DMG is modified to a working electrode area, and then the M-CMC / Mus / DMG / ILIG sensor is prepared, has higher sensitivity and excellent conductivity, remarkably reduces the cost of electrochemical detection, has the characteristics of portability and good flexibility, and can be applied to the field of electrochemical detection. New possibility and thought are provided for rapid field detection of Ni < 2 + >; according to the invention, CMC is modified, CuSO4 is taken as an initiator, the CuO-coated CMC / PANI composite material is synthesized by an oxidative polymerization reaction of aniline, the CMC is taken as a template and a one-step synthesis method, PANI and CuONPs are introduced to the CMC, and the CuO-coated CMC / PANI composite material has higher catalytic activity and stronger electron transfer ability. The M-CMC / Mus / DMG / ILIG prepared by the invention can be successfully applied to determination of Ni < 2 + > in an actual water sample, and has excellent stability, reproducibility and anti-interference performance.

Description

Technical Field

[0001] The present invention relates to the technical field of water body detection, in particular to a method for detecting Ni in water environment. 2+ Modified electrode for detection and detection method. Background Art

[0002] Nickel (Ni) is an important industrial metal, widely used in electroplating, stainless steel manufacturing, batteries (nickel-cadmium, nickel-metal hydride), alloys, catalysts, ceramic pigments and other fields. However, its widespread use has led to the discharge of a large amount of nickel-containing wastewater into the environment. Nickel in the water environment is mainly in the form of divalent cations (Ni 2+ ) form. Nickel (Ni) is an essential trace element for the human body, but excessive intake is significantly toxic and is classified as a Class 1 carcinogen (sufficient evidence of carcinogenicity to humans) by the International Agency for Research on Cancer (IARC). Long-term exposure to nickel-containing wastewater or drinking contaminated water can lead to dermatitis (nickel itch), respiratory diseases, liver and kidney damage, and significantly increase the risk of lung cancer, nasal cancer, etc. Therefore, the Ni in the water environment (including surface water, groundwater, drinking water sources, industrial wastewater, electroplating wastewater, etc.) 2+ Strict monitoring of concentrations is an urgent need to ensure ecological and environmental safety and public health.

[0003] At present, the laboratory detects Ni in water samples 2+ The mainstream methods include atomic absorption spectrometry (AAS), inductively coupled plasma optical emission spectrometry / mass spectrometry (ICP-OES / MS) and spectrophotometry. However, the above-mentioned existing mainstream methods generally have common disadvantages such as high cost, bulky equipment, complex operation, time-consuming, dependence on laboratory environment, and difficulty in achieving on-site real-time / online detection. They cannot meet the growing demand for fast, convenient and low-cost environmental monitoring, especially in emergency response to sudden pollution incidents, on-site law enforcement inspections and distributed monitoring points.

[0004] Electrochemical analysis methods, especially the sensing technology based on chemically modified electrodes (CME), have shown great potential in the field of environmental pollutant detection due to their significant advantages such as relatively simple equipment, low cost, fast response speed, simple operation, easy miniaturization and on-site / on-line detection. 2+ The specific and highly sensitive electrochemical detection has the problems of insufficient sensitivity, poor selectivity, and poor stability and reproducibility.

[0005] Based on the above content, the present invention proposes a Ni 2+ M-CMC / Mus / DMG modified electrode and detection method for Ni in water environment 2+ detection work. Summary of the Invention

[0006] The purpose of the present invention is to provide a Ni 2+ Modified electrodes and detection methods for more efficient and accurate detection of Ni in actual water samples 2+ Determination of.

[0007] To achieve the above object, the present invention adopts the following technical solutions:

[0008] Ni in a water environment 2+ The modified electrode used for detection is composed of a laser-induced graphene integrated electrode and M-CMC / Mus / DMG modified on its surface.

[0009] Preferably, the modified electrode preparation method is as follows:

[0010] A1. Prepare an electrode substrate and use laser-induced graphene integrated electrodes to replace the working electrode, counter electrode, and reference electrode of the traditional three-electrode system, integrating the three electrodes on the electrode substrate;

[0011] A2. Prepare Mus-DMG suspension for later use;

[0012] A3. Prepare M-CMC material for standby use;

[0013] A4, dissolving the M-CMC material prepared in A3 in deionized water and performing ultrasonic treatment to prepare an M-CMC solution;

[0014] A5. The M-CMC solution prepared in A4 and the Mus-DMG suspension prepared in A2 are successively drop-coated onto the working electrode area of ​​the integrated electrode to prepare an M-CMC / Mus / DMG modified electrode.

[0015] Preferably, A2 specifically includes the following contents:

[0016] A2.1. Weigh a certain amount of polystyrene and dissolve it in acetone solution. Shake the solution.

[0017] A2.2. Weigh a certain amount of DMG and Mus on an analytical balance and grind them in a mortar. Dissolve the mixed powder in an acetone solution containing polystyrene and sonicate for a certain period of time before use.

[0018] Preferably, A3 specifically includes the following contents:

[0019] A3.1. Use an analytical balance to weigh a certain amount of CuSO4·5H2O, dissolve it in deionized water, and then perform ultrasonic treatment.

[0020] A3.2. Weigh a certain amount of CMC and slowly add it dropwise to the stirred deionized water. Ultrasonicate for a certain period of time and then magnetically stir.

[0021] A3.3. Add aniline solution and continue stirring;

[0022] A3.4. Slowly add the CuSO4·5H2O solution prepared in A3.1 dropwise to the solution stirred in A3.3. Continue stirring after the addition is complete.

[0023] A3.5. Filter the solution in A3.4 and transfer it to an oven for drying to obtain a dark green CuONPs-CMC-PANI powder, which is the M-CMC material.

[0024] Ni in a water environment 2+ The detection method specifically comprises the following steps:

[0025] S1. Use a pipette to measure a certain amount of NH3 solution and NH4Cl solution into a beaker, and ultrasonically treat the mixture to obtain NH3-NH4Cl solution;

[0026] S2, constructing a three-electrode system by laser-induced graphene integrated electrode, treating the electrode with M-CMC / Mus / DMG solution to prepare M-CMC / Mus / DMG modified electrode;

[0027] S3, using the NH3-NH4Cl solution prepared in S1 as the electrolyte solution, based on the M-CMC / Mus / DMG modified electrode prepared in S2, the Ni in the water to be tested was completed by adsorption cathodic stripping voltammetry. 2+ Detection.

[0028] Preferably, the pH of the NH3-NH4Cl solution in S1 is 6.5.

[0029] Preferably, the Ni in the water to be tested is determined by adsorption cathode stripping voltammetry as described in S3. 2+ For detection, the stripping voltage range is -0.6 to -1.35 V, the deposition potential is set to -0.6 to -1.0 V, and the enrichment time is 160 to 200 s.

[0030] Compared with the prior art, the present invention provides a Ni 2+ The modified electrode and detection method for detection have the following beneficial effects:

[0031] (1) The present invention replaces the traditional working electrode, counter electrode and reference electrode by laser-induced graphene integrated electrode, and modifies M-CMC / Mus / DMG into the working electrode area, thereby preparing the M-CMC / Mus / DMG / ILIG sensor; compared with the traditional three-electrode system, the integrated composite electrode used in the present invention has higher sensitivity and excellent conductivity, significantly reduces the cost of electrochemical detection, and has the characteristics of portability and good flexibility, which is Ni 2+ The rapid on-site detection of carbon monoxide (CMC) provides new possibilities and ideas. For the modified material, the present invention modifies CMC, uses CuSO4 as an initiator, and synthesizes CuO@CMC / PANI composite material (i.e., M-CMC) through the oxidative polymerization reaction of aniline using CMC as a template by a one-step synthesis method. The composite material introduces PANI and CuONPs on CMC. The modified M-CMC material has higher catalytic activity and stronger electron transfer ability.

[0032] (2) The prepared electrode was characterized by SEM, TEM, XPS and other characterization methods, proving that the M-CMC / Mus / DMG / ILIG was successfully prepared. In addition, the electrochemical properties of the electrode were studied by various electrochemical methods such as CV and SW AdCSV. Under the optimal experimental conditions, the sensor prepared by the present invention showed a good linear relationship in the range of 1 to 90 μg / L, with a detection limit as low as 0.16 μg / L, and had excellent stability, reproducibility and anti-interference performance. The M-CMC / Mus / DMG / ILIG prepared by this method can be successfully applied to the detection of Ni in actual water samples. 2+ Determination of. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is a flow chart for the preparation of M-CMC / Mus / DMG / ILIG mentioned in Example 1 of the present invention;

[0034] Figure 2 This is the SEM image of the modified electrode mentioned in Example 1 of the present invention;

[0035] Figure 3 (A) is a TEM image of M-CMC mentioned in Example 1 of the present invention, (B) is the lattice spacing of M-CMC, and (C) is an EDS diagram of M-CMC;

[0036] Figure 4 This is the full XPS spectrum of the M-CMC / Mus / DMG composite material mentioned in Example 1 of the present invention;

[0037] Figure 5(A)-(F) are high-resolution spectra of C1s, Cu 2p, N 1s, K 2p, Al 2p, and Si 2p mentioned in Example 1 of the present invention;

[0038] Figure 6 This is a Raman spectrum analysis diagram before and after modification mentioned in Example 1 of the present invention;

[0039] Figure 7 is the contact angle of the different modified electrodes mentioned in Example 1 of the present invention;

[0040] Figure 8 (A) is the cyclic voltammogram of different electrodes mentioned in Example 1 of the present invention in a mixed solution containing 5mM K3[Fe(CN)6] and 0.1M KCl; (B) is the cyclic voltammogram of different electrodes for 20μg / L Ni 2+ SW AdCSV response graph;

[0041] Figure 9 (A) is the EIS graph of CMC before and after modification mentioned in Example 1 of the present invention, and (B) is the EIS graph of different modified electrodes;

[0042] Figure 10 (A)-(C) are CV images of ILIG, Mus / DMG / ILIG, and M-CMC / Mus / DMG / ILIG mentioned in Example 1 of the present invention at different scan rates; (B) is the relationship between scan rate and current density;

[0043] Figure 11 (A) is the CV response in a mixed solution of 5 mM K3[Fe(CN)6] and 0.1 M KCl mentioned in Example 1 of the present invention; (B) is the linear relationship between Ipa and the square root of the scan rate;

[0044] Figure 12 The current response of the M-CMC / Mus / DMG / ILIG buffer solutions at different pH values ​​to NH3-NH4Cl mentioned in Example 1 of the present invention;

[0045] Figure 13 (A) and (B) show the effects of different concentrations of M-CMC on the detection signal of the M-CMC / Mus / DMG / ILIG electrodes prepared in Example 1 of the present invention; (C) and (D) show the effects of different amounts of M-CMC on the detection signal of the M-CMC / Mus / DMG / ILIG electrodes prepared.

[0046] Figure 14 This is the effect of the M-CMC / Mus / DMG / ILIG electrode made with different dropwise coating amounts of the Mus-DMG suspension mentioned in Example 1 of the present invention on the detection signal.

[0047] Figure 15 (A) and (B) show the concentrations of M-CMC / Mus / DMG / ILIG at 20 μg / L Ni at different enrichment potentials mentioned in Example 1 of the present invention. 2+ SW AdCSV response; (C), (D) M-CMC / Mus / DMG / ILIG at different enrichment times in the presence of 20 μg / L Ni 2 + SW AdCSV response;

[0048] Figure 16 The Mus / DMG / ILIG reaction with different concentrations of Ni mentioned in Example 1 of the present invention 2+ SW AdCSV response and linear relationship graph;

[0049] Figure 17 The M-CMC / Mus / DMG / ILIG mentioned in Example 1 of the present invention contains different interfering ions in Ni 2+ Peak current signal value in solution;

[0050] Figure 18 (A) is the five modified electrodes prepared in the same manner as in Example 1 of the present invention to detect Ni 2+ Detection current in solution; (B) is the detection current of Ni by modified electrodes after being placed for different days 2+ Detection current in solution. DETAILED DESCRIPTION

[0051] The present invention will be further described below with reference to specific embodiments, and the advantages and features of the present invention will become clearer as the description proceeds. However, these embodiments are merely exemplary and do not constitute any limitation to the scope of the present invention. It should be understood by those skilled in the art that the details and forms of the technical solutions of the present invention may be modified or replaced without departing from the spirit and scope of the present invention, and such modifications and replacements fall within the scope of protection of the present invention.

[0052] It should be emphasized that unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs. Although any methods, devices, and materials similar or equivalent to those herein can be used in the practice or testing of the present invention, the preferred methods, devices, and materials are now described.

[0053] The present invention proposes a Ni in water environment 2+ A modified electrode for detection, namely a M-CMC / Mus / DMG / ILIG, is proposed. A method for applying the electrode to Ni in water environment is also proposed. 2+ The detection method and specific embodiments are as follows.

[0054] Example 1:

[0055] Ni in a water environment 2+ The detection method specifically comprises the following steps:

[0056] (1) Preparation of M-CMC / Mus / DMG / ILIG electrodes:

[0057] 1.1) Preparation of ILIG Electrode

[0058] An electrode substrate is prepared, and a laser-induced graphene integrated electrode is used to replace the working electrode, counter electrode and reference electrode of the traditional three-electrode system. The three electrodes are integrated on the electrode substrate to obtain an ILIG electrode.

[0059] 1.2) Preparation of CuONPs-CMC-PANI (M-CMC) materials

[0060] Dissolve 1.875 g of CuSO4·5H2O in 25 mL of deionized water and sonicate for 30 min;

[0061] 1.815 g of CMC was slowly added dropwise to 100 mL of stirred deionized water. Ultrasonication was performed for 30 minutes, followed by magnetic stirring for 1 hour. 1 mL of aniline solution was then added and stirring continued for 1 hour. CuSO₄·5H₂O was then slowly added dropwise to the stirred solution. A precipitate formed. Stirring was continued for 14 hours after the addition was complete. The solution was filtered and dried in an oven for 12 hours to obtain a dark green powder, the prepared M-CMC material.

[0062] 0.015 g of the M-CMC material obtained above was weighed and placed in 5 mL of deionized water and ultrasonicated for 10 min before use.

[0063] 1.3) Preparation of Mus-DMG Suspension

[0064] First, weigh 0.25 g of polystyrene and dissolve it in 50 ml of acetone solution, and shake it for 12 hours.

[0065] Next, 0.025 g of DMG and 0.1 g of Mus were weighed on an analytical balance and ground in a mortar for 10 min. The mixed powder was dissolved in 2.5 ml of acetone solution containing polystyrene and sonicated for 10 min before use.

[0066] (2)Ni 2+ Electrochemical detection

[0067] Ammonia-ammonium chloride (NH3-NH4Cl) solution with a pH of 9 was selected as the electrolyte solution, and adsorptive cathodic stripping voltammetry (SW AdCSV) was used for determination. The stripping voltage range was: -0.7V to -1.35V, the optimized deposition potential was -0.8V, and the deposition time was 180s. The cyclic voltammetry (CV) experiment for measuring the electrode active area was carried out in a 1M KOH solution, with the potential range set to -0.25V to -0.15V and the scan rate from 20mV / s to 100mV / s. The adsorption control experiment of the composite electrode was carried out in a mixed solution of 5mM K3[Fe(CN)6] and 0.1M KCl, with the potential range set to -0.4V to -0.8V and the scan rate from 20mV / s to 140mV / s.

[0068] (3) Material characterization

[0069] 3.1) Scanning electron microscopy (SEM) and transmission electron microscopy (TEM)

[0070] The image of the modified electrode is as follows Figure 2 As shown, Figure 2 (A) is to modify the unmodified CMC on the ILIG electrode, Figure 2 (B) Unmodified CMC, Mus, and DMG were modified on the ILIG electrode. The scale bars are 10 μm. Figure 2 (A) and Figure 2 (B) It can be seen that the unmodified CMC is larger in size, and CMC and Mus cross and intersect with each other to form a three-dimensional structure. Figure 2 (C) is M-CMC modified on ILIG electrode, Figure 2 (D) M-CMC, Mus, and DMG were modified on the ILIG electrode. The scale bars are 10 μm. Figure 2 (C) and Figure 2 (D) The modified CMC is smaller, and more M-CMC molecules adhere evenly to the Mus, creating a three-dimensional structure. The porous graphene structure on the composite electrode provides numerous adsorption sites. In summary, the M-CMC modified by CMC is smaller and adheres more to the mica sheet, resulting in a rougher, more wrinkled surface.

[0071] Then, TEM characterization of M-CMC was carried out. Figure 3 As shown, Figure 3 (A) is a transmission electron microscopy image of M-CMC, where spherical nanoparticles are evenly distributed on the dendritic CMC / PANI nanofibers. The spherical nanoparticles are CuONPs. Figure 3(B) shows that the spacing between the lattice fringes is 0.25 nm, which is the lattice spacing of CuO. Figure 3 (C) Select a smaller area and scan the electron beam with a fixed beam, obtaining an X-ray energy spectrum. This image shows the presence of C, N, O, and Cu in the composite material, demonstrating the successful integration of PANI and CuONPs onto the M-CMC.

[0072] 3.2) X-ray photoelectron spectroscopy (XPS) analysis

[0073] Figure 4 This is the XPS total spectrum of M-CMC / Mus / DMG. It can be seen that C, Cu, N, O, K, Al and Si elements exist in the composite material, that is, CMC modification is successful and the composite material is successfully prepared.

[0074] In order to further understand the element information and bond energy information of M-CMC / Mus / DMG composite materials, high-resolution spectrum analysis of some characteristic elements was performed. Figure 5 As shown, Figure 5 (A) is the spectrum of C1s, which shows peaks at 284.8 eV, 286.46 eV, and 288.1 eV, corresponding to CC, CO, and C=O bonds, respectively. Figure 5 (B) is the spectrum of Cu 2p, where Cu 2p was detected at 933.44 eV and 953.19 eV, respectively. 3 / 2 and Cu 2p 1 / 2 , which indicates that Cu exists in the modified material in the form of CuO. In addition, two satellite peaks were found at 944.16eV and 963.09eV, which also proves that Cu 2+ existence. Figure 5 (C) is the N1s spectrum, where aniline and protonated aniline were detected at 400.43 eV and 398.50 eV. Figure 5 (D), (E) and (F) correspond to KO bonds, Al-O bonds and Si-O bonds respectively. The above XPS can prove that the materials are successfully composited.

[0075] 3.3) Raman spectroscopy analysis

[0076] Raman analysis is a spectroscopic technique that is mainly used to evaluate the degree of defects at the electrode interface. Figure 6 As shown in the Raman spectrum of graphene, graphene has a wavelength of 1350 cm -1 、1580cm -1 There are obvious characteristic peaks at the D peak and the G peak respectively. The intensity ratio of the D peak to the G peak (I D / I G ) can reflect the degree of electrode defects. Figure 6The I of the ILIG electrode can be obtained by calculation. D / I G The I value of the modified M-CMC / Mus / DMG / ILIG electrode is 1. D / I G The value increased to 1.32. This result indicates that the modified M-CMC / Mus / DMG / ILIG electrode has a high degree of defects. This unique structure can provide more active sites for the adsorption of nickel ions, thereby improving the electrochemical performance of the electrode.

[0077] 3.4) Contact angle analysis

[0078] The contact angle test is used to evaluate the hydrophilicity and hydrophobicity of the LIG electrode surface. The smaller the contact angle, the stronger the hydrophilicity of the electrode. Figure 7 As shown in the figure, the contact angle of the unmodified ILIG electrode is 106.26°, indicating that the hydrophilicity of the electrode is poor. After modification with DMG and Mus, the contact angle is reduced to 86.88°, proving that the Mus-DMG composite material can effectively improve the hydrophilicity of the electrode. After further introduction of M-CMC, the contact angle of the modified electrode is further reduced to 56.81°. This significant change is mainly attributed to the introduction of CuO and PANI in M-CMC. The modification of these functional components on the surface of the composite electrode effectively enhances the hydrophilicity of the ILIG electrode, and more Ni 2+ It can be introduced to the electrode surface for subsequent redox reactions.

[0079] (4) Electrochemical behavior before and after electrode modification

[0080] 4.1)CV and SW AdCSV

[0081] like Figure 8 (A) Shows the CV responses of different electrodes in a mixed solution of 5 mM K3[Fe(CN)6] and 0.1 M KCl. The modified electrodes exhibit significantly different cyclic voltammetric responses. The unmodified ILIG electrode exhibits a subtle redox peak, while the redox peak current is lower when Mus / DMG is modified on the ILIG electrode. This demonstrates that the mineral material itself has limited conductivity and that the primary mechanism is to increase the electrode's electroactive area and provide abundant active sites. M-CMC modification on the ILIG electrode increases the redox peak current and decreases the redox peak potential difference. This indicates that M-CMC can effectively enhance the electrode's conductivity and promote electron transport. When M-CMC and Mus / DMG are used for composite modification, although the peak current decreases slightly, the overall conductivity is still significantly improved compared to the unmodified electrode.

[0082] Next, the SW AdCSV method was used to study the effects of different modified electrodes on 5 μg / L Ni 2+ The detection performance of Figure 8 (B) shows that there is almost no obvious reduction peak on the bare ILIG electrode. After Mus / DMG is modified on the ILIG electrode, the current value of the reduction peak is about 4.02μA, which is attributed to the synergistic adsorption effect of the specific adsorbent and the mineral. After the introduction of unmodified CMC, the current value is further increased to about 6.19μA, indicating that the synergistic effect of CMC and Mus can make Ni 2+ More adsorbed on the electrode undergoes redox reactions. After CMC modification, the reduction peak current on the ILIG electrode increased significantly to approximately 9.6 μA. These results suggest that CMC modification improves the electron transfer capacity of the composite electrode primarily by increasing the material's conductivity, significantly enhancing the sensor's sensitivity to nickel ion detection.

[0083] 4.2) EIS impedance spectrum

[0084] Electrochemical impedance spectroscopy (EIS) is an important method for studying electron transfer behavior at electrode interfaces. Its impedance value reflects the degree of resistance to electron transfer. The smaller the impedance value (Rct), the better the material's conductivity and the greater the number of electrons available for redox reactions at the electrode surface. In this experiment, EIS measurements were performed in a mixed solution containing 5 mM K3[Fe(CN)6] and 0.1 M KCl.

[0085] First, impedance analysis of CMC / ILIG electrode and M-CMC / ILIG electrode was performed. Figure 9 (A) The impedance arc radius corresponding to M-CMC is significantly reduced, indicating that the modified material has significantly improved conductivity and stronger electron transport capabilities, making it more suitable for use as a catalyst. Experimental results show that the material modification effectively enhances the electron transfer efficiency at the electrode interface and improves the conductivity of the composite electrode.

[0086] like Figure 9As shown in Figure (B), the ILIG electrode, Mus / DMG / ILIG electrode, M-CMC / ILIG electrode, and M-CMC / Mus / DMG / ILIG electrode were placed in a mixed solution containing 5mM K3[Fe(CN)6] and 0.1M KCl for testing. The results were then fitted using Zview software, resulting in impedances (Rct) of 63.86Ω, 24.68Ω, 101.7Ω, and 46.77Ω for the ILIG electrode, Mus / DMG / ILIG electrode, M-CMC / ILIG electrode, and M-CMC / Mus / DMG / ILIG electrode, respectively. The results show that the modified CMC significantly improves the conductivity of the composite electrode and enhances its electron transfer capacity, demonstrating the catalytic effect of M-CMC and compensating for the composite electrode's insufficient conductivity.

[0087] 4.3) Electrochemically active area (ECSA) study of electrodes

[0088] This experiment still uses the CV method to scan within the non-Faraday window. By plotting the linear relationship between current and scan rate, the slope is the double-layer capacitance. The ILIG, Mus / DMG / ILIG, and M-CMC / Mus / DMG / ILIG electrodes were placed in 1M KOH solution and tested at different scan rates. Figure 10 As shown, the double-sided capacitance of the integrated electrode is 6.51mF·cm -2 The double-sided capacitance of the Mus / DMG / ILIG electrode is 10.93 mF·cm -2 The double-sided capacitance of the M-CMC / Mus / DMG / ILIG electrode is 12.26 mF·cm -2 These data indicate that the modification of Mus / DMG significantly increases the electrochemical active area of ​​the electrode, while the introduction of CMC further optimizes the electrode surface structure, providing more adsorption sites, thereby improving the current response of the electrode in detecting nickel.

[0089] 4.4) Control process of electrode reaction

[0090] In order to explore the reaction mechanism of the M-CMC / Mus / DMG composite electrode, CV scans were performed on the M-CMC / Mus / DMG composite electrode at different scan rates (20-140 mV / s). The experimental results are shown in Figure 2. Figure 11 As shown in the figure, the anode peak current Ipa is related to the scan rate (v) and the square root of the scan rate (v 1 / 2 ) is the control step for judging the LIG electrode process. When Ipa and v are linearly related, the electroactive material is limited by the adsorption process; Ipa and v 1 / 2When the relationship is linear, the diffusion control is dominant on the LIG electrode surface. After fitting calculation, the peak current Ipa is related to the scan rate (v 1 / 2 ) is more linear, and the linear relationship is:

[0091] y=0.2297x+0.1851

[0092] R 2 =0.993

[0093] Therefore, it is concluded that the reaction occurring on the surface of the M-CMC / Mus / DMG composite electrode is mainly controlled by diffusion.

[0094] (5) Optimization of experimental conditions of the present invention

[0095] 5.1) Supporting electrolyte optimization

[0096] The optimization of the experimental conditions of the present invention is all at 20 μg / L Ni 2+ The buffer solution selected is NH3-NH4Cl.

[0097] Next, we will explore the effect of pH value on the detection current. M-CMC / Mus / DMG was immersed in different buffer solutions and the pH value was tested. Figure 12 It can be seen that the detection current increases with the increase of pH. When pH = 9, the current value reaches the maximum, which is about 7.02μA. When the pH increases further, the current drops sharply. This may be due to the fact that Ni 2+ It may combine with the hydroxyl groups in the water environment, resulting in a decrease in the current value. After comprehensive consideration, NH3-NH4Cl with a pH of 9 was selected as the best buffer solution.

[0098] 5.2) M-CMC Optimization

[0099] The concentration and drop amount of M-CMC will affect the detection current. As a catalyst that can promote electron transfer, the proportion of M-CMC in the composite material will affect the Ni 2+ The efficiency of migration to the ILIG electrode was investigated. Then, M-CMC prepared with different concentrations was used to treat 20 μg / L Ni 2+ The solution was tested.

[0100] The suspensions of M-CMC and Mus-DMG with different concentrations were successively dropped on the ILIG electrode for detection. Figure 13As shown in (A) and (B), the current response increases as the M-CMC concentration increases. This is because M-CMC, as a catalyst, enhances the electron transfer capacity of the electrode. Higher M-CMC concentrations enhance this capacity. Electron transfer capacity reaches its maximum at 3 g / L. Further increases in M-CMC concentration lead to a thicker M-CMC layer, which hinders electron transfer and reduces the electrode's conductivity, thus reducing the response current. Based on these considerations, an M-CMC concentration of 3 g / L was selected.

[0101] Next, the concentration of M-CMC was kept constant (3g / L) to explore the effect of different droplet amounts on the sensor. After the Mus-DMG composite material was modified on the electrode, 2μL, 4μL, 6μL, 8μL, and 10μL of M-CMC were droplet-coated respectively. The experimental results are shown in the figure. Figure 13 As shown in (C) and (D), when the drop coating volume increases from 2 μL to 8 μL, the current value gradually increases, which shows that the superposition of the drop coating volume is conducive to the full play of the electron transfer effect of M-CMC. 2+ It can adsorb onto the Mus-DMG modified layer, while the M-CMC molecules act as a catalyst, accelerating the detection process and thus increasing the detection current. However, when the droplet volume is increased, the current value increases slowly. This may be because electron transfer has reached its limit, and further increase will not allow further electron transfer to the redox reaction. To save material, the M-CMC droplet volume was selected as 8μL.

[0102] 5.3) Mus-DMG Optimization

[0103] In the Mus-DMG material, the concentration of DMG is 10 g / L, and the mass ratio of DMG to Mus is 1:4. Next, the effect of the droplet amount of Mus-DMG on the current value is investigated.

[0104] 1 μL, 2 μL, 3 μL, 4 μL, and 5 μL of Mus-DMG suspension were respectively applied and placed on a 20 μg / L Ni 2+ The test results are as follows: Figure 14 It shows that when the drop volume increases from 1μL to 3μL, the detection current increases from 4.51μA to 9.15μA. When the drop volume increases from 3μL to 5μL, the detection current gradually decreases. This is because the more Mus-DMG is dropped, the more Ni 2+ The more the amount, the higher the detection current. However, too much Mus-DMG layer will lead to a thicker modified layer, which will reduce the number of electron transfers and the electron transfer capacity. Considering all factors, 3μL, which has the highest detection current, was selected as the optimal droplet amount.

[0105] 5.4) Optimization of enrichment potential and enrichment time

[0106] The enrichment potential is the potential applied during the electrochemical enrichment step, which can 2+ Adsorbed onto the electrode surface, the experimental results are as follows Figure 15 As shown in (A) and (B), when the enrichment potential decreases from -0.6 V to -0.8 V, the reduction peak current also increases. This may be because the poor potential state will affect the state of the electrode surface, thereby affecting the Ni 2+ When the enrichment potential decreases from -0.8V to -1.0V, the current value decreases. Taking all factors into consideration, -0.8V is selected as the optimal enrichment potential.

[0107] The enrichment time is also an important parameter in electrochemical detection. Figure 15 As shown in (C) and (D), when the enrichment time increases from 120s to 180s, the current value also increases to 9.05μA. When the current value increases further, the growth rate of the current tends to be slow. This is because the longer the enrichment time, the more Ni 2+ The more electrons there are, the more electrons participate in the reaction. However, as the concentration time increases beyond 180 seconds, the current growth rate slows. Taking all factors into consideration, 180 seconds was chosen as the optimal concentration time.

[0108] (6) Linear range and detection limit

[0109] Through the above optimization experiments, the SW AdCSV detection method was selected, with a pH = 9 NH3-NH4Cl buffer solution, 3g / L M-CMC, a drop volume of 8μL, a drop volume of 3μL Mus-DMG (DMG concentration is 10g / L, the mass ratio of DMG to Mus is 1:4), an enrichment potential of -0.8V, and an enrichment time of 180s. Ni 2+ Under the above optimal experimental conditions, electrochemical detection was performed using an electrochemical sensor constructed with M-CMC / Mus / DMG as the working electrode. Figure 16 As shown in the figure, the sensor shows a good linear relationship in the range of 1 to 90 μg / L, and its linear regression equation is:

[0110] y=0.3124x+2.9548

[0111] R 2 =0.986

[0112] The detection limit was calculated using the formula LOD = k·σ / b, where k is the confidence factor (3 in the present invention), σ is the standard deviation of multiple blank samples, and b is the standard curve at low concentrations of Ni. 2+ The slope in the solution interval.

[0113] The detection limit of the sensor was calculated to be 0.16 μg / L. Compared with other sensors for detecting nickel, the electrochemical sensor prepared by the present invention has a wider linear range and a lower detection limit.

[0114] Compared with previous similar work, the prepared M-CMC / Mus / DMG / ILIG composite electrode has a better performance in detecting Ni 2+ It has a wide linear range and a low detection limit, as shown in Table 1:

[0115] Table 1 Other sensor detection data

[0116]

[0117] (7) Anti-interference and reproducibility of electrodes

[0118] In order to better verify the anti-interference performance of the sensor in water environment, the present invention selects the 20μg / L Ni 2+ 100 times the concentration of Zn 2+ 、Mn 2+ , Pb 2+ , K + , Ca 2+ 、Na + 、CO3 2- 、SO4 2- 、Cl - As an anti-interference substance. Figure 17 As shown, adding most of the anti-interference ions is relative to Ni without anti-interference 2+ Under these conditions, the peak current does not change much, indicating that the prepared M-CMC / Mus / DMG / ILIG electrode has good anti-interference performance.

[0119] Then the reproducibility and stability of the M-CMC / Mus / DMG / ILIG electrode were investigated. Five electrodes prepared in the same way were placed in 20 μg / L Ni 2+ The current is detected in the solution, and the experimental results show that Figure 18 (A) It can be seen that the detection current of the five electrodes is not much different, and the relative standard deviation is 2.7%, which shows good reproducibility. At the same time, in order to explore the stability of the M-CMC / Mus / DMG / ILIG electrode, the same electrode was placed for different days (1 day, 4 days, 7 days, 10 days, 13 days) to detect 20μg / L Ni 2+ In solution, the experimental results are as follows Figure 18 (B) shows that the degree of current attenuation is low, and the current of the electrode after two weeks is about 87.6% of the initial electrode, and its stability is good.

[0120] (8) Testing of actual water samples

[0121] In order to verify the application of the prepared sensor in water environment, the M-CMC / Mus / DMG / ILIG sensor was applied to the detection of actual water samples under the optimal detection conditions. The prepared electrode was evaluated using the spiked method. The collected water samples were simply filtered and then prepared with Ni at concentrations of 10μg / L, 20μg / L, and 40μg / L. 2+ The results are shown in Table 2. 2+ The recovery rate is 93.44% to 103.46%. 2+ The recovery rate was 101.85% to 109.41%.The results showed that the M-CMC / Mus / DMG / ILIG electrode can be used for the detection of actual water samples.

[0122] Table 2 Detection of actual water samples by M-CMC / Mus / DMG / ILIG

[0123]

[0124] In summary, the present invention first modifies CMC and then, using CuSO₄ as an initiator, binds aniline to cellulose. This oxidative polymerization reaction, which self-assembles within the cellulose macromolecular chain, produces CuONPs-CMC-PANI. This composite material simultaneously loads CuONPs and PANI. This modified material and the Mus / DMG composite are then applied to an ILIG electrode to achieve a synergistic effect, thereby improving the detection current of the electrochemical sensor. The successful preparation and elemental composition of the composite were confirmed by SEM, TEM, and XPS. Electrochemical impedance spectroscopy (EIS) experiments demonstrated that the prepared modified CMC material exhibited low impedance and high electron transfer capacity, resolving the composite's poor charge-discharge resistance. Furthermore, a single LIG electrode was upgraded to an integrated graphene electrode, combining a working electrode, reference electrode, and counter electrode. The prepared M-CMC / Mus / DMG / ILIG electrode was optimized using a controlled variable method for experimental conditions, including pH, M-CMC concentration and droplet amount, Mus-DMG droplet amount, enrichment potential, and enrichment time. Under the optimal experimental conditions, the electrochemical sensor showed a good linear relationship in the range of 1 to 90 μg / L, and its linear regression equation was y = 0.3124x + 2.9548, R 2 =0.986, with a detection limit of 0.16 μg / L. The sensor also exhibited good anti-interference, reproducibility, and stability. The resulting sensor exhibited a low detection limit and a wide linear range, and was capable of detecting actual water samples, meeting detection requirements.

[0125] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. Ni in a water environment 2+ The modified electrode for detection is characterized in that It consists of a laser-induced graphene integrated electrode and M-CMC / Mus / DMG modified on its surface.

2. Ni in a water environment according to claim 1 2+ The modified electrode for detection is characterized in that The modified electrode preparation method is as follows: A1. Prepare an electrode substrate and use laser-induced graphene integrated electrodes to replace the working electrode, counter electrode, and reference electrode of the traditional three-electrode system, integrating the three electrodes on the electrode substrate; A2. Prepare Mus-DMG suspension for later use; A3. Prepare M-CMC material for standby use; A4, dissolving the M-CMC material prepared in A3 in deionized water and performing ultrasonic treatment to prepare an M-CMC solution; A5. The M-CMC solution prepared in A4 and the Mus / DMG suspension prepared in A2 are successively drop-coated onto the working electrode area of ​​the integrated electrode to prepare an M-CMC / Mus / DMG modified electrode.

3. Ni in a water environment according to claim 1 2+ The modified electrode for detection is characterized in that A2 specifically includes the following: A2.

1. Weigh a certain amount of polystyrene and dissolve it in acetone solution. Shake the solution. A2.

2. Weigh a certain amount of DMG and Mus on an analytical balance and grind them in a mortar. Dissolve the mixed powder in an acetone solution containing polystyrene and sonicate for a certain period of time before use.

4. Ni in a water environment according to claim 1 2+ The modified electrode for detection is characterized in that The A3 specifically includes the following: A3.

1. Use an analytical balance to weigh a certain amount of CuSO4·5H2O, dissolve it in deionized water, and then perform ultrasonic treatment. A3.

2. Weigh a certain amount of CMC and slowly add it dropwise to the stirred deionized water. Ultrasonicate for a certain period of time and then magnetically stir. A3.

3. Add aniline solution and continue stirring; A3.

4. Slowly add the CuSO4·5H2O solution prepared in A3.1 dropwise to the solution stirred in A3.

3. Continue stirring after the addition is complete. A3.

5. Filter the solution in A3.4 and transfer it to an oven for drying to obtain a dark green CuONPs-CMC-PANI powder, which is the M-CMC material.

5. Ni in an aqueous environment using the modified electrode as described in any one of claims 1 to 4 2+ The detection method is characterized in that The specific steps include: S1. Use a pipette to measure a certain amount of NH3 solution and NH4Cl solution into a beaker, and ultrasonically treat the mixture to obtain NH3-NH4Cl solution; S2, constructing a three-electrode system by laser-induced graphene integrated electrode, treating the electrode with M-CMC / Mus / DMG solution to prepare M-CMC / Mus / DMG modified electrode; S3, using the NH3-NH4Cl solution prepared in S1 as the electrolyte solution, based on the M-CMC / Mus / DMG modified electrode prepared in S2, the Ni in the water to be tested was completed by adsorption cathodic stripping voltammetry. 2+ Detection.

6. Ni in a water environment according to claim 4 2+ The detection method is characterized in that The pH value of the NH3-NH4Cl solution in S1 is 6.

5.

7. according to claim 4 Ni in a water environment 2+ The detection method is characterized in that As described in S3, the Ni content in the water to be tested is determined by adsorption cathodic stripping voltammetry. 2+ For the detection, the stripping voltage range was -0.6~-1.35 V, the deposition potential was set at -0.6~-1.0 V, and the enrichment time was 160~200 s.

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