Ni in an aquatic environment 2+ Modified electrode for detection and detection method

Abstract

This invention discloses a Ni in an aquatic environment 2+ This invention relates to a modified electrode and detection method for water quality testing, belonging to the field of water quality testing technology. The invention replaces the traditional three-electrode system with a laser-induced graphene integrated electrode, modifying the working electrode region with M-CMC / Mus / DMG to obtain an M-CMC / Mus / DMG / ILIG sensor. This sensor exhibits higher sensitivity and excellent conductivity, significantly reducing the cost of electrochemical detection, and also possesses portability and flexibility. It is a Ni... 2+ This invention provides new possibilities and approaches for rapid on-site detection. It modifies CMC, using CuSO4 as an initiator and aniline oxidative polymerization, employing CMC as a template to synthesize a CuO@CMC / PANI composite material in a one-step process. The introduction of PANI and CuONPs onto CMC results in higher catalytic activity and stronger electron transfer capabilities. The M-CMC / Mus / DMG / ILIG prepared in this invention can be successfully applied to Ni in actual water samples. 2+ The determination exhibits excellent stability, reproducibility, and anti-interference performance.

Description

Technical Field

[0001] This invention relates to the field of water body detection technology, and more particularly to a Ni in aquatic environments. 2+ Modified electrode for detection and detection method. Background Technology

[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 leads to the discharge of large amounts of nickel-containing wastewater into the environment. Nickel in the aquatic environment mainly exists as divalent cations (Ni...). 2+ Nickel exists in a form that is not readily apparent. While nickel (Ni) is an essential trace element for the human body, excessive intake is significantly toxic and is classified as a Group 1 carcinogen by the International Agency for Research on Cancer (IARC) (there is sufficient evidence of its carcinogenicity in humans). 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 and nasal cancer. Therefore, the presence of Ni in aquatic environments (including surface water, groundwater, drinking water sources, industrial wastewater, electroplating wastewater, etc.) is a concern. 2+ Strict monitoring of concentrations is an urgent need to safeguard ecological and environmental security and public health.

[0003] Currently, laboratory testing of water samples shows Ni... 2+ The mainstream methods include atomic absorption spectrometry (AAS), inductively coupled plasma optical emission spectrometry / mass spectrometry (ICP-OES / MS), and spectrophotometry. However, these existing mainstream methods generally suffer from common drawbacks such as high cost, bulky equipment, complex operation, long time consumption, dependence on laboratory environment, and difficulty in achieving real-time / online detection on-site. They cannot meet the growing demand for rapid, 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, particularly sensing technologies based on chemically modified electrodes (CMEs), have shown great potential in the field of environmental pollutant detection due to their significant advantages, including relatively simple equipment, low cost, fast response speed, ease of operation, ease of miniaturization, and on-site / online detection. However, for Ni in aquatic environments... 2+ While possessing specificity and high sensitivity, electrochemical detection suffers from insufficient sensitivity, poor selectivity, and inadequate stability and reproducibility.

[0005] Based on the above, this invention proposes a Ni solution for use in aquatic environments. 2+ M-CMC / Mus / DMG modified electrode and detection method for detecting Ni in aquatic environments 2+ The testing work. Summary of the Invention

[0006] The purpose of this invention is to provide a Ni solution for use in aquatic environments. 2+ Modified electrodes and detection methods for detecting Ni in actual water samples to achieve more efficient and accurate detection. 2+ The determination.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] Ni in an aquatic environment 2+ The modified electrode for detection consists of a laser-induced graphene integrated electrode and M-CMC / Mus / DMG that modifies its surface.

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

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

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

[0012] A3. Prepare M-CMC materials for later use;

[0013] A4. Dissolve the M-CMC material obtained in A3 in deionized water and sonicate it to obtain 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 obtain the M-CMC / Mus / DMG modified electrode.

[0015] Preferably, A2 specifically includes the following:

[0016] A2.1 Weigh a certain amount of polystyrene and dissolve it in acetone solution, then shake it.

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

[0018] Preferably, A3 specifically includes the following:

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

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

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

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

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

[0024] Ni in an aquatic environment 2+ The detection method specifically includes the following steps:

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

[0026] S2. A three-electrode system was constructed by laser-induced graphene integrated electrodes, and the electrodes were treated with M-CMC / Mus / DMG solution to obtain M-CMC / Mus / DMG modified electrodes.

[0027] S3. Using the NH3-NH4Cl solution prepared in S1 as the electrolyte solution, and based on the M-CMC / Mus / DMG modified electrode prepared in S2, the Ni concentration in the water to be tested is determined by adsorption cathodic stripping voltammetry. 2+ The detection.

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

[0029] Preferably, in step S3, the Ni concentration in the water to be tested is determined by adsorption cathode stripping voltammetry. 2+ The detection was performed with a dissolution voltage range of -0.6 to -1.35V, a deposition potential of -0.6 to -1.0V, and an enrichment time of 160 to 200s.

[0030] Compared with the prior art, the present invention provides a Ni solution for use in aquatic environments. 2+ The modified electrode and detection method for detection have the following advantages:

[0031] (1) This invention replaces the traditional working electrode, counter electrode, and reference electrode with a laser-induced graphene integrated electrode, and modifies the working electrode region with M-CMC / Mus / DMG to obtain an M-CMC / Mus / DMG / ILIG sensor. Compared with the traditional three-electrode system, the integrated composite electrode used in this invention has higher sensitivity and excellent conductivity, significantly reduces the cost of electrochemical detection, and has the characteristics of portability and flexibility, providing a Ni 2+ Rapid on-site detection provides new possibilities and ideas; for the modified material, this 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 and CMC as a template using 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 methods, proving the successful preparation of M-CMC / Mus / DMG / ILIG. Furthermore, the electrochemical performance of the electrode was studied using various electrochemical methods such as CV and SW AdCSV. Under optimal experimental conditions, the sensor prepared by this invention exhibited good linearity in the range of 1–90 μg / L, with a detection limit as low as 0.16 μg / L, and demonstrated excellent stability, reproducibility, and anti-interference performance. The M-CMC / Mus / DMG / ILIG prepared using this method can be successfully applied to Ni in actual water samples. 2+ The determination. Attached Figure Description

[0033] Figure 1 This is a flowchart illustrating the preparation process of M-CMC / Mus / DMG / ILIG mentioned in Example 1 of this invention;

[0034] Figure 2 The image is a SEM image of the modified electrode mentioned in Embodiment 1 of this invention;

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

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

[0037] Figure 5(A)-(F) are the 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 These are the Raman spectra before and after modification mentioned in Example 1 of this invention;

[0039] Figure 7 The contact angles of the different modified electrodes mentioned in Embodiment 1 of this invention;

[0040] Figure 8 (A) Cyclic voltammetry diagrams of different electrodes mentioned in Example 1 of this invention in a mixed solution containing 5 mM K3[Fe(CN)6] and 0.1 M KCl; (B) Cyclic voltammetry diagrams of different electrodes with 20 μg / L Ni 2+ SW AdCSV response graph;

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

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

[0043] Figure 11 (A) is the CV response in the mixed solution of 5mM K3[Fe(CN)6] and 0.1M KCl mentioned in Example 1 of this 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 solution at different pH values ​​to NH3-NH4Cl mentioned in Example 1 of this invention;

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

[0046] Figure 14 The effect of M-CMC / Mus / DMG / ILIG electrodes prepared with different drop amounts of Mus-DMG suspension mentioned in Example 1 of this invention on the detection signal.

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

[0048] Figure 16 The Mus / DMG / ILIG mentioned in Example 1 of this invention is used to treat different concentrations of Ni. 2+ The SW AdCSV response and linear relationship graph;

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

[0050] Figure 18 (A) This refers to the detection of Ni using the five modified electrodes prepared in the same manner mentioned in Example 1 of this invention. 2+ (A) Detection current in solution; (B) Detection of Ni by modified electrodes placed for different days. 2+ Detection current in the solution. Detailed Implementation

[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 a result. However, these embodiments are merely exemplary and do not constitute any limitation on the scope of the present invention. Those skilled in the art should understand that modifications or substitutions can be made to the details and form of the technical solutions of the present invention without departing from the spirit and scope of the present invention, but all such modifications and substitutions fall within the protection scope 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 this invention pertains. While any methods, apparatus, and materials similar to or equivalent to those herein may be used in the practice or testing of this invention, preferred methods, apparatus, and materials are now described.

[0053] The present invention proposes a Ni in an aquatic environment 2+ A modified electrode for detection, namely an M-CMC / Mus / DMG / ILIG, was proposed, along with a method for applying this electrode to Ni in an aqueous environment. 2+ The detection method and specific implementation details are as follows.

[0054] Example 1:

[0055] Ni in an aquatic environment 2+ The detection method specifically includes the following steps:

[0056] (1) Fabrication of M-CMC / Mus / DMG / ILIG electrode:

[0057] 1.1) Preparation of ILIG electrode

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

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

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

[0061] 1.815 g of CMC was slowly added dropwise to 100 mL of stirred deionized water, sonicated for 30 min, and then magnetically stirred for 1 h. Then, 1 mL of aniline solution was added and stirring continued for 1 h. Next, CuSO4·5H2O was slowly added dropwise to the stirred solution. During this process, a precipitate continuously formed in the solution. After the addition was complete, stirring continued for 14 h. The solution was then filtered and dried in an oven for 12 h to obtain a blackish-green powder, which is the prepared M-CMC material.

[0062] Weigh 0.015g of the M-CMC material obtained above and sonicate it in 5mL of deionized water for 10min until ready for use.

[0063] 1.3) Preparation of Mus-DMG suspension

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

[0065] Next, weigh 0.025g DMG and 0.1g Mus on an analytical balance, grind them in a mortar for 10 minutes. Dissolve the mixed powder in 2.5ml of acetone solution containing polystyrene and sonicate for 10 minutes before use.

[0066] (2)Ni 2+ Electrochemical detection

[0067] Ammonia-ammonium chloride (NH3-NH4Cl) solution with pH=9 was selected as the electrolyte solution. Adsorption 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. Cyclic voltammetry (CV) was used to measure the active area of ​​the electrode in 1M KOH solution, with a potential range of -0.25V to -0.15V and a scan rate of 20mV / s to 100mV / s. Adsorption control experiments of the composite electrode were conducted in a mixed solution of 5mM K3[Fe(CN)6] and 0.1M KCl, with a potential range of -0.4V to -0.8V and a scan rate of 20mV / s to 140mV / s.

[0068] (3) Material characterization

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

[0070] Images of modified electrodes, such as Figure 2 As shown, Figure 2 (A) involves modifying the ILIG electrode with unmodified CMC. Figure 2 (B) shows unmodified CMC, Mus, and DMG modified onto an ILIG electrode, with a scale bar of 10 μm. From Figure 2 (A) and Figure 2 (B) It can be seen that the unmodified CMC is larger in size, and the CMC and Mus intersect and cross each other to form a three-dimensional structure. Figure 2 (C) is M-CMC modified on the ILIG electrode. Figure 2 (D) shows the modification of an ILIG electrode with M-CMC, Mus, and DMG, with a scale bar of 10 μm. From Figure 2 (C) and Figure 2 (D) It can be seen that the modified CMC is smaller in volume, and more M-CMC molecules are uniformly adhered to the Mus, exhibiting a three-dimensional structure. Furthermore, the porous graphene structure on the composite electrode provides more adsorption sites. In summary, after modifying CMC, the resulting M-CMC modified on the electrode has a smaller volume and adheres more to the mica sheet, forming a more rough and wrinkled structure.

[0071] Next, the M-CMC was characterized using TEM. Figure 3 As shown, Figure 3 (A) is a transmission electron microscope image of M-CMC, which shows that spherical nanoparticles are uniformly distributed on the dendritic CMC / PANI nanofibers. The spherical nanoparticles are CuONPs. Figure 3(B) shows that the spacing between the lattice stripes is 0.25 nm, which is the lattice spacing of CuO. Figure 3 (C) shows a small region where an electron beam is fixed and scanned to obtain an X-ray energy spectrum. The figure shows that the composite material contains C, N, O, and Cu elements, proving that PANI and CuONPs were successfully composited on M-CMC.

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

[0073] Figure 4 The XPS spectrum of M-CMC / Mus / DMG shows that the composite material contains C, Cu, N, O, K, Al and Si elements, indicating that the CMC modification was successful and the composite material was successfully prepared.

[0074] To further understand the elemental and bond energy information of the M-CMC / Mus / DMG composite material, high-resolution spectral analysis was performed on some characteristic elements. The results are as follows: Figure 5 As shown, Figure 5 (A) is the spectrum of C1s, showing peaks at 284.8 eV, 286.46 eV and 288.1 eV, corresponding to C, CO and C=O bonds, respectively. Figure 5 (B) is the spectrum of Cu 2p, where Cu 2p is detected at 933.44 eV and 953.19 eV, respectively. 3 / 2 and Cu 2p 1 / 2 This indicates that Cu exists in the modified material in the form of CuO. In addition, two satellite peaks were also found at 944.16 eV and 963.09 eV, which further confirms that Cu... 2+ The existence of. Figure 5 (C) is the N1s spectrum, with aniline and protonated aniline 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 XPS results above all prove that the material composite was successfully completed.

[0075] 3.3) Raman spectroscopy analysis

[0076] Raman analysis is a spectroscopic technique primarily used to assess the degree of defects at electrode interfaces. The results are as follows: Figure 6 As shown, in the Raman spectrum of graphene, graphene is located at 1350 cm⁻¹. -1 1580cm -1 There are distinct characteristic peaks at these locations, corresponding to the D peak and the G peak, respectively. The intensity ratio of the D peak to the G peak (I) D / I G This can reflect the degree of defect in the electrode. From... Figure 6The Ii of the IiIi electrode can be obtained through calculation. D / I G A value of 1 indicates the I value of the modified M-CMC / Mus / DMG / ILIG electrode. 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 defect, and this unique structure can provide more active sites for nickel ion adsorption, thereby improving the electrochemical performance of the electrode.

[0077] 3.4) Contact Angle Analysis

[0078] Contact angle experiments were used to evaluate the hydrophilicity / hydrophobicity of LIG electrode surfaces; the smaller the contact angle, the stronger the hydrophilicity of the electrode. Experimental results are as follows: Figure 7 As shown, the contact angle of the unmodified ILIG electrode is 106.26°, indicating poor hydrophilicity. After modification with DMG and Mus, the contact angle decreased to 86.88°, demonstrating that the Mus-DMG composite material can effectively improve the electrode's hydrophilicity. Further introduction of M-CMC further reduced the contact angle of the modified electrode to 56.81°. This significant change is mainly attributed to the introduction of CuO and PANI in M-CMC. The modification of the composite electrode surface by these functional components effectively enhances the hydrophilicity of the ILIG electrode, with more Ni... 2+ It can be introduced onto 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 cyclic voltammetric responses of different electrodes in a mixed solution of 5 mM K3[Fe(CN)6] and 0.1 M KCl. The modified electrodes exhibited significantly different cyclic voltammetric responses. The unmodified ILIG electrode showed indistinct redox peaks, while the redox peak current was lower when Mus / DMG was modified onto the ILIG electrode. This demonstrates that the conductivity of the mineral material itself is limited, and the main mechanism is to increase the electroactive area of ​​the electrode and provide abundant active sites. M-CMC modification on the ILIG electrode increased the redox peak current and decreased the redox peak potential difference. This indicates that M-CMC can effectively enhance the conductivity of the electrode and promote electron transport. When M-CMC and Mus / DMG were used for combined modification, although the peak current decreased slightly, the overall conductivity was still significantly improved compared to the unmodified electrode.

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

[0083] 4.2) EIS impedance spectrum

[0084] Electrochemical impedance spectroscopy (EIS) is an important characterization method for studying electron transport behavior at electrode interfaces. The impedance value reflects the degree of obstruction during electron transfer. A smaller impedance value (Rct) indicates better conductivity of the material and a greater number of electrons participating in redox reactions on the electrode surface. In this experiment, EIS tests were performed in a mixed solution containing 5 mM K₃[Fe(CN)₆] and 0.1 M KCl.

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

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

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

[0088] This experiment still used the CV method to scan within a non-Radgetese window. The slope of the linear relationship between current and scan rate was plotted, representing 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 two-sided capacitance of the integrated electrode is 6.51 mF·cm. -2 The two-sided capacitance of the Mus / DMG / ILIG electrode is 10.93 mF·cm. -2 The two-sided capacitance of the M-CMC / Mus / DMG / ILIG electrode is 12.26 mF·cm. -2 These data indicate that the modification with 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 and thus improving the current response of the electrode in detecting nickel.

[0089] 4.4) Control process of electrode reaction

[0090] To investigate 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 as follows: Figure 11 As shown, the anode peak current Ipa is related to the scan rate (v) and the square root of the scan rate (v). 1 / 2 The linear relationship between Ipa and v is used to determine the controlling step of the LIG electrode process. When Ipa and v are linearly related, the electroactive material is limited by the adsorption process; when Ipa and v are linearly related, the electroactive material is limited by the adsorption process. 1 / 2When the relationship is linear, diffusion control dominates at the LIG electrode surface. Through fitting calculations, the peak current Ipa and the scan rate (v) are... 1 / 2 The linear relationship is better, and the linear relationship is:

[0091] y = 0.2297x + 0.1851

[0092] R 2 =0.993

[0093] Therefore, it can be 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 for this invention

[0095] 5.1) Support electrolyte optimization

[0096] The experimental conditions of this invention were optimized to be at 20 μg / L Ni. 2+ The experiment was conducted in solution, and the selected buffer solution was NH3-NH4Cl.

[0097] Next, the effect of pH on the detection current was investigated. M-CMC / Mus / DMG was immersed in different buffer solutions at varying pH values ​​for detection. Figure 12 It can be seen that the detection current increases with increasing pH, reaching its maximum at pH = 9, at which point the current value is approximately 7.02 μA. When the pH increases further, the current decreases sharply, which may be due to the presence of Ni in an overly alkaline environment. 2+ It may combine with hydroxyl groups in the water environment, which may lead to a decrease in current value. Taking all factors into consideration, NH3-NH4Cl with pH=9 is selected as the best buffer solution.

[0098] 5.2) M-CMC Optimization

[0099] The concentration and amount of M-CMC applied affect the detection current. As a catalyst that promotes electron transfer, the proportion of M-CMC in the composite material affects the Ni content. 2+ The efficiency of migration to the ILIG electrode was then assessed using M-CMC prepared at different concentrations for 20 μg / L Ni. 2+ The solution was tested.

[0100] Different concentrations of M-CMC and Mus-DMG suspensions were sequentially drop-coated onto an ILIG electrode for detection. The results are as follows: Figure 13As shown in (A) and (B), the current response value increases with increasing M-CMC concentration. This is because M-CMC, as a catalyst, enhances the electron transfer capability on the electrode; the higher the M-CMC concentration, the stronger the electron transfer capability. The electron transfer capability reaches its maximum when the M-CMC concentration reaches 3 g / L. Further increasing the M-CMC concentration results in a thicker M-CMC layer, which hinders electron transfer, affects the electrode's conductivity, and thus reduces the response current. Considering all factors, a M-CMC concentration of 3 g / L was chosen.

[0101] Next, keeping the concentration of M-CMC constant (3 g / L), the effect of different drop-coating amounts on the sensor was investigated. After modifying the electrode with Mus-DMG composite material, 2 μL, 4 μL, 6 μL, 8 μL, and 10 μL of M-CMC were drop-coated, respectively. The experimental results are shown below. Figure 13 As shown in (C) and (D), the current value gradually increases when the coating amount increases from 2 μL to 8 μL. This indicates that the increasing coating amount is beneficial for M-CMC to fully utilize the electron transfer function. 2+ M-CMC molecules can adsorb onto the Mus-DMG modified layer, and their catalytic effect accelerates the detection process, thereby increasing the detection sealing current. However, when the drop volume is further increased, the current value increases slowly, suggesting that electron transfer has reached its limit, and further increases will not result in more electron transfer for redox reactions. Considering material conservation, 8 μL was chosen as the drop volume for M-CMC.

[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, we will investigate the effect of the amount of Mus-DMG applied on the current value.

[0104] 1 μL, 2 μL, 3 μL, 4 μL, and 5 μL of Mus-DMG suspension were dropped onto the substrate and placed in a 20 μg / L Ni solution. 2+ The test was performed in the solution to be tested, and the experimental results are as follows: Figure 14 The results showed that as the coating volume increased from 1 μL to 3 μL, the detection current increased from 4.51 μA to 9.15 μA. However, as the coating volume increased from 3 μL to 5 μL, the detection current gradually decreased. This is because the higher the coating volume of Mus-DMG, the more Ni it can adsorb. 2+ The more layers there are, the higher the detection current. However, too many Mus-DMG layers can lead to an excessively thick modification layer, reducing the number of electrons transferred and decreasing the electron transfer capability. Considering all factors, 3 μL, which has the highest detection current, was chosen as the optimal drop volume.

[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 enhance the enrichment of Ni. 2+ Adsorbed onto the electrode surface, the experimental results are as follows: Figure 15 As shown in (A) and (B), the reduction peak current increases as the enrichment potential decreases from -0.6V to -0.8V. This may be because a poor potential state affects the state of the electrode surface, thereby affecting the Ni. 2+ The adsorption and reduction reactions occur. When the enrichment potential decreases from -0.8V to -1.0V, the current value decreases. Considering all factors, -0.8V is selected as the optimal enrichment potential.

[0107] Enrichment time is also an important parameter in electrochemical detection, and the results are as follows: Figure 15 As shown in (C) and (D), when the enrichment time increases from 120 s to 180 s, the current value also increases to 9.05 μA. When the current value increases further, the rate of increase tends to level off. This is because the longer the enrichment time, the more Ni is adsorbed. 2+ The more electrons, the more electrons participate in the reaction; however, if the enrichment time is increased beyond 180s, the rate of current increase slows down. Considering all factors, 180s is chosen as the optimal enrichment time.

[0108] (6) Linear range and detection limit

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

[0110] y = 0.3124x + 2.9548

[0111] R 2 =0.986

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

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

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

[0115] Table 1 Other sensor detection data

[0116]

[0117] (7) Electrode anti-interference and reproducibility

[0118] To better verify the sensor's anti-interference performance in an aquatic environment, this invention selects a value relative to 20 μg / L Ni. 2+ 100 times concentration of Zn 2+ Mn 2+ Pb 2+ K + Ca 2+ Na + CO3 2- SO4 2- Cl - As an anti-interference material. From Figure 17 As shown, the addition of most of the anti-interference ions compared to Ni without anti-interference... 2+ The peak current did not change much under these conditions, indicating that the prepared M-CMC / Mus / DMG / ILIG electrode has good anti-interference performance.

[0119] The reproducibility and stability of the M-CMC / Mus / DMG / ILIG electrode were then investigated. Five electrodes prepared in the same manner were placed in 20 μg / L Ni. 2+ Detecting current in solution, from experimental results Figure 18 (A) It can be seen that the detection currents of the five electrodes are not significantly different, with a relative standard deviation of 2.7%, indicating good reproducibility. Meanwhile, to investigate the stability of the M-CMC / Mus / DMG / ILIG electrode, the same electrode was placed for different number of days (1 day, 4 days, 7 days, 10 days, and 13 days) to detect 20 μg / L Ni. 2+ In solution, the experimental results are as follows Figure 18 (B) shows that the current decay is low, and the electrode current after two weeks is about 87.6% of the initial electrode current, indicating good stability.

[0120] (8) Testing of actual water samples

[0121] To verify the application of the prepared sensor in an aquatic environment, the M-CMC / Mus / DMG / ILIG sensor was applied to the detection of actual water samples under optimal detection conditions. The prepared electrode was evaluated using a spiking method. Water samples were prepared by simple filtration and then spiked with Ni at concentrations of 10 μg / L, 20 μg / L, and 40 μg / L. 2+ Solution. The results are shown in Table 2. Ni in the tap water sample 2+ The recovery rate was 93.44%–103.46%, and the Ni content in the groundwater samples was [missing information]. 2+ The recovery rate was 101.85%–109.41%. The results indicate that the M-CMC / Mus / DMG / ILIG electrode can be applied to the detection of actual water samples.

[0122] Table 2 shows the detection results of M-CMC / Mus / DMG / ILIG on actual water samples.

[0123]

[0124] In summary, this invention modifies CMC and uses CuSO4 as an initiator to combine aniline with cellulose. They undergo a self-assembly oxidative polymerization reaction within the cellulose macromolecular chains to prepare CuONPs-CMC-PANI. This composite material simultaneously loads CuONPs and PANI. The sequential modification of this material and the Mus / DMG composite material on an ILIG electrode exhibits a synergistic effect, thereby improving the detection current of the electrochemical sensor. The successful preparation and elemental composition of the composite material were confirmed using SEM, TEM, and XPS. EIS experiments demonstrated that the prepared modified CMC material has a low impedance and high electron transfer capability, solving the problem of poor charge loss in composite materials. Simultaneously, the single ILIG electrode was upgraded to an integrated graphene electrode combining the working electrode, reference electrode, and counter electrode. The prepared M-CMC / Mus / DMG / ILIG electrode was optimized under controlled variable conditions, including pH value, M-CMC concentration and coating amount, Mus-DMG coating amount, enrichment potential, and enrichment time. Under optimal experimental conditions, the electrochemical sensor exhibits good linearity within the range of 1–90 μg / L, with a linear regression equation of y = 0.3124x + 2.9548, R0. 2 =0.986, with a detection limit of 0.16 μg / L. The prepared sensor also exhibits good anti-interference, reproducibility, and stability. The final prepared sensor has a low detection limit and a wide linear range, and can perform detection on actual water samples, meeting the detection requirements.

[0125] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A Ni in an aquatic environment 2+ The modified electrode for detection is characterized in that, The laser-induced graphene integrated electrode and M-CMC / Mus / DMG modified surface thereof are composed; wherein, CMC is hydroxymethyl cellulose; Mus is muscovite; and DMG is dimethylglyoxime; The preparation method of the modified electrode is as follows: A1, preparing an electrode substrate, using a laser-induced graphene integrated electrode to replace the working electrode, the counter electrode and the reference electrode of the traditional three-electrode system, and integrating the three electrodes on the electrode substrate; A2, preparing a Mus-DMG suspension for standby, specifically including the following contents: A2.1, a certain amount of polystyrene is weighed and dissolved in an acetone solution, and is subjected to oscillation treatment; A2.2, a certain amount of DMG and Mus are weighed on an analytical balance and are put into a mortar for grinding; the mixed powder is dissolved in the acetone solution containing polystyrene and is subjected to ultrasonic treatment for a certain time, and is ready for use; A3, preparing M-CMC material for standby, specifically including the following contents: A3.1, a certain amount of CuSO4·5H2O is weighed and dissolved in deionized water and is subjected to ultrasonic treatment; A3.2, a certain amount of CMC is weighed and slowly added to the stirred deionized water, and is subjected to ultrasonic treatment for a certain time and then is subjected to magnetic stirring; A3.3, aniline solution is added and stirring is continued; A3.4, the CuSO4·5H2O solution prepared in A3.1 is slowly added to the stirred solution in A3.3, and stirring is continued after the addition is completed; A3.5, the solution in A3.4 is subjected to suction filtration and is transferred to an oven for drying, to obtain black-green CuONPs-CMC-PANI powder, which is the M-CMC material; A4, the M-CMC material prepared in A3 is dissolved in deionized water and is subjected to ultrasonic treatment, to prepare 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 region of the integrated electrode, to prepare a M-CMC / Mus / DMG modified electrode.

2. A method for detecting Ni2+ in water environment by using the modified electrode as claimed in claim 1. 2+ A detection method characterized by, Specifically including the following steps: S1, a certain amount of NH3 solution and NH4Cl solution are measured by a pipette and are put into a beaker, and the mixture is subjected to ultrasonic treatment to obtain NH3-NH4Cl solution; S2, a three-electrode system is constructed by a laser-induced graphene integrated electrode, and the M-CMC / Mus / DMG solution is used to treat the electrode, to prepare a M-CMC / Mus / DMG modified electrode; S3, using the NH3-NH4Cl solution prepared in S1 as electrolyte solution, based on the M-CMC / Mus / DMG modified electrode prepared in S2, the detection of Ni2+ in the water sample to be tested was completed by adsorptive cathodic stripping voltammetry. 2+ S3, using the NH3-NH4Cl solution prepared in S1 as electrolyte solution, based on the M-CMC / Mus / DMG modified electrode prepared in S2, the detection of Ni2+ in the water sample to be tested was completed by adsorptive cathodic stripping voltammetry.

3. A method according to claim 2 for the determination of Ni 2+ A detection method characterized by, The NH3-NH4Cl solution in S1 has a pH of 6.

5.

4. A method according to claim 2 for the determination of Ni 2+ A detection method characterized by, S3 describes the use of adsorption cathode stripping voltammetry to determine Ni in the water sample. 2+ The detection was performed with a dissolution voltage range of -0.6 to -1.35 V, a deposition potential of -0.6 to -1.0 V, and an enrichment time of 160 to 200 s.

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