Electrochemical sensor based on modified glassy carbon electrode and manufacturing method thereof

Abstract

The invention discloses a manufacturing method of an electrochemical sensor based on a modified glassy carbon electrode. The manufacturing method comprises the following steps: step 1, preparing Ag2O nanoparticles; step 2, preparing Ag2O printing ink according to a product obtained in the step 1; step 3, preparing an MXene nanosheet; 4, preparing MXene printing ink according to a product obtained in the step 3; and step 5, sequentially dispensing the MXene ink obtained in the step 4 and the Ag2O ink obtained in the step 2 on a GC electrode to prepare an Ag2O-MXene modified GC working electrode, and then selecting a corresponding counter electrode and a reference electrode to form the electrochemical sensor. The invention further discloses an electrochemical sensor based on the modified glassy carbon electrode. The problems that an existing electrochemical sensor is easily interfered by bacteria in a 4-NP detection environment and is low in sensitivity, poor in stability and high in cost are solved.

Description

Technical Field

[0001] The invention belongs to the technical field of electrochemical sensors, and relates to an electrochemical sensor of a modified glassy carbon electrode. The invention also relates to a method for manufacturing the electrochemical sensor based on the modified glassy carbon electrode. Background Art

[0002] 4-Nitrophenol (4-NP) is an important intermediate raw material, widely used in the chemical production of dyes, pesticides, pharmaceuticals, etc. However, 4-NP has stable chemical properties and is difficult to decompose in nature, becoming one of the important sources of pollutants in water. Even at extremely low concentrations, 4-NP has potential toxicity such as carcinogenicity, teratogenicity, and mutagenicity to humans, animals, and plants. Therefore, it is of great significance to develop a method that can quickly, conveniently, efficiently, sensitively, and accurately detect the concentration of 4-NP.

[0003] A variety of methods for 4-NP detection have been developed, including gas phase liquid chromatography, high performance liquid chromatography, surface enhanced Raman scattering, fluorescence, electrochemical method, electrophoresis and electrochemical sensors. Among these methods, except for fluorescence and electrochemical sensors, other methods are time-consuming, require expensive equipment and professional processing, have high operating costs, and are difficult to detect on site, which is not conducive to the rapid and efficient detection of 4-NP. Electrochemical sensors stand out in real-time and on-site monitoring due to their advantages such as low cost, portability, rapid response, simple operation and high sensitivity. However, electrochemical sensors usually use bare electrodes of precious metals such as Au, Ag, and Cu, which have the problems of high cost, low sensitivity, poor stability, and susceptibility to bacterial interference, which limits their practical application. Summary of the invention

[0004] The purpose of the present invention is to provide a method for preparing an electrochemical sensor based on a modified glassy carbon electrode, which solves the problems of the existing electrochemical sensors being susceptible to bacterial interference in a 4-NP detection environment and having low sensitivity, poor stability and high cost.

[0005] Another object of the present invention is to provide an electrochemical sensor based on a modified glassy carbon electrode.

[0006] The first technical solution adopted by the present invention is a method for preparing an electrochemical sensor based on a modified glassy carbon electrode, which specifically comprises the following steps:

[0007] Step 1, Preparation of Ag 2 O nanoparticles;

[0008] Step 2, preparing Ag according to the product obtained in step 1 2 O ink;

[0009] Step 3, preparing MXene nanosheets;

[0010] Step 4, preparing MXene ink according to the product obtained in step 3;

[0011] Step 5: Mix the MXene ink obtained in step 4 with the Ag obtained in step 2. 2 O ink was dotted on the GC electrode to prepare Ag 2 O-MXene is used to modify the GC working electrode, and then the corresponding counter electrode and reference electrode are selected to form an electrochemical sensor.

[0012] The first technical solution of the present invention is also characterized in that:

[0013] The specific process of step 1 is:

[0014] A 0.1-0.2 mol / L silver nitrate solution and a 0.4-1.0 mol / L sodium hydroxide solution were stirred and mixed, reacted at 40-60°C for 1.5-3h, and then repeatedly washed, vacuum filtered, and dried to obtain Ag. 2 O nanoparticles.

[0015] The specific process of step 2 is:

[0016] Take 0.4~0.6mgAg 2 The AgO nanoparticles were dispersed in 1 mL of an organic solvent containing isopropanol and ultrasonicated on ice for 1 to 2 h to obtain AgO nanoparticles. 2 O ink.

[0017] In step 2, the volume ratio of isopropanol to the organic solvent is 4:1 or 7:3, and the organic solvent is at least one of N,N-dimethylformamide, N-methylpyrrolidone or N,N-dimethylacetamide.

[0018] The specific process of step 3 is:

[0019] Step 3.1, add 4.48 mL of deionized water to a reaction bottle, then add 15.52 mL of concentrated hydrochloric acid, stir for 30 min, then add 1.6 g of LiF to the hydrochloric acid solution in 20 portions to obtain a mixed etchant of LiF and HCl;

[0020] In step 3.2, weigh 1 g of MAX precursor, add the MAX precursor to the mixed etchant prepared in step 3.1 in 20 times, etch at 50°C for 24 hours, then centrifuge and wash at 3500 rpm for 6 minutes until the pH value of the solution is close to 6.5, then ultrasonically strip at 600 W for 1 hour, manually oscillate for 30 minutes after stripping, then centrifuge and wash at 3500 rpm for 1 hour, finally collect the upper MXene clear liquid, and freeze-dry for 24 hours to obtain MXene nanosheets.

[0021] The specific process of step 4 is:

[0022] Take 0.3-0.5 mg of MXene nanosheets and disperse them in 1 mL of mixed organic solvent, and ultrasonicate them in an ice bath for 0.5-1 h to obtain MXene ink.

[0023] In step 4, the mixed organic solvent includes 5% Nafion solution, water, and an organic solvent in a volume ratio of 3 to 5:20:40 to 42, and the organic solvent is at least one of ethanol, methanol, isopropanol, N,N-dimethylformamide, N-methylpyrrolidone or N,N-dimethylacetamide.

[0024] The specific process of step 5 is:

[0025] Take the MXene ink prepared in step 4 and drop it on the GC electrode. Dry it in a vacuum or nitrogen atmosphere at 35°C for 4 to 6 hours to obtain a MXene-modified GC electrode. Then take 4 μL of the Ag prepared in step 2. 2 O ink was drop-coated on the MXene-modified GC electrode and dried in a vacuum or nitrogen atmosphere at 35 °C for 6 to 8 h away from light to finally obtain Ag. 2 O-MXene was used to modify the GC working electrode. Meanwhile, a Pt wire electrode was used as the counter electrode and a saturated calomel electrode was used as the reference electrode to prepare an electrochemical sensor for 4-NP detection.

[0026] The second technical solution adopted by the present invention is an electrochemical sensor based on a modified glassy carbon electrode, which is prepared by the above-mentioned method for preparing an electrochemical sensor based on a modified glassy carbon electrode.

[0027] The beneficial effect of the present invention is that the electrochemical sensor prepared by the present invention makes full use of Ag 2 O nanomaterials’ excellent electrocatalytic ability, enhanced electronic communication ability, stability and strong antibacterial ability and MXene’s excellent electronic conductivity and large specific surface area. 2 The advantages of O nanomaterials and MXene are that they can provide more reactive sites, enhance the electrocatalytic effect, generate more sensitive electrochemical response signals, improve the detection range, sensitivity and accuracy of the sensor, and reduce the detection limit and cost. In addition, the hydrophilic functional groups on the surface of MXene are helpful for preparing uniform electrode inks, maintaining the uniformity of the electrode surface and the stability of electrochemical tests. 2 The electrochemical sensor of O-MXene modified GC electrode has a simple preparation process, simple sensor structure, and low cost, which is suitable for large-scale production applications and has important application prospects in the field of 4-NP detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 The present invention is based on Ag in the preparation method of the electrochemical sensor based on the modified glassy carbon electrode2 The electrochemical sensors of O-MXene modified GC electrode and bare GC electrode were tested in 5 mM [Fe(CN) 6 ] 3- CV curve in;

[0029] Figure 2 The present invention is based on Ag in the preparation method of the electrochemical sensor based on the modified glassy carbon electrode 2 CV curves of electrochemical sensors of O-MXene modified GC electrode and bare GC electrode in PBS solution containing 0.1 mM 4-NP;

[0030] FIG3(a) is a method for preparing an electrochemical sensor based on a modified glassy carbon electrode according to the present invention. 2 LSV curve of electrochemical sensor of O-MXene modified GC electrode;

[0031] FIG3( b ) is a linear fitting relationship diagram of the reduction peak current value and 4-NP concentration in the LSV curve in FIG3( a );

[0032] Figure 4 The present invention is based on the preparation method of the electrochemical sensor modified glassy carbon electrode prepared by Ag 2 DPV curves of O-MXene modified GC electrode in PBS solutions containing different organic pollutants;

[0033] FIG5( a ) is the colony growth result of E. coli not treated with the modified electrode after culturing for 1 day;

[0034] FIG5( b ) is a Ag prepared in Example 1 of the method for preparing an electrochemical sensor based on a modified glassy carbon electrode of the present invention. 2 Colony growth of O-MXene-modified GC electrode after co-culture with Escherichia coli for 1 day. DETAILED DESCRIPTION

[0035] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0036] The method for preparing the electrochemical sensor of the modified glassy carbon electrode of the present invention is implemented according to the following steps:

[0037] Step 1, 25 mL of a 0.1-0.2 mol / L silver nitrate solution and 50 mL of a 0.4-1.0 mol / L sodium hydroxide solution are mixed under strong stirring, reacted at 40-60° C. for 1.5-3 h, and then repeatedly washed, vacuum filtered, and dried to obtain Ag 2 O nanoparticles.

[0038] Step 2, take 0.4-0.6 mg of Ag from step 12 The AgO nanoparticles were dispersed in 1 mL of an organic solvent containing isopropanol and ultrasonicated on ice for 1 to 2 h to obtain AgO nanoparticles. 2 O ink. The volume ratio of isopropyl alcohol to the organic solvent is 4:1 or 7:3, and the organic solvent is at least one of N,N-dimethylformamide (DMF), N-methylpyrrolidone or N,N-dimethylacetamide (DMA).

[0039] Step 3, take 4.48mL of deionized water and add it to the reaction bottle, then add 15.52mL of concentrated hydrochloric acid, stir for 30min, and then add 1.6g of LiF to the hydrochloric acid solution in 20 times to obtain a mixed etchant of LiF and HCl. Then weigh 1g of MAX precursor, add the MAX precursor to the mixed etchant in 20 times, etch at 50°C for 24h, then centrifuge and wash at 3500rpm for 6min until the pH value of the solution is close to 6.5, and then ultrasonically strip at 600W for 1h, manually shake for 30min after stripping, then centrifuge and wash at 3500rpm for 1h, finally collect the upper MXene clear liquid, and freeze-dry for 24h to obtain MXene nanosheets.

[0040] Step 4, take 0.3-0.5 mg of the MXene nanosheets of step 3 and disperse them in 1 mL of a mixed organic solvent, and perform ice bath ultrasonication for 0.5-1 h to obtain a MXene ink. In the mixed organic solvent, the volume ratio of commercial 5% Nafion solution, water, and organic solvent is 3-5:20:40-42, and the organic solvent is at least one of ethanol, methanol, isopropanol, N,N-dimethylformamide (DMF), N-methylpyrrolidone, or N,N-dimethylacetamide (DMA).

[0041] Step 5: Take 4 μL of the MXene ink prepared in step 4 and apply it on the GC electrode. Dry it in a vacuum or nitrogen atmosphere at 35°C for 4 to 6 hours to obtain a MXene-modified GC electrode. Then take 4 μL of the Ag prepared in step 2 and apply it on the GC electrode. 2 O ink was drop-coated on the MXene-modified GC electrode and dried in a vacuum or nitrogen atmosphere at 35 °C for 6 to 8 h away from light to finally obtain Ag. 2 O-MXene was used to modify the GC working electrode. At the same time, a Pt wire electrode was used as the counter electrode and a saturated calomel electrode was used as the reference electrode to prepare an electrochemical sensor for 4-NP detection.

[0042] Through the above preparation method, the detection limit of 4-NP was as low as 0.29×10 -9 mol / L, sensitivity reaches 7.1591×10 -9 M·μA -1 cm -2 Ag-based 2Electrochemical sensor based on O-MXene modified GC electrode.

[0043] Example 1

[0044] The present invention provides a method for preparing an electrochemical sensor based on a modified glassy carbon electrode, which specifically comprises the following steps:

[0045] Step 1, 25 mL of 0.1 mol / L silver nitrate solution and 50 mL of 0.4 mol / L sodium hydroxide solution were mixed under strong stirring, stirred at 40°C for 1.5 h, and then repeatedly washed, vacuum filtered, and dried to obtain Ag 2 O nanoparticles.

[0046] Step 2, take 0.4 mg of Ag prepared in step 1 2 The AgO nanoparticles were dispersed in 1 mL of a mixed organic solvent of isopropanol and DMF in a volume ratio of 4:1 and ultrasonicated on ice for 1 h to obtain AgO nanoparticles. 2 O ink.

[0047] Step 3, take 4.48mL of deionized water and add it to the reaction bottle, then add 15.52mL of concentrated hydrochloric acid, stir for 30min, and then add 1.6g of LiF to the hydrochloric acid solution in 20 times to obtain a mixed etchant of LiF and HCl. Then weigh 1g of MAX precursor, add the MAX precursor to the mixed etchant of LiF and HCl in 20 times, etch at 50°C for 24h, then centrifuge and wash at 3500rpm for 6min until the pH value of the solution is close to 6.5, and then ultrasonically strip at 600W for 1h, manually shake for 30min after stripping, then centrifuge and wash at 3500rpm for 1h, finally collect the upper MXene clear liquid, and freeze-dry for 24h to obtain MXene nanosheets.

[0048] Step 4: Take 0.3 mg of the MXene nanosheets prepared in step 3 and disperse them in 1 mL of a mixed organic solvent (the volume ratio of commercial 5% Nafion solution, water, and ethanol is 3:20:42), and ultrasonicate in an ice bath for 0.5 h to obtain MXene ink.

[0049] Step 5: Take 4 μL of the MXene ink prepared in step 4 and apply it on the GC electrode, and dry it in vacuum at 35 °C for 4 h to obtain a MXene-modified GC electrode; then take 4 μL of the Ag prepared in step 2 and 2 O ink was drop-coated on the MXene-modified GC electrode and dried in a vacuum oven at 35 °C for 6 h to obtain Ag 2 O-MXene was used to modify the GC working electrode. At the same time, a Pt wire electrode was used as the counter electrode and a saturated calomel electrode was used as the reference electrode to prepare an electrochemical sensor for 4-NP detection.

[0050] Example 2

[0051] The present invention provides a method for preparing an electrochemical sensor based on a modified glassy carbon electrode, which specifically comprises the following steps:

[0052] Step 1: Mix 25 mL of 0.2 mol / L silver nitrate solution and 50 mL of 1.0 mol / L sodium hydroxide solution under strong stirring, stir and react at 60° C. for 3 h, then repeatedly wash, vacuum filter and dry to obtain Ag. 2 O nanoparticles.

[0053] Step 2, take 0.6 mg of Ag prepared in step 1 2 O nanoparticles were dispersed in 1 mL of a mixed organic solvent of isopropanol and N-methylpyrrolidone with a volume ratio of 7:3 and ultrasonicated on an ice bath for 2 h to obtain Ag 2 O ink.

[0054] Step 3, take 4.48mL of deionized water and add it to the reaction bottle, then add 15.52mL of concentrated hydrochloric acid, stir for 30min, and then add 1.6g of LiF to the hydrochloric acid solution in 20 times to obtain a mixed etchant of LiF and HCl. Then weigh 1g of MAX precursor, add the MAX precursor to the mixed etchant in 20 times, and etch at 50°C for 24h, then centrifuge and wash at 3500rpm for 6min until the pH value of the solution is close to 6.5, and then ultrasonically strip at 600W for 1h, manually shake for 30min after stripping, then centrifuge and wash at 3500rpm for 1h, finally collect the upper MXene clear liquid, and freeze-dry for 24h to obtain MXene nanosheets.

[0055] Step 4: Take 0.4 mg of the MXene nanosheets prepared in step 3 and disperse them in 1 mL of a mixed organic solvent (the volume ratio of commercial 5% Nafion solution, water, and isopropanol is 5:20:40), and ultrasonicate in an ice bath for 1 h to obtain MXene ink.

[0056] Step 5: Take 4 μL of the MXene ink prepared in step 4 and apply it on the GC electrode, and dry it in vacuum at 35 °C for 6 h to obtain a MXene-modified GC electrode; then take 4 μL of the Ag prepared in step 2 and 2 O ink was drop-coated on the MXene-modified GC electrode and dried in a vacuum oven at 35 °C for 8 h to obtain Ag 2 O-MXene was used to modify the GC working electrode. At the same time, a Pt wire electrode was used as the counter electrode and a saturated calomel electrode was used as the reference electrode to prepare an electrochemical sensor for 4-NP detection.

[0057] Example 3

[0058] The present invention provides a method for preparing an electrochemical sensor based on a modified glassy carbon electrode, which specifically comprises the following steps:

[0059] Step 1, 25 mL of 0.15 mol / L silver nitrate solution and 50 mL of 0.95 mol / L sodium hydroxide solution were mixed under strong stirring, stirred at 50° C. for 2 h, and then repeatedly washed, vacuum filtered, and dried to obtain Ag 2 O nanoparticles.

[0060] Step 2, take 0.6 mg of Ag prepared in step 1 2 O nanoparticles were dispersed in 1 mL of a mixed organic solvent of isopropanol and N-methylpyrrolidone with a volume ratio of 7:3 and ultrasonicated on an ice bath for 2 h to obtain Ag 2 O ink.

[0061] Step 3, take 4.48mL of deionized water and add it to the reaction bottle, then add 15.52mL of concentrated hydrochloric acid, stir for 30min, and then add 1.6g of LiF to the hydrochloric acid solution in 20 times to obtain a mixed etchant of LiF and HCl. Then weigh 1g of MAX precursor, add the MAX precursor to the mixed etchant in 20 times, and etch at 50°C for 24h, then centrifuge and wash at 3500rpm for 6min until the pH value of the solution is close to 6.5, and then ultrasonically strip at 600W for 1h, manually shake for 30min after stripping, then centrifuge and wash at 3500rpm for 1h, finally collect the upper MXene clear liquid, and freeze-dry for 24h to obtain MXene nanosheets.

[0062] Step 4: Take 0.5 mg of the MXene nanosheets prepared in step 3 and disperse them in 1 mL of a mixed organic solvent (commercial 5% Nafion solution, water, and methanol in a volume ratio of 5:20:40), and ultrasonicate them in an ice bath for 1 h to obtain MXene ink.

[0063] Step 5: Take 4 μL of the MXene ink prepared in step 4 and apply it on the GC electrode, and dry it in a nitrogen atmosphere at 35 °C for 6 h to obtain a MXene-modified GC electrode; then take 4 μL of the Ag prepared in step 2 2 O ink was drop-coated on the MXene-modified GC electrode and dried in a nitrogen atmosphere at 35 °C for 7 h in the dark to obtain Ag 2 O-MXene was used to modify the GC working electrode. At the same time, a Pt wire electrode was used as the counter electrode and a saturated calomel electrode was used as the reference electrode to prepare an electrochemical sensor for 4-NP detection.

[0064] Example 4

[0065] The present invention provides a method for preparing an electrochemical sensor based on a modified glassy carbon electrode, which specifically comprises the following steps:

[0066] Step 1: Mix 25 mL of 0.2 mol / L silver nitrate solution and 50 mL of 0.8 mol / L sodium hydroxide solution under strong stirring, stir at 45°C for 3 h, and then repeatedly wash, vacuum filter and dry to obtain Ag 2 O nanoparticles.

[0067] Step 2, take 0.4 mg of the Ag prepared in step 1 2 O nanoparticles were dispersed in 1 mL of a mixed organic solvent of isopropanol and DMA in a volume ratio of 7:3 and ultrasonicated on an ice bath for 1 h to obtain Ag 2 O ink.

[0068] Step 3, take 4.48mL of deionized water and add it to the reaction bottle, then add 15.52mL of concentrated hydrochloric acid, stir for 30min, and then add 1.6g of LiF to the hydrochloric acid solution in 20 times to obtain a mixed etchant of LiF and HCl. Then weigh 1g of MAX precursor, add the MAX precursor to the mixed etchant in 20 times, and etch at 50°C for 24h, then centrifuge and wash at 3500rpm for 6min until the pH value of the solution is close to 6.5, and then ultrasonically strip at 600W for 1h, manually shake for 30min after stripping, then centrifuge and wash at 3500rpm for 1h, finally collect the upper MXene clear liquid, and freeze-dry for 24h to obtain MXene nanosheets.

[0069] Step 4, take 0.5 mg of the MXene nanosheets from step 3 and disperse them in 1 mL of a mixed organic solvent (commercial 5% Nafion solution, water, and DMF in a volume ratio of 4:20:41), and ultrasonicate in an ice bath for 0.5 h to obtain MXene ink.

[0070] Step 5: Take 4 μL of the MXene ink prepared in step 4 and apply it on the GC electrode, and dry it in a nitrogen atmosphere at 35 °C for 5 h to obtain a MXene-modified GC electrode; then take 4 μL of the Ag prepared in step 2 and 2 O ink was drop-coated on the MXene-modified GC electrode and dried in a nitrogen atmosphere at 35 °C for 7 h in the dark to obtain Ag 2 O-MXene was used to modify the GC working electrode. At the same time, a Pt wire electrode was used as the counter electrode and a saturated calomel electrode was used as the reference electrode to prepare an electrochemical sensor for 4-NP detection.

[0071] Figure 1 The electrochemical sensor prepared in Example 1 of the present invention and the electrochemical sensor based on the bare GC electrode were subjected to 5 mM [Fe(CN) 6 ] 3-The CV curves in the test show that the electrochemical sensor based on the modified GC electrode has a better redox effect on 4-NP than the electrochemical sensor based on the bare GC electrode. 2 O-MXene modification increased the peak current of the GC electrode, indicating that the current response was enhanced and the modified electrode had better electrocatalytic activity and higher current response.

[0072] Figure 2 The DPV curves of the electrochemical sensor prepared in Example 2 of the present invention and the electrochemical sensor based on the bare GC electrode were measured in a PBS solution containing 0.1 mM 4-NP. In the DPV curve, the modified electrode showed a higher response current value than the bare electrode, indicating that Ag 2 The O-MXene modified electrode exhibits higher sensitivity and electrocatalytic activity for the electrochemical reduction reaction of 4-NP.

[0073] FIG3(a) is a Ag-based 2 The LSV curves of the O-MXene modified GC electrode electrochemical sensor measured in PBS solutions of 0, 0.0022, 0.0050, 0.0215, 0.0360, 0.0503, 0.2154, 0.3595, and 0.5026 μm / L 4-NP. 2 The linear fitting curve of the reduction peak current of the LSV curve measured by the O-MXene modified GC electrode electrochemical sensor in PBS solutions of 0, 0.0022, 0.0050, 0.0215, 0.0360, 0.0503, 0.2154, 0.3595, and 0.5026 μm / L 4-NP and the corresponding 4-NP concentration. As can be seen from Figure 3(a), the modified electrode can identify 4-NP, and the reduction peak current value increases with the increase of 4-NP concentration; Figure 3(b) shows that within a certain concentration range, the 4-NP concentration is linearly related to the reduction peak current value. Among them, the linear equation of 4-NP in the range of 0.0022-0.0503 μm / L is I PC (μA)=506.0487c+15.0954(R 2 =0.99165); the linear equation of 4-NP in the range of 0.0503-0.5026 μm / L is I PC (μA)=88.3334c+36.2642(R 2 =0.99989). Wherein, c in the linear equation is the concentration of 4-NP, in μm / L, I PC is the reduction peak current value obtained by linear sweep voltammetry, in μA. This indicates that the prepared modified electrode has a wide detection range for 4-NP.

[0074] According to the standard deviation method, the detection limit = 3S 0 / k,S 0 is the standard deviation of the blank sample (n=0), k is the slope of the regression equation, k=506.0487 for 4-NP in the range of 0.0022-0.0503μm / L, k=88.3334 for 4-NP in the range of 0.0503-0.5026μm / L, and the S of 4-NP in the range of 0.0022-0.0503μm / L is 0. 0 =0.0489, S in the range of 0.0503-0.5026 μm / L 0 =0.0461, the detection limit of 4-NP in the range of 0.0022-0.0503 μm / L is calculated to be 0.29×10 - 9 M, the detection limit in the range of 0.0503-0.5026 μm / L was 1.57×10 -9 M. This shows that Ag 2 The O-MXene modified GC electrode has a lower detection limit for 4-NP.

[0075] Figure 4 The Ag-based 2 DPV curves of O-MXene modified GC electrode electrochemical sensor in pure PBS, PBS solution containing tetracycline (TC), 4-nitrophenol (4-NP), resorcinol (RS), phloroglucinol (PL), ciprofloxacin (CIP), and melamine (MeL). It can be seen from the figure that the response of the modified electrode to the specific pollutant 4-NP is significantly different from that of other pollutants, which indicates that the electrode has good selectivity.

[0076] FIG5(a) is the colony growth result of E. coli after 1 day of culture without modified electrode treatment, and FIG5(b) is the Ag prepared in Example 1 of the present invention. 2 Colony growth of O-MXene modified GC electrode after co-culture with Escherichia coli for 1 day. 2 O-MXene modified GC electrode has a strong bactericidal effect, with a bactericidal rate of 99.99% against Escherichia coli

[0077] Table 1 is a comparison of the sensing performance of 4-NP by different electrochemical sensor electrode modification materials. As can be seen from Table 1, the electrochemical sensor prepared by the present invention has a linear relationship with the reduction peak current value in the concentration range of 0.0022-0.5026 μm / L, and its detection limit is as low as 0.00029 μm / L, indicating that the Ag of the present invention 2The O-MXene-modified GC electrode exhibits excellent 4-NP sensing performance, with a detection limit much lower than that based on electrodes modified with other materials, and the detection limit is significantly lower than the permissible limit of 4-NP in drinking water.

[0078] Table 1

[0079]

[0080] Example 5

[0081] The present invention provides a method for preparing an electrochemical sensor based on a modified glassy carbon electrode, which specifically comprises the following steps:

[0082] Step 1: Mix 25 mL of 0.2 mol / L silver nitrate solution and 50 mL of 1.0 mol / L sodium hydroxide solution under strong stirring, stir and react at 60° C. for 3 h, then repeatedly wash, vacuum filter and dry to obtain Ag. 2 O nanoparticles.

[0083] Step 2, take 0.6 mg of Ag prepared in step 1 2 O nanoparticles were dispersed in 1 mL of a mixed organic solvent of isopropanol and N-methylpyrrolidone with a volume ratio of 7:3, and ultrasonicated on an ice bath for 1.5 h to obtain Ag 2 O ink.

[0084] Step 3, take 4.48mL of deionized water and add it to the reaction bottle, then add 15.52mL of concentrated hydrochloric acid, stir for 30min, and then add 1.6g of LiF to the hydrochloric acid solution in 20 times to obtain a mixed etchant of LiF and HCl. Then weigh 1g of MAX precursor, add the MAX precursor to the mixed etchant in 20 times, and etch at 50°C for 24h, then centrifuge and wash at 3500rpm for 6min until the pH value of the solution is close to 6.5, and then ultrasonically strip at 600W for 1h, manually shake for 30min after stripping, then centrifuge and wash at 3500rpm for 1h, finally collect the upper MXene clear liquid, and freeze-dry for 24h to obtain MXene nanosheets.

[0085] Step 4: Take 0.4 mg of the MXene nanosheets prepared in step 3 and disperse them in 1 mL of a mixed organic solvent (the volume ratio of commercial 5% Nafion solution, water, and isopropanol is 5:20:40), and ultrasonicate in an ice bath for 0.8 h to obtain MXene ink.

[0086] Step 5: Take 4 μL of the MXene ink prepared in step 4 and apply it on the GC electrode, and dry it in vacuum at 35 °C for 6 h to obtain a MXene-modified GC electrode; then take 4 μL of the Ag prepared in step 2 and 2O ink was drop-coated on the MXene-modified GC electrode and dried in a vacuum oven at 35 °C for 8 h to obtain Ag 2 O-MXene was used to modify the GC working electrode. At the same time, a Pt wire electrode was used as the counter electrode and a saturated calomel electrode was used as the reference electrode to prepare an electrochemical sensor for 4-NP detection.

[0087] Example 6

[0088] The present invention provides a method for preparing an electrochemical sensor based on a modified glassy carbon electrode, which specifically comprises the following steps:

[0089] Step 1: Mix 25 mL of 0.1 mol / L silver nitrate solution and 50 mL of 0.4 mol / L sodium hydroxide solution under strong stirring, stir and react at 60° C. for 3 h, then repeatedly wash, vacuum filter and dry to obtain Ag 2 O nanoparticles.

[0090] Step 2, take 0.6 mg of Ag prepared in step 1 2 O nanoparticles were dispersed in 1 mL of a mixed organic solvent of isopropanol and N-methylpyrrolidone with a volume ratio of 7:3, and ultrasonicated on an ice bath for 1.5 h to obtain Ag 2 O ink.

[0091] Step 3, take 4.48mL of deionized water and add it to the reaction bottle, then add 15.52mL of concentrated hydrochloric acid, stir for 30min, and then add 1.6g of LiF to the hydrochloric acid solution in 20 times to obtain a mixed etchant of LiF and HCl. Then weigh 1g of MAX precursor, add the MAX precursor to the mixed etchant in 20 times, and etch at 50°C for 24h, then centrifuge and wash at 3500rpm for 6min until the pH value of the solution is close to 6.5, and then ultrasonically strip at 600W for 1h, manually shake for 30min after stripping, then centrifuge and wash at 3500rpm for 1h, finally collect the upper MXene clear liquid, and freeze-dry for 24h to obtain MXene nanosheets.

[0092] Step 4: Take 0.4 mg of the MXene nanosheets prepared in step 3 and disperse them in 1 mL of a mixed organic solvent (the volume ratio of commercial 5% Nafion solution, water, and isopropanol is 5:20:40), and ultrasonicate in an ice bath for 0.8 h to obtain MXene ink.

[0093] Step 5: Take 4 μL of the MXene ink prepared in step 4 and apply it on the GC electrode, and dry it in vacuum at 35 °C for 6 h to obtain a MXene-modified GC electrode; then take 4 μL of the Ag prepared in step 2 and 2 O ink was drop-coated on the MXene-modified GC electrode and dried in a vacuum oven at 35 °C for 8 h to obtain Ag2 O-MXene was used to modify the GC working electrode. At the same time, a Pt wire electrode was used as the counter electrode and a saturated calomel electrode was used as the reference electrode to prepare an electrochemical sensor for 4-NP detection.

[0094] Using functional materials to modify the electrode surface of electrochemical sensors can increase the electrode specific surface area and specific recognition sites and enhance its electrocatalytic performance, thereby improving the sensitivity and selectivity of electrochemical sensors and reducing detection limits and costs. Therefore, the modified material on the electrode surface is crucial to the electrosensing performance of the prepared electrochemical sensor. Due to its semiconductor properties and excellent electrocatalytic performance, Ag 2 O, ZnO, CuO and Mn 3 O 4 Nanoparticles such as Ag have been found to have important applications in electrochemical sensors for detecting organic pollutants. 2 O nanoparticles are the most promising narrow-bandgap p-type semiconductor materials, which show enhanced applicability in electrochemical sensors, such as high chemical stability, non-toxicity, enhanced electronic communication capability and chemical sensitivity, and low cost. 2 O itself has poor conductivity, which greatly hinders the electron transfer process and leads to limited overall efficiency. MXene is a two-dimensional material composed of metal carbides or nitrides, which has excellent flexibility, excellent conductivity and mechanical properties, and can quickly transfer electrons.

[0095] In order to solve the problems of low sensitivity, poor stability and high cost in the detection of 4-NP by the existing electrochemical sensor, the present invention adopts Ag by physical superposition method. 2 O nanoparticles and MXene were used to modify glassy carbon (GC) electrodes and prepare electrochemical sensors using semiconductor Ag 2 O nanomaterials modify the electrodes to enhance the electronic communication ability and chemical sensitivity of the electrochemical sensor, and use the strong conductivity and high specific surface area of ​​MXene to accelerate electron transfer. Through the synergistic effect of the two, the sensitivity and stability of the electrochemical sensor are improved, and the detection limit and cost are reduced. In addition, Ag 2 O nanoparticles also introduce excellent antibacterial properties, avoiding the interference of microbial adsorption on the test results and damage to the sensor during the test process.

Claims

1. A method for preparing an electrochemical sensor based on a modified glassy carbon electrode, characterized in that: The specific steps include: Step 1, preparing Ag2O nanoparticles; Step 2, preparing Ag2O ink according to the product obtained in step 1; Step 3, preparing MXene nanosheets; Step 4, preparing MXene ink according to the product obtained in step 3; Step 5, the MXene ink obtained in step 4 and the Ag2O ink obtained in step 2 are sequentially applied on the GC electrode to obtain an Ag2O-MXene modified GC working electrode, and then the corresponding counter electrode and reference electrode are selected to form an electrochemical sensor.

2. The method for preparing an electrochemical sensor based on a modified glassy carbon electrode according to claim 1, characterized in that: The specific process of step 1 is as follows: A silver nitrate solution with a concentration of 0.1 to 0.2 mol / L and a sodium hydroxide solution with a concentration of 0.4 to 1.0 mol / L are stirred and mixed, reacted at 40 to 60° C. for 1.5 to 3 hours, and then repeatedly washed, vacuum filtered, and dried to obtain Ag2O nanoparticles.

3. The method for preparing an electrochemical sensor based on a modified glassy carbon electrode according to claim 2, characterized in that: The specific process of step 2 is: 0.4-0.6 mg of Ag2O nanoparticles were dispersed in 1 mL of an organic solvent containing isopropanol, and ultrasonicated in an ice bath for 1-2 h to obtain Ag2O ink.

4. The method for preparing an electrochemical sensor based on a modified glassy carbon electrode according to claim 3, characterized in that: In step 2, the volume ratio of isopropanol to the organic solvent is 4:1 or 7:3, and the organic solvent is at least one of N,N-dimethylformamide, N-methylpyrrolidone or N,N-dimethylacetamide.

5. The method for preparing an electrochemical sensor based on a modified glassy carbon electrode according to claim 4, characterized in that: The specific process of step 3 is as follows: Step 3.1, add 4.48 mL of deionized water to a reaction bottle, then add 15.52 mL of concentrated hydrochloric acid, stir for 30 min, then add 1.6 g of LiF to the hydrochloric acid solution in 20 portions to obtain a mixed etchant of LiF and HCl; In step 3.2, weigh 1 g of MAX precursor, add the MAX precursor to the mixed etchant prepared in step 3.1 in 20 times, etch at 50°C for 24 hours, then centrifuge and wash at 3500 rpm for 6 minutes, and then ultrasonically peel at 600 W for 1 hour. After the peeling is completed, manually oscillate for 30 minutes, then centrifuge and wash at 3500 rpm for 1 hour, and finally collect the upper MXene clear liquid, and freeze-dry for 24 hours to obtain MXene nanosheets.

6. The method for preparing an electrochemical sensor based on a modified glassy carbon electrode according to claim 5, characterized in that: The specific process of step 4 is as follows: Take 0.3-0.5 mg of MXene nanosheets and disperse them in 1 mL of mixed organic solvent, and ultrasonicate them in an ice bath for 0.5-1 h to obtain MXene ink.

7. The method for preparing an electrochemical sensor based on a modified glassy carbon electrode according to claim 6, characterized in that: In step 4, the mixed organic solvent includes 5% Nafion solution, water, and an organic solvent in a volume ratio of 3 to 5:20:40 to 42, and the organic solvent is at least one of ethanol, methanol, isopropanol, N,N-dimethylformamide, N-methylpyrrolidone or N,N-dimethylacetamide.

8. The method for preparing an electrochemical sensor based on a modified glassy carbon electrode according to claim 6, characterized in that: The specific process of step 5 is as follows: The MXene ink prepared in step 4 was drop-coated on the GC electrode and dried in a vacuum or nitrogen atmosphere at 35°C for 4 to 6 hours to obtain a MXene-modified GC electrode; then 4 μL of the Ag2O ink prepared in step 2 was drop-coated on the MXene-modified GC electrode and dried in a vacuum or nitrogen atmosphere at 35°C for 6 to 8 hours in the dark to finally obtain an Ag2O-MXene-modified GC working electrode; at the same time, a Pt wire electrode was selected as a counter electrode and a saturated calomel electrode was selected as a reference electrode to obtain an electrochemical sensor for 4-NP detection.

9. An electrochemical sensor based on a modified glassy carbon electrode, prepared by the method for preparing an electrochemical sensor based on a modified glassy carbon electrode as claimed in any one of claims 1 to 8.

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