A polydopamine-graphene supported palladium prussiate nanoflower modified glassy carbon electrode, a preparation method and application thereof

Abstract

The application discloses a kind of polydopamine@graphene supported palladium ferricyanide nanoflower modified glassy carbon electrode and its preparation method and application, specifically a kind of using mercury ion specific enhancement polydopamine@graphene supported palladium ferricyanide nanoflower composite material (PdHCF / PDA@Gr) The peroxidase-like activity of oxide is enhanced, so as to enhance the oxidation peak current of o-phenylenediamine (OPD), and the concentration of mercury ion in aqueous solution is quantitatively analyzed.The modified electrode prepared by the application has good stability, low cost, simple preparation method, high sensitivity for mercury ion detection, good selectivity, wide linear range and rapid response, and can realize on-site rapid detection of mercury ion in water.

Description

Technical Field

[0001] This invention belongs to the fields of modified electrodes in electrochemical analysis and electrochemical analysis of heavy metal ions, specifically relating to a glassy carbon electrode modified with polydopamine@graphene supported palladium ferrocyanine nanoflowers, its preparation method, and its application. Background Technology

[0002] Mercury ions (Hg) 2+ Hg is one of the heavy metal ions that poses the greatest threat to public health and is difficult to biodegrade. Especially Hg... 2+ Hg is a highly toxic substance that can accumulate in the body through the food chain, affecting the nervous system and brain, altering genetic and enzyme systems, and leading to various diseases in humans such as cardiomyopathy, arrhythmia, and kidney failure. Hg in the environment... 2+ The water samples in question are complex, requiring not only specific identification but also quantification. Therefore, detecting Hg in environmental water samples... 2+ The content of these substances is of great significance for protecting the environment and human health.

[0003] To date, various methods for detecting Hg have been reported. 2+ Methods such as atomic absorption spectrometry (AAS), inductively coupled plasma mass spectrometry (ICP-MS), and fluorescence spectroscopy are available. While most of these methods achieve satisfactory detection limits and selectivity, they are limited by sophisticated and expensive instruments, complex sample pretreatment procedures, and drawbacks such as operational difficulty and lack of instrument portability. Electrochemical analysis methods, with their advantages of simple equipment, rapid response, convenient operation, and high sensitivity, are suitable for on-site detection of environmental water samples and have attracted widespread attention. Electrochemical analysis methods rely on specific redox reactions to convert the signal changes generated during the reaction process into electrical signals for quantitative analysis. Hg in the environment... 2+ The water samples present are complex, requiring not only specific identification but also quantification, which places higher demands on the sensitivity and specificity of the detection methods. This is particularly relevant in the electrochemical detection of Hg. 2+ During the process, the commonly used unmodified working electrode is suitable for low concentrations of Hg. 2+ The test solution exhibits poor response and lacks specificity, necessitating the selection of suitable modifying materials to modify the electrode surface, thereby improving the detection efficiency of Hg. 2+ Sensitivity and selectivity. Summary of the Invention

[0004] The purpose of this invention is to provide a glassy carbon electrode modified with polydopamine@graphene-supported palladium ferricyanide nanoflowers for the treatment of Hg. 2+ Highly sensitive and selective electrochemical detection is intended to overcome existing Hg... 2+Electrochemical detection methods suffer from low sensitivity, poor selectivity, and high cost. This invention, for the first time, loads palladium iron cyanide nanoflowers (PdHCF) with a diameter of approximately 20 nm onto the surface of polydopamine@graphene (PDA@Gr) material, preparing a glassy carbon electrode (PdHCF / PDA@Gr / GCE) modified with PdHCF nanoflowers supported on polydopamine@graphene for the determination of Hg. 2+ This method utilizes Hg 2+ The specific enhancement of the oxidase activity of polydopamine@graphene-supported palladium ferricyanide nanoflowers was achieved, thereby enhancing the oxidation peak current of o-phenylenediamine (OPD), thus realizing the effect of Hg oxidation. 2+ High-sensitivity electrochemical detection has enabled the detection of Hg in complex environments. 2+ Its highly selective detection has promising applications in the field of environmental analysis.

[0005] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0006] A method for preparing a glassy carbon electrode modified with polydopamine@graphene-supported palladium ferric cyanide nanoflowers includes the following steps:

[0007] (1) Preparation of polydopamine@graphene:

[0008] Ammonia, dopamine hydrochloride aqueous solution, hydrazine hydrate and deionized water were added sequentially to the graphene oxide solution. After ultrasonic dispersion, the mixture was reacted in a water bath. After the reaction was completed, the mixture was centrifuged and washed to obtain a polydopamine@graphene suspension.

[0009] (2) Preparation of polydopamine@graphene-supported palladium ferricyanide nanoflowers:

[0010] Under ultrasonic assistance, K3[Fe(CN)6] solution was added to the polydopamine@graphene suspension obtained in step (1), HCl solution was added to adjust the pH to 2.0, K2PdCl4 solution was added, and the mixture was stirred at room temperature until homogeneous. After centrifugation and washing, polydopamine@graphene supported palladium iron cyanide nanoflower composite material was obtained.

[0011] (3) Preparation of glassy carbon electrode modified with polydopamine@graphene-supported palladium ferric cyanide nanoflowers:

[0012] The polydopamine@graphene-supported palladium ferrocyanine nanoflower composite material obtained in step (2) was drop-coated onto the electrode surface and dried at room temperature to obtain a glassy carbon electrode modified with polydopamine@graphene-supported palladium ferrocyanine nanoflowers.

[0013] Furthermore, in step (1), the water bath reaction temperature is 75°C and the time is 2.5h.

[0014] Furthermore, in step (1), the mass ratio of graphene oxide to dopamine hydrochloride is 1:1.

[0015] Furthermore, the diameter of the palladium iron cyanide nanoflowers in step (2) is 20 nm.

[0016] Furthermore, in step (2), the concentration of the K3[Fe(CN)6] solution is 200 mM, and the concentration of the K2PdCl4 solution is 200 mM.

[0017] Furthermore, in step (3), the electrode is a treated glassy carbon electrode, specifically: the surface of the glassy carbon electrode is polished to a smooth surface with alumina powder, rinsed with water twice, and then dried with nitrogen.

[0018] A glassy carbon electrode modified with polydopamine@graphene supported palladium iron cyanide nanoflowers, wherein the glassy carbon electrode is prepared by the aforementioned preparation method.

[0019] Application of a glassy carbon electrode modified with palladium iron cyanide nanoflowers supported on polydopamine@graphene in the electrochemical detection of mercury ions.

[0020] An electrochemical method for detecting mercury ions includes the following steps:

[0021] (1) Using the aforementioned glassy carbon electrode modified with palladium ferricyanide nanoflowers supported on polydopamine@graphene as the working electrode, a platinum electrode as the counter electrode, and a saturated calomel electrode as the reference electrode, the three electrodes were placed in an acetate-sodium acetate buffer solution, and different concentrations of Hg were added. 2+ Standard solutions were enriched in acetate-sodium acetate buffer solution, followed by the addition of o-phenylenediamine solution. Differential pulse voltammetry was used to scan the potential range of -0.60 to -0.25 V, and the concentrations of Hg were recorded. 2+ The corresponding peak current value, based on the peak current value and the corresponding Hg 2+ Concentration, plot Hg 2+ The standard curve for analysis was obtained, and Hg was obtained. 2+ The linear equation relating concentration and peak current;

[0022] (2) Hg 2+ An unknown concentration of the test sample is added to a three-electrode system. The peak current corresponding to the test sample is recorded using differential pulse voltammetry. Substituting this peak current into the standard curve or linear equation obtained in step (1) yields the concentration of Hg in the test sample. 2+ The concentration.

[0023] Further, in step (1), the concentration of the acetate-sodium acetate buffer solution is 0.20M, the pH is 3.5-6.0, the enrichment time is 30-900 seconds, and the concentration of the o-phenylenediamine solution is 0.5-5.0mM.

[0024] The present invention has the following beneficial effects:

[0025] The PdHCF / PDA@Gr nanoflowers prepared in this invention are loaded with a large amount of palladium iron cyanide nanoflowers, possessing a large specific surface area and good conductivity, and exhibiting oxidase-like activity. 2+ Binding to PdHCF / PDA@Gr specifically enhances its oxidase-like activity. These properties effectively increase Hg 2+ Sensitivity and selectivity of detection. Compared with existing technologies, the PdHCF / PDA@Gr / GCE prepared in this invention is simple, convenient, and low-cost, and has high sensitivity and selectivity for Hg. 2+ The electrochemical detection method has advantages such as high sensitivity, strong selectivity, wide linear range, and short detection time, and can realize the detection of Hg in water. 2+ The on-site rapid testing method is simple and feasible. Attached Figure Description

[0026] Figure 1 Transmission electron microscope images of PDA@Gr loaded with PdHCF with a diameter of about 20 nm prepared in this invention at different magnifications;

[0027] Figure 2 The method of the present invention at different concentrations of Hg 2+ DPV scan in solution.

[0028] Figure 3 The method of the present invention for detecting different concentrations of Hg 2+ Standard curve of the solution.

[0029] Figure 4 The method of this invention is the same as that used for detecting Hg concentrations with conventional glassy carbon electrodes. 2+ Comparison of DPV of solutions.

[0030] Figure 5 Selective response diagrams of the method of the present invention under the presence of different interfering substances. Detailed Implementation

[0031] To make the objectives, technical solutions, and technical effects of the present invention clearer, the technical solutions in specific embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are some preferred embodiments of the present invention, but not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] Example 1

[0033] This embodiment provides a method for detecting Hg. 2+ The preparation steps of the glassy carbon electrode modified with polydopamine@graphene-supported palladium ferric cyanide nanoflowers are as follows:

[0034] (1) Preparation of polydopamine@graphene (PDA@Gr):

[0035] Add 200 μL of 28% ammonia to 7.0 mL of 1.0 mg / mL graphene oxide solution, then add 7.0 mL of 1.0 mg / mL dopamine hydrochloride aqueous solution and 40 μL of 80% hydrazine hydrate. Add an appropriate amount of deionized water to make a 20 mL reaction system. After sonication for 20 min, place the reaction flask in a 75℃ water bath for 2.5 h. Finally, centrifuge and wash the uniform black dispersion obtained from the reaction three times, and make up the volume to 28.0 mL to obtain 0.25 mg / mL PDA@Gr composite material.

[0036] (2) Preparation of polydopamine@graphene-supported palladium ferrocyanine nanoflowers (PdHCF / PDA@Gr):

[0037] Under ultrasonic assistance, 200 mM K3[Fe(CN)6] solution was added dropwise to a PDA@Gr (0.25 mg / mL) suspension. The pH was adjusted to 2.0 by slowly adding 0.20 M HCl solution. After waiting 10 min, 200 mM K2PdCl4 was added sequentially. The solution was stirred vigorously at room temperature for 3.5 h. The uniformly dispersed suspension was then centrifuged and washed twice to obtain the final product, PdHCF / PDA@Gr composite material, and a stock solution with a concentration of 1.0 mg / mL was prepared for later use. Figure 1 Transmission electron microscope images of PdHCF loaded with PDA@Gr at different magnifications (approximately 20 nm in diameter).

[0038] (3) Preparation of polydopamine@graphene-supported palladium ferric cyanide nanoflower modified glassy carbon electrode (PdHCF / PDA@Gr / GCE):

[0039] The surface of the GCE was polished to a smooth finish using 0.3 μm alumina powder, rinsed twice with water, and then dried with nitrogen. Next, 8.0 μL of the 0.25 mg / mL PdHCF / PDA@Gr material prepared in step (2) was drop-coated onto the electrode surface and allowed to air dry at room temperature to obtain a material for Hg detection. 2+ PdHCF / PDA@Gr modified glassy carbon electrode.

[0040] Example 2

[0041] This embodiment provides an electrochemical analysis method for mercury ions using a glassy carbon electrode modified with polydopamine@graphene-supported palladium ferricyanide nanoflowers. The analytical steps are as follows:

[0042] (1) Using the PdHCF / PDA@Gr / GCE prepared in Example 1 as the working electrode, a platinum electrode as the counter electrode, and a saturated calomel electrode as the reference electrode, the three electrodes were placed in a 0.20 M acetate-sodium acetate buffer solution (pH = 4.0), and different concentrations of Hg were added. 2+ The standard solutions were enriched in acetate-sodium acetate buffer for 240 seconds, followed by the addition of 2.5 mM OPD solution. Differential pulse voltammetry (DPV) was used to scan the potential range of -0.60 to -0.25 V (e.g., ...). Figure 2 As shown in the figure, different concentrations of Hg were recorded. 2+ The corresponding OPD oxidation peak current value, based on the peak current value and the corresponding Hg 2+ Concentration, plot Hg 2+ The standard curve for analysis (e.g.) Figure 3 (As shown) and the linear equation relating concentration and peak current. The linear equation is:

[0043] i pa (μA)=2.97+1.60lgC Hg2+ (μmol / L), R 2 =0.998.

[0044] Where i pc This represents the oxidation peak current value, where C is Hg. 2+ The concentration.

[0045] For Hg 2+ The linear range of detection is 0.060-1000 μmol / L, and the limit of detection is 18 nmol / L.

[0046] (2) Hg under the same system 2+ A DPV scan was performed on a solution with an unknown concentration to obtain the peak current value. The Hg in the solution was then quantified by substituting the peak current value into a standard curve or linear equation. 2+ The concentration.

[0047] (3) Simultaneously, under the same system, using the above-mentioned PdHCF / PDA@Gr / GCE electrode and the unmodified GCE electrode as working electrodes, respectively, for the same concentration of Hg 2+ The solution was subjected to DPV scanning. The results are as follows: Figure 4 As shown, by comparing the oxidation peak current of OPD, it can be seen that the GCE electrode modified by the present invention has a significantly enhanced response to the oxidation peak current of OPD compared with the unmodified GCE, indicating that the detection method of the present invention effectively improves the detection of Hg by the existing GCE electrode. 2+ Detection sensitivity.

[0048] Example 3

[0049] This embodiment provides a polydopamine@graphene-supported palladium ferrocyanine nanoflower composite material for Hg 2+ Selective response testing.

[0050] Preparation of Hg 2+ The solution and the interfering ion solution, wherein the interfering substance includes: calcium ions (Ca... 2+ ), magnesium ions (Mg 2 + ), cadmium ions (Cd) 3+ ), potassium ions (K) + Sodium ions (Na) + ), chromium ions (Cr 3+ ), lead ions (Pb) 2+ The prepared PdHCF / PDA@Gr composite material was added to 8 parts of the same acetate-sodium acetate buffer solution (pH=4.0), and then Hg of the same concentration was added to each solution. 2+ Solution, making Hg 2+ The final concentration was 1.0 μM. One solution was kept unchanged, and interfering ions were added to the remaining seven solutions to make the final concentration of interfering ions Hg. 2+ 100 times. Stir the reaction for 5 minutes, then add 2.5 mM OPD solution. Due to the interaction between PdHCF / PDA@Gr and Hg... 2+ Combined with enhanced oxidase-like activity, OPD was rapidly oxidized, and the solution changed from colorless to orange. The absorbance values ​​of eight solutions at 450 nm were measured, and the results are as follows: Figure 5 As shown. The results indicate that the absorbance value of the solution after adding interfering ions is similar to that containing only Hg. 2+ The absorbance values ​​of the solutions showed no significant difference, indicating that these seven ions have a strong effect on Hg. 2+ The detection showed no significant interference. The above experimental results indicate that the PdHCF / PDA@Gr material prepared in this invention exhibits good resistance to Hg. 2+ It has good selectivity.

[0051] The method of this invention has advantages such as high sensitivity, wide linear range, good selectivity, and low cost, and is easy to implement for Hg. 2+ The method is simple and feasible for on-site detection. Compared with reported electrochemical detection methods, it has excellent comprehensive performance in terms of detection sensitivity and linear range (see Table 1), and has very good application prospects.

[0052] Table 1 Hg with different electrode pairs 2+ Performance comparison of electrochemical detection

[0053]

[0054] Example 4

[0055] This embodiment provides a glassy carbon electrode modified with prepared polydopamine@graphene-supported palladium ferrocyanine nanoflowers for the detection of Hg in environmental water samples. 2+ Perform electrochemical analysis.

[0056] Water samples from the Fen River in Taiyuan City, Shanxi Province, were analyzed. The river water samples were first filtered through ordinary filter paper. Then, three different concentrations of Hg (0.1, 1.0, and 10.0 μM) were added to the treated samples. 2+ The standard solutions were spiked for recovery determination, as shown in Table 1. The results showed that the recoveries in environmental water samples ranged from 98.3% to 102%, with relative standard deviations of 2.78% to 4.02%. This indicates that the prepared electrode can overcome the influence of complex water bodies and is suitable for detecting Hg in actual environmental water samples. 2+ Measurement.

[0057] Table 2 Hg in environmental water samples 2+ Recovery results

[0058]

Claims

1. An application of a glassy carbon electrode modified with polydopamine@graphene-supported palladium iron cyanide nanoflowers, characterized in that, It is applied in the electrochemical detection of mercury ions; the glassy carbon electrode modified with polydopamine@graphene-supported palladium ferrocyanine nanoflowers is obtained by the following preparation method: (1) Preparation of polydopamine@graphene: Ammonia, dopamine hydrochloride aqueous solution, hydrazine hydrate and deionized water were added sequentially to the graphene oxide solution. After ultrasonic dispersion, the mixture was reacted in a water bath. After the reaction was completed, the mixture was centrifuged and washed to obtain a polydopamine@graphene suspension. (2) Preparation of polydopamine@graphene-supported palladium ferricyanide nanoflowers: Under ultrasonic assistance, K3[Fe(CN)6] solution was added to the polydopamine@graphene suspension obtained in step (1), HCl solution was added to adjust the pH to 2.0, K2PdCl4 solution was added, and the mixture was stirred at room temperature until homogeneous. After centrifugation and washing, polydopamine@graphene supported palladium iron cyanide nanoflower composite material was obtained. (3) Preparation of glassy carbon electrode modified with polydopamine@graphene-supported palladium ferric cyanide nanoflowers: The polydopamine@graphene-supported palladium ferric cyanide nanoflower composite material obtained in step (2) was drop-coated onto the electrode surface and dried at room temperature to obtain a glassy carbon electrode modified with polydopamine@graphene-supported palladium ferric cyanide nanoflowers.

2. The application of the glassy carbon electrode modified with polydopamine@graphene-supported palladium ferricyanide nanoflowers according to claim 1, characterized in that, The water bath reaction in step (1) is carried out at a temperature of 75°C for 2.5 h.

3. The application of the glassy carbon electrode modified with polydopamine@graphene-supported palladium ferrocyanine nanoflowers according to claim 1, characterized in that, In step (1), the mass ratio of graphene oxide to dopamine hydrochloride is 1:

1.

4. The application of the glassy carbon electrode modified with polydopamine@graphene-supported palladium ferricyanide nanoflowers according to claim 1, characterized in that, The diameter of the palladium iron cyanide nanoflowers in step (2) is 20 nm.

5. The application of the glassy carbon electrode modified with polydopamine@graphene-supported palladium ferricyanide nanoflowers according to claim 1, characterized in that, In step (2), the concentration of K3[Fe(CN)6] solution is 200 mM and the concentration of K2PdCl4 solution is 200 mM.

6. The application of the glassy carbon electrode modified with polydopamine@graphene-supported palladium ferrocyanine nanoflowers according to claim 1, characterized in that, In step (3), the electrode is a treated glassy carbon electrode. Specifically, the surface of the glassy carbon electrode is polished with alumina powder until it is flat, rinsed with water twice, and then dried with nitrogen.

7. The application of the glassy carbon electrode modified with polydopamine@graphene-supported palladium ferrocyanine nanoflowers according to any one of claims 1-6, characterized in that, Includes the following steps: (1) A glassy carbon electrode modified with palladium ferricyanide nanoflowers supported on polydopamine@graphene was used as the working electrode, a platinum electrode as the counter electrode, and a saturated calomel electrode as the reference electrode. The three electrodes were placed in an acetate-sodium acetate buffer solution, and different concentrations of Hg were added. 2+ Standard solutions were enriched in acetate-sodium acetate buffer solution, followed by the addition of o-phenylenediamine solution. Differential pulse voltammetry was used to scan the potential range of -0.60 to -0.25 V, and the concentrations of Hg were recorded. 2+ The corresponding peak current value, based on the peak current value and the corresponding Hg 2+ Concentration, plot Hg 2+ The standard curve for analysis was obtained, and Hg was obtained. 2+ The linear equation relating concentration and peak current; (2) Hg 2+ An unknown concentration of the test sample is added to a three-electrode system. The peak current corresponding to the test sample is recorded using differential pulse voltammetry. Substituting this current into the standard curve or linear equation obtained in step (1) yields the concentration of Hg in the test sample. 2+ The concentration.

8. The application of the glassy carbon electrode modified with polydopamine@graphene-supported palladium ferrocyanine nanoflowers according to claim 7, characterized in that, In step (1), the concentration of the acetate-sodium acetate buffer solution is 0.20 M, the pH is 3.5~6.0, the enrichment time is 30~900 seconds, and the concentration of the o-phenylenediamine solution is 0.5~5.0 mM.

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