Functionalized au@si o2 composite film modified electrode, preparation method thereof and application to detection of dopamine

Abstract

The application discloses a functionalized Au@SiO2 composite film modified electrode, which comprises a glassy carbon electrode as a base electrode, alkali-etched CoAl-LDH e / Au@SiO2 composite film as an electrode modification material. The alkali etching makes most of aluminum elements in the CoAl-LDH dissolve, generates abundant defects, and exposes more active sites; the SiO2 coating effectively inhibits the aggregation of Au nanoparticles; the combination of the CoAl-LDH e and the Au@SiO2 composite can fully exert the advantages and synergistic effect of each component, and effectively improves the electrochemical catalytic performance of the CoAl-LDH e / Au@SiO2 composite film modified electrode on the adsorption and capture capacity of dopamine and the selective electrochemical catalytic performance; the CoAl-LDH e / Au@SiO2 modified electrode has a wide linear range (0.5-850 μmol L −1 ) in detecting DA, a low detection limit (70.5 nmol L −1 , S / N=3), a high sensitivity (377.6 μA·μmol −1 L·cm −2 ), good stability and anti-interference ability.

Description

Technical Field

[0001] This invention belongs to the field of electroanalytical chemistry technology, specifically relating to a functionalized Au@SiO2 composite film modified electrode, its preparation method, and its application in electrochemical sensing for dopamine detection. Background Technology

[0002] Dopamine (DA) is one of the most important neurotransmitters in the mammalian brain, closely related to an individual's physical activity and mental health. Abnormal DA levels can potentially cause neurological and physiological problems such as pheochromocytoma, Alzheimer's disease, schizophrenia, Parkinson's disease, and attention deficit hyperactivity disorder. Therefore, simple and accurate detection of DA in physiological fluids is of great significance for providing useful therapeutic indicators. Currently used chromatographic, spectroscopic, and other traditional detection techniques have many problems, such as expensive instruments, complex sample pretreatment, and long processing times, making them difficult to meet today's requirements for online monitoring and rapid measurement. In contrast, electrochemical detection techniques have advantages such as simplicity, economy, high sensitivity, and rapid on-site analysis. Because the phenolic hydroxyl groups in DA are easily oxidized, electrochemical methods are widely used for the quantitative detection of DA concentration. However, DA has similar redox potentials on bare electrodes with coexisting ascorbic acid (AA) and uric acid (UA), therefore, information based on the identification and detection of DA, UA, and AA is crucial. Electrode modification materials determine the performance of electrochemical sensors. In order to achieve rapid, accurate and sensitive detection of DA, it is very important to find a suitable nanocomposite as an electrode modification material.

[0003] Layered bimetallic hydroxides (LDHs) are layered mixed hydroxides composed of positively charged host layers and interlayer anions. They have attracted widespread attention due to their low cost and excellent electrocatalytic activity. However, several major problems, such as low active site exposure, poor conductivity, and poor stability, limit their widespread application. Rational modification of the structure of LDHs to design LDH-based electrocatalysts with high catalytic performance is of great significance for improving electrocatalytic performance.

[0004] Gold nanoparticles (AuNPs) are widely used in electrode modification due to their excellent conductivity, high electrocatalytic activity, and large specific surface area. However, AuNPs are prone to aggregation, leading to poor sensing performance. Therefore, AuNPs can be composited with other nanomaterials to improve their catalytic performance. Silica (SiO2)-coated AuNPs can effectively prevent aggregation, thereby improving their stability and performance; furthermore, the composite of conductive components with LDHs may enhance the electrochemical sensing performance of the composite.

[0005] To address the shortcomings of using the above materials individually and to fully leverage the synergistic effects of the composite components, this invention proposes to prepare CoAl-LDH by alkaline etching of CoAl-LDH followed by composite formation with silica-encapsulated gold nanoparticles (Au@SiO2). e The / Au@SiO2 nanocomposite, in which the SiO2 encapsulation effectively prevents the aggregation of Au nanoparticles; the composite of Au nanoparticles with good dispersibility will effectively improve the poor conductivity of CoAl-LDH; alkaline etching can dissolve the aluminum in CoAl-LDH, which can impart more defects and active sites to the catalyst. The CoAl-LDH composite of this invention is used. e Modifying GCE with / Au@SiO2 will fully utilize the CoAl-LDH e Synergistic effect with Au@SiO2 as a modified electrode material. Based on CoAl-LDH e An electrochemical sensing platform constructed with / Au@SiO2 can be used to establish a highly sensitive, selective, and stable DA electrochemical detection method. Summary of the Invention:

[0006] To address the shortcomings of existing technologies and the needs of research and application in this field, one objective of this invention is to provide a functionalized Au@SiO2 composite film modified electrode. The modified electrode is characterized by using a glassy carbon electrode as the substrate electrode and an alkali-etched cobalt-aluminum hydrotalcite nanosheet / Au@SiO2 composite film as the electrode modification material. The alkali-etched cobalt-aluminum hydrotalcite nanosheet / Au@SiO2 composite material is obtained by combining alkali-etched cobalt-aluminum hydrotalcite nanosheets with silica-encapsulated gold nanoparticles. The glassy carbon electrode is denoted as GCE; the alkali-etched cobalt-aluminum hydrotalcite nanosheets are denoted as CoAl-LDH. e Gold nanoparticles encapsulated in silica are denoted as Au@SiO2; alkaline-etched cobalt-aluminum hydrotalcite nanosheets / Au@SiO2 are denoted as CoAl-LDH / Au@SiO2.

[0007] The second objective of this invention is to provide a method for preparing a functionalized Au@SiO2 composite film modified electrode, characterized by the following specific steps:

[0008] Preparation of CoAl-LDH

[0009] 1.748 g of Co(NO3)2·6H2O and 0.752 g of Al(NO3)3∙9H2O were added to 100 mL of ultrapure water at a molar ratio of 3:1. Then, 2.4 g of urea and 0.7408 g of ammonium fluoride were added, and the mixture was stirred continuously at 800 rpm to dissolve. The mixture was then poured into a high-pressure reactor lined with polytetrafluoroethylene and heated at 200 °C for 12 h. The solid sample was collected by centrifugation, washed three times each with deionized water and anhydrous ethanol, and dried in an oven at 50 °C for 12 h to obtain pink CoAl-LDH powder.

[0010] (b) CoAl-LDH e Preparation

[0011] Take 0.2 g of CoAl-LDH and place it in 40 mL of 3 mol L. −1 Etching in NaOH solution for 4 h at 9000 r / min −1 Centrifuge for 5 min, wash three times with deionized water, and then dry in an oven at 50 ℃ for 12 h to obtain CoAl-LDH. e ;

[0012] (c) Preparation of Au@SiO2

[0013] ① Mix 1 mL of ultrapure water with 1 mL of 1 mmol L... −1 After mixing with chloroauric acid, add 2 mL of 0.2 mol / L solution. −1 After thoroughly mixing CTAB, add 480 μL of a 5 mmol / L solution. −1 NaBH4 was used to obtain a seed solution.

[0014] ② At a concentration of 4 mmol / L in 10 mL −1 Add 10 mL of 0.2 mol / L AgNO3 solution. −1 After thoroughly mixing CTAB, add 1 mL of 1 mmol L solution. −1 Chloroauric acid is added to the seed solution prepared in step ① under stirring until it turns into a blue solution, which is then left to stand for later use.

[0015] ③ After centrifuging the gold nanoparticle solution prepared in step ② at 10000 rpm for 20 minutes, discard the supernatant and disperse the precipitate in 10 mL of solution with a concentration of 1 mmol / L. −1 In CTAB solution;

[0016] ④ Take 10 mL of the purified gold nanorod solution described in step ③, and add 100 μL of a solution with a concentration of 10.8 mmol / L. −1KH-590 was stirred for 5 hours, then ammonia was added, followed by 5 mL of 20% TEOS. After reacting for 12 hours, Au@SiO2 dispersion was obtained.

[0017] (d) CoAl-LDH e Preparation of / Au@SiO2

[0018] 0.2 g of CoAl-LDH prepared in step (b) e The material was dispersed in 5 mL of ethanol, and 2 mL of the Au@SiO2 dispersion prepared in step (b) was added under stirring. After stirring slowly for 12 h, the mixture was centrifuged at 8000 rpm for 5 min, washed three times with deionized water, and dried in an oven at 60 °C for 12 h to obtain CoAl-LDH. e / Au@SiO2.

[0019] (e) CoAl-LDH e Preparation of / Au@SiO2 composite material modified GCE

[0020] GCE was polished to a mirror finish, and then ultrasonically cleaned for 1 minute each with dilute nitric acid, anhydrous ethanol, and high-purity water, and allowed to air dry at room temperature for later use; the CoAl-LDH prepared in step (d) was then... e / Au@SiO2 complex was ultrasonically dispersed in 3 ml of deionized water to prepare 5 mg mL −1 CoAl-LDH e CoAl-LDH was prepared by drop-coating 3-7 μL of Au@SiO2 suspension onto a pretreated GCE surface and allowing it to air dry at room temperature. e / Au@SiO2 composite film modified GCE, denoted as CoAl-LDH e / Au@SiO2 / GCE.

[0021] The third objective of this invention is to provide a functionalized Au@SiO2 composite membrane modified electrode for detecting the content of DA in body fluids. The electrode is characterized by using a 0.1 mol / L pH 7.0 phosphate buffer as the supporting electrolyte, adding electrolyte solutions containing different amounts of DA to an electrolytic cell, using the modified electrode as the working electrode, and detecting the DA content using a chronoamperometry method to obtain a linear regression equation between the DA oxidation peak current and its concentration. The same method is used to determine the DA oxidation peak current in the sample to be tested, and substituting this into the linear regression equation yields the DA content in the sample.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] The CoAl-LDH eThe / Au@SiO2 composite film modified electrode plays a role in the electrocatalysis of DA and CoAl-LDH. e Synergistic effect with Au@SiO2: CoAl-LDH after alkaline etching e Most of the aluminum element is dissolved, creating more defects and exposing more active sites; SiO2 coating can effectively inhibit the aggregation of Au nanoparticles and ensure their uniform dispersion; CoAl-LDH e When combined with Au@SiO2, the advantages and synergistic effects of each component can be fully utilized, effectively improving the CoAl-LDH content. e / Au@SiO2 composite film modified electrode enhances DA adsorption and capture capacity and selective electrochemical catalytic performance;

[0024] (b) Based on the CoAl-LDH e An electrochemical sensing platform constructed with an Au@SiO2 modified electrode achieved a wide linear range (0.5 ~ 850 μmol L⁻¹) for DA detection. −1 ), and a relatively low detection limit (70.5 nmol L). −1 (S / N = 3), high sensitivity (377.6 μA·μmol) −1 L·cm −2 It has good stability and anti-interference ability. Attached Figure Description

[0025] Figure 1 (a) is a SEM image of CoAl-LDH / Au@SiO2 prepared in Comparative Example 5, and (b) is a SEM image of CoAl-LDH prepared in Example 1. e SEM images of / Au@SiO2. (c, d) are CoAl-LDH corresponding to Example 1. e TEM image of / Au@SiO2; (e, f) are CoAl-LDH corresponding to Comparative Example 4. e @Au's TEM image.

[0026] Figure 2 Comparative Examples 1, 2, 3, 4, and Example 1 correspond to GCE, CoAl-LDH / GCE, and CoAl-LDH, respectively. e / GCE、CoAl-LDH e / Au / GCE and CoAl-LDH e / Au@SiO2 / GCE in 5.0 mmol / L Fe(CN)6 containing 0.1 mol / L potassium chloride 3- / 4- (a) CV plot and (b) electrochemical impedance plot in (1:1) solution.

[0027] Figure 3Comparative Examples 1, 2, 3, 4, 6, and Example 1 correspond to GCE(b), CoAl-LDH / GCE(a), and CoAl-LDH, respectively. e / GCE (c), CoAl-LDH e / Au / GCE (d), CoAl-LDH / Au@SiO2 / GCE (e) and CoAl-LDH e / Au@SiO2 / GCE (f), in a solution containing 0.1 mmol L −1 0.1 mol L of DA −1 CV plot of phosphate buffer solution at pH 7.0.

[0028] Figure 4 For Example 1, corresponding to CoAl-LDH e Current density-time curves of / Au@SiO2 / GCE at 0.25 V for different concentrations of DA, with the inset showing the range from 0.5 to 20 μmol L. −1 (a) is a magnified view within the range; (b) is a time response diagram of the electrode to DA.

[0029] Figure 5 The graph shows the linear relationship between the concentration of added DA and the current density. The inset shows the linear relationship at low concentrations.

[0030] Figure 6 For Example 1, corresponding to CoAl-LDH e / Au@SiO2 / GCE at 0.2 V, (a) for 0.05 mmol L −1 (a) Current density-time response of DA and 50-fold concentration of interfering material, (b) Relationship between storage days and the percentage of peak DPV current (n = 5) relative to its initial value. Inset: Histogram of the percentage of peak DPV current (n = 5) relative to the initial electrode peak current. Detailed Implementation

[0031] To further understand the present invention, the following description, in conjunction with the accompanying drawings and embodiments, will further illustrate the present invention, but does not limit the present invention in any way. Example 1:

[0032] (a) Preparation of CoAl-LDH

[0033] 1.748 g of Co(NO3)2·6H2O and 0.752 g of Al(NO3)3·9H2O were added to 100 mL of ultrapure water at a molar ratio of 3:1. Then, 2.4 g of urea and 0.7408 g of ammonium fluoride were added, and the mixture was stirred continuously at 800 rpm to dissolve. The mixture was then poured into a high-pressure autoclave lined with polytetrafluoroethylene and heated at 200 °C for 12 h. The solid sample was collected by centrifugation, washed three times each with deionized water and anhydrous ethanol, and dried in an oven at 50 °C for 12 h to obtain pink CoAl-LDH powder.

[0034] (b) CoAl-LDH e Preparation

[0035] Take 0.2 g of CoAl-LDH and place it in 40 mL of 3 mol L. −1 Etching in NaOH solution for 4 h at 9000 r / min −1 Centrifuge for 5 min, wash three times with deionized water, and then dry in an oven at 50 ℃ for 12 h to obtain CoAl-LDH. e ;

[0036] (c) Preparation of Au@SiO2

[0037] ① Mix 1 mL of ultrapure water with 1 mL of 1 mmol L... −1 After mixing with chloroauric acid, add 2 mL of 0.2 mol / L solution. −1 After thoroughly mixing CTAB, add 480 μL of a 5 mmol / L solution. −1 NaBH4 was used to obtain a seed solution.

[0038] ② At a concentration of 4 mmol / L in 10 mL −1 Add 10 mL of 0.2 mol / L AgNO3 solution. −1 After thoroughly mixing CTAB, add 1 mL of 1 mmol L solution. −1 Chloroauric acid is added to the seed solution prepared in step ① under stirring until it turns into a blue solution, which is then left to stand for later use.

[0039] ③ After centrifuging the gold nanoparticle solution prepared in step ② at 10000 rpm for 20 minutes, discard the supernatant and disperse the precipitate in 10 mL of solution with a concentration of 1 mmol / L. −1 In CTAB solution;

[0040] ④ Take 10 mL of the purified gold nanorod solution from step ③ and add 100 μL of a solution with a concentration of 10.8 mmol / L. −1KH-590 was stirred for 5 hours, then ammonia was added, followed by 5 mL of 20% TEOS. After reacting for 12 hours, Au@SiO2 dispersion was obtained.

[0041] (d) CoAl-LDH e Preparation of / Au@SiO2

[0042] 0.2 g of CoAl-LDH prepared in step (b) e The material was dispersed in 5 mL of ethanol, and 2 mL of the Au@SiO2 dispersion prepared in step (b) was added under stirring. After stirring slowly for 12 h, the mixture was centrifuged at 8000 rpm for 5 min, washed three times with deionized water, and dried in an oven at 60 ℃ for 12 h to obtain CoAl-LDH. e / Au@SiO2;

[0043] (e) CoAl-LDH e Preparation of / Au@SiO2 composite film modified GCE

[0044] GCE was polished to a mirror finish, and then ultrasonically cleaned for 1 minute each with dilute nitric acid, anhydrous ethanol, and high-purity water, and allowed to air dry at room temperature for later use; the CoAl-LDH prepared in step (d) was then... e / Au@SiO2 complex was ultrasonically dispersed in 3 ml of deionized water to prepare 5 mg mL −1 CoAl-LDH e CoAl-LDH was prepared by drop-coating 3.0 μL of Au@SiO2 suspension onto a pretreated GCE surface and allowing it to air dry at room temperature. e / Au@SiO2 composite film modified GCE, denoted as CoAl-LDH e / Au@SiO2 / GCE. Example 2:

[0045] (a) Preparation of CoAl-LDH

[0046] Prepared according to the method and conditions of step (a) in Example 1;

[0047] (b)CoAl-LDH e Preparation

[0048] Prepared according to the method and conditions of step (b) in Example 1;

[0049] (c) Preparation of Au@SiO2

[0050] Prepared according to the method and conditions of step (c) in Example 1;

[0051] (d)CoAl-LDH e Preparation of / Au@SiO2

[0052] Prepared according to the method and conditions of step (d) in Example 1;

[0053] (e)CoAl-LDH e Preparation of / Au@SiO2 composite material modified GCE

[0054] Following the method and conditions of step (e) in Example 1, a CoAl-LDH solution with a concentration of 5 mg / mL was taken. e 4 μL of Au@SiO2 dispersion was drop-coated onto the treated GCE surface and allowed to air dry at room temperature to obtain CoAl-LDH. e / Au@SiO2 composite film modified GCE, denoted as CoAl-LDH e / Au@SiO2 / GCE. Example 3:

[0055] (a) Preparation of CoAl-LDH

[0056] Prepared according to the method and conditions of step (a) in Example 1;

[0057] (b)CoAl-LDH e Preparation

[0058] Prepared according to the method and conditions of step (b) in Example 1;

[0059] (c) Preparation of Au@SiO2

[0060] Prepared according to the method and conditions of step (c) in Example 1;

[0061] (d)CoAl-LDH e Preparation of / Au@SiO2

[0062] Prepared according to the method and conditions of step (d) in Example 1;

[0063] (e)CoAl-LDH e Preparation of / Au@SiO2 composite material modified GCE

[0064] Following the method and conditions of step (e) in Example 1, a CoAl-LDH solution with a concentration of 5 mg / mL was taken. e 5 μL of Au@SiO2 dispersion was drop-coated onto the treated GCE surface and allowed to air dry at room temperature to obtain CoAl-LDH. e / Au@SiO2 composite film modified GCE, denoted as CoAl-LDH e / Au@SiO2 / GCE. Example 4:

[0065] (a) Preparation of CoAl-LDH

[0066] Prepared according to the method and conditions of step (a) in Example 1;

[0067] (b)CoAl-LDH e Preparation

[0068] Prepared according to the method and conditions of step (b) in Example 1;

[0069] (c) Preparation of Au@SiO2

[0070] Prepared according to the method and conditions of step (c) in Example 1;

[0071] (d)CoAl-LDH e Preparation of / Au@SiO2

[0072] Prepared according to the method and conditions of step (d) in Example 1;

[0073] (e)CoAl-LDH e Preparation of / Au@SiO2 composite material modified GCE

[0074] Following the method and conditions of step (e) in Example 1, a CoAl-LDH solution with a concentration of 5 mg / mL was taken. e 6 μL of Au@SiO2 dispersion was drop-coated onto the treated GCE surface and allowed to air dry at room temperature to obtain CoAl-LDH. e / Au@SiO2 composite film modified GCE, denoted as CoAl-LDH e / Au@SiO2 / GCE. Example 5:

[0075] (a) Preparation of CoAl-LDH

[0076] Prepared according to the method and conditions of step (a) in Example 1;

[0077] (b)CoAl-LDH e Preparation

[0078] Prepared according to the method and conditions of step (b) in Example 1;

[0079] (c) Preparation of Au@SiO2

[0080] Prepared according to the method and conditions of step (c) in Example 1;

[0081] (d)CoAl-LDH ePreparation of / Au@SiO2

[0082] Prepared according to the method and conditions of step (d) in Example 1;

[0083] (e)CoAl-LDH e Preparation of / Au@SiO2 composite material modified GCE

[0084] Following the method and conditions of step (e) in Example 1, a CoAl-LDH solution with a concentration of 5 mg / mL was taken. e 7 μL of Au@SiO2 dispersion was drop-coated onto the treated GCE surface and allowed to air dry at room temperature to obtain CoAl-LDH. e / Au@SiO2 composite film modified GCE, denoted as CoAl-LDH e / Au@SiO2 / GCE.

[0085] Comparative Example 1:

[0086] The working electrode is GCE.

[0087] Comparative Example 2:

[0088] (a) Preparation of CoAl-LDH

[0089] Prepared according to the method and conditions of step (a) in Example 1;

[0090] (b) Preparation of CoAl-LDH / GCE

[0091] The substrate electrode was polished to a mirror finish according to the procedure, then ultrasonically cleaned with ultrapure water, and naturally dried at room temperature to obtain the treated GCE. The CoAl-LDH composite material prepared in step (a) was ultrasonically dispersed in deionized water solvent to prepare a dispersion with a concentration of 5 mg / mL. 5 μL of the dispersion was drop-coated onto the surface of the treated GCE and naturally dried at room temperature to obtain the CoAl-LDH modified GCE, denoted as CoAl-LDH / GCE.

[0092] Comparative Example 3:

[0093] (a) Preparation of CoAl-LDH

[0094] Prepared according to the method and conditions of step (a) in Example 1;

[0095] (b) CoAl-LDH e Preparation

[0096] Prepared according to the method and conditions of step (b) in Example 1;

[0097] (c)CoAl-LDH e / GCE preparation

[0098] The substrate electrode was polished to a mirror finish according to the procedure, then ultrasonically cleaned with ultrapure water, and naturally dried at room temperature to obtain the treated GCE; the CoAl-LDH prepared in step (b) was then used... e The composite material was ultrasonically dispersed in a deionized aqueous solvent to prepare a dispersion with a concentration of 5 mg / mL. 5 μL of this dispersion was drop-coated onto the treated GCE surface and allowed to air dry at room temperature to obtain CoAl-LDH. e Modifying GCE, denoted as CoAl-LDH e / GCE.

[0099] Comparative Example 4:

[0100] (a) Preparation of CoAl-LDH

[0101] Prepared according to the method and conditions of step (a) in Example 1;

[0102] (b) CoAl-LDH e Preparation

[0103] Prepared according to the method and conditions of step (b) in Example 1;

[0104] (c) CoAl-LDH e Preparation of Au

[0105] The CoAl-LDH obtained in step b e 0.2 g of the material was dissolved in 5 mL of ethanol, and 2 mL of Au nanorod solution was added under magnetic stirring. After stirring slowly for 12 h, the mixture was centrifuged at 8000 rpm for 5 min, washed several times with water, and finally dried in a 60 ℃ oven for 12 h to obtain CoAl-LDH. e / Au.

[0106] (d) CoAl-LDH e Preparation of / Au / GCE

[0107] The substrate electrode was polished to a mirror finish according to the procedure, then ultrasonically cleaned with ultrapure water, and naturally dried at room temperature to obtain the treated GCE; the CoAl-LDH prepared in step (c) was then processed. e / Au composite material was ultrasonically dispersed in deionized water solvent to prepare a dispersion with a concentration of 5 mg / mL. 5 μL of this dispersion was drop-coated onto the treated GCE surface and allowed to air dry at room temperature to obtain CoAl-LDH. e / Au modifies GCE, denoted as CoAl-LDH e / Au / GCE.

[0108] Comparative Example 5:

[0109] (a) Preparation of CoAl-LDH

[0110] Prepared according to the method and conditions of step (a) in Example 1;

[0111] (b) Preparation of Au@SiO2

[0112] Prepared according to the method and conditions of step (c) in Example 1;

[0113] (c) Preparation of CoAl-LDH / Au@SiO2

[0114] 0.2 g of the prepared CoAl-LDH material was dissolved in 5 mL of ethanol, and then 2 mL of Au@SiO2 solution was added under magnetic stirring. After stirring slowly for 12 h, the mixture was stirred at a speed of 8000 r / min. −1 Centrifuge for 5 min, wash three times with water, and finally dry in an oven at 60℃ for 12 h to obtain CoAl-LDH / Au@SiO2.

[0115] Comparative Example 6:

[0116] (a) Preparation of CoAl-LDH

[0117] Prepared according to the method and conditions of step (a) in Example 1;

[0118] (b) Preparation of Au@SiO2

[0119] Prepared according to the method and conditions of step (c) in Example 1;

[0120] (c) Preparation of CoAl-LDH / Au@SiO2

[0121] Prepared according to the method and conditions of step (c) in Comparative Example 5;

[0122] (d) Preparation of CoAl-LDH / Au@SiO2 / GCE

[0123] The substrate electrode is polished to a mirror finish according to the procedure, then ultrasonically cleaned with ultrapure water, and naturally dried at room temperature to obtain the treated GCE. The CoAl-LDH / Au@SiO2 composite material prepared in step (c) is ultrasonically dispersed in deionized water solvent to prepare a dispersion with a concentration of 5 mg / mL. 5 μL of the dispersion is drop-coated onto the treated GCE surface and naturally dried at room temperature to obtain CoAl-LDH / Au@SiO2 / GCE.

[0124] Figure 1 (a) is a SEM image of CoAl-LDH / Au@SiO2 prepared in Comparative Example 5, and (b) is a SEM image of CoAl-LDH prepared in Example 1.e SEM images of / Au@SiO2. (c, d) are CoAl-LDH corresponding to Example 1. e TEM image of / Au@SiO2; (e, f) are CoAl-LDH corresponding to Comparative Example 4. e TEM image of @Au. The image shows the composite material CoAl-LDH / Au@SiO2 (CoAl-LDH / Au@SiO2). Figure 1 a) It exhibits a relatively regular, smooth hexagonal sheet-like structure with an average lateral dimension of approximately 200 nm; while after alkaline etching, CoAl-LDH... e After being combined with Au@SiO2, CoAl-LDH e / Au@SiO2( Figure 1 b) The SEM images show irregular edges and a rough surface. This is mainly because alkaline etching dissolves most of the aluminum in CoAl-LDH, disrupting the regular shape of the LDH. This process generates more defects and active sites, effectively improving the performance of CoAl-LDH. e The catalytic performance of / Au@SiO2 on DA. To illustrate the role of silica-coated gold nanorods in the catalytic activity of CoAl-LDH. e / Au@SiO2(c, d) and CoAl-LDH e @Au (e, f) was characterized using TEM. It is clear from the figure that CoAl-LDH... e Au nanoparticles are uniformly dispersed in / Au@SiO2 on the alkaline-etched LDH, while in CoAl-LDH... e In @Au, Au nanorods exhibited significant aggregation.

[0125] Figure 2 Comparative Examples 1, 2, 3, 4, and Example 1 correspond to GCE, CoAl-LDH / GCE, and CoAl-LDH, respectively. e / GCE、CoAl-LDH e / Au / GCE and CoAl-LDH e / Au@SiO2 / GCE in 5.0 mmol / L Fe(CN)6 containing 0.1 mol / L potassium chloride 3- / 4- (1:1) CV plot and (b) electrochemical impedance plot in solution. Figure 2 a shows that, compared to GCE, CoAl-LDH / GCE and CoAl-LDH e / GCE and CoAl-LDH e @Au / GCE exhibits a lower peak current density and a larger inter-peak potential difference (ΔE). p ), of which CoAl-LDHe / Au / GCE is comparable to CoAl-LDH / GCE and CoAl-LDH e The high peak current density of / GCE may be due to the improved conductivity and electrocatalytic activity of the doped Au nanorods; while CoAl-LDH e The peak current density of / Au@SiO2 / GCE is significantly higher than that of CoAl-LDH. e The / Au / GCE ratio clearly demonstrates that the SiO2 encapsulation inhibits the aggregation of Au nanoparticles, ensuring their excellent dispersion and catalytic performance. Electrochemical impedance (EI) Figure 2 In b), the Randle equivalent circuit model was selected to fit the experimental data. The semicircle diameter of the EIS curve indicates the relationship between CoAl-LDH / GCE and CoAl-LDH. e The semicircular diameter of / GCE is larger than that of GCE, indicating that it has a larger R. ct This value is due to the poor conductivity of CoAl-LDH. e / Au / GCE's R ct The value is significantly smaller than GCE, but CoAl-LDH e / Au@SiO2 / GCE's R ct Value ratio of CoAl-LDH e The smaller / Au / GCE ratio indicates that the presence of Au nanoparticles improves conductivity. However, without SiO2 encapsulation, Au nanoparticles are prone to aggregation, leading to slightly poorer catalytic performance. The SiO2 encapsulation effectively inhibits Au nanoparticle aggregation, ensuring good dispersion and catalytic performance. Therefore, CoAl-LDH... e / Au@SiO2 / GCE's R ct The smallest value is more conducive to charge transfer, provides better conductivity, has more active centers and channels, and a larger specific surface area.

[0126] Figure 3 Comparative Examples 1, 2, 3, 4, 6, and Example 1 correspond to GCE(b), CoAl-LDH / GCE(a), and CoAl-LDH, respectively. e / GCE (c), CoAl-LDH e / Au / GCE (d), CoAl-LDH / Au@SiO2 / GCE (e) and CoAl-LDH e / Au@SiO2 / GCE (f), in a solution containing 0.1 mmol L −1 0.1 mol L of DA −1CV curves in phosphate buffer solution at pH 7.0. All modified electrodes detected redox peak currents of DA, including GCE, CoAl-LDH / GCE, and CoAl-LDH. e / GCE has a smaller peak current density, while CoAl-LDH e The peak current density of / Au / GCE and CoAl-LDH / Au@SiO2 / GCE is significantly improved, while that of CoAl-LDH is significantly improved. e The peak current density of / Au@SiO2 / GCE is higher than that of CoAl-LDH / Au@SiO2 / GCE. This is because alkaline etching increases defects and active sites, and the SiO2-coated Au nanoparticles are uniformly dispersed in the CoAl-LDH substrate. e This allows for the full utilization of the catalytic performance of Au nanoparticles. Therefore, CoAl-LDH... e / Au@SiO2 / GCE exhibited the best electrocatalytic performance for DA.

[0127] Figure 4 For Example 1, corresponding to CoAl-LDH e Current density-time curves of / Au@SiO2 / GCE at 0.25 V for different concentrations of DA, with the inset showing the range from 0.5 to 20 μmol L. −1 (a) is a magnified view within the range; (b) is the time response diagram of the electrode to DA. Figure 4 As shown in Figure a, after continuously adding different concentrations of DA, CoAl-LDH e The electrochemical response of / Au@SiO2 / GCE to DA increases with increasing concentration. Figure 4 b shows DA in CoAl-LDH e The current response on / Au@SiO2 / GCE stabilizes in just 2.2 s.

[0128] Figure 5 The graph shows the linear relationship between the concentration of added DA and the current density. The inset shows the linear relationship at low concentrations. It is displayed in the range of 0.5 ~ 850 μmol L. −1 Within the range of 0.5 ~ 20 μmol L −1 and 20 ~850 μmol L −1 Presenting two linear segments, respectively using j pa1 (10) −6 A cm −2 ) = − 0.3776 C − 2.113 (R 2 = 0.9965) and j pa2 (10) −6A cm −2 ) = − 0.2855 C − 2.368 (R 2 = 0.9856) is represented by two regression equations. The limit of detection (LOD) and limit of quantitation (LOQ) are 70.5 nmol / L. −1 (S / N = 3) and 235 nmol L −1 (S / N = 10), sensitivity is 377.6 μA·μmol − 1 L·cm −2 .

[0129] Figure 6 For Example 1, corresponding to CoAl-LDH e / Au@SiO2 / GCE at 0.2 V, (a) for 0.05 mmol L −1 (a) Current density-time response of DA and 50-fold concentration of interfering agent, (b) Relationship between storage days and the percentage of DPV peak current (n = 5) relative to its initial value. Inset: Histogram of the percentage of DPV peak current (n = 5) relative to the initial electrode peak current. Figure 6 As shown in a, when 0.05 mmol L... −1 A significant electrochemical signal was observed after DA, but no significant current signal was observed after adding 50 times the concentration of interfering substances (MnSO4, KCl, NaCl, AA, UA, Glu, H2O2, His, Met, Fe(NO3)3, Ni(NO3)2). This indicates that the high concentrations of these interfering substances have almost no effect on the detection of DA, proving that CoAl-LDH e / Au@SiO2 / GCE exhibits high electrochemical sensing selectivity for DA. For example... Figure 6 As shown in b; after being stored at room temperature for three weeks, CoAl-LDH e The oxidation peak response of / Au@SiO2 / GCE to DA remains above 83% of the initial level, indicating that the electrochemical sensor has good long-term stability.

[0130] Table 1: CoAl-LDH obtained in this invention e Performance comparison of Au@SiO2 / GCE for dopamine (DA) detection with other electroanalytical methods:

[0131]

[0132] As can be seen from Table 1, the CoAl-LDH described in this invention is used... eThe / Au@SiO2 / GCE electrode exhibits a linear range for dopamine (DA) detection that is close to or better than some previously reported modified electrodes, but its detection limit is significantly lower, indicating that CoAl-LDH… e / Au@SiO2 / GCE exhibits high electrocatalytic performance, good selectivity, and high sensitivity for DA.

[0133] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent conversion methods and shall be included within the protection scope of the present invention.

Claims

1. A functionalized Au@SiO2 composite film modified electrode, characterized in that... The modified electrode is composed of a glassy carbon electrode as the base electrode and an alkaline-etched cobalt-aluminum hydrotalcite nanosheet / Au@SiO2 composite film as the electrode modification material. The alkaline-etched cobalt-aluminum hydrotalcite nanosheet / Au@SiO2 composite material is obtained by combining alkaline-etched cobalt-aluminum hydrotalcite nanosheets with silica-encapsulated gold nanoparticles. The glassy carbon electrode is denoted as GCE; the alkaline-etched cobalt-aluminum hydrotalcite nanosheets are denoted as CoAl-LDH. e Gold nanoparticles encapsulated in silica are denoted as Au@SiO2; alkaline-etched cobalt-aluminum hydrotalcite nanosheets / Au@SiO2 are denoted as CoAl-LDH. e / Au@SiO2; The method for preparing the functionalized Au@SiO2 composite film modified electrode is characterized by comprising the following steps: Preparation of CoAl-LDH 1.748 g of Co(NO3)2·6H2O and 0.752 g of Al(NO3)3·9H2O were added to 100 mL of ultrapure water at a molar ratio of 3:

1. Then, 2.4 g of urea and 0.7408 g of ammonium fluoride were added, and the mixture was stirred continuously at 800 rpm to dissolve. The mixture was then poured into a high-pressure autoclave lined with polytetrafluoroethylene and heated at 200 °C for 12 h. The solid sample was collected by centrifugation, washed three times each with deionized water and anhydrous ethanol, and dried in an oven at 50 °C for 12 h to obtain pink CoAl-LDH powder. (b) CoAl-LDH e Preparation Take 0.2 g of CoAl-LDH and place it in 40 mL of 3 mol L. −1 Etching was performed in NaOH solution for 4 h, followed by centrifugation at 9000 rpm for 5 min, washing three times with deionized water, and drying in an oven at 50 ℃ for 12 h to obtain CoAl-LDH. e ; (c) Preparation of Au@SiO2 ① Mix 1 mL of ultrapure water with 1 mL of 1 mmol L... −1 After mixing with chloroauric acid, add 2 mL of 0.2 mol / L solution. −1 After thoroughly mixing CTAB, add 480 μL of a 5 mmol / L solution. −1 NaBH4 was used to obtain a seed solution. ② At a concentration of 4 mmol / L in 10 mL −1 Add 10 mL of 0.2 mol / L AgNO3 solution. −1 After thoroughly mixing CTAB, add 1 mL of 1 mmol L solution. −1 Chloroauric acid is added to the seed solution prepared in step ① under stirring until it turns into a blue solution, which is then left to stand for later use. ③ After centrifuging the gold nanoparticle solution prepared in step ② at 10000 rpm for 20 minutes, discard the supernatant and disperse the precipitate in 10 mL of solution with a concentration of 1 mmol / L. −1 In CTAB solution; ④ Take 10 mL of the purified gold nanorod solution from step ③ and add 100 μL of a solution with a concentration of 10.8 mmol / L. −1 KH-590 was stirred for 5 hours, then ammonia was added, followed by 5 mL of 20% TEOS. After reacting for 12 hours, Au@SiO2 dispersion was obtained. (d) CoAl-LDH e Preparation of / Au@SiO2 0.2 g of CoAl-LDH prepared in step (b) e The material was dispersed in 5 mL of ethanol, and then 2 mL of the Au@SiO2 dispersion prepared in step (b) was added under stirring. After stirring slowly for 12 h, the mixture was centrifuged at 8000 rpm for 5 min, washed three times with deionized water, and dried in an oven at 60 ℃ for 12 h to obtain CoAl-LDH. e / Au@SiO2; (e) CoAl-LDH e Preparation of / Au@SiO2 composite film modified GCE GCE was polished to a mirror finish, and then ultrasonically cleaned for 1 minute each with dilute nitric acid, anhydrous ethanol, and high-purity water, and allowed to air dry at room temperature for later use; the CoAl-LDH prepared in step (d) was then... e / Au@SiO2 complex was ultrasonically dispersed in 3 ml of deionized water to prepare 5 mg mL −1 CoAl-LDH e CoAl-LDH was prepared by drop-coating 3-7 μL of Au@SiO2 suspension onto a pretreated GCE surface and allowing it to air dry at room temperature. e / Au@SiO2 composite film modified GCE, denoted as CoAl-LDH e / Au@SiO2 / GCE.

2. The method for detecting the content of DA in body fluid using the functionalized Au@SiO2 composite film modified electrode as described in claim 1, characterized in that, Using 0.1 mol / L pH 7.0 phosphate buffer as the supporting electrolyte, electrolyte solutions containing different amounts of DA were added to the electrolytic cell. The modified electrode was used as the working electrode, and the oxidation peak current of DA was detected by chronoamperometry. The linear regression equation between the oxidation peak current of DA and its concentration was obtained. The oxidation peak current of DA in the test sample was measured by the same method. Substituting the current into the linear regression equation, the content of DA in the test sample was obtained.

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