A method for preparing a composite electrode

Abstract

This invention relates to the field of biosensor electrode technology and discloses a method for preparing a composite electrode, comprising the following steps: Ti sheet pretreatment, TNAs preparation, Ag film deposition, and PB film deposition. In the composite electrode prepared by this invention, the TNAs are uniformly and neatly arranged nanotube arrays grown directly on the Ti sheet substrate, exhibiting strong bonding, uniform distribution, and resistance to erosion, thus possessing high mechanical strength. Loading an Ag film onto TNAs not only improves the conductivity of the TNAs and enhances the electrocatalytic activity of the composite electrode, but also allows for tight electrostatic bonding with the PB film, solving the problem of PB easily detaching from the electrode surface and improving the stability of the composite electrode.

Description

Technical Field

[0001] This invention relates to the field of biosensor electrode technology, and in particular to a method for preparing a composite electrode. Background Technology

[0002] A biosensor is an instrument that is sensitive to biological substances and converts their concentration into an electrical signal for detection. Oxidase biosensors typically detect the product H₂O₂, which is the product of the enzyme-catalyzed oxidation reaction between the substrate and oxygen. This method can detect relatively low substrate concentrations and is therefore widely used in the fabrication of biosensors. Direct detection of H₂O₂ usually involves electrochemical oxidation detection at a platinum electrode with a voltage of 0.6 V (vs. Ag / AgCl). However, many electroactive substances in biological samples, such as ascorbic acid, bilirubin, and uric acid, can be oxidized even at such high potentials, interfering with the detection of H₂O₂ concentration. Therefore, how to selectively and efficiently catalyze H₂O₂ at lower potentials has become a current research hotspot.

[0003] Titanium dioxide nanotube arrays (TNAs) are nanostructures composed of single-layer or multi-layer titanium dioxide nanotubes. Currently, TNAs are primarily prepared using the anodic oxidation method. TNAs prepared by this method are directly grown on Ti substrates, arranged in an orderly array. The nanotubes are directly connected to the Ti substrate, resulting in a strong bond, uniform distribution, and resistance to erosion. They exhibit high active surface area, good chemical and thermal stability, and very high mechanical strength. Furthermore, the preparation technique is simple and inexpensive. These advantages make TNAs a promising functional material, widely used in fields such as hydrogen sensors, solar cells, and biosensors.

[0004] Prussian blue (PB), also known as ferric ferricyanide, is one of the classic coordination polymers. For a long time, it has been used as a light-stabilizing material in industrial production of coatings, baking enamels, printing ink colorants, and detergent additives. Prussian blue is also known as "artificial peroxidase," and its thin-film modified electrodes exhibit excellent catalytic performance for H2O2. Using PB as a medium for H2O2 reduction can effectively solve the problem of various interfering currents caused by excessively high potentials when detecting H2O2. Currently, the main methods for modifying electrodes with PB are electrochemical deposition, continuous ion adsorption, mechanical attachment to the electrode, and layer deposition. However, many problems still need to be solved, such as the weak binding force between PB and the electrode; it easily detaches from the electrode surface after a few cycles of cyclic voltammetry in solution, resulting in poor stability. Summary of the Invention

[0005] To overcome the shortcomings and deficiencies of the prior art, this invention aims to provide a method for preparing a composite electrode. The prepared composite electrode has excellent electrocatalytic activity, mechanical strength and stability, and is simple and low in cost.

[0006] The technical solution adopted by this invention to solve its technical problem is:

[0007] A method for preparing a composite electrode includes the following steps:

[0008] (1) The Ti wafers were ultrasonically cleaned in acetone, ethanol and deionized water for 15 min, then chemically polished in a mixed acid solution for 30 s with vigorous stirring, then removed and cleaned with deionized water, and dried at room temperature to obtain pretreated Ti wafers.

[0009] (2) A two-electrode system is formed with a constant voltage DC power supply, a pretreated Ti sheet as the anode and a Pt wire as the cathode. The pretreated Ti sheet is etched in HF ethanol solution, NaF and HF buffer solution and HF aqueous solution for 30-45 min under a voltage of 20-30V, respectively, and stirred continuously. Then it is cleaned with deionized water, placed in a muffle furnace and calcined for 1 h. After cooling, TNAs are obtained.

[0010] (3) Using a saturated calomel electrode as the reference electrode, a three-electrode system is formed with the two-electrode system. Under constant pressure, the TNAs are immersed in silver nitrate solution, maintaining a current density of 1-2 mA / cm². 2 After 4 minutes, a silver film was deposited on the surface of TNAs. After washing with deionized water and air drying, a TNAs / Ag composite electrode was obtained.

[0011] (4) Immerse the TNAs / Ag composite electrode in a mixed solution of K3Fe(CN)6 and KCl, scan 150 times using cyclic voltammetry with a scanning voltage of -0.2-0.6V, deposit a PB film on the TNAs / Ag composite electrode, wash with deionized water and air dry to obtain the TNAs / Ag / PB composite electrode.

[0012] Preferably, the size of the Ti sheet is 1mm × 15mm × 0.1mm.

[0013] Preferably, the Ti wafer has a purity of 99.9%.

[0014] Preferably, the mixed acid solution is a mixture of HF, concentrated nitric acid, and deionized water in a volume ratio of 1:4:5.

[0015] Preferably, the concentration of the HF ethanol solution is 0.2%-0.3%, and the concentration of the HF aqueous solution is 0.2%-0.3%.

[0016] Preferably, the pH value of the NaF and HF buffer solution is 5-5.2.

[0017] Preferably, the temperature of the muffle furnace is 500°C.

[0018] Preferably, the concentration of the silver nitrate solution is 20-30 mmol / L.

[0019] Preferably, the concentration of K3Fe(CN)6 in the mixed solution of K3Fe(CN)6 is 1-2 mmol / L and the concentration of KCl is 0.1-0.2 mol / L.

[0020] Preferably, the pH value of the mixed solution of K3Fe(CN)6 and KCl is 1.5-1.7.

[0021] The beneficial effects of this invention are:

[0022] The composite electrode prepared in this invention consists of a uniformly and neatly arranged array of TNA nanotubes grown directly on a Ti substrate. This results in a strong bond, uniform distribution, resistance to erosion, and high mechanical strength. Loading an Ag film onto TNA not only improves the conductivity of the TNAs and enhances the electrocatalytic activity of the composite electrode, but also allows for a tighter bond between the TNAs and the PB film via electrostatic forces. This solves the problem of PB easily detaching from the electrode surface, thus improving the stability of the composite electrode. Attached Figure Description

[0023] Figure 1 This is the cyclic voltammetry curve of Example 1 before and after 300 cycles;

[0024] Figure 2 This is the cyclic voltammetry curve of Comparative Example 2 before and after 300 cycles. Detailed Implementation

[0025] The following will describe the concept and technical effects of the present invention clearly and completely with reference to the embodiments, so as to fully understand the purpose, features and effects of the present invention. Example 1:

[0026] The method for preparing the composite electrode described in this embodiment includes the following steps:

[0027] (1) Ti sheet pretreatment: Ti sheets with a purity of 99.9% (1mm×15mm×0.1mm) were ultrasonically cleaned in acetone, ethanol and deionized water for 15min in sequence, and then chemically polished in a mixed solution of HF, concentrated nitric acid and deionized water in a volume ratio of 1:4:5 for 30s with vigorous stirring. Then they were taken out and cleaned with deionized water and dried at room temperature to obtain pretreated Ti sheets.

[0028] (2) Preparation of TNAs: A two-electrode system was formed with a constant voltage DC power supply as the power source, a pretreated Ti sheet as the anode and a Pt wire as the cathode. The pretreated Ti sheet was etched in 0.2% HF ethanol solution, a buffer solution of NaF and HF with a pH of 5, and a 0.2% HF aqueous solution for 30 min under a voltage of 20V, respectively, with constant stirring. Then it was cleaned with deionized water and calcined in a muffle furnace at 500℃ for 1 h. After cooling, TNAs were obtained.

[0029] (3) Deposition of Ag thin film: Using a saturated calomel electrode as the reference electrode, a three-electrode system was formed with the two-electrode system. Under constant pressure, TNAs were immersed in 20-30 mmol / L silver nitrate solution, and the current density was maintained at 1 mA / cm². 2 After 4 minutes, a silver film was deposited on the surface of TNAs. After washing with deionized water and air drying, a TNAs / Ag composite electrode was obtained.

[0030] (4) Deposition of PB film: The TNAs / Ag composite electrode was immersed in a mixed solution of 1 mmol / L K3Fe(CN)6 and 0.1 mol / L KCl at pH 1.5. Cyclic voltammetry was used to scan for 150 cycles at a scanning voltage of -0.2 to 0.6 V to deposit a PB film on the TNAs / Ag composite electrode. After washing with deionized water and air drying, the TNAs / Ag / PB composite electrode was obtained. Example 2:

[0031] The method for preparing the composite electrode described in this embodiment includes the following steps:

[0032] (1) Ti sheet pretreatment: Ti sheets with a purity of 99.9% (1mm×15mm×0.1mm) were ultrasonically cleaned in acetone, ethanol and deionized water for 15min in sequence, and then chemically polished in a mixed solution of HF, concentrated nitric acid and deionized water in a volume ratio of 1:4:5 for 30s with vigorous stirring. Then they were taken out and cleaned with deionized water and dried at room temperature to obtain pretreated Ti sheets.

[0033] (2) Preparation of TNAs: A two-electrode system was formed with a constant voltage DC power supply as the power source, a pretreated Ti sheet as the anode and a Pt wire as the cathode. The pretreated Ti sheet was etched in 0.25% HF ethanol solution, NaF and HF buffer solution with pH 5.1 and 0.25% HF aqueous solution for 35 min under 25V voltage, and stirred continuously. Then it was cleaned with deionized water and calcined in a muffle furnace at 500℃ for 1 h. After cooling, TNAs were obtained.

[0034] (3) Deposition of Ag thin film: Using a saturated calomel electrode as the reference electrode, a three-electrode system was formed with the two-electrode system. Under constant pressure, TNAs were immersed in a 25 mmol / L silver nitrate solution, maintaining a current density of 1.5 mA / cm². 2 After 4 minutes, a silver film was deposited on the surface of TNAs. After washing with deionized water and air drying, a TNAs / Ag composite electrode was obtained.

[0035] (4) Deposition of PB film: The TNAs / Ag composite electrode was immersed in a mixed solution of 1.5 mmol / L K3Fe(CN)6 and 0.15 mol / L KCl at pH 1.6. Cyclic voltammetry was used to scan for 150 cycles at a scanning voltage of -0.2 to 0.6 V to deposit a PB film on the TNAs / Ag composite electrode. After washing with deionized water and air drying, the TNAs / Ag / PB composite electrode was obtained. ... Example 3:

[0036] The method for preparing the composite electrode described in this embodiment includes the following steps:

[0037] (1) Ti sheet pretreatment: Ti sheets with a purity of 99.9% (1mm×15mm×0.1mm) were ultrasonically cleaned in acetone, ethanol and deionized water for 15min in sequence, and then chemically polished in a mixed solution of HF, concentrated nitric acid and deionized water in a volume ratio of 1:4:5 for 30s with vigorous stirring. Then they were taken out and cleaned with deionized water and dried at room temperature to obtain pretreated Ti sheets.

[0038] (2) Preparation of TNAs: A two-electrode system was formed with a constant voltage DC power supply as the power source, a pretreated Ti sheet as the anode and a Pt wire as the cathode. The pretreated Ti sheet was etched in 0.3% HF ethanol solution, NaF and HF buffer solution with pH 5.2 and 0.3% HF aqueous solution for 45 min under 30V voltage, and stirred continuously. Then it was cleaned with deionized water and calcined in a muffle furnace at 500℃ for 1 h. After cooling, TNAs were obtained.

[0039] (3) Deposition of Ag thin film: Using a saturated calomel electrode as the reference electrode, a three-electrode system was formed with the two-electrode system. Under constant pressure, TNAs were immersed in a 30 mmol / L silver nitrate solution, maintaining a current density of 2 mA / cm². 2 After 4 minutes, a silver film was deposited on the surface of TNAs. After washing with deionized water and air drying, a TNAs / Ag composite electrode was obtained.

[0040] (4) Deposition of PB film: The TNAs / Ag composite electrode was immersed in a mixed solution of 2 mmol / L K3Fe(CN)6 and 0.2 mol / L KCl at pH 1.7. Cyclic voltammetry was used to scan for 150 cycles at a scanning voltage of -0.2 to 0.6 V to deposit a PB film on the TNAs / Ag composite electrode. After washing with deionized water and air drying, the TNAs / Ag / PB composite electrode was obtained.

[0041] Comparative Example 1:

[0042] The only difference between this comparative example and Example 1 is that TNAs are not prepared and Ti sheets are used instead of TNAs for loading. The other raw materials and steps are the same as in Example 1.

[0043] Comparative Example 2:

[0044] The only difference between this comparative example and Example 1 is that Ag film deposition is not performed; the other raw materials and steps are the same as in Example 1.

[0045] Composite electrode performance testing:

[0046] Stability test: The electrodes prepared in Example 1 and Comparative Example 2 were placed in 0.1 mol / L PBS solution (pH 6.0, containing 0.1 mol / L KCl), and continuously scanned for 300 cycles at a voltage range of -0.05 to 0.5 V and a scan rate of 50 mV / s.

[0047] Depend on Figure 1 and Figure 2 It can be seen that the peak current of the electrode in Comparative Example 2 is smaller than that in Example 1, indicating poorer electrocatalytic activity. Furthermore, after 300 cycles, the electrochemical response to H2O2 decreases significantly, with a substantial drop in peak current, demonstrating poor stability. In contrast, the curve of Example 1 shows almost no change after 300 cycles, exhibiting excellent stability. This is because the Ag film loaded on TNAs in Example 1 not only improves the conductivity of TNAs and enhances the electrocatalytic activity of the composite electrode, but also allows for a tighter bond with the PB film via electrostatic forces, solving the problem of PB easily detaching from the electrode surface and improving the stability of the composite electrode.

[0048] Mechanical strength test: The composite electrodes prepared in Examples 1-3 and Comparative Examples 1-2 were placed in a compression testing machine, a certain pressure was applied, and the compression deformation and compressive force of the composite electrodes were measured to calculate the mechanical strength of the composite electrodes.

[0049] Table 1: Composite Electrode Strength Test

[0050] Strength / MPa Example 1 2.24 Example 2 2.37 Example 3 2.31 Comparative Example 1 1.06 Comparative Example 2 2.07

[0051] As can be seen from the table above, the mechanical strength of Comparative Example 1 is worse than that of Example 1. This is because Comparative Example 1 did not prepare TNAs and used Ti sheets instead of TNAs for loading, while the TNAs prepared in Example 1 are uniformly and neatly arranged nanotube arrays that grow directly on the Ti sheet substrate. They are firmly bonded, uniformly distributed, not easily washed away, and have strong mechanical strength.

[0052] The above embodiments are only some embodiments of the present invention, and not all embodiments. Other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are all within the scope of protection of the present invention.

Claims

1. A method for preparing a composite electrode, characterized in that, Includes the following steps: (1) Ti wafer pretreatment: The Ti wafer was ultrasonically cleaned in acetone, ethanol and deionized water for 15 min in sequence, then chemically polished in a mixed acid solution for 30 s with vigorous stirring, then taken out and cleaned with deionized water, and dried at room temperature to obtain pretreated Ti wafer. (2) Preparation of TNAs: A two-electrode system was formed with a constant voltage DC power supply, a pretreated Ti sheet as the anode and a Pt wire as the cathode. The pretreated Ti sheet was etched in HF ethanol solution, NaF and HF buffer solution and HF aqueous solution for 30-45 min under a voltage of 20-30V, respectively, with constant stirring. Then it was cleaned with deionized water, placed in a muffle furnace and calcined for 1 h. After cooling, TNAs were obtained. (3) Deposition of Ag thin film: Using a saturated calomel electrode as the reference electrode, a three-electrode system is formed with the two-electrode system. Under constant voltage, TNAs are immersed in silver nitrate solution, maintaining a current density of 1-2 mA / cm². 2 After 4 minutes, a silver film was deposited on the surface of TNAs. The film was then washed with deionized water and air-dried to obtain a TNAs / Ag composite electrode. (4) Deposition of PB film: The TNAs / Ag composite electrode was immersed in a mixed solution of K3Fe(CN)6 and KCl. Cyclic voltammetry was used to scan 150 times with a scanning voltage of -0.2-0.6V to deposit a PB film on the TNAs / Ag composite electrode. After washing with deionized water and air drying, the TNAs / Ag / PB composite electrode was obtained. The Ti wafer has a size of 1mm × 15mm × 0.1mm and a purity of 99.9%. The mixed acid solution is a mixture of HF, concentrated nitric acid, and deionized water in a volume ratio of 1:4:5; the concentration of the HF ethanol solution is 0.2%-0.3%, and the concentration of the HF aqueous solution is 0.2%-0.3%; the pH value of the NaF and HF buffer solution is 5-5.

2. The muffle furnace temperature is 500℃; the concentration of the silver nitrate solution is 20-30 mmol / L; the concentration of K3Fe(CN)6 in the mixed solution of K3Fe(CN)6 is 1-2 mmol / L, the concentration of KCl is 0.1-0.2 mol / L, and the pH value of the mixed solution of K3Fe(CN)6 and KCl is 1.5-1.7.

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