Composite electrode and preparation method and application thereof

Abstract

The invention relates to the technical field of biosensors, in particular to a composite electrode and a preparation method and application thereof. According to the preparation method, the electrode is modified by zinc oxide and polyoxometallate by utilizing an electrostatic adsorption effect and adopting a layer-by-layer self-assembly method, finally, the synthesized composite electrode is applied to preparation of the hydrogen peroxide biosensor, and the method has the advantages of low cost, simplicity and convenience in operation, high sensitivity, no need of pretreatment, quick response and the like. The PW11Co can improve the migration rate of electrons in a zinc oxide conduction band and can effectively delay compounding of photon-generated carriers in the migration process, and the PW11Co can absorb visible light and improve the utilization rate of light, so that the photoelectric property of the composite electrode can be remarkably enhanced, and the photoelectric performance of the composite electrode is improved. Therefore, the technical problem that an existing electrode material is difficult to meet the performance requirement of a biosensor for hydrogen peroxide detection is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of biosensors, and in particular to a composite electrode and a preparation method and application thereof. Background Art

[0002] Hydrogen peroxide is an important active small molecule, widely used in the fields of environment, food, medical treatment, and pharmaceuticals. Low concentrations of hydrogen peroxide are often used as disinfectants to disinfect wounds and medical devices, and have a good antibacterial effect. High concentrations of hydrogen peroxide are corrosive and may cause chronic diseases when in contact with human skin, respiratory tract, and mucous membranes. Abnormal concentrations in organisms can cause cardiovascular diseases, Alzheimer's disease, cancer, and other diseases. Therefore, efficient, rapid, and accurate trace detection of hydrogen peroxide helps to timely discover and diagnose related diseases. Currently reported methods for hydrogen peroxide detection include chemical titration, chemiluminescence, spectrophotometry, high performance liquid chromatography, biosensor detection, and the like.

[0003] Among them, biosensor detection mainly detects hydrogen peroxide by monitoring the electrochemical signal generated by the working electrode of the biosensor. However, zinc oxide electrode materials can only absorb ultraviolet light due to their wide band gap, which greatly reduces the efficiency of light utilization and limits the further improvement of photocatalytic and photoelectrocatalytic performance. In addition, the good carrier migration ability of zinc oxide materials themselves leads to the easy recombination of photogenerated carriers during the migration process, thereby weakening the catalytic performance. Therefore, the existing zinc oxide electrode materials are difficult to use for hydrogen peroxide detection due to their poor photoelectric performance. Summary of the invention

[0004] The purpose of the present invention is to overcome the deficiencies of the prior art and provide a composite electrode and a preparation method and application thereof, which solves the technical problem that the existing zinc oxide electrode material is difficult to be used for hydrogen peroxide detection due to its poor photoelectric performance.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions: The present invention provides a method for preparing a composite electrode, comprising the following steps: Using zinc alkoxide as raw material, zinc oxide sol was prepared by sol-gel method under alkaline conditions; using disodium hydrogen phosphate and sodium tungstate as raw materials, Na7PW was prepared by double decomposition reaction under acidic conditions. 11 O 39 ;Na7PW 11 O 39 With cobalt nitrate in a solvent system, through reflux reaction, PW was obtained. 11 Co; the activated indium tin oxide electrode material is immersed in PW 11 In Co solution and ZnO sol, ZnO and PW11 The indium tin oxide electrode material was modified by Co to prepare a composite electrode.

[0006] The present invention utilizes electrostatic adsorption and adopts a layer-by-layer self-assembly method to achieve the modification of indium tin oxide electrodes with zinc oxide and polyoxometalates, and finally applies the synthesized composite electrode to the preparation of hydrogen peroxide biosensors. This method has the advantages of low cost, simple operation, high sensitivity, no need for pretreatment, and rapid response. The present invention utilizes zinc oxide and polyoxometalates to modify indium tin oxide electrodes, mainly based on PW 11 Co can increase the migration rate of electrons in the conduction band of zinc oxide, effectively delay the recombination of photogenerated carriers during migration, and PW 11 Co absorbs visible light, which improves the utilization rate of light, and can thus significantly enhance the photoelectric performance of the composite electrode, thereby solving the technical problem that the existing zinc oxide electrode material is difficult to use for the detection of hydrogen peroxide due to its poor photoelectric performance.

[0007] Specifically, disodium hydrogen phosphate and sodium tungstate are dissolved in deionized water, stirred thoroughly to make them completely dissolved, and the pH is adjusted with concentrated nitric acid. The specific equation is: ; Finally, the monovacancy heteropoly compound Na7PW was prepared. 11 O 39 .

[0008] Optionally, the acidic conditions include a pH of 4 to 6, and the reaction temperature of the metathesis reaction is 70°C to 90°C.

[0009] Optionally, the molar ratio of the disodium hydrogen phosphate to the sodium tungstate is 1:11-12.

[0010] Optionally, the reaction temperature of the reflux reaction is 70°C to 90°C, and the Na7PW 11 O 39 The mass ratio of the cobalt nitrate to the cobalt nitrate is 6 to 7:1.

[0011] Optionally, the solvent is water Optionally, the PW 11 The concentration of the Co solution is 1.5 mmol / L to 2.5 mmol / L.

[0012] Optionally, the PW 11 The pH of the Co solution is 1-2.

[0013] The invention provides a composite electrode, which is prepared by adopting the composite electrode preparation method mentioned above.

[0014] The present invention provides an application of the composite electrode in preparing a biosensor for detecting hydrogen peroxide.

[0015] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention utilizes electrostatic adsorption and adopts a layer-by-layer self-assembly method to achieve the modification of zinc oxide and polyoxometalate electrodes, and finally applies the synthesized composite electrode to the preparation of hydrogen peroxide biosensor. This method has the advantages of low cost, simple operation, high sensitivity, no need for pretreatment, and rapid response. 11 Co can increase the migration rate of electrons in the conduction band of zinc oxide, which can effectively delay the recombination of photogenerated carriers during the migration process, and PW 11 Co absorbs visible light, which improves the utilization rate of light, and thus can significantly enhance the photoelectric performance of the composite electrode, thereby solving the technical problem that the existing zinc oxide electrode material is difficult to use for the detection of hydrogen peroxide due to its poor photoelectric performance.

[0016] 2. The composite electrode prepared by the present invention can test hydrogen peroxide solutions of different concentrations under light and is stable during the test process, which further verifies the superiority of the biosensor. The present invention has a positive effect on enriching the types and sources of biosensors. The present invention provides a new way to study and develop new biosensors. This technology is of great significance for the detection of hydrogen peroxide in the human body and the early diagnosis of cardiovascular diseases, and has potential for broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 The morphology and structure characterization diagrams of the zinc oxide sol prepared in Example 1. Among them, (A) is a UV-visible absorption spectrum diagram, (B) is an X-ray diffraction spectrum diagram, (C) is a Zeta potential test diagram, and (D) is a scanning electron microscope diagram.

[0018] Figure 2 PW prepared in Example 1 11 Co performance and morphology characterization diagram. Among them, (a) is the infrared spectrum, (b) is the cyclic voltammetry curve, and (c) is the UV-visible absorption spectrum.

[0019] Figure 3 PW prepared in Example 1 11 UV-visible absorption spectrum of Co / ZnO / ITO composite film electrode.

[0020] Figure 4 The curve of the photocurrent of the composite film electrode changing with time in phosphate buffer solution with different concentrations of hydrogen peroxide. DETAILED DESCRIPTION

[0021] In order to solve the above technical problems, the present invention provides a composite electrode and a preparation method and application thereof. The technical scheme and embodiments of the present invention are now described in detail in conjunction with the accompanying drawings.

[0022] ITO, the full English name is Indium tin oxide, and its Chinese meaning is indium tin oxide.

[0023] APS, the full English name is Ammonium persulfate, and its Chinese meaning is ammonium persulfate.

[0024] PSS, the full English name is Poly styrene sulfonic acid, and its Chinese meaning is polystyrene sulfonic acid.

[0025] The technical solution adopted by the present invention is as follows: (1) Prepare zinc oxide sol, put anhydrous ethanol solution containing zinc acetate into a reflux device and keep it at 80°C until a transparent solution is obtained. Slowly drop anhydrous ethanol solution of lithium hydroxide into the zinc acetate solution, and then ultrasonically treat it for about 1 hour to obtain zinc oxide sol.

[0026] Purpose of reflux: In order to prevent ethanol from volatilizing and decreasing, reflux is needed to maintain the stability of the solution volume and improve the reaction efficiency.

[0027] Lithium hydroxide and zinc acetate are prepared by a sol-gel method, and the purpose of ultrasonic treatment is to improve the uniformity and stability of zinc oxide sol.

[0028] (2) Preparation of PW 11 Co, first dissolve a certain proportion of disodium hydrogen phosphate and sodium tungstate in deionized water, stir thoroughly to dissolve them completely, adjust the pH to 4.8 with concentrated nitric acid, continue stirring and heat to 80℃~90℃. When the volume of the mixed solution is reduced to half of the original, stop heating. After cooling, add 80mL~100mL acetone, let it stand overnight, remove the upper acetone liquid, and place the lower system in a 50℃ oven to dry to obtain a white solid, which is the mono-lacunarity heteropoly acid salt Na7PW 11 O 39 .

[0029] Dissolve disodium hydrogen phosphate and sodium tungstate in deionized water, stir thoroughly to make them completely dissolved, adjust the pH with concentrated nitric acid, and the following reaction occurs: ; Then, acetone liquid-liquid extraction was used to separate the heteropoly anions in the dense lower layer. The extraction was repeated until there was no nitrate ion in the acetone extract, and then the lower layer system was dried to finally obtain the monovacancy heteropoly compound Na7PW 11 O 39 .

[0030] Then add a certain proportion of Na7PW to the aqueous solution of cobalt nitrate. 11 O 39 , then stir and heat to 70℃~90℃ on an oil bath, at which point the solution turns dark red, reflux for 1h~2h, then add acetone after evaporation and cooling, filter to remove sodium nitrate precipitate, and repeat adding acetone until no sodium nitrate precipitate is produced. Place the filtrate on an 80℃ oil bath to evaporate the acetone, and when a small amount of solution remains, place it in an oven at 50℃ to dry, and grind to obtain a dark red powder PW 11 Co.

[0031] Cobalt nitrate and the prepared mono-vacancy heteropoly compound Na7PW 11 O 39 The mixture was heated and stirred in an oil bath and refluxed for 2 h, and the following reaction occurred: , Then evaporate and cool, add acetone to filter and remove sodium nitrate precipitate, repeat the addition until no precipitate is produced, then dry the acetone and dry in an oven to obtain a dark red powder PW 11 Co.

[0032] It should be noted that PW 11 The specific composition of Co is Na5PW 11 O 39 Co(H2O).

[0033] (3) Clean the ITO electrode. Place the ITO electrode in a solution of ammonia, hydrogen peroxide, and water in a ratio of 1:1:1, and heat and boil at 80°C for 30 minutes. After cooling, rinse with distilled water, and then place it in acetone for 15 minutes for ultrasonic treatment. After ultrasonic treatment, rinse with distilled water, and then place it in distilled water for 15 minutes for ultrasonic treatment, and blow dry for later use.

[0034] (4) Preparation of composite biosensor: ITO electrode was immersed in APS solution for 12 h. Then, the APS-modified ITO electrode was immersed in hydrochloric acid solution with pH = 2.0 for 20 min to make its surface positively charged, and then washed with deionized water and dried with nitrogen. Then, PW was prepared by layer-by-layer self-assembly method. 11 Biosensor based on Co / ZnO / ITO composite material.

[0035] The Zeta potential test of zinc oxide sol shows that it is positively charged, and polyacid PW 11 Co is a highly electronegative metal-oxygen cluster compound and is negatively charged. The ITO electrode was immersed in the APS solution for 12 hours and then immersed in the hydrochloric acid solution to make it positively charged, and then immersed in the negatively charged PW 11Co solution and positively charged zinc oxide sol to prepare the biosensor.

[0036] The detection method of the hydrogen peroxide sensor using the zinc oxide / polyoxometalate composite material of the present invention comprises the following steps: (1) Use phosphate buffer solution with pH=7 as the test solution, zinc oxide and PW 11 The Co-modified ITO electrode was used as the working electrode, the saturated calomel electrode was used as the auxiliary electrode, and the platinum wire electrode was used as the counter electrode. Hydrogen peroxide solutions of different concentrations were added, and the relationship between the peak current and the concentration of hydrogen peroxide of different concentrations was detected.

[0037] (2) Detect the electrochemical signal of the working electrode.

[0038] The present invention is described in detail below through specific examples. The examples are exemplary and intended to be used to explain the present invention, but should not be understood as limiting the present invention.

[0039] Example 1 This embodiment provides a method for preparing a composite electrode, and the specific steps are as follows: Step 1: Preparation of zinc oxide sol.

[0040] 0.025 mol of zinc acetate was placed in a reflux device containing 300 mL of anhydrous ethanol and maintained at 80°C until a transparent solution I was obtained. 0.024 mol of lithium hydroxide was dissolved in 200 mL of anhydrous ethanol to obtain a solution II. Then, the solution II was slowly dripped into the solution I, and then ultrasonicated for about 1 h to obtain a zinc oxide sol.

[0041] Step 2: PW 11 Preparation of Co.

[0042] Dissolve 0.020 mol of disodium hydrogen phosphate and 0.225 mol of sodium tungstate in 150 mL of deionized water, stir thoroughly to dissolve completely, adjust pH to 4.8 with concentrated nitric acid, continue stirring and heat to 85 °C. When the volume of the mixed solution is reduced to half of the original, stop heating. After cooling, add 80 mL of acetone, let stand overnight, remove the upper acetone liquid, and place the lower system in a 50 °C oven to dry to obtain a white solid, and prepare the mono-lacunalist heteropolyacid salt Na7PW 11 O 39 .

[0043] 6.07 g Na7PW was added to 30 mL of aqueous solution containing 0.88 g cobalt nitrate. 11 O 39, then stir magnetically in an oil bath and heat to 90°C, at which point the solution turns dark red, reflux for 2 hours, and then evaporate until the volume of the solution is about 10 mL. After cooling, add about 80 mL of acetone, filter to remove the sodium nitrate precipitate, and repeat the addition of acetone until no sodium nitrate precipitate is produced. Place the filtrate in an 80°C oil bath to evaporate the acetone, and when a small amount of solution remains, place it in a 50°C oven to dry, and grind to obtain a dark red powder PW 11 Co.

[0044] Step 3: Preparation of composite electrode.

[0045] The ITO electrode was immersed in the APS solution for 12 h, and then immersed in a pH = 2.0 hydrochloric acid solution for 20 min to make its surface positively charged, and then washed with deionized water and dried with nitrogen. 11 The PW was obtained by immersing the mixture in a Co solution for 10 minutes and in a zinc oxide sol for 1 minute, and washing with deionized water and drying with nitrogen after each immersion. 11 Co / ZnO / ITO composite film electrode.

[0046] Example 2 This embodiment provides a method for preparing a composite electrode, which is different from Embodiment 1 in that only Step 1 and Step 3 are performed. The specific steps are as follows: Step 1: Preparation of zinc oxide sol.

[0047] 0.025 mol of zinc acetate was placed in a reflux device containing 300 mL of anhydrous ethanol and maintained at 80°C until a transparent solution I was obtained. 0.024 mol of lithium hydroxide was dissolved in 200 mL of anhydrous ethanol to obtain a solution II. Then, the solution II was slowly dripped into the solution I, and then ultrasonicated for about 1 h to obtain a zinc oxide sol.

[0048] Step 3: Preparation of composite electrode.

[0049] The zinc oxide sol was immersed in a PSS solution of pH=1.5 and 2 mM for 10 minutes, and then washed with deionized water and dried with nitrogen gas to obtain a PSS / ZnO composite membrane electrode.

[0050] Example 3 This embodiment provides a method for preparing a composite electrode, and the specific steps are as follows: Step 1, PW 11 Preparation of Co.

[0051] Dissolve 0.020 mol of disodium hydrogen phosphate and 0.225 mol of sodium tungstate in 150 mL of deionized water, stir thoroughly to dissolve completely, adjust pH to 4.8 with concentrated nitric acid, continue stirring and heat to 85°C. Stop heating when the volume of the mixed solution is reduced to half of the original volume. After cooling, add 80-100 mL of acetone, let stand overnight, remove the upper acetone solution, and place the lower system in a 50°C oven to dry to obtain a white solid, and obtain the mono-lacunalist heteropolyacid salt Na7PW 11 O 39 .

[0052] 6.07 g Na7PW was added to 30 mL of aqueous solution containing 0.88 g cobalt nitrate. 11 O 39 , then stir magnetically in an oil bath and heat to 90°C, at which point the solution turns dark red, reflux for 2 hours, and then evaporate until the volume of the solution is about 10 mL. After cooling, add about 80 mL of acetone, filter to remove the sodium nitrate precipitate, and repeat the addition of acetone until no sodium nitrate precipitate is produced. Place the filtrate in an 80°C oil bath to evaporate the acetone, and when a small amount of solution remains, place it in a 50°C oven to dry, and grind to obtain a dark red powder PW 11 Co.

[0053] Step 2: Preparation of composite electrode.

[0054] The ITO electrode was immersed in the APS solution for 12 h, and then immersed in a pH = 2.0 hydrochloric acid solution for 20 min to make its surface positively charged, and then washed with deionized water and dried with nitrogen. 11 Co solution for 10 minutes, and washed with deionized water and dried with nitrogen after each immersion to obtain PW 11 Co / ITO composite film electrode.

[0055] Structural characterization: Figure 1 The UV-visible absorption spectrum, X-ray diffraction spectrum, Zeta potential and scanning electron microscope characterization images of zinc oxide sol. The characteristic absorption peak of zinc oxide is 345nm as observed from the UV-visible absorption spectrum of image (A), and it can be seen from the X-ray diffraction spectrum of image (B) that zinc oxide is hexagonal wurtzite type. The Zeta potential of image (C) shows that zinc oxide is positively charged. Through the scanning electron microscope of image (D), it can be observed that the surface of zinc oxide has a porous structure.

[0056] Figure 2 PW 11The infrared spectrum, cyclic voltammetry curve, and UV-visible absorption spectrum of Co are shown in Figure 1. 11 Co was successfully prepared.

[0057] Figure 3 For PW assembled on quartz substrate 11 UV-visible absorption spectrum of Co / ZnO / ITO composite film electrode. As shown in the figure, there is a strong characteristic absorption peak at 200nm and 250nm, which is the characteristic absorption peak of Keggin type heteropoly anion, proving that PW 11 Co was adsorbed. Then a new characteristic absorption peak appeared at 353 nm, and the overall absorbance was greater, proving that zinc oxide was adsorbed.

[0058] Figure 4 The photocurrent of the composite film electrode changes with time in hydrogen peroxide phosphate buffer solution with different concentrations, where a is PW 11 Co / ITO composite film electrode, b is PSS / ZnO composite film electrode, c is PW 11 Co / ZnO / ITO composite film electrode. When the hydrogen peroxide concentration increased from 0.05mol / L to 0.3mol / L, PW 11 Co / ITO composite film electrode, PSS / ZnO composite film electrode and PW 11 The photocurrent of Co / ZnO / ITO composite film electrode increases accordingly. By comparison, under different hydrogen peroxide concentrations, PW 11 The Co / ZnO / ITO composite film electrode exhibits the highest photocurrent response. This proves that the composite electrode prepared by the present invention has high sensitivity in detecting hydrogen peroxide, solves the technical problem that the existing zinc oxide electrode material is difficult to be used for the detection of hydrogen peroxide due to its poor photoelectric performance, and the composite electrode can be used to prepare a biosensor for detecting hydrogen peroxide.

[0059] The above description is only a preferred embodiment of the present invention, and the above specific embodiment is not intended to limit the present invention. Various deformations and modifications may occur within the scope of the technical concept of the present invention, and any modification, modification or equivalent replacement made by a person of ordinary skill in the art based on the above description shall fall within the scope of protection of the present invention.

Claims

1. A method for preparing a composite electrode, characterized in that: The following steps are involved: Using zinc alkoxide as raw material, zinc oxide sol is prepared by sol-gel method under alkaline conditions. Using disodium hydrogen phosphate and sodium tungstate as raw materials, under acidic conditions, a double decomposition reaction was performed to obtain Na7PW. 11 O 39 ;Na7PW 11 O 39 With cobalt nitrate in a solvent system, through reflux reaction, PW was obtained. 11 Co; The activated indium tin oxide electrode material is immersed in PW 11 In Co solution and ZnO sol, ZnO and PW 11 The indium tin oxide electrode material was modified by Co to prepare a composite electrode.

2. The method for preparing a composite electrode according to claim 1, characterized in that: The acidic condition is a pH value of 4 to 6, and the reaction temperature of the double decomposition reaction is 70° C. to 90° C.

3. The method for preparing a composite electrode according to claim 1, characterized in that: The molar ratio of the disodium hydrogen phosphate to the sodium tungstate is 1:11-12.

4. The method for preparing a composite electrode according to claim 1, characterized in that: The reaction temperature of the reflux reaction is 70°C to 90°C, and the Na7PW 11 O 39 The mass ratio of the cobalt nitrate to the cobalt nitrate is 6 to 7:

1.

5. The method for preparing a composite electrode according to claim 1, characterized in that: The solvent is water.

6. The method for preparing a composite electrode according to claim 1, characterized in that: The PW 11 The concentration of the Co solution is 1.5 mmol / L to 2.5 mmol / L.

7. The method for preparing a composite electrode according to claim 2, characterized in that: The PW 11 The pH of the Co solution is 1-2.

8. A composite electrode, characterized in that: The composite electrode is prepared by the preparation method of any one of claims 1 to 7.

9. Use of the composite electrode according to claim 8 in preparing a biosensor for detecting hydrogen peroxide.

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