CN109781822B - Zinc oxide nanosheet array/three-dimensional foam graphene biosensor working electrode and preparation method and application thereof - Google Patents
Zinc oxide nanosheet array/three-dimensional foam graphene biosensor working electrode and preparation method and application thereof Download PDFInfo
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Abstract
The invention discloses a zinc oxide nanosheet array/three-dimensional foam graphene biosensor working electrode and a preparation method and application thereof. The method synthesizes high-conductivity and defect-free three-dimensional foam graphene by a chemical vapor deposition method, and simultaneously synthesizes a novel zinc oxide nanosheet array/three-dimensional foam graphene biosensor working electrode by growing a zinc oxide nanosheet array with a high specific surface area on the surface of the foam graphene by combining a hydrothermal method; the biosensor prepared by the working electrode can play a synergistic role of high-conductivity graphene and a high-specific-surface-area zinc oxide nano-sheet array, the combination of the zinc oxide nano-sheet array and graphene is improved, the zinc oxide nano-sheet array growing on the surface of the graphene can provide countless active points, electrons generated by reaction are directly transmitted to the graphene, the rapid transfer of the electrons is realized, the sensitivity of electrochemical detection of dopamine reaches 0.95 muA/mumol/L, and the problems of low sensitivity and high detection limit of the existing biosensor in dopamine detection are solved.
Description
Technical Field
The invention relates to a biosensor working electrode and a preparation method and application thereof, in particular to a zinc oxide nanosheet array/three-dimensional foam graphene biosensor working electrode and a preparation method and application thereof in dopamine detection. The invention belongs to the technical field of electrochemical detection.
Background
Dopamine (DA), chemically known as 3, 4-dihydroxy- β -phenylethylamine, is a key neurotransmitter that is distributed in the hypothalamus and pituitary glands to transmit biological impulses. The content of dopamine in human bodies is low, and once the concentration of dopamine is abnormal, neurological diseases such as Alzheimer disease, Parkinson disease and the like can be caused. Therefore, the accurate determination of the concentration of dopamine in human bodies is of great significance. Currently, many problems still exist in the detection of dopamine, such as low sensitivity and over-high detection limit.
The zinc oxide is an important semiconductor material, has a band gap of 3.37eV, an exciton confinement energy of 60meV at room temperature, has super-strong electron transfer capability, and is widely applied to various fields such as sensors, catalysis, solar cells, photoelectrons and the like. The zinc oxide has good biocompatibility and excellent electrochemical performance, and has great application value in the field of electrochemical biosensors. The nano zinc oxide has a variety of types, wherein the zinc oxide nano sheet array is concerned about because of having fewer defects and larger active specific surface area. At present, the preparation method of the zinc oxide nanosheet array mainly comprises a hydrothermal method, an electrochemical deposition method, a gas phase method and a reflux method. The hydrothermal method has the advantages of simple operation, low cost, mild reaction conditions and the like, and can be used for preparing the zinc oxide nanosheet array on a large scale.
Graphene is a monolayer of carbon atoms in sp2The hybridized hexagonal honeycomb two-dimensional material has good mechanical property, electric conduction and heat conduction performance, strong chemical stability and wide application prospect. The main methods for preparing graphene at present are a mechanical stripping method, a chemical oxidation method, a crystal epitaxial growth method, a chemical vapor deposition method, an organic synthesis method, a carbon nanotube stripping method and the like. The graphene prepared by the chemical vapor deposition method has fewer defects and higher conductivity. The foam graphene with the three-dimensional reticular structure prepared by using the foam nickel as the template through chemical vapor deposition has larger porosity and active specific surface area, is a graphene material andthe combination of the metal oxide nano material provides a good platform, and the composite material of the graphene and the metal oxide has more excellent electrochemical performance due to the good synergistic effect of the graphene and the metal oxide.
Disclosure of Invention
Aiming at the technical problems of low detection sensitivity and high detection limit of dopamine at present, the invention prepares the foam graphene by a chemical vapor deposition method, and then vertically grows a zinc oxide nano-sheet array on the surface of the three-dimensional foam graphene by a hydrothermal reaction, thereby preparing the novel zinc oxide nano-sheet array/three-dimensional foam graphene biosensor working electrode.
In order to achieve the purpose, the invention adopts the following technical means:
the invention relates to a preparation method of a zinc oxide nanosheet array/three-dimensional foam graphene biosensor working electrode, which comprises the following steps:
(1) placing foamed nickel in the center of a quartz tube furnace, heating the foamed nickel from room temperature to 1000-1100 ℃ at a heating rate of 20-40 ℃/min under the protection of argon and hydrogen, preserving the heat for 30-60 min at the temperature of 1000-1100 ℃, introducing methane gas into the tube furnace at a rate of 5-10 sccm for 5-20 min at the temperature of 1000-1100 ℃, and then cooling the quartz tube furnace from the temperature of 1000-1100 ℃ to room temperature at a cooling rate of 80-100 ℃/min to obtain the foamed nickel coated by graphene; the density of the foamed nickel in the step (1) is 420g/m2～440g/m2The thickness is 1.6 mm-2.0 mm; the flow rate of the argon in the step (1) is 480 sccm-500 sccm, and the flow rate of the hydrogen is 180 sccm-200 sccm;
(2) adding polymethyl methacrylate into ethyl lactate, heating and stirring for 1-2 h at the temperature of 80-120 ℃ to obtain a mixed solution, dropwise adding the mixed solution onto the surface of the graphene-coated foamed nickel obtained in the step (1) by using a sample adding gun according to the usage amount of 100-200 mu L per square centimeter, naturally drying at room temperature, and then preserving heat for 0.5-1 h at the temperature of 150-200 ℃ to obtain the foamed graphene with the surface coated with the polymethyl methacrylate; the mass fraction of the methyl methacrylate in the mixed solution in the step (2) is 4-5%;
(3) cutting the foamed graphene coated with the polymethyl methacrylate on the surface obtained in the step (2) into pieces with the surface area of 0.5cm2～2cm2The cube is completely soaked in a hydrochloric acid solution with the temperature of 80-90 ℃ and the concentration of 3-4 mol/L for 4-6 h to obtain the nickel-removed three-dimensional foam graphene;
(4) soaking the nickel-removed three-dimensional foam graphene obtained in the step (3) in acetone at the temperature of 60-70 ℃ for 0.5-1.5 h to obtain foam graphene with the polymethyl methacrylate removed, cleaning the foam graphene with the polymethyl methacrylate removed with distilled water, and transferring the cleaned foam graphene with the polymethyl methacrylate removed onto clean ITO glass for freeze drying to obtain foam graphene;
(5) dripping the clean foam graphene placed on the ITO glass obtained in the step (4) into a zinc oxide seed layer solution by using a sample injection gun according to the usage amount of 50-100 mu L per square centimeter, and preserving heat at the temperature of 150-200 ℃ for 15-30 min to obtain the foam graphene/ITO glass pre-prepared with the zinc oxide seed layer; the zinc oxide seed layer solution in the step (5) is prepared by the following steps: dissolving zinc acetate in methanol, and magnetically stirring at the rotating speed of 450-550 r/min for 3-5 min to obtain a zinc oxide seed layer solution; wherein the concentration of the zinc acetate solution is 0.01-0.5 mol/L;
(6) dissolving zinc nitrate, hexamethylenetetramine, ammonia water and polyethyleneimine in deionized water, and magnetically stirring at the rotating speed of 450-550 r/min for 3-5 min to obtain a hydrothermal solution; the concentration of the zinc nitrate in the step (6) is 0.05 mol/L-0.1 mol/L; the concentration of the hexamethylene tetramine is 0.05 mol/L-0.1 mol/L; the concentration of the ammonia water is 0.05 mol/L-0.1 mol/L; the concentration of the polyethyleneimine is 0.001-0.002 mol/L;
(7) pouring the hydrothermal solution obtained in the step (6) into a reaction kettle, then placing the foam graphene/ITO glass prefabricated with the zinc oxide seed layer obtained in the step (5) into the hydrothermal solution of the reaction kettle in a side-standing manner, simultaneously placing an aluminum sheet, covering a reaction kettle cover, preserving heat for 6-13 h at the temperature of 90-120 ℃, then taking out and cooling to room temperature, opening the reaction kettle, cleaning the composite material with distilled water, preserving heat for 1-1.5 h at the temperature of 400-450 ℃, and cooling to room temperature along with a furnace to obtain the zinc oxide nanosheet array/three-dimensional foam graphene biosensor working electrode.
Preferably, in the step (1), methane gas is introduced into the tubular furnace at a rate of 7sccm to 9sccm for 10min to 15min at a temperature of 1000 ℃ to 1100 ℃, and then the quartz tubular furnace is cooled from the temperature of 1000 ℃ to 1100 ℃ to room temperature at a cooling rate of 85 ℃/min to 95 ℃/min to obtain the graphene-coated nickel foam.
Preferably, in the step (2), the polymethyl methacrylate is added into ethyl lactate, the mixture is obtained by heating and stirring for 1 to 1.5 hours at the temperature of 90 to 110 ℃, and the mixed solution is dropwise added onto the surface of the graphene-coated nickel foam obtained in the step (1) by using a sample adding gun according to the usage amount of 130 to 170 μ L per square centimeter.
Preferably, in the step (5), the clean graphene foam placed on the ITO glass obtained in the step (4) is dripped with a zinc oxide seed layer solution by using a sample injection gun according to the usage amount of 70-90 muL per square centimeter, and the solution is kept at the temperature of 170-190 ℃ for 20-25 min to obtain the graphene foam/ITO glass prefabricated with the zinc oxide seed layer.
Wherein, the concentration of the zinc nitrate in the step (6) is preferably 0.06 mol/L-0.08 mol/L; the concentration of the hexamethylene tetramine is 0.06 mol/L-0.08 mol/L; the concentration of the ammonia water is 0.06 mol/L-0.08 mol/L.
Preferably, in the step (7), the hydrothermal solution obtained in the step (6) is poured into a reaction kettle, then the foamed graphene/ITO glass prefabricated with the zinc oxide seed layer obtained in the step (5) is placed in the hydrothermal solution of the reaction kettle in a side-standing mode, meanwhile, a piece of aluminum sheet is placed, a cover of the reaction kettle is covered, the temperature is kept at 100-110 ℃ for 7-12 hours, and then the foamed graphene/ITO glass is taken out and cooled to room temperature.
The preparation method of the zinc oxide nanosheet array/three-dimensional foam graphene biosensor preferably comprises the following steps:
(1) placing the foamed nickel in the center of a quartz tube furnace, heating the foamed nickel from room temperature to 1000 ℃ at a heating rate of 30 ℃/min under the protection of argon and hydrogen, preserving the heat for 30min at the temperature of 1000 ℃, introducing methane gas into the tube furnace at a rate of 10sccm for 10min at the temperature of 1000 ℃, and then cooling the quartz tube furnace from 1000 ℃ to room temperature at a cooling rate of 100 ℃/min to obtain graphene-coated foamed nickel; the density of the foamed nickel in the step (1) is 420g/m2The thickness is 1.6 mm; the flow rate of the argon in the step (1) is 500sccm, and the flow rate of the hydrogen is 200 sccm;
(2) adding polymethyl methacrylate into ethyl lactate, heating and stirring for 2h at the temperature of 100 ℃ to obtain a mixed solution, dropwise adding the mixed solution onto the surface of the graphene-coated foamed nickel obtained in the step (1) by using a sample adding gun according to the usage amount of 180 mu L per square centimeter, naturally drying at room temperature, and then preserving heat at the temperature of 200 ℃ for 1h to obtain the surface-coated polymethyl methacrylate foamed graphene; the mass fraction of methyl methacrylate in the mixed solution in the step (2) is 4%;
(3) cutting the foamed graphene coated with the polymethyl methacrylate on the surface obtained in the step (2) into pieces with the surface area of 1cm2The cube is completely soaked in a hydrochloric acid solution with the temperature of 80 ℃ and the concentration of 3mol/L for 6 hours to obtain the nickel-removed three-dimensional foam graphene;
(4) soaking the nickel-removed three-dimensional foam graphene obtained in the step (3) in acetone at the temperature of 60 ℃ for 1.5h to obtain foam graphene with the polymethyl methacrylate removed, cleaning the foam graphene with the polymethyl methacrylate removed by using distilled water, and then transferring the cleaned foam graphene with the polymethyl methacrylate removed onto clean ITO glass for freeze drying to obtain foam graphene;
(5) dropwise adding the zinc oxide seed layer solution into the clean graphene foam placed on the ITO glass obtained in the step (4) by using a sample adding gun according to the usage amount of 80 mu L per square centimeter, and keeping the temperature at 200 ℃ for 30min to obtain the graphene foam/ITO glass prefabricated with the zinc oxide seed layer; the zinc oxide seed layer solution in the step (5) is prepared by the following steps: dissolving zinc acetate in methanol, and magnetically stirring at a rotating speed of 500r/min for 5min to obtain a zinc oxide seed layer solution; wherein the concentration of the zinc acetate solution is 0.01 mol/L;
(6) dissolving zinc nitrate, hexamethylenetetramine, ammonia water and polyethyleneimine in deionized water, and magnetically stirring at the rotating speed of 500r/min for 5min to obtain a hydrothermal solution; the concentration of the zinc nitrate in the step (6) is 0.05 mol/L; the concentration of the hexamethylene tetramine is 0.05 mol/L; the concentration of ammonia water is 0.05 mol/L; the concentration of polyethyleneimine is 0.001 mol/L;
(7) pouring the hydrothermal solution obtained in the step (6) into a reaction kettle, then placing the foamed graphene/ITO glass prefabricated with the zinc oxide seed layer obtained in the step (5) into the hydrothermal solution of the reaction kettle in a side-standing manner, simultaneously placing an aluminum sheet, covering a reaction kettle cover, preserving heat for 12 hours at the temperature of 100 ℃, then taking out and cooling to room temperature, opening the reaction kettle, cleaning the composite material with distilled water, preserving heat for 1 hour at the temperature of 450 ℃, and cooling to room temperature along with a furnace to obtain the zinc oxide nanosheet array/three-dimensional foamed graphene biosensor working electrode.
Furthermore, the invention also provides the zinc oxide nano sheet array/three-dimensional foam graphene biosensor working electrode prepared by any one of the methods.
Furthermore, the invention also provides application of the zinc oxide nano sheet array/three-dimensional foam graphene biosensor working electrode in preparation of a biosensor for detecting dopamine.
Compared with the prior art, the invention has the beneficial effects that:
(1) according to the method, high-conductivity and defect-free three-dimensional foam graphene is synthesized by a chemical vapor deposition method, and a zinc oxide nanosheet array with a high specific surface area is grown on the surface of the foam graphene by combining a hydrothermal method, so that a novel zinc oxide nanosheet array/three-dimensional foam graphene biosensor working electrode is synthesized;
(2) the zinc oxide nano-sheet array/three-dimensional foam graphene biosensor working electrode prepared by the invention can play a synergistic effect of high-conductivity graphene and a high-specific-surface-area zinc oxide nano-sheet array, the combination of the zinc oxide nano-sheet array and the graphene can be improved by utilizing a seed layer process, the zinc oxide nano-sheet array growing on the surface of the graphene can provide countless active points, electrons generated by reaction can be directly transferred to the graphene, and the rapid transfer of the electrons is realized, so that the electrocatalytic performance can be remarkably improved, and the sensitivity of electrochemical detection of dopamine can reach 0.95 muA/mumol/L.
Drawings
FIG. 1 is a scanning electron micrograph (X200) of a working electrode of a zinc oxide nanosheet array/three-dimensional foamy graphene biosensor prepared in test one;
FIG. 2 is a scanning electron micrograph (X500) of a working electrode of a zinc oxide nanosheet array/three-dimensional foamy graphene biosensor prepared in test one;
FIG. 3 is a scanning electron micrograph (X5000) of a working electrode of a zinc oxide nanosheet array/three-dimensional foamy graphene biosensor prepared in test one;
FIG. 4 is an X-ray diffraction pattern of a zinc oxide nanoplatelet array/three-dimensional foamy graphene biosensor working electrode prepared in test one;
wherein: the diffraction peak of graphene and the diffraction peak of zinc oxide;
FIG. 5 is a Raman spectrum of a zinc oxide nanosheet array/three-dimensional foamy graphene biosensor working electrode prepared in test one;
FIG. 6 is a graph of differential pulse voltammetry for different concentrations of dopamine from run two;
fig. 7 is a linear fit of dopamine concentration to oxidation peak current obtained from experiment two.
Detailed Description
The following detailed description of the present invention will be made with reference to the accompanying drawings. Those of ordinary skill in the art will recognize that various modifications and adaptations can be made without departing from the spirit or scope of the invention. Such modifications and adaptations are intended to be included within the scope of the present invention. The following examples do not limit the invention in any way.
Example 1: preparation of zinc oxide nanosheet array/three-dimensional foam graphene biosensor working electrode
The preparation method of the zinc oxide nanosheet array/three-dimensional foam graphene biosensor working electrode comprises the following steps:
(1) placing foamed nickel in the center of a quartz tube furnace, heating the foamed nickel from room temperature to 1000-1100 ℃ at a heating rate of 20-40 ℃/min under the protection of argon and hydrogen, preserving the heat for 30-60 min at the temperature of 1000-1100 ℃, introducing methane gas into the tube furnace at a rate of 5-10 sccm for 5-20 min at the temperature of 1000-1100 ℃, and then cooling the quartz tube furnace from the temperature of 1000-1100 ℃ to room temperature at a cooling rate of 80-100 ℃/min to obtain the foamed nickel coated by graphene; the density of the foamed nickel in the step (1) is 420g/m2～440g/m2The thickness is 1.6 mm-2.0 mm; the flow rate of the argon in the step (1) is 480 sccm-500 sccm, and the flow rate of the hydrogen is 180 sccm-200 sccm;
(2) adding polymethyl methacrylate into ethyl lactate, heating and stirring for 1-2 h at the temperature of 80-120 ℃ to obtain a mixed solution, dropwise adding the mixed solution onto the surface of the graphene-coated foamed nickel obtained in the step (1) by using a sample adding gun according to the usage amount of 100-200 mu L per square centimeter, naturally drying at room temperature, and then preserving heat for 0.5-1 h at the temperature of 150-200 ℃ to obtain the foamed graphene with the surface coated with the polymethyl methacrylate; the mass fraction of the methyl methacrylate in the mixed solution in the step (2) is 4-5%;
(3) cutting the foamed graphene coated with the polymethyl methacrylate on the surface obtained in the step (2) into pieces with the surface area of 0.5cm2～2cm2The cube is completely soaked in a hydrochloric acid solution with the temperature of 80-90 ℃ and the concentration of 3-4 mol/L for 4-6 h to obtain the nickel-removed three-dimensional foam graphene;
(4) soaking the nickel-removed three-dimensional foam graphene obtained in the step (3) in acetone at the temperature of 60-70 ℃ for 0.5-1.5 h to obtain foam graphene with the polymethyl methacrylate removed, cleaning the foam graphene with the polymethyl methacrylate removed with distilled water, and transferring the cleaned foam graphene with the polymethyl methacrylate removed onto clean ITO glass for freeze drying to obtain foam graphene;
(5) dripping the clean foam graphene placed on the ITO glass obtained in the step (4) into a zinc oxide seed layer solution by using a sample injection gun according to the usage amount of 50-100 mu L per square centimeter, and preserving heat at the temperature of 150-200 ℃ for 15-30 min to obtain the foam graphene/ITO glass pre-prepared with the zinc oxide seed layer; the zinc oxide seed layer solution in the step (5) is prepared by the following steps: dissolving zinc acetate in methanol, and magnetically stirring at the rotating speed of 450-550 r/min for 3-5 min to obtain a zinc oxide seed layer solution; wherein the concentration of the zinc acetate solution is 0.01-0.5 mol/L;
(6) dissolving zinc nitrate, hexamethylenetetramine, ammonia water and polyethyleneimine in deionized water, and magnetically stirring at the rotating speed of 450-550 r/min for 3-5 min to obtain a hydrothermal solution; the concentration of the zinc nitrate in the step two (2) is 0.05 mol/L-0.1 mol/L; the concentration of the hexamethylene tetramine is 0.05 mol/L-0.1 mol/L; the concentration of the ammonia water is 0.05 mol/L-0.1 mol/L; the concentration of the polyethyleneimine is 0.001-0.002 mol/L;
(7) pouring the hydrothermal solution obtained in the step (6) into a reaction kettle, then placing the foam graphene/ITO glass prefabricated with the zinc oxide seed layer obtained in the step (5) into the hydrothermal solution of the reaction kettle in a side-standing manner, simultaneously placing an aluminum sheet, covering a reaction kettle cover, preserving heat for 6-13 h at the temperature of 90-120 ℃, then taking out and cooling to room temperature, opening the reaction kettle, cleaning the composite material with distilled water, preserving heat for 1-1.5 h at the temperature of 400-450 ℃, and cooling to room temperature along with a furnace to obtain the zinc oxide nanosheet array/three-dimensional foam graphene biosensor working electrode.
Example 2: preparation of zinc oxide nanosheet array/three-dimensional foam graphene biosensor working electrode
This example differs from example 1 in that: and (2) introducing methane gas into the tubular furnace at the temperature of 1000-1100 ℃ at the rate of 7-9 sccm for 10-15 min, and then cooling the quartz tubular furnace from the temperature of 1000-1100 ℃ to room temperature at the cooling rate of 85-95 ℃/min to obtain the graphene-coated foamed nickel. The rest is the same as in example 1.
Example 3: preparation of zinc oxide nanosheet array/three-dimensional foam graphene biosensor working electrode
This embodiment is different from embodiment 1 or embodiment 2 in that: adding polymethyl methacrylate into ethyl lactate in the step (2), heating and stirring for 1-1.5 h at the temperature of 90-110 ℃ to obtain a mixed solution, and dropwise adding the mixed solution onto the surface of the graphene-coated foamed nickel obtained in the step (1) by using a sample adding gun according to the usage amount of 130-170 mu L per square centimeter. The others are the same as in example 1 or example 2.
Example 4: preparation of zinc oxide nanosheet array/three-dimensional foam graphene biosensor working electrode
This example differs from examples 1-3 in that: and (5) dripping the zinc oxide seed layer solution into the clean graphene foam placed on the ITO glass obtained in the step (4) by using a sample adding gun according to the usage amount of 70-90 mu L per square centimeter, and preserving the temperature at 170-190 ℃ for 20-25 min to obtain the graphene foam/ITO glass prefabricated with the zinc oxide seed layer. The rest is the same as in examples 1 to 3.
Example 5: preparation of zinc oxide nanosheet array/three-dimensional foam graphene biosensor working electrode
This example differs from examples 1-4 in that: the concentration of the zinc nitrate in the step (6) is 0.06-0.08 mol/L; the concentration of the hexamethylene tetramine is 0.06 mol/L-0.08 mol/L; the concentration of the ammonia water is 0.06 mol/L-0.08 mol/L. The rest is the same as in examples 1 to 4.
Example 6: preparation of zinc oxide nanosheet array/three-dimensional foam graphene biosensor working electrode
This example differs from examples 1-5 in that: pouring the hydrothermal solution obtained in the step (6) into a reaction kettle, then placing the foamed graphene/ITO glass prefabricated with the zinc oxide seed layer obtained in the step (5) into the hydrothermal solution of the reaction kettle in a side-standing manner, simultaneously placing an aluminum sheet, covering a reaction kettle cover, keeping the temperature at 100-110 ℃ for 7-12 h, and then taking out and cooling to room temperature. The rest is the same as in examples 1 to 5.
The following tests are adopted to verify the effect of the invention:
test one: the preparation of the working electrode of the zinc oxide nanosheet array/three-dimensional foam graphene biosensor in the test is realized according to the following method:
(1) placing the foamed nickel in the center of a quartz tube furnace, heating the foamed nickel from room temperature to 1000 ℃ at a heating rate of 30 ℃/min under the protection of argon and hydrogen, preserving the heat for 30min at the temperature of 1000 ℃, introducing methane gas into the tube furnace at a rate of 10sccm for 10min at the temperature of 1000 ℃, and then cooling the quartz tube furnace from 1000 ℃ to room temperature at a cooling rate of 100 ℃/min to obtain graphene-coated foamed nickel; the density of the foamed nickel in the step (1) is 420g/m2The thickness is 1.6 mm; the flow rate of the argon in the step (1) is 500sccm, and the flow rate of the hydrogen is 200 sccm;
(2) adding polymethyl methacrylate into ethyl lactate, heating and stirring for 2h at the temperature of 100 ℃ to obtain a mixed solution, dropwise adding the mixed solution onto the surface of the graphene-coated foamed nickel obtained in the step (1) by using a sample adding gun according to the usage amount of 180 mu L per square centimeter, naturally drying at room temperature, and then preserving heat at the temperature of 200 ℃ for 1h to obtain the surface-coated polymethyl methacrylate foamed graphene; the mass fraction of methyl methacrylate in the mixed solution in the step (2) is 4%;
(3) cutting the foamed graphene coated with the polymethyl methacrylate on the surface obtained in the step (2) into pieces with the surface area of 1cm2The cube is completely soaked in a hydrochloric acid solution with the temperature of 80 ℃ and the concentration of 3mol/L for 6 hours to obtain the nickel-removed three-dimensional foam graphene;
(4) soaking the nickel-removed three-dimensional foam graphene obtained in the step (3) in acetone at the temperature of 60 ℃ for 1.5h to obtain foam graphene with the polymethyl methacrylate removed, cleaning the foam graphene with the polymethyl methacrylate removed by using distilled water, and then transferring the cleaned foam graphene with the polymethyl methacrylate removed onto clean ITO glass for freeze drying to obtain foam graphene;
(5) dropwise adding the zinc oxide seed layer solution into the clean graphene foam placed on the ITO glass obtained in the step (4) by using a sample adding gun according to the usage amount of 80 mu L per square centimeter, and keeping the temperature at 200 ℃ for 30min to obtain the graphene foam/ITO glass prefabricated with the zinc oxide seed layer; the zinc oxide seed layer solution in the step (5) is prepared by the following steps: dissolving zinc acetate in methanol, and magnetically stirring at a rotating speed of 500r/min for 5min to obtain a zinc oxide seed layer solution; wherein the concentration of the zinc acetate solution is 0.01 mol/L;
(6) dissolving zinc nitrate, hexamethylenetetramine, ammonia water and polyethyleneimine in deionized water, and magnetically stirring at the rotating speed of 500r/min for 5min to obtain a hydrothermal solution; the concentration of the zinc nitrate in the step (6) is 0.05 mol/L; the concentration of the hexamethylene tetramine is 0.05 mol/L; the concentration of ammonia water is 0.05 mol/L; the concentration of polyethyleneimine is 0.001 mol/L;
(7) pouring the hydrothermal solution obtained in the step (6) into a reaction kettle, then placing the foamed graphene/ITO glass prefabricated with the zinc oxide seed layer obtained in the step (5) into the hydrothermal solution of the reaction kettle in a side-standing manner, simultaneously placing an aluminum sheet, covering a reaction kettle cover, preserving heat for 12 hours at the temperature of 100 ℃, then taking out and cooling to room temperature, opening the reaction kettle, cleaning the composite material with distilled water, preserving heat for 1 hour at the temperature of 450 ℃, and cooling to room temperature along with a furnace to obtain the zinc oxide nanosheet array/three-dimensional foamed graphene biosensor working electrode.
Fig. 1-3 are scanning electron micrographs of a zinc oxide nanoplatelet array/three-dimensional foamy graphene biosensor working electrode prepared in test one, magnified step by step. It can be clearly seen from the figure that the zinc oxide nano-sheet array grows on the surface of the three-dimensional foam graphene, the size of the nano-sheet is about 10 μm, and the thickness is about 200-500 nm.
Figure 4 is an X-ray diffraction pattern of a zinc oxide nanoplatelet array/three-dimensional foamy graphene biosensor working electrode prepared in test one. The existence of diffraction peaks of zinc oxide and graphene can be obviously seen from the figure, and the composite material is shown to be composed of zinc oxide and graphene.
Figure 5 is a raman spectrum of a zinc oxide nanoplatelet array/three-dimensional foamy graphene biosensor working electrode prepared in test one. As can be seen from the figure, there are peaks of zinc oxide in addition to the G band and 2D band of graphene, also indicating that the composite material is composed of zinc oxide and graphene.
And (2) test II: detection test of zinc oxide nanosheet array/three-dimensional foam graphene biosensor working electrode
The specific operation is as follows:
the zinc oxide nano-sheet array/three-dimensional foam graphene is used as a working electrode of a biosensor, and the area of an effective material is 0.7cm2Silver/silver chloride is used as a reference electrode, a platinum wire is used as a counter electrode, a traditional three-electrode system is adopted, and the current response of the material to different dopamine concentrations is obtained through a pulse voltammetry test (potential increment is 50mV, pulse height is 4mV, and scanning rate is 8mV/s), wherein the dopamine concentrations are 0 mu mol/L, 1 mu mol/L, 5 mu mol/L, 20 mu mol/L, 35 mu mol/L, 50 mu mol/L, 65 mu mol/L and 80 mu mol/L in sequence; the zinc oxide nano-sheet array/three-dimensional foam graphene biosensor working electrode is prepared in a first test.
Fig. 6 is a differential pulse voltammogram of different concentrations of dopamine from experiment two. It can be seen that as the dopamine concentration increases, the oxidation peak current value increases with the actual detection limit being 1 μmol/L.
Fig. 7 is a linear fit of dopamine concentration to oxidation peak current obtained from experiment two. The linear relation between the change of the dopamine concentration and the oxidation peak current can be obtained, and the sensitivity of detecting dopamine, namely 0.95 muA/mumol/L, is the linear slope of the dopamine obtained in the concentration range of 1 mumol/L-80 mumol/L.
Claims (9)
1. A preparation method of a zinc oxide nanosheet array/three-dimensional foam graphene biosensor working electrode is characterized by comprising the following steps:
(1) placing foamed nickel in the center of a quartz tube furnace, heating the foamed nickel from room temperature to 1000-1100 ℃ at a heating rate of 20-40 ℃/min under the protection of argon and hydrogen, preserving the heat for 30-60 min at the temperature of 1000-1100 ℃, introducing methane gas into the tube furnace at a rate of 5-10 sccm for 5-20 min at the temperature of 1000-1100 ℃, and then cooling the quartz tube furnace from the temperature of 1000-1100 ℃ to room temperature at a cooling rate of 80-100 ℃/min to obtain the foamed nickel coated by graphene; the density of the foamed nickel in the step (1) is 420g/m2～440g/m2The thickness is 1.6 mm-2.0 mm; the flow rate of the argon in the step (1) is 480 sccm-500 sccm, and the flow rate of the hydrogen is 180 sccm-200 sccm;
(2) adding polymethyl methacrylate into ethyl lactate, heating and stirring for 1-2 h at the temperature of 80-120 ℃ to obtain a mixed solution, dropwise adding the mixed solution onto the surface of the graphene-coated foamed nickel obtained in the step (1) by using a sample adding gun according to the usage amount of 100-200 mu L per square centimeter, naturally drying at room temperature, and then preserving heat for 0.5-1 h at the temperature of 150-200 ℃ to obtain the foamed graphene with the surface coated with the polymethyl methacrylate; the mass fraction of the methyl methacrylate in the mixed solution in the step (2) is 4-5%;
(3) cutting the foamed graphene coated with the polymethyl methacrylate on the surface obtained in the step (2) into pieces with the surface area of 0.5cm2～2cm2The cube is completely soaked in a hydrochloric acid solution with the temperature of 80-90 ℃ and the concentration of 3-4 mol/L for 4-6 h to obtain the nickel-removed three-dimensional foam graphene;
(4) soaking the nickel-removed three-dimensional foam graphene obtained in the step (3) in acetone at the temperature of 60-70 ℃ for 0.5-1.5 h to obtain foam graphene with the polymethyl methacrylate removed, cleaning the foam graphene with the polymethyl methacrylate removed with distilled water, and transferring the cleaned foam graphene with the polymethyl methacrylate removed onto clean ITO glass for freeze drying to obtain foam graphene;
(5) dripping the clean foam graphene placed on the ITO glass obtained in the step (4) into a zinc oxide seed layer solution by using a sample injection gun according to the usage amount of 50-100 mu L per square centimeter, and preserving heat at the temperature of 150-200 ℃ for 15-30 min to obtain the foam graphene/ITO glass pre-prepared with the zinc oxide seed layer; the zinc oxide seed layer solution in the step (5) is prepared by the following steps: dissolving zinc acetate in methanol, and magnetically stirring at the rotating speed of 450-550 r/min for 3-5 min to obtain a zinc oxide seed layer solution; wherein the concentration of the zinc acetate solution is 0.01-0.5 mol/L;
(6) dissolving zinc nitrate, hexamethylenetetramine, ammonia water and polyethyleneimine in deionized water, and magnetically stirring at the rotating speed of 450-550 r/min for 3-5 min to obtain a hydrothermal solution; the concentration of the zinc nitrate in the step (6) is 0.05 mol/L-0.1 mol/L; the concentration of the hexamethylene tetramine is 0.05 mol/L-0.1 mol/L; the concentration of the ammonia water is 0.05 mol/L-0.1 mol/L; the concentration of the polyethyleneimine is 0.001-0.002 mol/L;
(7) pouring the hydrothermal solution obtained in the step (6) into a reaction kettle, then placing the foam graphene/ITO glass prefabricated with the zinc oxide seed layer obtained in the step (5) into the hydrothermal solution of the reaction kettle in a side-standing manner, simultaneously placing an aluminum sheet, covering a reaction kettle cover, preserving heat for 6-13 h at the temperature of 90-120 ℃, then taking out and cooling to room temperature, opening the reaction kettle, cleaning the composite material with distilled water, preserving heat for 1-1.5 h at the temperature of 400-450 ℃, and cooling to room temperature along with a furnace to obtain the zinc oxide nanosheet array/three-dimensional foam graphene biosensor working electrode.
2. The method as claimed in claim 1, wherein in the step (1), methane gas is introduced into the tube furnace at a rate of 7sccm to 9sccm for 10min to 15min at a temperature of 1000 ℃ to 1100 ℃, and then the quartz tube furnace is cooled from the temperature of 1000 ℃ to 1100 ℃ to room temperature at a cooling rate of 85 ℃/min to 95 ℃/min to obtain the graphene-coated nickel foam.
3. The method according to claim 1, wherein in the step (2), the polymethyl methacrylate is added into the ethyl lactate, the mixture is obtained by heating and stirring for 1h to 1.5h at the temperature of 90 ℃ to 110 ℃, and the mixture is dripped on the surface of the graphene-coated nickel foam obtained in the step (1) by using a sample-adding gun according to the usage amount of 130 μ L to 170 μ L per square centimeter.
4. The method as claimed in claim 1, wherein in the step (5), the clean graphene foam placed on the ITO glass obtained in the step (4) is dripped with a zinc oxide seed layer solution by using a sample feeding gun according to the usage amount of 70-90 μ L per square centimeter, and is kept at the temperature of 170-190 ℃ for 20-25 min to obtain the graphene foam/ITO glass prefabricated with the zinc oxide seed layer.
5. The method according to claim 1, wherein the concentration of the zinc nitrate in the step (6) is 0.06mol/L to 0.08 mol/L; the concentration of the hexamethylene tetramine is 0.06 mol/L-0.08 mol/L; the concentration of the ammonia water is 0.06 mol/L-0.08 mol/L.
6. The method as claimed in claim 1, wherein in the step (7), the hydrothermal solution obtained in the step (6) is poured into a reaction kettle, then the foamed graphene/ITO glass prefabricated with the zinc oxide seed layer obtained in the step (5) is placed in the hydrothermal solution of the reaction kettle on the side, a piece of aluminum sheet is placed at the same time, a cover of the reaction kettle is covered, the temperature is kept at 100-110 ℃ for 7-12 h, and then the foamed graphene/ITO glass is taken out and cooled to room temperature.
7. The method of claim 1, wherein the steps are performed as follows:
(1) placing foamed nickel in the center of a quartz tube furnace, heating from room temperature to 1000 deg.C at a heating rate of 30 deg.C/min under the protection of argon and hydrogen, maintaining the temperature at 1000 deg.C for 30min, and introducing into the tube furnace at 1000 deg.C at a rate of 10sccmIntroducing methane gas for 10min, and then cooling the quartz tube furnace from the temperature of 1000 ℃ to room temperature at the cooling rate of 100 ℃/min to obtain graphene-coated foamed nickel; the density of the foamed nickel in the step (1) is 420g/m2The thickness is 1.6 mm; the flow rate of the argon in the step (1) is 500sccm, and the flow rate of the hydrogen is 200 sccm;
(2) adding polymethyl methacrylate into ethyl lactate, heating and stirring for 2h at the temperature of 100 ℃ to obtain a mixed solution, dropwise adding the mixed solution onto the surface of the graphene-coated foamed nickel obtained in the step (1) by using a sample adding gun according to the usage amount of 180 mu L per square centimeter, naturally drying at room temperature, and then preserving heat at the temperature of 200 ℃ for 1h to obtain the surface-coated polymethyl methacrylate foamed graphene; the mass fraction of methyl methacrylate in the mixed solution in the step (2) is 4%;
(3) cutting the foamed graphene coated with the polymethyl methacrylate on the surface obtained in the step (2) into pieces with the surface area of 1cm2The cube is completely soaked in a hydrochloric acid solution with the temperature of 80 ℃ and the concentration of 3mol/L for 6 hours to obtain the nickel-removed three-dimensional foam graphene;
(4) soaking the nickel-removed three-dimensional foam graphene obtained in the step (3) in acetone at the temperature of 60 ℃ for 1.5h to obtain foam graphene with the polymethyl methacrylate removed, cleaning the foam graphene with the polymethyl methacrylate removed by using distilled water, and then transferring the cleaned foam graphene with the polymethyl methacrylate removed onto clean ITO glass for freeze drying to obtain foam graphene;
(5) dropwise adding the zinc oxide seed layer solution into the clean graphene foam placed on the ITO glass obtained in the step (4) by using a sample adding gun according to the usage amount of 80 mu L per square centimeter, and keeping the temperature at 200 ℃ for 30min to obtain the graphene foam/ITO glass prefabricated with the zinc oxide seed layer; the zinc oxide seed layer solution in the step (5) is prepared by the following steps: dissolving zinc acetate in methanol, and magnetically stirring at a rotating speed of 500r/min for 5min to obtain a zinc oxide seed layer solution; wherein the concentration of the zinc acetate solution is 0.01 mol/L;
(6) dissolving zinc nitrate, hexamethylenetetramine, ammonia water and polyethyleneimine in deionized water, and magnetically stirring at the rotating speed of 500r/min for 5min to obtain a hydrothermal solution; the concentration of the zinc nitrate in the step (6) is 0.05 mol/L; the concentration of the hexamethylene tetramine is 0.05 mol/L; the concentration of ammonia water is 0.05 mol/L; the concentration of polyethyleneimine is 0.001 mol/L;
(7) pouring the hydrothermal solution obtained in the step (6) into a reaction kettle, then placing the foamed graphene/ITO glass prefabricated with the zinc oxide seed layer obtained in the step (5) into the hydrothermal solution of the reaction kettle in a side-standing manner, simultaneously placing an aluminum sheet, covering a reaction kettle cover, preserving heat for 12 hours at the temperature of 100 ℃, then taking out and cooling to room temperature, opening the reaction kettle, cleaning the composite material with distilled water, preserving heat for 1 hour at the temperature of 450 ℃, and cooling to room temperature along with a furnace to obtain the zinc oxide nanosheet array/three-dimensional foamed graphene biosensor working electrode.
8. The zinc oxide nano-sheet array/three-dimensional foam graphene biosensor working electrode prepared according to the method of any one of claims 1 to 7.
9. The application of the zinc oxide nanosheet array/three-dimensional foam graphene biosensor working electrode of claim 8 in preparing a biosensor for detecting dopamine.
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