CN109342525B - Reduced graphene oxide and polyaspartic acid A double-layer film and preparation method and application thereof - Google Patents

Reduced graphene oxide and polyaspartic acid A double-layer film and preparation method and application thereof Download PDF

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CN109342525B
CN109342525B CN201811365079.2A CN201811365079A CN109342525B CN 109342525 B CN109342525 B CN 109342525B CN 201811365079 A CN201811365079 A CN 201811365079A CN 109342525 B CN109342525 B CN 109342525B
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陈传祥
周康
栾敏
马臻
宋楠楠
陈雅娴
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Jiangsu University of Science and Technology
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Abstract

The invention discloses a reduced graphene oxide and polyaspartic acid A double-layer film and a preparation method and application thereof, wherein the preparation method comprises the following steps: (1) preparing a graphene oxide dispersion liquid; (2) dropping graphene oxide dispersion liquid on the surface of the treated glassy carbon electrode, and airing; (3) preparing a PBS solution as a first electrolyte; (4) adding the first electrolyte into a first electrolytic cell, and carrying out electrochemical reduction on graphene in the first electrolyte to obtain electrically reduced graphene oxide; (5) preparing a second electrolyte from sulfuric acid and an azure A aqueous solution; (6) and adding the second electrolyte into a second electrolytic cell to synthesize a double-layer film of reduced graphene oxide and polyaspartic acid A. The reduced graphene oxide and polyaspartic acid A double-layer film is prepared by the preparation method. The application is the application of the reduced graphene oxide and the poly azure A double-layer film in ascorbic acid detection. The synthesis method is convenient to control, safe and convenient for actual operation in production.

Description

Reduced graphene oxide and polyaspartic acid A double-layer film and preparation method and application thereof
Technical Field
The invention relates to a double-layer film and a preparation method thereof, in particular to a reduced graphene oxide and polyaspartic acid A double-layer film and a preparation method and application thereof.
Background
Vitamin C, also known as Ascorbic Acid (AA), is a water-soluble vitamin that is widely found in many biological systems and in a variety of vegetables and fruits. Ascorbic acid is often used as an antioxidant to supplement the deficiency of people's daily dietary intake, and it is also a radical scavenger playing an important role in human metabolism, and it can prevent many induced diseases such as cancer, parkinson's disease, etc. In addition, the human body is deficient in ascorbic acid which can cause scurvy, and ascorbic acid also plays a leading role in the treatment of some disorders such as alzheimer's disease, arteriosclerosis, cancer, infertility, etc., and in the clinical manifestations of infectious diseases such as aids. Thus, the detection of ascorbic acid in a variety of natural and pre-processed food, beverage, vegetable and fruit, pharmaceutical and biological fluids is of paramount importance to the biological and agricultural industries.
Many methods have been explored for many years for the determination of ascorbic acid, such as chemiluminescence, spectrometry, chromatography, and electrochemical methods. Among them, the first three methods lack specificity and are easily interfered by other reducing agents in actual detection, electrochemical methods have been widely used for detection of various substances due to their low cost, simple operation and high sensitivity, and enzyme-based electrochemical sensors appearing in the past years cannot be widely used due to their low stability, high cost and limitation of many environmental conditions. Therefore, it is necessary to find an enzyme-free and specific electrochemical sensor.
Disclosure of Invention
The purpose of the invention is as follows: the invention aims to provide a preparation method of a reduced graphene oxide and poly azure A double-layer film with high electrochemical activity, the invention also aims to provide a reduced graphene oxide and poly azure A double-layer film and application thereof, and the invention also aims to provide an electrochemical sensor.
The technical scheme is as follows: the invention relates to a preparation method of a double-layer film of reduced graphene oxide and poly azure A, which comprises the following steps:
(1) putting graphene oxide in deionized water, performing ultrasonic treatment in an ultrasonic instrument to uniformly disperse the graphene oxide in the deionized water, and preparing 1-5 mg-cm−3The graphene oxide dispersion liquid of (a);
(2) dripping 3-8 mu L of graphene oxide dispersion liquid on the surface of the treated glassy carbon electrode with the diameter of 2-5 mm, and airing;
(3) the pH value is 4-7, and the concentration is 0.1-0.5 mol.L−1The PBS solution is a first electrolyte;
(4) adding the first electrolyte into a first electrolytic cell consisting of the glassy carbon electrode obtained in the step (2), a platinum sheet electrode and a saturated calomel electrode reference electrode, and performing electrochemical reduction on graphene in the first electrolyte by adopting a cyclic voltammetry method to obtain an electro-reduced graphene oxide (rGO), wherein the scanning potential is-1.4-0V, the scanning rate is 40-80 mV/s, the number of potential scanning turns is 20-100 turns, and the graphene is dried at the temperature of 40-80 ℃;
(5) taking 0.2-0.8 mol.dm-3Dm of sulfuric acid and 1-5 mmol-3Preparing a second electrolyte from an azure A aqueous solution;
(6) and adding the second electrolyte into a second electrolytic cell consisting of a glassy carbon electrode modified by reduced graphene oxide, a bare platinum sheet and a saturated calomel electrode reference electrode, and synthesizing a reduced graphene oxide and poly azure A double-layer film by using a cyclic voltammetry method, wherein the scanning potential is-0.20-1.0V, the scanning rate is 40-80 mV/s, and the number of potential scanning circles is 10-50 circles.
The reduced graphene oxide and poly azure A double-layer film prepared by the preparation method.
The application of the double-layer film of the reduced graphene oxide and the polyaspartic acid A in ascorbic acid detection. Specifically, a saturated calomel electrode as a reference electrode, a platinum sheet electrode as a counter electrode and the prepared working electrode were correctly connected to an electrochemical workstation at pH7.0 and 0.2mol dm-3And (3) adding ascorbic acid solutions with different concentrations into the PBS buffer solution serving as a base solution, measuring corresponding current values by adopting a cyclic voltammetry method, and drawing a corresponding working curve.
An electrochemical sensor comprises a working electrode, a reference electrode and a counter electrode, wherein a substrate electrode of the working electrode is a glassy carbon electrode, and a double-layer membrane of reduced graphene oxide and poly azure A is modified on the surface of the glassy carbon electrode.
Has the advantages that: compared with the prior art, the invention has the following remarkable characteristics: the reduced graphene oxide/poly azure A double-layer film is synthesized for the first time, the reduced graphene oxide and the azure A double-layer film have strong adhesion capacity, and the film is uniform and stable; the manufacturing time of the modified electrode is short, the method is convenient to control and safe, and the actual operation in production is facilitated; the prepared double-layer membrane modified electrode has the advantages of high sensitivity, low detection limit, high stability, simplicity in operation and high detection speed for the detection of the ascorbic acid, and meanwhile, under the condition that dopamine and uric acid exist simultaneously, the double-layer membrane modified electrode still has very good specificity and selectivity for resisting the ascorbic acid and is strong in anti-interference capacity; the invention has the advantages of excellent accuracy, stability, reproducibility and high sensitivity, and the analysis and the detection are rapid and convenient.
Drawings
FIG. 1 shows that the electrolyte pH of graphene oxide is 0.2mol dm-3Cyclic voltammograms in PBS solution;
FIG. 2 is an electrolytic diagram of a reduced graphene oxide modified electrode in azure A solution;
FIG. 3 is a scanning electron microscope image of the present invention, a, graphene oxide, b, reduced graphene oxide, c, poly azure A, d, reduced graphene oxide/poly azure A bilayer membrane;
FIG. 4 shows the reduced graphene oxide/polyaspartic acid A double-layer film modified electrode at 0.50 mol dm-3 Cyclic voltammograms in sulfuric acid solution at different scanning rates, the numbers on the curves representing the corresponding scanning rates;
FIG. 5 shows that the reduced graphene oxide/poly azure A double-layer film modified electrodes are respectively aligned to 0-10 mmmol dm in PBS solution with pH of 7.0-3Ascorbic acid catalyzed cyclic voltammogram;
FIG. 6 is 0.2mol dm of reduced graphene oxide/polyaspartic acid A bilayer membrane modified electrode at pH7.0-32.0 mmmol dm in PBS solution at different scanning rates-3 Ascorbic acid catalyzed cyclic voltammogram;
FIG. 7 is a current response curve of a reduced graphene oxide/polyaspartic acid A bilayer membrane modified electrode sensor to ascorbic acid;
fig. 8 is a graph of the anti-interference effect of dopamine and uric acid on a reduced graphene oxide/polyaspartic acid a bilayer membrane modified electrode sensor.
Detailed Description
Azure A of the following examples was produced by Mecanum of Shanghai with a purity of 99%. The reaction equation for poly azure A is: n C14H14ClN3S → [C14H14ClN3S]n。
The graphite powder of the following embodiments is 350-mesh graphite powder, and Graphene Oxide (GO) is prepared by an improved Hummers oxidation method by Shanghai chemical industry Co., Ltd, and the specific steps are as follows:
(1) pre-oxidizing graphite powder: dissolving 2.5 g of potassium persulfate and 2.5 g of phosphorus pentoxide in 12.5 mL of concentrated sulfuric acid, slowly adding 3.0 g of graphite powder, uniformly mixing, and putting the mixture into 80oStirring vigorously in oil bath for 6 h, diluting with 500 mL ultrapure water, standing overnight, filtering with 0.22 μm nylon filter membrane, washing with ultrapure water to neutral, and standing for 40%0Drying to obtain pre-oxidized graphene;
(2) cooling 115ml of concentrated sulfuric acid to 0 ℃ in an ice bath, slowly adding pre-oxidized graphite powder while vigorously stirring, slowly adding 15 g of potassium permanganate in batches under the condition of maintaining vigorous stirring, and controlling the reaction temperature to be lower than 10 DEGoC；
(3) After the addition was complete, the ice-water bath was removed and the temperature of the mixture was controlled at 35 deg.CoC, stirring the mixture for 2 hours, slowly adding 230 mL of ultrapure water, and keeping the temperature at 50 DEG CoContinuing to stir for reaction for 2 hours below C;
(4) diluting with 700 mL of ultrapure water, adding 2.5 mL of 30% hydrogen peroxide for oxidation, standing for settling for one day, pouring out supernatant, centrifuging the precipitate (8000 r/min), washing with 10% hydrochloric acid solution, and washing with ultrapure water to neutrality;
(5) dialyzing with dialysis bag for one week, and changing water every day. And finally. 60oAnd C, drying in vacuum to obtain the graphene oxide.
Example 1
Preparing a reduced graphene oxide/poly azure A double-layer film:
preparing raw materials:
preparing a first electrolyte: 0.1mol dm of pH 4-3 PBS solution;
preparing a second electrolyte: 0.2mol dm-3Sulfuric acid and 1 mmol dm-3Azure A aqueous solution;
preparing a third electrolyte: 0.1 to 0.5 mol/dm of pH 4-3 PBS solution;
preparation of the first electrolytic cell: a three-electrode system is adopted, a bare platinum sheet is used as an auxiliary electrode, a saturated calomel electrode is used as a reference electrode, and a working electrode bare glassy carbon electrode is adopted;
preparation of the second electrolytic cell: a three-electrode system is adopted, a bare platinum sheet is used as an auxiliary electrode, a saturated calomel electrode is used as a reference electrode, and a working electrode is a glassy carbon electrode modified by reduced graphene oxide;
preparation of the third electrolytic cell: a three-electrode system is adopted, a bare platinum sheet is used as an auxiliary electrode, a saturated calomel electrode is used as a reference electrode, and a working electrode is a glassy carbon electrode modified by a reduced graphene oxide/poly azure A double-layer film;
preparing a glassy carbon electrode modified by reduced graphene oxide: dripping 3 μ L of 1 mg/cm solution onto the surface of a glassy carbon electrode with a diameter of 2mm−3And naturally drying the graphene oxide dispersion liquid. Adding a first electrolyte into a first electrolytic cell, and reducing graphene oxide on a glassy carbon electrode by using a cyclic voltammetry method; wherein the scanning potential is-1.4-0V, the scanning rate is 40mV/s, and the number of potential scanning turns is 20 turns.
Synthesis of a reduced graphene oxide/poly azure A double-layer film: and adding a second electrolyte into a second electrolytic cell, and synthesizing a reduced graphene oxide/polysazurin A double-layer film on the surface of the reduced graphene oxide modified glassy carbon electrode by using a cyclic voltammetry method, wherein the scanning potential is-0.2-1.0V, the scanning rate is 40mV/s, and the number of potential scanning cycles is 10.
Example 2
Preparing a reduced graphene oxide/poly azure A double-layer film:
preparing raw materials:
preparing a first electrolyte: 0.5mol dm of pH7-3 PBS solution;
preparing a second electrolyte: 0.8 mol dm-3Sulfuric acid and 5 mmol dm-3Azure A aqueous solution;
preparing a third electrolyte: 0.5mol dm of pH7-3 PBS solution;
preparation of the first electrolytic cell: a three-electrode system is adopted, a bare platinum sheet is used as an auxiliary electrode, a saturated calomel electrode is used as a reference electrode, and a working electrode bare glassy carbon electrode is adopted;
preparation of the second electrolytic cell: a three-electrode system is adopted, a bare platinum sheet is used as an auxiliary electrode, a saturated calomel electrode is used as a reference electrode, and a working electrode is a glassy carbon electrode modified by reduced graphene oxide;
preparation of the third electrolytic cell: a three-electrode system is adopted, a bare platinum sheet is used as an auxiliary electrode, a saturated calomel electrode is used as a reference electrode, and a working electrode is a glassy carbon electrode modified by a reduced graphene oxide/poly azure A double-layer film;
preparing a glassy carbon electrode modified by reduced graphene oxide: dripping 8 μ L of 5 mg/cm solution onto the surface of glassy carbon electrode with diameter of 5mm−3And naturally drying the graphene oxide dispersion liquid. Adding a first electrolyte into a first electrolytic cell, and reducing graphene oxide on a glassy carbon electrode by using a cyclic voltammetry method; wherein the scanning potential is-1.4-0V V, the scanning rate is 80 mV/s, and the number of potential scanning turns is 100 turns.
Synthesis of a reduced graphene oxide/poly azure A double-layer film: and adding a second electrolyte into a second electrolytic cell, and synthesizing a reduced graphene oxide/polysazurin A double-layer film on the surface of the reduced graphene oxide modified glassy carbon electrode by using a cyclic voltammetry method, wherein the scanning potential is-0.2-1.0V, the scanning rate is 80 mV/s, and the number of potential scanning cycles is 50.
Example 3
Preparing a reduced graphene oxide/poly azure A double-layer film:
preparing raw materials:
preparing a first electrolyte: 0.3mol dm of pH 5-3 PBS solution;
preparing a second electrolyte: 0.5mol dm-3Sulfuric acid and 3 mmol dm-3Azure A aqueous solution;
preparing a third electrolyte: 0.3mol dm of pH 5-3 PBS solution;
preparation of the first electrolytic cell: a three-electrode system is adopted, a bare platinum sheet is used as an auxiliary electrode, a saturated calomel electrode is used as a reference electrode, and a working electrode bare glassy carbon electrode is adopted;
preparation of the second electrolytic cell: a three-electrode system is adopted, a bare platinum sheet is used as an auxiliary electrode, a saturated calomel electrode is used as a reference electrode, and a working electrode is a glassy carbon electrode modified by reduced graphene oxide;
preparation of the third electrolytic cell: a three-electrode system is adopted, a bare platinum sheet is used as an auxiliary electrode, a saturated calomel electrode is used as a reference electrode, and a working electrode is a glassy carbon electrode modified by a reduced graphene oxide/poly azure A double-layer film;
preparing a glassy carbon electrode modified by reduced graphene oxide: dripping 5.5 μ L of 3 mg/cm glass carbon electrode with diameter of 3mm on the surface−3And naturally drying the graphene oxide dispersion liquid. Adding a first electrolyte into a first electrolytic cell, and reducing graphene oxide on a glassy carbon electrode by using a cyclic voltammetry method; wherein the scanning potential is-1.4-0V, the scanning rate is 60 mV/s, and the number of potential scanning turns is 60 turns.
Synthesis of a reduced graphene oxide/poly azure A double-layer film: and adding a second electrolyte into a second electrolytic cell, and synthesizing a reduced graphene oxide/polysazurin A double-layer film on the surface of the reduced graphene oxide modified glassy carbon electrode by using a cyclic voltammetry method, wherein the scanning potential is-0.2-1.0V, the scanning rate is 60 mV/s, and the number of potential scanning cycles is 30.
Example 4
Preparing a reduced graphene oxide/poly azure A double-layer film:
preparing raw materials:
preparing a first electrolyte: 0.2mol dm of pH 5-3 PBS solution;
preparing a second electrolyte: 0.3mol dm-3Sulfuric acid and 2 mmol dm-3Azure A aqueous solution;
preparing a third electrolyte: 0.2mol dm of pH 5-3 PBS solution;
preparation of the first electrolytic cell: a three-electrode system is adopted, a bare platinum sheet is used as an auxiliary electrode, a saturated calomel electrode is used as a reference electrode, and a working electrode bare glassy carbon electrode is adopted;
preparation of the second electrolytic cell: a three-electrode system is adopted, a bare platinum sheet is used as an auxiliary electrode, a saturated calomel electrode is used as a reference electrode, and a working electrode is a glassy carbon electrode modified by reduced graphene oxide;
preparation of the third electrolytic cell: a three-electrode system is adopted, a bare platinum sheet is used as an auxiliary electrode, a saturated calomel electrode is used as a reference electrode, and a working electrode is a glassy carbon electrode modified by a reduced graphene oxide/poly azure A double-layer film;
preparing a glassy carbon electrode modified by reduced graphene oxide: dripping 4 μ L of 2 mg/cm on the surface of glassy carbon electrode with diameter of 3mm−3And naturally drying the graphene oxide dispersion liquid. Adding a first electrolyte into a first electrolytic cell, and reducing graphene oxide on a glassy carbon electrode by using a cyclic voltammetry method; wherein the scanning potential is-1.4-0V, the scanning rate is 45 mV/s, and the number of potential scanning turns is 35 turns.
Synthesis of a reduced graphene oxide/poly azure A double-layer film: and adding a second electrolyte into a second electrolytic cell, and synthesizing a reduced graphene oxide/polysazurin A double-layer film on the surface of the reduced graphene oxide modified glassy carbon electrode by using a cyclic voltammetry method, wherein the scanning potential is-0.2-1.0V, the scanning rate is 45 mV/s, and the number of potential scanning cycles is 20.
When the graphene oxide is subjected to cyclic voltammetry test in the PBS electrolyte of example 4, as shown in fig. 1, a significant reduction peak appears at-1.05V in the negative scan, which indicates that the oxygen-containing functional groups (hydroxyl, carboxyl, epoxy, etc.) on the graphene oxide are being reduced. And as the number of scanning turns is increased, the peak current of the reduction peak is smaller and smaller until the reduction peak is basically disappeared, which also indicates that the oxygen-containing functional groups in the graphene oxide are continuously reduced, and the process of electrochemically reducing the graphene oxide is an irreversible process.
Fig. 2 is an electrosynthesis cyclic voltammetry curve of polyaspartic acid A on a reduced graphene oxide modified electrode, and it can be seen from the graph that a small anode peak appears at about 0.15V and a small reduction peak appears at 0.16V. As the number of scans increases, the anode peak current moves in the positive direction and the peak current gradually increases. The above results indicate that the polyaspartic A film is growing continuously. And after electrolysis, obtaining the reduced graphene oxide/poly azure A double-layer film on the working electrode.
As can be seen from fig. 3a, graphene oxide shows a distinct lamellar stacking and wrinkling profile; as can be seen from fig. 3b, the electrochemically reduced graphene oxide possesses the same classic wrinkled morphology as graphene prepared by other methods, but the stacking is significantly reduced compared to graphene oxide, which also indicates that graphene oxide is successfully reduced to reduced graphene oxide; from the scanning electron microscope images of the polyaspartic azurin A of 3c and the reduced graphene oxide/polyaspartic azurin A bilayer film of FIG. 3d, the surface morphology of the polyaspartic azurin A film is composed of micro-nano-sized smooth particles and aggregates thereof, and the bilayer film is mainly composed of a block-shaped protruding structure with a rough surface. The results show that the reduced graphene oxide/polyaspartic acid A double-layer film is successfully prepared.
Example 5
Preparing a reduced graphene oxide/poly azure A double-layer film:
preparing raw materials:
preparing a first electrolyte: 0.4mol dm of pH6-3 PBS solution;
preparing a second electrolyte: 0.7 mol dm-3Sulfuric acid and 4 mmol dm-3Azure A aqueous solution;
preparing a third electrolyte: 0.4mol dm of pH6-3 PBS solution;
preparation of the first electrolytic cell: a three-electrode system is adopted, a bare platinum sheet is used as an auxiliary electrode, a saturated calomel electrode is used as a reference electrode, and a working electrode bare glassy carbon electrode is adopted;
preparation of the second electrolytic cell: a three-electrode system is adopted, a bare platinum sheet is used as an auxiliary electrode, a saturated calomel electrode is used as a reference electrode, and a working electrode is a glassy carbon electrode modified by reduced graphene oxide;
preparation of the third electrolytic cell: a three-electrode system is adopted, a bare platinum sheet is used as an auxiliary electrode, a saturated calomel electrode is used as a reference electrode, and a working electrode is a glassy carbon electrode modified by a reduced graphene oxide/poly azure A double-layer film;
preparing a glassy carbon electrode modified by reduced graphene oxide: dripping 7 μ L of 4 mg/cm solution onto the surface of glassy carbon electrode with diameter of 4mm−3And naturally drying the graphene oxide dispersion liquid. Adding a first electrolyte into a first electrolytic cell, and reducing graphene oxide on a glassy carbon electrode by using a cyclic voltammetry method; wherein the scanning potential is-1.4-0V, the scanning rate is 70 mV/s, and the number of potential scanning turns is 80 turns.
Synthesis of a reduced graphene oxide/poly azure A double-layer film: and adding a second electrolyte into a second electrolytic cell, and synthesizing a reduced graphene oxide/polysazurin A double-layer film on the surface of the reduced graphene oxide modified glassy carbon electrode by using a cyclic voltammetry method, wherein the scanning potential is-0.2-1.0V, the scanning rate is 70 mV/s, and the number of potential scanning cycles is 40.
Example 6
Preparing a reduced graphene oxide/poly azure A double-layer film:
preparing raw materials: graphene oxide dispersion liquid, PBS buffer solution, anhydrous sodium sulfate, concentrated sulfuric acid and azure A.
Preparing a first electrolyte: 0.2mol dm of pH7-3 PBS solution;
preparing a second electrolyte: 0.5mol dm-3Sulfuric acid and 4 mmol dm-3Azure A aqueous solution;
preparing a third electrolyte: 0.2mol dm of pH7-3 PBS solution;
preparation of the first electrolytic cell: a three-electrode system is adopted, a bare platinum sheet is used as an auxiliary electrode, a saturated calomel electrode is used as a reference electrode, and a working electrode bare glassy carbon electrode is adopted;
preparation of the second electrolytic cell: a three-electrode system is adopted, a bare platinum sheet is used as an auxiliary electrode, a saturated calomel electrode is used as a reference electrode, and a working electrode is a glassy carbon electrode modified by reduced graphene oxide;
preparation of the third electrolytic cell: a three-electrode system is adopted, a bare platinum sheet is used as an auxiliary electrode, a saturated calomel electrode is used as a reference electrode, and a working electrode is a glassy carbon electrode modified by a reduced graphene oxide/poly azure A double-layer film;
preparing a glassy carbon electrode modified by reduced graphene oxide: dripping 5 mu L of graphene oxide dispersion liquid on the surface of a glassy carbon electrode with the diameter of 3mm, and naturally airing. Adding a first electrolyte into a first electrolytic cell, and reducing graphene oxide on a glassy carbon electrode by using a cyclic voltammetry method; wherein the scanning speed is 50 mV/s for scanning potential of-1.4-0V, and the number of potential scanning turns is 25 turns.
Synthesis of a reduced graphene oxide/poly azure A double-layer film: and adding a second electrolyte into a second electrolytic cell, and synthesizing a reduced graphene oxide/polysazurin A double-layer film on the surface of the reduced graphene oxide modified glassy carbon electrode by using a cyclic voltammetry method, wherein the scanning potential is-0.2-1.0V (vs. SCE), the number of scanning cycles is 30, and the scanning speed is 60 mV/s.
The reduced graphene oxide/polyaspartic acid A double-layer membrane modified electrode prepared in example 6 is 0.50 mol-3Cyclic voltammetry tests are performed in a sulfuric acid solution at different scanning rates, as shown in fig. 4, the numbers on the curves are corresponding scanning rates, it can be seen that a pair of redox peaks appear in the reduced graphene oxide/polyaspartic blue a double-layer membrane modified electrode in the sulfuric acid solution, the current of the redox peaks is increased along with the increase of the scanning rate, and the peak potential is basically kept unchanged, which indicates that the composite electrode has better electrochemical reversibility.
Detection of ascorbic acid: adding a third electrolyte into a third electrolytic cell, adding ascorbic acid with different concentrations, measuring corresponding current values by using a cyclic voltammetry method and a chronoamperometry method, and drawing corresponding working curves, wherein the scanning potential is set to be-0.8V, and the scanning rate is set to be 50 mV. s-1The chronoamperometric operating voltage was 0.3V. FIG. 5 is 0.20 mol dm of the reduced graphene oxide/polyaspartic acid A bilayer membrane modified electrode of example 6 at pH7.0-3 For 0, 2, 4, 6, 8 and 10 mol dm in PBS solution respectively-3The figure on the curve is the corresponding ascorbic acid concentration, it can be seen from the figure that, curve 0 is that when no ascorbic acid is added into the PBS solution, only a pair of redox peaks appear at-0.2 and-0.3V, the reduction peak does not change with the addition of ascorbic acid, only an irreversible oxidation peak appears at about 0.15V due to oxidation of ascorbic acid, and the peak current of the oxidation peak increases with the increase of the ascorbic acid concentration, which also shows that the catalytic oxidation of the graphene/polyaspartic A double-layer membrane modified electrode to ascorbic acid is gradually enhanced with the increase of the ascorbic acid concentration, which shows that in the actual quantitative analysis, the composite electrode can be used for resisting ascorbic acidAnd (6) detecting. FIG. 6 is 0.20 mol dm of pH7.0 of the reduced graphene oxide/polyaspartic acid A bilayer film modified electrode in example 6-3 2mol dm in PBS solution-3The figure on the curve is the corresponding sweep rate, and it can be seen that the peak current is continuously increased and the peak potential is gradually shifted upwards along with the continuous increase of the sweep rate, which shows that the composite electrode has good catalytic oxidation performance against the ascorbic acid, and the electrode process for oxidizing the ascorbic acid is irreversible. FIG. 7 is 0.20 mol dm of pH7.0 of the reduced graphene oxide/polyaspartic acid A bilayer film modified electrode in example 6-3The current response curve of the ascorbic acid in the PBS solution is detected, and it can be seen that the current value changes every time the ascorbic acid is dripped, and the current value is kept stable after about 2s, which indicates that the composite modified electrode can rapidly generate current response to the ascorbic acid. This is mainly due to the fact that the addition of the reduced graphene oxide increases the electron transfer rate of the composite electrode.
And (3) anti-interference test: and adding the third electrolyte into a third electrolytic cell, and respectively adding ascorbic acid, dopamine and urea to measure the current value by using a chronoamperometry to test the anti-interference performance of the reduced graphene oxide/poly azure A double-layer membrane modified electrode sensor. FIG. 8 is 0.2 mol/dm of pH7.0 of dopamine, uric acid and ascorbic acid added to the reduced graphene oxide/polyaspartic acid bilayer membrane modified electrode pair in example 6-3According to the response current curve in the PBS solution, the addition of the interference substance can not cause the obvious change of the response current, which indicates that the selectivity of the reduced graphene oxide/polyaspartic acid A modified electrode for detecting ascorbic acid is high.

Claims (8)

1. A preparation method of a reduced graphene oxide and poly azure A double-layer film is characterized by comprising the following steps:
(1) preparing 1-5 mg/cm−3The graphene oxide dispersion liquid of (a);
(2) dripping 3-8 mu L of graphene oxide dispersion liquid on the surface of the treated glassy carbon electrode, and airing;
(3) the pH value is 4-7, and the concentration is 0.1-0.5 mol.L−1The PBS solution is a first electrolyte;
(4) adding the first electrolyte into a first electrolytic cell consisting of the glassy carbon electrode obtained in the step (2), a platinum sheet electrode and a saturated calomel electrode reference electrode, performing electrochemical reduction on graphene in the first electrolyte by adopting a cyclic voltammetry method to obtain an electroreduction graphene oxide, and drying at 40-80 ℃;
(5) taking 0.2-0.8 mol.dm-3Dm of sulfuric acid and 1-5 mmol-3Preparing a second electrolyte from an azure A aqueous solution;
(6) adding the second electrolyte into a second electrolytic cell consisting of a glassy carbon electrode modified by reduced graphene oxide, a bare platinum sheet and a saturated calomel electrode reference electrode, and synthesizing a reduced graphene oxide and polyaspartic blue A double-layer membrane by using a cyclic voltammetry method;
the specific preparation steps of the graphene oxide in the step (1) are as follows:
(a) pre-oxidizing graphite powder: dissolving 2.5 g of potassium persulfate and 2.5 g of phosphorus pentoxide in 12.5 mL of concentrated sulfuric acid, slowly adding 3.0 g of graphite powder, uniformly mixing, putting the mixture into an oil bath at 80 ℃, violently stirring for reaction for 6 hours, diluting with 500 mL of ultrapure water after the reaction is finished, standing overnight, filtering with a 0.22 mu m nylon filter membrane, washing with ultrapure water to be neutral, and drying at 40 ℃ to obtain pre-oxidized graphene;
(b) in an ice bath, cooling 115ml of concentrated sulfuric acid to 0 ℃, slowly adding pre-oxidized graphite powder while violently stirring, slowly adding 15 g of potassium permanganate in batches under the condition of maintaining violent stirring, and controlling the reaction temperature to be lower than 10 ℃;
(c) after the addition, the ice water bath is removed, then the temperature of the mixed solution is controlled at 35 ℃, the stirring reaction is continued for 2 hours, 230 mL of ultrapure water is slowly added, the temperature is kept below 50 ℃, and the stirring reaction is continued for 2 hours;
(d) diluting with 700 mL of ultrapure water, adding 2.5 mL of 30% hydrogen peroxide for oxidation, standing and settling for one day, pouring out supernatant, performing centrifugal separation on the precipitate, fully washing with 10% hydrochloric acid solution, and washing with ultrapure water to be neutral;
(e) dialyzing for one week by using a dialysis bag, changing water once every day, and finally, carrying out vacuum drying at 60 ℃ to obtain the graphene oxide.
2. The method for preparing a bilayer membrane of reduced graphene oxide and polyaspartic acid A according to claim 1, wherein the method comprises the following steps: the preparation method of the graphene oxide dispersion liquid in the step (1) comprises the following steps: and putting the graphene oxide in deionized water, and carrying out ultrasonic treatment in an ultrasonic instrument.
3. The method for preparing a bilayer membrane of reduced graphene oxide and polyaspartic acid A according to claim 1, wherein the method comprises the following steps: and (3) the diameter of the glassy carbon electrode in the step (2) is 2-5 mm.
4. The method for preparing a bilayer membrane of reduced graphene oxide and polyaspartic acid A according to claim 1, wherein the method comprises the following steps: the scanning potential of the cyclic voltammetry in the step (4) is-1.4-0V, the scanning rate is 40-80 mV/s, and the number of potential scanning cycles is 20-100 cycles.
5. The method for preparing a bilayer membrane of reduced graphene oxide and polyaspartic acid A according to claim 1, wherein the method comprises the following steps: the scanning potential of the cyclic voltammetry in the step (6) is-0.20-1.0V, the scanning rate is 40-80 mV/s, and the number of potential scanning cycles is 10-50 cycles.
6. The preparation method of claim 1, wherein the double-layer film of the reduced graphene oxide and the poly azure A is obtained.
7. The use of the reduced graphene oxide of claim 6 with a bilayer membrane of polyaspartic acid A for ascorbic acid detection.
8. An electrochemical sensor comprising a working electrode, a reference electrode, and a counter electrode, wherein: the substrate electrode of the working electrode is a glassy carbon electrode, and the surface of the glassy carbon electrode is modified with the reduced graphene oxide and poly azure A double-layer film according to claim 6.
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