CN112461907B - Application of a nano-zinc oxide and graphene oxide composite material in the electrochemical detection of dopamine - Google Patents

Abstract

The invention provides a nano zinc oxide and reduced graphene oxide composite material and a preparation method and application thereof. The surface of the nano zinc oxide is pretreated, and then the nano zinc oxide and the prepared redox graphene are stirred and mixed, the nano zinc oxide and the prepared redox graphene are self-assembled and uniformly dispersed, so that ZnO is uniformly dispersed, and an electrochemical sensor prepared by the composite material in the follow-up process has higher sensitivity to a measured substance; the electrochemical sensor has simple experimental method and easily-achieved experimental conditions, and effectively improves the specific surface area and the active sites of the electrode material of the sensor, thereby improving the detection sensitivity and reducing the detection limit.

Description

Electrochemical detection of dopamine by a nano-zinc oxide and graphene oxide composite application in

technical field

The invention relates to the technical field of electrochemical sensing, and more specifically relates to an electrochemical sensor made of nano-zinc oxide and reduced graphene oxide composite material and its preparation method and application.

Background technique

Graphene is a two-dimensional material with excellent performance, because of its unique structure, it has excellent electron transport ability. ZnO is widely used in biosensing due to its diverse structures and good thermal stability, coupled with its biomimetic properties and high electron transport capability. The nano-zinc oxide and reduced graphene oxide composite electrode has also been developed for the detection of dopamine, ascorbic acid and other substances. However, most of the methods used are one-pot method, and the uneven dispersion of ZnO reduces the sensitivity of the composite electrode to the measured substance.

Contents of the invention

The present invention overcomes the deficiencies in the prior art, and provides a nano-zinc oxide and reduced graphene oxide composite material and its preparation method and application, using gold as a conductive substrate, nano-zinc oxide (ZnO) and redox graphite Alkene is used as the base material, and the mixed suspension of the two is added dropwise on the conductive substrate, and the electrochemical sensor is obtained after electrochemical reduction of the composite electrode. The sensor has high selectivity to dopamine, and the sensitivity is significantly improved; More importantly, the method adopts electrochemical reduction instead of hydrothermal method, and the operation steps are simple.

The purpose of the present invention is achieved through the following technical solutions.

A kind of nano-zinc oxide and reduced graphene oxide composite material and preparation method thereof, carry out according to the following steps:

Step 1, carry out pretreatment to nano zinc oxide

Ultrasonically disperse nano-zinc oxide particles in absolute ethanol, then add 3-aminopropyltriethoxysilane (APTES) to the above dispersion, reflux in a water bath at 50-90°C, centrifuge, wash and dry, and obtain the pretreated Nano-zinc oxide, wherein, the mass-volume ratio of nano-zinc oxide and 3-aminopropyltriethoxysilane (APTES) is (0.1-12): (3-60);

Step 2, preparation of redox graphene (GO)

Add concentrated sulfuric acid into a beaker and heat it to 80-100°C, then add dipotassium persulfate and phosphorus pentoxide to the above concentrated sulfuric acid in sequence, then slowly add graphite powder, and heat and stir the mixture at 80-100°C for 4- 8h, after cooling, slowly dilute the above mixture with deionized water, then centrifugally wash the mixture with deionized water to pH = 7, and dry the obtained solid product in air at room temperature (20-25°C) to obtain Redox graphene (GO), wherein the added volume mass ratio of concentrated sulfuric acid, dipotassium persulfate, phosphorus pentoxide and graphite powder is (10-50): (1-8): (3-12): ( 1-12);

Step 3, making nano zinc oxide and redox graphene composite material

The pretreated nano-zinc oxide and water obtained in step 1 are configured into a nano-zinc oxide suspension, and the redox graphene (GO) obtained in step 2 is configured into a redox graphene having an equal mass portion with the nano-zinc oxide suspension. (GO) suspension, stir and mix the nano-zinc oxide suspension and the redox graphene (GO) suspension to obtain a mixed suspension, drop 4-10 μL of the above-mentioned mixed suspension on the surface of the gold electrode, and obtain nano-zinc oxide after air-drying A composite material with redox graphene, wherein the concentration of the nano-zinc oxide suspension is 1-15 mg/ml, and the concentration of the redox graphene (GO) suspension is 1-15 mg/ml.

In step 1, the mass of nano-zinc oxide is 0.2-10 parts by mass, the particle size is 20-70nm, the ultrasonic time is 10-120min, the volume fraction of APTES is 98%, the volume is 5-50 parts by volume, and the water bath reflux temperature It is 60-80°C.

In step 2, the volume of concentrated sulfuric acid (H ₂ SO ₄ ) is 15-40 parts by volume, the heating temperature is 90° C., the mass of dipotassium persulfate (K ₂ S ₂ O ₄ ) is 2-7 parts by mass, five The mass of phosphorus oxide (P ₂ O ₅ ) is 4-10 mass parts, and the mass of graphite powder is 2-10 mass parts.

In step 3, the concentration of the nano zinc oxide suspension is 1-10 mg/ml, and the concentration of the redox graphene (GO) suspension is 1-10 mg/ml.

However, one part by mass means 1 g, and one part by volume means 1 ml.

An application of a nano-zinc oxide and reduced graphene oxide composite material in the electrochemical detection of dopamine. The above-mentioned nano-zinc oxide and redox graphene composite material is placed in the solution to be measured for electrochemical reduction, and the current has a downward peak value. Record the peak value of the current downward change, and analyze it to obtain a concentration curve with good linearity. The curve formula is y=-0.26x-1.23, where y is the peak value of the current, x is the concentration of dopamine, and R ² =0.998 , with a sensitivity of 260nA/μmol.

The solution to be tested is dipotassium hydrogen phosphate and potassium dihydrogen phosphate buffer solution (PBS) of dopamine, the concentration of dopamine is 1-70μmol/L, the voltage of electrochemical reduction is -1.2-0V, and the scanning rate is 40-100mv/s , the number of cycles is 15-30 circles.

The beneficial effects of the present invention are as follows: the nano-zinc oxide and reduced graphene oxide composite material prepared by the present invention pretreats the surface of the nano-zinc oxide, and then stirs and mixes with the prepared redox graphene. The assembly is evenly dispersed, so that the ZnO is more uniformly dispersed, and the subsequent electrochemical sensor prepared by using the composite material is more sensitive to the measured substance; the nano-zinc oxide and reduced graphene oxide composite electrochemical sensor prepared by the present invention, the experimental The method is simple, the experimental conditions are easy to achieve, and the specific surface area and active sites of the sensor electrode material are effectively increased, thereby improving the detection sensitivity and reducing the detection limit, and providing a new method for the actual detection application of the electrochemical sensor.

Description of drawings

Fig. 1 is the photo of the suspension of nano-zinc oxide prepared by the present invention and redox graphene composite material;

Fig. 2 is the scanning electron micrograph of the nanometer zinc oxide that the present invention buys;

Fig. 3 is the electron micrograph of redox graphene prepared by the present invention;

Fig. 4 is the electron micrograph of nanometer zinc oxide and redox graphene composite material prepared by the present invention;

Fig. 5 is the picture that adopts differential pulse voltammetry to detect the dopamine of different concentrations at the electrochemical workstation using the nanometer zinc oxide prepared by the present invention and redox graphene composite material, wherein, (1) is DPV curve, (2) is concentration curve;

Fig. 6 is a scanning speed diagram of the electrochemical sensor electrode of nano-zinc oxide and redox graphene composite material prepared by the present invention, wherein (1) is a cyclic voltammetry curve, and (2) is a current intensity curve.

detailed description

The technical solutions of the present invention will be further described below through specific examples.

Example 1:

Ultrasonically disperse 0.5g nano-zinc oxide particles in 200ml of absolute ethanol, then add 0.5ml of APTES, reflux in a water bath at 60°C for 4h, then centrifuge the ZnO nanoparticles and wash them with absolute ethanol several times and place them in an oven at 70°C Fully dry inside, reflux in a water bath, centrifuge, wash and dry to obtain pretreated nanometer zinc oxide particles.

Add 25ml of concentrated sulfuric acid into a 250ml beaker and heat to 90°C. Then add 5g K ₂ S ₂ O ₈ and 5g P ₂ O ₅ in sequence, and then slowly add 5g graphite powder. The mixture was heated and stirred at 90 °C for 5 h. After cooling, the mixture was slowly diluted with deionized water. The mixture was then washed with deionized water to around pH=7, and the resulting product was dried at room temperature.

Prepare the nano-zinc oxide particles and redox graphene obtained above into a 5 mg/ml suspension with water, stir and mix to obtain the suspension as shown in Figure 1, drop 6 μL of the above-mentioned mixed suspension on the surface of the gold electrode and air-dried to obtain a composite material of nano-zinc oxide and redox graphene.

Scanning the morphology of the nano-zinc oxide in Example 1 through a scanning electron microscope (SEM), it is found that the particle size of the nano-zinc oxide is 10-40 nm, as shown in FIG. 2 .

The redox graphene prepared in Example 1 was scanned by a scanning electron microscope (SEM), and it was found that the redox graphene was in a thin layer, as shown in FIG. 3 .

As shown in Figure 4, it was found that the nano-ZnO was uniformly dispersed on the graphene surface by scanning electron microscopy.

Example 2:

Ultrasonic disperse 1g of zinc oxide nanoparticles in 250ml of absolute ethanol, then add 1ml of APTES, reflux in a water bath at 60°C for 4h, then centrifuge the ZnO nanoparticles and wash them with absolute ethanol several times, then place them in an oven at 70°C drying, reflux in a water bath, centrifugal washing and drying to obtain pretreated nanometer zinc oxide particles.

Add 20ml of concentrated sulfuric acid into a 250ml beaker and heat to 80°C. Then add 2.5g K ₂ S ₂ O ₈ and 2.5g P ₂ O ₅ in sequence, and then slowly add 5g of graphite powder. The mixture was heated and stirred at 80 °C for 5 h. After cooling, the mixture was slowly diluted with deionized water. The mixture was then washed with deionized water to around pH=7, and the resulting product was dried at room temperature.

Prepare the nano-zinc oxide particles and redox graphene obtained above with water to form a suspension of 3 mg/ml, stir and mix to obtain a suspension, drop 4 μL of the above-mentioned mixed suspension on the surface of the gold electrode, and air-dry to obtain nano-zinc oxide Composites with redox graphene.

Example 3:

Ultrasonically disperse 2.5g nano-zinc oxide particles in 200ml of absolute ethanol, then add 5ml of APTES, reflux in a water bath at 60°C for 4h, then centrifuge the ZnO nanoparticles and wash them with absolute ethanol for several times, then place them in an oven at 70°C Fully dry, reflux in a water bath, centrifuge, wash and dry to obtain pretreated nanometer zinc oxide particles.

Add 25ml of concentrated sulfuric acid into a 250ml beaker and heat to 100°C. Then add 5g K ₂ S ₂ O ₈ and 5g P ₂ O ₅ in sequence, and then slowly add 5g graphite powder. The mixture was heated and stirred at 100 °C for 5 h. After cooling, the mixture was slowly diluted with deionized water. The mixture was then washed with deionized water to around pH=7, and the resulting product was dried at room temperature.

The nano-zinc oxide particles and redox graphene obtained above were formulated with water to form a 5 mg/ml suspension, stirred and mixed to obtain a suspension, 10 μL of the above-mentioned mixed suspension was dropped on the surface of the gold electrode, and the nano-zinc oxide was obtained after air-drying Composites with redox graphene.

Example 3:

Ultrasonically disperse 0.1g nano-zinc oxide particles in 200ml of absolute ethanol, then add 3ml of APTES, reflux in a water bath at 60°C for 4h, then centrifuge the ZnO nanoparticles and wash them with absolute ethanol several times, then place them in an oven at 70°C Fully dry, reflux in a water bath, centrifuge, wash and dry to obtain pretreated nanometer zinc oxide particles.

Add 20ml of concentrated sulfuric acid into a 250ml beaker and heat to 95°C. Then add 1g K ₂ S ₂ O ₈ and 3g P ₂ O ₅ in sequence, and then slowly add 1g of graphite powder. The mixture was heated and stirred at 95 °C for 5 h. After cooling, the mixture was slowly diluted with deionized water. The mixture was then washed with deionized water to around pH=7, and the resulting product was dried at room temperature.

The nano-zinc oxide particles and redox graphene obtained above were formulated with water to form a 15 mg/ml suspension, stirred and mixed to obtain a suspension, 9 μL of the above-mentioned mixed suspension was dropped on the surface of the gold electrode, and the nano-zinc oxide was obtained after air-drying Composites with redox graphene.

Example 4:

Ultrasonically disperse 12g nanometer zinc oxide particles in 200ml of absolute ethanol, then add 3ml of APTES, reflux in a water bath at 60°C for 4h, then centrifuge the ZnO nanoparticles and wash them with absolute ethanol several times, then place them in an oven at 50°C drying, reflux in a water bath, centrifugal washing and drying to obtain pretreated nanometer zinc oxide particles.

Add 50ml of concentrated sulfuric acid into a 250ml beaker and heat to 85°C. Then add 8g K ₂ S ₂ O ₈ and 12g P ₂ O ₅ in sequence, and then slowly add 12g graphite powder. The mixture was heated and stirred at 90 °C for 5 h. After cooling, the mixture was slowly diluted with deionized water. The mixture was then washed with deionized water to around pH=7, and the resulting product was dried at room temperature.

Prepare the nano-zinc oxide particles and redox graphene obtained above with water to form a suspension of 1 mg/ml, stir and mix to obtain a suspension, drop 8 μL of the above-mentioned mixed suspension on the surface of the gold electrode, and air-dry to obtain nano-zinc oxide Composites with redox graphene.

Example 5:

The nano-zinc oxide and redox graphene composite material finally obtained in Example 3 is placed in a buffer solution for electrochemical reduction, the voltage of electrochemical reduction is-1.5-0V, the scan rate is 30-120mv/s, and the number of cycles is After 10-40 cycles, the electrochemical sensor of nano-zinc oxide and reduced graphene oxide composite material is obtained. The three-electrode test system was used for electrochemical reduction and testing of the samples, and the electrochemical workstation CHI-660E was used for electrochemical reduction and testing.

(1) Perform electrochemical reduction on the dried electrode in PBS solution (PH=7): the voltage range is: -1.2-0V, the scan rate is 50mv/s, and the number of cycles is 15 times.

(2) Perform electrochemical test on the reduced electrode obtained in (1) by differential pulse voltammetry: put the electrode in PBS buffer solution to test the peak current by differential pulse voltammetry, and the voltage range is 0 to 0.5 V, the scan rate is 100mv/s, and the pulse period is 0.05s ^-1 . The substance to be tested is dopamine, and the dopamine concentration ranges from 1 to 70 μmol/L, and the specific concentration is 5 10 15 20 25 30 35 40 45 50 60 70 μmol/L. Finally, the DPV curve is obtained, as shown in Figure 5(1). When it is 0.15±0.01V, the current has a downward peak value, and after analysis, a well-linear concentration curve can be obtained as shown in Figure 5(2), y=-0.26x-1.23, wherein, y is the current peak value, and x is dopamine Concentration, R ² =0.998, sensitivity 260 nA/μmol.

(3) The reduced electrode obtained in (1) is subjected to a scanning electrochemical test, and the electrode is placed in PBS buffer solution for cyclic voltammetry to test the peak current, the voltage range is -0.2-0.6V, and the scanning The rate is 20 40 60 80 100mv/s. The cyclic voltammetry curve shown in Figure 6(1) was obtained, and the linearity of the scan rate and current intensity was very good, as shown in Figure 6(2).

The present invention has been described as an example above, and it should be noted that, without departing from the core of the present invention, any simple deformation, modification or other equivalent replacements that can be made by those skilled in the art without creative labor all fall within the scope of this invention. protection scope of the invention.

Claims (5)

1. An application of a nano zinc oxide and graphene oxide composite material in electrochemical detection of dopamine is characterized in that: the nano zinc oxide and graphene oxide composite material is prepared according to the following steps:

step 1, carrying out pretreatment on nano zinc oxide

Ultrasonically dispersing nano zinc oxide particles in absolute ethyl alcohol, then adding 3-aminopropyltriethoxysilane APTES into dispersion liquid, refluxing in a water bath at 50-90 ℃, centrifugally washing and drying to obtain pretreated nano zinc oxide, wherein the addition mass volume ratio of the nano zinc oxide to the 3-aminopropyltriethoxysilane APTES is (0.1-12): (3-60); the mass of the nano zinc oxide particles is 0.2-10 parts, and the particle size is 20-70 nm;

step 2, preparing graphene oxide GO

Adding concentrated sulfuric acid into a beaker, heating to 80-100 ℃, then sequentially adding dipotassium persulfate and phosphorus pentoxide into the concentrated sulfuric acid, then slowly adding graphite powder, heating and stirring the mixture at 80-100 ℃ for 4-8h, cooling, slowly diluting the mixture with deionized water, then centrifugally washing the mixture with deionized water to pH =7, and drying the obtained solid product in air at room temperature of 20-25 ℃ to obtain graphene oxide GO, wherein the adding volume-mass ratio of the concentrated sulfuric acid, the dipotassium persulfate, the phosphorus pentoxide and the graphite powder is (10-50): (1-8): (3-12): (1-12);

step 3, preparing the nano zinc oxide and graphene oxide composite material

Preparing the pretreated nano zinc oxide obtained in the step 1 and water into a nano zinc oxide suspension, preparing the graphene oxide GO obtained in the step 2 into a graphene oxide GO suspension with the same mass part as the nano zinc oxide suspension, stirring and mixing the nano zinc oxide suspension and the graphene oxide GO suspension to obtain a mixed suspension, dripping 4-10 mu L of the mixed suspension on the surface of a gold electrode, and air-drying to obtain a nano zinc oxide and graphene oxide composite material, wherein the concentration of the nano zinc oxide suspension is 1-15mg/ml, and the concentration of the graphene oxide GO suspension is 1-15mg/ml;

placing the nano zinc oxide and graphene oxide composite material in a solution to be detected for electrochemical reduction, recording the downward peak value of current when the current appears at the downward peak value, and analyzing the downward peak value of current to obtain a concentration curve with good linearity, wherein the curve formula is y = -0.26x-1.23, y is the current peak value, x is the dopamine concentration, and R is the dopamine concentration ² =0.998, sensitivity 260nA/μmol.

2. The application of the nano zinc oxide and graphene oxide composite material in the electrochemical detection of dopamine according to claim 1 is characterized in that: in step 1, the ultrasonic time is 10-120min, the volume fraction of APTES is 98%, the volume is 5-50 parts, and the reflux temperature of the water bath is 60-80 ℃.

3. The application of the nano zinc oxide and graphene oxide composite material in the electrochemical detection of dopamine according to claim 1 is characterized in that: in step 2, concentrated sulfuric acid H ₂ SO ₄ 15-40 parts by volume of (A), the heating temperature is 90 ℃, and the dipotassium persulfate K ₂ S ₂ O ₄ 2-7 parts by mass of phosphorus pentoxide P ₂ O ₅ The mass of the graphite powder is 4-10 parts by mass, and the mass of the graphite powder is 2-10 parts by mass.

4. The application of the nano zinc oxide and graphene oxide composite material in the electrochemical detection of dopamine according to claim 1 is characterized in that: in step 3, the concentration of the nano zinc oxide suspension is 1-10mg/ml, and the concentration of the graphene oxide GO suspension is 1-10mg/ml.

5. The application of the nano zinc oxide and graphene oxide composite material in the electrochemical detection of dopamine according to claim 1 is characterized in that: the solution to be detected is buffer solution PBS of dipotassium hydrogen phosphate and potassium dihydrogen phosphate of dopamine, the concentration of dopamine is 1-70 mu mol/L, the voltage of electrochemical reduction is-1.2-0V, the scanning speed is 40-100mv/s, and the cycle number is 15-30 circles.

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