阅读说明：本技术 一种ha-石墨烯柔性电极及其制备方法、应用 (HA-graphene flexible electrode and preparation method and application thereof ) 是由 樊凯 张海霞 李杜娟 郑岩 王高峰 苏畅 杨安琪 于 2019-11-07 设计创作，主要内容包括：本发明属于食品安全检测领域,涉及一种HA-石墨烯柔性电极的制备方法,包括如下步骤：步骤一、将氧化石墨烯溶液通过多孔性氧化铝基板进行真空过滤,得到氧化石墨烯薄膜；步骤二、将己胺的甲醇溶液通过步骤一的氧化石墨烯薄膜和多孔性氧化铝基板进行真空过滤,得到己胺改性的氧化石墨烯纸,即HA-氧化石墨烯纸；步骤三、将还原剂以预设的温度在HA-氧化石墨烯纸表面流动,得到HA-石墨烯纸；步骤四、对HA-石墨烯纸进行退火处理,制得HA-石墨烯柔性电极。本发明制得的HA-石墨烯柔性电极,与传统电极的检测结果相比,HA-石墨烯柔性电极检测灵敏度更高,检测结果更稳定,检测范围更广,可根据各种应用场合对结构进行微型化。(The invention belongs to the field of food safety detection, and relates to a preparation method of an HA-graphene flexible electrode, which comprises the following steps: step one, carrying out vacuum filtration on a graphene oxide solution through a porous alumina substrate to obtain a graphene oxide film; step two, performing vacuum filtration on a hexylamine methanol solution through the graphene oxide film and the porous alumina substrate obtained in the step one to obtain hexylamine modified graphene oxide paper, namely HA-graphene oxide paper; thirdly, flowing a reducing agent on the surface of the HA-graphene oxide paper at a preset temperature to obtain HA-graphene paper; and step four, annealing the HA-graphene paper to obtain the HA-graphene flexible electrode. Compared with the detection result of the traditional electrode, the HA-graphene flexible electrode prepared by the invention HAs higher detection sensitivity, more stable detection result and wider detection range, and can be miniaturized according to various application occasions.)

1. A preparation method of an HA-graphene flexible electrode is characterized by comprising the following steps:

step one, carrying out vacuum filtration on a graphene oxide solution through a porous alumina substrate to obtain a graphene oxide film;

step two, performing vacuum filtration on a hexylamine methanol solution through the graphene oxide film and the porous alumina substrate obtained in the step one to obtain hexylamine modified graphene oxide paper, namely HA-graphene oxide paper;

thirdly, flowing a reducing agent on the surface of the HA-graphene oxide paper at a preset temperature to obtain HA-graphene paper;

and step four, annealing the HA-graphene paper to obtain the HA-graphene flexible electrode.

2. The method for preparing the HA-graphene flexible electrode according to claim 1, wherein before the first step, the graphene oxide solution is subjected to ultrasonic dispersion treatment for 2-3 hours.

3. The method for preparing the HA-graphene flexible electrode according to claim 1, wherein the reducing agent is a hydrazine monohydrate solution.

4. The method for preparing the HA-graphene flexible electrode according to claim 3, wherein the preset temperature is 50-120 ℃.

5. The method for preparing the HA-graphene flexible electrode according to claim 1, wherein the flow time in the third step is 3-15 h.

6. The method for preparing the HA-graphene flexible electrode according to claim 1, wherein the step three is performed under vacuum condition.

7. The method for preparing the HA-graphene flexible electrode according to claim 1, wherein the annealing treatment is performed under a vacuum condition, the annealing temperature is 180-500 ℃, and the annealing time is 3-12 h.

8. An HA-graphene flexible electrode, characterized by being prepared by the preparation method of any one of claims 1 to 7.

9. The application of the HA-graphene flexible electrode according to claim 8, wherein the HA-graphene flexible electrode is used for measuring the content of nitrite ions.

10. The application of the HA-graphene flexible electrode according to claim 9, wherein the determination of the content of nitrite ions comprises the following steps:

(a) obtaining a standard curve of nitrite ion concentration-peak current magnitude of a characteristic peak, comprising: (a1) clamping an HA-graphene flexible electrode by using an electrode, and forming a three-electrode system with a platinum wire electrode and a saturated silver chloride electrode; (a2) placing a sulfuric acid-sodium sulfate buffer solution and a sodium nitrite standard solution in an electrolytic cell, and performing cyclic voltammetry scanning at a preset scanning speed within a voltage range of 0-1.0V; (a3) obtaining a standard curve of nitrite ion concentration-peak current magnitude of a characteristic peak according to the relation between sodium nitrite standard solutions with different concentrations and oxidation peak current;

(b) adding a sample to be detected into an electrolytic cell, carrying out cyclic voltammetry scanning at a preset scanning speed within a voltage range of 0-1.0V to obtain the peak current of a characteristic peak corresponding to nitrite ions of the sample to be detected, and comparing the peak current with a standard curve of concentration-peak current of the characteristic peak to obtain the content of the nitrite ions of the sample to be detected.

Technical Field

The invention belongs to the field of food safety detection, and relates to an HA-graphene flexible electrode and a preparation method and application thereof.

Background

Nitrite ion is a toxic substance present in drinking water, soil, various food and environmental systems. If nitrite ions are eaten by mistake, the nitrite ions can interact with proteins in a body to generate a high-efficiency carcinogenic substance N-ammonium nitrite, so that gastric cancer and esophageal cancer can be caused, and the health of human beings is seriously threatened. Therefore, detection of nitrite ions is important.

At present, the existing methods for detecting nitrite ions include spectrophotometry, raman spectroscopy, chromatography, fluorescence, capillary electrophoresis and the like. These detection methods all involve complicated and time-consuming procedures, require expensive equipment and technicians, and are not capable of performing simple, rapid, and efficient detection of nitrite ions. Compared with the prior art, the electrochemical method has the advantages of simple operation, high detection sensitivity, short detection time, low detection cost and the like. However, the existing electrodes for electrochemically detecting nitrite are all made by modifying materials on the surface of a common bare electrode, the modified materials comprise metal organic framework compounds, enzymes, metal and metal oxide nanoparticles and nanoclusters, carbon nanotubes, chitosan, sol-gel and the modification and combination of the above materials, and the composite electrodes made of the modified materials have poor environmental adaptability and cannot change the size according to the detection site. There is a need in the art to develop a new electrode material.

Disclosure of Invention

Based on the defects in the prior art, the invention provides an HA-graphene flexible electrode and a preparation method and application thereof.

In order to achieve the purpose, the invention adopts the following technical scheme:

a preparation method of an HA-graphene flexible electrode comprises the following steps:

step one, carrying out vacuum filtration on a graphene oxide solution through a porous alumina substrate to obtain a graphene oxide film;

step two, performing vacuum filtration on a hexylamine methanol solution through the graphene oxide film and the porous alumina substrate obtained in the step one to obtain hexylamine-graphene oxide paper, namely HA-graphene oxide paper;

thirdly, flowing a reducing agent on the surface of the HA-graphene oxide paper at a preset temperature to obtain HA-graphene paper;

and step four, annealing the HA-graphene paper to obtain the HA-graphene flexible electrode.

Preferably, before the first step, the graphene oxide solution is subjected to ultrasonic dispersion treatment, wherein the ultrasonic time is 2-3 hours.

Preferably, the reducing agent is a hydrazine monohydrate solution.

Preferably, the preset temperature is 50-120 ℃.

Preferably, the flowing time in the third step is 3-15 h.

Preferably, the third step is performed under vacuum.

Preferably, the annealing treatment is carried out under a vacuum condition, the annealing temperature is 180-500 ℃, and the annealing time is 3-12 hours.

The invention also provides an HA-graphene flexible electrode prepared by the preparation method of any one of the above schemes.

The invention also provides an application of the HA-graphene flexible electrode, and the HA-graphene flexible electrode is used for measuring the content of nitrite ions.

Preferably, the determination of the content of nitrite ions comprises the following steps:

(a) obtaining a standard curve of nitrite ion concentration-peak current magnitude of a characteristic peak, comprising: (a1) clamping an HA-graphene flexible electrode by using an electrode, and forming a three-electrode system with a platinum wire electrode and a saturated silver chloride electrode; (a2) placing a sulfuric acid-sodium sulfate buffer solution and a sodium nitrite standard solution in an electrolytic cell, and performing cyclic voltammetry scanning at a preset scanning speed within a voltage range of 0-1.0V; (a3) obtaining a standard curve of nitrite ion concentration-peak current magnitude of a characteristic peak according to the relation between sodium nitrite standard solutions with different concentrations and oxidation peak current;

(b) adding a sample to be detected into an electrolytic cell, carrying out cyclic voltammetry scanning at a preset scanning speed within a voltage range of 0-1.0V to obtain the peak current of a characteristic peak corresponding to nitrite ions of the sample to be detected, and comparing the peak current with a standard curve of concentration-peak current of the characteristic peak to obtain the content of the nitrite ions of the sample to be detected.

Compared with the prior art, the invention has the beneficial effects that:

compared with the detection result of the traditional electrode, the HA-graphene flexible electrode prepared by the invention HAs higher detection sensitivity, more stable detection result and wider detection range, and can be miniaturized according to various application occasions.

Drawings

Fig. 1 is a schematic structural diagram of HA-graphene paper according to an embodiment of the present invention;

FIG. 2 is a cyclic voltammetry graph of an HA-graphene flexible electrode of an embodiment of the invention with different concentrations of nitrite ions;

FIG. 3 is a standard curve of nitrite concentration versus peak current magnitude for a characteristic peak for an example of the present invention.

Detailed Description

The technical solution of the present invention will be described in detail by the following specific examples.

The preparation method of the HA-graphene flexible electrode of the embodiment of the present invention includes the following steps:

(1) placing 5mL of graphene oxide solution with the concentration of 2mg/mL and 15mL of deionized water in a 50mL centrifuge tube by using a liquid transfer gun, and then carrying out ultrasonic dispersion treatment for 2-3 h to obtain a water dispersion solution of graphene oxide sheets;

(2) vacuum filtering the graphene oxide water dispersion solution through a porous alumina substrate to obtain a black paper-shaped graphene oxide film;

(3) vacuum-filtering a methanol solution (50-100 mM) of hexylamine HA through the prepared wet black graphene oxide and porous alumina substrate to prepare hexylamine modified graphene oxide paper, namely HA-graphene oxide paper;

(4) then (1-2M) hydrazine monohydrate solution flows through the HA-graphene oxide paper at the temperature of 50 ℃, 90 ℃ or 120 ℃ for 3-15 hours under the assistance of vacuum, and the HA-graphene oxide paper is obtained by reducing the hydrazine monohydrate solution;

(5) annealing the HA-graphene paper for 3-12 hours at the temperature of 180-500 ℃ under a vacuum condition;

(6) and (3) sticking one side of the annealed HA-graphene paper by using a transparent adhesive tape, and then cutting the HA-graphene paper into the size of 0.7 multiplied by 1.2cm to obtain the HA-graphene flexible electrode.

From the TGA and EA test results, the influence of the annealing temperature on the conductivity of the HA-graphene flexible electrode and the retention degree of the hexylamine is known, as shown in tables 1 and 2, respectively, and it is known that the selection of the annealing temperature of 180 ℃ is better for maintaining the conductivity and mechanical properties of the HA-graphene paper.

Table 1 table of the influence of different annealing temperatures on the conductivity of the HA-graphene flexible electrode

Annealing temperature (. degree.C.)	Annealing time (h)	Electric conductivity (S.m)-1)
			--	--	57±20
50	12	300±20
			180	12	1500±200
300	3	1700±200
			500	3	1700±200

Table 2 influence of different annealing temperatures on the degree of retention of the hexanamine of HA-graphene flexible electrodes

Annealing temperature (. degree.C.)	Cgraphene/O	Namine/Cgraphene	Summary of the invention
				150～200	16.9	0.03	Retention of the hexamine within this annealing temperature range
200～450	3.6	0.124	Gradual loss of amine

The following is a detailed description of a method for preparing an HA-graphene flexible electrode according to a more specific example, and the specific steps are as follows:

1) absorbing 5mL of graphene oxide solution with the concentration of 2mg/mL and 15mL of deionized water by using a liquid transfer gun, putting the solution and the deionized water into a 50mL centrifuge tube, and carrying out ultrasonic treatment for 3h to obtain a graphene oxide water dispersion solution;

2) vacuum filtering the graphene oxide aqueous dispersion solution through a porous alumina substrate to obtain a black paper-shaped graphene oxide film;

3) vacuum-filtering a methanol solution of 100mM hexylamine HA through the prepared black paper-shaped graphene oxide thin film and a porous alumina substrate to prepare HA-graphene oxide paper;

4) flowing a 2M hydrazine monohydrate solution through HA-graphene oxide paper at a temperature of 90 ℃ for 3h under the assistance of vacuum, and reducing the solution to obtain HA-graphene paper, wherein the HA-graphene paper is shown in figure 1;

5) annealing the HA-graphene paper for 12 hours at the temperature of 180 ℃ under vacuum to obtain the HA-graphene paper with good conductivity and mechanical property;

6) and then, sticking one side of the HA-graphene paper prepared in the step 5) by using a transparent adhesive tape, and then cutting the HA-graphene paper into small strips with the specification of 0.7 multiplied by 1.2cm to obtain the HA-graphene flexible electrode.

The HA-redox graphene electrode prepared by the example HAs high flexibility and good mechanical property, and HAs better electronic conductivity compared with a solid electrode.

The HA-graphene flexible electrode prepared by the above example is applied to nitrite ion quantitative measurement in water. Specifically, the quantitative measurement of nitrite ions comprises the following steps:

fixing an HA-graphene flexible electrode by using an electrode clamp, connecting the HA-graphene flexible electrode, a platinum wire electrode and saturated calomel to an electrochemical workstation through an electrode converter, inserting the three electrodes into a 10mL electrolytic cell of phosphoric acid buffer solution (pH is 5) with the concentration of 0.1M, and scanning the HA-graphene flexible electrode and the platinum wire electrode to be stable within a set scanning voltage range of 0-1.0V by adopting a cyclic voltammetry method;

respectively adding a plurality of standard solutions of nitrite to-be-detected components with different concentrations into an electrolytic cell, and measuring and recording the peak current of a characteristic peak corresponding to the to-be-detected components by adopting a cyclic voltammetry method;

and obtaining a concentration-characteristic peak current standard curve of the component to be detected according to the peak current of the characteristic peak corresponding to the component to be detected of the nitrite with different concentrations.

Adding a sample to be measured into an electrolytic cell, measuring and recording the peak current of the characteristic peak corresponding to the component to be measured of the sample to be measured by adopting a cyclic voltammetry method, and comparing the peak current with a standard curve of the peak current of the concentration-characteristic peak to obtain the content of the component to be measured in the sample to be measured.

Specifically, taking the detection of fresh pork as an example, the sample to be detected is prepared by soaking 100g of fresh pork in 500mL of deionized water, standing, and then taking the supernatant, adding a phosphate buffer solution (0.1mol/L, pH 5) to dilute 5 times.

When the HA-graphene flexible electrode prepared by the example is applied to the content measurement of nitrous acid, the characteristic peak of nitrite ions is 0.6V; therefore, when the nitrite content is detected, the scanning voltage range of the cyclic voltammetry is set to be 0-1.0V.

Adding 10 muL, 20 muL, 30 muL, 40 muL, 50 muL, 60 muL, 70 muL and 80 muL of sodium nitrite solution with the concentration of 10mg/L into the electrolytic cell, respectively, obtaining cyclic voltammetry curves of nitrite with different concentrations by adopting cyclic voltammetry, and measuring and recording peak current sizes of characteristic peaks corresponding to different concentrations, as shown in figure 2.

According to the peak current of the characteristic peak corresponding to the nitrite with different concentrations, a standard curve of the peak current of the characteristic peak with the nitrite concentration of 0.6V is obtained, as shown in FIG. 3.

Then, measuring the content of nitrite in the meat product, namely adding 500mL of deionized water into 100g of fresh pork for soaking, standing, and adding a phosphoric acid buffer solution (0.1mol/L, pH 5) into the supernatant for diluting by 5 times;

adding the diluted fresh pork sample into an electrolytic cell, measuring and recording the peak current of the characteristic peak corresponding to the diluted fresh pork sample by adopting a cyclic voltammetry, comparing the peak current with a standard curve of the concentration of nitrite to the peak current of the characteristic peak, and obtaining the content of the component to be measured in the sample to be measured through conversion.

The foregoing has outlined rather broadly the preferred embodiments and principles of the present invention and it will be appreciated that those skilled in the art may devise variations of the present invention that are within the spirit and scope of the appended claims.