阅读说明：本技术 一种气敏复合材料及其制备方法、气敏电极和传感设备 (Gas-sensitive composite material, preparation method thereof, gas-sensitive electrode and sensing equipment ) 是由 王耀 刘文波 周国富 于 2020-12-14 设计创作，主要内容包括：本发明公开了一种气敏复合材料及其制备方法、气敏电极和传感设备,该气敏复合材料包括石墨烯和附着在所述石墨烯上的有机小分子,所述有机小分子通过超分子作用附着在石墨烯上；有机小分子具有氧化还原性质。本发明气敏复合材料可实现在室温条件下对一定浓度的氧化性气体发生快速响应,具有高灵敏度。(The invention discloses a gas-sensitive composite material, a preparation method thereof, a gas-sensitive electrode and sensing equipment, wherein the gas-sensitive composite material comprises graphene and small organic molecules attached to the graphene, and the small organic molecules are attached to the graphene through a supermolecule effect; small organic molecules have redox properties. The gas-sensitive composite material can realize quick response to oxidizing gas with certain concentration at room temperature, and has high sensitivity.)

1. A gas-sensitive composite material, comprising graphene and small organic molecules attached to the graphene, wherein the small organic molecules are attached to the graphene through supramolecular interactions; the small organic molecules have redox properties.

2. The gas-sensitive composite of claim 1, wherein the small organic molecule has a conjugated structure.

3. The gas-sensitive composite of claim 2, wherein the small organic molecules are selected from at least one of methylene blue, indigo carmine, anthraquinone-2-sulfonic acid sodium.

4. The gas-sensitive composite of any one of claims 1 to 3, wherein the supramolecular interaction is at least one of a pi-pi interaction, an electrostatic force, and hydrogen bonding assembly.

5. Process for the preparation of a gas-sensitive composite according to any of claims 1 to 4, characterized in that it comprises the following steps:

s1, dissolving graphene oxide in a solvent to prepare a graphene oxide dispersion liquid;

s2, uniformly mixing the graphene oxide dispersion liquid with the organic micromolecules and the pH regulator to obtain a first mixed liquid; the small organic molecules have redox properties; the first mixed solution is alkaline;

s3, adding a reducing agent into the first mixed solution, and carrying out reduction reaction to obtain a second mixed solution;

and S4, carrying out solid-liquid separation on the second mixed solution to obtain the gas-sensitive composite material.

6. The preparation method of the gas-sensitive composite material according to claim 5, wherein the mass ratio of the organic small molecules to the graphene oxide is (15-25): 1.

7. the preparation method of the gas-sensitive composite material according to claim 5, wherein the mass ratio of the reducing agent to the graphene oxide is (1-8): 1.

8. the method for preparing a gas-sensitive composite according to claim 7, wherein the reducing agent is selected from hydrazine hydrate.

9. A gas-sensitive electrode, characterized in that a gas-sensitive coating is arranged on the gas-sensitive electrode, and the material of the gas-sensitive coating comprises the gas-sensitive composite material as claimed in any one of claims 1 to 4.

10. A sensing device comprising the gas sensing electrode of claim 9.

Technical Field

The invention relates to the technical field of gas-sensitive materials, in particular to a gas-sensitive composite material, a preparation method thereof, a gas-sensitive electrode and sensing equipment.

Background

With the social monitoring of the environment, the control of air quality, and the increasing demand for detecting pollutants, toxic gases, and combustible gases, there is an increasing demand for chemical sensors. Commercial chemical sensors are required to have high sensitivity, fast response and recovery characteristics at the same time in practical applications.

Oxidizing gases (e.g. NO)₂) Is one of the atmospheric pollutants discharged by fuel combustion and automobile engines, and can cause a plurality of environmental problems such as dense fog, acid rain and the like. In addition, prolonged exposure to oxidizing gases (e.g., NO)₂) Can adversely affect the respiratory system and skin of the human body. Thus, nitrogen dioxide detection is receiving increasing attention. Oxidizing gases based on metal oxides (e.g. NO)₂) Sensor due to its heightThe method has the advantages that the sensitivity, the high selectivity and other excellent performances are achieved, however, the working temperature is high, the energy consumption problem exists, and great safety risks are set for the realization of wider application. Therefore, room temperature oxidizing gases (e.g., NO) were investigated₂) The sensing material has important significance.

The functionalized graphene has remarkable prospect in the aspect of gas sensors due to the large specific surface area and high carrier mobility. However, unmodified graphene has poor responsiveness and selectivity to gas, and conventional covalent bond modification destroys the inherent electrical properties of graphene, so that a method for preparing graphene oxide with oxidizing gas (such as NO) at room temperature is urgently needed₂) A fast response gas sensitive material occurs.

Disclosure of Invention

The present invention is directed to solving at least one of the problems of the prior art. Therefore, the invention provides a gas-sensitive composite material, a preparation method thereof, a gas-sensitive electrode and sensing equipment.

In a first aspect of the present invention, a gas-sensitive composite material is provided, which includes graphene and small organic molecules attached to the graphene, wherein the small organic molecules are attached to the graphene through a supramolecular interaction; the small organic molecules have redox properties.

The gas-sensitive composite material provided by the embodiment of the invention has at least the following beneficial effects: the gas-sensitive composite material utilizes organic micromolecules with redox property to modify graphene, and specifically utilizes supermolecular interaction to assemble and attach the organic micromolecules with redox property on the graphene so as to improve the sensitivity of the graphene to oxidizing gas (such as NO)₂) Responsiveness and selectivity. The gas-sensitive composite material is prepared by non-covalent bond supramolecular composite assembly between organic micromolecules with redox property and graphene, does not damage the two-dimensional planar structure of the graphene, and can keep the intrinsic electrical and thermodynamic properties of the graphene; the organic micromolecules with redox property can accelerate the electron transfer rate between graphene and oxidizing gas molecules, so that the electrical property of the material is changed, the response property of the material to the oxidizing gas is improved, and the strip at room temperature can be realizedThe sensor has quick response to oxidizing gas with certain concentration under the condition, has high sensitivity, and can be widely applied to the fields of detection of the oxidizing gas and the like.

According to some embodiments of the invention, the small organic molecule has a conjugated structure. The use of small organic molecules with conjugated structures may facilitate the transport of electrons.

According to some embodiments of the invention, the small organic molecule is selected from at least one of methylene blue, indigo carmine and anthraquinone-2-sulfonic acid sodium.

According to some embodiments of the invention, the supramolecular interaction is at least one of pi-pi interaction, electrostatic force, and hydrogen bonding assembly.

In a second aspect of the present invention, there is provided a method for preparing any one of the gas-sensitive composite materials provided in the first aspect of the present invention, comprising the steps of:

s1, dissolving graphene oxide in a solvent to prepare a graphene oxide dispersion liquid;

s2, uniformly mixing the graphene oxide dispersion liquid with the organic micromolecules and the pH regulator to obtain a first mixed liquid; the small organic molecules have redox properties; the first mixed solution is alkaline;

s3, adding a reducing agent into the first mixed solution, and carrying out reduction reaction to obtain a second mixed solution;

and S4, carrying out solid-liquid separation on the second mixed solution to obtain the gas-sensitive composite material.

The preparation method of the gas-sensitive composite material provided by the embodiment of the invention has at least the following beneficial effects: the preparation method comprises the steps of firstly modifying graphene oxide by using organic micromolecules with redox properties, specifically using the graphene oxide as a matrix material, assembling the organic micromolecules with redox properties on the graphene oxide by using supermolecular interaction, and reducing to obtain the graphene oxide material so as to improve the oxidation resistance of the graphene oxide to oxidizing gases (such as NO)₂) Responsiveness and selectivity. The preparation method has the advantages of simple raw materials and low cost; the matrix material graphene oxide is relatively friendly to the environment, and no redundant energy is consumed in the synthesis process; in addition, organic compounds having redox propertiesThe molecules and the graphene are subjected to non-covalent bond supermolecular composite assembly, the two-dimensional planar structure of the graphene cannot be damaged, and the intrinsic electrical and thermodynamic properties of the graphene can be maintained in the obtained product material; and the organic micromolecules with redox property and graphene are subjected to supramolecular composite assembly to prepare the gas-sensitive composite material, the organic micromolecules with redox property in the product material can accelerate the electron transfer rate between the graphene and the oxidizing gas molecules, so that the electrical property of the material is changed, the response performance of the material to the oxidizing gas is improved, the rapid response to the oxidizing gas with certain concentration under the room temperature condition can be realized, and the gas-sensitive composite material has high sensitivity and can be widely applied to the fields of detection of the oxidizing gas and the like.

In step S2, the graphene oxide dispersion liquid is mixed with the small organic molecules, and the graphene oxide and the small organic molecules having redox properties form a supramolecular assembly through supramolecular interaction. According to some embodiments of the invention, the mass ratio of the organic small molecule to the graphene oxide is (15-25): 1, preferably 23: 1.

in step S3, a reducing agent is added to the first mixed solution to perform a reduction reaction, whereby the supramolecular assembly in the first mixed solution is reduced to a graphene assembly modified with a small organic molecule having redox properties. According to some embodiments of the invention, the mass ratio of the reducing agent to the graphene oxide is (1-8): 1, preferably 3: 1. when the reducing agent is added, the reducing agent can be slowly added and uniformly stirred so as to ensure that the reducing agent is fully contacted with the graphene oxide in the supermolecular assembly; the reduction reaction may be carried out in a heating environment, and the heating temperature of the heating environment is generally controlled to 75 to 85 ℃.

According to some embodiments of the invention, the reducing agent is selected from hydrazine hydrate.

In addition, in step S1, water may be used as the solvent. In the process of dissolving graphene oxide in the solvent, the graphene oxide can be fully dissolved by methods such as physical stirring, shaking and ultrasonic waves, so as to obtain a stable and uniformly dispersed graphene oxide dispersion liquid. The concentration of the graphene oxide dispersion liquid is generally controlled to be 0.5-2 mg/mL, preferably 1 mg/mL.

In a third aspect of the present invention, a gas-sensitive electrode is provided, where the gas-sensitive electrode is provided with a gas-sensitive coating, and the material of the gas-sensitive coating includes any one of the gas-sensitive composite materials provided in the first aspect of the present invention.

In a fourth aspect of the invention, there is provided a sensing device comprising any one of the gas sensing electrodes provided in the third aspect of the invention.

Drawings

The invention is further described with reference to the following figures and examples, in which:

FIG. 1 is a schematic structural diagram of methylene blue, an organic small molecule, used in example 1;

FIG. 2 is a schematic structural view of a gas-sensitive composite material according to example 1;

FIG. 3 is an SEM topography for the gas-sensitive composite of example 1;

FIG. 4 shows the gas-sensitive composite materials of examples 1-3 and the gas-sensitive material of comparative example 1 for NO₂Gas-sensitive detection curve graph of gas;

FIG. 5 is a graph of the stability test results for the gas-sensitive composite of example 1;

FIG. 6 shows the gas-sensitive composite of example 1 for different concentrations of NO₂Response test results of the gas.

Detailed Description

The concept and technical effects of the present invention will be clearly and completely described below in conjunction with the embodiments to fully understand the objects, features and effects of the present invention. It is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments, and those skilled in the art can obtain other embodiments without inventive effort based on the embodiments of the present invention, and all embodiments are within the protection scope of the present invention.

Example 1

An air-sensitive composite material is prepared by using graphene oxide as a matrix material, assembling organic micromolecule methylene blue with redox property on the graphene oxide by utilizing supermolecular interaction, and reducing. The specific synthesis steps comprise:

s1, weighing a proper amount of Graphene Oxide (GO) and dissolving the graphene oxide in deionized water, and stirring to prepare a stable and completely dissolved matrix dispersion liquid with the concentration of 1 mg/mL;

s2, putting part of the prepared matrix dispersion liquid into a round-bottom flask, and then adding organic micromolecule Methylene Blue (MB) and sodium hydroxide with redox property into the round-bottom flask, wherein the mass ratio of the methylene blue to the graphene oxide is 23:1, and the mass ratio of the sodium hydroxide to the graphene oxide is 5: 1; fully contacting graphene oxide with methylene blue by stirring, wherein the graphene oxide and the methylene blue form a supramolecular assembly through supramolecular action (pi-pi action), and obtaining a first mixed solution; wherein, the structural formula of the methylene blue is as follows:the structure schematic diagram is shown in figure 1;

s3, adding a hydrazine hydrate solution into the first mixed solution obtained in the step S2, wherein the mass ratio of hydrazine hydrate to graphene oxide is 5.6: 1; then placing the graphene composite material in a heating device at the temperature of 75-85 ℃ for reduction reaction to obtain a graphene composite material modified by methylene blue; and (3) carrying out suction filtration and washing to obtain the gas-sensitive composite material (MB-rGO) of the product, wherein the structural schematic diagram is shown in figure 2.

The gas-sensitive composite material obtained above was observed with a Scanning Electron Microscope (SEM), and the obtained results are shown in fig. 3.

Example 2

The specific preparation method of the gas-sensitive composite material comprises the following steps:

s1, weighing a proper amount of Graphene Oxide (GO) and dissolving the graphene oxide in deionized water, and stirring to prepare a stable and completely dissolved matrix dispersion liquid with the concentration of 1 mg/mL;

s2, putting part of the prepared matrix dispersion liquid into a round-bottom flask, and then adding organic small-molecule Indigo Carmine (IC) with redox property and sodium hydroxide into the round-bottom flask, wherein the mass ratio of the indigo carmine to the graphene oxide is 23:1, and the mass ratio of the sodium hydroxide to the graphene oxide is 5: 1; the oxidized stone is stirredFully contacting the graphene with the indigo carmine, wherein the graphene oxide and the indigo carmine form a supramolecular assembly through supramolecular action (pi-pi action), and obtaining a first mixed solution; wherein the structure formula of the indigo carmine is as follows:

s3, adding a hydrazine hydrate solution into the first mixed solution obtained in the step S2, wherein the mass ratio of hydrazine hydrate to graphene oxide is 5.6: 1; then placing the graphene composite material in a heating device at the temperature of 75-85 ℃ for reduction reaction to obtain a graphene composite material modified by indigo carmine; and (4) performing suction filtration and impurity removal to obtain the gas-sensitive composite material (IC-rGO).

Example 3

The specific preparation method of the gas-sensitive composite material comprises the following steps:

s1, weighing a proper amount of Graphene Oxide (GO) and dissolving the graphene oxide in deionized water, and stirring to prepare a stable and completely dissolved matrix dispersion liquid with the concentration of 1 mg/mL;

s2, putting part of the prepared matrix dispersion liquid into a round-bottom flask, and then adding small organic molecular anthraquinone-2-sodium sulfonate (AQS) and sodium hydroxide with redox properties into the round-bottom flask, wherein the mass ratio of the anthraquinone-2-sodium sulfonate to the graphene oxide is 23:1, and the mass ratio of the sodium hydroxide to the graphene oxide is 5: 1; fully contacting the graphene oxide with anthraquinone-2-sodium sulfonate by stirring, wherein the graphene oxide and the anthraquinone-2-sodium sulfonate form a supermolecular assembly through supermolecular action (pi-pi action), so as to obtain a first mixed solution; wherein, the structural formula of the anthraquinone-2-sodium sulfonate is as follows:

s3, adding a hydrazine hydrate solution into the first mixed solution obtained in the step S2, wherein the mass ratio of hydrazine hydrate to graphene oxide is 5.6: 1; then placing the graphene composite material in a heating device at the temperature of 75-85 ℃ for reduction reaction to obtain a graphene composite material modified by anthraquinone-2-sodium sulfonate; and (4) performing suction filtration and impurity removal to obtain the gas-sensitive composite material (AQS-rGO).

Comparative example 1

Pure graphene (rGO) was used as gas sensitive material and as comparative example.

The gas-sensitive composite material and the gas-sensitive material prepared by the method can be applied to gas-sensitive detection, and taking the gas-sensitive composite material (MB-rGO) prepared in the embodiment 1 as an example, the method comprises the following steps:

1) dissolving the gas-sensitive composite material prepared in the embodiment 1 in deionized water, performing ultrasonic treatment to obtain stable dispersion liquid, then dripping 0.006mL of the dispersion liquid on an interdigital electrode for testing, and naturally volatilizing water in the solution at room temperature to obtain a gas-sensitive electrode for testing; the coating amount of the gas-sensitive composite material can be adjusted according to the situation;

2) and connecting the prepared gas-sensitive electrode on a gas-sensitive testing device to obtain the product sensing equipment.

Similarly, the gas sensitive material (IC-rGO) prepared in example 2, the gas sensitive material (AQS-rGO) prepared in example 3, and the gas sensitive material (rGO) in comparative example 1 were used to prepare gas sensitive electrodes and then sensor devices, respectively, according to the above methods. The prepared sensing equipment comprises a gas-sensitive electrode, wherein a gas-sensitive coating is arranged on the gas-sensitive electrode, and the material of the gas-sensitive coating is respectively corresponding to the gas-sensitive composite material or the gas-sensitive material.

The sensing device prepared by the method can be further applied to the detection of oxidizing gas, and the specific detection method comprises the following steps: the gas-sensitive electrode of the sensing device can be placed in a closed test cavity in the air atmosphere to test the initial resistance, and then oxidizing gas (NO) with a certain concentration is injected into the test cavity₂) And recording the resistance value (real-time resistance), opening the test cavity after the response is finished, recovering the air atmosphere in the test cavity, and recording the change of the gas-sensitive electrode resistance.

By adopting the method, the sensing devices prepared by respectively applying the gas-sensitive composite materials of the examples 1-3 and the gas-sensitive material of the comparative example 1 can be used for the oxidizing gas NO with the concentration of 10ppm₂Performing gas-sensitive response and recovery test to investigate NO of each gas-sensitive material by gas-sensitive detection₂The response and recovery performance of (a) are shown in fig. 4. As can be seen from FIG. 4, embodiment 1E3 gas sensitive composite to NO₂The gas has high response value, wherein the gas-sensitive composite material MB-rGO has NO₂The response time of the gas is about 100s, while the gas sensitive material (rGO) of comparative example 1 has NO response₂The gas response was not significant.

Application example 1 gas-sensitive composite (MB-rGO) the oxidizing gas NO at a concentration of 10ppm was detected according to the above method₂And a repeated test experiment was performed to perform the cycle stability test, and the results are shown in fig. 5. As can be seen from FIG. 5, the results obtained by performing multiple tests on the gas-sensitive composite material (MB-rGO) prepared in example 1 in the same environment are substantially consistent, so that the application of the gas-sensitive composite material in NO can be proved₂The gas detection has good cycle stability.

Sensing devices made with the gas sensitive composite (MB-rGO) of example 1 were tested for different concentrations (0.5ppm, 1ppm, 2ppm, 4ppm, 6ppm, 8ppm, 10ppm) of NO₂The gas is subjected to response test to investigate the gas-sensitive composite material for different concentrations of NO₂The response performance of the gas, the results obtained are shown in FIG. 6; FIG. 6 (a) shows the gas sensitive composite for different concentrations of NO₂Gas response data, (b) shows the gas-sensitive composite material versus NO₂Response data of gas and NO₂Relationship of gas concentration. As can be seen from FIG. 6, the gas sensitive composite (MB-rGO) of example 1 has a low detection limit (as low as 0.5ppm) and it has NO₂The gas response has a linear relationship with concentration.

The embodiments of the present invention have been described in detail with reference to the accompanying drawings, but the present invention is not limited to the above embodiments, and various changes can be made within the knowledge of those skilled in the art without departing from the gist of the present invention.