CN115165977A - Gas sensing nano composite material, preparation method and application method - Google Patents
Gas sensing nano composite material, preparation method and application method Download PDFInfo
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- RJNPRNCPYHCHHV-UHFFFAOYSA-N cobalt(2+) dinitrate tetrahydrate Chemical compound O.O.O.O.[Co+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O RJNPRNCPYHCHHV-UHFFFAOYSA-N 0.000 description 1
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- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/02—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance
- G01N27/04—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance
- G01N27/12—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance of a solid body in dependence upon absorption of a fluid; of a solid body in dependence upon reaction with a fluid, for detecting components in the fluid
- G01N27/125—Composition of the body, e.g. the composition of its sensitive layer
- G01N27/127—Composition of the body, e.g. the composition of its sensitive layer comprising nanoparticles
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Abstract
The invention provides a gas sensing nano composite material, a preparation method and an application method thereof, belonging to the field of nano sensing materials and preparation. The composite material is formed by compounding a P-type semiconductor metal oxide and graphene oxide through a hydrothermal synthesis method, the mass ratio of the P-type semiconductor metal oxide to the graphene oxide is 40-200, the P-type semiconductor metal oxide nanoparticles are stably loaded on two sides of a graphene oxide nanosheet after calcination by virtue of the bridging effect of salicylate in the hydrothermal reaction process, a contact interface of the P-type semiconductor metal oxide nanoparticles and the graphene oxide forms a hybrid structure, and meanwhile, the nanoparticles loaded on the surface of the graphene oxide are stacked to form a nanopore structure; the size of the nano particles is 3-12 nm; the heterogeneous interface has adsorption sites for selective gas molecules and has high carrier mobility. The gas sensing nano composite material has high specific surface area, abundant surface properties and high electron transfer rate, reduces the resistance of the material, improves the gas sensitivity performance, and reduces the working temperature and power consumption.
Description
Technical Field
The invention belongs to the field of nano sensing materials and preparation, and particularly relates to a gas sensing nano composite material, a preparation method and an application method thereof.
Background
With the advance of industrialization, more and more harmful gases, such as formaldehyde, volatile organic compounds and the like, are released in the air environment where people live and work. Therefore, there is a need for formaldehyde in the environmentAnd the content of harmful gases is monitored in real time to avoid irreversible damage to human bodies. Gas sensors are commonly used to monitor the content of harmful gases in the air. As a typical gas sensor, the chemical resistance type gas sensor senses harmful gas in the environment through selective gas sensitive material on the surface and converts the concentration of the harmful gas into corresponding signals (respectively detecting the resistance R of the semiconductor gas sensitive material in the air) a And its resistance R in a gas atmosphere to be measured of a specific concentration g ) Thereby obtaining a response value of the specific gas concentration (N-type semiconductor gas sensitive response value: r a /R g P-type semiconductor response value: r is g /R a )。
In the prior art, a P-type semiconductor metal oxide such as cobalt oxide is taken as a typical gas sensing material, has narrower band gap width and outstanding catalytic performance, and can be taken as a sensitive coating material in gas sensing application; however, a gas sensor based on a single semiconductor metal oxide often has disadvantages of high operating temperature, low response sensitivity, and the like, and the device has high requirements for operating environment such as temperature and humidity. Meanwhile, the currently synthesized P-type semiconductor metal oxide for the gas sensor is generally micron-sized particles, has a low specific surface area, is not favorable for gas diffusion, has a small contact area with gas, is difficult to provide abundant surface catalytic sites, and limits the sensing performance of the sensor.
Disclosure of Invention
In view of the above-mentioned defects or shortcomings in the prior art, the present invention aims to provide a gas sensing nanocomposite material, a preparation method and an application method thereof, which optimize sensing performance by compounding a gas sensing material with other materials, not only fully consider the mutual cooperation between the composite materials in a synthetic bond type, but also consider the performance optimization which can be realized by structural cooperation, reduce the working temperature of the gas sensing material, and improve the sensitivity.
In order to achieve the above purpose, the embodiment of the present invention adopts the following technical solutions:
in a first aspect, the embodiment of the invention provides a preparation method of a gas sensing nano composite material, which comprises the steps of taking metal salt and graphene oxide as raw materials, taking ethanol as a solvent, synthesizing small-sized P-type semiconductor metal oxide loaded graphene oxide porous composite nano particles by a one-step hydrothermal method, adsorbing solvent molecules by hydrogen bonds to gather on the surfaces of the metal oxide nano particles to inhibit the nano particles from further growing up, realizing the combination of the metal oxide and the graphene oxide by the hydrogen bonds, dispersing the P-type semiconductor metal oxide on two sides of the graphene oxide to reduce the gathering of the metal oxide, and inhibiting the gathering of the metal oxide nano particles; the contact interface of the graphene oxide and the metal oxide nanoparticles forms a hybrid structure, so that the gas-sensitive performance of the gas sensing nanocomposite is improved. Meanwhile, the high specific surface area of the graphene oxide is beneficial to generating a large number of graphene oxide/metal oxide heterogeneous interfaces with hybrid structures, more adsorption active sites are provided for gas molecules, and carrier migration is promoted, so that the gas sensing performance of the P-type semiconductor metal oxide is effectively improved. In addition, the graphene oxide is used as an excellent conductor, and the P-type semiconductor metal oxide can reduce the baseline resistance and reduce the working energy consumption by compounding with the graphene oxide.
The preparation method of the gas sensing nano composite material comprises the following steps:
step S1, stirring and dissolving a metal salt precursor in absolute ethyl alcohol, and slowly adding ammonia water and sodium salicylate under continuous stirring to obtain a metal salt ethanol solution;
s2, adding graphene oxide into absolute ethyl alcohol according to a preset proportion, and performing ultrasonic dispersion for 30-60 min to obtain a graphene oxide ethanol solution;
s3, pouring the graphene oxide ethanol solution into the metal salt ethanol solution for mixing, and transferring the mixed solution into a reaction kettle for hydrothermal reaction; in the reaction process, the carboxyl of the sodium salicylate is anchored on the surface of the metal oxide nano-particles, and meanwhile, the benzene ring of the sodium salicylate and the graphene oxide have pi-pi action, so that the metal oxide nano-particles and the graphene oxide are compounded, and the growth of the metal oxide nano-particles is inhibited;
and S4, cooling and centrifuging the solution obtained through the hydrothermal reaction, cleaning and drying the obtained solute, and calcining the solute in a muffle furnace at 350-500 ℃ to obtain the gas sensing nanocomposite material with the P-type semiconductor metal oxide nanoparticles loaded with graphene oxide. The particle size of the obtained nanocomposite is 3 to 12nm.
In the step S1, the metal salt precursor comprises at least one of cobalt acetate tetrahydrate, copper nitrate pentahydrate and nickel nitrate hexahydrate; the concentration of the metal salt ethanol solution is 0.02-0.1g/ml, and the stirring time is 30-60 min; the concentration of the graphene oxide ethanol solution is (0.02-1) multiplied by 10 -3 g/ml, and the ultrasonic time is 30-120 min. The size of the nano particles is accurately regulated and controlled by regulating and controlling the amount of the precursor and the solvent, and the particle size of the nano particles is 3-12 nm. By controlling the size of the nano-particles, oxygen molecules in the air fully react with conduction band electrons of the metal oxide nano-particles at the working temperature and are converted into active oxygen ions adsorbed on the surface in situ, so that a hole accumulation layer of a semiconductor material is increased, and the resistance of the material is sharply reduced (R) a ) After the surface oxidation reaction by contact with the reducing gas, the hole accumulation layer becomes thin due to the injection of electrons, and the material resistance is remarkably increased (R) g ) Thereby remarkably improving the gas sensitive response value (R) g /R a )。
In the step S2, the mass ratio of the metal salt precursor to the graphene oxide is converted into a mass ratio of the metal oxide to the graphene oxide of 40-200.
In the step S3, the mixed solution is stirred for 30-60 min; the hydrothermal reaction temperature is 150 ℃, and the hydrothermal reaction time is 3-5 h.
In the step S4, the cleaning solvent is absolute ethyl alcohol, the centrifugal rotating speed is 8000-10000 rpm, the centrifugal time is 10-30min, the drying temperature is 70-100 ℃, and the drying time is 12-24 h.
The preparation method has the advantages of simple and efficient process and high yield, and the prepared gas sensing nano composite material has good uniformity, low working temperature and excellent gas sensitivity.
In a second aspect, embodiments of the present invention further provide a gas sensing nanocomposite, where the gas sensing nanocomposite is formed by compounding P-type semiconductor metal oxide nanoparticles and graphene oxide by a hydrothermal method, a mass ratio of the metal oxide to the graphene oxide is 40-200, the P-type semiconductor metal oxide nanoparticles are stably loaded on two sides of the graphene oxide nanosheets after calcination by virtue of a bridging effect of salicylate during a hydrothermal reaction, a contact interface between the two forms a hybrid structure, and the metal oxide nanoparticles loaded on the surface of the graphene oxide are stacked together to form a nanopore structure. The graphene oxide-based single-layer structure comprises nanoparticles with large specific surface area, and the size of the nanoparticles is 3-12 nm; the high specific surface area of the graphene oxide is beneficial to generating a large number of graphene oxide/metal oxide heterogeneous interfaces, more adsorption active sites are provided for selective gas molecules, and meanwhile, the heterogeneous interfaces are provided with carrier migration channels in direct proportion to the surface area, so that carrier migration can be effectively promoted.
The gas sensing nanocomposite provided by the embodiment utilizes the bridging function of sodium salicylate, namely, in the hydrothermal synthesis process, carboxylate radicals of sodium salicylate can be anchored on the surface of metal nanoparticles, so that particles are prevented from growing too fast and large particles are prevented from growing, and particles with the particle size of 3-12nm are obtained. On the other hand, the benzene ring of the sodium salicylate can generate pi-pi action with the graphene oxide, so that the nano particles and the graphene oxide nano sheets can be effectively compounded, namely, the sodium salicylate acts with the nano particles on one hand and acts with the graphene on the other hand, and a bridging effect is achieved.
Through the compounding of the P-type semiconductor metal oxide and the graphene oxide, the obtained gas sensing nano composite material has the advantages of high specific surface area, abundant surface properties and high electron transfer rate, the resistance of the material is reduced, the energy consumption is reduced, the surface catalytic reaction is promoted and the working temperature is reduced by introducing more oxygen vacancies, and the gas-sensitive performance is improved.
In a third aspect, an embodiment of the present invention further provides an application method of the gas sensing nanocomposite, where the gas sensing nanocomposite is applied to preparation of a gas sensor.
Specifically, the steps of preparing the gas sensor by using the gas sensing nanocomposite material are as follows:
step S21, mixing 20-50 mg of P-type semiconductor metal oxide nanoparticle-loaded graphene oxide porous composite material and absolute ethyl alcohol in a mortar, grinding into paste, and uniformly coating the paste material on Al with two annular gold electrodes by using a brush 2 O 3 Drying the surface of the ceramic tube;
step S22, passing Ni-Cr heating wires through Al 2 O 3 And welding the ceramic tube on a circuit board, and aging to obtain the gas sensor.
When the prepared gas sensor is used for monitoring gas, oxygen molecules in the air fully react with conduction band electrons of metal oxide nano particles at the working temperature and are converted into active oxygen ions adsorbed on the surface in situ, so that a hole accumulation layer of a semiconductor material is increased, and the resistance of the material is sharply reduced (R) a ) After the surface oxidation reaction by contact with the reducing gas, the hole accumulation layer becomes thin due to the injection of electrons, and the material resistance is remarkably increased (R) g ) Thereby remarkably improving the gas sensitive response value (R) g /R a ) (ii) a (ii) a The response value of the sensor to 50ppm formaldehyde at low temperature of 78 ℃ reaches 4.3, which is much higher than the gas-sensitive performance (1.60) of single P-type semiconductor metal oxide.
The embodiment of the invention has the following beneficial effects:
according to the gas sensing nano composite material, the preparation method and the application method, in the preparation process, P-type semiconductor metal oxide nano particles are stably loaded on two sides of the graphene oxide nanosheets by virtue of the bridging effect of salicylate, the contact interfaces of the P-type semiconductor metal oxide nano particles and the graphene oxide nanosheets form a hybrid structure, and meanwhile, the metal oxide nano particles loaded on the surfaces of the graphene oxide are stacked to form a nano-pore structure; the prepared gas sensing nano composite material has strong selectivity to sensitive gas, so that the gas sensor prepared by applying the nano composite material has low working temperature and excellent gas-sensitive performance.
Of course, it is not necessary for any product or method to achieve all of the above-described advantages at the same time for practicing the invention.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.
Fig. 1 is an SEM image of a graphene oxide composite material supported by cobalt oxide nanocrystals synthesized in example 1 of the present invention;
fig. 2 is a TEM image of the cobalt oxide nanocrystal loaded graphene oxide composite material synthesized in example 1 of the present invention;
FIG. 3 is a drawing showing nitrogen adsorption-desorption of the gas sensing nanocomposite material of example 1 of the present invention;
FIG. 4 is a pore size distribution diagram of the gas sensing nanocomposite material of example 1 of the present invention;
fig. 5 is a graph of the concentration resistance of the cobalt oxide nanocrystals loaded on the graphene oxide composite material in example 1 of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention. It is to be understood that the described embodiments are merely a few embodiments of the invention, and not all embodiments. The components of embodiments of the present invention generally described and illustrated in the figures herein may be arranged and designed in a wide variety of different configurations. It should be noted that the embodiments and features of the embodiments of the present invention may be combined with each other without conflict.
It should be noted that: like reference numbers and letters refer to like items in the following figures, and thus, once an item is defined in one figure, it need not be further defined and explained in subsequent figures. In the description of the present invention, the terms "first," "second," "third," "fourth," etc. are used merely to distinguish one description from another, and are not intended to indicate or imply relative importance.
Example 1
The embodiment provides a gas sensing nano composite material, a preparation method and an application method.
The gas sensing nano composite material is formed by compounding cobalt oxide nano particles (3 nm) loaded on graphene oxide, the mass ratio of the cobalt oxide nano particles to the graphene oxide nano particles is 85, the p-type semiconductor metal oxide cobalt oxide nano particles are stably loaded on two sides of a graphene oxide nano sheet by virtue of the bridging effect of salicylate, the contact interfaces of the cobalt oxide nano particles and the graphene oxide nano sheet form a hybrid structure, and the cobalt oxide nano particles loaded on the surface of the graphene oxide are stacked to form a nano-pore structure.
The preparation method of the gas sensing nano composite material comprises the following steps:
step S1, dissolving 0.5g of cobalt nitrate tetrahydrate in 15mL of absolute ethanol under the condition of continuous stirring; adding 2.5mL of ammonia water and 10mg of sodium salicylate into the cobalt nitrate ethanol solution under the condition of continuous stirring;
s2, dispersing 6mg of graphene oxide in 10mL of absolute ethanol, and performing ultrasonic dispersion for 30min to obtain a graphene oxide ethanol solution;
s3, pouring the oxidized graphene ethanol solution into a cobalt nitrate ethanol solution for mixing, transferring the mixed solution into a reaction kettle for hydrothermal reaction, and carrying out hydrothermal treatment for 3 hours at 150 ℃;
and S4, cooling the solution obtained by the reaction, centrifuging at 9000rpm, cleaning and drying to obtain the gas sensing nano composite material of the graphene oxide-loaded cobalt oxide nanoparticles.
The application method of the gas sensing nano composite material comprises the following steps of:
step S21, grinding 50mg of the gas sensing nanocomposite material and absolute ethyl alcohol into paste in a mortar, and uniformly coating the paste on Al with a pair of gold electrodes 2 O 3 Curing the mixture on a ceramic tube for 2 hours in an oven at 70 ℃;
step S22, passing Ni-Cr heating wires through Al 2 O 3 Welding ceramic tube on card-inserted substrate at 150 deg.CAnd taking 2 days to obtain the gas sensor.
And performing performance characterization on the prepared gas sensing nano composite material and the gas sensor. As shown in fig. 1 and fig. 2, the cobalt oxide nanoparticles are highly dispersed on the surface of the two-dimensional graphene oxide, and the particle size is relatively uniform, and particularly, there are no cobalt oxide nanoparticles scattered around the graphene oxide nanosheets, which indicates that the two are stably compounded together.
Preparing a gas sensor by taking the synthesized graphene oxide-loaded cobalt oxide nanoparticles as a gas sensing nanocomposite, testing the gas-sensitive performance of the gas sensor, and monitoring 50ppm of formaldehyde under the condition of low temperature (78 ℃); as shown in fig. 3, the synthesized composite material has a typical IV-type nitrogen adsorption-desorption isotherm for nitrogen, which indicates that the material has a nanopore structure; as shown in fig. 4, the synthesized composite material has a narrow pore size distribution curve, and the pore size is about 3.76nm; as shown in FIG. 5, the prepared gas sensor has a gas-sensitive response value of 4.30 under the test condition of low temperature (78 ℃), and has high response and recovery speed for 50ppm of formaldehyde.
Example 2
The embodiment provides a gas sensing nano composite material, a preparation method and an application method.
The gas sensing nano composite material is formed by compounding copper oxide nano particles (6 nm) loaded on graphene oxide, the mass ratio of the copper oxide nano particles to the graphene oxide nano sheets is 100, the copper oxide nano particles are uniformly distributed on two sides of the graphene oxide nano sheets, a contact interface of the copper oxide nano particles and the graphene oxide nano sheets forms a hybrid structure, nano crystal particles with large specific surface area are formed on the basis of a single-layer structure of the graphene oxide, adsorption sites of selective gas molecules are arranged on the surfaces of the particles, and a carrier migration channel in direct proportion to the surface area is arranged on the surfaces of the particles.
The preparation method of the gas sensing nano composite material comprises the following steps:
step S1, dissolving 0.5g of copper nitrate pentahydrate in 15mL of absolute ethanol under the condition of continuous stirring; adding 2.5mL of ammonia water and 10mg of sodium salicylate into the cupric nitrate ethanol solution under the condition of continuous stirring;
s2, dispersing 6mg of graphene oxide in 10mL of absolute ethanol, and performing ultrasonic dispersion for 30min to obtain a graphene oxide ethanol solution;
s3, pouring the graphene oxide ethanol solution into the copper nitrate ethanol solution for mixing, transferring the mixed solution into a reaction kettle for hydrothermal reaction, and carrying out hydrothermal treatment at 150 ℃ for 3 hours;
and S4, cooling the solution obtained by the reaction, centrifuging at 9000rpm, cleaning and drying to obtain the copper oxide nanoparticle-loaded graphene oxide nanosheet gas sensing nanocomposite.
The application method of the gas sensing nano composite material comprises the following steps of:
step S21, grinding 50mg of the gas sensing nanocomposite material and absolute ethyl alcohol into paste in a mortar, and uniformly coating the paste on Al with a pair of gold electrodes 2 O 3 Curing the mixture on a ceramic tube in an oven at 70 ℃ for 2 hours;
step S22, passing Ni-Cr heating wires through Al 2 O 3 And welding the ceramic tube on the plug-in type substrate, and aging at 150 ℃ for 2 days to obtain the gas sensor.
And performing performance characterization on the prepared gas sensing nano composite material and the gas sensor, and monitoring 2.5-100ppm of hydrogen sulfide by using the prepared gas sensor under the test condition of 120 ℃. The monitoring result shows that the response value of the gas sensor prepared by the embodiment to 50ppm hydrogen sulfide reaches 25 under the condition of 100 ℃, and the response recovery speed is high.
Example 3
The embodiment provides a gas sensing nano composite material, a preparation method and an application method.
The gas sensing nano composite material is formed by compounding oxidized graphene loaded with ferric oxide nano particles (11 nm), the mass ratio of the ferric oxide nano particles to the oxidized graphene is 200.
The preparation method of the gas sensing nano composite material comprises the following steps:
step S1, dissolving 0.5g of ferric nitrate pentahydrate in 15mL of absolute ethanol under the condition of continuous stirring; adding 2.5mL of ammonia water and 10mg of sodium salicylate into the cupric nitrate ethanol solution under the condition of continuous stirring;
s2, dispersing 6mg of graphene oxide in 10mL of absolute ethanol, and performing ultrasonic dispersion for 30min to obtain a graphene oxide ethanol solution;
s3, pouring the graphene oxide ethanol solution into the ferric nitrate ethanol solution for mixing, transferring the mixed solution into a reaction kettle for hydrothermal reaction, and carrying out hydrothermal treatment at 150 ℃ for 3 hours;
and S4, cooling the solution obtained by the reaction, centrifuging at 9000rpm, cleaning and drying to obtain the oxidized graphene nanosheet gas sensing nanocomposite loaded with ferric oxide nanoparticles.
The application method of the gas sensing nano composite material comprises the following steps of:
step S21, grinding 50mg of the gas sensing nanocomposite material and absolute ethyl alcohol into paste in a mortar, and uniformly coating the paste on Al with a pair of gold electrodes 2 O 3 Curing the mixture on a ceramic tube in an oven at 70 ℃ for 2 hours;
step S22, passing Ni-Cr heating wires through Al 2 O 3 And welding the ceramic tube on the plug-in type substrate, and aging at 150 ℃ for 2 days to obtain the gas sensor.
And performing performance characterization on the prepared gas sensing nano composite material and the gas sensor, and monitoring 25-800ppm of ethanol by using the prepared gas sensor under the test condition of 100 ℃. The monitoring result shows that the gas sensor prepared by the embodiment has a gas sensitivity response value of 36 to 50ppm of ethanol under the condition of 250 ℃, and the response recovery speed is high.
The above description is only a preferred embodiment of the invention and an illustration of the applied technical principle and is not intended to limit the scope of the claimed invention but only to represent a preferred embodiment of the invention. It will be appreciated by those skilled in the art that the scope of the invention herein disclosed is not limited to the particular combination of features described above, but also encompasses other arrangements formed by any combination of the above features or their equivalents without departing from the spirit of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments of the present invention without making any creative effort, shall fall within the protection scope of the present invention.
Claims (9)
1. A gas sensing nanocomposite material is characterized in that the gas sensing nanocomposite material is formed by compounding a P-type semiconductor metal oxide and graphene oxide through a hydrothermal method, the mass ratio of the metal oxide to the graphene oxide is 40-200, the P-type semiconductor metal oxide nanoparticles are stably loaded on two sides of a graphene oxide nanosheet after calcination through the bridging effect of salicylate radicals in the hydrothermal reaction process, the contact interface of the metal oxide nanoparticles and the graphene oxide nanosheet forms a hybrid structure, and meanwhile, the metal oxide nanoparticles loaded on the surface of the graphene oxide are stacked to form a nanopore structure; the size of the nano particles is 3-12 nm; the heterogeneous interface of the nano particles and the graphene oxide has adsorption sites for selective gas molecules, and has a carrier migration channel in proportion to the surface area.
2. A preparation method of a gas sensing nano composite material is characterized by comprising the following steps:
step S1, stirring and dissolving a metal salt precursor in absolute ethyl alcohol, and dropwise adding ammonia water and sodium salicylate under continuous stirring to obtain a metal salt ethanol solution;
s2, adding graphene oxide into the absolute ethanol solution according to a preset proportion, and performing ultrasonic dispersion for 30-60 min to obtain a graphene oxide ethanol solution;
s3, pouring the oxidized graphene ethanol solution into the metal salt ethanol solution for mixing, transferring the mixed solution into a reaction kettle for hydrothermal reaction, wherein in the reaction process, carboxyl of sodium salicylate is anchored on the surface of the metal oxide nano-particles, and meanwhile, benzene ring of the sodium salicylate and the oxidized graphene generate pi-pi action, so that the metal oxide nano-particles and the oxidized graphene are compounded, and the growth of the metal oxide nano-particles is inhibited;
and S4, cooling the solution obtained by the hydrothermal treatment, centrifuging, cleaning and drying to obtain the gas sensing nano composite material of which the P-type semiconductor metal oxide nano particles are loaded on the graphene oxide.
3. The method of claim 2, wherein in step S1, the metal salt precursor comprises at least one of cobalt acetate tetrahydrate, copper nitrate pentahydrate, and nickel nitrate hexahydrate.
4. The method for preparing the gas sensing nanocomposite material according to claim 2, wherein the concentration of the metal salt ethanol solution is 0.02 to 0.1g/ml, and the stirring time is 30 to 60min; the concentration of the graphene oxide ethanol solution is (0.02-1) multiplied by 10 -3 g/ml, and the ultrasonic time is 30-120 min.
5. The method for preparing a gas-sensing nanocomposite material according to claim 2, wherein in step S2, the predetermined ratio, the mass ratio of the metal salt precursor to the graphene oxide, is 40 to 200 in terms of the mass ratio of the metal oxide to the graphene oxide.
6. The method for preparing the gas sensing nanocomposite material according to claim 3, wherein in the step S3, the mixed solution is stirred for 30-60 min; the hydrothermal reaction temperature is 150 ℃, and the hydrothermal reaction time is 3-5 h.
7. The method for preparing the gas sensing nanocomposite material according to claim 3, wherein in the step S4, the cleaning solvent is absolute ethyl alcohol, the centrifugal rotation speed is 8000-10000 rpm, the centrifugal time is 10min, the drying temperature is 70-100 ℃, and the drying time is 12-24 h.
8. A method of using a gas sensing nanocomposite material, wherein the gas sensing nanocomposite material according to claims 1-2 is used to manufacture a gas sensor.
9. The method for using a gas-sensing nanocomposite material according to claim 8, wherein the step of preparing a gas sensor is as follows:
step S21, mixing 20-50 mg of P-type semiconductor metal oxide nanoparticle-graphene oxide composite material and absolute ethyl alcohol in a mortar, grinding into paste, and uniformly coating the paste on Al with two annular gold electrodes by using a brush 2 O 3 Drying the surface of the ceramic tube;
step S22, passing Ni-Cr heating wires through Al 2 O 3 And welding the ceramic tube on the circuit board, and aging to obtain the gas sensor.
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