CN113120890A - Preparation method and application of graphene and titanium oxide nanocomposite - Google Patents
Preparation method and application of graphene and titanium oxide nanocomposite Download PDFInfo
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Abstract
The invention provides a preparation method of a graphene and titanium oxide nano composite material. The invention further provides a graphene and titanium oxide nanocomposite and application thereof as a gas sensitive material in a gas sensor. The invention also provides a gas sensor. The preparation method and the application of the graphene and titanium oxide nanocomposite provided by the invention can effectively improve the gas-sensitive performance of the material and effectively improve the sensing capability and the gas-sensitive response capability of the material. The prepared gas sensor has excellent response performance to different gases, and has excellent stability and recovery characteristics.
Description
Technical Field
The invention belongs to the technical field of gas sensors, relates to a preparation method and application of a graphene and titanium oxide nano composite material, and particularly relates to mesoporous titanium oxide (mTiO) serving as a gas sensitive material2) A preparation method of a graphene aerogel coated nanocomposite and application of the graphene aerogel coated nanocomposite in a gas sensor.
Background
With the rapid development of science and technology and industry, in the daily production and life of people, Volatile Organic Compounds (VOC) are often contacted, and the VOC gas has great harm to the health of human bodies. When the VOC gas in a certain space reaches a certain concentration, the health of people is affected, symptoms such as fatigue, dizziness, muscle weakness and the like can appear, symptoms such as convulsion, coma and the like can be caused in severe cases, and even nerves and kidneys of people can be damaged. Therefore, it is necessary to detect the concentration of VOC gas in a certain environment, and development of a gas sensor having excellent performance is very important for production, living and medical diagnosis.
Among gas sensors, a semiconductor metal oxide type gas sensor has been widely studied because of its high sensitivity, good stability and rapid detection capability for various gases. WO3，TiO2，In2O5And SnO2And the metal oxides are common gas sensing materials by virtue of the characteristics of low price, abundant resources, stable performance and the like. Wherein the TiO is2As an n-type wide band gap semiconductor material with a porous structure, the material has the advantages of high stability, no toxicity, rich sources, low cost and the like, and is widely applied to formaldehyde and NH3And detection of harmful gases such as acetone. In addition, a great deal of research shows that the combination of the metal oxide and other materials forms a physical interface (such as a heterojunction) between two different materials, so that the gas sensing performance of the metal oxide can be effectively improved. Graphene as novel two-dimensional carbon-based materialHaving a unique structure and excellent properties, is considered to be one of the outstanding candidates for sensor materials. The combination of the metal oxide and the graphene or the derivative thereof can enhance the gas sensing capability by improving the adsorption/desorption capability of the combined molecule, the carrier transfer and the formation of a local heterojunction; in addition, the electronic characteristic and the gas sensitivity characteristic of the graphene can be improved by compounding the graphene and the metal oxide, so that the compounding of the metal oxide and the graphene has wide research prospects in the field of gas sensors.
Disclosure of Invention
In view of the above-mentioned disadvantages of the prior art, the present invention is directed to a method for preparing a graphene and titanium oxide nanocomposite and the application thereof, which is prepared from mesoporous titanium oxide (mTiO)2) The graphene aerogel-coated nanocomposite serves as a sensitive material, and has uniform TiO with multi-level holes2The mesoporous material and the high specific surface area and pore volume can form a local heterojunction, so that the sensing capability and the response capability of the gas can be effectively enhanced, and the problems of low response speed and poor stability of the existing gas sensor are solved.
To achieve the above and other related objects, a first aspect of the present invention provides graphene and titanium oxide (GA @ mTiO)2) The preparation method of the nano composite material comprises the following steps:
1) carrying out self-assembly reaction on Graphene Aerogel (GA) and a titanium source in the presence of a soft template, a chelating agent and a reaction solvent;
2) curing and calcining the product obtained in the step 1) to provide a nanocomposite;
the titanium source is titanium dioxide; the soft template is a diblock copolymer PEO-b-PS; the chelating agent is acetylacetone.
Preferably, in step 1), the preparation method of the graphene aerogel comprises: and carrying out hydrothermal reaction and freeze drying on the graphene oxide dispersion liquid.
More preferably, the concentration of graphene oxide in the graphene oxide dispersion liquid is 0.5-3.0mg/mL, preferably 1.0-2.0 mg/mL.
The graphene oxide in the graphene oxide dispersion liquid is synthesized by taking natural graphite powder as a raw material and adopting a Hummers method. The CAS number of the graphene oxide is 7782-42-5. The graphene aerogel is an auxiliary template.
More preferably, the graphene oxide dispersion liquid is stored in a hydrothermal kettle and placed in an oven for hydrothermal reaction.
More preferably, the amount of the graphene oxide dispersion used in the hydrothermal reaction is 5-20mL, preferably 8-16 mL.
More preferably, the reaction temperature of the hydrothermal reaction is 100-200 ℃.
More preferably, the reaction time of the hydrothermal reaction is 10-20 h.
More preferably, the temperature of the freeze-drying is-20 to-40 ℃. The freeze-drying is to remove moisture.
More preferably, the freeze-drying time is 12-24h, preferably 24 h.
Preferably, in step 1), the chemical structural formula of the polyethylene oxide-b-polystyrene (PEO-b-PS) is as follows:
in the structural formula, n is more than 0, and m is more than 0.
The PEO-b-PS is an amphiphilic block copolymer, is synthesized by adopting Atom Transfer Radical Polymerization (ATRP) and is used as a soft template.
More preferably, in the PEO-b-PS, the polymerization degree n of the PEO is 100-140, and the polymerization degree m of the PS is 160-200.
Preferably, in step 1), the molecular weight of the PEO-b-PS is 20000-30000 g/mol.
Preferably, in step 1), the reaction solvent is an organic solvent.
More preferably, the reaction solvent is selected from a combination of one or more of alcohol solvents and ether solvents, preferably from a combination of alcohol solvents and ether solvents, and more preferably from a combination of ethanol and tetrahydrofuran.
Preferably, in the step 1), the mass ratio of the added PEO-b-PS to the added graphene aerogel is 0.05-0.5: 0.02-0.04.
Preferably, in step 1), the ratio of the added mass of the PEO-b-PS to the titanium dioxide is 0.05-0.5: 0.2-0.8.
Preferably, in the step 1), the mass ratio of the titanium dioxide to the acetylacetone is 0.2-0.8: 0.2-1.0.
Preferably, in step 1), the reaction temperature of the self-assembly reaction is room temperature. The room temperature is 20-30 ℃.
Preferably, in step 1), the reaction time of the self-assembly reaction is 1-4 h. The solvent in the PEO-b-PS solution and the titanium dioxide solution is convenient to volatilize.
The self-assembly reaction is to guide TiO through volatilization of solvent and capillary action2And self-assembling the precursor hydrolysis and polycondensation products on the surface of the sheet layer of the graphene aerogel.
Preferably, in step 1), the PEO-b-PS may be first mixed with a titanium source, a reaction solvent, to provide a PEO-b-PS solution.
More preferably, the ratio of the mass g of PEO-b-PS added to the volume mL of reaction solvent added is 0.05-0.5: 2-15.
More preferably, the reaction solvent is an ethereal solvent, preferably Tetrahydrofuran (THF).
More preferably, the time for stirring and mixing the PEO-b-PS, the titanium source and the reaction solvent is 10-40min, and preferably 10 min.
Preferably, in step 1), the titanium dioxide may be first mixed with a chelating agent, a reaction solvent, to provide a titanium dioxide solution.
More preferably, the titanium dioxide (TiO)2) The mass ratio of the added reaction solvent to the added reaction solvent is 0.2-0.8: 0.4-1.2.
More preferably, the reaction solvent is an alcoholic solvent, preferably ethanol.
More preferably, the time for stirring and mixing the titanium dioxide, the chelating agent and the reaction solvent is 10-30 min.
When the above PEO-b-PS solution is mixed with the titanium dioxide solution, the PEO-b-PS solution is rapidly added to the titanium dioxide solution.
In the step 2), the product is the graphene aerogel taken out after the self-assembly reaction.
Preferably, in step 2), the reaction temperature of the curing is 80-150 ℃.
Preferably, in step 2), the reaction time for curing is 18-24 h.
Preferably, in step 2), the curing reaction device is an oven.
The TiO self-assembled on the surface of the sheet layer of the graphene aerogel is solidified2The product of hydrolysis and polycondensation of the precursor is solidified to give GA @ TiO having an amorphous skeleton structure2A composite material.
Preferably, in step 2), the atmosphere of the calcination is an inert atmosphere, preferably an Ar atmosphere.
Preferably, in step 2), the reaction temperature of the calcination is 400-600 ℃.
Preferably, in step 2), the reaction time of the calcination is 1-4 h.
The above calcination enables the formation of GA @ TiO having an amorphous skeleton structure2Composite material transformed into GA @ mTiO having ordered mesostructure2A nanocomposite material.
The second aspect of the present invention provides graphene and titanium oxide (GA @ mTiO)2) A nanocomposite prepared by the above method.
The third aspect of the present invention provides graphene and titanium oxide (GA @ mTiO)2) Use of a nanocomposite material as a gas sensitive material in a gas sensor.
In a fourth aspect, the present invention provides a gas sensor comprising the above gas-sensitive material.
The preparation method of the gas sensor comprises the following steps:
A) the GA @ mTiO2Adding an organic solvent into the nano composite material, mixing and grinding to obtain slurry;
B) and coating the slurry on the surface of the gas sensor, and drying and aging.
Preferably, in step A), the GA @ mTiO2The ratio of the added mass mg of the nano composite material to the added volume mL of the organic solvent is 30-60: 1-10.
Preferably, in step a), the organic solvent is ethanol.
Preferably, in step a), the time of milling is 20 to 30 min.
In the step A), the slurry is viscous.
Preferably, in step B), the thickness of the slurry coated on the surface of the gas sensor is 10-40 μm.
And in the step B), the slurry is coated on the surface of the gas sensor by adopting a hairbrush with a thin head to form a sensitive layer, and the surface cannot have obvious gaps and cracks.
In the step B), the slurry is coated on the surface of the gas sensor, namely the slurry is coated on the surface of a ceramic tube of the gas sensor and covers Au electrodes and Pt leads on two sides of the ceramic tube. The Pt wire is welded on the test base, and a Ni-Cr alloy heating wire is placed in the ceramic tube to control the working temperature of the sensor.
Preferably, in the step B), the drying comprises secondary drying which is sequentially carried out, the temperature of the primary drying is 80-160 ℃, and the time of the primary drying is 1-4 h; the temperature of the second drying is 100-200 ℃, and the time of the second drying is 18-24 h.
The drying is carried out in an oven.
The first drying is used for removing moisture in the solvent. And the second drying is used for enhancing the bonding force of the slurry on the surface of the gas sensor.
Preferably, in step B), the temperature of the aging is 100-200 ℃.
Preferably, in step B), the aging time is 2 to 5 days.
Preferably, in step B), the atmosphere of aging is an air atmosphere.
The aging is carried out in a sintering furnace.
As described above, the present inventionThe invention provides a preparation method and application of a graphene and titanium oxide nano composite material. The GA @ mTiO with the surface of the graphene sheet layer uniformly coated with mesoporous titanium oxide is successfully obtained by utilizing an interface-oriented co-assembly mode2Nanocomposites, i.e. guiding TiO by volatilization of solvent and capillary action2Self-assembling the products of precursor hydrolysis and polycondensation on the surface of a sheet layer of the graphene aerogel to obtain GA @ TiO with an amorphous framework structure2Composite material synthesized GA @ TiO2The nano composite material is calcined at high temperature to obtain the GA @ mTiO with the ordered mesoscopic structure2A nanocomposite material. Coating the composite material on the surface of a ceramic tube to prepare the composite material based on GA @ mTiO2A gas sensor of nanocomposite material. Has the following beneficial effects:
(1) the invention provides a preparation method and application of a graphene and titanium oxide nanocomposite, which realizes the compounding of mesoporous metal oxide and Graphene Aerogel (GA) by adopting an interface-oriented co-assembly mode, wherein the surfaces of two sides of a sheet graphene, which is a building unit of the Graphene Aerogel (GA), are coated with uniform mesoporous titanium oxide (mesoporus TiO)2，mTiO2). The combination of the two materials can form local heterojunction contact, and the composite material has a connected hierarchical pore and uniform mTiO2The mesoporous material has high specific surface area and pore volume, can effectively improve the gas-sensitive performance of the material, and effectively improves the sensing capability and the gas-sensitive response capability of the material. Particularly, the nano composite material is used as a sensitive material, not only is a macroporous rGO network and a higher specific surface area which are mutually connected applied, but also the excellent chemical and electronic properties of the rGO and the excellent chemical and electronic properties of metal oxide TiO can be effectively utilized2High sensitivity to the target gas improves the gas sensitive response.
(2) The invention provides a preparation method and application of a graphene and titanium oxide nano composite material, and a prepared gas sensor only needs to be preparedThe active substance GA @ mTiO2The nano composite material is coated on a sensitive element, has the advantages of simple preparation method and low cost, and is suitable for industrial mass production.
(3) According to the preparation method and the application of the graphene and titanium oxide nanocomposite, the prepared gas sensor has excellent response performance to different gases, and has the characteristics of high response speed, stability, recovery characteristics, reversibility and the like.
Drawings
FIG. 1 shows GA @ mTiO prepared in example 1 of the present invention2SEM images 1a, 1b of the nanocomposite, wherein FIG. 1a is GA @ mTiO2SEM image at Low magnification, FIG. 1b is GA @ mTiO2SEM images at high magnification.
FIG. 2 shows GA @ mTiO prepared in example 2 of the present invention2TEM images 2a, 2b of the nanocomposite material, wherein FIG. 2a is GA @ mTiO2TEM image at low magnification, FIG. 2b is GA @ mTiO2TEM images at high magnification.
FIG. 3 is a schematic structural view of gas sensors prepared in embodiments 1 to 3 of the present invention.
FIG. 4 shows GA @ mTiO prepared in example 3 of the present invention2Pore size distribution profile of the nanocomposite.
FIG. 5 shows the preparation of the present invention based on GA @ mTiO as prepared in example 22The nanocomposite gas sensor response plots for 20ppm acetone at different temperatures.
FIG. 6 shows the preparation of the present invention based on GA @ mTiO as prepared in example 32Nanocomposite gas sensor response/recovery curves for 400ppm ethanol concentration.
Detailed Description
The present invention is further illustrated below with reference to specific examples, which are intended to be illustrative only and not to limit the scope of the invention.
The embodiments of the present invention are described below with reference to specific embodiments, and other advantages and effects of the present invention will be easily understood by those skilled in the art from the disclosure of the present specification. The invention is capable of other and different embodiments and of being practiced or of being carried out in various ways, and its several details are capable of modification in various respects, all without departing from the spirit and scope of the present invention.
It should be understood that the processing equipment or devices not specifically mentioned in the following examples are conventional in the art; all pressure values and ranges refer to relative pressures.
Furthermore, it is to be understood that one or more method steps mentioned in the present invention does not exclude that other method steps may also be present before or after the combined steps or that other method steps may also be inserted between these explicitly mentioned steps, unless otherwise indicated; it is also to be understood that a combined connection between one or more devices/apparatus as referred to in the present application does not exclude that further devices/apparatus may be present before or after the combined device/apparatus or that further devices/apparatus may be interposed between two devices/apparatus explicitly referred to, unless otherwise indicated. Moreover, unless otherwise indicated, the numbering of the various method steps is merely a convenient tool for identifying the various method steps, and is not intended to limit the order in which the method steps are arranged or the scope of the invention in which the invention may be practiced, and changes or modifications in the relative relationship may be made without substantially changing the technical content.
Example 1
0.1g of PEO-b-PS was dissolved in 5ml of THF and stirred for 10min to obtain a PEO-b-PS solution. 0.4g of TiO2Dissolved in 0.4g of acetylacetone and 0.8g of ethanol and stirred continuously for 15min to obtain a titanium dioxide solution.
Transferring 16mL of 1.0mg/mL graphene oxide dispersion liquid into a hydrothermal kettle, carrying out hydrothermal reaction in an oven at 180 ℃ for 12h, and carrying out freeze drying for 24h to remove water, thereby obtaining the cylindrical graphene aerogel. The graphene oxide in the graphene oxide dispersion liquid is synthesized by taking natural graphite powder as a raw material and adopting a Hummers method.
The PEO-b-PS solution was quickly added to the titanium dioxide solution,putting 32mg of graphene aerogel into the mixed solution, putting the reaction system at room temperature, taking out the graphene aerogel after the solvent is volatilized for 1h, and putting the graphene aerogel in a drying oven at 100 ℃ for curing for 24h to obtain GA @ TiO with an amorphous framework structure2A composite material.
Adding GA @ TiO2Calcining the composite material in Ar atmosphere at 550 ℃ for 2h to obtain GA @ mTiO with an ordered mesostructure2Nanocomposite sample # 1.
Example 2
The GA @ mTiO prepared in example 1 was mixed2And taking 50mg of the nanocomposite sample No. 1, mixing with 1mL of ethanol, and grinding for 20min to obtain viscous slurry.
The slurry was uniformly coated on the outer side of the ceramic tube of the gas sensor and fully covered the Au electrode and the Pt lead wire at both sides, which had a thickness of 20 μm. The Pt wire is welded on the test base, and a Ni-Cr alloy heating wire is placed in the ceramic tube to control the working temperature of the sensor. The coated gas sensor was dried in an oven at 100 ℃ for 2h to remove moisture from the solvent, and then the gas sensor was placed in an oven at 150 ℃ for a further heat treatment for 24 h.
The GAs sensor was then aged on a heater at 150 ℃ for 3 days to obtain a GAs sensor based on GA @ mTiO2Nanocomposite gas sensor sample 1. The structure of gas sensor sample 1 is shown in fig. 3.
Example 3
0.1g of PEO-b-PS was dissolved in 5ml of THF and stirred for 10min to obtain a PEO-b-PS solution. 0.4g of TiO2Dissolved in 0.4g of acetylacetone and 0.8g of ethanol and stirred continuously for 15min to obtain a titanium dioxide solution.
Transferring 16mL of 1.0mg/mL graphene oxide dispersion liquid into a hydrothermal kettle, carrying out hydrothermal reaction in an oven at 180 ℃ for 12h, and carrying out freeze drying for 24h to remove water, thereby obtaining the cylindrical graphene aerogel. The graphene oxide in the graphene oxide dispersion liquid is synthesized by taking natural graphite powder as a raw material and adopting a Hummers method.
The PEO-b-PS solution was added rapidly to the titanium dioxidePutting 20mg of graphene aerogel into the mixed solution, putting the reaction system at room temperature, taking out the graphene aerogel after the solvent is volatilized for 1h, and putting the graphene aerogel into a drying oven at 100 ℃ for curing for 24h to obtain GA @ TiO with an amorphous framework structure2A composite material.
Adding GA @ TiO2Calcining the composite material in Ar atmosphere at 550 ℃ for 2h to obtain GA @ mTiO with an ordered mesostructure2 Nanocomposite sample # 2.
Example 4
The GA @ mTiO prepared in example 3 was mixed2And mixing 60mg of the nanocomposite sample No. 2 with 3mL of ethanol, and grinding for 30min to obtain viscous slurry.
The slurry was uniformly coated on the outer side of the ceramic tube of the gas sensor and fully covered the Au electrode and the Pt lead wire at both sides, which had a thickness of 20 μm. The Pt wire is welded on the test base, and a Ni-Cr alloy heating wire is placed in the ceramic tube to control the working temperature of the sensor. The coated gas sensor was dried in an oven at 100 ℃ for 2h to remove moisture from the solvent, and then the gas sensor was placed in an oven at 150 ℃ for a further heat treatment for 24 h.
The GAs sensor was then aged on a heater at 150 ℃ for 3 days to obtain a GAs sensor based on GA @ mTiO2Nanocomposite gas sensor sample 2. The structure of gas sensor sample 2 is shown in fig. 3.
Example 5
0.1g of PEO-b-PS was dissolved in 5ml of THF and stirred for 10min to obtain a PEO-b-PS solution. 0.4g of TiO2Dissolved in 0.4g of acetylacetone and 0.8g of ethanol and stirred continuously for 15min to obtain a titanium dioxide solution.
Transferring 8mL of 2.0mg/mL graphene oxide dispersion liquid into a hydrothermal kettle, placing the hydrothermal kettle in an oven at 180 ℃ for hydrothermal reaction for 12 hours, and freeze-drying for 24 hours to remove water to obtain the cylindrical graphene aerogel. The graphene oxide in the graphene oxide dispersion liquid is synthesized by taking natural graphite powder as a raw material and adopting a Hummers method.
The PEO-b-PS solution was added rapidly to the secondPutting 20mg of graphene aerogel into a titanium oxide solution, putting a reaction system at room temperature, taking out the graphene aerogel after the solvent is volatilized for 1h, putting the graphene aerogel into a drying oven at 100 ℃ for curing for 24h to obtain GA @ TiO with an amorphous framework structure2A composite material.
Adding GA @ TiO2Calcining the composite material in Ar atmosphere at 600 ℃ for 2h to obtain GA @ mTiO with an ordered mesostructure2Nanocomposite sample # 3.
Example 6
The GA @ mTiO prepared in example 5 was mixed2And mixing 60mg of the nanocomposite sample No. 3 with 3mL of ethanol, and grinding for 30min to obtain viscous slurry.
The slurry was uniformly coated on the outer side of the ceramic tube of the gas sensor, and fully covered the Au electrode and the Pt lead wire at both sides, which had a thickness of 10 μm. The Pt wire is welded on the test base, and a Ni-Cr alloy heating wire is placed in the ceramic tube to control the working temperature of the sensor. The coated gas sensor was dried in an oven at 100 ℃ for 2h to remove moisture from the solvent, and then the gas sensor was placed in an oven at 150 ℃ for a further heat treatment for 24 h.
The GAs sensor was then aged on a heater at 150 ℃ for 3 days to obtain a GAs sensor based on GA @ mTiO2Nanocomposite gas sensor sample 3. The structure of the gas sensor sample 3 is shown in fig. 3.
Comparative example 1
With GA and mTiO2The gas sensors are respectively used as gas sensitive materials to prepare the gas sensors, and the specific preparation process is as follows:
transferring 16mL of 1.0mg/mL graphene oxide dispersion liquid into a hydrothermal kettle, carrying out hydrothermal reaction in an oven at 180 ℃ for 12h, and carrying out freeze drying for 24h to remove water, thereby obtaining the cylindrical graphene aerogel. The graphene oxide in the graphene oxide dispersion liquid is synthesized by taking natural graphite powder as a raw material and adopting a Hummers method.
50mg of graphene aerogel and 1mL of ethanol are mixed and ground for 20min to obtain viscous slurry 1. Meanwhile, 50mg of titanium dioxide was mixed with 1mL of ethanol, and this was ground for 20min to obtain a viscous slurry 2.
The paste 1 and the paste 2 were uniformly coated on the outer side of the ceramic tube of the gas sensor, respectively, and fully covered the Au electrode and the Pt lead wire on both sides, and had a thickness of 20 μm. The Pt wire is welded on the test base, and a Ni-Cr alloy heating wire is placed in the ceramic tube to control the working temperature of the sensor. The coated gas sensor was dried in an oven at 100 ℃ for 2h to remove moisture from the solvent, and then the gas sensor was placed in an oven at 150 ℃ for a further heat treatment for 24 h.
The GAs sensor was further aged on a heater at 150 ℃ for 3 days, thereby obtaining GAs sensor sample 1 prepared based on GA and GAs sensor sample 1 based on mTiO, respectively2Prepared gas sensor sample 2.
Test example 1
The GA @ mTiO prepared in example 1 was added2The result of taking SEM image of nanocomposite sample No. 1 is shown in FIG. 1. As can be seen from fig. 1a and 1b, the secondary structural unit of the graphene aerogel, namely a layer of mesoporous TiO, is uniformly distributed on both sides of the lamellar graphene2And an open mesoporous structure can be clearly observed on the surface, and the connectivity of the interior is ensured by the sheet-assembled porous structure.
Test example 2
The GA @ mTiO prepared in example 3 was used2The nano composite material sample 2# was taken for TEM image, and the detailed result is shown in fig. 2. As can be seen from FIGS. 2a and 2b, GA @ mTiO2The nanocomposites had very clear lattice striations and irregular "water ripples", which further illustrate that GA @ mTiO2The nanocomposite has a highly crystallized framework structure.
Test example 3
The GA @ mTiO prepared in example 5 was mixed2Nanocomposite sample # 3, N2The specific results of the adsorption-desorption isotherm test are shown in fig. 4. As can be seen from FIG. 4, GA @ mTiO2The pore size of nanocomposite sample No. 3 was 4nm, further illustrating GA @ mTiO2The nanocomposite has a uniformly distributed mesoporous structure.
Test example 4
Based on GA @ mTiO prepared in example 42The gas sensor sample 2 of nanocomposite sample 2# was tested for a response to 20ppm acetone at different temperatures, and the results are shown in fig. 5. As can be seen from FIG. 5, in the test range of 50-150 deg.C, with the increase of the test temperature, oxygen molecules are adsorbed on TiO due to the adsorption of oxygen molecules2Surface, from TiO2The conduction band of (1) is trapped by electrons to form adsorbed oxygen ions, so that GA @ mTiO2The response value of the material to acetone gas gradually increases, and reaches the highest value at 150 ℃. When the temperature is higher than 150 c, the response value starts to decrease as the temperature increases due to desorption of the adsorbed gas at high temperature. This indicates GA @ mTiO2The material has the highest response value to acetone gas at 150 ℃.
Test example 5
Based on GA @ mTiO prepared in example 62Nanocomposite sample 3# gas sensor sample 3 was subjected to a response/recovery test at 400ppm ethanol concentration, with specific results shown in fig. 6. As can be seen from FIG. 6, the response value of the gas sensor to 400ppm ethanol does not significantly decay after a long-term cycle of 30 days, and still maintains a good response value.
In conclusion, the preparation method and the application of the graphene and titanium oxide nanocomposite provided by the invention can effectively improve the gas-sensitive performance of the material and effectively improve the sensing capability and the gas-sensitive response capability of the material. The prepared gas sensor has excellent response performance to different gases, and has excellent stability and recovery characteristics. Therefore, the invention effectively overcomes various defects in the prior art and has high industrial utilization value.
The foregoing embodiments are merely illustrative of the principles and utilities of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or change the above-mentioned embodiments without departing from the spirit and scope of the present invention. Accordingly, it is intended that all equivalent modifications or changes which can be made by those skilled in the art without departing from the spirit and technical spirit of the present invention be covered by the claims of the present invention.
Claims (10)
1. A preparation method of a graphene and titanium oxide nanocomposite comprises the following steps:
1) carrying out self-assembly reaction on the graphene aerogel and a titanium source in the presence of a soft template, a chelating agent and a reaction solvent;
2) curing and calcining the product obtained in the step 1) to provide a nanocomposite;
the titanium source is titanium dioxide; the soft template is a diblock copolymer PEO-b-PS; the chelating agent is acetylacetone.
2. The method for preparing the graphene and titanium oxide nanocomposite material according to claim 1, wherein in the step 1), the method for preparing the graphene aerogel comprises: and carrying out hydrothermal reaction and freeze drying on the graphene oxide dispersion liquid.
3. The method as claimed in claim 2, wherein the hydrothermal reaction is carried out at a temperature of 100-200 ℃.
4. The method for preparing the graphene and titanium oxide nanocomposite material according to claim 1, wherein in the step 1), the reaction solvent is an organic solvent.
5. The preparation method of the graphene and titanium oxide nanocomposite material according to claim 4, wherein the reaction solvent is selected from a combination of one or more of alcohol solvents and ether solvents, preferably from a combination of alcohol solvents and ether solvents, and more preferably from a combination of ethanol and tetrahydrofuran.
6. The method for preparing the graphene and titanium oxide nanocomposite material according to claim 1, wherein any one or more of the following conditions is included in the step 1):
A1) the mass ratio of the PEO-b-PS to the graphene aerogel is 0.05-0.5: 0.02-0.04;
A2) the mass ratio of the added PEO-b-PS to the added titanium dioxide is 0.05-0.5: 0.2-0.8;
A3) the mass ratio of the titanium dioxide to the acetylacetone is 0.2-0.8: 0.2-1.0;
A4) the reaction temperature of the self-assembly reaction is room temperature.
7. The method for preparing the graphene and titanium oxide nanocomposite material according to claim 1, wherein any one or more of the following conditions is included in the step 2):
B1) the reaction temperature of the curing is 80-150 ℃;
B2) the calcining atmosphere is inert atmosphere;
B3) the reaction temperature for the calcination is 400-600 ℃.
8. A graphene and titanium oxide nanocomposite material prepared by the method according to any one of claims 1 to 7.
9. Use of the graphene and titanium oxide nanocomposite according to claim 8 as a gas sensitive material in a gas sensor.
10. A gas sensor comprising the gas sensitive material of claim 9.
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