CN111624237A

CN111624237A - Nickel oxide/titanium dioxide nanorod composite structure gas sensor and preparation method and application thereof

Info

Publication number: CN111624237A
Application number: CN202010629574.0A
Authority: CN
Inventors: 夏晓红; 张欢欢; 高云; 鲍钰文; 凯文·赫姆伍德
Original assignee: Hubei University
Current assignee: Hubei University
Priority date: 2020-07-01
Filing date: 2020-07-01
Publication date: 2020-09-04
Anticipated expiration: 2040-07-01
Also published as: CN111624237B

Abstract

The invention relates to the technical field of gas sensors, and provides a nickel oxide/titanium dioxide nanorod composite structure gas sensor as well as a preparation method and application thereof. The gas sensor provided by the invention comprises a substrate, a nickel oxide/titanium dioxide nanorod composite structure layer and an interdigital electrode which are sequentially contacted from bottom to top. The nickel oxide and the titanium dioxide in the nickel oxide/titanium dioxide nanorod composite structure layer are compounded to form a heterojunction, so that the gas-sensitive performance of the sensor is improved, and the unique redox characteristic of the nickel oxide can also improve the gas-sensitive characteristic of the sensor. The gas sensor provided by the invention has the advantages of increased detection range of gas concentration, short response recovery time, high sensitivity and repeatability, good response to gases such as hydrogen, carbon monoxide and ammonia, and high-sensitivity detection at room temperature. The preparation method provided by the invention has the advantages of simple steps, low cost, strong operability and low requirement on equipment, and can be used for mass synthesis.

Description

Nickel oxide/titanium dioxide nanorod composite structure gas sensor and preparation method and application thereof

Technical Field

The invention relates to the technical field of gas sensors, in particular to a nickel oxide/titanium dioxide nanorod composite structure gas sensor and a preparation method and application thereof.

Background

Gas sensing studies are aimed at creating an electronic nose that can detect the presence and concentration levels of various gases in the surrounding air, with sufficient sensitivity, selectivity and repeatability. Several common gases include hydrogen, carbon monoxide, ammonia gas and the like, and the toxic, harmful, flammable and explosive characteristics of the gases bring great potential safety hazards to the application, storage and transportation of the gases, so that obtaining a gas sensor which has high sensitivity, high response and recovery speed, stable performance and low price at room temperature becomes an urgent need in the current industrial field.

TiO₂Is an important wide-band-gap (anatase 3.2eV, rutile 3.0eV) semiconductor functional material. TiO, a common n-type semiconductor oxide material₂The material has the advantages of stable surface performance, no toxicity, easy synthesis, low cost and the like, and becomes one of the most popular materials in the field of gas sensors as a sensitive material. However, most are based on TiO₂The gas sensor still has low sensitivity at room temperature (most TiO)₂The optimal working temperature of the gas sensor is 100-200 ℃), and the response recovery time is long, so that the practical application of the gas sensor is limited to a certain extent.

Disclosure of Invention

In view of the above, the present invention aims to provide a nickel oxide/titanium dioxide nanorod composite structure gas sensor, and a preparation method and an application thereof. The gas sensor provided by the invention has the advantages of high sensitivity at room temperature, short response recovery time and large gas concentration detection range.

In order to achieve the above object, the present invention provides the following technical solutions:

a nickel oxide/titanium dioxide nanorod composite structure gas sensor comprises a substrate, a nickel oxide/titanium dioxide nanorod composite structure layer arranged on the surface of the substrate and an interdigital electrode arranged on the surface of the nickel oxide/titanium dioxide nanorod composite structure layer from bottom to top; the nickel oxide/titanium dioxide nanorod composite structure layer consists of nickel oxide and titanium dioxide nanorods.

Preferably, the nickel oxide/titanium dioxide nanorod composite structure layer comprises titanium dioxide nanorods and nickel oxide filled between the titanium dioxide nanorods;

or comprises a titanium dioxide nanorod/nickel oxide composite layer and a nickel oxide layer growing on the upper surface of the titanium dioxide nanorod/nickel oxide composite layer; the titanium dioxide nanorod/nickel oxide composite layer comprises titanium dioxide nanorods and nickel oxide filled among the titanium dioxide nanorods;

or comprises a titanium dioxide nano rod layer and a nickel oxide layer grown on the upper surface of the titanium dioxide nano rod layer.

Preferably, when the nickel oxide/titanium dioxide nanorod composite structure layer comprises titanium dioxide nanorods and nickel oxide filled among the titanium dioxide nanorods, the thickness of the nickel oxide/titanium dioxide nanorod composite structure layer is 1.6-2.0 μm;

when the nickel oxide/titanium dioxide nanorod composite structure layer comprises a titanium dioxide nanorod/nickel oxide composite layer and a nickel oxide layer growing on the upper surface of the titanium dioxide nanorod/nickel oxide composite layer, the thickness of the titanium dioxide nanorod/nickel oxide composite layer is 2.1-2.5 mu m, and the thickness of the nickel oxide layer is 150-200 nm;

when the nickel oxide/titanium dioxide nanorod composite structure layer comprises a titanium dioxide nanorod layer and a nickel oxide layer growing on the upper surface of the titanium dioxide nanorod layer, the thickness of the titanium dioxide nanorod layer is 3.2-3.6 microns, and the thickness of the nickel oxide layer is 250-300 nm.

Preferably, the substrate is an FTO substrate; the interdigital electrode is a platinum interdigital electrode.

The invention provides a preparation method of the gas sensor in the scheme, which comprises the following steps:

(1) preparing a titanium dioxide nanorod film on the surface of the substrate by a hydrothermal method, and then performing first annealing;

(2) growing nickel oxide on the titanium dioxide nanorod film subjected to the first annealing, and then performing second annealing to obtain a nickel oxide/titanium dioxide nanorod composite structure layer;

(3) and preparing an interdigital electrode on the surface of the nickel oxide/titanium dioxide nanorod composite structure to obtain the nickel oxide/titanium dioxide nanorod composite structure gas sensor.

Preferably, the hydrothermal temperature of the hydrothermal method in the step (1) is 120-180 ℃, and the hydrothermal time is 6-16 h; the solvent used in the hydrothermal method is water or a mixed solvent of water and ethanol.

Preferably, the first annealing temperature is 300-500 ℃, the time is 20-60 min, and the annealing atmosphere is air.

Preferably, the method for growing the nickel oxide in the step (2) is a hydrothermal method or a magnetron sputtering method, the hydrothermal temperature of the hydrothermal method is 120-150 ℃, the hydrothermal time is 4-12 h, and the back pressure of the magnetron sputtering is 6 × 10^-4Pa, the radio frequency power for sputtering NiO is 60-100W, and the sputtering time is 15-60 min.

Preferably, the temperature of the second annealing is 300-500 ℃, the time is 60-120 min, and the annealing atmosphere is air.

The invention provides an application of the nickel oxide/titanium dioxide nanorod composite structure gas sensor or the nickel oxide/titanium dioxide nanorod composite structure gas sensor prepared by the preparation method in a gas test.

The invention provides a nickel oxide/titanium dioxide nanorod composite structure gas sensor which comprises a substrate, a nickel oxide/titanium dioxide nanorod composite structure layer arranged on the surface of the substrate and an interdigital electrode arranged on the surface of the nickel oxide/titanium dioxide nanorod composite structure layer. The gas sensor provided by the invention comprises a nickel oxide/titanium dioxide nanorod composite structure layer, wherein nickel oxide and titanium dioxide are compounded to form a heterojunction, so that the gas-sensitive performance of the sensor is improved, and the unique redox characteristic of nickel oxide can also improve the gas-sensitive characteristic of the sensor. The gas sensor provided by the invention has the advantages of increased gas concentration detection range, short response recovery time, high sensitivity and repeatability, and can realize high-sensitivity detection at room temperature.

The invention also provides a preparation method of the nickel oxide/titanium dioxide nanorod composite structure gas sensor. The preparation method provided by the invention has the advantages of simple steps, low cost, strong operability, high repeatability and low equipment requirement, and can be used for mass synthesis of finally obtained TiO₂The nano-rod keeps good orientation, NiO is not easy to agglomerate, and the specific surface area of the obtained nickel oxide/titanium dioxide nano-rod composite structure is large.

The invention also provides the application of the nickel oxide/titanium dioxide nanorod composite structure gas sensor in gas detection. The gas sensor provided by the invention has good response to gases such as hydrogen, carbon monoxide, ammonia and the like at room temperature.

The example results show that when the ethanol dosage in the titanium dioxide nano-rod grown by the hydrothermal method is 0ml, the first annealing temperature is 400 ℃, the time is 20min, the temperature of the nickel oxide grown by the hydrothermal method is 150 ℃, and the time is 8h, the obtained gas sensor has the detectable range of 1ppm to 12000ppm for hydrogen, 1ppm to 8000ppm for carbon monoxide and 1200ppm to 12000ppm for ammonia at room temperature.

Drawings

FIG. 1 shows TiO in comparative example 1₂XRD pattern of nanorods (after annealing);

FIG. 2 shows TiO in comparative example 1₂FESEM picture of the surface of the nanorod film (after annealing);

FIG. 3 shows a graph of a comparative example 1TiO₂The resistance value-time change curve of the nanorod gas sensor responding to hydrogen;

FIG. 4 is an XRD pattern of NiO synthesized in example 1 (after annealing);

FIG. 5 shows NiO/TiO in example 1₂FESEM image of the surface of the nanorod composite structure gas sensor;

FIG. 6 shows NiO/TiO in example 1₂A sectional FESEM image of the nanorod composite structure gas sensor;

FIG. 7 shows NiO/TiO in example 1₂The resistance value-time change curve of the nanorod composite structure gas sensor responding to hydrogen;

FIG. 8 shows NiO/TiO in example 1₂The resistance value-time change curve of the nanorod composite structure gas sensor responding to carbon monoxide;

FIG. 9 shows NiO/TiO in example 1₂The resistance value-time change curve of the nanorod composite structure gas sensor responding to ammonia gas;

FIG. 10 shows NiO/TiO in example 1₂The resistance value-time change curve of the nanorod composite structure gas sensor responding to nitrogen dioxide;

FIG. 11 shows NiO/TiO in example 2₂The resistance value-time change curve of the nanorod composite structure gas sensor responding to hydrogen;

FIG. 12 shows NiO/TiO in example 3₂Resistance value-time change curve of the nanorod composite structure gas sensor in response to hydrogen.

Detailed Description

The invention provides a nickel oxide/titanium dioxide nanorod composite structure gas sensor which comprises a substrate, a nickel oxide/titanium dioxide nanorod composite structure layer arranged on the surface of the substrate and an interdigital electrode arranged on the surface of the nickel oxide/titanium dioxide nanorod composite structure layer.

The invention provides a gas sensor comprising a substrate. In the present invention, the substrate is preferably an FTO substrate, and the dimension of the FTO substrate is preferably 2.5cm × 2.5 cm; the thickness of the FTO substrate is not particularly required by the invention, and the FTO substrate known to those skilled in the art can be used.

The gas sensor provided by the invention comprises a nickel oxide/titanium dioxide nanorod composite structure layer arranged on the upper surface of an substrate. In the present invention, the nickel oxide/titanium dioxide nanorod composite structure layer is obtained by growing nickel oxide on the surface of the titanium dioxide nanorod layer, and the specific structure of the nickel oxide/titanium dioxide nanorod composite structure layer can be divided into the following three cases because the preparation conditions are different (specifically described in the introduction of the preparation method in the following description), and the density of the titanium dioxide nanorods and the thickness of the nickel oxide layer are different:

firstly, titanium dioxide nanorods in a titanium dioxide nanorod layer are sparse, nickel oxide can be filled among the titanium dioxide nanorods during growth, and the nickel oxide/titanium dioxide nanorod composite structure layer at the moment comprises the titanium dioxide nanorods and nickel oxide filled among the titanium dioxide nanorods; the thickness of the nickel oxide/titanium dioxide nanorod composite structure layer is preferably 1.6-2.0 μm.

Secondly, titanium dioxide nanorods in the titanium dioxide nanorod layer are sparse, nickel oxide is filled between the titanium dioxide nanorods at first to form a titanium dioxide nanorod/nickel oxide composite layer (namely the structure in the first case), then the titanium dioxide nanorod/nickel oxide composite layer continuously grows to form a nickel oxide layer, the nickel oxide/titanium dioxide nanorod composite structure layer at the moment comprises the titanium dioxide nanorod/nickel oxide composite layer and a nickel oxide layer growing on the upper surface of the titanium dioxide nanorod/nickel oxide composite layer, the thickness of the titanium dioxide nanorod/nickel oxide composite layer is preferably 2.1-2.5 micrometers, the size of each titanium dioxide nanorod is preferably 50-80 nm, and the thickness of the nickel oxide layer is preferably 150-200 nm.

Thirdly, the titanium dioxide nanorods in the titanium dioxide nanorod layer are compact, nickel oxide directly grows on the upper surface of the titanium dioxide nanorod layer, the nickel oxide/titanium dioxide nanorod composite structure layer comprises the titanium dioxide nanorod layer and a nickel oxide layer growing on the upper surface of the titanium dioxide nanorod layer, the thickness of the titanium dioxide nanorod layer is preferably 3.2-3.6 microns, and the size of the titanium dioxide nanorods is preferably 70-120 nm; the thickness of the nickel oxide layer is preferably 250-300 nm.

The shape of the nickel oxide in the nickel oxide/titanium dioxide nanorod composite structure layer is not particularly limited, and the nickel oxide with the shape common in the field can be used, and specifically can be a nickel oxide nanosheet.

The gas sensor provided by the invention comprises an interdigital electrode arranged on the upper surface of a nickel oxide/titanium dioxide nanorod composite structure layer. In the invention, the interdigital electrode is preferably a platinum interdigital electrode, and the thickness of the interdigital electrode is preferably 800-900 nm.

The invention also provides a preparation method of the gas sensor, which comprises the following steps:

The method adopts a hydrothermal method to prepare the titanium dioxide nanorod film on the surface of the substrate, and then sequentially carries out drying and first annealing. In the present invention, the substrate is preferably washed and dried before use; the cleaning is preferably performed in acetone, ethanol and deionized water sequentially.

In the invention, the hydrothermal temperature for preparing the titanium dioxide nanorod film by the hydrothermal method is preferably 120-180 ℃, more preferably 150 ℃, and the hydrothermal time is preferably 6-16 h, more preferably 8 h; the solvent used in the hydrothermal method is preferably water or a mixed solvent of water and ethanol, the ethanol is preferably absolute ethanol, in a specific embodiment of the invention, the volume of the solvent used in the hydrothermal method is preferably fixed to be 30mL, specifically, 30mL of water is used as the solvent, or 30mL of a mixed solvent of water and ethanol is used as the solvent, and the ratio of water to ethanol in the mixed solvent can be specifically 30mL:0mL, 28mL:2mL, and 15mL:15 mL; in the present invention, in the case of the present invention,TiO with different densities and thicknesses can be obtained by adjusting the alcohol-water ratio₂In the nano-rod film, the condensation kinetics can be enhanced by adding ethanol into the solvent, so that the nucleation and the growth are promoted, more crystal seeds are provided, and in the range, the larger the adding amount of the ethanol is, the more compact the titanium dioxide nano-rods are, and when the using amount of the ethanol is 0 (namely, the solvent is water), the most sparse the titanium dioxide nano-rods in the obtained titanium dioxide nano-rod film are. In a specific embodiment of the present invention, when the specific structure of the nickel oxide/titanium dioxide nanorod composite structure layer is the first case or the second case (i.e. the titanium dioxide nanorods are sparse), the volume ratio of the water to the ethanol is preferably controlled to be 30mL:0 mL-20 mL:10 mL; when the specific structure of the nickel oxide/titanium dioxide nanorod composite structure layer is the third case (i.e. the titanium dioxide nanorods are dense), the volume ratio of the water to the ethanol is preferably controlled to be 15mL:15 mL-0 mL:30 mL.

In a specific embodiment of the invention, the hydrothermal method for preparing the titanium dioxide nanorod film specifically comprises the following steps:

(a) mixing water, ethanol, concentrated hydrochloric acid and a titanium source to obtain a titanium dioxide precursor solution;

(b) and (3) leading the conductive surfaces of the two substrates to be downward and leaning against the inner wall of the reaction kettle in a V shape, and transferring the titanium dioxide precursor solution into the reaction kettle for hydrothermal reaction.

In the invention, the concentrated hydrochloric acid is used for providing an acidic environment and inhibiting hydrolysis of a titanium source, and the pH value of the acidic environment is specifically 2; the titanium source is preferably tetrabutyl titanate, titanium tetrachloride or titanium isopropoxide; the volume fraction of the titanium source in the titanium dioxide precursor solution is preferably 1.5-5%.

After the hydrothermal reaction is finished, the substrate on which the titanium dioxide nano-rods grow is preferably washed and dried in sequence, and the titanium dioxide nano-rod film is obtained on the substrate. In the invention, the detergent for washing is preferably deionized water, and the washing method specifically comprises the following steps: soaking the substrate of the titanium dioxide nanorod film in deionized water for 6 hours, and changing water once every 3 hours; the drying temperature is preferably 60-90 ℃.

After the titanium dioxide nanorod film is obtained, the titanium dioxide nanorod film is subjected to first annealing. In the invention, the temperature of the first annealing is preferably 300-500 ℃, more preferably 350-400 ℃, the time of the first annealing is preferably 20-60 min, more preferably 30-40 min, and the annealing atmosphere is preferably air. The invention improves TiO by first annealing₂Crystallinity of the nanorod and adhesion to FTO.

According to the method, a hydrothermal method or a magnetron sputtering method is preferred, when the hydrothermal method is adopted, the hydrothermal temperature of the hydrothermal method is preferably 120-150 ℃, more preferably 130-140 ℃, the hydrothermal time is preferably 4-12 h, more preferably 6-10 h, wherein the longer the hydrothermal time is, the larger the growth thickness of the nickel oxide is, and when a magnetron sputtering method is adopted to sputter the NiO film, the back pressure of the magnetron sputtering is 6 × 10^-4Pa, keeping the working air pressure in the cavity to be 1-2 Pa in the sputtering process, sputtering NiO with the radio frequency power of 60-100 w and the sputtering time of 15-60 min.

In the present invention, the hydrothermal growth of nickel oxide preferably comprises the steps of:

(i) mixing a nickel source, water and ammonia water to obtain a nickel oxide precursor solution;

(ii) and (3) facing the titanium dioxide nanorod films of the two substrates on which the titanium dioxide nanorod films grow downwards and leaning against the inner wall of the reaction kettle in a V shape, and transferring the nickel oxide precursor solution into the reaction kettle for hydrothermal reaction.

In the present invention, the nickel source is preferably nickel chloride hexahydrate or nickel nitrate hexahydrate; the dosage ratio of the nickel source, the water and the ammonia water is preferably 0.59g to 100mL to 2 mL; the water is preferably deionized water. The pH value of the nickel oxide precursor solution is adjusted to 8-10 by adding ammonia water.

After the hydrothermal reaction is finished, taking out a sample with nickel oxide, and then washing and drying the sample in sequence to obtain nickel oxide growing on the titanium dioxide nanorod film; the washing detergent is preferably deionized water; the drying temperature is preferably 60-90 ℃.

In the invention, the temperature of the second annealing is preferably 300-500 ℃, more preferably 350-450 ℃, and the time of the second annealing is preferably 60-120 min, more preferably 80-100 min; the annealing atmosphere is preferably air. The invention improves the crystallinity of NiO and TiO through the second annealing₂The contact condition of (1).

After the nickel oxide/titanium dioxide nanorod composite structure layer is obtained, the interdigital electrode is prepared on the surface of the nickel oxide/titanium dioxide nanorod composite structure to obtain the nickel oxide/titanium dioxide nanorod composite structure gas sensor, the interdigital electrode is preferably prepared by a direct-current magnetron sputtering method, and the parameters of the direct-current magnetron sputtering method preferably include that the degree of vacuum of the back bottom is 6 × 10^-4Pa, Ar flow rate of 10-20 sccm, working pressure of 0.5-1 Pa, DC sputtering power of 40-60W, and sputtering time of 5-10 min.

The invention also provides application of the nickel oxide/titanium dioxide nanorod composite structure gas sensor in a gas test. In the present invention, the gas is particularly preferably hydrogen, carbon monoxide, ammonia, nitrogen dioxide, acetone, ethanol, or the like; the temperature of the application is preferably room temperature; the present invention is not particularly limited to the specific method of application, and may be applied according to a method known to those skilled in the art.

The embodiments of the present invention will be described in detail with reference to the following examples, but they should not be construed as limiting the scope of the present invention.

Comparative example 1

Leaning an FTO substrate against the inner wall of polytetrafluoroethylene of a hydrothermal reaction kettle in a V shape, pouring a precursor solution prepared from 15mL of deionized water, 0mL of absolute ethyl alcohol, 30mL of concentrated hydrochloric acid and 1mL of tetrabutyl titanate, and carrying out hydrothermal reaction for 8h at 150 ℃ to obtain TiO₂Cooling the reaction kettle to room temperature, washing the film with deionized water, soaking in deionized water, changing water every 3 hr for 6 hrDrying at constant temperature of 70 ℃, and annealing at 400 ℃ for 20min in the air atmosphere of a tube furnace for later use.

The Pt target material with the purity of 99.99 percent is arranged at the cathode target position of a magnetron sputtering system, the distance between a fixed target and a substrate is 60mm, and the Pt target material is arranged on TiO₂Covering the interdigital mask plate on the surface of the film, respectively opening a mechanical pump and a solenoid valve molecular pump pumping system, and pumping to 6 × 10 when the background vacuum degree^-4And when Pa is needed, setting the flow rate of argon gas to be 14.4sccm, keeping the working pressure of the chamber to be 0.5Pa, setting the direct-current sputtering power to be 40W, and carrying out 5-min sputtering coating on the target to prepare the metal Pt interdigital electrode.

FIG. 1 is TiO₂XRD pattern of nanorod film (after annealing), from which it can be seen that the obtained sample is rutile phase TiO with highly exposed (101) crystal face₂；

FIG. 2 is TiO₂FESEM surface map of nanorod film (after annealing), from which it can be seen that the sample obtained is TiO₂The nano rods have the diameter of 50-80 nm (the diameter of each nano rod is not the same and is distributed in a certain range);

for the obtained TiO at room temperature₂The nanorod gas sensor performs detection, and the obtained result is shown in fig. 3. According to the formula 3, the detection concentration range of the obtained gas sensor to the hydrogen is 1-4000 ppm.

Example 1

Leaning an FTO substrate against the inner wall of polytetrafluoroethylene of a hydrothermal reaction kettle in a V shape, pouring a precursor solution prepared from 30mL of deionized water, 0mL of absolute ethyl alcohol, 30mL of concentrated hydrochloric acid and 1mL of tetrabutyl titanate, and carrying out hydrothermal reaction for 8h at 150 ℃ to obtain TiO₂Cooling the reaction kettle to room temperature, washing the film with deionized water, soaking in deionized water, changing water every 3 hours, soaking for 6 hours, drying at constant temperature of 70 ℃, and annealing at 400 ℃ for 20min in a tube furnace air atmosphere for later use.

Putting a precursor solution (prepared by nickel chloride hexahydrate with the mass of 0.59g, deionized water with the volume of 100mL and ammonia water with the volume of 2 mL) into a hydrothermal reaction kettle, and placing two pieces of FTO (fluorine-doped tin oxide) (containing TiO)₂Nanorod film face down) is arranged in a V shape at poly-tetraCarrying out hydrothermal reaction on the inner wall of the vinyl fluoride reaction kettle by using TiO₂Growing NiO by taking the nano rod as a substrate; adding nickel chloride hexahydrate with the mass of 0.59g, adding deionized water with the volume of 100mL, adding ammonia water with the volume of 2mL, carrying out hydrothermal reaction for 8h at 150 ℃, cooling the reaction kettle to room temperature, cleaning the film with deionized water, soaking in deionized water, changing water every 3h, soaking for 6h, drying at constant temperature of 70 ℃, annealing at 500 ℃ for 120min in an air atmosphere of a tubular furnace for later use.

The Pt target material with the purity of 99.99 percent is arranged at the cathode target position of a magnetron sputtering system, the distance between a fixed target and a substrate is 60mm, and the Pt target material is arranged on TiO₂Covering the interdigital mask plate on the surface of the film, respectively opening a mechanical pump and a solenoid valve molecular pump pumping system, and pumping to 6 × 10 when the background vacuum degree^-4And when Pa is needed, setting the flow rate of argon gas to be 14.4sccm, keeping the working pressure of the chamber to be 0.5Pa, setting the direct-current sputtering power to be 40W, and carrying out 5-min sputtering coating on the target to prepare the metal Pt electrode.

FIG. 4 is an XRD spectrum of NiO (after annealing);

FIG. 5 shows NiO/TiO₂FESEM image of the surface of the nanorod composite structure gas sensor;

FIG. 6 shows NiO/TiO₂FESEM image of the section of the nanorod composite structure gas sensor.

As can be seen from FIGS. 4 to 6, NiO/TiO was successfully synthesized in the example 1₂The nano-rod composite structure specifically comprises titanium dioxide nano-rods and nickel oxide filled among the titanium dioxide nano-rods (namely, the first condition is described above), and the thickness of the composite structure is 1.7 μm.

For the obtained NiO/TiO at room temperature₂The nanorod composite structure gas sensor is detected in a hydrogen atmosphere, and the obtained result is shown in fig. 7. The result shows that the detectable range of the sensor for the hydrogen concentration is 1ppm to 12000 ppm. As can be seen from the combination of comparative example 1, NiO/TiO in the present invention₂The nanorod composite structure can remarkably increase the detection range of the sensor.

For NiO/TiO at room temperature₂The nano-rod composite structure gas sensor detects in the atmosphere of carbon monoxide,the results are shown in FIG. 8. The result shows that the detectable range of the sensor to the concentration of the carbon monoxide is 1-8000 ppm.

NiO/TiO at room temperature₂The nanorod composite structure gas sensor is detected in an ammonia atmosphere, and the obtained result is shown in fig. 9. The result shows that the detectable range of the sensor to the ammonia concentration is 1200-12000 ppm.

NiO/TiO at room temperature₂The nanorod composite structure gas sensor is detected in a nitrogen dioxide atmosphere, and the obtained result is shown in fig. 10. The result shows that the detectable range of the sensor to the concentration of the nitrogen dioxide is 100-4000 ppm.

Example 2

Leaning an FTO substrate against the inner wall of polytetrafluoroethylene of a hydrothermal reaction kettle in a V shape, pouring a precursor solution prepared from 28mL of deionized water, 2mL of absolute ethyl alcohol, 30mL of concentrated hydrochloric acid and 1mL of tetrabutyl titanate, and carrying out hydrothermal reaction for 8h at 150 ℃ to obtain TiO₂Cooling the reaction kettle to room temperature, washing the film with deionized water, soaking in deionized water, changing water every 3 hours, soaking for 6 hours, drying at constant temperature of 70 ℃, and annealing at 400 ℃ for 20min in a tube furnace air atmosphere for later use.

Putting the precursor solution (prepared by nickel chloride hexahydrate with the mass of 0.59g, deionized water with the volume of 100mL and ammonia water with the volume of 2 mL) into a hydrothermal reaction kettle, and placing two pieces of FTO (fluorine-doped tin oxide) (containing TiO)₂The nano-rod film faces downwards) is arranged on the inner wall of a polytetrafluoroethylene reaction kettle in a V shape to carry out hydrothermal reaction, and TiO is used₂Growing NiO by taking the nano rod as a substrate; adding nickel chloride hexahydrate with the mass of 0.59g, adding deionized water with the volume of 100mL, adding ammonia water with the volume of 2mL, carrying out hydrothermal reaction for 8h at 150 ℃, cooling the reaction kettle to room temperature, cleaning the film with deionized water, soaking in deionized water, changing water every 3h, soaking for 6h, drying at constant temperature of 70 ℃, annealing at 500 ℃ for 120min in an air atmosphere of a tubular furnace for later use.

The Pt target material with the purity of 99.99 percent is arranged at the cathode target position of a magnetron sputtering system, the distance between a fixed target and a substrate is 60mm, and the Pt target material is arranged on TiO₂The surface of the film is coated with an interdigital maskThe template is respectively opened by a mechanical pump and a solenoid valve molecular pump pumping system, and the vacuum degree is pumped to 6 × 10 when the background vacuum degree^-4And when Pa is needed, setting the flow rate of argon gas to be 14.4sccm, keeping the working pressure of the chamber to be 0.5Pa, setting the direct-current sputtering power to be 40W, and carrying out 5-min sputtering coating on the target to prepare the metal Pt interdigital electrode.

For the obtained NiO/TiO at room temperature₂The nanorod composite structure gas sensor is detected in a hydrogen atmosphere, and the obtained result is shown in fig. 11. The results show that the detectable range of the obtained gas sensor for the hydrogen concentration at room temperature is 1ppm to 12000 ppm.

Example 3

Leaning an FTO substrate against the inner wall of polytetrafluoroethylene of a hydrothermal reaction kettle in a V shape, pouring a precursor solution prepared from 15mL of deionized water, 15mL of absolute ethyl alcohol, 30mL of concentrated hydrochloric acid and 1mL of tetrabutyl titanate, and carrying out hydrothermal reaction for 8h at 150 ℃ to obtain TiO₂Cooling the reaction kettle to room temperature, washing the film with deionized water, soaking in deionized water, changing water every 3 hours, soaking for 6 hours, drying at constant temperature of 70 ℃, and annealing at 400 ℃ for 20min in a tube furnace air atmosphere for later use.

Putting the precursor solution (prepared by nickel chloride hexahydrate with the mass of 0.59g, deionized water with the volume of 100mL and ammonia water with the volume of 2 mL) into a hydrothermal reaction kettle, and placing two pieces of FTO (fluorine-doped tin oxide) (containing TiO)₂The nano-rod film faces downwards) is arranged on the inner wall of a polytetrafluoroethylene reaction kettle in a V shape to carry out hydrothermal reaction, and TiO is used₂Growing NiO on the nanorod serving as a substrate, carrying out hydrothermal reaction for 8h at 150 ℃, cooling the reaction kettle to room temperature, cleaning the film with deionized water, soaking in the deionized water, changing water every 3 hours, soaking for 6 hours, drying at a constant temperature of 70 ℃, and annealing in a tube furnace in the air atmosphere at 500 ℃ for 120min for later use.

The Pt target material with the purity of 99.99 percent is arranged at the cathode target position of a magnetron sputtering system, the distance between a fixed target and a substrate is 60mm, and the Pt target material is arranged on TiO₂Covering the interdigital mask plate on the surface of the film, respectively opening a mechanical pump and a solenoid valve molecular pump pumping system, and pumping to 6 × 10 when the background vacuum degree^-4When Pa, the flow rate of argon is set to14.4sccm, keeping the working pressure of the chamber at 0.5Pa, setting the direct-current sputtering power to 40W, and performing sputtering coating on the target for 5min to prepare the metal Pt interdigital electrode.

For the obtained NiO/TiO at room temperature₂The nanorod gas composite structure gas sensor is detected in a hydrogen atmosphere, and the obtained result is shown in fig. 12. The results show that the obtained gas sensor exhibits P-type response at low concentration and n-type response at high concentration to hydrogen at room temperature.

As can be seen from the above examples, the NiO/TiO provided by the invention₂The nanorod composite structure gas sensor shows different degrees of response to various gases such as hydrogen, carbon monoxide, ammonia and the like at room temperature, has the highest sensitivity to hydrogen, has good repeatability, and effectively improves the detection range of the gas sensor.

The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.

Claims

1. A nickel oxide/titanium dioxide nanorod composite structure gas sensor comprises a substrate, a nickel oxide/titanium dioxide nanorod composite structure layer arranged on the surface of the substrate and an interdigital electrode arranged on the surface of the nickel oxide/titanium dioxide nanorod composite structure layer from bottom to top; the nickel oxide/titanium dioxide nanorod composite structure layer consists of nickel oxide and titanium dioxide nanorods.

2. The gas sensor according to claim 1, wherein the nickel oxide/titanium dioxide nanorod composite structure layer comprises titanium dioxide nanorods and nickel oxide filled between the titanium dioxide nanorods;

3. The gas sensor according to claim 2, wherein when the nickel oxide/titanium dioxide nanorod composite structure layer comprises titanium dioxide nanorods and nickel oxide filled between the titanium dioxide nanorods, the thickness of the nickel oxide/titanium dioxide nanorod composite structure layer is 1.6-2.0 μm;

4. The gas sensor of claim 1, wherein the substrate is an FTO substrate; the interdigital electrode is a platinum interdigital electrode.

5. A method for producing a gas sensor according to any one of claims 1 to 4, comprising the steps of:

6. The preparation method according to claim 5, wherein the hydrothermal method in the step (1) has a hydrothermal temperature of 120-180 ℃ and a hydrothermal time of 6-16 h; the solvent used in the hydrothermal method is water or a mixed solvent of water and ethanol.

7. The method according to claim 5 or 6, wherein the first annealing is performed at a temperature of 300 to 500 ℃ for 20 to 60min in an atmosphere of air.

8. The preparation method according to claim 5, wherein the method for growing the nickel oxide in the step (2) is a hydrothermal method or a magnetron sputtering method, the hydrothermal temperature of the hydrothermal method is 120-150 ℃, the hydrothermal time is 4-12 h, and the back pressure of the magnetron sputtering is 6 × 10^-4Pa, the radio frequency power for sputtering NiO is 60-100W, and the sputtering time is 15-60 min.

9. The preparation method according to claim 5 or 8, wherein the temperature of the second annealing is 300-500 ℃, the time is 60-120 min, and the annealing atmosphere is air.

10. The use of the nickel oxide/titanium dioxide nanorod composite structure gas sensor as defined in any one of claims 1 to 4 or the nickel oxide/titanium dioxide nanorod composite structure gas sensor prepared by the preparation method as defined in any one of claims 5 to 9 in a gas test.