In-situ free-growing flower-shaped nano WO3Gas-sensitive material and preparation method and application thereof
阅读说明：本技术 一种原位自由生长花状纳米wo3气敏材料及其制备方法和应用 (In-situ free-growing flower-shaped nano WO3Gas-sensitive material and preparation method and application thereof ) 是由 桂阳海 田宽 钱琳琳 郭智荣 郭会师 秦肖芸 秦笑梅 于 2021-09-30 设计创作，主要内容包括：本发明公开了一种原位自由生长花状纳米WO-(3)气敏材料及其制备方法和应用,采用原位自由生长的方式,在Al-(2)O-(3)陶瓷管上原位生长得到单斜晶系的WO-(3)纳米花；所述WO-(3)纳米花是由WO-(3)纳米片组成的多级结构；所述WO-(3)纳米花直径为0.5μm～1μm；所述纳米片大小为150 nm～250 nm、纳米片厚度为8～20 nm。本发明还提供了一种WO-(3)气敏材料的制备方法,通过P123为表面活性剂,WCl-(6)为钨源,在乙醇溶液中自组装生成WO-(3)超薄纳米薄片,再由这些纳米片自组装成WO-(3)纳米花结构。气敏测试结果表明,该敏感材料对NO-(2)气体具有灵敏度高、响应恢复速度快、选择性好等优点。(The invention discloses an in-situ free-growth flower-shaped nano WO 3 The gas-sensitive material adopts an in-situ free growth mode and is applied to Al 2 O 3 WO for obtaining monoclinic system by in-situ growth on ceramic tube 3 A nanoflower; said WO 3 The nanometer flower is composed of WO 3 A multilevel structure composed of nanosheets; said WO 3 The diameter of the nanoflower is 0.5-1 mu m; the size of the nano sheet is 150 nm-250 nm, and the thickness of the nano sheet is 8-20 nm. The invention also provides a WO 3 The preparation method of the gas sensitive material adopts P123 as a surfactant and WCl 6 Is a tungsten source and self-assembles in ethanol solution to generate WO 3 Ultrathin nano-sheets, and self-assembly of these nano-sheets into WO 3 The nanometer flower structure. The gas-sensitive test result shows that the sensitive material has NO 2 Gas has high sensitivity, fast response and recovery speed, and selectiveGood selectivity and the like.)
1. In-situ free-growing flower-shaped nano WO3A gas sensitive material characterized by: in-situ free growth mode is adopted for Al2O3WO for obtaining monoclinic system by in-situ growth on ceramic tube3A nanoflower; said WO3The nanometer flower is composed of WO3A multilevel structure composed of nanosheets; said WO3The diameter of the nanoflower is 0.5-1 mu m; the size of the nano sheet is 150 nm-250 nm, and the thickness of the nano sheet is 8-20 nm.
2. In-situ free-growing flower-shaped nano WO3The preparation method of the gas sensitive material is characterized by comprising the following steps: the method comprises the following steps:
A. weighing a certain amount of polyethylene oxide-polypropylene oxide-polyethylene oxide triblock polymer (P123) to be dissolved in a mixed solution of absolute ethyl alcohol and water, and weighing a certain amount of WCl6Dissolving in the above mixed solution, and stirring thoroughly to WCl6Completely dissolved to form P123, EtOH and H2O and WCl6The mixed solution of (1);
B. immersing a clean ceramic tube into the solution for 2-3 min, taking out, airing and immersing again, repeatedly immersing for 2-4 times, ensuring good tightness in the process, then transferring the ceramic tube and the solution to a reaction kettle for hydrothermal reaction, naturally cooling after the reaction is finished, repeatedly washing the ceramic tube with absolute ethyl alcohol and deionized water, and drying at 55-65 ℃ to obtain the in-situ free-growing nano WO3A gas sensitive material.
3. In situ free-growing flower-like nano-WO according to claim 23The preparation method of the gas sensitive material is characterized by comprising the following steps: p123 and WCl in step A6The mass ratio of the anhydrous ethanol to the water is 1: 1-1: 5, and the mass ratio of the anhydrous ethanol to the water is 15: 1-40: 1.
4. In situ free-growing flower-like nano-WO according to claim 23The preparation method of the gas sensitive material is characterized by comprising the following steps: said step (c) isThe temperature of the hydrothermal synthesis reaction in the step B is 110-150 ℃, and the reaction time is 80-240 min.
5. In situ free-growing flower-like nano-WO according to claim 23The preparation method of the gas sensitive material is characterized by comprising the following steps: the nano WO prepared in the step B3And annealing the gas sensitive material, wherein the annealing temperature is 300-450 ℃, the heating rate is 1-3 ℃/min, and the heat preservation time is 2-4 h.
6. In situ free-growing flower-like nano-WO of claim 13Gas sensitive material in NO2Application to real-time detection.
7. A preparation method of an in-situ free growth gas sensor is characterized by comprising the following steps: the method comprises the following steps:
(1) weighing a certain amount of polyethylene oxide-polypropylene oxide-polyethylene oxide triblock polymer (P123) to be dissolved in a mixed solution of absolute ethyl alcohol and water, and weighing a certain amount of WCl6Dissolving in the above mixed solution, and stirring thoroughly to WCl6Completely dissolved to form P123, EtOH and H2O and WCl6The mixed solution of (1);
(2) immersing a clean ceramic tube into the solution for 2-3 min, taking out, airing and immersing again, repeatedly immersing for 2-4 times, ensuring good tightness in the process, then transferring the ceramic tube together with the solution to a reaction kettle for hydrothermal reaction, naturally cooling after the reaction is finished, repeatedly washing the ceramic tube with absolute ethyl alcohol and deionized water, and drying at 55-65 ℃ to obtain the in-situ free-grown WO3A ceramic tube of gas sensitive material;
(3) welding the ceramic tube with the sensitive material grown in situ prepared in the step (2) on a hexagonal base, welding a Ni-Cr heating wire on the hexagonal base by penetrating the ceramic tube, and aging at room temperature for 7 days to prepare the WO grown in situ3A gas sensor.
8. The in situ free form of claim 7The preparation method of the growth gas sensor is characterized by comprising the following steps: p123 and WCl in the step (1)6The mass ratio of the anhydrous ethanol to the water is 1: 1-1: 5, and the mass ratio of the anhydrous ethanol to the water is 15: 1-40: 1.
9. The method for preparing an in-situ free-growth gas sensor according to claim 7, wherein: the temperature of the hydrothermal synthesis reaction in the step (2) is 110-150 ℃, and the reaction time is 80-240 min.
10. The method for preparing an in-situ free-growth gas sensor according to claim 7, wherein: and (3) annealing the ceramic tube with the sensitive material grown in situ prepared in the step (2), wherein the annealing temperature is 300-450 ℃, the heating rate is 1-3 ℃/min, and the heat preservation time is 2-4 h.
Technical Field
The invention relates to the technical field of semiconductor gas-sensitive components, in particular to an in-situ free-growth flower-shaped nano WO3A gas sensitive material, a preparation method and application thereof.
Background
Nitrogen oxides, NO, are the most common polluting gases in the atmosphere2Is a reddish brown irritant gas, which can be inhaled into human body through respiratory tract to cause damage to respiratory system and lung tissue, and can cause bronchitis, dental erosion and pulmonary edema, and seriously cause syncope and serious harm to human health, and NO is2Is also one of the main sources of acid rain and is an important component of urban atmospheric pollution, so that the method for detecting NO in air in real time is designed2Gas sensors are very urgent.
The gas sensor is a component which converts gas components in the atmosphere into electric signals and feeds the electric signals back to human beings by sensing the gas components, and is widely concerned by researchers due to the characteristics of portability, simple preparation, low cost, high sensitivity and the like, while WO3As a typical wide-bandgap semiconductor, the semiconductor has been widely researched and used for gas sensors due to its characteristics of variable morphology, high sensitivity, fast response speed, good selectivity and the like. The traditional preparation method of the gas sensor usually adopts a nano powder coating method, and the gas sensitive material and ethanol or terpineol are prepared into slurry to be coated on the gas sensor, but the defects that the coating of the artificial coating material is uneven, the thickness cannot be controlled, the morphology can be damaged in the slurry preparation process, particles are stacked, the material is not tightly combined with a ceramic tube and the like can be caused, and the phenomena of element powder falling, poor consistency and poor repeatability and the like can be caused in the long-term use process, so that the gas sensitive performance is influenced. Therefore, there is a need to develop a NO suitable for low concentration detection with good selectivity2A gas sensor.
Disclosure of Invention
In view of the above, in order to solve the defects in the prior art, the invention adopts an in-situ free growth mode to prepare the flower-shaped nano WO3The gas-sensitive material is prepared by reacting a ceramic tube in a hydrothermal reaction kettle, so that the gas-sensitive material can freely grow on the surface of the ceramic tube.
The invention also provides a method for in-situ free growth of the gas sensor used for NO2Has excellent selectivity, high response recovery rate, good stability and low cost in detection, and is NO2Provides an effective way for rapid detection.
The following technical scheme is adopted specifically:
the invention discloses an in-situ free-growth flower-shaped nano WO3Gas-sensitive material, which adopts an in-situ free growth mode, is prepared on Al2O3WO for obtaining monoclinic system by in-situ growth on ceramic tube3Nanoflower, said WO3The nanometer flower is composed of WO3Multilevel structure composed of nanosheets, WO3The diameter of the nanoflower is 0.5-1 mu m; the size of the nano sheet is 150 nm-250 nm, and the thickness of the nano sheet is 8-20 nm.
The invention discloses an in-situ free-growth flower-shaped nano WO3The preparation method of the gas sensitive material comprises the following steps:
A. weighing a certain amount of polyethylene oxide-polypropylene oxide-polyethylene oxide triblock polymer (P123) to be dissolved in a mixed solution of absolute ethyl alcohol and water, and weighing a certain amount of WCl6Dissolving in the above mixed solution, and stirring thoroughly to WCl6Completely dissolved to form P123, EtOH and H2O and WCl6The mixed solution of (1);
B. immersing a clean ceramic tube into the solution for 2-3 min, taking out, airing and immersing again, repeatedly immersing for 2-4 times, ensuring good tightness in the process, then transferring the ceramic tube and the solution to a reaction kettle for hydrothermal reaction, naturally cooling after the reaction is finished, repeatedly washing the ceramic tube with absolute ethyl alcohol and deionized water, and drying at 60 ℃ to obtain the in-situ free-growing nano WO3A gas sensitive material.
Preferably, P123 and WCl in the step A6The mass ratio of the anhydrous ethanol to the water is 1: 1-1: 5, and the mass ratio of the anhydrous ethanol to the water is 15: 1-40: 1.
Preferably, the temperature of the hydrothermal synthesis reaction in the step B is 110-150 ℃, and the reaction time is 80-240 min.
Preferably, the nano WO prepared in the step B3And annealing the gas sensitive material, wherein the annealing temperature is 300-450 ℃, the heating rate is 1-3 ℃/min, and the heat preservation time is 2-4 h.
The invention discloses an in-situ free-growth flower-shaped nano WO3Gas sensitive material in NO2Application to real-time detection.
The invention also discloses a preparation method of the in-situ free growth gas sensor, which comprises the following steps:
(1) weighing a certain amount of polyethylene oxide-polypropylene oxide-polyethylene oxide triblock polymer (P123) to be dissolved in a mixed solution of absolute ethyl alcohol and water, and weighing a certain amount of WCl6Dissolving in the above mixed solution, and stirring thoroughly to WCl6Completely dissolved to form P123, EtOH and H2O and WCl6The mixed solution of (1);
(2) immersing a clean ceramic tube into the solution for 2-3 min, taking out, airing and immersing again, repeatedly immersing for 2-4 times, ensuring good tightness in the process, then transferring the ceramic tube and the solution to a reaction kettle for hydrothermal reaction, naturally cooling after the reaction is finished, repeatedly washing the ceramic tube with absolute ethyl alcohol and deionized water, and drying at 55-65 ℃ to obtain the in-situ free-growing WO3A ceramic tube of nano gas sensitive material;
(3) welding the ceramic tube with the sensitive material grown in situ prepared in the step (2) on a hexagonal base, welding a Ni-Cr heating wire on the hexagonal base by penetrating the ceramic tube, and aging at room temperature for 7 days to prepare the WO grown in situ3A gas sensor.
The specific operation method comprises the following steps:
(1) mixing Al2O3Ceramic tube, polytetrafluoroethyleneCleaning and drying the bracket; immersing the treated ceramic tube into a solution containing P123, EtOH and H2O and WCl6Soaking the mixed solution for 2-4 min, taking out, airing, and repeating for 2-4 times;
(2) suspending the ceramic tube treated in the step (1) on a polytetrafluoroethylene support to ensure that the ceramic tube
Placing the solution in the central position of the solution, filling a hydrothermal reaction kettle, and then placing the solution in a drying box with a good temperature rise for reaction; after the reaction is finished, cooling to room temperature, taking out the reaction kettle, repeatedly washing the ceramic tube with absolute ethyl alcohol and deionized water, putting the ceramic tube into a drying oven, and drying at the temperature of 60 ℃ for 20-60 min to obtain the ceramic tube with the sensitive material growing in situ;
(3) welding the ceramic tube with the sensitive material grown in situ prepared in the step (2) on a hexagonal base, welding a Ni-Cr heating wire on the hexagonal base by penetrating the ceramic tube, and aging at room temperature for 7 days to prepare the WO grown in situ3A gas sensor.
Preferably, in the step (1), P123 and WCl6The mass ratio of the anhydrous ethanol to the water is 1: 1-1: 5, and the mass ratio of the anhydrous ethanol to the water is 15: 1-40: 1.
Preferably, the temperature of the hydrothermal synthesis reaction in the step (2) is 110-150 ℃, and the reaction time is 80-240 min.
Preferably, the ceramic tube with the sensitive material grown in situ prepared in the step (2) is annealed at the temperature of 300-450 ℃, the heating rate of 1-3 ℃/min and the heat preservation time of 2-4 h.
The invention adopts in-situ free growth WO3Compared with the traditional semiconductor thick film sensor, the nano material mode has the advantages that the in-situ free growth of the nano material is beneficial to the tight combination of the gas sensitive material layer and the ceramic tube, the preparation mode is simple, the repeatability is good, and the error existing in the process of manually coating the gas sensitive material is reduced.
The invention has the following characteristics:
(1) the working temperature is low, compared with the traditional WO3Pure materials generally have the best response at high temperature (300-400 ℃), and the invention utilizes a surfactant self-assembly methodTo obtain two-dimensional WO3The nano-sheet improves the specific surface area of the material, and meanwhile, the ultrathin nano-sheet prepared by the invention has rich active sites and defects on the surface, so that WO3The nano-sheet has higher activation energy at a lower working temperature of 210 ℃, thereby promoting O2WO prepared by fully capturing electrons on the surface of the WO and converting the electrons into oxygen anions3Nanosheet sensor for NO at 210 DEG C2Exhibits excellent response and lowers the operating temperature.
(2) High sensitivity, preparation of WO provided by the invention3The gas-sensitive material obtained by the method of the gas sensor has large specific surface area, is composed of a two-dimensional ultrathin sheet structure, has rich active sites and defects, greatly improves the sensitivity, and can treat 100 ppm of NO at 210 DEG C2The gas has excellent response to 100 ppm NO2Response value reaches 234.00, 10 ppm NO2Up to 37.93, 5 ppm NO2Up to 15.54, 3 ppm NO2Up to 6.34.
(3) Good selectivity, WO of the invention3The gas sensor performs gas-sensitive tests on 17 gases of acetonitrile, benzene, toluene, dimethylbenzene, absolute ethyl alcohol, isopropanol, n-butanol, acetone, diethyl ether, formaldehyde, acetaldehyde, trimethylamine, triethylamine, ammonia water, formamide, aniline and nitrogen dioxide at the optimal working temperature of 210 ℃, and shows that the gas sensor performs gas-sensitive tests on NO2The catalyst has ultrahigh selectivity and is not sensitive to other gases. The main reason is that the nano-sheet prepared by the method has a special crystal face which adsorbs NO2The bonding energy required for the molecule is lower, indicating that NO2May be preferred to adsorption of other VOCs molecules on crystal planes.
(4) The response recovery speed is high, and the WO grown in situ and annealed is provided by the invention3Gas sensor at 210 ℃ for 100 ppm NO2Gas response time of 28 s and recovery time within 5 s, which is mainly benefited by NO2Gas molecules along two dimensions WO3The surface is rapidly diffused and reacts with negative oxygen ions rapidly.
(5) Good cycling stability, WO of the invention3Gas sensorIn situ free growth mode on Al2O3WO directly growing on surface of ceramic tube3The gas-sensitive layer avoids the coating process of the traditional semiconductor gas-sensitive sensor, avoids the problem of poor element stability caused by powder falling due to untight combination of the material of the gas-sensitive layer and the substrate of the ceramic tube, and also avoids the factors of uneven thickness and the like caused by manual coating. High response values were maintained for a one month duration of operation.
According to the invention, the P123 surfactant is added to construct a two-dimensional layered structure, so that the specific surface area of the material is increased, the adsorption and desorption rate of the surface of the material is further increased, and the pure WO is further expanded3For NO2The use of (1). The gas sensor disclosed by the invention is used for NO2In gas detection, the method has the advantages of high sensitivity, good selectivity, quick response recovery, good stability, simple preparation process and low cost. Solves the problems of NO caused by uneven manual coating, over-thick gas-sensitive layer or untight combination of gas-sensitive material and ceramic tube2Slow response and recovery time in gas detection.
Drawings
In order to illustrate the embodiments of the invention more clearly, the drawings that are needed in the description of the embodiments will be briefly described below, it being apparent that the drawings in the following description are only some embodiments of the invention, and that other drawings may be derived from those drawings by a person skilled in the art without inventive effort.
FIG. 1 shows the in-situ free-grown flower-like nano-WO of the present invention3Schematic diagram of hydrothermal reaction device of gas sensitive element (hydrothermal reaction kettle 1; polytetrafluoroethylene support 2; polytetrafluoroethylene lining 3; Al2O3A ceramic tube 4);
FIG. 2 is SEM pictures before and after annealing of the gas sensing material in example 1 (picture (a) shows no annealing treatment; picture (b) shows annealing treatment; picture (c) shows SEM size marks of the sample after annealing treatment);
FIG. 3 is an XRD pattern before and after annealing of the gas sensitive material in example 1 (pattern (a) shows no annealing treatment; pattern (b) shows annealing treatment);
FIG. 4 shows the gas sensor of example 2 operating at 210 ℃ to 100 ppm NO2Gas dynamic response and recovery time curve chart;
FIG. 5 shows the gas sensor of example 2 for different concentrations of NO at an operating temperature of 210 deg.C2A dynamic response profile of the gas;
FIG. 6 shows the gas sensor of example 2 operating at 210 ℃ to 100 ppm NO2A stability profile of the gas;
FIG. 7 is a graph showing the selectivity of the gas sensors of example 2, comparative example 1, comparative example 2, and comparative example 3 for different kinds of gases;
FIG. 8 shows the gas sensors in example 2, comparative example 1, comparative example 2 and comparative example 3 for 100 ppm NO2Graph of sensitivity of gas versus operating temperature.
Detailed Description
For a further understanding of the invention, reference will now be made to the following examples which illustrate embodiments of the invention, but it is to be understood that the description is intended to illustrate features and advantages of the invention, rather than to limit the scope of the invention.
The test methods described in the examples of the present invention are all conventional methods unless otherwise specified; the reagents and materials are commercially available, unless otherwise specified.
The following will combine specific embodiments to provide an in-situ free-growth flower-like nano WO3The preparation method and the application of the gas sensor are illustrated, and the protection scope of the present invention is not limited by the following examples.
Example 1
Example 1
In-situ free-growing flower-shaped nano WO3Gas-sensitive material, which adopts an in-situ free growth mode, is prepared on Al2O3WO for obtaining monoclinic system by in-situ growth on ceramic tube3The WO3 nanometer flower is composed of WO3Multilevel structure composed of nanosheets, WO3The diameter of the nanoflower is 0.5-1 mu m; the size of the nano sheet is 150nm to 250 nm, and the thickness of the nano-sheet is 8 to 20 nm.
Example 2
In-situ free-growing flower-shaped nano WO3The preparation method of the gas sensitive material comprises the following steps:
A. weighing a certain amount of polyethylene oxide-polypropylene oxide-polyethylene oxide triblock polymer (P123) to be dissolved in a mixed solution of absolute ethyl alcohol and water, and weighing a certain amount of WCl6Dissolving in the above mixed solution, and stirring thoroughly until WCl6Completely dissolved to form P123, EtOH and H2O and WCl6The mixed solution of (1);
B. immersing a clean ceramic tube into the solution for 2-3 min, taking out, airing and immersing again, repeatedly immersing for 2-4 times, ensuring good tightness in the process, then transferring the ceramic tube and the solution to a reaction kettle for hydrothermal reaction, naturally cooling after the reaction is finished, repeatedly washing the ceramic tube with absolute ethyl alcohol and deionized water, and drying at 55-65 ℃ to obtain the in-situ free-growing nano WO3A gas sensitive material.
In-situ free growth flower-like nano WO3The specific preparation method of the gas sensitive material comprises the following steps:
weighing 0.2 g P123 dissolved in 16.5 ml EtOH and 0.5 ml H2O, stirring for 15 min to completely dissolve P123, and weighing 0.4 g WCl6Dissolving in the above mixed solution, and stirring thoroughly for 20 min to WCl6Completely dissolved to form P123, EtOH and H2O and WCl6The mixed solution of (1).
Secondly, putting the ceramic tube and the polytetrafluoroethylene bracket into a beaker with alcohol, cleaning for 5 min by a KQ-50DA type ultrasonic cleaner, putting the beaker into an electric heating blast drying oven to dry at 60 ℃, then putting the beaker into the mixed solution in the step I to soak for 3 min, taking out and drying in the air, and repeating for 4 times.
Thirdly, suspending the ceramic tube processed in the second step on a polytetrafluoroethylene support, clamping the ceramic tube into a polytetrafluoroethylene lining, placing the ceramic tube in the center of the solution, placing the hydrothermal synthesis reaction kettle in a forced air drying oven with a good advance temperature rise, and reacting for 120 min at 110 ℃, wherein the schematic diagram of the hydrothermal reaction device is shown in figure 1.
Fourthly, after the hydrothermal synthesis reaction in the third step is finished and the reaction kettle and the polytetrafluoroethylene bracket are taken out after being cooled to room temperature, the ceramic tube is respectively washed by absolute ethyl alcohol and deionized water and then is put into a blast drying oven to be dried at 60 ℃, and the in-situ grown flower-shaped nano WO can be obtained3The ceramic tube of (1). Then annealing the obtained product for 2 hours at 400 ℃ to obtain the flower-shaped nano WO growing in situ after annealing3The ceramic tube of (1).
FIG. 2 shows flower-like nano-particles WO prepared in example 2 and grown in situ on a ceramic tube3Samples before and after annealing were subjected to electron microscopy Scanning (SEM). Wherein, fig. 2 (a) and (b) are SEM images of the sample before and after annealing respectively, fig. 2 (c) is an SEM dimension mark image of the sample after annealing treatment, fig. 2 (a) and (b) show that the sample is still in a two-dimensional sheet-shaped nano flower structure before and after annealing, and fig. 2 (c) shows that the diameter of the nano flower obtained after annealing is 0.5-1 μm.
FIG. 3 shows flower-like nano-particles WO prepared in example 2 and grown in situ on a ceramic tube3And (4) carrying out X-ray diffraction pattern (XRD) detection on the samples before and after the annealing treatment. Wherein, FIGS. 3 (a) and (b) are XRD patterns of the sample before and after annealing respectively, and as can be seen from FIG. 3 (a), flower-like nano-WO grown in situ on the ceramic tube3Orthorhombic when not annealed; as is clear from FIG. 3 (b), the crystal was monoclinic after annealing and had good crystallinity.
EXAMPLE 3 method for preparing in-situ free-growth gas sensor
The procedure of example 2 was repeated to obtain in-situ grown flower-like nano-sized WO3The ceramic tube of (1).
Growing flower-shaped nano WO on the prepared in-situ annealing3The ceramic tube is welded on a hexagonal base, and is packaged and aged to obtain the annealed in-situ grown flower-shaped nano WO3The gas sensor of (1).
FIG. 4 shows the gas sensor obtained in example 3 at an operating temperature of 210 ℃ with respect to NO2Dynamic response curve at gas concentration of 100 ppm. Can be seen from the figureIn-situ grown flower-shaped nano WO after annealing3Gas sensor pair NO2The gas response time was 28 s and the recovery time was 3 s, which showed a fast response recovery rate.
FIG. 5 shows the gas sensor of example 3 at an operating temperature of 210 ℃ for different concentrations of NO2Dynamic response profile of gas. As can be seen from the graph, the gas sensor can be used for different concentrations of NO2The gas has good response reversibility and gas sensitivity along with NO2The increase in gas.
FIG. 6 shows the in-situ grown flower-like nano-scale WO after annealing in example 33The gas sensor has a working temperature of 210 ℃ and NO2Stability profile at a gas concentration of 100 ppm. As can be seen from the figure, the gas sensor can quickly recover to the initial sensitivity after being used for one week or one month, thereby showing that the gas sensor has good consistency and stability in the long-term use process, namely the gas sensor has NO for the gas sensor2The gas has good reproducibility and reversibility.
FIG. 7 shows WO prepared in example 3 and comparative examples 1, 2 and 3 described below3The gas sensor carries out gas-sensitive test on 17 gases of acetonitrile, benzene, toluene, dimethylbenzene, absolute ethyl alcohol, isopropanol, n-butanol, acetone, diethyl ether, formaldehyde, acetaldehyde, trimethylamine, triethylamine, ammonia water, formamide, aniline and nitrogen dioxide. As can be seen from the figure, WO3Gas sensor pair NO2The selectivity of the gas is best, the selectivity to other gases is poor, and the WO prepared by the invention3Gas sensor pair NO2The selectivity of the gas is obviously superior to that of the other three kinds of WO3A gas sensor.
FIG. 8 shows WO prepared in example 3 and comparative examples 1, 2 and 3 described below3Gas sensor for 100 ppm NO at different working temperatures2Gas sensitivity curve. As can be seen from the figure, WO3Gas sensor pair NO2The sensitivity of the gas tends to increase and decrease with increasing operating temperature, and at 210 ℃, WO3Gas sensor pairNO2The sensitivity of the gas is maximum; as can also be seen from the figure, the WO produced by the invention3Gas sensor pair NO2Sensitivity of gas compared with other 3 kinds of WO3The gas sensor is high.
Example 4
A preparation method of an in-situ free growth gas sensor comprises the following steps:
(1) weighing a certain amount of polyethylene oxide-polypropylene oxide-polyethylene oxide triblock polymer (P123) to dissolve in a mixed solution of absolute ethyl alcohol and water, weighing a certain amount of WCl6 to dissolve in the mixed solution, and fully stirring until WC is reachedl6Completely dissolving to form a mixed solution of P123, EtOH, H2O and WCl 6; in the step (1), the mass ratio of P123 to WCl6 is 1: 1-1: 5, and the mass ratio of absolute ethyl alcohol to water is 15: 1-40: 1.
(2) Immersing a clean ceramic tube into the solution for 2-3 min, taking out, airing and immersing again, repeatedly immersing for 2-4 times, ensuring good tightness in the process, then transferring the ceramic tube together with the solution to a reaction kettle for hydrothermal reaction, naturally cooling after the reaction is finished, repeatedly washing the ceramic tube with absolute ethyl alcohol and deionized water, and drying at 55-65 ℃ to obtain the in-situ free-grown WO3A ceramic tube of gas sensitive material; the temperature of the hydrothermal synthesis reaction in the step (2) is 110-150 ℃, and the reaction time is 80-240 min. And (3) annealing the ceramic tube with the sensitive material grown in situ prepared in the step (2), wherein the annealing temperature is 300-450 ℃, the heating rate is 1-3 ℃/min, and the heat preservation time is 2-4 h.
(3) Welding the ceramic tube with the sensitive material grown in situ prepared in the step (2) on a hexagonal base, welding a Ni-Cr heating wire on the hexagonal base by penetrating the ceramic tube, and aging at room temperature for 7 days to prepare the WO grown in situ3A gas sensor.
Example 5
The preparation method of the gas sensor of in-situ free-growth flower-shaped nanometer WO3 comprises the following steps:
weighing 0.15 g P123 dissolved in 16.5 ml EtOH and 1.0 ml waterIn the above process, the mixture was stirred for 15 min to completely dissolve P123, and then 0.4 g of WCl was weighed6Dissolving in the above mixed solution, and stirring thoroughly for 20 min to WCl6Completely dissolved to form P123, EtOH and H2O and WCl6The mixed solution of (1).
Secondly, putting the ceramic tube and the polytetrafluoroethylene support into a beaker with alcohol, cleaning the ceramic tube and the polytetrafluoroethylene support for 5 min by using a KQ-50DA type ultrasonic cleaner, then putting the cleaned ceramic tube and the polytetrafluoroethylene support into an electric heating blast drying oven to dry the cleaned ceramic tube and the cleaned polytetrafluoroethylene support at the temperature of 60 ℃, then putting the dried ceramic tube and the dried polytetrafluoroethylene support into the mixed solution obtained in the step I to soak for 3 min, taking out and drying the soaked ceramic tube and the polytetrafluoroethylene support, and repeating the steps for 2 times.
Thirdly, suspending the ceramic tube processed in the second step on a polytetrafluoroethylene support, clamping the ceramic tube into a polytetrafluoroethylene lining, placing the ceramic tube at the central position of the solution, placing the ceramic tube into a forced air drying oven with a good temperature rise in advance after a hydrothermal synthesis reaction kettle is installed, and reacting for 80 min at 150 ℃, wherein the schematic diagram of the hydrothermal reaction device is shown in figure 1.
Fourthly, after the hydrothermal synthesis reaction in the third step is finished and the reaction kettle and the polytetrafluoroethylene bracket are taken out after being cooled to room temperature, the ceramic tube is respectively washed by absolute ethyl alcohol and deionized water and then is put into a blast drying oven to be dried at the temperature of 55 ℃, and the in-situ grown flower-shaped nano WO can be obtained3The ceramic tube of (1). Then annealing the obtained product at the temperature of 450 ℃ for 2 hours to obtain the flower-shaped nano WO grown in situ after annealing3The ceramic tube of (1).
Fifthly, the flower-shaped nanometer WO grown in situ by annealing prepared in the step IV3The ceramic tube is welded on a hexagonal base, and is packaged and aged to obtain the annealed in-situ grown flower-shaped nano WO3The gas sensor of (1).
Through detection, the annealed in-situ grown flower-shaped nano WO prepared in the embodiment3Gas sensor pair NO2The gas has good selectivity, high sensitivity, high response recovery speed and good stability.
Example 6
The preparation method of the gas sensor of in-situ free-growth flower-shaped nanometer WO3 comprises the following steps:
weighingDissolving 0.2 g P123 in a mixed solution of 16.5 ml EtOH and 0.66 ml water, stirring for 15 min to completely dissolve P123, and weighing 0.4 g WCl6Dissolving in the above mixed solution, and stirring thoroughly for 20 min to WCl6Completely dissolved to form P123, EtOH and H2O and WCl6The mixed solution of (1).
Secondly, putting the ceramic tube and the polytetrafluoroethylene support into a beaker with alcohol, cleaning the ceramic tube and the polytetrafluoroethylene support for 5 min by using a KQ-50DA type ultrasonic cleaner, then putting the cleaned ceramic tube and the polytetrafluoroethylene support into an electric heating blast drying oven to dry the cleaned ceramic tube and the cleaned polytetrafluoroethylene support at the temperature of 60 ℃, then putting the dried ceramic tube and the dried polytetrafluoroethylene support into the mixed solution obtained in the step I to soak for 2 min, taking out and drying the soaked ceramic tube and the polytetrafluoroethylene support, and repeating the steps for 4 times.
Thirdly, suspending the ceramic tube processed in the second step on a polytetrafluoroethylene support, clamping the ceramic tube into a polytetrafluoroethylene lining, placing the ceramic tube in the center of the solution, placing the hydrothermal synthesis reaction kettle in a forced air drying oven with a good advance temperature rise, and reacting for 150 min at 120 ℃, wherein the schematic diagram of the hydrothermal reaction device is shown in figure 1.
Fourthly, after the hydrothermal synthesis reaction in the third step is finished and the reaction kettle and the polytetrafluoroethylene bracket are taken out after being cooled to room temperature, the ceramic tube is respectively washed by absolute ethyl alcohol and deionized water and then is placed into a blast drying oven to be dried at 65 ℃, and the in-situ grown flower-shaped nano WO can be obtained3The ceramic tube of (1). Then annealing the obtained product for 4 hours at the temperature of 300 ℃ to obtain the flower-shaped nano WO grown in situ after annealing3The ceramic tube of (1).
Fifthly, the flower-shaped nanometer WO grown in situ by annealing prepared in the step IV3The ceramic tube is welded on a hexagonal base, and is packaged and aged to obtain the annealed in-situ grown flower-shaped nano WO3The gas sensor of (1).
Upon examination, the annealed in situ grown flower-like nano-WO prepared in this example3Gas sensor pair NO2The gas has good selectivity, high sensitivity, high response recovery speed and good stability.
Comparative example 1
In-situ growth WO without annealing treatment3The gas sensor of (1) is,the preparation method comprises the following steps:
weighing 0.2 g P123 dissolved in 16.5 ml EtOH and 0.5 ml H2O, stirring for 15 min to completely dissolve P123, and weighing 0.4 g WCl6Dissolving in the above mixed solution, and stirring thoroughly for 20 min to WCl6Completely dissolved to form P123, EtOH and H2O and WCl6The mixed solution of (1).
Secondly, putting the ceramic tube and the polytetrafluoroethylene support into a beaker with alcohol, cleaning the ceramic tube and the polytetrafluoroethylene support for 5 min by using a KQ-50DA type ultrasonic cleaner, then putting the cleaned ceramic tube and the polytetrafluoroethylene support into an electric heating blast drying oven to dry the cleaned ceramic tube and the cleaned polytetrafluoroethylene support at the temperature of 60 ℃, then putting the dried ceramic tube and the dried polytetrafluoroethylene support into the mixed solution obtained in the step I to soak for 3 min, taking out and drying the soaked ceramic tube and the polytetrafluoroethylene support, and repeating the steps for 4 times.
Thirdly, suspending the ceramic tube processed in the second step on a polytetrafluoroethylene support, clamping the ceramic tube into a polytetrafluoroethylene lining, placing the ceramic tube in the center of the solution, placing the hydrothermal synthesis reaction kettle in a forced air drying oven with a good advance temperature rise, and reacting for 120 min at 110 ℃, wherein the schematic diagram of the hydrothermal reaction device is shown in figure 1.
Fourthly, after the hydrothermal synthesis reaction in the third step is finished and the reaction kettle and the polytetrafluoroethylene bracket are taken out after being cooled to room temperature, the ceramic tube is respectively washed by absolute ethyl alcohol and deionized water and then is put into a blast drying oven to be dried at 60 ℃, and the in-situ grown flower-shaped nano WO can be obtained3The ceramic tube of (1).
Fifthly, the in-situ grown flower-shaped nanometer WO prepared in the step IV3The ceramic tube is welded on a hexagonal base, and is packaged and aged to prepare the in-situ grown flower-shaped nano WO3The gas sensor of (1).
From FIG. 7, it can be seen that the annealed in-situ grown flower-like nano-scale WO3Gas sensor pair NO2The selectivity of the gas is better than that of comparative example 1. From FIG. 8, it can be seen that the annealed in-situ grown flower-like nano-scale WO3Gas sensor pair NO2The sensitivity of the gas was higher than that of comparative example 1.
Comparative example 2
Manually-coated flower-shaped nanoWO3The preparation steps of the gas sensor are as follows:
firstly, 0.2 g P123 is taken to be dissolved in 16.5 ml of EtOH and 0.5 ml of H2Stirring the mixed solution of O for 15 min to completely dissolve P123 to obtain a clear and transparent uniform solution;
② take 0.4 g WCl6Adding the powder into the solution in the step (i), and stirring for 20 min to ensure that WCl is formed6And completely dissolving to obtain a bright yellow solution.
Thirdly, quickly transferring the solution obtained in the second step to a 50 ml polytetrafluoroethylene high-pressure reaction kettle, putting the reaction kettle into a drying oven which is heated to 110 ℃ in advance, reacting for 120 min, and naturally cooling to room temperature.
Fourthly, the solution after the reaction is taken out and placed in a centrifuge tube, the solution is repeatedly washed and centrifuged by absolute ethyl alcohol and deionized water, the solution is centrifuged for 5 min each time, and the position of the solution is replaced by an ultrasonic cell crusher for 3 times to assist in dispersing and peeling WO3Nanosheets.
Fifthly, adding a proper amount of deionized water into the washed sample, and freeze-drying to obtain a blue powder sample, namely the WO3And (3) precursor gas-sensitive material.
Sixthly, mixing the prepared gas-sensitive material with terpineol respectively, grinding the mixture evenly to obtain gas-sensitive slurry, then evenly coating the gas-sensitive slurry on the surface of a clean ceramic tube, baking the gas-sensitive slurry by using an infrared lamp, welding the gas-sensitive slurry on a black hexagonal base, penetrating a Ni-Cr heating wire into the ceramic tube and welding the heating wire on the base, and then aging the prepared gas-sensitive element at room temperature for 7 days to obtain the hand-coated flower-shaped nano WO3The gas sensor of (1).
From FIG. 7, it can be seen that the gas sensor prepared in this comparative example is paired with NO2The gas selectivity was poorer than that of the gas sensor prepared in example 2 of the present invention. From FIG. 8, it can be seen that the gas sensor manufactured by the present comparative example is aligned with NO2The sensitivity of the gas is lower than that of the gas sensor prepared in the embodiment 2 of the invention.
Comparative example 3
Hand-coated annealed flower-shaped nano WO3The preparation steps of the gas sensor are as follows:
firstly, 0.2 g P123 is taken to be dissolved in 16.5 ml of EtOH and 0.5ml H2And stirring the mixed solution of O for 15 min to completely dissolve P123 to obtain a clear and transparent uniform solution.
② take 0.4 g WCl6Adding the powder into the solution in the step (i), and stirring for 20 min to ensure that WCl is formed6And completely dissolving to obtain a bright yellow solution.
Thirdly, quickly transferring the solution obtained in the second step to a 50 ml polytetrafluoroethylene high-pressure reaction kettle, putting the reaction kettle into a drying oven which is heated to 110 ℃ in advance, reacting for 120 min, and naturally cooling to room temperature.
Fourthly, the solution after the reaction is taken out and placed in a centrifuge tube, the solution is repeatedly washed and centrifuged by absolute ethyl alcohol and deionized water, the solution is centrifuged for 5 min each time, and the position of the solution is replaced by an ultrasonic cell crusher for 3 times to assist in dispersing and peeling WO3Nanosheets.
Fifthly, adding a proper amount of deionized water into the washed sample, freezing and drying to obtain a blue powder sample, and annealing the blue powder sample in a tube furnace at 400 ℃ for 2 hours to obtain yellow WO3Powder, i.e. the annealed WO is prepared3And (3) precursor gas-sensitive material.
Sixthly, mixing the gas-sensitive material prepared in the fifth step with terpineol respectively, grinding the mixture evenly to obtain gas-sensitive slurry, then evenly coating the gas-sensitive slurry on the surface of a clean ceramic tube, baking the gas-sensitive slurry by using an infrared lamp, welding the gas-sensitive slurry on a black hexagonal base, penetrating a Ni-Cr heating wire into the ceramic tube and welding the heating wire on the base, and then aging the prepared gas-sensitive element for 7 days at room temperature to obtain the hand-coated flower-shaped nano WO3The gas sensor of (1).
FIG. 7 shows that the gas sensor pair NO prepared in this comparative example2The gas selectivity was poorer than that of the gas sensor prepared in example 2 of the present invention. From FIG. 8, it can be seen that the gas sensor manufactured by the present comparative example is aligned with NO2The sensitivity of the gas is lower than that of the gas sensor prepared in the embodiment 2 of the invention.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.
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