CN113860374B - Flower-shaped nano WO (WO) capable of freely growing in situ 3 Gas-sensitive material, preparation method and application thereof - Google Patents
Flower-shaped nano WO (WO) capable of freely growing in situ 3 Gas-sensitive material, preparation method and application thereof Download PDFInfo
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- CN113860374B CN113860374B CN202111164158.9A CN202111164158A CN113860374B CN 113860374 B CN113860374 B CN 113860374B CN 202111164158 A CN202111164158 A CN 202111164158A CN 113860374 B CN113860374 B CN 113860374B
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Abstract
The invention discloses an in-situ free-growth flower-shaped nanometer WO 3 Gas sensitive materialMaterial, preparation method and application thereof, and in-situ free growth mode is adopted in Al 2 O 3 WO of monoclinic system obtained by in-situ growth on ceramic tube 3 A nanoflower; said WO 3 The nanoflower is prepared from WO 3 A multi-stage structure composed of nano-sheets; 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 Preparation method of gas-sensitive material by using P123 as surfactant and WCl 6 Self-assembly in ethanol solution to produce WO for tungsten source 3 Ultrathin nano-sheets, self-assembled into WO by the nano-sheets 3 A nano flower structure. The gas-sensitive test result shows that the sensitive material has NO effect on NO 2 The gas has the advantages of high sensitivity, high response recovery speed, good selectivity and the like.
Description
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 WO 3 A gas sensitive material, and its preparation method and application are provided.
Background
Nitrogen oxides are the most common polluting gases in the atmosphere, NO 2 Is a reddish brown irritant gas, which can be inhaled into human body through respiratory tract to damage respiratory system and lung tissue, and can cause bronchitis, dental erosion and pulmonary edema, and can also cause syncope, and seriously harm human health, and NO 2 Is also one of the main sources of acid rain and is an important constituent component of urban atmospheric pollution, thus designing a device for detecting NO in air in real time 2 Gas sensors for gases are very urgent.
The gas sensor is a component which converts the gas component in the atmosphere into an electric signal and feeds the electric signal back to human beings by sensing the gas component in the atmosphere, and is widely focused by researchers due to the characteristics of portability, simple preparation, low cost, high sensitivity and the like, and WO 3 As a typical wide-bandgap semiconductor, the semiconductor is widely studied and used for a gas sensor due to the characteristics of variable morphology, high sensitivity, high response speed, good selectivity and the like. The traditional preparation method of the gas sensor generally adopts a nano powder coating method, and the gas sensor material and ethanol or terpineol are prepared into slurry to be coated on the gas sensor, but the artificial coating material is easy to cause uneven coating, uncontrollable thickness, possible defects of morphology damage, loose combination of particles, poor consistency and repeatability of the material and ceramic tubes and the like in the slurry preparation process, and the phenomena of powder falling, poor consistency and repeatability of the element in the long-term use process are caused, so that the gas sensor performance is affected. Therefore, there is a need to develop a method for detecting NO with low concentration and good selectivity 2 A 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 WO 3 The gas-sensitive material is prepared by reacting the ceramic tube in a hydrothermal reaction kettle to enable the ceramic tube to grow freely on the surface of the ceramic tube, and the method is simple and has good repeatability.
The invention also provides a method for in-situ free growth of a gas sensor for NO 2 The method has the advantages of excellent selectivity in detection, fast response recovery rate, good stability, low cost and NO 2 Provides an effective way to detect the test rapidly.
The technical scheme is as follows:
the invention discloses an in-situ free-growth flower-shaped nanometer WO 3 The gas sensitive material adopts an in-situ free growth mode and is prepared by the following steps of 2 O 3 WO of monoclinic system obtained by in-situ growth on ceramic tube 3 Nanoflower of said WO 3 The nanoflower is prepared from WO 3 Multistage structure of nanoplatelets, providedSaid 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 discloses an in-situ free-growth flower-shaped nanometer WO 3 The 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) dissolved in a mixed solution of absolute ethyl alcohol and water, and then weighing a certain amount of WCl 6 Dissolving in the above mixed solution, stirring thoroughly until WCl 6 Completely dissolve to form P123, etOH, H 2 O and WCl 6 Is a mixed solution of (a) and (b);
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, then transferring the ceramic tube and the solution together into a reaction kettle for hydrothermal reaction, naturally cooling after the reaction is finished, repeatedly flushing the ceramic tube with absolute ethyl alcohol and deionized water, and drying at 60 ℃ to obtain the nano WO freely growing in situ 3 A gas sensitive material.
Preferably, in the step A, P123 and WCl 6 The 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 step B 3 And (3) carrying out annealing treatment on the gas-sensitive material, wherein the annealing temperature is 300-450 ℃, the heating rate is 1-3 ℃ per minute, and the heat preservation time is 2-4 hours.
The invention discloses an in-situ free-growth flower-shaped nanometer WO 3 Gas-sensitive material in NO 2 Application 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) and dissolving in a mixed solution of absolute ethyl alcohol and water, and thenWeigh a certain amount of WCl 6 Dissolving in the above mixed solution, stirring thoroughly until WCl 6 Completely dissolve to form P123, etOH, H 2 O and WCl 6 Is a mixed solution of (a) and (b);
(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, then transferring the ceramic tube and the solution together into a reaction kettle for hydrothermal reaction, naturally cooling after the reaction is finished, repeatedly flushing the ceramic tube with absolute ethyl alcohol and deionized water, and drying at 55-65 ℃ to obtain the WO freely growing in situ 3 Ceramic tubes 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 through the ceramic tube, and aging for 7 days at room temperature to obtain the WO with the in-situ growth 3 A gas sensor.
The specific operation method comprises the following steps:
(1) Al is added with 2 O 3 Cleaning and drying a ceramic tube and a polytetrafluoroethylene support; immersing the treated ceramic tube in a solution containing P123, etOH, H 2 O and WCl 6 Soaking in the mixed solution for 2-4 min, taking out, airing, and repeating for 2-4 times;
(2) Suspending the ceramic tube processed in the step (1) on a polytetrafluoroethylene bracket to enable the ceramic tube to be
Placing the mixture in the center of the solution, placing the mixture in a heated drying box after the hydrothermal reaction kettle is arranged, and carrying out reaction; after the reaction is finished, cooling to room temperature, taking out the reaction kettle, repeatedly flushing the ceramic tube with absolute ethyl alcohol and deionized water, putting the ceramic tube into a drying box, and drying for 20-60 min at the temperature of 60 ℃ 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 through the ceramic tube, and aging for 7 days at room temperature to obtain the WO with the in-situ growth 3 A gas sensor.
Preferably, the steps are1) P123 and WCl in 6 The 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 annealing temperature of 300-450 ℃ at the heating rate of 1-3 ℃/min and the heat preservation time of 2-4 hours.
The invention adopts in-situ free growth WO 3 Compared with the traditional semiconductor thick film sensor, the nano material mode is beneficial to the close combination of the gas sensitive material layer and the ceramic tube by the free growth in situ, has simple preparation mode and good repeatability, and reduces errors in the process of manually coating the gas sensitive material.
The invention has the following characteristics:
(1) Low working temperature compared with the traditional WO 3 The pure material generally has the best response at high temperature (300-400 ℃), and the invention utilizes the surfactant self-assembly method to obtain the two-dimensional WO 3 The nano sheet improves the specific surface area of the material, and meanwhile, the surface of the ultrathin nano sheet prepared by the invention has rich active sites and defects, so that WO 3 The nano-sheet has higher activation energy at the lower working temperature of 210 ℃ so as to promote O 2 The surface of the material is fully captured with electrons to be converted into oxyanions, thus obtaining the WO 3 The nano-sheet sensor is used for detecting NO at 210 DEG C 2 Exhibits excellent response and lowers the operating temperature.
(2) The invention provides the preparation WO with high sensitivity 3 The gas-sensitive material has large specific surface area, is composed of a two-dimensional ultrathin sheet structure, has rich active sites and defects, greatly improves sensitivity, and has NO concentration of 100 ppm at 210 DEG C 2 The gas has excellent response to 100 ppm NO 2 Response value reaches 234.00, 10 ppm NO 2 Up to 37.93,5 ppm NO 2 Up to 15.54,3 ppm NO 2 Up to 6.34.
(3) Good selectivity, the inventionSaid WO 3 The gas sensor performs gas-sensitive test on 17 gases of acetonitrile, benzene, toluene, xylene, absolute ethyl alcohol, isopropanol, n-butyl alcohol, acetone, diethyl ether, formaldehyde, acetaldehyde, trimethylamine, triethylamine, ammonia water, formamide, aniline and nitrogen dioxide at the optimal working temperature of 210 ℃ to show that the gas-sensitive sensor has NO-sensitive effect on the gas 2 Is insensitive to other gases. This is mainly due to the fact that the nanoplatelets prepared using this method have specific crystal planes that are adsorbing NO 2 The lower bond energy required for the molecule indicates NO 2 Adsorption of other VOCs molecules on the crystal plane may be preferred.
(4) The response recovery speed is high, the WO which grows in situ and is subjected to annealing treatment is disclosed in the invention 3 The gas sensor is sensitive to 100 ppm of NO at 210 DEG C 2 The gas response time was 28 s and recovery time was within 5 s, which is mainly due to NO 2 Gas molecules along two dimensions WO 3 The surface rapidly diffuses and reacts rapidly with negative oxygen ions.
(5) Good cycle stability, WO of the invention 3 The gas sensor adopts an in-situ free growth mode to grow on Al 2 O 3 Direct growth of WO on the surface of ceramic tubes 3 The 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 the fact that the gas-sensitive layer material is not tightly combined with the ceramic tube substrate, and also avoids factors such as uneven thickness caused by manual coating. The response value can be kept high for a month of operation.
The invention builds a two-dimensional lamellar structure by adding the P123 surfactant, improves the specific surface area of the material, further improves the adsorption and desorption rate of the surface of the material, and further expands the pure WO 3 For NO 2 Is used in the application of (a). The gas sensor disclosed by the invention is used for NO 2 In the 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 problem that NO is caused by uneven manual coating, too thick gas sensitive layer or untight combination of gas sensitive material and ceramic tube 2 Response and recovery in gas detectionSlow time.
Drawings
In order to more clearly illustrate the embodiments of the present invention, the drawings that are required for 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 present invention and that other drawings may be obtained from these drawings without inventive effort for a person of ordinary skill in the art.
FIG. 1 shows in situ free-growth flower-like nano WO of the present invention 3 Schematic diagram of hydrothermal reaction device of gas sensor (hydrothermal reaction kettle 1; polytetrafluoroethylene support 2; polytetrafluoroethylene lining 3; al) 2 O 3 A ceramic tube 4);
FIG. 2 is an SEM image before and after annealing of the gas-sensitive material in example 1 (FIG. a shows that the gas-sensitive material has not been annealed; FIG. b shows that the gas-sensitive material has been annealed; and FIG. c shows that the gas-sensitive material has been annealed;
FIG. 3 shows XRD patterns of the gas sensitive material of example 1 before and after annealing (pattern (a) is not annealed; pattern (b) is annealed);
FIG. 4 shows the gas sensor of example 2 at an operating temperature of 210℃for 100 ppm NO 2 A gas dynamic response and recovery time graph;
FIG. 5 shows the concentration of NO at 210℃for the gas sensor of example 2 2 A dynamic response graph of the gas;
FIG. 6 shows the gas sensor of example 2 at an operating temperature of 210℃for 100 ppm NO 2 A 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 to different kinds of gases;
FIG. 8 shows the gas sensor pairs of example 2, comparative example 1, comparative example 2 and comparative example 3 for 100 ppm NO 2 A plot of sensitivity of the gas versus operating temperature.
Detailed Description
For a further understanding of the present invention, embodiments of the invention are described below in conjunction with the examples, but it should be understood that these descriptions are merely intended to illustrate further features and advantages of the invention and are not limiting of the invention claimed.
The test methods in the embodiment of the invention are all conventional methods unless specified otherwise; the reagents and materials, unless otherwise specified, are commercially available.
The invention provides an in-situ free-growth flower-shaped nanometer WO with the combination of specific examples 3 The preparation method and application of the gas sensor are described, and the protection scope of the invention is not limited by the following examples.
Example 1
Example 1
Flower-shaped nano WO (WO) capable of freely growing in situ 3 The gas sensitive material adopts an in-situ free growth mode and is prepared by the following steps of 2 O 3 WO of monoclinic system obtained by in-situ growth on ceramic tube 3 Nanoflower, said WO3 nanoflower is made from WO 3 Multistage structures of nanoplatelets, 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.
Example 2
Flower-shaped nano WO (WO) capable of freely growing in situ 3 The preparation method of the gas-sensitive material comprises the following steps:
A. a certain amount of polyethylene oxide-polypropylene oxide-polyethylene oxide triblock polymer (P123) is weighed and dissolved in a mixed solution of absolute ethyl alcohol and water, and then a certain amount of WC is weighed l6 Dissolving in the above mixed solution, stirring thoroughly until WC l6 Completely dissolve to form P123, etOH, H 2 O and WC l6 Is a mixed solution of (a) and (b);
B. immersing a clean ceramic tube in the solution for 2-3 min, taking out, airing, immersing again, repeatedly immersing for 2-4 times, ensuring good tightness, then transferring the ceramic tube and the solution together into a reaction kettle for hydrothermal reaction, naturally cooling after the reaction is finished, repeatedly flushing the ceramic tube with absolute ethyl alcohol and deionized water, and drying at 55-65 ℃ to obtain the ceramic tube in-situFree-grown nano WO 3 A gas sensitive material.
In situ free growth flower-like nano WO 3 The specific preparation method of the gas-sensitive material comprises the following steps:
(1) 0.2 g of P123 was weighed out in 16.5 ml of EtOH and 0.5 ml of H 2 In the mixed solution of O, stirring for 15 min to dissolve P123 completely, and weighing 0.4 g WCl 6 Dissolving in the above mixed solution, stirring thoroughly for 20 min to WCl 6 Completely dissolve to form P123, etOH, H 2 O and WCl 6 Is a mixed solution of (a) and (b).
(2) Placing the ceramic tube and the polytetrafluoroethylene support into a beaker filled with alcohol, cleaning for 5 min by using a KQ-50DA ultrasonic cleaner, drying at 60 ℃ by using an electrothermal blowing drying box, then placing the ceramic tube and the polytetrafluoroethylene support into the mixed solution in the step (1) for soaking for 3 min, taking out, airing, and repeating for 4 times.
(3) Hanging the ceramic tube treated in the step (2) on a polytetrafluoroethylene bracket, clamping the ceramic tube into a polytetrafluoroethylene lining, placing the ceramic tube in the center of a solution, placing the ceramic tube into a blast drying oven with a temperature rising in advance after a hydrothermal synthesis reaction kettle is arranged, and reacting for 120 min at 110 ℃, wherein the schematic diagram of a hydrothermal reaction device is shown in figure 1.
(4) After the hydrothermal synthesis reaction in the step (3) is finished, cooling to room temperature, taking out the reaction kettle and the polytetrafluoroethylene support, respectively washing the ceramic tube with anhydrous ethanol and deionized water, and then putting the ceramic tube into a blast drying oven for drying at 60 ℃ to obtain the in-situ grown flower-shaped nano WO 3 Is a ceramic tube of (a). Annealing at 400 ℃ for 2 h to obtain the flower-shaped nanometer WO grown in situ after annealing 3 Is a ceramic tube of (a).
FIG. 2 is a flower-like nano WO grown on a ceramic tube in situ prepared in example 2 3 Samples before and after annealing were subjected to electron microscope Scanning (SEM). Wherein FIGS. 2 (a) and (b) are SEM images before and after annealing, respectively, FIG. 2 (c) is an SEM dimension mark image of a sample after annealing, and FIGS. 2 (a) and (b) show that the sample is still a two-dimensional lamellar 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 μm~1 μm。
FIG. 3 is a flower-like nano WO grown on a ceramic tube in situ prepared in example 2 3 The samples before and after the annealing treatment were subjected to X-ray diffraction pattern (XRD) detection. Wherein FIGS. 3 (a) and (b) are XRD patterns before and after annealing, respectively, and FIG. 3 (a) shows that flower-like nano WO grows on a ceramic tube in situ 3 The crystal system is orthorhombic when not annealed; as is clear from fig. 3 (b), the annealed material is monoclinic and has a good crystallinity.
Example 3 preparation method of in situ free growth gas sensor
The procedure of example 2 was repeated to obtain in-situ grown flower-like nano WO 3 Is a ceramic tube of (a).
The prepared in-situ annealing is used for growing flower-shaped nanometer WO 3 The ceramic tube is welded on a hexagonal base, and is packaged and aged, thus obtaining the annealed in-situ grown flower-shaped nanometer WO 3 Is provided.
FIG. 4 shows the gas sensor produced in example 3 at an operating temperature of 210℃and NO 2 Dynamic response curve for a gas concentration of 100 ppm. From the figure, it can be seen that the annealed in-situ grown flower-like nano WO 3 Gas sensor pair NO of (c) 2 The gas response time was 28 s and the recovery time was 3 s, which exhibited a fast response recovery rate.
FIG. 5 shows the gas sensor of example 3 at an operating temperature of 210℃for different concentrations of NO 2 Dynamic response curve of gas. As can be seen from the figure, the gas sensor has NO with different concentrations 2 The gas has good response reversibility, and the gas sensitivity is along with NO 2 The increase in gas increases.
FIG. 6 shows in-situ grown flower-like nano WO after annealing in example 3 3 The gas sensor of (2) has an operating temperature of 210 ℃ and NO 2 Stability 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 in one week or one month of use, thereby indicating that the gas sensor has good consistency in long-term useSex and stability, i.e. the gas sensor is sensitive to NO 2 The gas has good reproducibility and reversibility.
FIG. 7 shows WO's prepared in example 3 and comparative examples 1, 2 and 3 described below 3 The gas sensor performs gas-sensitive test on 17 gases of acetonitrile, benzene, toluene, xylene, absolute ethyl alcohol, isopropanol, n-butanol, acetone, diethyl ether, formaldehyde, acetaldehyde, trimethylamine, triethylamine, ammonia water, formamide, aniline and nitrogen dioxide. From the figure, WO 3 Gas sensor pair NO 2 The selectivity of the gas is best, the selectivity to other gases is poor, and the WO prepared by the invention 3 Gas sensor pair NO 2 The selectivity of the gas is obviously better than that of other three WO 3 A gas sensor.
FIG. 8 shows WO's prepared in example 3 and comparative examples 1, 2 and 3 described below 3 Gas sensor for 100 ppm NO at different working temperatures 2 A gas sensitivity curve. From the figure, WO 3 Gas sensor pair NO 2 The sensitivity of the gas shows a tendency to increase and decrease with increasing operating temperature, and WO at 210 °c 3 Gas sensor pair NO 2 The sensitivity of the gas is maximum; as can also be seen from the figure, the WO made by the invention 3 Gas sensor pair NO 2 Sensitivity to gases compared with other 3 WO 3 The gas sensor is high.
Example 4
The preparation method of the 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) and dissolving in a mixed solution of absolute ethyl alcohol and water, then weighing a certain amount of WCl6 and dissolving in the mixed solution, and fully stirring until WC is reached l6 Completely 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 the clean ceramic tube in the solution for 2-3 min, taking out, airing, immersing again for 2-4 times,the process ensures good tightness, then the ceramic tube and the solution are transferred to a reaction kettle together for hydrothermal reaction, after the reaction is finished, the ceramic tube is naturally cooled, and then the ceramic tube is repeatedly washed by absolute ethyl alcohol and deionized water and dried at 55-65 ℃ to obtain the WO freely growing in situ 3 Ceramic tubes 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, 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 through the ceramic tube, and aging for 7 days at room temperature to obtain the WO with the in-situ growth 3 A gas sensor.
Example 5
The preparation method of the gas sensor of the in-situ free-growth flower-shaped nano WO3 comprises the following steps:
(1) weighing 0.15 g of P123, dissolving in a mixed solution of 16.5 ml of EtOH and 1.0 g of ml water, stirring for 15 min to completely dissolve the P123, and weighing 0.4 g of WCl 6 Dissolving in the above mixed solution, stirring thoroughly for 20 min to WCl 6 Completely dissolve to form P123, etOH, H 2 O and WCl 6 Is a mixed solution of (a) and (b).
(2) Placing a ceramic tube and a polytetrafluoroethylene support into a beaker filled with alcohol, cleaning for 5 min by using a KQ-50DA ultrasonic cleaner, then placing the ceramic tube and the polytetrafluoroethylene support into an electrothermal blowing drying box for drying at 60 ℃, then placing the ceramic tube and the polytetrafluoroethylene support into the mixed solution in the step (1) for soaking for 3 min, taking out, airing, and repeating for 2 times.
(3) Hanging the ceramic tube treated in the step (2) on a polytetrafluoroethylene support, clamping the ceramic tube in a polytetrafluoroethylene lining, placing the ceramic tube in the center of a solution, placing the ceramic tube in a hydrothermal synthesis reaction kettle, placing the ceramic tube in a blast drying oven with a temperature rising in advance, and reacting for 80 min at 150 ℃, wherein the schematic diagram of the hydrothermal reaction device is shown in figure 1.
(4) After the hydrothermal synthesis reaction in the step (3) is finished, cooling to room temperature, taking out the reaction kettle and the polytetrafluoroethylene support, respectively flushing the ceramic tube with anhydrous ethanol and deionized water, putting the ceramic tube into a blast drying oven, and drying at 55 ℃ to obtain the in-situ grown flower-shaped nano WO 3 Is a ceramic tube of (a). Annealing at 450 ℃ for 2 h to obtain the flower-shaped nanometer WO grown in situ after annealing 3 Is a ceramic tube of (a).
(5) In-situ annealing to grow flower-like nanometer WO (WO) prepared in the step (4) 3 The ceramic tube of (2) is welded on a hexagonal base, and is packaged and aged, thus obtaining the annealed in-situ grown flower-shaped nano WO 3 Is provided.
According to detection, the annealed in-situ grown flower-like nano WO prepared in the embodiment 3 Gas sensor pair NO of (c) 2 The gas has good selectivity, high sensitivity, fast response recovery speed and good stability.
Example 6
The preparation method of the gas sensor of the in-situ free-growth flower-shaped nano WO3 comprises the following steps:
(1) weighing 0.2 g of P123, dissolving in a mixed solution of 16.5 ml of EtOH and 0.66 and ml water, stirring for 15 min to completely dissolve P123, and weighing 0.4 g of WCl 6 Dissolving in the above mixed solution, stirring thoroughly for 20 min to WCl 6 Completely dissolve to form P123, etOH, H 2 O and WCl 6 Is a mixed solution of (a) and (b).
(2) Placing a ceramic tube and a polytetrafluoroethylene support into a beaker filled with alcohol, cleaning for 5 min by using a KQ-50DA ultrasonic cleaner, then placing the ceramic tube and the polytetrafluoroethylene support into an electrothermal blowing drying box for drying at 60 ℃, then placing the ceramic tube and the polytetrafluoroethylene support into the mixed solution in the step (1) for soaking for 2 min, taking out, airing, and repeating for 4 times.
(3) Hanging the ceramic tube treated in the step (2) on a polytetrafluoroethylene support, clamping the ceramic tube in a polytetrafluoroethylene lining, placing the ceramic tube in the center of a solution, placing the ceramic tube in a hydrothermal synthesis reaction kettle, placing the ceramic tube in a blast drying oven with a temperature rising in advance, and reacting for 150 min at 120 ℃, wherein the schematic diagram of the hydrothermal reaction device is shown in figure 1.
(4) After the hydrothermal synthesis reaction in the step (3) is finished, cooling to room temperature, taking out the reaction kettle and the polytetrafluoroethylene support, respectively flushing the ceramic tube with absolute ethyl alcohol and deionized water, putting the ceramic tube into a blast drying oven, and drying at 65 ℃ to obtain the in-situ grown flower-shaped nano WO 3 Is a ceramic tube of (a). Annealing at 300 deg.c for 4 h to obtain annealed flower-shaped nanometer WO 3 Is a ceramic tube of (a).
(5) In-situ annealing to grow flower-like nanometer WO (WO) prepared in the step (4) 3 The ceramic tube is welded on a hexagonal base, and is packaged and aged, thus obtaining the annealed in-situ grown flower-shaped nanometer WO 3 Is provided.
According to detection, the annealed in-situ grown flower-like nano WO prepared in the embodiment 3 Gas sensor pair NO of (c) 2 The gas has good selectivity, high sensitivity, fast response recovery speed and good stability.
Comparative example 1
In-situ growth WO without annealing treatment 3 The preparation method of the gas sensor comprises the following steps:
(1) 0.2 g of P123 was weighed out in 16.5 ml of EtOH and 0.5 ml of H 2 In the mixed solution of O, stirring for 15 min to dissolve P123 completely, and weighing 0.4 g WCl 6 Dissolving in the above mixed solution, stirring thoroughly for 20 min to WCl 6 Completely dissolve to form P123, etOH, H 2 O and WCl 6 Is a mixed solution of (a) and (b).
(2) Placing a ceramic tube and a polytetrafluoroethylene support into a beaker filled with alcohol, cleaning for 5 min by using a KQ-50DA ultrasonic cleaner, then placing the ceramic tube and the polytetrafluoroethylene support into an electrothermal blowing drying box for drying at 60 ℃, then placing the ceramic tube and the polytetrafluoroethylene support into the mixed solution in the step (1) for soaking for 3 min, taking out, airing, and repeating for 4 times.
(3) Hanging the ceramic tube treated in the step (2) on a polytetrafluoroethylene bracket, clamping the ceramic tube into a polytetrafluoroethylene lining, placing the ceramic tube in the center of a solution, placing the ceramic tube into a blast drying oven with a temperature rising in advance after a hydrothermal synthesis reaction kettle is arranged, and reacting for 120 min at 110 ℃, wherein the schematic diagram of a hydrothermal reaction device is shown in figure 1.
(4) After the hydrothermal synthesis reaction in the step (3) is finished, cooling to room temperature, taking out the reaction kettle and the polytetrafluoroethylene support, respectively washing the ceramic tube with anhydrous ethanol and deionized water, and then putting the ceramic tube into a blast drying oven for drying at 60 ℃ to obtain the in-situ grown flower-shaped nano WO 3 Is a ceramic tube of (a).
(5) In-situ growing flower-shaped nanometer WO (WO) prepared in step (4) 3 The ceramic tube of (2) is welded on a hexagonal base, and is packaged and aged to obtain the in-situ grown flower-like nano WO 3 Is provided.
It can be seen from FIG. 7 that the annealed in-situ grown flower-like nano WO 3 Gas sensor pair NO of (c) 2 The selectivity of the gas was better than that of comparative example 1. From FIG. 8, it can be seen that the annealed in-situ grown flower-like nano WO 3 Gas sensor pair NO of (c) 2 The sensitivity of the gas was higher than that of comparative example 1.
Comparative example 2
Manual coating flower-shaped nanometer WO 3 The preparation steps of the gas sensor are as follows:
(1) 0.2 g of P123 was dissolved in 16.5 ml of EtOH and 0.5 ml of H 2 Stirring the mixed solution of O for 15 min to completely dissolve P123, so as to obtain a clear and transparent uniform solution;
(2) 0.4 g WCl was taken 6 Adding the powder into the solution obtained in the step (1), stirring for 20 min to obtain WCl 6 Completely dissolved to prepare bright yellow solution.
(3) And (3) rapidly transferring the solution obtained in the step (2) into a 50 ml polytetrafluoroethylene high-pressure reaction kettle, putting the reaction kettle into an oven which is heated to 110 ℃ in advance, reacting for 120 min, and naturally cooling to room temperature.
(4) Taking out the solution after reaction, placing into a centrifuge tube, repeatedly washing and centrifuging with absolute ethyl alcohol and deionized water, centrifuging for 5 min each time, and replacing the position with an ultrasonic cell pulverizer to perform ultrasonic 3 times to assist in dispersion and stripping WO 3 A nano-sheet.
(5) Adding deionized water into the washed sample, and lyophilizing to obtain blue powder sample, i.e. WO 3 Precursor gas sensitive materials.
(6) Mixing the prepared gas-sensitive material with terpineol respectively, grinding uniformly to obtain gas-sensitive slurry, then uniformly coating the gas-sensitive slurry on the surface of a clean ceramic tube, baking by an infrared lamp, welding the gas-sensitive slurry on a black hexagonal base, passing a Ni-Cr heating wire through the ceramic tube and welding the Ni-Cr heating wire on the base, and aging the prepared gas-sensitive element at room temperature for 7 days to obtain the manual-coated flower-shaped nano WO 3 Is provided.
As can be seen from FIG. 7, the gas sensor pair NO produced in this comparative example 2 The selectivity of the gas was inferior to that of the gas sensor prepared in example 2 of the present invention. From FIG. 8, it can be seen that the gas sensor pair NO prepared by this comparative example 2 The sensitivity of the gas was lower than that of the gas sensor prepared in example 2 of the present invention.
Comparative example 3
Manual coating annealing flower-shaped nanometer WO 3 The preparation steps of the gas sensor are as follows:
(1) 0.2 g of P123 was dissolved in 16.5 ml of EtOH and 0.5 ml of H 2 And (3) stirring the mixed solution of O for 15 min to completely dissolve the P123, so as to obtain a clear and transparent uniform solution.
(2) 0.4 g WCl was taken 6 Adding the powder into the solution obtained in the step (1), stirring for 20 min to obtain WCl 6 Completely dissolved to prepare bright yellow solution.
(3) And (3) rapidly transferring the solution obtained in the step (2) into a 50 ml polytetrafluoroethylene high-pressure reaction kettle, putting the reaction kettle into an oven which is heated to 110 ℃ in advance, reacting for 120 min, and naturally cooling to room temperature.
(4) Taking out the solution after reaction, placing into a centrifuge tube, repeatedly washing and centrifuging with absolute ethyl alcohol and deionized water, centrifuging for 5 min each time, and replacing the position with an ultrasonic cell pulverizer to perform ultrasonic 3 times to assist in dispersion and stripping WO 3 A nano-sheet.
(5) Adding proper deionized water into the washed sample, and freeze-drying to obtain blue powder sampleAnnealing the blue powder sample in a tube furnace at 400 ℃ for 2 h to obtain yellow WO 3 Powder, thus obtaining the annealed WO 3 Precursor gas sensitive materials.
(6) Mixing the gas-sensitive material prepared in the step (5) with terpineol respectively, grinding uniformly to obtain gas-sensitive slurry, then uniformly coating the gas-sensitive slurry on the surface of a clean ceramic tube, baking by an infrared lamp, welding the gas-sensitive slurry on a black hexagonal base, passing a Ni-Cr heating wire through the interior of the ceramic tube and welding the Ni-Cr heating wire on the base, and aging the prepared gas-sensitive element at room temperature for 7 days to obtain the manual-coated flower-shaped nano WO 3 Is provided.
From FIG. 7, it can be seen that the gas sensor pair NO prepared in this comparative example 2 The selectivity of the gas was inferior to that of the gas sensor prepared in example 2 of the present invention. From FIG. 8, it can be seen that the gas sensor pair NO prepared by this comparative example 2 The sensitivity of the gas was lower than that of the gas sensor prepared in example 2 of the present invention.
The foregoing description of the preferred embodiments of the invention is not intended to be limiting, but rather is intended to cover all modifications, equivalents, alternatives, and improvements that fall within the spirit and scope of the invention.
Claims (3)
1. Flower-shaped nano WO (WO) capable of freely growing in situ 3 The 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, dissolving in a mixed solution of absolute ethyl alcohol and water, and then weighing a certain amount of WCl 6 Dissolving in the above mixed solution, stirring thoroughly until WCl 6 Completely dissolve to form P123, etOH, H 2 O and WCl 6 Is a mixed solution of (a) and (b); the P123 and WCl 6 The mass ratio of the absolute ethyl alcohol to the water is 1:1-1:5, and the mass ratio of the absolute ethyl alcohol to the water is 15:1-40:1;
B. immersing a clean ceramic tube in the solution for 2-3 min, taking out, airing, immersing again, and repeatedly immersing for 2-4 times, wherein the process ensures good tightness, and then hanging the ceramic tube in the polymerClamping the ceramic tube on a polytetrafluoroethylene lining on a tetrafluoroethylene bracket, and transferring the ceramic tube and the solution to a reaction kettle together at the center of the solution for hydrothermal reaction, wherein the temperature of the hydrothermal reaction is 110-150 ℃ and the reaction time is 80-240 min; after the reaction is finished, naturally cooling, repeatedly flushing the ceramic tube with absolute ethyl alcohol and deionized water, drying at 55-65 ℃ and then carrying out annealing treatment, wherein the annealing temperature is 300-450 ℃, the heating rate is 1-3 ℃/min, and the heat preservation time is 2-4 hours, so that the in-situ free-growth nano WO can be obtained 3 A gas sensitive material;
said WO 3 The gas-sensitive material is prepared by WO 3 WO of monoclinic system composed of nanoplates 3 A nanoflower; 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.
2. In situ free-growth flower-like nano WO prepared according to the method of claim 1 3 Gas-sensitive material in NO 2 Application to real-time detection.
3. A preparation method of an in-situ free growth gas sensor is characterized by comprising the following steps of: the method comprises the following steps:
(1) Weighing a certain amount of polyethylene oxide-polypropylene oxide-polyethylene oxide triblock polymer P123, dissolving in a mixed solution of absolute ethyl alcohol and water, and then weighing a certain amount of WCl 6 Dissolving in the above mixed solution, stirring thoroughly until WCl 6 Completely dissolve to form P123, etOH, H 2 O and WCl 6 Is a mixed solution of (a) and (b); the P123 and WCl 6 The mass ratio of the absolute ethyl alcohol to the water is 1:1-1:5, and the mass ratio of the absolute ethyl alcohol to the water is 15:1-40:1;
(2) Immersing a clean ceramic tube in a solution for 2-3 min, taking out, airing, immersing again, repeatedly immersing for 2-4 times, wherein the process ensures good tightness, then hanging the ceramic tube on a polytetrafluoroethylene bracket, clamping the ceramic tube in a polytetrafluoroethylene lining, placing the ceramic tube in the center of the solution, transferring the ceramic tube together with the solution to a reaction kettle for hydrothermal reaction, wherein the temperature of the hydrothermal reaction is that110. The temperature is between 150 ℃ and the reaction time is between 80 and 240 minutes; after the reaction is finished, naturally cooling, repeatedly flushing the ceramic tube with absolute ethyl alcohol and deionized water, drying at 55-65 ℃ and then carrying out annealing treatment, wherein the annealing temperature is 300-450 ℃, the heating rate is 1-3 ℃/min, and the heat preservation time is 2-4 hours, so that the WO freely growing in situ can be obtained 3 Ceramic tubes 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 through the ceramic tube, and aging for 7 days at room temperature to obtain the WO with the in-situ growth 3 A gas sensor.
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