CN114609197A - Gas sensitive material, preparation method and application thereof in NH3Application in gas sensor - Google Patents

Abstract

The invention provides a composite material based on MoO ₃ @MoS ₂ /PTH, a preparation method and an application in an ammonia gas gas sensor, and relates to the field of gas detection, wherein MoO ₃ @MoS ₂ accounts for MoO ₃ @MoS ₂ /PTH 20% of the mass fraction; its working temperature is room temperature, and its sensitivity to 50ppm ammonia gas reaches 1.4; the preparation method is as follows: first, flower-like MoO ₃ is prepared by hydrothermal method, and MoO ₃ @MoS is prepared by using MoO ₃ as a precursor. ₂ , and then the MoO ₃ @MoS ₂ /PTH gas-sensing material was prepared by in-situ polymerization; the MoO ₃ @MoS ₂ /PTH material was coated on the surface of the Al ₂ O ₃ ceramic tube coated with gold electrodes to make a gas-sensing element . The MoO ₃ @MoS ₂ /PTH gas-sensing material prepared by the in-situ polymerization method in the present invention has higher sensitivity to ammonia gas, faster response time and faster recovery time.

Description

Gas-sensing material and preparation method and its application in NH3 gas-sensing sensor

technical field

The invention relates to the technical field of preparation of functional nanomaterials, and also to the technical field of gas sensor detection, in particular to a gas-sensing material, a preparation method and its application in a gas sensor.

Background technique

In recent years, with the rapid development of modern industry, environmental and ecological issues have attracted more and more attention. Environmental protection and monitoring of harmful substances have become top priorities. Air pollution is closely related to human health, and it is increasingly necessary to detect harmful gases. . Ammonia is a very common gas in daily life. It is not only the raw material of many chemical products, but also the exhaust gas of many chemical products. When the concentration of ammonia gas exceeds a certain range, it will cause damage to our body. Therefore, we need to monitor Ammonia concentration to ensure product quality and environmental safety.

There are many types of chemical resistance sensors in the world. Most of them use metal semiconductors as sensitive materials. Semiconductor sensors have high sensitivity, but high temperature and poor gas selectivity. Therefore, new resistance sensors are urgently needed to improve the application of the sensor. Sex and selectivity. Polythiophene in conducting polymers is considered to be an extremely promising sensing material due to its advantages of easy polymerization, high electrical conductivity, good thermal and environmental stability, etc., between polythiophene and inorganic components. It is of great significance to improve the gas-sensing performance of components.

In recent years, new _two -dimensional materials have developed rapidly. Among them, MoS2 has the characteristics of good conductivity, strong adsorption, high reactivity, good flexibility, etc., and has a natural band gap. MoS2 is a strictly _two -dimensional material with large specific surface area, unsaturated bonds at the edges, etc., which provide active sites for gas molecule adsorption reactions. These properties make _MoS2 a hot spot in the research of gas sensing materials. MoS ₂ is not sensitive to some gases. Therefore, doping and compounding methods are used to improve its gas sensing performance. Device development provides new ideas.

MoO ₃ is a broadband transition metal oxide semiconductor material with a special layer structure and good redox catalytic activity. Its physical and chemical properties are stable, and the morphology and structure can be well controlled by controlling the reaction conditions. The construction of heterostructures can improve the gas-sensing properties of materials.

CN105510403A The invention adopts a chemical or physical etching method to form a quasi-periodic structure on the surface of a single crystal silicon wafer, and forms electrodes by thermal evaporation to detect ammonia gas, but this process requires high equipment, high operation requirements, and production costs. high, which is not conducive to large-scale applications. CN102978578A adopts sputtering method to prepare an ammonia gas sensor with copper oxide doped tin dioxide matrix. The sensor has high sensitivity and short response recovery time, but has high working temperature and large volume. CN104502415A invented an ammonia gas sensor based on precious metal composite material, which has good gas sensing performance but high cost. CN110702752 invented a catalytic gas sensor, but its recovery time is long. CN102103103A discloses a sensor for detecting ammonia gas and a preparation method thereof. The sensor for detecting ammonia gas is made of organic thin film transistors. However, the transistor sensor has the disadvantages of complicated processing technology, long production cycle, harsh production conditions, etc. In addition, the chemical reagents used in the preparation process are not environmentally friendly.

In view of this, the present invention provides a gas sensor and its application in ammonia gas detection, which is used to solve the defect in the prior art that the gas sensor needs to be heated up or under an ultraviolet lamp to work.

SUMMARY OF THE INVENTION

In view of the deficiencies of the prior art, the purpose of the present invention is to provide a gas sensing material of MoO ₃ @MoS ₂ /PTH, a preparation method and its application in a gas sensing sensor.

In order to realize the above-mentioned purpose of the invention, the technical scheme of the present invention is as follows:

A gas-sensing material, the material is MoO ₃ @MoS ₂ /PTH, which is obtained by using MoO ₃ as a core and MoS ₂ as a shell to form a core-shell structure MoO ₃ @ MoS ₂ , and then polymerizing with a thiophene monomer, wherein _The core _- shell structures _of MoO3 and MoS2, MoO3@MoS2, account for 10–30 _% of the material mass fraction.

As a preferred way, the flower-like nano-molybdenum trioxide was prepared by hydrothermal method first, and then the core-shell structures of MoO ₃ and MoS ₂ were prepared, and MoO ₃ @MoS ₂ /PTH was prepared by in-situ polymerization.

As a preferred manner, the gas-sensing material has a sheet-like stacking structure, the working temperature of the MoO ₃ @MoS ₂ /PTH gas-sensing material is room temperature, and the sensitivity to 50 ppm of ammonia gas reaches 1.4.

The present invention also provides a method for preparing the gas-sensitive material, which specifically includes the following steps:

S1: Preparation of flower-like molybdenum trioxide: Heptamolybdic acid tetrahydrate in a molar ratio of 1:10 to 3:10 was prepared by (NH ₄ ) ₆ Mo ₇ O ₂₄ ·4H ₂ O and ammonium sulfate (NH ₄ ) ₂ SO ₄ Dissolve in 50 mL of deionized water, then continue to add 0.93 mol of ammonia water and an appropriate amount of deionized water to make up to 70 mL, stir the obtained solution, and then add 1.817 g of thioacetamide and stir to obtain a clear solution. Next, transfer the solution into a 100mL hydrothermal reactor, and heated at 180-240°C for 24 hours; after naturally cooling to room temperature, the resulting precipitate was collected, washed several times with deionized water and ethanol, and finally vacuum-dried at 60°C for 10 hours;

S2: Preparation of MoO ₃ @MoS ₂ : Weigh 1mM MoO ₃ powder, and ultrasonically disperse it in a 100 mL mixed solution of water and ethanol. The volume ratio of water and ethanol in the mixed solution is 2:3. To obtain a homogeneous MoO ₃ After the dispersion, add thiourea in different molar ratios, and the molar ratio of MoO ₃ : H ₂ NSNH ₂ is 1:1 to 1:10. After the thiourea is completely dissolved, transfer the entire mixed dispersion to a hydrothermal solution with a capacity of 100 mL. In the kettle, the filling ratio of the hydrothermal kettle is 70%, the hydrothermal temperature is 180°C-220°C, and the hydrothermal time is 18-24h; after the reaction is completed, it is cooled to room temperature, washed with water and ethanol by centrifugation several times, and dried. get MoO ₃ @MoS ₂ ;

S3: Preparation of materials, weigh anhydrous ferric chloride and dissolve it in chloroform, the molar ratio of thiophene monomer and anhydrous ferric chloride is 3:1, stir for 1 hour to obtain dark green turbid liquid, weigh thiophene monomer and MoO ₃ @MoS ₂ was dissolved in chloroform, the mass ratio of thiophene monomer and MoO ₃ @MoS ₂ was 10:1 ~ 10:3, ultrasonic for 1 h to obtain a dispersion of thiophene and molybdenum disulfide, and the dispersion was slowly added dropwise to chlorine After the reaction was completed, the solvent was evaporated to dryness at room temperature, and an appropriate amount of 1 mol/L HCl was added and stirred at room temperature for 12 hours; the obtained product was washed with HCl for several times, and then washed with deionized water at 60-80 Dry at ℃ for 6 to 8 hours.

As a preferred way, in S1, the solution is transferred to a hydrothermal reactor and reacted at 180° C. for 24 hours.

As a preferred way, in S2, MoO ₃ and H ₂ NSNH ₂ with a molar ratio of 1:3 are weighed and added to the solution.

As a preferred way, in S3, the thiophene monomer and MoO ₃ @MoS ₂ with a mass ratio of 10:2 are weighed and dissolved in chloroform.

_The invention also provides the application _of a gas _- sensing material in an NH ₃ gas _- sensing sensor. sensitive sensor element.

As a preferred way, the preparation method of the NH ₃ gas sensing element is as follows: take the MoO ₃ @MoS ₂ /PTH powder product and grind it for 10 minutes, then add anhydrous ethanol and mix and grind to a paste, and the obtained paste is uniform Smear on the surface of Al ₂ O ₃ ceramic tube covered with gold electrode, evaporate ethanol to dryness at room temperature, and then weld the gold electrode on the ceramic base.

Beneficial effects of the present invention: The present invention provides a gas sensor, which can detect different concentrations of ammonia under the condition of visible light at room temperature, and has the advantages of good responsiveness, high sensitivity, fast response and recovery time, and selectivity. Strong advantages; and simple preparation, low production cost, suitable for ammonia detection in certain environments. The technical defect in the prior art that the gas sensor can only work under high temperature or ultraviolet light is solved.

Description of drawings

Fig. 1 is the SEM image of the flower-like MoO ₃ of the present invention. (a) is low magnification, (b) is high magnification

Figure 2 is a SEM image of the polythiophene of the present invention. (a) is low magnification, (b) is high magnification

FIG. 3 is a SEM image of MoO ₃ @MoS ₂ /PTH of the present invention. (a) is low magnification, (b) is high magnification

FIG. 4 is an XPS diagram of MoO ₃ @MoS ₂ /PTH of the present invention.

FIG. 5 is the FTIR diagram of PTH, MoO ₃ @MoS ₂ and MoO ₃ @MoS ₂ /PTH of the present invention.

FIG. 6 is the response curve of MoO ₃ @MoS ₂ /PTH to different concentrations of ammonia gas at room temperature in the present invention.

Detailed ways

The embodiments of the present invention are described below through specific specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

Example 1

This embodiment provides a gas-sensing material, which is MoO ₃ @MoS ₂ /PTH. The core-shell structure MoO ₃ @MoS ₂ is formed by using MoO ₃ as the core and MoS ₂ as the shell, and then reacts with thiophene monomer. The core-shell structure MoO ₃ @MoS ₂ of MoO ₃ and MoS ₂ accounts for 10-30% of the material mass fraction.

The gas-sensing material has a sheet-like stacking structure, the MoO ₃ @MoS ₂ /PTH gas-sensing material has a working temperature of room temperature, and has a sensitivity of 1.4 to 50 ppm of ammonia gas.

This embodiment also provides a method for preparing the gas-sensing material. First, a flower-shaped nano-molybdenum trioxide is prepared by a hydrothermal method, and then a core-shell structure of MoO ₃ and MoS ₂ is prepared, which is prepared by an in-situ polymerization method. out MoO ₃ @MoS ₂ /PTH.

Specifically include the following steps:

S1: Preparation of flower-like molybdenum trioxide: Dissolve tetrahydrate heptamolybdic acid with a molar ratio of 1:10 according to (NH ₄ ) ₆ Mo ₇ O ₂₄ ·4H ₂ O and ammonium sulfate (NH ₄ ) ₂ SO ₄ in 50 mL of ionized water, then continue to add 0.93mol ammonia water and an appropriate amount of deionized water to make the volume to 70mL, stir the obtained solution uniformly, then add 1.817g thioacetamide and stir well to obtain a clear solution, next, transfer the solution to 100mL of water In a thermal reaction kettle, and heated at 180 ° C for 24 hours; after naturally cooling to room temperature, the obtained precipitate was collected, washed several times with deionized water and ethanol, and finally vacuum-dried at 60 ° C for 10 hours;

S2: Preparation of MoO ₃ @MoS ₂ : Weigh 1mM MoO ₃ powder, and ultrasonically disperse it in a 100 mL mixed solution of water and ethanol. The volume ratio of water and ethanol in the mixed solution is 2:3. To obtain a homogeneous MoO ₃ After the dispersion, add thiourea in different molar ratios, and the molar ratio of MoO ₃ : H ₂ NSNH ₂ is 1:1. After the thiourea is completely dissolved, the entire mixed dispersion is transferred to a hydrothermal kettle with a capacity of 100 mL. The filling ratio of the hot kettle is 70%, the hydrothermal temperature is 180°C, and the hydrothermal time is 24h; after the reaction, after cooling to room temperature, centrifugal washing with water and ethanol for several times respectively, and drying to obtain MoO ₃ @MoS ₂ ;

S3: Preparation of materials, weigh anhydrous ferric chloride and dissolve it in chloroform, the molar ratio of thiophene monomer and anhydrous ferric chloride is 3:1, stir for 1 hour to obtain dark green turbid liquid, weigh thiophene monomer and MoO ₃ @MoS ₂ was dissolved in chloroform, the mass ratio of thiophene monomer and MoO ₃ @MoS ₂ was 10:1, and the dispersion of thiophene and molybdenum disulfide was obtained by ultrasonic for 1 h, and the dispersion was slowly added dropwise to the ferric chloride turbidity. , and stirred at room temperature for 9 h; after the reaction was completed, the solvent was evaporated to dryness at room temperature, and an appropriate amount of 1 mol/L HCl was added and stirred at room temperature for 12 h; the obtained product was washed with HCl for several times, then washed with deionized water, and dried at 60 °C for 6 hours.

Example 2

This embodiment provides a gas-sensing material, which is MoO ₃ @MoS ₂ /PTH. The core-shell structure MoO ₃ @MoS ₂ is formed by using MoO ₃ as the core and MoS ₂ as the shell, and then reacts with thiophene monomer. The core-shell structure MoO ₃ @MoS ₂ of MoO ₃ and MoS ₂ accounts for 10-30% of the material mass fraction.

The gas-sensing material has a sheet-like stacking structure, the MoO ₃ @MoS ₂ /PTH gas-sensing material has a working temperature of room temperature, and has a sensitivity of 1.4 to 50 ppm of ammonia gas.

This embodiment also provides a method for preparing the gas-sensing material. First, a flower-shaped nano-molybdenum trioxide is prepared by a hydrothermal method, and then a core-shell structure of MoO ₃ and MoS ₂ is prepared, which is prepared by an in-situ polymerization method. out MoO ₃ @MoS ₂ /PTH.

Specifically include the following steps:

S1: Preparation of flower-like molybdenum trioxide: Dissolve tetrahydrate heptamolybdic acid with a molar ratio of 3:10 according to (NH ₄ ) ₆ Mo ₇ O ₂₄ ·4H ₂ O and ammonium sulfate (NH ₄ ) ₂ SO ₄ in 50 mL of ionized water, then continue to add 0.93mol ammonia water and an appropriate amount of deionized water to make the volume to 70mL, stir the obtained solution uniformly, then add 1.817g thioacetamide and stir well to obtain a clear solution, next, transfer the solution to 100mL of water In a thermal reaction kettle, and heated at 240°C for 24 hours; after naturally cooling to room temperature, the obtained precipitate was collected, washed several times with deionized water and ethanol, and finally vacuum-dried at 60°C for 10 hours;

S2: Preparation of MoO ₃ @MoS ₂ : Weigh 1mM MoO ₃ powder, and ultrasonically disperse it in a 100 mL mixed solution of water and ethanol. The volume ratio of water and ethanol in the mixed solution is 2:3. To obtain a homogeneous MoO ₃ After the dispersion, add thiourea in different molar ratios, and the molar ratio of MoO ₃ : H ₂ NSNH ₂ is 1:10. After the thiourea is completely dissolved, the entire mixed dispersion is transferred to a hydrothermal kettle with a capacity of 100 mL. The filling ratio of the hot kettle is 70%, the hydrothermal temperature is 220°C, and the hydrothermal time is 18h; after the reaction, after cooling to room temperature, centrifugal washing with water and ethanol for several times respectively, and drying to obtain MoO ₃ @MoS ₂ ;

S3: Preparation of materials, weigh anhydrous ferric chloride and dissolve it in chloroform, the molar ratio of thiophene monomer and anhydrous ferric chloride is 3:1, stir for 1 hour to obtain dark green turbid liquid, weigh thiophene monomer and MoO ₃ @MoS ₂ was dissolved in chloroform, the mass ratio of thiophene monomer and MoO ₃ @MoS ₂ was 10:3, and the dispersion of thiophene and molybdenum disulfide was obtained by ultrasonic for 1 h, and the dispersion was slowly added dropwise to the ferric chloride turbidity. , and stirred at room temperature for 9 h; after the reaction was completed, the solvent was evaporated to dryness at room temperature, and an appropriate amount of 1 mol/L HCl was added and stirred at room temperature for 12 h; the obtained product was washed with HCl for several times, then washed with deionized water, and dried at 60-80 ° C for 6- 8 hours.

Example 3

This embodiment provides a gas-sensing material, which is MoO ₃ @MoS ₂ /PTH. The core-shell structure MoO ₃ @MoS ₂ is formed by using MoO ₃ as the core and MoS ₂ as the shell, and then reacts with thiophene monomer. The core-shell structure MoO ₃ @MoS ₂ of MoO ₃ and MoS ₂ accounts for 10-30% of the material mass fraction.

The gas-sensing material has a sheet-like stacking structure, the MoO ₃ @MoS ₂ /PTH gas-sensing material has a working temperature of room temperature, and has a sensitivity of 1.4 to 50 ppm of ammonia gas.

This embodiment also provides a method for preparing the gas-sensing material. First, a flower-shaped nano-molybdenum trioxide is prepared by a hydrothermal method, and then a core-shell structure of MoO ₃ and MoS ₂ is prepared, which is prepared by an in-situ polymerization method. out MoO ₃ @MoS ₂ /PTH.

Specifically include the following steps:

S1: Preparation of flower-like molybdenum trioxide: The molar ratio of 2:10 of tetrahydrate heptamolybdic acid was dissolved in 50 mL of (NH ₄ ) ₆ Mo ₇ O ₂₄ ·4H ₂ O and ammonium sulfate (NH ₄ ) ₂ SO ₄ ionized water, then continue to add 0.93mol ammonia water and an appropriate amount of deionized water to make the volume to 70mL, stir the obtained solution uniformly, then add 1.817g thioacetamide and stir well to obtain a clear solution, next, transfer the solution to 100mL of water In a thermal reaction kettle, and heated at 200 ° C for 24 hours; after naturally cooling to room temperature, the obtained precipitate was collected, washed several times with deionized water and ethanol, and finally vacuum-dried at 60 ° C for 10 hours;

S2: Preparation of MoO ₃ @MoS ₂ : Weigh 1mM MoO ₃ powder, and ultrasonically disperse it in a 100 mL mixed solution of water and ethanol. The volume ratio of water and ethanol in the mixed solution is 2:3. To obtain a homogeneous MoO ₃ After the dispersion, add thiourea with different molar ratios, and the molar ratio of MoO ₃ : H ₂ NSNH ₂ is 1:3. When the thiourea is completely dissolved, the entire mixed dispersion is transferred to a hydrothermal kettle with a capacity of 100 mL. The filling ratio of the hot kettle is 70%, the hydrothermal temperature is 200°C, and the hydrothermal time is 20h; after the reaction, after cooling to room temperature, centrifugal washing with water and ethanol for several times respectively, and drying to obtain MoO ₃ @MoS ₂ ;

S3: Preparation of materials, weigh anhydrous ferric chloride and dissolve it in chloroform, the molar ratio of thiophene monomer and anhydrous ferric chloride is 3:1, stir for 1 hour to obtain dark green turbid liquid, weigh thiophene monomer and MoO ₃ @MoS ₂ was dissolved in chloroform, the mass ratio of thiophene monomer and MoO ₃ @MoS ₂ was 10:2, and the dispersion of thiophene and molybdenum disulfide was obtained by ultrasound for 1 h, and the dispersion was slowly added dropwise to the ferric chloride turbidity. , and stirred at room temperature for 9 h; after the reaction was completed, the solvent was evaporated to dryness at room temperature, and an appropriate amount of 1 mol/L HCl was added and stirred at room temperature for 12 h; the obtained product was washed with HCl for several times, then washed with deionized water, and dried at 70 °C for 7 hours.

Performance Testing

The MoO ₃ @MoS ₂ /PTH gas-sensing materials of 3 examples were characterized:

The MoO ₃ @MoS ₂ /PTH gas-sensing material prepared in the example was characterized physically or chemically by scanning electron microscope, Fourier transform infrared spectrometer and X-ray photoelectron spectrometer, as shown in Figure 1, Figure 2, Figure 3, Figure 4, Figure 5:

Figure 1 is a scanning electron microscope image of MoO ₃ , from which it can be seen that the synthesized MoO ₃ is a flower-like structure;

Figure 2 is a scanning electron microscope image of polythiophene, from which it can be seen that the rod-shaped polythiophene is synthesized and connected into a network structure;

Figure 3 is the scanning electron microscope image of MoO ₃ @MoS ₂ /PTH. It can be seen from the figure that PTH was successfully polymerized on MoO ₃ @MoS ₂ ;

Figure 4 is the X-ray photoelectron spectrum of MoO ₃ @MoS ₂ /PTH: it can be seen from the figure that the composite material is composed of C, O, S, Mo, and four elements, which are shown in the figure at 164.41eV, 229.08eV, The four peaks at 285.07eV and 532.33eV are assigned to the binding energies of S2p, Mo3d, C1s and O1s, respectively.

Figure 5 is the FT-IR images of PTH, MoO ₃ @MoS ₂ , MoO ₃ @MoS ₂ /PTH, MoO ₃ @MoS ₂ /PTH nanocomposite shows peaks similar to PTH. 785.03 cm ^-1 corresponds to the CH out-of-plane stretching vibration of the 2,5-substituted thiophene ring generated by the polymerization of thiophene monomer. The peak at 670.5 cm ^-1 is the CS bond bending vibration, and the peak band at _462.92 cm _- ¹ can be attributed to the ring deformation mode of the CSC bond, demonstrating the successful polymerization of thiophene on MoO3@MoS2.

Example 4 Preparation of MoO ₃ @MoS ₂ /PTH ammonia gas sensor

Take the MoO ₃ @MoS ₂ /PTH powder product and grind it for 10 min, then add anhydrous ethanol and mix and grind to a paste. The obtained paste is evenly smeared on the surface of the Al ₂ O ₃ ceramic tube coated with gold electrodes. The ethanol was evaporated to dryness, and then the gold electrode was welded on the ceramic base to obtain the NH ₃ gas sensor.

Test the sensitivity of the MoO ₃ @MoS ₂ /PTH ammonia gas sensor of Example 4

The sensitivity of the gas sensor material was determined by the static gas distribution method: the prepared MoO ₃ @MoS ₂ /PTH sensor was tested by adding different concentrations of ammonia gas at room temperature, and the formula S=R/R ₀ was used to calculate the Sensitivity, where R is the resistance value of the sensor after exposure to ammonia, and R ₀ is the initial resistance value of the sensor in air, resulting in MoO ₃ @MoS ₂ /PTH gas sensing material for 50ppm, 100ppm, 200ppm, 300ppm, 500ppm , 800ppm sensitivity, as shown in Figure 6.

The above-mentioned embodiments merely illustrate the principles and effects of the present invention, but are not intended to limit the present invention. Anyone skilled in the art can make modifications or changes to the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or changes made by those with ordinary knowledge in the technical field without departing from the spirit and technical idea disclosed in the present invention should still be covered by the claims of the present invention.

Claims (9)

1. A gas-sensing material, characterized in that: the material is MoO ₃ @MoS ₂ /PTH, and a core-shell structure MoO ₃ @ MoS ₂ is formed by using MoO ₃ as a core and MoS ₂ as a shell, and then combined with thiophene monolayer. The core-shell structure MoO ₃ @MoS ₂ of MoO ₃ and MoS ₂ accounts for 10-30% of the mass fraction of the material. 2. gas sensor material according to claim 1, is characterized in that: first adopt the hydrothermal method to prepare flower-shaped nano molybdenum trioxide, then prepare the core-shell structure of MoO ₃ and MoS ₂ , prepare by in-situ polymerization method out MoO ₃ @MoS ₂ /PTH. 3. The gas-sensing material according to claim 1, wherein the gas-sensing material is a sheet-like stacking structure, and the MoO ₃ @MoS ₂ /PTH gas-sensing material operating temperature is room temperature, and is sensitive to 50ppm of ammonia gas to 1.4. 4. the preparation method of the gas-sensitive material described in any one of claim 1 to 3, is characterized in that: specifically comprises the following steps: S1: Preparation of flower-like molybdenum trioxide: Heptamolybdic acid tetrahydrate in a molar ratio of 1:10 to 3:10 was prepared by (NH ₄ ) ₆ Mo ₇ O ₂₄ ·4H ₂ O and ammonium sulfate (NH ₄ ) ₂ SO ₄ Dissolve in 50 mL of deionized water, then continue to add 0.93 mol of ammonia water and an appropriate amount of deionized water to make up to 70 mL, stir the obtained solution, and then add 1.817 g of thioacetamide and stir to obtain a clear solution. Next, transfer the solution into a 100mL hydrothermal reactor, and heated at 180-240°C for 24 hours; after naturally cooling to room temperature, the resulting precipitate was collected, washed several times with deionized water and ethanol, and finally vacuum-dried at 60°C for 10 hours; S2: Preparation of MoO ₃ @MoS ₂ : Weigh 1mM MoO ₃ powder, and ultrasonically disperse it in a 100 mL mixed solution of water and ethanol. The volume ratio of water and ethanol in the mixed solution is 2:3. To obtain a homogeneous MoO ₃ After the dispersion, add thiourea in different molar ratios, and the molar ratio of MoO ₃ : H ₂ NSNH ₂ is 1:1 to 1:10. After the thiourea is completely dissolved, transfer the entire mixed dispersion to a hydrothermal solution with a capacity of 100 mL. In the kettle, the filling ratio of the hydrothermal kettle is 70%, the hydrothermal temperature is 180°C-220°C, and the hydrothermal time is 18-24h; after the reaction is completed, it is cooled to room temperature, washed with water and ethanol by centrifugation several times, and dried. get MoO ₃ @MoS ₂ ; S3: Preparation of materials, weigh anhydrous ferric chloride and dissolve it in chloroform, the molar ratio of thiophene monomer and anhydrous ferric chloride is 3:1, stir for 1 hour to obtain dark green turbid liquid, weigh thiophene monomer and MoO ₃ @MoS ₂ was dissolved in chloroform, the mass ratio of thiophene monomer and MoO ₃ @MoS ₂ was 10:1 ~ 10:3, ultrasonic for 1 h to obtain a dispersion of thiophene and molybdenum disulfide, and the dispersion was slowly added dropwise to chlorine After the reaction was completed, the solvent was evaporated to dryness at room temperature, and an appropriate amount of 1 mol/L HCl was added and stirred at room temperature for 12 hours; the obtained product was washed with HCl for several times, and then washed with deionized water at 60-80 Dry at ℃ for 6 to 8 hours. 5 . The method for preparing a gas sensitive material according to claim 4 , wherein in S1 , the solution is transferred to a hydrothermal reaction kettle, and the reaction is carried out at 180° C. for 24 hours. 6 . 6 . The method for preparing a gas-sensing material according to claim 4 , wherein: in S2 , MoO ₃ and H ₂ NSNH ₂ with a molar ratio of 1:3 are weighed and added to the solution. 7 . 7 . The preparation method of a gas-sensing material according to claim 4 , wherein in S3 , the thiophene monomer and MoO ₃ @MoS ₂ with a mass ratio of 10:2 are weighed and dissolved in chloroform. 8 . 8. The application of a gas-sensing material in a NH ₃ gas-sensing sensor, characterized in that: the surface of the Al ₂ O ₃ ceramic tube coated with the MoO ₃ @MoS ₂ /PTH sensitive material and the gold electrode coating is made into NH ₃ Gas sensing element. 9. The application of the gas-sensing material according to claim 8 in an NH ₃ gas-sensing sensor, wherein: the preparation method of the NH ₃ gas-sensing element is as follows: take MoO ₃ @MoS ₂ /PTH powder The product was ground for 10 min, and then mixed with anhydrous ethanol and ground to a paste. The obtained paste was evenly smeared on the surface of the Al ₂ O ₃ ceramic tube covered by the gold electrode. The ethanol was evaporated to dryness at room temperature, and then the gold electrode was welded. on a ceramic base.

Images