A high-sensitivity gas-sensitive sensor material, a preparation method and application thereof

Abstract

This invention provides a high-sensitivity gas sensor material, its preparation method, and its applications. The preparation scheme uses ammonium tetrathiotungstate as the tungsten source, water and ethanol as solvents, acetic acid and dilute hydrochloric acid as microstructure modifiers and pH adjusters, and anhydrous ferric chloride and crystalline tin tetrachloride as co-dopersants. Through a one-step hydrothermal reaction and calcination, urchin-like hierarchical tungsten oxide with a self-assembled nanowire structure is obtained. The obtained hierarchical structure provides more adsorption-desorption channels and active sites for the material. Fe and Sn co-doping can regulate the band structure of the tungsten oxide material, thereby improving its electronic conductivity. S doping generates a large number of oxygen vacancy structures, resulting in high adsorption, excellent response performance, and selectivity for dimethyl trisulfide gas. This invention eliminates the need for templates and noble metal doping steps, resulting in low production costs and environmental friendliness. The synthesis route is simple and highly reproducible. The prepared sensor exhibits an ultra-low detection limit (1 ppb level) for dimethyl trisulfide gas, showing promising market prospects in cryogenic protection, aquaculture detection, energy conservation and environmental protection, microbial contamination detection, and food quality testing.

Description

Technical Field

[0001] This invention relates to the field of gas-sensitive materials technology, specifically to a high-sensitivity gas-sensitive sensor material, its preparation method, and its application. Background Technology

[0002] With the rapid development of today's industrial economy, various chemical plants are emitting large amounts of toxic and harmful gases, leading to SO2 emissions. x H2S, NO x Harmful gases such as CO are ubiquitous in our lives. When these gases adhere to the surface of airborne dust, they easily produce photochemical pollution under sunlight, seriously endangering human physical and mental health and polluting the living environment for humans, animals, and plants. Therefore, the monitoring and control of air pollution is becoming increasingly urgent. To enable timely monitoring of harmful gases, various monitoring technologies have flourished, and gas sensors have played a crucial role, finding widespread application in common locations such as chemical plants and residential buildings. [2] A gas sensor is a device that converts certain information about a gas (such as concentration and type) into usable digital information. Gas sensors can be used to monitor gas leaks, and if connected to a control system, they can trigger automatic shut-off or shut-off based on the gas concentration in a closed environment. Gas sensors are the core of gas monitoring and play a decisive role. [3] .

[0003] In the 1950s, Bielanski and his research group discovered that semiconductor materials have high sensitivity. This discovery spurred many researchers to begin studying semiconductor gas sensors. (ZnO, SnO2, WO3, In2O3, TiO2) [5] Many novel semiconductor gas-sensitive materials have been developed. Despite their development, researchers continue to work on improving their gas-sensing performance. On one hand, researchers are constantly searching for new doping materials to enhance the performance of existing materials, particularly by selecting different proportions of the same doping material. On the other hand, they are preparing novel materials such as nanomaterials and thin films to improve various aspects of performance. Tungsten oxide, with its intrinsic non-stoichiometry and resistance to strong acids and high temperatures, is one of the most promising gas-sensing materials for semiconductor gas sensors.

[0004] To date, WO3 nanomaterials have demonstrated good gas-sensing properties for oxidizing gases such as ethanol, acetone, hydrogen, ammonia, and hydrogen sulfide, but reports on gas sensors for dimethyl trisulfide (DMT) are extremely limited. DMT is a unique volatile biomarker released by Listeria monocytogenes after mononuclear cell proliferation, a major culprit in fatal foodborne illnesses, and poses a significant threat to human health. Xiafen et al. prepared WO3 nanobundle films on Al2O3 substrates via a hydrothermal method, exhibiting good response performance to DMT, with response and recovery times of 10 s and 265 s, respectively, at the optimal operating temperature of 260 °C [Sens. Actuators B, 2020.0925-4005]. Most reported DMT gas sensing materials are tungsten oxide materials, and they have certain shortcomings in terms of preparation process, operating temperature, response performance, and response and recovery times, requiring further optimization. Furthermore, the detection limits of currently reported materials are generally at the ppm level. In reality, a lower detection limit is crucial for developing high-sensitivity sensors and expanding their application range. Therefore, developing a 1ppb-level dimethyl trisulfide gas sensor with superior response performance, low manufacturing cost, and rapid response recovery is of great significance. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the first technical problem this invention aims to solve is to provide a high-sensitivity gas sensor material and its preparation method. The resulting material exhibits the small size effect of low-dimensional nanomaterials and the stability of high-dimensional nanomaterials. The obtained hierarchical structure provides the material with more adsorption-desorption channels and active sites. Fe and Sn co-doping can regulate the band structure of tungsten oxide material, thereby improving its electronic conductivity. S doping generates a large number of oxygen vacancy structures, enabling the material to exhibit high adsorption, excellent response performance, and selectivity for dimethyl trisulfide gas. This effectively improves the response performance of the obtained tungsten oxide nanomaterial to dimethyl trisulfide gas, resulting in an ultra-low detection limit (1 ppb) for dimethyl trisulfide gas. The one-step hydrothermal synthesis route is simple, highly reproducible, has a low detection limit, superior response performance, and low preparation cost.

[0006] The second technical problem to be solved by the present invention is to provide a high-sensitivity gas sensor material.

[0007] The third technical problem to be solved by the present invention is to provide an application of a high-sensitivity gas sensor material in the fabrication of sensor devices.

[0008] The fourth technical problem to be solved by the present invention is to provide a hierarchical tungsten oxide dimethyl trisulfide gas sensor with low detection limit and high sensitivity for the efficient detection of dimethyl trisulfide gas.

[0009] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: using ammonium tetrathiotungstate as the tungsten source, water and ethylene glycol as solvents, acetic acid and dilute hydrochloric acid as microstructure regulators and pH adjusters, and anhydrous ferric chloride and crystalline tin tetrachloride as co-dopersants, a tungsten oxide gas sensor material with a hierarchical structure of sea urchins assembled from nanowires is obtained through a one-step hydrothermal reaction and calcination treatment.

[0010] The specific steps of the above-mentioned high-sensitivity gas sensor material and its preparation method are as follows: ① Weigh 0.5 g of ammonium tetrathiotungstate into a beaker and dissolve it in deionized water by ultrasonication; ② After the above materials are completely dissolved, add ethylene glycol and stir evenly, then add acetic acid as a regulator and stir for 10 min. Add 10 mM anhydrous ferric chloride and crystalline tin tetrachloride as co-dopersants and dissolve evenly by ultrasonication; ③ After the above materials are completely dissolved, add 1 mol / L dilute hydrochloric acid to adjust the pH of the solution and stir vigorously for 15 min; ④ Place the above-stirred solution in a high-pressure reactor and hydrothermally heat for 10 h; ⑤ After the reaction is completed, take the sample into a centrifuge tube and wash it alternately with deionized water and ethanol by centrifugation; ⑤ After centrifugation, heat-treat the precipitate, dry it, and calcine it to obtain tungsten oxide gas sensor material with a sea urchin-like hierarchical structure assembled by nanowires.

[0011] The volume ratio of water to ethylene glycol is 5:1 to 1:1; the molar ratio of acetic acid to hydrochloric acid is 1 / 1 to 1 / 3, and the acid concentration is between 0.05M and 0.01M; the molar ratio of anhydrous ferric chloride to crystalline tin tetrachloride is 5:1 to 2:1; the hydrothermal reaction temperature is 160 to 200℃; the calcination temperature is 560 to 650℃, and the calcination time is 1 h.

[0012] The diameter range of the hierarchical structure material is 1-5 μm; the total doping concentration of Fe and Sn in the obtained WO3 is 0.3-0.5% (atomic ratio concentration); the doping concentration of S is 0.5-1.5% (atomic ratio concentration).

[0013] The gas sensor is made of the tungsten oxide gas sensor material with a hierarchical structure as described in claim 1.

[0014] The operating temperature is as low as 200℃, and it can detect dimethyl trisulfide gas at the 1ppb level, with a low detection limit and high sensitivity. Beneficial effects

[0015] Compared with existing technologies, the high-sensitivity gas sensor material, its preparation method, and its application disclosed in this invention have the following advantages: This invention utilizes ammonium tetrathiotungstate as both the tungsten source and the sulfur-doped sulfur source, water and ethylene glycol as solvents, acetic acid and dilute hydrochloric acid as microstructure modifiers and pH adjusters, and anhydrous ferric chloride and crystalline tin tetrachloride as co-dopersants. Through a one-step hydrothermal reaction and calcination, a hierarchical tungsten oxide gas sensor material with a sea urchin-like structure, assembled from nanowires, is obtained. The resulting hierarchical structure provides the material with more adsorption-desorption channels and active sites. The Fe and Sn co-doping can modulate the band structure of the tungsten oxide material, thereby improving its electronic conductivity. S doping generates a large number of oxygen vacancy structures, resulting in high adsorption, excellent response performance, and selectivity for dimethyl trisulfide gas. This invention eliminates the need for templates and noble metal doping steps, resulting in low production costs and environmental friendliness. The synthesis route is simple and highly reproducible. The prepared sensor exhibits an ultra-low detection limit (1 ppb level) for dimethyl trisulfide gas, showing promising market applications in cryogenic protection, aquaculture detection, energy conservation and environmental protection, microbial contamination detection, and food quality testing. Attached Figure Description

[0016] Figure 1 The XRD patterns of Embodiment 1 and its comparative examples are shown below. Figure 2 SEM images of Embodiment 1 and its comparative examples of the present invention; Figure 3 The graphs show the gas-sensing performance of Example 1 and its comparative examples at different temperatures against 25 ppm dimethyl trisulfide. Figure 4 This is a repeatability graph of dimethyl trisulfide gas concentrations from 1 ppb to 20 ppb at the optimal operating temperature of 200°C in Example 1 of the present invention. Implementation

[0017] The following description, in conjunction with the accompanying drawings, further illustrates the embodiments of the present invention: The following embodiments provide detailed implementation methods and specific operation processes based on the technical solutions of the present invention, but the scope of protection of the present invention is not limited to the following embodiments. Example

[0018] A method for preparing a tungsten oxide gas-sensitive sensor material with a hierarchical sea urchin-like structure, characterized by the following steps: ① Weigh 0.5 g of ammonium tetrathiotungstate into a beaker and dissolve it in deionized water by ultrasonication; ② After the above material is stirred until completely dissolved, add ethylene glycol (the volume ratio of water to ethylene glycol is 5:1), stir evenly, then add acetic acid regulator and stir for 10 min, with a total mass of 10 mM. Anhydrous ferric chloride and crystalline tin tetrachloride were used as co-dopersants and dissolved uniformly by ultrasonication (the molar ratio of anhydrous ferric chloride to crystalline tin tetrachloride was 3:1); ③ After the above materials were stirred until completely dissolved, 1 mol / L dilute hydrochloric acid was added to adjust the pH of the solution (the molar ratio of acetic acid to hydrochloric acid was 1 / 1, and the total acid concentration was 0.05 M), and the solution was stirred vigorously for 15 min; ④ The stirred solution was placed in a high-pressure reactor and hydrothermally heated at 200℃ for 10 h; ⑤ After the reaction was completed, the sample was taken into a centrifuge tube and washed and centrifuged alternately with deionized water and ethanol; ⑤ The precipitate after centrifugation was heated, dried, and calcined at 560℃ for 1 h, finally obtaining tungsten oxide gas sensor material with a sea urchin-like hierarchical structure formed by nanowire self-assembly.

[0019] The material prepared according to the method in the claims is used to fabricate a gas sensor with a side-heated structure, and the specific steps are as follows: Take 0.1g of the annealed sample and pour it into an agate mortar. Use a dropper to add 2mL of terpineol to the mortar containing the sample and grind it into a suitable paste. Use a toothpick to take a ceramic tube and straighten the four platinum wires on the ceramic tube with tweezers. Use a pre-sharpened bamboo stick to evenly spread the ground paste on the outer wall of the ceramic tube, so that the gas sensor material forms a dense oxide film of 0.2-0.4mm on the outer surface. Then place it in a clean porcelain boat and let it dry naturally. After that, put the porcelain boat into a muffle furnace and calcine it at 450℃ for 2 hours. h. Allow it to cool naturally, remove the ceramic boat, and take out the ceramic tube inside the boat for later use; fix the base of the side-heated sensor element, and drop a drop of welding flux on each of the 6 electrode rods of the base in turn. Use an electric soldering pen to weld the two pairs of platinum wires of the ceramic tube to the tube seat. Pass the heating resistance wire through the ceramic tube and weld both ends to the other two poles of the tube seat; make a side-heated gas sensor, mark it, insert the prepared gas sensing element into the aging table in the aging machine, and start the gas sensing test after aging for 7 days. Example

[0020] A method for preparing a tungsten oxide gas-sensitive sensor material with a hierarchical sea urchin-like structure, characterized by the following steps: ① Weigh 0.5 g of ammonium tetrathiotungstate into a beaker and dissolve it in deionized water by ultrasonication; ② After the above material is stirred until completely dissolved, add ethylene glycol (the volume ratio of water to ethylene glycol is 3:1), stir evenly, then add acetic acid regulator and stir for 10 min, with a total mass of 10 mM. Anhydrous ferric chloride and crystalline tin tetrachloride were used as co-dopersants and dissolved uniformly by ultrasonication (the molar ratio of anhydrous ferric chloride to crystalline tin tetrachloride was 5:1); ③ After the above materials were stirred until completely dissolved, 1 mol / L dilute hydrochloric acid was added to adjust the pH of the solution (the molar ratio of acetic acid to hydrochloric acid was 1 / 2, and the total acid concentration was 0.07 M), and the solution was stirred vigorously for 15 min; ④ The stirred solution was placed in a high-pressure reactor and hydrothermally heated at 180℃ for 10 h; ⑤ After the reaction was completed, the sample was taken into a centrifuge tube and washed and centrifuged alternately with deionized water and ethanol; ⑤ The precipitate after centrifugation was heated, dried, and calcined at 650℃ for 1 h, finally obtaining a tungsten oxide gas sensor material with a sea urchin-like hierarchical structure formed by nanowire self-assembly. Example

[0021] A method for preparing a tungsten oxide gas-sensitive sensor material with a hierarchical sea urchin-like structure, characterized by the following steps: ① Weigh 0.5 g of ammonium tetrathiotungstate into a beaker and dissolve it in deionized water by ultrasonication; ② After the above material is stirred until completely dissolved, add ethylene glycol (the volume ratio of water to ethylene glycol is 1:1), stir evenly, then add acetic acid regulator and stir for 10 min, with a total mass of 10 mM. Anhydrous ferric chloride and crystalline tin tetrachloride were used as co-dopersants and dissolved uniformly by ultrasonication (the molar ratio of anhydrous ferric chloride to crystalline tin tetrachloride was 2:1); ③ After the above materials were stirred until completely dissolved, 1 mol / L dilute hydrochloric acid was added to adjust the pH of the solution (the molar ratio of acetic acid to hydrochloric acid was 1 / 3, and the total acid concentration was 0.1 M), and the solution was stirred vigorously for 15 min; ④ The stirred solution was placed in a high-pressure reactor and hydrothermally heated at 160℃ for 10 h; ⑤ After the reaction was completed, the sample was taken into a centrifuge tube and washed and centrifuged alternately with deionized water and ethanol; ⑤ The precipitate after centrifugation was heated, dried, and calcined at 600℃ for 1 h, finally obtaining a tungsten oxide gas sensor material with a sea urchin-like hierarchical structure assembled by nanowires.

[0022] The gas sensor with a side-heated structure was prepared according to the preparation method in Example 1, and then gas sensitivity testing was performed.

[0023] The morphology and structure of the materials prepared in Examples 1-3 of this invention are tested and characterized by phase analysis.

[0024] 1. Structural Analysis Figure 1 The figures show the XRD patterns of Examples 1 and 2. As shown in the figure, the suitable 2θ angle range selected in the figure is 10°-70°. By comparing with the standard card, it was found that there are diffraction peaks corresponding to the standard card (JCPDS No. 33-1387) at 2θ values ​​of 13.22, 22.99, 24.58, 27.26, and 33.02. The standard card corresponds to the hexagonal WO3 crystal system.

[0025] 2. Morphological analysis Figure 2 SEM images of WO3 doped with Fe / Sn at different ratios are shown. Figure (a) shows the undoped sample, which clearly shows a relatively dispersed nanowire structure with some gaps and short nanowire length. Figure (b) shows the comparative sample of Example 1, where the mass ratio of anhydrous ferric chloride and crystalline tin tetrachloride is 6:1. The sample mainly presents as clustered nanorods with an average length of about 270 nm. The nanorods are closely connected to form microspheres resembling walnuts, with a diameter of about 1 μm. Figures (c) and (d) show the SEM images of Examples 1 and 2. Figure (c) shows that the sample presents a nanowire structure with some gaps, assembled into a spherical shape resembling a sea urchin with large gaps and a diameter of about 1 μm. Magnified SEM image (d) clearly shows that there are many gaps in the nanowires, and they are longer than the original sample, with a nanowire length of about 200-700 nm. Compared to undoped samples and samples with an Fe / Sn ratio of 6:1, the prepared sample structure resembles a sea urchin sphere, with more uniform nanowire length and increased contact area between the sample and the gas, thus affecting the gas-sensing performance of the device.

[0026] Figure 3 The graph shows the gas sensitivity performance of Example 1 of the present invention to 25 ppm dimethyl trisulfide gas at different temperatures. It can be seen from the graph that the sample exhibits the best response performance to 25 ppm dimethyl trisulfide gas at an operating temperature of 200℃, showing a relatively low operating temperature range.

[0027] Figure 4 This is a graph showing the gas-sensing performance of Example 1 of the present invention at the optimal operating temperature of 200℃ for 5 ppb dimethyl trisulfide. As can be seen from the graph, after three repetitions at a dimethyl trisulfide gas concentration of 5 ppb, the response value of the sample in Example 1 was consistently above 13.5. Compared with general sensor devices, the present invention exhibits superior response performance and shorter response and recovery times. In summary, the high-sensitivity gas sensor material prepared by this invention is tungsten oxide with a hierarchical, urchin-like structure formed by the self-assembly of nanowires. The resulting hierarchical structure provides the material with more adsorption-desorption channels and active sites. Fe and Sn co-doping can modulate the band structure of the tungsten oxide material, thereby improving its electronic conductivity. S doping generates a large number of oxygen vacancy structures, resulting in high adsorption capacity, excellent response performance, and selectivity for dimethyl trisulfide gas. This invention eliminates the need for templates and noble metal doping steps, resulting in low production costs and environmental friendliness. The synthesis route is simple and highly reproducible. The prepared sensor exhibits an ultra-low detection limit (5 ppb level) for dimethyl trisulfide gas, showing promising market applications in cryogenic protection, aquaculture detection, energy conservation and environmental protection, microbial contamination detection, and food quality testing.

Claims

1. A method for preparing a high-sensitivity gas sensor material, characterized in that, The material is tungsten oxide with a hierarchical, urchin-like structure assembled from nanowires, wherein the tungsten oxide is doped with Fe, Sn, and S elements. The process includes the following steps: ① Weigh 0.5 g of ammonium tetrathiotungstate into a beaker and dissolve it in deionized water using ultrasonication; ② After the above material is completely dissolved, add ethylene glycol and stir until homogeneous, then add acetic acid and stir for 10 min. Next, add 10 mM of anhydrous ferric chloride and crystalline tin tetrachloride as co-dopersants and dissolve them using ultrasonication; ③ After the above material is completely dissolved, add 1 mol / L dilute hydrochloric acid to adjust the pH of the solution and stir for 15 min; ④ Place the stirred solution in a high-pressure reactor for hydrothermal reaction at a temperature of 160–200 °C for 10 h; ⑤ After the reaction, transfer the sample to a centrifuge tube and wash it alternately with deionized water and ethanol before centrifugation; ⑥ Heat the centrifuged precipitate to dry and calcine it at a temperature of 560–650 °C for 1 hour. h, thus obtaining the high-sensitivity gas sensor material.

2. The preparation method according to claim 1, characterized in that, The volume ratio of deionized water to ethylene glycol is 5:1 to 1:1; the molar ratio of acetic acid to dilute hydrochloric acid is 1:1 to 1:3, and the acid concentration is 0.05M to 0.1M; the molar ratio of anhydrous ferric chloride to crystalline tin tetrachloride is 5:1 to 2:

1.

3. The preparation method according to claim 1, characterized in that, The high-sensitivity gas sensor material has a sea urchin-like hierarchical structure with a diameter ranging from 1 to 5 μm; the total doping concentration of Fe and Sn elements is 0.3% to 0.5% in atomic percentage, and the doping concentration of S element is 0.5% to 1.5% in atomic percentage.

4. A gas sensor, characterized in that, The sensitive material of the gas sensor is a high-sensitivity gas sensor material prepared by the preparation method described in any one of claims 1-3.

5. The application of the gas sensor according to claim 4 in the detection of dimethyl trisulfide gas, characterized in that, The gas sensor operates at temperatures as low as 200°C and has a detection limit of 1 ppb for dimethyl trisulfide gas.

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