A selective gas sensitive material for complex gas environment and its preparation method and application

Abstract

The application belongs to the technical field of semiconductor gas sensitive material and sensor, and particularly relates to a selective gas sensitive material for a complex gas environment and a preparation method and application thereof. The gas sensitive material takes WO3 nanofiber as a substrate, composites ZnO nanoparticles on the surface of the substrate, and loads noble metal Ir to form an Ir-ZnO / WO3 ternary composite structure. The composite structure is obtained by adding WO3 nanofiber prepared by an electrospinning method, ZIF-8 precursor and Ir nanoparticles into an anhydrous ethanol solution, and then performing ultrasonic treatment and drying, and finally calcining under an air atmosphere. The material and the sensor exhibit high sensitivity and high selectivity to BTXs, and have good anti-interference ability and stability, and are suitable for real-time monitoring and early warning of BTXs leakage in a complex industrial site with multiple gas interference such as petrochemical industry and waste treatment.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor gas-sensitive materials and sensors, specifically relating to a selective gas-sensitive material for complex gas environments, its preparation method, and its application. Background Technology

[0002] Benzene, toluene, xylene, and other benzene series compounds (BTXs) are common toxic and harmful volatile organic compounds in industries such as petrochemicals, storage and transportation, spraying, and waste treatment. They not only pose serious health hazards to humans, including carcinogenicity and teratogenicity, but are also flammable and explosive, and their leaks pose a significant risk to industrial safety. Therefore, developing sensors capable of real-time and accurate monitoring of BTX concentrations is crucial.

[0003] Currently, gas detection technologies for BTXs mainly include gas chromatography, mass spectrometry, and semiconductor sensor methods. Among these, gas sensors based on metal oxide semiconductors (such as WO3, SnO2, and In2O3) have attracted much attention due to their low cost, small size, and ease of integration. However, the gas environment in actual industrial settings (such as chemical plants and waste treatment plants) is extremely complex, often accompanied by large amounts of small molecule gases such as CO, H2S, CH4, and NH3. Traditional single or simply doped semiconductor gas-sensitive materials (such as pure WO3) generally suffer from inherent defects of poor selectivity, exhibiting cross-responses to multiple gases. This leads to a significant decrease in the accuracy of BTX identification in complex backgrounds, resulting in a high false alarm rate and making it difficult to meet the needs of precise monitoring. Existing gas-sensitive materials and sensors still struggle to effectively solve the challenge of high-selectivity detection in complex multi-component gas environments when applied to BTX detection. Developing a novel gas-sensitive material system that can actively "filter" or "consume" common small molecule interfering gases, thereby creating a "clean" reaction interface for BTX detection, is an urgent need for achieving reliable monitoring in industrial settings. Summary of the Invention

[0004] To address the shortcomings of existing semiconductor gas-sensitive materials, such as poor selectivity for BTXs in complex gas environments and susceptibility to interference from small molecule gases like CO and H2S, this invention aims to provide a ternary composite gas-sensitive material with a "sacrificial site" design, its preparation method, and a sensor. This material significantly improves the response sensitivity to BTXs and achieves efficient shielding against major interfering gases, thereby enabling highly selective and accurate detection of BTXs in multi-component coexisting gases.

[0005] In a first aspect, the present invention provides a method for preparing the above-mentioned gas-sensitive material, comprising the following steps: (1) Preparation of WO3 nanofibers: Inorganic tungsten salt was dissolved in a solvent, a polymer template agent was added, and precursor fibers were obtained by electrospinning. After calcination, WO3 nanofibers were obtained. (2) Preparation of ZIF-8 precursor: Soluble zinc salt was dissolved in deionized water and magnetically stirred to obtain solution A; 2-methylimidazolium (2-MIM) and hexadecyltrimethylammonium bromide (CTAB) were dissolved in deionized water to obtain solution B; then, solution A was added to solution B with stirring, and a white precipitate was formed after the mixed solution was allowed to stand; solid-liquid separation was performed, and the precipitate was dried to obtain ZIF-8 precursor; (3) Preparation of noble metal Ir: Ir chloride IrCl3 is used as the iridium source. Reduction is carried out in the aqueous phase under the action of a reducing agent. After the reduction is completed, Ir nanoparticles are obtained after solid-liquid separation and drying. (4) Preparation of Ir-ZnO / WO3 composite material: The WO3 nanofibers obtained in step (1), the ZIF-8 precursor obtained in step (2) and the Ir nanoparticles obtained in step (3) are added to anhydrous ethanol, and after sonication and drying, they are finally calcined in air atmosphere to obtain the Ir-ZnO / WO3 composite material, which is a selective gas-sensitive material for complex gas environments.

[0006] Preferably, in step (1), the inorganic tungsten salt is ammonium tungstate, the solvent is a mixture of ethanol and water, and the polymer template agent is polyvinylpyrrolidone (PVP). The electrospinning process conditions are as follows: the electrospinning conditions are a voltage of 10-20 kV, a feed rate of 0.4-0.6 mL·h⁻¹, a calcination temperature of 650-750℃, a heating rate of 1-3℃·min⁻¹, and a reaction time of 1-3 hours.

[0007] Preferably, in step (2), the soluble zinc salt is zinc nitrate hexahydrate; the solid-liquid separation is carried out by centrifugation, with a centrifugation speed of 8000-12000 rpm, a centrifugation time of 3-6 min, and centrifugation washing 2-4 times.

[0008] Preferably, in step (3), the reducing agent is sodium borohydride (NaBH4) and ascorbic acid (AA); the solid-liquid separation is carried out by centrifugation, with a centrifugation speed of 8000-12000 rpm and a centrifugation time of 3-6 min, followed by centrifugation and washing 2-4 times.

[0009] Preferably, in step (4), the ultrasonic time is 10-30 min; the calcination temperature is 680-720℃, the heating rate is 4-6℃·min⁻¹, and the calcination time is 1-3 hours.

[0010] Secondly, the present invention provides a selective gas-sensitive material for complex gas environments; the gas-sensitive material is a ternary composite structure, with WO3 nanofibers as the substrate, ZnO nanoparticles composited on the surface of the WO3 nanofibers, and Ir nanoparticles loaded on both the WO3 and ZnO surfaces.

[0011] Preferably, the ZnO nanoparticles account for 1-10 wt% of the total mass of the gas-sensitive material, more preferably 5 wt%. The Ir nanoparticles account for 0.5-3 wt% of the total mass of the gas-sensitive material, more preferably 2 wt%.

[0012] Preferably, the diameter of the WO3 nanofibers is 80-300 nm, the particle size of the ZnO nanoparticles is 20-50 nm, and the particle size of the Ir nanoparticles is 1.2-3 nm.

[0013] Thirdly, the present invention provides a gas sensor, comprising an insulating substrate, electrodes, and a gas-sensitive film coated on the electrode surface. The gas-sensitive film is formed on the electrode surface by coating the aforementioned gas-sensitive material. Specifically, the Ir-ZnO / WO3 gas-sensitive material is dispersed in anhydrous ethanol, then drop-coated onto the surface of a planar electrode using a pipette, and allowed to dry naturally to obtain the gas-sensitive film, which is then used to construct the gas sensor.

[0014] Fourthly, the present invention provides the application of the above-mentioned gas sensor in detecting benzene series BTXs gas in complex gas environments, which is particularly suitable for petrochemical, storage and transportation and waste treatment scenarios where CO and H2S interference exists.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: Material Design and Mechanism Innovation: This invention pioneers a "sacrificial site" selective filtration mechanism. By specifically compositing ZnO nanoparticles onto the surface of a WO3 substrate, a dual spatial and functional partitioning is constructed. ZnO exhibits stronger adsorption and reactivity for small molecule interfering gases such as CO and H2S, preferentially capturing and converting them, acting as a "sacrificial layer" to consume interfering gases; while BTX molecules can penetrate or bypass this layer, fully reacting with the inner WO3 sensitive substrate. Simultaneously, the loaded noble metal Ir not only serves as a catalytic sensitization site for BTXs on WO3 but also accelerates the reaction kinetics of interfering gas removal on ZnO. This dual synergistic mechanism, with its "internal and external cooperation and distinct functions," achieves the distinction between target and interfering gases at both physical and chemical levels, representing the core innovation of this invention.

[0016] Significantly improved performance: Example data shows that the Ir-ZnO / WO3 material prepared in this invention exhibits a significantly improved response value (Ri) to 10 ppm p-xylene. a / R gThe selectivity (response value ratio) of the sensor for para-xylene (10 ppm) reached 185%, significantly higher than that of pure WO3 (30.3%) and Ir-WO3 (114%). In a mixed gas of 10 ppm para-xylene, 0-5 ppm CO, and 0-5 ppm H2S, its selectivity coefficient for para-xylene (response value ratio) was more than 7 times higher than that of pure WO3. In a complex simulated environment containing multiple interfering gases, the sensor's response signal attenuation rate to BTXs was less than 12%, while the attenuation rate of the control sample exceeded 65%. After continuous operation at 310℃ for 35 days, the fluctuation in the response value to BTXs was less than ±5%.

[0017] Structural advantages: The WO3 nanofiber substrate provides a continuous electronic conduction pathway and a large specific surface area; the uniform dispersion of ZnO particles avoids agglomeration and maximizes the effectiveness of the "sacrificial sites"; the high dispersion of the noble metal Ir further optimizes the interfacial catalytic performance.

[0018] Technology and Practical Value: The fabrication method is mature, highly controllable, and reproducible. The fabricated sensor is suitable for harsh industrial environments, providing a low-cost, highly reliable online monitoring solution for BTX leaks in petrochemical, environmental protection, and other fields, demonstrating significant practical value and market potential. Attached Figure Description

[0019] Figure 1 This is a SEM image of the WO3 nanofibers prepared in Example 1 of this invention.

[0020] Figure 2 This is a SEM image of the Ir-ZnO / WO3 composite material prepared in Example 1 of this invention.

[0021] Figure 3 This is a comparative bar chart showing the single-gas response of the materials in Embodiment 1 and Comparative Examples 1-3 of the present invention to 10 ppm BTXs, CO, and H2S.

[0022] Figure 4 These are anti-interference test diagrams of the materials in Embodiment 1 and Comparative Example 2 of the present invention under a mixed atmosphere of p-xylene and interfering gases (CO, H2S).

[0023] Figure 5 This is the dynamic response-recovery curve of the sensor prepared in Example 1 of this invention to paraxylene.

[0024] Figure 6 This is a graph showing the long-term stability test of the sensor prepared in Example 1 of this invention against 10 ppm BTXs at 310°C. Detailed Implementation

[0025] The present invention will now be described in detail with reference to the accompanying drawings and embodiments, but the scope of protection of the present invention is not limited thereto.

[0026] Example 1: Preparation of Ir (2%)-ZnO (5%) / WO3 gas-sensitive material (1) Preparation of WO3 nanofibers: 1.0 g of ammonium tungstate was dissolved in a mixed solution of 10 mL of deionized water and 10 mL of ethanol, and 0.3 g of polyvinylpyrrolidone (PVP, Mw = 1,300,000) was added. The solution was magnetically stirred for 12 hours to form a homogeneous spinning solution. Electrospinning was performed (voltage 15 kV, feed rate 0.5 mL / h, receiving distance 20 cm) to obtain a precursor fiber membrane. The fiber membrane was calcined in air at 700 °C for 2 h at a rate of 2 °C / min to obtain WO3 nanofibers (see...). Figure 1 The diameter is approximately 180 nm; (2) Dissolve 0.3626 g of zinc nitrate hexahydrate in 12.5 mL of deionized water and stir magnetically for 5 min to obtain solution A; dissolve 5.6752 g of 2-methylimidazole and 0.0175 g of cetyltrimethylammonium bromide in 87.5 mL of deionized water to obtain solution B; then, slowly pour solution A into solution B with stirring, and let the mixed solution stand for 3 h to form a white precipitate; centrifuge at 10000 rpm for 5 min and pour off the supernatant, and dry the precipitate at 60 °C to obtain ZIF-8 precursor; (3) Add 10 mL of H2O solution containing 20 mg NaBH4 to 50 mL of IrCl3 (0.1 mM, about 1.4929 mg IrCl3) solution containing 2.64 mg AA (ascorbic acid). Stir the mixture in an 80°C water bath for 3 h, centrifuge at 12000 rpm, wash and collect Ir particles. (4) Weigh 300 mg of WO3 nanofibers obtained in step (1), 45.5 mg of ZIF-8 precursor obtained in step (2), and 6.45 mg of noble metal Ir obtained in step (3) and add them to 10 mL of anhydrous ethanol solution. After sonication for 10 min, drying at 60 °C for 2 h, and finally calcination at 700 °C in air atmosphere for 2 h, the Ir (2%)-ZnO (5%) / WO3 composite material is obtained (see Figure 2 ).

[0027] Example 2: Preparation of Ir (2%)-ZnO (10%) / WO3 gas-sensitive material (1) Preparation of WO3 nanofibers: The steps are the same as in Example 1 (1); (2) Preparation of ZIF-8 precursor: The steps are the same as in Example 1 (2); (3) Preparation of Ir particles: The steps are the same as in Example 1 (3); (4) Weigh 300 mg of WO3 nanofibers obtained in step (1), 96.1 mg of ZIF-8 precursor obtained in step (2), and 6.82 mg of noble metal Ir obtained in step (3) and add them to 10 mL of anhydrous ethanol solution. After sonication for 10 min, drying at 60 °C for 2 h, and finally calcination at 700 °C in air atmosphere for 2 h, the Ir (2%)-ZnO (10%) / WO3 composite material is obtained.

[0028] Example 3: Preparation of Ir (1%)-ZnO (5%) / WO3 gas-sensitive material (1) Preparation of WO3 nanofibers: The steps are the same as in Example 1 (1); (2) Preparation of ZIF-8 precursor: The steps are the same as in Example 1 (2); (3) Preparation of Ir particles: The steps are the same as in Example 1 (3); (4) Weigh 300 mg of WO3 nanofibers obtained in step (1), 45.0 mg of ZIF-8 precursor obtained in step (2), and 3.19 mg of noble metal Ir obtained in step (3) and add them to 10 mL of anhydrous ethanol solution. After sonication for 10 min, drying at 60 °C for 2 h, and finally calcination at 700 °C in air atmosphere for 2 h, the Ir (1%)-ZnO (5%) / WO3 composite material is obtained.

[0029] Example 4: Preparation of Ir (1%)-ZnO (10%) / WO3 gas-sensitive material (1) Preparation of WO3 nanofibers: The steps are the same as in Example 1 (1); (2) Preparation of ZIF-8 precursor: The steps are the same as in Example 1 (2); (3) Preparation of Ir particles: The steps are the same as in Example 1 (3); (4) Weigh 300 mg of WO3 nanofibers obtained in step (1), 95.0 mg of ZIF-8 precursor obtained in step (2), and 3.37 mg of noble metal Ir obtained in step (3) and add them to 10 mL of anhydrous ethanol solution. After sonication for 10 min, drying at 60 °C for 2 h, and finally calcination at 700 °C in air atmosphere for 2 h, the Ir (1%)-ZnO (10%) / WO3 composite material is obtained.

[0030] Example 5: Fabrication of a Gas Sensor The Ir-ZnO / WO3 material obtained in Example 1 was mixed and ground with anhydrous ethanol at a mass ratio of 1:3 to form a slurry. The slurry was then coated onto the surface of an alumina ceramic tube with gold interdigitated electrodes using a pipette to form a sensitive film. After air drying for 2 hours, the film was soldered onto a sensor base and placed on an aging stage for aging in air at 180°C for 72 hours to obtain a gas sensor element.

[0031] Comparative Example 1: Pure WO3 material and sensor Preparation of WO3 nanofibers: 1.0 g of ammonium tungstate was dissolved in a mixed solution of 10 mL of deionized water and 10 mL of ethanol. 0.3 g of polyvinylpyrrolidone (PVP, Mw = 1,300,000) was added, and the solution was magnetically stirred for 12 hours to form a homogeneous spinning solution. Electrospinning was performed (voltage 15 kV, feed rate 0.5 mL / h, receiving distance 20 cm) to obtain a precursor fiber membrane. The fiber membrane was calcined in air at 700 °C for 2 h at a rate of 2 °C / min to obtain WO3 nanofibers.

[0032] The pure WO3 material obtained in Comparative Example 1 was mixed and ground with anhydrous ethanol at a mass ratio of 1:3 to form a slurry. The slurry was then coated onto the surface of an alumina ceramic tube with gold interdigitated electrodes using a pipette to form a sensitive film. After air drying for 2 hours, the film was soldered onto a sensor base and placed on an aging stage for aging in air at 180°C for 72 hours to obtain a gas sensor element.

[0033] Comparative Example 2: Ir-WO3 Materials and Sensors Steps (1), (3), and (4) of Example 1 were performed, but in step (4), pure WO3 nanofibers were used directly as a carrier to prepare Ir-WO3 material with an Ir loading of approximately 2 wt%. The sensor was fabricated using the same process as in Example 2.

[0034] Comparative Example 3: Ir-ZnO Materials and Sensors Steps (2), (3), and (4) of Example 1 were performed. The ZIF-8 precursor obtained in step (2) was calcined at 700°C for 2 hours to obtain ZnO nanoparticles. In step (4), pure ZnO nanoparticles were directly used as a carrier to prepare Ir-WO3 material with an Ir loading of approximately 2 wt%. The sensor was fabricated using the same process as in Example 2.

[0035] Test Example 1: Gas Sensing Performance Test The sensors fabricated in Example 1 and Comparative Examples 1-3 were connected to a commercial gas-sensitive testing system (CGS-8, Beijing Elite). The operating temperature was set to 310℃, the background gas was dry air, and the flow rate was 200 sccm. Standard gases of 10 ppm each of BTXs, CO, and H2S were introduced. After the response stabilized, the system was switched back to air, and the resistance change of the sensor was recorded. The response value S was defined as S = (R... a / R g -1) x 100% (for reducing gases), where Ra is the resistance in air and Rg is the resistance in the target gas.

[0036] Result: As Figure 3 As shown, for the target gases BTXs, the response values ​​of Ir-ZnO / WO3 (benzene: 78.6%, toluene: 81.5%, o-xylene: 135%, m-xylene: 74.8%, p-xylene: 185%) are much higher than those of pure WO3 (benzene: 11.8%, toluene: 12.4%, o-xylene: 23.9%, m-xylene: 14%, p-xylene: 30.3%) and Ir-WO3 (benzene: 55.8%, toluene: 63.8%, o-xylene: 91.9%, m-xylene: 64%, p-xylene: 114%). For interfering gases CO and H2S, both pure WO3 and Ir-WO3 showed significant responses, while the response values ​​of Ir-ZnO / WO3 were extremely low (CO: 11.7%, H2S: 3.7%). We found that the bare Ir-WO3 sensor exhibited excellent response to BTX gases, but inevitably suffered from interference responses to H2S and CO. When an appropriate amount of ZnO material (sensitive to H2S and CO gases) was introduced onto the Ir-WO3 surface, the Ir-ZnO / WO3 sensor showed significant anti-interference characteristics against small molecule gases. This indicates that ZnO can act as a sacrificial site for adsorption and interaction with small molecule interfering substances, leading to the excitation of more BTX molecules on the Ir-WO3 surface. Simultaneously, the Ir species enhanced the electronic and chemical sensitization effects of the ZnO and WO3 supports.

[0037] Test Example 2: Anti-interference performance test Under the same conditions as in Test Example 1, taking p-xylene as an example, a mixed gas containing 10 ppm p-xylene, 5 ppm CO, and 5 ppm H2S was introduced into the test chamber. The apparent response values ​​of each sensor to p-xylene in the mixed gas were compared.

[0038] Result: As Figure 4 As shown, in the mixed gas atmosphere, the response value of the Ir-WO3 sensor to p-xylene increased by 69.8% compared to that in a single p-xylene atmosphere, indicating that the interfering gas severely affected its detection of the target gas. In contrast, the response value of the Ir-ZnO / WO3 sensor only decreased by 12%, and the absolute response value remained at a high level (approximately 185%), demonstrating excellent anti-interference capability and selectivity.

[0039] Test Example 3: Dynamic Response and Stability Test The dynamic response-recovery curves of the sensor in Example 1 at different concentrations of paraxylene (10, 20, 50 ppm) are shown in the figure below. Figure 5As shown, the sensor exhibits fast response (3.5s) and recovery (40s) characteristics, and the response value shows a good linear relationship with the concentration. The sensor was continuously exposed to an air atmosphere containing a low concentration of interfering gas at 310℃ for 35 days, and its response to 10ppm paraxylene was tested at intervals. The results are as follows. Figure 6 As shown, the response value fluctuates within ±5%, indicating that the material has excellent long-term stability.

[0040] The above embodiments fully illustrate that the Ir-ZnO / WO3 ternary composite gas-sensitive material and its sensor provided by the present invention, through a unique "sacrificial site" design, successfully achieves high sensitivity and high selectivity detection of BTXs in the presence of small molecule interfering gases such as CO and H2S, solving the technical problem of accurate identification of target gases in complex industrial environments.

[0041] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing a selective gas-sensitive material for complex gas environments, characterized in that, Includes the following steps: (1) Preparation of WO3 nanofibers: Inorganic tungsten salt was dissolved in a solvent, a polymer template agent was added, and precursor fibers were obtained by electrospinning. After calcination, WO3 nanofibers were obtained. (2) Preparation of ZIF-8 precursor: Soluble zinc salt was dissolved in deionized water and solution A was obtained by magnetic stirring; Solution B was obtained by dissolving 2-methylimidazolium (2-MIM) and hexadecyltrimethylammonium bromide (CTAB) in deionized water. Subsequently, solution A was added to solution B with stirring, and a white precipitate formed after the mixed solution was allowed to stand. Solid-liquid separation was performed, and the precipitate was dried to obtain the ZIF-8 precursor. (3) Preparation of noble metal Ir: Ir chloride IrCl3 is used as the iridium source. Reduction is carried out in the aqueous phase under the action of a reducing agent. After the reduction is completed, Ir nanoparticles are obtained after solid-liquid separation and drying. (4) Preparation of Ir-ZnO / WO3 composite material: The WO3 nanofibers obtained in step (1), the ZIF-8 precursor obtained in step (2) and the Ir nanoparticles obtained in step (3) are added to anhydrous ethanol solution, and after sonication and drying, the Ir-ZnO / WO3 composite material is obtained by calcination in air atmosphere, which is a selective gas-sensitive material for complex gas environments.

2. The preparation method according to claim 1, characterized in that, In step (1), the inorganic tungsten salt is ammonium tungstate, the solvent is a mixture of ethanol and water, and the polymer template agent is polyvinylpyrrolidone (PVP). The electrospinning process conditions are as follows: the electrospinning conditions are a voltage of 10-20 kV, a feed rate of 0.4-0.6 mL·h⁻¹, a calcination temperature of 650-750℃, a heating rate of 1-3℃·min⁻¹, and a reaction time of 1-3 hours.

3. The preparation method according to claim 1, characterized in that, In step (2), the soluble zinc salt is zinc nitrate hexahydrate; the solid-liquid separation is carried out by centrifugation, with a centrifugation speed of 8000-12000 rpm and a centrifugation time of 3-6 min, followed by centrifugation and washing 2-4 times.

4. The preparation method according to claim 1, characterized in that, In step (3), the reducing agent is sodium borohydride NaBH4 and ascorbic acid AA; the solid-liquid separation is carried out by centrifugation, with a centrifugation speed of 8000-12000 rpm and a centrifugation time of 3-6 min, and centrifugation washing 2-4 times.

5. The preparation method according to claim 1, characterized in that, In step (4), the ultrasonic time is 10-30 min; the calcination temperature is 680-720℃, the heating rate is 4-6℃·min⁻¹, and the calcination time is 1-3 hours.

6. A selective gas-sensitive material for complex gas environments prepared by the method according to any one of claims 1-5, characterized in that, It has a ternary composite structure with WO3 nanofibers as the substrate, ZnO nanoparticles composited on the surface of the WO3 nanofibers, and Ir nanoparticles loaded on both the WO3 and ZnO surfaces.

7. The gas-sensitive material according to claim 6, characterized in that, The ZnO nanoparticles account for 1-10 wt% of the total mass of the gas-sensitive material; the Ir nanoparticles account for 0.5-3 wt% of the total mass of the gas-sensitive material.

8. The gas-sensitive material according to claim 6, characterized in that, The WO3 nanofibers have a diameter of 80-300 nm; the ZnO nanoparticles have a particle size of 20-50 nm; and the Ir nanoparticles have a particle size of 1.2-3 nm.

9. A gas sensor, characterized in that, It includes an insulating substrate, an electrode disposed on the insulating substrate, and a gas-sensitive membrane, wherein the gas-sensitive membrane is made by coating the gas-sensitive material of claim 6 onto the surface of the electrode.

10. The application of the gas sensor as described in claim 9 in detecting benzene series gases in a complex gas environment, characterized in that, The benzene series gases include one or more of benzene, toluene, o-xylene, m-xylene, and p-xylene; the complex gas environment includes one or more of CO and H2S as interfering gases; the operating temperature of the gas sensor is 150-380℃.

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