A method for preparing tungsten oxide semiconductor gas-sensitive material and its sensor

Abstract

This invention provides a method for preparing tungsten oxide semiconductor gas-sensitive materials and a corresponding sensor, belonging to the field of sensors. First, a tungsten precursor is dissolved in a solvent to obtain a clear and transparent solution. Then, a sensitizing material precursor is added to the clear and transparent solution to obtain a homogeneous mixed solution. The mixed solution is placed in a reactor and centrifuged to obtain a solid reactant. The solid reactant is washed and dried. Next, metal nanoparticles are dissolved in deionized water, and the tungsten oxide semiconductor gas-sensitive material with single-atom metal sensitization treatment is added to react. The product is collected by centrifugation, washed, and dried to obtain a dual-functional site tungsten oxide semiconductor gas-sensitive material with simultaneous sensitization by both single atoms and metal nanoparticles. This invention also provides a method for preparing the above gas-sensitive material and a gas sensor. This invention solves the problems of slow response, weak response, and insufficient stability in existing oxide semiconductor gas sensors.

Description

Technical Field

[0001] This invention belongs to the field of gas sensors, and more specifically, relates to a method for preparing tungsten oxide semiconductor gas-sensitive material and a sensor thereof. Background Technology

[0002] In recent years, with the acceleration of industrialization, the emissions of volatile organic compounds (VOCs) have increased rapidly, becoming a major source of secondary pollution and adversely affecting human health. Toluene, formaldehyde, and acetone, as typical VOCs, mainly originate from the pharmaceutical and chemical industries. They are carcinogenic, adversely affect the eyes, cardiovascular system, and lungs, and may damage the nervous system. Therefore, developing VOCs monitoring technologies is imperative.

[0003] Sensors are fundamental components supporting the development of next-generation Internet of Things (IoT) and artificial intelligence, with broad application prospects in industrial and agricultural production, environmental IoT, and healthcare. Chemi-resistive gas sensors, due to their low cost, ease of miniaturization, and environmental friendliness, are increasingly important in public safety, environmental monitoring, and medical diagnostics. However, developing efficient and low-cost catalysts for the redox reactions of gas molecules on the sensitive layer is urgently needed.

[0004] Currently, transition metal-based materials are considered the most effective catalysts, capable of meeting the demands for high selectivity and high response in practical applications. The interfacial charge transfer between the metal and the support can effectively modulate the electronic and chemical properties of the active sites, thereby improving the activity, selectivity, and stability of supported transition metal-based catalysts.

[0005] Currently, various MOSs have been reported as sensing materials, such as ZnO, SnO2, In2O3, and WO3. x Tungsten oxide, such as Co3O4, is used in the manufacture of gas sensors. Tungsten oxide, an n-type semiconductor with many defects, has attracted widespread attention in gas sensors, electrochromic systems, photocatalysis, and energy storage. In the field of gas sensors, due to its excellent electrical properties, non-toxicity, high stability, and high electron mobility, it has been used as a sensing material for detecting gases such as nitrogen dioxide, hydrogen, ethanol, and trimethylamine. However, currently reported gas sensors based on tungsten oxide semiconductors still suffer from slow response speeds, low sensitivity, and an inability to accurately detect low-concentration gases, especially ppb-level gases, which present significant challenges for rapid detection. Furthermore, accurate monitoring of low-concentration gases is impossible in high-humidity environments. These limitations significantly hinder the practical application of tungsten oxide semiconductors in the field of gas sensors.

[0006] Chinese patent application CN110511059A discloses a tungsten trioxide gas-sensitive membrane material, a tungsten trioxide-based composite gas-sensitive membrane material, its preparation method, and its application. The prepared sensor enables the monitoring of gases such as NO2 and H2S. While this sensor shows promise for gas-sensing applications, it suffers from slow and weak response, making it unable to achieve practical detection of low-concentration gases, especially rapid detection of ppb-level gases, thus limiting its mass industrial production and practical application.

[0007] Chinese patent application CN107966479B discloses a method for preparing a Pd-modified tungsten trioxide composite material to improve the performance of a hydrogen sensor. The urchin-like tungsten trioxide powder in this invention has a hierarchical structure composed of many nanorods, providing more active sites for gas reactions. However, the method for synthesizing the tungsten trioxide sensing material provided by this invention utilizes the noble metal Pd to improve gas sensing performance. This method results in high preparation costs for the sensing material, which is not suitable for mass industrial production.

[0008] Chinese patent application CN112098473A discloses a method for preparing a spherical tungsten trioxide sensitive material, a sulfur dioxide gas sensor, and a method for evaluating the performance of the gas-sensitive sensor. The preparation method uses tungsten hexachloride as a raw material, anhydrous ethanol as a solvent, and adds diammonium citrate to control the morphology of the product. The dried product precursor is then sintered in a muffle furnace to obtain the spherical tungsten trioxide sensitive material. This invention provides a method for synthesizing spherical tungsten trioxide sensitive materials. However, to obtain a product with more pores, diammonium citrate needs to be added. This method is cumbersome and cannot meet the requirements for large-scale industrial production.

[0009] Chinese patent application CN113184912B discloses a method for microwave-assisted preparation of hierarchical tungsten trioxide. This method involves first obtaining a tungsten trioxide precursor using microwave-assisted precipitation, followed by calcination to obtain the hierarchical tungsten trioxide. However, this method requires the addition of oxalic acid and consumes a relatively large amount of raw materials, making it difficult to promote in industrial applications.

[0010] Therefore, there is a need to develop a novel method for preparing tungsten oxide semiconductor gas-sensitive materials, which requires low process cost, simple preparation process, and ease of industrialization and mass production. Summary of the Invention

[0011] To address the shortcomings of existing technologies, the present invention aims to provide a method for preparing tungsten oxide semiconductor gas-sensitive materials and a sensor thereof. This method utilizes the influence of single-atom and nano-metallic states of Pt, Pd, Au, Cu, Co, and Mn on the surface chemical and electronic structure of tungsten oxide semiconductor gas-sensitive materials to synergistically regulate oxygen vacancies and interfacial charge transfer in the tungsten oxide semiconductor, thereby enhancing gas-sensing performance. Based on this, a sensor with high sensitivity and good stability can be prepared, enabling rapid, accurate, efficient, and stable detection of ppb-level gases. This solves the problems of slow response, weak response, and insufficient stability in existing oxide semiconductor gas sensors.

[0012] According to one aspect of the present invention, a method for preparing a tungsten oxide semiconductor gas-sensitive material is provided, comprising first performing a single-atom sensitization treatment, and then performing a nanoparticle sensitization treatment.

[0013] In the single-atom sensitization process, firstly, a tungsten precursor is dissolved in a solvent to obtain a clear and transparent solution. Then, the sensitizing material precursor is added to the clear and transparent solution to obtain a homogeneous mixed solution. The mixed solution is reacted at 160℃~220℃ for 14h~24h. After centrifugation, a solid reactant is obtained. The solid reactant is washed and dried to obtain a single-atom metal-sensitized tungsten oxide semiconductor gas-sensitive material.

[0014] Alternatively, in single-atom sensitization treatment, ammonium tungstate is first calcined to obtain WO3 powder. Then, the WO3 powder is added to the precursor solution of the sensitizing material, and the reaction is carried out at 160℃~220℃ for 14h~24h. After centrifugation, the solid reactant is obtained, washed, and dried to obtain a single-atom metal-sensitized tungsten oxide semiconductor gas-sensitive material.

[0015] Single-atom metals are used as catalysts, and the precursors of the sensitizing materials are selected from copper nitrate CuNO3, cobalt nitrate Co(NO3)2, manganese chloride MnCl2, palladium chloride PdCl2, and chloroplatinic acid H2PtCl6.

[0016] In the nanoparticle sensitization process, firstly, metal nanoparticles are dissolved in deionized water, and then the tungsten oxide semiconductor gas-sensitive material with single-atom metal sensitization treatment is added to the solution for mixing and reaction. Next, the product is collected by centrifugation, and the product is washed and vacuum dried to obtain a bifunctional tungsten oxide semiconductor gas-sensitive material with both single-atom and metal nanoparticle sensitization treatments.

[0017] Furthermore, the precursor of tungsten is WCl6, and the content of the precursor of the sensitizing material is 2% to 8% of the mass of WCl6.

[0018] Furthermore, the metal nanoparticles are nanoparticles formed from elemental metals, and the elemental metals are one or more of Pt, Pd, Au, Cu, Co and Mn.

[0019] Furthermore, the metal nanoparticles are alloy nanoparticles, and the alloy is an alloy formed of at least two elements selected from Pt, Pd, Au, Cu, Co and Mn.

[0020] Furthermore, the content of metal nanoparticles is 0.5% to 3% of the mass of the tungsten oxide semiconductor gas-sensitive material treated with single-atom metal sensitization, and the particle size is 2nm to 10nm.

[0021] Furthermore, the solvent is ethanol, and the ratio of WCl6 to ethanol is less than 5g:1000ml.

[0022] According to a second aspect of the present invention, a dual-functional site tungsten oxide semiconductor gas-sensitive material prepared by the method described above is also provided, which is in the form of particles with a particle size of 5 μm to 80 μm, and the surface of the particles is covered with a nanoparticle layer.

[0023] Furthermore, the nanoparticle layer is composed of closely adjacent nanoparticles with a particle size of 50nm to 120nm.

[0024] According to a third aspect of the present invention, a VOCs gas sensor prepared using the dual-functional site tungsten oxide semiconductor gas-sensitive material as described above is also provided, having a dynamic response range of 1.9 to 160 and a response speed of 15 to 60 s.

[0025] According to a fourth aspect of the present invention, a method for preparing the VOCs gas sensor as described above is also provided, comprising the following steps:

[0026] First, a dual-functional tungsten oxide semiconductor gas-sensitive material was prepared.

[0027] Next, the bifunctional tungsten oxide semiconductor gas-sensitive material was dissolved in a volatile solvent and dispersed evenly to obtain a suspension.

[0028] The suspension is then drop-coated onto a substrate, allowed to air dry naturally, and aged for at least 36 hours after the volatile solvent has evaporated to obtain a VOCs gas sensor. The preferred volatile solvent is ethanol.

[0029] In summary, compared with the prior art, the above-described technical solutions conceived by this invention have the following advantages:

[0030] Beneficial effects:

[0031] To address the issues of insufficient sensitivity and low responsivity in current semiconductor sensors, this invention discloses a method for preparing tungsten oxide semiconductor materials modified with transition-state metals. The method employs in-situ pyrolysis for controllable synthesis of the sensitive material, utilizing transition-state metals to enhance the sensitivity of the tungsten oxide semiconductor, thereby increasing the specific surface area and active sites of the sensitive material. Specifically, by introducing different transition-state metal species (single atoms, nanoparticles, and alloy nanoparticles) to form bifunctional sites, the performance of transition-state metal-based catalysts in the detection of volatile organic compounds (VOCs) can be effectively improved.

[0032] Specifically, in the surface and interface control strategy of oxide semiconductor gas-sensitive materials, the influence of different transition state metal species (single atoms, nanoparticles, and alloy nanoparticles) on the surface chemistry and electronic structure of tungsten oxide semiconductor gas-sensitive materials is utilized to synergistically regulate oxygen vacancies and interface charge transfer in tungsten oxide semiconductors, thereby improving gas-sensing performance. Based on this, a sensor with high sensitivity and good stability is designed and fabricated.

[0033] This invention introduces different transition-state metal species (single atoms, nanoparticles, and alloy nanoparticles) to form bifunctional sites, which can regulate the morphology and particle size of tungsten oxide. The transition-state metals increase the number of defects in the tungsten oxide material. Through this combined effect, the sensitivity of the tungsten oxide semiconductor gas sensor is improved, overcoming the problems of slow and weak gas sensing response. It enables rapid, accurate, efficient, and stable detection of ppb-level gases. Furthermore, by selecting different combinations of transition-state metals to act on the tungsten oxide semiconductor gas-sensitive material, high response to specific VOCs gases and low response to other interfering gases can be achieved, resulting in high selectivity. Attached Figure Description

[0034] Figure 1 This is an X-ray diffraction pattern of the sample provided in an embodiment of the present invention.

[0035] Figure 2 This is a microscopic morphology diagram of the sample provided in an embodiment of the present invention.

[0036] Figure 3 This is a cyclic performance diagram of the gas sensor provided in an embodiment of the present invention.

[0037] Figure 4 This is a performance diagram of the gas sensor response provided in an embodiment of the present invention. Detailed Implementation

[0038] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0039] The effects of single-atom and nano-metallic Pt, Pd, Au, Cu, Co, and Mn on the surface chemistry and electronic structure of tungsten oxide semiconductor gas-sensitive materials are used to synergistically regulate oxygen vacancies and interfacial charge transfer in tungsten oxide semiconductors, thereby enhancing gas-sensing performance. The preparation method of this invention employs in-situ pyrolysis, which is simple, requires minimal instrumentation, and has relatively low overall cost. By utilizing the synergistic effect of bifunctional sites of different transition state metal species (single atoms, nanoparticles, and alloy nanoparticles) to enhance the sensitivity of tungsten oxide semiconductors, the sensor's performance is improved, thereby reducing manufacturing costs and enabling rapid, accurate, efficient, and stable detection of ppb-level VOCs gases.

[0040] In this invention, based on the interface regulation strategy of oxide semiconductor gas-sensitive materials, tungsten oxide semiconductor gas-sensitive materials are treated using a combination of nanoparticles and single atoms. The influence of nanoparticles and single atoms on the surface chemistry and electronic structure of the oxide gas-sensitive material synergistically regulates oxygen vacancies and interfacial charge transfer in the tungsten oxide semiconductor, thereby improving gas-sensing performance. Here, single atoms refer to valenced single atoms of Pt, Pd, Au, Cu, Co, and Mn. Valenced single atoms of Pt, Pd, Au, Cu, Co, and Mn can regulate oxygen defects on the surface of the tungsten oxide semiconductor, facilitating the adsorption of more oxygen molecules on the surface and their ionization into reactive oxygen species, thus improving gas-sensing performance. Simultaneously, valenced single atoms have a catalytic effect, lowering the activation energy of the gas-sensing reaction and increasing the reaction rate, achieving the goal of improving gas-sensing performance. Furthermore, the formation of numerous interfaces between nanoparticles and the tungsten oxide semiconductor facilitates rapid charge transfer. The influence of nanoparticles on the surface chemistry and electronic structure of the tungsten oxide semiconductor gas-sensitive material, regulating oxygen vacancies and interfacial charge transfer, further enhances gas-sensing performance. At the same time, nanoparticles also have a catalytic effect, which can reduce the activation energy of gas-sensitive reactions, further increase the reaction rate, and achieve the purpose of improving gas-sensitive performance.

[0041] To illustrate the method and product of the present invention in more detail, the following description is provided in conjunction with specific embodiments.

[0042] Example 1

[0043] The dual-functional tungsten oxide semiconductor gas-sensitive material prepared in this embodiment is granular with a particle size of 5 μm to 15 μm, and its surface is covered with a nanoparticle layer. The nanoparticle layer is composed of closely adjacent nanoparticles with a particle size of 50 nm to 80 nm.

[0044] The method for preparing tungsten oxide semiconductor gas-sensitive materials is as follows:

[0045] First, a single-atom sensitization treatment was performed, followed by a nanoparticle sensitization treatment. In the single-atom sensitization treatment, the tungsten precursor WCl6 was first dissolved in ethanol, with a WCl6 to ethanol ratio less than 5g:1000ml (this ratio was determined based on experimental control experience). A clear, transparent solution was obtained. Then, a sensitizing material precursor, copper nitrate (CuNO3), was added to this clear, transparent solution at 6% of the WCl6 mass. A homogeneous mixed solution was obtained and placed in a reactor. The solution was reacted at 160℃ for 14 hours, followed by centrifugation to obtain a solid reactant. The solid reactant was washed multiple times with deionized water and then dried at 60℃–80℃ to obtain a single-atom metal-sensitized tungsten oxide semiconductor gas-sensitive material, where the single-atom metal served as a catalyst.

[0046] In the nanoparticle sensitization treatment, firstly, metal nanoparticles are dissolved in deionized water. Then, the tungsten oxide semiconductor gas-sensitive material with single-atom metal sensitization treatment is added to the solution for a mixed reaction at 25°C for 4 hours. The product is then collected by centrifugation, washed, and vacuum dried at 60°C for 12 hours to obtain a bifunctional tungsten oxide semiconductor gas-sensitive material with both single-atom and metal nanoparticle sensitization treatments. The metal nanoparticles are nanoparticles formed from a single-atom metal, specifically Pt. The content of the metal nanoparticles is 0.5% of the mass of the tungsten oxide semiconductor gas-sensitive material with single-atom metal sensitization treatment, and the particle size is 2 nm to 10 nm.

[0047] The method for fabricating a VOCs gas sensor using a dual-functional tungsten oxide semiconductor gas-sensitive material is as follows:

[0048] First, a dual-functional tungsten oxide semiconductor gas-sensitive material was prepared.

[0049] Next, the bifunctional tungsten oxide semiconductor gas-sensitive material was dissolved in ethanol and dispersed evenly to obtain a suspension.

[0050] Then, the suspension is drop-coated onto the substrate, air-dried naturally, and aged for 40 hours after the volatile solvent evaporates to obtain the VOCs gas sensor.

[0051] The VOCs gas sensor prepared from the dual-functional site tungsten oxide semiconductor gas-sensitive material in this embodiment has excellent performance, with a dynamic response range of 1.9 to 140 and a response speed of 15 to 30 seconds.

[0052] Example 2

[0053] The dual-functional tungsten oxide semiconductor gas-sensitive material prepared in this embodiment is granular with a particle size of 10 μm to 25 μm, and its surface is covered with a nanoparticle layer. The nanoparticle layer is composed of closely adjacent nanoparticles with a particle size of 70 nm to 100 nm.

[0054] The method for preparing tungsten oxide semiconductor gas-sensitive materials is as follows:

[0055] First, a single-atom sensitization treatment is performed, followed by a nanoparticle sensitization treatment. In the single-atom sensitization treatment, the tungsten precursor WCl6 is first dissolved in ethanol at a ratio of less than 5g:1000ml to obtain a clear and transparent solution. Then, a sensitizing material precursor, selected from chloroplatinic acid H₂PtCl₆, is added to this solution at a concentration of 2% of the WCl₆ mass. A homogeneous mixed solution is obtained and placed in a reactor. The solution is reacted at 170°C for 24 hours, followed by centrifugation to obtain a solid reactant. The solid reactant is then washed and dried to obtain a single-atom metal-sensitized tungsten oxide semiconductor gas-sensitive material, where the single-atom metal is used as a catalyst.

[0056] In the nanoparticle sensitization treatment, firstly, metal nanoparticles are dissolved in deionized water. Then, the tungsten oxide semiconductor gas-sensitive material with single-atom metal sensitization treatment is added to the solution for a mixed reaction at 30°C for 3.5 hours. The product is then collected by centrifugation, washed, and vacuum dried at 60°C for 12 hours to obtain a bifunctional tungsten oxide semiconductor gas-sensitive material with both single-atom and metal nanoparticle sensitization treatments. The metal nanoparticles are nanoparticles formed from a single-atom metal, specifically Pd. The content of the metal nanoparticles is 1.0% of the mass of the tungsten oxide semiconductor gas-sensitive material with single-atom metal sensitization treatment, and the particle size is 2 nm to 8 nm.

[0057] The method for fabricating a VOCs gas sensor using a dual-functional tungsten oxide semiconductor gas-sensitive material is as follows:

[0058] First, a dual-functional site tungsten oxide semiconductor gas-sensitive material was prepared. Then, the dual-functional site tungsten oxide semiconductor gas-sensitive material was dissolved in ethanol and dispersed evenly to obtain a suspension. The suspension was then drop-coated onto a substrate and allowed to air dry naturally. After the volatile solvent evaporated, the material was aged for 50 hours to obtain a VOCs gas sensor.

[0059] The VOCs gas sensor prepared from the dual-functional site tungsten oxide semiconductor gas-sensitive material in this embodiment has excellent performance, with a dynamic response range of 50 to 150 and a response speed of 20 to 40 seconds.

[0060] Example 3

[0061] The dual-functional tungsten oxide semiconductor gas-sensitive material prepared in this embodiment is granular with a particle size of 20 μm to 40 μm, and its surface is covered with a nanoparticle layer. The nanoparticle layer is composed of closely adjacent nanoparticles with a particle size of 80 nm to 120 nm.

[0062] The method for preparing tungsten oxide semiconductor gas-sensitive materials is as follows:

[0063] First, a single-atom sensitization treatment is performed, followed by a nanoparticle sensitization treatment. In the single-atom sensitization treatment, the tungsten precursor WCl6 is first dissolved in ethanol, with a WCl6 to ethanol ratio of less than 5g:1000ml, resulting in a clear and transparent solution. Then, a sensitizing material precursor, selected from cobalt nitrate Co(NO3)2, is added to this clear and transparent solution at 8% of the WCl6 mass. A homogeneous mixed solution is obtained and placed in a reactor, reacting at 180°C for 17 hours. The mixture is then centrifuged to obtain a solid reactant. This solid reactant is washed and dried to obtain a single-atom metal-sensitized tungsten oxide semiconductor gas-sensitive material, where the single-atom metal is used as a catalyst.

[0064] In the nanoparticle sensitization treatment, firstly, metal nanoparticles are dissolved in deionized water. Then, the tungsten oxide semiconductor gas-sensitive material with single-atom metal sensitization treatment is added to the solution for mixing and reaction. The reaction temperature is 25°C, and the reaction time is 4 hours. The product is then collected by centrifugation, washed, and vacuum dried at 75°C for 10 hours to obtain a bifunctional tungsten oxide semiconductor gas-sensitive material with both single-atom and metal nanoparticle sensitization treatments. The metal element is Au, and the content of the metal nanoparticles is 1.5% of the mass of the tungsten oxide semiconductor gas-sensitive material with single-atom metal sensitization treatment, with a particle size of 2 nm to 10 nm.

[0065] The method for fabricating a VOCs gas sensor using a dual-functional tungsten oxide semiconductor gas-sensitive material is as follows:

[0066] First, a dual-site tungsten oxide semiconductor gas-sensitive material was prepared. Then, the dual-site tungsten oxide semiconductor gas-sensitive material was dissolved in ethanol and dispersed evenly to obtain a suspension. The suspension was then drop-coated onto a substrate and allowed to air dry naturally. After the volatile solvent evaporated, the material was aged for at least 48 hours to obtain a VOCs gas sensor.

[0067] The VOCs gas sensor prepared from the dual-functional site tungsten oxide semiconductor gas-sensitive material in this embodiment has excellent performance, with a dynamic response range of 2 to 80 and a response speed of 45 to 60 seconds.

[0068] Example 4

[0069] The dual-functional tungsten oxide semiconductor gas-sensitive material prepared in this embodiment is granular with a particle size of 60 μm to 80 μm, and its surface is covered with a nanoparticle layer. The nanoparticle layer is composed of closely adjacent nanoparticles with a particle size of 90 nm to 105 nm.

[0070] The method for preparing tungsten oxide semiconductor gas-sensitive materials is as follows:

[0071] First, a single-atom sensitization treatment is performed, followed by a nanoparticle sensitization treatment. In the single-atom sensitization treatment, the tungsten precursor WCl6 is first dissolved in ethanol, with a WCl6 to ethanol ratio of less than 5g:1000ml, resulting in a clear and transparent solution. Then, a sensitizing material precursor, selected from manganese chloride (MnCl2), is added to this clear and transparent solution at 7% of the WCl6 mass. A homogeneous mixed solution is obtained and placed in a reactor, reacting at 190°C for 18 hours. The mixture is then centrifuged to obtain a solid reactant. This solid reactant is washed and dried to obtain a single-atom metal-sensitized tungsten oxide semiconductor gas-sensitive material, where the single-atom metal is used as a catalyst.

[0072] In the nanoparticle sensitization process, firstly, metal nanoparticles are dissolved in deionized water. Then, the tungsten oxide semiconductor gas-sensitive material with single-atom metal sensitization is added to the solution for a mixed reaction at 25°C for 4 hours. The product is then collected by centrifugation, washed, and vacuum-dried at 65°C for 10 hours to obtain a bifunctional tungsten oxide semiconductor gas-sensitive material simultaneously sensitized by single-atom and metal nanoparticles. The metal nanoparticles are alloy nanoparticles, formed from an alloy of Cu, Co, and Mn. The content of the metal nanoparticles is 3% of the mass of the tungsten oxide semiconductor gas-sensitive material with single-atom metal sensitization, and the particle size is 2nm–10nm.

[0073] The method for fabricating a VOCs gas sensor using a dual-functional tungsten oxide semiconductor gas-sensitive material is as follows:

[0074] First, a dual-site tungsten oxide semiconductor gas-sensitive material was prepared. Then, the dual-site tungsten oxide semiconductor gas-sensitive material was dissolved in ethanol and dispersed evenly to obtain a suspension. The suspension was then drop-coated onto a substrate and allowed to air dry naturally. After the volatile solvent evaporated, the material was aged for 40 hours to obtain a VOCs gas sensor.

[0075] The VOCs gas sensor prepared from the dual-functional site tungsten oxide semiconductor gas-sensitive material in this embodiment has excellent performance, with a dynamic response range of 30–160 and a response speed of 25–50 s.

[0076] Example 5

[0077] The dual-functional tungsten oxide semiconductor gas-sensitive material prepared in this embodiment is granular with a particle size of 35 μm to 55 μm, and its surface is covered with a nanoparticle layer. The nanoparticle layer is composed of closely adjacent nanoparticles with a particle size of 80 nm to 110 nm.

[0078] The method for preparing tungsten oxide semiconductor gas-sensitive materials is as follows:

[0079] First, a single-atom sensitization treatment is performed, followed by a nanoparticle sensitization treatment. In the single-atom sensitization treatment, the tungsten precursor WCl6 is first dissolved in ethanol, with a WCl6 to ethanol ratio of less than 5g:1000ml, resulting in a clear and transparent solution. Then, a sensitizing material precursor, selected from palladium chloride (PdCl2), is added to this clear and transparent solution at 3% of the WCl6 mass. A homogeneous mixed solution is obtained and placed in a reactor, reacting at 200℃~220℃ for 22h. The mixture is then centrifuged to obtain a solid reactant. This solid reactant is washed and dried to obtain a single-atom metal-sensitized tungsten oxide semiconductor gas-sensitive material, where the single-atom metal is used as a catalyst.

[0080] In the nanoparticle sensitization treatment, firstly, metal nanoparticles are dissolved in deionized water, and then the tungsten oxide semiconductor gas-sensitive material with single-atom metal sensitization treatment is added to it for mixing and reaction. The reaction temperature is 30℃ and the reaction time is 3.5h. Then, the product is collected by centrifugation, washed, and vacuum dried at 30℃ for 8h to obtain a bifunctional tungsten oxide semiconductor gas-sensitive material with both single-atom and metal nanoparticle sensitization treatment. The metal element is Cu, and the content of metal nanoparticles is 2% of the mass of the tungsten oxide semiconductor gas-sensitive material with single-atom metal sensitization treatment, with a particle size of 2nm to 10nm.

[0081] The method for fabricating a VOCs gas sensor using a dual-functional tungsten oxide semiconductor gas-sensitive material is as follows:

[0082] First, a dual-site tungsten oxide semiconductor gas-sensitive material was prepared. Then, the dual-site tungsten oxide semiconductor gas-sensitive material was dissolved in ethanol and dispersed evenly to obtain a suspension. The suspension was then drop-coated onto a substrate and allowed to air dry naturally. After the volatile solvent evaporated, the material was aged for 36.5 hours to obtain a VOCs gas sensor.

[0083] The VOCs gas sensor prepared from the dual-functional site tungsten oxide semiconductor gas-sensitive material in this embodiment has excellent performance, with a dynamic response range of 40–120 and a response speed of 25–60 s.

[0084] Example 6

[0085] First, ammonium tungstate hydrate was ground in an agate mortar and then calcined in a muffle furnace. The temperature program was initially set to 400°C with a heating rate of 2°C / min, and then further heated to 600°C at a rate of 1°C / min. After cooling to room temperature, the desired WO3 powder was obtained.

[0086] Then, 0.1 g of chloroplatinum hexahydrate was dissolved in 50 mL of deionized water, and 3 g of WO3 powder was added to the prepared solution.

[0087] Subsequently, the suspension was treated alternately with ultrasound and magnetic stirring for 4 hours. The product was collected by centrifugation, washed three times with water, and dried under vacuum at 60°C overnight to obtain Pt1 / WO3.

[0088] Finally, 0.05 g of platinum nanoparticles were dispersed in 50 mL of deionized water at room temperature. 1.5 g of Pt1 / WO3 powder was then introduced and mixed. The product was collected by centrifugation, washed several times with water, and vacuum-dried overnight at 60 °C to obtain Pt. 1+NPs / WO3.

[0089] Thus, a dual-site tungsten oxide semiconductor gas-sensitive material with both single-atom Pt and metallic Pt nanoparticles simultaneously enhanced was obtained.

[0090] The method for preparing a gas sensor using a dual-functional site tungsten oxide semiconductor gas-sensitive material that is simultaneously enhanced by both single-atom Pt and metallic Pt nanoparticles is as follows:

[0091] The obtained Pt 1+NPs WO3 is mixed with anhydrous ethanol and dispersed evenly. The evenly dispersed suspension is dripped onto an alumina substrate using a syringe, and the device is then allowed to air dry naturally. After the ethanol evaporates, the prepared sensor is aged for 36 hours to produce the sensor.

[0092] Figure 1This is a SEM image of the dual-site tungsten oxide semiconductor gas-sensitive material in Example 6 of the present invention, which is simultaneously sensitized by single-atom Pt and metallic Pt nanoparticles. As can be seen from the image, the tungsten oxide has a solid block structure, indicating that the material has good crystallinity.

[0093] Figure 2 yes Figure 1 A magnified image of the surface of the tungsten oxide semiconductor gas-sensitive material particles with dual functional sites shows that the tungsten oxide surface has a hierarchical structure composed of multiple nanoparticles, indicating that the gas-sensitive material has more active sites, which is beneficial to improving the gas-sensing performance.

[0094] Example 7

[0095] First, ammonium tungstate hydrate was ground in an agate mortar and then calcined in a muffle furnace. The temperature program was initially set to 500°C with a heating rate of 2°C / min, and then further heated to 500°C at a rate of 1°C / min. After cooling to room temperature, the desired WO3 powder was obtained.

[0096] Then, 0.05 g of chloroplatinum hexahydrate was dissolved in 50 mL of deionized water, and 1.5 g of WO3 powder was added to the prepared solution.

[0097] Subsequently, the suspension was treated alternately with ultrasound and magnetic stirring for 5 hours. The product was collected by centrifugation, washed three times with water, and vacuum dried overnight at 60°C to obtain Pt1 / WO3.

[0098] Finally, 0.05 g of platinum nanoparticles were dispersed in 50 mL of deionized water at room temperature. 1.5 g of Pt1 / WO3 powder was then introduced and mixed. The product was collected by centrifugation, washed several times with water, and vacuum dried overnight at 60 °C to obtain Pt. 1+NPs / WO3.

[0099] The method for preparing a gas sensor using a dual-functional site tungsten oxide semiconductor gas-sensitive material that is simultaneously enhanced by both single-atom Pt and metallic Pt nanoparticles is as follows:

[0100] The obtained Pt 1+NPs WO3 is mixed with anhydrous ethanol and dispersed evenly. The evenly dispersed suspension is dripped onto an alumina substrate using a syringe, and the device is then allowed to air dry naturally. After the ethanol evaporates, the prepared sensor is aged for 48 hours to produce the sensor.

[0101] like Figure 3The figure shows the performance of the sensor in Example 7. As can be seen from the figure, the prepared sensor has good cycle stability. This indicates that the synergistic enhancement of transition state metal single atoms and nanoparticles can improve gas sensing performance. The synergistic enhancement of transition state metal single atoms and nanoparticles can improve the sensor's response and response speed. This is mainly attributed to the fact that the transition state metal catalyst lowers the activation energy of the gas sensing reaction, and the synergistic effect of the interface between the transition state metal single atoms and nanoparticles and tungsten oxide promotes charge transfer, thereby improving the performance of the gas sensor.

[0102] Example 8

[0103] First, ammonium tungstate hydrate was ground in an agate mortar and then calcined in a muffle furnace. The temperature program was initially set to 400°C with a heating rate of 2°C / min, and then further heated to 600°C at a rate of 1°C / min. After cooling to room temperature, the desired WO3 powder was obtained.

[0104] Then, 0.1 g of palladium chloride was dissolved in 50 mL of deionized water, and 3 g of WO3 powder was added to the prepared solution.

[0105] Subsequently, the suspension was treated alternately with ultrasound and magnetic stirring for 4 hours. The product was collected by centrifugation, washed three times with water, and vacuum dried overnight at 60°C to obtain Pd1 / WO3.

[0106] Finally, 0.05 g of platinum nanoparticles were dispersed in 50 mL of deionized water at room temperature. 1.5 g of Pd1 / WO3 powder was then introduced and mixed. The product was collected by centrifugation, washed several times with water, and vacuum-dried overnight at 60 °C to obtain Pd1 / WO3. 1+NPs / WO3.

[0107] The method for preparing a gas sensor using a dual-functional site tungsten oxide semiconductor gas-sensitive material that is simultaneously enhanced by both single-atom Pd and metallic Pt nanoparticles is as follows:

[0108] The obtained Pd 1+NPs WO3 is mixed with distilled water and dispersed evenly. The evenly dispersed suspension is dripped onto an alumina substrate using a syringe, and the device is then allowed to air dry naturally. After the ethanol evaporates, the prepared sensor is aged for 48 hours to produce the sensor.

[0109] Figure 4 The image shows the dynamic response of the sensor in Example 8. It can be seen that the sensor's performance is significantly enhanced after the synergistic enhancement of transition state metal single atoms and nanoparticles.

[0110] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing tungsten oxide semiconductor gas-sensitive material, characterized in that, First, single-atom sensitization is performed, followed by nanoparticle sensitization. In the single-atom sensitization process, firstly, a tungsten precursor is dissolved in a solvent to obtain a clear and transparent solution. Then, the sensitizing material precursor is added to the clear and transparent solution to obtain a homogeneous mixed solution. The mixed solution is reacted at 160℃~220℃ for 14h~24h. After centrifugation, a solid reactant is obtained. The solid reactant is washed and dried to obtain a single-atom metal-sensitized tungsten oxide semiconductor gas-sensitive material. Alternatively, in single-atom sensitization treatment, ammonium tungstate is first calcined to obtain tungsten oxide powder. Then, the tungsten oxide powder is added to a precursor solution of the sensitizing material, and the reaction is carried out at 160℃~220℃ for 14h~24h. After centrifugation, a solid reactant is obtained. The solid reactant is then washed and dried to obtain a single-atom metal-sensitized tungsten oxide semiconductor gas-sensitive material. Single-atom metals are used as catalysts, and the sensitizing material precursors are selected from copper nitrate, cobalt nitrate, manganese chloride, palladium chloride, and chloroplatinic acid. In the nanoparticle sensitization process, firstly, metal nanoparticles are dissolved in deionized water, and then the tungsten oxide semiconductor gas-sensitive material with single-atom metal sensitization treatment is added to the solution for mixing and reaction. Next, the product is collected by centrifugation, and the product is washed and vacuum dried to obtain a bifunctional tungsten oxide semiconductor gas-sensitive material with both single-atom and metal nanoparticle sensitization treatments.

2. The method for preparing tungsten oxide semiconductor gas-sensitive material as described in claim 1, characterized in that, The precursor of tungsten is WCl6, and the content of the precursor of the sensitizing material is 2% to 8% of the mass of WCl6.

3. The method for preparing tungsten oxide semiconductor gas-sensitive material as described in claim 2, characterized in that, Metal nanoparticles are nanoparticles formed from elemental metals, which are one or more of Pt, Pd, Au, Cu, Co, and Mn.

4. The method for preparing tungsten oxide semiconductor gas-sensitive material as described in claim 2, characterized in that, The metal nanoparticles are alloy nanoparticles, and the alloy is an alloy formed by at least two elements selected from Pt, Pd, Au, Cu, Co and Mn.

5. The method for preparing tungsten oxide semiconductor gas-sensitive material as described in claim 2, characterized in that, The content of metal nanoparticles is 0.5% to 3% of the mass of the tungsten oxide semiconductor gas-sensitive material treated with single-atom metal sensitization, and the particle size is 2nm to 10nm.

6. The method for preparing tungsten oxide semiconductor gas-sensitive material as described in claim 2, characterized in that, The solvent is ethanol, and the ratio of WCl6 to ethanol is less than 5g:1000ml.

7. The bifunctional tungsten oxide semiconductor gas-sensitive material prepared by the method according to any one of claims 1-6, characterized in that, It is granular with a particle size of 5μm to 80μm, and its surface is covered with a layer of nanoparticles.

8. The dual-functional tungsten oxide semiconductor gas-sensitive material as described in claim 7, characterized in that, The nanoparticle layer is composed of closely adjacent nanoparticles with a particle size of 50nm to 120nm.

9. A VOCs gas sensor prepared using the dual-functional site tungsten oxide semiconductor gas-sensitive material as described in claim 7 or 8, characterized in that, Its dynamic response range is 1.9 to 160, and its response speed is 15 to 60 seconds.

10. A method for preparing the VOCs gas sensor as described in claim 9, characterized in that, It includes the following steps: First, a dual-functional tungsten oxide semiconductor gas-sensitive material was prepared. Next, the bifunctional tungsten oxide semiconductor gas-sensitive material was dissolved in a volatile solvent and dispersed evenly to obtain a suspension. Then, the suspension is drop-coated onto the substrate, and after the volatile solvent evaporates, it is aged for at least 36 hours to obtain a VOCs gas sensor.

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