Graphene-like supported tungsten oxide nanomaterials with dual strategy of sensitization of binary noble metal loading, preparation method and application thereof

Abstract

The application discloses a kind of graphite-like double strategy sensitized tungsten oxide nanomaterials supported and binary noble metal loading, its preparation method and application, the method of the present application, comprising the following steps: using nitrogen-containing compound, the precursor of two noble metals and tungsten source as raw material, preparation C3N4 / binary noble metal-WO3;Then C3N4 / binary noble metal-WO3 is annealed in tube furnace, and C3N4 / binary noble metal-WO3 with the mass fraction of 2-10wt% of C3N4 is obtained.The tungsten oxide nanomaterials of the present application are used as sensitive material, and the sensitive film of MEMS sensor is made to detect acetone in the gas sample to be measured, and the gas sample to be measured includes human exhaled gas.The double strategy sensitized tungsten oxide nanomaterials of the present application have very high sensitivity, and the sensor can also maintain good signal stability and reliability.On the basis of graphite phase C3N4 support, binary noble metal is loaded, so that the sensor has higher sensitivity and faster response time.

Description

Technical Field

[0001] This invention relates to a method for preparing tungsten oxide nanomaterials with a dual strategy of graphene-like support and multi-element noble metal loading, and their application. It belongs to the field of materials technology, and particularly relates to a tungsten oxide nanomaterial with high sensitivity to acetone gas, its preparation method, and its application. Background Technology

[0002] Noble metals possess unique electronic orbital structures, demonstrating immense application potential in industrial catalysis, energy, and sensors. Graphene-like materials refer to materials with two-dimensional structures or properties similar to graphene. While graphene is a single-layer crystal structure composed of carbon atoms, graphene-like materials can be composed of other elements or compounds, forming similar two-dimensional structures. C3N4 nanosheets, due to their excellent two-dimensional structural characteristics and unique electrical properties, have attracted extensive research in energy storage, optoelectronic devices, sensors, and photocatalysis. Furthermore, compared to materials like graphene oxide, C3N4 exhibits superior thermal stability, making it potentially usable as a sensitizer in gas-sensitive materials at high operating temperatures, resulting in better lifespan and a higher number of cycles. Tungsten oxide, a compound composed of tungsten and oxygen atoms, is an important inorganic material with diverse structures and properties, widely used in catalysis, optics, electrochemistry, and sensing.

[0003] Patent document CN1043830A discloses a method for manufacturing a zinc stannate butane gas-sensitive element. It uses ZnSnO3, WO3, and SnO2 as the main materials, with appropriate amounts of PtO2, Sb, Al2O3, TiO2, Co2O3, Ta2O5, acid-washed asbestos, and Kunming porcelain powder added, followed by sintering. The resulting element combines the advantages of various butane gas-sensitive elements while overcoming problems such as low sensitivity, short lifespan, high operating temperature, or poor humidity resistance. It exhibits high sensitivity and selectivity for butane (or liquefied petroleum gas), making it particularly suitable for leak detection, alarm, leak finding, and control in liquefied petroleum gas tanks, stations, their pipelines, and other locations using liquefied petroleum gas. The gas-sensitive material used in this invention is a SnO2-based composite oxide gas-sensitive material. Although it contains WO3 and the precious metal Pt, its gas adsorption capacity is limited, resulting in a relatively high minimum measurement limit and less than ideal gas sensitivity.

[0004] Patent document CN113340956A discloses an rGO-Au@PdPt composite nanomaterial, comprising reduced graphene oxide and Au@PdPt core-shell nanoparticles supported on the reduced graphene oxide, wherein the diameter of the Au@PdPt core-shell nanoparticles is less than 50 nm. This rGO-Au@PdPt composite nanomaterial is a novel composite nanomaterial with excellent ammonia nitrogen sensitivity. Graphene possesses excellent physicochemical properties, a large specific surface area, and numerous potential active sites. Therefore, the electrode material obtained by combining graphene with nanomaterials containing multiple noble metal components can combine the advantages of noble metals and graphene, thereby achieving high-performance ammonia nitrogen detection. This invention also provides a method for preparing the rGO-Au@PdPt composite nanomaterial and an ammonia nitrogen detection electrode. This technology uses reduced graphene oxide, with AuPdPt as the metal, and does not contain W, forming a core-shell structure catalyst material. The target gas for testing is ammonia, and it cannot be determined whether it is sensitive to acetone gas.

[0005] Patent document CN116899587A discloses a supported PdPt-M ternary metal catalyst, its preparation method, and its application. The steps are as follows: a pretreated activated carbon support, a soluble salt of palladium, a soluble salt of the inexpensive metal M, and a stabilizer are dissolved in deionized water. A soluble salt solution of platinum is added, and the resulting suspension is ultrasonically dispersed uniformly. The reaction is stirred at 60°C. After the reaction is complete, the temperature is lowered to 10°C, and sodium borohydride solution is slowly added dropwise to ensure complete reduction of the metal ions to elemental metal. Acetone is added for aging. After washing with water and ethanol, the catalyst is vacuum dried at 60°C and subsequently modified with KOH solution to obtain the PdPt-M / C catalyst. The PdPt-M / C catalyst prepared by this technology can catalyze the dehydrogenation of cyclohexanone trimer to 2,6-diphenylphenol in the liquid phase at 250°C–290°C, achieving a 100% conversion rate for the cyclohexanone trimer and a selectivity for 2,6-diphenylphenol exceeding 65%. This technology does not contain graphene or graphene-like materials, nor does it contain tungsten oxide. As a ternary metal catalyst, it is mainly used in chemical synthesis, and its application to the sensitive detection of acetone, formaldehyde, and ethanol gases has not been disclosed.

[0006] Patent document CN115015328A discloses a p-pentanol gas sensor based on a PtAu alloy nanocrystal-modified flower-shaped WO3 sensitive material and its preparation method, belonging to the field of semiconductor metal oxide gas sensor technology. The PtAu alloy nanocrystals are synthesized using oleylamine, and the flower-shaped WO3 is prepared using a simple hydrothermal method. The PtAu alloy nanocrystals are then loaded onto the surface of the flower-shaped WO3 using an impregnation method to prepare the PtAu alloy nanocrystal-modified flower-shaped WO3 sensitive material. The sensor consists of an Al2O3 ceramic tube with gold electrodes on its outer surface, the coated sensitive material, and a Cr-Ni alloy heating wire. The p-pentanol sensor in this technology exhibits excellent gas-sensing performance. Test results show that the sensor's response to 20 ppm p-pentanol gas reaches 161.7, with a response time of only 1 second. Furthermore, the sensor also shows good selectivity for p-pentanol. This sensor is expected to achieve rapid detection of p-pentanol gas. This technology does not add carbon materials, and its target gas for measurement is p-pentanol gas; it does not disclose its application to acetone, formaldehyde, and ethanol gases for sensitive information.

[0007] Patent document CN108760833A discloses a sensitive material for detecting acetone gas, composed of WO3 nanosheets and C3N4 composites. The WO3 nanosheets serve as the matrix, and the C3N4 acts as the sensitizer, with a C3N4 content in the sensitive material ranging from 0.5% to 10 wt%. This technology also provides a method for preparing the aforementioned sensitive material. Ultrathin WO3 nanosheets are prepared via self-assembly, and the prepared C3N4 is ultrasonically exfoliated in a solvent to obtain a dispersion. This dispersion is then dropwise added onto the WO3 nanosheet layer according to a specific mass percentage to form a composite gas-sensitive material. This technology enhances the acetone detection performance of WO3 nanosheets by modifying them with C3N4, which has a two-dimensional layered structure. It uses C3N4 as the sensitizer and does not use precious metals. Although it has a good sensitivity to acetone gas at a concentration of 100 ppm and discloses a detection limit of 0.5-500 ppm, it does not disclose direct data evidence of detection effect for lower concentrations such as acetone below 10 ppm. Therefore, it is impossible to know the response data and detection capability for acetone concentrations below 10 ppm.

[0008] Volatile organic compounds (VOCs) in human exhaled breath are important markers for non-invasive, rapid, and simple disease diagnosis. Among them, the concentration of acetone in human exhaled breath is a key indicator for diagnosing diabetes. Therefore, a highly sensitive acetone vapor sensor is essential for accurate diabetes diagnosis. Currently, metal-oxide-semiconductor (MOS) based gas sensors are promising candidates for exhaled breath analyzers and are being used for disease diagnosis. Compared to chromatography-mass spectrometry (GC-MS) coupled detection techniques, these MOS-based gas sensors offer significant advantages in terms of miniaturization, low cost, and ease of operation.

[0009] When semiconductor oxide sensitive materials are used for acetone gas detection, the reaction generally relies on the redox reaction between acetone gas molecules and adsorbed oxygen species on the surface of the sensitive material. By controlling the nanostructure or forming heterojunctions with other materials, the effective specific surface area and charge conduction channels of the metal oxide can be increased, thereby improving its gas-sensing performance. For example, Zhang JN et al. prepared NiO / WO3 composite fibers using a simple electrospinning and calcination method. These fibers achieved a detection sensitivity of 22.5 for 100 ppm acetone at 375℃, which is 2.1 times higher than that of pure WO3 nanofibers. This improvement in gas-sensing performance is also attributed to the formation of heterojunctions. While this technology effectively improves the sensitivity and selectivity of sensitive materials for acetone gas detection, problems such as slow response recovery, unsatisfactory detection limits, and poor stability still exist. Currently, high-sensitivity acetone sensors on the market are generally expensive, while cheaper ones suffer from low sensitivity, slow response recovery, and poor anti-interference capabilities, failing to meet market demands.

[0010] Therefore, in medical diagnostics, as one of the components of human exhaled gas, people can detect certain diseases, such as diabetes, based on the gas concentration of acetone. However, the advancement of exhaled gas testing technology is limited by the weak gas-sensing properties of materials, especially for the detection of target gases not exceeding 20 ppm or even 10 ppm. Therefore, inventing a functional material that can significantly improve the response level to specific gases is of great significance for improving the performance of sensors. Summary of the Invention

[0011] To address the problems of existing technologies, the present invention aims to overcome the shortcomings of existing technologies and provide a tungsten oxide nanomaterial with dual-strategy sensitization through graphene-like support and binary noble metal loading, its preparation method, and its application. The C3N4 / PdPt-WO3 composite nanomaterial of the present invention, with a C3N4 mass fraction of 2-10%, exhibits high sensitivity to acetone gas at room temperature and reacts rapidly, meeting the requirements for detecting trace amounts of acetone. In particular, it demonstrates excellent sensitivity to gas samples with acetone concentrations not exceeding 10 ppm, and its gas-sensitivity performance is not affected over an extremely wide humidity range.

[0012] To achieve the above objectives, the present invention adopts the following technical solution:

[0013] A method for preparing graphene-like supported and binary noble metal-loaded tungsten oxide nanomaterials includes the following steps:

[0014] Step S1: Using nitrogen-containing compounds, two noble metal precursors, and a tungsten source as raw materials, C3N4 / binary noble metal-WO3 is prepared; the two noble metal precursors are noble metal salts, including at least Pd salt or Pt salt.

[0015] Step S2: The C3N4 / binary precious metal-WO3 is heated to not less than 500°C in a tube furnace for annealing and annealed in air for at least 3 hours to obtain C3N4 / binary precious metal-WO3 with a C3N4 mass fraction of 2-10 wt%.

[0016] As a preferred technical solution of the present invention, step S1 includes the following steps:

[0017] Step S101: The nitrogen-containing compound is placed in a furnace tube and pyrolyzed at high temperature to obtain the treated C3N4.

[0018] In step S102, the tungsten source is tungsten salt, which is dissolved in a solvent to form a tungsten salt solution; the precursors of the two noble metals are dissolved in another solvent to form a binary noble metal salt solution.

[0019] Then, at 20-30℃, the binary noble metal salt solution was added dropwise to the tungsten salt solution and stirred for a period of time to make the binary noble metal salt uniformly dispersed in the tungsten salt solution, so that the binary noble metal combined with WO3 to form an intermediate product solution; then the intermediate product solution was subjected to centrifugation, washing and drying steps to obtain WO3 loaded with binary noble metal.

[0020] In step S103, the prepared C3N4 and binary noble metal-loaded WO3 are dispersed in separate solvents to form C3N4 solution and binary noble metal-loaded WO3 solution, respectively. Then, at 20-30℃, the C3N4 solution is added dropwise to the binary noble metal-loaded WO3 solution and stirred for a period of time to ensure that C3N4 is uniformly dispersed in the binary noble metal-loaded WO3, thus obtaining the final product solution. The final product solution is then subjected to centrifugation, washing, and drying steps to obtain C3N4 / binary noble metal-WO3.

[0021] As a preferred embodiment of the present invention, in step S1, the nitrogen-containing compound is at least one of dicyandiamide, urea, melamine and thiourea.

[0022] As a preferred technical solution of the present invention, in step S1, the tungsten source is at least one of ammonium tungstate, sodium tungstate, calcium tungstate, and zinc tungstate.

[0023] As a preferred technical solution of the present invention, in step S1, the precursors of the two noble metals are PdCl2 and PtCl2; in step S2, the final graphene-like supported and binary noble metal-loaded tungsten oxide nanomaterial is C3N4 / PdPt-WO3.

[0024] As a preferred technical solution of the present invention, in step S1, the mass ratio of C3N4 and binary noble metal is 2-10:1.

[0025] As a preferred embodiment of the present invention, in step S1, the mass ratio of WO3 to C3N4 is 8-50:1. More preferably, the mass ratio of WO3 to C3N4 is 8.5-49.0:1.

[0026] As a preferred technical solution of the present invention, in steps S102 and S103, the drying process is as follows: the intermediate product or the final product is placed in a drying oven for at least 6 hours, and the temperature of the drying oven is controlled to be not lower than 60°C.

[0027] As a preferred technical solution of the present invention, in steps S102 and S103, the product is synthesized at room temperature and stirred during the low-temperature thermal polymerization reaction to ensure that the reactants are in full contact. The stirring time is at least 2 hours, and more preferably at least 2-8 hours.

[0028] As a preferred technical solution of the present invention, in steps S102 and S103, the solvent is water.

[0029] As a preferred technical solution of the present invention, in step S101, the pyrolysis temperature of the nitrogen-containing compound is not lower than 500°C and the pyrolysis time is not lower than 2 hours.

[0030] A tungsten oxide nanomaterial with dual-strategy sensitization of graphene-like support and binary noble metal loading is prepared using the preparation method of tungsten oxide nanomaterial with graphene-like support and binary noble metal loading described in this invention.

[0031] As a preferred technical solution of the present invention, the tungsten oxide nanomaterial with a dual strategy of graphene-like support and binary noble metal loading exhibits a flocculent microstructure. Based on a graphitic C3N4 support, WO3 is modified and loaded with the binary noble metal PdPt, forming a graphene-like supported and binary noble metal loaded tungsten oxide nanomaterial, namely C3N4 / PdPt-WO3. By controlling the nanostructure or forming a multi-element heterojunction with other materials, the effective specific surface area of ​​the metal oxide and its sensitivity to acetone are further improved.

[0032] An application of the graphene-like supported and binary noble metal loaded dual-strategy sensitization tungsten oxide nanomaterial of the present invention is disclosed. The graphene-like supported and binary noble metal loaded dual-strategy sensitization tungsten oxide nanomaterial is used as the sensitive material to fabricate the sensitive membrane of a MEMS sensor to detect acetone in a gas sample to be tested, wherein the gas sample to be tested includes human exhaled gas.

[0033] As a preferred technical solution of the present invention, the sensitive membrane of the present invention is a graphene-like supported tungsten oxide nanomaterial C3N4 / PdPt-WO3 loaded with a binary noble metal. When detecting acetone at ambient pressure, the response is significant when detecting a gas sample with an acetone concentration of not less than 10 ppm at 180-300℃. The response is also significant when detecting a gas sample with an acetone concentration of not less than 10 ppm at 180-300℃. Particularly significant is the response when detecting a gas sample with an acetone concentration of not less than 5 ppm at 180-240℃. Preferably, when the sensitive membrane of the MEMS sensor prepared by the present invention detects acetone, the operating temperature is set to 180-300℃ and the operating pressure is ambient pressure; more preferably, the operating temperature is 180-240℃.

[0034] Compared with the prior art, the present invention has the following obvious and prominent substantive features and significant advantages:

[0035] 1. The graphene-supported and binary noble metal-loaded tungsten oxide nanomaterials of this invention exhibit high sensitivity to acetone gas at room temperature, reacting rapidly to meet the requirements for detecting trace amounts of acetone, and the gas-sensing performance remains unaffected over an extremely wide humidity range. The tungsten oxide nanomaterials prepared by this invention with gas-sensing properties can be used for the detection of acetone gas in human exhaled breath at room temperature. C3N4 and PdPt significantly enhance the gas-sensing performance of WO3.

[0036] 2. The C3N4 / PdPt-WO3 with a C3N4 mass fraction of 2-10 wt.% of the present invention has a higher response to 3 ppm acetone than C3N4 / PdPt-WO3 with other mass fractions, indicating that C3N4 and PdPt have an effective sensitizing effect on tungsten oxide nanomaterials;

[0037] 3. This invention utilizes functionalized graphene composite materials to manufacture a gas sensor that enables specific analysis of acetone. The graphene composite material of this invention has extremely high sensitivity, and the sensor can also maintain good signal stability and reliability. Based on the graphite phase C3N4 support, the binary noble metal PdPt is loaded, thereby making the sensor have higher sensitivity and faster response time. Attached Figure Description

[0038] Figure 1 This is a SEM image of C3N4 / PdPt-WO3 with a C3N4 mass fraction of 10wt% according to a preferred embodiment of the present invention.

[0039] Figure 2 This is the fabrication process of the MEMS sensor according to a preferred embodiment of the present invention.

[0040] Figure 3This is a graph showing the test results of a MEMS sensor based on C3N4 / PdPt-WO3 with a C3N4 mass fraction of 10wt% according to a preferred embodiment of the present invention, on acetone in human exhaled breath. Detailed Implementation

[0041] In the following embodiments of the present invention, the nitrogen-containing compound is at least one selected from dicyandiamide, urea, melamine, and thiourea; the tungsten source is at least one selected from ammonium tungstate, sodium tungstate, calcium tungstate, and zinc tungstate. The precursors for the two noble metals are PdCl2 and PtCl2; the final graphene-like supported and binary noble metal-loaded tungsten oxide nanomaterial is C3N4 / PdPt-WO3. The mass fraction of C3N4 in C3N4 / PdPt-WO3 is 2-10 wt%.

[0042] The mass ratio of C3N4 to the binary noble metal PdPt is 2-10:1.

[0043] The mass ratio of WO3 to C3N4 is 8-50:1.

[0044] The drying process involves placing the intermediate or final product in a drying oven for at least 6 hours, while controlling the temperature of the drying oven to be no lower than 60°C. The solvent used in each step is primarily water.

[0045] The pyrolysis temperature of nitrogen-containing compounds is not lower than 500℃, and the pyrolysis time is not lower than 2 hours. The preferred pyrolysis method for preparing C3N4 involves the following steps: first, melamine or other cyanate substances are placed in a furnace tube, and then the furnace tube is placed in the furnace for pyrolysis. The pyrolysis temperature is generally above 500℃, and the pyrolysis time is generally 2-4 hours, yielding C3N4. Preferably, the C3N4 in the following examples is g-C3N4.

[0046] The above solution will be further described below with reference to specific embodiments. The preferred embodiments of the present invention are described in detail below:

[0047] Example 1:

[0048] In this embodiment, a method for preparing graphene-like supported and binary noble metal-loaded tungsten oxide nanomaterials, specifically C3N4 / PdPt-WO3, includes the following steps:

[0049] Step S1: C3N4 / PdPt-WO3 is prepared by thermal polymerization, and the steps are as follows:

[0050] Step S101: The nitrogen-containing compound is placed in a furnace tube and pyrolyzed at high temperature to obtain the treated C3N4.

[0051] In step S102, the tungsten source is ammonium tungstate, which is dissolved in water to form an ammonium tungstate solution; the precursors of the binary noble metal PdPt, PdCl2 and PtCl2, are dissolved in another aqueous solvent to form a binary noble metal PdPt salt solution.

[0052] Then, at room temperature of 25℃±5℃, the binary noble metal PdPt salt solution was added dropwise to the ammonium tungstate solution and stirred for a period of time to ensure that the binary noble metal PdPt salt was uniformly dispersed in the ammonium tungstate solution, allowing the binary noble metal PdPt to combine with WO3 to form an intermediate product solution; the intermediate product solution was then subjected to centrifugation, washing and drying steps to obtain WO3 loaded with binary noble metal PdPt; the mass ratio of WO3 to C3N4 was 85:10.

[0053] In step S103, according to the mass ratio of C3N4 to binary noble metal PdPt of 2:1, the prepared C3N4 and PdPt-loaded WO3 are dispersed in separate aqueous solvents to form C3N4 solution and PdPt-loaded WO3 solution, respectively. Then, at 25℃±5℃, the C3N4 solution is added dropwise to the PdPt-loaded WO3 solution and stirred for a period of time to ensure that C3N4 is uniformly dispersed in the PdPt-loaded WO3, thus obtaining the final product solution. The final product solution is then subjected to centrifugation, washing, and drying steps to obtain C3N4 / PdPt-WO3.

[0054] Step S2: The C3N4 / binary precious metal-WO3 is heated to not less than 500°C in a tube furnace for annealing and then annealed in air for 3 hours to obtain C3N4 / PdPt-WO3 with a C3N4 mass fraction of 10wt%.

[0055] Experimental test analysis:

[0056] Microscopic observation was performed on the C3N4 / binary noble metal-WO3 prepared in this embodiment. Figure 1 This is a SEM image of C3N4 / PdPt-WO3 with a C3N4 mass fraction of 10 wt% in this embodiment. The microstructure of C3N4 / PdPt-WO3 in this embodiment is cotton-like. WO3 is modified on a graphene-phase C3N4 support, and the binary noble metal PdPt is loaded to form a graphene-like tungsten oxide nanomaterial supported by a binary noble metal, namely C3N4 / PdPt-WO3. By controlling the nanostructure or forming multi-component heterojunctions with other materials, the effective specific surface area of ​​the metal oxide and its sensitivity to acetone are further improved.

[0057] Example 2:

[0058] In this embodiment, the fabrication of the MEMS sensor with gas-sensitive properties involves the following steps:

[0059] like Figure 2 As shown, the sensitive material C3N4 / PdPt-WO3 and terpineol solution prepared in Example 1 were ground into a sensing paste in an agate mortar. A spoonful of the synthesized sensitive material was placed in the agate mortar, and 0.02 mL of terpineol was added. The mixture was then ground for 2–5 minutes to obtain a uniformly mixed paste. A multimeter was used to check whether the connections of each MEMS pin were intact and whether the heating resistor was normal. Intact MEMS devices were selected and placed in the prepared device housing. Finally, the ground sample paste was brushed onto the interdigitated electrodes of the prepared MEMS devices, which had dimensions of 1.0 mm × 1.0 mm × 0.5 mm, to form a sensitive film. After the coated chip was allowed to air dry at room temperature for 24 hours, the MEMS sensor was obtained. The prepared MEMS sensor, along with the heating electrode and the test electrode, was placed on a base. Finally, the prepared MEMS sensor was aged at 250°C for 12 hours to improve its stability.

[0060] A target gas with a specific acetone concentration is injected into the test chamber of a gas-sensitive tester, and the sensor's operating temperature is controlled by adjusting the heating voltage. When the same gas concentration is injected, the sensor's response values ​​differ at different operating temperatures; the optimal operating temperature is calculated by collecting data. Different gases of specified concentrations, such as acetone, formaldehyde, and ethanol, are introduced into the test chamber, and different response values ​​are obtained. The selectivity of the MEMS sensor is then determined by calculation to identify the gas to which it responds best. After selecting the target gas, the concentration gradient and repeatability of the MEMS sensor are tested at the optimal operating temperature; repeatability reflects stability.

[0061] Experimental test analysis:

[0062] The C3N4 / PdPt-WO3 prepared in Example 1 is a tungsten oxide nanomaterial with gas-sensitive properties, which can be used to detect acetone gas in human exhaled breath at room temperature. C3N4 and PdPt significantly enhance the gas-sensitive properties of WO3. Specifically, the response of C3N4 / PdPt-WO3 to 5 ppm acetone is higher than that of WO3, PdPt-WO3, and g-C3N4-WO3. Figure 3 As shown in the figure. This embodiment uses a dual-strategy enhancement of graphene-like support and binary noble metal loading, employing tungsten oxide nanomaterial C3N4 / PdPt-WO3 as the sensing material to fabricate the sensitive membrane of a MEMS sensor. It detects at least one gaseous component from acetone, formaldehyde, and ethanol in a gas sample, including human exhaled gas. The selectivity for acetone is particularly significant.

[0063] Example 1: The sensitive membrane is a graphene-like support and a binary noble metal-loaded tungsten oxide nanomaterial, C3N4 / PdPt-WO3. When detecting acetone, it showed a significant response at 180-300℃ for a sample with an acetone concentration of 5 ppm. Especially at 180-240℃, it showed a significant response for samples with an acetone concentration of at least 5 ppm. Figure 3 As shown in the figure. In this embodiment, C3N4 / PdPt-WO3 material was used to fabricate a MEMS sensor, and selectivity tests were conducted at 190°C. Various vapor samples of acetone, formaldehyde, and ethanol were introduced at 3 ppm, respectively, and it was found that the sensor had a high response to acetone and exhibited significant selectivity for acetone.

[0064] Example 3:

[0065] This embodiment is basically the same as the previous embodiments, except that:

[0066] A method for preparing graphene-like supported and binary noble metal-loaded tungsten oxide nanomaterials, specifically C3N4 / PdPt-WO3, includes the following steps:

[0067] Step S1: C3N4 / PdPt-WO3 is prepared by thermal polymerization, and the steps are as follows:

[0068] Step S101: The nitrogen-containing compound is placed in a furnace tube and pyrolyzed at high temperature to obtain the treated C3N4.

[0069] In step S102, the tungsten source is ammonium tungstate, which is dissolved in water to form an ammonium tungstate solution; the precursors of the binary noble metal PdPt, PdCl2 and PtCl2, are dissolved in another aqueous solvent to form a binary noble metal PdPt salt solution.

[0070] Then, at 20℃, the binary noble metal PdPt salt solution was added dropwise to the ammonium tungstate solution and stirred for a period of time to ensure that the binary noble metal PdPt salt was uniformly dispersed in the ammonium tungstate solution, allowing the binary noble metal PdPt to combine with WO3 to form an intermediate product solution; the intermediate product solution was then subjected to centrifugation, washing and drying steps to obtain WO3 loaded with binary noble metal PdPt; the mass ratio of WO3 to C3N4 was 489:10.

[0071] In step S103, according to the mass ratio of C3N4 to binary noble metal PdPt of 10:1, the prepared C3N4 and PdPt-loaded WO3 are dispersed in separate aqueous solvents to form C3N4 solution and PdPt-loaded WO3 solution, respectively. Then, at 20°C, the C3N4 solution is added dropwise to the PdPt-loaded WO3 solution and stirred for a period of time to ensure that C3N4 is uniformly dispersed in the PdPt-loaded WO3, thus obtaining the final product solution. The final product solution is then subjected to centrifugation, washing, and drying steps to obtain C3N4 / PdPt-WO3.

[0072] Step S2: The C3N4 / binary precious metal-WO3 is heated to not less than 500°C in a tube furnace for annealing and then annealed in air for 3 hours to obtain C3N4 / PdPt-WO3 with a C3N4 mass fraction of 2wt%.

[0073] Experimental test analysis:

[0074] Microscopic observation of the C3N4 / binary noble metal-WO3 prepared in this embodiment revealed that the C3N4 / PdPt-WO3 exhibited a flocculent morphology. By modifying WO3 onto a graphene-supported C3N4 base and loading it with the binary noble metal PdPt, a graphene-like tungsten oxide nanomaterial with a binary noble metal load, C3N4 / PdPt-WO3, is formed. By controlling the nanostructure or combining it with other materials to form a multi-element heterojunction, the effective specific surface area of ​​the metal oxide and its sensitivity to acetone can be further improved.

[0075] Example 4:

[0076] This embodiment is basically the same as the previous embodiments, except that:

[0077] A method for preparing graphene-like supported and binary noble metal-loaded tungsten oxide nanomaterials, specifically C3N4 / PdPt-WO3, includes the following steps:

[0078] Step S1: C3N4 / PdPt-WO3 is prepared by thermal polymerization, and the steps are as follows:

[0079] Step S101: The nitrogen-containing compound is placed in a furnace tube and pyrolyzed at high temperature to obtain the treated C3N4.

[0080] In step S102, the tungsten source is ammonium tungstate, which is dissolved in water to form an ammonium tungstate solution; the precursors of the binary noble metal PdPt, PdCl2 and PtCl2, are dissolved in another aqueous solvent to form a binary noble metal PdPt salt solution.

[0081] Then, at 30℃, the binary noble metal PdPt salt solution was added dropwise to the ammonium tungstate solution and stirred for a period of time to ensure that the binary noble metal PdPt salt was uniformly dispersed in the ammonium tungstate solution, allowing the binary noble metal PdPt to combine with WO3 to form an intermediate product solution; the intermediate product solution was then subjected to centrifugation, washing and drying steps to obtain WO3 loaded with binary noble metal PdPt; the mass ratio of WO3 to C3N4 was 94:5.

[0082] In step S103, according to the mass ratio of C3N4 to binary noble metal PdPt of 5:1, the prepared C3N4 and PdPt-loaded WO3 are dispersed in separate aqueous solvents to form C3N4 solution and PdPt-loaded WO3 solution, respectively. Then, at 30°C, the C3N4 solution is added dropwise to the PdPt-loaded WO3 solution and stirred for a period of time to ensure that C3N4 is uniformly dispersed in the PdPt-loaded WO3, thus obtaining the final product solution. The final product solution is then subjected to centrifugation, washing, and drying steps to obtain C3N4 / PdPt-WO3.

[0083] Step S2: The C3N4 / binary precious metal-WO3 is heated to not less than 500°C in a tube furnace for annealing and then annealed in air for 3 hours to obtain C3N4 / PdPt-WO3 with a C3N4 mass fraction of 5wt%.

[0084] Experimental test analysis:

[0085] Microscopic observation of the C3N4 / binary noble metal-WO3 prepared in this embodiment revealed that the C3N4 / PdPt-WO3 exhibited a flocculent morphology. By modifying WO3 onto a graphene-supported C3N4 base and loading it with the binary noble metal PdPt, a graphene-like tungsten oxide nanomaterial with a binary noble metal load, C3N4 / PdPt-WO3, is formed. By controlling the nanostructure or combining it with other materials to form a multi-element heterojunction, the effective specific surface area of ​​the metal oxide and its sensitivity to acetone can be further improved.

[0086] Example 5:

[0087] This embodiment is basically the same as the previous embodiments, except that:

[0088] A method for preparing graphene-like supported and binary noble metal-loaded tungsten oxide nanomaterials, specifically C3N4 / PdPt-WO3, includes the following steps:

[0089] Step S1: C3N4 / PdPt-WO3 is prepared by thermal polymerization, and the steps are as follows:

[0090] Step S101: The nitrogen-containing compound is placed in a furnace tube and pyrolyzed at high temperature to obtain the treated C3N4.

[0091] In step S102, the tungsten source is ammonium tungstate, which is dissolved in water to form an ammonium tungstate solution; the precursors of the binary noble metal PdPt, PdCl2 and PtCl2, are dissolved in another aqueous solvent to form a binary noble metal PdPt salt solution.

[0092] Then, at 25℃, the binary noble metal PdPt salt solution was added dropwise to the ammonium tungstate solution and stirred for a period of time to ensure that the binary noble metal PdPt salt was uniformly dispersed in the ammonium tungstate solution, allowing the binary noble metal PdPt to combine with WO3 to form an intermediate product solution; the intermediate product solution was then subjected to centrifugation, washing and drying steps to obtain WO3 loaded with binary noble metal PdPt; the mass ratio of WO3 to C3N4 was 45:4.

[0093] In step S103, the prepared C3N4 and PdPt-loaded WO3 are dispersed in separate aqueous solvents according to a mass ratio of 4:1, forming a C3N4 solution and a PdPt-loaded WO3 solution. Then, at 25°C, the C3N4 solution is added dropwise to the PdPt-loaded WO3 solution and stirred for a period of time to ensure that C3N4 is uniformly dispersed in the PdPt-loaded WO3, resulting in the final product solution. The final product solution is then subjected to centrifugation, washing, and drying steps to obtain C3N4 / PdPt-WO3.

[0094] Step S2: The C3N4 / binary precious metal-WO3 is heated to not less than 500°C in a tube furnace for annealing and then annealed in air for 3 hours to obtain C3N4 / PdPt-WO3 with a C3N4 mass fraction of 8wt%.

[0095] Experimental test analysis:

[0096] Microscopic observation of the C3N4 / binary noble metal-WO3 prepared in this embodiment revealed that the C3N4 / PdPt-WO3 exhibited a flocculent morphology. By modifying WO3 onto a graphene-supported C3N4 base and loading it with the binary noble metal PdPt, a graphene-like tungsten oxide nanomaterial with a binary noble metal load, C3N4 / PdPt-WO3, is formed. By controlling the nanostructure or combining it with other materials to form a multi-element heterojunction, the effective specific surface area of ​​the metal oxide and its sensitivity to acetone can be further improved.

[0097] The sensitive membranes in Examples 3-5 are graphene-like supported tungsten oxide nanomaterials (C3N4 / PdPt-WO3) loaded with binary noble metals. When detecting acetone, the response is significant when detecting a gas sample with an acetone concentration of 5 ppm at 180-300°C. Particularly significant is the response when detecting gas samples with an acetone concentration of at least 5 ppm at 180-240°C. A MEMS sensor was fabricated using the C3N4 / PdPt-WO3 material from the above examples, and selectivity tests were conducted at 190°C. Multiple vapor samples of acetone, formaldehyde, and ethanol (3 ppm each) were introduced, and the sensor showed a high response to acetone, exhibiting significant selectivity for it.

[0098] In summary, this invention relates to a dual-strategy sensitized tungsten oxide nanomaterial supported by graphene and loaded with a binary noble metal, belonging to the field of materials technology. Specifically, it relates to a method for preparing tungsten oxide nanomaterials for responding to exhaled gases in patients with chronic diseases. The preparation method of the tungsten oxide nanomaterials includes the following steps: First, C3N4 / PdPt-WO3 is prepared by hydrothermal synthesis. After annealing, C3N4 / PdPt-WO3 with a C3N4 mass fraction of 2-10% is obtained. The C3N4 / PdPt-WO3 material is then fabricated into a MEMS sensor, and selectivity testing is performed at 190°C. Passing through 3 ppm of vapor reveals a high response to acetone. Therefore, the functionalized graphene prepared in the above embodiments of this invention can be used to further fabricate a gas sensor to achieve specific analysis of acetone. The graphene material prepared using the technical solution of this invention has extremely high sensitivity, and the sensor maintains good signal stability and reliability. By loading the binary noble metal PdPt onto the graphene-phase C3N4 support, the sensor exhibits higher sensitivity and a faster response time.

[0099] The embodiments of the present invention have been described above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. Various changes can be made according to the purpose of the invention. Any changes, modifications, substitutions, combinations or simplifications made based on the spirit and principle of the technical solution of the present invention shall be equivalent substitutions. As long as they meet the purpose of the invention and do not deviate from the technical principle and inventive concept of the present invention, they shall fall within the protection scope of the present invention.

Claims

1. A method for preparing tungsten oxide nanomaterials supported by graphene-like structures and loaded with binary noble metals, characterized in that, Includes the following steps: Step S1: Using nitrogen-containing compounds, two noble metal precursors, and a tungsten source as raw materials, C3N4 / binary noble metal-WO3 is prepared; the two noble metal precursors are PdCl2 and PtCl2; the mass ratio of C3N4 to the binary noble metal is 2-10:1; the mass ratio of WO3 to C3N4 is 85-489:

10. Step S2: The C3N4 / binary precious metal-WO3 is heated to not less than 500°C in a tube furnace for annealing and annealed in air for at least 3 hours to obtain C3N4 / PdPt-WO3 with a C3N4 mass fraction of 8-10wt%. Step S1 includes the following steps: Step S101: The nitrogen-containing compound is placed in a furnace tube and pyrolyzed at high temperature to obtain the treated C3N4. Step S102: The tungsten source is ammonium tungstate, which is dissolved in a solvent to form an ammonium tungstate solution; the precursors of the two noble metals are dissolved in another solvent to form a binary noble metal salt solution; the solvent is water. Then, at 20-30℃, the binary noble metal salt solution was added dropwise to the ammonium tungstate solution and stirred for a period of time to make the binary noble metal salt uniformly dispersed in the tungsten salt solution, so that the binary noble metal combined with WO3 to form an intermediate product solution; then, the intermediate product solution was subjected to centrifugation, washing and drying steps to obtain WO3 loaded with binary noble metal. In step S103, the prepared C3N4 and binary noble metal-loaded WO3 are dispersed in separate solvents to form C3N4 solution and binary noble metal-loaded WO3 solution, respectively. Then, at 20-30℃, the C3N4 solution is added dropwise to the binary noble metal-loaded WO3 solution and stirred for a period of time to ensure that C3N4 is uniformly dispersed in the binary noble metal-loaded WO3, thus obtaining the final product solution. The final product solution is then subjected to centrifugation, washing, and drying steps to obtain C3N4 / PdPt-WO3.

2. The method for preparing graphene-like supported and binary noble metal-loaded tungsten oxide nanomaterials according to claim 1, characterized in that: In step S1, the nitrogen-containing compound is at least one of dicyandiamide, urea, melamine, and thiourea.

3. The method for preparing graphene-like supported and binary noble metal-loaded tungsten oxide nanomaterials according to claim 1, characterized in that: In steps S102 and S103, the drying process involves placing the intermediate or final product in a drying oven for at least 6 hours, while controlling the temperature of the drying oven to be no lower than 60°C.

4. The method for preparing graphene-like supported and binary noble metal-loaded tungsten oxide nanomaterials according to claim 1, characterized in that: In step S101, the pyrolysis temperature of the nitrogen-containing compound is not lower than 500°C, and the pyrolysis time is not lower than 2 hours.

5. A tungsten oxide nanomaterial with dual-strategy sensitization via graphene-like support and binary noble metal loading, characterized in that: The tungsten oxide nanomaterials were prepared using the method described in any one of claims 1-4, which is based on graphene-like support and binary noble metal loading.

6. The application of the tungsten oxide nanomaterial with dual-strategy sensitization of graphene-like support and binary noble metal loading as described in claim 5, characterized in that: A sensitive membrane for a MEMS sensor was fabricated using tungsten oxide nanomaterials with a dual-strategy enhancement of graphene-like support and binary noble metal loading as the sensitive material. The sensor was used to detect acetone in a gas sample to be tested, which included human exhaled gas.

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