Method for detecting trimethylamine gas by SnO2-WO3 gas sensitive material

Abstract

The application discloses a SnO2-WO3 gas-sensitive material and a method for detecting trimethylamine gas, and relates to a method for detecting trimethylamine gas. The application adopts a two-step hydrothermal method, changes a raw material ratio to construct an optimal structure, and makes the material have excellent application performance. The whole production process is simple in process, low in cost, good in controllability, non-toxic and harmless, and the prepared material is high in purity, good in crystallization and dispersity, and suitable for large-scale industrial production. The prepared SnO2-WO3 has high sensitivity to trimethylamine, good selectivity and fast response-recovery characteristics, so that the SnO2-WO3 has wide application prospects in food industry and health safety product detection application.

Description

Technical Field

[0001] This invention relates to a method for detecting trimethylamine gas, and more particularly to a method for detecting trimethylamine gas using a SnO2-WO3 gas-sensitive material. Background Technology

[0002] Nitrogenous volatile organic compounds with a pungent odor, such as trimethylamine, are mainly used as disinfectants, natural gas alarms, analytical reagents, and raw materials for organic synthesis. They are also used in pharmaceuticals, pesticides, photographic materials, rubber additives, explosives, synthetic fiber solvents, surfactants, and dyes. Trimethylamine is also closely linked to seafood; it is released during fish spoilage, and the concentration released is directly proportional to the degree of spoilage. Concentrations below 10 ppm are considered fresh; concentrations between 10-50 ppm indicate spoilage; and concentrations above 50 ppm are considered severely spoiled. International safety agencies recommend that airborne trimethylamine concentrations should be below 10 ppm. Prolonged exposure to trimethylamine gas can severely burn the cornea, damage the skin, irritate the respiratory system, and, when inhaled, cause disorders in the liver and nervous system. In addition, trimethylamine is flammable, and its vapor forms an explosive mixture with air, posing a serious threat to human life, health, and property safety. Therefore, the detection of trimethylamine is of great significance. At the same time, in order to create a friendly environment and ensure human health, it is imperative to develop a gas sensor for rapid and selective detection of trimethylamine.

[0003] Since the advent of gas sensors in the 1960s, gas sensors have undergone extensive research and rapid development. Advanced intelligent gas sensors, as a product of emerging technology, have attracted considerable attention for their research progress and application scenarios. Although traditional gas sensor technology is relatively mature, the performance of gas sensors falls far short of the demands of intelligent devices, significantly hindering the development of information technology. As gas sensors are applied in more complex fields such as national defense and medical testing, higher sensitivity, better selectivity, and miniaturization are required. Designing gas sensors that meet practical applications has become a key research direction in this field. Researchers have designed various types of gas sensors based on different working principles to fully address more flexible application scenarios.

[0004] Tungsten trioxide (WO3) is a common N-type semiconductor widely used in gas sensing, solar cells, and electrode materials. WO3 is a narrow band (2.6-2.8 eV) transition metal oxide, a non-toxic solid at room temperature, and stable in air and high-temperature environments, but almost insoluble in acidic solutions. In gas sensing, WO3 possesses stable physical and chemical properties, and WO3 nanomaterials offer advantages such as excellent gas-sensing performance, low cost, and simple preparation. With the rise and rapid development of nanotechnology, synthesizing high-performance WO3 nanostructured sensitive materials using advanced nanotechnology, and designing and constructing gas sensing platforms by controlling the microstructure and composition of these materials, is an effective technical means to improve gas-sensing performance. Summary of the Invention

[0005] The purpose of this invention is to provide a method for detecting trimethylamine gas using SnO2-WO3 gas-sensitive material. This invention prepares a nano-assembled SnO2-WO3 material, which is used as a gas-sensitive material in a gas sensor, enabling efficient and accurate selective detection of gases.

[0006] The objective of this invention is achieved through the following technical solution:

[0007] A method for detecting trimethylamine gas using a SnO2-WO3 gas-sensitive material, the method comprising the following steps:

[0008] a. Preparation of SnO2-WO3:

[0009] Weigh out tungstic acid (H2WO4) and disperse it in 50 mL of H2O and 34 mL of H2O2. Heat the resulting mixed solution to 95°C in a water bath and stir until the solution is clear. Dilute with water to 200 mL to obtain a tungstic acid (H2WO4) solution.

[0010] Acetonitrile and HCl solution were added to the tungstic acid (H2WO4) solution prepared above. Oxalic acid and urea were added while stirring until the solution became clear. The solution was then transferred to a 50 mL sealed reaction vessel and heated to 180 °C in an oven for 12 h. After natural cooling, the powder was collected, washed three times each with deionized water and ethanol by centrifugation, and then dried at 60 °C to obtain pure WO3 powder.

[0011] Stannous chloride dihydrate (SnCl2·2H2O) and thiourea (CH4N2S) were dissolved in deionized water and stirred at room temperature for 30 min. The prepared WO3 powder was ultrasonically dispersed and added to the solution. The mixture was stirred at room temperature for 6 h. The solution was centrifuged, washed twice with deionized water and anhydrous ethanol, and dried in a vacuum oven at 70 °C.

[0012] The dried product was placed in a clean crucible and then placed in a muffle furnace and calcined at 300°C for 2 h to obtain SnO2-WO3, which was then stored in a desiccator for analysis and detection.

[0013] b. SnO2-WO3 material is used as a gas-sensitive material to fabricate a gas sensor for the detection of trimethylamine gas:

[0014] (1) SnO2-WO3 was added to anhydrous ethanol to make a slurry, which was then coated on the outer wall of an alumina ceramic tube with two gold electrodes and four platinum wires.

[0015] (2) Pass the nickel-chromium alloy heating wire through the alumina ceramic tube to which the sample is attached, and keep the heating wire parallel to the ceramic tube and away from the ceramic tube;

[0016] (3) Weld the four conductive wires of the ceramic tube and the two ends of the heating wire to the six-legged base respectively to obtain the gas sensor element;

[0017] (4) The gas sensitivity characteristics of the sensor were tested using a WS-30A gas sensitivity tester. The test temperature was 25~400℃.

[0018] The advantages and effects of this invention are:

[0019] (1) This invention uses tungstic acid, stannous chloride and thiourea as raw materials to prepare SnO2-WO3 assembled from nanoparticles via a two-step hydrothermal method. It has the advantages of low cost, good controllability, high purity, good crystallinity and good dispersibility of the prepared material, and is suitable for large-scale industrial production.

[0020] (2) The SnO2-WO3 prepared by this invention has a unique spatial structure, which not only increases the specific surface area of ​​the material, but also constructs a well-developed hierarchical pore channel, making the material more permeable. As a gas sensor prepared by gas sensing material, it exhibits high sensitivity, good selectivity and fast response-recovery characteristics to trimethylamine at room temperature, and has broad application prospects in detecting organic volatile gases in the environment. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the gas sensor structure;

[0022] Figure 2 The sensitivity curve of the gas sensor at 10 ppm trimethylamine gas under test temperatures of 25~400℃ is shown.

[0023] Figure 3 The response-recovery curve of the sensor in Example 3 to 10 ppm trimethylamine gas at 250°C is shown.

[0024] Figure 4This is a test graph showing the selectivity of the sensor in Example 3 for 10 ppm gas at 250°C. Implementation

[0025] The present invention will now be described in detail with reference to the embodiments shown in the accompanying drawings.

[0026] The starting materials for this invention are inexpensive and readily available tungstic acid, thionyl chloride, and thiourea. These are obtained through a hydrothermal reaction, followed by centrifugation, washing, drying, and calcination. The resulting SnO2-WO3 has a diameter of 2–4 nm, is composed of nano-self-assembled particles, exhibits good dispersibility, and has numerous pores on its surface. When SnO2-WO3 is used to fabricate a gas sensor, its unique spatial structure demonstrates high sensitivity, good selectivity, and stability towards trimethylamine.

[0027] The preparation method of SnO2-WO3 includes the following steps:

[0028] Weigh out tungstic acid (H2WO4) and disperse it in 50 mL of H2O and 34 mL of H2O2. Heat the resulting mixed solution to 95°C in a water bath and stir until the solution becomes clear. Dilute with water to 200 mL to obtain a tungstic acid (H2WO4) solution.

[0029] Acetonitrile and HCl solution were added to the tungstic acid (H2WO4) solution prepared in step 1. Oxalic acid and urea were added while stirring until the solution became clear. The solution was then transferred to a 50 ml sealed reaction vessel and heated to 180 °C in an oven for 12 h. After natural cooling, the powder was collected, washed three times each with deionized water and ethanol by centrifugation, and then dried at 60 °C to obtain pure WO3 powder.

[0030] Stannous chloride dihydrate (SnCl2·2H2O) and thiourea (CH4N2S) were dissolved in deionized water and stirred at room temperature for 30 min. The α-WO3 powder obtained in step 2 was ultrasonically dispersed and added to the above solution, and stirred at room temperature for 6 h.

[0031] The solution obtained in step 3 was centrifuged, washed twice with deionized water and anhydrous ethanol respectively, and dried in a vacuum oven at 70°C.

[0032] The dried product from step 4 was placed in a clean crucible and then placed in a muffle furnace and calcined at 300°C for 2 h to obtain SnO2-MoO3, which was then stored in a desiccator for analysis and detection. Example 1

[0033] Preparation of WO3 materials

[0034] Step 1: Weigh 2.5g of tungstic acid and disperse it in 50mL of H2O and 34mL of H2O2. Heat the resulting mixed solution to 95℃ in a water bath and stir until the solution becomes clear. Dilute with water to a concentration of 200 mL (0.05 L / mol) to obtain a tungstic acid (H2WO4) solution.

[0035] Step 2: Take 7.5 mL of the tungstic acid (H2WO4) solution obtained in Step 1 and add 31.5 mL of acetonitrile and 2.5 mL of HCl solution. While stirring, add oxalic acid and urea until the mixture becomes clear.

[0036] Step 3: Transfer the solution from Step 2 into a 50 mL sealed reaction vessel, place it in an oven and heat it to 180℃ for 12 h. After natural cooling, collect the powder.

[0037] Step 4: After washing the powder collected in Step 3 by centrifugation three times with deionized water and ethanol respectively, dry it at 60°C for later use.

[0038] Step 5: Place the precursor from Step 4 directly into a muffle furnace and heat it to 400℃ for 2 hours to obtain pure WO3 material. Example 2

[0039] Preparation of 2.5% SnO2-WO3

[0040] Steps one through five are the same as in Example 1.

[0041] Step Six: Dissolve 0.0073 g of stannous chloride dihydrate (SnCl2·2H2O) and 0.0086 g of thiourea (CH4N2S) in 30 mL of deionized water and stir at room temperature for 30 min. Take 0.3012 g of WO3 obtained in Step Five, disperse it ultrasonically, add it to the above solution, and stir at room temperature for 6 h.

[0042] Step 7: Centrifuge the solution obtained in Step 6, wash it twice with deionized water and anhydrous ethanol respectively, and dry it in a vacuum oven at 70°C.

[0043] Step 8: Place the dried product from Step 7 into a clean crucible and place it in a muffle furnace. Calcine at 300℃ for 2 h to obtain calcined 2.5%-SnO2-WO3. Store it in a desiccator for analysis and detection. Example 3

[0044] Preparation of 5%-SnO2-WO3

[0045] Steps one, two, three, four, and five are the same as in Example 1.

[0046] Step Six: Dissolve 0.0146 g of stannous chloride dihydrate (SnCl2·2H2O) and 0.0172 g of thiourea (CH4N2S) in 30 mL of deionized water and stir at room temperature for 30 min. Take 0.3012 g of WO3 obtained in Step Five, disperse it ultrasonically, add it to the above solution, and stir at room temperature for 6 h.

[0047] Step 7: Centrifuge the solution obtained in Step 6, wash it twice with deionized water and anhydrous ethanol respectively, and dry it in a vacuum oven at 70°C.

[0048] Step 8: Place the dried product from Step 7 into a clean crucible and place it in a muffle furnace. Calcine at 300℃ for 2 hours to obtain 5%-SnO2-WO3 after calcination. Store it in a desiccator for analysis and detection. Example 4

[0049] Preparation of 7.5% SnO2-WO3

[0050] Steps one through five are the same as in Example 1.

[0051] Step Six: Dissolve 0.0219 g of stannous chloride dihydrate (SnCl2·2H2O) and 0.0258 g of thiourea (CH4N2S) in 30 ml of deionized water and stir at room temperature for 30 min. Disperse 0.3012 g of WO3 powder obtained in Step Five using ultrasound, add it to the above solution, and stir at room temperature for 6 h.

[0052] Step 7: Centrifuge the solution obtained in Step 6, wash it twice with deionized water and anhydrous ethanol respectively, and dry it in a vacuum oven at 70°C.

[0053] Step 8: Place the dried product from Step 7 into a clean crucible and place it in a muffle furnace. Calcine at 300℃ for 2 hours to obtain calcined 7.5%-SnO2-WO3. Store it in a desiccator for analysis and detection.

[0054] A gas sensor was fabricated using the obtained SnO2-WO3 product, and its gas-sensing performance for trimethylamine was tested.

[0055] A certain amount of SnO2-WO3 product was weighed and added to anhydrous ethanol to prepare a slurry, which was then coated onto an alumina ceramic tube. The alumina ceramic tube had two gold electrodes and four platinum wires, and a nickel-chromium heating wire was installed inside the tube. The ceramic tube was then welded to a six-pin base to obtain a gas sensor element, such as... Figure 1 As shown.

[0056] The sensitivity curve of the gas sensor to 10 ppm trimethylamine gas at the operating temperature is shown in the figure. Figure 2As shown in the figure, it is clear from the figure that the sensitivities of the several gas sensors differ within the test range. With increasing operating temperature, the response values ​​of all samples tend to increase first and then decrease. This is likely due to the competition between the reduction of active sites and the increase in surface reaction rate at high temperatures. Specifically, the optimal response value for the sensor in Example 1 is 2.0; for Example 2, it is 5.2; for Example 3, it is 14.4; and for Example 4, it is 8.2. The comparison reveals that the sensor in Example 3 exhibits superior sensitivity characteristics. Figure 3 The figure shows the response-recovery curve of the sensor of Example 3 to 10 ppm trimethylamine gas at an operating temperature of 250℃. As can be seen from the figure, the sensor of Example 3 has good response-recovery characteristics to trimethylamine. Figure 4 The results of the selective test of six gases at 10 ppm by the sensor in Example 3 show that the sensor has very high selectivity for trimethylamine gas, and shows broad application prospects in the field of trimethylamine detection.

Claims

1. A method for detecting trimethylamine gas using a SnO2-WO3 gas-sensitive material, characterized in that, The method includes the following procedures: a. Preparation of SnO2-WO3: Weigh out tungstic acid (H2WO4) and disperse it in 50 mL of H2O and 34 mL of H2O2. Heat the resulting mixed solution to 95°C in a water bath and stir until the solution is clear. Dilute with water to 200 mL to obtain a tungstic acid (H2WO4) solution. Acetonitrile and HCl solution were added to the tungstic acid (H2WO4) solution prepared above. Oxalic acid and urea were added while stirring until the mixture became clear. The solution was then transferred to a 50 mL sealed reaction vessel and heated to 180 °C in an oven for 12 h. After natural cooling, the powder was collected and washed three times by centrifugation with deionized water and ethanol, respectively. The powder was then dried at 60 °C to obtain pure WO3 powder. Stannous chloride dihydrate (SnCl2·2H2O) and thiourea (CH4N2S) were dissolved in deionized water and stirred at room temperature for 30 min. The prepared WO3 powder was ultrasonically dispersed and added to the solution. The mixture was stirred at room temperature for 6 h. The solution was centrifuged, washed twice with deionized water and anhydrous ethanol, and dried in a vacuum oven at 70 °C. The dried product was placed in a clean crucible and then placed in a muffle furnace and calcined at 300°C for 2 h to obtain SnO2-WO3, which was then stored in a desiccator for analysis and detection. b. SnO2-WO3 material is used as a gas-sensitive material to fabricate a gas sensor for the detection of trimethylamine gas: (1) SnO2-WO3 was added to anhydrous ethanol to make a slurry, which was then coated on the outer wall of an alumina ceramic tube with two gold electrodes and four platinum wires. (2) Pass the nickel-chromium alloy heating wire through the alumina ceramic tube to which the sample is attached, and keep the heating wire parallel to the ceramic tube and away from the ceramic tube; (3) Weld the four conductive wires of the ceramic tube and the two ends of the heating wire to the six-legged base respectively to obtain the gas sensor element; (4) The gas sensitivity characteristics of the sensor were tested using a WS-30A gas sensitivity tester at a temperature of 25~400℃.

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