A trimethylamine gas sensor detection method based on SnS-MoO3 nanosheets

Abstract

The present invention discloses a trimethylamine gas sensor detection method based on SnS-MoO3 nanosheets, and relates to a gas sensor detection method. The method of the present invention adopts a hydrothermal method in the preparation of gas-sensitive materials, and constructs an optimal structure by changing the ratio of raw materials, so that it has excellent application performance. The entire production process is simple, low-cost, controllable, non-toxic and harmless. The prepared materials are high in purity, good in crystallization, and good in dispersibility, and are suitable for large-scale industrial production. The SnS-MoO3 nanosheets prepared by the present invention show high sensitivity, good selectivity and response recovery characteristics to trimethylamine, so that it shows broad application prospects in detecting trimethylamine gas in the environment.

Description

Technical Field

[0001] The present invention relates to a gas sensor detection method, in particular to a trimethylamine gas sensor detection method based on SnS-MoO3 nanosheets. Background Art

[0002] Trimethylamine (TMA) is an organic amine compound that is a colorless, odorous gas at room temperature. It is widely used in industrial production as an analytical reagent and raw material for organic synthesis. However, it is toxic, flammable, and explosive, and can be highly irritating to the eyes, nose, throat, and respiratory tract. During the decay of seafood, trimethylamine oxide (TMAO) is also produced through the decomposition of this substance. When TMA concentrations exceed 10 ppm, seafood is considered "rotten." Low-concentration TMA detection is an important strategy for ensuring safety. To reduce environmental pollution and protect human health, it is necessary to effectively monitor trace amounts of TMA in industrial production and complex environments. Therefore, an effective method for highly sensitive detection and real-time monitoring is urgently needed.

[0003] Metal oxide semiconductor (MOS) gas sensors have high gas sensitivity and stability to target gases, simple preparation methods, low cost, and rapid detection. They have great potential in monitoring volatile gases and have become the most commonly used and practical type of gas sensor today. The sensitive material is the main factor affecting the performance of gas sensors. MoO3, as a typical environmentally friendly n-type semiconductor metal oxide, has been widely studied and applied in fields such as electrochemistry, gas sensing, and catalysis. In particular, MoO3 nanomaterials have potential applications as sensitive materials due to their high specific surface area and high active sites. However, gas sensors based on single MoO3 nanomaterials still suffer from poor selectivity and response recovery in practical applications. Therefore, it is necessary to design a MoO3 gas sensor that can operate effectively at lower operating temperatures. Studying its sensitivity to volatile organic compounds such as trimethylamine is of great commercial value. Compared to traditional metal oxide materials, metal sulfide materials typically have narrower band gaps, which facilitates their room-temperature or near-room-temperature gas-sensing response processes. They also possess superior conductivity and lower requirements for light excitation sources, offering rich research potential for light-assisted enhanced gas-sensing effects. Furthermore, their synthesis methods are simple, often without the need for high temperatures. Their microstructures, such as morphology and size, are easily regulated, and they possess a richer array of surface defect control mechanisms. Therefore, highly sensitive, low-detection-limit room-temperature gas sensors based on sulfide semiconductor materials hold great potential for future applications in a variety of scenarios. Summary of the Invention

[0004] The present invention aims to propose a trimethylamine gas sensor detection method based on SnS-MoO3 nanosheets. The method of the present invention uses a two-step hydrothermal method to prepare SnS-MoO3 nanosheet sensitive materials, which exhibits good detection characteristics for trimethylamine gas, realizes efficient and accurate detection, and provides a simple and rapid technical means for on-site online monitoring of ambient air pollutants.

[0005] The purpose of the present invention is achieved through the following technical solutions:

[0006] A trimethylamine gas sensor detection method based on SnS-MoO3 nanosheets, the method comprising the following preparation process:

[0007] a. Preparation of SnS-MoO3 nanosheets, the steps are as follows:

[0008] (1) Weigh ammonium molybdate tetrahydrate ((NH4)6Mo7S4·4H2O) and calcine at 500℃ for 2 h to obtain MoO3 nanosheets;

[0009] (2) The MoO3 nanosheets prepared above were dissolved in H2O2 (30%) and stirred for 5 minutes, and then methanol was added and stirred for 24 hours, and ultrasonically treated at room temperature for 30 minutes. The solution was then transferred into a closed reactor with a capacity of 50 mL, placed in an oven and heated to 180°C for 12 hours. After cooling naturally, the powder was collected and washed with deionized water and ethanol by centrifugation three times, and then kept at 60°C for drying. The precursor was directly placed in a muffle furnace and heated to 400°C for 2 hours to obtain pure MoO3 nanosheet material. The obtained MoO3 nanosheets were dissolved in water and ultrasonically dispersed to obtain a MoO3 nanosheet suspension.

[0010] (3) Dissolve stannous chloride dihydrate (SnCl2·2H2O) and thiourea (CH4N2S) in deionized water and stir at room temperature for 30 min. Add the prepared MoO3 nanosheet suspension to the above solution and stir at room temperature for 1 h. Transfer the solution into a 50 mL sealed reactor and heat it in an oven to 180°C for 12 h. After cooling naturally, centrifuge and wash twice with deionized water and anhydrous ethanol, respectively. Dry in a vacuum oven at 70°C to obtain SnS-MoO3 nanosheets, which are then stored in a desiccator for analysis and testing.

[0011] b. This material is used as a gas sensitive material to make a gas sensor for detecting trimethylamine gas. The steps are as follows:

[0012] (1) SnS-MoO3 nanosheets were added to anhydrous ethanol to prepare a slurry, which was then coated on the outer wall of an alumina ceramic tube with two gold electrodes and four platinum wires;

[0013] (2) Pass the nickel-chromium alloy heating wire through the alumina ceramic tube with the sample adhered to it, and keep the heating wire parallel to the ceramic tube and away from the ceramic tube;

[0014] (3) The four conductive wires and the two ends of the heating wire of the ceramic tube were welded to the six-pin base to make a gas sensor element; the gas sensitivity characteristics of the sensor were tested using a WS-30A gas sensor tester; the test temperature was 25~350℃.

[0015] Advantages and beneficial effects of the present invention:

[0016] (1) The present invention uses ammonium molybdate, stannous chloride, and thiourea as raw materials to prepare SnS-MoO3 nanosheets via a two-step hydrothermal method. This method has the advantages of low cost, good controllability, high purity, good crystallinity, and good dispersibility of the prepared material, making it suitable for large-scale industrial production.

[0017] (2) The SnS-MoO3 nanosheets prepared by the present invention have a unique spatial structure, which not only increases the specific surface area of ​​the material, but also constructs a developed hierarchical pore channel, making the material have better permeability. The gas sensor prepared as a gas-sensitive material shows high sensitivity to trimethylamine at room temperature, good selectivity and response recovery characteristics, and has broad application prospects in detecting organic volatile gases in the environment.

[0018] (3) The SnS-MoO3 nanosheet gas sensor produced by the present invention has a simple production process and low cost, and is suitable for industrial mass production. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Schematic diagram of the structure of the trimethylamine sensor;

[0020] Figure 2 This is the response value graph of the gas sensor to 10 ppm trimethylamine gas at test temperatures of 25~350℃;

[0021] Figure 3 This is the response recovery curve of the gas sensor to 10 ppm trimethylamine gas at 200°C;

[0022] Figure 4 This is a sensitivity diagram of the selectivity test of Example 3 at 200°C for 10 ppm gas. Implementation Method

[0023] The present invention will be described in detail below with reference to the embodiments shown in the accompanying drawings.

[0024] The present invention uses inexpensive and readily available starting materials, ammonium molybdate, chloronitrite, and thiourea, through a two-step hydrothermal reaction followed by centrifugation, washing, drying, and calcination. The resulting SnS-MoO3 nanosheets have a diameter of 2-4 nm and a thickness of 28 nm. They are self-assembled, exhibit good dispersibility, and possess numerous pores on the powder surface. The SnS-MoO3 nanosheets, fabricated into a gas sensor, exhibit high sensitivity, good selectivity, and stability to trimethylamine due to their unique spatial structure.

[0025] The preparation process is as follows: the SnS-MoO3 nanosheet preparation method comprises the following steps:

[0026] (1) Weigh ammonium molybdate tetrahydrate ((NH4)6Mo7S4·4H2O) and calcine at 500℃ for 2 hours to obtain MoO3 nanosheets;

[0027] (2) The MoO3 nanosheets prepared in step 1 were dissolved in H2O2 (30%) and stirred for 5 minutes. Methanol was then added and stirred for 24 hours. The mixture was ultrasonically treated at room temperature for 30 minutes. The solution was then transferred into a 50ml sealed reactor and placed in an oven heated to 180°C for 12 hours. After cooling naturally, the powder was collected and washed three times with deionized water and ethanol respectively by centrifugation. The powder was then dried at 60°C for later use. The precursor was directly placed in a muffle furnace and heated to 400°C for 2 hours to obtain pure MoO3 nanosheet material.

[0028] (3) Dissolve stannous chloride dihydrate (SnCl2·2H2O) and thiourea (CH4N2S) in deionized water and stir at room temperature for 30 min. Add the prepared MoO3 nanosheet suspension to the above solution and stir at room temperature for 1 h. Then transfer the solution into a 50 mL sealed reactor and heat it in an oven to 180°C for 12 h. After cooling naturally, centrifuge and wash twice with deionized water and anhydrous ethanol, respectively. Dry in a vacuum oven at 70°C to obtain SnS-MoO3 nanosheets, which are then stored in a desiccator for analysis and testing.

[0029] To use SnS-MoO3 nanosheets in a trimethylamine gas sensor, grind them in a mortar for 20 minutes. Then, add anhydrous ethanol and continue grinding for another 20 minutes to form a slurry. A small amount of the slurry is applied to a brush and evenly coated on the surface of a ceramic tube. The tube is then dried at 80°C. A nickel-chromium alloy heating wire is passed through the sample-attached ceramic tube and soldered to the four conductive wires of the ceramic tube to form a six-pin base. The gas sensor element is then aged on an aging table for 48 hours. The gas sensitivity characteristics of the sensor are then tested using a WS-30A gas sensor tester. Example 1

[0030] Preparation of MoO3 nanosheet materials

[0031] Step 1: Weigh 10.00 g of ammonium molybdate tetrahydrate ((NH4)6Mo7S4·4H2O) and calcine at 500°C for 2 hours to obtain MoO3 nanosheets;

[0032] Step 2: Weigh 0.72 g of the MoO3 nanosheets prepared in step 1 and dissolve them in H2O2 (30%) and stir for 5 minutes. Then add methanol and stir for 24 hours, and then ultrasonicate at room temperature for 30 minutes.

[0033] Step 3: Transfer the solution from step 2 into a 50ml sealed reaction vessel, heat it in an oven to 180°C for 12 hours, and collect the powder after cooling naturally;

[0034] Step 4: The powder collected in step 3 was washed by centrifugation with deionized water and ethanol three times respectively, and then dried at 60°C for later use;

[0035] Step 5: Place the precursor prepared in step 4 directly into a muffle furnace and heat it to 400°C and maintain it for 2 h to obtain pure MoO3 nanosheet material. Example 2

[0036] Preparation of 5%-SnS-MoO3 nanosheets

[0037] Steps 1, 2, 3, 4, and 5 are the same as in Example 1;

[0038] Step 6: Dissolve 0.0079 g of stannous chloride dihydrate (SnCl2·2H2O) and 0.0074 g of thiourea (CH4N2S) in 30 mL of deionized water and stir at room temperature for 30 min. Using ultrasound, disperse 0.1006 g of the MoO3 nanosheets prepared in Step 5 into the solution. After stirring at room temperature for 1 h, transfer the solution to a 50 mL sealed reactor and heat to 180°C in an oven for 12 h. Allow the solution to cool naturally and collect the solution.

[0039] Step 7: The solution obtained in step 6 was centrifuged, washed twice with deionized water and anhydrous ethanol respectively, and dried in a vacuum oven at 70°C overnight to obtain 5%-SnS-MoO3 nanosheets, which were stored in a desiccator for analysis and detection. Example 3

[0040] Preparation of 10%-SnS-MoO3 nanosheets

[0041] Steps 1, 2, 3, 4, and 5 are the same as those in Example 1;

[0042] Step 6: Dissolve 0.0262 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 0.1503 g of the MoO3 nanosheets prepared in Step 5 into this solution under ultrasound assistance. After stirring at room temperature for 1 h, transfer the solution to a 50 mL sealed reactor and heat it in an oven to 180°C for 12 h. Allow the solution to cool naturally and collect the solution.

[0043] Step 7: The solution obtained in step 6 was centrifuged, washed twice with deionized water and anhydrous ethanol respectively, and dried in a vacuum oven at 70°C overnight to obtain 10%-SnS-MoO3 nanosheets, which were stored in a desiccator for analysis and detection. Example 4

[0044] Preparation of 15%-SnS-MoO3 nanosheets

[0045] Steps 1, 2, 3, 4, and 5 are the same as in Example 1;

[0046] Step 6: Dissolve 0.0407 g of stannous chloride dihydrate (SnCl2·2H2O) and 0.0404 g of thiourea (CH4N2S) in 30 mL of deionized water and stir at room temperature for 30 min. With the aid of ultrasound, disperse 0.3007 g of the MoO3 nanosheets prepared in Step 5 into the solution. After stirring at room temperature for 1 h, transfer the solution to a 50 mL sealed reactor and heat it in an oven to 180°C for 12 h. Allow the solution to cool naturally and collect the solution.

[0047] Step 7: The solution obtained in step 6 was centrifuged, washed twice with deionized water and anhydrous ethanol respectively, and dried in a vacuum oven at 70°C overnight to obtain 15%-SnS-MoO3 nanosheets, which were stored in a desiccator for analysis and detection.

[0048] The obtained SnS-MoO3 nanosheets were made into gas sensors, and their gas-sensing properties were tested for trimethylamine:

[0049] Weigh the SnS-MoO3 nanosheets and add anhydrous ethanol to make a slurry. Then coat it on an alumina ceramic tube. The alumina ceramic tube has two gold electrodes and four platinum wires. Inside the tube is a nickel-chromium heating wire. The ceramic tube is welded to a six-legged base to produce a gas sensor element. Figure 1 shown.

[0050] In order to evaluate the effect of working temperature on the gas sensor to obtain its optimal working parameters, the gas sensing performance of the sample in the range of 25 to 350 °C was studied with TMA concentration of 10 ppm as the target. The sensitivity curve of the gas sensor to 10 ppm trimethylamine gas is shown in the figure below. Figure 2 As shown in the figure, it is clear that within the test range, the sensitivity of the various gas sensors varies. As the operating temperature increases, 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. The optimal response value for the sensor in Example 1 is 3.0; for Example 2, it is 5.6; for Example 3, it is 7.0; and for Example 4, it is 6.1. By comparison, the sensor in Example 3 exhibits superior sensitivity (2.3 times that of Example 1). Figure 3 The figure shows the response-recovery curve to 10 ppm trimethylamine gas at an operating temperature of 200° C. As can be seen from the figure, the sensor in Example 3 has good response-recovery characteristics to trimethylamine. Figure 4 The selectivity test results for six gases at 10 ppm using Example 3 as an example show that the sensor exhibits very high sensitivity to trimethylamine. The gas sensor in Example 3 shows almost no significant response to interfering gases, while its response to TMA is the highest, approximately 4.7 to 7.0 times that of the other interfering gases. This demonstrates that Example 3 has excellent selectivity for TMA, demonstrating its ability to selectively identify trimethylamine among organic volatile gases and promising potential applications in trimethylamine monitoring.

Claims

1. A trimethylamine gas sensor detection method based on SnS-MoO3 nanosheets, characterized in that: The method comprises the following preparation process: a. Preparation of SnS-MoO3 nanosheets, the steps are as follows: (1) Weigh ammonium molybdate tetrahydrate ((NH4)6Mo7S4·4H2O) and calcine at 500℃ for 2 h to obtain MoO3 nanosheets; (2) The above-mentioned MoO3 nanosheets were dissolved in H2O2 (30%) and stirred for 5 minutes, and then methanol was added and stirred for 24 hours, and ultrasonically treated at room temperature for 30 minutes. The solution was then transferred into a closed reactor with a capacity of 50 mL, placed in an oven and heated to 180°C for 12 hours. After cooling naturally, the powder was collected, washed with deionized water and ethanol by centrifugation three times, and then kept at 60°C for drying. The precursor was directly placed in a muffle furnace and heated to 400°C for 2 hours to obtain pure MoO3 nanosheet material. The obtained MoO3 nanosheets were dissolved in water and ultrasonically dispersed to obtain a MoO3 nanosheet suspension. (3) Dissolve stannous chloride dihydrate (SnCl2·2H2O) and thiourea (CH4N2S) in deionized water and stir at room temperature for 30 min. Add the prepared MoO3 nanosheet suspension to the above solution and stir at room temperature for 1 h. Transfer the solution into a 50 mL closed reactor and heat it in an oven to 180°C for 12 h. After cooling naturally, centrifuge and wash twice with deionized water and anhydrous ethanol respectively. Dry in a vacuum oven at 70°C to obtain SnS-MoO3 nanosheets, which are stored in a desiccator for analysis and detection. b. This material is used as a gas sensitive material to make a gas sensor for detecting trimethylamine gas. The steps are as follows: (1) SnS-MoO3 nanosheets were added to anhydrous ethanol to prepare 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 with the sample adhered to it, and keep the heating wire parallel to the ceramic tube and away from the ceramic tube; (3) The four conductive wires and the two ends of the heating wire of the ceramic tube were welded to the six-pin base to make a gas sensor element; the gas sensitivity characteristics of the sensor were tested using a WS-30A gas sensor tester; the test temperature was 25~350℃.

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