A method for preparing trimethylamine gas sensor using flower-like structure NiO-In2O3 material

Abstract

A method for preparing a trimethylamine gas sensor from a flower-like structured NiO-In2O3 material relates to a method for preparing a sensor from a composite material. The gas sensor of the present invention is composed of an alumina ceramic tube, a nickel-cadmium alloy heating wire, a platinum wire, a gold electrode and a NiO-In2O3 composite sensitive material. The present invention adopts a simple one-step hydrothermal method, and finally determines the optimal surface loading amount and the optimal composite structure of In2O3 by adjusting the molar content of the nickel source in the composite material. The method has the advantages of simple preparation process, low cost, green environmental protection, and suitability for industrial production. The flower-like structured NiO-In2O3 composite material prepared by the present invention exhibits good sensitive characteristics in trimethylamine gas detection, and has the advantages of high sensitivity, good reproducibility and stability, high selectivity and low detection limit, etc. At the same time, the synthesis method is simple, the cost is low, the volume is small, and it is suitable for industrial mass production, showing broad application prospects in the field of high-performance gas sensors.

Description

Technical Field

[0001] The present invention relates to a method for preparing a sensor using a composite material, in particular to a flower-shaped NiO-In 2 O 3 Material preparation method for trimethylamine gas sensor. Background Art

[0002] Indium oxide (In 2 O 3 ) is a wide bandgap semiconductor material. Due to its simple synthesis method, excellent conductivity and photoelectrochemical stability, it is widely used in photocatalysis, solar cells, liquid crystal displays and thin film transistors. 2 O 3 Due to its high catalytic activity and easy construction of microstructures, its application in the field of gas sensors has received increasing attention. In order to meet the needs of gas detection, various morphologies of In 2 O 3 In has been used in gas sensor research, such as nanowires, nanosheets, nanoflowers and hollow tube structures. In these structures, flower-shaped In 2 O 3 The microporous structure has a large specific surface area, high porosity, good permeability and other advantages, which makes it have a good application prospect in the field of gas sensors. A simple synthetic route was used to prepare porous flower-shaped In with significant gas sensing performance. 2 O 3 Sensing materials, and use them to monitor various toxic and harmful gases in the environment, have important practical significance. 2 O 3 As gas-sensitive materials, sensing materials have problems such as low sensitivity and poor selectivity during the detection process, which limits their application.

[0003] With the development of human production activities and the acceleration of social industrialization, the problem of air pollution is becoming increasingly serious, posing a huge threat to the environment and human health. Trimethylamine is an important chemical raw material, which can be used as an organic solvent, analytical reagent, catalyst, etc., and is widely used in various fields such as medicine and agriculture. However, trimethylamine itself has great toxicity. Exposure to trimethylamine gas will cause irritation to the eyes, nose, throat and respiratory tract, causing headaches, nausea, pulmonary edema and even death. Fish and other marine organisms release a large amount of trimethylamine during the corruption process. Therefore, trimethylamine can be used as an effective indicator for detecting the freshness of seafood. At present, the methods for detecting trimethylamine include spectrophotometry, gas chromatography-mass spectrometry, ion chromatography, etc., but the equipment required in these processes is complex and expensive, and it is difficult to be applied on a large scale in practice. Therefore, the development of a trimethylamine gas sensor with high sensitivity, excellent selectivity and stability will provide strong technical support for protecting the atmospheric environment, human health and medical science. The present invention is used to detect trimethylamine by constructing a flower-shaped NiO-In2O3 heterostructure composite material, which has broad application prospects in industrial detection and food safety fields. Summary of the invention

[0004] The object of the present invention is to provide a flower-like structure NiO-In 2 O 3 The present invention adopts a simple one-step hydrothermal method to adjust the molar content of the nickel source in the composite material to finally determine the In 2 O 3 Optimal surface loading and optimal composite structure, preparation of flower-like NiO-In 2 O 3 The composite material is applied to trimethylamine gas detection sensor, showing good sensitive characteristics, high sensitivity, good reproducibility and stability, high selectivity and low detection limit.

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

[0006] A flower-like structure NiO-In 2 O 3 A method for preparing a trimethylamine gas sensor from a material, the method comprising the following preparation process:

[0007] First, the flower-like structure NiO-In 2 O 3 Composite materials are achieved through the following steps:

[0008] (1) Weigh indium chloride tetrahydrate InC l3 ⋅4H 2 O and nickel nitrate hexahydrate Ni(NO 3 )2 ⋅6H 2 O is dissolved in a mixed solution of distilled water and anhydrous ethanol, and stirred continuously for 30 minutes at 40°C with a magnetic stirrer, and then appropriate amounts of sodium dodecyl sulfate and urea are added to the solution, and stirring is continued for 30 minutes to completely dissolve the solution, thereby preparing a hydrothermal synthesis precursor reaction solution;

[0009] (2) pouring the hydrothermal synthesis precursor reaction solution into a stainless steel reactor lined with polytetrachloroethylene and sealing it; keeping it at 160° C. in a drying oven for 5 hours, and then cooling it to room temperature with the furnace to obtain a reaction product;

[0010] (3) Centrifuging the reaction solution to obtain the reaction product, and then repeatedly washing it with distilled water and anhydrous ethanol;

[0011] (4) placing the washed reaction product in a drying oven at a constant temperature of 60°C for drying, and cooling after drying;

[0012] (5) The dried product is placed in a clean crucible and calcined in a muffle furnace at 500°C to obtain NiO-In 2 O 3 The composite material is stored in a desiccator until analytical testing;

[0013] Then, the flower-like structure NiO-In 2 O 3 Composite material trimethylamine gas sensor, the process is as follows:

[0014] The powdery flower-like structure NiO-In 2 O 3 The composite material is ground in an agate mortar for 20 minutes, and then anhydrous ethanol is added and ground for another 20 minutes to obtain a slurry raw material; the slurry is taken with a brush and evenly coated on the surface of the alumina ceramic tube, and then naturally dried; a nickel-chromium alloy heating wire is passed through the alumina ceramic tube coated with the sample, and the heating wire and four conductive wires of the alumina ceramic tube are respectively welded to a six-legged base to obtain an initial gas sensor element; then it is placed on an aging bench for 48 hours to obtain the final required gas sensor element, and the gas sensitive characteristics of the sensor are tested using a WS-30A gas sensitive tester.

[0015] The flower-like structure NiO-In 2 O 3 The method for preparing a trimethylamine gas sensor comprises weighing indium chloride tetrahydrate InC l3 ⋅4H 2 O and nickel nitrate hexahydrate Ni(NO 3 ) 2 ⋅6H 2O was dissolved in a mixed solution of 30 mL of distilled water and 10 mL of anhydrous ethanol.

[0016] The flower-like structure NiO-In 2 O 3 The material preparation method of the trimethylamine gas sensor comprises the following steps: pouring the hydrothermal synthesis precursor reaction solution into a 50 mL stainless steel reactor with a polytetrachloroethylene liner, and the filling degree is 80% sealed.

[0017] The flower-like structure NiO-In 2 O 3 The method for preparing a trimethylamine gas sensor comprises placing the washed reaction product in a constant temperature drying oven at 60° C. for 12 hours for drying.

[0018] The flower-like structure NiO-In 2 O 3 The material preparation method of the trimethylamine gas sensor comprises the following steps: placing the dried product into a clean crucible, placing the crucible into a muffle furnace, and calcining the crucible at 500° C. for 4 hours.

[0019] The flower-like structure NiO-In 2 O 3 The method for preparing a trimethylamine gas sensor comprises the following steps: using a brush to pick up the slurry, uniformly coating the slurry on the surface of an alumina ceramic tube, and then naturally drying the tube at 80°C.

[0020] Advantages and beneficial effects of the present invention:

[0021] (1) The present invention uses indium chloride tetrahydrate, nickel nitrate hexahydrate, sodium dodecyl sulfate and urea as raw materials, and prepares the flower-like structure NiO-In by self-assembly of nanosheets composed of a large number of nanoneedles by a one-step hydrothermal method. 2 O 3 Composite materials. They have the advantages of low cost, simple reaction process, stable synthesis system, easy control, novel morphology, high purity and good dispersibility. They are suitable for mass production and show broad application prospects in the field of high-performance gas sensors. They solve the problems of low sensitivity, poor selectivity and long-term instability of gas sensors in existing technologies.

[0022] (2) Flower-like structure NiO-In prepared by the present invention 2 O 3 The composite material has a unique three-dimensional 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 gas, good selectivity and stability.

[0023] (3) NiO-In based on the present invention 2 O 3 The composite gas sensor uses a simple process and produces a small device, which is suitable for large-scale production and has important commercial application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 is the X-ray diffraction spectrum of the present invention;

[0025] Figure 2a This is a scanning electron microscope image of the product prepared in Example 1 of the present invention;

[0026] Figure 2b This is a scanning electron microscope image of the product prepared in Example 1 of the present invention;

[0027] Figure 2c This is a scanning electron microscope image of the product prepared in Example 2 of the present invention;

[0028] Figure 2d This is a scanning electron microscope image of the product prepared in Example 2 of the present invention;

[0029] Figure 2e This is a scanning electron microscope image of the product prepared in Example 3 of the present invention;

[0030] Figure 2f This is a scanning electron microscope image of the product prepared in Example 3 of the present invention;

[0031] Figure 2g This is a scanning electron microscope image of the product prepared in Example 4 of the present invention;

[0032] Figure 2h This is a scanning electron microscope image of the product prepared in Example 4 of the present invention;

[0033] Figure 2i This is a scanning electron microscope image of the product prepared in Example 5 of the present invention;

[0034] Figure 2j This is a scanning electron microscope image of the product prepared in Example 5 of the present invention;

[0035] Figure 3a This is a schematic diagram of the device structure of the trimethylamine sensor prepared by the present invention;

[0036] Figure 3b The trimethylamine gas sensor of the present invention is a device sensitivity-operating temperature characteristic curve diagram when the gas concentration is 10 ppm;

[0037] Figure 3c The following is a dynamic response curve diagram of the trimethylamine gas sensor in Example 3 of the present invention at an operating temperature of 200° C. to trimethylamine gas of different concentrations;

[0038] Figure 3d The trimethylamine gas concentration-sensitivity change curve of the trimethylamine gas sensor in Example 3 of the present invention at an operating temperature of 200° C.;

[0039] Figure 3e The selectivity diagram of the trimethylamine gas sensor in Example 3 of the present invention at an operating temperature of 200° C. and a concentration of different reducing gases of 10 ppm;

[0040] Figure 3f This is a stability diagram of the trimethylamine gas sensor in Example 3 of the present invention at an operating temperature of 200° C. and a trimethylamine gas concentration of 10 ppm. DETAILED DESCRIPTION

[0041] The present invention will be further described below in conjunction with the embodiments shown in the accompanying drawings.

[0042] The starting materials of the present invention are indium chloride tetrahydrate, nickel nitrate hexahydrate, sodium dodecyl sulfate and urea, which are easily available. After the hydrothermal reaction, the raw materials are centrifuged, washed, dried and calcined. 2 O 3 The composite material has a diameter of 1-2 µm and is self-assembled from a large number of nanosheets. Each nanosheet is a multilayer structure formed by a cluster of 5-10 nm nanoneedles. The flower-like composite material has good overall dispersion and a large number of pores on the powder surface. 2 O 3 The composite material is prepared into a gas sensor, which exhibits higher sensitivity, good selectivity and stability to trimethylamine gas due to its unique three-dimensional spatial structure.

[0043] Flower-like structure NiO-In 2 O 3 The method for preparing a composite material comprises the following steps:

[0044] Step 1: Weigh a certain amount of indium chloride tetrahydrate InC l3 ⋅4H 2 O and nickel nitrate hexahydrate Ni(NO 3 ) 2 ⋅6H 2 O was dissolved in a mixed solution of 30 mL of distilled water and 10 mL of anhydrous ethanol, and stirred continuously for 30 minutes at 40°C with a magnetic stirrer, and then appropriate amounts of sodium dodecyl sulfate and urea were added to the above solution, and stirred for another 30 minutes to completely dissolve it, thereby preparing a hydrothermal synthesis precursor reaction solution;

[0045] Step 2: Pour the precursor reaction solution obtained in step 1 into a 50 mL stainless steel reactor lined with polytetrachloroethylene, with a filling degree of 80% and sealing; keep it at 160°C in a drying oven for 5 hours, and then cool it to room temperature with the furnace to obtain a reaction product;

[0046] Step 3: Centrifuge the solution after the reaction in step 2 to obtain the reaction product, and then repeatedly wash it with distilled water and anhydrous ethanol;

[0047] Step 4: Place the reaction product after washing in step 3 in a constant temperature drying oven at 60°C for 12 hours for drying, and cool after drying;

[0048] Step 5: Place the dried product from step 4 into a clean crucible and place it in a muffle furnace for calcination at 500°C for 4 hours to obtain NiO-In 2 O 3 Composite materials.

[0049] The present invention utilizes flower-like structure NiO-In 2 O 3 Steps for preparing gas sensors from composite materials:

[0050] Step 1: Powdered flower-like structure NiO-In 2 O 3 The composite material was ground in an agate mortar for 20 minutes, and then a small amount of anhydrous ethanol was added and fully ground for another 20 minutes to make a slurry, which was evenly coated on the surface of an alumina ceramic tube with two gold electrodes and four platinum wires.

[0051] Step 2: Pass the nickel-chromium alloy heating wire through the alumina ceramic tube coated with the sample, and place the heating wire parallel to the ceramic tube and away from the ceramic tube.

[0052] Step 3: Weld the four conductive wires and both ends of the heating wire of the ceramic tube to the six-legged base respectively, place them on an aging table for 48 hours, and obtain a gas sensor element.

[0053] Step 4: Use WS-30A gas sensor tester to test the gas sensitivity of the sensor. The test temperature is 100-350℃. Example 1

[0054] (1) Preparation of flower-like structures In 2 O 3 Material

[0055] Step 1: Weigh 0.1466 g of indium chloride tetrahydrate InCl 3 ⋅4H 2O was dissolved in a mixed solution of 30 mL of distilled water and 10 mL of anhydrous ethanol, and stirred continuously for 30 minutes at 40°C with a magnetic stirrer, and then 0.2595 g of sodium dodecyl sulfate and 1.021 g of urea were added to the above solution, and stirred for another 30 minutes to completely dissolve it, thereby preparing a hydrothermal synthesis precursor reaction solution;

[0056] Step 2: Pour the precursor reaction solution prepared in step 1 into a 50 mL stainless steel reactor with a polytetrachloroethylene liner, with a filling degree of 80% sealed;

[0057] Step 3: placing the reactor of step 2 in a drying oven at 160° C. for 5 hours, and then cooling to room temperature with the oven to obtain a reaction product;

[0058] Step 4: Centrifuge the solution after the reaction in step 3 to obtain a white reaction product, and then repeatedly wash it with distilled water and anhydrous ethanol;

[0059] Step 5: Place the reaction product after washing in step 4 in a constant temperature drying oven at 60°C for 12 hours for drying, and cool after drying;

[0060] Step 6: Place the dried product from step 5 into a clean crucible and place it in a muffle furnace for calcination at 500°C for 4 hours to obtain flower-shaped In 2 O 3 White powder, store it in a desiccator until analysis.

[0061] (2) Flower-like structure In 2 O 3 Structural characterization of materials

[0062] The crystal structure of the product was characterized by XRD powder diffractometer (XRD, PANalytical X'Pert Pro). Figure 1 The X-ray diffraction (XRD) spectrum of the sample. It can be seen from the figure that all the diffraction characteristic peaks are strong and sharp, and there are no other impurity peaks, indicating that the prepared sample has good purity and crystallinity. The diffraction characteristic peaks are completely consistent with NO.06-0416 in the standard PDF card, indicating that the sample is a cubic phase In 2 O 3 .

[0063] Scanning electron microscopy (FESEM, ZEISS Ultra Plus) was used to characterize the morphology of the product. Figure 2a , Figure 2bAs shown, the product has a flower-like structure with a diameter of 1~2 µm. It is self-assembled from a large number of nanosheets, each of which is a multilayer structure formed by 5~10 nm nanoneedle clusters. The overall dispersion is good, and there are a large number of pores on the surface of the powder, which plays an important role in improving the detection of trimethylamine gas. Example 2

[0064] (1) Preparation of flower-like NiO-In 2 O 3 Composite Materials

[0065] Step 1: Weigh 0.1466 g of indium chloride tetrahydrate InCl 3 ⋅4H 2 O and 0.0044 g nickel nitrate hexahydrate Ni(NO 3 ) 2 ⋅6H 2 O was dissolved in a mixed solution of 30 mL of distilled water and 10 mL of anhydrous ethanol, and stirred continuously for 30 minutes at 40°C with a magnetic stirrer, and then 0.2595 g of sodium dodecyl sulfate and 1.021 g of urea were added to the above solution, and stirred for another 30 minutes to completely dissolve it, thereby preparing a hydrothermal synthesis precursor reaction solution;

[0066] Steps 2, 3, 4, 5 and 6 are the same as those in Example 1.

[0067] (2) Flower-like structure NiO-In 2 O 3 Structural characterization of composite materials

[0068] The crystal structure of the product was characterized by XRD powder diffractometer (XRD, PANalytical X'Pert Pro). Figure 1 is the X-ray diffraction (XRD) spectrum of the sample. From the figure, it can be seen that except for the cubic phase In 2 O 3 Except for the peak of Ni, there is no Ni diffraction peak. All diffraction characteristic peaks are very sharp, without any miscellaneous peaks, indicating that the prepared samples have good purity and crystallinity.

[0069] Scanning electron microscopy (FESEM, ZEISS Ultra Plus) was used to characterize the morphology of the product. Figure 2c , Figure 2d As shown, the product still presents a flower-like structure, which is consistent with the example without obvious changes. Example 3

[0070] (1) Preparation of flower-like NiO-In 2 O 3 Composite Materials

[0071] Step 1: Weigh 0.1466 g of indium chloride tetrahydrate InCl 3 ⋅4H 2 O and 0.0073 g nickel nitrate hexahydrate Ni(NO 3 ) 2 ⋅6H 2 O was dissolved in a mixed solution of 30 mL of distilled water and 10 mL of anhydrous ethanol, and stirred continuously for 30 minutes at 40°C with a magnetic stirrer, and then 0.2595 g of sodium dodecyl sulfate and 1.021 g of urea were added to the above solution, and stirred for another 30 minutes to completely dissolve it, thereby preparing a hydrothermal synthesis precursor reaction solution;

[0072] Steps 2, 3, 4, 5 and 6 are the same as those in Example 1.

[0073] (2) Flower-like structure NiO-In 2 O 3 Structural characterization of composite materials

[0074] The crystal structure of the product was characterized by XRD powder diffractometer (XRD, PANalytical X'Pert Pro). Figure 1 is the X-ray diffraction (XRD) spectrum of the sample. From the figure, it can be seen that except for the cubic phase In 2 O 3 Except for the peak of Ni, there is still no Ni diffraction peak. All diffraction characteristic peaks are very sharp, and no other impurity peaks appear, indicating that the prepared samples have good purity and crystallinity.

[0075] Scanning electron microscopy (FESEM, ZEISS Ultra Plus) was used to characterize the morphology of the product. Figure 2e , Figure 2f As shown, the product still presents a flower-like structure, which is consistent with the example without obvious changes. Example 4

[0076] (1) Preparation of flower-like NiO-In 2 O 3 Composite Materials

[0077] Step 1: Weigh 0.1466 g of indium chloride tetrahydrate InCl 3 ⋅4H 2 O and 0.0147 g nickel nitrate hexahydrate Ni(NO 3 ) 2 ⋅6H 2O was dissolved in a mixed solution of 30 mL of distilled water and 10 mL of anhydrous ethanol, and stirred continuously for 30 minutes at 40°C with a magnetic stirrer, and then 0.2595 g of sodium dodecyl sulfate and 1.021 g of urea were added to the above solution, and stirred for another 30 minutes to completely dissolve it, thereby preparing a hydrothermal synthesis precursor reaction solution;

[0078] Steps 2, 3, 4, 5 and 6 are the same as those in Example 1.

[0079] (2) Flower-like structure NiO-In 2 O 3 Structural characterization of composite materials

[0080] The crystal structure of the product was characterized by XRD powder diffractometer (XRD, PANalytical X'Pert Pro). Figure 1 is the X-ray diffraction (XRD) spectrum of the sample. From the figure, it can be seen that except for the cubic phase In 2 O 3 Except for the peak of Ni, there is still no Ni diffraction peak. All diffraction characteristic peaks are very sharp, and no other impurity peaks appear, indicating that the prepared samples have good purity and crystallinity.

[0081] Scanning electron microscopy (FESEM, ZEISS Ultra Plus) was used to characterize the morphology of the product. Figure 2g , Figure 2h As shown, the flower-like structure is still present, which is consistent with the embodiment and has no obvious changes. Example 5

[0082] (1) Preparation of flower-like NiO-In 2 O 3 Composite Materials

[0083] Step 1: Weigh 0.1466 g of indium chloride tetrahydrate InCl 3 ⋅4H 2 O and 0.0293 g nickel nitrate hexahydrate Ni(NO 3 ) 2 ⋅6H 2 O was dissolved in a mixed solution of 30 mL of distilled water and 10 mL of anhydrous ethanol, and stirred continuously for 30 minutes at 40°C with a magnetic stirrer, and then 0.2595 g of sodium dodecyl sulfate and 1.021 g of urea were added to the above solution, and stirred for another 30 minutes to completely dissolve it, thereby preparing a hydrothermal synthesis precursor reaction solution;

[0084] Steps 2, 3, 4, 5 and 6 are the same as those in Example 1.

[0085] (2) Flower-like structure NiO-In 2O 3 Structural characterization of composite materials

[0086] The crystal structure of the product was characterized by XRD powder diffractometer (XRD, PANalytical X'Pert Pro). Figure 1 is the X-ray diffraction (XRD) spectrum of the sample. From the figure, it can be seen that except for the cubic phase In 2 O 3 In addition to the peaks of NiO, some small diffraction peaks related to NiO began to appear. The characteristic diffraction peaks were completely consistent with NO.47-1049 in the standard PDF card, indicating that it was cubic structure NiO. In addition, no other impurity diffraction peaks were found in the characteristic peaks of all products, indicating that the products were mainly composed of In 2 O 3 It is composed of NiO and has good purity and crystallinity.

[0087] Scanning electron microscopy (FESEM, ZEISS Ultra Plus) was used to characterize the morphology of the product. Figure 2i , Figure 2j As shown, the difference is that the nanoneedles that make up the nanosheets evolve into nanosheets with a diameter less than 50 nm, but still present a flower-like structure.

[0088] The flower-like structure NiO-In 2 O 3 The composite material product was made into a gas sensor, and the gas-sensing performance of trimethylamine was tested:

[0089] Weigh the powdery flower-like structure NiO-In 2 O 3 The composite material was ground in an agate mortar for 20 minutes, then a small amount of anhydrous ethanol was added and ground for another 20 minutes to obtain a slurry of raw materials; a small amount of slurry was applied to the surface of the alumina ceramic tube with a brush and then the nickel-chromium alloy heating wire was passed through the alumina ceramic tube coated with the sample. The heating wire and the four conductive wires of the alumina ceramic tube were welded to a six-foot base to obtain a gas sensor element, such as Figure 3a shown.

[0090] The sensitivity-operating temperature characteristic curve of the sensor device, such as Figure 3b As shown in the figure, it can be clearly seen that in the range of working temperature of 100-350°C, the response of all sensor devices first increases with the working temperature until the highest response is reached, and then decreases with further increase in temperature, showing typical semiconductor metal oxide gas sensor characteristics. Compared with the sensor devices prepared in other embodiments, the sensor device of embodiment 3 shows the best sensitivity, that is, when the optimal working temperature is 200°C, its maximum sensitivity is 20.5. Figure 3c The figure shows the response-recovery curve for 0.5-200 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 for different concentrations of trimethylamine, indicating that it has good resolution for different concentrations of trimethylamine. Its sensitivity increases with the increase of concentration ( Figure 3d ). The response characteristics to 10 ppm of different reducing gases at an operating temperature of 200°C, such as Figure 3e As shown in the figure, it can be seen that the sensor device in Example 3 has a much higher sensitivity to trimethylamine than other detection gases among the six reducing gases tested, showing good selectivity. The stability monitoring results of 10 ppm trimethylamine gas within 60 days at an operating temperature of 200°C are as follows: Figure 3f As shown in the figure, it can be seen that the sensitivity of the sensor device in Example 3 has no obvious decline during the tested period, indicating that the sensor device prepared in Example 3 has good long-term stability.

Claims

1. A method for preparing a trimethylamine gas sensor using a flower-like structure NiO-In2O3 material, characterized in that: The method comprises the following preparation process: First, prepare the flower-like structure NiO-In2O3 composite material by the following steps: (1) Weigh indium chloride tetrahydrate InC l3 ⋅4H2O and nickel nitrate hexahydrate Ni(NO3)2⋅6H2O are dissolved in a mixed solution prepared by distilled water and anhydrous ethanol, and stirred continuously for 30 minutes with a magnetic stirrer at 40°C, and then appropriate amounts of sodium dodecyl sulfate and urea are added to the above solution, and stirring is continued for 30 minutes to completely dissolve them, thereby preparing a hydrothermal synthesis precursor reaction solution; (2) pouring the hydrothermal synthesis precursor reaction solution into a stainless steel reactor lined with polytetrachloroethylene and sealing it; keeping it at 160° C. in a drying oven for 5 hours, and then cooling it to room temperature with the furnace to obtain a reaction product; (3) Centrifuging the reaction solution to obtain the reaction product, and then repeatedly washing it with distilled water and anhydrous ethanol; (4) placing the washed reaction product in a drying oven at a constant temperature of 60°C for drying, and cooling after drying; (5) placing the dried product into a clean crucible and calcining it in a muffle furnace at 500°C to obtain a NiO-In2O3 composite material, which is then stored in a desiccator for analysis and testing; Then, a flower-like structure NiO-In2O3 composite trimethylamine gas sensor was prepared, and the process was as follows: The powdered flower-like structure NiO-In2O3 composite material is placed in an agate mortar and ground for 20 minutes, and then anhydrous ethanol is added and fully ground for another 20 minutes to obtain a slurry raw material; the slurry is taken with a brush and evenly coated on the surface of an alumina ceramic tube, and then naturally dried, a nickel-chromium alloy heating wire is passed through the alumina ceramic tube coated with the sample, and the heating wire and four conductive wires of the alumina ceramic tube are respectively welded on a six-legged base to obtain an initial gas sensor element; then it is placed on an aging table for 48 hours to obtain the final required gas sensor element, and the gas sensitive characteristics of the sensor are tested using a WS-30A gas sensitive tester; Weigh indium chloride tetrahydrate InC l3 ⋅4H2O and nickel nitrate hexahydrate Ni(NO3)2⋅6H2O were dissolved in a mixed solution prepared by 30 mL of distilled water and 10 mL of anhydrous ethanol; The hydrothermal synthesis precursor reaction solution was poured into a 50 mL stainless steel reactor lined with polytetrachloroethylene, with a filling degree of 80% sealed.

2. The method for preparing a trimethylamine gas sensor using a flower-like structure NiO-In2O3 material according to claim 1, characterized in that: The washed reaction product is placed in a constant temperature drying oven at 60° C. for 12 hours for drying.

3. The method for preparing a trimethylamine gas sensor using a flower-like structure NiO-In2O3 material according to claim 1, characterized in that: The dried product is placed in a clean crucible and placed in a muffle furnace for calcination at 500° C. for 4 hours.

4. The method for preparing a trimethylamine gas sensor using a flower-like structure NiO-In2O3 material according to claim 1, characterized in that: The slurry is picked up with a brush and evenly coated on the surface of the alumina ceramic tube, and then naturally dried at 80°C.

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