A method for detecting trimethylamine gas using a CuO-In2O3 gas-sensitive material sensor

Abstract

A method for detecting trimethylamine gas using a CuO-In2O3 gas-sensitive material sensor is disclosed. This invention relates to a method for detecting trimethylamine gas. The gas-sensitive material is synthesized using a simple and efficient chemical method. By changing the proportion of raw materials, a CuO-In2O3 composite material with a hollow tubular structure is constructed, giving it excellent application performance. The entire production process is simple, low-cost, highly controllable, non-toxic, and harmless. The prepared material has high purity, good crystallinity, and good dispersibility, making it suitable for large-scale industrial production. The CuO-In2O3 composite material prepared by this invention exhibits high sensitivity, good selectivity, and rapid response recovery characteristics to trimethylamine at 100℃, showing broad application prospects in fields such as food safety monitoring.

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 CuO-In2O3 gas-sensitive material sensor. Background Technology

[0002] Trimethylamine (TMA) is a nitrogen-containing volatile organic compound with a pungent odor. It is primarily used as a disinfectant, a natural gas alarm, an analytical reagent, and a raw material for organic synthesis. It is also used in pharmaceuticals, pesticides, photographic materials, rubber additives, explosives, synthetic fiber solvents, surfactants, and dyes. TMA 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 TMA concentrations should be below 10 ppm. Prolonged exposure to TMA 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] Indium oxide (In₂O₃) is an n-type semiconductor material with a direct band gap of 3.55-3.75 eV and an indirect band gap of 2.62 eV. Due to its good electrical conductivity, unique gas adsorption and catalytic properties, and low electron affinity, In₂O₃ has broad application prospects in the field of microelectronics. Therefore, using In₂O₃ as a gas-sensitive material to study its sensitivity to volatile organic compounds such as trimethylamine has significant commercial value. With the rise and rapid development of nanotechnology, synthesizing high-performance In₂O₃ nanostructured sensitive materials using advanced nanotechnology and further improving gas-sensing performance through component optimization is an effective technical means to construct low-power, intelligent, and integrated gas sensors. Therefore, this invention uses a simple hydrothermal synthesis method to prepare a CuO-In₂O₃ composite material with a hollow tubular structure. The equipment used is simple and inexpensive, the product has high purity, is suitable for large-scale industrial production, and exhibits good detection characteristics for trimethylamine gas. Summary of the Invention

[0004] The purpose of this invention is to provide a method for detecting trimethylamine gas using a CuO-In2O3 gas-sensitive material sensor. This invention uses indium nitrate 4.5 hydrate and copper acetate as raw materials and prepares a CuO-In2O3 composite material with a hollow tubular structure through a two-step hydrothermal method. This composite material is used for detecting trimethylamine gas in a gas-sensitive material sensor. It exhibits high sensitivity, good selectivity and stability for trimethylamine at low temperatures and has broad application prospects in fields such as food safety monitoring.

[0005] The objective of this invention is achieved through the following technical solution:

[0006] A method for detecting trimethylamine gas using a CuO-In2O3 gas-sensitive material sensor, the method comprising the following preparation process:

[0007] a. Preparation of CuO-In2O3 composite materials with hollow tubular structures:

[0008] Weigh out indium nitrate 4.5 hydrate and terephthalic acid, dissolve them in 30 mL of N,N-dimethylformamide solution, and stir all the mixed solutions in a constant temperature oil bath at 100℃ for 10 minutes to obtain the precursor reaction solution.

[0009] The reaction product was obtained by centrifugation of the solution after reaction, and then washed repeatedly with N,N-dimethylformamide and anhydrous ethanol. The washed reaction product was then placed in a drying oven at a constant temperature of 60°C for 12 hours to dry, and a white powder was obtained after drying.

[0010] The dried product was placed in a clean crucible and then placed in a muffle furnace. It was calcined at 120°C for 2 hours, and then heated to 500°C for 2 hours to obtain In2O3.

[0011] Add In2O3 and polyvinylpyrrolidone to a 30 mL mixture of ethanol:N,N-dimethylformamide:deionized water = 1:1:1, stir for 3 hours, then add copper acetate and continue stirring for another 3 hours.

[0012] The reaction product was obtained by centrifugation of the solution after reaction, and then washed 6 times with anhydrous ethanol. The washed reaction product was placed in a drying oven at a constant temperature of 60°C for 12 hours for drying.

[0013] The dried product was placed in a clean crucible and then placed in a muffle furnace. It was calcined at 120°C for 2 hours, and then heated to 500°C for 2 hours to obtain CuO-In2O3 composite material. It was stored in a desiccator for analysis and detection.

[0014] b. This material can be used as a gas-sensitive material to fabricate a gas sensor for the detection of trimethylamine gas. The steps are as follows:

[0015] (1) CuO-In2O3 composite material 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.

[0016] (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;

[0017] (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;

[0018] (4) The gas sensitivity characteristics of the sensor were tested using a WS-30A gas sensitivity tester; the test temperature was 100℃.

[0019] The advantages and effects of this invention are:

[0020] (1) This invention uses indium nitrate hydrate 4.5% and copper acetate as raw materials to prepare CuO-In2O3 composite material with hollow tubular structure by a two-step hydrothermal method. It has the advantages of good controllability, high purity of the prepared material, good crystallinity and good dispersibility, and is suitable for large-scale industrial production.

[0021] (2) The CuO-In2O3 composite material prepared by the present invention has a unique hollow structure, which not only increases the specific surface area of ​​the material, but also constructs a well-developed gas transmission channel, making the material more permeable. As a gas sensor prepared by the gas-sensitive material, it exhibits high sensitivity, good selectivity and stability to trimethylamine at low temperature, and has broad application prospects in the fields of food safety monitoring.

[0022] (3) The CuO-In2O3-based trimethylamine gas sensor produced by this invention has a simple manufacturing process and low cost, and is suitable for industrial mass production. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the trimethylamine sensor.

[0024] Figure 2 This is a sensitivity graph of a gas sensor to 10 ppm trimethylamine gas at 100℃;

[0025] Figure 3 The response recovery curve of the gas sensor in Example 3 to 10 ppm trimethylamine gas at 100°C is shown.

[0026] Figure 4 This is a sensitivity graph for selective testing of 10 ppm trimethylamine gas at 100°C in Example 3. Implementation

[0027] The present invention will now be described in detail with reference to the embodiments shown in the accompanying drawings.

[0028] The starting materials for this invention are inexpensive and readily available indium nitrate and copper acetate. Through hydrothermal reaction, followed by centrifugation, washing, drying, and calcination, the prepared CuO-In₂O₃ hollow tube has a diameter of 2-3 µm, with CuO particles uniformly dispersed on the surface of the In₂O₃ hollow tube. When the CuO-In₂O₃ composite material is used to fabricate a gas sensor, its unique hollow porous structure exhibits high sensitivity, good selectivity, and excellent response recovery characteristics for trimethylamine at an operating temperature of 100°C.

[0029] A method for preparing CuO-In2O3 composite materials with hollow tubular structures includes the following steps:

[0030] Step 1: Weigh indium nitrate and terephthalic acid, dissolve them in 30 mL of N,N-dimethylformamide solution, and stir all the mixed solutions in a constant temperature oil bath at 100℃ for 10 minutes to obtain the precursor reaction solution;

[0031] Step 2: Centrifuge the reaction solution to obtain the reaction product, then wash it repeatedly with N,N-dimethylformamide and anhydrous ethanol; then place the washed reaction product in a drying oven at a constant temperature of 60°C for 12 hours to dry it, and a white powder is obtained after drying.

[0032] Step 3: Place the dried product into a clean crucible and put it into a muffle furnace. Calcine at 120°C for 2 hours, then raise the temperature to 500°C and calcine for 2 hours to obtain In2O3.

[0033] Step 4: Add In2O3 and polyvinylpyrrolidone to 30 mL of a mixed solution of ethanol: N,N-dimethylformamide: deionized water = 1:1:1, stir for 3 hours, add copper acetate to the solution and continue stirring for 3 hours.

[0034] Step 5: Centrifuge the reaction solution to obtain the reaction product, then wash it 6 times with anhydrous ethanol. Place the washed reaction product in a drying oven at a constant temperature of 60°C for 12 hours to dry it.

[0035] Step 6: Place the dried product into a clean crucible and put it into a muffle furnace. Calcine at 120°C for 2 hours, then raise the temperature to 500°C and calcine for 2 hours to obtain the In2O3-CuO composite material. Store it in a desiccator for analysis and testing.

[0036] The CuO-In2O3 composite material was ground in a mortar for 20 minutes; then anhydrous ethanol was added, and grinding continued for another 20 minutes to prepare a slurry; a small amount of the slurry was applied evenly to the surface of a ceramic tube with a brush, and then dried at 80°C. A nickel-chromium alloy heating wire was passed through the ceramic tube with the sample attached, and the heating wire was soldered to the four conductive wires of the ceramic tube onto a six-legged base to obtain a gas sensor element. This element was then aged on an aging table for 48 hours to obtain the gas sensor element; the gas sensitivity characteristics of the sensor were then tested using a WS-30A gas sensor. Example 1

[0037] Preparation of 3% CuO-In2O3 composite material

[0038] Step 1: Weigh 0.267g In(NO3)3·4.5H2O and 0.107g terephthalic acid, dissolve them in 30 mL N,N-dimethylformamide solution, and stir all the mixed solutions in a constant temperature oil bath at 100℃ for 10 minutes to obtain the precursor reaction solution.

[0039] Step 2: Centrifuge the solution after the reaction in Step 1 to obtain the reaction product, and then wash it repeatedly with N,N-dimethylformamide and anhydrous ethanol; then place the washed reaction product in a drying oven at a constant temperature of 60°C for 12 hours to dry it, and a white powder is obtained after drying.

[0040] Step 3: Place the dried product from Step 2 into a clean crucible and place it in a muffle furnace. Calcine at 120°C for 2 hours, then raise the temperature to 500°C and continue calcining for another 2 hours to obtain In2O3 material. Store it in a desiccator for analysis and testing.

[0041] Step 4: Add In2O3 and polyvinylpyrrolidone to 30 mL of a mixed solution of ethanol: N,N-dimethylformamide: deionized water = 1:1:1, stir for 3 hours, add 0.0012 g of copper acetate to the solution and continue stirring for 3 hours;

[0042] Step 5: Centrifuge the reaction solution to obtain the reaction product, then wash it 6 times with anhydrous ethanol. Place the washed reaction product in a drying oven at a constant temperature of 60°C for 12 hours to dry it.

[0043] Step 6: Place the dried product into a clean crucible and put it into a muffle furnace. Calcine at 120°C for 2 hours, then raise the temperature to 500°C and calcine for 2 hours to obtain the CuO-In2O3 composite material. Store it in a desiccator for analysis and testing. Example 2

[0044] Preparation of 5% CuO-In2O3 composite material

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

[0046] Step 4: Add In2O3 and polyvinylpyrrolidone to a 30 mL mixture of ethanol:N,N-dimethylformamide:deionized water = 1:1:1, stir for 3 hours, then add 0.002 g of copper acetate and continue stirring for another 3 hours.

[0047] Step 5: Same as Example 1. Example 3

[0048] Preparation of 7% CuO-In2O3 composite material

[0049] Steps one, two, and three are the same as in Example 1.

[0050] Step 4: Add In2O3 and polyvinylpyrrolidone to a 30 mL mixture of ethanol:N,N-dimethylformamide:deionized water = 1:1:1, stir for 3 hours, then add 0.0028 g of copper acetate and continue stirring for another 3 hours.

[0051] Step 5: Same as Example 1. Example 4

[0052] Preparation of 10% CuO-In2O3 composite material

[0053] Steps one, two, and three are the same as in Example 1.

[0054] Step 4: Add In2O3 and polyvinylpyrrolidone to a 30 mL mixture of ethanol:N,N-dimethylformamide:deionized water = 1:1:1, stir for 3 hours, then add 0.0038 g of copper acetate and continue stirring for another 3 hours.

[0055] Step 5: Same as Example 1.

[0056] A gas sensor was fabricated using the prepared CuO-In2O3 composite material, and its gas-sensing performance for trimethylamine was tested.

[0057] A certain amount of CuO-In2O3 composite material was weighed and mixed with anhydrous ethanol to prepare a slurry, which was then coated onto an alumina ceramic tube. The alumina ceramic tube contained two gold electrodes and four platinum wires, with a nickel-chromium heating wire inside. The ceramic tube was then welded to a six-legged base to obtain a gas sensor element, such as... Figure 1 As shown.

[0058] To evaluate the effect of operating temperature on the gas sensor and obtain its optimal operating parameters, the gas-sensing performance of the sample at a concentration of 10 ppm trimethylamine was studied in the range of 25 to 350 °C. 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 from the figure that the sensitivities of the gas sensors prepared in the different embodiments differ within the test range. With increasing operating temperature, the response values ​​of all samples tend to increase first and then decrease, exhibiting the highest sensitivity at an operating temperature of 100 °C. Specifically, the optimal sensitivity of the sensor in Example 1 is 4.3; in Example 2, it is 5.3; in Example 3, it is 9.6; and in Example 4, it is 6.6. Through comparison, it was found that the sensor in Example 3 performs better in terms of sensitivity characteristics, and it should be further studied as the optimal sensor. Figure 3 The figure shows the response-recovery curve of the gas sensor in Example 3 to 10 ppm trimethylamine gas at an operating temperature of 100°C. As can be seen from the figure, the sensor in Example 3 has good response-recovery characteristics to trimethylamine. Figure 4 The results of the selective test on 10 ppm of 6 gases are shown in Example 3. It can be seen that the sensor has very high sensitivity to trimethylamine gas, but low sensitivity to interfering gases. This indicates that the sensor in Example 3 has excellent selectivity for trimethylamine gas and has broad application prospects in the field of trimethylamine monitoring.

Claims

1. A method for preparing a CuO-In2O3 gas sensitive material sensor, characterized in that, The method comprises the following preparation process: a. Preparation of CuO-In2O3 composite material with hollow tubular structure: (1) Take indium nitrate tetrahydrate and terephthalic acid, dissolve in 30 mL N,N-dimethylformamide solution, after stirring all the mixed solution using constant temperature oil bath pot 100℃ for 10 minutes, get the precursor reaction solution; (2) centrifugal separation after reaction solution to obtain the reaction product, and then use N,N-dimethylformamide, anhydrous ethanol repeatedly washed; again, the washed reaction product is put into constant temperature drying box, 60℃, 12 hours drying treatment, after drying to obtain white powder; (3) the dried product is put into clean crucible, placed in muffle furnace, calcined at 120℃ for 2 hours, heated to 500℃ for 2 hours, to obtain In2O3; (4) In2O3 and polyvinylpyrrolidone are added to 30 mL ethanol: N,N-dimethylformamide: deionized water = 1:1:1 mixed solution, stirring for 3 hours, adding copper acetate to the solution and continuing to stir for 3 hours; (5) centrifugal separation after reaction solution to obtain the reaction product, and then use anhydrous ethanol to wash 6 times, the washed reaction product is put into constant temperature drying box, 60℃, 12 hours drying treatment; (6) the dried product is put into clean crucible, placed in muffle furnace, calcined at 120℃ for 2 hours, heated to 500℃ for 2 hours, to obtain CuO-In2O3 composite material, which is stored in a desiccator for analysis and detection; b. The material can be used as gas sensitive material to make gas sensor for detecting trimethylamine gas, the steps are as follows: (1) CuO-In2O3 composite material is added to anhydrous ethanol to make slurry, which is coated on the outer wall of alumina ceramic tube with two gold electrodes and four platinum wires; (2) nickel-chromium alloy heating wire is passed through the alumina ceramic tube with sample adhered, and the heating wire is parallel to the ceramic tube, far away from the ceramic tube; (3) the four conductive wires of the ceramic tube and the two ends of the heating wire are respectively welded on the six-pin base, to obtain gas sensor element; (4) WS-30A gas sensitive tester is used to test the gas sensitive characteristics of the sensor; the test temperature is 100℃.

Images