Method for detecting formaldehyde gas by Zn2SnO4 gas-sensitive material sensor

Abstract

The invention discloses a method for detecting formaldehyde gas by using a Zn2SnO4 gas-sensitive material sensor, and relates to a formaldehyde gas detection method. According to the method, the Zn2SnO4 gas-sensitive material is prepared by combining a one-step hydrothermal method with a subsequent calcination process, the material is easy to prepare and low in cost, different samples are prepared by setting different calcination temperatures, then the optimal calcination temperature is obtained, and the influence of the temperature on the performance of the samples is determined. The prepared sensing device is small in size and low in cost, has good selectivity and low detection limit, and has a wide application prospect in the aspect of detecting formaldehyde at a relatively low temperature of 150 DEG C. In addition, the Zn2SnO4 gas-sensitive material is mature and stable in preparation process, suitable for mass production, portable in equipment, simple to operate and suitable for safety monitoring of indoor air.

Description

Technical Field

[0001] The present invention relates to a method for detecting formaldehyde gas, in particular to a method for detecting formaldehyde gas by a Zn2SnO4 gas-sensitive material sensor. Background Art

[0002] As a common colorless, odorless, toxic and harmful gas, formaldehyde can easily cause skin allergies, bronchial asthma and other diseases when the human body is exposed to it for a long time. In recent years, with the increasing demand for environmental air quality by the public, the demand for detecting trace formaldehyde gas has also increased. Therefore, it is very necessary to develop a simple and efficient detection method to monitor formaldehyde.

[0003] Currently, the main methods for detecting formaldehyde include fluorescence method, chromatography, spectrophotometry, etc. However, due to the high cost and cumbersome operation of these methods themselves, the real-time detection of formaldehyde gas is greatly restricted. Compared with the above detection methods, semiconductor gas sensors have attracted extensive research by domestic and foreign scholars due to their advantages such as low cost, simple operation, and the ability to achieve long-term continuous real-time online detection. Summary of the Invention

[0004] The purpose of the present invention is to propose a method for detecting formaldehyde gas by a Zn2SnO4 gas-sensitive material sensor. This method uses a one-step hydrothermal method combined with a subsequent calcination process to prepare the Zn2SnO4 gas-sensitive material, which can achieve selective detection of formaldehyde gas at a lower working temperature, with high sensitivity and good selectivity.

[0005] The purpose of the present invention is achieved by the following technical solutions: A method for detecting formaldehyde gas by a Zn2SnO4 gas-sensitive material sensor, the steps of the method are as follows: (1) Prepare the Zn2SnO4 gas-sensitive material: 1) Weigh zinc chloride and tin tetrachloride pentahydrate and dissolve them in deionized water, stir for 10 min to form a homogeneous solution; then, weigh sodium hydroxide and add it to the above solution, and continue to stir for 10 min to make it evenly dispersed; 2) Let the solution in step one stand overnight, centrifuge the obtained product, and wash it 6 times with anhydrous ethanol and deionized water respectively; Put the washed reaction product into a constant-temperature drying oven and dry it at 60°C for 12 h; 4) Place the dried reaction product in a muffle furnace and calcine it at 600 - 800°C in an air atmosphere for 2 h to obtain the Zn2SnO4 gas-sensitive material; The above material is used as a gas-sensitive material to make a gas sensor for detecting formaldehyde gas: 1) Add the above Zn2SnO4 gas-sensitive material to ethanol to make a slurry, and coat it on the outer surface of an Al2O3 ceramic tube with two gold electrodes and four platinum wires. 2) Pass a heating wire through the Al2O3 ceramic tube and weld its two ends to the heating electrodes on the base. Then, weld the platinum wire connected to the gold electrode on the ceramic tube surface to the measuring electrode on the base to obtain a gas sensor element. Place the fabricated gas-sensing element on an aging table and age it for 48 hours at 150 °C in an air environment. 4) Use a WS-30A gas-sensing tester to test the gas-sensing characteristics of the sensor, and the test temperature is 25 - 250 °C.

[0006] Advantages and beneficial effects of the present invention: For the Zn2SnO4 gas-sensitive material gas sensor of the present invention, the electrical properties of Zn2SnO4 will change significantly with the change in the amount of formaldehyde adsorbed, and it can efficiently convert formaldehyde concentration information into measurable electrical signals. Its crystal structure endows the material with good stability. Under different working conditions, such as high temperature, high pressure, etc., the structure of the material is not easily damaged, thus ensuring the stable performance of the gas-sensing property. By adjusting the preparation process, the gas-sensing performance of the material towards formaldehyde can be further improved, showing great potential in the field of developing high-performance formaldehyde gas sensors. The Zn2SnO4 gas-sensitive material has the advantages of simple synthesis, low cost, high product purity, etc., and is suitable for industrial large-scale production and application. At the same time, the Zn2SnO4 gas-sensitive material itself is non-toxic and pollution-free, and will not cause harm to the environment and human health during use. The Zn2SnO4 gas-sensitive material can have a good response performance towards formaldehyde at a relatively low temperature of 150 °C, has good application prospects, shows great potential in the field of developing high-performance formaldehyde gas sensors, and is expected to provide a more reliable and convenient solution for indoor formaldehyde detection.

[0007] (1) The present invention prepares the Zn2SnO4 gas-sensitive material by hydrothermal method combined with subsequent calcination treatment. The raw materials are easily obtained and the preparation process is simple, which is suitable for large-scale production.

[0008] (2) The Zn2SnO4 gas-sensitive material prepared by the present invention can have good detection performance, high selectivity and low detection limit for formaldehyde gas at 150 °C.

[0009] (3) The formaldehyde gas sensor based on the Zn2SnO4 gas-sensitive material prepared by the present invention adopts a simple manufacturing process and is small in size, suitable for industrial large-scale production, and has broad application prospects in the field of smart home. Description of the Drawings

[0010] Figure 1 It is a schematic structural diagram of a formaldehyde sensor. Figure 2 is the response value of the sensor to 10 ppm formaldehyde gas at different temperatures; Figure 3 is the relationship between the response value and the formaldehyde concentration in Example 3 at 150 °C; Figure 4 is the selectivity test chart of Example 3 to 10 ppm gas at 150 °C. Detailed implementation mode

[0011] The present invention will be further described below in conjunction with the embodiments shown in the drawings.

[0012] The preparation method of the Zn2SnO4 gas-sensitive material includes the following preparation steps: Step 1: Weigh 1 mmol of ZnCl2 and 1 mmol of SnCl4·5H2O and dissolve them in deionized water, stir for 10 min to form a uniform solution. Subsequently, weigh 10 mmol of NaOH, add it to the above solution, and continue to stir for 10 min to make it disperse evenly; Step 2: Let the solution in Step 1 stand overnight, centrifuge the obtained product, and wash it 6 times each with absolute ethanol and deionized water; Step 3: Put the washed reaction product into a drying oven at a constant temperature and dry it at 60 °C for 12 h; Step 4: Place the dried reaction product in a muffle furnace and calcine it at 600 °C in an air atmosphere for 2 h to obtain the Zn2SnO4 gas-sensitive material.

[0013] The steps of the present invention for preparing a gas sensor using the Zn2SnO4 gas-sensitive material: Step 1: Add the Zn2SnO4 gas-sensitive material described in Claim 1 to ethanol to make a slurry, and coat it on the outer surface of an Al2O3 ceramic tube with two gold electrodes and four platinum wires; Step 2: Pass a heating wire through the Al2O3 ceramic tube and weld its two ends to the heating electrodes on the base. Then, weld the platinum wire connected to the gold electrode on the ceramic tube surface to the measuring electrode on the base to obtain a gas sensor element; Step 3: Place the fabricated gas sensing element on an aging table and age it at 150 °C in an air environment for 48 hours; Step 4: Use a WS-30A gas sensor tester to test the gas-sensitive characteristics of the sensor, and the test temperature is 25~250 °C. Example 1

[0014] Step 1: Weigh a certain amount of ZnCl2 and SnCl4·5H2O and dissolve them in deionized water. Stir for 10 min to form a homogeneous solution. Subsequently, weigh a certain amount of NaOH and add it to the above solution. Continue to stir for 10 min to make it disperse evenly; Step 2: Let the solution in Step 1 stand overnight. Centrifuge the reacted solution to obtain the reaction product, and wash it 6 times each with absolute ethanol and deionized water respectively; Step 3: Put the washed reaction product into a drying oven at a constant temperature and dry it at 60 °C for 12 h; Step 4: Place the dried reaction product in a muffle furnace and calcine it in an air atmosphere at 400 °C for 2 h to obtain the Zn2SnO4 gas-sensing material. Example 2

[0015] Steps 1, 2, and 3 are the same as in Example 1.

[0016] Step 4: Place the dried reaction product in a muffle furnace and calcine it in an air atmosphere at 500 °C for 2 h to obtain the Zn2SnO4 gas-sensing material. Example 3

[0017] Steps 1, 2, and 3 are the same as in Example 1.

[0018] Step 4: Place the dried reaction product in a muffle furnace and calcine it in an air atmosphere at 600 °C for 2 h to obtain the Zn2SnO4 gas-sensing material. Example 4

[0019] Steps 1, 2, and 3 are the same as in Example 1.

[0020] Step 4: Place the dried reaction product in a muffle furnace and calcine it in an air atmosphere at 700 °C for 2 h to obtain the Zn2SnO4 gas-sensing material. Example 5

[0021] Steps 1, 2, and 3 are the same as in Example 1.

[0022] Step 4: Place the dried reaction product in a muffle furnace and calcine it in an air atmosphere at 800 °C for 2 h to obtain the Zn2SnO4 gas-sensing material.

[0023] As Figure 1 shown, add the Zn2SnO4 gas-sensing material to ethanol to make a slurry, coat it on the outer surface of an alumina ceramic tube with two gold electrodes and four platinum wires, pass the heating wire through the Al2O3 ceramic tube and weld its two ends to the heating electrodes on the base, and then weld the platinum wire connected to the gold electrode on the ceramic tube surface to the measuring electrode on the base to obtain the gas sensor element.

[0024] To evaluate the influence of temperature on the gas sensor to obtain the optimal working parameters and simultaneously reflect the influence of different calcination temperatures on the gas-sensing performance of the product, using formaldehyde with a concentration of 10 ppm as the target, the gas-sensing performance of five samples in the range of 25 - 250 °C was studied, as Figure 2 shown. It can be clearly seen from the figure that the response of the sensor increases with the increase of the working temperature until the optimal working temperature is reached. When the working temperature continues to rise, the response of the sensor shows a downward trend. Among the five samples, Example 3 exhibits superior gas-sensing performance. With the continuous increase of the calcination temperature, the gas-sensing performance of the obtained samples decreases significantly. It is worth noting that Example 3 reaches the maximum response value of 14.76 at the optimal working temperature of 150 °C, showing excellent gas-sensing performance at a lower detection temperature.

[0025] In the concentration range of 0.1 to 100 ppm, with the increase of the formaldehyde concentration, the response value of Example 3 increases significantly. However, when the formaldehyde concentration exceeds 5 ppm, due to the extensive coverage of formaldehyde molecules on the sensor surface, the surface reaction decreases, and the response value increment shows a decreasing trend. It is worth noting that even at an extremely low concentration of 0.1 ppm, the sensor still has a large response to formaldehyde, reaching 2.89. This result fully demonstrates its potential in measuring trace formaldehyde.

[0026] Figure 4 Figure shows the response values of Example 3 to 10 ppm of different gases at the optimal working temperature of 150 °C. Among the five gases, the response value to formaldehyde gas is significantly higher than that to ammonia water, ethanol, trimethylamine, and acetone, indicating that the material has excellent selectivity to formaldehyde. It can realize the identification of formaldehyde existing in organic volatile gases and has broad development prospects in the field of formaldehyde monitoring.

Claims

1. A detection method of a Zn2SnO4 gas-sensitive material sensor for formaldehyde gas, characterized in that The method steps are as follows: (1) Prepare the Zn2SnO4 gas-sensitive material: 1) Weigh zinc chloride and tin tetrachloride pentahydrate and dissolve them in deionized water, stir for 10 min to form a homogeneous solution; subsequently, weigh sodium hydroxide, add it to the above solution, and continue to stir for 10 min to make it disperse evenly; 2) Let the solution in step one stand overnight, centrifuge the obtained product, and wash it 6 times each with absolute ethanol and deionized water alternately; 3) Put the washed reaction product into a drying oven at a constant temperature and dry it at 60 °C for 12 h; 4) Place the dried reaction product in a muffle furnace and calcine it for 2 h in an air atmosphere at 600 - 800 °C to obtain the Zn2SnO4 gas-sensitive material; Use the above material as a gas-sensitive material to fabricate a gas sensor for the detection of formaldehyde gas: 1) Add the above Zn2SnO4 gas-sensitive material to ethanol to make a slurry, and coat it on the outer surface of an Al2O3 ceramic tube with two gold electrodes and four platinum wires; 2) Pass the heating wire through the Al2O3 ceramic tube and weld its two ends to the heating electrodes on the base, and then weld the platinum wire connected to the gold electrode on the ceramic tube surface to the measuring electrode on the base to obtain a gas sensor element; 3) Place the fabricated gas sensing element on an aging table and age it at 150 °C for 48 hours in an air environment; 4) Use a WS-30A gas-sensing tester to test the gas-sensitive characteristics of the sensor, and the test temperature is 25 - 250 °C.

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