Research On Gas Sensing Performance Of Indium-Based Semiconductor Materials And Signal Processing Of Gas Sensors

Gas sensors are widely used in many fields including atmospheric environment monitoring,enterprise safety production monitoring,indoor pollution gas detection,disease diagnosis and so on.There are many types of gas sensors in the market.Due to their advantages such as low manufacturing cost,easy integration and high sensitivity,semiconductor gas sensors represented by metal oxide semiconductor materials have attracted extensive attention from researchers and a lot of research has done.This thesis mainly studies on the preparation of indium-based semiconductor nanomaterials,gas-sensing performance testing,and signal optimization of gas sensor devices.The specific research work is as follows:(1)Using indium isopropoxide and concentrated hydrochloric acid as raw materials,pure InOCl nanosheet materials were prepared by the sol-gel method following high-temperature calcination and were used as gas sensing material to detect different gases.Our research found that this material has a good response to formaldehyde gas.Under the optimal working temperature of 200?,the highest response of 45 to 50 ppm HCHO was obtained for the sensor based InOCl,and it has good selectivity compared with acetone,ethanol,benzene,toluene.At the same time,humidity has a great influence on the gas-sensing performance of the material.At the same concentration,the sensitivity under high humidity environment(?80%)is only one-eighth compared with low humidity environment(?20%).The reason why the material has high gas sensitivity is that InOCl is rich in oxygen vacancy defects.(2)Using indium chloride and ammonia as raw materials,indium oxide nanomaterials were prepared by precipitation method and subsequent high-temperature calcination,its high specific surface area is 128.9 m2·g-1.The gas-sensing performances of samples prepared at different calcination were obtained.it was found that with a concentration of 50 ppm HCHO,the samples prepared at 300?had the highest response of 30,which was caused by the difference in specific surface area.The largest specific surface area makes the best formaldehyde gas-sensing performance.The materials were treated in different atmospheres,and it was found that although the specific surface area of the oxygen-treated material did not change much,the sensitivity decreased.This can be attributed to the reduction of oxygen vacancy defects in the material itself when the oxygen is sufficient;The surface area decreased significantly after hydrogen treatment,so the sensitivity also decreased(3)The field effect transistor(FET)amplifier circuit was used to optimize the signal of the gas sensor.The relationship between the magnification of the FET amplifier circuit and the measured voltage was studied.In the range of 2.5?10 V,the corresponding magnification was 4?11 times.The circuit was further optimized and toluene as the equivalent,a total volatile organic compounds(TVOCs)tester was made to explore preliminarily its practical application.