Monitoring And Analysis Of Indoor Gas By Semiconductor Metal Oxide Sensor

In recent years,with the growing attention to environmental problems and the increase of the standard of living,there are imperative needs for gas sensors with high sensitivity and excellent selectivity for monitoring toxic and combustible gas.Metal oxide semiconductors based gas sensors have been intensively studied due to low cost and excellent gas sensing performances.The gas sensing performance of the gas sensor depends on the characteristic of the sensitive material.therefore,it is always a key and difficult point to prepare high-performance gas-sensitive materials in the research of semiconductor gas sensors.In this work,the properties of gas-sensing materials were studied by regulating and controling the morphology and structure of gas-sensing materials aiming at preparing high-performance gas-sensitive materials.The main research achievements are summarized as follows:?1?Chemiresistive gas sensors employing p-n heterostructures offer a compelling combination of high sensitivity and specific selectivity due to the synergic effects at interface.In this study,the p-Co₃O₄/n-SnO₂ composites with different molar ratio of Co/Sn have been prepared using a simple soak-calcination method and their sensing properties are systematically investigated.The sensors demonstrate exclusive H₂ sensing properties,which show an n-type sensing response to the typical reducing gases such as CO,H₂S and NH₃,but the sensor resistance increased under exposure to H₂ which suggest a p-type sensing response toward H₂.We propose that the abnormal sensing behaviors might be associated with the modulation of potential barrier heights formed in p-Co₃O₄/n-SnO₂ heterojunctions,namely the modulation from the asymmetric gas sensing reactivity of SnO₂ and Co₃O₄ to the reducing gases.This study may open up a general approach for tailoring the sensing selectivity of gas sensors by modulation of potential barrier heights in p-n heterojunctions utilizing the asymmetric gas sensing reactivity of heteromaterials.?2?It was studied that the NH₃ sensing properties of Ag₃PO₄ nanomaterials at room temperature.There are a lot of reports about Ag₃PO₄ as a photocatalyst,but there are few reports regarding its use as the gas-sensitive material.In this study,the nanotubes and nanoparticles Ag₃PO₄ nanomaterials in two different morphologies have been prepared using ion exchange method and solid phase grinding method,and their sensing properties are systematically investigated.Compared with Ag₃PO₄ nanotube gas sensor,the results showed that Ag₃PO₄ nanotubes exhibit higher sensitivity and better selectivity to NH₃ gas at room temperature,and detection limit as low as 10 ppm.This work laid the foundation for studying the room temperature sensing mechanism of Ag₃PO₄ gas sensors and the effect of morphologies on the sensing reactivity of Ag₃PO₄.