(Invited) Highly Selective Detection of Propanol and Ethanol Gas Sensing Characteristics of SnO2/NiO and SnO2/NiO/Au Hollowspheres Based Chemiresistive Sensors

Introduction The enormous market demands for gas sensors to detect and monitor volatile organic compounds (VOCs) and toxic gases in environmental protection, medical treatment and safety requirements of industry and daily life have motivated enormous awareness in the fabrication of high performance gas sensing materials. Generally, VOCs are considered as low boiling point carbon-comprising materials that can evaporate simply at room temperature and contribute in atmospheric photochemical reactions, such as photochemistry smog and ozone formation. Besides, controlling and detection of these VOCs, such as methanol, ethanol, propanol and acetone is significant because they are considered as widespread concerns for common pollutants in indoor/outdoor air quality and for testing alcohol levels of drivers [1]. In comparison to other VOCS, propanol is less toxic, nonetheless its usage for numerous daily applications, for example hand sanitizer, cosmetics, may be imagined to be polluting the breathing air. Besides, Iso-propanol was presented to behave as an aesthetic and central nervous system sedative, leading in symptoms that can frighten the mental ability of the individual [2]. Yet, the fabrication of the anticipated gas sensor with superior sensitivity, low detection limit, and exceptional long-term stability is still a significant research issue. In addition, the high operating temperatures and poor selectivity often limits the application and commercialization of semiconductor metal oxide (SMO) gas sensors. Thus, this work is directed to improve the selective, sensitivity, stability and to reduce the operating temperatures of the metal oxides based sensors, by exploiting SnO2 hollowspheres loaded with various NiO nanoparticles contents and SnO2/NiO loaded with various Au nanoparticles contents synthesized using a simple hydrothermal method. Our findings showed improved stability upon loading SnO2 hollowspheres with various NiO contents. Amongst the various NiO contents, the 0.01 wt.% NiO loaded SnO2 demonstrated higher response and sensitivity towards propanol (C3H7OH) in dry air and in the presence of 40 and 60 % RH at an operating temperature of 150 °C. While the as-fabricated SnO2/NiO/Au (2.5 wt.%) based sensor exhibited a response that is more than 2 times higher in comparison to that of SnO2/NiO (0.01wt. %) and lower operating temperature 75 °C towards ethanol (C2H5OH) and C3H7OH. The long-term stability analyses established that both the fabricated Sn