Potentiality of Semiconducting Metal Oxide Nanoforms as Solid State Vapor Sensors

Abstract

Nanostructured semiconducting metal oxides have been slotted as the potential material for its applications in gas/vapor sensing systems. During the last couple of decades, extensive efforts have been devoted in maximizing the parameters like sensitivity and selectivity and minimizing the response and recovery times. The efforts are essentially directed towards modification of chemical, dimensional and morphological attributes of the metal oxides. The evolution started with the optimization of particles size and thickness of the thin films, but was accelerated, particularly since last decade, with the incorporation of several unprecedented interesting nanoforms of metal oxides like nanorods, nanowires, nanosheets, nanohollowspheres and nanotubes. It has been established that the vapour/gas sensing characteristics (e.g., operating temperature, sensitivity, response time and recovery time) of the semiconducting oxides improved dramatically if the nanostructure is changed from three dimensional to two dimensional and then to one dimensional. Thus, the domain calls for basketting of the state of knowledge with the contemporary relevance. In view of the above, the present article aims to discuss the underlying mechanisms governing the formation of metal oxide nanoforms under different process routes and correlation of the structural attributes with the semiconducting behavior with special reference to the sensing of acetone vapor. The beginning of the chapter elaborates the necessity of nanoforms in improving the sensing performance with the help of grain surface/boundary model. Subsequently, different semiconducting oxide nanostructure/nanoform (like nanorods, nanowires, nanosheets, nanohollowspheres and nanotubes) synthesis and their sensing properties with emphasis on their respective advantages and bottlenecks have been discussed. The chapter concludes with the salient features of the advancement of oxide nanoform based acetone sensors and predicting the future direction of research.