Processing and Characterization of Nanostructured Metal Oxides for Gas Sensing Applications

Abstract

Nanoscience and nanotechnology involve materials and systems with at least one dimension in the range of 1-100nm that exhibit novel and size-dependent properties. This article reviews the main processing techniques used to fabricate nanomaterials, ranging from sol-gel to vapor deposition to electrospinning. Emphasis is given to metal oxide nanostructures, such as SnO₂ nanoribbons and MoO₃ nanowires. Their electronic properties and their gas detection behavior are presented and discussed. The high surface-to-volume ratio of metal oxide nanostructures has been exploited to develop gas sensors with higher stability, faster response, and higher sensitivity to the analytes of interest than their conventional counterparts. Commonly observed p-n type transition phenomena in nanostructured metal oxides are explained on the basis of the sensing mechanism involved in gas detection by semiconducting oxides and the size-related effects of nanomaterials in the concentration of free charge carriers. Insights are given on the future challenges in resistive gas sensing and how nanotechnology may be helpful in overcoming these burdens