Investigations on the performance of nanotechnology based dynamic metal oxide gas sensor devices

Abstract

newline In recent years, the development of gas sensors for the detection of dangerous and combustible gases has become crucial due to uncertainty around environmental pollution and industry safety laws. Gas sensing devices obtained with semiconductor nanostructures of metal oxides (such as SnO2, TiO2, ZnO) or metal sulphides (SnS, CdS) have presumed greater significance due to their abundant availability, tunable properties, durability, excellent responses, and the ability to control and customize their chemical, electrical and interaction with the target gas molecules properties. Oxides like SnO2 and ZnO, possesses oxygen vacancies, n-type conductivity and enriched surface area with dangling bonds at nanoscale, suitable for interacting with the gaseous molecules . ZnO has been employed as a sensing material extensively, particularly because of its inexpensive cost, high sensitivity, rapid reaction, and quick recovery. ZnO nanomaterial-based gas sensors have been developed to address the industrial and automobile exhaust gases sensing such as NOx, SOx and also the gaseous molecules present in the breath such as hydrogen sulphide and acetone, as a non-invasive medical diagnostic device. ZnO forms extraordinarily strong exciton-binding structure known as wurtzite (60 meV), which has a wide band gap (3.37 eV). However, ZnO nanostructure also possess disadvantages including relatively low gas sensitivity and need for operating temperature, typically 300 °C to 450 °C, which is very high in practical applications. To address the drawbacks, a variety of investigations and methods, including doping, crystal structural modifications and nano-sizing, have been explored.