Ceramic materials and nanostructures for chemical sensing

Abstract

High selectivity, enhanced sensitivity, short response time and long shelf-life are some of the key features sought in the solid-state ceramic-based chemical sensors. Since the sensing mechanism and catalytic activity are predominantly surface-dominated, benign surface features in terms of higher aspect ratio, large surface area and, open and connected porosity, are required to realize a successful material. In order to incorporate these morphological features, a technique based on rigorous thermodynamic consideration of the metal/metal oxide coexistence, is described. By modulating the partial pressure across the equilibrium M/MO proximity line, formation and growth of new oxide surface on an atomic/ submolecular level under conditions of oxygen deprivation , with exotic morphological features has been achieved in a number of metal oxides that are potential sensor materials. This paper describes the methodology and discusses the results obtained in the case of two model systems, viz., tungsten oxide (WO 3 ) and titanium oxide (TiO 2 ).