ZnO Nanostructures-Based Resistive Gas Sensors: Sensing Mechanism and Sensor Response Enhancement Approaches

Abstract

There has been significant research in metal oxide semiconductors-based gas sensors for making energy-efficient, reliable, and cost-effective sensors. Real-time monitoring and early finding of explosive and lethal gases are among the utmost requirements in the domestic and industrial sectors. Zinc Oxide (ZnO) semiconductor material is considered an efficient material for resistive gas sensor fabrication. Although the requirement of high operating temperature for resistive gas sensor’s limits its effectiveness, durability, is less energy-efficient, and increases the risk of explosions. The development of ZnO nanostructures-based sensors can demonstrate high sensor response, selectivity, low temperature, and durability. In this chapter, the fundamentals of a resistive gas sensor with a sensing mechanism have been studied. Enhancement in sensor response with low operation temperature, ZnO surface modification approach (thick film to nanostructures) is essential in this chapter. Much more consideration has been given to fabricate energy-efficient ZnO nanostructures-based gas sensors using various approaches, mainly including the functionalization of ZnO nanostructures (doping and metal nanoparticle decorations), p-n heterojunctions, decoration with 1-D carbonaceous materials and UV activation. A detailed discussion of the sensing mechanism of ZnO nanostructures-based gas sensors has been given.