Zinc oxide nanowire gas sensors: fabrication, functionalisation and devices

With the progress in the synthesis of high quality ZnO nanowires, their implementation as gas sensors has gained popularity. Relying on the surface ionosorption, these devices have demonstrated exquisite sensitivity with further improvement achieved through various functionalisation methods. Both resistive and transistor based methodologies are employed for gas sensing while integration of micro-heaters has also been attempted for portability of the devices. In order to achieve successful inclusion amongst semiconductor fabrication processes, top-down approaches are being explored along with conventional bottom-up synthesis routes. Major challenge of low selectivity can be overcome by Electronic Nose systems. This article reviews the progress in synthesis, functionalisation, and device implementation of ZnO nanowire gas sensors, concluding with remarks on associated challenges and future prospects.