Prospects of spray pyrolysis technique for gas sensor applications-A comprehensive review

Nanostructured materials have been extensively used in various applications such as photocatalytic activity, solar cells, electrochromic devices, batteries, supercapacitors, and gas sensors. Nowadays, many advanced synthesis techniques are available to construct these nanostructured materials, including hydrothermal, atomic layer deposition, spin coating, spray pyrolysis, electroplating, sputtering, and chemical vapour deposition techniques. The spray pyrolysis method is a simple, low-cost, flexible, non-vacuum requirement, applicable on a large scale, extreme productivity, and a scalable continuous aerosol process for fabricating different nano structured materials and thin films. This method efficiently synthesizes multiple metal oxides and chemical compounds with other morphological nanostructures. The effect of controlled deposition parameters includes substrate temperature, flow rate, deposition time, the distance between nozzle and substrate, precursor solution, and carrier gas type on nanostructures' morphology such as nanorods and nanowires, nanospheres, and nano flowers. The morphology of a nanostructured material significantly affects its gas sensing characteristics, including selectivity, sensitivity, response, and recovery times. This review focuses on a detailed discussion of the basic principles and recent advances in the spray pyrolysis method to deposit various nanostructures. Finally, this paper explores the prospects and challenges in spray pyrolysis deposition for gas sensing applications for the future research community.