Fabrication of a highly flexible low-cost H2 gas sensor using ZnO nanorods grown on an ultra-thin nylon substrate

Abstract

A “highly flexible low-cost” H2 gas sensor was fabricated via inclined and vertically well-aligned ZnO nanorods on a “cheap, thin (15 µm), and highly flexible” nylon substrate using the hydrothermal method. Morphological, crystallinity, and optical properties of the prepared ZnO nanorods were studied by field emission scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray analysis, X-ray diffraction, and photoluminescence measurements. Results revealed the formation of aligned hexagonal-like nanorods with high aspect ratio and density. The results confirmed the formation of würtzite ZnO phase with a preferred orientation along the (002) direction with high crystallinity, excellent quality, and few defects. The sensitivity and response time behaviors of the ZnO-based gas sensor to hydrogen gas at different operation temperatures and in various hydrogen concentrations were investigated. Under 500 ppm of H2 exposure at different temperatures from room temperature to 180 °C, the sensitivity increased from 109 to 264 %. When the exposed H2 gas increased from 750 to 2000 ppm at a fixed temperature of 75 °C, the sensitivity also sharply increased from 246 to 578 %. Moreover, both the response and recovery time of the device during both tests were enhanced. The hydrogen gas sensing mechanisms of ZnO nanorods in low and high operation temperatures were discussed.