Ammonia gas detection by solution combustion-processed pristine & Ti-doped ZnO transparent films: a reverse effect of doping on gas response

In this contribution, pure, polycrystalline wurtzite crystal structured, spin-coated pristine ZnO and Ti-doped (1, 2, and 3 wt%) ZnO transparent films were accomplished at 400 °C through a facile solution combustion synthesis method. Crystallinity, roughness, and porosity in the pristine film were relatively higher than in the doped films. The demonstrated films were transparent, with ~ 70 to 90% in the visible region. The room temperature detection of ammonia (NH₃) gas (25–100 ppm) was recognized in all the films. The pristine film revealed a superior gas response at every concentration of NH₃ gas in contrast to all the doped films; it is probably due to comparatively high crystallinity, porosity, more oxygen vacancy concentration (1.788), and high fraction of adsorbed oxygen (20.55%). The film exhibited the highest gas response of 34.7 at 100 ppm of NH₃ gas and a limit of detection of ~ 10.7 ppm with superior selectivity towards NH₃ gas. Although doping enhanced the transparency but diminished the NH₃ gas response due to the combined effect of deterioration in the mentioned properties achieved in pristine film.