Core–shell structure of zinc oxide/indium oxide nanorod based hydrogen sensors

A simple method is used to produce a new zinc oxide/indium oxide (ZnO/In2O3) core–shell nanorod (CS-NR) based hydrogen sensor. ZnO NRs are first formed using the aqueous chemical process and are covered with a shell of In2O3 nanoparticles (NPs) by a combination of sputtering (for 5, 10, 15, 20 and 30 min) and low temperature thermal oxidation (at 200 °C). SEM, XRD and UV–visible spectroscopy are used to analyze surface morphology, chemical composition and optical properties. The pristine ZnO NR sensors and ZnO/In2O3 CS-NR sensors are then measured for hydrogen response in concentrations from 5 to 500 ppm at room temperature. It is found that the hydrogen response for all the ZnO/In2O3 CS-NR based hydrogen sensors is almost 2 or 3 times higher than that of the pristine ZnO NRs sensors (7.6%, at 500 ppm). It is noted that the ZnO/In2O3 CS-NRs with a continuous and well-distributed In2O3 NPs (24 nm) shell layer exhibits the best response for hydrogen sensing (20.5%, at 500 ppm).