Synthesis and characterization of ZnO/SnO2 nanorods core–shell arrays for high performance gas sensors

In this work, three samples were synthesized; SnO2 nanoparticles, ZnO nanorods and ZnO/SnO2 core–shell nanorods. The preparation of the ZnO/SnO2 composite included two steps, the first was to spin ZnO thin film as a seed layer. The second step is to grow ZnO/SnO2 to produce core–shell nanorod devices. The structure and morphology of the prepared samples were characterized by X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM). Meanwhile, the optical properties were investigated by ultraviolet–visible (UV–Vis) and photoluminescence (PL) spectroscopy. The morphology of the prepared sample revealed that ZnO nanorods were capped by SnO2 shell. The energy band gap of ZnO/SnO2 is lower than that of both bare ZnO and SnO2. Evaluations to near-band (PL) emission of bare ZnO nanorod arrays were considerably reduced by capping with SnO2 sell. The performance of the gas sensor was further examined on the basis of ZnO/SnO2. The response and sensitivity were measured to be 86.6 ( ± 0.5) at optimum operating temperature of 225 °C toward 100 ppm ethanol vapor, which is even higher than those of the bare ZnO nanorods. The local sites added by the SnO2 shell layer could probably stop the excitons from becoming captured by intrinsic defects, leading to improved sensitivity of the gas sensor.