Facile template-free hydrothermal fabrication of ZnO hollow microspheres for gas sensing applications

Monodisperse ZnO hollow microspheres (ZnO–HMs) with average diameter about 2 μm and shell thickness about 300 nm were prepared through a facile template-free, glycerol-mediated hydrothermal route. Their structures and morphologies were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and high-resolution transmission electron microscopy (HRTEM). A possible crystal growth and hollowing mechanism were suggested based on the detailed experimental results. Moreover, gas sensors were fabricated based on as-prepared hollow spheres and exhibited high response and good selectivity to ethanol at the optimum working temperature of 380 °C.