A simple one-step solvothermal synthesis of hierarchically structured ZnO hollow spheres for enhanced selective ethanol sensing properties

A simple one-step solvothermal method, using ethanolamine as solvent without any additives except zinc source, has been employed to synthesize hierarchically structured ZnO hollow spheres consisting of numerous orderly and radical nanorods with diameter of several tens nanometers and length of 2–3 μm. The ethanolamine and the solvothermal process play the critical role in the synthesis of the ZnO hollow spheres by the primary formation of ZnO crystal nucleus and subsequent transformation into nanorods, which self-assemble into hollow spheres. The morphology and structure of the spheres have been characterized by transmission electron microscopy, field emission scanning electron microscopy, X-ray powder diffraction, high-resolution transmission electron microscopy, and Brunauer–Emmett–Teller N₂ adsorption–desorption analyses. The results also indicate that the sensor based on the prepared ZnO hollow spheres exhibit good ethanol sensing performance, which can be attributed to its structural defects and high surface-to-volume ratio that significantly facilitate the absorption of oxygen species and diffusion of target gas. Besides, the sensor shows high selectivity to ethanol because ZnO as a basic oxide is favored for dehydrogenation of ethanol.