Self-assembly of ZnO nanoparticles into hollow microspheres via a facile solvothermal route and their application as gas sensor

In order to enrich the variety of zinc oxide (ZnO), well-defined ZnO hollow microspheres self-assembled by a mass of nanoparticles were successfully synthesized through a facile solvothermal process employing polyethylene glycol 400 (PEG 400) as the solvent. PEG 400 played a crucial role as a nonionic surfactant in the formation of the ZnO hollow spheres. The plausible formation mechanism was described as self-assembly of nanoparticles, Ostwald ripening, and crystal growth process. The gas sensing performances of the ZnO hollow spheres have been investigated carefully. The results indicate that the prepared ZnO hollow sphere architecture is a promising material for gas sensing applications. In addition, hollow structures have attracted considerable attention because of their unique properties and wide potential applications. The present chemical technique is expected to be useful to prepare other metal oxides or hollow architectures.