A general method for mass and template-free production of hierarchical metal oxide spheres at room-temperature

Hierarchical metal oxide spheres (HMOS) have various applications that stem from their special architectures. Here a novel template-free method is developed for mass fabrication of HMOS at room temperature. It is only composed of the facile processes of PEG modification and self-assembly (PMSA). Its powerful fabrication capability is demonstrated by fabricating HMOS of TiO2, Fe2O3, ZrO2 and their mixtures with high quality. The related mechanism is investigated and the peculiar PEG configuration on the surface of the nanoparticle is believed to be the origin of the HMOS formation. Several possible applications of HOMS are also exhibited, such as the superhydrophobic properties, the enhanced light scattering ability and the improved solar cell performance. Considering the unique fabrication abilities and industrial mass production potentials, this method may be used as a powerful tool for the synthesis of HMOS with extended applications.