No abstract

A simple and facile sonochemical route has been demonstrated for the shape-selective preparation of highly crystalline ZnO nanostructures, such as nanorods, nanocups, nanodisks, nanoflowers, and nanospheres. The concentration of precursor chemicals, the kind of hydroxide anion-generating agents, the ultrasonication time, and the use of a capping agent are key factors in the morphological control of ZnO nanostructures. This method is fast, simple, convenient, economical, and environmentally benign. On the basis of our shape-control of the ZnO nanostructures by the sonochemical technique, growth mechanisms of ZnO nanostructures were also proposed. We believe this technique will be readily adopted in realizing other forms of various nanostructured materials.

We report mesoporous composite materials (m-GeO2, m-GeO2/C, and m-Ge-GeO2/C) with large pore size which are synthesized by a simple block copolymer directed self-assembly. m-Ge/GeO2/C shows greatly enhanced Coulombic efficiency, high reversible capacity (1631 mA h g(-1)), and stable cycle life compared with the other mesoporous and bulk GeO2 electrodes. m-Ge/GeO2/C exhibits one of the highest areal capacities (1.65 mA h cm(-2)) among previously reported Ge- and GeO2-based anodes. The superior electrochemical performance in m-Ge/GeO2/C arises from the highly improved kinetics of conversion reaction due to the synergistic effects of the mesoporous structures and the conductive carbon and metallic Ge.