General Synthesis and Gas-Sensing Properties of Multiple-Shell Metal Oxide Hollow Microspheres

摘要

Hollow spheres with nanometer-to-micrometer dimensions, controlled internal structure, and shell composition have attracted tremendous attention because of their potential application in catalysis, drug delivery, nanoreactors, energy conversion and storage systems, photonic devices, chemical sensors, and biotechnology.Single-shell and double-shell hollow spheres of various compositions have been synthesized by a number of methods, such as vesicles, emulsions, micelles, gas-bubble, and hard-templating methods. More recently, efforts have focused on the fabrication of hollow spheres with multiple shells, as these materials are expected to have better properties for applications such as drug release with prolonged release time, heterogeneous catalysis, lithium-ion batteries, and photocatalysis. For example, multiple-shell hollow microspheres of Cu2O have been prepared by vesicle templating and an intermediate-templating phase-transformation process. Multiple-shell azithromycin hollow microspheres were fabricated by hierarchical assembly.Cao and co-workers reported the synthesis of triple-shelled SnO2 hollow microspheres by chemically induced self-assembly in the hydrothermal environment which exhibited enhanced electrochemical performance. Yao and co-workers reported excellent cycle performance and enhanced lithium storage capacity of multiple-shell Co3O4 hollow microspheres synthesized by oriented self-assembly. These preparative methods, however, are suited for each specific material and cannot be applied generally to a wide range of materials. Currently, there is no general synthetic approach for fabricating multiple-shell hollow nanostructures of any desired material.