Grafting branches and diameter adjustment to nanotubes

Control of channel diameter and branching of a hierarchical tubular nanostructure are two essential operations for fabricating nanotubes into nanodevices such as nanochannels or nanocontainers for applications. Here, we present a thermo-evaporation approach to synthesize branching SiO nanotubes using ZnS and SiO as alternative sources. In this process, ZnS nanowires were first synthesized by Au-catalyzed vapor - liquid - solid growth as templates on which to form amorphous SiO nanotubes via evaporation of the ZnS wire core. A temperature gradient redistributed the Au nanoparticles, which catalyzed the growth of new ZnS wire branches onto the original SiO tube. Successive SiO coating and ZnS core removal would graft new branches to the original tube. The diameter of SiO nanotubes could be postprocessed by electron beam irradiation. The present template growth approach may be applicable to the formation of a nanofluidic channel network for applications in bioanalytical and chemical separations. © 2008 American Chemical Society.