Hollow Silica Nanotubes for Space-Confined Synthesis of Noble Metal Nanorods and Nanopeapods

Realizing precise control over the size and functionality of nanomaterials is a prerequisite to their diverse applications in the areas of biology, environment, energy, and other emerging nanotechnologies. Herein, we demonstrate a general template strategy capable of fabricating functional noble metallic nanorods and nanopeapods. The templates are hollow silica nanotubes (HSNTs) produced from unimolecular micelles of bottlebrush copolymers. The variation of chain length and chemical composition of bottlebrush copolymers achieved through the reversible-deactivation radical polymerization dictates the length (L), inner diameter (D), and thickness (h) of HSNTs. Using such HSNTs as nanoreactors enables the fabrication of noble metals such as Au, Ag, and Pt nanorods or nanopeapods with silica shells in a space-confined manner. While the thickness and the interior space of HSNTs regulate the diffusion and intake of metal ion precursors, the formation of nanorods or nanopeapods with different lengths and diameters is well controlled. Upon etching out the silica shell, the resulting metallic nanorods are readily functionalized with polymeric ligands for excellent dispersity in aqueous and/or organic media. This feasible and versatile strategy represents a great leap forward in the controlled synthesis of one-dimensional metallic nanomaterials and hopefully promotes understanding their structure-determined physiochemical properties and board applications in medicine and catalysis.