Salt-assisted deposition of SnO 2 on α-moO 3 nanorods and fabrication of polycrystalline SnO 2 nanotubes

Abstract

Rutile-like tin dioxide (SnO 2; tetragonal symmetry) is a strategic material for a wide range of important applications. Although numerous methods have been developed for preparations of SnO 2 nanoparticles, nanowires, and nanorods, there has been no rational synthetic method reported to prepare this functional material into tubular nanostructures. In this article, we describe a facile template method for synthesis of free-standing polycrystalline SnO 2 nanotubes in aqueous solution. With soluble α-MoO 3 nanorod templates, polycrystalline SnO 2 can be first deposited under normal atmospheric pressure (room temperature to 100°C) or hydrothermal conditions (180°C). In particular, salt additives such as Na 2SO 4 have been proven to be indispensable for the deposition of SnO 2 skins. Various preparative parameters have been examined in detail, and dissolution modes of α-MoO 3 have also been investigated to address the formation mechanism. The optical band gap determined for the nanotubes is 3.92 eV (for crystallites with an average size of ∼4 nm). This salt-assisted "one-pot" method promises large-scale production of polycrystalline SnO 2 nanotubes with both structural engineering and crystallite size control.