Tailoring nanobranches in three-dimensional hierarchical rutile heterostructures: a case study of TiO2？SnO2

Abstract

We employed HNO3 as a hydrolysis control agent and developed three-dimensional (3D) hierarchical rutile heterostructures (TiO2-SnO2) with a high-density, uniform, and epitaxial TiO2 nanobranch tailored by a facile CBD method at a low temperature (similar to 50 degrees C). By investigating the influence of acids such as HNO3, HCl, H2SO4, and HCOOH on the formation of TiO2 nanobranches on SnO2 nanobelts (NBs), we demonstrate that the rate of crystal growth can be promoted by HNO3 and that the poor ligand affinity of NO3- and the total charge variation of the Ti complex by H+ alter the precipitation rates, eventually controlling the length of the TiO2 nanorods. Additionally, it was found that short and long TiO2 nanorods were generated via the mechanism of diffusional- and reaction-controlled growth under moderate and high concentrations of HNO3, respectively. TiO2 nanorods grew epitaxially along the [001] direction on all four sides of SnO2 NB like the spokes of a wheel. This was attributed to the minimization of surface energy and lattice mismatch. This facile, surfactant-free, and low-temperature synthetic strategy may provide an alternative route for fabricating uniform and length-controlled nanobranches in 3D heterostructures.