Controlled growth of oxygen-deficient tin oxide nanostructures via a solvothermal approach in mixed solvents and their optical properties

SnO2 nanostructures such as flower-like nanorod clusters, nanorods with arc or ring hierarchical structures, and individual nanorods were obtained via a solvothermal approach in mixed solvents of ethylenediamine and distilled water. By just simply adjusting growth parameters such as the volume ratio of the two kinds of solvents and dosage of NaOH, the size and hierarchical structures of SnO2 crystals could be easily varied. X-ray diffraction patterns revealed the as-prepared products to be pure tetragonal SnO2 with rutile structure. The energy-dispersive x-ray spectroscopy analysis displayed evidence of nonstoichiometry, indicating that a high concentration of oxygen vacancies exist in the nanorods. High-resolution transmission electron microscopy images revealed that the obtained nanorods exhibited preferential growth along [1 (1) over bar 2] and many structural defects existed in the nanorods. The crystal growth mechanism of the SnO2 nanostructures is discussed. Their size-dependent optical properties including UV-vis absorption spectra and room-temperature photoluminescence spectra were also studied.