Controlled synthesis of monodisperse sub-100 nm hollow SnO_2 nanospheres: A template-and surfactant-free solution-phase route, the growth mechanism, optical properties, and application as a photocatalyst

摘要

Controlled synthesis of low-dimensional materials, such as nanoparticles, nanorods, and hollow nanospheres, is vitally important for achieving desired properties and fabricating functional devices. We report a systematic investigation of the growth of low-dimensional sub-100 nm SnO_2 hollow nanostructures by a mild template-and surfactant-free hydrothermal route, aiming to achieve precise control of morphology and size. The starting materials are potassium stannate and urea in an ethylene glycol (EG)/H_2O system. We found the size of the SnO_2 hollow nanospheres can be controlled by simply adjusting the urea concentration. Investigation of the mechanism of formation of the SnO_2 hollow nanospheres revealed that reaction time, urea concentration, and reaction temperature make significant contributions to the growth of hollow nanospheres. On switching the solvent from EG/H_2O to H_2O or ethanol, the SnO_2 nanostructures changed from nanospheres to ultrafine nanorods and nanoparticles. On the basis of reaction parameter dependent experiments, oriented self-assembly and subsequent evacuation through Ostwald ripening are proposed to explain the formation of hollow nanostructures. Their size-dependent optical properties, including UV/Vis absorption spectra and room-temperature fluorescence spectra, were also studied. Moreover, the studies on the photocatalytic property demonstrate that the fabricated hollow structures have slightly enhanced photocatalytic degradation activity for rhodamine B when exposed to mercury light irradiation compared to solid SnO_2 nanospheres under the same conditions. The synthesized tin oxide nanoparticles display high photocatalytic efficiency and have potential applications for cleaning polluted water in the textile industry.