A new route to self-assembled tin dioxide nanospheres: Fabrication and characterization

Nearly monodispersed self-assembled tin dioxide (SnO₂) nanospheres with intense photoluminescence (PL) were synthesized using a new wet chemistry technique. Instead of coprecipitating stannous salts, bulk tin (Sn) metal was oxidized at room temperature in a solution of hydrogen peroxide and deionized water containing polyvinylpyrrolidone (PVP) and ethylenediamine (EDA). SnO₂ nanocrystals were produced with diameters of ∼3.8 nm that spontaneously self-assembled into uniform SnO₂ nanospheres with diameters of ∼30 nm. Analysis was performed by X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, high-resolution transmission electron microscopy, selected area electron diffraction, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, UV-vis absorption spectroscopy, PL spectroscopy, and fluorescence lifetime measurements. The SnO₂ nanospheres displayed room-temperature purple luminescence with an intense band at 394 nm (∼3.15 eV) and a high quantum yield of ∼ 15%, likely as a result of emission from the surface states of SnO₂/PVP complexes. The present study could open a new avenue to large-scale synthesis of self-assembled functional oxide nanostructures with technological applications as purple emitters, biological labels, gas sensors, lithium batteries, and dye-sensitized solar cells.