Sol-gel synthesis and photoluminescent properties of metal oxide-metal oxide coupled nanocomposites

Tin oxide (SnO2) and zinc oxide (ZnO) coupled metal-oxide nanocomposites or SnO2-ZnO were prepared using a sol-gel method. The stretching mode frequencies and crystal structures were examined by using Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD), respectively. The microscopic analyses by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) showed a flower-like morphology of the nanocomposites. The analysis of surface chemical and electronic states was conducted by X-ray photoelectron spectroscopy (XPS). The band gap energies as confirmed from the ultraviolet-visible spectroscopy (UV-Vis) data were found to be larger than those of the bulk band gaps due to the increase between energy levels associated with smaller particle sizes. The UV (380 nm) and orange (595) photoluminescence (PL) emissions observed from the SnO2:ZnO nanocomposites were attributed to a combinatorial contribution from radiative transitions in SnO2 and ZnO components. The proposed mechanisms of these emissions are discussed.