Preparation and spectroscopy study of monodispersed metal oxide nanocrystals

SnO2 nanocrystals with an average particle size of 3.5 nm are obtained by heating the mixture of hydrous SnO2 nanoparticles and SrCO3 particles. SrCO3 can be removed from the product by washing with diluted HNO3 acid. A series of SnO2 nanocrystal samples with different particle size are prepared by heating at different temperature. All the samples obtained are characterized by XPS and Raman spectra. XPS result shows that the binding energy of Sn3d5/2 decreases as the particle size increases. There is a surface-related Raman peak observed, which increases in intensity when the SnO2 particles size decreases. The size-related change of the surface structure is responsible for the properties of nanocrystals.