Controlled synthesis and optical properties of CeO2 nanoparticles by a N2H4.H2O-assisted hydrothermal method

Ceria (CeO₂) nanoparticles were successfully synthesised by a novel hydrothermal synthesis process using Ce(NO₃)₃·6H₂O as cerium source and hydrazine hydrate (N₂H₄·H₂O) as mineraliser. The crystal phases, surface morphology and optical properties of CeO₂ nanoparticles were characterised by X-ray diffraction, scanning electron microscope, UV-vis spectrophotometer and fluorescence spectrometer. The particle size (ranging from 10 to 20 nm) decreases with the increase of N₂H₄·H₂O from 2 to 8 ml and its mechanism has been proposed and can be mainly attributed to the effect of N₂H₄·H₂O on OH^- ionic concentration in the solution. The lattice parameter (~0.54~nm) decreases with the increase of the crystallite size that can be attributed to both lattice relaxation and valence effect of Ce ions. The absorbance in UV light region increases with the increases of N₂H₄·H₂O from 2 up to 6 ml and then decreases when the dosage of N₂H₄·H₂O is 8 ml. The bandgap energy increases from 3.13 to 3.23 eV with the increases of N₂H₄·H₂O from 2 up to 6 ml because of electrostatic potential effect and then decreases to 2.97 eV when the dosages of N₂H₄·H₂O is 8 ml. The emission intensity increases with the increase of N₂H₄·H₂O from 2 ml up to 6 ml and then unobviously decreases when dosage of N₂H₄·H₂O is 8 ml.