Morphology-controllable synthesis and characterization of CeO2 nanocrystals

CeO 2 nanocrystals with different morphologies were synthesized by adjusting the pH value of the starting solution in water-in-oil microemulsion.The obtained samples were characterized by transmission electron microscopy (TEM),X-ray diffraction (XRD),thermogravimetric analysis and different thermal analysis (TGA/DTA),Brunauer-Emmet-Teller (BET) surface area measurement,ultraviolet-visible absorption (UV-vis) spectroscopy and photoluminescence (PL) spectroscopy.Results show that the morphologies of CeO 2 were transformed from granular to spherical and to rod-like while the pH of the starting solution varied from 5 to 8 and to 11.All samples were indexed to the phase of CeO 2 and Ce(OH) 4,and the molar ratio of CeO 2 to Ce(OH) 4 was deduced to be about 0.25.The morphologies of CeO 2 nanocrystals had but slight influence on their specific surface areas,UV-vis spectra and PL spectra.The band gap energies of different morphological samples were estimated by UV-vis spectroscopic method.