Characterization and optical properties of pole-like nano-CeO2 synthesized by a facile hydrothermal method

CeO2 nanopoles have been successfully synthesized by a hydrothermal method using CeCl3·7H2O as cerium source, NaOH as mineralizer, and ethylenediamine as complexant. The pole-like nano-CeO2 was examined by XRD, TEM, XPS, UV-vis, PL, and Raman scattering. The results show that the crystallinity of the nanopoles is not so good, and the main valence of cerium is +4. The estimated direct band gaps are 3.014, 3.099, 2.931, and 2.927 eV for the samples synthesized within 2, 18, 50, and 100 h, respectively. These band gaps are smaller than bulk CeO2, oxygen vacancies and Ce3+ ions result in an effective red shifting of the band gap. The visible luminescence exhibits similar emission peaks of room temperature photoluminescence and the emission intensity increases with the increase of concentration of oxygen vacancies and Ce3+ ions.