Intermediate Ce3+ defect level induced photoluminescence and third-order nonlinear optical effects in TiO2-CeO2 nanocomposites (Publication with Expression of Concern. See vol. 123, 2017)

We report on the linear and nonlinear optical studies of TiO2-CeO2 nanocomposites. It was found that the band gap of the nanocomposite can be tuned by varying Ce/Ti content. Nonlinear absorption characteristics of these samples were studied by employing open aperture Z-scan technique using an Nd:YAG laser (532 nm, 7 ns, 10 Hz). It has been observed that as the CeO2 amount increases, band gap of the nanocomposites decreases and the reason proposed for the change in band gap is the smudging of localised states of Ce3+ into the forbidden energy gap, thus acting as the intermediate state. Fluorescence studies confirmed the above argument. Nonlinear investigation revealed that with increase in the CeO2 amount, the two-photon absorption coefficient increased due to the modification of TiO2 dipole symmetry. Suitable candidature of the nanocomposites for the fabrication of nonlinear optical devices was proved by determining the optical limiting threshold.