Bandgap modification of titanium dioxide doped with rare earth ions for luminescent processes

Yttrium oxide nanostructures doped with erbium and ytterbium ions were incorporated into a titanium dioxide (TiO2) host by a hydrothermal method to modify the bandgap of TiO2. The samples were prepared with different concentrations of nanophosphors (Y2O3: Er3+-Yb3+). Then, the samples were characterized by x-ray diffraction (XRD), transmission electron microscopy (TEM), diffuse reflectance spectroscopy (DRS), x-ray photoelectron spectroscopy (XPS), and photoluminescence spectroscopy. The XRD analysis revealed the mixture of anatase and rutile crystal structures for all the samples. The TEM measurements showed agglomerated particles with a spherical shape of around 50 nm. TiO2 doped with a high concentration of Y2O3:Er3+-Yb3+ exhibited a strong visible upconversion luminescence under the excitation of 980 nm (infrared laser) as compared to other samples. Photoluminescence studies revealed the green (522 nm), yellow (563 nm), and red emissions (661 nm) corresponding to 2H11/2 → 4I15/2, 4S3/2 → 4I15/2, and 4F9/2 → 4I15/2 transitions of Er3+ in Y2O3:Er3+-Yb3+@TiO2 nanophosphors, respectively. Furthermore, DRS and XPS analyses revealed that Y2O3:Er3+-Yb3+ modified the bandgap of the TiO2 host.