One-pot synthesis and optical properties of Eu 3+ -doped nanocrystalline TiO 2 and ZrO 2

A simple and versatile one-pot sol–gel synthesis of Eu 3+ -doped nanocrystalline TiO 2 and ZrO 2 nanomaterials is reported in this paper. It consists of the controlled crystallization of Eu 3+ -doped TiO 2 or ZrO 2 nanoparticles from an initial solution containing the metal alkoxide, the lanthanide precursor, a complexing agent and a non-complexing acid. The main interest is that it could be extended to different lanthanide ions and inorganic metal oxides to prepare other multifunctional nanomaterials. The characterization by XRD, HRTEM and SAED techniques showed that the TiO 2 and ZrO 2 crystallization takes place at very low temperatures (60 °C) and that the crystallite size can be tailored by modifying the synthetic conditions. The optical properties of the resulting materials were studied by emission spectra and decay measurements. Both Eu 3+ :TiO 2 and Eu 3+ :ZrO 2 samples exhibited long lifetime values after removing organic components (τ = 0.7 and 1.3 ms, respectively), but the Eu 3+ :ZrO 2 system is specially promising for photonic applications since its τ value is longer than some reported for other inorganic or hybrid matrices in which Eu 3+ ions are complexed. This behaviour has been explained through an effective dispersion of the lanthanide ions within the ZrO 2 nanocrystals.