Color-tunable nanophosphors by co-doping flame-made Y₂O₃ with Tb and Eu

Rare-earth phosphors with tunable optical properties are used in display panels and fluorescent lamps and have potential applications in lasers and bio-imaging. Here, non-aggregated Y₂O₃ nanocrystals either doped with Tb³⁺ (1-5 at%) or co-doped with Tb³⁺ (2 at%) and Eu³⁺ (0.1-2 at%) ions are made in one-step by scalable flame spray pyrolysis. The morphology of these nanophosphors is investigated by X-ray diffraction, electron microscopy and N₂ adsorption while their optical properties are monitored by photoluminescent spectroscopy. When yttria nanocrystals are doped with terbium, a bright green emission is obtained at an optimum Tb-content of 2 at%. When, however, europium is added, the emission color of these Tb-doped yttria nanophosphors can be tuned precisely from green to red depending on the Tb/Eu ratio. Furthermore, energy-transfer from Tb³⁺ to Eu³⁺ is observed, thus allowing the control of the excitation spectra of the co-doped nanophosphors.