Tri-color upconversion luminescence of Rare earth doped BaTiO3 nanocrystals and lowered color separation

Upconversion tri-color luminescence of Er(3+)/Tm(3+)/Yb(3+) doped BaTiO3 nanocrystals is observed under the excitation of a 980 nm laser diode. Especially, Er(3+) emission has a considerable contribution to the blue portion of the UC spectra, different from the ever-reported results, in which blue emission originates only from Tm(3+). This realization is beneficial to lower the color separation between blue and green (or red) emissions, in fluorescent labeling. The analysis of excitation power dependence and decay time revealed that blue emission of Er(3+) ion is induced by a dual energy transfer upconversion, while Tm(3+) plays a role of both emitter and activator.