NIR-to-blue, green, orange and white up-conversion luminescence in Yb ~(3+)/Tm~(3+)/Er~(3+)/Ho~(3+)-doped Na _(0.5)Gd_(0.5)WO_4 nanocrystals

摘要

Yb~(3+)/Tm~(3+)/Er~(3+)/Ho~(3+)-doped Na_(0.5)Gd_(0.5)WO_4 nanocrystals have been fabricated by a facile hydrothermal method. The blue, green and orange upconversion (UC) emissions coming from Yb~(3+)/Tm~(3+), Yb3+/Er3+, Yb ~(3+)/Ho~(3+) dopant ions are observed in this study. Bright white luminescence upon 980 nm excitation can be produced via the UC process by tuning the dopant ions Yb~(3+)/Tm~(3+)/Ho~(3+), which consists of the blue, green and red UC emissions, and they correspond to the transitions ~1G_4 → ~3H_4 of Tm~(3+), ~5F_4(~5S_2) → ~5I_8, and ~5F_5 → ~5I_8 of Ho~(3+) ions, respectively. The UC mechanisms and temperature dependent UC luminescence were also discussed.