Yb3+-sensitized upconversion and downshifting luminescence in Nd3+ ions through energy migration.

A core-shell-shell nanostructure composed of NaGdF4:Yb/Tm@NaGdF4:Nd@NaYF4 is developed to realize Yb3+-sensitized upconversion and downshifting luminescence in Nd3+ ions. The unusual photon conversion property stems from a gadolinium sublattice mediated Yb3+→ Tm3+→ Gd3+→ Nd3+ energy transfer pathway. The energy transfer processes are investigated by varying the dopant concentration and distribution, in conjunction with time decay measurements.