Sc³⁺-induced morphology, phase structure, and upconversion luminescence evolution of YF₃:Yb/Er nanocrystals

The increasingly wide application of lanthanide-based upconversion nanocrystals has generated an urgent need to control and manipulate both the morphological and optical properties of these materials. In this work, Sc³⁺ ions were utilized to modulate the morphology, phase structure, and upconversion luminescence properties of YF₃:Yb/Er nanocrystals. At a Sc³⁺ doping concentration of 0-25 mol% the YF₃:Yb/Er nanocrystals gradually changed from ∼16 nm rhombic nanodots to ∼57 nm zigzag-shaped nanorods, and the upconversion luminescence was enhanced by 5 times. The co-existence of the YF₃:Yb/Er and ScF₃:Yb/Er nanocrystals was then seen at 25-60 mol% Sc³⁺ doping, and finally the ScF₃:Yb/Er nanocrystals became the only product at >60 mol% Sc³⁺ doping. A mechanism of oriented attachment growth has been proposed to explain the morphology evolution, and the upconversion luminescence details have been discussed from the crystal structure point of view.