Two-mode upconversion color-tuning of Er:NaYbF4 nanocrystals and their high-efficiency photothermal conversion

Abstract

Color-tunable upconversion luminescence of lanthanide nanomaterials is attractive in many fields of application. To date, the available strategies for real-time color-tuning are still limited. Herein, we reveal a relatively universal technique to release orthogonal emission with different colors at a single nanocrystal level. Using Er:NaYbF₄@NaLuF₄ core–shell nanocrystals, besides their traditional excitation power-induced color tuning, green/red-dominant emission is activated accordingly by short/long pulse excitation. The key to this time-domain color-tuning is the varied population rate and the number of lanthanide activators. In addition, the efficient photothermal conversion of the formed core–shell nanocrystals is proven, and their possible laser ablation application is demonstrated. The Er:NaYbF₄@NaLuF₄ core–shell nanocrystals, with color-tunable luminescence, small particle size, high photothermal conversion efficiency, and effective laser ablation ability, are highly promising for non-invasive cancer diagnosis and treatment.