Upconversion multicolor fine-tuning: visible to near-infrared emission from lanthanide-doped NaYF4 nanoparticles.

A general approach to fine-tuning the upconversion emission colors, based upon a single host source of NaYF4 nanoparticles doped with Yb3+, Tm3+, and Er3+, is presented. The emission intensity balance can be precisely controlled using different host-activator systems and dopant concentrations. The approach allows access to a wide range of luminescence emission from visible to near-infrared by single-wavelength excitation.