Lattice Perturbation by Optically Inert Sc³⁺ Grants NaGdF₄ Upconversion Nanocrystals Giant Emission and Excitation-Gated Thermal Response

Abstract

We report a host-modification strategy using optically inert Sc³⁺ doping in NaGdF₄ nanocrystals. This lattice perturbation enhances NaGdF₄:Er upconversion (by up to 146-fold) and exhibits an excitation-gated thermal response: emission is temperature-invariant at 980 nm but shows a green-to-red shift at 1550 nm, thus establishing a versatile platform for programmable luminescent materials.