Ultra-broadband near-infrared excitable upconversion core/shell nanocrystals

Abstract

Monodisperse Er³⁺:NaGdF₄@Ho³⁺:NaGdF₄@NaGdF₄ active-core/active-shell/inert-shell nanocrystals, which can extend the near-infrared wavelength excitable range for upconversion (UC) emissions, were successfully fabricated for the first time. Importantly, doping of Er³⁺ and Ho³⁺ into the core and shell respectively suppresses adverse energy transfers between them, resulting in intense UC emissions for both Er³⁺ and Ho³⁺ dopants.