A novel strategy for markedly enhancing the red upconversion emission in Er3+/Tm3+ cooperated nanoparticles

A novel core–shell structured nanocrystal with energy trapping centers of Tm³⁺ ions doped in the Er³⁺-hosted core zone and Yb³⁺ ions doped in the shell portion is innovated to achieve super-bright red upconversion emission upon low 980 nm laser excitation.