Synthesis of hexagonal-phase core-shell NaYF4 nanocrystals with tunable upconversion fluorescence

Abstract

Hexagonal-phase core-shell-structured NaYF4: Yb,Tmatβ-NaYF4: Yb,Er and β-NaYF4: Yb,Tmatβ-NaYF4: Yb,Eratβ-NaYF4:Yb,Tm nanocrystals were synthesized by a seeded growth approach. β-NaYF 4:Yb,Tm nanocrystals with 20 nm diameter were used as seed crystals to induce the growth of β-NaYF4:Yb,Er and then β-NaYF 4: Yb,Tm crystals, resulting in the formation of core-shell- structured nanocrystals with upconverting lanthanide ions Tm and Er doped in the core and shell, respectively. © 2008 American Chemical Society.