Highly bright multicolour emission through energy migration in core/shell nanotubes†
This paper describes a simple and environmentally-friendly approach that allowed for the facile synthesis of a gadolinium-based core/shell/shell nanotube structure with a set of lanthanide ions incorporated into separated layers. In addition, by the rational design of a core/shell structure we systematically investigated the luminescence properties of different lanthanide ions in NaGdF4 host, and efficient down-conversion emission can be realized through gadolinium sublattice-mediated energy migration. The Gd3+ ions play an intermediate role in this process. By changing the doped lanthanide ions, we generated multicolour emissions from the luminescent Ln3+ centers via energy transfer of Ce3+→Gd3+→Ln3+ and Ce3+→Ln3+ (Ln = Eu, Tb, Dy and Sm) in separated layers. Due to the strong absorption of ultraviolet (UV) irradiation by Ce3+ ions, the luminescence efficiency could be enhanced after doping Ce3+ ions in the shell. In NaGdF4:5% Eu3+@NaGdF4@NaGdF4:5% Ce3+ core/shell/shell nanotubes, with increasing the NaGdF4 interlayer thickness, a gradual decrease in emission intensity was observed for the Eu3+ activator.