Excitation pulse width-dependent luminescence decay of lanthanide-doped upconversion nanoparticles

Abstract

Upconversion luminescence decay, a key feature of lanthanide-doped upconversion nanoparticles (UCNPs) that is crucial for both the fundamental studies and practical applications of UCNPs, typically is obtained under pulsed excitation. However, little attention has been paid to the influence of pulsed excitation on the luminescence decay of UCNPs. Herein, using NaYF4:Yb/Er (5/2 mol%) UCNPs as an archetype, we show that the luminescence decay of UCNPs can be largely affected by the excitation pulse width. With the increase of excitation pulse width, the lifetime, derived from the luminescence decay, can increase by ∼100 %. Our experimental studies, together with numerical simulations, reveal that the excitation pulse width-dependent luminescence decay can be due to the presence of luminescent centers with multi-decay properties in UCNPs. These results can pave new ways to the modulation of upconversion luminescence decay and offer new opportunities for the application of UCNPs in the temporal domain.