Single band red emission of Er3+ ions heavily doped upconversion nanoparticles realized by active-core/active-shell structure

Abstract

The applications of lanthanide-doped upconversion (UC) nanoparticles are limited by unsatisfactory photoluminescence intensity. Herein, we construct a simplified energy migration mediated upconversion (EMU) to improve the upconversion luminescence (UCL) of heavily doped particles with an active-core/active-shell structure. Er3+ ions in the shell have a temporary effect on energy, and then transfer energy to the Er3+ ions in the core, thus sensitizing the red emission of the Er3+ ions in the core. The EMU process of [Yb3+→Er3+] → [Er3+→ Er3+] and [Er3+→Er3+] → [Er3+→ Er3+] excited by 980 and 808 nm, respectively, were realized by the high doping concentration of Er3+ ions in NaErF4:xYb,40Mn@NaErF4:40Yb, 40Mn (x = 0–40) particles. The UCL intensity of NaErF4:20Yb40Mn@NaErF4:40Yb40Mn is significantly higher than that of α-NaErF4:40%Mn hollow nanocubes by 230 times under 980 nm diode laser excitation, also increased by 9.8 times under 808 nm laser excitation. The NaErF4:20Yb40Mn@NaErF4:40Yb40Mn particles can realize single-band red emission excited by 378, 522, 808 and 980 nm laser, respectively. This multiwavelength excited character of NaErF4:20Yb40Mn@NaErF4:40Yb40Mn makes it a potential candidate in anti-counterfeiting application potential.