Manipulating emissions of an intensive red-emitting NaLuF4:Yb/Er microrod by controlling its temporal behaviors

Lanthanide ions (Ln3+) doped upconversion materials have attracted great attention due to their potential applications in volumetric display, anti-counterfeiting, biodetection and biotherapy. However, red-emitting upconversion phosphors are scarcely reported especially basing on NaLnF4, which is the most efficient host matrix. Herein, we reported intensive red emissions observed in a low doping content NaLuF4:Yb/Er (20/1 mol%) microrod. The intensive red emission is considered to be obtained by the facilitated three-photon population routes of 4F9/2 energy levels of Er3+. Moreover, upon pulsed laser excitation its emission color can be rationally manipulated from red to yellow and to green. This is attributed to the temporal response deviation between 4S3/2 and 4F9/2 energy levels of Er3+, which impels green and red emission bands to reach different ratios under pulsed laser excitation. The color-manipulation method can also be applied to other red-emitting upconversion phosphors, enabling extended applications in volumetric colorful display, high-security-level anti-counterfeiting and deep-tissue bioimaging.