Tuning Long‐Lived Mn(II) Upconversion Luminescence through Alkaline‐Earth Metal Doping and Energy‐Level Tailoring

Abstract

AbstractCrystal‐site engineering of hexagonal‐phase NaGdF4:Mn through alkaline‐earth metal (A2+) doping is used to tune the upconversion luminescence of the Mn2+ dopants. Experimental and calculated results show the ability of A2+ doping to alter the occupancy site of Mn2+ ion from Na+ to Gd3+, thus enabling an emission change from green (520 nm) to yellow (583 nm) upon excitation at 980 nm. The yellow emission of Mn2+ shows a long emission lifetime of 65 ms, more than three times longer than the green emission of Mn2+ (20 ms). The combination of tunable long‐lived Mn2+ emission with lanthanide emission at a single‐particle level provides a convenient route to triple transient upconversion color codes upon dynamic excitation, which offers an attractive optical feature particularly suitable for efficient document encoding.