Infrared to ultraviolet upconversion fluorescence of Gd3+ in β-NaYF4 microcrystals induced by 1560nm excitation

Abstract Under 1560 nm excitation, ultraviolet (UV) upconversion (UC) emissions of Gd3+ and Er3+ ions were observed in β-NaYF4:Yb3+/Gd3+/Er3+ microcrystals, which were synthesized through a facile EDTA-assisted hydrothermal method. Experimental analysis exhibited that these UV emissions came from high-order UC processes. In the Yb3+–Gd3+–Er3+ codoped system, ground state absorption (GSA) and excited state absorption (ESA) of Er3+, ESA of Gd3+, energy transfers (ETs) from Yb3+ to Er3+ and from Er3+ to Gd3+ ions worked simultaneously in populating these high-energy states of Er3+ and Gd3+ ions.