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

Abstract Under 1560 nm excitation, ultraviolet (UV) upconversion (UC) emissions of Gd 3+ and Er 3+ ions were observed in β-NaYF 4 :Yb 3+ /Gd 3+ /Er 3+ 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 Yb 3+ –Gd 3+ –Er 3+ codoped system, ground state absorption (GSA) and excited state absorption (ESA) of Er 3+ , ESA of Gd 3+ , energy transfers (ETs) from Yb 3+ to Er 3+ and from Er 3+ to Gd 3+ ions worked simultaneously in populating these high-energy states of Er 3+ and Gd 3+ ions.