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

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.

Under 1560 nm excitation, ultraviolet (UV) upconversion (UC) emissions of Gd3+ and Er3+ were observed in β-NaYF4:Yb3+/Gd3+/Er3+ microcrystals. In the complex frequency UC processes, energy transfers (ETs) from Er3+ to Gd3+ play crucial roles in populating the high-energy excited states of Gd3+ ions.Figure optionsDownload high-quality image (124 K)Download as PowerPoint slideResearch highlights
► UV UC emissions of Gd3+ were observed in NaYF4:Yb3+/Gd3+/Er3+ microcrystals under IR excitation.
► Er3+ were used as bridging ion to populate the excited states of Gd3+ in the codoped sample.
► Experiments on concentration variation demonstrated the ET processes from Er3+ to Gd3+ ions.
► Under IR excitation, UV emissions of Gd3+ came from eight- and nine-photon UC processes.