Multicolor Emission Tuning and Red/Green Ratio Enhancement of Yb3+/Er3+ Codoped KGdF4 Upconversion Nanoparticles

Herein, a series of KGdF4:Yb3+/Er3+ upconversion nanoparticles (UCNPs) were synthesized through a one-pot hydrothermal method using polyethylene glycol (PEG) as capping ligands. The phase and microstructure studies show all these as-prepared UCNPs are pure cubic phase and uniformed nanoparticle shape by changing the doped Yb3+ concentration from 18% to 98%. The as-prepared UCNPs can realize the multicolor emissions from yellow to red and the red-to-green (R/G) ratio can be enhanced from 2.05 to 8.35 when Yb3+ varies from 18% to 98%. In addition, the proposed upconversion (UC) mechanisms of these PEGylated UCNPs are investigated in detail. The realization of multicolor tuning and enhanced R/G ratio by only increasing the doping concentration of Yb3+ ions in KGdF4 host indicates that the PEGylated KGdF4:Yb3+/Er3+ UCNPs can find their application on lighting devices, anticounterfeit technology, and even bioimaging field.