Fig. 3: Tuning rise and decay times of blue upconversion of Tm3+.
From: Full-color tuning in multi-layer core-shell nanoparticles from single-wavelength excitation
a Schematic of blue upconversion of Tm3+ in Yb/Tm coupled system and possible CR processes that may result in quenching of the emissions. CR3 and CR4 stand for CR processes of [1G4; 3H6] → [3F2; 3F4] and [1D2; 3H6] → [1G4; 3F4], respectively. Insets compare the ionic interactions with and without CR for lower and higher Tm3+ dopant cases. b Upconversion emission spectra of NaYF4:Yb/Tm(20/0.1-1.0 mol%)@NaYF4 core-shell nanoparticles under 980 nm excitation. c Dependence of 475 nm emission intensity and lifetime on Tm3+ dopant concentration for (b) samples. d, e Time-dependent upconversion emission profiles of Tm3+ at 475 nm from (b) samples and NaYF4:Yb/Tm(10-40/0.1 mol%)@NaYF4 core–shell nanoparticles upon pulse 980 nm excitation with a pulse width of 8 ms.
