Fig. 2: Linear and nonlnear luminescence and relevant simulation results.
From: Internal OH− induced cascade quenching of upconversion luminescence in NaYF4:Yb/Er nanocrystals
a UCL spectra of NaYF4-x(OH)x:2%Er@NaYF4 nanoparticles with variable OH− contents in the core (x: 0–0.23). Inset shows the corresponding UCL emission intensity (integrated from 500 to 700 nm), which can be well fitted by Eq. (2). b Luminescence decay curves of the 2F5/2 → 2F7/2 transition of Yb3+ in co-doped NaYF4-x(OH)x:Yb/Er@NaYF4 nanoparticles (Ex: 980 nm, Em: 1020 nm). Inset shows internal OH− content-dependent decay lifetime, which can be well fitted by Eq. (3). c Top: internal OH− content-dependent UCL intensity (integrated from 500 to 700 nm) of NaYF4-x(OH)x:Yb/Er@NaYF4 nanoparticles. Green dots are the experimental values and the curve is the calculated result from Eq. (4); bottom: comparison of experimental (circle) and simulation (triangle, RYb-OH = 2100 s−1) results for the Yb3+ decay lifetimes (black color) and UCL intensities (red color) of NaYF4-x(OH)x:Yb/Er@NaYF4 core/shell nanoparticles
