Fig. 4: Temporal control of upconversion.
From: Spatiotemporal control of photochromic upconversion through interfacial energy transfer
a Dependence of green-to-red upconversion emission intensity ratio on the pulse width of 980 nm excitation for the NaErF4:Ho(0.5 mol%)@NaYF4:Yb(0–100 mol%)@NaYF4 core-shell-shell nanoparticles. b CIE coordinates of the emission colors of (a) samples under 980 nm excitation with pulse width of 0.5 ms (red label) and that of NaErF4:Ho(0.5 mol%)@NaYF4:Yb(10 mol%)@NaYF4 core-shell-shell nanoparticles under 980 nm excitation with different pulse widths (blue label). Insets show their emission photographs. c Normalized upconversion emission spectra of NaErF4:Ho(0.5 mol%)@NaYF4:Yb(10 mol%)@NaYF4 core-shell-shell nanoparticles under 980 nm excitation with different pulse widths. d Time-dependent emission profiles of Er3+ measured at 540 and 653 nm for c sample. e Schematic of possible mechanism for the upconversion emission color change under non-steady-state excitation. f Two-dimensional time-resolved photoluminescence spectra of NaErF4(0.5 mol%)@NaYF4:Yb(20 mol%)@NaYF4 core-shell-shell nanoparticles under 980 nm excitation. All excitation power densities were 11.6 W cm‒2. Source data are provided as a Source Data file.
