Fig. 4: Single-wavelength responsive full-color tuning of upconversion and its potential application.
From: Full-color tuning in multi-layer core-shell nanoparticles from single-wavelength excitation
a, b Schematic of the NaYF4:Yb/Tm(20/0.1 mol%)@NaYF4@NaYbF4:Er/Tm(15/0.5 mol%)@NaYF4 MLCS sample and corresponding TEM image, high-resolution TEM image and Fourier transform diffraction pattern. c Decay curves of the upconverted red, green, and blue emissions from (b) sample under pulse 980 nm excitation. d, e Upconversion emission spectra of (b) sample under 980 nm excitation with modes of c.w., short pulse, and time-gating technique, respectively. f Schematic of the full-color volumetric display using the (b) sample by simply altering the excitation modes. The pattern (A butterfly fluttering over a rose) shows a blue butterfly, a red rose, and green leaves under suitable excitation mode. As a control, it shows only red color under regular c.w. 980 nm excitation. g Fine color tuning through modulating the excitation laser modes. h Identification of concealed information (Canton tower facing the moon) through tuning excitation modes. The concealed information pattern was painted using (b) sample, and the interference information using NaYF4:Yb/Er/Tm(40/2/0.25 mol%)@NaYF4, NaYF4:Yb/Tm(30/1.5 mol%)@NaYF4, and NaYF4:Yb/Ho/Ce(20/2/16 mol%)@NaYF4 core–shell nanoparticles.
