Fig. 5: Application of color-switchable upconversion.
From: Spatiotemporal control of photochromic upconversion through interfacial energy transfer
a Schematic of multi-mode modulation of upconversion emission colors. Long pulse (width >10 ms) and short pulse (width <1 ms) excitations lead to red and green emission colors, respectively, and a tuning of excitation pump power or pulse width results in a gradual color change between red and green. b Decoding the pattern information (left panels) through high pump power (middle panels) or short pulse irradiation (right panels). The photographs were taken with and without a 600 nm short-pass filter, respectively. Scale bar, 5 mm. c Fast recognition of multidimensional optical signals. Scale bar, 5 mm. d Schematic of transforming luminescence information from temporal to spatial dimension. Scale bar, 5 mm. e Photographs of the rotating turnplate with increasing speed under steady-state 980 nm laser excitation. The corresponding speed (km/h) is marked at the bottom. f Speed-dependent upconversion emission spectra of NaErF4:Ho(0.5 mol%)@NaYF4:Yb(20 mol%)@NaYF4 core-shell-shell nanoparticles under steady-state 980 nm excitation. The spectra were normalized to red emission intensity. g Plot of luminescence intensity ratio (LIR) versus speed together with the fitting by an exponential function. h Dependence of calculated absolute (Sa) and relative (Sr) sensitivity on speed. Source data are provided as a Source Data file.
