Figure 3 (a) Steady-state PL/excitation (blue line,
excited at 340 nm) and
phosphorescence/excitation (green line, excited at 280 nm) spectra,
and the UV–visible absorption spectra of S-dots powder; (b)
emission decay curves of S-dots in solution (blue line) and powder
states (green line), excited at 280 nm; (c) digital photos of S-dots
powder before and after switching off 302 nm UV light at room temperature;
(d) temperature-dependent phosphorescence (solid line) and excitation
(dashed line) spectra of S-dots powder; (e) schematic illustration
of the RTP mechanism of sulfur powder and S-dots.