Time-resolved emission spectra of sample S1 under 337 nm excitation for different time delays of:  (a) 0, 1 µs; (b) 1 µs; (c) 4 µs but with the same integration time of 50 ns; (d) Decay curves measured for 589 nm emission from ZnS:Mn2+ nanocrystals under 1 Hz 370 nm excitation (black squares) and 337 nm excitation (red circles).