Fluorescence and absorption spectra were measured after 3 min of
ultrasonic agitation. The NMR spectra were obtained in D2O with
DSS (3-(trimethyl-silyl)-1-propanesulfonic acid sodium salt) as
internal standard; the protonation form of DSMI was determined
by the color of the solution changing from yellow to colorless, and
then the pH of the solution was checked by pH test paper.