Fluorescence measurements were performed with an F97Pro
Fluorescence Spectrometer (Lengguang, Shanghai, PR China),
which is a fully computer-controlled instrument using a doublegrating
monochromator for excitation and a single-grating
monochromator for emission. The widths of both excitation and
emission slit were set to 5 nm. The acquisition interval and integration
time were set to 1 nm and 0.3 s, respectively. The fluorescent
emission spectra (range 370–700 nm, 1 nm interval) of oils
were collected with 5 nm excitation slits, 5 nm emission slits,
and 360 nm excitation radiation. Samples were directly injected
into a 10 10 45 mm quartz cell and then scanned using right
angle geometry. After each series of measurements, the cell was
cleaned with hexane. Each sample was analyzed in triplicates,
and the results were reported as mean values.