Question

Why do we see “spurious” peaks in the spectra when a non-fluorescent solvent/ blank is used in the spectrofluorometer whereas the UV-Vis spectrum is a flat baseline?

Answer 1

Spurious peaks in a a fluorescence experiments with a a spectrofluorometer are due to the mutiple diffractions from scattered excitation lines and cannot be entirely avoided when measuring either multicrystalline samples or samples that have very low fluorescent intensity the latter is the case for a non-fluorescent solvent/blank.

This type of a phenomenon does not happen in a UV-vis spectrum as here we are testing absorbance and there is no possibility of internal multiple diffractions of scattering.