ABSTRACT
In many organic molecules, the absorption of a photon of given wavelength creates an excited state of
the molecule (an ‘exciton’) which in turn is capable of re-emitting light of longer wavelength. This is
known as fluorescence. The common feature of fluorescent dyes is the presence of alternating single-and
double-bonds between carbon atoms (‘conjugated’ units), resulting in delocalized p-electron clouds.
A wide range of fluorescent organic dyes, spanning the entire visible and near-IR spectrum, is now
available, e.g. for dye laser applications.
