Novel Fluorophores

Abstract

In the previous chapters we discussed small organic fluo-rophorestypified by the Dansyl, fluorescein, rhodamine, and cyanine dyes.Numerous probes of this type have been characterized and are commerciallyavailable. The majority of these probes have extinction coefficientsranging from 10,000 to 100,000 M−1 cm−1 and decay times rangingfrom 1 to 10 ns. Some of these probes are photostable, but all theorganic fluorophores display some photobleaching, especially in fluorescencemicroscopy with high illumination intensities. We now describe differenttypes of luminophores that are mostly inorganic or display unusuallylong lifetimes. These classes of probes are semiconductor nanoparticles,lanthanides, and transition metal—ligand complexes (MLCs). We occasionallyuse the term luminophore, especially with the MLCs, because it isnot clear if the emission occurs from a singlet or triplet state,but we will mostly use the term fluorescent to describe the emissionfrom any of these species.