u Chapter 20: Novel Fluorophores

Abstract

In the previous chapters we discussed small organic fluo-rophores typified by the Dansyl, fluorescein, rhodamine, and cyanine dyes. Numerous probes of this type have been characterized and are commercially available. The majority of these probes have extinction coefficients ranging from 10,000 to 100,000 M−1 cm−1 and decay times ranging from 1 to 10 ns. Some of these probes are photostable, but all the organic fluorophores display some photobleaching, especially in fluorescence microscopy with high illumination intensities. We now describe different types of luminophores that are mostly inorganic or display unusually long lifetimes. These classes of probes are semiconductor nanoparticles, lanthanides, and transition metal—ligand complexes (MLCs). We occasionally use the term luminophore, especially with the MLCs, because it is not clear if the emission occurs from a singlet or triplet state, but we will mostly use the term fluorescent to describe the emission from any of these species.