Fluorescence Lifetime Measurements, Applications of

Abstract

Abstract Over the years, the emissive characteristics (spectral, temporal, and polarization) of fluorophores have been widely used to probe the local environments of fluorescent centers. Fluorescence lifetime and rotational reorientation time measurements, in particular, offer a means to elucidate subtle features when examining, for example, complex systems involving environmental heterogeneity, energy transfer, quenching pathways, or excited state reactions. Further, because fluorescence occurs on the nanosecond (10 −9 s) timescale, competing or perturbing kinetic processes like collisional quenching, solvent relaxation, energy transfer, and rotational reorientation can affect the fluorescence. Thus, a carefully chosen fluorophore can serve as an internal nanosecond or faster stopwatch of environmental fluctuations. This article is divided into a brief introduction, a short discussion on instrumentation, and several sections on various applications of excited state fluorescence measurements.