Fluorescence Spectroscopy to Probe Ionic Liquid‐Based Systems

Abstract

Owing to its inherent sensitivity coupled with multidimensionality, fluorescence spectroscopy has established itself as a versatile tool to investigate complex chemical systems in analytical chemistry. Ionic liquids, for the last couple of decades or so, have emerged as intriguing modern materials in science and technology that display an array of useful and sometimes unconventional features. Steady‐state fluorescence intensity and anisotropy and time‐resolved excited‐state emission intensity and anisotropy decays along with other advanced fluorescence techniques have been employed effectively to analyze, characterize, and explore ionic liquids and ionic liquid‐based systems. The extent of dipolarity afforded by ionic liquids as well as cosolvent/supercritical fluid‐added ionic liquid systems is readily manifested through the response of judiciously selected fluorescence polarity probes. Transient solvation measurements carried out by means of time‐resolved fluorescence measurements are particularly powerful for their ability to parameterize the kinetics of the solvation process within ionic liquids. Dynamic Stokes' shift of appropriate fluorescence probes reveals the presence of several components, thus highlighting the complexity of solvation within ionic liquids and ionic liquid‐based media. Various fluorescence spectroscopic tools are used to establish and characterize macromolecular (surfactant and polymer) and dye aggregation within ionic liquids and ionic liquid‐based media along with aggregation of surface‐active ionic liquids (SAILs) in water.