Solution-Phase Tuning of Emission of Divalent Europium

The key to developing smart light-emitting systems lies in the ability to tune luminescence with only modest changes in the chemical environment. Divalent europium-based luminophores are unique materials that access emissions ranging from the blue to red regions of the visible spectrum. Early studies demonstrate the tunability of the emission of Eu-II in solid-state host lattices, and recent research has shown that altering counter anions, solvents, and ligands also enables tuning of the emission of Eu-II. These findings are supported by numerous publications, and mechanistic studies shed light on the underlying theories behind the tunable emissions of Eu-II. The purpose of this article is to present the most recent hypotheses and understanding regarding the effect of counter anions, solvents, and ligands on luminescence properties of Eu-II based systems.