Using the Turn-On Fluorescence Effect in Chemical and Biochemical Analysis

Recently, the term “turn-on” fluorescence (TF) has been widely used in luminescence analysis. This paper presents a review of reagents and analytes suitable for turn-on fluorescence analysis and assesses the potentials of the method in chemical and biochemical analysis, including for studying real samples of complex chemical composition. Not all effects grouped under the name turn-on fluorescence are qualitatively new; one of the goals of this work was to harmonize the terms used in modern English-language publications with the terms adopted in the domestic literature on luminescence. A turn-on fluorescence reagent is a good phosphor with a structural “defect” that lowers the quantum yield, for example, an open cycle, a disruption in a system of conjugated bonds, or an attached quencher. The defect is eliminated by the reaction with the analyte, and an intensely luminescent product is formed. The types of defects and reactions for their “correction” form a basis of the proposed classification of reagents with turn-on fluorescence.