Selectively sensing first-row transition metal ions through fluorescence enhancement

Transition metal ions, especially the first-row ones are ubiquitous in nature and they perform many biological functions. However, high accumulation of these ions can be quite detrimental to health. Their spatial distribution with high fidelity inside as well as outside cells is, therefore, of paramount importance. In addition to biological sensing, fluorescence enhancement by transition metal ions can be potentially useful in other areas of science. However, most of the transition metal ions are paramagnetic and they very effectively quench fluorescence. Surmounting this problem of fluorescence quenching, a number of systems have been reported which are the topic of the present review.