A highly selective probe for fluorescence turn-on detection of Fe3+ ion based on a novel spiropyran derivative

Abstract

A new spiropyran bearing multiple phenolic hydroxyl groups is synthesized. It acts as a chemosensor for selective detection of Fe3+ ions in both organic and aqueous solution. The optimal pH range for Fe3+ fluorescent detection by the sensor is pH 4.5–10.5. Upon addition of Fe3+ to the sensor solution the fluorescence emission intensity is enhanced by around 50 fold. Other common competitive metal ions including Li+, Na+, K+, Ag+, Cu2+, Fe2+, Zn2+, Co2+, Ni2+, Mn2+, Sr2+, Hg2+, Ca2+, Mg2+, Al3+ and Cr3+ do not substantially interfere with the selective detection of Fe3+ by the sensor. Changes in the fluorescence emission intensity with the equivalent ratio of Fe3+/sensor exhibits an approximate linear relationship, from which the concentration of Fe3+ ion may be estimated. The detection limit of Fe3+ ion by the sensor is measured to be 1.93 × 10–7 M. A plausible sensing mechanism for selective Fe3+ ion detection by the sensor is proposed based on the Job’s plot measurement.