A novel "off-on" rhodamine-based colorimetric and fluorescent chemosensor based on hydrolysis driven by aqueous medium for the detection of Fe 3 .

A novel “off-on” colorimetric and fluorescent chemosensor N2,N6-bis(2-(rhodamine B amido)ethyl)pyridine-2,6-dicarboxamide (RhBEP) has been designed and synthesized, which can selectively detect the presence of Fe3+ with about 75-fold enhancement in fluorescence emission intensity at 585 nm over various environmentally relevant metal cations such as Hg2+, Cu2+, Cr3+, Li+, Na+, K+, Ag+, Zn2+, Mg2+, Ca2+, Ba2+, Fe2+, Cd2+, Ni2+, Mn2+, Al3+, Bi3+ and Au3+ in PBS reaction media. The remarkable color change from UV–Vis titration experiments indicates that RhBEP can be used as a colorimetric chemosensor for Fe3+. The ultrasensitive detection limit for Fe3+ in the fluorescence measurement is down to 2.0 × 10−8 mol·L−1. The recognition mechanism of RhBEP to Fe3+ was analyzed by Job's plot and mass spectrometry analysis. In addition, the data from fluorescent cell imaging experiments confirmed that the chemosensor RhBEP has a promising application for the detection of Fe3+ in biological systems.