A Rhodamine‐based Fluorescent Chemodosimeter for Au3+ in Aqueous Solution and Living Cells

Abstract

A highly selective rhodamine hydrazide-based fluorescent chemosensor for Au 3+ detection was developed. The aqueous solution of rhodamine N -hydroxysemicarbazide ( RHS ), in the presence of Au 3+ , exhibited a significant 55-fold turn-on fluorescence response at 591 nm and a colorimetric change from colorless to pink. Other interested ions including Li + , Na + , K + , Cs + , Mg 2+ , Ca 2+ , Ba 2+ , Pb 2+ , Mn 2+ , Co 2+ , Ni 2+ , Ag + , Cd 2+ , Cu 2+ , Hg 2+ , Zn 2+ , Sn 2+ , Fe 2+ , Fe 3+ , Cr 3+ , Ce 3+ did not induce any distinct color/spectral changes. The irreversible detection mechanism occurred via Au 3+ -promoted 5- exo - trig ring closure to yield 1,3,4-oxadiazole-2-one product. The RHS probe is non-responsive to other biologically relevant metal ions and the limit of detection for Au 3+ was calculated to be 0.5 µM with a linear range of 0 to 90 µM. Fluorescence bioimaging of Au 3+ in HepG2 cells was also successfully demonstrated.