A cyanine‐based dual‐modal probe for fluorimetric detection of mercury ion and colorimetric sensing of pH.

A fluorescent probe derived from cyanine‐rhodanine conjugate was developed for dual detection of mercury (Hg2+) ion and pH. Addition of Hg2+ ion to the weakly fluorescent probe solution in dimethyl sulphoxide/water (DMSO/H2O, 7:3, v/v) induced discernible colour change and fluorescence enhancement while other metal cations including Li+, Na+, K+, Ag+, Cu2+, Fe2+, Zn2+, Co2+, Ni2+, Mn2+, Sr2+, Ca2+, Mg2+, Al3+, Cr3+ and Fe3+ did not cause obvious change in colour and fluorescence emission. The detection limit of the probe toward Hg2+ ion is 1.61 × 10−7 M. The probe also exhibited remarkable pH‐responsive effect. It acts as a dual chromogenic and spectroscopic probe for determining different pH scales over a wide range of pH 1.0–14.0: bright yellow with maximum wavelength (λmax) 416 nm for pH 1.0–2.0, orange with λmax 470 nm for pH 3.0–9.0, and pale yellow with λmax below 400 nm for pH 10.0–14.0. Plausible sensing mechanisms of the probe toward Hg2+ ion and pH have been proposed. [ABSTRACT FROM AUTHOR]