Novel Rhodamine-Derivated Dual-Responsive ColorimetricFluorescent Chemoprobe for the Hypersensitive Detection of Ga 3+ and Hg 2+ and Biological Imaging

A unique rhodamine-based derivative, (2-amino-3-(((1E,2E)-2- ((3',6'-bis(diethylamino)- 3-oxospiro[isoindoline-1,9'-xanthen]-2-yl)imino)ethylidene)amino)maleonitrile) (RhGDM) was easily fabricated just by Schiff-base condensation. RhGDM displays superb selectivity and sensitivity for specifically detecting the biologically and ecologically important Ga3+ and Hg2+ cations via fluorescence “off-on” type in aqueous medium with high quantum yields and also the ultralow detection-limits down to nanomolar-level, which are far below the maximum permissible dosage values set by the WHO, indicating high efficiency and reliability of the chemoprobe. Meanwhile, RhGDM exhibits Hg2+-selective chromogenic behavior and can detect Hg2+ by naked-eye. Interestingly, the plausible sensing machanism is the above metal cations-promoted hydrolysis of the rhodamine-based Schiff-base skeleton, which was conformed by the mass spectra, IR spectra, and DFT calculations as well as the irreversibilities of fluorescence signals in the...