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A new carbazole-azine based fluorescent sensor was synthesized and characterized. The selectivity of the sensor for Cu over other counter ions in a dimethyl sulfoxide/H O mixture was shown through enhancement in fluorescence - an off to on transformation. The specificity of the probe towards Cu was evident in ultraviolet/visible, fluorescence, Fourier transform infrared and mass studies. Application of the probe in the cell imaging and cytotoxicity of living cells is illustrated.

A phenothiazine-rhodamine (PTRH) fluorescent dyad was synthesized and its ability to selectively sense Zn 2+ ions in solution and in in vitro cell lines was tested using various techniques. When compared with other competing metal ions, the PTRH probe showed the high selectivity for Zn 2+ ions that was supported by electronic and emission spectral analyses. The emission band at 528 nm for the PTRH probe indicated the ring closed form of PTRH, as for Zn 2+ ion binding to PTRH, the λ em get shift to 608 nm was accompanied by a pale yellow to pink colour (under visible light) and green to pinkish red fluorescence emission (under UV light) due to ring opening of the spirolactam moiety in the PTRH ligand. Spectral overlap of the donor emission band and the absorption band of the ring opened form of the acceptor moiety contributed towards the fluorescence resonance energy transfer ON mechanism for Zn 2+ ion detection. The PTRH sensor had the lowest detection limit for Zn 2+ , found to be 2.89 × 10 −8 M. The sensor also demonstrated good sensing application with minimum toxicity for in vitro analyses using HeLa cells.

The synthesis of a novel, and highly selective Fe3+ ion sensor based on anthrone‐spirolactam and its quinoline hybrid ligand is reported. The designed ligand displayed selective detection of Fe3+ ions with enhanced fluorescence emission. The complexation of Fe3+ ion led to a red shift of 32 nm from 420 nm to 452 nm, and a several fold increase in intensity with fluorescent green emission. The complexation (detection) of Fe3+ ions with ligand resulted in chelation enhanced fluorescence and intramolecular charge transfer through the inhibition of C=N isomerization. This hybrid sensor shows high sensitivity and selectivity, spontaneous response, and works on a wide pH range a minimum detection limit of 6.83 × 10−8 M. Importantly, the sensor works through the fluorescence turn‐on mechanism that overcomes the paramagnetic effect of Fe3+ ions. The binding mechanism between the ligand and the Fe3+ ions was established from the Job's plot method, optical studies, Fourier transfor infrared spectroscopy, NMR titration, fluorescence life‐time studies, and density functional theory optimization. The sensor displayed excellent results in the quantification of Fe3+ ions from real water samples. Furthermore, due to its biocompatibility nature, fluorescent spotting of Fe3+ ions in live cells revealed its bioimaging applications.