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A Rhodamine B- quinoline conjugate ( RSQ ) functions as a colorimetric and fluorescence probe for selective recognition of Bi 3+ ion based on CHEF assisted FRET process. RSQ visibly changes its colour and fluorescence profile upon addition of Bi 3+ ion. The distinctive colour change allows facile discrimination of Bi 3+ over other common cations. Lowest concentration of Bi 3+ detected by RSQ is 0.05 μM. RSQ efficiently images intracellular Bi 3+ in live SiHa cells. [ABSTRACT FROM AUTHOR]

A new rhodamine based fluorescent turn on sensor L has been reported as a highly selective and sensitive chemosensor for the Cr 3+ ion in a CH 3 CN-H 2 O solution. In presence of Cr 3+ ion, the strong fluorescence enhancement is attributed due to the interaction of Cr 3+ with L, leading to opening of the spirolactam ring of rhodamine B to the amide form. The Cr 3+ sensing mechanism is also supported by the Job’s plot, ESI-MS, 1 H NMR titration experiments. Importantly, this probe shows high selectivity over other biologically relevant metal ions. Also, anions do not show any effect. In addition, the detection limit is found to be up to 7.5 nM which is acceptable within the EPA (US) limit. The probe is also able to function within a broad biological pH range of 4–8. Furthermore, the probe L shows cellular penetrability for its potential use in confocal cell imaging studies. [ABSTRACT FROM AUTHOR]

A new rhodamine 6G derived chemosensor L has been synthesized that selectively detects the presence of Cu 2+ ion over a host of other biologically important and environmentally relevant metal ions in aqueous alcoholic medium under physiological pH (ethanol: water, 1:1, v/v, pH 7.2). The significant enhancement of fluorescence intensity of L is caused by Cu 2+ ion induced cleavage of spirolactum bond in the rhodamine moiety. This mechanism is well supported by the crystal structure of the L-Cu 2+ complex that depicts two ligand units are bonded to two Cu 2+ ions. Color of the solution changes from light orange to dark pink upon metal binding which allows naked eye detection ion as well. Confocal microscopic experiments validate that the dye is potentially useful for the selective detection of Cu 2+ ion in living cells. Therefore the dye is an excellent fluorogenic and chromogenic chemosensor for the Cu 2+ ion in aqueous ethanolic medium and the living cell as well. [ABSTRACT FROM AUTHOR]

A new rhodamine hydrazone obtained by the condensation of rhodamine hydrazide with 5-iodo-3-methoxy salicylaldehyde (NLAC) is synthesized and characterized using spectroscopic (IR, UV–vis, 1 H, 13 CNMR, ESI-MS) and X-ray diffraction techniques. It binds selectively with Al 3+ ions and a strong fluorescence signal is displayed from [ NLAC − Al 3+ ] ensemble and has also been supported by DFT calculation. The color change of NLAC in presence of Al 3+ ions is further corroborated by UV-visible and fluorescence spectral titrations. The spectral changes are significant in the visible region of the spectrum and enable the detection of Al 3+ ions with naked eye. The 1:1 stoichiometry of NLAC:Al 3+ is supported by Job’s plot and ESI-MS data. The fluorescence signal displayed from [ NLAC − Al 3+ ] is quenched on the addition of N 3 − ions as an aqueous solution of NaN 3 salt which reverts back further on the addition of Al 3+ ions. This recognition process is also displayed in a human cervical cancer cell lines (SiHa cells) in an aqueous-acetonitrile medium. The process is repeated several times showing that the system is robust and reversible in the recognition process. A strip tests supports its feasibility for the laboratory demonstration. [ABSTRACT FROM AUTHOR]

• A "turn-on" fluorescent probe ol -PIP selectively responded to Hg2+ with large Stokes shift of 180 nm. • Subsequently, strong emission of ol -PIP–Hg2+ was quenched followed by S2–. • The process of the sequential sensing was realized in cells imaging. An excited state intramolecular proton transfer (ESIPT) characteristic "turn-on" fluorescence sensor for Hg2+ with large Stokes shift was fabricated and then it had ability to sequentially detect S2– by the "turn-off" fluorescent signal in aqueous media. On account of it, a simple fluorescence probe ol -PIP based on the phenanthro[9,10- d imidazole moiety bearing two phenol fragments was synthesized. Probe ol -PIP showed gradually the fluorescence enhancement with the increasing of water fraction due to the aggregation affect. Sequentially, the moderate fluorescence emission of ol -PIP in aqueous media was continuously and selectively illumined by the successive addition of Hg2+ with about 180 nm Stokes shift. Furthermore, the persistent "turn-on" fluorescence intensity could be quenched to the original state of ol -PIP in presence of S2–. This on–off sensing process was sustained for five times with the alternative addition of Hg2+ and S2–. The limits of detection for Hg2+ and S2– were 6.45 × 10–7 and 3.46 × 10–7 M, respectively. In addition, ol -PIP was successfully applied in Hg2+ detection in real water samples; simultaneously, ol -PIP with low cytotoxicity was also successfully used as a bioimaging reagent to detect Hg2+ and S2– in living cells. [ABSTRACT FROM AUTHOR]

• Novel phenothiazine-based colorimetric and ratiometric fluorescent sensor PPM for Hg2+ is synthesized. • PPM shows high selectivity and low detection limit of 12.5 nM in a wide pH range. • The response time of PPM for Hg2+ is within 1 min and suitable for ultrafast detection of Hg2+. • PPM for Hg2+ shows good applicability for paper/TLC-based "naked-eye" colorimetric assay. • PPM was used for fluorescence imaging of Hg2+ in living cells. A new phenothiazine-based sensor PPM was successfully designed and synthesized, which shows highly selective, ultrafast, naked-eye colorimetric and turn-on ratiometric fluorescence sensing of Hg2+ on the basis of the ICT from phenothiazine to aldehyde. Upon addition of Hg2+, obvious blue fluorescence at 455 nm decreased while green fluorescence at 528 nm enhanced, which exhibits ratiometric fluorescent turn-on response along with a "naked-eye" color change from pale-blue to bright-green. The PPM for highly sensing of Hg2+ with a quite low detection limit (12.5 nM) and a wide pH application range. The sensing mechanism proved to be the Hg2+-triggered thioacetal deprotection reaction was confirmed. Importantly, PPM was successfully employed for highly selective detecting and imaging of Hg2+ in living cells, as well as on paper/TLC-based "naked-eye" colorimetric assay. [ABSTRACT FROM AUTHOR]