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• A novel fluorescence sensor (TCS) for Pd2+ was designed and synthesized. • TCS exhibited selective sensing abilities for Pd2+ among various metallic ions. • The detection limit for Pd2+ was as low as 4.32 × 10−8 M. • The sensing mechanism of 1:1 stoichiometry ratio was confirmed. • TCS displayed good bioimaging performance on Pd2+ detection in living system. Although some Pd2+ sensors were presented, the in-situ and real-time examination of Pd2+ based on fluorescent sensor is still a challenging task. In this work, a novel thiourea-cyanostilbene derivative (TCS) was designed and synthesized as the effective fluorescent sensor on in-situ and real-time sensing Pd2+ in aqueous media. TCS possessed good AIE fluorescence in THF/H 2 O solution. The fluorescence was selectively quenched by Pd2+ among all kinds of metallic ions. The sensing mechanism of 1:1 stoichiometry ratio for TCS with Pd2+was confirmed by Job's plot, 1H NMR and MS spectra. The detection limit was as low as 4.32 × 10−8 M. TCS exhibited the good sensing application for Pd2+ in tested paper and simulated samples with low errors. TCS had the excellent fluorescence imaging performance in living cells with the fluorescence imaging response on Pd2+. This research not only reported an effective fluorescence sensor for Pd2+, but also suggested the good application prospect on in-situ and real-time sensing Pd2+ in complicated environment. [ABSTRACT FROM AUTHOR]

The selective fluorescence zinc(II) sensing properties of a Schiff-base compound, 2-methoxy-6-(2-morpholinoethyliminomethyl)phenol (HL) have been explored. The emission intensity of HL in the presence of one equivalent of Zn 2+ ion increases by about 25 times. Several other metal ions, except Cd 2+ and Ni 2+ , have not been able to increase the emission intensity of HL significantly. The quantum yield and life-time of HL have also been increased in the presence of Zn 2+ ions. The enhancement in fluorescence intensity of HL is mainly due to the restriction of ESIPT, CHEF and PET on complex formation. HL forms a complex with Zn 2+ in 1:1 ratio as evidenced by Job's plot analysis and X-ray single crystal structure determination. Some theoretical calculations have been performed to get a better view on the nature of the observed electronic transitions. The probe has been applied for imaging of DLD-1, human colorectal adenocarcinoma cell. [ABSTRACT FROM AUTHOR]

• 2, 4-dinitrophenyl hydrazine based Schiff-base (L) was synthesized. • The fluorescence of L corresponds to excited state intra-molecular proton transfer (ESIPT) emission. • The intriguing chemo-sensing properties of L were evaluated by fluorescence studies. • The L-Zn2+ complex formation is reversible upon addition of strong chelating agent EDTA. • The probe L is highly selective for Zn2+ in DMSO-H 2 O and living Hela cell. • The probe L is the first molecule, which is highly selective sensor for Zn2+ in solid phase. Luminescent chemosensors based on Schiff bases have drawn tremendous research interest owing to their easy synthesis, enriched photophysical properties, and potential applications in biology and materials science. A dinitrophenyl-based Schiff base molecular probe (L) was synthesized and characterized to estimate its selective detection of Zn2+. The probe L exhibits weak emission in the DMSO-H 2 O solvent mixture due to excited-state intramolecular proton transfer (ESIPT). Interestingly, fluorescence is enhanced with the addition of Zn2+ to the DMSO-H 2 O solution of L , whereas the emission remains unchanged with the addition of other ions. This specifies that probe L acts as a selective chemosensor for Zn2+. The binding stoichiometry for the L : Zn2+ complex is 1:1, which was calculated using the Benesi-Hildebrand plot from fluorescence data. Furthermore, the binding modes are also supported by density functional theory (DFT) calculation. The binding constant and detection limits are 6.35 × 107 M−1 and 1.1 × 10−8 M, respectively. The L-Zn2+ complex formation is reversible upon the addition of a strong chelating EDTA ligand. In addition, L is also used to detect Zn2+ in living Hela cells and selective sensing of Zn2+ in the solid phase. [Display omitted] [ABSTRACT FROM AUTHOR]

• The chemosensor H 3 L can selectively detect Zn(II), Al(III) and SO 4 =. • Sensing phenomena deals with turn on –off fluorescence. • The HR-MS, NMR, IR spectroscopic study confirm the 1:1 probe-analyte binding. • DFT study optimizes the three 1: 1 probe-analyte structures. • Cell imaging study assures the biosensing activity of the chemosensor. A Salen type Schiff base H 3 L , generated by the one step condensation of 1, 3 diamino 2-propanol and 3- ethoxy salicylaldehyde, for selective and easy detection of the two different cations Zn(II), Al(III) and one specific anion SO 4 = among several competitive cations and anions in 1:9 methanol water HEPES buffer medium. This probe with moderate luminescence property exhibits elevated fluorescence enhancement with different shifting of spectral position during detection of Al(III) / Zn(II) and fluorescence diminution at the time of SO 4 = detection. One another interesting noticeable fact is that, with the help of F − ion Zn(II) can be detected in presence of Al(III) whereas by using CN− ion Al(III) can be detected in presence of Zn(II). The moderately higher binding constant values, measured from the probe-analytes electronic titration and the results obtained from the fluorescence lifetime study, convince us regarding the formation of Zinc/Aluminum/SO 4 = -probe complexes during sensing by the chemosensor H 3 L. The 1:1 binding mechanisms between H 3 L and Al(III)/Zn(II)/SO 4 = ions are propped up by HR-MS analysis and NMR/FTIR titration. The mononuclear structure of Zn(II)- H 3 L / Al(III)- H 3 L and SO 4 = H 3 L complexes are optimized by implementing Density Functional Theory (DFT) study. The sensing phenomena of two metal ions are further utilized to form a molecular logic gate formulation. Interestingly, this chemosensor can effectively detect and quantify all the aforementioned ions in tap water. Finally, the bio sensing ability of the chemosensor has been inspected by performing the fluorescence live cell imaging study, showing the intercellular Zn(II) sensing efficacy. [Display omitted] [ABSTRACT FROM AUTHOR]

• A phenolphthalein-aminophenol (PFAP)-based chemosensor for Al3+ was synthesized. • PFAP showed a LOD of 1.5 µM and a fast response time of 10 s. • PFAP was used to detect Al3+ in the intracellular region of the A549 cancer cells. Monitoring of excess Al3+ and its selective detection in biological and environmental samples are important tasks for researcher due to its harmful effects. Herein, we present a phenolphthalein-aminophenol derived sensor (PFAP) for the selective fluorescent response of Al3+ in an "OFF-ON" mode over a pool of analytes including eighteen cations with striking greenish emission. It has a prominent limit of detection (LOD) value (1.5 µM), fast response time (10 s) for Al3+ detection. The complexation properties of PFAP with Al3+ ions were clarified by UV–vis, 1H & 13C NMR, HRMS, and FTIR spectroscopic experiments. The recognition mechanism of PFAP for Al3+working with chelation enhanced fluorescence (CHEF) and is verified with two model compounds PF and PFAN in the light of UV–vis, PL, TRPL, and NMR experiment. To check its applicability, easily prepared test paper and TLC strip of PFAP was produced for rapid and selective onsite detection of Al3+ ions. Bio-imaging application of PFAP in human lung cancer cell lines A549 demonstrated excellent results with negligible cytotoxicity and as an excellent marker to detect traces of Al3+ ion in a time-dependent as well as concentration-dependent manner. Actual sample analysis for Al3+ with the probe PFAP produces fruitful result. [Display omitted] [ABSTRACT FROM AUTHOR]

• Benzo-imidazo-pyrrolo[3,4-c] pyridines based fluorescent chemosensor for Fe2+ ion detection. • The chemosensor shows a high selectivity for Fe2+ over other common metal ions. • This chemosensor was successfully applied for imaging Fe2+ion in living hela cells. • The probe can be recycled and reused with good efficiency upto twenty cycles. A new fluorescent chemosensor with benzo-imidazo-pyrrolo[3,4-c] pyridines core was synthesized and characterized. The free chemosensor exhibited high fluorescence intensity with quantum yield (φ) of 0.498. The fluorescence intensity was quenched completely in the presence of iron over other common metal ions at physiological pH. The chemosensor formed 1:1 complex with iron and the quantum yield was determined to be 0.04 for the complex. Quenching mechanism of the chemosensor can be confirmed by various analytical methods such as UV–vis titration, Job plot and mass spectrometry analysis. DFT calculation of the complex was also carried out which confirmed the formation of complex between metal and chemosensor. Further, this chemosensor was applied for in vitro cell imaging in HeLa cells to illustrate that the chemosensor can be used as a fluorescent probe for monitoring Fe2+ in living cells. [Display omitted] [ABSTRACT FROM AUTHOR]

A new naphthyl hydrazone anchored nitrosalicyl unit has been developed as a host for the selective and sensitive detection of Ag+, Hg2+ and F− ions in DMSO/water (9:1) medium. An obvious fluorescence enhancement was observed towards Ag+, Hg2+ and F− ions due to the inhibition of both photoinduced electron transfer (PET) process and C N isomerization phenomenon. Moreover, the binding stoichiometry of probe with Ag+, Hg2+ and F− ions was established based on Job's plot, 1H NMR, 19F NMR titrations and ESI-MS analysis. Furthermore, the sensing behavior of probe for Ag+, Hg2+ and F− ions was supported by Density Functional Theory (DFT) calculations. Besides, cell viability of the probe was demonstrated using live cell imaging experiment and the probe is proved to be an excellent chemical tool for mapping F− and Ag+ ions distribution in HeLa cells and Zebrafish embryos respectively in biological environments. • We reported a new naphthyl hydrazone anchored salicyl unit for the detection of Ag+/Hg2+/F− ions in DMSO/H 2 O (9:1 v/v) medium. • The binding ratio of ghost/guest was confirmed by Job's plot, 1H NMR titration, 19F NMR and ESI-MS analysis. • The probe has followed the inhibition of both PET and C N isomerization mechanistic pathway for sensing analytes. • The sensing mechanism was supported by DFT calculations. • The cell viability of the probe was demonstrated via live cell imaging experiments. [ABSTRACT FROM AUTHOR]