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Designing an imine-based fluorescent probe capable of greatly suppressing the tendency of intrinsic hydrolysis reaction is an attractive topic in the field of chemo-/biosensing. In this work, hydrophobic 1,1'-binaphthyl-2,2'-diamine containing two amine groups was introduced to synthesize probe R-1 bearing two imine bonds linked by two salicylaldehyde (SAs). The hydrophobicity of binaphthyl moiety and the unique clamp-like structure formed from double imine bonds and from ortho-OH on SA part make probe R-1 is able to function as an ideal receptor to coordinate with Al3+ ions, leading to the fluorescence originated from the complex rather than from the assumed hydrolyzed fluorescent amine is turned on. Further study revealed that, when Al3+ ions were introduced, both the hydrophobic binaphthyl moiety and the clamp-like double imine structure in the designed imine-based probe showed important contributions to suppress the intrinsic hydrolysis reaction, resulting in generating a stable coordination complex with an extremely high selectivity in fluorescence response.

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Nowadays, algae are becoming more and more popular as a food group rich in nutrients, cosmetic raw materials full of antioxidants or valuable dietary supplements. They are of interest for the industry because they are found almost all over the world, in all climatic zones, both in fresh and salt waters. The aim of this study was to take a broad look at green algae (Chlorophyta) and to show how large the variability of the content of active compounds may depend on the species and the place and time of sample collection. Particular attention was paid to compounds with antioxidant activity, whose simplified profiles were created on the basis of complementary, semi-quantitative methods. Additionally, time-yield extraction optimizations were performed. Three different specimens of Ulva lactuca were compared: from the coastal zone of the Baltic Sea, from the open Baltic Sea area around Bornholm and Ulva spiralis (Ulva lactuca polymorph) from the Atlantic Ocean. The studied algae of the Cladophora genera were three different species of freshwater algae from various habitats: a lake (Cladophora glomerata), a river (Cladophora rivularis) and aquarium farming (Cladophora aegagropila, syn. Aegagropila linnaei). The content of antioxidants and the extraction efficiency varied significantly depending on the species.

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Here, we report glutathione-protected water-soluble copper nanoclusters (Cu8 NCs) with excellent properties of high stability, large Stokes shift, and low toxicity. The molecular formula and structure of the Cu8 NCs were confirmed through good agreement between spectroscopic results and theoretical calculations. The origin of optical properties and chemical stability of the Cu8 NCs was determined through natural bond orbital analysis combined with time-dependent density functional theory calculations. It was found that the fluorescence emission and quantum yields of Cu8 NCs could be effectively enhanced by aluminum(III) ions (Al3+) through the aggregation-induced enhanced emission mechanism. On the basis of the strong reaction of Al3+ with F-, the enhanced fluorescence of the obtained Cu8 NC-Al3+ ensemble could be selectively turned off by fluoride ions (F-), achieving highly sensitive detection of F- in aqueous with a detection limit of 0.16 µM. Also, the fluorescence of Cu8 NC-Al3+ ensemble quenched by F- could be enhanced again upon binding additional Al3+. In addition, the proposed Cu8 NC-Al3+ ensemble with enhanced fluorescence was used for bioimaging in vitro and in vivo. These results indicated that Cu8 NCs are promising materials for sequential sensing and bioimaging in the future.

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A simple water-soluble polymer PEGBHB based on polyethylene glycol bearing a Schiff base derivative moiety was successfully designed and synthesized. PEGBHB showed high selectivity and sensitivity towards Al3+ as a turn-on fluorescent chemosensor without influence by other competitive metal ions in 100% aqueous solution. The detection limit of PEGBHB for Al3+ was found to be 9.67 × 10-9 M. A 1:1 stoichiometry between PEGBHB and Al3+ has been confirmed by Job plot analysis. PEGBHB could detect Al3+ over a wide pH range from 4 to 10. The chemosensor was reversible by adding EDTA to the solution of PEGBHB-Al3+ complex. An INHIBIT molecular logic gate was constructed with the help of OFF-ON-OFF signal on alternate addition of Al3+ and EDTA to the chemosensor. Furthermore, test papers were fabricated facilely using PEGBHB for convenient and visual detection of practical Al3+.

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This manuscript studies the fluorescent property of 3-[(2-hydroxy-1-naphthyl)methylideneamino]benzoic acid (H2L). Fluorescent spectra show that in different solvents, H2L displays different fluorescent properties, which can be attributed to the interaction between the solvents and H2L. Further study indicates that H2L exhibits a highly selective and sensitive recognition for Hg2+ ions in dimethylsulfoxide (DMSO), Al3+ ions in methanol and N,N'-dimethylformamide/water (DMF/H2O, 1/1, v/v). The bonding modes and bonding ratio of H2L and metal ions in different solvents are explored by Job's plot, 1H NMR titration, and electrospray ionization mass spectrometry (ESI-MS). The probable mechanisms were discussed.

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Bay functionalized perylene diimide substituted with pyridine isomers, (2-pyridine (2HMP-PDI), 3-pyridine (3-HMP-PDI) and 4-pyridine (4-HMP-PDI)) have been synthesized and explored for selective coloro/fluorimetric sensing of heavy transition metal ions. HMP-PDIs showed strong NIR absorption (760-765 nm) in DMF. The absorption and fluorescence of HMP-PDIs have been tuned by make use of pyridine isomers. Reddish-orange color was observed for 2-HMP-PDI (λmax = 437, 551, 765 nm) whereas 4-HMP-PDI exhibited light green (λmax = 432, 522, 765 nm). 3-HMP-PDI showed orange-yellow (λmax = 431, 524, 762 nm). The fluorescence spectra of 2-, 3- and 4-HMP-PDI showed λmax at 585, 538, 546 nm, respectively. Interestingly, HMP-PDI dyes showed selective color change (intense pink color) and fluorescence quenching for Fe3+ and Al3+ metal ions in DMF. Absorbance spectra revealed complete disappearance of NIR absorption and intensification/appearance of new peak at lower wavelength. The concentration dependent studies suggest that 4-HMP-PDI can detect up to 36.52 ppb of Fe3+ and 43.12 ppb of Al3+ colorimetrically. The interference studies in presence of other metal ions confirmed the good selectivity for Fe3+ and Al3+. The mechanistic studies indicate that Lewis acidic character of Fe3+ and Al3+ ions were responsible for selective color change and fluorescence quenching.

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BaO-B2 O3 -P2 O5 glasses doped with a fixed concentration of Tb3+ ions and varying concentrations of Al2 O3 were synthesized, and the influence of the Al3+ ion concentration on the luminescence efficiency of the green emission of Tb3+ ions was investigated. The optical absorption, excitation, luminescence spectra and fluorescence decay curves of these glasses were recorded at ambient temperature. The emission spectra of terbium ions when excited at 393 nm exhibited two main groups of bands, corresponding to 5 D3  â†’ 7 Fj (blue region) and 5 D4  â†’ 7Fj (green region). From these spectra, the radiative parameters, viz., spontaneous emission probability A, total emission probability AT , radiative lifetime τ and fluorescent branching ratio ß, of different transitions originating from the 5 D4 level of Tb3+ ions were evaluated based on the Judd-Ofelt theory. A clear increase in the quantum efficiency and luminescence of the green emission of Tb3+ ions corresponding to 5 D4  â†’ 7 F5 transition is observed with increases in the concentration of Al2 O3 up to 3.0 mol%. The improvement in emission is attributed to the de-clustering of terbium ions by Al3+ ions and also to the possible admixing of wave functions of opposite parities. Copyright © 2016 John Wiley & Sons, Ltd.

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