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Fluorescence Sensing (fluorescence + sensing)

Distribution by Scientific Domains

Chemistry	50%

Selected Abstracts

Ratiometric Fluorescence Sensing of Fluoride Ions by an Asymmetric Bidentate Receptor Containing a Boronic Acid and Imidazolium Group

EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 18 2009
Zhaochao Xu
Abstract The synthesis of the first examples of anion receptors that utilize boron,fluoride interactions and (C,H)+···F, -type ionic hydrogen-bond interactions in the binding of F ions is reported herein. o -, m -, and p -Phenylboronic acids were linked to naphthoimidazolium through a methylene group. On the basis of fluorescence and 19F NMR studies, we have confirmed that the addition of fluoride to a boron center occurs prior to the formation of (C,H)+···F, -type ionic hydrogen bond with the imidazolium moiety. More importantly, these investigations have demonstrated that only the receptor bearing the ortho -directed boron and imidazolium exhibits enhanced fluoride binding. The increased binding ability of the asymmetric bidentate receptor of ortho -boronic acid and imidazolium towards F, enables it to sense fluoride ions in a 95:5 CH3CN/HEPES aqueous solution. The fluorescence responses to different anions were also explored; the ortho -boron-imidazolium receptor displayed ratiometric fluorescence changes and a high selectivity towards fluoride ions over other anions (Cl,, Br,, CH3CO2,, HSO4,, and H2PO4,).(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source]

Selective Zinc(II)-Ion Fluorescence Sensing by a Functionalized Mesoporous Material Covalently Grafted with a Fluorescent Chromophore and Consequent Biological Applications

ADVANCED FUNCTIONAL MATERIALS, Issue 2 2009
Krishanu Sarkar
Abstract A highly ordered 2D-hexagonal mesoporous silica material is functionalized with 3-aminopropyltriethoxysilane. This organically modified mesoporous material is grafted with a dialdehyde fluorescent chromophore, 4-methyl-2,6-diformyl phenol. Powder X-ray diffraction, transmission electron microscopy, N2 sorption, Fourier transform infrared spectroscopy, and UV-visible absorption and emission have been employed to characterize the material. This material shows excellent selective Zn2+ sensing, which is due to the fluorophore moiety present at its surface. Fluorescence measurements reveal that the emission intensity of the Zn2+ -bound mesoporous material increases significantly upon addition of various concentrations of Zn2+, while the introduction of other biologically relevant (Ca2+, Mg2+, Na+, and K+) and environmentally hazardous transition-metal ions results in either unchanged or weakened intensity. The enhancement of fluorescence is attributed to the strong covalent binding of Zn2+, evident from the large binding constant value (0.87,×,104M,1). Thus, this functionalized mesoporous material grafted with the fluorescent chromophore could monitor or recognize Zn2+ from a mixture of ions that contains Zn2+ even in trace amounts and can be considered as a selective fluorescent probe. We have examined the application of this mesoporous zinc(II) sensor to cultured living cells (A375 human melanoma and human cervical cancer cell, HeLa) by fluorescence microscopy. [source]

Enantioselective Fluorescence Sensing of Amino Acids by Modified Cyclodextrins: Role of the Cavity and Sensing Mechanism

CHEMISTRY - A EUROPEAN JOURNAL, Issue 11 2004
Sara Pagliari Dr.
Abstract Two selectors based on modified cyclodextrins containing a metal binding site and a dansyl fluorophore,6-deoxy-6- N -(N, -[(5-dimethylamino-1-naphthalenesulfonyl)aminoethyl]phenylalanylamino-,-cyclodextrin,containing D -Phe (3) and L -Phe (4) moieties were synthesized. The conformations of the two selectors were studied by circular dichroism, two-dimensional NMR spectroscopy and time-resolved fluorescence spectroscopy. Cyclodextrin 4 was found to have a predominant conformation in which the dansyl group is self-included in the cyclodextrin cavity, while 3 showed a larger proportion of the conformation with the dansyl group outside the cavity. As a consequence, the two cyclodextrins were found to bind copper(II) with different affinities, as revealed by fluorescence quenching in competitive binding measurements. Addition of D - or L -amino acids induced increases in fluorescence intensity, which were dependent on the amino acid used and in some cases on its absolute configuration. The cyclodextrin 4 was found to be more enantioselective than 3, suggesting that the self-inclusion in the cyclodextrin cavity strongly increases the chiral discrimination ability of the copper(II) complex. Accordingly, a linear fluorescent ligand N, -[(5-dimethylamino-1-naphthalenesulfonyl)aminoethyl]- N1 -propyl-phenylalaninamide, which has the same binding site and absolute configuration as 4, showed very low chiral discrimination ability. The enantioselectivity in fluorescence response was found to be due to the formation of diastereomeric ternary complexes, which were detected by ESI-MS and by circular dichroism. Time-resolved fluorescence studies showed that the fluorescence of the dansyl group was completely quenched in the ternary complexes formed, and that the residual fluorescence was due to uncomplexed ligand. [source]

Supramolecular Assembly of Perylene Bisimide with , -Cyclodextrin Grafts as a Solid-State Fluorescence Sensor for Vapor Detection

ADVANCED FUNCTIONAL MATERIALS, Issue 14 2009
Yu Liu
Abstract A nanoscopic supramolecular aggregate is constructed from perylene bisimide-bridged bis-(permethyl- , -cyclodextrins) 1 via ,,, stacking interactions. Its self-assembly behavior in organic and aqueous solutions is investigated by UV,Vis, fluorescence, and 1H NMR spectroscopy. Transmission electron microscopy and scanning electron microscopy images show the 1D nanorod aggregation of 1, which is birefringent under crossed polarizer conditions and strongly fluorescent as depicted in the fluorescence microscopy image. X-ray powder diffraction measurements indicate that 1 forms a well-ordered crystalline arrangement with a ,,, stacking distance of 4.02,Å. Furthermore, the solid-state fluorescence sensing is explored by utilizing the poly(vinylidene fluoride) membrane-embedded 1, giving that 1, as a novel vapor detecting material, can probe several kinds of volatile organic compounds and, especially, exhibits high sensitivity to organic amines. [source]