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Strong Emission (strong + emission)
Selected AbstractsConstruction of 1D and 2D Copper(I) Coordination Polymers Assembled by PhS(CH2)nSPh (n = 1, 2) Dithioether Ligands: Surprising Effect of the Spacer Length on the Dimensionality, Cluster Nuclearity and the Fluorescence Properties of the Metal,Organic Framework,EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 13 2007Harmel N. Peindy Abstract Treatment of CuI with PhSCH2SPh in MeCN solution affords, by a self-assembly reaction, the monodimensional metal,organic coordination polymer [Cu4I4{,-PhS2CH2SPh}2]n (1), in which Cu4(,3 -I)4 cluster units are linked by the dithioether ligand in a 1D necklace structure. In contrast, the reaction of PhSCH2CH2SPh with CuI results in the formation of the metallopolymer [(CuI)2{,-PhS(CH2)2SPh}2]n (2). The 2D network of 2 is built from dimeric Cu2I2 units which are connected by 1,2-bis(phenylthio)ethane bridging ligands. The solid-state luminescence spectrum of 1 exhibits a strong emission around 532 nm, whereas a weak emission centred at 413 nm is observed in the case of 2. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] A Graphene Nanoprobe for Rapid, Sensitive, and Multicolor Fluorescent DNA AnalysisADVANCED FUNCTIONAL MATERIALS, Issue 3 2010Shijiang He Abstract Coupling nanomaterials with biomolecular recognition events represents a new direction in nanotechnology toward the development of novel molecular diagnostic tools. Here a graphene oxide (GO)-based multicolor fluorescent DNA nanoprobe that allows rapid, sensitive, and selective detection of DNA targets in homogeneous solution by exploiting interactions between GO and DNA molecules is reported. Because of the extraordinarily high quenching efficiency of GO, the fluorescent ssDNA probe exhibits minimal background fluorescence, while strong emission is observed when it forms a double helix with the specific targets, leading to a high signal-to-background ratio. Importantly, the large planar surface of GO allows simultaneous quenching of multiple DNA probes labeled with different dyes, leading to a multicolor sensor for the detection of multiple DNA targets in the same solution. It is also demonstrated that this GO-based sensing platform is suitable for the detection of a range of analytes when complemented with the use of functional DNA structures. [source] Defect-Related Optical Behavior in Surface Modified TiO2 NanostructuresADVANCED FUNCTIONAL MATERIALS, Issue 1 2005M. Prokes Abstract The surface modification of TiO2 nanostructures to incorporate nitrogen and form visible light absorbing titanium oxynitride centers is studied. Anatase TiO2 structures in the 5,20,nm range, formed by a wet chemical technique, were surface modified and the nitridation of the highly reactive TiO2 nanocolloid surface, as determined by X-ray photoelectron spectroscopy (XPS) studies, is achieved by a quick and simple treatment in alkyl ammonium compounds. The nitriding process was also simultaneously accompanied by metal seeding resulting in a metal coating layer on the TiO2 structures. The structure of the resultant titanium oxynitride nanostructures remains anatase. These freshly prepared samples exhibited a strong emission near 560,nm (2.21,eV), which red-shifted to 660,nm (1.88,eV) and dropped in intensity with aging in the atmosphere. This behavior was also evident in some of the combined nitrogen doped and metal seeded TiO2 nanocolloids. Electron spin resonance (ESR) performed on these samples identified a resonance at g,=,2.0035, which increased significantly with nitridation. The resonance is attributed to an oxygen hole center created near the surface of the nanocolloid, which correlates well with the observed optical activity. [source] Electronic structure of GaN(0001)-2 × 2 thin films grown by PAMBEPHYSICA STATUS SOLIDI - RAPID RESEARCH LETTERS, Issue 5 2008R. Gutt Abstract Gallium nitride thin films were grown on silicon carbide (0001) by plasma-assisted molecular beam epitaxy (PAMBE). The samples were cooled down in nitrogen plasma and characterized in situ by reflection high energy electron diffraction (RHEED), photoelectron spectroscopy (XPS/UPS), and atomic force microscopy (AFM) revealing stoichiometric and smooth GaN films virtually free of contaminations. We present valence band data obtained by UPS with strong emission from surface states inside the fundamental band gap. These states and the observed 2 × 2 surface reconstruction are highly sensitive towards residual molecules. Once these surface states have disappeared the original state could not be recovered by surface preparation methods underlining the necessity of in situ investigations on as-grown surfaces. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Cathodoluminescence, High-Resolution X-Ray Diffraction and Transmission-Electron-Microscopy Investigations of Cubic AlGaN/GaN Quantum WellsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 1 2003D.J. As Abstract The structural and optical properties of cubic Al0.25Ga0.75N/GaN multi quantum well structures grown on GaAs (001) substrates by radio-frequency plasma-assisted molecular beam epitaxy (MBE) are reported. Transmission electron microscopy (TEM), high resolution X-ray diffraction (HRXRD), and cathodoluminescence (CL) measurements are used to characterize the cubic Al0.25Ga0.75N/GaN quantum wells. The interfaces between the quantum-well and barrier layers are well resolved, abrupt and the entire structure shows an excellent periodicity. Due to the high dislocation density of about 1010 cm,2 a severe broadening of the XRD-reflection is observed and superlattice satellite peaks are only weakly indicated. Further, a wavy structure is seen in TEM at the coalescence of submicron-size grains. Nevertheless, CL at room temperature shows a strong emission of quantized states at 3.352 eV. [source] The layered compound poly[,2 -4,4,-bipyridyl-di-,2 -chlorido-mercury(II)]ACTA CRYSTALLOGRAPHICA SECTION C, Issue 5 2007Yi-Ming Xie The title compound, [HgCl2(C10H8N2)]n, features two-dimensional [HgCl2(4,4,-bipy)]n neutral networks (4,4,-bipy is 4,4,-bipyridine), based on an octahedral Hg atom coordinated by four ,2 -Cl atoms and two ,2 -4,4,-bipy ligands in trans positions, yielding a HgCl4N2 octahedron. The structure has mmm symmetry about the Hg atoms, with most of the atoms on at least one mirror plane, but the unsubstituted C atoms of the 4,4,-bipy rings are disordered across a mirror plane. Photoluminescent investigations reveal that the title compound displays a strong emission in the green region, which probably originates from a ligand-to-ligand charge-transfer transition. [source] Discrimination of Single-Nucleotide Alterations by G-Specific Fluorescence QuenchingCHEMBIOCHEM, Issue 6 2005Chikara Dohno Dr. Abstract A new strategy for the detection of single-base alterations through fluorescence quenching by guanine (G) is described. We have devised a novel base-discriminating fluorescent (BDF) nucleoside, 4,PyT, that contains a pyrenecarboxamide fluorophore at the thymidine sugar's C4,-position. 4,PyT-containing oligodeoxynucleotides only exhibited enhanced fluorescence in response to the presence of a complementary adenine base. In contrast, the fluorescence of mismatched duplexes containing 4,PyT/N base pairs (N=C, G, or T) was considerably weaker. This highly A-selective fluorescence was a product of guanine-specific quenching efficiency; when the complementary base to 4,PyT was a mismatch, the pyrenecarboxamide fluorophore was able to interact intimately with neighboring G bases (the most likely interaction in the case of intercalation), so effective quenching by the G bases occurred in the mismatched duplexes. In contrast, duplexes containing 4,PyT/A base pairs exhibited strong emission, since in this case the fluorophores were positioned in the minor groove and able to escape fluorescence quenching by the G bases. [source] An Efficient Fluorescence Resonance Energy Transfer (FRET) between Pyrene and Perylene Assembled in a DNA Duplex and Its Potential for Discriminating Single-Base ChangesCHEMISTRY - A EUROPEAN JOURNAL, Issue 8 2010Hiromu Kashida Dr. Abstract To increase the apparent Stokes' shift of perylene, pyrene (donor) and perylene (acceptor) were assembled in a DNA duplex to achieve the efficient fluorescence resonance energy transfer (FRET) from pyrene to perylene. Multiple donors were introduced in the vicinity of acceptors through D -threoninol and natural base pairs were inserted between the dyes. Accordingly, donors and acceptors could be accumulated inside the DNA without forming an undesired excimer/exciplex. When two pyrene moieties were located in proximity to one perylene with one base pair inserted between them, efficient FRET occurred within the duplex. Thus, strong emission at 460,nm was observed from perylene when excited at 345,nm at which pyrene has its absorption. The apparent Stokes' shift became as large as 115,nm with a high apparent FRET efficiency (,>1). However, the introduction of more than two pyrenes did not enhance the fluorescence intensity of perylene, due to the short Förster radius (R0) of the donor pyrene. Next, this FRET system was used to enlarge the Stokes' shift of the DNA probe, which can discriminate a one-base deletion mutant from wild type with a model system by incorporation of multiple donors into DNA. Two perylene moieties were tethered to the DNA on both sides of the intervening base, and two pyrenes were further inserted in the vicinity of the perylenes as an antenna. Hybridization of this FRET probe with a fully matched DNA allowed monomer emission of perylene when the pyrenes were excited. In contrast, excimer emission was generated by hybridization with a one-base deletion mutant. Thus, the apparent Stokes' shift was enhanced without loss of efficiency in the detection of the deletion mutant. [source] Hybridization-Sensitive On,Off DNA Probe: Application of the Exciton Coupling Effect to Effective Fluorescence QuenchingCHEMISTRY - AN ASIAN JOURNAL, Issue 6 2008Shuji Ikeda Dr. Abstract The design of dyes that emit fluorescence only when they recognize the target molecule, that is, chemistry for the effective quenching of free dyes, must play a significant role in the development of the next generation of functional fluorescent dyes. On the basis of this concept, we designed a doubly fluorescence-labeled nucleoside. Two thiazole orange dyes were covalently linked to a single nucleotide in a DNA probe. An absorption band at approximately 480,nm appeared strongly when the probe was in a single-stranded state, whereas an absorption band at approximately 510,nm became predominant when the probe was hybridized with the complementary strand. The shift in the absorption bands shows the existence of an excitonic interaction caused by the formation of an H aggregate between dyes, and as a result, emission from the probe before hybridization was suppressed. Dissociation of aggregates by hybridization with the complementary strand resulted in the disruption of the excitonic interaction and strong emission from the hybrid. This clear change in fluorescence intensity that is dependent on hybridization is useful for visible gene analysis. [source] Three Novel Functional CdII Dicarboxylates with Nanometer Channels: Hydrothermal Synthesis, Crystal Structures, and Luminescence PropertiesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 2 2007Yu-Peng Tian Abstract Three novel functional transition-metal complexes with H2A (H2A = 9-ethylcarbazole-3,6-dicarboxylic acid), Cd(HA)2(H2O)2 (1), [Cd(A)(phen)]·1.5H2O (2) (phen = 1,10-phenanthroline), and Cd(HA)2(bipy) (3) (bipy = 4,4,-bipyridine), have been successfully synthesized by a hydrothermal synthetic method and characterized by single-crystal X-ray diffraction, infrared spectroscopy, elemental analysis, thermogravimetric analysis, and photoluminescence. The results show that all of the complexes contain nanometer channels, while the coordination modes were changed by the addition of the mixed ligands. The 2D supramolecular open-framework 1 is constructed through hydrogen-bond and aromatic ,,, interactions. 2D coordination polymer 2 is constructed by ,,, interactions between adjacent metal-organic polymeric coordination chains. Interestingly, the 3D supramolecular architecture of 3 first formed 2D grid layers from 1D chains by intermolecular hydrogen bonds and then extended into a 3D structure through aromatic ,,, interactions. Furthermore, strong emissions from these complexes were also changed by the coordination modes in the solid state. However, complexes 1,3 show high thermal stability.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Colloidal Tm3+/Yb3+ -Doped LiYF4 Nanocrystals: Multiple Luminescence Spanning the UV to NIR Regions via Low-Energy ExcitationADVANCED MATERIALS, Issue 40 2009Venkataramanan Mahalingam Highly dispersible Tm3+/Yb3+ -doped LiYF4 nanocrystals were synthesized using a thermal decomposition method. Upon excitation with a NIR diode laser (980,nm), the dilute dispersion of the nanocrystals exhibits several strong emissions in regions spanning the deep-UV to NIR, all originating from a single dopant/sensitizer (Tm3+/Yb3+) combination. The material is envisioned to have potential interests in anti-counterfeiting, biomedicine and solution-based scintillation applications. [source] [Pt(topy)(Htopy)(ONO2)] complex (Htopy = 2- p -tolylpyridine) and its analogs: 195Pt NMR spectra and fabrication of light-emitting devicesAPPLIED ORGANOMETALLIC CHEMISTRY, Issue 4 2009Hiroto Fukuda Abstract We report fast, high-yield syntheses of a series of [Pt(C,N)(HC,N)X] complexes, where HC,N is 2-phenylpyridine (Hppy) or 2- p -tolylpyridine (Htopy) and X, is Cl,, Br,, I,, ONO2,, NO2, or SCN,. The structure of [Pt(topy)(Htopy)(ONO2)] was analyzed by single-crystal X-ray diffraction. Substitution of Cl, with Br, or I, in our complexes shifted the 195Pt NMR peaks upfield in the order Cl, < Br, < I,, but the magnitudes of their shifts were one-tenth those observed for non-cyclometalated platinum(II) complexes. As the two nitrato complexes showed strong emissions in acetonitrile solution,three to six times those of other complexes,they were used to fabricate OLEDs. Although their emissions were not particularly strong, devices fabricated with platinum(II) complexes containing bulky ligands emitted green light with a short lifetime (,). Copyright © 2009 John Wiley & Sons, Ltd. [source] Molten-salt Synthesis and Properties of ZnS with Hexagonal Prism MorphologyCHINESE JOURNAL OF CHEMISTRY, Issue 10 2007Jin-Song LIU Abstract ZnS with hexagonal prism morphology has been synthesized successfully by molten-salt method with ZnS nanoparticles as precursors, and the ZnS nanoparticles were prepared by one-step solid-state reaction of Zn(CH3COO)2·2H2O with Na2S·9H2O at ambient temperature. Crystal structure and morphology of the product were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and HRTEM. Ultraviolet-visible optical absorption spectrum of the ZnS hexagonal prism shows a distinct red shift from that of bulk ZnS crystals and photoluminescence spectrum exhibits strong emissions at 380 and 500 nm, respectively. Further experiments were designed and the formation mechanism of the ZnS hexagonal prism has been also discussed in brief. [source] | ||||||||||||||||