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UV Excitation (uv + excitation)
Selected AbstractsDetection of nematode antagonistic bacteria by fluorogenic molecular probes,EPPO BULLETIN, Issue 3-4 2000A. Ciancio Last-generation DNA probes include molecules yielding a fluorogenic emission through an intramolecular change occurring after hybridization to a complementary sequence. They display a high sequence specificity and may detect even single-base mutations in polymerase chain reaction (PCR) amplification products. We applied Scorpion primers for the detection of an unculturable nematode-parasitic bacterium, Pasteuria sp., with potential as a biological control agent. A 16S rDNA oligonucleotide sequence unique to Pasteuria spp. was used to detect the parasite in juveniles of Heterodera goettingiana or in soil. The parasitized nematodes came from a population with a Pasteuria prevalence of 40,80% and were individually checked for parasitism. Probes with 6-carboxy-fluorescein (FAM) at the 5'terminus, used for PCR with nematodes or soil, successfully detected the parasite from both samples. The amplification of the expected 139bp fragment was shown both by fluorescence observed under UV excitation in the eppendorfs and by gel electrophoresis of the corresponding amplicons. The potential of this detection method for the study of unculturable bacteria is discussed. [source] Regiospecific Three-Component Access to Fluorescent 2,4-Disubstituted Quinolines via One-Pot Coupling-Addition-Cyclocondensation-Sulfur Extrusion Sequence,EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 18 2010Sven Rotzoll Abstract 2,4-Di- and 2,4,7-trisubstituted quinolines are readily synthesized in a regioselective fashion from acyl chlorides, terminal alkynes, and 2-aminothiophenols by a consecutive, microwave-assisted one-pot three-component Sonogashira coupling-Michael addition,cyclocondensation sequence and following sulfur extrusion in moderate to good yields. The terminal sulfur extrusion step was studied by DFT computations. The absorption spectra of 2,4-disubstituted quinolines can be rationalized by DFT-ZINDO-CI calculations and all derivatives show intense blue emission upon UV excitation. [source] Plasmonic Enhancement or Energy Transfer?ADVANCED FUNCTIONAL MATERIALS, Issue 13 2009Its Potential for Light-Emitting Devices, Lanthanide-Doped Silicate Glasses, On the Luminescence of Gold-, Silver- Abstract With the technique of synchrotron X-ray activation, molecule-like, non-plasmonic gold and silver particles in soda-lime silicate glasses can be generated. The luminescence energy transfer between these species and lanthanide(III) ions is studied. As a result, a significant lanthanide luminescence enhancement by a factor of up to 250 under non-resonant UV excitation is observed. The absence of a distinct gold and silver plasmon resonance absorption, respectively, the missing nanoparticle signals in previous SAXS and TEM experiments, the unaltered luminescence lifetime of the lanthanide ions compared to the non-enhanced case, and an excitation maximum at 300,350,nm (equivalent to the absorption range of small noble metal particles) indicate unambiguously that the observed enhancement is due to a classical energy transfer between small noble metal particles and lanthanide ions, and not to a plasmonic field enhancement effect. It is proposed that very small, molecule-like noble metal particles (such as dimers, trimers, and tetramers) first absorb the excitation light, undergo a singlet-triplet intersystem crossing, and finally transfer the energy to an excited multiplet state of adjacent lanthanide(III) ions. X-ray lithographic microstructuring and excitation with a commercial UV LED show the potential of the activated glass samples as bright light-emitting devices with tunable emission colors. [source] Dual-Mode Luminescent Colloidal Spheres from Monodisperse Rare-Earth Fluoride NanocrystalsADVANCED MATERIALS, Issue 19 2009Peng Li Monodisperse rare-earth fluoride nanocrystals are synthesized and used as building blocks to fabricate dual-mode luminescent colloidal spheres, which are composed of two distinct units, one offering down-converting luminescence under UV excitation and the other providing up-converting luminescent emission when excited with a 980,nm laser, and have potential applications in multiplexed and highly sensitive bioassays. [source] Photophysical Properties of Terbium Molecular-based Hybrids Assembled with Novel Ureasil LinkagesPHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 4 2007Bing Yan Three silica-based organic,inorganic hybrid systems composed of hydroxyl aromatic derivatives (2-acetylphenol [HAP], 2-hydroxy-3-methylbenzoic acid [HMBA], 3-hydroxy-meta-phthalic acid [HMPHTH] complexes) were prepared via a sol,gel process. The active hydroxyl groups of the three ligands grafted by 3-(triethoxysilyl)-propyl isocyanate (TESPIC) through hydrogen transfer addition reaction were used as multi-functional bridge components, which can coordinate to Tb3+ with carbonyl groups, strongly absorb ultraviolet light and effectively transfer energy to Tb3+ through their triplet excited state, as well as undergo polymerization or crosslinking reactions with tetraethoxysilane (TEOS), for anchoring terbium ions to silica backbone. NMR, FT-IR, UV,vis absorption, luminescence spectroscopy was used to investigate the obtained hybrid material. UV excitation in the organic component resulted in strong green emission from Tb3+ ions due to an efficient ligand-to-metal energy transfer mechanism. [source] Thermal quenching of luminescence and isovalent trap model for rare-earth-ion-doped AlNPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 6 2007H. J. Lozykowski Abstract Investigations of the luminescent properties of Pr-, Eu-, Tb- and Tm-implanted AlN thin films at temperature in the range 9,830 K are reported. The temperature studies of photoluminescence and cathodoluminescence spectra revealed unexpectedly weak thermal quenching for all investigated rare earth (RE) ions. The maximum CL emission is observed from Eu (red) at 485 K, Tb (green) at 590 K and Tm (blue) at 530 K, respectively. For Tb- and Tm-doped AlN samples, temperature-dependent crossrelaxation processes were observed. Photoluminescence excitation spectra, obtained under UV excitation in the spectral range 200,400 nm, exhibit several bands. It is proposed that the RE ions exist in semiconductors as isolated ions (singlet), nearest-neighbor (nn) ion pairs (dimer), and three ions (trimer). The Koster,Slater and simple spherical potential-well models for RE-structured isovalent (RESI) hole trap are proposed. The exciton binding energies of RESI traps are calculated and compared with experimental thermal-quenching energies. The energy-transfer processes between the AlN host and the 4f-shell systems are emphasized as the main mechanisms for thermal-quenching processes rather than nonradiative decay of 4f transitions. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Defects in Ce3+ doped Y2SiO5PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 1 2005T. Aitasalo Abstract The crystal defects in the Ce3+ doped X2 -type yttrium oxyorthosilicate, X2 -Y2SiO5:Ce3+, were studied by high-resolution time-resolved laser excited photoluminescence (PL), thermoluminescence (TL) and EPR spectroscopy. X2 -Y2SiO5:Ce3+ shows two strong 5d1,4f1 emission bands with maxima at about 395 (25300) and 430 nm (23250 cm,1) with ca. 40 ns decay times. In addition, two very weak emission bands at 484 (20660) and 577 nm (17330 cm,1) under wide band UV excitation (maximum at 360 nm) from a pulsed Xe lamp can be observed with decay times in the millisecond range. Under the third harmonic of a Nd:YAG laser (355 nm) excitation these bands are split into a number of sharper bands. The EPR shows the presence of electrons occupying anion vacancies in Y2SiO5 lattice while thermoluminescence revealed the presence of two different traps which are, however, too deep for efficient persistent luminescence materials. The defects play a crucial role in the creation of the Ce3+,Ce4+ charge transfer luminescence. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] | ||||||||||||||||