Search results for "luminescence."

showing 10 items of 1568 documents

Luminescence of oxygen related defects in zirconia nanocrystals

2007

The luminescence of undoped tetragonal structure ZrO2 nanocrystals was studied. The luminescence intensity depends on oxygen content in gases mixture in which the nanocrystals were annealed. The distorted Zr-O bond is suggested to be the recombination center for band carriers. The oxygen deficient defect is proposed to be responsible for photoluminescence. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Tetragonal crystal systemPhotoluminescenceOxygen deficientNanocrystalChemistrychemistry.chemical_elementCubic zirconiaCondensed Matter PhysicsLuminescencePhotochemistryOxygen contentOxygenphysica status solidi c
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Rapid and eco-friendly synthesis of graphene oxide-silica nanohybrids

2014

The increasing interest in Graphene oxide (GO) is due to many issues: the presence of both sp2-conjugated atoms and oxygen-containing functional groups provides a strong hydrophilicity and the possibility to further functionalize it with other molecules (i.e. π-π interactions covalent attachment etc.) [1]. Furthermore since the GO is biocompatible and noncytotoxic many studies have been recently focused on the development of GO-based nanodevices for bioimaging DNA detection drug delivery. Due to their low cytotoxicity and large internal surface area silica nanoparticles have been taken into account as promising material for biolabeling and drug loading/delivery. Particular consideration has recently been demonstrated for GO-silica composites because of the potentialities for electrical applications their chemical inertia and stability toward ions exposure. The possibility to combine the extraordinary properties of GO and silica offers several advantages for the realization of nanoprobes for biological applications and of biosensor [12]. The strategy for the fabrication of GO-nanosilica nanohybrids can be schematized as follows: (i) synthesis of GO by oxidizing graphite powder with the method described by Marcano et al. [3] (ii) Preparation of oxygen-loaded silica nanoparticles by thermal treatments in controlled atmosphere in order to induce high NIR emission at 1272 nm from high purity silica nanoparticles. (iii) preparation of GrO-silica nanohybrid films via rapid solvent casting in water. The nanohybrids were tested by XPS FTIR Raman analysis UV photoluminescence analysis TGA Zeta potential measurements electrical tests AFM and SEM. Several nanohybrids were prepared by combining two different typologies of GO and two different samples of silica.
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Chalcopyrite Semiconductors for Quantum Well Solar Cells

2011

We explore here the possibilities of using highly absorbing chalcopyrite semiconductors of the type Cu(In,Ga)Se2 in a quantum well solar cell structure. Thin alternating layers of 50 nm CuInSe2 and CuGaSe2 were grown epitaxially on a GaAs(100) substrate employing metalorganic vapor phase epitaxy. The optical properties of a resulting structure of three layers were investigated by photoluminescence and photoreflectance, indicating charge carrier confinement ∗To whom correspondence should be addressed †Helmholtz-Zentrum Berlin ‡Universidad Politecnica de Madrid ¶University of Illinois §University of Jyvaskyla ‖Current address: Universitat des Saarlandes, Uni Campus, Gebaude A5.1, 66123 Saarbr…

Theory of solar cellsPhotoluminescenceMaterials scienceta114Renewable Energy Sustainability and the Environmentbusiness.industryHybrid solar cellQuantum dot solar cellEpitaxylaw.inventionlawSolar cellOptoelectronicsGeneral Materials ScienceCharge carrierbusinessQuantum wellAdvanced Energy Materials
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ChemInform Abstract: Relaxation Phenomena of a Triplet Spin Probe in Glassy and Crystalline o-Terphenyl.

2010

The authors used quinoxaline in its photoexcited triplet state as a spin probe in order to measure the spin-lattice relaxation rate in o-terphenyl glass as a function of temperature. They found a power law with an exponent close to 2. Since o-terphenyl can easily be crystallized, they investigated the crystal, too. Below 3.5 K the spin is highly polarized, contrary to the behavior in the glass, where it reaches thermal equilibrium down to the lowest temperatures of their experiment (1.4 K). Around 3.5 K the polarization in the crystal vanishes. Above it appears with opposite sign due to thermal equilibration.

Thermal equilibriumCondensed matter physicsGeneral MedicinePolarization (waves)Condensed Matter::Disordered Systems and Neural NetworksSpin probeCrystalchemistry.chemical_compoundchemistryTerphenylOrganic chemistryTriplet stateLuminescenceSpin (physics)ChemInform
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Thermochromic Fluorescence from B18H20(NC5H5)2: An Inorganic–Organic Composite Luminescent Compound with an Unusual Molecular Geometry

2017

BH(NCH) is a rare example of two conjoined boron hydride subclusters of nido and arachno geometrical character. At room temperature, solutions of BH(NCH) emit a 690 nm fluorescence. In the solid state, this emission is shifted to 620 nm and intensifies due to restriction of the rotation of the pyridine ligands. In addition, there is a thermochromicity to the fluorescence of BH(NCH). Cooling to 8 K engenders a further shift in the emission wavelength to 585 nm and a twofold increase in intensity. Immobilization in a polystyrene thin-film matrix results in an efficient absorption of pumping excitation energy at 414 nm and a 609 nm photostable fluorescence. Such fluorescence from polystyrene t…

ThermochromismMaterials scienceHydrideBoranes02 engineering and technology010402 general chemistry021001 nanoscience & nanotechnologyPhotochemistry01 natural sciencesFluorescenceAtomic and Molecular Physics and Optics0104 chemical sciencesElectronic Optical and Magnetic Materialschemistry.chemical_compoundchemistryPolystyrene0210 nano-technologySpectroscopyLuminescenceAbsorption (electromagnetic radiation)
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Study on the thermotropic properties of highly fluorinated 1,2,4-oxadiazolylpyridinium salts and their perspective applications as ionic liquid cryst…

2007

A new series of fluorinated salts, iodides and trifluoromethanesulfonates, was synthesized from perfluoroalkylated 1,2,4-oxadiazolylpyridines. Their thermotropic properties were investigated by combined temperature resolved small angle and wide angle X-ray scattering, differential scanning calorimetry and polarised optical microscopy. The UV–visible and photoluminescence properties were studied for all compounds. The results showed for two compounds the existence of an enantiotropic mesomorphic smectic liquid crystal phase. All iodides showed thermochromism phenomena suggesting prospective applications in optoelectronics.

ThermochromismPhotoluminescenceChemistryOrganic salts ionic liquid crystals perfluoroalkyl oxadiazolylpyridiniumGeneral ChemistryThermotropic crystallaw.inventionCrystallographychemistry.chemical_compoundDifferential scanning calorimetryOptical microscopelawLiquid crystalPhase (matter)Ionic liquidMaterials ChemistryJournal of Materials Chemistry
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Polymorphism-Triggered Reversible Thermochromic Fluorescence of a simple 1,8-Naphthyridine

2013

The fluorescent behavior in the solid state of a naphthyridine-based donor–acceptor heterocycle is presented. Synthesized as a crystalline blue-emissive solid (Pbca), the compound can easily be transformed in its P21/c polymorphic form by heating. The latter material shows blue to cyan emission switching triggered by a reversible thermally induced phase transformation. This fact, the reversible acidochromism, and the strong anisotropic fluorescence of the compound in the solid state, account for the potential of 1,8-naphthyridines as simple and highly tunable organic compounds in materials science.

ThermochromismnaphthyridinesChemistryStereochemistryfield-effect transistorsSolid-statefood and beverageschemical sensorsGeneral ChemistrylassersCondensed Matter PhysicsFluorescenceCombinatorial chemistrysolid-state fluorescencePolymorphism (materials science)emissionconjugated polymersluminescencepackingGeneral Materials ScienceLuminescencephotocromism
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DIFFERENT APPROACHES TO DATE BRICKS FROM HISTORICAL BUILDINGS

2014

Abstract The application of Thermally (TL) and Optically (OSL) Stimulated Luminescence on bricks used as building material has allowed solving an chronological issue in the field of historical building dating. The possibility to use one or more methodologies of dating is closely related to the luminescent and granulometric characteristics of the sample. Using some brick samples collected in the church of Sain Seurin in Bordeaux (France), this paper discusses the implications and the possibility to use different approaches and techniques for dating. With this aim luminescence measurements were performed on both polymineral fine grain and quartz inclusion phases extracted from each brick. For…

Thermoluminescence datingField (physics)Earth scienceEarth and Planetary Sciences (miscellaneous)engineeringMineralogyBuilding materialengineering.materialGeology
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Luminescence Dating of Fluvial Deposits in the Rock Shelter of Cueva Antón, Spain

2015

Abstract The fluvial sediments at Cueva Antón, a Middle Palaeolithic rock shelter located in the valley of the River Mula (Southeast Spain), produced abundant lithic assemblages of Mousterian affinities. Radiocarbon dates are available for the upper part of the archaeological succession, while for the middle to lower parts chronometric data have been missing. Here we present luminescence dating results for these parts of the succession. Quartz OSL on small aliquots and single grain measurements yield ages ranging from 69 ± 7 ka to 82 ± 8 ka with a weighted mean of 72 ± 4 ka for sub-complexes AS2 to AS5. Equivalent dose estimates from large aliquots were highest and inconsistent with those f…

Thermoluminescence datingLuminescence datingFluvial sedimentGeochemistryFluvialMousterianEcological successionArqueologiaFeldsparlaw.inventionlawvisual_artEarth and Planetary Sciences (miscellaneous)visual_art.visual_art_mediumMiddle PalaeolithicRadiocarbon datingSingle grain datingPost-IR IRSLCueva AntónQuartzGeomorphologyRock shelterGeologyGeochronometria
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Middle to Upper Pleistocene morphostructural evolution of the NW-coast of Sicily: thermoluminescence dating and palaeontological-stratigraphical eval…

1997

Abstract Infralittoral and terrigenous Middle to Upper Pleistocene deposits outcropping at the NW-coast of Sicily (Gulf of Castellammare and peninsula of Capo San Vito) were investigated in order to recognise glacio-eustatically caused sea level highstands and the interference between tectonics, eustasy and local conditions of the coast. The results, originating from a stratigraphically important area, were obtained by palaeontological-stratigraphical analyses, physical age determination with the thermoluminescence method and by detailed morphostructural studies. The marine deposits, situated at 3–40 m a.s.l., mainly provide an oligotypic molluscan fauna referable to modern SGCF-, SFHN- and…

Thermoluminescence datingPleistoceneOutcropTerrigenous sedimentPaleontologyOceanographyDeep seaPaleontologyStage (stratigraphy)Glacial periodEcology Evolution Behavior and SystematicsGeologySea levelEarth-Surface ProcessesPalaeogeography, Palaeoclimatology, Palaeoecology
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