Search results for "luminescence."
showing 10 items of 1568 documents
Spectral Characteristics of Native Defects in BN
2002
Spectral characteristics of native defects from the crystalline lattice of c-BN were studied. It is found that the photoluminescence (PL) spectrum under exposure to ultraviolet-blue light has a complex structure containing a predominant wide 2.5 eV luminescence band at room temperature. The photostimulated luminescence (PSL) consists of a band, which is coincident with the 2.5 eV PL. The results obtained allow to conclude that the same defects are responsible for both the PL and PSL formation.
Luminescence of intrinsic defects in YAG polycrystalline powder
1997
In the present work we have investigated luminescence properties of the fine, well-crystallized undoped YAG polycrystalline powders and thermochemically treated YAG polycrystalline powders. Presented work give evidence of significant role of 'antisite' defects (AD), i.e., where some portion of one type of cations (Y 3+ ) occupy another cations (Al 3+ Oh ) sites and vice versa in YAG structure, on the creation and structure of luminescence centers in complex multi-component oxides.
<title>Origin of visible photoluminescence in NiO and Ni<formula><inf><roman>c</roman></inf></formula>Mg<…
2003
A study of the visible photoluminescence in single-crystal NiO and NicMg1-cO (c = 0.99, 0.98 and 0.95) solid solutions is presented for the first time. Two wide luminescence bands, peaked at approximately 12000 cm-1 and approximately 18500 cm-1, were observed. The dependence of their intensity and position on the excitation energy, temperature, and composition were investigated. We attribute the origin of two photoluminescence bands to the impurity- or defect perturbed Ni2+ excitons.© (2003) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
The role of Nb in intensity increase of Er ion upconversion luminescence in zirconia
2014
It is found that Nb co-doping increases the luminescence and upconversion luminescence intensity in rare earth doped zirconia. Er and Yb-doped nanocrystalline samples with or without Nb co-doping were prepared by sol-gel method and thermally annealed to check for the impact of phase transition on luminescence properties. Phase composition and grain sizes were examined by X-ray diffraction; the morphology was checked by scanning- and high-resolution transmission electron microscopes. Both steady-state and time-resolved luminescence were studied. Comparison of samples with different oxygen vacancy concentrations and different Nb concentrations confirmed the known assumption that oxygen vacanc…
<title>Primary radiation defect formation in silver halides</title>
1998
Under irradiation the formation of primary intrinsic defects in silver halide solid solutions AgBr1-xClx take place via strong exciton-phonon interaction. Efficiency of these defects formation depend on solid solution composition and within 0 <EQ x <EQ 0.15 dependence on temperature was observed too. Estimation shows efficiency of defects creation is approximately 0.01 for AgCl and noticeably higher for AgBr.© (1998) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
Tetrahedra from Aryleneethenylenes – From small Molecules to Luminescent Glasses
2004
AbstractThe fourfold Horner olefination of tetraphenylmethane or –silane with fourp-methyl- phosphonate groups and a variety of aromatic aldehydes with donor groups or extended conjugated systems results in the formation of tetrahedra from four chromophores connected via a central atom. Electronic spectra in solution reveal an electronic interaction between the π-systems. In the solid state, the emission of compounds with a dense packing is nearly identical to the solution spectra, more open structures show significant red shifts. The emission of scaffolds with 1-styrylpyrene chromophores is nearly completely quenched. Most of these tetrahedra are thermally stable up to 420°C. Depending on …
Size dependent carrier thermal escape and transfer in bimodally distributed self assembled InAs/GaAs quantum dots
2012
We have investigated the temperature dependent recombination dynamics in two bimodally distributed InAs self assembled quantum dots samples. A rate equations model has been implemented to investigate the thermally activated carrier escape mechanism which changes from exciton-like to uncorrelated electron and hole pairs as the quantum dot size varies. For the smaller dots, we find a hot exciton thermal escape process. We evaluated the thermal transfer process between quantum dots by the quantum dot density and carrier escape properties of both samples. © 2012 American Institute of Physics.
Transglutaminase and polyamine dependence of effector functions of human immunocompetent cells
1982
AbstractThe effects of the transglutaminase inhibitor dansyl cadaverine (DC) and the polyamine antagonist methyl glyoxal-bis-(guanylhydrazone) (MeGbG) on the response of lymphocytes towards allogeneic and lectin stimulation and on the zymosan-induced chemiluminescence of neutrophilic granulocytes was studied. Application of DC resulted in dose-dependent suppression of chemiluminiscence and lymphocyte proliferation; no difference of inhibitory potential occurred with variation of incubation time in the latter system. MeGbG was inactive in granulocytes, but inhibited lymphocyte proliferation; its effect increased with time. The experiments provide further evidence for the importance of transg…
Scintillation properties of possible cross-luminescence materials
1993
Abstract Employing X-ray and gamma-ray excitation, we studied the scintillation properties of KMgF 3 , KYF 4 :Rb, K 2 YF 5 , KLuF 4 , RbMgF 3 , KZnF 3 and BaTm 2 F 8 crystals. The first four crystals produce intrinsic cross-luminescence (CL) with a decay time of about 1.5 ns. Intrinsic CL was not observed for the other crystals. Emission spectra, results of decay time measurements, and estimates for the absolute light yield are presented.
Structural and Luminescent Properties of Homoleptic Silver(I), Gold(I), and Palladium(II) Complexes with nNHC-tzNHC Heteroditopic Carbene Ligands
2019
Novel silver(I), gold(I), and palladium(II) complexes were synthesized with bidentate heteroditopic carbene ligands that combine an imidazol-2-ylidene (nNHC) with a 1,2,3-triazol-5-ylidene (tzNHC) connected by a propylene bridge. The silver(I) and gold(I) complexes were dinuclear species, [M-2(nNHC-tzNHC)(2)](PF6)(2) (M = Ag or Au), with the two bidentate ligands bridging the metal centers, whereas in the palladium(II) complex [Pd(nNHC-tzNHC)(2)]-(PF6)(2), the two ligands were chelated on the same metal center. Because of the presence of two different carbene units, isomers were observed for the gold(I) and palladium(II) complexes. The molecular structures of the head-to-tail isomer for gol…