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PL Properties (pl + property)

Distribution by Scientific Domains

Polymers and Materials Science	60%
Physics and Astronomy	40%

Selected Abstracts

Preparation-Condition Dependence of Hybrid SiO2 -Coated CdTe Nanocrystals with Intense and Tunable Photoluminescence

ADVANCED FUNCTIONAL MATERIALS, Issue 8 2010
Ping Yang
Abstract When aqueously prepared CdTe nanocrystals (NCs) are coated with a SiO2 shell containing Cd ions and a sulfur source, they show a drastic increase in photoluminescence (PL) efficiency with a significant red shift and spectral narrowing after reflux. This is ascribed to the creation of a hybrid structure characterized by the formation of CdS-like clusters in the vicinity of the NCs in the SiO2 shell. Since these clusters are close to the NCs, their effective size increases to reduce the quantum size effect. The dependences of the PL properties on the preparation conditions are systematically investigated. The PL efficiency increases from 28% to 80% in the best case with a red shift of 80,nm. The PL behaviors differ from those of normal CdTe NCs and include less temperature quenching and longer PL lifetime. The SiO2 coating enables bioconjugation with IgG without deterioration of PL efficiency, making hybrid NCs amenable for bioapplication. [source]

Composition- and Shape-Controlled Synthesis and Optical Properties of ZnxCd1,xS Alloyed Nanocrystals,

ADVANCED FUNCTIONAL MATERIALS, Issue 3 2005
C. Li
Abstract Composition-tunable ZnxCd1,xS alloyed nanocrystals have been synthesized by a new approach consisting of thermolyzing a mixture of cadmium ethylxanthate (Cd(exan)2) and zinc ethylxanthate (Zn(exan)2) precursors in hot, coordinating solvents at relatively low temperatures (180,210,°C). The composition of the alloyed nanocrystals was accurately adjusted by controlling the molar ratio of Cd(exan)2 to Zn(exan)2 in the mixed reactants. The alloyed ZnxCd1,xS nanocrystals prepared in HDA/TOP (HDA: hexadecylamine; TOP: trioctylphosphine) solution exhibit composition-dependent shape and phase structures as well as composition-dependent optical properties. The shape of the ZnxCd1,xS nanocrystals changed from dot to single-armed rod then to multi-armed rod with a decrease of Zn content in the ternary nanoparticles. The alloying nature of the ZnxCd1,xS nanocrystals was consistently confirmed by the results of high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), and UV-vis absorption and photoluminescence (PL) spectroscopy. Further, the shape-controlled synthesis of the ternary alloyed nanocrystals was realized by selecting appropriate solvents. Uniform nanodots in the whole composition range were obtained from TOPO/TOP solution, (TOPO: trioctylphosphine oxide) and uniform nanorods in the whole composition range were prepared from HDA/OA solution (OA: octylamine). The effect of the reaction conditions, such as solvent, reaction temperature, and reaction time, on the PL spectra of the alloyed ZnxCd1,xS nanocrystals was also systematically studied, and the reaction conditions were optimized for improving the PL properties of the nanocrystals. [source]

High quantum yield photoluminescence of new polyamides containing oligo-PPV amino derivatives and related oligomers

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 10 2009
Antonio Roviello
Abstract The synthesis and the chemical physical characterization of new photoluminescent (PL) chromophores and polymers are reported. Chromophores (oligo-PPV symmetric derivatives ending with amino groups) are strong blue emitters with a PL quantum yield of ,70% in dioxane solution. They have been used to prepare polyamides by reaction with aliphatic acyl dichlorides in which emitting and non emitting units are alternated. PL properties of the synthesized polyamides have been evaluated in solution and reveal a strong blue emission (PL quantum yield ,60%), To increase the solubility of these systems, oligomers have been purposely prepared and then characterized. They show a peculiar white emission when excited in DMF solution; to get insight into this interesting behavior, asymmetric monoacetylated chromophores have been prepared as model compounds for the chromophoric end groups of the polyamide chains. The emission spectra of these compounds reveal a broad excimeric yellow emission which is responsible, along with the blue emission of the inner chromophoric units, of the overall white emission of the oligomers. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2677,2689, 2009 [source]

Spacer layer thickness effects on the photoluminescence properties of InAs/GaAs quantum dot superlattices

PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 3 2003
B. Ilahi
Abstract InAs/GaAs vertically stacked self-assembled quantum dot (QD) structures with different GaAs spacer layer thicknesses are grown by solid source molecular beam epitaxy (SSMBE) and investigated by transmission electron microscopy (TEM) and photoluminescence (PL) spectroscopy. An increase in the polarization anisotropy is observed when the spacer layer thickness decreases. For a 10 monolayer (ML) thick inter-dots GaAs spacer, the TEM image shows an increase in the QD size when moving to the upper layer accompanied by the generation of dislocations. Consequently, the corresponding temperature-dependant PL properties are found to exhibit an unusual behaviour. The main PL peak is quenched at a temperature around 190 K giving rise to a broad background correlated with the formation of a miniband in the growth direction due to the strong interlayer coupling. For a thicker GaAs spacer layer (30 ML), multilayer QDs align vertically in stacks with no apparent structural defects. Over the whole temperature range, the excitonic band energies are governed by the Varshni empirical relation using InAs bulk parameters and the PL line width shows a slight monotonic increase. For a thinner GaAs interlayer, the thermal activation energies of the carrier emission out of the quantum dots are found to be considerably small (about 25 meV) due to the existence of defects. By combining these structural and optical results, we can conclude that a thinner GaAs spacer has a poorer quality. (© 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Post-annealing effect upon phosphorus-doped ZnTe homoepitaxial layers grown by MOVPE

PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 5 2007
Katsuhiko Saito
Abstract The effect of post-annealing treatment upon the photoluminescence (PL) spectra of phosphorus-doped ZnTe homoepitaxial layers grown by metalorganic vapour phase epitaxy using tris-dimethylaminophosphorus (TDMAP) has been investigated. PL properties at 4 K of the layers are dramatically improved by the post-annealing in nitrogen flow, i.e. donor,acceptor pair emission vanishes and instead free-to-bound transition emission (FB) and broadened acceptor-related excitonic emission (Ia) appear. PL intensity at room temperature is enhanced remarkably by the treatment. While the post-annealing treatment in hydrogen flow also gives an increase in PL intensity at room temperature of the layer, PL spectrum at 4 K is almost unchanged. The intensity ratio of FB to broadened Ia for the layer after post-annealing treatment in nitrogen flow increases and the broadened Ia shifts towards longer wavelength side with increasing TDMAP transport rate. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]