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Quantum Size Effect (quantum + size_effect)

Distribution by Scientific Domains

Physics and Astronomy	60%
Polymers and Materials Science	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]

Water-Soluble Silicon Quantum Dots with Wavelength-Tunable Photoluminescence

ADVANCED MATERIALS, Issue 6 2009
Zhenhui Kang
H-terminated Si quantum dots (Si QDs) with 3,nm diameter are converted to water-soluble uniform-sized Si QDs after controlled oxidation in an EtOH/H2O2 solution. These dots present Si/SiOxHy core/shell nanostructures, and can be finely tuned to emit light in seven different colors due to the quantum size effect in the Si cores, exhibiting excellent photocatalytic activity in the visible range. [source]

Correlation of anatase particle size with photocatalytic properties

PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 10 2010
Sangwook Lee
Abstract The influence of the anatase TiO2 particle size on the photocatalytic properties was systematically investigated on the nanometer-size scale. The anatase TiO2 crystallite size estimated using the Scherrer equation was varied from 8.0 to 16.4,nm, and the photocatalytic properties were significantly deteriorated with decreasing crystallites size. The photocurrent measurements showed that the charge generation diminished with decreasing TiO2 particle size. The bandgap energies were measured as a function of the particle size using UV,Vis spectroscopy in order to investigate the origin of the lowered charge-generation characteristics. The absorption band edge shift was found in the anatase nanocrystallites, which was attributed to the quantum size effect. Therefore, the increased bandgap energy induced the low light absorption capability, which was responsible for the low photoactivity of the very tiny anatase nanoparticles. These findings demonstrated that the particle-size reduction was not the best way to maximize the photocatalytic properties of TiO2 because of the diminished light absorption. [source]

Ab initio modeling of small diameter silicon nanowires

PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 2 2006
Murat Durandurdu
Abstract Using ab initio calculations, we predict stable small diameter silicon nanowires. The wires are constructed from the expended phases of silicon, clathrate Si(34) and Si(46) structures, and found to be energetically more favorable than the diamond type nanowires at the same diameters. Furthermore, the wires are semiconducting with band gap energy of 0.22 eV and 0.34 eV. Chemical passivation of the wires with hydrogen induces a broadening of band gap energy due to the quantum size effect and increases the hardness of the wires. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

High efficiency violet to blue light emission in porous SiC produced by anodic method

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 10 2010
T. Nishimura
Abstract Porous fluorescent (f-) SiC containing N and B was produced by anodic oxidation. The average crystal size can be controlled by adding K2S2O8 as an oxidant to dilute HF solution during the anodic process. With the reduction of the average crystal size of the porous crystal, the PL peak wavelength becomes shorter, and its intensity increases. Such behavior can be explained by the quantum size effect of donor-acceptor-pair recombination. Finally, we confirmed the superior fluorescent property of blue light emission in porous f-SiC crystal (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]