We have synthesized highly luminescent Cu-In-S(CIS) nanocrystals (NCs) by heating the mixture of metal carboxylates
and alkylthiol under inert atmosphere. We modified the surface of CIS NCs with zinc carboxylate and subsequent
injection of alkylthiol. As a result of the surface modification, highly luminescent CIS@ZnS core/shell nanocrystals were
synthesized. The luminescence quantum yield (QY) of best CIS@ZnS NCs was above 50%, which is 10 times higher
than the initial QY of CIS NCs before surface modification (QY=3%). Detailed study on the luminescence mechanism
implies that etching of the surface of NCs by dissociated carboxylate group (CH3COO-) and formation of epitaxial shell
by Zn with sulfur from alkylthiol efficiently removed the surface defects which are known to be major non-radiative
recombination sites in semiconductor nanocrystals. In this study, we developed a novel surface modification route for
monodispersed highly luminescent Cu-In-S NCs with less toxic and highly stable precursors. Investigation with the timeand
the temperature-dependent photoluminescence showed that the trap related emission was minimized by surface
modification and the donor-acceptor pair recombination was enhanced by controlling copper stoichiometry.xb
Highly luminescent semiconductor nanocrystals with graded band gap were synthesized using hot injection method. The
band gap of nanocrystals were controlled by gradual incorporation of sulfur to CdSe nanocrystals by applying severely
asymmetric composition of reactants ([Cd]/[Se,S]>>1). The maximum emission wavelength of the grown nanocrystals
was varied by controlling the concentration ratio of VI group element, ie. Se and S. A green light was emitted from
Cd(Se,S) nanocrystals with [Se]:[S]=1:3 in the reactant mixture and the maximum quantum yield measured by
comparing with Rhodamine 6G exceeded 80%
The photonic band gap of colloidal crystal films made of polystyrene nanospheres was controlled by dry etching
technology using hyperthermal neutral beam. Vertical deposition technique was applied to prepare colloidal crystal films
with face centered cubic lattice structure using aqueous suspension of monodispersed polystyrene particles. The
pseudogap of these colloidal photonic crystals was tuned by etching the films with neutral beam, which reduces the size
of the constituent polystyrene particles. Isotropic reduction of the particles in collodial crystal films resulted in the blue
shift of stop band of the photonic band gap materials. By changing the etching time, the reflected colors of the dry-etched
colloidal crystals were successfully controlled.
Colloidal dispersion of bimodal particles were self-organized inside water-in-oil emulsion droplets by evaporationdriven
self-assembly method. After droplet shrinkage by heating the complex fluid system, small numbers of
microspheres were packed into minimal second moment clusters, which are partially coated with silica nanospheres,
resulting in the generation of patchy particles. The patchy particles in this study possess potential applications for selfassembly
of non-isotropic particles such as dimmers or tetramers for colloidal photonic crystals with diamond lattice
structures. The composite micro-clusters of amidine polystyrene microspheres and titania nanoparticles were also
generated by evaporation-driven self-assembly to fabricate nonspherical hollow micro-particles made of titania shell.
Stable dispersion of colloidal indium tin oxide nanoparticles was prepared by using indium tin oxide nanopowder,
organic solvent, and suitable dispersants through attrition process. Various comminution parameters during the attrition
step were studied to optimize the process for the stable dispersion of indium tin oxide sol. The transparent and
conductive films were fabricated on glass substrate using the indium tin oxide sol by spin coating process. To obtain
antireflective function, partially hydrolyzed alkyl silicate was deposited as over-coat layer on the pre-fabricated indium
tin oxide film by spin coating technique. This double-layered structure of the nanostructured film was characterized by
measuring the surface resistance and reflectance spectrum in the visible wavelength region. The final film structure was
enough to satisfy the TCO regulations for EMI shielding purposes.
CdSe quantum dots had been synthesized with a hot injection method. It was shown that the addition of Pb ions in the
initial precursor solution changed the morphology of CdSe nanocrystals from slightly prolate ellipsoid to branched rod.
Photoluminescence (PL) of the branched nanocrystals showed rapid depression of emission intensity due to the
morphological development to the branched nanocrystal induced by Pb addition. Low temperature PL spectrum
indicated that the surface recombination of charge carrier resulted in the large depression of emission from the branched
nanocrystal.
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