We have developed a novel route to highly luminescent Cd-free core-shell nanocrystals. By simply refluxing assynthesized
CuInS2 nanocrystals with zinc acetate and palmitic acid, highly luminescent CuInS2/ZnS nanocrystals were
synthesized. We modified the photoluminescence of the grown nanocrystal by alloying foreign atoms. Nanocrystals with
alloyed cores were synthesized by adding selenium and nanocrystals with alloyed shell layers were synthesized by
refluxing the as-synthesized CuInS2 nanocrystals with mixture of cadmium acetate, zinc acetate and palmitic acid. It was
found that the emission wavelength of the nanocrystals was shifted to longer wavelength side by alloying. The
photoluminescence spectra showed clear red-shift without significant minimization of emission intensity. A Detailed
study on the emission process of nanocrystals implies that the formation of shell layers with small lattice mismatch
minimized mismatch strain generated from the shell layers in contrast to core alloyed nanocrystals.
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%
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.
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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