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ABSTRACT: The dimension-controlled synthesis of CdS nanocrystals in the strong quantum confinement regime is reported. Zero-, one-, and two-dimensional CdS nanocrystals are selectively synthesized via low-temperature reactions using alkylamines as surface-capping ligands. The shape of the nanocrystals is controlled systematically by using different amines and reaction conditions. The 2D nanoplates have a uniform thickness as low as 1.2 nm. Furthermore, their optical absorption and emission spectra show very narrow peaks indicating extremely uniform thickness. It is demonstrated that 2D nanoplates are generated by 2D assembly of CdS magic-sized clusters formed at the nucleation stage, and subsequent attachment of the clusters. The stability of magic-sized clusters in amine solvent strongly influences the final shapes of the nanocrystals. The thickness of the nanoplates increases in a stepwise manner while retaining their uniformity, similar to the growth behavior of inorganic clusters. The 2D CdS nanoplates are a new type of quantum well with novel nanoscale properties in the strong quantum confinement regime.
Small 05/2012; 8(15):2394-402. · 8.35 Impact Factor
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Jae Sung Son,
Moon Kee Choi,
Mi-Kyung Han, Kunsu Park,
Jae-Yeol Kim,
Seong Joon Lim,
Myunghwan Oh,
Young Kuk,
Chan Park,
Sung-Jin Kim,
Taeghwan Hyeon
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ABSTRACT: We herein report on the large-scale synthesis of ultrathin Bi(2)Te(3) nanoplates and subsequent spark plasma sintering to fabricate n-type nanostructured bulk thermoelectric materials. Bi(2)Te(3) nanoplates were synthesized by the reaction between bismuth thiolate and tri-n-octylphosphine telluride in oleylamine. The thickness of the nanoplates was ~1 nm, which corresponds to a single layer in Bi(2)Te(3) crystals. Bi(2)Te(3) nanostructured bulk materials were prepared by sintering of surfactant-removed Bi(2)Te(3) nanoplates using spark plasma sintering. We found that the grain size and density were strongly dependent on the sintering temperature, and we investigated the effect of the sintering temperature on the thermoelectric properties of the Bi(2)Te(3) nanostructured bulk materials. The electrical conductivities increased with an increase in the sintering temperature, owing to the decreased interface density arising from the grain growth and densification. The Seebeck coefficients roughly decreased with an increase in the sintering temperature. Interestingly, the electron concentrations and mobilities strongly depended on the sintering temperature, suggesting the potential barrier scattering at interfaces and the doping effect of defects and organic residues. The thermal conductivities also increased with an increase in the sintering temperature because of grain growth and densification. The maximum thermoelectric figure-of-merit, ZT, is 0.62 at 400 K, which is one of the highest among the reported values of n-type nanostructured materials based on chemically synthesized nanoparticles. This increase in ZT shows the possibility of the preparation of highly efficient thermoelectric materials by chemical synthesis.
Nano Letters 02/2012; 12(2):640-7. · 13.20 Impact Factor
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Angewandte Chemie International Edition 02/2011; 50(6):1363-6. · 13.45 Impact Factor
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Jae Sung Son,
Xiao-Dong Wen,
Jin Joo,
Jungseok Chae,
Sung-Il Baek, Kunsu Park,
Jeong Hyun Kim,
Kwangjin An,
Jung Ho Yu,
Soon Gu Kwon,
Sang-Hyun Choi,
Zhongwu Wang,
Young-Woon Kim,
Young Kuk,
Roald Hoffmann,
Taeghwan Hyeon
Angewandte Chemie International Edition 09/2009; 48(37):6861-4. · 13.45 Impact Factor
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Jae Sung Son,
Xiao-Dong Wen Dr,
Jin Joo Dr,
Jungseok Chae,
Sung-il Baek, Kunsu Park,
Jeong Hyun Kim Dr,
Kwangjin An Dr,
Jung Ho Yu,
Soon Gu Kwon,
Sang-Hyun Choi Dr,
Zhongwu Wang Dr,
Young-Woon Kim Prof,
Young Kuk Prof,
Roald Hoffmann Prof,
Taeghwan Hyeon Prof
Angewandte Chemie International Edition 08/2009; 48(37):6861 - 6864. · 13.45 Impact Factor
