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|21. [Evolutionary Nanomaterials & Nanodevices] Young-wook Jun, Sang-Min Lee, Nam-Jung Kang, Jinwoo Cheon
Controlled synthesis of multi-armed CdS nanorod architectures using monosurfactant system
J. Am. Chem. Soc., 123 (21), 5150-5151 (May 30, 2001) DOI : https://pubs.acs.org/doi/full/10.1021/ja0157595
Recently, nanomaterials have drawn interests owing to their special characteristics which differ from bulk crystals.1-7 The synthesis of colloidal inorganic nanocrystals especially with respect to the control of their shape, however, is under developed and still complicated. Since novel properties of nanomaterials depend on their size and shape, a new direction for synthetic methods and an understanding of the mechanisms by which the size and shape of the nanocrystals can be easily varied are key issues in nanochemistry
|20. [Evolutionary Nanomaterials & Nanodevices] K‐B Lee, S‐M Lee, Jinwoo Cheon
Size‐Controlled Synthesis of Pd Nanowires Using a Mesoporous Silica Template via Chemical Vapor Infiltration
Advanced Materials, 13 (7), 517-520 (Apr 6, 2001) DOI : https://onlinelibrary.wiley.com/doi/abs/10.1002/1521-4095(200104)13:7%3C517::AID-ADMA517%3E3.0.CO;2-8
Free‐standing Pd nanowires of controlled size are synthesized by these authors via chemical vapor infiltration of an organometallic precursor into mesoporous silicate. The thus generated Pd nanowires can be isolated by addition of HF to remove the silicate matrix. Wires ranging from 3.7–8.8 nm in diameter and up to several hundred nanometers in length can be obtained (see Figure), depending on the silica template used.
|19. [Evolutionary Nanomaterials & Nanodevices] Young-wook Jun, Chang-Shik Choi and Jinwoo Cheon*
Size and shape controlled ZnTe nanocrystals with quantum confinement effect
Royal Society of Chemistry, 1, 101-102 (Dec 19, 2000) DOI : https://pubs.rsc.org/en/content/articlehtml/2001/cc/b008376n
A simple one-pot synthesis of size and shape controlled ZnTe nanocrystals using a monomeric molecular precursor, [Zn(TePh)2][TMEDA], has been studied by varying the growth temperature or the templating surfactants.
|18. [Evolutionary Nanomaterials & Nanodevices] Hongkyu Kang, Young-wook Jun, Jong-Il Park, Kyung-Bok Lee, Jinwoo Cheon
Synthesis of porous palladium superlattice nanoballs and nanowires
Chem. Mater., 12 (12), 3530-3532 (Dec 18, 2000) DOI : https://pubs.acs.org/doi/abs/10.1021/cm000617f
Ordered arrays of palladium nanostructures have been obtained inside MCM-48 and SBA-15, using chemical vapor infiltration. Removal of the silica matrix affords porous three-dimensional Pd nanoballs and one-dimensional Pd nanowires, depending on the architecture of the silicate host.
|17. [Evolutionary Nanomaterials & Nanodevices] Young-wook Jun, Ja-Eung Koo, Jinwoo Cheon
One-step synthesis of size tuned zinc selenide quantum dots via a temperature controlled molecular precursor approach
Chemical Communications, 14, 1243-1244 (May 30, 2000) DOI : https://pubs.rsc.org/en/content/articlehtml/2000/cc/b002983l
One-step size-controlled synthesis of ZnSe quantum dots is studied and the obtained QDs are luminescent with the emission wavelength varying over a wide range (up to 100 nm) depending on the particle size; the single-molecular precursor is an air-stable bis(phenylselenolato)zinc N,N,N′,N′-tetramethylethylenediamine (TMEDA) complex, which effectively affords different sizes of ZnSe QDs depending on growth temperatures.
|16. [Evolutionary Nanomaterials & Nanodevices] Jinwoo Cheon, Hong-Kyu Kang, Jeffrey I Zink
Spectroscopic identification of gas phase photofragments from coordination compound chemical vapor deposition precursors
Coordination Chemistry Reviews, 200, 1009-1032 (May 1, 2000) DOI : https://www.sciencedirect.com/science/article/pii/S0010854500003258
This review focuses on the gas phase photochemical fragmentation processes of coordination compounds that are precursors for the laser driven synthesis of solid-state materials such as thin films and nanoclusters from the gas phase. Specific emphasis is placed on the identification of photofragments by luminescence spectroscopy during the deposition process. In several cases, results from mass spectroscopy and from photofragmentation under the collision-free conditions of a molecular beam are included to clarify the identifications and mechanisms. Detailed experimental measurements have been made on metal diketonates, metal amides, metal xanthates and metal thiocarbamates. These compounds are useful as molecular precursors for the synthesis of thin films and nanoparticles of metals, binary and ternary materials, and semiconductor films.
|15. [Evolutionary Nanomaterials & Nanodevices] Jinwoo Cheon, Peter Muraoka, Jeffrey I Zink
Laser-induced deposition of palladium and gas-phase photofragmentation pathways from (2-methylallyl)(1, 1, 1, 5, 5, 5-hexafluoro-2, 4-pentanedionato) palladium
Chemistry of materials, 12 (2), 511-516 (Feb 21, 2000) DOI : https://pubs.acs.org/doi/abs/10.1021/cm990566q
Metallic palladium films are prepared at 10-2 Torr by 308 nm irradiation of gaseous (2-methylallyl)(1,1,1,5,5,5-hexafluoro-2,4-pentanedionato) palladium. Gas-phase luminescence spectra recorded during the photochemical deposition process are used to identify photofragments. X-ray photoelectron analysis of the films shows that they consist primarily of palladium metal; the films produced with H2 carrier gas have no detectable fluorine and barely discernible carbon contaminants. The Pd films are polycrystalline fcc (face-centered cubic) palladium with preferential growth along the 111 direction. Scanning electron microscopy shows that the films formed with H2 carrier gas are smooth and consist of granules less than 35 nm in diameter. Further characterization of the gas-phase photofragmentation process is carried out by time-of-flight mass spectroscopy. The dominant peak present in the mass spectrum under 308 nm irradiation arises from palladium ions. No fragments containing palladium and
|14. [Evolutionary Nanomaterials & Nanodevices] Ana Acosta, Jeffrey I Zink, Jinwoo Cheon
Ligand to ligand charge transfer in (hydrotris (pyrazolyl) borato)(triphenylarsine) copper (I)
Inorganic chemistry, 39 (3), 427-432 (Feb 7, 2000) DOI : https://pubs.acs.org/doi/abs/10.1021/ic9908773
Emission and UV−vis absorption spectra of (hydrotris(pyrazolyl)borato)(triphenylarsine)copper(I), (CuTpAsPh3), (hydrotris(pyrazolyl)borato)(triethylamine)copper(I), (CuTpNEt3), and (hydrotris(pyrazolyl)borato)(triphenylphosphine)copper(I), (CuTpPPh3), are reported. The spectra of the arsine complex contain low-energy bands (with a band maximum at 16 500 cm-1 in emission and a weak shoulder centered at about 25 000 cm-1 in absorption) that are not present in the corresponding spectra of the amine or phosphine complexes. The lowest energy electronic transition is assigned to ligand to ligand charge transfer (LLCT) with some contribution from the metal. This assignment is consistent with PM3(tm) molecular orbital calculations that show the HOMO to consist primarily of π orbitals on the Tp ligand (with some metal orbital character) and the LUMO to be primarily antibonding orbitals on the AsPh3 ligand (also with some metal orbital character). The absorption shoulder shows a strong negative
|13. [Evolutionary Nanomaterials & Nanodevices] Jinwoo Cheon, Jeffrey I Zink
In-Situ Gas-Phase Luminescence and Time-of-Flight Mass Spectroscopic Detection of Photofragments during Photochemical Synthesis of Copper Particles from Bis(tert-butylacetoacetato)copper
Inorganic chemistry, 39 (3), 433-436 (Jan 21, 2000) DOI : https://pubs.acs.org/doi/abs/10.1021/ic990962a
During the 308 nm laser-driven photochemical synthesis of Cu particles from bis(tert-butylacetoacetato)copper, gas-phase photogenerated intermediates are identified by luminescence and time-of-flight mass spectroscopies. Pure Cu deposits are obtained as homogeneous, granular 200 nm particles. In the gas phase, luminescent photoproducts are observed and atomic Cu, Cu2, and dissociated ligand are identified spectroscopically. In addition, mass spectroscopy identifies Cu atoms, the dissociated ligand, a monoligated complex, and fragments of the ligands. The implications of the photofragmentation that produces copper atoms and dimers for the laser-assisted production of the Cu deposits are discussed.
|12. [Evolutionary Nanomaterials & Nanodevices] Jinwoo Cheon, Matthew Guile, Peter Muraoka, Jeffrey I Zink
Gas phase photoproduction of diatomic metal nitrides during metal nitride laser chemical vapor deposition
Inorganic chemistry, 38 (9), 2238-2239 (May 3, 1999) DOI : https://pubs.acs.org/doi/full/10.1021/ic981365b
Photolysis of M(NEt2)4 in the gas phase produces diatomic MN molecules (M = Ti, Zr, Hf). TiN and ZrN molecules were identified in the gas phase under CVD conditions by emission spectroscopy and time-of-flight mass spectroscopy. Nanostructured deposits of TiN were formed on quartz substrates by irradiating Ti(NEt2)4 gas at 355 nm. These studies demonstrate the gas phase formation of diatomic molecules having the same stoichiometry as that of the desired solid-phase deposit.