|[Evolutionary Nanomaterials & Nanodevices] Young-Kyu Hong, Hanchul Kim, Geunseop Lee, Wondong Kim, Jong-Il Park, Jinwoo Cheon, Ja-Yong Koo
Controlled two-dimensional distribution of nanoparticles by spin-coating method
Applied Physics Letters, 80 (5), 844-846 (Feb 4, 2002) DOI : https://aip.scitation.org/doi/abs/10.1063/1.1445811
We demonstrate that the controlled distribution of nanoparticles can be achieved by employing the spin-coating method. The Co and Ag nanoparticles were uniformly distributed on the Si and SiO2 substrates with this method. The particle density was controllable by varying the concentration of colloids. The spatial distribution of the nanoparticles within the patterned area was also shown to be uniform with small boundary effect, which is favorable for current microelectronics technology. We propose that the spin-coating method can be utilized in developing mass production processes for future nanodevices.
|[Evolutionary Nanomaterials & Nanodevices] Jong-Il Park, Sang-Min Lee, Sehun Kim, SJ Oh, HC Ri, Jinwoo Cheon
Enhanced magnetic transition of core-shell Cobalt-Platinum nanoalloys
MRS Online Proceedings Library Archive (Feb 1, 2002) DOI : https://www.cambridge.org/core/journals/mrs-online-proceedings-library-archive/article/enhanced-magnetic-transition-of-coreshell-cobaltplatinum-nanoalloys/A726BE2E42C707DB549EC6598245F30C
Synthesis of ‘solid solution’ and ‘core-shell’ types of well defined Co-Pt based nanoalloys smaller than 10nm have been achieved by redox transmetalation reactions. This redox transmetalation are selectively observed only if the redox potential between two metals is favorable. The composition of the magnetic alloys can also be tuned by adjusting the ratio of reactants. Annealed core-shell nanoparticles transformed into mixed nanoalloys with face centered tetragonal (fct) structures, which show large coercivity and ferromagnetism at room temperature. These nanoparticles can potentially be used as an independent single magnetic bit of tera-bit information storage. Also, this kind of redox transmetalation reaction can be utilized as a general process to synthesize various types of nanoalloys with controlled composition in a selective fashion.
|[Evolutionary Nanomaterials & Nanodevices] Young-wook Jun, Yoon-young Jung, Jinwoo Cheon
Architectural control of magnetic semiconductor nanocrystals
Journal of the American chemical society, 124 (4), 615-619 (Jan 30, 2002) DOI : https://pubs.acs.org/doi/abs/10.1021/ja016887w
Shape- and dopant-controlled magnetic semiconductor nanocrystals have been achieved by the thermolysis of nonpyrophoric and less reactive single molecular precursors under a monosurfactant system. Reaction parameters governing both the intrinsic crystalline phase and the growth regime (kinetic vs thermodynamic) are found to be important for the synthesis of various shapes of MnS nanocrystals that include cubes, spheres, 1-dimensional (1-D) monowires, and branched wires (bipods, tripods, and tetrapods). Obtained nanowires exhibit enhanced optical and magnetic properties compared to those of 0-D nanospheres. Proper choice of molecular precursors and kinetically driven low-temperature growth afford dopant controlled 1-D Cd1-xMnxS nanorods at high levels (up to ∼12%) of Mn, which is supported by repeated surface exchange experiments and X-ray diffraction (XRD) and electron paramagnetic resonance (EPR) analyses.
|[Evolutionary Nanomaterials & Nanodevices] K-B Lee, C-S Choi, SJ Oh, H-C Ri, J Cheon
Synthesis of nanocomposite Pd balls and wires by chemical vapor infiltration
Le Journal de Physique IV, 11 (PR3), Pr3-481-Pr3-486 (Aug 1, 2001) DOI : https://jp4.journaldephysique.org/articles/jp4/abs/2001/03/jp4200111PR361/jp4200111PR361.html
Our study presents the preparation of well-defined Pd nanoballs and nanowires using the different pore size of cubic and hexagonal shaped MCM type mesoporous silicate materials as matrix templates. The synthesis involves loading the organometallic precursor into template matrix via chemical vapor infiltration (CVI), followed by mild thermal decomposition to generate Pd metals self-organized inside the template. For Pd@MCM-48, the Pd metal forms spherical domains (~38 nm) consisting of three dimensionally interconnected into Pd arrays; for Pd@SBA-15 and Pd@MCM-41, the Pd metal forms of one-dimensional wires. Etching out the matrix produces porous Pd nanoballs (pore sizes of ~1.5 - 2.0 nm) with retaining original domain sizes of ~38 nm; similarly Pd@SBA-15 and Pd@MCM-41 afford freestanding Pd nanowires. In addition, phase transition behavior and melting point depression of the Pd nanowires is studied.
|[Evolutionary Nanomaterials & Nanodevices] Jong-Il Park, Jinwoo Cheon
Synthesis of “solid solution” and “core-shell” type cobalt− platinum magnetic nanoparticles via transmetalation reactions
American Chemical Society, 123 (24), 5743-5746 (Jun 20, 2001) DOI : https://pubs.acs.org/doi/abs/10.1021/ja0156340
In this article, we report the synthesis of “solid solution” and “core-shell” types of well-defined Co−Pt nanoalloys smaller than 10 nm. The formation of these alloys is driven by redox transmetalation reactions between the reagents without the need for any additional reductants. Also the reaction proceeds selectively as long as the redox potential between the two metals is favorable. The reaction between Co2(CO)8 and Pt(hfac)2 (hfac = hexafluoroacetylacetonate) results in the formation of “solid solution” type alloys such as CoPt3 nanoparticles. On the other hand, the reaction of Co nanoparticles with Pt(hfac)2 in solution results in “CocorePtshell” type nanoalloys. Nanoparticles synthesized by both reactions are moderately monodispersed (σ < 10%) without any further size selection processes. The composition of the alloys can also be tuned by adjusting the ratio of reactants. The magnetic and structural properties of the obtained nanoparticles and reaction byproducts are characterized
|[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
American Chemical Society, 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
|[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.
|[Evolutionary Nanomaterials & Nanodevices] Young-wook Jun, Jong-Il Park, Jinwoo Cheon
Convenient molecular approach of size and shape controlled ZnSe and ZnTe nanocrystals
MRS Online Proceedings Library Archive, 635 (Mar 17, 2001) DOI : https://www.cambridge.org/core/journals/mrs-online-proceedings-library-archive/article/convenient-molecular-approach-of-size-and-shape-controlled-znse-and-znte-nanocrystals/46F9CF381061BC6C8793B5759DEC0DDC
Our study describes a convenient one-step synthesis of ZnSe and ZnTe nanocrystals (NC) whose sizes and shapes are precisely tuned by varing the growth temperature or stabilizing surfactants. We utilized molecular precursors, bis(phenylselenolate or phenyltellurolato)zinc -N,N,N',N'-tetramethylethylenediamine (TMEDA), which effectively produce 0-dimensional sphere or 1-dimensional nanorods of ZnSe or ZnTe, respectively. Nanocrystals are highly monodispersed and luminescent; the emission wavelength varies over a wide range depending on the particle size. This study constitutes a nice demonstration of direct size and shape controlled synthesis of semiconductor nanocrystals and this method can be extended to the synthesis of nanocrystals of other materials.
|[Evolutionary Nanomaterials & Nanodevices] Jinwoo Cheon, Kyung-Bok Lee, Hongkyu Kang, SJ Oh, H-C Ri
Matrix-assisted synthesis of palladium nanocage and nanowires
MRS Online Proceedings Library Archive, 635 (Jan 1, 2001) DOI : https://www.cambridge.org/core/journals/mrs-online-proceedings-library-archive/article/matrixassisted-synthesis-of-palladium-nanocage-and-nanowires/B84C1BFE39B3699BE472F30C805D20D2
Our study describes the synthesis of novel nanoscale Pd cage and wires whose sizes and shapes are templated by mesoporous matrices. The templates used are cubic phase MCM-48 and hexagonal phase CnMCM-41 (n = 16, and 22), SBA-15, which have pore diameters of ∼3, ∼3.8, ∼4.7, and ∼9 nm, respectively. For Pd@MCM-48, the Pd metal forms spherical domains (∼38 nm) consisting of three dimensionally interconnected into Pd arrays; for Pd@SBA-15 and Pd@MCM-41, the Pd metal forms of one-dimensional wires. Etching out the matrix produces porous Pd cages (pore sizes of ∼1.5 - 2.0 nm) with retaining original domain sizes of ∼38 nm; similarly Pd@SBA-15 and Pd@MCM-41 afford freestanding Pd nanowires. All the materials are examined by TEM, XRD, BET, and EDAX analysis. Furthermore, the thermal behavior of Pd nanowire is briefly described.
|[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.