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Son, Hoseung,Yang, Mun Ho,Mutyala, Anil Kumar,Chang, Dong Wook,Park, Jong S. Elsevier 2019 Dyes and pigments Vol.162 No.-
<P><B>Abstract</B></P> <P>Polyisobutylene-substituted metallophthalocyanines (PIB-MPcs) were prepared by direct tetramerization of PIB-phthalonitrile in the presence of lithium, followed by demetallation, and subsequent insertion of Co(II) and Fe(II) into the central cavity of the phthalocyanines (Pcs). Due to the nonpolar nature of the PIB substituents and the flat molecular structure of the Pc macrocycles, the PIB-MPcs exhibited high affinity and strong adhesion to single-walled carbon nanotubes (SWCNTs), which consequently enabled and stabilized the dispersion of the SWCNTs in most common solvents. The prepared PIB-MPc/SWCNT complexes were characterized by various characterization methods. Furthermore, the electrocatalytic performances of the PIB-MPc/SWCNT complexes for an oxygen reduction reaction (ORR) were evaluated by electrochemical investigations. In particular, the PIB-FePc/SWCNT complexes exhibited superior electrocatalytic properties of ORR activity, with electron transfer numbers of up to 3.92 over all applied voltages, promoting four electron pathways. The results of this study suggest that the PIB- MPcs supported on SWCNTs have facilitated ORR processes and would be one of potential candidates for Pt-free electrocatalysts.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Polyisobutylene-substituted metallophthalocyanines were prepared by direct tetramerization. </LI> <LI> The prepared metallophthalocyanines exhibited high affinity and strong adhesion to SWCNTs. </LI> <LI> The metallophthalocyanine and SWCNT complexes showed high solubility in organic solvents. </LI> <LI> The iron-phthalocyanine and SWCNT complex exhibited superior oxygen reduction reaction activity. </LI> <LI> High electron transfer numbers of 3.92 confirmed four electron pathways. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Mun, S.C.,Kim, M.,Prakashan, K.,Jung, H.J.,Son, Y.,Park, O.O. Pergamon Press ; Elsevier Science Ltd 2014 Carbon Vol.67 No.-
We demonstrate the rheological percolation of carbon nanotubes (CNTs) in microstructured polymer matrices. Polymer/CNT composites are fabricated from polycarbonates with different molecular weights to diversify the microstructures, which vary with the polymer radius of gyration and entanglements. We propose a model for the dispersion of CNTs in polymer matrices, which explains the electrical and rheological properties. The percolation theory represented by a power-law relation cannot account for the rheological percolation of CNTs in this work. Therefore, we investigate the crossover points to provide a quantitative indication of the rheological percolation threshold of nanofillers in polymer matrices. For the first time, the rheological percolation threshold is determined experimentally with this definition. The effects of molecular weight and shear viscosity of the medium on the percolation of CNTs are demonstrated separately.
문성민(S. M. Mun),장정환(J. H. Jang),주병돈(B. D. Joo),손영명(Y. M. Son),문영훈(Y. H. Moon) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.11
Direct laser melting technologies have been used to restore the damaged mold surface. The objective of this research work is to investigate hardness and wear-resistance of the restored mold steels. A detailed wearresistance analysis using a Pin-on-Disk (POD) testing machine compares the wear rate and the friction coefficient for various test specimens, such as the as-received AISI H13 steel, the direct melted surface without powder, the direct melted surface with Fe-Cr powder and Fe-Ni powder. Experimental results show that the micro-hardness of the melted layer is approximately 2.3 times higher than the measured hardness of the as-received specimen. The melted layer of metal powder shows the frictional reduction effect more than 10%. The wear resistance of melted layer is about 2.3 times higher than that of as-received specimen.
Han, S.,Son, H. Y.,Kang, B.,Jang, E.,Ki, J.,Lee, N. G.,Park, J.,Shin, M. K.,Mun, B.,Min, J. K. SPRINGER SCIENCE + BUSINESS MEDIA 2017 NANO RESEARCH Vol.10 No.8
<P>The isolation of high-grade (i.e. high-pluripotency) human induced pluripotent stem cells (hiPSCs) is a decisive factor for enhancing the purity of hiPSC populations or differentiation efficiency. A non-invasive imaging system that can monitor microRNA (miRNA) expression provides a useful tool to identify and analyze specific cell populations. However, previous studies on the monitoring/isolation of hiPSCs by miRNA expression have limited hiPSCs' differentiation system owing to long-term incubation with miRNA imaging probe-nanocarriers. Therefore, we focused on monitoring high-grade hiPSCs without influencing the pluripotency of hiPSCs. We reduced nanoparticle transfection time, because hiPSCs are prone to spontaneous differentiation under external factors during incubation. The fluorescent nanoswitch ('ON' with target miRNA), which can be applied for either imaging or sorting specific cells by fluorescence signals, contains an miRNA imaging probe (miP) and a PEI-PEG nanoparticle (miP-P). Consequently, this nanoswitch can sense various endogenous target miRNAs within 30 min in vitro, and demonstrates strong potential for not only imaging but also sorting pluripotent hiPSCs without affecting pluripotency. Moreover, miP-P-treated hiPSCs differentiate well into endothelial cells, indicating that miP-P does not alter the pluripotency of hiPSCs. We envisage that this miRNA imaging system could be valuable for identifying and sorting high-grade hiPSCs for improved practical applications.</P>