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HyunJoon Shin,Mikang Kim,Namdong Kim,Hyeong-Do Kim,Changhoon Jung,JaeGwan Chung,KiHong Kim,Woo Sung Jeon 한국진공학회(ASCT) 2020 Applied Science and Convergence Technology Vol.29 No.4
Pristine and 4.35 V charged-state particles of the Li1.0Ni0.88Co0.08Mn0.04O₂ lithium–ion battery (LIB) cathode material were cross-sectioned by the focused-ion-beam method to allow the acquisition of spatially resolved Ni L₃-edge, Co L₃-edge, Mn L₃-edge, and O K-edge X-ray absorption spectra by scanning transmission X-ray microscopy with a spatial resolution of ~30 ㎚. The Co L₃-edge and the Mn L₃-edge spectra, respectively, displayed almost the same features throughout the particles for both the pristine-state and charged-state samples. The average oxidation states of the Co and Mn ions were estimated to be ~3+ and ~4+, respectively. The Ni L₃-edge and O K-edge spectra included different features, depending on the charge state and intra-particle location. The estimated average oxidation state of the Ni ions ranged from ~2.7+ to ~3.0+ for the pristine-state sample (space-averaged value: ~2.9+) and from ~2.7+ to ~3.5+ for the charged-state sample (space-averaged value: ~3.3+). A correlation was observed between the changes in the features of the O K-edge and Ni L₃-edge. These results would provide important implications for the development of high-performance LIBs.
Chang, Hyeshik,Yeo, Jinah,Kim, Jeong-gyun,Kim, Hyunjoon,Lim, Jaechul,Lee, Mihye,Kim, Hyun Ho,Ohk, Jiyeon,Jeon, Hee-Yeon,Lee, Hyunsook,Jung, Hosung,Kim, Kyu-Won,Kim, V. Narry Elsevier 2018 Molecular cell Vol.70 No.1
<P><B>Summary</B></P> <P>During the maternal-to-zygotic transition (MZT), maternal RNAs are actively degraded and replaced by newly synthesized zygotic transcripts in a highly coordinated manner. However, it remains largely unknown how maternal mRNA decay is triggered in early vertebrate embryos. Here, through genome-wide profiling of RNA abundance and 3′ modification, we show that uridylation is induced at the onset of maternal mRNA clearance. The temporal control of uridylation is conserved in vertebrates. When the homologs of terminal uridylyltransferases TUT4 and TUT7 (TUT4/7) are depleted in zebrafish and <I>Xenopus</I>, maternal mRNA clearance is significantly delayed, leading to developmental defects during gastrulation. Short-tailed mRNAs are selectively uridylated by TUT4/7, with the highly uridylated transcripts degraded faster during the MZT than those with unmodified poly(A) tails. Our study demonstrates that uridylation plays a crucial role in timely mRNA degradation, thereby allowing the progression of early development.</P> <P><B>Highlights</B></P> <P> <UL> <LI> TUT4 and TUT7 are conserved writers of U tail in vertebrates </LI> <LI> mRNA uridylation is induced during early embryogenesis </LI> <LI> Uridylation facilitates the programmed elimination of maternal RNAs </LI> <LI> TUT4 and TUT7 are required for gastrulation in zebrafish and <I>Xenopus</I> </LI> </UL> </P> <P><B>Graphical Abstract</B></P> <P>[DISPLAY OMISSION]</P>
Kim, Jae Young,Choi, Nak-Jin,Park, Hyung Ju,Kim, Jinmo,Lee, Dae-Sik,Song, Hyunjoon American Chemical Society 2014 The Journal of Physical Chemistry Part C Vol.118 No.45
<P>The detection of formaldehyde at a very low concentration is a significant research topic, due to its detrimental impact on human health. In the present study, we fabricated a hierarchical structure by the rational assembly of single-crystalline Co<SUB>3</SUB>O<SUB>4</SUB> nanoparticles. A hollow morphology using sacrificial ZnO spheres could form a three-dimensional conducting network in a solid state. The resulting structure was selectively active for formaldehyde sensing, and the detection limit was 50 ppb, which was nearly close to the record-high value among the other semiconducting materials. Such superior properties were attributed to the regular, hierarchically assembled structures with a small crystalline domain size, a thin hollow morphology with a large surface area, and a three-dimensional conductive network with a narrow diameter. We believe that this hierarchical assembly can show great potential as a platform for improving human health through the monitoring of indoor environments.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jpccck/2014/jpccck.2014.118.issue-45/jp505791v/production/images/medium/jp-2014-05791v_0009.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/jp505791v'>ACS Electronic Supporting Info</A></P>
Far-Field and Near-Field Investigation of Longitudinal Plasmons of AgAuAg Nanorods
Kim, Deok-Soo,Ahn, Sung-Hyun,Kim, Jinwook,Seo, Daeha,Song, Hyunjoon,Kim, Zee Hwan American Chemical Society 2016 The Journal of Physical Chemistry Part C Vol.120 No.37
<P>We studied the localized surface plasmons of AgAuAg-nanorods (NRs) using far-field dark-field spectromicroscopy and scattering-type scanning near-field optical microscopy (sSNOM) techniques. We observe that the far-field scattering spectra of individual AgAuAg-NRs exhibit longitudinal dipolar and octupolar resonances that are mainly determined by the overall lengths of the NRs and are fairly insensitive to the relative compositions of Ag and Au. Corresponding near-field distributions measured by sSNOM further reveal plasmonic local field patterns that closely resemble those of monolithic Au-NRs. These show that the longitudinal plasmons of AgAuAg-NRs oscillate along the entire length of the NRs, although resonance widths indicate appreciable damping by the Ag Au interfaces. The result constitutes an interesting counter-example of tunability of plasmons by composition variation and, thus, provides an important design rule for composition-tunable bimetallic plasmonic structures.</P>
Kim, Mijong,Park, Ji Chan,Kim, Aram,Park, Kang Hyun,Song, Hyunjoon American ChemicalSociety 2012 Langmuir Vol.28 No.15
<P>The surface of Pd@SiO<SUB>2</SUB> core–shell nanoparticles(<B>1</B>) was simply modified by the formation of nickel phyllosilicate.The addition of nickel salts formed branched nickel phyllosilicatesand generated pores in the silica shells, yielding Pd@SiO<SUB>2</SUB>–Niphy nanoparticles (Niphy = nickel phyllosilicate; <B>2</B>, <B>3</B>). By removal of the silica residue, Pd@Niphyyolk–shell nanoparticles (<B>4</B>) was uniformly obtained.The four distinct nanostructures (<B>1</B>–<B>4</B>) were employed as catalysts for Suzuki coupling reactions with arylbromide and phenylboronic acid, and the conversion yields were inthe order of <B>1</B> < <B>2</B> < <B>3</B> < <B>4</B> as the pore volume and surface area of the catalystsincreased. The reaction rates were strongly correlated with shellporosity and surface exposure of the metal cores. The chemical inertnessof nickel phyllosilicate under the basic conditions rendered the catalystsreusable for more than five times without loss of activity.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/langd5/2012/langd5.2012.28.issue-15/la300148e/production/images/medium/la-2012-00148e_0009.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/la300148e'>ACS Electronic Supporting Info</A></P>
Kim, Jinmo,Choi, Woong,Park, Joon Woo,Kim, Cheonghee,Kim, Minjun,Song, Hyunjoon American Chemical Society 2019 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.141 No.17
<P>For long-term storage of renewable energy, the electrochemical carbon dioxide reduction reaction (CO<SUB>2</SUB>RR) offers a promising option for converting electricity to permanent forms of chemical energy. In this work, we present highly selective ethylene production dependent upon the catalyst morphology using copper oxide nanoparticles. The branched CuO nanoparticles were synthesized and then deposited on conductive carbon materials. After activation, the major copper species changed to Cu<SUP>+</SUP>, and the resulting electrocatalyst exhibited a high Faradaic efficiency (FE) of ethylene reaching over 70% and a hydrogen FE of 30% without any byproducts in a neutral aqueous solution. The catalyst also showed high durability (up to 12 h) with the ethylene FE over 65%. Compared to cubic morphology, the initial branched copper oxide structure formed highly active domains with interfaces and junctions in-between during activation, which caused large surface area with high local pH leading to high selectivity and activity for ethylene production.</P> [FIG OMISSION]</BR>
Kim, Sun Mi,Lee, Seon Joo,Kim, Seung Hyun,Kwon, Sangku,Yee, Ki Ju,Song, Hyunjoon,Somorjai, Gabor A.,Park, Jeong Young American Chemical Society 2013 Nano letters Vol.13 No.3
<P>Hybrid nanocatalysts consisting of metal nanoparticle–semiconductor junctions offer an interesting platform to study the role of metal–oxide interfaces and hot electron flows in heterogeneous catalysis. Here, we report that hot carriers generated upon photon absorption significantly impact the catalytic activity of CO oxidation. We found that Pt–CdSe–Pt nanodumbbells exhibit a higher turnover frequency by a factor of 2 during irradiation by light with energy higher than the bandgap of CdSe, while the turnover rate on bare Pt nanoparticles did not depend on light irradiation. We found that Pt nanoparticles deposited on a GaN substrate under light irradiation exhibit changes in catalytic activity of CO oxidation that depends on the type of doping of the GaN. We suppose that hot electrons are generated upon the absorption of photons by the semiconducting nanorods or substrates, whereafter the hot electrons are injected into the Pt nanoparticles, resulting in the change in catalytic activity. The results imply that hot carrier flows generated during light irradiation significantly influence the catalytic activity of CO oxidation, leading to potential applications as a hot electron-based catalytic actuator.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/nalefd/2013/nalefd.2013.13.issue-3/nl400367m/production/images/medium/nl-2013-00367m_0007.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nl400367m'>ACS Electronic Supporting Info</A></P>
Acetic Acid Production Using Xylose and Corn Steep Liquor by thermoaceticum Strain
Kim, Jun Seok,Kim, Hyunjoon,Oh, Kyeong Keun,Kim, Young Soo 한국공업화학회 2002 Journal of Industrial and Engineering Chemistry Vol.8 No.6
Acetic acid production from xylose by Clostridium thermoaceticum (ATCC 49707) requires adaptation of the strain to xylose medium. It preferentially consumes xylose over glucose using a mixture of glucose and xylose as a carbon source. The initial concentration of xylose in the medium affects the final concentration and the yield of acetic acid. Batch fermentation of 20 g/L of xylose with 5 g/L of yeast extract (YE) as a nitrogen source results a maximum acetate concentration of 15.2 g/L and yield of 0.76 g acid/g xylose. Corn steep liquor (CSL) is a good substitute for yeast extract and results in similar fermentation profiles. The organism consumes fructose, xylose and glucose when from a mixture of sugars in batch fermentation. Arabinose, mannose and galactose are consumed only slightly. This organism loses viability upon fed-batch operation even with supplementation of all the required nutrients. In fed-batch fermentation with CSL supplementation, D-xylulose (an intermediate in the xylose metabolic pathway) accumulates in large quantities.