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Jeon, Cheolho,Hwang, Han-Na,Lee, Wang-Geun,Jung, Yong Gyun,Kim, Kwang S,Park, Chong-Yun,Hwang, Chan-Cuk RSC Pub 2013 Nanoscale Vol.5 No.17
<P>Copper is considered to be the most promising substrate for the growth of high-quality and large area graphene by chemical vapor deposition (CVD), in particular, on the (111) facet. Because the interactions between graphene and Cu substrates influence the orientation, quality, and properties of the synthesized graphene, we studied the interactions using angle-resolved photoemission spectroscopy. The evolution of both the Shockley surface state of the Cu(111) and the π band of the graphene was measured from the initial stage of CVD growth to the formation of a monolayer. Graphene growth was initiated along the Cu(111) lattice, where the Dirac band crossed the Fermi energy (EF) at the K point without hybridization with the d-band of Cu. Then two rotated domains were additionally grown as the area covered with graphene became wider. The Dirac energy was about -0.4 eV and the energy of the Shockley surface state of Cu(111) shifted toward the EF by ~0.15 eV upon graphene formation. These results indicate weak interactions between graphene and Cu, and that the electron transfer is limited to that between the Shockley surface state of Cu(111) and the π band of graphene. This weak interaction and slight lattice mismatch between graphene and Cu resulted in the growth of rotated graphene domains (9.6 and 8.4), which showed no significant differences in the Dirac band with respect to different orientations. These rotated graphene domains resulted in grain boundaries which would hinder a large-sized single monolayer growth on Cu substrates.</P>
Mubarak, Mahfuza,Jeon, Hyokyung,Islam, Md. Shahinul,Yoon, Cheolho,Bae, Jong-Seong,Hwang, Seong-Ju,Choi, Won San,Lee, Ha-Jin Elsevier 2018 CHEMOSPHERE - Vol.201 No.-
<P><B>Abstract</B></P> <P>Herein, Mg/Fe layered double hydroxide (MF-LDH) hollow nanospheres were successfully prepared by a one-step thermal method. After the thermal treatment of MF-LDH nanospheres at 400 °C, the MF-LDH was converted into the corresponding oxide, Mg/Fe layered double oxide (MF-LDO), which maintained the hollow nanosphere structure. The MF-LDO hollow nanospheres exhibited excellent adsorption efficiency for both As(V) and Cr(VI), showing 99% removal within 5 min and providing maximum removal capacities of 178.6 mg g<SUP>−1</SUP> [As(VI)] and 148.7 mg g<SUP>−1</SUP> [Cr(VI)]. Moreover, it met the maximum contaminant level requirements recommended by World Health Organization (WHO); 10 ppm for As(V) and 50 ppm for Cr(VI) in 10 and 20 min, respectively. Furthermore, Au nanoparticles were successfully introduced in the MF-LDO hollow nanospheres, and the products showed a conversion rate of 100% for the reduction of 4-nitrophenol into 4-aminophenol within 5 min. It is believed that these excellent and versatile abilities integrated with a facile synthetic strategy will facilitate the practical application of this material in cost-effective wastewater purification.</P> <P><B>Highlights</B></P> <P> <UL> <LI> MF-LDH and MF-LDO hollow nanospheres were prepared by one-step thermal method. </LI> <LI> MF-LDH and MF-LDO showed ultrafast removal efficiency for As(V) and Cr(VI). </LI> <LI> MF-LDO purified contaminated water up to drinking water level within 20 min. </LI> <LI> Gold nanoparticles were successfully introduced into MF-LDO hollow nanosphere structure. </LI> <LI> Au-MF-LDO completely reduced 4-nitrophenol to 4-aminophenol within 5 min. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Synthesis of Bandgap-Controlled Semiconducting Single-Walled Carbon Nanotubes
Song, Wooseok,Jeon, Cheolho,Kim, Yoo Seok,Kwon, Young Taek,Jung, Dae Sung,Jang, Sung Won,Choi, Won Chel,Park, Jin Sung,Saito, Riichiro,Park, Chong-Yun American Chemical Society 2010 ACS NANO Vol.4 No.2
<P>Bandgap-controlled semiconducting single-walled carbon nanotubes (s-SWNTs) were synthesized using a uniquely designed catalytic layer (Al<SUB>2</SUB>O<SUB>3</SUB>/Fe/Al<SUB>2</SUB>O<SUB>3</SUB>) and conventional thermal chemical vapor deposition. Homogeneously sized Fe catalytic nanoparticles were prepared on the Al<SUB>2</SUB>O<SUB>3</SUB> layer and their sizes were controlled by simply modulating the annealing time <I>via</I> heat-driven diffusion and subsequent evaporation of Fe at 800 °C. Transmission electron microscopy and Raman spectroscopy revealed that the synthesized SWNTs diameter was manipulated from 1.4 to 0.8 nm with an extremely narrow diameter distribution below 0.1 nm as the annealing time is increased. As a result, the bandgap of semiconducting SWNTs was successfully controlled, ranging from 0.53 to 0.83 eV, with a sufficiently narrow energy distribution, which can be applied to field-effect transistors based on SWNTs.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancac3/2010/ancac3.2010.4.issue-2/nn901135b/production/images/medium/nn-2009-01135b_0007.gif'></P>
An electrochemical approach to graphene oxide coated sulfur for long cycle life
Moon, Joonhee,Park, Jungjin,Jeon, Cheolho,Lee, Jouhahn,Jo, Insu,Yu, Seung-Ho,Cho, Sung-Pyo,Sung, Yung-Eun,Hong, Byung Hee The Royal Society of Chemistry 2015 Nanoscale Vol.7 No.31
<P>Owing to the possibilities of achieving high theoretical energy density and gravimetric capacity, sulfur has been considered as a promising cathode material for rechargeable lithium batteries. However, sulfur shows rapid capacity fading due to the irreversible loss of soluble polysulfides and the decrease in active sites needed for conducting agents. Furthermore, the low electrical conductivity of sulfur hampers the full utilization of active materials. Here we report that graphene oxide coated sulfur composites (GO-S/CB) exhibit improved electrochemical stability as well as enhanced rate performance, evidenced by various electrochemical analyses. The cyclic voltammetry and the galvanostatic cycling analysis revealed that the GO plays key roles in homogenizing the nanocomposite structures of the electrodes, in improving the electrochemical contact, and in minimizing the loss of soluble polysulfide intermediates. An electrochemical impedance spectroscopy analysis also confirms the enhanced structural stability of the GO-S/CB composites after battery operation. As a result, the GO-S/CB exhibited excellent cycle stability and specific capacity as high as ???723.7 mA h g(-1) even after 100 cycles at 0.5 C.</P>