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Yoo, Hana,Park, Soojin IOP Pub 2010 Nanotechnology Vol.21 No.24
<P>We demonstrate the fabrication of highly ordered silicon oxide dotted arrays prepared from polydimethylsiloxane (PDMS) filled nanoporous block copolymer (BCP) films and the preparation of nanoporous, flexible Teflon or polyimide films. Polystyrene-<I>block</I>-poly(2-vinylpyridine) (PS-<I>b</I>-P2VP) films were annealed in toluene vapor to enhance the lateral order of micellar arrays and were subsequently immersed in alcohol to produce nano-sized pores, which can be used as templates for filling a thin layer of PDMS. When a thin layer of PDMS was spin-coated onto nanoporous BCP films and thermally annealed at a certain temperature, the PDMS was drawn into the pores by capillary action. PDMS filled BCP templates were exposed to oxygen plasma environments in order to fabricate silicon oxide dotted arrays. By addition of PS homopolymer to PS-<I>b</I>-P2VP copolymer, the separation distances of micellar arrays were tuned. As-prepared silicon oxide dotted arrays were used as a hard master for fabricating nanoporous Teflon or polyimide films by spin-coating polymer precursor solutions onto silicon patterns and peeling off. This simple process enables us to fabricate highly ordered nanoporous BCP templates, silicon oxide dots, and flexible nanoporous polymer patterns with feature size of sub-20 nm over 5 cm × 5 cm. </P>
Helical Silicon/Silicon Oxide Core–Shell Anodes Grown onto the Surface of Bulk Silicon
Yoo, Hana,Lee, Jung-In,Kim, Hyunjung,Lee, Jung-Pil,Cho, Jaephil,Park, Soojin American Chemical Society 2011 NANO LETTERS Vol.11 No.10
<P>We demonstrate a simple route for preparing Si/SiO<SUB><I>x</I></SUB> urchin-like structures in which Si/SiO<SUB><I>x</I></SUB> core–shell nanocoils protruded out from the surface of bulk Si, via high-temperature annealing of Pt-decorated Si powders. The carbon-coated urchin-like anodes with micro- and nanostructured composite exhibit a significantly improved electrochemical performance with a high specific capacity of 1600 mAh/g and a superior cycling performance of 70 cycles at a rate of 0.2 C due to the nanocoil conformation and SiO<SUB><I>x</I></SUB> buffer layer. More importantly, the composite results in a significantly enhanced the volumetric capacity with ∼3780 mAh/cc, compared to bulk Si (∼2720 mAh/cc) after fully lithiation to 0 V.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/nalefd/2011/nalefd.2011.11.issue-10/nl202417c/production/images/medium/nl-2011-02417c_0004.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nl202417c'>ACS Electronic Supporting Info</A></P>
Yoo, Hana,Choi, Jungseok,Wang, Gunuk,Kim, Tae-Wook,Noh, Jaegeun,Lee, Takhee American Scientific Publishers 2009 Journal of Nanoscience and Nanotechnology Vol.9 No.12
<P>We fabricated a large number of microscale via-hole structure molecular devices (2240 devices) using octane-Se [CH3(CH2)7Se] self assembled monolayers (SAMs) and compared their charge transport properties with those of octane-S [CH3(CH2)7S] SAMs molecular devices in terms of current density, resistance, and tunneling decay coefficient. The device yield of the 'working' octane-Se molecular devices was found to be approximately 1.7% (38/2240), which was similar to the yield of approximately 1.1% (50/4480) for octane-S devices. Our statistical analysis revealed that for octane-Se devices the tunneling current was slightly smaller and the low-bias resistance and decay coefficient were slightly larger than those for octane-S devices. The standard deviations of these transport parameters of octane-Se devices were found to be broader than those for octane-S devices due to irregularity of the binding sites of octane-Se on Au electrode surface.</P>
Volumetric Capacitance of In-Plane- and Out-of-Plane-Structured Multilayer Graphene Supercapacitors
Yoo, Jungjoon,Kim, Yongil,Lee, Chan-Woo,Yoon, Hana,Yoo, Seunghwan,Jeong, Hakgeun The Korean Electrochemical Society 2017 Journal of electrochemical science and technology Vol.8 No.3
A graphene electrode with a novel in-plane structure is proposed and successfully adopted for use in supercapacitor applications. The in-plane structure allows electrolyte ions to interact with all the graphene layers in the electrode, thereby maximizing the utilization of the electrochemical surface area. This novel structure contrasts with the conventional out-of-plane stacked structure of such supercapacitors. We herein compare the volumetric capacitances of in-plane- and out-of-plane-structured devices with reduced multi-layer graphene oxide films as electrodes. The in-plane-structured device exhibits a capacitance 2.5 times higher (i.e., $327F\;cm^{-3}$) than that of the out-of-plane-structured device, in addition to an energy density of $11.4mWh\;cm^{-3}$, which is higher than that of lithium-ion thin-film batteries and is the highest among in-plane-structured ultra-small graphene-based supercapacitors reported to date. Therefore, this study demonstrates the potential of in-plane-structured supercapacitors with high volumetric performances as ultra-small energy storage devices.