Nanostructured Carbon Capsules with Hollow Core/Mesoporous Shell Structure
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NANOSTRUCTURED CARBON CAPSULES WITH HOLLOW CORE/MESOPOROUS SHELL STRUCTURE Jong-Sung Yu,1 Suk Bon Yoon,1 Kwonnam Sohn,2 Jeong Yeon Kim1 and Taeghwan Hyeon2 1 Department of Chemistry and Institute of Infor-Bio-Nano Materials, Hannam University, Taejon, 306-791, Korea 2 School of Chemical Engineering and Institute of Chemical Processes, Seoul National University, Seoul 151-742, Korea ABSTRACT Carbon capsules with hollow macroporous core/mesoporous shell were synthesized using sacrificial submicrometer-size solid core/mesoporous shell (SCMS) silica spheres as templates. Size of the hollow macroporous core and thickness of the mesoporous shell can be easily controlled by the choice of silica spheres and the amount of TEOS/C18-TMS mixture, respectively. INTRODUCTION A new class of nanoporous carbon [1] and polymer [2] materials with well-ordered uniform mesopores of 2 nm ~ 5 nm was synthesized using mesoporous silica materials as templates. Various colloidal crystals based on the ordered aggregation of spherical nanoparticles such as silica or latex polymer spheres have been used as templates for synthesizing new macroporous materials including polymers [3], metals [4], carbons [5] and inorganic materials [6]. Several interesting materials have been reported, in which both macropores and micro- or mesopores are incorporated into the structure [7]. There has been great deal of interest to create core-shell composite materials and capsules with tailored structural, optical and surface properties using spherical nanoparticles as molds [8]. Various procedures have been applied to fabricate uniform coated and stable colloidal particles. Caruso and coworkers have introduced a layer-bylayer (LbL) self-assembly approach to fabricate many different core-shell materials. The alternating depositions of oppositely charged species have been applied to form various shell compositions, including silicas, titanias, polymers, silica-polymer nanocomposites,
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magnetic materials, and proteins [9]. Either hard core spheres or hollow shells can be produced, depending on the removal of core templates. Many other core-shell structures have been fabricated through different synthetic approaches [10]. After the first report by the Mobil researchers, many different mesoporous inorganic materials have been synthesized using organic surfactants and block copolymers as templates [11]. Recently, Unger et al. reported the synthesis of submicrometer-size solid core/mesoporous shell (SCMS) silica spheres from the simultaneous sol-gel polymerization of tetraethoxysilane (TEOS) and octadecyltrimethoxysilane followed by the removal of the organic group [12]. Herein we report the fabrication of carbon capsules with hollow core/mesoporous shell (HCMS) structures using the submicrometer-size solid core/mesopor
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