Controllable Mesopore-size and Outer Diameter of Silica Nanoparticles Prepared by a Novel Water/Oil-Phase Technique
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Controllable Mesopore-size and Outer Diameter of Silica Nanoparticles Prepared by a Novel Water/Oil-Phase Technique Asep Bayu Dani Nandiyanto, Yutaka Kaihatsu, Ferry Iskandar, and Kikuo Okuyama* Department of Chemical Engineering, Graduate School of Engineering, Hiroshima University, 14-1 Kagamiyama, Higashi Hiroshima 739-8527, Japan *Corresponding author: Tel.: +81-82-424-7850. Email: [email protected] ABSTRACT Tunable pore size and outer particle diameter of spherical mesoporous silica particles in the nanometer range were successfully synthesized using a novel water/oil-phase synthesis technique. This method involves (i) simultaneous hydrolytic condensation of tetraorthosilicate to form silica and polymerization of styrene into polystyrene (PS), (ii) self-assembly nanocluster silica and nanocluster PS to form silica/PSL nanoparticle, and (iii) calcination process to remove organic components and to produce mesoporous silica particle. In this study, an amino acid (e.g. lysine) was utilized to catalyze and to maintain the silica formation due to its ability in covering prepared silica after reaction. Further, another advantage of this catalyst is more harmless than other catalysts (e.g. ammonia, N2H4). The result showed spherical particles with controllable pore size (from 4 to 15 nm) and outer diameter (from 20 to 80 nm) was produced. The ability to control pore size and outer diameter was drastically altered by adjusting the concentration of styrene and hydrophobic molecules, respectively. After the preparation of particle was understood clearly, the large-molecule-adsorption performance of the prepared porous particles was conducted. As expected, relatively large organic molecules (i.e. Rhodamine B) were wellabsorbed in the prepared sample but not by the commercial non-porous particles. With this reason, the prepared mesoporous silica particles may be used efficiently in various applications, including electronic devices, sensors, pharmaceuticals, and environmentally sensitive pursuits, due to its harmless process, compatibility for bio-application, and excellent adsorption properties. INTRODUCTION Recently, porous structured materials have attracted tremendous attention due to a larger surface area, well-organized pore size and shape, lower density and dielectric constant compared with dense materials. They have many potential applications: a catalyst, an adsorbent, as gas sensors and in electro optics. Silica is one of the more well-known porous materials because it is chemically inert, thermally stable, harmless and inexpensive. Furthermore, the additional silica as coating material shows enhancing the unique optical, electronic, magnetic and mechanical properties.[1] Many preparation methods for silica, containing meso and macropore structures known as the MCM- and SBA-series, have been reported with various morphologies, such as thin films, spheres and fibers.[2] Various silica sources (i.e., alkoxide[3] and silica nanoparticle[4]) using either acid, ammonia, or strong bases as a catal
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