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Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 32, Number 5
BKCSDE 32(5)
May 20, 2011 

Fabrication of Uniform Hollow Silica Nanospheres using a Cationic Polystyrene Core
Dong Shin Yun, Ho Gyeom Jang,*, Jung Whan Yoo*,
Hollow silica sphere, Cationic polystyrene, TEOS, Sacrificial core method
Uniform, hollow nanosilica spheres were prepared by the chemical coating of cationic polystyrene (cPS) with tetraethylorthosilicate (TEOS), followed by calcination at 600 oC under air. cPS was synthesized by surfactantfree emulsion polymerization using 2,2'-azobis (2-methyl propionamidine) dihydrochloride as the cationic initiator, and poly(vinyl pyrrolidone) as a stabilizer. The resulting cPS spheres were 280 nm in diameter, and showed monodispersion. After coating, the hollow silica product was spherically shaped, and 330 nm in diameter, with a narrow distribution of sizes. Dispersion was uniform. Wall thickness was 25 nm, and surface area was 96.4 m2/g, as determined by BET. The uniformity of the wall thickness was strongly dependent upon the cPS surface charge. The effects of TEOS and ammonia concentrations on shape, size, wall thickness, and surface roughness of hollow SiO2 spheres were investigated. We observed that the wall thicknesses of hollow SiO2 spheres increased and that silica size was simultaneously enhanced with increases in TEOS concentrations. When ammonia concentrations were increased, the irregularity of rough surfaces and aggregation of spherical particles were more severe because higher concentrations of ammonia result in faster hydrolysis and condensation of TEOS. These changes caused the silica to grow faster, resulting in hollow SiO2 spheres with irregular, rough surfaces.
1534 - 1538
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