title: Influence of surfactant concentration on the surface morphology of hollow silica microspheres and its explanation.
abstract: The surface morphology of hollow silica microspheres has influence on their applications. After a thorough investigation of the deposition of silica nanoparticles on polystyrene (PS) beads and the surface morphology and texture of the resultant hollow silica shells with scanning electron microscopy, transmission electron microscopy, and N2-sorption measurements, the influence of surfactant [cetyltrimethylammonium bromide (CTAB)] concentration on the surface morphology of hollow silica microspheres templated by PS beads is explained. Previously, CTAB was believed to turn the surface charge of PS beads from negative into positive so that negatively charged silica could be deposited on the PS template. Here, we show CTA+ cations preferentially assemble with silica species to form silica-CTA+ composite nanoparticles. Since the zeta potential of silica-CTA+ composite nanoparticles is smaller than that of pure silica nanoparticles, these composite nanoparticles encounter less repulsion when they are deposited on the surface of PS beads and close to each other. As more CTAB is added, the silica-CTA+ nanoparticles are less negatively charged, and more compact and smooth hollow silica microspheres are obtained.
authors.affiliation: School of Materials Science and Engineering, University of Jinan, Jinan, Shandong 250022, China. vctrliu@hotmail.com
authors.forename: Shiquan
authors.initials: S
authors.lastname: Liu
authors.forename: Meiying
authors.initials: M
authors.lastname: Wei
authors.forename: Pegie
authors.initials: P
authors.lastname: Cool
authors.forename: Cynthia
authors.initials: C
authors.lastname: Van Oers
authors.forename: Jiancun
authors.initials: J
authors.lastname: Rao