title: The Dissociated Amorphous Silica Surface: Model Development and Evaluation.
abstract: At pH 7, amorphous silica has a characteristic negative charge due to the deprotonation of silanol groups on the surface. Electrokinetic phenomena and transport of biomolecules in devices depend sensitively on the surface morphology, distribution of ions and solvent, and adsorption properties of solutes close to the surface in the electrical double layer region. Hence, simulation of these phenomena requires detailed atomistic models of the double layer region. In this Article, we extend our undissociated silica surface model [J. Phys. Chem. B 2007, 111, 11181-11193] to include dissociated Si-O(-) groups, which interact with both water and salt (Na(+) and Cl(-)). We have also conducted ab initio molecular dynamics (AIMD) simulations of a smaller system consisting of a hydrated silica slab. The radial distribution functions predicted by the empirical model are in qualitative agreement with those from the AIMD simulations. The hydrophobic and hydrophilic nature of silanol-poor and silanol-rich regions of the amorphous silica surface observed in our empirical model is reproduced in the AIMD simulations of the smaller slab. In the initial stages of our AIMD simulations, we observe various chemical processes that represent different hydroxylation mechanisms of the surface.
authors.affiliation: Biophysics Program, and Department of Chemistry, Ohio State University, Columbus, Ohio 43210, United States.
authors.forename: Ali A
authors.initials: AA
authors.lastname: Hassanali
authors.affiliation: Biophysics Program, and Department of Chemistry, Ohio State University, Columbus, Ohio 43210, United States.
authors.forename: Hui
authors.initials: H
authors.lastname: Zhang
authors.affiliation: Biophysics Program, and Department of Chemistry, Ohio State University, Columbus, Ohio 43210, United States.
authors.forename: Chris
authors.initials: C
authors.lastname: Knight
authors.affiliation: Biophysics Program, and Department of Chemistry, Ohio State University, Columbus, Ohio 43210, United States.
authors.forename: Yun Kyung
authors.initials: YK
authors.lastname: Shin
authors.affiliation: Biophysics Program, and Department of Chemistry, Ohio State University, Columbus, Ohio 43210, United States.
authors.forename: Sherwin J
authors.initials: SJ
authors.lastname: Singer