Graphene Oxide-Stabilized Oil-in-Water Emulsions: pH-Controlled Dispersion and Flocculation

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• 作者：Thomas M. McCoy ; Matthew J. Pottage ; Rico F. Tabor
• 刊名：Journal of Physical Chemistry C
• 出版年：2014
• 出版时间：February 27, 2014
• 年：2014
• 卷：118
• 期：8
• 页码：4529-4535
• 全文大小：379K
• 年卷期：v.118,no.8(February 27, 2014)
• ISSN：1932-7455

文摘

Oil-in-water emulsions stabilized by graphene oxide (GO) can be flocculated by either an increase or a decrease in pH. At highly acidic pH, fully reversible flocculation of emulsion droplets can be achieved, whereas when adjusted to high pH, the flocculation is irreversible, which we interpret as a permanent chemical change in the GO. We correlate the effectiveness of GO as a stabilizer to its aqueous aggregation state and explore the effects of the GO surface charge in determining emulsion properties. By directly measuring the interaction forces between two emulsion droplets coated in GO using the atomic force microscope, we demonstrate the basis for the pH-dependent flocculation behavior. It is shown that interfacial charge of the GO and oil鈥搘ater interface is the overriding drive for the exceptional stability of acidic GO emulsions.