Understanding Aqueous Dispersibility of Graphene Oxide and Reduced Graphene Oxide through pK(a) Measurements

Konkena, Bharathi and Vasudevan, Sukumaran (2012) Understanding Aqueous Dispersibility of Graphene Oxide and Reduced Graphene Oxide through pK(a) Measurements. In: Journal of physical chemistry letters, 3 (7). pp. 867-872.

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Abstract

The chemistry underlying the aqueous dispersibility of graphene oxide (GO) and reduced graphene oxide (r-GO) is a key consideration in the design of solution processing techniques for the preparation of processable graphene sheets. Here, we use zeta potential measurements, pH titrations, and infrared spectroscopy to establish the chemistry underlying the aqueous dispersibility of GO and r-GO sheets at different values of pH. We show that r-GO sheets have ionizable groups with a single pK value (8.0) while GO sheets have groups that are more acidic (pK = 4.3), in addition to groups with pK values of 6.6 and 9.0. Infrared spectroscopy has been used to follow the sequence of ionization events. In both GO and r-GO sheets, it is ionization of the carboxylic groups that is primarily responsible for the build up of charge, but on GO sheets, the presence of phenolic and hydroxyl groups in close proximity to the carboxylic groups lowers the pK(a) value by stabilizing the carboxylate anion, resulting in superior water dispersibility.

Item Type:	Journal Article
Publication:	Journal of physical chemistry letters
Publisher:	Elsevier Science
Additional Information:	Copyright of this article is belongs to Elsevier Science.
Department/Centre:	Division of Chemical Sciences > Inorganic & Physical Chemistry
Date Deposited:	23 Aug 2012 07:41
Last Modified:	23 Aug 2012 07:41
URI:	http://eprints.iisc.ac.in/id/eprint/44472

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