Abstract
Graphene Oxides (GO) typically contains different oxygen containing groups such as hydroxyl, carboxyl and epoxy, and reduced GO (r-GO) represents a family of material with diverse chemical properties. In an effort to understand how properties of r-GO change as GO is reduced, a stepwise reduction of the same GO to r-GO containing different levels of oxygen was carried out, and their corresponding chemical and colloidal properties are reported. Starting with GO containing 49 percent oxygen, r-GOs containing 31, 19 and 9 percent oxygen were synthesized. The aqueous behavior in terms of solubility gradually decreased from 7.4 µg/ml for GO to nearly zero for r-GO with 9% oxygen, while dispersibility under sonication decreased from 8 to 2.5 µg/ml for the same samples. Hydrophobicity index as measured as the octanol water partition coefficient decreased from −3.89 to 5.2% as oxygen content dropped from 49 to 9%. Colloidal behavior was also dramatically affected by reduction, and critical coagulation concentration (CCC) dropped from 28 to 15 in presence of 0.5 mmole/l NaCl and from 6 to 2 in presence of 0.5 mmole/l MgCl2 as the oxygen in the original GO was reduced to 9%.
Highlights
The level of reduction in r-Graphene Oxides (GO) is expected to alter aqueous dispersibility of these species
The resulting reduced GO (r-GO) are listed in Table 1 and these were classified based on the oxygen content
Controlled, step wise reduction of GO was carried out by nascent hydrogen generated from a reaction between metallic zinc and HCl. r-GOs containing 31, 19 and 9% oxygen were synthesized and studied
Summary
The level of reduction in r-GO is expected to alter aqueous dispersibility of these species Besides chemical behavior, this has ecological consequences. Since GO and r-GO form different sources show a wide range of variability in both structure as well as the presence of functional groups, they cannot be compared directly To address this issue, the objective of this work is the stepwise reduction of the same GO to generate r-GO containing different levels of oxygen and study their chemical properties. The use of the same GO to form r-GO eliminates the variability associated with different sources of this highly diverse material Another objective is to study the colloidal behavior of the r-GOs representing different levels of GO reduction
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