A graphene oxide Cookbook: Exploring chemical and colloidal properties as a function of synthesis parameters

Siyuan An; Qingqing Zeng; Wenlu Li; John Fortner

doi:10.1016/j.jcis.2020.11.102

A graphene oxide Cookbook: Exploring chemical and colloidal properties as a function of synthesis parameters

J Colloid Interface Sci. 2021 Apr 15:588:725-736. doi: 10.1016/j.jcis.2020.11.102. Epub 2020 Nov 30.

Authors

Siyuan An¹, Qingqing Zeng², Wenlu Li³, John Fortner⁴

Affiliations

¹ Department of Energy, Environmental and Chemical Engineering, Washington University in St. Louis, MO 63130, USA.
² Department of Energy, Environmental and Chemical Engineering, Washington University in St. Louis, MO 63130, USA; Department of Chemical and Environmental Engineering, Yale University, CT 06520, USA.
³ School of Ecology and Environment, Northwestern Polytechnical University, Xi'an 710129, PR China; Department of Chemical and Environmental Engineering, Yale University, CT 06520, USA. Electronic address: wenlu.li@yale.edu.
⁴ Department of Energy, Environmental and Chemical Engineering, Washington University in St. Louis, MO 63130, USA; Department of Chemical and Environmental Engineering, Yale University, CT 06520, USA. Electronic address: john.fortner@yale.edu.

PMID: 33309143
DOI: 10.1016/j.jcis.2020.11.102

Abstract

Herein, we describe the synthesis of graphene oxide (GO) over a large range of conditions, exploring the effects of reaction temperature, reaction time, oxidant ratio, and sonication time on the chemical and colloidal properties of the product. As a function of reaction parameters, modified from Hummers' method, GO products were characterized and described via a suite of spectroscopic, structural, and morphological techniques, including TEM, UV-vis spectroscopy, XPS, Raman spectroscopy, FTIR, and DLS. Average carbon oxidation state and the yield (upon sonication) were chosen as the two criteria to evaluate synthesized GO materials. It was observed that as reaction temperature increased, GO oxidation state and yield of the sonication step both increased. Further, increasing reaction time and oxidant ratio not only increased the oxidation state, but also had a pronounced effect on the final yield. As synthesized, GO with higher degrees of oxidization exhibited higher negative ζ-potential, slightly smaller hydrodynamic diameter, and higher critical coagulation concentration(s). Data sets collectively demonstrate that carbon oxidation state, functional group ratios, and the aggregation kinetics of GO products can be readily controlled by varying processing time and conditions with expected changes in aqueous behavior(s), including stability/aggregation.

Keywords: Chemical synthesis; Colloidal stability; Critical coagulation concentration; Graphene oxide (GO); Graphite; Oxidation state.