Investigation on the use of graphene oxide as novel surfactant to stabilize weakly charged graphene nanoplatelets.

Salim Newaz Kazi,Huang Nay Ming,Emad Sadeghinezhad,Misni Misran,Ahmad Badarudin,Mohd Nashrul Mohd Zubir,Mohammad Mehrali,Nur Ily Syuhada

doi:10.1186/s11671-015-0882-7

Salim Newaz Kazi, Huang Nay Ming + Show 6 more

Open Access

https://doi.org/10.1186/s11671-015-0882-7

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Abstract

This paper presents a unique synergistic behavior between a graphene oxide (GO) and graphene nanoplatelet (GnP) composite in an aqueous medium. The results showed that GO stabilized GnP colloid near its isoelectric point and prevented rapid agglomeration and sedimentation. It was considered that a rarely encountered charge-dependent electrostatic interaction between the highly charged GO and weakly charged GnP particles kept GnP suspended at its rapid coagulation and phase separation pH. Sedimentation and transmission electron microscope (TEM) micrograph images revealed the evidence of highly stable colloidal mixtures while zeta potential measurement provided semi-quantitative explanation on the mechanism of stabilization. GnP suspension was confirmed via UV-vis spectral data while contact angle measurement elucidated the close resemblance to an aqueous solution indicating the ability of GO to mediate the flocculation prone GnP colloids. About a tenfold increase in viscosity was recorded at a low shear rate in comparison to an individual GO solution due to a strong interaction manifested between participating colloids. An optimum level of mixing ratio between the two constituents was also obtained. These new findings related to an interaction between charge-based graphitic carbon materials would open new avenues for further exploration on the enhancement of both GO and GnP functionalities particularly in mechanical and electrical domains.

Highlights

Graphene, a single atomic layer of interconnected carbon atoms in honeycomb configuration, and graphene oxide (GO), which earns its name from the oxidation process of graphite, are known to be the most researched materials at present in academia alongside carbon nanotube [1]
Some fragments of much smaller graphene nanoplatelet (GnP) particles were seen entrapped on the basal plane which may occur due to size reduction phase involving pulverization process
For GO-GnP hybrid configuration, it was shown that GnP particles were mostly anchored onto GO sheet which was mostly attributed to the electrostatic and hydrophobic interaction between the particles

Summary

Introduction

A single atomic layer of interconnected carbon atoms in honeycomb configuration, and graphene oxide (GO), which earns its name from the oxidation process of graphite, are known to be the most researched materials at present in academia alongside carbon nanotube [1]. GO is known to exist in the form several layers of graphene, and its chemical composition is classified into rich oxidized region where hydrophilic functional groups (i.e., epoxy and hydroxyl at the planar surface and carboxyl, carbonyl, ester, ether, diol, ketone, phenol, quinine, and lactones at the edges) are anchored to sp carbon atoms as well as pools of un-oxidized graphitic domains which consist of unperturbed hexagonal aromatic chains of sp bonded carbon atoms [13,14,15]. The chemical structure of GO renders the material amphifilic in nature similar to that of surfactant and demonstrate high solubility in aqueous-based solvents [14,16,17,18].

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