Liquid phase production of graphene by exfoliation of graphite in surfactant/water solutions

TL;DR

This paper presents a method for producing graphene via liquid phase exfoliation of graphite in water-surfactant solutions, resulting in stable, small, few-layer flakes suitable for transparent conductive films.

Contribution

The study introduces an effective liquid phase exfoliation process in surfactant/water solutions for scalable graphene production with detailed characterization.

Findings

Over 40% of flakes have fewer than 5 layers.

Approximately 3% of flakes are monolayers.

Deposited films are semi-transparent and reasonably conductive.

Abstract

We have demonstrated a method to disperse and exfoliate graphite to give graphene suspended in water-surfactant solutions. Optical characterisation of these suspensions allowed the partial optimisation of the dispersion process. Transmission electron microscopy showed the dispersed phase to consist of small graphitic flakes. More than 40% of these flakes had <5 layers with ~3% of flakes consisting of monolayers. These flakes are stabilised against reaggregation by Coulomb repulsion due to the adsorbed surfactant. However, the larger flakes tend to sediment out over ~6 weeks, leaving only small flakes dispersed. It is possible to form thin films by vacuum filtration of these dispersions. Raman and IR spectroscopic analysis of these films suggests the flakes to be largely free of defects and oxides. The deposited films are reasonably conductive and are semi-transparent. Further improvements may result in the development of cheap transparent conductors.