On the Nature of Defects in Liquid-Phase Exfoliated Graphene

TL;DR

This paper investigates the types and locations of defects in liquid-phase exfoliated graphene, revealing defect accumulation in the bulk with longer sonication times, which impacts the quality of graphene dispersions.

Contribution

It provides new insights into defect formation and localization in liquid-phase exfoliated graphene, challenging the assumption of defect-free multilayers.

Findings

Defects are mainly at edges for short sonication times.

Bulk defects increase with sonication times above 2 hours.

Defect localization depends on sonication duration.

Abstract

Liquid-phase exfoliation is one of the most promising routes for large scale production of multilayer graphene dispersions. These dispersions, which may be used in coatings, composites or paints, are believed to contain disorder-free graphene multilayers. Here we address the nature of defects in such samples obtained by liquid-phase exfoliation of graphite powder in N-methyl--2--pyrrolidone. Our Raman spectroscopy data challenges the assumption that these multilayers are free of bulk defects, revealing that defect localization strongly depends on the sonication time. For short ultrasound times, defects are located mainly at the layer edges but they turn out to build up in the bulk for ultrasonic times above 2 h. This knowledge may help to devise better strategies to achieve high-quality graphene dispersions.