Optical Properties of Graphene Nanoflakes: Shape Matters

TL;DR

This study demonstrates that the edge shape of graphene nanoflakes significantly influences their optical absorption spectra and electronic properties, with simulations revealing fundamental differences based on edge type and shape.

Contribution

The paper provides computational evidence that edge type and shape critically affect the optical and electronic properties of graphene nanoflakes, clarifying debates in the field.

Findings

Absorption spectra differ notably between armchair and zigzag edges.

Edge-localized electronic states near the Fermi level influence optical properties.

Band gap trends vary distinctly with shape and edge geometry.

Abstract

In recent years there has been significant debate on whether the edge type of graphene nanoflakes (GNF) or graphene quantum dots (GQD) are relevant for their electronic structure, thermal stability and optical properties. Using computer simulations, we have proven that there is a fundamental difference in the calculated absorption spectra between samples of the same shape, similar size but different edge type, namely, armchair or zigzag edges. These can be explained by the presence of electronic structures near the Fermi level which are localized on the edges. These features are also evident from the dependence of band gap on the GNF size, which shows three very distinct trends for different shapes and edge geometries.