Defects in Graphene-Based Twisted Nanoribbons: Structural, Electronic and Optical Properties

TL;DR

This study uses computational simulations to analyze how defects and twists in graphene nanoribbons affect their structural, electronic, and optical properties, revealing significant variations in energy gaps and spectral signatures.

Contribution

It introduces a detailed computational analysis of defective twisted graphene nanoribbons, highlighting the impact of defects and twists on their properties for the first time.

Findings

Increased local curvature at defect sites with more twists.

Significant variation in HOMO-LUMO gaps with twist number.

Distinct optical absorption signatures in UV/Visible range.

Abstract

We present some computational simulations of graphene-based nanoribbons with a number of half-twists varying from 0 to 4 and two types of defects obtained by removing a single carbon atom from two different sites. Optimized geometries are found by using a mix of classical-quantum semiempirical computations. According with the simulations results, the local curvature of the nanoribbons increases at the defect sites, specially for a higher number of half-twists. The HOMO-LUMO energy gap of the nanostructures has significant variation when the number of half-twists increases for the defective nanoribbons. At the quantum semiempirical level, the first optically active transitions and oscillator strengths are calculated using the full configuration interaction (CI) framework, and the optical absorption in the UV/Visible range (electronic transitions) and in the infrared (vibrational transitions) are achieved. Distinct nanoribbons show unique spectral signatures in the UV/Visible range, with the first absorption peaks in wavelengths ranging from the orange to the violet. Strong absorption is observed in the ultraviolet region, although differences in their infrared spectra are hardly discernible.