Defects in graphene-based twisted nanoribbons: structural, electronic, and optical properties.

Area of Science:

• Materials Science
• Computational Chemistry
• Condensed Matter Physics

Background:

• Graphene nanoribbons (GNRs) are promising materials for nanoelectronic and optoelectronic devices.
• Understanding the impact of structural defects and geometric variations on GNR properties is crucial for their application.
• Half-twists and atomic defects can significantly alter the electronic and optical behavior of GNRs.

Purpose of the Study:

• To investigate the effects of varying numbers of half-twists and single-atom defects on the structural, electronic, and optical properties of graphene nanoribbons.
• To computationally simulate and analyze the behavior of these modified nanostructures.
• To determine how defects and twists influence the energy gap and optical absorption spectra.

Main Methods:

• Computational simulations employing a hybrid approach of classical and quantum semiempirical methods.
• Geometry optimization to find stable configurations of defective graphene nanoribbons.
• Calculation of electronic properties, including the HOMO-LUMO energy gap.
• Quantum chemical calculations using the full configuration interaction (CI) framework to determine optical transitions and oscillator strengths.
• Analysis of optical absorption spectra in the UV/Vis and infrared regions.

Main Results:

• Local curvature increases at defect sites, particularly with a higher number of half-twists.
• The HOMO-LUMO energy gap shows significant variation with increasing half-twists in defective nanoribbons.
• Distinct spectral signatures in the UV/Vis range were observed, with absorption peaks shifting from orange to violet.
• Strong absorption was noted in the ultraviolet region.
• Differences in infrared spectra (vibrational transitions) were minimal.

Conclusions:

• Defects and half-twists introduce significant changes to the electronic and optical properties of graphene nanoribbons.
• The observed unique spectral signatures in the UV/Vis range suggest potential for tailored optoelectronic applications.
• Computational simulations provide valuable insights into the structure-property relationships of defective graphene nanoribbons.