Relationship between reactivity, energy-gap and absorption spectra study of armchair-, zigzag- and chiral-edged hexagonal graphene quantum dots Tristan Stephens-Jones 1 and Francisco Martin-Martinez 2,3 1 King's College London, UK, 2 Swansea University, UK 3 Massachusetts Institute of Technology, USA Graphene quantum dots (GQDs) are a type of carbon nanoparticle with a sp 2 honeycomb lattice. The special symmetry and size of GQDs causes a unique confinement of electrons resulting in them having distinct optical, electronic, and magnetic properties. 1 Hence why in recent years they have received a lot of attention in the field of bioelectronics, biosensing and photovoltaics. 2 The following research focuses on GQD flakes with hexagonal symmetry and, how size, edge type and nitrogen doping affect their reactivity and energy-gap. The three highly symmetrical edges that are studied were armchair , zigzag and chiral edges. They were first studied using density functional theory (DFT) to understand how increasing their size affected the undoped flakes. Then these flakes were doped on the edge and the centre to see how this would change their reactivity and energy-gap. The chiral edged flakes were also doped on their edge with up to six nitrogen atoms to determine if multi-doping made the flake more reactive than single doping. Time-dependent DFT (TD-DFT) calculations were conducted to produce absorption spectra to see how these were affected as well. The study found that edge doping for the armchair hexagonal graphene (AHG) flake, zigzag hexagonal graphene (ZHG) flake, and chiral hexagonal graphene (CHG) flake had very similar reactivity and energy-gap compared to their undoped flake. However, when centrally doped, the AHG, ZHG, and CHG flakes showed increased reactivity and an energy-gap that was in the desirable ~1 eV semiconducting range seen in traditional inorganic semiconductors. 3 It was also found that the absorption shifted to higher wavelengths in the centrally-doped flakes but remained unchanged in the edge-doped flakes. References 1. S. S. Yamijala, A. Bandyopadhyay and S. K. Pati, Journal of Physical Chemistry C , 2013, 117 , 23295–23304.
2. Wang and A. Hu, Journal of Materials Chemistry C , 2014, 2 , 6921–6939. 3. M. Z. Hu and T. Zhu, Nanoscale Research Letters , 2015, 10, 1–15.
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