Effect and Characterization of Stone–Wales Defects on Graphene Quantum Dot: A First-Principles Study

Abstract

A first principles based density functional theory (DFT) has been employed to identify the signature of Stone-Wales (SW) defects in semiconducting graphene quantum dot (GQD). Results show that the G mode in the Raman spectra of GQD has been red shifted to 1544.21 cm −1 in the presence of 2.08% SW defect concentration. In addition, the intensity ratio between a robust low intense contraction-elongation mode and G mode is found to be reduced for the defected structure. We have also observed a Raman mode at 1674.04 cm −1 due to the solo contribution of the defected bond. The increase in defect concentration, however, reduces the stability of the structures. As a consequence, the systems undergo structural buckling due to the presence of SW defect generated additional stresses. We have further explored that the 1615.45 cm −1 Raman mode and 1619.29 cm −1 infra-red mode are due to the collective stretching of two distinct SW defects separated at a distance 7.98 Å. Therefore, this is the smallest separation between the SW defects for their distinct existence. The pristine structure possesses maximum electrical conductivity and the same reduces to 0.37 times for 2.08% SW defect. On the other hand, the work function is reduced in the presence of defects except for the structure with SW defects separated at 7.98 Å. All these results will serve as an important reference to facilitate the potential applications of GQD based nano-devices with inherent topological SW defects.

Stone–Wales Defect in Graphene

“…They conclude that such results are very valid and will indeed operate as a valuable reference for the possible application of GQD-based nanodevices (including inherent topological SW defect) to experimental systems. [122] Recently (in 2019), Zhou and co-workers showed a thorough DFT study on the effect of the SW defects and 3d TM (scandium (Sc), vanadium (V), chromium (Cr), manganese (Mn), cobalt (Co), and copper (Cu)) dopants on arsenene by describing the structural, magnetic, and electronic features. Such influential features have been efficiently changed by SW defect and TM doping.…”

Stone–Wales Decorated Phagraphene: A Potential Candidate for Supercapacitor Electrodes and Thermal Transport

“…This further indicates that a slight variation in the morphology of the structure due to SW defects may result in significant modifications of physical properties. 30,32 Interestingly, the C 1 -and C 6 -type atoms of phagraphene become equivalent in the defective structures, resulting in an increased symmetry of the defected structures. It is expected that the interchange in the role of inequivalent and equivalent carbon atoms may lead to some exotic behavior of the electronic properties of the system.…”

“…30 Moreover, tuned electronic and enhanced transport properties have been observed in SW-defective graphene nanoribbons 31 quantum dots. 32 Particularly, SW defects are very important due to their moderate energy cost, and no atom is lost during the process. Such defects are experimentally viable to form during the growth process.…”

“…For graphene-based materials, SW defects are an effective way to modify their structural and electronic properties . Moreover, tuned electronic and enhanced transport properties have been observed in SW-defective graphene nanoribbons and quantum dots . Particularly, SW defects are very important due to their moderate energy cost, and no atom is lost during the process.…”

Effect of defects on optical and electronic properties of graphene quantum dots: a density functional theory study

“…30 Chakraborti et al have found that an increase in the concentration of SW defects in GQDs results in a decrease in the electrical conductivity of GQDs. 31 Moreover, some studies have reported that defects induced heteroatom doping, such as nitrogen and sulfur dopants, can reduce the band gap of GQDs, leading to improve light absorption and prolonged luminescence lifetime. 24,[32][33][34][35][36][37][38] In addition, the presence of defects in GQDs has been exploited for specic applications.…”