The optical and electronic properties of graphene quantum dots with oxygen-containing groups: a density functional theory study

Abstract

The effects of five types of oxygen-containing functional groups (–COOH, –COC–, –OH, –CHO, and –OCH3) on graphene quantum dots (GQDs) are investigated using time-dependent density functional theory (TD-DFT).

Graphene and silicene quantum dots for nanomedical diagnostics

“…The large hybridization of HOMO and LUMO levels results in the reduction of the H-L gap in accordance with C 123 QDs functionalized using oxygen containing groups. 28 Additionally, it is clear that the HOMO and LUMO levels of both -CH 3 and -OH edgefunctionalized structures shi toward higher energies with respect to pyrene, while they shi toward lower energies in COOH-CQDs. This nding can be assigned to the presence of the double bond in the COOH functional group.…”

“…26) and, (ii) C 123 H 38 QDs functionalized with oxygen containing groups. 28 Accordingly, upon functionalization, the H-L gap drops by 9.1-23.14% for CQDs since -CH 3 functionalized structures possess the highest H-L gap while the lowest gap is that of -COOH. For SiQDs, carboxylation resulted in decreasing the H-L gap due to the existence of the C]O double bonds in the -COOH molecules.…”

“…27 Additionally, the edge and surface functionalization of the CQDs with oxygencontaining groups leads to a remarkable change in the electronic gap and absorption spectra. 28 Experimentally, size-controllable amine-functionalized CQDs show low cytotoxicity and high biocompatibility, in addition to prominent multicolored uorescence and antimycoplasma properties. 29 Likewise, the optical properties have also been tuned by the contour functionalization in green uorescent CQDs synthesized using a single-step large scale synthesis through acidic treatment of the graphite powder.…”

Excitons in Carbonic Nanostructures

“…It is a question if these conditions can be realized in carbonic nanostructures. However, theoretical studies have shown the possibility of generating the loosely bound excitons in graphene nanoscale monolayers with the inclusion of polar groups at the sheet edges [205,206]. The evidence for their presence was obtained in experiments on graphene oxide sheets [207].…”

Size engineering optoelectronic features of C, Si and CSi hybrid diamond-shaped quantum dots

“…23 Consequently, the control of the preparation conditions as well as the choice of the manufacturing process opens the gap and tunes the optical properties of these nanostructures. 24,25 In parallel, the theoretical calculations have proven that many factors, namely; the size, the shape such as triangular and hexagonal, the edge conguration (zigzag/armchair), 26,27 the atom type, 28 the application of the electric eld, the chemical modication 29,30 which includes adsorption, substitution 31 as well as functionalization, 32,33 have a great impact on the optoelectronic properties and chemical reactivity of QDs. Indeed, they tailor the highest occupied-lowest unoccupied molecular orbital (HOMO)-(LUMO) energy gap.…”