A first principles approach to the interactions of alkali metal atoms with carbon quantum dots

• Published in: Computational materials science Vol. 197; p. 110614
• Main Authors: Politi, J.R.S., Martins, J.B.L., Cabral, B.J.C.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.09.2021
• Subjects: Binding energies; Carbon quantum dots; Density functional theory; Electron affinities; Electronic absorption spectra and charge transfer; Ionization energies; Time dependent density functional theory; Ionization energies; Time dependent density functional theory; Electronic absorption spectra and charge transfer; Binding energies; Electron affinities; Density functional theory; Carbon quantum dots
• ISSN: 0927-0256; 1879-0801
• DOI: 10.1016/j.commatsci.2021.110614

[Display omitted] •Carbon quantum dots (CQDs) exhibit high electron affinities.•Ionization energies of CQD-M complexes depend on the alkali metal M.•CQD-M interactions lead to the formation of carbon macrocycles.•Absorption of CQD-M in the visible is enhanced by charge-transfer excitations. We investigate the interactions between alkali metal atoms (M = Li,Na,K) and carbon quantum dot models (CQDs) by density functional theory. For systems where Li and Na metal atoms are initially placed between two nearly planar CQDs, the interaction with the metal species induces a significant reorganization of the carbon network with the formation of macrocycles, which keep some similarity with fragments of carbon nanotubes. Binding energies of metal atoms to CQDs are significantly stronger than what is observed in pristine graphene and also in graphene nanoribbons. CQDs are characterized by high electron affinities. For a model with 32 carbon atoms [CQD32] the first and second electron affinities are 4.3 and 2.1 eV, respectively. Time dependent density functional (TDDFT) calculations for the electronic spectra of [CQD-M] complexes are compared with experimental information for similar carbon based structures. The results relying on TDDFT for [CQD-M] indicate that the enhancement of the absorption in the visible region in comparison with isolated [CQD] is related to excitations with a significant charge-transfer character.