Issue 18, 2019

Excited states and excitonic interactions in prototypic polycyclic aromatic hydrocarbon dimers as models for graphitic interactions in carbon dots

Abstract

The study of electronically excited states of stacked polycyclic aromatic hydrocarbons (PAHs) is of great interest due to promising applications of these compounds as luminescent carbon nanomaterials such as graphene quantum dots (GQDs) and carbon dots (CDs). In this study, the excited states and excitonic interactions are described in detail based on four CD model dimer systems of pyrene, coronene, circum-1-pyrene and circum-1-coronene. Two multi-reference methods, DFT/MRCI and SC-NEVPT2, and two single-reference methods, ADC(2) and CAM-B3LYP, have been used for excited state calculations. The DFT/MRCI method has been used as a benchmark method to evaluate the performance of the other ones. All methods produce useful lists of excited states. However, an overestimation of excitation energies and an inverted ordering of states, especially concerning the bright HOMO–LUMO excitation, are observed. In the pyrene-based systems, the first bright state appears among the first four states, whereas the number of dark states is significantly larger for the coronene-based systems. Fluorescence emission properties are addressed by means of geometry optimization in the S1 state. The inter sheet distances for the S1 state decrease in comparison to the corresponding ground-state values. These reductions are largest for the pyrene dimer and decrease significantly for the larger dimers. Several minima have been determined on the S1 energy surface for most of the dimers. The largest variability in emission energies is found for the pyrene dimer, whereas in the other cases a more regular behavior of the emission spectra is observed.

Graphical abstract: Excited states and excitonic interactions in prototypic polycyclic aromatic hydrocarbon dimers as models for graphitic interactions in carbon dots

Supplementary files

Article information

Article type
Paper
Submitted
31 Jan 2019
Accepted
04 Mar 2019
First published
04 Mar 2019

Phys. Chem. Chem. Phys., 2019,21, 9077-9088

Author version available

Excited states and excitonic interactions in prototypic polycyclic aromatic hydrocarbon dimers as models for graphitic interactions in carbon dots

B. Shi, D. Nachtigallová, A. J. A. Aquino, F. B. C. Machado and H. Lischka, Phys. Chem. Chem. Phys., 2019, 21, 9077 DOI: 10.1039/C9CP00635D

To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page.

If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given.

If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page.

Read more about how to correctly acknowledge RSC content.

Social activity

Spotlight

Advertisements