SIPS 2018

DETAILLED PROGRAM OVERVIEW

The Diverse Role of Polycyclic Aromatic Hydrocarbons: Basis for Polyradicaloid Character Leading to New Optoelectronic Devices and Origin for Luminescence in Carbon Nanodots
Hans Lischka¹;
¹TIANJIN UNIVERSITY, Tianjin, China;
PAPER: 377/SISAM/Keynote (Oral)
SCHEDULED: 15:55/Tue./Copacabana A (150/1st)

ABSTRACT:
The development of new functionalized materials is one of the key goals in science and technology. Since the discovery of fullerenes, carbon nanotubes and graphene, carbon-based material have attracted peak interest because of its versatility and the outstanding electronic and mechanical properties. In addition to these now well-known compounds, other types of carbon material have been found recently in the form of graphene quantum dots and carbon nanodots, which offer new alternatives to the previously mentioned examples. The key to a successful systematic development of new compounds is the possibility of chemical functionalization by means of covalent and non-covalent derivatization. In the present talk, two aspects in the wide range of applications indicated above are discussed. One is the doping of polycyclic aromatic hydrocarbons (PAHs) by nitrogen with application to the important class of zethrenes [1] as one example. High-level quantum chemical calculations have been performed for the computation of the electronic structure of the different PAHs investigated. The calculations demonstrate clearly how drastic enhancements to the biradicaloid character and reductions of the excitation energy gaps can be achieved by different doping positions. In the second part of the talk, a first approach to the quantum chemical calculation of luminescence properties of carbon nanodots [2,3] is presented. These properties are of great interest since they can be utilized in bioimaging applications, for dye-sensitized solar cells and supercapacitors. The great advantage of the carbon nanodots for the purpose of bioimaging is their low toxicity and excellent biocompatibility. The current challenge is to move their blue fluorescence to the red, which can be achieved by chemical doping. In our investigations, excimer formation and charge transfer in the nanodots have been modeled by means of stacked dimers of pyrene, coronene and circum-coronene sheets. Doping has been performed by replacing carbon atoms by nitrogen atoms or by substituting hydrogen atoms by halogen at the periphery of the PAHs. The absorption and emission spectra have been calculated, which show a characteristic dependence on the doping positions.

References:
[1] Z. Sun, Z. Zeng, J. Wu Acc. Chem. Res. 47 (2014) 2582-2591.
[2] H. T. Li, Z. H. Kang, Y. Liu, S. T. Lee, J. Mater. Chem. 22 (2012) 24230-24253.
[3] S. N. Baker, G. A. Baker Angew. Chem., Int. Ed. 49 (2010) 6726-6744