Authors:	Yang, Bo
Title:	Bottom-up synthesis of graphene nanoribbons and nanographene molecules with new types of periphery
Online publication date:	6-Apr-2016
Year of first publication:	2016
Language:	english
Abstract:	Graphene, a mono layer of graphite, has been shown to have a variety of exceptional properties, particularly extremely high charge-carrier mobilities, making it a promising material for future nanoelectronics. However, the absence of a bandgap hinders the application of graphene in field-effect transistor (FET) devices. In contrast to infinite graphene, cutting graphene into structurally defined nanoscale segments such as pieces or stripes, which are called nanographene molecules (NGs) and graphene nanoribbons (GNRs), respectively, are feasible solutions. Because of the quantum confinement effect, the NGs and GNRs exhibit non-zero bandgaps that are mainly governed by their size and edge configurations. Moreover, the edge configurations of nanographene can mainly be classified as armchair and zigzag type. In contrast to plenty examples of armchair-type nanographene, syntheses of atomically precise nanographene with zigzag-type edge structures remain challenging. In the first part of this thesis, bottom-up fabrications of novel GNRs with zigzag edge structures through surface-assisted and solution-mediated methods are demonstrated in chapter 2 and 3, respectively. By utilizing the surface-assisted method, four novel GNRs with different edge structures were fabricated, including GNRs with hybrid of zigzag and gulf edges, hybrid of zigzag and cove-type edges, zigzag edge with fluoranthrene subunits, and perfect full zigzag edge structures. In particular, the last two GNRs demonstrated theoretically predicted spin-polarized edge states and antiferromagnetic properties, which was investigated by spin-polarized STM. Regarding the solution-mediated method, we claimed successful synthesis of a liquid-phase processable GNR with hybrid of zigzag and gulf edge structure and an estimated average length of >100 nm. The obtained GNR was comprehensively characterized by means of Raman, FTIR, solid-state NMR, UV-Vis-NIR, as well as AFM. The GNRs revealed a low optical bandgap (Eg = 1.54 eV) for its narrow width (~1 nm), indicating that incorporation of zigzag edge structures can effectively lower the bandgaps of GNRs. The second and the third parts of this thesis summarize attempts of synthesizing novel NGs with partial/or full zigzag edge structures, as well as chemical functionalization of NGs. For the former, we tested series of synthetic routes to obtain desired target molecules. Although we did not get our desired products, a series of new molecules were obtained and pave the way towards our targets, e.g., tetra-zigzag HBC molecule. For the chemical functionalization of NGs, we successfully utilized the edge chlorination method to a series of reported NGs with carbon numbers spanning from 42 to 222. The efficient edge chlorination severed as a feasible way to modulate the properties of NGs, for example, solubility, HOMO-LUMO energy gap, energetic positions of the frontier molecular orbital, and charge transport.
DDC:	540 Chemie 540 Chemistry and allied sciences
Institution:	Johannes Gutenberg-Universität Mainz
Department:	FB 09 Chemie, Pharmazie u. Geowissensch.
Place:	Mainz
ROR:	https://ror.org/023b0x485
DOI:	http://doi.org/10.25358/openscience-4549
URN:	urn:nbn:de:hebis:77-diss-1000003705
Version:	Original work
Publication type:	Dissertation
License:	In Copyright
Information on rights of use:	https://rightsstatements.org/vocab/InC/1.0/
Extent:	248 S.
Appears in collections:	JGU-Publikationen