Hydrogen bonding and covalent coupling in adsorbed molecular monolayers

Garfitt, Jason Michael (2014) Hydrogen bonding and covalent coupling in adsorbed molecular monolayers. PhD thesis, University of Nottingham.

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Abstract

This thesis examines multiple different molecular networks adsorbed on several different substrates, namely, highly oriented pyrolytic graphite (HOPG), Au(111) and graphene.

STM investigations into hydrogen-bonded structures formed by closely related tetracarboxylic acid molecules were performed. The molecule pterphenyl-3,5,3,5-tetracarboxylic acid (TPTC), which is known to form random tiling networks, was observed on a graphene on copper substrate. The network formed from deposition of TPTC from nonanoic acid was examined statistically. Aqueous solutions of TPTC were also examined on HOPG where a new structure, distinct from the random tiling, was observed. Aqueous solutions of related molecules biphenyl-3,3',5,5'-tetracarboxylic acid (BPTC) and quaterphenyl-3,3',5,5'-tetracarboxylic acid (QPTC), were also studied on HOPG. QPTC formed a similar structure to the aqueous solutions of TPTC, but BPTC formed two different phases, one of which was a kagome network.

Addition of nonanoic acid to a dried network of TPTC deposited from aqueous solution resulted in solvent induced recrystallisation into a random tiling network comparable to that observed on graphene on copper, which was statistically analysed. Studies investigating the potential for covalent bonded molecular networks identified two distinct phases of the molecule 1,3,5-Tri(4-bromophenyl-benzene (TBPB) adsorbed on Au(111). Concentration variation indicates an island based growth mechanism for these domains from solution. Dimerisation of TBPB was achieved by deposition onto heated substrates and a discussion of possible reasons for the reaction termination at dimers is provided.

Attempts to repeat the TBPB experiments on graphene on copper failed due to excessive corrosion. Variations using larger molecules failed due to lack of solubility. Preliminary experiments on 10,10'-dibromo-9,9'-bianthryl (DBrBA) showed promise but were irreproducible, however micron scale dendritic structures were observed suggesting poor compatibility with the solvent.

Finally, a discussion of the development of a nickel catalysis based graphene fabrication method is given and the limits of what is achievable with this method are discussed.

The results from this thesis highlight the importance of solvent selection for the future understanding of molecular network fabrication. We also demonstrated the feasibility of covalently bonded networks prepared in ambient

conditions.

Item Type: Thesis (University of Nottingham only) (PhD)
Supervisors: Beton, P.H.
Moriarty, P.J.
Keywords: Nano, Scanning tunnelling microscope, STM, SPM, microscopy, Au, gold, graphite, HOPG, graphene, tetracarboxylic, conjugated, molecular networks, self assembly, monolayer
Subjects: Q Science > QC Physics > QC770 Nuclear and particle physics. Atomic energy. Radioactivity
Q Science > QD Chemistry > QD450 Physical and theoretical chemistry
Faculties/Schools: UK Campuses > Faculty of Science > School of Physics and Astronomy
Item ID: 27728
Depositing User: Garfitt, Jason
Date Deposited: 25 Feb 2015 09:38
Last Modified: 26 Oct 2016 13:11
URI: http://eprints.nottingham.ac.uk/id/eprint/27728

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