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Title: Synthesis and characterisation of BN-isosteres of polyaromatic hydrocarbons
Author: Limberti, Simone
ISNI:       0000 0004 7961 4119
Awarding Body: University of Bath
Current Institution: University of Bath
Date of Award: 2019
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In the last few decades graphene-based materials have attracted a great amount of interest in the scientific and academic world because of their fascinating properties. Recently, graphene, because of the extraordinary electronic, optoelectronic and physical feature, has been proposed as innovative material for future electronic devices. However, one of the key challenges in advancing the graphene-based technologies in this area is the lack of an energy gap between the conduction and valence bands, limiting its application to replace silicon-based semiconductors in electronics. Therefore, the ability to impose a band gap in graphene and tailor the size of the band gap is of great significance to materials chemists. One of the most promising strategy that is currently emerging to overcome these limitations is the replacement of C=C bonds by isostructural and isoelectronic bonds such as polar B-N bond. Hybridised atomic sheets containing bonds between elements boron, nitrogen and carbon over wide compositional ranges could results in new materials with properties complimentary to those of graphene and the insulating h-BN, enabling a rich variety of electronic structures, properties and applications. While various materialsprocessing technologies to produce these materials in sizable quantities are improving in their synthetic methodologies, the organic electronic research is moving towards the synthesis of new BN doped polycyclic aromatic hydrocarbons (PAHs), which have showed interesting electronic properties. In this regard borazine based materials have the right requirements in terms of chemical and electronic properties, therefore they can provide new opportunities in the efforts to develop BN-PAHs materials. Chapter 1 surveys the history of graphene, hexagonal boron-nitride and their corresponding boron, nitrogen and carbon hybrid materials, detailing the range of synthetic methods and analytical techniques used to analyse these materials. This section is followed by an introduction to polycyclic aromatic hydrocarbons (PAHs) exploring the most important synthetic methods and the physical and chemical properties of these materials. A particular attention is focused on a polyaromatic hydrocarbon known as truxene, who C3 symmetric structure is the basis of our single organic molecules described. We then introduce the effects of boron and nitrogen incorporated into polyaromatic systems and how they alter optoelectronic properties in relation to their extent of doping. The chapter is concluded with a review of borazine, aminoborane and amine-borane synthesis and characterisation. Isoelectronic to benzene, the borazine core has been used as motif to construct our CBN-hybrid molecules. Chapters 2 and 3 describes the total synthesis of novel single organic molecules known as borazatruxenes and benzo(c)naphtho(2,1-p)borazachrysenes. These molecules are well characterized by NMR and Mass Spectroscopy analysis. The electronic properties are studied by UV-Visible spectroscopic analysis. Finally, the self-assembly process characterizing the supramolecular aggregation of such systems is explored by variable temperature 1H NMR studies. Chapters 4 and 5 explores the possibility of synthesising hybrid boron, nitrogen and carbon extended 2D materials. In particular Chapter 4 is focused on the development of a synthetic method for the synthesis of BN-doped hemifullerene by either dehydrogenation or flash vacuum pyrolysis (FVP) of engineered borazatruxenes and benzo(c)naphtho(2,1-p)borazachrysenes. Chapter 5 details the attempted synthesis of 2D-CBN hybrid oligomers and polymer networks combining benzene and borazine regions. Synthesis of such materials is achieved using a protocol outlined for borazatruxenes utilising microwave-dielectric heating. Oligomer materials are characterised using the common analytical techniques while polymers are characterized by solid-state analytical techniques.
Supervisor: James, Tony ; Pantos, Gheorghe Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available