Design and Synthesis of Graphene-Based Sensors

Abstract

The work embodied in this thesis describes the synthesis of polyvalent pyrene scaffolds decorated with maleimide and carbohydrate moieties for use in the fabrication of graphene-supported field effect transistors. This thesis describes three areas of research that were investigated for the development of graphene-based sensors: The first strand of research concerned the synthesis of multivalent graphene binding scaffold containing nitrogen-based linkers for the non-covalentl attachment to the surface of graphene. For this reason, pyrene-based tripods 57 and 74 were synthesized and fully characterized. Incorporation a versatile functional group to the centre of the graphene binding scaffold was also considered. The synthesis of a series of dipod and tripod scaffolds incorporating an alkyne moiety was undertaken. Dipods 68 and 69 as well as quaternized tripod 58 were successfully constructed. Unfortunately, none of the attempts to introduce an alkyne appendage to tripod 74 were successful. The second component was concerned with the identification of a chemosensing domain capable of attachment to a graphene binding scaffold. To this end N-(4-azidophenyl)-maleimide 91 was prepared and its viability in participating in click reactions investigated. Compounds 93a and 94a were prepared via (CuAAC) click reaction while 94b was synthesized using (RuAAC) click reactions. Dipod-maleimide compounds 95 and 96 were also prepared via (CuAAC) click reaction. Finally, several attempts to link maleimide 91 and its derivatives to tripods 57 and 74 were undertaken. The success of a CuAAC click reaction between tripod 58 with azido-pyrene 52 leading to the synthesis of triazole 98a is noteworthy. Sensing reaction of the maleimide appendage of compounds 64, 93a, and 113 as well as dipod 95 with 1-dodecanethiol 110 was achieved via a thiol-Michael addition reaction. The course of these reactions was also investigated using fluorescence spectroscopy. The enhancement of the excimer emission at 488 nm of the pyrene fluorophore in products during the course of these reactions is an indicator of the course of the addition reaction. The reaction between N-(t-butoxycarbonyl)-L-cysteine methyl ester 111 and representative maleimides was also investigated. Finally, the fabrication of 126 a sensor candidate containing two pyrene "feet" and a model carbohydrate binding site was accomplished using a CuAAC reaction in the conjugating step.