Porphyrin-Graphene Nanoribbon (PGNR) Conjugates: Solution Syntheses and Properties

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Graphene nanoribbons (GNRs) have attracted tremendous interest in recent years for their high charge carrier mobility and adjustable bandgap, making them potential to be used as carbon-based semiconductors. Controllable introduction of structural defects, such as non-hexagonal rings and heteroatoms, represents a useful strategy to tune their optoelectronic properties. Among all building blocks, porphyrin is an ideal candidate containing both of these two factors. Combining porphyrin with GNR holds great promise to create “super material”, which could benefit from advantages of each component. The applicant has over five years’ working experience in nanographene synthesis and developed one efficient method to fuse graphene molecules with porphyrin during his PhD. In this proposal, the applicant will apply the previous method to synthesize longitudinal extended porphyrin-fused graphene nanoribbons (PGNRs) and investigate their optoelectronic properties using interdisciplinary methodology. Specifically, two new types of structurally complex PGNRs will be designed and synthesized: one has porphyrin moieties embedded in the backbone of 9-atom wide GNR and the other has porphyrin units fused to the zigzag edges of chevron type GNR. Three main questions will be addressed in the current project: 1) How to synthesize PGNRs with atomically precise structures? As the exact structures of GNRs are crucial for their electronic properties and performances in devices, it’s vital to hold atomically precise control over their chemical structures. Here, a solution synthesis method will be applied, which involves rational design and synthesis of monomer building blocks and applying efficient polymerization method; 2) What are the properties of PGNRs and their advantages over their all carbon-based GNR counterparts? To answer this question, we will synthesize both normal 9-AGNRs/Chevron GNRs and PGNRs. Their optoelectronic and charge mobility properties will be compared and investigated in parallel, which will reflect the real effect of porphyrin doping; 3) What could these new PGNRs be used for? Both of these two PGNRs are highly conjugated and should have low energy gap and high charge mobility. So, they will be tried to fabricate single-molecule field-effect transistor devices. On the other hand, the porphyrin core could be coordinated with magnetic ions, which will make them promising for fabricating memory devices and spintronic devices. The results from this project will not only broaden our understanding of fundamental properties of GNRs, but also pave the way for their future applications in molecular devices.