Seminar
Tuesday, December 4, 2018 - 12:00am
Graduate Student Muhammad Imran will present
"Solution Phase Synthesis of Graphene Nanoribbons (GNRs) for Nanoelectronic Applications"
on December 4, 2018 at 4:10pm in Neville Hall, room 3
Since the discovery of graphene in 2004, its chemistry has attracted a lot of attention due to its exciting and unique properties [1]. Graphene is a one atom thick 2D sheet of sp2 carbon atoms arranged in a hexagonal pattern. This unique material can conduct electricity, absorb and emit light, and exhibits interesting magnetic properties. The importance of this elegant compound has been recognized, and the discovery of graphene was awarded the Nobel Prize in Physics in 2010. However, despite very exciting properties, graphene has no band gap i.e. it is semi-metallic. In order to use it in electronics such as LEDs or transistors, its band gap must be non-zero [2]. Graphene nanoribbons (GNRs) are members of the graphene family with widths less than 10 nm and a large aspect ratio. GNRs do have a band gap due to quantum confinement and edge effects [3]. However, a GNR band gap is highly dependent on the structure and edge topology of the ribbon. Therefore, future applications of GNRs in electronics require ribbons with atomically precise edges. Currently, there are two basic approaches to make GNRs; one is the top-down approach and the other is a bottom-up approach. Experts mostly agree that it is nearly impossible to control atomic precision in GNRs using current top-down approaches such as arc discharge, laser depletion, or lithography of bulk graphite. The bottom-up approach requires synthetic organic chemistry and is very promising to build highly precise graphene structures by molecular design. Advantageously, bottom-up approach allows tuning the band gap of GNRs through molecular size, edge structure, or incorporation of heteroatoms [4]. Of the two prevalent bottom-up methods, solution-phase versus surface-assisted synthesis shows an incomparable advantage for large scale production of GNRs with well-defined structures [5]. Despite many attempts, solution-phase synthesis has presented a challenge due to poor dispersibility and aggregation effects of GNRs [6]. Therefore, poor solubility has limited investigation of fundamental physiochemical properties of GNRs and impeded applications of GNRs in functional devices [7]. Here, some major breakthroughs in the dispersibility of GNRs will be presented which have provided access to atomically precise single GNRs and opened possibilities for their testing in nanoelectronic devices. Synthetic approaches and spectroscopic characterization of GNRs will also be discussed. References (1) Novoselov, K. S., Falko, V. I., Colombo, L., et al., A roadmap for graphene, Nature 2012, 490, 192. (2) Narita, A., Wang, X., Feng, X., et al., New advances in nanographene chemistry, Chem. Soc. Rev. 2015, 44, 6616. (3) Cai, J., Ruffieux, P., Jaafar, R., et al., Atomically precise bottom-up fabrication of graphene nanoribbons, Nature 2010, 466, 470. (4) Yang, X., Dou, X., Rouhanipour, A., et al., Two-dimensional graphene nanoribbons, J. Am. Chem. Soc. 2008,130, 4217. (5) Ruffieux, P., Wang, S., Yang, B., et al., On-surface synthesis of graphene nanoribbons with zigzag edge topology, Nature 2016, 531, 489. (6) Huang, Y., Mai, Y., Beser, U., et al., Poly(ethylene oxide) functionalized graphene nanoribbons with excellent solution processability, J. Am. Chem. Soc. 2016, 138, 10136. (7) Huang, Y., Xu, F., Ganzer, L., et al., Intrinsic properties of single graphene nanoribbons in solution: synthetic and spectroscopic studies, J. Am. Chem. Soc. 2018, 140, 10416.