Emerging Functionalities of Carbon-Based 1D and 2D Nanoarchitectures

Nanostructuring graphene at the atomic scale is now possible by on-surface synthesis methods, which unite the sturdiness of covalently bonded networks with the easy tunability of molecular materials.[1,2] These experimental advances have boosted the research attempts to create novel 1D and 2D carbon-based structures aimed at the development of new nanoelectronic, spintronic or optoelectronic devices. However, before graphene nanostructures can be used in practical applications, an atomic level understanding and control of their properties is required. As such, <i>ab-initio</i> simulation has developed as an essential partner in the search of optimal carbon-based low dimensional materials.<br/><br/>In this talk, I will present some studies of prototype graphene nanostructures, such as graphene nanoribbons (GNRs) and nanoporous graphene (NPG), that we have recently performed in our group. Using mainly density functional theory (DFT), and in collaboration with our experimental colleagues, we have investigated their structural, electronic, magnetic and transport properties. On the one hand, we have explored the emergence of localized spins in metallic GNRs realized by substitutionally doping a narrow band gap GNR with boron atoms in its interior.[3] We have also reported on a novel NPG structure, which can be envisioned as GNRs laterally fused by phenylene bridges. Interestingly, electron transport simulations demonstrate the capability of modulating the interribon coupling by different degrees of freedom provided by the phenylene bridges.[4] Our results thus show that chemical doping offers the perspective of electronically controlling spins in 1D carbon nanoarchitectures, while molecular bridges emerge as an efficient tool to engineer quantum transport in 2D networks.<br/><br/>From a purely theoretical perspective, we have investigated prototypical hybrid GNRs formed using two existing carbon-based precursor molecules and a porphyrin center.[5] Our results reveal that narrow band gap hybrid GNRs might be achieved, and that embedding an iron atom in the porphyrin center gives rise to a spin-polarized ground state. Besides, our electron transmission calculations demonstrate how strain or chemical adsorption on the Fe atom gives rise to spin-crossover. This work highlights the potential of porphyrin-based hybrid GNRs as a highly tunable and flexible platform for spintronics and sensing applications.<br/><br/><b>References</b><br/>[1] Cai <i>et al., </i>Nature 466, 470 (2010)<br/>[2] Moreno <i>et al</i>., Science 360, 199 (2018)<br/>[3] Friedrich <i>et al.,</i> ACS Nano 16, 14819 (2022)<br/>[4] Moreno <i>et al., </i>J. Am. Chem. Soc. 145, 8988 (2023)<br/>[5] Gao <i>et al., </i>Comm. Phys. 6, 115 (2023)