Porphyrin-Functionalized Graphene Nanoribbons in Solution Phase

Abstract

Structurally defined graphene nanoribbons (sd-GNRs) have gained attention due to their alluring physical properties and potential applications in optoelectronic devices. Edge functionalization of GNRs has proven to be an effective strategy to tailor their optoelectronic properties. However, progress in this area has been hindered by challenges associated with the controlled synthesis of sd-GNRs, resulting in limited exploration of edge-functionalized variants. Here, we report the synthesis of sd-GNRs functionalized with porphyrin groups at opposite edges (denoted as GNR-Por) in the solution phase. The GNR backbones feature a chevron-type structure with a uniform width of 0.94 nm and an average length of 60 nm. It is calculated that the bulky porphyrin substituents can endow the GNRs with a periodic wavy geometry unprecedented in the reported GNRs, which facilitates single-ribbon dispersibility in common organic solvents (e.g., <5 μg mL-1 in tetrahydrofuran). For the achieved GNRs, the longest variant exhibits a long charge scattering time of 70 ± 5 fs and demonstrates exceptionally high charge-carrier mobility of ∼460 ± 30 cm2 V-1 s-1, among one of the highest reported values for GNR-based materials. A distinct energy transfer process occurs from the porphyrin to the backbone of the longest GNR with a high-rate constant of 6.7 ps-1. Solid-state GNR-Por displays room-temperature phosphorescence emission, a new emission behavior in GNRs, within a near-infrared window having a lifetime of 1.3 μs. The present synthesis enables single-ribbon dispersibility of GNRs in the solution phase and confers new optoelectronic properties through edge engineering.