Synthetic Engineering of Graphene Nanoribbons with Excellent Liquid-Phase Processability

Abstract

Over the past decade, the bottom-up synthesis of structurally defined graphene nanoribbons (GNRs) with various topologies has attracted significant attention due to the extraordinary optical, electronic, and magnetic properties of GNRs, rendering them suitable for a wide range of potential applications (e.g., nanoelectronics, spintronics, photodetectors, and hydrothermal conversion). Remarkable achievements have been made in GNR synthesis with tunable widths, edge structures, and tailor-made functional substitutions. In particular, GNRs with liquid-phase dispersibility have been achieved through the decoration of various functional substituents at the edges, providing opportunities for revealing unknown GNR physiochemical properties. Because of the promise of liquid-phase dispersible GNRs, this mini-review highlights recent advances in their synthetic strategies, physiochemical properties, and potential applications. In particular, deep insights into the advantages and challenges of their syntheses and chemical methodologies are provided to encourage future endeavors and developments. Bottom-up Synthesis of Structurally Defined Graphene Nanoribbons Graphene nanoribbons (GNRs), defined as nanometer-wide strips of graphene, have attracted significant attention as candidates for next-generation semiconductor materials [1-6]. Quantum confinement effects provide GNRs with semiconducting properties, namely, with a finite bandgap that critically depends on their width and edge structures [7-10]. In the past decade, significant effort has been devoted to the synthesis of high-quality GNRs with narrow widths and smooth edges [9,11,12]. Two main strategies have been established for the synthesis of GNRs thus far: 'topdown' and 'bottom-up' approaches. The top-down approach includes the lithographic etching of graphene and unzipping of carbon nanotubes [13-17]. However, these methods generally suffer from low yields and poor structural precision, leading to GNRs with uncontrollable widths and edge structures. Moreover, to achieve precise bandgap control, GNRs should be narrower than 5 nm, which is at the precision limit for the start-of-the-art top-down techniques. In contrast, bottom-up strategies based on the 'on-surface synthesis' or 'solution-based chemical synthesis', namely, 'graphitization' and 'planarization' of tailor-made three-dimensional (3D) polyphenylene precursors, allows access to structurally well-defined GNRs with tunable widths as well as atomically precise edges, including armchair, zigzag, and cove structures [18-22]. Moreover, the precise positioning of heteroatom dopants in GNRs can be realized via this strategy, opening up another pathway for tailoring their optical and electronic properties [23-26]. The liquid-phase processability of GNRs is essential for investigating their fundamental physiochemical properties in solution and for the fabrication of nanoelectronic devices via dip coating or drop casting GNR dispersions on solid substrates [1,27-39].

Spatially Resolved Bottom‐Side Fluorination of Graphene by Two‐Dimensional Substrate Patterning

“…However, such structures requires facile and flexible synthetic methods for the rational design of spatially resolved two‐dimensional (2D) patterning of graphene. In preceding reports, graphene patterning has been accomplished by two general approaches: 1) etching away selected parts of the graphene lattice in a top‐down manner or bottom‐up surface assisted polymerizations of aromatic precursors to form nanoribbons, and 2) covalent surface patterning of addends on defined areas of the graphene basal plane . The latter method allows for combining the outstanding properties of graphene with those of other compound classes.…”

Recent advances in organic‐based materials for resistive memory applications

“…Graphene is an elemental carbon allotrope with sp 2 configuration of a honeycomb crystal lattice in a single‐layer sheet, and it is regarded as the first member of 2D materials family. Since its discovery, graphene has undergone a rapid development and shown broad prospects in a variety of fields including batteries, sensors, field‐effect transistors, and optoelectronic devices 142‐150 . Notably, graphene‐based materials have also demonstrated as promising alternatives for resistive memory applications, thanks to its easy solution‐processing features, outstanding physical and chemical adjustability, 3D stacking capability, and possibility of obtaining heterostructures 51,151‐167 .…”

Degradation of Structurally Defined Graphene Nanoribbons by Myeloperoxidase and the Photo‐Fenton Reaction

“…In recent years, graphene and its derivatives have been widely studied in the fields of medicine and gene delivery, bioimaging, biodetection, immune‐modulation and cancer treatment . As an emerging member in the graphene family, structurally well‐defined graphene nanoribbons (GNRs) have attracted enormous attention due to their controllable structures including length, width and edges . GNRs have proven great potential in various applications such as photothermal therapy, super‐resolution imaging and semiconductor materials.…”