Synthesis Of Graphene Nanoribbons Research Articles

Deposition temperature-mediated growth of helically shaped polymers and chevron-type graphene nanoribbons from a fluorinated precursor

Graphene nanoribbons (GNRs) of precise size and shape, critical for controlling electronic properties and future device applications, can be realized via precision synthesis on surfaces using rationally designed molecular precursors. Fluorine-bearing precursors have the potential to form GNRs on nonmetallic substrates suitable for device fabrication. Here, we investigate the deposition temperature-mediated growth of a new fluorine-bearing precursor, 6,11-diiodo-1,4-bis(2-fluorophenyl)-2,3-diphenyltriphenylene (C42H24F2I2), into helically shaped polymer intermediates and chevron-type GNRs on Au(111) by combining scanning tunneling microscopy, X-ray photoelectron spectroscopy, and density functional theory simulations. The fluorinated precursors do not adsorb on the Au(111) surface at lower temperatures, necessitating an optimum substrate temperature to achieve maximum polymer and GNR lengths. We compare the adsorption behavior with that of pristine chevron precursors and discuss the effects of C-H and C-F bonds. The results elucidate the growth mechanism of GNRs with fluorine-bearing precursors and establish a foundation for future synthesis of GNRs on nonmetallic substrates.

Polymerization of brominated aromatic compounds in a metal–organic framework for the bottom-up synthesis of graphene nanoribbons with either pyridinic or tertiary nitrogen

Polymerization of brominated aromatic compounds in a metal–organic framework for the bottom-up synthesis of graphene nanoribbons with either pyridinic or tertiary nitrogen

Evolution of PTCDA-derived seeds prior to graphene nanoribbon growth on Ge(001)

The synthesis of graphene nanoribbons (GNRs) can be realized via CH4 chemical vapor deposition (CVD) on substrates such as Ge(001) that promote highly anisotropic growth. Small polycyclic aromatic hydrocarbons (PAHs) are first sublimed onto Ge at relatively low temperature to form graphene-like seeds that subsequently initiate GNR growth with CH4 exposure at 1173 K. The behaviors of PAHs between their sublimation onto Ge and GNR growth are unclear. Here, we study an archetypical PAH – perylene-3,4,9,10-tetracarboxyl acid dianhydride (PTCDA) – on Ge(001) using both scanning tunneling microscopy (STM) and density functional theory (DFT) to characterize PAH configuration, surface diffusivity, and clustering. PTCDA becomes mobile above 673 K, consistent with a DFT diffusion barrier of 1.74 eV. The mobile PTCDA molecules meet, cluster, and fuse at Ge step edges, dehydrogenating at higher temperatures. These clusters have a height of 0.4 nm, similar to small graphene islands, and grow laterally with increasing temperature – reaching 1.2–2.1 nm in width at 1173 K, consistent with extrapolated CVD experiments. These results provide a plausible picture for how PTCDA forms seeds for anisotropic GNR CVD and show that PAHs with reduced surface diffusivity and inter-molecular reactivity are needed to enable more monodisperse PAH-seeded GNR synthesis.

Topologically Localized Vibronic Excitations in Second-Layer Graphene Nanoribbons.

It is of fundamental importance to characterize the intrinsic properties, like the topological end states, in the on-surface synthesized graphene nanoribbons (GNRs), but the strong electronic interaction with the metal substrate usually smears out their characteristic features. Here, we report our approach to investigate the vibronic excitations of the topological end states in self-decoupled second-layer GNRs, which are grown using an on-surface squeezing-induced spillover strategy. The vibronic progressions show highly spatially localized distributions at the second-layer GNR ends, which can be ascribed to the decoupling-extended lifetime of charging through resonant electron tunneling at the topological end states. In combination with theoretical calculations, we assign the vibronic progressions to specific vibrational modes that mediate the vibronic excitations. The spatial distribution of each resolved excitation shows evident characteristics beyond the conventional Franck-Condon picture. Our work by direct growth of second-layer GNRs provides an effective way to explore the interplay between the intrinsic electronic, vibrational, and topological properties.

High Performance Piezoelectric Nanogenerators Based on Polyvinylidene Fluoride-Graphene Nanoribbon Composite Thin Films.

In this study, a highly efficient, sensitive, and lightweight piezoelectric nanogenerator (PENG) is developed using graphene nanoribbons (GNRs) incorporated into the polyvinylidene fluoride (PVDF) matrix. Unzipping multi-walled carbon nanotubes is an effective and scalable strategy for synthesizing graphene nanoribbons. The synthesized GNRs are employed to prepare nanometer-scale piezoelectric polymer composite films showing higher piezoelectric performance than neat PVDF. The impact of GNR concentration in the PVDF matrix on the electroactive phase content and piezoelectric properties of the composites is systematically investigated. X-ray diffraction (XRD) and Fourier-transformed infrared spectroscopy (FT-IR) analysis demonstrate an increase in the electroactive β and γ phases of PVDF by incorporating GNRs in the composites. With the optimized concentration of GNRs (1 wt%), the fabricated piezoelectric device can generate open-circuit voltage and an output power density of 26V and 16.52 µWcm2, respectively. It is also found that the PVDF-GNR 1 nanogenerator can be used to generate electrical power by converting mechanical energy from different human activities such as wrist bending, palm tapping, and toe tapping. The findings indicate that (PVDF-GNR 1) PENGcan be applied in self-powered portable and wearable electronic devices.

Chain-growth polymerization enables the controlled synthesis of graphene nanoribbons

Chain-growth polymerization enables the controlled synthesis of graphene nanoribbons

Polymerization of Brominated Aromatic Compounds within a Metal-Organic Framework toward Bottom-up Synthesis of Graphene Nanoribbons with Either Pyridinic or Tertiary Nitrogen

Polymerization of Brominated Aromatic Compounds within a Metal-Organic Framework toward Bottom-up Synthesis of Graphene Nanoribbons with Either Pyridinic or Tertiary Nitrogen

Radical-Mediated Graphene Nanoribbon Synthesis

Radical-Mediated Graphene Nanoribbon Synthesis

Controlled catalyst-transfer polymerization in graphene nanoribbon synthesis

Controlled catalyst-transfer polymerization in graphene nanoribbon synthesis

B and N substitutional co-doping in 7AGNRs

On-surface synthesis of graphene nanoribbons enables engineering their electronic and magnetic properties, which sensitively depend on their precise bonding structure, morphology and chemical composition. Here, we investigate nitrogen and boron co-doping in order to better understand the effects of simultaneous chemical substitution in sites along the backbone of 7AGNRs. In a comparative analysis with the pristine system, the origin of the impurity bands that nitro-borylated systems exhibit was addressed. In addition to this, we studied the appearance of an electric dipolar moment, the charge transfer mechanism behind it and its dependence on the distance between BN centres. The high defect concentration limit and the dilute limit were investigated, along with various doping schemes with four substitutional doping sites and the possible emergence of magnetism in these systems.

Impacts of Graphene Nanoribbon Production Methods on Oxygen‐Reduction Electrocatalysis in Different Environments

AbstractGraphene‐based materials have emerged as highly promising catalysts for enhancing oxygen reduction reaction (ORR), a pivotal process in diverse energy conversion applications and the production of eco‐friendly oxidants like hydrogen peroxide (H2O2). To design exceptionally efficient catalysts tailored to specific applications, it is essentially crucial to have a thorough understanding of their electrocatalytic behaviour. This involves ascribing functions to structural characteristics like defects and exploring heteroatom doping in graphene matrices. In this work, we study the synthesis of graphene nanoribbons (GNRs) derived from multi‐walled carbon nanotubes (MWCNTs) and their doping with nitrogen (N) and phosphorus (P). We investigate how edge defects and oxygenated groups retained from the MWCNT opening process impact both the doping process and GNR electrocatalytic characteristics, with a focus on their relevance to ORR. Our findings underscore the need to optimize GNR structures and doping strategies for specific reaction conditions. We demonstrate how GNR characteristics are effectively influenced by varying MWCNT opening methods, ultimately affecting ORR performance and H2O2 selectivity. The findings show that when MWCNTs are opened to create GNRs with a broader distribution of oxygen atoms across the basal plane and fewer exposed edges, N‐insertion enhances catalytic activity, resulting in improved ORR performance. However, this alteration reduces H2O2 selectivity in both acidic and alkaline media. On the other hand, generating GNRs with abundant edges and widespread oxygen functional groups on both the basal plane and edges yields a high oxygen group concentration. This configuration not only facilitates phosphorus insertion at the edges but also plays a crucial role in enhancing ORR performance, leading to selectivities of over 92 % for H2O2 production in alkaline media. This study not only advances our understanding of graphene‐based catalysts but also offers meaningful contributions and insights into the development of more efficient and sustainable electrochemical technologies in the realm of energy conversion.

On-Surface Synthesis of Edge-Extended Zigzag Graphene Nanoribbons.

Graphene nanoribbons (GNRs) have gained significant attention in nanoelectronics due to their potential for precise tuning of electronic properties through variations in edge structure and ribbon width. However, the synthesis of GNRs with highly sought-after zigzag edges (ZGNRs), critical for spintronics and quantum information technologies, remains challenging. In this study, a design motif for synthesizing a novel class of GNRs termed edge-extended ZGNRs is presented. This motif enables the controlled incorporation of edge extensions along the zigzag edges at regular intervals. The synthesis of a specific GNR instance-a 3-zigzag-rows-wide ZGNR-with bisanthene units fused to the zigzag edges on alternating sides of the ribbon axis is successfully demonstrated. The resulting edge-extended 3-ZGNR is comprehensively characterized for its chemical structure and electronic properties using scanning probe techniques, complemented by density functional theory calculations. The design motif showcased here opens up new possibilities for synthesizing a diverse range of edge-extended ZGNRs, expanding the structural landscape of GNRs and facilitating the exploration of their structure-dependent electronic properties.

Introducing Design Strategies to Preserve N-Heterocycles Throughout the On-Surface Synthesis of Graphene Nanostructures.

Despite the impressive advances in the synthesis of atomically precise graphene nanostructures witnessed during the last decade, advancing in compositional complexity faces major challenges. The concept of introducing the desired functional groups or dopants in the molecular precursor often fails due to their lack of stability during the reaction path. Here, a study on the stability of different pyridine and pyrimidine moieties during the on-surface synthesis of graphene nanoribbons on Au(111) is presented. Combining bond-resolved scanning tunneling microscopy with X-ray photoelectron spectroscopy, the thermal evolution of the nitrogen dopants throughout the whole reaction sequence is tracked. A comparative experimental and ab initio electronic characterization confirms the presence of dopants in the final structures, revealing also that the pyridinic nitrogen leads to a significant band downshift. The results demonstrate that, by using synthetic strategies to lower the reaction temperatures, one can preserve specific N-heterocycles throughout all the reaction steps of the synthesis of graphene nanoribbons and beyond the interibbon coupling reaction that leads to nanoporousgraphene.

On-Surface Synthesis of Graphene Nanoribbons: Photoelectron Spectroscopy Reveals Impact of Substrate Reactivity

On-Surface Synthesis of Graphene Nanoribbons: Photoelectron Spectroscopy Reveals Impact of Substrate Reactivity

Design and synthesis of graphene nanoribbons from organic precursors

Design and synthesis of graphene nanoribbons from organic precursors

Determining the Number of Graphene Nanoribbons in Dual-Gate Field-Effect Transistors.

Bottom-up synthesized graphene nanoribbons (GNRs) are increasingly attracting interest due to their atomically controlled structure and customizable physical properties. In recent years, a range of GNR-based field-effect transistors (FETs) has been fabricated, with several demonstrating quantum-dot (QD) behavior at cryogenic temperatures. However, understanding the relationship between the cryogenic charge-transport characteristics and the number of the GNRs in the device is challenging, as the length and location of the GNRs in the junction are not precisely controlled. Here, we present a methodology based on a dual-gate FET that allows us to identify different scenarios, such as single GNRs, double or multiple GNRs in parallel, and a single GNR interacting with charge traps. Our dual-gate FET architecture therefore offers a quantitative approach for comprehending charge transport in atomically precise GNRs.

On-Surface Synthesis of Graphene Nanoribbons with Atomically Precise Structural Heterogeneities and On-Site Characterizations.

Graphene nanoribbons (GNRs) are strips of graphene, with widths of a few nanometers, that are promising candidates for future applications in nanodevices and quantum information processing due to their highly tunable structure-dependent electronic, spintronic, topological, and optical properties. Implantation of periodic structural heterogeneities, such as heteroatoms, nanopores, and non-hexagonal rings, has become a powerful manner for tailoring the designer properties of GNRs. The bottom-up synthesis approach, by combining on-surface chemical reactions based on rationally designed molecular precursors and in situ tip-based microscopic and spectroscopic techniques, promotes the construction of atomically precise GNRs with periodic structural modulations. However, there are still obstacles and challenges lying on the way toward the understanding of the intrinsic structure-property relations, such as the strong screening and Fermi level pinning effect of the normally used transition metal substrates and the lack of collective tip-based techniques that can cover multi-internal degrees of freedom of the GNRs. In this Perspective, we briefly review the recent progress in the on-surface synthesis of GNRs with diverse structural heterogeneities and highlight the structure-property relations as characterized by the noncontact atomic force microscopy and scanning tunneling microscopy/spectroscopy. We furthermore motivate to deliver the need for developing strategies to achieve quasi-freestanding GNRs and for exploiting multifunctional tip-based techniques to collectively probe the intrinsic properties.

Double quantum dots in atomically-precise graphene nanoribbons

Bottom-up synthesized graphene nanoribbons (GNRs) are precise quantum materials, offering a high degree of tunability of their physical properties. While field-effect transistors and single quantum dot (QD) devices have been reported, the fabrication of double QD devices using GNRs remains challenging due to their nanometer-scale dimensions. In this study, we present a multi-gate double QD device based on atomically precise GNRs that are contacted by a pair of single-walled carbon nanotube electrodes. At low temperatures, the device can be tuned with multiple gates and reveals triangular features characteristic for charge transport through a double QD system. From these features, the QD level spacing, as well as the interdot tunnel coupling and lead-dot tunnel couplings are extracted. Double QD systems serve as essential building blocks for developing different types of qubits based on atomically precise GNRs.

Contacting individual graphene nanoribbons using carbon nanotube electrodes.

Graphene nanoribbons synthesized using bottom-up approaches can be structured with atomic precision, allowing their physical properties to be precisely controlled. For applications in quantum technology, the manipulation of single charges, spins or photons is required. However, achieving this at the level of single graphene nanoribbons is experimentally challenging due to the difficulty of contacting individual nanoribbons, particularly on-surface synthesized ones. Here we report the contacting and electrical characterization of on-surface synthesized graphene nanoribbons in a multigate device architecture using single-walled carbon nanotubes as the electrodes. The approach relies on the self-aligned nature of both nanotubes, which have diameters as small as 1 nm, and the nanoribbon growth on their respective growth substrates. The resulting nanoribbon-nanotube devices exhibit quantum transport phenomena-including Coulomb blockade, excited states of vibrational origin and Franck-Condon blockade-that indicate the contacting of individual graphene nanoribbons.

PEGylated bottom-up synthesized graphene nanoribbons loaded with camptothecin as potential drug carriers

This work discusses the potential use of bottom-up synthesized graphene nanoribbons (GNRs) as nano-carriers for drug delivery systems (DDSs). GNRs have a high loading capacity for anticancer drugs due to their high specific surface area and non-covalent adsorption with hydrophobic anticancer drug molecules. Herein, we synthesized GNRs using a bottom-up approach, modified with PEG2000 (GNR-PEG) and PEG2000 carrying folic acid chains (GNR-PEG-FA), and then loaded with camptothecin (CPT). The targeting ability mediated by folic acid of the GNR derivative was evaluated using cellular assays, and the cytotoxicity of GNR systems loaded with CPT was assessed by in vitro studies. They suggest that the functionalization of GNR derivatives with folic acid significantly affects their interaction with cells expressing different levels of folic acid receptors. The authors also explore the possibility to employ GNRs in photothermal therapy (PTT). GNR-PEG and GNR-PEG-FA display minor or no toxicity in standard cell cultures, but they show remarkable thermal response upon NIR irradiation, causing complete loss of cell viability within a few hours of treatment. This work highlights the potential of GNRs as DDSs and emphasizes the importance of further research on their biocompatibility and as a platform for PTT.