Low-dimensional Carbon Structures Research Articles

On-Surface Synthesis of Macrocycles, Non-Planar Carbon Ribbons and Heteroatom-Doped Nanographenes

On-surface synthesis via covalent coupling of adsorbed molecules on metal surfaces has attracted significant attention recently due to its potential to fabricate low-dimensional carbon materials with atomic precision. The bottom-up, atomically precise synthesis of carbon nanostructures enables the tailoring of their electronic properties at a molecular level. To understand and control the surface-chemistry-driven synthesis, many efforts have been made to design innovative precursors, explore novel reaction schemes, and utilize templating effects from the substrate.My presentation focuses on high-resolution scanning probe microscopy experiments combined with density functional theory to demonstrate recent highlights on the assembly of surface-supported low-dimensional carbon structures on metal surfaces. First, the assembly and electronic structure of planar π-extended cycloparaphenylene macrocycles, representing the first nanographene with an all-armchair edge topology, will be presented [1]. The second part will discuss the bottom-up synthesis of covalently-linked non-planar carbon ribbons and their electronic properties depending on their adsorption geometry. Finally, I will conclude with the on-surface cyclomerization of oxygen heterocycles to understand the on-surface synthesis of furan and pyran derivatives from ketone-functionalized precursors on metal surfaces.[1] Xiang, et al. Nature Chem., 2022 14, 871–876.

Modeling of second sound in carbon nanostructures

The study of thermal transport in low-dimensional materials has attracted a lot of attention recently after discovery of high thermal conductivity of graphene. Here we study numerically phonon transport in low-dimensional carbon structures being interested in the hydrodynamic regime revealed through the observation of second sound. We demonstrate that correct numerical modeling of such two-dimensional systems requires semi-classical molecular dynamics simulations of temperature waves that take into account quantum statistics of thermalized phonons. We reveal that second sound can be attributed to the maximum group velocity of bending optical oscillations of carbon structures, and the hydrodynamic effects disappear for $T>200$K, being replaced by diffusive dynamics of thermal waves. Our numerical results suggest that the velocity of second sound in such low-dimensional structures is about 6 km/s, and the hydrodynamic effects are manifested stronger in carbon nanotubes rather than in carbon nanoribbons.

Role of Defect Engineering and Surface Functionalization in the Design of Carbon Nanotube-Based Nitrogen Oxide Sensors.

Nitrogen oxides (NOx) are among the main atmospheric pollutants; therefore, it is important to monitor and detect their presence in the atmosphere. To this end, low-dimensional carbon structures have been widely used as NOx sensors for their outstanding properties. In particular, carbon nanotubes (CNTs) have been widely used as toxic-gas sensors owing to their high specific surface area and excellent mechanical properties. Although pristine CNTs have shown promising performance for NOx detection, several strategies have been developed such as surface functionalization and defect engineering to improve the NOx sensing of pristine CNT-based sensors. Through these strategies, the sensing properties of modified CNTs toward NOx gases have been substantially improved. Therefore, in this review, we have analyzed the defect engineering and surface functionalization strategies used in the last decade to modify the sensitivity and the selectivity of CNTs to NOx. First, the different types of surface functionalization and defect engineering were reviewed. Thereafter, we analyzed experimental, theoretical, and coupled experimental–theoretical studies on CNTs modified through surface functionalization and defect engineering to improve the sensitivity and selectivity to NOx. Finally, we presented the conclusions and the future directions of modified CNTs as NOx sensors.

A theoretical quest for high temperature superconductivity on the example of low-dimensional carbon structures

High temperature superconductivity does not necessarily require correlated electron systems with complex competing or coexisting orders. Instead, it may be achieved in a phonon-mediated classical superconductor having a high Debye temperature and large electronic density of states at the Fermi level in a material with light atoms and strong covalent bonds. Quasi-1D conductors seem promising due to the Van Hove singularities in their electronic density of states. In this sense, quasi-1D carbon structures are good candidates. In thin carbon nanotubes, superconductivity at ~15 K has been reported, and it is likely the strong curvature of the graphene sheet which enhances the electron-phonon coupling. We use an ab-initio approach to optimize superconducting quasi-1D carbon structures. We start by calculating a Tc of 13.9 K for (4.2) carbon nanotubes (CNT) that agrees well with experiments. Then we reduce the CNT to a ring, open the ring to form chains, optimize bond length and kink structure, and finally form a new type of carbon ring that reaches a Tc value of 115 K.

Interaction of femtosecond laser radiation with carbon materials: exfoliation of graphene structures and synthesis of low-dimensional carbon structures

Carbon is represented in modern nanomaterials by a large variety of modifications. Various methods and technologies have been developed to create these various forms. Methods utilizing laser irradiation constitute a large portion of these techniques. The action of laser pulses upon graphite may result in the exfoliation of graphene layers. This paper presents the results of implementing method of laser-induced cleavage of graphite in liquid nitrogen using femtosecond laser radiation pulses. The process of obtaining graphene from the laser processing of graphite is accompanied by the formation of various types of low-dimensional carbon structures.

Origin of Anomalous Water Permeation through Graphene Oxide Membrane

Water inside the low-dimensional carbon structures has been considered seriously owing to fundamental interest in its flow and structures as well as its practical impact. Recently, the anomalous perfect penetration of water through graphene oxide membrane was demonstrated although the membrane was impenetrable for other liquids and even gases. The unusual auxetic behavior of graphene oxide in the presence of water was also reported. Here, on the basis of first-principles calculations, we establish atomistic models for hybrid systems composed of water and graphene oxides revealing the anomalous water behavior inside the stacked graphene oxides. We show that formation of hexagonal ice bilayer in between the flakes as well as melting transition of ice at the edges of flakes are crucial to realize the perfect water permeation across the whole stacked structures. The distance between adjacent layers that can be controlled either by oxygen reduction process or pressure is shown to determine the water flow thus highlighting a unique water dynamics in randomly connected two-dimensional spaces.

Electronic transport in graphene-based structures: An effective cross-section approach

We show that transport in low-dimensional carbon structures with finite concentrations of scatterers can be modeled by utilizing scaling theory and effective cross sections. Our results are based on large-scale numerical simulations of carbon nanotubes and graphene nanoribbons, using a tight-binding model with parameters obtained from first-principles electronic structure calculations. As shown by a comprehensive statistical analysis, the scattering cross sections can be used to estimate the conductance of a quasi-one-dimensional system both in the Ohmic and localized regimes. They can be computed with good accuracy from the transmission functions of single defects, greatly reducing the computational cost and paving the way toward using first-principles methods to evaluate the conductance of mesoscopic systems, consisting of millions of atoms.

Preface: Phys. Status Solidi C 7/3‐4

AbstractThe papers included in this issue are a selection from the wide variety of presentations at Symposium N of the European Materials Research Society (E‐MRS) Spring Meeting in Strasbourg from 8–12 June 2009. The subject of Symposium N was “Carbon Nanotubes and Graphene – Low Dimensional Carbon Structures”. The symposium was organized by Viera Skákalová of the Max Planck Institute for Solid State Research in Stuttgart (Germany), Alan B. Kaiser of the Victoria University of Wellington (New Zealand), Po‐Wen Chiu of the National Tsing Hua University in Hsinchu (Taiwan), Jannik C. Meyer of the University of Ulm (Germany) and Francesco Mauri of the Université Pierre et Marie Curie in Paris (France).The Symposium attracted researchers from a variety of countries around the world, as well as from within Europe. The papers published here are divided into three sections classified according to the materials they investigate: firstly carbon nanotubes, secondly graphene, and lastly a smaller number on other related structures. In each section, papers cover the synthesis, characterization, theory and applications of the material.The intense international research effort on carbon nanotubes continues unabated, with a shift as the field matures towards applications and new ways of synthesizing nanotubes. This is reflected in the papers included in these proceedings. Carbon nanotube applications investigated range from sensors (Kukovecz et al.) to field‐emission devices (Chiang et al.) and optoelectronic device anodes (Antony et al.). Other topics are electrodeposited PdNi as possible ferromagnetic contacts for carbon nanotubes (Usgaocar et al.), and using unconventional lithography to fabricate ordered carbon nanotubes structures (Cavallini et al.). Synthesis methods for carbon nanotubes discussed are by arc discharge in liquid nitrogen (Salvatore et al.), using screen‐printing catalyst (Chiang et al.), and plasma‐enhanced chemical vapour deposition, which can lead to interesting shapes (Duraia et al.). On the other hand, low cost carbon nanotubes are the goal of Smadja et al. In a theoretical study, Popov et al. investigate the effect of defects on the intermediate frequency Raman spectrum.Graphene is of course one of the hottest new fields in materials science, and is well represented in these proceedings. Growth of few‐layer graphene by gas‐source molecular beam epitaxy is described by Maeda et al. Characterization of the graphene‐SiO2 interface is carried out by Giannazzo et al., and of the graphene‐SiC interface by Sonde et al., who also investigate the nanoscale capacitive behaviour of ion‐irradiated graphene in a separate paper. The etching of graphene layers (Nemes‐Incze et al.) and the formation and properties of graphene nanoribbons (Dobrik et al., La Magna et al.) are of great interest for applications. Graphene devices are now being developed: Hummel, Pezoldt et al. investigate the electric properties of backgate graphene transistors.The third category of papers on Other Related Structures emphasizes the wide utility of carbon nanostructures and composites (Fleaca et al., Matzui et al., Vovchenko et al., Tolvanen et al.). There is also an additional paper (Lehtinen et al.) on boron nitride nanotubes that (while not containing carbon) have interesting similarities and differences compared to carbon nanotubes.On Wednesday, 10 June 2009, the Student Award competition took place. A five‐member committee – Davide Ricci (Italy), Jannik Meyer (Germany), Po‐Wen Chiu (Taiwan), Arkady Krasheninnikov (Finland) and Arnaud Magrez (Switzerland)) – selected two from a total number of five applicants for the prize: Péter Nemes‐Incze (Research Institute for Technical Physics and Materials Science, Hungary) for the work ‘Crystalloraphic orientation dependent etching of graphene layers’, and Sushant Sonde (Scuola Superiore di Catania and CNR‐IMM, Italy) for the work ‘Nanoscale capacitive behaviour of ion irradiated graphene’.Finally, we acknowledge the perfect organization of the conference by the Headquarter of E‐MRS. We particularly thank the participants of Symposium N who presented their exciting scientific results, initiated discussions with arguments and new ideas, and formed new collaborations and friendships (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Superconductivity in a single-C60 transistor

Single-molecule transistors have enabled studies of magnetism and other correlated nanoscale behaviour, but superconductivity has not been observed with this approach. It is now shown that superconducting junctions on both sides of a C60 molecule induce superconductivity across the whole device. Single-molecule transistors are currently attracting enormous attention as possible quantum information processing devices1,2,3,4,5. An intrinsic limitation to their prospects, however, is associated with the presence of a small number of quantized conductance channels, each channel with a high access resistance of at best RK/2=h/2e2=12.9 kΩ. However, when the contacting leads become superconducting, long-range correlations can extend throughout the whole system by means of the proximity effect. This not only lifts the resistive limitation of normal-state contacts, but further paves the way to probe electron transport through a single molecule. Here we demonstrate the realization of superconducting single-molecule transistors involving a single C60 fullerene molecule. In the past few years, we have seen gate-controlled Josephson supercurrents induced in the family of low-dimensional carbon structures such as flakes of two-dimensional graphene6 and portions of one-dimensional carbon nanotubes7. The present study, involving a full zero-dimensional fullerene, completes the picture.

Electrophysical properties of bromine-intercalated low-dimensional carbon structures

The temperature dependence of the resistivity ρ of a brominated material containing multiwall carbon nanotubes, and also that of brominated crystalline and pyrolytic graphites, are measured in the temperature interval 4.2–700K. The temperature dependence of the resistivity is investigated at different rates of heating and cooling in two gaseous media — air and helium. A comparison of ρ(T) for the initial and brominated materials is made. For the brominated materials unusual behavior of ρ(T) at temperatures above 390K is revealed. A conjecture is put forth which describes the behavior found.

Electronic properties and superconductivity of low-dimensional carbon structures

A review of research on the electronic properties of low-dimensional structures based on various modifications of carbon is presented. The following effects are discussed: the Shubnikov–de Haas effect in graphite intercalation compounds (GICs) of the acceptor type, superconductivity of GICs of the donor type, weak localization and superconductivity of carbon fibers, the negative magnetoresistance of a carbon foil obtained by pressing of exfoliated graphite, and the superconductivity and spectroscopy of new heterofullerides.