Synthesis of corrugated C-based nanostructures by Br-corannulene oligomerization (original) (raw)
Nanoscale, 2012
Low-dimensional carbon nanostructures, such as nanotubes and graphenes, represent one of the most promising classes of materials, in view of their potential use in nanotechnology. However, their exploitation in applications is often hindered by difficulties in their synthesis and purification. Despite the huge efforts by the research community, the production of nanostructured carbon materials with controlled properties is still beyond reach. Nonetheless, this step is nowadays mandatory for significant progresses in the realization of advanced applications and devices based on low-dimensional carbon nanostructures. Although promising alternative routes for the fabrication of nanostructured carbon materials have recently been proposed, a comprehensive understanding of the key factors governing the bottom-up assembly of simple precursors to form complex systems with tailored properties is still at its early stages. In this paper, following a survey of recent experimental efforts in the bottom-up synthesis of carbon nanostructures, we attempt to clarify generalized criteria for the design of suitable precursors that can be used as building blocks in the production of complex systems based on sp 2 carbon atoms and discuss potential synthetic strategies. In particular, the approaches presented in this feature article are based on the application of concepts borrowed from traditional organic chemistry, such as valence-bond theory and Clar sextet theory, and on their extension to the case of complex carbon nanomaterials. We also present and discuss a validation of these approaches through first-principle calculations on prototypical systems. Detailed studies on the processes involved in the bottom-up fabrication of low-dimensional carbon nanostructures are expected to pave the way for the design and optimization of precursors and efficient synthetic routes, thus allowing the development of novel materials with controlled morphology and properties that can be used in technological applications.
Synthesis of corannulene-based nanographenes
Communications Chemistry, 2019
Corannulene (C 20 H 10) is a polycyclic hydrocarbon in which five six-membered rings surround a central five-membered ring to construct a bowl-like aromatic structure. Here we examine the development of synthetic strategies that allow for the growth of the peripheral aromatic rings as a means to extend the aromatic area of the central corannulene nucleus and provide access to unique nanocarbon molecules. s p 2-hybridised structures of carbon have fascinated the research community for a very long time. In 1985, buckminsterfullerene, otherwise known as C 60 , was discovered (Fig. 1a) 1. In this ball-shaped molecule, the curvature in the structure stems from the presence of fivemembered rings. In 1991, carbon nanotubes arrived on the scene 2. Here, the structure is cylindrical and composed of only rolled-up six-membered rings. In 2004, a sheet-like single layer from graphite-graphene-was isolated 3. All of these materials were shown to have extraordinary electronic and mechanical properties due to their unique curved or planar sp 2-hybridised aromatic structures. Inspired by these discoveries, chemists have been developing strategies to access such aromatic hydrocarbons through rational ('bottom-up') synthetic approaches. Scott's 12-step chemical synthesis of fullerene C 60 from a rationally designed precursor is a testament to the ingenuity and resourcefulness of organic chemists 4. In planar structures, nanographenes (well-defined cutouts of graphene with nano-scale dimensions) can now be prepared on a regular basis with a very diverse portfolio 5. It is expected that combining the planar structure of graphene with the curvature of fullerenes may produce hybrid materials with interesting properties 6-8. To induce non-planarity into nanographenes, a practical approach would be to introduce a fivemembered ring such as in the case of fullerene, C 60. A perfect building block that allows for such a structural arrangement to happen is corannulene (1)-a molecule in which five six-membered rings surround a central five-membered ring to give a bowl-like structure (Fig. 1b) 9-20. Corannulene also offers many beneficial features as a molecular building block. It has high solubility in common organic solvents. It can be derivatized in a well-defined manner. Due to synthetic ease, the derivatives can be prepared on a multigram scale. These attributes are important as they allow for the scalable preparation of carefully designed corannulene-based building blocks and the subsequent synthesis, purification and structural analysis of the larger (fused) aromatic systems. Recently, therefore, there has been a surge in employment of corannulene as a core molecule in the synthesis of extended aromatic structures. Our aim in this review article is to discuss
Recent Progress on the Synthesis and Applications of Carbon Based Nanostructures
This article reviews the latest developments in the synthesis of Graphene, Carbon nanotubes and graphene/CNT based devices based on patents, patent applications and articles published in the last two years. A brief introduction about CNT and Graphene is presented, followed by the latest techniques and advanced processing for the large scale synthesis of Graphene and CNTs. Furthermore, a brief account of emerging devices based on applications of CNTs and graphene not limited to sensors, high speed electronics, energy harvesting and storage applications are presented.
A series of experiments has identified mechanisms of carbon nano-and micro-structure formation at room temperature, without catalyst and in the environment of immiscible metallic surroundings. The structures include threaded nano fibres, graphitic sheets and carbon onions. Copper as substrate was used due to its immiscibility with carbon. Energetic carbon ions (C 1 +) of 0.2-2.0 MeV irradiated Cu targets. Cu substrates, apertures and 3 mm dia TEM Cu grids were implanted with the carbon. We observed wide range of µm-size structures formed on Cu grids and along the edges of the irradiated apertures. These are shown to be threaded nano fibers (TNF) of few µm thicknesses with lengths varying from 10 to 3000 µm. Secondary electron microscopy (SEM) identifies the µm-size structures while Confocal microscopy was used to learn about the mechanisms by which C 1 + irradiated Cu provides the growth environment. Huge carbon onions of diameters ranging from hundreds of nm to µm were observed in the as-grown and annealed samples. Transformations of the nanostructures were observed under prolonged electron irradiations of SEM and TEM. A mechanism for the formation of carbon nano-and micro-structures is proposed. 1. Introduction A novel technique of producing carbon onions with unique characteristics is reported. Carbon atoms emerging out of the edges of C 1 + irradiated Cu sheets are shown to form graphitic layered networks studded with carbon onions that are non-spherical, hollow and often contain smaller ones inside. Carbon onions, the multishelled fullerenes, were discovered by intense electron beam irradiation of soot 1 with their structural manipulation reported later 2 , have also been produced by C 1 + implantation 3-5 and other high temperature techniques 6-8. Their remarkable spherical shelled nanostructures found few applications; the difficulty of their structural manipulation lies in the perfect shelled symmetry. In the experiments reported here we show that energetic C 1 + irradiated Cu sheets with vertical holes allow C atoms at the end of their implantation range to emerge out and form nanostructures along the edges of the holes. This technique for the formation of graphitic nanostructures that include C onions 1 and networks of graphene 9,10. It is different from similar C onion growing methods that utilize C 1
Angewandte Chemie, 2018
Herein we report the synthesis, photophysical, and supramolecular properties of a novel three-dimensional capsulelike hexa-peri-hexabenzocoronene (HBC)-containing carbon nanocage, tripodal-[2]HBC, which represents the first synthetic model of the capped zigzag [12,0] carbon nanotubes (CNTs). Tripodal-[2]HBC was achieved by rationally designed palladium-catalyzed coupling of triborylhexabenzocoronene and L-shaped cyclohexane units, followed by nickel-mediated C-Br/C-Br coupling and the subsequent aromatization of the cyclohexane moieties. The physical properties of tripodal-[2]HBC and its supramolecular host-guest interaction with C70 were further studied by UV-vis and fluorescence spectroscopy. Theoretical calculations reveal that the strain energy of tripodal-[2]HBC is as high as 55.2 kcalmol-1 .
Selective chemical functionalization of carbon nanobuds
Carbon, 2012
Carbon nanobuds (CNBs) are a novel nanoscale carbon hybrid material consisting of fullerene-like structures covalently bonded to the outer surface of single-walled carbon nanotubes (CNTs). The successful covalent modification of CNBs by double carboxylic group in Bingel reaction was demonstrated. It was found that CNBs have higher chemical reactivity compared to CNTs in the reactions of cyclopropanation. Chemical structures of the modified CNBs and CNTs were confirmed by FTIR spectroscopy, TEM and EDXspectroscopy. Using light sensitive molecule -5,10,15,20-tetra(4-pyridyl)porphyrin, it was shown that the resistance of modified CNB network can be reversibly switched by low power UV illumination with the detection speed less than 0.3 s.