Showing papers on "Fullerene published in 2010"

Graphene oxide, highly reduced graphene oxide, and graphene: versatile building blocks for carbon-based materials.

Abstract: Isolated graphene, a nanometer-thick two-dimensional analog of fullerenes and carbon nanotubes, has recently sparked great excitement in the scientific community given its excellent mechanical and electronic properties. Particularly attractive is the availability of bulk quantities of graphene as both colloidal dispersions and powders, which enables the facile fabrication of many carbon-based materials. The fact that such large amounts of graphene are most easily produced via the reduction of graphene oxide--oxygenated graphene sheets covered with epoxy, hydroxyl, and carboxyl groups--offers tremendous opportunities for access to functionalized graphene-based materials. Both graphene oxide and graphene can be processed into a wide variety of novel materials with distinctly different morphological features, where the carbonaceous nanosheets can serve as either the sole component, as in papers and thin films, or as fillers in polymer and/or inorganic nanocomposites. This Review summarizes techniques for preparing such advanced materials via stable graphene oxide, highly reduced graphene oxide, and graphene dispersions in aqueous and organic media. The excellent mechanical and electronic properties of the resulting materials are highlighted with a forward outlook on their applications.

The era of carbon allotropes

Abstract: Twenty-five years on from the discovery of C60, the outstanding properties and potential applications of the synthetic carbon allotropes — fullerenes, nanotubes and graphene — overwhelmingly illustrate their unique scientific and technological importance.

Synthesis of polyynes to model the sp-carbon allotrope carbyne

Abstract: Carbyne is an allotrope of carbon composed of sp-hybridized carbon atoms. Although its formation in the laboratory is suggested, no well-defined sample is described. Interest in carbyne and its potential properties remains intense because of, at least in part, technological breakthroughs offered by other carbon allotropes, such as fullerenes, carbon nanotubes and graphene. Here, we describe the synthesis of a series of conjugated polyynes as models for carbyne. The longest of the series consists of 44 contiguous acetylenic carbons, and it maintains a framework clearly composed of alternating single and triple bonds. Spectroscopic analyses for these polyynes reveal a distinct trend towards a finite gap between the highest occupied molecular orbital and the lowest unoccupied molecular orbital for carbyne, which is estimated to be ∼485 nm (∼2.56 eV). Even the longest members of this series of polyynes are not particularly sensitive to light, moisture or oxygen, and they can be handled and characterized under normal laboratory conditions.

Direct transformation of graphene to fullerene

Abstract: Although fullerenes have been synthesized from graphite for a long time, the exact mechanism is relatively unknown. Now, in situ microscopy and quantum chemical modelling have directly followed the formation of fullerenes from a single graphitic sheet — graphene.

Photoinduced Degradation of Polymer and Polymer–Fullerene Active Layers: Experiment and Theory

Abstract: As organic photovoltaic effi ciencies steadily improve, understanding degradation pathways becomes increasingly important. In this paper, the stability under prolonged illumination of a prototypical polymer:fullerene active layer is studied without the complications introduced by additional layers and interfaces in complete devices. Combining contactless photoconductivity with spectroscopy, structural characterization at the molecular and fi lm level, and quantum chemical calculations, the mechanism of photoinduced degradation in bulk heterojunctions of poly (3-hexylthiophene) (P3HT) and [6,6]-phenyl C61-butyric acid methyl ester (PCBM) is studied. Bare fi lms are subjected to four conditions for 1000 h with either constant illumination or dark and either ambient or inert atmosphere. All samples are found to be intrinsically stable for 1000 + h under inert conditions, in contrast to complete devices. While PCBM stabilizes P3HT fi lms exposed to air, its fullerene cage is found to undergo a series of oxidations that are responsible for the deterioration of the photoconductivity of the material. Quantum chemical calculations show that PCBM oxides have deeper LUMO levels than pristine PCBM and therefore act as traps for electrons in the PCBM domains.

A layered ionic crystal of polar Li@C 60 superatoms

Abstract: If the physical properties of C(60) fullerene molecules can be controlled in C(60) products already in use in various applications, the potential for industrial development will be significant. Encapsulation of a metal atom in the C(60) fullerene molecule is a promising way to control its physical properties. However, the isolation of C(60)-based metallofullerenes has been difficult due to their insolubility. Here, we report the complete isolation and determination of the molecular and crystal structure of polar cationic Li@C(60) metallofullerene. The physical and chemical properties of Li@C(60) cation are compared with those of pristine C(60). It is found that the lithium cation is located at off-centre positions in the C(60)-I(h) cage interior and that the [Li(+)@C(60)] salt has a unique two-dimensional structure. The present method of purification and crystallization of C(60)-based metallofullerenes provides a new C(60) fullerene material that contains a metal atom.

Endohedral metal atoms in pristine and functionalized fullerene cages.

Abstract: Fullerene, an allotropic form of carbon made up of spherical molecules formed from pentagonal and hexagonal rings, was first discovered in 1985. Because fullerenes have spacious inner cavities, atoms and clusters can be encapsulated inside the fullerene cages to form endohedral fullerenes. In particular, the unique structural and electronic properties of endohedral metallofullerenes (EMFs), where metal atoms are encapsulated within the fullerene, have attracted wide interest from physicists and chemists as well as materials scientists and biologists. The remarkable characteristics of these molecules originate in the electron transfer from the encapsulated metal atoms to the carbon cage. The positions and movements of the encapsulated metal atoms are important determinants of the chemical and physical properties of EMFs. In this Account, we specifically describe the positions and dynamic behavior of the metal atoms encapsulated in pristine and functionalized fullerene cages. First, we examined whether the ...

Open-cage fullerenes: towards the construction of nanosized molecular containers

Abstract: Open-cage fullerene derivatives have excited organic chemists’ creativity over the past decade. These adducts, generated via consecutive cleavage of σ- and π-carbon–carbon bonds on the fullerene cage, allow small atoms or molecules to pass through their opening and be placed inside the cavity. Restoration of the ruptured fullerene back to the pristine fullerene cage affords the corresponding endohedral complexes. This “molecular surgery” approach has been proposed as an alternative to the synthesis of endohedral fullerenes via the conventional physical methods of production, which restrict the availability of endohedral fullerenes to milligram quantities after laborious isolation procedures. In this critical review, we survey all published techniques for the creation of an orifice, as well as for the expansion of an existing one, on the fullerene framework. Successful encapsulation experiments employing cage-opened fullerene derivatives are also comprehensively discussed (160 references).

Formation of Fullerenes in H-containing Planetary Nebulae

Abstract: Hydrogen depleted environments are considered an essential requirement for the formation of fullerenes. The recent detection of C60 and C70 fullerenes in what was interpreted as the hydrogen-poor inner region of a post-final helium shell flash planetary nebula (PN) seemed to confirm this picture. Here, we present strong evidence that challenges the current paradigm regarding fullerene formation, showing that it can take place in circumstellar environments containing hydrogen. We report the simultaneous detection of polycyclic aromatic hydrocarbons (PAHs) and fullerenes toward C-rich and H-containing PNe belonging to environments with very different chemical histories such as our own Galaxy and the Small Magellanic Cloud. We suggest that PAHs and fullerenes may be formed by the photochemical processing of hydrogenated amorphous carbon. These observations suggest that modifications may be needed to our current understanding of the chemistry of large organic molecules as well as the chemical processing in space.

Solubility of Light Fullerenes in Organic Solvents

Abstract: Experimental and literature data concerning the solubility of individual light fullerenes (C60 and C70) in binary (individual fullerene + solvent), ternary (C60 + C70 fullerenes + solvent; C60 or C70 fullerenes + solvent 1 + solvent 2), and multicomponent (fullerenes + natural fats and oils) systems as well as the data on solubility of industrial fullerene mixtures and fullerene derivatives in various organic solvents are presented and discussed.

Nanomorphology and Charge Generation in Bulk Heterojunctions Based on Low‐Bandgap Dithiophene Polymers with Different Bridging Atoms

Abstract: Carbon bridged (C-PCPDTBT) and silicon-bridged (Si-PCPDTBT) dithiophene donor-acceptor copolymers belong to a promising class of low bandgap materials. Their higher field-effect mobility, as high as 10 -2 cm 2 V -1 s -1 in pristine films, and their more balanced charge transport in blends with fullerenes make silicon-bridged materials better candidates for use in photovoltaic devices. Striking morphological changes are observed in polymer:fullerene bulk heterojunctions upon the substitution of the bridging atom. XRD investigation indicates increased π-π stacking in Si-PCPDTBT compared to the carbon-bridged analogue. The fluorescence of this polymer and that of its counterpart C-PCPDTBT indicates that the higher photogeneration achieved in Si-PCPDTBT:fullerene films (with either [C60]PCBM or [C70]PCBM) can be correlated to the inactivation of a charge-transfer complex and to a favorable length of the donor-acceptor phase separation. TEM studies of Si-PCPDTBT:fullerene blended films suggest the formation of an interpenetrating network whose phase distribution is comparable to the one achieved in C-PCPDTBT-fullerene using 1,8-octanedithiol as an additive. In order to achieve a balanced hole and electron transport, Si-PCPDTBT requires a lower fullerene content (between 50 to 60 wt%) than C-PCPDTBT (more than 70 wt%). The Si-PCPDTBT:[C70]PCBM OBHJ solar cells deliver power conversion efficiencies of over 5%.

The Unusually Stable B100 Fullerene, Structural Transitions in Boron Nanostructures, and a Comparative Study of α- and γ-Boron and Sheets

Abstract: Solid α-B12 rhombohedral and γ-B28 orthorhombic boron as well as boron nanostructures in the form of spheres, sheets, and multirings beside a ring consisting of icosahedral B12 units were investigated using ab initio quantum chemical and density functional methods. The structure of the B100 fullerene exhibits unusual stability among all noninteracting free-standing clusters, and is more stable than the B120 cluster fragment of the γ-B28 solid, recently predicted and observed by Oganov et al. (Nature 2009, 457, 863). In addition, we compared the stability of the multirings and reported the structural transition from double-ring to triple-ring systems. This structural transition occurs between B52 and B54 clusters. We confirm that the noninteracting free-standing triangular buckled-sheet is more stable than the γ-sheet, assembled in this work, and than the α-sheet, proposed by Tang and Ismail-Beigi (Phys. Rev. Lett. 2007, 99, 115501). In contrast, however, when these sheets are considered as infinite period...

Influence of the Intermediate Density-of-States Occupancy on Open-Circuit Voltage of Bulk Heterojunction Solar Cells with Different Fullerene Acceptors

Abstract: Electron density of states (DOS) and recombination kinetics of bulk heterojunction solar cells consisting of a poly(3-hexylthiophene) (P3HT) donor and two fullerene acceptors, either [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) or 4,4′-dihexyloxydiphenylmethano[60]fullerene (DPM6), have been determined by means of impedance spectroscopy. The observed difference of 125 mV in the output open-circuit voltage is attributed to significant differences of the occupancy of the DOS in both fullerenes. Whereas DPM6 exhibits a full occupation of the electronic band, occupancy is restricted to the tail of the DOS in the case of PCBM-based devices, implying a higher rise of the Fermi level in the DPM6 fullerene. Carrier lifetime describes a negative exponential dependence on the open-circuit voltage, exhibiting values on the microsecond scale at 1 sun illumination.

Metal Sulfide in a C82 Fullerene Cage: A New Form of Endohedral Clusterfullerenes

Abstract: The row of endohedral fullerenes is extended by a new type of sulfur-containing clusterfullerenes: the metal sulfide (M2S) has been stabilized within a fullerene cage for the first time. The new sulfur-containing clusterfullerenes M2S@C82-C3v(8) have been isolated for a variety of metals (M = Sc, Y, Dy, and Lu). The UV−vis−NIR, electrochemical, and FTIR spectroscopic characterization and extended DFT calculations point to a close similarity of the M2S@C82 cage isomeric and electronic structure to that of the carbide clusterfullerenes M2C2@C2n. The bonding in M2S@C82 is studied in detail by molecular orbital analysis as well as with the use of quantum theory of atom-in-molecules (QTAIM) and electron localization function (ELF) approaches. The metal sulfide cluster formally transfers four electrons to the carbon cage, and metal−sulfur and metal−carbon cage bonds with a high degree of covalency are formed. Molecular dynamics simulations show that Sc2S cluster exhibits an almost free rotation around the C3 ax...

Geminate charge recombination in polymer/fullerene bulk heterojunction films and implications for solar cell function.

Abstract: We have studied the influence of three different fullerene derivatives on the charge generation and recombination dynamics of polymer/fullerene bulk heterojunction (BHJ) solar cell blends. Charge generation in APFO3/[70]PCBM and APFO3/[60]PCBM is very similar and somewhat slower than charge generation in APFO3/[70]BTPF. This difference qualitatively matches the trend in free energy change of electron transfer estimated from the LUMO energies of the polymer and fullerene derivatives. The first order (geminate) charge recombination rate is significantly different for the three fullerene derivatives studied and increases in the order APFO3/[70]PCBM < APFO3/[60]PCBM < APFO3/[70]BTPF. The variation in electron transfer rate cannot be explained from the LUMO energies of the fullerene derivatives and single-step electron transfer in the Marcus inverted region and simple considerations of expected trends for the reorganization energy and free energy change. Instead we suggest that geminate charge recombination occurs from a state where electrons and holes have separated to different distances in the various materials because of an initially high charge mobility, different for different materials. In a BHJ thin film this charge separation distance is not sufficient to overcome the electrostatic attraction between electrons and holes and geminate recombination occurs on the nanosecond to hundreds of nanoseconds time scale. In a BHJ solar cell, we suggest that the internal electric field in combination with polarization effects and the dynamic nature of polarons are key features to overcome electron-hole interactions to form free extractable charges.

Planar Quinary Cluster inside a Fullerene Cage: Synthesis and Structural Characterizations of Sc3NC@C80-Ih

Abstract: The endohedral fullerene Sc(3)NC@C(80)-I(h) has been synthesized and characterized; it has an unprecedented planar quinary cluster in a fullerene cage. It is also the first chemical compound in which the presence of an unprecedented (NC)(3-) trianion has been disclosed. The fascinating intramolecular dynamics in Sc(3)NC@C(80)-I(h) enables the whole molecule to display high polarity and promising ferroelectricity. This finding inspires the possibility that such a planar quinary cluster may be useful in constructing many other endohedral fullerenes.

Growth of large-area graphene films from metal-carbon melts

Abstract: We have demonstrated a new method for the large-area graphene growth, which can lead to a scalable low-cost high-throughput production technology. The method is based on growing single layer or few-layer graphene films from a molten phase. The process involves dissolving carbon inside a molten metal at a specified temperature and then allowing the dissolved carbon to nucleate and grow on top of the melt at a lower temperature. The examined metals for the metal-carbon melt included copper and nickel. For the latter, the high-quality single layer graphene was grown successfully. The resulting graphene layers were subjected to detailed microscopic and Raman spectroscopic characterization. The deconvolution of the Raman 2D band was used to accurately determine the number of atomic planes in the resulting graphene layers and access their quality. The results indicate that our technology can provide bulk graphite films, few-layer graphene as well as high-quality single layer graphene on metals. Our approach can also be used for producing graphene-metal thermal interface materials for thermal management applications. © 2010 American Institute of Physics.

Remarkable diversity of carbon–carbon bonds: structures and properties of fullerenes, carbon nanotubes, and graphene

Abstract: Large scientific community has been passionate in understanding different carbon nanostructures for last two decades. In this review, we present the general description of low-dimensional carbon allotropes such as fullerenes (0D), carbon nanotubes (1D), and graphene (2D). These structures have unique diversity of carbon–carbon bonds. Structures and electronic properties of fullerenes, small closed carbon cages, and giant fullerenes are illustrated. We point out the complexity in the area of fullerene research because of a wide range of structures and number of possible isomers of fullerenes. The concept of isolated pentagon rule in fullerenes is highlighted. We delineate the usefulness of pyramidalization angle in evaluating the curvature of fullerenes. The role of computational chemistry in identifying different isomers of fullerenes and validating the experimental results in ambiguous situations is also briefly mentioned. Properties of different types of carbon nanotubes, particularly single-walled carbon nanotubes (SWCNTs) and their structural features are summarized. The use of pyramidalization angle (θP) and π-orbital misalignment angles in predicting the reactivity of different carbon atom sites of SWCNTs is discussed. Finally, we outline the structures and electronic properties of graphene, and discuss the status of experimental investigations of this species.

Carbon nanotubes and related structures : synthesis, characterization, functionalization, and applications

Abstract: CARBON NANOTUBES AND RELATED STRUCTURES: PRODUCTION AND FORMATION Introduction Carbon Nanotube Production Catalysts Growth Enhancement Growth Mechanisms Functionalization Purification Futures Perspectives THEORY OF ELECTRONIC AND OPTICAL PROPERTIES OF DNA-SWNT HYBRIDS Introduction Physical Structure and Bonding in Nanotube-DNA Hybrids: A Short Review Quantum Mechanical Modeling of the Hybrid Structure: Tight Binding Band Structure Calculation Self-Consistent Computation Scheme: Acting Potential Screening Factor and the Dielectric Permittivity Polarization Component of Cohesion Energy of the SWNT-ssDNA Hybrid Optical Absorption of SWNT-DNA Hybrids Summary ELECTROCHEMISTRY Introduction Electronic Properties of SWNTs Electrode Potentials Versus Work Functions Electrochemistry at SWNTs Versus Electrochemistry of SWNTs Carbon Nanotubes for Electrochemical Sensors and Biosensors Electrochemistry of Carbon Nanotubes Cyclic Voltammetric Investigations of Solutions of Individual SWNTs Vis-NIR Spectroelectrochemical Investigation of True Solutions of Unfunctionalized SWNTs Standard Redox Potentials of Individual SWNTs in Solution Fermi Level and Excitonic Binding Energy of the Nanotubes Conclusions and Perspectives PHOTOPHYSICS Introduction Molecular Nanoparticles: Carbon Nanotubes Have it All Understanding Optical Properties The Coulomb Interaction and Bound States Colloidal Chemistry Facilitates Detailed Study of Nanotube Optics Excited State Dynamics and Nonlinear Optics Outlook NONCOVALENT FUNCTIONALIZATION OF CARBON NANOTUBES Introduction Early Insights in the Noncovalent Interaction of CNTs with Solvents and Classical Macrocyclic Scaffolds Noncovalent Interactions of CNTs with Small Aromatic Molecules Noncovalent Interactions of CNTs with Heterocyclic Polyaromatic Systems Noncovalent Interactions of CNTs with Surfactants and Ionic Liquids Noncovalent Interactions of CNTs with Polymers Optically Active SWCNTS Noncovalent Interactions of CNTs with Nanoparticles Summary and Conclusions COVALENT FUNCTIONALIZATION OF CARBON NANOTUBES Introduction Chemical Functionalization of Carbon Nanotubes Defect Group Functionalization of Carbon Nanotubes Direct Sidewall Functionalization of Carbon Nanotubes Conclusions CARBON-BASED NANOMATERIAL APPLICATIONS IN BIOMEDICINE Introduction Carbon Nanotubes Carbon Nanohorns Carbon Nanodiamonds Conclusions GROUND AND EXCITED STATE CHARGE TRANSFER AND ITS IMPLICATIONS Introduction Ground and Excited State Features Ground State Charge Transfer ? CNT as Electron Acceptors Ground State Charge Transfer ? CNT as Electron Donors Excited State Charge Transfer ? CNT as Excited State Electron Acceptor Excited State Charge Transfer ? CNT as Ground State Electron Acceptor Excited State Charge Transfer ? CNT as Ground State Electron Donor Implications of Ground State Charge Transfer Implications of Excited State Charge Transfer PHOTOVOLTAIC DEVICES BASED ON CARBON NANOTUBES AND RELATED STRUCTURES Introduction Photovoltaic Cells Based on Carbon Nanotubes Related Structures Future Directions LAYER-BY-LAYER ASSEMBLY OF MULTIFUNCTIONAL CARBON NANOTUBE THIN FILMS Introduction Structure and Properties of CNTs Structural Organization in Multilayers of Carbon Nanotubes Electrical Conductor Applications Sensor Applications Fuel Cell Applications Nano-/Microshell LBL Coatings and Biomedical Applications Conclusions CARBON NANOTUBES FOR CATALYTIC APPLICATIONS Introduction Macroscopic shaping of CNTs Specific Metal-Support Interaction Dispersion of the Active Phase Electrically and Thermally Conductive Supports Mass Transfer Limitations Confinement Effect Conclusions CARBON NANOTUBES AS CONTAINERS Introduction Mechanisms of Nanotube Filling Fullerenes as Guest Molecules Other Types of Molecules Ionic Compounds Nnaoparticles in Nanotubes Concluding Remarks CARBON NANOHORN Introduction Production Structure and Growth Mechanism Properties Functionalization Toxicity Drug Delivery Applications Summary SELF-ORGANIZATION OF NANOGRAPHENES Introduction Single Sheets of Nanographenes Organization in the Bulk State Charge Carrier Transport Along Nanographene Stacks Solution Aggregation and Fiber Formation Solution Alignment on Surfaces Thermal Processing Nanographenes in Heterojunctions for Solar Cells Processing of Nondiscotic Nanographenes Conclusions ENDOHEDRALS Introduction Recent Investigations in the Synthesis of Endohedral Metallofullerenes Advances in Nonchromatographic Techniques for Separation on Endohedral Metallofullerenes Structures of Endohedral Metallofullerenes Determined by X-Ray Crystallographic Method Electrochemical Properties of Endohedral Metallofullerenes Chemical Reactivity of Endohedral Metallofullerenes Applications of Endohedral Metallofullerenes Concluding Remarks CARBON NANOSTRUCTURES: CALCULATIONS OF THEIR ENERGETICS, THERMODYNAMICS, AND STABILITY Introduction Energetics and Thermodynamics of Clusters Stabilities of Empty Fullerenes Stabilities of Metallofullerenes Stabilities of Nonmetal Endohedral Kinetic Control

Analysis of the reactivity and selectivity of fullerene dimerization reactions at the atomic level

Abstract: High-resolution transmission electron microscopy has proved useful for its ability to provide time-resolved images of small molecules and their movements. One of the next challenges in this area is to visualize chemical reactions by monitoring time-dependent changes in the atomic positions of reacting molecules. Such images may provide information that is not available with other experimental methods. Here we report a study on bimolecular reactions of fullerene and metallofullerene molecules inside carbon nanotubes as a function of electron dose. Images of how the fullerenes move during the dimerization process reveal the specific orientations in which two molecules interact, as well as how bond reorganization occurs after their initial contact. Studies on the concentration, specimen temperature, effect of catalyst and accelerating voltage indicate that the reactions can be imaged under a variety of conditions. Well-resolved images of small molecules and their motions can be obtained with high-resolution transmission electron microscopy. It has now been shown that this technique can also be used to visualize individual chemical reactions involving the dimerization of fullerenes and metallo-fullerenes trapped inside carbon nanotubes by monitoring how the positions of their atoms change over time.

Sc2(μ2-O) Trapped in a Fullerene Cage: The Isolation and Structural Characterization of Sc2(μ2-O)@Cs(6)-C82 and the Relevance of the Thermal and Entropic Effects in Fullerene Isomer Selection

Abstract: The new endohedral fullerene, Sc2(μ2-O)@Cs(6)-C82, has been isolated from the carbon soot obtained by electric arc generation of fullerenes utilizing graphite rods doped with 90% Sc2O3 and 10% Cu (w/w). Sc2(μ2-O)@Cs(6)-C82 has been characterized by single crystal X-ray diffraction, mass spectrometry, and UV/vis spectroscopy. Computational studies have shown that, among the nine isomers that follow the isolated pentagon rule (IPR) for C82, cage 6 with Cs symmetry is the most favorable to encapsulate the cluster at T > 1200 K. Sc2(μ2-O)@Cs(6)-C82 is the first example in which the relevance of the thermal and entropic contributions to the stability of the fullerene isomer has been clearly confirmed through the characterization of the X-ray crystal structure.

Effect of curvature on C–F bonding in fluorinated carbons: from fullerene and derivatives to graphite

Abstract: The effect of the curvature of the carbon lattice is discussed taking into account NMR data on various fluorinated carbons including C60 fullerenes, single, double and multiwall carbon nanotubes. Graphite fluorides and highly fluorinated fullerenes are used as limit model compounds for planar and spherical geometries, respectively. The curvature results in a weakening of the C–F bonding covalence. First of all, various highly fluorinated fullerenes with increasing F/C molar ratio were prepared by treatment with pure gaseous fluorine. A preliminary study using XRD, EPR and IR spectroscopy confirms that the highest fluorination level can be reached either at 133 or at 300 °C. In order to extract the correlation between fluorine and carbon atoms and the C–F bond length, specific sequences such as solid echo, two-dimensional 19F → 13C cross polarization wide-line separation and inverse 19F → 13C cross polarization were also used for fluorinated C60.

Energetic Disorder in Higher Fullerene Adducts: A Quantum Chemical and Voltammetric Study

Abstract: www.MaterialsViews.com C O M M U Energetic Disorder in Higher Fullerene Adducts: A Quantum Chemical and Voltammetric Study N IC By Jarvist Moore Frost , Mark Anton Faist , and Jenny Nelson * A IO N The abundance of new pi-conjugated materials with electronic and structural properties that can be controlled, in principle, through chemical synthesis offers the potential to generate improved materials for a wide range of applications in organic optoelectronics. However, the lack of a thorough understanding of how chemical structure infl uences electronic properties still limits the design and selection of suitable materials. A case of particular recent interest is the use of multiple adducts of fullerene derivatives to boost the power conversion effi ciency of polymer:fullerene blend organic solar cells. [ 1–3 ] The addition of multiple side chains raises the energy of the lowest unoccupied molecular orbital (LUMO) of the acceptor, so raising the open-circuit voltage, [ 4 ] but inhibits the close packing of the fullerenes. Moreover, the current synthetic routes invariably generate a mix of isomers which introduces disorder into both the molecular packing and the electronic energy levels, both of which could adversely affect electronic properties. Design of new materials thus requires a means of evaluating the positive effects of raised LUMO level in relation to the adverse effects, of increased energetic or structural disorder. [ 5 ] However, no direct study of energetic disorder of higher adduct fullerenes has yet been reported, nor has any accurate computational method of predicting spread in LUMO energy levels been demonstrated. In this paper, we use a quantum chemical method that combines density functional theory (DFT) with time-dependent density functional theory (TDDFT) using a hybrid functional to calculate the LUMO energies of all possible isomers of the bis and tris adducts of the fullerene, [6,6]-phenyl-C61-butyric acid methyl ester (PCBM). The calculated energy level distributions agree well with the observed mean and spread of LUMO energies as determined using solution differential pulse voltammetry (DPV). We propose this method as a powerful tool for the design and functional optimisation of novel fullerenes, as well as other classes of pi-conjugated molecules with multiple isomers. Computational Method : Different fullerene adducts were generated as SMILES [ 6 ] strings, which uniquely defi ne a molecular chemistry as a simple linear code. Smi23D [ 7 ] was

Nonlinear optical transmission of nanographene and its composites

Abstract: Low-cost broad-band optical limiters based on nanographene have been studied, finding optical-limiting properties superior to those of current standards, carbon fullerenes (C60) solutions and carbon black suspensions. Further examination indicates that the presence of π conjugation improves the optical-limiting responses. Superior limiting performance is retained regardless of solvent viscosity and polarity, a unique feature of graphene not observed in C60 and carbon black. Graphene suspensions in organic solvents can work under 10 Hz laser pulses without losing excellent limiting performance. More significantly, outstanding limiting properties are also preserved in a gel matrix. These nanographene-based optical limiters can thus work in solutions and solid matrixes for devices used for protecting human eyes and optical sensors from high-power lasers.

A Review of the Properties and CVD Synthesis of Coiled Carbon Nanotubes

Abstract: synthesis supplied a very surprising result, namely the growth of fullerene tubes was observed on the carbon cathode. In this method carbon nanotubes are always grown out of the ends of carbon electrodes of the arc but they have never been found in the soot condensing from the vapour. Maybe this recognition led to the discovery of other nanotube synthesis methods such as plasma decomposition of hydrocarbons and co-evaporating catalyst during a carbon