Fullerene

About: Fullerene is a research topic. Over the lifetime, 12723 publications have been published within this topic receiving 359173 citations.

Magnetic properties of carbon structures

Abstract: Magnetic properties of the main allotropic modifications of carbon (diamond, graphite, nanographite, nanotubes, and fullerenes) are described. Properties of nanocarbon are considered from the standpoint of the interrelation between structural imperfection and magnetic ordering. Experimental data on high-temperature ferromagnetism in carbon structures and some theoretical models of magnetic carbon are reported.

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.

Preparation of Carbon Nanotubes by Arc-Discharge Evaporation

Abstract: Extremely thin graphite filaments with a tubular structure were grown in carbon deposits formed on the negative electrode during generation of fullerenes by dc carbon-arc-discharge evaporation. The filaments and small graphite particles coexist in the central portion of the deposits. Three kinds of morphologies of carbon, namely nanotubes, polyhedra and sheets were observed in transmission electron micrographs. The filaments were formed in He, Ar or CH4 gas environment at a pressure between 20-200 Torr.

Chemistry Inside Carbon Nanotubes: the Menshutkin SN2 Reaction

Abstract: In an effort to gain insight into the effect of carbon nanotube confinement on reaction enthalpies and activation energies, calculations using hybrid density functional theory have been carried out for the Menshutkin S N2 reaction in gas phase and inside carbon nanotubes. The polarizability of the carbon nanotubes provides an interaction mechanism, which leads to the stabilization of confined dipolar species. Inside hydrogen-terminated (8,0) and (9,0) carbon nanotubes, the activation energy and reaction endothermicity for the Menshutkin S N2 reaction are significantly reduced compared to those in the gas phase. Polarizable continuum models, using dielectric constants calculated from the carbon nanotube polarizabilities, are found to provide results in remarkable agreement with all electron nanotube-confined calculations, confirming the stabilization mechanism and offering a cost-effective approach for further exploration of the effects of the carbon nanotube environment. Overall, the effect of carbon nanotube confinement on reaction enthalpies closely resembles solvation in a low-dielectric solvent. Therefore, chemical reactions in which there is a separation of charge along the reaction coordinate may be enhanced inside fullerene-based materials because of their large electronic polarizabilities.