L. P. Felipe Chibante

Bio: L. P. Felipe Chibante is an academic researcher from Rice University. The author has contributed to research in topics: Fullerene & Ozone. The author has an hindex of 11, co-authored 13 publications receiving 1615 citations.

Fullerenes with metals inside

Abstract: Fullerenes with a single lanthanum atom trapped on the inside of the carbon cage were produced by laser vaporization of a lanthanum oxide/graphite composite rod in a flow of argon gas at 1200 °C. When sublimed with C_(60) and C_(70), they formed an air-stable film containing principally LaC_(60), LaC_(70), LaC_(74), and LaC_(82). When dissolved in toluene and exposed to air, LaC_(82) was found to be uniquely stable. Evidence was also obtained for coalescence reactions between these fullerenes at high temperatures to form larger cages with as many as three lanthanum atoms inside. Indications have also been obtained for the successful production of KC_(60), C_(59)B, and KC_(59)B where the boron has substituted for a carbon in the soccerball cage. The use of the @ symbol is advocated for specifying such complex fullerenes as (K@C_(59)B).

Fullerenes in the cretaceous-tertiary boundary layer.

Abstract: High-pressure liquid chromatography with ultraviolet-visible spectral analysis of toluene extracts of samples from two Cretaceous-Tertiary (K-T) boundary sites in New Zealand has revealed the presence of C 60 at concentrations of 0.1 to 0.2 parts per million of the associated soot. This technique verified also that fullerenes are produced in similar amounts in the soots of common flames under ambient atmospheric conditions. Therefore, the C 60 in the K-T boundary layer may have originated in the extensive wildfires that were associated with the cataclysmic impact event that terminated the Mezozoic era about 65 million years ago.

Reversible Fullerene Electrochemistry: Correlation with the HOMO-LUMO Energy Difference for C60, C70, C76, C78, and C84

Abstract: Reversible one-electron oxidations and reductions have been observed by Osteryoung square wave voltammetry (OSWV) for the three higher fullerenes C{sub 76}, C{sub 78}, and C{sub 84} in 1,1,2,2-tetrachloroethane (TCE) containing 0.1 M tetrabutylammonium hexafluorophosphate (TBA)PF{sub 6}. Potentials are reported versus the internal ferrocene redox couple. Under these conditions C{sub 76} displays a reversible oxidation at 0.81 V, an irreversible oxidation at 1.30 V, and two reversible reductions at -0.83 and -1.12 V. The oxidations of C{sub 78} show evidence of two species, which is consistent with the proposed isomerism for C{sub 78}. The predominant C{sub 78} species shows a reversible oxidation at 0.95 V, an irreversible oxidation at 1.43 V, and two reversible reductions at -0.77 and -1.08 V. The minor species displays a reversible oxidation at 0.70 V and an irreversible oxidation at 1.17 V, while the reductions seem to coincide with those of the other isomer. Finally, C{sub 84} yielded an oxidation at 0.93 V and three reversible reductions at -0.67, -0.96, and -1.27 V. A comparison of the differences in potential of the first reduction and first oxidation, (E{sub ox} - E{sub red}), shows that this difference becomes generally smaller as fullerene size increases. 43 refs., 4more » figs., 1 tab.« less

Synthesis, Characterization, and Neutron Activation of Holmium Metallofullerenes

Abstract: Isolation of the first macroscopic quantities of endohedral holmium metallofullerenes (principally Ho@C{sub 82}, Ho{sub 2}@C{sub 82}, and Ho{sub 3}@C{sub 82} by LD-TOF mass spectrometry) has been accomplished by carbon-arc and preparative HPLC methodologies. The detailed procedure for production and isolation of the metallofullerenes includes a new technique whereby holmium-impregnated electrodes are prepared simply by soaking porous graphite rods in an ethanolic solution of Ho(NO{sub 3}){sub 3}.xH{sub 2}O. Monoisotopic {sup 165}Ho offers a unique combination of advantages for neutron-activation studies of metallofullerenes, and purified samples containing {sup 165}Ho@C{sub 82}, {sup 165}Ho{sub 2}@C{sub 82}, and {sup 165}Ho{sub 3}@C{sub 82} have been activated by high-flux neutron irradiation ({Phi} = 4 x 10{sup 13}n cm{sup -2} s{sup -1}) to generate {sup 166}Ho metallofullerenes, which undergo {beta}{sup -} decay to produce stable {sup 166}Er. Chemical workup of the irradiated samples, followed by re-irradiation, has been used to demonstrate that observed decomposition of holmium metallofullerenes is due mainly to `fast` neutron damage rather than to holmium atom nuclear recoil (E{sub max} = 200 eV). This implies that metallofullerene damage can be minimized by using neutron fluxes with the highest possible thermal component. 60 refs., 4 figs.

Curling and closure of graphitic networks under electron-beam irradiation

Abstract: THE discovery1 of buckminsterfullerene (C60) and its production in macroscopic quantities2 has stimulated a great deal of research. More recently, attention has turned towards other curved graphitic networks, such as the giant fullerenes (Cn, n > 100)3,4 and carbon nanotubes5–8. A general mechanism has been proposed9 in which the graphitic sheets bend in an attempt to eliminate the highly energetic dangling bonds present at the edge of the growing structure. Here, I report the response of carbon soot particles and tubular graphitic structures to intense electron-beam irradiation in a high-resolution electron microscope; such conditions resemble a high-temperature regime, permitting a degree of structural fluidity. With increased irradiation, there is a gradual reorganization of the initial material into quasi-spherical particles composed of concentric graphitic shells. This lends weight to the nucleation scheme proposed9 for fullerenes, and moreover, suggests that planar graphite may not be the most stable allotrope of carbon in systems of limited size.

n-Type organic semiconductors in organic electronics.

Abstract: Organic semiconductors have been the subject of intensive academic and commercial interest over the past two decades, and successful commercial devices incorporating them are slowly beginning to enter the market. Much of the focus has been on the development of hole transporting, or p-type, semiconductors that have seen a dramatic rise in performance over the last decade. Much less attention has been devoted to electron transporting, or so called n-type, materials, and in this paper we focus upon recent developments in several classes of n-type materials and the design guidelines used to develop them.

Small-bandgap endohedral metallofullerenes in high yield and purity

Abstract: The idea1 that fullerenes might be able to encapsulate atoms and molecules has been verified by the successful synthesis of a range of endohedral fullerenes, in which metallic or non-metallic species are trapped inside the carbon cage2,3,4,5,6,7,8,9,10,11,12,13. Metal-containing endohedral fullerenes have attracted particular interest as they might exhibit unusual material properties associated with charge transfer from the metal to the carbon shell. However, current synthesis methods have typical yields of less than 0.5%, and produce multiple endohedral fullerene isomers, which makes it difficult to perform detailed studies of their properties. Here we show that the introduction of small amounts of nitrogen into an electric-arc reactor allows for the efficient production of a new family of stable endohedral fullerenes encapsulating trimetallic nitride clusters, ErxSc3-xN@C80 (x = 0–3). This ‘trimetallic nitride template’ process generates milligram quantities of product containing 3–5% Sc3N@C80, which allows us to isolate the material and determine its crystal structure, and its optical and electronic properties. We find that the Sc3N moiety is encapsulated in a highly symmetric, icosahedral C80 cage, which is stabilized as a result of charge transfer between the nitride cluster and the fullerene cage. We expect that our method will provide access to a range of small-bandgap fullerene materials, whose electronic properties can be tuned by encapsulating nitride clusters containing different metals and metal mixtures.