C. Pan

Bio: C. Pan is an academic researcher from Rice University. The author has contributed to research in topics: Diamond & Sublimation (phase transition). The author has an hindex of 7, co-authored 10 publications receiving 1132 citations.

Efficient production of C60 (buckminsterfullerene), C60H36, and the solvated buckide ion

Abstract: Buckminsterfullerene, C{sub 60}, was prepared in gram quantities by contact-arc vaporization of a graphite rod in a 100-Torr atmosphere of helium, followed by extraction of the resultant graphite soot with toluene. The dominance of C{sub 60} in this extract was verified by mass, FTIR, and NMR spectroscopy. The molecule was successfully hydrogenated to C{sub 60}H{sub 36} via a Birch reduction and dehydrogenated back to bare C{sub 60} by treatment with DDQ reagent. Cyclic voltammetry of C{sub 60} in methylene chloride revealed highly reversible formation of at least two stable anionic forms of C{sub 60} in solution. A broad new class of these fulleride and fulleronium ions is anticipated, both with the internal cavity empty and with any one of a large number of elements inside, thus providing a means of fine-tuning the chemical, optical, and redox properties.

Heats of sublimation from a polycrystalline mixture of carbon clusters (C60 and C70)

Abstract: Knudsen effusion mass spectrometric measurements of vapors in equilibrium with a polycrystalline mixture of C 60 and C 70 were carried out over the temperature range 640-800 K. From the second-law method, average values obtained for the heats of sublimation of C 60 and C 70 from a polycrystalline C 60 matrix were found to be respectively 40.1±1.3 and 43.0±2.2 kcal mol −1 , at the average temperatures 707 and 739 K. It was also noted that it was necessary to heat treat the samples at temperatures of at least 170°C for greater than 12 h to achieve stable vaporization. This was consistent with the sample becoming more crystalline

Chlorine‐Activated Diamond Chemical Vapor Deposition

Abstract: A novel method of producing atomic hydrogen and the active carbon species necessary for diamond chemical vapor deposition (CVD) has been demonstrated. This method starts with the generation of atomic chlorine from the thermal dissociation of molecular chlorine in a resistively heated graphite furnace at temperatures from 1300–1500°C. Atomic hydrogen and the carbon precursors are subsequently produced through rapid hydrogen abstraction reactions of atomic chlorine with molecular hydrogen and hydrocarbons at the point where they mix. It was found that the quality of the diamond deposits depends on both substrate temperatures and mole ratios. Substrate temperatures are found to be ~150° lower than for a hydrogen/hydrocarbon hot filament system for similar growth rates.

Determination of sublimation pressures of a fullerene (C60/C70) solid solution

Abstract: The sublimation pressures in equilibrium with a polycrystalline C 60 /C 70 solid solution have been measured with a quartz crystal microbalance (QCM) and by transpiration methods, in the temperature range 772-857 and 806-929 K, respectively. The results from the two independent methods show good agreement. The solid solution was found to have a total vapor pressure of 8.1×10 -4 Torr at 800 K. It is estimated that the total vapor pressure of the C 60 /C 70 solid solution could reach 1 atm at ca. 1523 K

ReaxFF: A Reactive Force Field for Hydrocarbons

Abstract: To make practical the molecular dynamics simulation of large scale reactive chemical systems (1000s of atoms), we developed ReaxFF, a force field for reactive systems. ReaxFF uses a general relationship between bond distance and bond order on one hand and between bond order and bond energy on the other hand that leads to proper dissociation of bonds to separated atoms. Other valence terms present in the force field (angle and torsion) are defined in terms of the same bond orders so that all these terms go to zero smoothly as bonds break. In addition, ReaxFF has Coulomb and Morse (van der Waals) potentials to describe nonbond interactions between all atoms (no exclusions). These nonbond interactions are shielded at short range so that the Coulomb and van der Waals interactions become constant as Rij → 0. We report here the ReaxFF for hydrocarbons. The parameters were derived from quantum chemical calculations on bond dissociation and reactions of small molecules plus heat of formation and geometry data for...

Assessing the risks of manufactured nanomaterials.

Abstract: Although progress has recently been made toward understanding the health and environmental consequences of these materials, challenges ramain for future research.

Lithium Storage in Carbon Nanostructures

Abstract: In this review article we discuss the progress of lithium storage in different carbon forms starting from intercalation in graphite to the lithium storage in fullerenes, nanotubes, diamond and most recently, graphene. The recent advances in lithium storage in various novel morphological variants of carbons prepared by a variety of techniques are also discussed with the most important models in literature that have been set out to explain the excess lithium storage. The major emphasis lies on the real structure.

Organic molecular soft ferromagnetism in a fullerene c60.

Abstract: The properties of an organic molecular ferromagnet [C(60)TDAE(086); TDAE is tetrakis(dimethylamino)ethylene] with a Curie temperature ;T(c) = 161 kelvin are described The ferromagnetic state shows no remanence, and the temperature dependence of the magnetization below ;T(c) does not follow the behavior expected of a conventional ferromagnet These results are interpreted as a reflection of a three-dimensional system leading to a soft ferromagnet

Conducting films of C60 and C70 by alkali-metal doping

Abstract: THE recent syntheses1,2 of macroscopic quantities of C60 have suggested possible applications in host–guest and organic chemistry, tribology, electrochemistry and semiconductor tech-nology. Here we report the preparation of alkali-metal-doped films of C60 and C70 which have electrical conductivities at room temperature that are comparable to those attained by n-type doped polyacetylene. The highest conductivities observed in the doped films are: 4Scm−1 (Cs/C60), 100 (Rb/C60), 500 (K/C60), 20 (Na/C60), 10 (Li/C60), 2 (K/C70). The doping process is reversed on exposure of the films to the atmosphere. At high doping levels, the films become more resistive. We attribute the conductivity induced in these films to the formation of energy bands from the π orbitals of C60 or C70, which become partially filled with carriers on doping. The smaller alkali metal ions should be able to fit into the interstices in the lattice without disrupting the network of contacts between the carbon spheroids. In the case of C60, this would allow the development of an isotropic band structure, and we therefore propose that these materials may constitute the first three-dimensional 'organic' conductors.