Fullerene Mixture Research Articles

Molecular dynamics simulation study of binary fullerene mixtures

We report constant-pressure molecular dynamics (MD) simulations of binary ${\mathrm{C}}_{60}∕{C}_{n}$ fullerene-mixtures ($n=70$, 76, 84, 96) modeled in terms of a spherically symmetric two-body potential. By starting from a liquid configuration of the system, we cool mixtures down to freezing and beyond, until room temperature is reached, in order to verify the formation of solid solutions, namely, of configurations characterized by a unique crystalline lattice whose sites are randomly occupied by the two component fullerene species. We first explore the entire concentration range of the ${\mathrm{C}}_{60x}∕{\mathrm{C}}_{70(1\ensuremath{-}x)}(0lxl1)$ mixture and find fairly good agreement with experimental data, exhibiting partial reciprocal solubility of the two components into each other with an immiscibility gap at intermediate compositions. In fact, the system we simulate forms substitutional solid solutions over a wide range of concentrations except for $0.3\ensuremath{\leqslant}x\ensuremath{\leqslant}0.5$; over such an interval, it turns out that the initially liquid mixture can be supercooled down to relatively low temperatures, until eventually a glassy phase is formed. The study is then extended to fullerene mixtures of molecular diameter ratio $\ensuremath{\alpha}={\ensuremath{\sigma}}_{{\mathrm{C}}_{60}}∕{\ensuremath{\sigma}}_{{\mathrm{C}}_{n}}$ smaller than in ${\mathrm{C}}_{60}∕{\mathrm{C}}_{70}$ (where $\ensuremath{\alpha}=0.93$), as is the case for ${\mathrm{C}}_{60}∕{\mathrm{C}}_{76}$ $(\ensuremath{\alpha}=0.89)$, ${\mathrm{C}}_{60}∕{\mathrm{C}}_{84}(\ensuremath{\alpha}=0.85)$ and ${\mathrm{C}}_{60}∕{\mathrm{C}}_{96}$ $(\ensuremath{\alpha}=0.79)$. The effect of the size mismatch between the two species is dramatic: The solid immiscibility region rapidly expands even upon a tiny reduction of $\ensuremath{\alpha}$, with formation of an amorphous phase at sufficiently low temperature, as found for the ${\mathrm{C}}_{60}∕{\mathrm{C}}_{70}$ mixture. For the smallest $\ensuremath{\alpha}({\mathrm{C}}_{60}∕{\mathrm{C}}_{96})$ cocrystallization of the two components turns out to be forbidden over the whole concentration axis. A mapping of the MD evidences of the fullerene mixtures' phase behavior onto the phase diagram of binary hard-sphere mixtures (determined by other authors) turns out to be worthwhile and enlightnening. In particular, size ratio effects and the onset of glassy phases emerge in qualitative good agreement with such studies, and with results of phase coexistence calculations in model binary colloidal systems.

Magnetite Nanoparticles in Fullerite C60Powder

Data are presented on the resonance and magnetic properties of Fe–fullerene nanomaterials prepared by heating a mixture of C60 fullerene and iron(III) acetylacetonate. The starting-mixture composition is shown to have a significant effect on the particle size and properties of the resulting magnetite and the magnetic properties of the material. The influence of chemical treatment on the properties of the material is analyzed.

Selective extraction of higher fullerenes using cyclic dimers of zinc porphyrins.

Higher fullerenes (>/=C76) were selectively extracted from a fullerene mixture obtained from a combustion-based industrial production source by cyclic dimers of beta-unsubstituted porphyrin zinc complexes 2C5-2C7 with C5-C7 alkylene spacers as host molecules. Results of single extraction of the fullerene mixture with 2C5-2C7 together with a beta-substituted analogue of 2C6 (1C6) and spectroscopic titration of 2C6 and 1C6 with C60, C70, and C96 indicated that the host selectivity toward higher fullerenes is much dependent on the structure of the porphyrin units and the size of the host cavity. Sequential three-stage extraction of the fullerene mixture with the best-behaved 2C6 resulted in considerable enrichment in very rare fullerenes C102-C110 (<0.1 abs %) up to 82 abs % (C76-C114, 99 abs %) (356 nm) of total fullerenes.

Characterization of combustion fullerene soot, C 60, and mixed fullerene

Three commercially available carbon nanoparticles, i.e., combustion fullerene soot, C 60-fullerene, and mixed fullerene, have been characterized using field emission scanning electron microscope (FESEM), high-resolution transmission electron microscope (HRTEM) equipped with energy dispersive X-ray spectrometry (EDS), X-ray diffraction (XRD) as well as surface measurements. Fullerene soot contained a mixture of fullerenic carbons and carbon blacks. Face-centered cubic structure was a predominant phase in the C 60-fullerene sample with graphitic and amorphous carbons being minor phases, whereas mixed fullerene was a mixture of fullerene, multiwalled carbon nanotubes, and trace amounts of amorphous carbons.

Computing enthalpy–entropy interplay for isomeric fullerenes

AbstractFullerenes represent unique species in many respects, one of them being one of the highest temperature regions ever used for preparation of chemical species. This very factor automatically substantially enhances the importance of the TS part of the Gibbs function. The essential feature of fullerenic systems has consistently been ignored in computational studies of fullerenes, almost always drawing their conclusions from potential energies or heats of formation. This report demonstrates that the simplified treatment cannot really describe all the features of complex mixtures of isomeric fullerenes. General formulas are surveyed and illustrated on C96—the biggest set of isomeric fullerenes characterized by 13C NMR spectra to date. Computations are carried out for the complete set of 187 isolated‐pentagon‐rule (IPR) isomers of C96, using four semiempirical quantum chemical methods (MNDO, AM1, PM3, and SAM1). Entropy terms are also computed and the relative‐stability problem is entirely treated in terms of the Gibbs function. In overall, the computed data match the observed data reasonably well, although no method can really reproduce the complete ten‐membered observed set. There are however still several aspects to be checked and several possibilities how to improve quality of the computed terms. In principle, such developments are, however, only a question of available computing power. There are, nevertheless, some remaining questions, such as inclusion of anharmonicity effects, contribution from electronic partition function, or even interactions between individual, yet separated motions. This article also discusses a subsequent, more general task of relative stabilities of carbon cages of different dimensions, i.e., relative stabilities of nonisomeric fullerenes. The computational treatment of isomeric mixtures has several interesting features: the results depend on temperature, but not on pressure; only the relative, and not the absolute, values of the heats of formation are needed; and the form of the master equation allows for an ample cancellation of terms in the partition functions. In contrast, for the more general task—relative stabilities of fullerenes of different dimensions—the absolute values of the heats of formation are required, the mentioned cancellations do not operate there, and the scheme is essentially pressure dependent. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004

Optimizing fullerene synthesis in a 50 kW solar reactor

Fullerene mixture of C 60 and C 70 was produced in gram quantities in a solar reactor using partially (50 kW) the power of the 1 MW CNRS solar furnace at Odeillo. Fullerene yield was studied as a function of buffer gas (helium and argon), pressure (in the range 80–500 hPa) and gas flow rate. Mean Fullerene yield of 13.5% was measured with helium at 450 hPa and 10 sm 3/h, at a carbon vaporization rate of 21 g/h. This mean value refers to three samples collected inside the experimental set up; the maximum yield for one single sample (inside the reactor) was 16%. The dramatic effect of pressure and gas flow rate on the process selectivity is correlated to the dilution number (number of carbon atoms versus number of buffer gas atoms) and to the results of a numerical simulation related to the temperature distribution in the annealing zone of the reactor.

The First Crystal Structure of a Halogenated Higher Fullerene, C78Br18, Obtained by Bromination of a Fullerene Mixture.

Simple bromination of a fullerene mixture allowed the separation of C78 from other fullerenes in form of crystalline C78Br18. The first X-ray single-crystal structure of a halogenated higher fullerene, C78Br18, revealed that the addition pattern of 18 bromine atoms on the C78 cage corresponds to a partial retention of the conjugated double bond systems and the formation of isolated C−C double bonds. Evidently, even a separation of the C2v and D3 isomers of C78 occurred in the course of bromination and precipitation. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)

Organic functionalization and optical properties of carbon onions.

We report, for the first time, the organic functionalization of carbon onions. The functionalization was achieved via 1,3-dipolar cycloaddition of azomethine ylides to a mixture of amorphous carbon and concentric fullerenes. Once functionalized, the onions become soluble in organic solvents and it is possible to purify them from the rest of carbon. Their nonlinear optical properties have been studied in solution for application as broadband optical limiters. It was found that the functionalized onions are an example of soluble material that functions equally well in both the visible and the NIR regions.

The First Crystal Structure of a Halogenated Higher Fullerene, C78Br18, Obtained by Bromination of a Fullerene Mixture

AbstractSimple bromination of a fullerene mixture allowed the separation of C78 from other fullerenes in form of crystalline C78Br18. The first X‐ray single‐crystal structure of a halogenated higher fullerene, C78Br18, revealed that the addition pattern of 18 bromine atoms on the C78 cage corresponds to a partial retention of the conjugated double bond systems and the formation of isolated C−C double bonds. Evidently, even a separation of the C2v and D3 isomers of C78 occurred in the course of bromination and precipitation. (© Wiley‐VCH Verlag GmbH &amp; Co. KGaA, 69451 Weinheim, Germany, 2003)

The photoluminescence of amorphous carbon in a-C:C60 films obtained by fullerene C60 deposition

The results of experimental investigations of the carbon deposits obtained in the course of fullerene C60 sublimation are presented. It is shown that the films formed at a high deposition rate possess a composite structure representing a mixture of fullerenes and an amorphous carbon phase with a graphitelike short-range order. The films containing amorphous nonhydrogenated carbon possess photoluminescent properties analogous to those of hydrogenated amorphous carbon films with a high hydrogen content. The possible mechanism of photoluminescence of the composite carbon films is discussed.

Separation and identification of perchlorinated polycyclic aromatic hydrocarbons and fullerenes (C 60, C 70) by coupling high-performance liquid chromatography with ultraviolet absorption spectroscopy and atmospheric pressure chemical ionization mass spectrometry

Simultaneous separation and identification of perchlorinated polycyclic aromatic hydrocarbons (PCPAHs) and fullerenes is of practical interest due to the growth mechanism of fullerenes involved with PCPAHs. Non-aqueous reversed-phase high-performance liquid chromatography (HPLC), with an ODS column and a gradient mobile phase of methanol–ethanol–cyclohexane mixtures, was combined with both rapid-scan ultraviolet spectrometry (UV) and atmospheric pressure chemical ionization mass spectrometry (APCI-MS) for the separation and identification of over 80 PCPAHs as well as fullerenes C 60 and C 70, that were synthesized in the discharge reaction of chloroform. PCPAH retention was found to depend on the number of aromatic rings and the degree of non-planarity of PCPAH structure. Based on the isotopic pattern of molecular ion or/and quasi-molecular ion peaks in corresponding mass spectra, molecular compositions of the PCPAH products were unambiguously determined. The results obtained from the HPLC–UV–MS analysis not only are helpful for the understanding of the fullerenes formation mechanism, but also contribute to the analytical technique capable of separating and identifying the complicated mixture of PCPAHs and fullerenes.

Atomic Force Microscope Studies on Condensation of Plasmid DNA with Functionalized Fullerenes This research was supported by Grant-in-Aid for Specially Promoted Research from Ministry of Education, Culture, Sports, Science, and Technology.

DNA condensation by a fullerene vector has been imaged at the molecular level by atomic force microscopy (AFM); analysis of a mixture of plasmid DNA and DNA-binding fullerene with the aid of this carbonaceous vector provided the first information on the mechanism of transfection. The picture shows AFM images of pBR322 DNA in the absence of (left) and partially condensed by the fullerene (right).

Feasibility of the solar-pumped fullerene-oxygen-iodine laser (Sun-light FOIL)

The feasibility of the optically pumped (in particular, solar-pumped) fullerene-oxygen-iodine laser (FOIL) is considered. The singlet oxygen is assumed to be formed through the interaction of molecular oxygen with a mixture of (both lower and higher) fullerenes in a photogenerated triplet metastable state. The estimates based on a photokinetic model show that the solar-pumped FOIL efficiency can reach several tens of percent. The singlet-oxygen yield resulting from the interaction of optical pumping radiation with fullerenes in solutions is studied both theoretically and experimentally. As the optical pumping, we used laser radiation at 532 nm and broad-band emission of a lamp with a solarlike spectrum.

Magnetic resonance studies on conjugated polymer fullerene mixtures

In this paper photoluminesence (PLDMR) and photocurrent detected magnetic resonance (PCDMR) studies on pure and fullerene doped conjugated polymer films and photodiodes are reported. A strong dependence of the PLDMR and PCDMR signals on the fullerene concentration is observed.

SIMULTANEOUS DETERMINATION OF C60 AND C70 FULLERENES BY A SPECTROPHOTOMETRIC METHOD

In all fullerene-producing systems, reaction products were black soot extracts reported to contain a 5–25% fullerene mixture. Toluene extraction of the soot results in a solution of C60, C70, and higherc fullerenes. Without separation, absolute determination of the contents is not possible, leaving the researcher to comment only on the C60/C70 ratio of the solution. High-performance liquid chromatography, nuclear magnetic resonance, and scanning tunneling microscopy imaging techniques were reported in the literature for determining the C60/C70 ratio of the mixtures. These methods require tedious experiments and produce slightly differing results as well. In this communication, a new and relatively quick method is proposed for the simultaneous determination of the yields of C60 and C70 (not the ratio) in fullerene-containing solutions by ultraviolet-visible spectrophotometric analysis.

Near infra-red emission of charge-transfer complexes of porphyrin–fullerene films

Solid porphyrin–fullerene films were prepared by evaporating a mixture of porphyrin and fullerene in solution and by deposition of Langmuir–Blodgett films where the dyes were covalently linked to each other. Both types of the films exhibited an emission band shifted to the near infrared region, ca. 800 nm, where neither porphyrin nor fullerene emits alone nor mixed in solution. The emission is attributed to an emitting charge transfer (CT) state formed by porphyrin and fullerene moieties. It is characterized by a long lifetime, ca. 2 ns, and high quantum yield, 0.14%. Remarkably small total reorganization energies, less than 0.2 eV, are deduced from the CT emission spectra of the porphyrin–fullerene films.

Some features of analysis of solutions of fullerenes C60 and C70 by their absorption spectra

The absorption spectra of a series of solutions of C60 and C70 and of their mixture in o-xylene are studied. The deviation from the Bouguer-Lambert-Beer law was observed in the UV absorption band of the solutions. The possible reasons for this effect were analyzed. It is shown that to calculate reliably the composition and concentrations of fullerene mixtures, it is necessary to determine preliminarily the linearity region for the 335-nm absorption band.

Cyano adduct anions of higher fullerenes: electrospray mass spectrometric studies

Negative-ion electrospray mass spectrometry of fullerene/CN − solutions was used to study the cyano adduct-anions of a mixture of higher fullerenes, revealing both monoanionic and dianionic species. The most abundant anions observed are C m (CN) − and C m (CN) 2 2− for the higher fullerenes m = 76, 78, 84, 86, 90, 92, 96, and 98, which show some variation with the behaviour of C 60 and C 70. In addition, some of the higher fullerenes exhibit reduced forms under the conditions of these measurements. In particular, C 84 −, C 86 −, and C 90 − are observed, as well as the dianions C 84 2−, C 86 2−, and C 90 2−.

Molecular mass distributions and structural characterisation of coal derived liquids

Calibration data for size exclusion chromatography and results from the analysis of MALDI–TOF mass-spectra of coal derived liquids have been presented. The work provides the means for obtaining much more quantitative information from these two techniques than has hitherto been possible. The polystyrene based calibration has been matched against elution times of a wide range of model compounds (PAH, azaarenes, other nitrogen bearing compounds, several dyes, polars and numerous oxygenated compounds), covering a molecular mass range up to 1086u. Compounds in all groups appeared to elute with a predominantly size dependent mechanism. With the exception of the somewhat atypical fullerene mixture, none of the model compounds eluted at times so early as to be detected in the excluded region of the chromatogram (i.e. near 10.5min). Several semi-quantitative methods have been used to establish the upper mass limit of corresponding MALDI–TOF mass-spectra, which can be safely considered as representing signal. Spectra of a coal tar pitch and its pyridine insoluble fraction were analysed. The highest estimates of the high mass limits based on the calculation of number and weight average parameters was >300,000u. A conservative estimate obtained with a new method based on subtracting multiples of the standard deviation from the signal gave 42,000 and 95,600u, for the two samples, respectively. Fractions of the same coal tar pitch (separated by planar chromatography) have been characterised, to test for changes in structural features with changing MM-distributions. SEC and MALDI–TOF–MS showed decreasing MM-distributions with increasing mobility in planar chromatography. However, 13C NMR and pyrolysis–GC–MS showed that the immobile fraction contained greater proportions of aliphatic material compared to more mobile fractions. The mobile material consists of the aromatic systems normally associated with coal tar. The relatively immobile (larger-MM) fractions consisted of aromatic systems too large to elute through the chromatographic column (in pyrolysis–GC–MS) and linked together by aliphatic chains, which were released on pyrolysis and detected as major pyrolysis products.

Photoexcitations in carbazolyl substituted polydiacetylene (PDA) fullerene composites

It is well known that many non-degenerate ground state conjugated polymers like PPV derivatives show an ultrafast electron transfer to fullerenes upon photoexcitation. In this work we investigate the photoexcited states of fullerene — carbazolyl substituted PDA composites and compare them to the pristine components. We report the finding of photoexcited spins as well as charges in one asymmetric carbazolyl substituted PDA, the CPDO (poly(1-N-carbazolyl-penta-1,3-diyne-5-ol)). While PIA FTIR measurements show strong IRAV bands for this material, LESR studies on the same samples reveal photoexcited spins. Although CPDO samples show a dark ESR signal, which is well known for the topochemical polymerization, photoexcitation studies clearly reveal, that the LESR does not come from photoinduced polymerization. No enhancement of LESR signal is found for mixtures of CPDO and fullerenes, in our case a special solubilized fullerene, PCBM. We conclude therefore, that even PDA which show photoexcited charges and spins, do not exhibit a photoexcited charge transfer to fullerenes.