Fullerene Formation Research Articles

Possible mechanism of BN fullerene formation from a boron cluster: Density-functional tight-binding molecular dynamics simulations.

We simulate the formation of a BN fullerene from an amorphous B cluster at 2000 K by quantum mechanical molecular dynamics based on the density-functional tight-binding method. We run 30 trajectories 200 ps in length, where N atoms are supplied around the target cluster, which is initially an amorphous B36 cluster. Most of the incident N atoms are promptly incorporated into the target cluster to form B-N-B bridges or NB3 pyramidal local substructures. BN fullerene formation is initiated by alternating BN ring condensation. Spontaneous atomic rearrangement and N2 dissociation lead to the construction of an sp(2) single-shelled structure, during which the BN cluster undergoes a transition from a liquid-like to a solid-like state. Continual atomic rearrangement and sporadic N2 dissociation decrease the number of defective rings in the BN cluster and increase the number of six-membered rings, forming a more regular shell structure. The number of four-membered rings tends to remain constant, and contributes to more ordered isolated-tetragon-rule ring placement.

Warning to Theoretical Structure Elucidation of Endohedral Metallofullerenes

Endohedral scandium fullerenes have attracted substantial interest since they were synthesized and isolated in 1992. The Sc2C74 series including both Sc2@C74 and Sc2C2@C72 forms were thoroughly investigated with density functional theory (DFT) methods including B3LYP, CAM-B3LYP, M06-2X, wB97XD, and some other DFT methods combined with statistical mechanics in the present work. Among all the Sc2C74 isomers, Sc2C2@Cs(10528)-C72 is the most thermodynamically stable one, and it is overwhelming at the temperature region of fullerene formation, which is very consistent with experiments. A deviation that the B3LYP method as well as other DFT methods without long-range corrections tends to overestimate energies of Sc2C2@C72 series was exposed for the first time to our best knowledge, and this deviation may not only be restricted to the Sc2C2@C72 series but also apply to other scandium carbide fullerenes Sc2C2@C2n (2n ≠ 72) and even other metal carbide fullerenes. Misleading conclusions will be drawn on the basis ...

Formation of onion-like fullerene and chemically converted graphene-like nanosheets from low-quality coals: application in photocatalytic degradation of 2-nitrophenol

The formation of onion-like fullerene and chemically converted graphene-like nanosheets from low-quality coals were observed during an oxidation-cum-extraction (OCE) process.

Sc3N@Cs(39715)–C82: a missing isomer linked to Sc3N@C2v(39718)–C82 by a single step Stone–Wales transformation

Density functional theory combined with statistical mechanics calculations indicate that Sc3N@C2v(39718)–C82 and Sc3N@Cs(39715)–C82 linked by a single Stone–Wales transformation can be obtained at the fullerene formation temperature region.

Molecular dynamical modelling of endohedral fullerenes formation in plasma

The initial stages of fullerene and endohedral metallofullerene (EMF) synthesis in carbon-helium plasma at 1500 K and 2500 K have been simulated with quantum chemical molecular dynamics (MD) based on density-functional tight-binding (DFTB). The cases of formation of large (>100 atoms) sp2-carbon clusters with scandium atoms inside were observed. These clusters are considered as precursors of fullerenes or EMFs, and thus it is shown that formation of EMFs can be explained within the framework of "shrinking hot giant" mechanism. Also, the dependence of formation rates on plasma parameters, including temperature, buffer gas and metal atoms concentrations, has been studied.

Supracolloidal fullerene-like cages: design principles and formation mechanisms.

How to create novel desired structures by rational design of building blocks represents a significant challenge in materials science. Here we report a conceptually new design principle for creating supracolloidal fullerene-like cages through the self-assembly of soft patchy particles interacting via directional nonbonded interactions by mimicking non-planar sp2 hybridized carbon atoms in C60. Our numerical investigations demonstrate that the rational design of patch configuration, size, and interaction can drive soft three-patch particles to reversibly self-assemble into a vast collection of supracolloidal fullerene-like cages. We further elucidate the formation mechanisms of supracolloidal fullerene-like cages by analyzing the structural characteristics and the formation process. Our results provide conceptual and practical guidance towards the experimental realization of supracolloidal fullerene-like cages, as well as a new perspective on understanding the fullerene formation mechanisms.

Anticorrelated formation of fullerenes and polyynes upon laser ablation of graphite under various concentrations of hydrogen sources

Soluble fullerenes were produced with a somewhat unexpectedly high yield (10−2wt% of the evaporated carbons) by laser ablation of graphite in a ‘room-temperature’ argon gas flow. The high yield was likely due to the high temperature of the graphite after heating by the ablation laser. Laser ablation experiments using argon-diluted propane gas showed that fullerene formation was strongly inhibited by the addition of propane, while the formation of hydrogen-terminated, chain-form carbon molecules (polyynes) was enhanced. The reactivities of the fullerene precursors and chain-form carbon clusters are discussed based on the anticorrelation of the yields of fullerenes and polyynes.

Thermal Isomerizations of Diethynyl Cyclobutadienes and Implications for Fullerene Formation.

The mechanism by which carbon condenses to form PAHs or fullerenes is a problem that has garnered considerable theoretical and experimental attention. The ring-coalescence and annealing model for the formation of C(60) involves a [2 + 2] cycloaddition reaction of a cyclopolyyne to form a tetraalkynyl cyclobuta-1,3-diene intermediate, followed by a Bergman cycloaromatization reaction of the enediyne moiety. Intramolecular trapping of the incipient p-benzyne diradical across a diyne moiety of the macrocyclic ring affords an aromatic ring that must undergo further intramolecular reactions via polyradical intermediates to produce a condensed graphitic structure or fullerene. Computational studies of a model system for the intriguing tetraalkynylcyclobuta-1,3-diene intermediate, however, reveal that the corresponding p-benzyne diradical lies in a shallow minimum with a very low barrier to ring opening to cyclooctadienediyne. This pathway has not been previously considered in the mechanism for carbon condensation.

The quest for inorganic fullerenes

Experimental results of the search for inorganic fullerenes are presented. MonSm− and WnSm− clusters are generated with a pulsed arc cluster ion source equipped with an annealing stage. This is known to enhance fullerene formation in the case of carbon. Analogous to carbon, the mass spectra of the metal chalcogenide clusters produced in this way exhibit a bimodal structure. The species in the first maximum at low mass are known to be platelets. Here, the structure of the species in the second maximum is studied by anion photoelectron spectroscopy, scanning transmission electron microscopy, and scanning tunneling microcopy. All experimental results indicate a two-dimensional structure of these species and disagree with a three-dimensional fullerene-like geometry. A possible explanation for this preference of two-dimensional structures is the ability of a two-element material to saturate the dangling bonds at the edges of a platelet by excess atoms of one element. A platelet consisting of a single element only cannot do this. Accordingly, graphite and boron might be the only materials forming nano-spheres because they are the only single element materials assuming two-dimensional structures.

Deposition Growth and Morphologies of C60 on DTDCTB Surfaces: An Atomistic Insight into the Integrated Impact of Surface Stability, Landscape, and Molecular Orientation

The influence of stability, landscape, and molecular orientation of different donor surfaces on fullerene packing and donor–fullerene interface morphologies are analyzed comprehensively through state-of-the-art atomistic simulations taking the DTDCTB-C60 system as an example. The results provide helpful insight into the formation of crystalline fullerene in the active layer to achieve efficient charge separation for organic solar cells.

Quantum-Chemical Calculation of Carbododecahedron Formation in Carbon Plasma.

The ground state of the molecule consisting of 10 carbon atoms in C10(rg) "ring" conformation and the energy of its metastable C10(st) "star" conformation are reported. The reaction coordinate for the isomeric transition C10(st) → C10(rg) was calculated using density functional theory (DFT) with UB3LYP/6-31G(d,p). It was established that a 5-fold symmetry axis is conserved in this isomeric transition. The total energy of the ring isomer is by 10.33 eV (9.16 eV as zero-point energy corrected) lower than that of the star isomer. The energy barrier for the transition from the metastable star state to the ring state is 2.87 eV (3.57 eV as zero-point energy corrected). An analysis of possible chemical reactions in carbon plasma involving C10(st) and C10(rg) and leading to the formation of C20 fullerenes was performed. It was revealed that the presence of the C10(st) conformation in the reaction medium is a necessary condition for C20 fullerene formation. It was shown that the presence of hydrogen atoms in carbon plasma and UV radiation accelerate the C10(st) → C10(rg) transition and thus suppress the C20 fullerene formation.

Non-IPR Chlorofullerenes

The rule per excellence governing the stability of fullerene cages is the well-known Isolated Pentagon Rule, or IPR. Fullerenes violating the pentagon rule have been obtained in situ through (i) encapsulation of metallic clusters inside the cavity or by (ii) external addition of halogenated species. The endohedral non-IPR cages (type i) appeared in the 2000, with the simultaneous discovery of Sc2@C66 and Sc3N@C68;[ 1 ] the halogenated IPR-violating fullerenes (type ii) appeared in 2004 with the characterization of the first empty non-IPR cage C50Cl10.[ 2 ] From then on, the list of non-IPR cages synthesized with any of the two functionalizations has increased significantly. It is important to note that there exists no IPR-violating isomer obtained both as metallo-endohedral and chlorinated fullerene, suggesting that isomers encapsulating metals are not suitable to be obtained with halogen derivatization. The factors that govern the formation of metalloendohedral fullerenes are well-known.[ 3 ] Now, we intend to discover which are the elements that favor the formation of chlorinated species. With this goal, we have analyzed several isomers for C66 and other fullerenes that have been observed as chloro- and endofullerenes in order to unravel the features of the non-IPR isomers that make them suitable to be trapped as halogenated fullerenes. (1) Stevenson, S.; Fowler, P. W.; Heine, T.; Duchamp, J. C.; Rice, G.; Glass, T.; Harich, K.; Hajdu, E.; Bible, R.; Dorn, H. C. Nature 2000, 408, 427. (2) Xie, S.-Y.; Gao, F.; Lu, X.; Huang, R.-B.; Wang, C.-R.; Zhang, X.; Liu, M.-L.; Deng, S.-L.; Zheng, L.-S. Science 2004, 304, 699. (3) a) Rodriguez-Fortea, A.; Alegret, N.; Balch, A. L.; Poblet, J. M. Nature Chem. 2010, 2, 955; b) Campanera, J. M.; Bo, C.; Poblet, J. M. Angew. Chem., Int. Ed. 2005, 44, 7230. Figure 1

CHARACTERIZING THE INFRARED SPECTRA OF SMALL, NEUTRAL, FULLY DEHYDROGENATED POLYCYCLIC AROMATIC HYDROCARBONS

We present the results of a computational study to investigate the infrared spectroscopic properties of a large number of polycyclic aromatic hydrocarbon (PAH) molecules and their fully dehydrogenated counterparts. We constructed a database of fully optimized geometries for PAHs that is complete for eight or fewer fused benzene rings, thus containing 1550 PAHs and 805 fully dehydrogenated aromatics. A large fraction of the species in our database have clearly non-planar or curved geometries. For each species, we determined the frequencies and intensities of their normal modes using density functional theory calculations. Whereas most PAH spectra are fairly similar, the spectra of fully dehydrogenated aromatics are much more diverse. Nevertheless, these fully dehydrogenated species show characteristic emission features at 5.2$\mu$m, 5.5$\mu$m and 10.6$\mu$m; at longer wavelengths, there is a forest of emission features in the 16--30$\mu$m range that appears as a structured continuum, but with a clear peak centered around 19$\mu$m. We searched for these features in Spitzer-IRS spectra of various positions in the reflection nebula NGC 7023. We find a weak emission feature at 10.68$\mu$m in all positions except that closest to the central star. We also find evidence for a weak 19$\mu$m feature at all positions that is not likely due to C$_{60}$. We interpret these features as tentative evidence for the presence of a small population of fully dehydrogenated PAHs, and discuss our results in the framework of PAH photolysis and the formation of fullerenes.

Development and Characterization of Biocompatible Fullerene [C60]/Amphiphilic Block Copolymer Nanocomposite

We report a supramolecular process for the synthesis of well-defined fullerene (C60)/polymer colloid nanocomposites in an aqueous solution via complex formation. A biocompatible triblock poly(4-vinylpyridine)-b-polyethylene-b-poly(4-vinylpyridine), P4VP8-b-PEO105-b-P4VP8, was synthesized by atom transfer radical polymerization. The block copolymer formed complexes with C60in toluene and resulted in fullerene assembly in cluster form. Nanocomposite dispersion in an aqueous solution could be obtained using an aged solution of the polymer/C60/toluene solution by a solvent evaporation technique. The UV-Vis and FTIR spectroscopy confirmed the complex formation of fullerene with the polymer which plays a significant role in controlling the PDI and size of polymer/C60micelles in the toluene solution. The particle size and morphology of P4VP8-b-PEO105-b-P4VP8and P4VP8-b-PEO105-b-P4VP8/C60mixture were studied by dynamic light scattering (DLS) and transmission electron microscopy (TEM). In a cytotoxicity test, both pure polymer and the resulting polymer/C60composite in water showed more than 90% cell viability at 1 mg/mL concentration.

Persistent homology for the quantitative prediction of fullerene stability.

Persistent homology is a relatively new tool often used for qualitative analysis of intrinsic topological features in images and data originated from scientific and engineering applications. In this article, we report novel quantitative predictions of the energy and stability of fullerene molecules, the very first attempt in using persistent homology in this context. The ground-state structures of a series of small fullerene molecules are first investigated with the standard Vietoris-Rips complex. We decipher all the barcodes, including both short-lived local bars and long-lived global bars arising from topological invariants, and associate them with fullerene structural details. Using accumulated bar lengths, we build quantitative models to correlate local and global Betti-2 bars, respectively with the heat of formation and total curvature energies of fullerenes. It is found that the heat of formation energy is related to the local hexagonal cavities of small fullerenes, while the total curvature energies of fullerene isomers are associated with their sphericities, which are measured by the lengths of their long-lived Betti-2 bars. Excellent correlation coefficients (>0.94) between persistent homology predictions and those of quantum or curvature analysis have been observed. A correlation matrix based filtration is introduced to further verify our findings.

Fullerenes, PAHs, Amino Acids and High Energy Astrophysics

We present theoretical, observational and laboratory work on the spectral properties of fullerenes and hydrogenated fullerenes. Fullerenes in its various forms (individual, endohedral, hydrogenated, etc.) can contribute to the UV bump in the extinction curves measured in many lines of sight of the Galaxy. They can also produce a large number of absorption features in the optical and near infrared which could be associated with diffuse interstellar bands. We summarise recent laboratory work on the spectral characterisation of fullerenes and hydrogenated fullerenes (for a range of temperatures). The recent detection of mid-IR bands of fullerenes in various astrophysical environments (planetary nebulae, reflection nebulae) provide additional evidence for a link between fullerene families and diffuse interstellar bands. We describe recent observational work on near IR bands of C<sub>60</sub><sup>+</sup> in a protoplanetary nebula which support fullerene formation during the post-AGB phase. We also report on the survival of fullerenes to irradiation by high energy particles and gamma photons and laboratory work to explore the chemical reactions that take place when fullerenes are exposed to this radiations in the presence of water, ammonia and other molecules as a potential path to form amino acids.

Experimental study into the formation of nanodiamonds and fullerenes during cavitation in an ethanol-aniline mixture

In this study, products forming due to cavitation synthesis in an ethanol-aniline mixture are investigated. A procedure of chemical purification of nanodiamonds, which makes it possible to isolate chemically pure products, is developed. Nanodiamond particles 3–5 nm in size are obtained. New data that indicate that complex fullerenes C70, C60, and C84 form during cavitation synthesis along with the diamond phase are presented, and a question on the account for the development of the sequence of complex forms of carbon during bubble collapse is stated.

Fullerene growth from encapsulated graphene flakes.

The direct in situ observation of fullerene formation encapsulated within a graphene ridge has been made possible using an aberration corrected transmission electron microscope (AC-TEM). An atom-by-atom mechanism was proposed based on in situ AC-TEM observations. First principle calculations found a continuous energy decrease upon the addition of carbon atoms to the edge of the graphene flakes, which mimics the fullerene growth steps and supports the atom-by-atom mechanism. The ridged graphene structure worked as a container for pinning small graphene flakes and capturing carbon atoms, which increased the growth probability of the fullerene structure within the small encapsulated space.

Dramatic enhancement of fullerene anion formation in polymer solar cells by thermal annealing: Direct observation by electron spin resonance

Using electron spin resonance (ESR), we clarified the origin of the efficiency degradation of polymer solar cells containing a lithium-fluoride (LiF) buffer layer created by a thermal annealing process after the deposition of an Al electrode (post-annealing). The device structure was indium-tin-oxide/ poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate)/poly(3-hexylthiophene):phenyl-C61-butyric acid methyl ester (P3HT:PCBM)/LiF/Al. Three samples consisting of quartz/P3HT:PCBM/LiF/Al, quartz/P3HT:PCBM/Al, and quartz/PCBM/LiF/Al were investigated and compared. A clear ESR signal from radical anions on the PCBM was observed after LiF/Al was deposited onto a P3HT:PCBM layer because of charge transfer at the interface between the PCBM and the LiF/Al, which indicated the formation of PCBM−Li+ complexes. The number of radical anions on the PCBM was enhanced remarkably by the post-annealing process; this enhancement was caused by the surface segregation of PCBM and by the dissociation of LiF at the Al interface by the post-annealing process. The formation of a greater number of anions enhanced the electron scattering, decreased the electron-transport properties of the PCBM molecules, and caused an energy-level shift at the interface. These effects led to degradation in the device performance.

Soot and Nanomaterials Formation in Flame

<p>The seventieth anniversary of Professor Jürgen Warnatz is an important event for the scientific community of investigators of chemical kinetics and computation of combustion. His brilliant research in the field of combustion, particularly in the chemical kinetics reactions should be noted. His manuscript «Combustion»<br />with co-authors is a handbook for specialists in the field of combustion and under my supervision was translated to Kazakh. Professor J.Warnatz contributed much to the development of combustion processes modeling and education of scientists from various countries, including Kazakhstan. The general scheme of conversion of hydrocarbon fuels with new experimental data on the formation of fullerenes and graphenes, taking into account the pressure effect is proposed for the fuel-rich flames. It is shown that the formation of fullerenes is important to the corresponding spatial orientation of PAH, possible at low pressures. The formation of hydrophobic soot surface on silicon and nickel substrates during combustion of propane-oxygen flame was studied. It is stated that the hydrophobic properties are due to the presence of soot particles in the form of nanobeads.</p><p> </p>