Formation Of Fullerene Clusters Research Articles

On a specific state of C60 fullerene in N-methyl-2-pyrrolidone solution: Mass spectrometric study

A solution of fullerene C60 in N-methylpyrrolidone (NMP) presents a suitable system for obtaining fullerene's clusters with the tunable size. However, the mechanism of fullerenes interaction with polar NMP molecules is still elusive. Herein, we present the measured laser desorption/ionization mass spectra (LDI MS) of the precipitates produced from C60/NMP solutions of different age in comparison with the typical spectra of C60 crystallized from toluene and benzene. The distinctive characteristics of the C60/NMP mass spectra were identified and carefully examined. The number of characteristic peaks and their relative intensities in the spectra strongly depend on the age of initial C60/NMP solutions. This effect was attributed to the specific C60-NMP interactions in the solution, namely to the formation of charge-transfer complexes of C60 with NMP molecules followed by fullerene cluster formation. The results of additional measurements carried out by means of small-angle X-ray scattering (SAXS), nuclear magnetic resonance (NMR), UV–Vis absorption spectroscopy together with the density functional theory (DFT) calculations are in accord with the proposed hypothesis.

Specifics of C60 Fullerene Cluster Formation in a Solvent Mixture of Toluene and N-Methyl-2-Pyrollidone

The two-level organization of C60 fullerene clusters in solutions of C60 in pure toluene and toluene/N-methyl-2-pyrrolidone solvent mixtures is studied by small-angle X-ray scattering (SAXS). The SAXS data for freshly prepared solutions are compared with the data obtained by dynamic light scattering, a technique we use to assess the temporal stability of the prepared solutions. For all solutions in the mixed solvent, regardless of the ratio between the polar and nonpolar components, the UV−Vis absorption spectra tend to become featureless with time. We attribute this behavior primarily to the presence of the polar component in the molecular environment of fullerene molecules.

The features of the formation of the hybrid nanostructures of C60 fullerene and amphiphilic copolymer of N-vinylpyrrolidone with (di)methacrylates in isopropyl alcohol and its mixtures with water

The aggregation of the amphiphilic copolymer N-vinylpyrrolidone with lauryl methacrylate and triethylene glycol dimethacrylate in isopropyl alcohol and its mixtures with water was studied by the dynamic light scattering and transmission electron microscopy. It was shown that the aggregation of amphiphilic macromolecules was enhanced at increase of the media polarity. The TEM images of the terpolymer aggregates demonstrated the presence of spherical shape particles with diameter ca. 50 and 300–500 nm after evaporation of isopropyl alcohol and isopropyl alcohol-water mixture of 60:40 vol% composition, respectively. The fullerene hybrid macromolecular structures were produced owing to spontaneous aggregation of the fullerene C60 and the terpolymer colloids. According to dynamic light scattering (DLS), in isopropyl alcohol, the monodisperse C60-copolymer structure was formed in which the fullerene was held by the copolymer particles due to hydrophobic interactions. According to the electronic absorption spectroscopy, the encapsulated fullerene kept its electronic structure in isopropyl alcohol in contrast to the isopropyl alcohol-water mixtures. The fullerene absorption band at λ 330 nm shifted to the red region due to donor-acceptor interaction between the terpolymer and C60, and the absorption band appears in the 400–500-nm region as a result of the fullerene cluster formation in the isopropyl alcohol-water mixtures. Stable macromolecular hybrid nanostructures of the amorphous fullerene produced in isopropyl alcohol were spherical particles and uneven surface. In 60:40 vol% isopropyl alcohol-water mixture, the fullerene as clusters of crystalline nature with a size of ~50 nm was found.

FT-ICR MS analysis of asphaltenes: Asphaltenes go in, fullerenes come out

Asphaltenes analysis still remains a challenge due to their unknown molecular structure and self-associative behavior. FT-ICR MS analyses using five different ionization methods, ESI, APCI, APPI, LDI and MALDI, in both positive and negative mode were performed. A characteristic and typical behavior was observed for the experiments using LDI(±) and MALDI(±)FT-ICR analyses: a broadband mass spectrum ranging from m/z 500 to 3000 was observed with a 24Da interval. This phenomenon was attributed to fullerene cluster formation. The most abundant allotropic form of fullerene, C60, was observed at m/z 719.99914. These species were not observed in APCI(+)/APPI(+) analyses. This last analysis of asphaltene samples doped with the C60 solution promptly reveals the typical fullerene ions. LDI(+) analyses of pure C60 showed condensation products. These results indicate a clusterization of asphaltenes in the LDI/MALDI plume, which showed a highly dependency on the laser power density. The dispersion of LDI results on carbonaceus samples in the literature is associated with the lack of control of these parameters. However, to access the sample composition, APPI and APCI should be more suitable.

Numerical simulation of synthesis of fullerenes by the arc discharge method

A mathematical model of the fullerene formation process by carbon vapor clustering in an arc discharge camera was developed. Numerical simulation of formation of fullerene clusters up to C60 and C70 from carbon vapor produced by an arc discharge in a plasma reactor camera was carried out. A geometrical model of the reactor was built, and a numerical model of the processes occurring in the gas flow in the reactor and at clustering of carbon vapor including 82 components and 522 chemical reactions was developed.

Comparative study: the effect of annealing conditions on the properties of P3HT:PCBM blends

This paper presents a detailed study on the role of various annealing treatments on organic poly(3-hexylthiophene) and [6]-phenyl-C61-butyric acid methyl ester blends under different experimental conditions. A combination of analytical tools is used to study the alteration of the phase separation, structure and photovoltaic properties of the P3HT:PCBM blend during the annealing process. Results showed that the thermal annealing yields PCBM “needle-like” crystals and that prolonged heat treatment leads to extensive phase separation, as demonstrated by the growth in the size and quantity of PCBM crystals. The substrate annealing method demonstrated an optimal morphology by eradicating and suppressing the formation of fullerene clusters across the film, resulting in longer P3HT fibrils with smaller diameter. Improved optical constants, PL quenching and a decrease in the P3HT optical bad-gap were demonstrated for the substrate annealed films due to the limited diffusion of the PCBM molecules. An effective strategy for determining an optimized morphology through substrate annealing treatment is therefore revealed for improved device efficiency.

Solvatochromism and Fullerene Cluster Formation in C60/N-methyl-2-pyrrolidone

UV-Vis spectroscopy and small-angle neutron scattering experiments are performed on the cluster solution of fullerene C60 in N-methyl-2-pyrrolidone before and after dilution of the system with pure solvent. Some changes in the UV-Vis spectra showing solvatochromism at dilution are observed, while the neutron scattering signal does not change. The effect is discussed with respect to the relation between solvatochromism and cluster formation for fullerene solutions in nitrogen-containing solvents.

Models of cluster formation in solutions of fullerenes

A review of experimental and theoretical studies of the formation and growth of clusters in solutions of fullerenes is given. General problems of fullerene cluster formation in solutions are considered. The main directions and goals of studies are specified. The experimental data on solutions with various polarities obtained by various methods, including visible and UV spectroscopy, dynamic light scattering, small-angle neutron scattering, mass spectrometry, transmission electron microscopy, etc., are generalized. The conditions of cluster formation and mechanism of cluster stabilization and the role played by clusters in certain effects observed in the corresponding systems are discussed. Cluster growth models are considered on the basis of nucleation theory for solutions of fullerenes with various polarities. It is shown that the description of the observed cluster state requires modification of the kinetic equations of the classic approach using the drop model of clusters. Modified kinetic equations with corrections for the mechanism of cluster stabilization are used to analyze cluster growth and related phenomena.

Formation of fullerene clusters in carbon disulfide: Data on small-angle neutron scattering and molecular dynamics

Fullerene solutions in carbon disulfide are studied by small-angle neutron scattering (SANS). In addition to earlier experiments on the given system, the range of measured transmitted impulses is extended and the influence of solution preparation methods on C60 cluster formation in these solutions is studied. It is shown that the formation of large C60 clusters (with a size of about 10 nm) is due to nonequilibrium methods of solution preparation. For nonequilibrium dissolution, there is a 10% excess of the observed fullerene size in the solution over the calculated value. It has been established by simulation of the C60/CS2 interface by molecular dymanics methods that inclusion of how solvent molecules are organized on the C60 surface leads to a decrease in the fullerene size in the solution, observed by using SANS. In this paper, the effect of excess Rg is explained by the presence of small clusters in the solution (approximately 10% of dissolved C60 molecules). It is discovered that there is a time variation in the concentration of the saturated solution. The explanation of this effect using a model of formation and sedimentation of large clusters (with a size of 100 nm or more) is proposed.

Formation of fullerene clusters in the system C 60/NMP/water by SANS

Solutions of fullerenes in nitrogen-containing solvents constitute a specific class characterized by the formation of fullerene clusters. In the given work, we report the effect of cluster rearrangement in the system C 60/ N-methylpyrrolidone (NMP) after addition of water (miscible with NMP) as observed by small-angle neutron scattering (SANS). The effect has a critical character and takes place if the water relative content is higher than 40%. Despite a small scattering signal, estimates of the mean scattering length density of the clusters by SANS contrast variation can be done.

Cluster growth and dissolution of fullerenes in non-polar solvents

The processes of fullerene cluster formation and growth in non-polar solvents are described basing on the numerical solutions of kinetic equations of nucleation theory. The liquid drop model and the limited growth model are analyzed. For supersaturated solutions it is shown, that the model of limited growth is an adequate model and can qualitatively describe the experimental data. The model of fullerene dissolution processes is proposed.

Growth and Formation of Fullerene Clusters

Theoretical studies on the stability and electronic structure of small carbon clusters assuming chain, ring, bowl, and fullerene structures have been carried out using a linear combination of atomic orbitals molecular orbital approach within a density functional formalism. Our studies on clusters containing between 12 and 60 atoms indicate three regimes for the growth and formation of carbon clusters. In clusters containing less than 20 atoms, the most stable geometry is the ring arrangements. Between 20 and 28 atoms, clusters with very different geometry have comparable energies. For clusters with larger than 30 atoms, the fullerene structures are the most stable structures. An analysis of the electronic structure shows a distinct correlation between the geometry and the nature of electronic states.

Photochemical reduction of water-soluble fullerene C 60(C 4H 10N +) in titanium dioxide suspensions (EPR-study): a comparison with radiolytically-induced reduction

N-methylfulleropyrrolidinium (C 60(C 4H 10N +)/I −) was found to be efficiently reduced in photoexcited TiO 2 suspensions in a toluene/ acetonitrile/2-propanol (10:10:1 v/v) solvent mixture. The formation of the π-radical anion, (C 60 −) (C 4H 10N +), was monitored by in situ EPR spectroscopy. Despite the fullerene's functionalization, the reduction process proceeds analogously to that reported earlier for pristine C 60. In aqueous solutions, the behaviour of C 60(C 4H 10N +)/I − towards reduction is, however, very complex. Although the N-methylfulleropyrrolidinium is sufficiently water-soluble, no reduction could be observed in irradiated aqueous TiO 2 suspension. This is attributed to the formation of fullerene clusters in aqueous solutions which seems to prevent transfer of an electron. Addition of a surfactant, such as lauryl sulfate, successfully inhibited fullerene clustering and, in turn after prolonged irradiation (C 60 −) (C 4H 10N +) was observed in low yields. Using γ-cyclodextrin (γ-CD) encapsulated fullerene, C 60(C 4H 10N +)/γ-CD, instead of the surfactant capped fullerene, the fullerene's π-anion-radical was formed immediately. These observations underline the dominant role of cluster formation with respect to reduction and other processes, in general, of water-soluble monofunctionalized fullerene derivatives. A considerably lower activity was also noticed for the reduction of C 60(C 4H 10N +)-clusters by (CH 3) 4 .C(OH) radicals relative to the analogous reduction of C 60(C 4H 10N +)/γ-CD. This emerged from competitive experiments with applying 5,5-dimethyl-1-pyrroline- N-oxide (DMPO) as a spin trap in aqueous TiO 2 suspensions, containing 2-propanol.

Capped Fullerenes: Stabilization of Water-Soluble Fullerene Monomers As Studied by Flash Photolysis and Pulse Radiolysis

Functionalization of C60 with hydrophilic groups promotes the water solubility of the fullerene core which leads in aqueous solution to the irreversible formation of clusters. Capping the surface of water-soluble fullerene derivatives with surfactants (cetyltrimethylammonium chloride or Triton X-100) was found to exclude formation of fullerene clusters and, in turn, to stabilize fullerene monomers. Flash photolytic and pulse radiolytic techniques were employed to generated excited and reduced states of fullerene monomers and fullerene clusters 1−3. Fullerene aggregation was found to have no significant effects on the physicochemical properties related to the generation and lifetime of the excited singlet state. Nanosecond studies of the processes following photoexcitation revealed noticeable differences between monomeric and colloidal derivatives 1−3 for the absorption maximum of the corresponding *T1 → *Tn absorptions. Clustering was found to invoke also remarkable changes for the decay of the fullerene's excited triplet state. Similarly, λmax of the π-radical anions 1−3 is very sensitive to the environmental parameters of the accommodating assembly. In surfactant media, the maxima ([(C60•-)(C4H10N+)]surfactant 1010 nm) were generally blue-shifted relative to the analogous γ-CD complexes ([(C60•-)(C4H10N+)]/γ-CD 1030 nm). On the basis of comparison with fullerene clusters and γ-CD-incorporated complexes, evidence was found that suggests the presence of fullerene monomers in a core(fullerene)−shell(surfactant) type structure.