Preparing samples for fullerene C60 hazard tests: Stable dispersion of fullerene crystals in water using a bead mill

A dispersion method using a bead mill was developed for preparing suspensions used in hazard testing of nanosize fullerenes. Fullerene crystals (C₆₀) of several μm to 100 μm in size were wet ground using a bead mill and dispersed in pure water containing Tween 80 as a dispersant. The particle size, dispersing condition, crystallization and fullerene oxide in the suspension prepared by bead milling were evaluated. As a result, the conditions of bead milling where the sizes of fullerene crystals were reduced to 100 nm or less were found, which made it possible to prepare a fullerene aqueous dispersion system using Tween 80. Furthermore, by centrifugation, it became possible to prepare fullerene suspensions in which the particle size of the majority of the suspended particles was 100 nm or less. The prepared suspensions remained stable for almost two months. Controlling milling conditions and milling time made it possible to achieve dispersion while maintaining the crystallized state of the fullerenes, and operating in anaerobic conditions under shade effectively suppressed the production of oxidized fullerenes. The fullerene suspensions prepared by bead milling and centrifugation were suitable for endotracheal administration tests and inhalation tests using rats.     

Ordered fullerene nanocylinders in large-diameter carbon nanotubes

A new ordered fullerene phase encapsulated by large-diameter CNTs is systematically investigated by combining a growth technique by chemical vapour deposition, high-resolution transmission electron microscopy and molecular-dynamics simulations. In contrast to fullerenes in smaller (1-2?nm) diameter CNTs, where fullerenes are packed in linear or helical chains, fullerenes form a nanoscale cylinder in double-walled CNTs with diameters of ～4?nm. The fullerenes were shown to form a nanocylinder with a side wall that resembled the (111) plane of solid C(60). This ordered phase is different from peapods or fullerene solids known so far, and a result of the interaction between the CNT wall and fullerenes. This finding will open up a new field of fullerene science.     

掺富勒烯SiO2气凝胶的制备与发光性质研究

本文利用溶胶－凝胶工艺成功地将富勒烯掺入了ＳｉＯ２气凝胶的纳米孔洞中，在Ａｒ＾＋离子激光激发下，观察到了很强的可见光发射，对该现象作了初步的解释。     

Kinetically controlled fabrication of C60 1-dimensional crystals

Considering the current application of fullerenes in the field of organic semiconductor devices, the highly crystalline or single crystal fullerene nanostructures with controlled shape and size contains some breakthrough for improved efficiency. Recently, fullerene 1-dimensional nanostructures, including nanowhiskers and nanotubes, become attractive kind of materials since the development of liquid-liquid interface precipitation (LLIP) process. The LLIP process has critical advantage; the fabrication of highly crystalline, even single crystal, fullerene 1-dimensional nanostructures with simple apparatus. However, the fabrication fullerene 1-dimensional structures by LLIP process requires long process time from one day to several days. In order to overcome this drawback, a modified process from conventional LLIP process is suggested. In the modified LLIP process, the nucleation step and growth step were divided. For the nucleation step, saturated fullerene solution is mixed with small amount of alcohols such as 2-propanol or ethanol. For the controlled growth step, the fullerenes in the nucleated solution are precipitated by addition of alcohol, which is injected to the bottom of the solution with controlled flow rate. In this modified process, the shape of the precipitated fullerene crystals is critically dependent on the nucleation steps and the size is dependent on the precipitation rate. By combination of proper nucleation step and growth rate, a well defined fullerene 1-dimensional structures, of 200-500 nm width and of hundreds microm length can be fabricated within two hours. In addition, by controlling injection rate and degree of supersaturation, several types of 1-dimensional structures including micro-tubes can be prepared and, by changing solvent and alcohol, several shape of C60 crystals including polyhedral particles and plates can be prepared.     

Photolytic breakdown of fullerene C60 cages in an aqueous suspension

Fullerene C60, a class of carbon nanomaterials, is widely used and is likely to reach the environment. The degradation and transformation of C60 aqueous suspensions exposed to simulated sunlight were studied. C60 aqueous suspensions prepared by stirring pristine C60 in water under sunlight exposure undergo breakdown with formation of a mixture of compounds with unknown chemical structure. The mass and infrared spectrometric analysis of the breakdown products shows the presence of broken C60 cages, as well as of oxygen and hydrogen atoms in their structure. The presence of oxygen in the breakdown products indicates a possible interaction of C60 molecule with oxygen from the air as well as with water. Interaction with water could also explain the presence of H atoms in the breakdown products. This demonstrates that fullerenes C60 are not stable in the environment and that the breakdown products should be considered when evaluating the environmental impact of fullerenes C60.     

Structural patterns in fullerenes showing adjacent pentagons: C20 to C72

We have analyzed in detail the structure of the smallest fullerenes C(n) (20 < or = n < or = 72) obtained in B3LYP/6-31G* calculations. All these systems, except for C60, C70, and C72, necessarily present adjacent pentagons in their structure. For the most stable classical isomers, we have studied the variation of bond distances, HOMO-LUMO gaps and enthalpies of formation with fullerene size. A classification of the bonds in 9 different motifs permits to gain insight in the factors determining the fullerene stability. A simplified model that assumes a fixed energy per bond is able to reproduce the calculated enthalpies of formation and to estimate the energy change associated with each structural motif. An extra stabilization of 30-40 kcal/mol is predicted for the fullerenes showing spherical aromaticity.     

Comparative study of carbon nanotubes- and fullerenes-doped liquid crystal for different electrophoretic parameters

This research focuses on the study of different electrokinetic parameters of carbon nanotubes (CNTs) and fullerene aggregates in liquid crystal (LC) host medium, which are investigated in the homogeneously aligned nematic LC cells driven by in-plane field. The colloidal CNTs in LC medium are observed to move towards the negative electrodes whereas the fullerenes in LC medium are observed to move towards positive electrode at low frequencies. We propose a model to estimate the charge and zeta potential of colloidal particles by incorporating both the dielectrophoresis and electrophoresis forces in order to probe the reason of moving the colloidal particles in opposite direction. Interestingly, charge and zeta potential values on CNTs and fullerenes estimated from given model were positive and negative, respectively. The CNTs and fullerenes at high frequency and field are found to stretch along the direction of electric field. The CNTs dispersed whereas fullerenes start to move in perpendicular direction to the applied electric field with increasing electric field at high frequency.     

Stability studies on colloidal suspensions of polyurethane nanocapsules

Generally nanocapsules suspensions are a colloidal system in a metastable state, there is aggregation due to attraction and repulsion forces between particles. The objective of this work was to bring the role of the polymeric membrane in the protection of the active drug against damaging caused by external agents and to select the monomer which leads to obtain stable formulation with the highest possible payload of the active drug. The stability testing involving visual aspect, particle size measurement, transmission electron microscopy (TEM) examination, and drug loss was conduced after 6 months of storage at different temperatures (4, 25, and 45 degrees C). The colloidal suspensions of nanocapsules were obtained using the combined interfacial polycondensation and spontaneous emulsification, the technique was used to encapsulate alpha-tocopherol using polyurethanes polymers. It is a one step procedure: An organic phase composed of a water miscible solvent (acetone), lipophilic monomer (Isophorone diisocyanate IPDI), oil, and a lipophilic surfactant, is injected in an aqueous phase containing hydrophilic monomer (diol with various molecular weight: 1,2-ethanediol (ED), 1,4-butanediol (BD), and 1,6-hexanediol (HD)) and hydrophilic emulsifying agent. The water miscible solvent diffuses to the aqueous phase, the oil precipitates as nano-droplets, and the two monomers react at the interface, forming a membrane around the nanoemulsion leading to nanocapsules. A good physical stability of suspensions corresponds to absence of symptoms such as sedimentation or agglomeration, significant size change and alpha-tocopherol degradation due to external agents such as oxygen, temperature, and ultraviolet (UV) irradiation. The size of nanocapsules before storage was about 232 +/- 3, 258 +/- 29, and 312 +/- 4 nm for ED, BD, and HD, respectively. After 6 months of storage, polyurethanes nanocapsules possess good stability against aggregation at 4 and 25 degrees C. Comparing results obtained using different monomers, it reveals that the polyurethane based on HD offers good protection of alpha-tocopherol against damaging caused by the temperature and UV irradiation.     

Rotating fullerene chains in carbon nanopeapods

The rotation of fullerene chains in SWNT peapods is studied using low-voltage high resolution transmission electron microscopy. Anisotropic fullerene chain structures (i.e., C300) are formed in situ in carbon nanopeapods via electron beam induced coalescence of individual fullerenes (i.e., C60). A low electron accelerating voltage of 80 kV is used to prevent damage to the SWNT. The large asymmetric C300 fullerene structure exhibits translational motion inside the SWNT and unique corkscrew like rotation motion. Another asymmetric fullerene chain containing mixed fullerene species is prepared by fusing smaller C60 fullerenes to a larger Sc@C82 fullerene, and this also exhibits corkscrew rotational motion. Chains of Sc3C2@C80 in SWNT peapods adopt a zigzag packing structure, and the entire zigzag chain rotates inside the SWNT to induce structural modifications to the SWNT diameter and cross-sectional shape of the SWNT. The expansion and contraction of the diameter of the SWNT is measured as 17%, demonstrating nanoactuation behavior in carbon nanopeapods.     

Quantum chemical molecular dynamics study of "shrinking" of hot giant fullerenes

We present a detailed analysis of size-down trajectories of the "Shrinking Hot Giant" road of fullerene formation, revealed before by our quantum chemical molecular dynamics simulations. It is found that shrinkage of giant fullerenes occurs in two stages, fall-off and pop-out stage, respectively, and that it is an irreversible process occurring naturally at high temperatures. The driving force behind the energetically unfavorable C2 evaporation is the increase in entropy and pi-conjugation stabilization of the increasingly more spherical fullerene cages. A comparison of the theoretical results with existing experimental data shows the importance of annealing for the synthesis of smaller (C60, C70) fullerenes.     

C60(Nd) nanoparticles enhance chemotherapeutic susceptibility of cancer cells by modulation of autophagy

Autophagy, an evolutionally conserved intracellular process degrading cytoplasmic proteins and organelles for recycling, has become one of the most remarkable strategies applied in cancer research. The fullerene C60 nanoparticle (nC60) has been shown to induce autophagy and sensitize chemotherapeutic killing of cancer cells, but the details still remain unknown. Here we show that a water-dispersed nanoparticle solution of derivatized fullerene C60, C60(Nd) nanoparticles (nC60(Nd)), has greater potential in inducing autophagy and sensitizing chemotherapeutic killing of both normal and drug-resistant cancer cells than nC60 does in an autophagy-dependent fashion. Additionally we further demonstrated that autophagy induced by nC60/C60(Nd) and Rapamycin had completely different roles in cancer chemotherapy. Our results, for the first time, revealed a novel and more potent derivative of the C60 nanoparticle in enhancing the cytotoxicity of chemotherapeutic agents and reducing drug resistance through autophagy modulation, which may ultimately lead to novel therapeutic strategies in cancer therapy.     

Synthesis of Fullerenes by Ablation Using Pulsed and cw-Nd:YAG Lasers

Macroscopic quantities of fullerenes were synthesized by ablation of a graphite rod heated with a cw-Nd:YAG laser in Ar gas flow. The ablation was carried out by irradiation of fundamental, second, and third harmonic light emitted from a pulsed-Nd:YAG laser. It was necessary to heat the graphite rod up to a higher temperature than 700 °C for producing macroscopic quantities of fullerenes. The amount of ablation, the fullerene yield and the relative fullerene yield increased with increasing temperature of graphite. The fullerpne yields depended on the pressure of Ar buffer gas as well, in which the j ablation plume was formed, and an optimum pressure range was found to be 53-80 kPa. Relatively high yield of C₇₀ was obtained by ablation method under these conditions.     

Lanthanide metals adsorbed in an open-cage Fullerene: first-principles calculations

In this paper, the properties of a 12-membered-ring open-cage fullerene, which encapsulate La, Ce, Pr, Nd, Pm, Sm, Eu or Gd, as a guest atom, were calculated using first-principle calculations. Calculations show that La etc. lanthanide metal atoms can be stably adsorbed on the openings of the fullerenes. The average adsorption energy is about -3.65 eV in which Pr and Nd have relatively large adsorption energy with -4.75 eV and -4.63 eV, respectively. The Gd is stably adsorbed on the side wall near bottom of the fullerene with adsorption energy of -3.05 eV. The PDOS of adsorbed lanthanides were analyzed, respectively. Magnetic property of adsorbed lanthanides was also discussed. From the calculation, it is proved that most of the adsorbed lanthanides keep good magnetic property. Finally, vertical ionization potential and vertical electron affinity of the complex compounds were researched. The results show that the possibility of donating electrons of the 12-membered-ring open-cage fullerene is significantly affected by the endohedral lanthanide metals. From our calculations, it is believed that the complex compounds could be promising candidates for medicine-carrier.     

Geometrical model for the retention of fullerenes in high-performance liquid chromatography

In high-performance liquid chromatography (HPLC) using a poly(octadecylsiloxane) as a stationary phase, methanol as a mobile phase, C(60) and C(70) fullerenes as solutes, and water as a mobile phase modifier, a study on the surface tension effect of water on fullerene retention was carried out by varying the water concentration [W] and the column temperature T. The thermodynamic parameters for fullerene transfer from the mobile to the stationary phase were determined from linear van't Hoff plots. An enthalpy-entropy compensation revealed that the types of interactions between fullerenes and the stationary phase were independent of the fullerene structure and the mobile phase composition. An analysis of the experimental variations of the retention factor and the selectivity values with [W] was performed using a novel geometrical model. It was shown that the increase in fullerene retention accompanying the water concentration was due to the increased effects of surface tension. This brought about an increase in the interactions between fullerene and the stationary phase, explaining the observed thermodynamic parameter trends over the water concentration range. The theoretical model provided an estimation of the radius of fullerene which was found for C(60) to be equal to 3.3 ? and an activation energy during the transfer equal to 9.8 kJ/mol.     

C60 and Giant Fullerenes in Soot Condensed in Vapors with Variable C/H2 Ratio

A transmission electron microscope (TEM) study of individual soot grains forming fluffy carbon particles produced using the arc-discharge technique revealed close-packed arrangements of single-wall ring structures with average diameters of 0.7, 1.1, 3.0, 5.5, and 8.2 nm. These structures were hypothesized to be C₆₀ and giant, C₅₄₀, C₉₆₀, and C₁₅₀₀, fullerenes that could form by coalescence during condensation and soot agglomeration, although in situ solid-state growth cannot be excluded. Mass spectroscopy and high performance liquid chromatography (HPLC) chromatography of the samples confirmed the presence of C₆₀ fullerene in all samples giving confidence to the giant fullerene growth scenario. Our results suggest that fullerenes could be common in soot grains produced by this technique as well as being an important carbon phase in C-rich accretion disks around young stellar objects and among the dust in the interstellar medium.     

Extraction of Exotic Fullerenes and Purification of Single-Walled Nanotubes

In this report, we presented a novel and simple extraction method, namely Hydrothermally Initiated Dynamic Extraction (HIDE) method, which allows the extraction of exotic fullerenes remaining in the fullerene soot. In the HIDE method, the soot was treated in boiling water that neither dissolved fullerenes nor produced minimal by-products but untangles the fullerenes from the soot, prior to the extraction by organic solvent. As a result, the HIDE method allowed the extraction of exotic fullerenes, such as dimeric fullerene oxides, higher fullerenes having a low symmetry and oxidized higher fullerenes. Accordingly, the single walled nanotubes (SWNTs) with a purity of 99% by wt was achieved for the first time with the application of the HIDE method.     

Construction and electrochemistry of Langmuir-Blodgett films of fullerene lipid composite/hybrid materials

Studies of the electrochemistry of Langmuir-Blodgett (LB) films of C70/artificial lipids including tridodecylmethylammonium bromide (3C12N+Br-, 1), didodecylphosphate (2C12PO4H, 2), and dioleoylphosphatidylcholine (DOPC, 3) and of LB films of a fullerene lipid (4) bearing triple alkyl chains on a C60 moiety on electrodes were carried out in aqueous media. Stable Langmuir monolayers of fullerene C70/artificial lipid composites and the fullerene lipid (4) were formed at the air-water interface and these monolayers were transferred onto electrodes as LB films. Here, we focus on the importance of cationic matrix lipid films to the facile electrochemistry of C70 embedded in a LB film of cationic lipids on an electrode in aqueous media. On the basis of the electrolyte dependence and the charge dependence of the matrix lipids, a possible electron-transfer mechanism of the C70/artificial lipid LB film-modified electrodes is presented. Electrochemistry of a LB film of 4 was also obtained in an aqueous medium. We demonstrate that the introduction of the chemistry of lipid bilayer membranes to the LB films of fullerenes guides us toward the construction of fullerene/lipid bilayer devices.     

Interaction between fullerenes and single-wall carbon nanotubes: the influence of fullerene size and electronic structure

A series of fullerenes and endohedral metallofullerenes peapods have been synthesized by supercritical method in high filling rate. The interaction between SWNTs and various kinds of fullerenes (C60, C70, C78, C84) and metallofullerenes (Gd@C82, Er@C82, Ho@C82, Y@C82) has been further investigated. The slight blue shift of G-band in Raman spectra with respect to pristine SWNTs was attributed to the charge transfer from SWNTs to fullerenes cage. The obvious RBM shift strongly depended on the distance between the inner wall of the SWNTs and the fullerene cage and also partly associated with the electronic structure of the fullerene. These results indicated that the interaction between fullerenes and SWNTs, which was considered to be the van de walls interaction, can be influenced by the cage size and the kind of fullerenes.     

Extraction of Exotic Fullerenes and Purification of Single-Walled Nanotubes

Abstract

In this report, we presented a novel and simple extraction method, namely Hydrothermally Initiated Dynamic Extraction (HIDE) method, which allows the extraction of exotic fullerenes remaining in the fullerene soot. In the HIDE method, the soot was treated in boiling water that neither dissolved fullerenes nor produced minimal by-products but untangles the fullerenes from the soot, prior to the extraction by organic solvent. As a result, the HIDE method allowed the extraction of exotic fullerenes, such as dimeric fullerene oxides, higher fullerenes having a low symmetry and oxidized higher fullerenes. Accordingly, the single walled nanotubes (SWNTs) with a purity of 99% by wt was achieved for the first time with the application of the HIDE method.     

Preparation and dielectric properties of fullerene-doped polyarylene ether nitrile film

In order to obtain polymer films with low dielectric constant (≤2.0) and enhanced mechanical strength, fullerene-doped polyarylene ether nitrile (PEN) film was designed and prepared according to the following step. At first, fullerene and PEN were dissolved in toluene and N-methyl pyrrolidone, respectively, and the solutions were mixed together. The films were prepared by solution casting/solvent evaporation method on glass sheet. The morphology and thermal analysis of the films were characterized by visual & SEM observation and DSC & TGA test, respectively. The mechanical properties and dielectric properties of the films were also measured. The results showed that the dispersion of fullerene was largely dependent on the evaporation methods of the solvents. The glass transition temperature (Tg) and thermal decomposition temperature (Td) of PEN films were improved with the addition of fullerene. The dielectric constant sharply decreased from 4.0 to about 2.0 with the addition of fullerene. At the same time, the mechanical properties were improved, which might be caused by the physical entanglement of PEN chains with fullerenes. The lowest ε value (1.75 at 1 MHz) and the highest tensile strength (142.2 Mpa) were simultaneously obtained in samples containing 3 wt% fullerenes, which indicated it’s the optimal content of fullerene.