Pristine C60 Research Articles

In situ Raman and photoluminescence study on pressure‐induced phase transition in C60 nanotubes

Single crystalline C60 nanotubes having face‐centered‐cubic structure with diameters in the nanometer range were synthesized by a solution method. In situ Raman and photoluminescence spectroscopy under high pressure were employed to study the structural stabilities and transitions of the pristine C60 nanotubes. A phase transition, probably because of the orientational ordering of C60 molecules, from face‐centered‐cubic structure to simple cubic structure occurred at the pressure between 1.46 and 2.26 GPa. At above 20.41 GPa, the Raman spectrum became very diffuse and lost its fine structure in all wavenumber regions, and only two broad and asymmetry peaks initially centered at 1469 and 1570 cm–1 were observed, indicating an occurrence of amorphization. This amorphous phase remained to be reversible until 31.1 GPa, and it became irreversible to the ambient pressure after the pressure cycle of 34.3 GPa was applied. Copyright © 2012 John Wiley & Sons, Ltd.

ChemInform Abstract: Pyrazolinofullerenes: A Less Known Type of Highly Versatile Fullerene Derivatives

AbstractReview: ca. 100 refs.

Cytotoxicity of Pristine C<sub>60</sub> Fullerene on Baby Hamster Kidney Cells in Solution

Research on biological effects of C60 and its derivatives is one of the hotspots in the area of biological effects of nanomaterials. Compared with surface-modified C60 derivatives, reports on the biological effects of unmodified pristine C60 are relatively less. This work aimed to investigate the interaction between baby hamster kidney cells and pristine C60 in solution. The C60 suspension was prepared using solvent exchange method and characterized by UV spectrophotometry, electronic transmission microscopy and dynamic light scattering techniques. The baby hamster kidney cells were incubated with different concentrations of C60 suspensions, and light microscopy, cell counting kit 8 assay, and acridine orange staining were used to observe the cell growth and morphology. The results showed that C60 could ihibit the cell growth and induce cell apoptosis with a dose-effect relationship. C60 might enter cells and the possible way it enters cells were also proposed.

Effect of Catalysts on the Reaction of C60 with Hydrogen

The reaction of C60/catalyst with hydrogen gas was studied at 400°C and 50 bar of H2 pressure. The addition of Pt- or Ni-catalysts significantly accelerated kinetics of the hydrogenation reaction and resulted in a dramatic change of the C60Hx crystal structure. Samples reacted without catalyst preserved the fcc structure typical for pristine C60 but with expanded unit cells. Fulleranes C60Hx obtained using catalytic hydrogenation exhibited not only the fcc structure (at relatively low hydrogenation degree) but also the bcc structure of C60Hx (with x > 18). The bcc structure corresponds to highly hydrogenated material with an average volume per C60 molecule of 817–849 Å3.

Regioselective 1,2,3-bisazfulleroid: doubly N-bridged bisimino-PCBMs for polymer solar cells

The direct bisaddition of methyl 5-azido-5-phenylpentanoate to C60 takes place in the two neighboring pentagon–hexagon junctions of the same five-membered ring, yielding a regioselective bisazfulleroid, namely bisimino-PCBM. Because of its open annulene structure, this new bisheterofullerene is not only considered to be an isoelectronic analogue of pristine C60, but also it is less symmetrical than previous reported mono-functionalized fullerenes, thereby displaying a stronger absorption in the visible region. The BHJ devices based on P3HT:bisimino-PCBM give a higher VOC of 0.77 V relative to those using the PCBM in the literature, which can be attributed to the combination of the nature of the nitrogen atom and the open bridged mode in a fullerene cage. Furthermore, the bisimino-PCBM consisting exclusively of a doubly bridged open 11-membered ring with a hydroacenaphthylene perimeter is very new, therefore there is still plenty of room to establish better efficiencies of BHJ photovoltaic cells.

Polymer nanocomposites reinforced with C60 fullerene: effect of hydroxylation

Novel nanocomposite films of polycarbonate (PC) with fullerene derivatives, such as pristine fullerene C60 and polyhydroxylated-fullerenes, C60(OH)12 and C60(OH)36, were prepared. The optical, thermal, and mechanical properties of the composites were measured. Nanocomposite films of poly (vinyl alcohol) (PVA) with C60(OH)36 were prepared as a reference to show how improved dispersion of the nanofiller affects the overall transparency of the composites. Ultraviolet-visible spectroscopy showed that the addition of hydroxylated fullerenes did not affect visible light transmittance of the films significantly in the range of 400–800 nm. Differential scanning calorimetry (DSC) and thermo–gravimetric analysis (TGA) measurements showed the increased thermal stability of PC/C60(OH)12 film as compared to pristine PC film. This phenomenon was explained by the rigid polymer interphase regions formed around C60(OH)12 due to the plausible hydrogen bonding and hydrophobic interaction. On the other hand, the lower thermal stability of PC–C60(OH)36 was assumed to be caused by large agglomeration of the C60(OH)36 particles and the partial hydrolysis of the polycarbonate matrix. Tensile testing of the composites showed reduction in elongation at break and yield tensile strength. These results may be caused by the particle agglomerations which act as the initiation points for cracks.

Avoidance, weight loss, and cocoon production assessment for Eisenia fetida exposed to C60 in soil

Eisenia fetida was used as a model terrestrial organism to assess the potential ecotoxicity of molecular pristine C₆₀ in soil. Reproduction (assessed by counting cocoon numbers) was hindered only at very high C₆₀ concentrations (5% by weight), and C₆₀ (up to 1%) was not avoided and did not hinder earthworm growth. This suggests that E. fetida is unlikely to experience acute toxicity as a result of C₆₀ occurrence in soil. Whether sublethal toxicity may decrease earthworm populations that are chronically exposed to C₆₀ at lower concentrations remains to be determined.

Doping of Calcium in C60 Fullerene for Enhancing CO2 Capture and N2O Transformation: A Theoretical Study

Recently, capturing or transforming greenhouse gases, such as CO(2) and N(2)O, have attracted considerable interest from the perspective of environmental protection. In the present work, by studying CO(2) and N(2)O adsorption on pristine and calcium (Ca)-decorated fullerenes (C(60)) with density functional theory (DFT) methods, we have evaluated the potential application of this C(60)-based complex for the capture of CO(2) and transformation of N(2)O. The results indicate that the adsorptions of CO(2) and N(2)O molecules on the pristine C(60) are considerably weak accompanied by neglectable charge transfer. When C(60) is decorated with Ca atoms, however, it is found that CO(2) and N(2)O adsorptions on the C(60) are greatly enhanced. Up to five CO(2) molecules can be adsorbed on the CaC(60) system due to the electrostatic interaction. For N(2)O molecule, it is first molecularly adsorbed on the Ca atom with the adsorption energy of -0.534 eV, followed by the N(2) formation with a low barrier and high exothermicity. Moreover, when four Ca atoms are decorated on the surface of C(60), the maximum number of the adsorbed CO(2) molecules is 16. Our results might be useful not only to widen the potential applications of fullerene but also to provide an effective method to capture or transform greenhouse gases.

Hydrogen Adsorption on Pd- and Ru-Doped C60 Fullerene at an Ambient Temperature

Palladium- and ruthenium-doped C(60) fullerene compounds were synthesized by incipient wetness impregnation of C(60) fullerene with the corresponding metal acetylacetonate precursors. Transmission electron microscopy (TEM) imaging of the metal-doped C(60) fullerene samples showed different dispersion morphologies of palladium and ruthenium particles on the C(60) matrix. Raman spectra revealed a drastic decrease in peak intensity followed by disappearance of several bands indicating the distortion of the C(60) cage structure. The amorphous nature of the C(60) fullerene compounds was confirmed by the X-ray diffraction study. Hydrogen adsorption amount of 0.85 wt % and 0. 69 wt % on Pd-C(60) and Ru-C(60), respectively, as compared to 0.3 wt % on the pure C(60) fullerene were measured at 300 bar and 298 K. The enhancement in the hydrogen uptakes can be attributed to several factors, including adsorption of molecular H(2) on the defect sites, metallic hydride formation, spillover of hydrogen, and bond formation with atomic hydrogen with different active sites of carbon of host fullerene. The hydrogen adsorption isotherms are of type III and can be correlated by the Freundlich (for Ru-C(60)) and modified Oswin equations (for Pd-C(60) and pristine C(60)).

High-pressure Raman study of the Sm2.75C60 fulleride

The high-pressure response of the Sm2.75C60 fulleride is probed by Raman spectroscopy. The Raman spectrum of Sm2.75C60 and its pressure evolution differ significantly from those of pristine C60. The initial well-resolved Raman spectrum of the fulleride disappears above 4 GPa. This change is reversible; however, the original low-pressure Raman profiles are recovered only below 2 GPa. These observations are in line with the pressure-induced hysteretic phase transition of the compound observed earlier by X-ray diffraction and the proposed insulator to metal transition.

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.

Facile and scalable synthesis of a highly hydroxylated water-soluble fullerenol as a single nanoparticle

A water-soluble polyhydroxylated fullerene, i.e. a fullerenol, with 44 hydroxyl groups and 8 secondary bound water molecules, C60(OH)44·8H2O (estimated average structure), has been synthesized in a facile one step reaction from pristine C60 by hydroxylation with hydrogen peroxide in the presence of a phase-transfer catalyst, tetra-n-butylammonium hydroxide (TBAH), under organic/aqueous bilayer conditions. The fullerenol exhibited high water solubility, up to 64.9 mg/mL, under neutral (pH = 7) conditions. Dynamic light-scattering (DLS) analysis showed a narrow particle size distribution, of 1–2 nm, indicating that the fullerenol had high dispersion properties in water. The results of particle size analyses, which both focused on a single nanoregion and were conducted using a novel induced grating (IG) method and a scanning probe microscope (SPM), were consistent with the DLS results. A plausible reaction mechanism, which includes fullerene oxide intermediates detected by liquid chromatography-mass spectrometry (LC-MS), has been proposed.

ChemInform Abstract: Synthesis and Regiochemistry of [60]Fullerenyl 2‐Methylmalonate Bisadducts and Their Facile Electron‐Accepting Properties.

A simple one-pot reaction using in situ chemically generated Na-naphthalenide as an electron reductant in the preferential generation of C602− is described. Trapping of C602− intermediate with 2 molar equiv of sterically hindered 2-bromo-2-methylmalonate ester afforded two singly bonded fullerenyl bisadducts C60[-CMe(CO2Et)2]2 in 35% and 7% yield, respectively. The regiochemistry of these two products was determined to be 1,4- and 1,16-bisadducts, respectively, by NMR, UV−vis−NIR, LCMS, and X-ray single crystal structural analysis. The minor 1,16-bisadduct 2 exhibits long wavelength absorption bands in the near-IR region and prominent electron-accepting characteristics as compared with those of the major 1,4-bisadduct and pristine C60. As revealed by DFT calculation, we propose that the origin of these unusual characters of 2 arises from the moiety of [18π]-trannulene, in close resemblance to that of the highly symmetrical emerald green 1,16,29,38,43,60-hexaadduct of C60, EF-6MCn. Accordingly, we anticipa...

In vitro evaluation of cellular responses induced by stable fullerene C60 medium dispersion

Because of the expansion of the functionalities available for modification of fullerene C60 and its derivatives, their uses are increasing. However, the consequences of fullerene exposure to human health have not been fully studied. In vitro experiments are useful for risk assessment and for understanding potential applications. However, the insolubility of pristine C60 in water makes the in vitro evaluation of cellular responses difficult. To overcome this problem, we prepared a stable and uniform C60-medium dispersion for in vitro examinations. In addition, we examined the effect of the C60-medium dispersion on human keratinocyte HaCaT cells and human lung carcinoma A549 cells to understand the cellular responses induced by exposure to C60. Results indicated that exposure to C60 did not affect cell viability; neither apoptosis nor necrosis were induced, while cell proliferation was inhibited. Furthermore, intracellular oxidative stress was induced by C60 exposure in both HaCaT and A549 cells. Transmission electron microscopy indicated the cellular uptake of C60 aggregates. The results obtained from this study indicate that C60 has oxidative stress induction potential. Further examinations including in vivo studies are necessary for a more accurate evaluation of biological influences by C60.

Synthesis and Regiochemistry of [60]Fullerenyl 2-Methylmalonate Bisadducts and their Facile Electron-Accepting Properties

A simple one-pot reaction using in situ chemically generated Na-naphthalenide as an electron reductant in the preferential generation of C(60)(2-) is described. Trapping of C(60)(2-) intermediate with 2 molar equiv of sterically hindered 2-bromo-2-methylmalonate ester afforded two singly bonded fullerenyl bisadducts C(60)[-CMe(CO(2)Et)(2)](2) in 35% and 7% yield, respectively. The regiochemistry of these two products was determined to be 1,4- and 1,16-bisadducts, respectively, by NMR, UV-vis-NIR, LCMS, and X-ray single crystal structural analysis. The minor 1,16-bisadduct 2 exhibits long wavelength absorption bands in the near-IR region and prominent electron-accepting characteristics as compared with those of the major 1,4-bisadduct and pristine C(60). As revealed by DFT calculation, we propose that the origin of these unusual characters of 2 arises from the moiety of [18pi]-trannulene, in close resemblance to that of the highly symmetrical emerald green 1,16,29,38,43,60-hexaadduct of C(60), EF-6MC(n). Accordingly, we anticipate a fast progressive formation of plausible 1,16-bisadduct-like intermediate moieties on a C(60) cage as the precursor structure leading to the formation of EF-6MC(n), by taking the corresponding regiochemistry and electronic properties into account.

Magnetic Interaction of Solution-State Paramagnets with Encapsulated H2O and H2

The bimolecular contribution, R1 (M−1 s−1), to the T1 of isolated H2 and H2O protons, as well as free H2O in organic solution, by paramagnetic metal complexes was determined. Isolation was achieved by encapsulation in a fullerene: H2 was trapped in pristine C60 or in C60 with a 13-atom opening, and H2O in an open-C60 with a 19-atom opening. The R1 values in the presence of the various M(acac)x complexes [M = Fe(III), Cr(III), Cu(II), Co(III)] scale with μeff2 of the metal complex. The R1 values were significantly smaller for the trapped species than the free H2O. Surprisingly, R1 was nearly identical for the all three endohedral proton pairs, even in different solvents. This suggests that the magnetic isolation effects of the carbon cage are not significantly affected by the solvent, the completeness of the carbon cage, or separation of the hydrogens by an oxygen atom.

Exploring the Surface Reactivity of 3d Metal Endofullerenes: A Density-Functional Theory Study

Changes in the preferential sites of electrophilic, nucleophilic, and radical attacks on the pristine C60 surface with endohedral doping using 3d transition metal atoms were studied via two useful reactivity indices, namely the Fukui functions and the molecular electrostatic potential. Both of these were calculated at the density functional BPW91 level of theory with the DNP basis set. Our results clearly show changes in the preferential reactivity sites on the fullerene surface when it is doped with Mn, Fe, Co, or Ni atoms, whereas there are no significant changes in the preferential reactivity sites on the C60 surface upon endohedral doping with Cu and Zn atoms. Electron affinities (EA), ionization potentials (IP), and HOMO-LUMO gaps (Eg) were also calculated to complete the study of the endofullerene's surface reactivity. These findings provide insight into endofullerene functionalization, an important issue in their application.

Thermal Decomposition of C60H18

Products of thermal dehydrogenation of C60H18 (which mainly occurs at 450−600 °C) were studied by XRD, Raman, IR and mass spectrometry. IR spectra indicate that dehydrogenation resulted in partial recovery of pristine C60. XRD data indicate that the cell parameter of the face-centered cubic structure, which is higher for C60H18 (14.55 A) than for C60 (14.17 A), remained higher following heat treatment, and heating at >500 °C caused further expansion (to 14.78 A). The increase in the cell parameter correlates with the beginning of partial fullerene cage collapse (corroborated by IR, Raman and MS data) and is suggested to result from “self-doping”.

Click Coupling Fullerene onto Thermoresponsive Water-Soluble Diblock Copolymer and Homopolymer Chains at Defined Positions

We report on the synthesis of well-defined thermoresponsive water-soluble diblock copolymer and homopolymers functionalized with controlled numbers of C60 moieties at predetermined positions via the combination of atom transfer radical polymerization (ATRP) and click chemistry. Azide-containing polymer precursors including monoazide-terminated and α,α-diazide-terminated poly(N-isopropylacrylamide), N3- PNIPAM and (N3)2-PNIPAM, as well as poly(ethylene glycol)-b-PNIPAM with one azide moiety at the diblock junction, PEG(-N3)-b-PNIPAM, were synthesized via ATRP using specific azide-functionalized small molecule and polymeric initiators. On the other hand, the reaction of 4-prop-2-ynyloxybenzaldehyde with pristine C60 in the presence of glycine afforded alkynyl-modified C60, alkynyl-C60. Subsequently, the click reaction of N3-PNIPAM, (N3)2-PNIPAM, and PEG(-N3)-b-PNIPAM led to the facile preparation of thermoresponsive diblock copolymer and homopolymers functionalized with controlled numbers of C60 at designed positions, including C60-PNIPAM, (C60)2-PNIPAM, and PEG(-C60)-b-PNIPAM. All the intermediate and final products were characterized by 1H NMR, Fourier transform infrared spectroscopy (FT-IR), UV−vis spectroscopy, thermogravimetric analysis (TGA), and gel permeation chromatograph (GPC) equipped with UV/RI dual detectors. C60-containing hybrid nanoparticles were then fabricated via supramolecular self-assembly of C60-PNIPAM, (C60)2-PNIPAM, and PEG(-C60)-b-PNIPAM in aqueous solution, which were characterized by dynamic and static laser light scattering (LLS) and transmission electron microscopy (TEM). These novel fullerenated polymers retain the thermoresponsiveness of PNIPAM-based precursors, and self-assembled hybrid nanoparticles exhibit thermo-induced collapse/aggregation behavior due to the lower critical solution temperature (LCST) phase transition of PNIPAM chains.

Molecular dynamics of fullerene-nanowhiskers studied by solid state NMR

The properties of molecular motion of as-grown C60 nanowhiskers and C70 nanowhiskers were investigated by 13C-CP/MAS NMR, wideline 13C-NMR and '1-NMR techniques. It was confirmed that m-xylene molecules are contained in both C60 and C70 nanowhisekers. It was found that C60 nanowhiskers exhibit an orientational order phase transition at 250 K. The activation energy of C60 molecules below 250 K was evaluated to be 14.7 kJ/mol, which is smaller than that of pristine C60 solid. For C70 nanowhiskers, no clear phase transition was found from 270 K to 170 K. The activation energy of C70 molecules was evaluated to be 13.7 kJ/mol between 270 K and 170 K, which is smaller than that of pristine C70 solid.