Pristine C60 Research Articles

Electrochemical Characterization of Catalytic Activities of C60 Nanowhiskers to Oxygen Reduction in Aqueous Solution

We have investigated the catalytic function and activity of C60 nanowhiskers (C60NWs) on glassy carbon electrodes to the electrochemical O2 reduction in aqueous solution by cyclic voltammetry. It is found that C60NWs are active catalysts for O2 reduction in aqueous solution, although pristine C60 powders do not show any activities. The porous and conductive features of C60NWs play important roles in the electrochemical O2 reduction.

Demonstration of ultrarapid interfacial formation of 1D fullerene nanorods with photovoltaic properties.

We demonstrate ultrarapid interfacial formation of one-dimensional (1D) single-crystalline fullerene C60 nanorods at room temperature in 5 s. The nanorods of ∼ 11 μm in length and ∼ 215 nm in diameter are developed in a hexagonal close-pack crystal structure, contrary to the cubic crystal structure of pristine C60. Vibrational and electronic spectroscopy provide strong evidence that the nanorods are a van der Waals solid, as evidenced from the preservation of the electronic structure of the C60 molecules within the rods. Steady state optical spectroscopy reveals a dominance of charge transfer excitonic transitions in the nanorods. A significant enhancement of photogenerated charge carriers is observed in the nanorods in comparison to pristine C60, revealing the effect of shape on the photovoltaic properties. Due to their ultrarapid, large-scale, room-temperature synthesis with single-crystalline structure and excellent optoelectronic properties, the nanorods are expected to be promising for photosensitive devices applications.

Influence of C60 Aggregation on Pseudorotation in the Excited Triplet State Probed by Multifrequency Time-Resolved EPR

The influence of C60 aggregation on time-resolved (TR) electron paramagnetic resonance (EPR) of C60 in the excited triplet state was investigated by multifrequency EPR techniques. Temperature-independent X-band (9.7 GHz) TR-EPR spectra were observed in a fresh toluene solution, while temperature-dependent ones were reported in literatures. The experimental spectra in this study indicated that the pseudorotation of pristine C60 in frozen toluene solution is not frozen out even at lower temperatures. Careful investigations of TR-EPR and its decay kinetics demonstrated that the pseudorotation can be affected by C60 aggregation. A comparison between X- and W-band (94.9 GHz) results indicated that the aggregation can be accelerated by a capillary effect. Three decay constants were extracted from the analysis of the decay kinetics. The fastest component was ascribed to the pseudorotation, which was independent of temperature in the range of 10–40 K. The temperature dependences of the decay kinetics showed that the pseudorotation is not affected by C60 aggregation at higher temperatures.

Redox reactions of organic C60 derivatives

The redox reactions of organic polyadducts of fullerene R n C60 (R = But, n = 4, 8, 12; R = PhCH2, n = 12) with various oxidants (I2, AgBF4, tetracyanoethylene (TCNE), 3,6-di-tert-butyl-o-benzoquinone, 3,6-di-tert-butyl-4,5-difluoro-o-benzoquinone, C60) and the reductant (potassium) are reported. The oxidation of R n C60 proceeds under mild conditions, in contrast to the oxidation of pristine C60. The formation of radical oxidation products was confirmed by ESR spectroscopy. For But 12C60 the reaction with excess of TCNE leads to further oxidation of the But 12C60 +· radical cation. The reduction of R n C60 with potassium does not occur at room temperature. Only on heating to 60 °C the corresponding radical anions were detected. To explain the experimental results the R n C60 molecules were studied by DFT. The calculations reveal an essential decrease in the ionization energies and electron affinities on going from C60 to R n C60.

Directed assembly of optoelectronically active alkyl-π-conjugated molecules by adding n-alkanes or π-conjugated species.

Supramolecular assembly can yield ordered structures by taking advantage of the cumulative effect of multiple non-covalent interactions between adjacent molecules. The thermodynamic origin of many self-assembled structures in water is the balance between the hydrophilic and hydrophobic segments of the molecule. Here, we show that this approach can be generalized to use solvophobic and solvophilic segments of fully hydrophobic alkylated fullerene molecules. Addition of n-alkanes results in their assembly--due to the antipathy of C60 towards n-alkanes--into micelles and hexagonally packed gel-fibres containing insulated C60 nanowires. The addition of pristine C60 instead directs the assembly into lamellar mesophases by increasing the proportion of π-conjugated material in the mixture. The assembled structures contain a large fraction of optoelectronically active material and exhibit comparably high photoconductivities. This method is shown to be applicable to several alkyl-π-conjugated molecules, and can be used to construct organized functional materials with π-conjugated sections.

Interceptor effect of C60 fullerene on the in vitro action of aromatic drug molecules.

C60 fullerenes are spherical molecules composed purely of carbon atoms. They inspire a particularly strong scientific interest because of their specific physico-chemical properties and potential medical and nanotechnological applications. In this work we are focusing on studying the influence of the pristine C60 fullerene on biological activity of some aromatic drug molecules in human buccal epithelial cells. Assessment of the heterochromatin structure in the cell nucleus as well as the barrier function of the cell membrane was performed. The methods of cell microelectrophoresis and atomic force microscopy were also applied. A concentration-dependent restoration of the functional activity of the cellular nucleus after exposure to DNA-binding drugs (doxorubicin, proflavine and ethidium bromide) has been observed in human buccal epithelial cells upon addition of C60 fullerene at a concentration of ~10(-5 )M. The results were shown to follow the framework of interceptor/protector action theory, assuming that non-covalent complexation between C60 fullerene and the drugs (i.e., hetero-association) is the major process responsible for the observed biological effects. An independent confirmation of this hypothesis was obtained via investigation of the cellular response of buccal epithelium to the coadministration of the aromatic drugs and caffeine, and it is based on the well-established role of hetero-association in drug-caffeine systems. The results indicate that C60 fullerene may reverse the effects caused by the aromatic drugs, thereby pointing out the potential possibility of the use of aromatic drugs in combination with C60 fullerene for regulation of their medico-biological action.

On the Origin of C60 Fullerene Solubility in Aqueous Solution

In this work, we report that the surface hydroxylation of C60 molecules is the most likely mechanism for pristine C60 fullerenes/C60 fullerene aggregate stabilization in water, being independent of the method of C60 fullerene aqueous solution preparation.

Water-soluble inclusion complex of fullerene with γ-cyclodextrin polymer for photodynamic therapy.

A stable aqueous inclusion complex of fullerene (C60) with macromolecules (C60 concentration as high as 3 × 10-4 mol L-1) was achieved by a one-step strategy using γ-cyclodextrin polymer (γ-CDP). The inclusion complex of C60 with γ-CDP (C60-γ-CDP) was characterized by ultraviolet-visible, Raman and 1H-NMR spectroscopies, powder X-ray diffraction analysis, and thermogravimetric analysis. The supramolecular interactions and the equilibrium constant for a 1 : 2 (C60 : CD unit in γ-CDP) complex of C60 with γ-CDP were studied. Under ultraviolet A (UVA) irradiation C60-γ-CDP in water could generate singlet oxygen, which was detected by electron paramagnetic resonance spectroscopy. We also evaluated the cytotoxicities of C60-γ-CDP, and investigated the phototoxicity of C60-γ-CDP and pristine C60 toward B16-F10 melanoma cells. The cell viability test showed that C60-γ-CDP had a significantly higher photodynamic ability than that of the pristine C60 under UVA irradiation. This work demonstrated both a CDP-functionalized strategy for enhancing the water-solubility and phototoxicity of fullerenes for applications in cancer photodynamic therapy, as well as remediating the negative biological effects of pristine fullerenes.

Highly efficient organic solar cells using a solution-processed active layer with a small molecule donor and pristine fullerene

Efficient SMOSCs with a solution-processed active layer composed of organic compounds without long alkyl chains as donors and pristine C70 as the acceptor have been successfully achieved by spin- and bar-coating methods.

C60 FULLERENE EFFECT ON THE DYNAMICS OF FATIGUE PROCESSES IN RAT SOLEUS MUSCLE AFTER ISCHEMIA-REPERFUSION

43 The purposeful application of bio compatible nanomaterials of low toxicity is a relevant problem in modern biotechnology. It is assumed that the use of nanoparticles will help to solve the problems of early disease diagnostics and targeted delivery of drugs into tissues and cells, as well as new methods of selective therapies. C60 fullerene has a prominent position among other potentially effective therapeutic agents [1]. It is known that C60 molecule normalizes cellular metabolism and neural processes, increases resistance to stress, exhibits antiviral properties, has pronounced anti-inflammatory and anti-allergic effects, enhances activity of enzymes and regenerative capacity of tissues [1]. Finally, C60 fullerene and its derivatives can be used for the treatment of cancer [2–4]. C60 fullerene can be readily dissolved in organic solvents, yet it is practically insoluble in water [5]. Poor solubility in water severely hampers investigation of physiological and pharmacological effects of C60 fullerene. As a consequence, a number of C60 fullerene derivatives with better solubility in polar solvents have been synthesized to date [5–6]. Pristine C60 fullerene aqueous solution (С60FAS) has been received by transferring C60 molecules from toluene to water followed by sonication [7–8]. The dark brown solution was identified to be a typical colloid system containing a single C60 molecule and spherical clusters with the diameter of 2–3 nm or more (depending on the C60 fullerene concentration in water) in a hydrated state [7–9]. Due to its nanoscale dimensions, the watersoluble pristine C60 fullerene can penetrate the cell membrane [10]. Toxicity is a major concern for the use of C60 fullerene-containing drugs for biomedical УДК 546.26.043

Alkali-Metal Trichloroacetates for Dichloromethylenation of Fullerenes: Nucleophilic Addition-Substitution Route

The first experimental evidence that fullerenes react with alkali-metal trichloroacetates through a nucleophilic addition-substitution route, yielding dichloromethylenefullerenes as the final products, is reported. The intermediates, C60 (CCl3 )(-) and C70 (CCl3 )(-) anions, have been isolated in their protonated forms as ortho-C60 (CCl3 )H, as well as three ortho and one para isomer of C70 (CCl3 )H. The structures were unambiguously determined by means of (1) H, (13) C, and (1) H-(13) C HMBC NMR spectroscopy along with UV/Vis spectroscopy. The observed regiochemistry was analyzed with the aid of quantum chemical calculations. Conversion of the protonated compounds into the [6,6]-closed C60/70 (CCl2 ) cycloadducts under basic conditions can be effected only for the ortho isomers, whereas para-C70 (CCl3 )H decomposes back into pristine C70 .

Encapsulation of pristine fullerene C60 within block copolymer micelles through interfacial instabilities of emulsion droplets

We report a facile and versatile strategy to encapsulate pristine fullerene (C60) within spherical or wormlike block copolymer micelles through interfacial instability of emulsion droplets. C60 and amphiphilic block copolymer polystyrene-b-poly(ethylene oxide) were firstly dispersed in chloroform. The resulting solution was emulsified with aqueous sodium dodecylsulfate solution by simply shaking it. The emulsion droplets were collected in an open container and the solvent was allowed to evaporate. During solvent evaporation, the emulsion droplets became unstable and broke into tiny droplets, i.e., interfacial instabilities occurred, triggering the formation of uniform spherical micelles with encapsulated fullerenes in the micellar cores. More interestingly, fullerene addition induced a morphological transition from cylindrical micelles to string-of-vesicles and then to spherical micelles with increasing fullerene contents of 5wt%, 10wt%, and 30wt%, respectively. We show that the optical properties of the confined C60 molecules can be modified by varying the quantity of fullerenes in the micelles. In addition, poly(3-hexylthiophene) (P3HT) can be co-encapsulated with C60 into the micellar cores when P3HT was dissolved in the initial polymer solution prior to emulsification. Presence of C60 in the micellar cores induced fluorescence quenching of P3HT due to photoinduced energy transfer from electron-donating P3HT to electron-accepting C60 molecules. Hybrid micelles with well-controlled structures and components can be potentially useful in the area of photodynamic therapy and photovoltaics.

Largely enhanced thermal and mechanical properties of polymer nanocomposites via incorporating C60@graphene nanocarbon hybrid

Although considerable progress has been achieved to create advanced polymer nanocomposites using nanocarbons including fullerene (C60) and graphene, it remains a major challenge to effectively disperse them in a polymer matrix and to fully exert their extraordinary properties. Here we report a novel approach to fabricate the C60@graphene nanocarbon hybrid (C60: ∼47.9 wt%, graphene: ∼35.1%) via three-step reactions. The presence of C60 on a graphene sheet surface can effectively prevent the aggregation of the latter which in turn helps the dispersion of the former in a polymer matrix during melt-processing. C60@graphene is found to be uniformly dispersed in a polypropylene (PP) matrix. Compared with pristine C60 or graphene, C60@graphene further improves the thermal stability and mechanical properties of PP. The incorporation of 2.0 wt% C60@graphene (relative to PP) can remarkably increase the initial degradation temperature by around 59 ° C and simultaneously enhance the tensile strength and Young’s modulus by 67% and 76%, respectively, all of which are higher than those of corresponding PP/C60 (graphene) nanocomposites. These significant performance improvements are mainly due to the free-radical-trapping effect of C60, and the thermal barrier and reinforcing effects of graphene nanosheets as well as the effective stress load transfer. This work provides a new methodology to design multifunctional nanohybrids for creating advanced materials.

6,6]-Open and [6,6]-Closed Isomers of C70(CF2): Synthesis, Electrochemical and Quantum Chemical Investigation

Novel difluoromethylenated [70]fullerene derivatives, C70(CF2 )n (n=1-3), were obtained by the reaction of C70 with sodium difluorochloroacetate. Two major products, isomeric C70(CF2 ) mono-adducts with [6,6]-open and [6,6]-closed configurations, were isolated and their homofullerene and methanofullerene structures were reliably determined by a variety of methods that included X-ray analysis and high-level spectroscopic techniques. The [6,6]-open isomer of C70(CF2 ) constitutes the first homofullerene example of a non-hetero [70]fullerene derivative in which functionalisation involves the most reactive bond in the polar region of the cage. Voltammetric estimation of the electron affinity of the C70(CF2 ) isomers showed that it is substantially higher for the [6,6]-open isomer (the 70-electron π-conjugated system is retained) than the [6,6]-closed form, the latter being similar to the electron affinity of pristine C70. In situ ESR spectroelectrochemical investigation of the C70(CF2 ) radical anions and DFT calculations of the hyperfine coupling constants provide evidence for the first example of an inter-conversion between the [6,6]-closed and [6,6]-open forms of a cage-modified fullerene driven by an electrochemical one-electron transfer. Thus, [6,6]-closed C70(CF2 ) constitutes an interesting example of a redox-switchable fullerene derivative.

Low-LUMO 56π-electron fullerene acceptors bearing electron-withdrawing cyano groups for small-molecule organic solar cells

56π-Electron fullerene derivatives with electron-withdrawing cyano groups were synthesized by the reaction of 58π-electron fullerenes with NaCN, followed by in situ treatment with TsCN or MeOTf. The fullerene derivatives have low-lying LUMO levels, which are comparable with or lower than that of pristine C60. They were used as solution-processable electron acceptors in small-molecule organic solar cells that showed a maximum power conversion efficiency of 2.0% (JSC=7.05mA/cm2, VOC=0.62V and FF=0.45) using chloroindium phthalocyanine as an electron donor.

Cyclodextrin complexed [60]fullerene derivatives with high levels of photodynamic activity by long wavelength excitation.

We have evaluated the photodynamic activities of C60 derivative·γ-cyclodextrin (γ-CDx) complexes and demonstrated that they were significantly higher than those of the pristine C60 and C70·γ-CDx complexes under photoirradiation at long wavelengths (610-720 nm), which represent the optimal wavelengths for photodynamic therapy (PDT). In particular, the cationic C60 derivative·γ-CDx complex had the highest photodynamic ability because the complex possessed the ability to generate high levels of (1)O2 and provided a higher level of intracellular uptake. The photodynamic activity of this complex was greater than that of photofrin, which is the most widely used of the known clinical photosensitizers. These findings therefore provide a significant level of information toward the optimization of molecular design strategies for the synthesis of fullerene derivatives for PDT.

Structural and electronic properties of pyrrolidine-functionalized [60]fullerenes

We have investigated energetic, geometric, electronic, and field emission properties of three recently synthesized fulleropyrrolidines based on the density functional theory method B3LYP/6-31G(d). Fulleropyrrolidines show higher conductivity, and solubility in water, and smaller work function in comparison with the pristine C60 fullerene. The functionalization of C60 with different pyrrolidines containing 3NH2, NO, or NO2 groups transforms it to an n-type semiconductor. The functionalization can also dramatically enhance the electrophilicity of the C60 about 23–37%. Moreover, it should be mentioned that the work function is mainly influenced by the pyrrolidine containing 3NO2 group whereas the conductivity is largely affected by the one containing 3NH2 functionality.

Nanostructured Few-Layer Graphene with Superior Optical Limiting Properties Fabricated by a Catalytic Steam Etching Process

Tailoring the morphology and structure of graphene can result in novel properties for advanced applications. Here, we demonstrate the fabrication of nanostructured few-layer graphene through a mild etching process via catalytic steam gasification of carbon by Fe nanoparticles (NPs). Controlling the reaction temperature, steam concentration, and the loading density of the NPs enables the fine-tuning of the etching level of graphene. Well-defined nanotrenches with a width of less than 25 nm were formed by channeling of the catalytic NPs. Etching caves and quasi-semicircular etched edges were observed as well. The nonlinear optical properties of the resulting nanostructured graphene were studied under a 532 nm nanosecond pulse laser through an open-aperture apparatus. At the same level of the linear extinction coefficient, it exhibits superior optical limiting performance in comparison with pristine graphene and C60, showing a large potential in nanophotonic devices. This enhancement is ascribed to the defec...

Effect of fullerene C(60) on ATPase activity and superprecipitation of skeletal muscle actomyosin

Creation of new biocompatible nanomaterials, which can exhibit the specific biological effects, is an important complex problem that requires the use of last accomplishments of biotechnology. The effect of pristine water-soluble fullerene C60 on ATPase activity and superprecipitation reaction of rabbit skeletal muscle natural actomyosin has been revealed, namely an increase of actomyosin superprecipitation and Мg2+, Са2+– and K+-ATPase activity by fullerene was investigated. We conclude that this finding offers a real possibility for the regulation of contraction-relaxation of skeletal muscle with fullerene C60.

Photoconductivity as loss mechanism in organic solar cells

AbstractWe observe that the reverse current under illumination in solar cells containing C60 and ZnPc is dominated by a photoshunt. This shunt, not present in the dark, causes a linear current–voltage relation under illumination showing no saturation. Although observable in bulk heterojunctions, this effect is more pronounced in the presence of a pristine C60 layer. An internal quantum efficiency larger than unity under an applied negative voltage and in the spectral range where C60 absorbs identifies charges which are injected in addition to those photogenerated. The photoshunt is also present in the power‐generating region and represents a loss mechanism limiting the fill factor in particular for flat heterojunction devices. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)