Pristine C60 Research Articles

Protective effect of pristine C60 fullerene nanoparticle in combination with curcumin against hyperglycemia-induced kidney damage in diabetes caused by streptozotocin.

The present study aims to examine the protective effects of C60 fullerene (C60), Curcumin (CUR; Curcuma longa), C60+CUR combination against oxidative stress, apoptosis, and changes in cellular level in kidney tissue of diabetic rats. Treatment practices were administered separately to groups for 8weeks following the approval of diabetes induction. It was observed that the treatment groups had increased antioxidant potential, decreased oxidative stress levels, decreased cholesterol, alpha tocopherol, retinol levels along with improved important changes in fatty acid metabolism compared with the diabetic group. C60, CUR, and C60+CUR were also determined to act in the direction of reducing kidney damage by activating apoptotic pathways. It can be concluded based on these findings that C60, CUR, and especially C60+CUR combination has beneficial properties in maintaining kidney tissue and function by effectively preventing oxidative stress, apoptotic changes, and changes at the cellular level in kidney tissue under hyperglycemia conditions. PRACTICAL APPLICATIONS: C60 and CUR have various biological activities which can be indicated as antioxidant, anti-inflammatory, anticancer, neuroprotective, and hepatoprotective. It has been reported that C60 and CUR protect the cells against oxidative injury brought about by reactive oxygen species (ROS). Data acquired from the present study puts forth that C60 and C60+CUR may be promising agents to prevent damage induced by hyperglycemic conditions in kidney tissue.

Water-Soluble Pristine C60 Fullerene Inhibits Liver Alterations Associated with Hepatocellular Carcinoma in Rat

Excessive production of reactive oxygen species is the main cause of hepatocellular carcinoma (HCC) initiation and progression. Water-soluble pristine C60 fullerene is a powerful and non-toxic antioxidant, therefore, its effect under rat HCC model and its possible mechanisms were aimed to be discovered. Studies on HepG2 cells (human HCC) demonstrated C60 fullerene ability to inhibit cell growth (IC50 = 108.2 μmol), to induce apoptosis, to downregulate glucose-6-phosphate dehydrogenase, to upregulate vimentin and p53 expression and to alter HepG2 redox state. If applied to animals experienced HCC in dose of 0.25 mg/kg per day starting at liver cirrhosis stage, C60 fullerene improved post-treatment survival similar to reference 5-fluorouracil (31 and 30 compared to 17 weeks) and inhibited metastasis unlike the latter. Furthermore, C60 fullerene substantially attenuated liver injury and fibrosis, decreased liver enzymes, and normalized bilirubin and redox markers (elevated by 1.7–7.7 times under HCC). Thus, C60 fullerene ability to inhibit HepG2 cell growth and HCC development and metastasis and to improve animal survival was concluded. C60 fullerene cytostatic action might be realized through apoptosis induction and glucose-6-phosphate dehydrogenase downregulation in addition to its antioxidant activity.

Hydrogen Adsorption on Ru-Encapsulated, -Doped and -Supported Surfaces of C60

Hydrogen is considered as one of the promising clean energy sources for future applications including transportation. Nevertheless, the development of materials for its storage is challenging particularly as a fuel in vehicular transport. In the present study, density functional theory simulations for hydrogen adsorption on the surfaces of pristine, Ru-encapsulated, -doped and -supported C60 are reported. The results show that adsorption on the pristine C60 is exoergic and there is an enhancement in the adsorption upon encapsulation of a single Ru atom. The Ru-doped surface also adsorbs H2 more strongly than the pristine surface, but its efficacy is slightly less than the Ru-encapsulated surface. The strongest adsorption is calculated for the C60 surface supported with Ru.

Electron-beam irradiation of photopolymerized C60 film studied using in situ scanning tunneling microscope, in situ Fourier-transform infrared spectroscopy, and first-principles calculations

We have examined the formation of a two-dimensional (2D) new carbon network by inducing the general Stone–Wales transformation between adjacent C60 molecules in a 2D dumbbell-type C60 polymer film. Structural changes in pristine C60 films after ultraviolet-visible (UV-vis) light and electron-beam (EB) irradiations were studied using in situ scanning tunneling microscope (STM) and in situ Fourier-transformed infrared (IR) spectroscopy, in combination with first-principles calculations based on density functional theory. Analyses of STM images and depth profiles found that three types of photopolymerized dumbbell-shaped dimers and trimers are formed on the surface layers of pristine C60 films: (i) [2+2] C60 dimers formed in a lateral direction, (ii) [2+2] dimerization of C60 between the first and second layers, and (iii) a triangular [2+2] C60 trimer along a lateral direction. As UV-vis light irradiation time increases, a comparison between experimental and theoretical IR spectra indicated that 2D dumbbell-shaped C60 polymers are formed within a few surface layers of the C60 film (in a similar manner, a 1D dumbbell-shaped polymer is also formed in a shallow space of the C60 film), whereas a [2+2] dumbbell-shaped dimer is formed in any bulk space of the film. Thereafter, when the EB was irradiated to the photopolymerized C60 film, the evolution of IR spectra with respect to EB irradiation time suggested that the 2D dumbbell-type C60 polymer is not decomposed but structurally changed to form a new network polymer.

Pristine C60 Fullerene Nanoparticles Ameliorate Hyperglycemia-Induced Disturbances via Modulation of Apoptosis and Autophagy Flux.

Diabetes mellitus is a prevalent metabolic disorder associated with multiple complications including neuropathy, memory loss and cognitive decline. Despite a long history of studies on diabetic complications, there are no effective therapeutic strategies for neuroprotection in diabetes. Hyperglycemia-induced imbalance in programmed cell death could initiate a decline in neural tissue cells viability. Various nanomaterials can induce either cell death or cell survival dependent on the type and surface features. Pristine C60 fullerene is a nontoxic nanomaterial, which exhibits antioxidant and cytoprotective properties. However, the precise molecular mechanism with which the C60 nanoparticle exerts cytoprotective effect in diabetic subjects has not yet been fully addressed. Thus, this study aimed to determine whether C60 fullerene prevents oxidative stress impairment and to explore the effects of C60 fullerene on apoptosis and autophagy in diabetes mellitus to clarify its potential mechanisms. These effects have been examined for olive oil extracted C60 fullerene on the hippocampus of STZ diabetic rats. Up-regulation of Caspase-3, Beclin-1 and oxidative stress indexes and down-regulation of Bcl-2 were observed in the brain of STZ-diabetic rats. The exposure to C60 fullerene for a period of 12weeks ameliorate redox imbalance, hyperglycemia-induced disturbances in apoptosis and autophagy flux via modulation of Caspase-3, Bcl-2, Beclin-1 and LC3I/II contents. Furthermore, C60 fullerene ameliorated the LC3I/II ratio and prevented extremely increased autophagy flux. Contrarily, pristine C60 fullerene had no modulatory effect on all studied apoptotic and autophagy markers in non-diabetic groups. Therefore, oil extracted C60 fullerene exhibits cytoprotective effect in hyperglycemia-stressed hippocampal cells. The presented results confirm that pristine C60 fullerene nanoparticles can protect hippocampal cells against hyperglycemic stress via anti-oxidant, anti-apoptotic effects and amelioration of autophagy flux. Moreover, C60 fullerene regulates a balance of autophagy via BCL-2/Beclin-1 reciprocal expression that could prevent functional disturbances in hippocampus.

Evaluation of the Biocompatibility of Water-Soluble Pristine С60 Fullerenes in Rabbit

C60 fullerenes have proved their therapeutic effects and efficacy by the results of countless experiments. For further usage of these nanoparticles, the systematic toxicological investigations are required. Blood compatibility should be studied for C60 fullerenes due to the potential blood contact. Currently, available data is not systematic and has not provided insights into possible side effects of C60 fullerenes on blood components. In this study, water-soluble pristine C60 fullerenes were tested in vitro to assess their biocompatibility in rabbit. The blood compatibility has been evaluated looking at the impact of C60 fullerenes on erythrocyte integrity, platelet aggregation, and some blood factors involved in coagulation. Our results revealed that C60 fullerenes cannot elicit hemolysis at studied concentrations and did not show any effect on coagulation process. C60 fullerenes in concentration-dependent manner increased ADP-dependent platelet aggregation and changed the key kinetic parameters of these processes. C60 fullerenes inhibited thrombin amidolytic activity but did not affect the activities of other studied coagulation factors. The prothrombotic property of C60 fullerenes could be the potential risk factor that leads to enhancement of vascular thrombosis. The ability of fullerene to inhibit thrombin activity is important for the pharmacological use of these carbon nanoparticles as anticoagulant agents.

Vortex-Aligned Ordered Film of Crystalline Fullerene C70 Microtubes with Enhanced Photoluminescence and Photovoltaics Properties

Crystalline fullerene C70 microtubes (FMTs) were produced employing ultrasound-assisted liquid- liquid interfacial precipitation (ULLIP) technique at the interface between fullerene C70 solution in 1,2 dichlorobenzene (DCB) and isopropanol (IPA) at 15 °C. Using the vortex-flow motion of the subphase water (also called Vortex-Langmuir-Blodgett technique), the FMTs were aligned and homogeneous films were prepared at the air-water interface. The aligned FMTs film exhibited enhanced photoluminescence (PL) with PL intensity ~5 times higher than that of the pristine C70. Moreover, the aligned FMT film showed better photovoltaics properties compared with randomly oriented FMTs and pristine C70 film obtained from the spin coating. The compact, directional orientation and proper surface coverage of the FMT film enhanced the charge transport properties in the photovoltaic device.

Synthesis and Characterization of Supramolecules of Li + @C60 and Fluorinated Porphyrins

Metal endohedral [60]fullerenes (M@C60) have a unique structure encapsulating a metal atom (M) inside the π−conjugated spherical C60 cage. Lithium cation endohedral fullerene (Li + @C60) is a commercially available M@C60 and has a potential for application in nano material fields. The cationic Li+@C60 crystallizes with weakly coordinated anions such as SbCl6 − [1], PF6 − [2], Tetrakis[3,5-bis(trifluoromethyl)phenyl]borate anion (TFPB−) [3], and bis(trifluoromethanesulfonyl)imide anion (TFSI−) [3]. Due to the inside Li+ cation, the first reduction potential of Li+@C60 is shifted to positive direction by 0.7 eV than that of pristine C60. As a result, Li+@C60 has larger electron acceptability than C60 [1]. Li+@C60 also forms a guest–host type supramolecule with [10]cycloparaphenylene ([10]CPP) [4] and π−π stacking supramolecules with porphyrins or phthalocyanines [5][6]. A supramolecule of Li+@C60 and 5,10,15,20-tetrakis(4–sulfonatophenyl) zinc porphyrin anion (ZnTPPS4 –), [Li+@C60 – ZnTPPS4 –] with the binding constant of ca. 105 M– 1 shows a long−lived electron charge separation state by photoinduced electron transfer and can be used in photovoltaic cells [5]. The [Li+@C60 – ZnTPPS4 –] based photovoltaic cell shows maximum incident photon-to-photocurrent efficiency (IPCE) value of 78% under the certain condition [7]. The performance of the photovoltaic cells would be changed by the chemical modification of porphyrins.Here, we synthesized two kinds of porphyrins to obtain new supramolecules of Li+@C60. The first one is neutral 5,10,15,20-Tetrakis(1,2,4,5-tetrafluorophenyl) porphyrin (H2TTFPP). H2TTFPP was synthesized by Lindsey method and characterized by 1H NMR, 19F NMR, UV-vis, CV, DPV, and XRD. The second one is anionic 5,10,15,20-Tetrakis(4-carboxymethylthio-2,3,5,6-tetrafluorophenyl) zinc porphyrin tetrabutylammonium (ZnTFPP4TC4 −4TBA+). ZnTFPP4TC4 −4TBA+ was synthesized according to the modified Lourenço method [8] and characterized by 1H NMR, 19F NMR, UV-vis, CV, and DPV.H2TTFPP was confirmed to form supramolecular structure with Li+@C60 in the co-crystal by X-ray structure analysis. ZnTFPP4TC4 − was confirmed to form a supramolecule with Li+@C60 in solution by UV-vis titration experiment. The binding constant of [ZnTFPP4TC4 − − Li+@C60] is significantly larger than that of [H2TTFPP − Li+@C60] because of strong coulomb interactions between anionic ZnTFPP4TC4 − and cationic Li+@C60.

Quenching induced enhancement of coupling between the molecule reorientation and grain boundary relaxation in polycrystalline C60

Dielectric spectroscopy was performed on polycrystalline C60 powder at selected frequencies from 111 Hz to 2 MHz as the temperature rose from 100 K to 473 K. About 3 K increase of the first-order phase transition temperature caused by quenching was observed, but disappeared in the second heating cycle. The apparent activation energy of dipole relaxation in low temperature range increases to 387 ± 4 meV which is 19 meV higher than that of pristine C60. Meanwhile, a novel grain boundary (GB) relaxation was also found in the quenched C60. It is suggested that quenching increase the GB viscosity, which facilitates the coupling between the GB motion and C60 orientation jump.

Fullerene-induced crystallization toward improved mechanical properties of solvent casting polycarbonate films

This work provides a facile strategy to induce crystallization of polycarbonate (PC) through solvent casting method. Pristine fullerene (C60) and PC-modified C60 nanoparticles are applied as nucleating agents for PC, and the crystallization behavior of PC nanocomposite films is controlled by solvent casting preparation conditions. To investigate the relationship between crystallization behavior and mechanical properties of PC nanocomposite films, X-ray diffraction, differential scanning calorimetry, polarizing microscope and tensile tests are carried out. Pristine C60 can only induce the formation of bulk PC spherocrystals which have no help or even deteriorates the mechanical properties of PC/C60 nanocomposite films. By contrast, the PC-modified C60 achieves uniformly disperse in the matrix and induces the formation of microcrystalline structures. It is found that appropriate degree of crystallinity for the PC/modified C60 nanocomposite films can effectively improve the mechanical properties. Typically, the PC/0.50 wt%-modified C60 nanocomposite films prepared under 40 °C by tetrahydrofuran exhibits up to a 33% increment in tensile strength and 45% increment in Young’s modulus compared to neat PC films.

Exohedral Cuprofullerene: Sequentially Expanding Metal Olefin Up to a C60@Cu24 Rhombicuboctahedron

Exohedral cuprofullerenes with 6-, 12-, or 24-nuclearity were obtained by utilizing fluorocarboxylic/dicarboxylic acid under solvothermal conditions. The 24-nuclear molecule presents a C60@Cu24 core-shell structure with a rhombicuboctahedron Cu24 coated on a C60 core, representing the highest nuclearity in metallofullerene. The resultant complexes show an efficient absorption of visible light as opposed to the pristine C60. DFT calculations revealed the charge transfer from Cu(I) and O at-oms to fullerene moiety dominate the photophysical process.

Quantitative Mono‐Formation and Crystallographic Characterization of Pyrazole‐ and Pyrrole‐Ring Fused Derivatives of C60

Nitrogen‐heterocyclic fullerene derivatives have received great interest in the past years due to their potential biological activities and optical properties. Herein, we report a quantitative mono‐formation of the pyrazole‐ and pyrrole‐ring fused derivatives of fullerene C60, i.e., C60 (C13N2H10) (3) and C60 (C9NH11) (4), from the respective reactions between C60 and diphenylnitrilimine (1) and N‐benzylazomethine ylide (2). Single‐crystal X‐ray diffraction (XRD) crystallographic results unambiguously confirm the formation of [6,6]‐closed derivatives (3 and 4). Interestingly, the intermolecular π–π interactions between the phenyl groups and C60 spheres are observed in the crystal of 3, but they are absent from 4, indicating that the number of the external phenyl groups has an important influence on the stacking pattern of derivatives during crystallization. Electrochemical results show that the reduction potentials of 3 are positively shifted compared with the corresponding values of pristine C60, while the reduction potentials of 4 are all cathodically shifted, revealing the redox processes of C60 can be selectively modulated by changing the structures of the addends. Notably, our theoretical results demonstrate that the quantitative formation of merely one mono‐adduct without any bis‐ or multi‐adducts detected in both reactions is a direct result from the steric hindrance of the existing bulky pyrazole‐ or pyrrole‐ring moiety on the C60 cage. This work thus presents a quantitative way for the mono‐formation of the pyrrole‐ and pyrazole‐ring fused derivatives of C60, which are potentially useful as organic photovoltaic devices and biological reagents.

Water-Soluble Pristine C60 Fullerenes Inhibit Liver Fibrotic Alteration and Prevent Liver Cirrhosis in Rats.

Liver cirrhosis is an outcome of a wide range of liver chronic diseases. It is attributed to oxidative stress; therefore, antioxidant usage could be a promising treatment of that. So, exploring the impact of effective free radical scavenger pristine C60 fullerenes on liver fibrosis and cirrhosis and their ability to interact with main growth factor receptors involved in liver fibrogenesis was aimed to be discovered. We used N-diethylnitrosamine/carbon tetrachloride-induced simulations of rat liver fibrosis (10 weeks) and cirrhosis (15 weeks). Pristine C60 fullerene aqueous colloid solution (C60FAS) was injected daily at a dose of 0.25 mg/kg throughout the experiment. Liver morphology and functional and redox states were assessed. C60 fullerenes' ability to interact with epidermal, vasoendothelial, platelet-derived, and fibroblast growth factor receptors (EGFR, VEGFR, PDGFR, and FGFR, respectively) was estimated by computational modeling. We observed that C60FAS reduced the severity of fibrosis in fibrotic rats (0.75 vs. 3.0 points according to Ishak score), attenuated the hepatocyte injury, normalized elevated blood serum alkaline phosphatase (ALP) and lactate dehydrogenase (LDH), and mitigated oxidative stress manifestation in liver tissue restoring its redox balance. When applied to cirrhotic animals, C60FAS reduced connective tissue deposition as well (2.4 vs. 5.4 points according to Ishak score), diminished ALP and LDH (by 16% and 61%), and normalized conjugated and nonconjugated bilirubin, restoring the liver function. Altered liver lipid and protein peroxides and glutathione peroxidase activity were also leveled. Within a computer simulation, it was shown that C60 fullerenes can block hinge prohibiting ATP binding for EGFR and FGFR and thus blocking associated signal pathways. This ability in addition to their antioxidant properties may contribute to C60 fullerene's antifibrotic action. Thus, C60FAS may have a substantial therapeutic potential as an inhibitor of liver fibrosis and cirrhosis.

Pristine and Hydroxylated Fullerenes Prevent the Aggregation of Human Islet Amyloid Polypeptide and Display Different Inhibitory Mechanisms.

Protein aggregation, involving the formation of dimers, oligomers, and fibrils, is associated with many human diseases. Type 2 diabetes is one of the common amyloidosis and linked with the aggregation of human islet amyloid polypeptide (hIAPP). A series of nanoparticles are reported to be able to interact with proteins and enhance/inhibit protein aggregation. However, the effects of C60 (a model system of hydrophobic nanoparticle) and C60(OH)8 (a hydroxylated fullerene) on hIAPP aggregation remain unknown. In this study, we investigate the influences of pristine fullerene C60 and hydroxylated C60 on the dimerization of hIAPP using molecular dynamics (MD) simulations. Extensive replica exchange molecular dynamics (REMD) simulations show that isolated hIAPP dimers adopt β-sheet structure containing the amyloid-precursor (β-hairpin). Both C60 and C60(OH)8 notably inhibit the β-sheet formation of hIAPP dimer and induce the formation of collapsed disordered coil-rich conformations. Protein—nanoparticle interaction analyses reveal that the inhibition of hIAPP aggregation by C60 is mainly via hydrophobic and aromatic-stacking interactions, while the prevention of hIAPP aggregation by C60(OH)8 is mostly through collective hydrogen bonding and aromatic-stacking interactions. Conventional MD simulations indicate that both C60 and C60(OH)8 weaken the interactions within hIAPP protofibril and disrupt the β-sheet structure. These results provide mechanistic insights into the possible inhibitory mechanism of C60 and C60(OH)8 toward hIAPP aggregation, and they are of great reference value for the screening of potent amyloid inhibitors.

Probing the Catalytic Activity and Poisoning-Tolerance Ability of Endohedral Metallofullerene Fen@C60 (n = 1−7) Catalysts in the Oxygen Reduction Reaction

In this paper, the oxygen reduction reaction catalytic activity and poisoning-tolerance ability of endohedral metallofullerene Fen@C60 (n = 1−7) catalysts are investigated by using DFT calculations. The calculation predicts very low catalytic activity of the pristine C60 fullerene, but significant activity enhancement is obtained when encapsulating iron clusters into C60 cage due to improved energy gaps between the highest occupied molecular orbital and the lowest unoccupied molecular orbital. With the increase of the size of encapsulated Fen cluster, the adsorption energies of all the oxygen reduction intermediates, such as OOH, O, and OH, become jointly stronger. Among all the screened Fen@C60 (n = 1−7) catalysts, Fe3@C60 possesses the highest oxygen reduction activity, with a predicted limiting potential of about 0.73 V that is comparable to that of Pt(111) surface (0.78 V). The limiting potentials for Fe2@C60, Fe4@C60 and Fe5@C60 are also relatively high, with the values of 0.64, 0.69, and 0.64 V, respectively. In addition, the above screened Fen@C60 catalysts also exhibit excellent poisoning-tolerance ability to SO2, H2S, CO, NO, and NH3 species, which is originated from the unstable physisorption interaction between these species and the catalysts that is completely different from the case of the easily poisoned Pt catalyst.

A DFT study on the detection of isoniazid drug by pristine, Si and Al doped C70 fullerenes

Abstract Using density functional theory calculations, the electronic sensitivity and reactivity of pristine, Al and Si doped C70 fullerenes are inspected toward anti-tuberculosis isoniazid (IS) drug. We found that the IS prefers to be physically adsorbed on the pristine C70 via its O-head with adsorption energy about −1.3 kcal/mol and no effect on the C70 electrical conductivity. Substituting a C atom of C70 by Al and Si atoms, the C70 reactivity meaningfully increases, and the predicted adsorption energies are about −67.9 and −51.3 kcal/mol, respectively. The HOMO-LUMO gap (Eg) and work function of Al–C70 are not sensibly affected by the IS drug. While because of a large HOMO destabilization in the Si–C70 upon the IS adsorption, the Eg of Si–C70 largely decreases from 2.24 to 1.12 eV, increasing its electrical conductivity which can generate an electrical signal. This signal is connected to the presence of IS in the environment. Therefore, we concluded that the Si–C70 may be a promising electronic sensor for the IS drug detection. Similar to the case of Al–C70, the Fermi level and work function of Si–C70 are not sensibly affected by IS adsorption, indicating that the Si–C70 can be used only as an electronic sensor not a work function type sensor.

Fabrication of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide-decorated fullerene to improve the anti-oxidative and flame-retardant properties of polypropylene

Fullerene (C60) is readily to capture chain radicals and delays the scission of macromolecular chains during the degradation or combustion of polymers, because of its high reactivity with free radicals. In this work, C60 was functionalized with 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO), trying to combine their free radical-trapping effects both in gaseous phase and in condensed phase. Through an addition reaction between C60 and DOPO, DOPO has decorated onto the surface of C60via P–H bond at the molar ratio of 1:1. From the images of transmission electron micrographs (TEM) and scanning electron microscopy (SEM), the introduction of DOPO onto C60 surface prevented C60 from clumping together and achieved a looser morphology. Thermogravimetry (TG), differential scanning calorimetry (DSC) and cone calorimetry measurements showed that compared with pristine C60, DOPO-d-C60 further increased the anti-oxidative properties and restrained the combustion process of polypropylene.

Simultaneous Unlocking Optoelectronic and Interfacial Properties of C60 for Ultrasensitive Immunosensing by Coupling to Metal-Organic Framework.

Due to exceptional electron-accepting ability, light-absorption, and a delocalized conjugated structure, buckminsterfullerene (C60) has attracted fascinating interest in the field of organic solar cells. However, poor delocalization and accumulation of electrons for pristine C60 in physiological aqueous solution and difficulties in conjugation with biomolecules limit its extended photovoltaic applications in bioassay. Herein, we reported the noncovalent coupling of C60 to an electronically complementary porphyrin-derived metal-organic framework (PCN-224) with carboxyl-group terminals. Such assembly not only offered a friendly interface for bioconjugation but also resulted in a long-range ordering C60@PCN-224 donor-acceptor system that demonstrated an unprecedented photocurrent enhancement up to 10 times with respect to each component. As an example, by further cooperating with Nanobodies, the as-prepared C60@PCN-224 was applied to a photoelectrochemical (PEC) immunosensor for S100 calcium-binding protein B with by far the most promising detection activities. This work may open a new venue to unlock the great potential of C60 in PEC biosensing with excellent performances.

The photopolymerization rate and activation energy of C60 rotations in fullerene and its molecular complexes

The temperature dependence of the photopolymerization rate in pristine C60 and fullerene molecular complexes {Pt(dbdtc)2}•C60 and {Pt(nPr2dtc)2}•(C60)2 was studied. The Raman spectra measured in the temperature region 190–323 K exhibit an intensity increase of the dimer-related Ag(2) mode of the C60 molecule and a decrease of the monomer’s one under long laser irradiation. The photopolymer content grows exponentially with the laser exposure time while the growth time constant decreases with the increase of temperature. Since the polymerization via the 2 + 2 cycloaddition reaction necessitates the parallel orientation of double C = C bonds of neighboring C60 molecules, the acceleration of fullerene rotations at elevated temperatures affects the polymerization rate. The photopolymerization rate under fixed conditions of laser power, excitation wavelength and beam focusing exhibits an activation-type dependence on temperature. The activation energy EA, obtained from the Arrhenius dependence of the polymer growth time constant on the temperature, increases from (0.13 ± 0.01) eV and (0.18 ± 0.01) eV for {Pt(nPr2dtc)2}•(C60)2 and {Pt(dbdtc)2}•C60 molecular complexes to (0.24 ± 0.04) eV for pristine C60.

Polymer network of graphene oxide with covalently attached 2-(4′-Hydroxyphenyl)fulleropyrrolidine and Palladium: Synthesis, properties and theoretical studies

A new single layer graphene oxide hybrid polymeric material was fabricated in which the fullerene moieties covalently attached to the edges of surface of SLGO sheets were coordinated to palladium atom in an η2-fasion, SLGO-php-C60/Pd. The polymer was characterized by SEM, TEM, FT-IR and Raman techniques. The newly formed material exhibited reversible electrochemical activity in the negative potential range due to the reduction of fullerene cages with an overall electrochemical behavior resembling that of typical organic conducting polymers. The electron density of states calculated using DFT method clearly confirmed the fullerene cage reduction via electron transfer from the low-lying SLGO states. Therefore, coordination polymers of fullerene moieties bonded to the graphene sheets are easier to reduce in comparison to the coordination polymers of pristine C60. In addition, the spectroscopic and electrochemical properties of SLGO-php-C60/Pd hybrid polymeric material were also compared with php-C60/Pd polymer and SLGO-php-C60 hybrid films to seek film morphology-property relations. The present study extends the application of graphene oxide providing electrically conducting, redox-active polymer material for different applications.