Pristine C60 Research Articles

Fullerene-C60 and crown ether doped on C60 sensors for high sensitive detection of alkali and alkaline earth cations

Fullerenes are effective acceptor components with high electron affinity for charge transfer. The significant influences of chemical adsorption of the cations on the electrical sensitivity of pristine C60 and 15-(C2H4O)5/C60 nanocages could be the basis of new generation of electronic sensor design. The density functional theory calculation for alkali and alkaline earth cations detection by pristine C60 and 15-(C2H4O)5/C60 nanocages are considered at B3LYP level of theory with 6–31G(d) basis set. The quantum theory of atoms in molecules analysis have been performed to understand the nature of intermolecular interactions between the cations and nanocages. Also, the natural bond orbital analysis have been performed to assess the intermolecular interactions in detail. Furthermore, the frontier molecular orbital, energy gap, work function, electronegativity, number of transferred electron (∆N), dipole moment as well as the related chemical hardness and softness are investigated and calculated in this study. The results show that the adsorption of cations (M=Na+, K+, Mg2+ and Ca2+) are exothermic and the binding energy in pristine C60 nanocage and 15-(C2H4O)5/C60 increases with respect to the cations charge. The results also denote a decrease in the energy gap and an increase in the electrical conductivity upon the adsorption process. In order to validate the obtained results, the density of state calculations are employed and presented in the end as well.

Theoretical study on the phenylpropanolamine drug interaction with the pristine, Si and Al doped [60] fullerenes

Phenylpropanolamine (PPA) is a popular drug of abuse and its detection is of great importance for police and drug communities. Herein, we investigated the electronic sensitivity and reactivity of pristine, Al and Si doped C60 fullerenes to the PPA drug, using density functional theory calculations. Two adsorption mechanisms were predicted for PPA on the pristine C60 including cycloaddition and adsorption via –NH2 group. It was found that the pristine C60 has a good sensitivity to this drug but suffers from a weak interaction (adsorption energy ~−0.1kcal/mol) because of structural deformation and aromaticity break. The PPA is adsorbed on the Al or Si doped C60 from its –OH or –NH2 groups. The Al-doping significantly improves the reactivity of C60 but decreases its electronic sensitivity. Unlike the Al-doping, the Si-doping increases both the reactivity and electronic sensitivity to the PPA drug. At the presence of PPA drug, the conductivity of the Si-doped C60 considerably increases due to the HOMO-LUMO gap reduction by about 30.3%. Different analyses were used to obtain the results including nucleus independent chemical shift (NICS), density of states (DOS), molecular electrostatic potential (MEP), frontier molecular orbitals (FMO), etc.

Molecular Dynamics Simulations Predict the Pathways via Which Pristine Fullerenes Penetrate Bacterial Membranes.

Carbon fullerenes are emerging as effective devices for different biomedical applications, including the transportation of nanosized drugs and extraction of harmful oxidants and radicals. It has been proposed that fullerenes could be used as novel antibacterial agents, given the realization that the nanoparticles can kill pathogenic Gram-negative bacteria. To explore this at the molecular level, we simulated C60 fullerenes with bacterial membranes using the coarse-grain molecular dynamics Martini force field. We found that pristine C60 has a limited tendency to penetrate (incomplete core) Re mutant lipopolysaccharide (LPS) leaflets, but the translocation of C60 fullerenes into (complete core) Ra mutant LPS leaflets is not thermodynamically favored. Moreover, we showed that the permeability of the Re LPS bilayers depends sensitively on the system temperature, charge of ambient ions, and prevalence of palmitoyloleoylphosphoethanolamine (POPE) defect domains. The different permeabilities are rationalized in terms of transitory head group pore formation, which underpins the translocation of C60 into the lipid core. The Re LPS lipids readily form transient micropores when they are linked with monovalent cations or when they are heated to a high temperature. POPE lipids are shown to be particularly adept at forming these transient surface cavities, and their inclusion into Re LPS membranes facilitates the formation of particularly large pores that are tunneled by C60 aggregates of a significant size (∼5 nm wide). After insertion into the lipid core, the aggregates dissociate, and the disbanded nanoparticles migrate to the interface between separate POPE and LPS domains, where they weaken the boundaries between the coexisting lipid fractions and thereby promote lipid mixing.

Are there reliable DFT approaches for 13C NMR chemical shift predictions of fullerene C60 derivatives?

AbstractThe relationships between experimental and theoretical 13C NMR chemical shifts of a pristine fullerene C60, monoadducts from [2 + n] cycloaddition (n = 1–3), and one [2 + 1] bis‐adduct are systematically analyzed for the first time by using diverse quantum‐chemical levels of theory. These levels involved B3LYP, B3PW91, B97‐2, mPW1PW91, PBE1PBE, and X3LYP hybrid functionals combined with 3‐21G, 6‐31G, 6‐31G(d), 6‐31G(d,p), 6‐31G(d,2p), LanL2DZ, and SDDAll basis sets. X3LYP/6‐31G approach is determined to have the lowest deviations from the 13C NMR experimental data compared to the other methods for all the fullerene compounds (mean absolute error value is 0.856 ppm and root mean squared error value is 1.197 ppm). The highest deviations are characteristic for α (sp2 C2/C5/C8/C10) and β (sp2 C6/C7/C11/C12) carbon atoms relative to a functionalization site and for those (sp3 C1/C9) directly attached with a side fragment in the [2 + n] monoadducts (n = 1–3). A probable reason of such deviation is that the approaches do not take into account a contribution of paramagnetic ring currents to 13C NMR chemical shifts. The results will be useful in design of novel fullerene derivatives and in performing unambiguous 13C NMR chemical shift assignments with modern quantum chemistry calculations.

Quasi-equilibrium distribution of pristine fullerenes C60 and C70 in a water–toluene system

An improved technique of the ultrasound-assisted reversible liquid–liquid transfer of pristine (unmodified) C60 and C70 fullerenes between organic solutions and aqueous fullerene dispersions (AFD; another notation in general use, nC60, nC70) without any additional reagents (media modifiers) was developed. To our knowledge, this is the first report of such a fullerene transfer from an AFD to an organic phase. Based on the observation of this fullerene reversible transfer, their distribution between the aqueous and organic phases was considered. A quasi-equilibrium transfer mechanism was proposed, which makes it possible to estimate distribution constants, KD, as 6 and 2, for C60 and C70 respectively, in a water–toluene system. Under the optimum conditions, AFDs of C60 and C70 with the concentrations 180 ± 20 and 70 ± 20 μM, respectively, were obtained from the corresponding solutions in toluene. Based on UV/vis spectroscopy, total organic carbon, headspace GC–MS, and MALDI measurements, a reliable analytical procedure to measure fullerene concentrations and to monitor the concentration of residual toluene in AFDs was proposed. AFDs of a mixture of fullerenes C60 and C70 were characterized by the developed technique.

Alkylated fullerene as lubricant additive in paraffin oil for steel/steel contacts

ABSTRACTAn alkylated fullerene which bears three eicosyl chains (3,4,5-C20C60, 1) was synthesized via [3 + 2] cycloaddition. At 25°C where the aliphatic chains are in the crystalline state, 1 exhibits a moderately improved solubility in paraffin oil compared to pristine C60. At 80°C which is well-above the chain melting temperature (Tc), a significant solubility increase was observed. Upon cooling to 25°C, suspension containing plate-like aggregates composed of lamellar subunits form, which can be stable for several days. Applications of 1 as a lubricant additive in paraffin oil (PO) for steel/steel contacts both below and above Tc have been investigated in detail. It was found that the addition of 1.0 wt% 1 to PO can reduce the friction coefficient by ∼24% at 25°C. Moderate reduction of the friction coefficient at 90°C was also observed. Analysis on the worn surfaces revealed a pronounced antiwear property of 1 by reducing the areas of the worn surfaces and smoothing the scuffing. Our results show that alkylated fullerenes can be potentially used as a new generation of lubricant additives. Finally, the lubrication mechanisms of 1 at different temperatures were discussed.

Fullerene C60 Derivatives as High-Temperature Inhibitors of Oxidative Degradation of Saturated Hydrocarbons

Fullerene C60 is a free-radical scavenger, but its antioxidant activity is limited to some polymers and hydrocarbons at high temperatures. Here we demonstrate that for high-temperature oxidation of saturated hydrocarbons, the conjugates of C60 with simple phenols are more active antioxidants than the building blocks (pristine C60 and phenols) used alone. The overall kinetic parameters calculated by the Ozawa–Flynn–Wall method for nonisothermal oxidation of model hydrocarbons: saturated stearic acid (STA) and polyunsaturated linolenic acid (LNA) indicate that C60 and its derivatives are effective antioxidants during oxidation of pure STA, but not during oxidation of LNA. These findings indicate that conjugates of C60 and phenols are candidates for potential use in base oils or lubricants as new hybrid antioxidants able to work at temperatures above 100 °C.

New pyrazolino and pyrrolidino[60]fullerenes: the introduction of the hydrazone moiety for the formation of metal complexes

The [3 + 2] cycloaddition reaction of C60 with pyridine‐derived hydrazones (acting as dipolar reagents) was successfully conducted resulting in fullerene derivatives 5a, 5b. The compounds were characterized by means of NMR, UV–Vis spectroscopy, and X‐ray crystallography. The electrochemical behavior was also investigated. The fulleropyrazoline 5a exhibits anodically shifted reduction potentials of about 100 mV when compared with those for C60, whereas 5b exhibits cathodic shifts relative to pristine C60. The complexation reaction of 5b with metallic ions (Zn2+, Cd2+, and Fe2+) was achieved. Job and Benesi–Hildebrand analysis confirmed the formation of complexes with a molar ratio of 1:1 and binding constants between 2.26 × 105 and 1.59 × 105 M−1. Electrochemistry of these complexes showed a marked influence of the metal ion on the reduction potentials. Copyright © 2016 John Wiley & Sons, Ltd.

Hierarchically Structured Fullerene C70 Cube for Sensing Volatile Aromatic Solvent Vapors.

We report the preparation of hierarchically structured fullerene C70 cubes (HFC) composed of mesoporous C70 nanorods with crystalline pore walls. Highly crystalline cubic shape C70 crystals (FC) were grown at a liquid-liquid interface formed between tert-butyl alcohol and C70 solution in mesitylene. HFCs were then prepared by washing with isopropanol of the FC at 25 °C. The growth directions and diameters of C70 nanorods could be controlled by varying washing conditions. HFCs perform as an excellent sensing system for vapor-phase aromatic solvents due to their easy diffusion through the mesoporous architecture and strong π-π interactions with the sp(2) carbon-rich pore walls. Moreover, HFCs offer an enhanced electrochemically active surface area resulting in an energy storage capacity 1 order of magnitude greater than pristine C70 and fullerene C70 cubes not containing mesoporous nanorods.

Fullerenes: Characteristics of the substance, biological effects and occupational exposure levels

Fullerenes are molecules composed of an even number of carbon atoms of a spherical or an ellipsoidal, closed spatial structure. The most common fullerene is the C60 molecule with a spherical structure - a truncated icosahedron, compared to a football. Fullerenes are widely used in the diagnostics and medicine, but also in the electronics and energy industry. Occupational exposure to fullerene may occur during its production. The occupational concentrations of fullerenes reached 0.12-1.2 μ/m3 for nanoparticles fraction (< 100 nm), which may evidence low exposure levels. However, fullerene mostly agglomerates into larger particles. Absorption of fullerene by oral and respiratory routes is low, and it is not absorbed by skin. After intravenous administration, fullerene accumulates mainly in the liver but also in the spleen and the kidneys. In animal experiments there was no irritation or skin sensitization caused by fullerene, and only mild irritation to the eyes. Fullerene induced transient inflammation in the lungs in inhalation studies in rodents. Oral exposure does not lead to major adverse effects. Fullerene was not mutagenic, genotoxic or carcinogenic in experimental research. However, fullerene may cause harmful effects on the mice fetus when administered intraperitoneally or intravenously. Pristine C60 fullerene is characterized by poor absorption and low toxicity, and it does not pose a risk in the occupational environment. The authors of this study are of the opinion that there is no ground for estimating the maximum allowable concentration (NDS) of pristine fullerene C60. Fullerene derivatives, due to different characteristics, require separate analysis in terms of occupational risk assessment. Med Pr 2016;67(3):397-410.

Solvent-Free Covalent Functionalization of Fullerene C60 and Pristine Multi-Walled Carbon Nanotubes with Crown Ethers.

The goal of the present work was to test the feasibility of simple, one-step and solvent-free covalent functionalization of pristine multi-walled carbon nanotubes (MWNTs) and fullerene C60 (as a model system) with amino-substituted crown ethers, namely, 4'-aminobenzo-15-crown-5 and 4'-aminobenzo-1 8-crown-6. The attachment technique proposed is based on thermal instead of chemical activation, and can be considered as ecologically friendly. The suggested covalent binding mechanism is the nucleophilic addition of amino functionalities of crown ethers to the 6,6 bonds of pyracylene units in the case of C60, and to pentagonal (and probably other) defects of similar nature in the case of pristine MWNTs. The hybrids of crown ethers with MWNTs were characterized by means of scanning and transmission electron microscopy, Fourier-transform infrared and Raman spectroscopy, as well as thermogravimetric analysis. The functionalized C60 samples were additionally studied by means of 13C cross-polarization magic angle spinning nuclear magnetic resonance spectroscopy and laser desorption/ionization time-of-flight mass spectrometry. The approach proposed allows for a facile preparation of crown ether-functionalized pristine MWNTs without contamination with other chemical reagents, detergents and solvents, which is especially important for a vast variety of nanotube applications ranging from nanoelectronics to nanomedicine.

A comprehensive study on step-wise surface modification of C60: Effect of oxidation and silanization on dynamic mechanical and thermal stability of epoxy nanocomposite

Fullerenes (C60) are regarded as exceptional reinforcing material in composites for their capability to enrich multi-functional properties. In the present work, pristine C60 has been stepwise modified through oxidation in the presence of nitric acid and then silanized using 3-aminopropyltriethoxysilane (APTES) to generate oxygenated and siloxane functional group elements onto their surfaces. The morphological investigation of oxidized and silanized C60 was done under FESEM and TEM. On the other hand, FTIR spectroscopy and TGA analysis confirms the attachment of oxygenated and siloxane functional groups. The increase in structural defect, creating sites for APTES grafting is evident from Raman spectroscopy. Epoxy nanocomposites were prepared by incorporating 0.5 wt% of pristine and stepwise modified C60. The effect of surface modification of C60 on epoxy nanocomposite is studied under DMA and TGA. The silanized C60/epoxy nanocomposite showed significant enhancement of storage modulus (∼491%) and enhanced intensity of tan δ peak compared to the neat epoxy. This is mainly attributed to high energy absorption during viscoelastic motion. From the TGA, silanized C60/epoxy nanocomposite showed modest increment in initial decomposition temperature. This behavior is suggestive for potential espousal of silanized C60 to enhance the stiffness and molecular relaxation of epoxy nanocomposites.

Aqueous solubilization of C60 fullerene by natural protein surfactants, latherin and ranaspumin-2

C60 fullerene is not soluble in water and dispersion usually requires organic solvents, sonication or vigorous mechanical mixing. However, we show here that mixing of pristine C60 in water with natural surfactant proteins latherin and ranaspumin-2 (Rsn-2) at low concentrations yields stable aqueous dispersions with spectroscopic properties similar to those previously obtained by more vigorous methods. Particle sizes are significantly smaller than those achieved by mechanical dispersion alone, and concentrations are compatible with clusters approximating 1:1 protein:C60 stoichiometry. These proteins can also be adsorbed onto more intractable carbon nanotubes. This promises to be a convenient way to interface a range of hydrophobic nanoparticles and related materials with biological macromolecules, with potential to exploit the versatility of recombinant protein engineering in the development of nano-bio interface devices. It also has potential consequences for toxicological aspects of these and similar nanoparticles.

Density functional study of the electronic structure of dye-functionalized fullerenes and their model donor-acceptor complexes containing P3HT.

We study the electronic structure of C60 fullerenes functionalized with a thiophene-diketo-pyrrolopyrrole-thiophene based chromophore using density functional theory combined with large polarized basis sets. As the attached chromophore has electron donor character, the functionalization of the fullerene leads to a donor-acceptor (DA) system. We examine in detail the effect of the linker and the addition site on the electronic structure of the functionalized fullerenes. We further study the electronic structure of these DA complexes with a focus on the charge transfer excitations. Finally, we examine the interface of the functionalized fullerenes with the widely used poly(3-hexylthiophene-2,5-diyl) (P3HT) donor. Our results show that all functionalized fullerenes with an exception of the C60-pyrrolidine [6,6], where the pyrrolidine is attached at a [6,6] site, have larger electron affinities relative to the pristine C60 fullerene. We also estimate the quasi-particle gap, lowest charge transfer excitation energy, and the exciton binding energies of the functionalized fullerene-P3MT model systems. Results show that the exciton binding energies in these model complexes are slightly smaller compared to a similarly prepared phenyl-C61-butyric acid methyl ester (PCBM)-P3MT complex.

Mechanism for doping induced p type C60 using thermally evaporated molybdenum trioxide (MoO3) as a dopant

Thermally evaporated molybdenum trioxide (MoO3) doped C60 films, which could change n type features of pristine C60 to form a p type mixed C60 layer, are investigated by x-ray and ultraviolet photoelectron spectroscopy. It is found that C60 HOMO progressively shifts closer to the Fermi level after increased MoO3 doping concentration, and final onset of C60 HOMO is pinned at binding energy of 0.20 eV, indicating the formation of p type C60 films. It is proposed that in charge transfer induced p type C60 formation, due to large electron affinity of MoO3 (6.37 eV), electrons from HOMO of C60 could easily transfer to MoO3 to form cations and therefore increase hole concentration, which could gradually push C60 HOMO to the Fermi level and finally form p type C60 films. Moreover, clear different types of C60 species have been confirmed from UPS spectra in highly doped films.

Building Carbon Bridges on and between Fullerenes in Helium Nanodroplets.

We report the observation of sequential encounters of fullerenes with C atoms in an extremely cold environment. Experiments were performed with helium droplets at 0.37 K doped with C60 molecules and C atoms derived from a novel, pure source of C atoms. Very high-resolution mass spectra revealed the formation of carbenes of the type C60(C:)n with n up to 6. Bridge-type bonding of the C adatoms to form the known dumbbell C60=C=C60 also was observed. Density functional theory calculations were performed that elucidated the carbene character of the C60(C:)n species and their structures. Mass spectra taken in the presence of water impurities and in separate experiments with added H2 also revealed the formation of the adducts C60Cn(H2O)n and C60Cn(H2)n probably by H–OH and H–H bond insertion, respectively, and nonreactivity for the dumbell. So C adatoms that form carbenes C60(C:)n can endow pristine C60 with a higher chemical reactivity.

Copolymers based on thiazolothiazole-dithienosilole as hole-transporting materials for high efficient perovskite solar cells

The interlayers, including hole transporting layer (HTL) and electron transporting layer (ETL), segregating photoactive layer and the electrodes play an important role in charge extraction and transportation in perovskite solar cells (pero-SCs). Two novel copolymers, PDTSTTz and PDTSTTz-4, for the first time were applied as HTL in the n-i-p type pero-SCs, with the device structure of ITO/compact TiO2/CH3NH3PbI3-xClx/HTL/MoO3/Ag. The highest occupied molecular orbitals (HOMO) levels of PDTSTTz and PDTSTTz-4 exhibit a suitable band alignment with the valence band edge of the perovskite. Both of them lead to improved device performances compared with reference pero-SCs based on P3HT as HTL. To further balance the charge extraction and the diffusion length of charge carriers, pristine C60 was introduced at the cathode side of the pero-SCs, working together with TiO2 as ETL. With insertion of both the HTL and ETL, the performance of pero-SCs was greatly enhanced. The optimized devices exhibited impressive PCEs of 14.4% and 15.8% for devices based on PDTSTTz and PDTSTTz-4. The improved performance is attributed to better light harvest ability, decreased interface resistance and faster decay time due to the introduction of the interlayers.

Optoelectronic properties of one-dimensional fullerene Nanorods

One-dimensional (1D) C60 nanorods were synthesized using a liquid-liquid interfacial precipitation method. TEM and SEM were used to characterize the C60 structure. The C60 nanorod growth direction was mainly limited to the [110] direction. Surface photovoltage spectroscopy (SPS) was used to study the optoelectronic property of 1D C60 nanorods film, and greatly enhanced SPS response was observed compared with the pristine C60 film, indicating that the 1D structure of the C60 nanorods is beneficial for the separation and transport of photo-generated charges. The charge transport property of a single C60 nanorod assembled on Au electrodes was also investigated, and it was found that its I-V curve exhibits special rectifying behavior.

Self-Organization and Vesicle Formation of Amphiphilic Fulleromonodendrons Bearing Oligo(poly(ethylene oxide)) Chains.

A new series of N-methylfulleropyrrolidines bearing oligo(poly(ethylene oxide))-appended Percec monodendrons (fulleromonodendrons, 4a-f) have been synthesized. The substituted position of the oligo(poly(ethylene oxide)) chain(s) on the phenyl group of the Percec monodendron for 4a-f was varied, which is at the 4-, 2,4-, 3,5-, 3,4,5-, 2,3,4- and 2,4,6- position, respectively. 4a-e are obtained as solids at 25 °C and can self-organize into lamellar phases as revealed by X-ray diffraction (XRD) and small-angle X-ray scattering (SAXS) measurements, while 4f appears as a viscous liquid. The substitution patterns of the oligo(poly(ethylene oxide)) chain(s) also significantly influence the solubility of 4a-f, especially in ethanol and water. Formation of self-organized supramolecular structures of 4d and 4e in water as well as 4d in ethanol is evidenced from UV-vis and dynamic light scattering (DLS) measurements. Further studies in water using various imaging techniques including transmission electron microscopy (TEM), freeze-fracture TEM (FF-TEM), cryo-TEM and atomic force microscopy (AFM) observations revealed the formation of well-defined vesicles for 4d and plate-like aggregates for 4e, indicating that the aggregation behavior of the fulleromonodendrons is highly dependent on their molecular structures. For 4d in ethanol, only irregular aggregates were noticed, indicating the solvent also plays a role on regulating the aggregation behavior. After functionalization with the Percec monodendrons, 4a-f can preserve the intriguing electrochemical properties of pristine C60 as revealed by cyclic voltammetries. The thermotropic properties of 4a-f have also been investigated. It was found that all of them show good thermal stability, but no mesophases were detected within the investigated temperature ranges.

Comparative Raman study of photo-oligomer stability in the donor-acceptor fullerene complex {Pt(dbdtc)2}•C60 and pristine C60

Comparative Raman study of photo-oligomer stability in the donor-acceptor fullerene complex {Pt(dbdtc)2}•C60 and pristine C60