Search

The toxicity of C 60 (OH) 30 , C 70 (OH) 30 , and C 120 O(OH) n fullerenols, prepared by a new original method, has been studied. This method allowed us to obtain high-purity fullerenols and eliminate the risks of synthesis of preparations containing insoluble fractions contaminated with impurities such as fullerenes not completely reacted by hydroxylation. All fullerenols were detected inside cultured cells. The MTT assay as well as the analysis of apoptosis and cell cycle showed that С 60 (ОН) 30 and С 70 (OH) 30 are non-toxic for cultured V79 и HeLa cells at concentrations exceeding physiological levels by an order of magnitude. С 120 O(OH) n caused low toxicity. Studies in Drosophila melanogaster showed that any preparations used did not result in a decreased lifespan or in behavior abnormalities in flies., (Copyright © 2019 Elsevier B.V. All rights reserved.)

A mixture of iron carbides and fullerene C60 formed by electric arc synthesis has been hydroxylated by adding OH groups to the fullerene surface, which made it possible, according to the EXAFS data, to obtain almost pure fullerenol Fe@C60(OH)30. Powder samples of the fullerenol and the product obtained after its dehydroxylation have been examined using Mössbauer spectroscopy. The Mössbauer spectra have been processed under the assumption of superposition of three partial doublets of spectral lines. It is established that two doublets due to Fe3+ dominate in the fullerenol spectrum. For the reduced fullerene Fe@C60 sample, two doublets are due to Fe3+ and the Fe2+ doublet dominates. Thus, attachment of OH groups from the outer side of the fullerene carbon frame increases the oxidation state of iron, which shows that the iron atom is located inside the frame. [ABSTRACT FROM AUTHOR]

Fullerenols C60(OH)X and C70(OH)X (X ∼ 30) have been studied in aqueous solutions at the concentrations 0.05–22wt% by X-ray and neutron scattering and using modeling hydroxyls' arrangements on carbon cages to explain the molecular assembly defined by hydrophobic and hydrophilic interactions of molecules. In the case of C60 quantum chemical calculations minimizing molecular energy for different configurations of OH-groups on the carbon cages showed their preferred localization at C60 spheroids' equatorial zone and at the opposite poles. However, less symmetric hydroxyls' localization on C70 molecules was found since hydroxyls do not create closed chains on them. As a result, the molecules C60(OH)X are associated into primary chain-like aggregates (∼20 units, few nanometers in size) more likely in water than the fullerenols C70(OH)X forming similar groups of lower aggregation degree. For C60(OH)X and C70(OH)X the peculiarities in hydroxyls' grafting affected a coordination of primary groups integrated into secondary and tertiary structures at the distances R ∼ 5 nm and R ∼ 30 nm at the concentrations C > 5wt% and C > 10wt%, respectively. The discovered mechanism of fullerenols' assembly in water will facilitate their use in chemistry and biomedicine. [ABSTRACT FROM AUTHOR]

Endohedral metallofullerenes Me@C2n (n = 30-50), their hydroxylated derivatives Me@C2n(OH)38-40 (Me = Tm, Ho, Eu, Sm, Co), and fullerenol С60(ОН)38 have been synthesized The radiation resistance of these structures under irradiation in reactor by thermal and fast neutron fluxes in the fluence range of 1018-1019 cm-2 (cadmium ratio of ~10) has been analyzed. Endofullerenols are shown to be more stable in comparison with initial endohedral fullerenes; the molecules containing Eu and Sm (atoms characterized by the largest slow-neutron absorption cross section) turned out to be most stable. The mechanism of the formation of secondary Eu and Sm endofullerenols is discussed taking into account the neutron capture and emission of γ quanta by excited nuclei, which acquire the recoil energy. [ABSTRACT FROM AUTHOR]

New diffusion membranes were prepared by introducing endofullerenes with encapsulated iron atoms, Fe@C, into the poly-2,6-dimethyl-1,4-phenylene oxide matrix. The structure of transport channels in the films upon swelling in deuteromethanol was determined by small-angle neutron scattering. The mechanical and transport properties of the modified membranes were studied. [ABSTRACT FROM AUTHOR]

Nanocomposites of polyblock polysiloxane copolymers and fullerenes by the method of small-angle neutron scattering are investigated. It was shown that a uniform distribution of threshold additive of fullerenes in ultrathin polymeric films is possible. The main results of the investigation involve: (1) in the range of radiuses below 70 nm in the films there are observed scattering structures with radiuses ∼5 nm, ∼35 nm, and ∼60 nm; (2) in the sample free of fullerene, structures of radius ∼60 nm are not detected; (3) structures of radius 60 nm appear only in the samples, which contain fullerenes, therewith their part grows with the increase of the fullerenes content. In the work was suggested, that the critical role in formation C60 clusters is played by the supramolecular organization of the initial block. [ABSTRACT FROM AUTHOR]

The parameters of an electric-arc facility for the synthesis of fullerenes and endohedral metallofullerenes are optimized. The resistance of С and С fullerenes and С(ОН) and С(ОН) fullerenols against neutron irradiation is studied. It is established that the radiation resistance of the fullerenes is higher than that of the fullerenols, but the radiation resistance of the Gd@C endometallofullerenes is lower than that of the corresponding Gd@C(OH) fullerenols. The radiation resistance of mixtures of Ме@C(OH) ( Me = Gd, Tb, Sc, Fe, and Pr) endometallofullerenes with C(OH) is determined. The factors affecting the radiation resistance of the fullerenes and fullerenols are discussed. [ABSTRACT FROM AUTHOR]

The endohedral metallofullerenols Me@C(OH) + C(OH) ( Me = Tb, Sc, Gd, Fe, Pr, Mo) have been obtained and their radiation resistance under irradiation by a neutron flux of 8 × 10 cm s has been studied. The factors affecting the radiation resistance of endohedral metallofullerenols are discussed. [ABSTRACT FROM AUTHOR]

Nature of structuring of aqueous solutions of paramagnetic endofullerenols Gd@C(OH) was determined in relation to the concentration and pH factor from small-angle neutron scattering, viscometric, and conductometric data. Molecular fractal clusters of the type of branched polymers were found, with their correlation radius being about 20 nm and aggregation numbers reaching a value of 104. The clusterized systems obtained are promising as a basis for MRI-contrasting agents and other biomedical preparations for diagnostics and therapy. [ABSTRACT FROM AUTHOR]

Composite films based on poly(2,6-dimethyl-1,4-phenylene oxide) modified with a hybrid star-like polymer (1, 3, and 5 wt %) with a fullerene C60 branching center and polymer chain arms of various structures (nonpolar polystyrene and the polar poly(2-vinylpyridine)- block-poly( tert-butyl methacrylate) diblock copolymer) are investigated via small-angle neutron scattering. The data analysis for initially dry samples of the matrix polymer and composites and for samples dried after swelling in deuterated methanol shows that the latter samples fil diffusion channels, a circumstance that provides a high contrast between them and the protonated matrix. This fact allows the distribution of methanol in swollen membranes and the geometry of diffusion channels to be studied. It is found that the matrix polymer possesses highly branched channels. However, removal of the solvent from the swollen polymer results in partial disappearance of the channels and transformation of the polymer into a more homogeneous material. In the case of composites, in contrast, as the fraction of the starlike polymer is increased, a well-developed system of linear channels that survive after solvent removal is formed in the matrix. [ABSTRACT FROM AUTHOR]

Higher empty and endohedral gadolinium metallofullerenes were prepared by electric arc synthesis, isolated, and separated chromatographically to high degree of purity (99 wt %). The samples obtained were characterized by chromatography, optical spectroscopy, and mass spectrometry. According to small-angle neutron scattering data, the endohedral metallofullerenes in o-xylene form a molecular solution in which the molecules interact to form molecular pairs. [ABSTRACT FROM AUTHOR]

Structure formation of propylene oxide oligomers with terminal hydrophobic aliphatic fragment and of oligo(propylene oxides) additionally containing covalently bonded fullerene C in deuterium water was studied by small-angle neutron scattering. Propylene oxide chains containing a long hydrophobic fragment undergo organization into spherical micelles, whereas the fullerene(C)-containing derivatives form rodlike structures (elongated 'chains' of cross-linked micelles). [ABSTRACT FROM AUTHOR]

The effect of the fullerene C branching center on the structure and conformation of star-shaped polystyrenes with different arm lengths at equal concentrations in deuterotoluene ( c = 1 g/dL) is studied by the method of small-angle neutron scattering. The analysis of neutron scattering for linear PS precursors and stars (the molecular masses of arms are ∼7 × 10 and ∼4 × 10) shows that the stars have ∼6 arms that form a dense excluded-volume zone around a core inaccessible to other macromolecules. In low-molecular-mass stars (the molecular mass of the arm is ∼7 × 10), strengthening of the static rigidity of arms is observed; as a result, the size of arms increases relative to the size of free PS chains in a good solvent. At a greater length of arms ( M ∼ 4 × 10), their individual properties are weakly pronounced in the correlation spectrum of the arm because of the interpenetration of arms, thereby demonstrating similarity in the structures of stars and their linear analogs. The mechanism controlling the effect of fullerene C on the conformations of stars via solvent structuring by fullerene is discussed. [ABSTRACT FROM AUTHOR]

Fullerenols' C60(OH)X self-assembly in aqueous solutions (25°C, pH = 5–8) has been studied by small-angle neutron scattering. The solution of C60(OH)X (X ∼ 20, content CF = 0.5 mg/ml, pH = 5) has shown the increase of short-range order by the addition of Na-citrates, while the Na-phosphates have induced the formation of two-level structures with tiny particles (size ∼ 6 nm) packed into large clusters (gyration radius ∼ 30 nm, fullerenols' volume fraction ∼ 50%). The observed peculiarities of fullerenes association are important for the development of their medical applications. [ABSTRACT FROM AUTHOR]

The supramolecular structure of nanocomposites based on polyblock siloxane copolymers, formed upon their modification with C60 fullerenes, has been studied using a number of physical methods, including Rutherford backscattering, neutron scattering and scanning electron microscopy. The effect of modification with C60 fullerenes on the strength polyblock siloxane copolymers has been examined. [ABSTRACT FROM AUTHOR]

Abstract: A review of recent activity in SANS-studies of fullerene-containing star-shaped polymers in solutions has been presented. The structural analysis of the internal ordering, conformational changes and self-assembly of stars polymers having only one or different kinds of arms (polar + non polar) attached to fullerene centre has been performed. It was performed the analysis of SANS-patterns using Benoit and Daoud-Cotton model in reciprocal space and the treatment of molecular correlations to understand a specific role of fullerene in formation of arms’ conformation. [Copyright &y& Elsevier]

Endohedral lanthanide metallofullerenes and their water-soluble biocompatible derivatives have been synthesized. The effect that fast-neutron irradiation has on the stability and nuclear physical properties of endohedral metallofullerenes that are used as magnetocontrast materials (Sc, La, Nd, Sm, Eu, Eu, Sm, Tb, Yb, Tm (isomers I and III), and Lu) is studied. Our hypothesis, according to which carbon-shell relaxation is based on the fast nonradiative processes of an electron shake-off type, is confirmed. [ABSTRACT FROM AUTHOR]

The self-organization of star-shaped polymers in toluene has been studied by small-angle neutron scattering. Polystyrene stars with a mono-C branching center are ordered into globular clusters (∼1700 nm in diameter), whereas stars with a double (C-C) center are ordered into anisotropic structures (superchains), which are linked (depending on the concentration) into triads (chain clusters ∼2500 nm in diameter). On the contrary, heteroarm polystyrene and poly-2-vinylpyridine stars with a C center are weakly associated into dimers. Moderately polar stars with arms composed of polystyrene and diblock copolymer (poly-2-vinylpyridine-poly- tret-butyl methacrylate) form short chains composed of four macromolecules, while stars of higher polarity based on polystyrene and poly- tret-butyl methacrylate form clusters containing ∼12 macromolecules ∼50 nm in diameter. Thus, by varying the structure of the center and the arm polarity, one can control the modes of star structuring. [ABSTRACT FROM AUTHOR]

Small-angle neutron scattering method was used to study self-organization phenomena in regular fullerene-containing star-shaped polystyrenes differing in the number of arms (6 and 12) and branching center structure (one or two covalently bound molecules of C fullerene) in deuterotoluene. [ABSTRACT FROM AUTHOR]

This paper presents some useful results filling the gap in the knowledge about the aggregation of hydroxylated endohedral fullerene Gd@C82(OH)18(contrast agent for magnetic resonance imaging) in aqueous solutions at different pH. A supramolecular ordering study by small-angle neutron scattering has shown that fullerenols exist in cluster form (correlation radius RC ∼ 20-30 nm, fractal dimension D). At pH increasing from 4-5 to 7-8 there was observed a transition from dense branched structures (D ∼ 2.5) to rare coil-like objects (D ∼ 1.5). [ABSTRACT FROM AUTHOR]

Deuterated star-shaped polystyrenes, (PS)6C60, dissolved in protonated analogs (1; 10% mas.), have been studied (20°C) by small-angle neutron scattering as compared to linear chains with arm's mass MA ∼ 5∙103. Using correlation functions of chain units in stars regarding to linear PS, we have developed a model of star where the arms' centers lay on the orthogonal axes, whose origin is attached to fullerene. Neutron scattering data detected more stretched arms' conformation in stars than for linear chains. [ABSTRACT FROM AUTHOR]

The gadolinium endometallofullerene/empty fullerene hydroxylated mixtures were prepared and studied as MRI-contrasting agents. The mixtures were prepared with metallofullerene enrichment of more than 80 mol.% by simple liquid extraction. The hydroxylation was performed by H2O2 oxidation at elevated temperature. Nanoaggregation of mixed fullerenes in water solution was studied by SANS. It was observed that at pH = 7 the cluster correlation diameter is 25 nm. NMR tomography in-vivo reveals that contrasting action of hydroxylated gadofullerene mixtures is 15-30 times its commercial 'Gadovist' contrasting agent. [ABSTRACT FROM AUTHOR]

The structure of first synthesized Poly(N-vinylcaprolactam)-C60 complexes in aqueous solution has been investigated by neutron small-angle scattering in the temperature range of 20-40°C around the coil-globule transition (TC ∼ 32°C). A strong action of linked fullerenes on polymer conformation is revealed far below the critical region (T ∼ TC). The complex even at 20°C exists in globular state. Polymer concentration in globule is increased by one order in magnitude as compared to this one in a coil. Along with a condensation of macromolecule to globular structure, the fullerenes stabilize a stretched chain conformation at segmental scale. The structural peculiarities of fullerene-polymer complex are expected to be useful for complexes' biological and medical applications assuming the C60 antiviral activity. [ABSTRACT FROM AUTHOR]

Structural peculiarities star‐shape polyvinylformamide (PVF) grafted to C 60 have been studied by small‐angle neutron scattering in heavy water at 20°C in the range of neutron momentum transfer q=0.03–4 nm -1 to cover spatial scales from monomer unit (fullerene) size up to star diameter and clusters dimension. In stars (functionality f∼⃒4) the arms take a very strained conformation regarding to free chains in solution that induces molecular assembly. [ABSTRACT FROM AUTHOR]

Samples containing endohedral metallofullerenes of gadolinium (Gd@C[sub 82]) and dysprosium (Dy@C[sub 82]) are investigated by the Rutherford backscattering of protons. It is shown that the concentration of endohedral metallofullerenes can be determined to within a few percent. The measured concentration of endohedral metallofullerenes Gd@C[sub 82] and Dy@C[sub 82] in samples prepared by selective multistep extraction is ∼60%. [ABSTRACT FROM AUTHOR]