Adsorption of midmolecular peptides by fullerene modified silica gel

The adsorption properties of raw and processed silica gels and of silica gels modified with fullerene (fullerene-silica gel nanosystems) toward serum midmolecular peptides of ischemic origin were examined. A high adsorption capacity of the nanosorbents was found. The influence of fullerenes on the condition of silica gel was studied by solid-state NMR, and an increase in the silanol fraction at the adsorbent surface was demonstrated. It was shown that presence of fullerene C₆₀ in nanosorbents enables oxidation reaction of the adsorbed peptides, i.e., sorption of metabolites.     

Fullerene-silica complexes for medical chemistry

A quantum-chemical study of the interaction of C₆₀ fullerene with nanosized silica was performed. It was demonstrated that a fullerene molecule forms a weakly bound complex with a pyrogenic silica (Aerosil) particle only via the interaction with the silanediol groups of the hydroxyl covering on the particle. By contrast, a fullerene molecule is not bonded to an individual siloxane cycle, and, therefore, fullerosilica gel is formed due to the retention of fullerene molecules in pores of silica gel as a result cooperative action of the siloxane cycles comprising the pore. In both cases, the predicted medico-biological action of medicinal preparations is due to the radical-like and donor-acceptor characteristics of the C₆₀ molecule.     

Selective separation behavior of silica gel for zirconium in simulated high level radioactive liquid waste

Zirconium in simulated high level radioactive liquid waste (HLLW) was selectively adsorbed and separated by self-made high adsorption activity silica gel. The selective adsorption mechanism was analyzed according to the structure character of self-made silica gel and performance of zirconium in acid simulated HLLW. The results show that the adsorption selectivity of self-made silica gel for zirconium is strong, because zirconium has higher positive charge and zirconium ion hydrolyzes easily. Distribution coefficient of self-made silica gels for zirconium is 53.5 ml/g. There are 6.5 (OH)/nm² on the surface on self-made silica gels which provide more adsorption activity places, thus self-made silica gels have higher adsorption capacity for zirconium (31.4 mg/g). The elution rate of the adsorption of zirconium on self-made silica gel by 0.2 mol/l H₂C₂O₄ is more than 99%. The solubility of the self-made silica gel in nitric acid is low, the chemical stability of self-made silica gel is very strong.     

C60 Based Hybrid Nanocomposites Obtained in the Presence of Ultrasounds

Since their discovery, fullerenes in general and buckminsterfullerene C₆₀ in particular, became a subject of great interest for studies. Being compatible with the sol–gel process, one of the promising approaches is to incorporate the fullerene molecules in sol–gel oxide matrices. Great part of studies deals with SiO₂ sol–gel oxide as the optimal matrix for entrapment of organic molecules. C₆₀-doped silica matrices used through our present study have been prepared by sol–gel processing, using different alkoxide precursors, as a silicon oxide source: tetraethoxysilane (a), methyltriethoxysilane (b), phenyltriethoxysilane (c) and a mixture of phenyltriethoxysilane and tetraethoxysilane (d). C₆₀-to-Si molar ratio was chosen to be 1.0 × 10^?3:1 for all materials synthesized, final oxide composition remaining unchanged in all cases. The effect of ultrasounds on the gelation process was established by preparing two series of samples, either via sonication or in the absence of ultrasound processing. The properties of the resulted materials were also established. The prepared samples were characterized by XRD, IR, RPE and UV-VIS spectrometry. All methods have put in evidence the embedment of the fullerene into the silica matrix.     

Specifics of light scattering in solutions of fullerene-containing polymers

The molecular mass and hydrodynamic dimensions of molecules of two fullerene-containing polymers which differ in the preparation procedure and the mode of fullerene C₆₀ binding were determined by means of static and dynamic light scattering and transport techniques (diffusion, sedimentation, gel permeation chromatography). It was established that the molecular masses of polymeric C₆₀ derivatives determined by means of static light scattering are substantially above those measured by means of the transport techniques. Using as an example a polystyrene specimen containing 6.2 wt % C₆₀ prepared according to the widespread technique of solvent evaporation from a mutual fullerene and polymer solution, it was shown that the multicomponent nature, the compositional inhomogeneity, and a lack of coincidence in the signs of refractive index increments for structurally different components of fullerene-containing polymers may cause anomalies in the intensity of light scattering by solutions of these compounds.     

Boosting Activation of Oxygen Molecules on C60 Fullerene by Boron Doping

The activation of oxygen molecules on boron‐doped C₆₀ fullerene (C₅₉B) and the subsequent water formation reaction are systematically investigated by using hybrid density functional calculations. Results indicate that C₅₉B shows a favorable ability to activate oxygen molecules both kinetically and thermodynamically. The oxygen molecule is first adsorbed on the boron atom, which is identified to be the most reactive site in C₅₉B for O₂ adsorption because of its high positive charge and spin density. The adsorption structure C₅₉B?O₂ can further isomerize to form two products with small reaction barriers. Water formation reactions upon these two structures are energetically favorable and suggest a four‐electron mechanism for the oxygen reduction reaction catalyzed by C₅₉B. This work provides a reliable theoretical insight into the catalytic properties of boron‐doped fullerene, which is believed to be helpful to explore fullerene catalysts.     

Complexation of C60 Fullerene with Aromatic Drugs

The contributions of various physical factors to the energetics of complexation of aromatic drug molecules with C₆₀ fullerene are investigated in terms of the calculated magnitudes of equilibrium complexation constants and the components of the net Gibbs free energy. Models of complexation are developed taking into account the polydisperse nature of fullerene solutions in terms of the continuous or discrete (fractal) aggregation of C₆₀ molecules. Analysis of the energetics has shown that stabilization of the ligand–fullerene complexes in aqueous solution is mainly determined by intermolecular van der Waals interactions and, to lesser extent, by hydrophobic interactions. The results provide a physicochemical basis for a potentially new biotechnological application of fullerenes as modulators of biological activity of aromatic drugs.     

Study of structural and thermodynamic parameters of adsorption layers using density functional theory. Local density and adsorption isotherms on spherical surfaces

Local density profiles in adsorption layers of Lennard-Jones fluids on two-dimensional adsorbents with spherical geometry and isotherms of excess (Gibbs) adsorption have been calculated using the classical density functional theory (approximations with weighting coefficients). The local density profiles have been found in hydrogen adsorption layers on C₆₀, C₂₄₀, and C₅₄₀ fullerene molecules. The calculations have been performed for both subcritical and supercritical temperature ranges. It has been shown that, at a pressure of 10 MPa and a temperature of 77 K, the gravimetric (mass) hydrogen density on C₆₀ fullerene is 7.6 wt %, which is in good agreement with the results of molecular dynamics simulation and experimental data. It has also been established that the gravimetric hydrogen density on C₆₀ fullerene is higher than that on C₂₄₀ and C₅₄₀ fullerenes, being comparable with its value in a slitlike pore of a carbon adsorbent.     

ECSTM study of adsorption of C60, C70, C86 and Y@C82 on Au(111)

The adsorption of a variety of fullerenes (C₆₀, C₇₀, C₈₆, Y@C₈₂) on Au(111) electrode surfaces was comprehensively investigated in 0.1 M HClO₄ by electrochemical scanning tunneling microscopy (ECSTM). In the ordered C₆₀’s adlayer, C₆₀ molecules formed either (2 $ \sqrt 3 $ ×2 $ \sqrt 3 $ ) or “in-phase” structure. The high resolution STM image shows that the C₆₀ cage is not simply round but shows a bifurcated feature. The adsorption orientation of C₆₀ on Au(111) is tentatively suggested. In the ordered C₇₀’s adlayer, the perpendicular fullerene molecules are the main adsorption mode and form (2 $ \sqrt 3 $ ×2 $ \sqrt 3 $ ) structure. However, for C₈₆ and Y@C₈₂, the ordered adlayer could not be obtained on Au(111) under the present condition. These differences may be due to the different molecular shapes and sizes, and the encapsulated metal atom which affects the lattice matches with the substrate. The adsorption of fullerene molecules on Au(111) from disorder to order could be tuned simply by steering the dimensional sizes or shapes of the fullerenes used.     

Time-resolved EPR study of 3C60 in solid matrices

Using time-resolved cw EPR and pulsed EPR techniques, a study was made of the characteristics of the photoexcited triplet state of C₆₀ adsorbed in silica gel pores and embedded in a polymethylmethacrylate matrix. It was found that the time-resolved spectra from ³C₆₀ in these matrices at room temperature retain the absorption/emission features of spectra from ³C₆₀ in frozen solution (≤120 K). Apparently, the combination of molecular rotation and pseudo rotation (resulting from interconversion between Jahn-Teller states) is not fast enough, to lead to complete averaging of the dipole-dipole interaction between the unpaired electrons. The study explored the effect of introduction of solvent molecules in the silica gel pores on the ³C₆₀ spectrum and quenching of the triplet by electron donors.     

Poly(aryl ether) Dendrons with Monopyrrolotetrathiafulvalene Unit‐Based Organogels exhibiting Gel‐Induced Enhanced Emission (GIEE)

A series of poly(aryl ether) dendrons with a monopyrrolo‐tetrathiafulvalene unit linked through an acyl hydrazone linkage were designed and synthesized as low molecular mass organogelators (LMOGs). Two of the dendrons could gelate the aromatic solvents and some solvent mixtures, but the others could not gel all solvents tested except for n‐pentanol. A subtle change on the molecular structure produces a great influence on the gelation behavior. Note that the dendrons could form the stable gel in the DMSO/water mixture without thermal treatment and could also form the binary gel with fullerene (C₆₀) in toluene. The formed gels undergo a reversible gel–sol phase transition upon exposure to external stimuli, such as temperature and chemical oxidation/reduction. A number of experiments (SEM, FTIR spectroscopy, ¹H NMR spectroscopy, and UV/Vis absorption spectroscopy, and XRD) revealed that these dendritic molecules self‐assembled into elastically interpenetrating one‐dimensional fibrillar aggregates and maintain rectangular molecular‐packing mode in organogels. The hydrogen bonding, π–π, and donor–acceptor interactions were found to be the main driving forces for formation of the gels. Moreover, the gel system exhibited gel‐induced enhanced emission (GIEE) property in the visible region in spite of the absence of a conventional fluorophore unit and the fluorescence was effectively quenched by introduction of C₆₀.     

Synthesis of fullerene-silica hybrid materials

Fullerene/silica hybrid materials were obtained by radiation grafting on silica surface of toluene or decalin solutions of C₆₀. As determined by thermogravimetric analysis, the amount of C₆₀ grafted on silica surface was dependent from the radiation dose administered and independent from the C₆₀ concentration and the nature of the organic solvent. In absence of air, a dose of 48 kGy was sufficient to ensure a grafting level of 30% by weight of C₆₀ in the hybrid material. The fullerene/silica hybrid material shows a remarkable thermal stability, since the early decomposition starts above 300 °C as measured by DTG and DTA. The chemical structure of the fullerene/silica hybrid material was determined by FT-IR spectroscopy and with solid state ¹³C CP-MAS NMR. The potential application of such materials has been outlined.     

Unique Separation Behavior of a C60 Fullerene‐Bonded Silica Monolith Prepared by an Effective Thermal Coupling Agent

Herein, we report a newly developed C₆₀ fullerene‐bonded silica monolith in a capillary with unique retention behavior due to the structure of C₆₀ fullerene. N‐Hydroxysuccinimide (NHS)‐conjugated C₆₀ fullerene was successfully synthesized by a thermal coupling agent, perfluorophenyl azide (PFPA), and assigned by spectroscopic analyses. Then, NHS‐PFPA‐C₆₀ fullerene was attached onto the surface of a silica monolith in a capillary. The capillary provided specific separation ability for polycyclic aromatic hydrocarbons in liquid chromatography by an effective π–π interaction. Furthermore, corannulene, which has a hemispherical structure, was selectively retained in the capillary based on the specific structural recognition due to the spherical C₆₀ fullerene. This is the first report revealing the spherical recognition ability by C₆₀ fullerene in liquid chromatographic separation.     

Regulation of Glucose Oxidase Activity through Interaction with Fullerene Derivatives

The 2‐(hydroxymethyl)pyridine modified C₆₀ (PY‐C₆₀) and methoxydiglycol modified C₆₀ (MDG‐C₆₀) are synthesized using Bingel‐Hirsch reaction and characterized by nuclear magnetic resonance (NMR) and mass spectra. PY‐C₆₀ and MDG‐C₆₀ can bind to glucose oxidase (GOx) and quench the fluorescence of tryptophan (Trp) residue in GOx through static mechanism. The conformation of GOx is disturbed after formation of complex with these fullerene derivatives. Kinetic analysis indicates that PY‐C₆₀ and MDG‐C₆₀ may affect the catalytic activity of GOx with a partial mixed‐type inhibition mechanism. In the plasma glucose concentration range (3.6–5.2 mmol·L^?1), PY‐C₆₀ may significantly accelerate the catalytic velocity of GOx, however, MDG‐C₆₀ exerts almost no obvious change to the initial velocity of GOx, suggesting that elaborate design of molecular structure of fullerene derivative is very important for regulating the biological activity of fullerene‐enzyme complex.     

Morphology Engineering of Fullerene (C60) Microstructures Featuring Surface Cracks with Enhanced Photoluminescence and Microscopic Recognition Properties

Surface cracks could improve the optical and photoelectronic properties of crystalline materials as they increase specific surface area, but the controlled self-assembly of fullerene (C₆₀) molecules into micro-/nanostructures with surface cracks is still challenging. Herein, we report the morphology engineering of novel C₆₀ microstructures bearing surface cracks for the first time, selecting phenetole and propan-1-ol (NPA) as good and poor solvents, respectively. Our systematic investigations reveal that phenetole molecules initially participate in the formation of the ends of the C₆₀ microstructures, and then NPA molecules are involved in the gradual growth of the sidewalls of the microstructures. Therefore, the surface cracks of C₆₀ microstructures can be finely regulated by adjusting the addition of NPA and the crystallization time. Interestingly, the cracked C₆₀ microstructures show superior photoluminescence properties relative to the smooth microstructures due to the increased specific surface area. In addition, C₆₀ microstructures with wide cracks show preferential recognition of silica particles over C₆₀ particles owing to electrostatic interactions between the negatively charged C₆₀ microstructures and the positively charged silica microparticles. These C₆₀ crystals with surface cracks have potential applications from optoelectronics to biology.     

New low-temperature method for joint synthesis of C60 fullerene and new carbon molecules in the form of C3-C15 and quasi-fullerenes C48, C42, C40

Method for joint synthesis of C₆₀ fullerene and new carbon molecules in the form of C₃-C₁₅ and quasifullerenes C₄₈, C₄₂, and C₄₀, alternative to arc-discharge technique, was developed for the first time. The process of fullerenization of benzene molecules into carbon molecules is performed at comparatively low (～1000°C) temperatures. It is shown that C₃-C₁₈ nanoclusters are generated as main components of a monoatomic carbon vapor under conditions that rule out sublimation of carbon. Crystalline substances containing exceedingly active small carbon molecules were synthesized for the first time. The products of benzene fullerenization were studied by methods of mass-spectrometric analysis, electron-probe X-ray microanalysis, and optical microscopy.     

Stockage de l’hydrogène dans les nanotubes de carbone à paroi unique : nouvelle méthode de préparation par excitation laser

A new mode for hydrogen adsorption and storage in single-wall carbon nanotubes is used, on the basis of laser excitation. Remember that this method has been useful to obtain, in the case of the fullerene C₆₀, many complex C₆₀-atoms or C₆₀-molecules, where atoms or molecular particles are trapped inside the C₆₀-molecules. We think this method might be important to store many hydrogen molecules inside carbon nanotubes.     

On the initial stage of the free-radical polymerizations of styrene and methyl methacrylate in the presence of fullerene C<Subscript>60</Subscript>

It has been demonstrated experimentally and theoretically that the essentially different inhibiting effects of fullerene C₆₀ on the initial stage of the polymerizations of styrene and methyl methacrylate (including complete hampering of styrene polymerization throughout a long induction period) are of common kinetic nature. The difference arises from the competition between C₆₀ and the monomer not for initiating radicals but for radicals originating from the monomer; that is, the difference stems from the competition between the chain propagation reactions and the termination reactions on fullerene molecules. As a consequence, the further development of the process is determined by the relative reactivities of the radicals toward C₆₀ and towards their parent monomers.     

Transition metal coated fullerenes

Compound clusters of fullerene molecules and transition metal atoms having the composition C₆₀M_x and C₇₀M_x with x = 0..150 and M ∈ {Ti, Zr, V, Y, Ta, Nb} were produced using laser vaporisation in a low-pressure inert gas aggregation cell. Intensity anomalies in the mass spectra correlate with the atomic radii of the different metals indicating the formation of complete metal layers around the central fullerene molecule. Using high laser intensities the metal-fullerene clusters can be transformed into metcars and metal-carbides. Photofragmentation spectra of preselected C₆₀Ta_x indicate that the fullerene cage is destroyed for x ≥ 3.     

New products of a new method for pyrolysis of pyridine

New method for pyrolysis of pyridine is suggested. One of yielded by the method is a new type of heteroatomic molecules in the form of exohedrally hydrogenated and hydroxylated azafullerenes (C₃₅N₅)H₉, (C₄₅N₅) (OH)₃H₁₄, and (C₄₉N₁₁)(OH)₅H₁₈. C₆₀ fullerene, its hydrides, and new carbon molecules, such as quasi-fullerene C₄₈ and C₃-C₁₅, are detected for the first time in pyridine pyrolysis products by mass-spectral analysis. Hydrides of the carbon molecules are synthesized for the first time without using fullerene.