Aggregation of iron-containing fullerenols in aqueous solutions

Endometallofullerenols Fe@C₆₀(OH)₃₀ were synthesized by a new procedure using a special molecular precursor in the course of electric arc evaporation of a composite carbon electrode. Aqueous solutions of fullerenols Fe@C₆₀(OH)₃₀ were studied by small-angle neutron scattering (SANS) and viscometry under the conditions of transition from dilute to concentrated systems in two media: acidic (pH 3.7) and weakly alkaline (pH 7.8). In a weakly alkaline medium, fullerenols form relatively dense clusters (correlation radius R _C ~ 17 nm), and in acidic medium, less dense structures of size R _C ~ 18 nm in the concentration interval с = 0.5–1.4 wt %. The mechanisms of aggregation of fullerenol molecules in aqueous solutions are discussed. The water-soluble derivatives Fe@C₆₀(OH)₃₀ obtained show promise for biomedical applications in magnetic resonance imaging as contrasting agents that are potentially less toxic than presently used contrasts based on gadolinium chelate complexes.     

Investigation of polymer hydrogels with memory effect for cefazolin immobilization by small-angle neutron scattering

The method of small-angle neutron scattering has been used for the investigation of hydrogels synthesized on the basis of a cross-linked copolymer of 2-hydroxyethyl methacrylate and functional monomers (acrylic acid or dimethylaminoethyl methacrylate) which possess the memory effect with respect to the target pharmaceutical substance — cefazolin. The difference in the structure of anionic, cationic and amphiphilic hydrogels has been shown as well as the relation between the structure and the ability of a hydrogel for water sorption in the presence and in the absence of cefazolin. Certain structural features of the hydrogels confirmed the conditions for the appearance of the memory effect for the sorption and liberation of cefazolin.     

Spicules of glass sponges as a new type of self-organizing natural photonic crystal

The results of studying the optical characteristics of basal spicules of sea glass sponges Hyalonema sieboldi are presented. These objects are shown to be a natural nanocomposite biomaterial and to consist of a large number of axial layers of hydrated quartz that possesses a number of unique optical properties. It is found that, upon the excitation of spicules by second-harmonic pulses from an Nd:YAG laser, a considerable increase in the fluorescence intensity in the long-wavelength range with a maximum at 770 nm, saturation and anomalously large fluorescence lifetimes are observed. It has been shown experimentally that spicules exposed to femtosecond radiation pulses exhibit nonlinear optical properties. Based on the data obtained, it is concluded that spicules of glass sponges are a new type of self-organizing natural photonic crystals and are a promising object for photonics.     

Excitation functions of <Superscript>6</Superscript>Li incomplete fusion reactions with Pt nuclei

Experimentally determined excitation functions of the transfer reactions producing ^194–199Au and ^197m Hg isotopes during the interaction of ⁶Li with Pt nuclei are presented. An analysis of the experimental data as compared to EMPIRE-2.18 model calculations and experimental results on the d + ^natPt and α + ^natPt reactions allow determination of the interaction channels of d- and α-clusters in ⁶Li with the target nucleus. The results from model calculations of the reaction cross sections appear considerably lower than the experimental data. This discrepancy in describing the reactions with weakly bound nuclei is probably associated with the incomplete consideration of various interaction channels in the EMPERE-2.18 software. It is clear that a complete understanding of the interaction pattern in these processes requires consideration of the direct channels of ⁶Li nucleus cluster transfer during ⁶Li breakup near the Coulomb barrier.     

Theoretical study of hydrogen absorption near symmetric tilt grain boundaries in Pd and TiFe

The results of calculations of the atomic and electron structure of Pd and TiFe with symmetrical Σ5 tilt grain boundaries obtained using the methods of electron density functional theory are reported. Hydrogen sorption at tilt grain boundaries and corresponding surfaces is considered. It is shown that the hydrogen absorption energy increases in magnitude by ∼0.2 eV at the Pd Σ5(210) grain boundary and by ∼0.5 eV in B2-TiFe with the Σ5(310) grain boundary. The binding energy of hydrogen in palladium, as well as in TiFe, in the most preferred positions at the surface is higher than near grain boundaries. It is found that, as in the case of a defect-free material, the following tendency is observed at a symmetrical tilt grain boundary: the strong bond of the impurity at the grain boundary in the metal or alloy matrix reduces the sorption energy of hydrogen.     

Effect of oxygen vacancies on adhesion at the Nb/Al2O3 and Ni/ZrO2 interfaces

The atomic and electronic structures of the Nb/Al₂O₃(0001) and Ni/ZrO₂(001) interfaces are calculated using density-functional theory. The formation energy of oxygen vacancies is estimated in bulk materials and in surface layers and interfaces for different uppermost atomic layers of oxide surfaces. The work of separation of metal films from oxide surfaces is determined. The effect of oxygen vacancies on the bonding of transition metals to atoms of a substrate determining adhesion at the metal-oxide interfaces is discussed. It is shown that the Nb(Ni)-O interaction at the interfaces weakens in the presence of surface oxygen vacancies.     

Investigation of Heusler alloy-semiconductor interfaces

Using the electron density functional theory, the electronic structure and magnetic properties of possible contacts on the (001) interface between XYZ and X ₂ YZ Heusler alloys (NiMnSb, Co₂ MnSi) and III–V semiconductors (InP, GaAs) are studied. It is demonstrated that, in both cases, the high degree of spin polarization is achieved in Ni/P(As) or Co/As contacts. The influence of structure defects located on the surface and interfaces on the spin polarization at the Fermi level is studied. The nature of surface states at the Heusler alloy-semiconductor interface and electron factors that favor preservation or loss of the half-metallic behavior in the contacts are analyzed. Calculations of the local magnetic moments show that the magnetic properties of atoms in the contact are not changed significantly at the interface because of the partial compensation of their coordination by atoms of the semiconductor. The spin polarization can be increased by doping of the X element sublattice.     

Effect of ultrasound on the thermal behavior of the mixtures for the LTA zeolite synthesis based on metakaolin

The effect of ultrasonic treatment on the thermal behavior of the mixtures from metakaolin, sodium hydroxide and alumina designed for LTA zeolites synthesis was studied. X-ray diffraction analysis, infrared spectroscopy, scanning electron microscopy and synchronous thermal analysis have been used. It was shown that after evaporation of the suspension, LTA zeolite (24 mass%) is contained in the samples. It was established that the new phase (sodium aluminum silicate) is formed at a calcination temperature of about 600 °C. It was demonstrated that at a calcination temperature over 800 °C, nepheline is synthesized. The reaction of nepheline formation has been described by the topochemical equation of four-dimensional nucleation/nucleus growth according to Avrami/Erofeev. Using the Ozawa–Flynn–Wall analysis for non-isothermal data, the values of the activation energy and the pre-exponential factor have been calculated. It is shown that after the ultrasonic treatment the activation energy of the nepheline synthesis reaction has smaller values than in the sample without pretreatment. These phenomena have been explained by differences between the structural parameters of the particles (dimension of the coherent scattering region, the value of microdeformations).     

Identification of traces of oil contamination of biogenic sediments by solid-phase extraction combined with thin layer chromatography

The possibility of identifying industry-related traces of oil contamination in biogenic sediments is investigated on an example of model oil-contaminated peat samples. It is shown that oil pollution of <1 wt % in biogenic samples cannot be identified using a conventional IR spectrometric procedure. An additional study of organic extracts, isolated in sample preparation, by solid-phase extraction and thin layer chromatography can detect specific oil aromatic hydrocarbons in contaminated samples uncharacteristic for background samples of the same type.