Effect of the multistage chemical treatment of carbon nanotubes on their purity and quality of walls

The effect of chemical methods that include the gas-phase and liquid-phase selective oxidation methods, of hydrochloric acid when used in different sequences, and of concentrated nitric acid on the purification efficiency of carbon nanotubes after their synthesis is studied. Changes in the quality of walls of this material at different stages of purification are studied physicochemically.     

Crystal structures of pyridinemonocarboxylic acid peroxosolvates

The crystal structures of new peroxosolvates of the following pyridinemonocarboxylic acids were studied: picolinic 2-C₅H₄NCOOH·H₂O₂ (1), nicotinic 3-C₅H₄NCOOH·H₂O₂ (2), and isonicotinic 4-C₅H₄NCOOH·2H₂O₂ (3). In these compounds, the acids exist exclusively as zwitterions, as opposed to non-solvated crystals. In compounds 1–3, the hydrogen peroxide molecules form two donor hydrogen bonds and, in some cases, one additional acceptor hydrogen bond. Peroxosolvate 2 can be considered as a novel drug formulation of vitamin B₃.     

Magnetic properties of single crystals of a new cobaltite TbBaCo<Subscript>4</Subscript>O<Subscript>7+<Emphasis Type="Italic">x</Emphasis></Subscript>

The temperature and field dependences of the magnetization of a single crystal of a new class of layered cobaltites, TbBaCo₄O_7+x , with a structure containing a Kagomé lattice and a triangular lattice were measured. The measurements were performed on a SQUID magnetometer at temperatures in the range 2–300 K and in magnetic fields of up to 55 kOe for two field orientations. The anisotropy of the magnetization was studied, and the presence of antiferromagnetic ordering in fields H < H _c and a weak magnetic-field-induced (H > H _c ) ferromagnetic component in the low-temperature range was demonstrated. The magnetic characteristics of the initial TbBaCo₄O_7+x single crystal and the single crystal annealed in an O₂ atmosphere were compared.     

On the Effect of Weak Attenuation of Acoustic Waves from High-Altitude Explosions

Acoustical Physics - The article analyzes difficult to explain experimental data on acoustic signals recorded from explosions and injections of matter at heights of 120–150 km. It is noted...     

Structural Analysis of Defects in Layered Double Hydroxides and Related Mixed Oxides

Russian Journal of General Chemistry - Results of studying the structural defects in MgAl and NiAl layered double hydroxides and in the products of their thermal decomposition to 1000°C,...     

Humic-based bionanocomposites containing stable paramagnetic gold nanoparticles for prospective use in pharmaceuticals

Structural peculiarities and supramolecular organization of medicinally promising nanocomposites, synthesized from humic substances, which essentially differ depending on decomposition degree, have been studied using electron spin resonance, transmission electron, and confocal laser scanning microscopy techniques and some other modern physical–chemical methods. It is shown that stable zero-valent gold nanoparticle of about 10–17?nm in size are formed in a natural macromolecular matrix. The nanocomposites obtained turn out to be stable in aggregative state for a long time and preserve their properties that are extremely important for prospective medicinal substances.     

Synthesis of new polycarbonate-polysiloxanes based on oligomeric organosilicon bisphenols

New linear polycarbonate-polysiloxanes are synthesized through the heterophase polycondensation of α,ω-bis[3-(4-hydroxy-3-methoxyphenyl)propyl]oligoorganosiloxanes (P_Si-bisphenols) with α,ω-bis(chloroformato)oligocarbonates (method I), the phosgenation of P_Si-bisphenol-diphenylolpropane mixtures (method II), the interaction of the same bisphenols with bis(4-chloroformatophenyl)propane (method III), and the polycondensation of the latter with P_Si-bisphenol-α,ω-dihydroxyoligocarbonate mixtures (method IV). The highest molecular masses (as high as 130 × 10³ at a degree of multiblockiness of 11–14 block pairs) are inherent in poly-carbonate-polysiloxanes synthesized by methods II and III; moreover, the same copolymers have the highest mechanical characteristics (σ_br and ?_br are as high as 48 MPa and 300%, respectively).     

Properties of carrageenan gels with immobilized lysozyme

Absract  Rheological properties of 3% carrageenan gels formed in 0.4 M sodium chloride solution in the presence of lysozyme are studied in detail. It is shown that the addition of protein results in an increase in the gel-sol transition temperature by 2°C (transition temperature of 3% gel is 48°C, lysozyme concentration is 0.5 mg/ml). Based on the frequency dependences of dynamic moduli at various temperatures, it is revealed that systems possess viscoelastic properties at low frequencies. Within a wide frequency range up to gel-sol transition temperature, systems become elastoviscous and, at higher frequencies, they demonstrate forced transition to glassy state. It is shown that carrageenan inhibits enzyme activity of lysozyme. The interaction between enzyme and carrageenan leads to changes in lysozyme conformations, i.e., the content of α-helices increases and that of turns decreases. It is demonstrated for the first time that, in the presence of a so-called nonspecific (for the gelation of carrageenan) sodium ion, it is possible to prepare gels with the necessary structure and rheological properties and gel-sol transition temperature. These gels can release a lysozyme under the conditions of transmucosal prolonged delivery. Original Russian Text ? G.P. Yampol’skaya, A.A. Elenskii, N.V. Pan’kina, B.N. Tarasevich, V.G. Kulichikhin, 2009, published in Kolloidnyi Zhurnal, 2009, Vol. 71, No. 2, pp. 275–284.     

Identification of peroxo groups in supramolecular layered structures as probed by Raman spectroscopy

Peroxide-containing supramolecular structures prepared by reacting lithium aluminum layered double hydroxides (Li-Al LDHs) with concentrated hydrogen peroxide solutions were characterized by Raman spectroscopy. These compounds were formulated as [LiAl₂(OH)₆](OH) · H₂O₂ · H₂O(I) and [LiAl₂(OH)₆](OOH) · H₂O₂ · H₂O(II). The frequencies 830 and 849 cm⁻¹ in the spectra of compounds I and II were assigned to O—C stretching vibrations in two nonequivalent peroxo groups. The band at 866 cm⁻¹ in compound II was assigned to O—O vibrations in the hydroperoxo group (OOH)⁻. Proceeding from calculated strength factors, we inferred that the O—O bond in the hydroperoxo group of compound II is stronger than in the H₂O₂ solvating group. Original Russian Text ? T.A. Tripol’skaya, I.V. Pokhabova, P.V. Prikhodchenko, G.P. Pilipenko, E.A. Legurova, N.A. Chumaevskii, 2009, published in Zhurnal Neorganicheskoi Khimii, 2009, Vol. 54, No. 3, pp. 513–515.     

Effect of Liquid-Phase Oxidative Treatments on the Purity,Hydrophilicity, and Structure of Single-Wall Carbon Nanotubes and on the Electrical Conductivity of Their Arrays

Russian Journal of Applied Chemistry - A study using a set of physicochemical methods has shown that treatment of single-wall carbon nanotubes synthesized by the electric arc method with an aqueous...