• Articles | Статьи

Constrained growth of anisotropic magnetic δ-FeOOH nanoparticles in the presence of humic substances

Function distribution magnetic splitting the mossbauer spectrum for different temperatures of the composite d-FeOOH-HSConstrained growth of anisotropic magnetic δ-FeOOH nanoparticles in the presence of humic substances. Polyakov A.Yu., Goldt A.E., Sorkina T.A., Perminova I.V., Pankratov D.A., Goodilin E.A., Tretyakov Y.D. //CrystEngComm. 2012. V.14. №23. P.8097-8102.Search the full text below. Ищи полный текст ниже.

Natural polyelectrolytes, humic substances, are suggested to control in situ growth of feroxyhyte nanoparticles of a highly reduced mean size and with enhanced colloidal stability in salt solutions. The feroxyhyte is formed as 2-5 nm thick and 20 × 20 nm wide nanoflakes due to the blocking of developing facets of feroxyhyte and constraints caused by diffusion limitations of ionic constituents across partially charged branches of humic substances.

Superparamagnetic iron oxide nanoparticles (SPIONs) are known as effective biocompatible agents for various biomedical applications like drug delivery, in vivo magnetic resonance imaging, cell and protein separation, hyperthermia and transfection. At present, synthesis and application of rods, disks, fibers, tubes, sheets, ellipsoids, dumbbell-shaped, acorn-shaped and other anisotropic nanoparticles attract growing attention because of their unique properties. Aggregation is a serious problem in the preparation and storage of such magnetic nanoparticles limiting considerably their practical applications. This problem can be solved by a surface modification of nanoparticles with organic macromolecules, their preparation in the presence of surfactants, application of hydrophilic, surface-active ligands improving biocompatibility and resulting in multifunctional nanoparticles for medical diagnostics.

Подробнее...

Печать E-mail

Possibilities of cryogenic autoradiography

Characteristic curves obtained under different conditions: 1, at room temperature; 2, at the temperature of liquid nitrogen (experimental data, approximating straight lines of the regions of normal exposures, regions of photographic latitude, and inertia points are shown).

Possibilities of cryogenic autoradiography. Pankratov D.A., Korobkov V.I. //Journal of Analytical Chemistry. 2014. V. 69. Is. 7. P. 632–637Search the full text below. Ищи полный текст ниже.

Photographic properties of the nuclear photographic detector BioMax MR Film from KODAK are studied at the temperature of liquid nitrogen. The characteristic curves obtained at room and cryogenic temperatures indicate that the detector retains its physical and photographic properties, and its possibilities can be expanded to studies of deeply frozen samples. The data obtained point to an increase in the sensitivity of the photographic material frozen to cryogenic temperatures at short exposures.

Подробнее...

Печать E-mail

Investigation of iron(III) complex with crown-porphyrin

57Fe complex of 5-(4-(((4-hydroxy-benzo-15-crown-5)-5-yl)diazo)phenyl)-10,15,20-triphenylporphyrin contains iron atoms in two sites, porphyrin and crown-ether rings

Investigation Of Iron(III) Complex With Crown-Porphyrin. Pankratov D.A., Dolzhenko V.D., Kiselev Y.M., Stukan R.A., Al Ansari Y.F., Savinkina E.V. //Hyperfine Interactions. 2013. V.222. Is.1 (Suppl). P. S1-S11Search the full text below. Ищи полный текст ниже.

Iron complex of 5-(4-(((4′-hydroxy-benzo-15-crown-5)-5′-yl)diazo)phenyl)-10,15,20-triphenylporphyrin was investigated by 57Fe Mössbauer spectroscopy and EPR. Two Fe sites were identified; they give two differing signals, doublet and wide absorption in a large velocity interval. EPR spectra of solutions of the complex in chloroform at room temperature also show two signals with g = 2.064, AFe = 0.032 cm− 1; g = 2.015, AFe = 0.0034 cm− 1. The doublet asymmetry is studied vs. temperature and normal angle to the sample plane and gamma-beam. The isomer shift δ in the doublet varies from 0.41 to 0.25 mm/s in the 5÷360 K temperature range, whereas quadruple splitting value is constant, Δ ∼ 0.65 mm/s. The relax absorption may be described as a wide singlet (δ = 0.30 ÷ 0.44 mm/s and Γ = 2.83 ÷ 3.38 mm/s); its relative area strongly depends on temperature. According to δ, both signals are assigned to Fe(III).

Structures and properties of metal porhyrins (MPs) (hemoglobin, chlorophyll, vitamin B12, etc.) participating in vital processes depend on a central metal and peripheral substituents. Most MPs possess chemical and thermal stability, high extinctions coefficients in UV, visible and near IR ranges and reversible red-ox transitions. Therefore, detail study of their properties with the use of various physicochemical methods is of interest.

Подробнее...

Печать E-mail

Electron paramagnetic resonance spectra near the spin-glass transition in iron oxide nanoparticles

Low-temperature EPR spectra in iron-oxide nanoparticles. HL and HR are left and right spectrum peaks, correspondingly.

Electron paramagnetic resonance spectra near the spin-glass transition in iron oxide nanoparticles. Koksharov Yu.A., Gubin S.P., Kosobudsky I.D., Yurkov G.Yu., Pankratov D.A., Ponomarenko L.A., Mikheev M.G., Beltran M., Khodorkovsky Y., Tishin A.M. //Physical Review B: Condensed Matter and Materials Physics. 2001. V. 63. № 1. P. 124071-124074Search the full text below. Ищи полный текст ниже.

Electron paramagnetic resonance (EPR) in iron-oxide nanoparticles (∼ 2.5 nm) embedded in a polyethylene matrix reveals the sharp line broadening and the resonance field shift on sample cooling below TF ≈ 40 K. At the same temperature a distinct anomaly in the field-cooled magnetization is detected. The temperature dependences of EPR parameters below TF are definitely different than those found for various nanoparticles in the superparamagnetic regime. In contrast to canonical bulk spin glasses, a linear fall-off of the EPR linewidth is observed. Such behavior can be explained in terms of the random-field model of exchange anisotropy.

Подробнее...

Печать E-mail

Potassium hexahydroperoxostannate: synthesis and structure

Mossbauer spectra of (1) K2Sn(OH)6 and (2) K2Sn(00H)6
Potassium hexahydroperoxostannate: synthesis and structure.
 Ippolitov E.G., Tripol'skaya T.A., Prikhodchenko P.V., Pankratov D.A.
//Russian Journal of Inorganic Chemistry. 2001. V.46. №6. P.851-857 Search the full text below. Ищи полный текст ниже.

Polycrystalline potassium hexahydroperoxostannate was prepared by replacement of hydroxo groups in potassium hexahydroxostannate upon its dissolution in hydrogen peroxide. A comparative study of the product and the starting hydroxostannate by powder X-ray diffraction analysis, thermogravimetry, and IR, 2H, 39K, and 119Sn NMR, and Mössbauer spectroscopy was carried out. The peroxo compound K2Sn(OOH)6 crystallizes in the hexagonal system with a = 7.264(7) Å, c = 10.168(4) Å. IR, NMR, and Mössbauer spectroscopy data show that the tin coordination polyhedron in the peroxo compound is an octahedron formed by the coordinated hydroperoxo groups.

Previously, sodium hexahydroperoxostannate was prepared and characterized by powder X-ray diffraction analysis, thermogravimetry, IR, 1H NMR, and Mossbauer spectroscopy, and by thermodynamic and kinetic method. The tin atom in this compound were found to occur in the octahedral environment of hydroperoxo group. It appeared pertinent to confirm the possibility of formation of this type of tin compound by preparing a new hydroperoxo complex. To this end, we performed the first synthesis of potassium hexahydroperoxostannate. Comparative study of potassium hexahydrosstannate (1) and hexahydroperoxosstannate (2) and their deuterated analogue (1a and 2a, respectively) was carried out by powder X-ray diffraction analysis, thermogravimetry, and IR, NMR (2H, 39K and 119Sn), and Mossbauer spectroscopy.

Подробнее...

Печать E-mail

Materials on the same topic | Материалы по этой же теме

Рейтинг@Mail.ru

http://www.youtube.com/RuRedOx