scholarly journals EPR study of paramagnetic centers in SiO2:C: Zn nanocomposites obtained by infiltration of fumed silica with luminescent Zn(acac)2 solution

2021 ◽  
Vol 24 (02) ◽  
pp. 124-130
Author(s):  
D.V. Savchenko ◽  
◽  
V.S. Memon ◽  
A.V. Vasin ◽  
D.V. Kysil ◽  
...  
Keyword(s):  
Fumed Silica ◽  
Ethanol Solution ◽  
Paramagnetic Centers ◽  
Dangling Bonds ◽  
Epr Spectrum ◽  
Ferromagnetic Exchange ◽  
Before And After ◽  
Integrated Intensity ◽  
Epr Signal ◽  
Luminescent Centers

Silica-carbon with zinc (SiO2:C:Zn) nanocomposites obtained via infiltration with aged luminescent zinc acetylacetonate (Zn(acac)2) ethanol solution of two concentrations (1 or 4%) into the fumed silica (SiO2) matrix have been studied using EPR within the temperature range 6…296 K before and after thermal annealing. The EPR spectrum of SiO2:C:Zn nanocomposites consists of three signals with the Lorentzian lineshape corresponding to paramagnetic centers with S = 1/2, which are related to carbon dangling bonds (CDB) (g = 2.0029(3)), silicon dangling bonds (g = 2.0062(3)) and oxygen-centered carbon-related radicals (CRR) (g = 2.0042(3)). A small EPR linewidth (<1 mT) observed for CDB and oxygen-centered CRR allows us to conclude that they are in the sp3-hybridized state. It was found that the temperature dependence of the EPR signal integrated intensity of the CDB and oxygen-centered CRR follows the Curie–Weiss law with a small positive value of the Curie–Weiss constant, which indicates that the weak ferromagnetic exchange interaction takes place in the spin system of CDB and oxygen-centered CRR. It was supposed that the carbon-related centers are clustered in SiO2:C:Zn nanocomposites. We assume that the oxygen-centered CRR in the sp3-hybridized state are associated with luminescent centers in previously reported aged Zn(acac)2/C2H5OH solution.

Evaluation of systemic blood NO dynamics by EPR spectroscopy: HbNO as an endogenous index of NO

2003 ◽  
Vol 285 (2) ◽  
pp. H589-H596 ◽  
Author(s):  
Kazuyoshi Kirima ◽  
Koichiro Tsuchiya ◽  
Hiroyoshi Sei ◽  
Toyoshi Hasegawa ◽  
Michiyo Shikishima ◽  
...  
Keyword(s):  
Endothelial Dysfunction ◽  
Whole Blood ◽  
Computer Assisted ◽  
Subtraction Method ◽  
Epr Spectrum ◽  
Systemic Blood ◽  
Paramagnetic Resonance ◽  
Species Overlap ◽  
Epr Signal ◽  
Electron Paramagnetic

The measurement of hemoglobin-nitric oxide (NO) adduct (HbNO) in whole blood by the electron paramagnetic resonance (EPR) method seems relevant for the assessment of systemic NO levels. However, ceruloplasmin and unknown radical species overlap the same magnetic field as that of HbNO. To reveal the EPR spectrum of HbNO, we then introduced the EPR signal subtraction method, which is based on the computer-assisted subtraction of the digitized EPR spectrum of HbNO-depleted blood from that of sample blood using the software. Rats were treated with Nω-nitro-l-arginine methyl ester (l-NAME; 120 mg · kg–1 · day–1) for 1 wk to obtain HbNO-depleted blood. When this method was applied to the analysis of untreated fresh whole blood, the five-coordinate state of HbNO was observed. HbNO concentration in pentobarbital-anesthetized rats was augmented (change in [HbNO] = 1.6–5.5 μM) by infusion of l-arginine (0.2–0.6 g/kg) but not d-arginine. Using this method, we attempted to evaluate the effects of temocapril on HbNO dynamics in an l-NAME-induced rat endothelial dysfunction model. The oral administration of l-NAME for 2 wk induced a serious hypertension, and the HbNO concentration was reduced (change in [HbNO] = 5.7 μM). Coadministration of temocapril dose dependently improved both changes in blood pressure and the systemic HbNO concentration. In this study, we succeeded in measuring the blood HbNO level as an index of NO by the EPR HbNO signal subtraction method. We also demonstrated that temocapril improves abnormalities of NO dynamics in l-NAME-induced endothelial dysfunction rats using the EPR HbNO signal subtraction method.

An Experimental Technique for Studying Chemisorption Reactions by Means of Electron Paramagnetic Resonance Spectroscopy

1972 ◽  
Vol 26 (2) ◽  
pp. 239-241 ◽  
Author(s):  
Eugene P. Scheide ◽  
George G. Guilbault
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Experimental Method ◽  
Electron Paramagnetic Resonance Spectroscopy ◽  
Cupric Chloride ◽  
Resonance Spectroscopy ◽  
Epr Spectrum ◽  
Paramagnetic Resonance ◽  
Before And After ◽  
Chemisorption Bond ◽  
Electron Paramagnetic

A new experimental method and a specially designed EPR cell are described for use in the study of chemisorption reactions. By studying the EPR spectrum of a surface both before and after chemisorption, it can be shown whether unpaired d electrons are used in the chemisorption bond and the nature of this bond. The EPR spectra of a cupric chloride surface, both before and after a gaseous ligand (diisopropyl methyl phosphonate) is chemisorbed, are shown and the results are interpreted in terms of the type of bond formed.

EPR spectra of a new radiation-induced paramagnetic centre in kaolins

Clay Minerals ◽  
2016 ◽  
Vol 51 (5) ◽  
pp. 707-714 ◽  
Author(s):  
Bernard A. Goodman ◽  
Niramon Worasith ◽  
Wen Deng
Keyword(s):  
Radiation Dose ◽  
Spin Hamiltonian ◽  
Paramagnetic Centre ◽  
Epr Spectrum ◽  
Γ Radiation ◽  
Rhombic Symmetry ◽  
Radiation Induced ◽  
Epr Signal ◽  
A Minor ◽  
Hamiltonian Parameters

AbstractThe EPR spectrum of a previously unreported paramagnetic centre formed in kaolin minerals by exposure to γ radiation is described. This centre, which is referred to here as the ‘C-centre’, was seen initially during an investigation of the radiation dose response of the EPR signal in the natural Lampang kaolin from northern Thailand, and its EPR properties are now presented for a purified sample from this material. They suggest a paramagnetic centre with rhombic symmetry based on O− associated with a single 27Al atom. Computer simulations suggest spin Hamiltonian parameters of g1 = 1.976, g3 = 2.0417 and A(27Al) = 2.10 mT, with g2 ≈ 2.01. This C-centre was also seen as a minor radiationinduced component in both crude and purified Ranong kaolin samples, along with a stronger signal from the B-centre radical. It seems to be associated with the kaolinite component, but was lost on annealing to 300°C after which only the signal from the A-centre was visible.

Electron paramagnetic resonance study of paramagnetic centers in carbon-fumed silica adsorbent

2014 ◽  
Vol 115 (13) ◽  
pp. 133704 ◽  
Author(s):  
D. V. Savchenko ◽  
B. D. Shanina ◽  
E. N. Kalabukhova ◽  
A. A. Sitnikov ◽  
V. S. Lysenko ◽  
...  
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Fumed Silica ◽  
Electron Paramagnetic Resonance Study ◽  
Paramagnetic Centers ◽  
Paramagnetic Resonance ◽  
Silica Adsorbent ◽  
Electron Paramagnetic

scholarly journals Temperature study of magnetic resonance spectra of co-modified (Co,N)-TiO2 nanocomposites

2016 ◽  
Vol 34 (2) ◽  
pp. 242-250 ◽  
Author(s):  
Nikos Guskos ◽  
Janusz Typek ◽  
Grzegorz Zolnierkiewicz ◽  
Aleksander Guskos ◽  
Pawel Berczynski ◽  
...  
Keyword(s):  
Magnetic Resonance ◽  
Low Temperature ◽  
Cobalt Nanoparticles ◽  
Resonance Spectroscopy ◽  
Temperature Analysis ◽  
Epr Spectrum ◽  
Paramagnetic Resonance ◽  
Magnetic Polarons ◽  
Integrated Intensity ◽  
Electron Paramagnetic

AbstractThe (nCo,N)-TiO2 (n = 1, 5 and 10 wt.% of Co) nanocomposites were investigated by magnetic resonance spectroscopy in 4 K to 290 K range. Analyses of ferromagnetic/electron paramagnetic resonance (FMR/EPR) spectra in terms of four Callen lineshape components revealed the existence of two types of magnetic centers, one derived from metallic cobalt nanoparticles in superparamagnetic (SPM) phase and the other from cobalt clusters in the TiO2 lattice. Additionally, at low temperature the EPR spectrum arising from Ti3+ ions was also registered. Both relaxations of the Landau-Lifshitz type and the Bloch-Bloembergen type played an important role at high temperature in determining the linewidths and the latter relaxation was prevailing at low temperature. Analysis of the integrated intensity showed that the SPM signal is due to small size FM cobalt nanoparticles while the paramagnetic signal from Co clusters originates from those nanoparticles in which the concentration of magnetic polarons is below the percolation threshold.

scholarly journals DEPENDENCE OF ELECTRON PARAMAGNETIC RESONANCE (EPR) SPECTRUM PARAMETERS ON THE KIND OF MEAT AND FISH TREATED BY IONIZING RADIATION

2018 ◽  
Vol 97 (9) ◽  
pp. 873-876
Author(s):  
R. T. Timakova ◽  
Sergei L. Tikhonov ◽  
O. V. Evdokimova ◽  
I. V. Butenko
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Ionizing Radiation ◽  
Bone Tissue ◽  
Radiation Treatment ◽  
Raw Materials ◽  
Food Products ◽  
Epr Spectrum ◽  
Paramagnetic Resonance ◽  
Epr Signal ◽  
Electron Paramagnetic

Regulation of the use of ionizing radiation for treating food products and agricultural raw materials in Russia in 2017 suggests a wide dissemination of radiation technologies in the food industry, but manufacturers of food products processed by ionizing radiation do not indicate on the label the relevant information. Because of this, the identification of the domestic consumer market of food products processed by ionizing radiation will reduce the number of violations of requirements of state standard State standards (GOST) 33800-2016 “Production of food irradiated. General labeling requirements”. To determine whether irradiation of food raw materials and foodstuff, used the method of electron paramagnetic resonance (EPR), with each of the food products treated by ionizing radiation has its own characteristic EPR spectrum. In this regard, the aim of the research is to identify the dependence of the parameters of the EPR spectrum from meat, fish and poultry treated with ionizing radiation. Samples of bone tissue (SBT) meat, fish and poultry were subjected to radiation treatment with a linear electron accelerator model UELR-10-10С2 with energies up to 10 MeV. Studies of samples were carried out on the portable automated EPR spectrometer brand Labrador Expert X-band. Found that despite treatment samples of bone tissue with the same dose of ionizing radiation (12 kGy), the EPR signal depends on the type of vertebrates, the structure of the tissue sample, and other factors. Bone samples of beef and pork have a higher sensitivity to irradiation. Recorded a steady correlation between increasing the area of the EPR signal parameters: amplitude is of 0.99, the width of the peak signal, respectively 0,979 (the degree of strength of statistical relationships Chedoke very high). Processing of the obtained results of the EPR spectrum provides a high degree of confidence (p≤0.05) to identify how previously non-irradiated and radiation-processed various meats, fish and poultry.

scholarly journals Epr Spectrum Angular Dependences In Liyf4 Crystal / Epr Spektru Leņķiskās Atkarības Liyf4 Kristālā

2012 ◽  
Vol 49 (6-I) ◽  
pp. 49-54
Author(s):  
A. Antuzevics ◽  
A. Fedotovs ◽  
U. Rogulis
Keyword(s):  
Room Temperature ◽  
Temperature Analysis ◽  
Epr Spectrum ◽  
Spectral Parameters ◽  
Paramagnetic Resonance ◽  
X Ray ◽  
Crystal Growth Process ◽  
Before And After ◽  
Impurity Ion ◽  
Electron Paramagnetic

Abstract Electron paramagnetic resonance (EPR) measurements have been made for two perpendicular planes in a LiYF4 crystal before and after x-ray irradiation at room temperature. Analysis of the EPR spectrum angular dependence shows the presence of two defects - an impurity ion, which was embedded during the crystal growth process, and an x-ray induced defect with the g-factor of approx. 2.0. Spectral parameters and possible defect models are discussed.

Synthesis and Characterization of CaO-SiO2-MgO Bioactive Glass Produced by Sol-Gel

2016 ◽  
Vol 720 ◽  
pp. 252-256
Author(s):  
Nadia Mohammed Elmassalami Ayad ◽  
Andre Ben Hur da Silva Figueiredo ◽  
Wilma de Araujo Gonzalez ◽  
Daniel Navarro da Rocha ◽  
Rubens Lincoln Santana Blazutti Marçal ◽  
...  
Keyword(s):  
Fumed Silica ◽  
High Surface ◽  
Sol Gel ◽  
High Surface Area ◽  
Gel Method ◽  
Sol Gel Method ◽  
Before And After ◽  
Ft Ir ◽  
Silica Precursor ◽  
Gelling Time

Bioactive glasses have widely used in biomedical applications such as bone filler due to their excellent biocompatibility, bioactivity and osteoconduction characteristics. In this work, a silicate-rich glass was synthesized by the sol-gel method with 60% SiO2 – 30%CaO – 10% MgO composition where fumed silica acts as the silica precursor. This new method was hypothesized to reduce the gel formation time, due to the high surface area of the fumed silica. In addition, this would presumably increase the nanoporosity of the glass. For comparison purposes, we used a glass of the same composition, but with the conventional silica precursor, tetraethyl orthosilicate (TEOS), through the sol gel method. Both were heat treated at 450°C. FT-IR analysis before and after heat treatment at 450°C showed the presence of nitrate groups, especially in the TEOS samples. This is consistent with the more hygroscopic aspect of those samples. The fumed silica samples had significantly less pronounced peaks corresponding to the nitrate groups, consistent with the more porous structure and the less hygroscopic aspect. The fumed silica samples indeed had a lower gelling time and showed similar results obtained by XRD and FT-IR analyses, showing that the use of fumed silica is viable and advantageous in the glass synthesis by the sol-gel process

Nitric Oxide Sensors obtained through the entrapment of iron complexes in sol-gel matrix

2002 ◽  
Vol 723 ◽  
Author(s):  
Juliana C. Biazzotto ◽  
João F. Borin ◽  
Roberto Mendonça Faria ◽  
Carlos F.O Graeff ◽  
Ribeirão Preto
Keyword(s):  
Nitric Oxide ◽  
Sol Gel ◽  
Soret Band ◽  
Sodium Dithionite ◽  
Good Evidence ◽  
Silica Matrix ◽  
Epr Spectrum ◽  
The Matrix ◽  
Epr Signal ◽  
Nitric Oxide Sensors

AbstractIron(III)-diethyldithiocarbamate (Fe3DETC) or iron(III)-tetra-pentafluorophenyl porphyrin (FeTFPP) was entrapped within a silica matrix by the sol-gel process. The obtained sol-gel materials SGFeDETC and SGFeTFPP were investigated as sensors for nitric oxide (NO). UV/Vis spectra of the SGFeTFPP present a Soret band at 410 nm similar to that found in the solution. The binding of gaseous NO resulted in a red shift in the Soret absorption band (410 to 419 nm) of the FeTFPP in the matrix unlike FeTFPP:NO in solution. In the case of SGFeDETC, after addition of sodium dithionite solution and bubbling NO we have good evidence that the complex is formed. The EPR spectrum of the SGFeDETC:NO in solid form exhibited a signal similar to that found in a solution of FeDETC:NO at 77K. The UV/Vis spectrum of SGFeDETC:NO shows a band at 367 nm also found in FeDETC:NO solutions. It is observed that the FeDETC:NO is more stable entrapped in the sol-gel than in aqueous solution. In the former the EPR signal decreases by a factor of 4 after one week, in the latter in 2 days the EPR signal cannot be observed anymore.

The Effects of Kcn Etching on Cu-Rich Epitaxial CuInSe2 Thin Films

1996 ◽  
Vol 426 ◽  
Author(s):  
P. Fons ◽  
S. Nikl ◽  
A. Yamada ◽  
M. Nishitanp ◽  
T. Wada ◽  
...  
Keyword(s):  
Thin Films ◽  
Surface Region ◽  
Etching Time ◽  
Cation Sublattice ◽  
Epitaxial Thin Films ◽  
Near Surface ◽  
Force Microscopy ◽  
Atomic Force ◽  
Before And After ◽  
Integrated Intensity

AbstractA series of Cu-rich CuInSe2 epitaxial thin films were grown by molecular beam epitaxy on GaAs(001) substrates from elemental sources at a growth temperature of 450 °C. All samples were grown with an excess of Cu. Electron microprobe analysis (EPMA) indicated a Cu/ In ratio of about 2.1–2.6 in the as-grown films. Additionally, the Se/ (In+Cu) ratio was observed to be ∼0.95 indicating that the films were slightly Se poor. These Cu-rich samples were etched in a KCN solution for periods ranging from 30 seconds to 3 minutes. EPMA measurements indicated that the bulk Cu/ In ratio was reduced to ∼0.92 in all films regardless of etching time. Atomic force microscopy (AFM) was used to characterize the topology of each sample before and after etching. These measurements indicated that the precipitates present on the as-grown films were removed and large nearly isotropic holes were etched into the sample to a depth of over 1000 Å even for etching times as short as 30 seconds. The samples were also evaluated both before and after etching using a Phillips MRD diffractometer with parallel beam optics and a 18,000 watt Cu rotating anode X-ray source in the chalcopyrite [001], [101], and [112] directions. A peak was observed at ∼15 degrees in the [001] scan after etching consistant with the presence of the ordered vacancy compound, CuIn3Se5. Additionally the integrated intensity ratios of the chalcopyrite (202) reflection to the chalcopyrite (101) reflection ∝(fCu-fIn)2 along the [101] direction indicated the presence of a near-surface region containing cation sublattice disorder that was subsequently removed by the etching process.

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