Search results for "spin resonance"
showing 10 items of 156 documents
Variability of the Si-O-Si angle in amorphous-SiO2 probed by electron paramagnetic resonance and Raman spectroscopy
2009
We report an experimental investigation by electron paramagnetic resonance (EPR) and Raman spectroscopy on a variety of amorphous silicon dioxide materials. Our study by EPR have permitted us to point out that the splitting of the primary hyperfine doublet of the Eγ′ center shows a relevant sample-to-sample variability, changing from ∼41.8 to ∼42.6 mT in the set of materials we considered. The parallel study by Raman spectroscopy has enabled us to state that this variability is attributable to the different Si-O-Si angle characterizing the matrices of the different materials. © 2009 Elsevier B.V. All rights reserved.
Structural properties of the range-II- and range-III order in amorphous-SiO2 probed by electron paramagnetic resonance and Raman spectroscopy
2010
In the present work we report an experimental investigation by electron paramagnetic resonance spectroscopy on the hyperfine structure of the E. point defect, probing the local arrangement of the network (range-II order), and by Raman spectroscopy on the D 1 and D 2 lines, probing mean features of the network (range-III order). Our studies, performed on a-SiO 2 samples thermally treated at 1000 °C in air for different time durations, show that changes of the hyperfine structure and of the D 1 and D 2 lines occur in a correlated way. These results give strong evidence that the range-II and range-III order properties are intimately related to each other and that these properties are determine…
ESR study of the liposome membrane physical parameters in the heating-cooling cycles.
1998
Abstract Changes of dynamic and structural parameters of egg yolk lecithin (EYL) liposome membranes in the heating-cooling cycles have been studied using the E S R spin probe method. The investigations were conducted in the range of temperatures from -18 °C to +60 °C. It has been found that in the range of temperatures -15 °C to +45 °C in both the heating and the cooling run the spectroscopic parameters changed practically along the same curve (reversible changes). However, after exceeding this range of temperatures one of the parameters (partition coefficient of the spin probe 2,2,6,6 -tetramethylpiperidine -1-oxyl; TEMPO) changed along a closed curve, showing the phenomenon of thermal h…
Testing and linearity calibration of films of phenol compounds exposed to thermal neutron field for EPR dosimetry
2015
This paper reports the preliminary results obtained by Electron Paramagnetic Resonance (EPR) measurements on films of IRGANOX® 1076 phenols with and without low content (5% by weight) of gadolinium oxide (Gd2O3) exposed in the thermal column of the Triga Mark II reactor of LENA (Laboratorio Energia Nucleare Applicata) of Pavia (Italy). Thanks to their size, the phenolic films here presented are good devices for the dosimetry of beams with high dose gradient and which require accurate knowledge of the precise dose delivered. The dependence of EPR signal as function of neutron dose was investigated in the fluence range between 10(11) cm(-2) and 10(14) cm(-2). Linearity of EPR response was fou…
Metal complexes of the carbonic anhydrase inhibitor methazolamide (Hmacm). Crystal structure of the Zn(macm)2 (NH3)2. Anticonvulsant properties of th…
1995
Complexes of Co(II), Cu(II), and Zn(II) with deprotonated methazolamide and ammonia are synthesized and characterized. The complex Zn(macm)2(NH3)2 crystallizes in the monoclinic C2/c space group with a = 13.468(1), b = 6.759(1), c = 23.014(2) A, beta = 90.27(1), and Z = 4. The structure was refined to R = 0.049 (Rw = 0.053). The Zn(II) ion is coordinated to two deprotonated sulfonamido nitrogen atoms of the macm- ligand and two nitrogen atoms of the ammonia ligands in a distorted tetrahedron. The Zn(macm)2(NH3)2 complex is shown to be a simple model for the methazolamide inhibition of CA. EHMO calculations applied to fractional coordinates of the Zn(macm)2(NH3)2 complex indicate that the at…
Synthesis, characterization, and crystal structure of [Cu(cinoxacinate)2] · 2H2O complex: A square-planar CuO4 chromophore. Antibacterial studies
1995
The structural and spectroscopic properties of a new copper (II) complex of cinoxacin (HCx) have been investigated. The complex [Cu(Cx)2].2H2O crystallizes in the monoclinic system, space group P2(1)/c. The cell dimensions are: a = 7.998(2), b = 7.622(1), c = 18.955(6) A, beta = 94.38(2) degree, V = 1154.6(6) A3, Z = 2. The structure was refined to R = 0.051. The crystal is composed of [Cu(Cx)2] units and uncoordinated water molecules. The Cu(II) ion, at a center of symmetry, is coordinated to two cinoxacinate (Cx) ligands related by the inversion center. Each cinoxacinate acts as bidentate ligand bonded to the cation through its carboxylate oxygen atom and through its exocyclic carbonyl ox…
Influence of neutron and gamma-ray irradiations on rad-hard optical fiber
2015
We investigated point defects induced in rad-hard Fluorine-doped optical fibers using both a mixed source of neutrons (fluences from 1015 to 1017 n/cm2) and γ-rays (doses from 0.02 to 2 MGy) and by a γ-ray source (dose up to 10 MGy). By combining several complementary spectroscopic techniques such as radiation-induced attenuation, confocal micro-luminescence, time-resolved photo-luminescence and electron paramagnetic resonance, we evidenced intrinsic and hydrogen-related defects. The comparison between the two irradiation sources highlights close similarities among the spectroscopic properties of the induced defects and the linear correlation of their concentration up to 1016 n/cm2. These r…
Ascorbic Acid Oxidation in Sucrose Aqueous Model Systems at Subzero Temperatures
2004
The reduction of Tempol by ascorbic acid in concentrated sucrose solutions was measured by electron paramagnetic resonance (EPR) at temperatures ranging from 16 to −16 °C. This method allowed the determination of the rate constants (k) of this fast reaction, by recording the Tempol reduction as a function of time. The two reactants were initially separated and had to migrate for the reaction to occur. The experimental findings were compared with predicted values according to the equation for diffusion-controlled reaction proposed by Atkins. The experimental reaction rate constants were observed to be lower than the calculated ones. However, the experimental values were found to be controlle…
DNA cleavage reaction induced by dimeric copper(II) complexes of N-substituted thiazole sulfonamides
2005
A new dinuclear copper(II) complex has been synthesised and structurally characterised: [Cu2(tz-ben)4] (Htz-ben = N-thiazol-2-yl-benzenesulfonamide). Its crystal structure, magnetic properties and electronic paramagnetic resonance (EPR) spectra were studied in detail. In the compound the metal centres are bridged by four non-linear triatomic NCN groups. The coordination geometry of the copper ions in the dinuclear entity is distorted square pyramidal (4+1). Two thiazole N and two sulfonamido N atoms occupy the equatorial positions and one sulfonamido O atom is in the axial position. Magnetic susceptibility data show a strong antiferromagnetic coupling, -2J = 114.1 cm(-1). The EPR spectra of…
Reinforced Room-Temperature Spin Filtering in Chiral Paramagnetic Metallopeptides
2020
Chirality-induced spin selectivity (CISS), whereby helical molecules polarize the spin of electrical current, is an intriguing effect with potential applications in nanospintronics. In this nascent field, the study of the CISS effect using paramagnetic chiral molecules, which could introduce another degree of freedom in controlling the spin transport, remains so far unexplored. To address this challenge, herein we propose the use of self-assembled monolayers (SAMs) of helical lanthanide-binding peptides. To elucidate the effect of the paramagnetic nuclei, monolayers of the peptide coordinating paramagnetic or diamagnetic ions are prepared. By means of spin-dependent electrochemistry, the CI…