Search results for "Paramagnetic"

Bimetallic MnIII–FeII hybrid complexes formed by a functionalized MnIII Anderson polyoxometalate coordinated to FeII: observation of a field-induced …

2015

The synthesis and crystal structure of an Anderson POM functionalized with two 2,6-di(pyrazol-1-yl)-pyridine (1-bpp) ligands are reported (compound 1). High-frequency electron paramagnetic resonance (HF-EPR) and magnetic measurements show that it presents a significant negative axial zero-field splitting and field-induced slow relaxation of magnetization due to the presence of isolated MnIII anisotropic magnetic ions. Complexation of 1 with FeII gives rise to a 2D cationic network formed by Anderson POMs coordinated to two FeII ions through the two tridentate 1-bpp ligands and to other two FeII ions through two oxo ligands in compound 2, and to an anionic polymeric network formed by Anderso…

Gamma and x-ray irradiation effects on different Ge and Ge/F doped optical fibers

2015

International audience; We performed electron paramagnetic resonance (EPR) measurements on γ and X ray irradiated Ge doped and Ge/F co-doped optical fibers. We considered three different drawing conditions (speed and tension), and for each type of drawing, we studied Ge and Ge/F doped samples having Ge doping level above 4% by weight. The EPR data recorded for the γ ray irradiated fibers confirm that all the samples exhibit a very close radiation response regardless of the drawing conditions corresponding to values used for the production of specialty fibers. Furthermore, as for the X irradiated materials, in the γ ray irradiated F co-doped fibers, we observed that the Ge(1) and the Ge(2) d…

Optical and photonic material hardness for energetic environments

2009

We studied the effects of dielectric change in the chemical composition and in the realization procedures under radiation exposure. We have compared the radiation effects on Ge-doped and F-doped fibers and preforms: the first play a crucial role in the photosensitivity property, the second improves the dielectric radiation hardness even at low concentrations. The use of different spectroscopic techniques (RIA, OA, EPR) allow the identification of the point defect formation mechanisms at the origin of the optical degradation properties.

Magneto-structural diversity of Co(ii) compounds with 1-benzylimidazole induced by linear pseudohalide coligands

2020

We report the preparation, spectroscopic characterisation, crystal structure determination and cryomagnetic investigation of three cobalt(II) complexes of formula trans-[Co(bim)4(NCS)2] (1), [Co(bim)2(NCO)2] (2) and [Co(bim)2(N3)2]n (3) (bim = 1-benzylimidazole). The structure of 1 is made up of neutral [Co(bim)4(NCS)2] mononuclear units, where the cobalt(II) ion is six-coordinate with four monodentate bim ligands in equatorial positions and two N-thiocyanato groups in the axial sites building a slightly compressed octahedron. In contrast to 1, each cobalt(II) ion in 2 is four-coordinate with two imidazole-nitrogen atoms from two bim molecules and two N-cyanato ligands describing a slightly…

Electron spin resonance as a tool to monitor the influence of novel processing technologies on food properties

2020

Abstract Background Nowadays, electron spin resonance (ESR) is widely used as a powerful, non-destructive and very sensitive technique for the detection of free radicals in food systems. It can be applied for the direct identification of highly reactive oxygen species, organic and inorganic paramagnetic species and screening of food for potential toxicity. Its applications cover investigating food oxidative stability and properties of irradiated foods including fruits and vegetables, meats and fishes, spices, cereal grains, and oil seeds. Scope and approach This review aims at providing specialists in food science and industry with the fundamentals of ESR spectroscopy, typical radicals pres…

Radiation Defects in LiBaF3 Perovskites

2000

We investigated the electron paramagnetic resonance (EPR), recombination afterglow, thermostimulated luminescence (TSL) and absorption of LiBaF3 perovskites crystals X-irradiated at 80 K The self-trapped hole centre VK(F2-) oriented along the [110] axis and electron F type (FA) centres are identified. X-irradiation at temperatures below 200 K results in creation of a long-term temperature-independent afterglow-tunnelling luminescence (TL), with main emission bands at 300, 370 nm and 430 nm. The short wavelength TL bands are associated with the tunnelling recombination of the F type centre with the VK centre. The thermal stability of VK centre is estimated to be about 130 K.

Silica-coated superparamagnetic nanoparticles as contrast agent for magnetic resonance imaging: Synthesis and physicological charaterizations

2015

Superparamagnetic iron oxide nanoparticles (SPIONs) have received a growing interest for various biomedical applications due to their interesting magnetic properties. Herein, we report a method for facile synthesis of colloidal silica-coated superparamagnetic iron oxide nanoparticles (Si-SPIONs). The polyvinyl alcohol (PVA)-SPIONs were successfully prepared and then coated with silica by the modified Stober method. The obtained Si-SPIONs are highly monodisperse with uniform morphology. Notably, comparing to uncoated SPIONs, silica coated ones show colloidal stability region at physiological pH which is applicable in biomedical applications and synthesis at the scale of grams was easily obta…

Phenol compounds as new materials for electron spin resonance dosimetry in radiotherapy

2016

O-Doped Nanographenes: A Pyrano/Pyrylium Route Towards Semiconducting Cationic Mixed-Valence Complexes

2020

Herein we report an efficient synthesis to prepare O‐doped nanographenes, which derive from the longitudinally and latitudinally p‐extension of pyrene. The derivatives are highly fluorescent and feature low‐oxidation potentials. Exploiting electrooxidation, crystals of cationic mixed valence (MV) complexes were grown in which the organic salts organize into face‐to‐face p‐ p stacks, a favorable solid‐state arrangement for organic electronics. Variable‐temperature EPR measurements and relaxation studies suggest a strong electron delocalization along the longitudinal axis of the columnar p‐stacking architectures. Electric measurements of single crystals of the MV salts exhibited a semiconduct…

Low-temperature metastabilization of tetragonal V+4-containing ZrO2 solid solutions

2001

Abstract The formation and characterization of tetragonal vanadium–zirconia solid solutions with different vanadium contents have been investigated. Vanadium–zirconia precursors were prepared by gelling mixtures of zirconium n-propoxide and vanadyl acetylacetonate, and studied over the range of temperature up to the tetragonal–monoclinic phase transformation. The formation of the tetragonal phase has been investigated by X-ray powder diffraction (XRD). It was found that it took place after annealing around 450°C for all specimens independently of the vanadium loading. In contrast, the temperature for the subsequent tetragonal to monoclinic transformation was dependent on the nominal vanadiu…