Search results for "Paramagnetic"

An EPR method for discriminating radiation beams in ammonium tartrate and tooth enamel

2008

The radiation linear energy transfer (LET), which is the energy released by ionizing radiation per path unit, arouses great scientific interest because the biological damage produced by ionizing radiation in tissues is strictly related to LET. Radiation beams with different LETs will cause different spatial energy distribution and therefore different effects inside matter. In the last twenty years the EPR spectroscopy has become a valuable dosimetric tool. This technique allows absorbed dose measurements through the detection of free radicals produced by ionizing radiation in organic and/or inorganic compounds. In this work we have analyzed the possibility of using the acquisition of two co…

Catalytic oxidation of n-hexane promoted by Ce1-xCuxO2 catalysts prepared by one-step polymeric precursor method

2013

Abstract Ceria-supported copper catalysts (Ce1−xCuxO2, with x (mol) = 0, 0.01, 0.03, 0.05 and 0.10) were prepared in one step through the polymeric precursor method. The textural properties of the catalysts were investigated by X-ray diffraction (XRD), Rietveld refinement, N2-physisorption (BET surface area), electron paramagnetic resonance (EPR), UV–visible diffuse reflectance and photoluminescence spectroscopies and temperature-programmed reduction (TPR). In a previous study ceria-supported copper catalysts were found to be efficient in the preferential oxidation of CO. In this study, we extended the catalytic application of Ce1−xCuxO2 systems to n-hexane oxidation and it was verified tha…

Behaviour of advanced tritium breeder pebbles under simultaneous action of accelerated electrons and high temperature

2017

The authors greatly acknowledge the technical and experimen-tal support of O. Valtenbergs and L. Avotina (Institute of Chemical Physics, University of Latvia). The work is performed in the frames of the University of Latvia financed project No. Y9-B044-ZF-N-300, “Nano, Quantum Technologies, and Innovative Materials for Eco-nomics”.

Enhancement of persistent luminescence in Ca2SnO4: Sm3+

2021

Abstract Reddish-orange persistent luminescent Ca2SnO4: 0.1% Sm3+ co-doped with 0–10% Gd3+ was prepared using solid state synthesis. The phase formation and morphology was analyzed using X-ray diffraction and scanning electron microscopy. Incorporation of Sm3+ and Gd3+ in Ca2SnO4 lattice was investigated using site-selective spectroscopy and electron paramagnetic resonance. In all samples reddish-orange persistent luminescence and photochromic effect was observed after excitation with UV as well as X-rays. The thermostimulated luminescence curves indicated that the introduction of Gd3+ increases the number of shallow traps of charges which enhance the intensity of persistent luminescence. I…

Neutron ESR dosimetry through ammonium tartrate with low Gd content.

2014

This paper continues analyses on organic compounds for application in neutron dosimetry performed through electron spin resonance (ESR). Here, the authors present the results obtained by ESR measurements of a blend of ammonium tartrate dosemeters and gadolinium oxide (5 % by weight). The choice of low amount of Gd is due to the need of improving neutron sensitivity while not significantly influencing tissue equivalence. A study of the effect of gadolinium presence on tissue equivalence was carried out. The experiments show that the neutron sensitivity is enhanced by more than an order of magnitude even with this small additive content. Monte Carlo simulations on the increment of energy rele…

Contactless Nanoparticle-Based Guiding of Cells by Controllable Magnetic Fields

2021

Peter Blümler,1 Ralf P Friedrich,2 Jorge Pereira,3 Olga Baun,1 Christoph Alexiou,2 Volker Mailänder3,4 1Institute of Physics, Johannes Gutenberg-University Mainz, Mainz, 55128, Germany; 2Department of Otorhinolaryngology, Head and Neck Surgery, Section of Experimental Oncology and Nanomedicine (SEON), Else Kröner-Fresenius-Stiftung-Professorship, Universitätsklinikum Erlangen, Erlangen, 91054, Germany; 3Department of Physical Chemistry, Max Planck Institute for Polymer Research, Mainz, 55128, Germany; 4Department of Dermatology, University Medical Center of the Johannes Gutenberg-University Mainz, Mainz, 55131, GermanyCorrespondence: Peter Blümle…

Hydrogen-Related Paramagnetic Centers in Ge-Doped Sol-Gel Silica Induced by γ-Ray Irradiation

2006

We have studied the generation mechanisms of H(II) paramagnetic centers in Ge-doped silica by investigating up to 104 mol ppm sol-gel Ge-doped silica materials. We have considered materials with the same concentrations of Ge but that are produced by two different densification routes that give rise to different concentrations of Ge-related oxygen deficient centers (GeODC(II)). These centers are characterized by an optical absorption band at ∼5.2 eV (B2 β band) and two related emissions at ∼3.2 eV and ∼4.3 eV. The GeODC(II) content was estimated by absorption and emission measurements. The H(II) centers were induced by room temperature γ-ray irradiation and their concentration was determined…

Delocalized Nature of theEδ′Center in Amorphous Silicon Dioxide

2005

We report an experimental study by electron paramagnetic resonance (EPR) of E(')(delta) point defect induced by gamma-ray irradiation in amorphous SiO2. We obtained an estimation of the intensity of the 10 mT doublet characterizing the EPR spectrum of such a defect arising from hyperfine interaction of the unpaired electron with a 29Si (I=1/2) nucleus. Moreover, determining the intensity ratio between this hyperfine doublet and the main resonance line of E(')(delta) center, we pointed out that the unpaired electron wave function of this center is actually delocalized over four nearly equivalent silicon atoms.

2015

Electrically detected magnetic resonance (EDMR) is a commonly used technique for the study of spin-dependent transport processes in semiconductor materials and electro-optical devices. Here, we present the design and implementation of a compact setup to measure EDMR, which is based on a commercially available benchtop electron paramagnetic resonance (EPR) spectrometer. The electrical detection part uses mostly off-the-shelf electrical components and is thus highly customizable. We present a characterization and calibration procedure for the instrument that allowed us to quantitatively reproduce results obtained on a silicon-based reference sample with a “large-scale” state-of-the-art instru…

EPR study of Ce3+ luminescent centers in the Y2SiO5 single crystalline films

2017

Abstract The work reports results of EPR investigation of the Ce3+ incorporation in the Y2SiO5 and (Y,La)2SiO5 single crystalline films (SCFs), grown by liquid phase epitaxy method. The Ce3+ content determined from EPR spectra varied between 0.49 and 0.65 at. % in Y2SiO5 SCFs and strongly increased up to 1.9 at. % in (Y,La)2SiO5 SCF, suggesting a positive role of the La dopant in the incorporation of the Ce3+ ions into Y2SiO5 host. The EPR study showed the presence of only one type of Ce3+ centers (Ce1) corresponding to the localization of Ce3+ ions in the seven–fold coordinated positions of the Y2SiO5 host. No Ce2 center spectra (six-fold coordinated Ce3+ positions) were detected in films …