Electron Paramagnetic Resonance Study of Defects in γ-irradiated Marine Mussel (Mytilus galloprovincialis) and Scallop (Pecten jacobaeus) Shells

2004 ◽  
Vol 59 (11) ◽  
pp. 773-779
Author(s):  
R. Köseoğlu ◽  
F. Köksal ◽  
M. Birey
Keyword(s):  
Free Radicals ◽  
Mytilus Galloprovincialis ◽  
Electron Paramagnetic Resonance Study ◽  
Γ Irradiation ◽  
Paramagnetic Resonance ◽  
Scallop Shells ◽  
Marine Mussels ◽  
Gamma Irradiated ◽  
Induced Defects ◽  
Irradiation Induced Defects

EPR studies have been performed on some gamma-irradiated marine mussels (Mytilus galloprovincialis) and scallops (Pecten jacobaeus) from the families of Mytilidae and Pectinidae, respectively. Before γ-irradiation, the EPR lines of Mytilus galloprovincialis indicated the existence of Mn2+ ions, which were not observed in the powders of scallop shells. γ -irradiation induced defects in powders of Mytilus galloprovincialis shells, were attributed to orthorhombic CO−3 , axial CO3−3 , orthorhombic CO−2 , freely rotating CO−2 , freely rotating SO−2 , axial SO−3 , isotropic PO2−4 and organic free radicals. γ -irradiation induced defects in powders of Pecten jacobaeus shells were attributed to orthorhombic CO−3 , axial CO3−3 , orthorhombic CO−2 , freely rotating CO−2 , freely rotating SO−2 , and axial SO−3 free radicals. The EPR parameters of the free radicals were compared with literature data on similar defects

Radiation-induced defects in montebrasite: An electron paramagnetic resonance study of O – hole and Ti3+ electron centers

2020 ◽  
Vol 105 (7) ◽  
pp. 1051-1059
Author(s):  
José R. Toledo ◽  
Raphaela de Oliveira ◽  
Lorena N. Dias ◽  
Mário L.C. Chaves ◽  
Joachim Karfunkel ◽  
...  
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Electron Irradiation ◽  
Color Centers ◽  
Hydroxyl Groups ◽  
Γ Irradiation ◽  
Paramagnetic Resonance ◽  
Radiation Induced ◽  
Induced Defects ◽  
Electron Paramagnetic ◽  
Hole Centers

Abstract Montebrasite is a lithium aluminum phosphate mineral with the chemical formula LiAlPO4(Fx,OH1–x) and considered a rare gemstone material when exhibiting good crystallinity. In general, montebrasite is colorless, sometimes pale yellow or pale blue. Many minerals that do not have colors contain hydroxyl ions in their crystal structures and can develop color centers after ionization or particle irradiation, examples of which are topaz, quartz, and tourmaline. The color centers in these minerals are often related to O− hole centers, where the color is produced by bound small polarons inducing absorption bands in the near UV to the visible spectral range. In this work, colorless montebrasite specimens from Minas Gerais state, Brazil, were investigated by electron paramagnetic resonance (EPR) for radiation-induced defects and color centers. Although γ irradiation (up to a total dose of 1 MGy) did not visibly modify color, a 10 MeV electron irradiation (80 MGy) induced a pale greenish-blue color. Using EPR, O− hole centers were identified in both γ- or electron-irradiated montebrasite samples showing superhyperfine interactions with two nearly equivalent 27Al nuclei. In addition, two different Ti3+ electron centers were also observed. From the γ irradiation dose dependency and thermal stability experiments, it is concluded that production of O− hole centers is limited by simultaneous creation of Ti3+ electron centers located between two equivalent hydroxyl groups. In contrast, the concentration of O− hole centers can be strongly increased by high-dose electron irradiation independent of the type of Ti3+ electron centers. From detailed analysis of the EPR angular rotation patterns, microscopic models for the O− hole and Ti3+ electron centers are presented, as well as their role in the formation of color centers discussed and compared to other minerals.

scholarly journals Electron-paramagnetic-resonance study of silver-induced defects in silicon

1997 ◽  
Vol 56 (8) ◽  
pp. 4614-4619 ◽  
Author(s):  
P. N. Hai ◽  
T. Gregorkiewicz ◽  
C. A. J. Ammerlaan ◽  
D. T. Don
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Electron Paramagnetic Resonance Study ◽  
Paramagnetic Resonance ◽  
Induced Defects ◽  
Electron Paramagnetic

scholarly journals Electron Paramagnetic Resonance Study of Thermally Treated Bismuth Subgallate

2014 ◽  
Vol 2014 ◽  
pp. 1-9 ◽  
Author(s):  
Paweł Ramos ◽  
Barbara Pilawa
Keyword(s):  
Free Radicals ◽  
Free Radical ◽  
Epr Spectroscopy ◽  
Electron Paramagnetic Resonance Study ◽  
Strong Interactions ◽  
Paramagnetic Resonance ◽  
Model Free ◽  
Different Temperatures ◽  
Bismuth Subgallate ◽  
Thermal Sterilization

Complex of bismuth, an anti-inflammatory drug, was studied by EPR spectroscopy. The aim of this study was to determine concentrations and properties of free radicals formed during thermal sterilization of bismuth subgallate according to pharmacopoeia norms to optimize its sterilization process. Different temperatures (160°C, 170°C, and 180°C) and times (120 minutes, 60 minutes, and 30 minutes) of sterilization were used. Interactions of bismuth subgallate with DPPH, the model free radical reference, were checked.g-Factors, amplitudes (A), integral intensities (I), and linewidths (ΔBpp) were obtained. Integral intensities were obtained by double integration of the first-derivative EPR lines. The influence of microwave power in the range of 2.2–70 mW on shape and parameters of the EPR spectra was examined. Thermal sterilization produced free radicals in bismuth subgallate in all tested cases. Strong interactions with free radicals were pointed out for all the analysed samples containing bismuth independent of sterilization conditions. Optimal conditions of thermal sterilization for bismuth subgallate with the lowest free radical formation are temperature 170°C and time of heating 60 minutes. Strong dipolar interactions exist in thermally sterilized bismuth subgallate. EPR spectroscopy is a useful method of examination of thermal sterilization conditions.

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