Radiation Defects in Lime Mortars and Plasters Studied by EPR Spectroscopy

Radiocarbon ◽  
2020 ◽  
Vol 62 (3) ◽  
pp. 713-724
Author(s):  
Zuzanna Kabacińska ◽  
Danuta Michalska ◽  
Bernadeta Dobosz
Keyword(s):  
Epr Spectroscopy ◽  
Organic Radical ◽  
Radiation Defects ◽  
Paramagnetic Centers ◽  
Γ Irradiation ◽  
Paramagnetic Resonance ◽  
Crystalline Materials ◽  
Lime Mortars ◽  
Radiation Induced ◽  
Artificial Uv

ABSTRACTElectron paramagnetic resonance (EPR) spectroscopy is a well-established method of dating based on trapped charges, applied to various crystalline materials, including carbonates, bones, and teeth. It provides a detailed insight into the structure of radiation defects—paramagnetic centers generated by irradiation, without the need of a painstaking sample preparation, often challenging in other methods. Using EPR we studied the effect of γ radiation on lime mortars and plasters from ancient settlement Hippos in Israel, in order to analyze the process of defect generation. Analysis of the complex spectra revealed the presence of radiation-induced species, including CO2–, NO32– and organic radical. Using an artificial UV source, we generated relatively strong signals of paramagnetic centers, analogous to those created by γ irradiation, reaching their maximum intensity after 5–6 hr of UV exposure. Our results confirm the previous reports that radiation defects can also be generated, instead of bleached, in calcite by UV radiation, which is crucial for identifying the issues related to light exposition, affecting the accuracy of age determinations in trapped-charge dating methods.

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.

Electron paramagnetic resonance of radiation-induced paramagnetic centers in an aerogel

JETP Letters ◽  
2008 ◽  
Vol 88 (4) ◽  
pp. 244-248 ◽  
Author(s):  
G. V. Mamin ◽  
A. A. Rodionov ◽  
M. S. Tagirov ◽  
D. A. Tayurskii ◽  
N. Mulders
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Paramagnetic Centers ◽  
Paramagnetic Resonance ◽  
Radiation Induced ◽  
Electron Paramagnetic

scholarly journals Multifrequency EPR study on radiation induced centers in calcium carbonates labeled with 13C

Nukleonika ◽  
2015 ◽  
Vol 60 (3) ◽  
pp. 429-434 ◽  
Author(s):  
Jarosław Sadło ◽  
Anna Bugaj ◽  
Grażyna Strzelczak ◽  
Marcin Sterniczuk ◽  
Zbigniew Jaegermann
Keyword(s):  
Calcium Carbonate ◽  
Epr Spectroscopy ◽  
Orthorhombic Symmetry ◽  
Paramagnetic Centers ◽  
Calcium Carbonates ◽  
Radiation Induced

AbstractIn calcite and aragonite, γ-irradiated at 77 K, several paramagnetic centers were generated and detected by EPR spectroscopy; in calcite, CO3−(orthorhombic symmetry, bulk and bonded to surface), CO33−, NO32−, O3−, and in aragonite CO2−(isotropic and orthorhombic symmetry) depending on the type of calcium carbonate used. For calcium carbonates enriched with13C more detailed information about the formed radicals was possible to be obtained. In both natural (white coral) and synthetic aragonite the same radicals were identified with main differences in the properties of CO2−radicals. An application of Q-band EPR allowed to avoid the signals overlap giving the characteristics of radical anisotropy.

Electron Paramagnetic Resonance of Organic and Inorganic Centers in γ-Irradiated Natural Sepiolite Minerals

2006 ◽  
Vol 61 (7-8) ◽  
pp. 413-417 ◽  
Author(s):  
Rahmi Köseoğlua ◽  
Fevzi Köksalb ◽  
Mehmet Akkurt ◽  
Emin Çiftçi
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Microwave Power ◽  
Room Temperature ◽  
Paramagnetic Centers ◽  
Γ Irradiation ◽  
Paramagnetic Resonance ◽  
Electron Paramagnetic

Natural sepiolite minerals and their γ -irradiated forms were investigated by electron paramagnetic resonance (EPR) at room temperature and at 113 K. The EPR signals in powders of natural sepiolite were observed due to clusters of Fe3+ ions. The paramagnetic centers produced by γ - irradiation of natural sepiolite minerals were attributed to the ĊH3 at room temperature and ṠO−2 and ṠO−3 radicals at 113 K. These centers were found to be perfectly observable above 20 mW microwave power. The g values of all paramagnetic centers have been measured and the A values of some of them have been reported. The results were consistent with the literature data for similar paramagnetic centers.

Kinetics of hydrogen isotope exchange reactions - XXVIII. Steric course of radiation-induced tritium exchange between water and cyclohexane-1, 2-diols

1975 ◽  
Vol 346 (1647) ◽  
pp. 427-441 ◽  
Keyword(s):  
Hydrogen Abstraction ◽  
Tritiated Water ◽  
Organic Radical ◽  
Radical Scavengers ◽  
Exchange Reactions ◽  
Solvated Electron ◽  
Γ Irradiation ◽  
Reaction Proceeds ◽  
Radiation Induced ◽  
Kinetics Of

Under the influence of tritium β-radiation, dissolved trans -cyclohexane- 1, 2-diol exchanges carbon-bound hydrogen with the solvent (tritiated water). The exchange occurs not only at the hydroxyl-substituted (α) carbon atoms but also at non-α positions, which are, on the average, less reactive. The overall G -value for exchange in all positions is ca . 0.33. With γ-irradiation, exchange takes place with a slightly lower overall G -value. Exchange at α-positions occurs with predominant retention of con­figuration (76%). In the corresponding α-exchange of cis -cyclohexane-1, 2-diol, 79% of the reaction proceeds with inversion, i. e. the labelled products are in both reactions formed in practically the same ratio ( trans -diol: cis -diol ⋍ 3.5:1). It is concluded that the reactions go through a common intermediate (or rapidly equilibrating common set of inter­mediates), for both diols as substrates. A chemically reasonable mechanism in accordance with this requirement involves as the first step hydrogen abstraction (mainly by hydroxyl radicals) from a C—H grouping, followed by conversion of the organic radical produced to the carbanion by electron capture. The carbanion then reverts to a diol by protonation (tritonation). Equilibration of diastereomers can occur in the radical and/or in the carbanion. The involvement of both the hydroxyl radical and the solvated electron is qualitatively in accord with the action of electron and radical scavengers on the velocity of the exchange reaction.

scholarly journals Electron paramagnetic resonance (EPR) study of DOPA–melanin complexes with kanamycin and copper(II) ions

2011 ◽  
Vol 25 (3-4) ◽  
pp. 197-205 ◽  
Author(s):  
Lidia Najder-Kozdrowska ◽  
Barbara Pilawa ◽  
Ewa Buszman ◽  
Dorota Wrzesniok ◽  
Andrzej B. Więckowski
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Epr Spectroscopy ◽  
Paramagnetic Centers ◽  
High Concentration ◽  
Paramagnetic Resonance ◽  
Fitting Method ◽  
Epr Parameters ◽  
Dopa Melanin ◽  
Electron Paramagnetic ◽  
Paramagnetic Centres

This work comprises the study of DOPA–melanin complexes with kanamycin and copper(II) ions made by electron paramagnetic resonance EPR spectroscopy. The high concentration of paramagnetic centers in melanin makes the use of EPR spectroscopy possible. The unpaired electron localized on the oxygen atom in indol-5,6-quinone groups is the paramagnetic centers in this polymer. The aim of this work was the analysis of EPR parameters of recorded spectra. For researches were prepared melanin complexes which differed in complexing order of drug and Cu(II) ions, and in concentration of CuCl2solutions used during synthesis. The introduction of drugs and metal ions into melanin causes changes in EPR parameters of recorded spectra. Kanamycin causes the increase and copper(II) ions the decrease of concentrations of paramagnetic centres in melanin. Shape of EPR signal of DOPA–melanin was analyzed by fitting method. Results indicate that EPR line of DOPA–melanin is superposition of Gaussian and Lorentzian function.

Nitroxyl Modified Tobacco Mosaic Virus as a Metal-Free High-Relaxivity MRI and EPR Active Superoxide Sensor

2018 ◽  
Author(s):  
Madushani Dharmarwardana ◽  
André F. Martins ◽  
Zhuo Chen ◽  
Philip M. Palacios ◽  
Chance M. Nowak ◽  
...  
Keyword(s):  
Tobacco Mosaic Virus ◽  
Mosaic Virus ◽  
Single Molecule ◽  
Biological Fluids ◽  
Cellular Respiration ◽  
Organic Radical ◽  
Paramagnetic Resonance ◽  
Metal Free ◽  
Disease States

Superoxide overproduction is known to occur in multiple disease states requiring critical care yet non-invasive detection of superoxide in deep tissue remains a challenge. Herein, we report a metal-free magnetic resonance imaging (MRI) and electron paramagnetic resonance (EPR) active contrast agent prepared by “click conjugating” paramagnetic organic radical contrast agents (ORCAs) to the surface of tobacco mosaic virus (TMV). While ORCAs are known to be reduced <i>in vivo</i> to an MRI/EPR silent state, their oxidation is facilitated specifically by reactive oxygen species—in particular superoxide—and are largely unaffected by peroxides and molecular oxygen. Unfortunately, single molecule ORCAs typically offer weak MRI contrast. In contrast, our data confirm that the macromolecular ORCA-TMV conjugates show marked enhancement for <i>T<sub>1</sub></i> contrast at low field (<3.0 T), and <i>T<sub>2</sub></i> contrast at high field (9.4 T). Additionally, we demonstrated that the unique topology of TMV allows for “quenchless fluorescent” bimodal probe for concurrent fluorescence and MRI/EPR imaging, which was made possible by exploiting the unique inner and outer surface of the TMV nanoparticle. <a>Finally, we show TMV-ORCAs do not respond to normal cellular respiration, minimizing the likelihood for background, yet still respond to enzymatically produced superoxide in complicated biological fluids like serum.</a>

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