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1
Content available Multifrequency EPR study on radiation induced centers in calcium carbonates labeled with 13C
Sadło J., Bugaj A., Strzelczak G., Sterniczuk M., Jaegermann Z.
Nukleonika
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2015
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Vol. 60, No. 3, part 1
429--434
EN
In 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), CO3 3–, NO3 2–, O3 –, and in aragonite CO2 – (isotropic and orthorhombic symmetry) depending on the type of calcium carbonate used. For calcium carbonates enriched with 13C more detailed information about the formed radicals was possible to be obtained. In both natural (white coral) and synthetic aragonite the same radicals were identifi ed 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.
2
Content available EPR study of γ-irradiated feather keratin and human fingernails concerning retrospective dose assessment
Strzelczak G., Sterniczuk M., Sadło J., Kowalska M., Michalik J.
Nukleonika
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2013
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Vol. 58, No. 4
505--509
EN
In this paper we report the results of comparative EPR studies on free radicals generated in γ-irradiated powder samples of feather keratin powder and human fingernails. In degassed samples of both materials irradiated at 77 K the major component of EPR spectrum represents sulphur-centred radicals in cysteine residues. It quickly decays after air admission at room temperature while a singlet assigned to semiquinone melanin radicals remains the only one seen. The singlet recorded with fingernails decays slowly at room temperature and might be potentially useful for dose assessment by EPR. The advantages and limitations of fingernails EPR dosimetry are discussed.
3
Content available X- and Q-band EPR study on dosimetric biomaterials
Strzelczak G., Sadło J., Michalik J.
Nukleonika
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2009
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Vol. 54, No. 4
247-250
EN
Electron paramagnetic resonance (EPR) spectroscopy (X- and Q-band) was used for identification of stable radicals in: compact bone powder, shell of arcidae mollusc and crystalline alanine. The aim of our investigation was to analyze the complex EPR spectra of these materials and to identify paramagnetic species contributing to it. The most successful results were obtained in the EPR study (X- and Q-band) on deproteinized and irradiated bone powder and arcidae shell at room temperature.
4
Content available EPR study on biominerals as materials for retrospective dosimetry
Sadło J., Michalik J., Stachowicz W., Strzelczak G., Dziedzic-Gocławska A., Ostrowski K.
Nukleonika
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2006
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Vol. 51,suppl.1
95-100
EN
Stable paramagnetic species, induced by irradiation in biominerals, can be successfully used as an EPR dosimeter in numerous domains of scientific activity. In hydroxyapatite, the main mineral component of bones, the most stable signal is assigned to CO2 - ion radical. The signal is dose dependent and allows to determine the absorbed dose in a wide range till 20 kGy, with detection limit for tooth enamel below 1 Gy. The additive dose method was applied to EPR dating of archeological objects and EPR dosimetry after accidental overexposing during radiotherapy. It was found that the age of remains excavated from the “tomb of giants” belonging to Nuraghic culture developed in Sardinia island is about 3160 years old (1160 years BC). The dose obtained by patients during the accident at the Białystok Oncological Center was evaluated at about 75 Gy. Searching for potential dosimeters among other biominerals shows that mollusc shells have very promising properties. The lowest dose detection limit was found for an Arcidae shell. Both fresh water and sea mollusc shells are useful to be used for dosimetry in the low dose range.
5
Content available EPR and ESEEM study of silver clusters in ZK-4 molecular sieves
Sadło J., Michalik J., Kevan L.
Nukleonika
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2006
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Vol. 51,suppl.1
49-54
EN
Silver clusters generated by g-irradiation in ZK-4 zeolites – isostructural with Linde type A (LTA) zeolite, have been studied by electron paramagnetic resonance (EPR) spectroscopy. It was shown that even a small decrease of cation capacity resulting from a lower Si/Al ratio in the framework affects distinctly silver agglomeration. In dehydrated ZK-4 with Si/Al = 1.2 and 2.4 only silver dimers are stabilized, whereas in Linde 4A silver hexamers were trapped. In ZK-4 exposed to H2O and CH3OH, silver tetramers Ag43+ efficiently are formed. The results of electron spin echo envelope modulation (ESEEM) showed that the adsorbate molecules are in close vicinity to the clusters. It was postulated that in zeolites with low cation capacity the adsorbate molecules make difficult Ag0 migration promoting the reactions with Ag+ cations located in the same sodalite cage.
6
Content available EPR study of highly stable methyl radicals trapped in synthetic H-rho zeolite
Danilczuk M., Sadło J., Lund A., Yamada H., Michalik J.
Nukleonika
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2005
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Vol. 50,suppl.2
51-54
EN
Methyl radicals generated by ă-irradiation in the proton form of synthetic rho zeolite exposed to CH4 have been investigated by electron paramagnetic resonance (EPR) in the temperature range 110-370 K. Depending on the methane adsorption temperature two EPR spectra of oCH3 radicals were recorded. The isotropic quartet observed after CH4 adsorption at room temperature was assigned to oCH3 radicals freely rotating in the middle of octagonal prism. After adsorption at 413 K, the isotropic quartet is overlapped with the second signal characterized with anisotropy of hyperfine splitting and g-value. It is postulated that anisotropic signal represents the oCH3 radicals located in á-cages and strongly interacting with silicaalumina framework. The mechanisms of radiolytic formation of methyl radicals and the possible stabilization sites are also discussed.
7
Content available Wpływ promieniowania jonizującego na poli(siloksanouretany) - materiału przeznaczonego do zastosowań biomedycznych
Legocka I., Sadło J., Warchoł S., Przybytniak G.
Inżynieria Biomateriałów
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2004
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R. 7, nr 38-42
197-198
8
Stability and ESR Spectra of Ni(III) Tetraazamacrocyclic Complexes in Nitrate and Chloride Solutions
Taraszewska J., Sadło J., Michalik J., Korybut-Daszkiewicz B.
Polish Journal of Chemistry
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2000
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Vol. 74, nr 6
813-822
EN
Complexes [NiIII(cyclam)Cl2]Cl (10, NiIII(cyclam)(NO3)2]lO4 (2) and [NiIII(2-methyl-cyclam)(NO3)2]ClO4 (3) were isolated and the stability of Ni(III) was studied by UV-VIS spectrophotometry as a function of NaCl and NaNO3 concentration. In complexes 2 and 3 the decay of Ni(III) followed the first order kinetics in aqueous and nitrate solutions up to 1 ol/dm3. In complex 1 the first order kinetics was observed only in aqueous and saturated NaCl solutions. With increase in NaNO3 concentration the stability of Ni(III) in complexes 2 and 3 increased however, in complex 3 it was lower than in complex 2. Stability of Ni(III) in complex 1 increased also with increasing NaCl concentration but it diminished starting from 2 mol/dm3 NaCl. The forms of complexes depending on the salt concentration were characterized by the ESR technique.
9
Content available remote Procesy radiacyjne w polipropylenie modyfikowanym melanianem rycynolo-2-oksazoliny
Jeziórska R., Sadło J., Bojarski J., Zimek Z.
Polimery
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2000
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T. 45, nr 5
416-422
PL
Napromieniowano polipropylen (PP) oraz polipropylen modyfikowany maleinianem rycynylo-2-oksazoliny (MRO) wiązką elektronów 10 MeV (z akceleratora liniowego LAE 13/9) i powstające rodniki badano metodą EPR. Wykazano instnienie wpływu modyfikacji na mechanizm tworzenia się rodników.
EN
Polypropylene (PP) and ricinyl-2-oxazoline maleate-modified polypropylene were irradiated with a 10-MeV electron beam (from a LAE 13/9 linear accelerator). The resulting radicals were studied by electron paramegnetic resonance spectroscopy.
10
Content available remote Radiation-induced oxidation of thiaproline derivatives in frozen acidic aqueous solutions: theoretical and Electron Spin Resonance study
Pogocki D., Sadło J.
Nukleonika
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2000
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Vol. 45, nr 1
101-108
EN
Radicals formed by gamma-radiolysis of thiaproline (thiazolidine-4-carboxylic acid) amino acid and its derivatives in a frozen acidic aqueous solution at 77 K and by subsequent warming from 95 to 200 K have been studied by electron spin resonance (ESR). The experimental parameters of radical spectra were compared with those obtained by quantum-mechanical calculations on AM1 and PM3 semiempirical levels.
11
ESR studies of silver clusters in the isostructural A and ZK-4 molecular sieves
Michalik J., Yu J.-S., Sadło J.
Bulletin of the Polish Academy of Sciences. Chemistry
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2000
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Vol. 48, No. 4
293-301
EN
Cationic silver clusters formed in l-irradiated Ag+-exchanged Linde 4A zeolite and isostructural synthetic ZK-4 zeolite with Si/ Al ratio of 1.2 and 2.4 have been studied by electron spin resonance (ESR) spectroscopy. Whereas dehydrated AgNa-A zeolite shows rem.arkable ability for stabilization of Ag(6)n+ clusters in AgNa-ZK-4 zeolites hexameric silver clusters are not formed at all. .In ZK-4 samples exposed to water or methanol tetrameric silver clusters Ag(3)(4)+ are efficiently produced. Although geometri-cal size constraints play a crucial role with respect to cluster nuclearity and stability, in this paper we show that other factors like total cation capacity and/ or the presence of molecular adsorbates can affect the silver agglomeration process to a great extent.
12
Content available remote Radiation effects in poly(ethylene terephthalate) - polypropylene composite materials
Sadło J., Bojarski J., Michalik J., Strzelczak G.
Polimery
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1999
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T. 44, nr 3
226-228
EN
Radiation-induced radicals in poly(ethylene terephthalate) (PET) and polypropylene (PP) and in their composites were studied by ESR. In pure PET, the radicals were not stabilized at room temperature but, in PET/PP composites (10-20% of PP), peroxy radicals were recorded at concentrations indicating the radical centers formed originally in PET units to be able to migrate to PP units where they become stabilized. Changes in polymer viscosity observed in the molten state proved degradation to be the major radiation effect.
PL
Napromieniowano kompozyty (80:20) i (90:10) PP-PET oraz czysty PP i PET wiązką elektronów 10 MeV (z akceleratora liniowego LAE 13/9) i wytworzone rodniki badano metodą EPR. W czystym PET rodniki nie ulegały stabilizacji w temperaturze pokojowej, natomiast w kompozytach stwierdzono obecność ustabilizowanych rodników nad tlenkowych. Ich stężenie wskazuje, że najpierw tworzą się one w łańcuchach PET, a następnie migrują do łańcuchów PP, gdzie ulegają stabilizacji. Zbadano lepkość polimerów w stanie stopionym; wyniki wskazują, że głównym efektem promieniowania jest degradacja polimerów.
13
Content available remote Radiation proceses in poly(ethylene terephthalate) composite materials
Sadło J., Bojarski J., Strzelczak G., Michalik J.
Nukleonika
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1999
|
Vol. 44, nr 1
59-69
EN
The radiation - induced radicals in poly(ethylene terephthalate) - PET composite with polypropylene - PP and polyetherester KPEE have been studied by ESR spectroscopy. In pure PET matrix radicals are not stabilized at room temperature but in PET/PP composite (10-20% of PP) similary to pure PP matrix peroxy radicals are recorded at room temperature with the concentrations indicating that radicals formed originally in PET units are stabilized during migration along polymer chain by PP units enabling the formation of peroxy radicals. In contrast, in PET/KPEE composite materials the radical processes are the same as in PET homopolymers. The changes of polymer viscosity in melting state prove that polymer degradation is major radiation effect in the majority of composite materials.
PL
Przy użyciu spektroskopii Elektronowego Rezonansu Paramagnetycznego (EPR) badano inicjowane radiacyjnie rodniki w kompozytach polimerowych na bazie politereftalanu etylenu (PET) z domieszką polipropylenu (PP) lub kopolieteroestru (KPEE). W czystym PET wolne rodniki w temperaturze pokojowej nie stabilizują się, natomiast w kompozytach PET/PP zawierających 10 i 20% PP rejestruje się, podobnie jak w czystym PP, rodniki nadtlenkowe. Stężenie rodników w tych kompozytach jest większe niż procentowy udział polipropylenu w matrycy polimerowej. Wskazuje to, że rodniki powstające początkowo we fragmentach politereftalanowych migrują wzdłuż łańcuchów ulegając stabilizacji we fragmentach polipropylenowych w wyniku powstawania rodników nadtlenkowych. Efektu tego nie obserwuje się w kompozytach PET/KPEE, w których procesy rodnikowe przebiegają w ten sam sposób jak w homopolimerze PET. Na podstawie zmian lepkości polimerów w stanie stopionym stwierdzono, że w badanych polimerach głównym efektem radiacyjnym jest degradacja.
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