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1

Study on radiation-induced radicals giving rise to stable EPR signal suitable for the detection of irradiation in L-sorbose-containing fruits

Guzik G. P., Stachowicz W.

Nukleonika

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2016

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Vol. 61, No. 4

461--465

EN

The stable and complex EPR signals produced by the action of ionizing radiation on crystalline L-sorbose (C6H12O6) separated from rowan berries (Sorbus aucuparia) were studied. Isothermal heating of the samples at the temperature close to the melting point of L-sorbose (140°C) results in the modification and simplification of the EPR signal involved. In the EPR signal of heated L-sorbose, the isotropic quartet was distinguished. In the differential spectrum obtained by subtraction of normalized spectra of unheated and heated L-sorbose, the isotropic doublet was identified in addition. The DFT fitting offers the probable assignment of the EPR signals to specifi c radical structures.

2

Identification of irradiated dried fruits using EPR spectroscopy

Guzik G. P., Stachowicz W., Michalik J.

Nukleonika

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2015

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Vol. 60, No. 3, part 2

627--631

EN

The dominating carbohydrates in fruits are monosaccharides like fructose, glucose, sorbose and mannose. In dehydrated fruits, concentration of monosaccharides is higher than in fresh fruits resulting in the formation of sugar crystallites. In most of dried fruits, crystalline fructose, and glucose dominate and appear in proportion near to 1:1. Irradiation of dried fruits stimulates radiation chemical processes resulting in the formation of new chemical products and free radicals giving rise to multicomponent EPR signal which can be detected for a long period of time. For that reason, it is used as a marker for the detection of radiation treatment of dried fruits. It has been found that EPR spectra recorded in dried banana, pineapple, papaya, and fig samples resemble the EPR spectrum obtained by computer addition of fructose and glucose spectra taken in proportion 1:1. The decay of radiation induced EPR signals proceeds in dried fruits fast during the first month of observation and becomes much slower and almost negligible after prolonged storage. However, it remains intense enough for EPR detection even one year after processing. The radiation induced EPR signal is easily detected in dried fruits exposed to 0.5 kGy of gamma rays. Thus, the EPR method of the detection of irradiated fruits can be used for the control of dried fruits undergoing quarantine treatment with 200–300 Gy of ionizing radiation.

3

Determination of the fraction of paramagnetic centers not-fulfilling the Curie law in coal macerals by the two-temperature EPR measurement method

Słowik G. P., Więckowski A. B.

Nukleonika

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2015

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Vol. 60, No. 3, part 1

389--393

EN

Two-temperature electron paramagnetic resonance (EPR) measurements, applied to determine the relative contributions of paramagnetic centers – fulfilling and not-fulfilling the Curie law, were carried out. The measurements were made on the macerals – exinite and vitrinite, separated from clarain of the Polish medium- -rank coal (85.6 wt% C). The two-temperature EPR measurements, presented in this work, were performed respectively, at temperatures: T1 = 293 K and T2 = 173 K for exinite, and T1 = 293 K and T2 = 153 K for vitrinite. The relative contributions X of spins not-fulfilling the Curie law present in the studied macerals were calculated. A comparison of different methods of calculating the relative contributions of paramagnetic centers – fulfilling and not-fulfilling the Curie law, present in exinite and vitrinite studied by EPR was made.

4

Photoinduced charge separation in aqueous solution of porphyrin-quinone end-capped poly(methacrylic acid)

Zapotoczny S., Kataoka F., Nowakowska M.

Polimery

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2014

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T. 59, nr 1

95--100

EN

Photoinduced charge separation from porphyrin (P) to benzoquinone (Q) moieties covalently attached to the opposite chain ends of poly(methacrylic acid) (PMMA) was studied. The effect of polymer chain length, pH and ionic strength of the aqueous solution on the rate constant of charge separation and efficiency of P+• - Q-• radical ion pair formation was determined.

PL

Badano proces fotoindukowanej separacji ładunku pomiędzy cząsteczkami porfiryny (P) i benzochinonu (Q), kowalencyjnie przyłączonymi na przeciwnych końcach łańcucha poli(kwasu metakrylowego) (PMMA). Określono wpływ długości łańcucha, pH, siły jonowej wodnych roztworów polimeru na wartość stałej szybkości separacji ładunku i wydajności tworzenia pary rodniko-jonów P+• -Q-•.

5

Electron paramagnetic resonance studies of manganese and cobalt ions in YAlO3 crystals

Stefaniuk I., Rogalska I, Suchocki A, Berkowski M., Cieniek B., Potera P.

Optica Applicata

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2014

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Vol. 44, nr 1

113--121

EN

The results of X-band electron paramagnetic resonance measurements of Mn2+ and Mn4+ ions in YAlO3 (YAP) crystals in the temperature range 100–300 K are presented. Additionally, we observe electron paramagnetic resonance spectra of unintentional impurities Fe3+ and Cr3+ in YAP crystals. The angular dependence for Mn ions in YAP crystals can be presented. We aim at obtaining a better insight into the spectroscopic properties of paramagnetic Mn centers and structural information about their nearest environment in YAP host and at determining the valence of manganese ion. In this paper we compare electron paramagnetic resonance spectra for Co and Mn ions in YAP crystals.

6

Modification of the hydrogen bonding network at the reversed micelles interface by near infrared radiation

Walski T., Gałecka T., Grzeszczuk-Kuć K., Komorowska M.

Nukleonika

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2013

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Vol. 58, No. 3

435--438

EN

The purpose of this paper is to prove that near infrared radiation (NIR) modifies hydrogen bonds localized in the interface of reversed micelles. The degree of modification of the hydrogen bonds was monitored by TEMPO-palmitate spin probe introduced into the structure of reverse micelles formed by cetyltrimethylammonium bromide (CTAB) (TCAB/phosphate buffer/isooctane/hexanol and TCAB/NaCl/isooctane/hexanol (W = 15)). Electron paramagnetic resonance (EPR) spectra were performed on the argonated samples. The isotropic tumbling correlation time (τc) and the hyperfine coupling constant A+ = h0 – h+1 (h+1, and h0 correspond to the low-, and centre-field lines, respectively) were determined from the EPR spectra as a quantitative measure for monitoring the action of NIR radiation. A+ values depend on the composition of the water pool (1.640 mT for phosphate buffer and 1.630 mT for NaCl). NIR irradiation led to decrease in A+. This parameter reached the same value for both solutions (1.625 ± 0.003 and 1.626 ± 0.003 mT) after exposition to NIR. The tumbling correlation time after exposure to NIR decreased for TCAB/phosphate buffer/ isooctane/hexanol reversed micelles from 2.10 × 10–10 s to 1.44 × 10–10 s but did not change for TCAB/NaCl/isooctane/ hexanol). The results obtained confirm the possibility of modification of the hydrogen bonds by NIR radiation.

7

Localized states in nanocarbons

Kempiński W., Kempiński M., Markowski D., Łoś M.

Nukleonika

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2013

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Vol. 58, No. 3

371--373

EN

Localization phenomenon is studied in different modern nanocarbon materials: pristine C60, C60-fullerides, carbon nanotubes and graphene-based structures in the form of activated carbon fibers built of quantum dot-like basic structural units. Two experimental methods are used to define the localization and population control of spins (charge carriers) in the nanocarbon materials – electron paramagnetic resonance (EPR) and direct current (d.c.) electrical conductivity measurements. Results are discussed in the frame of the possible applications of the aforementioned materials in the molecular electronics or spintronics.

8

EPR study of ZnO:Co thin films grown by the PLD method

Cieniek B., Stefaniuk I., Virt I.

Nukleonika

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2013

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Vol. 58, No. 3

359--363

EN

We have studied magnetic properties of zinc-oxide composite doped with a relatively high concentration (4%) of Co ions. Samples were obtained by the pulsed laser deposition (PLD) method with different parameters of the laser ablation. For various samples, the power of laser was changed as well as the temperature of sample heating. Electron paramagnetic resonance (EPR) measurements were carried out and temperature dependence of the EPR spectra was obtained. Analysis of the temperature dependences of the integral intensity of EPR spectra was carried out using the Curie-Weiss law. Fitting yields the following values θCW = 150 K and C = 1.6710, where C is the Curie constant, and θCW is the paramagnetic Curie temperature.

9

EPR study of guanidine zinc sulphate crystals

Gruszka K., Hrabański R., Ozga J., Czapla Z.

Nukleonika

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2013

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Vol. 58, No. 3

387--390

EN

X-band electron paramagnetic resonance (EPR) investigations of Mn2+-doped guanidine zinc sulphate [C(NH2)3]2Zn(SO4)2 – abbreviated as GZS – are presented. The EPR spectrum in the temperature range 273–393 K exhibits a group of five fine structure transitions each splits into six hyperfine components. The angular variation of EPR spectra reveals the presence of only one magnetic complex, which correspond to one distinct site of Mn2+ ions in the crystal lattice. From the observed EPR spectrum, the spin-Hamiltonian parameters have been evaluated. The variation of zero-field splitting (ZFS) parameter, intensity and line width with temperature are measured and discussed.

10

EPR measurements of ceramic cores used in the aircraft industry

Stefaniuk I., Rogalska I.., Potera P., Wróbel D.

Nukleonika

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2013

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Vol. 58, No. 3

391--395

EN

In this work the electron paramagnetic resonance (EPR) spectra of Al2O3 and ZrO2 powders were measured for different size of grains (0.074, 0.044 mm) as well as the mullites (0.07 and 0.12 mm). Also were investigated the ceramic cores. The measurements were performed at room temperature and in the temperature range from 140 up to 380 K. The main purpose of this work was to investigate the possible relationships between the EPR spectra and the size of powder grains as well as the identification of EPR spectra in view of the potential application of EPR technique as a fingerprinting method.

11

Bloch - Siegert shift in the Rabi oscillations on the “dressed” electron spin states

Fedaruk R., Kolasa A., Saiko A. P.

Nukleonika

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2013

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Vol. 58, No. 3

375--378

EN

Using electron paramagnetic resonance (EPR) at Rabi frequencies, we study the Bloch-Siegert effect in the coherent dynamics of electron spin states driven by a bichromatic radiation consisting of a transverse microwave (MW) and longitudinal radio frequency (RF) fields. The Rabi oscillations on the electron spin states “dressed” by the MW field are observed at the double resonance, when the MW frequency equals the Larmor frequency of the spin system and the frequency ωrf of the RF field is close to the Rabi frequency ω1 in the MW field. The dispersive (|ωrf – ω1| ~ ωrf, ω1) and near-resonant (ωrf ≈ ω1) regimes are investigated. We demonstrate that the Bloch-Siegert shift increases with increasing RF amplitude and at the fixed RF amplitude it has the largest values in the “low-frequency” (ωrf < ω1) range of the dispersive regime. Experimental results were obtained in the time-resolved EPR for E’1 centres in quartz.

12

Synthesis and optical spectroscopy of the lithium tetraborate glasses, doped with terbium and dysprosium

Padlyak B., Ryba-Romanowski W., Lisiecki R., Pieprzyk B., Drzewiecki A., Adamiv V., Burak Y., Teslyuk I.

Optica Applicata

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2012

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Vol. 42, nr 2

365-379

EN

A series of the Tb- and Dy-doped glasses with Li2O-2B2O3 (or Li2B4O7:Tb and Li2B4O7:Dy) composition were synthesised and their spectroscopic properties were investigated. The Li2B4O7:Tb and Li2B4O7:Dy glasses of high chemical purity and optical quality were obtained from corresponding polycrystalline compounds in the air using standard glass technology. The Tb and Dy impurities were added to Li2B4O7 composition in the form of Tb2O3 and Dy2O3 oxide compounds in amounts of 0.5 and 1.0 mol%. The electron paramagnetic resonance (EPR), luminescence excitation and emission spectra of the Li2B4O7:Tb and Li2B4O7:Dy glasses were investigated. On the basis of EPR and photoluminescence spectra analysis it was shown that the Tb and Dy impurities are incorporated in the Li2B4O7 glass network as Tb3+ (4f8, 7F6) and Dy3+ (4f9, 6H15/2) ions, exclusively. All observed transitions of the Tb3+ and Dy3+ centres in the luminescence excitation and emission spectra were identified. The luminescence kinetics shows single exponential decay for Tb3+ and Dy3+ centres in Li2B4O7 glasses. The lifetime values for main emission transitions of the Tb3+ and Dy3+ centres in the Li2B4O7 glasses containing 0.5 and 1.0 mol% Tb2O3 and Dy2O3 are determined at T = 300 K. Peculiarities of optical properties and local structure of the Tb3+ and Dy3+ centres in the Li2B4O7:Tb and Li2B4O7:Dy glasses as well as their potential applications have been discussed.

13

EPR study on sugar radicals utilized for detection of radiation treatment of food

Guzik G. P., Stachowicz W., Michalik J.

Nukleonika

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2012

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Vol. 57, No. 4

545-549

EN

Radicals produced by ionizing radiation in sugars, the components of dried and raw fruits give rise to stable multicomponent electron paramagnetic resonance (EPR) signals unidentified so far. The subject of the present EPR study is to identify the radicals stabilized in gamma-irradiated crystalline sugars, D(+)mannose and L(-)sorbose extracted from cranberries (Vaccininum oxycoccos) and rowan berries (Sorbus aucuparia), respectively. EPR measurements and density functional theory (DFT) simulations were employed for that purpose.

14

Alanine dosimetry of 60 MeV proton beam - preliminary results

Michalec B., Mierzwińska G., Sowa U., Ptaszkiewicz M., Nowak T., Swakoń J.

Nukleonika

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2012

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Vol. 57, No. 4

503-506

EN

Electron paramagnetic resonance (EPR) spectrometry (X-band) was used to determine the dose absorbed in alanine detectors, of different shapes and different alanine content, irradiated with Co-60 gamma rays and in a 60 MeV proton beam. The goal of our study was to confirm applicability of alanine as a passive detector in therapeutic proton beam. In the paper dose response characteristic and relative efficiency of alanine are shown. The study confirmed that alanine detectors with a high alanine content (ca. 95%) may be a useful and convenient tool for dose measurements in proton beams, used for eye cancer treatment.

15

Electron paramagnetic resonance and scanning electron microscopy characterization of diamond films fabricated by HF CVD method

Fabisiak K., Szreiber M., Uniszkiewicz C., Runka T., Kasprowicz D.

Optica Applicata

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2009

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Vol. 39, nr 4

833-837

EN

Defects in diamond films, produced by the hot filament chemical vapour deposition (HF CVD) of methanol and hydrogen mixture as function of gas composition, were investigated by electron paramagnetic resonance (EPR), scanning electron microscopy (SEM) and Raman spectroscopy measurements. We found an isotropic g-value (2.003š0.0002) independent of growth conditions. The peak-to-peak of EPR line width changes from 0.3 to 0.6 mT and the spin density increases from 2.3ź1017 to 3.2ź1018 spin/cm-3 with increasing concentration of methanol vapour. The EPR line in general shows double character and was found to be superposition of two components, a narrower Lorentzian and a broader Gaussian, suggesting the existence of two different types of defects in diamond layer. EPR measurements were supported by SEM observation.