Evaluation of rare-earth sesquioxides nanoparticles as a bottom-up strategy toward the formation of functional structures

Background: The strategy to form functional structures based on powder technology relies on the concept of nanoparticles characteristics. Rare-earth sesquioxides (RE2O3; RE as Y, Tm, Eu) exhibit remarkable properties, and their fields of application cover energy, astronomy, environmental, medical, information technology, industry, and materials science. The purpose of this paper is to evaluate the RE2O3 nanoparticles characteristics as a bottom-up strategy to form functional materials for radiation dosimetry. Methods: The RE2O3 nanoparticles were characterized by the following techniques: XRD, SEM, PCS, FTIR, ICP, EPR, and zeta potential. Results: All RE2O3 samples exhibited cubic C-type structure in accordance with the sesquioxide diagram, chemical composition over 99.9%, monomodal mean particle size distribution, in which (d50) was inferior than 130nm. Among all samples, only yttrium oxide exhibited EPR signal, in which the most intense peak was recorded at 358mT and g 1.9701. Conclusion: The evaluation of nanoparticle characteristics is extremely important taking into account a bottom-up strategy to form functional materials. The RE2O3 nanoparticles exhibited promising characteristics for application in radiation dosimetry.

Application of Pyroelectric Sensors Based on PVDF Films for EPR Spectra Detection by Heat Release

Pyroelectrics are a wide class of materials that change their polarization when the system temperature varies. This effect is utilized for a number of different commercial and industrial applications ranging from simple thermal sensors and laser interferometers to water vapor harvesting. Electron paramagnetic resonance (EPR) spectroscopy is a powerful tool for studying the structure and dynamics of materials with unpaired electrons. Since heating accompanies a resonant change of the orientation of electron spins in an external magnetic field, pyroelectrics can be utilized as versatile detectors for so-called indirect detection of the EPR signal. In this work, we investigated three different types of PVDF (polyvinylidene difluoride) standard pyroelectric films with indium tin oxide, Cu/Ni, and Au coatings to determine their sensitivity for detecting EPR signals. All the films were shown to be able to detect the EPR spectra of about 1 μg of a standard stable free radical by heat release. A comparative study based on the calculation of the noise-equivalent power and specific detectivity from experimental spectra showed that the Au coated PVDF film is the most promising active element for measuring the EPR signal. Using the best achieved sensitivity, estimation is given whether this is sufficient for using a PVDF-based pyrodetector for indirectly detecting EPR spectra by recombination heat release or not.

Investigation of the Radiation-Induced Signal of Electron Paramagnetic Resonance of Eggshell after Irradiation with Electron Beams

Because of the development of radiation processing of food and agricultural products it requires new methods of control over the processing and turnover of products. A promising method for monitoring is EPR spectrometry. This research presents the results of a study of the radiation induced EPR signal in eggshells. The URT-0.5 (0.5 MeV) and UALR-10-10 S2 (10 MeV) accelerators were used for irradiation. It shows the kinetics of radicals over time. The dependences of the EPR signal intensity on the absorbed dose were obtained, and a comparative analysis of the irradiation of chicken eggs with different energies was performed. The kinetics of radicals over time and the dependence of the intensity of the EPR signal on the absorbed dose are shown. A comparative analysis of the irradiation of chicken eggs with different energies is carried out.

EPR study of paramagnetic centers in SiO2:C: Zn nanocomposites obtained by infiltration of fumed silica with luminescent Zn(acac)2 solution

Silica-carbon with zinc (SiO2:C:Zn) nanocomposites obtained via infiltration with aged luminescent zinc acetylacetonate (Zn(acac)2) ethanol solution of two concentrations (1 or 4%) into the fumed silica (SiO2) matrix have been studied using EPR within the temperature range 6…296 K before and after thermal annealing. The EPR spectrum of SiO2:C:Zn nanocomposites consists of three signals with the Lorentzian lineshape corresponding to paramagnetic centers with S = 1/2, which are related to carbon dangling bonds (CDB) (g = 2.0029(3)), silicon dangling bonds (g = 2.0062(3)) and oxygen-centered carbon-related radicals (CRR) (g = 2.0042(3)). A small EPR linewidth (<1 mT) observed for CDB and oxygen-centered CRR allows us to conclude that they are in the sp3-hybridized state. It was found that the temperature dependence of the EPR signal integrated intensity of the CDB and oxygen-centered CRR follows the Curie–Weiss law with a small positive value of the Curie–Weiss constant, which indicates that the weak ferromagnetic exchange interaction takes place in the spin system of CDB and oxygen-centered CRR. It was supposed that the carbon-related centers are clustered in SiO2:C:Zn nanocomposites. We assume that the oxygen-centered CRR in the sp3-hybridized state are associated with luminescent centers in previously reported aged Zn(acac)2/C2H5OH solution.

THE INVESTIGATION OF THE PENETRATION OF MICROELEMENTS OF A DIETARY SUPPLEMENT IN CRUCIAN MEAT BY VARIOUS METHODS OF SALTING

The expediency of improving the technological methods of processing unprofitable small fish and expanding the range of food products from them is substantiated. It is proposed to enrich the meat of freshwater fish with trace elements by adding to salt or brine during the salting of raw materials dietary supplements based on chelate complexes. The kinetics of penetration of micronutrients of a dietary supplement based on a chelate complex into the muscle tissue of crucian carp was studied by electronic paramagnetic resonance. The ambassador was held in three ways. According to the first dry method of salting, the fish was mixed with sodium chloride NaCl with the addition of a dietary supplement based on a chelate complex in the amount of 20… 25% and 0.1% by weight of raw materials, respectively. According to the second brine method, the fish was salted in brine, which was a solution of sodium chloride NaCl in the amount of 2 kg of salt per 1 kg of raw material. The amount of dietary supplement based on the chelate complex was 0.1% by weight of raw materials. According to the third method, the ambassador was carried out in brine with the same concentrations of sodium chloride and dietary supplements, but previously the fish raw materials were treated with ultrasound. Salting of fish was carried out for 6 days. The distribution of Mn ions in the plane (i, j) is investigated. The kinetics of the penetration of a microelement into the volume of crucian muscle tissue was studied by the EPR method. The kinetics of Mn2 + ion distribution in the studied muscle tissue samples and the tomogram of these surfaces were determined. The values of the area under the EPR spectra are normalized to the values of the area under the maximum EPR signal. For the maximum EPR signal for dry pickling, the signal from the liquid in which the raw material was during salting, and during the brine - the signal from the brine sample was selected. It is noted that the kinetics of penetration of the trace element is determined by the area of contact of the raw material with diffusing substances and the method of intensification of the internal transfer of these substances within the raw material. It was found that for brine and brine with pre-sonication, the amount of trace element in the depth of the crucian muscle tissue differs within the error. This indicates the homogeneity of the distribution of the trace element of the dietary supplement based on the chelate complex by such methods of salting.

Large Breathing Effect Induced by Water Sorption in the Exceptionally Stable Nonporous Non-MOF Crystalline Material

We report a non-MOF crystalline material {[Mn(imH)]2[Mo(CN)8]}n (imH = imidazole) with exceptional water sorption properties and a very large breathing effect accompanied by an outstanding stability and cyclability – properties that are absolutely unique for this class of compounds (Prussian Blue Analogs). Some previously published PBAs indeed show some sorption properties, but their cyclability is extremely limited - usually 1-3 cycles - followed by significant decomposition/amorphization. Our compound can be cycled more than 50 times without any fatigue and the sorption/desorption proceeds through four different crystal phases, which we have fully characterized structurally enabling the complete understanding of the sorption and breathing mechanism in this material - an achievement rarely reported for MOFs or PBAs. <br>The unique structure of {[Mn(imH)]2[Mo(CN)8]}n enables very strong coupling of its exceptional water sorption performance with the magnetic and photomagnetic properties of the framework, e.g. the sorption process can be followed by in-situ EPR spectroscopy with huge changes in the EPR signal intensity depending on the hydration level.<br><br>

Large Breathing Effect Induced by Water Sorption in the Exceptionally Stable Nonporous Non-MOF Crystalline Material

We report a non-MOF crystalline material {[Mn(imH)]2[Mo(CN)8]}n (imH = imidazole) with exceptional water sorption properties and a very large breathing effect accompanied by an outstanding stability and cyclability – properties that are absolutely unique for this class of compounds (Prussian Blue Analogs). Some previously published PBAs indeed show some sorption properties, but their cyclability is extremely limited - usually 1-3 cycles - followed by significant decomposition/amorphization. Our compound can be cycled more than 50 times without any fatigue and the sorption/desorption proceeds through four different crystal phases, which we have fully characterized structurally enabling the complete understanding of the sorption and breathing mechanism in this material - an achievement rarely reported for MOFs or PBAs. <br>The unique structure of {[Mn(imH)]2[Mo(CN)8]}n enables very strong coupling of its exceptional water sorption performance with the magnetic and photomagnetic properties of the framework, e.g. the sorption process can be followed by in-situ EPR spectroscopy with huge changes in the EPR signal intensity depending on the hydration level.<br><br>

Heme Binding to HupZ with a C-Terminal Tag from Group A Streptococcus

HupZ is an expected heme degrading enzyme in the heme acquisition and utilization pathway in Group A Streptococcus. The isolated HupZ protein containing a C-terminal V5-His6 tag exhibits a weak heme degradation activity. Here, we revisited and characterized the HupZ-V5-His6 protein via biochemical, mutagenesis, protein quaternary structure, UV–vis, EPR, and resonance Raman spectroscopies. The results show that the ferric heme-protein complex did not display an expected ferric EPR signal and that heme binding to HupZ triggered the formation of higher oligomeric states. We found that heme binding to HupZ was an O2-dependent process. The single histidine residue in the HupZ sequence, His111, did not bind to the ferric heme, nor was it involved with the weak heme-degradation activity. Our results do not favor the heme oxygenase assignment because of the slow binding of heme and the newly discovered association of the weak heme degradation activity with the His6-tag. Altogether, the data suggest that the protein binds heme by its His6-tag, resulting in a heme-induced higher-order oligomeric structure and heme stacking. This work emphasizes the importance of considering exogenous tags when interpreting experimental observations during the study of heme utilization proteins.

Unrevealing the nature of α-keratin EPR signal: an ab-initio study

Fingernail as a biodosimetry material analyzed by the EPR technique has been of great attention in several experimental studies. One of the most challenging issues that should be addressed is...

Observation and deconvolution of a unique EPR signal from two cocrystallized spin triangles

A 16-line pattern has been theoretically predicted, but hitherto not reported, for the Electron Paramagnetic Resonance (EPR) spectrum of antiferromagnetically coupled CuII triangles experiencing isotropic exchange of isosceles magnetic symmetry....