Maria A. Augustyniak-Jabłokow

Electron Paramagnetic Resonance Imaging and Spectroscopy of Polydopamine Radicals

A thorough investigation of biomimetic polydopamine (PDA) by Electron Paramagnetic Resonance (EPR) is shown. In addition, temperature dependent spectroscopic EPR data are presented in the range 3.8-300 K. Small discrepancies in magnetic susceptibility behavior are observed between previously reported melanin samples. These variations were attributed to thermally acitivated processes. More importantly, EPR spatial-spatial 2D imaging of polydopamine radicals on a phantom is presented for the first time. In consequence, a new possible application of polydopamine as EPR imagining marker is addressed.

Evaluation of in vivo graphene oxide toxicity for Acheta domesticus in relation to nanomaterial purity and time passed from the exposure

Graphene and its oxidized form-graphene oxide (GO) have become exceptionally popular in industry and medicine due to their unique properties. However, there are suspicions that GO can cause adverse effects. Therefore, comprehensive knowledge on its potential toxicity is essential. This research assesses the in vivo toxicity of pure and manganese ion contaminated GO, which were injected into the hemolymph of Acheta domesticus. The activity of catalase (CAT) and gluthiathione peroxidases (GSTPx) as well as heat shock protein (HSP 70) and total antioxidant capacity (TAC) levels were measured at consecutive time points-1h, 24h, 48h and 72h after injection. Neither pure GO nor GO contaminated with manganese were neutral to the organism. The results proved the intensification of oxidative stress after GO injection, which was confirmed by increased enzyme activity. The organism seems to cope with this stress, especially in the first 24h after injection. In the following days, increasing HSP 70 levels were observed, which might suggest the synthesis of new proteins and the removal of old and damaged ones. With that in mind, the potential toxicity of the studied material, which could lead to serious and permanent damage to the organism, should still be taken into consideration.

EPR study of the magnetic states of a mixed-valence VIV4VV2 alkoxypolyoxovanadium cluster

The EPR studies of the hexanuclear vanadium cluster in a [VIV4VV2O7(OCH3)12] single crystal are reported. The spectrum of the mixed valence clusters consists of a single lorentzian line and additional signals in the magnetic field range ∼240–440 mT and is observed in the 4.2–300 K temperature range. At about 190 K, on cooling, an abrupt change of the spectrum due to the structural phase transition, followed by a strong hysteresis, is discovered. Temperature dependence of the EPR spectra indicates an electron transfer between VIV and VV. Obtained results are discussed in the framework of the Heisenberg–Anderson–Zener Hamiltonian approach. The possibilities of other approaches is also considered.

Size effects in the conduction electron spin resonance of anthracite and higher anthraxolite.

Electron paramagnetic resonance spectroscopy of conduction electrons, i.e. Conduction Electron Spin Resonance (CESR), is a powerful tool for studies of carbon samples. Conductive samples cause additional effects in CESR spectra that influence the shape and intensity of the signals. In cases where conduction electrons play a dominant role, whilst the influence of localized paramagnetic centres is small or negligible, the effects because of the spins on conduction electrons will dominate the spectra. It has been shown that for some ratios of the bulk sample sizes (d) to the skin depth (δ), which depend on the electrical conductivity, additional size effects become visible in the line asymmetry parameter A/|B|, which is the ratio of the maximum to the absolute, minimum value of the resonance signal. To study these effects the electrical direct current–conductivity and CESR measurements are carried out for two amorphous bulk coal samples of anthracite and a higher anthraxolite. The observed effects are described and discussed in terms of the Dyson theory. Copyright

The Mechanisms of Jahn-Teller Complex Reorientations

The process of reorientations of the Jahn–Teller (JT) complex with trigonal site symmetry as well as slightly elongated and compressed ones are studied by X-band and Q-band electron paramagnetic resonance (EPR). The observed phenomena of the resonance line broadening and the dispersion of the resonance signal followed by its coalescence are discussed taking into consideration the increase in the transition rate with a rise in temperature. We conclude that even for a complex located at low symmetry sites the transitions between JT conformations can have a tunneling character.

Chronic toxicity of nanodiamonds can disturb development and reproduction of Acheta domesticus L

ABSTRACT The use of nanodiamonds in numerous materials designed for industry and medicine is growing rapidly. Consequently health and environmental risks associated with the exposure of humans and other biota to nanodiamonds‐based materials are of the utmost importance. Scarcity of toxicological data for these particles led us to examine the potentially deleterious effects of nanodiamonds in model insect species, Acheta domesticus (Orthoptera) chronically exposed to ND in its diet. Organism‐level end‐point indices (lifespan, body weight, consumption, caloric value of faeces, reproduction) revealed adverse changes in the treated crickets in comparison with the control. Preliminary studies of oxidative stress level in the offspring of ND‐treated crickets suggest toxicity of these particles limited to the exposed individuals. EPR analysis showing increase of radical signal in the faeces of ND‐fed crickets led us to propose novel mechanism of nanodiamonds toxicity that is discussed in the light of literature data. Capsule: Development and reproduction of Acheta domesticus can be disturbed by the chronic exposure to nanodiamonds HighlightsThe in vivo toxicity of ND was measured in A. domesticus after long‐term exposure.Organism‐level end‐point indices revealed adverse changes in the treated crickets.EPR analysis showed increase of radical signal in the faeces of ND‐fed crickets.Adverse effects of NDs in crickets seem to be limited to the exposed generation only. Graphical abstract: Figure. No caption available.

Effect of Rabi splitting on the low-temperature electron paramagnetic resonance signal of anthracite

Specific distortions of the EPR signal of bulk anthracite are observed at low temperatures. They are accompanied by variations in the microwave oscillator frequency and are explained by the manifestation of the Rabi splitting due to the strong coupling between electron spins and the cavity, combined with the use of an automatic frequency-control (AFC) system. EPR signals are recorded at negligible saturation in the temperature range of 4-300K with use of the AFC system to keep the oscillator frequency locked to the resonant frequency of the TM110 cylinder cavity loaded with the sample. For the sample with a mass of 3.6mg the line distortions are observed below 50K and increase with temperature lowering. The oscillator frequency variations are used to estimate the coupling strength as well as the number of spins in the sample. It is shown that the spin-cavity coupling strength is inversely proportional to temperature and can be used for the absolute determination of the number of spins in a sample. Our results indicate that at low temperatures even 1016 spins of the anthracite sample, with a mass of about 0.5mg, can distort the EPR line.

Formation of the Jahn-Teller Glassy State in the Mixed Potassium- Ammonium Tuton Salts

EPR studies of the mixed crystals NH4KZn1−xCUx(SO4)26(H2O) are presented. It is shown that the increase of the Cu2+ concentration can lead to the appearance of a co-operative interaction and the formation of a glassy state.