Jahn-Teller effect and features of divalent copper ion behavior in multicomponent borate crystals.

Crystals of YGa3(BO3)4, YAl3(BO3)4, EuGa3(BO3)4 and EuAl3(BO3)4 with copper alloy were studied by electron paramagnetic resonance and X-ray diffraction analysis. The lattice parameters and coordinates of copper-doped boron atoms were determined. The study of EPR spectra showed that copper is in the divalent state and replaces aluminum ions with C2 node symmetry. In YAl3(BO3)4:Cu crystals, a ligand structure exists due to the interaction of copper electrons with yttrium nuclei. The parameters of the spin Hamiltonian describing the behavior of the Cu2+ spectrum have been determined. The deviation of the Z-axis spectra from the C3 axis by 54(1)° is due to Jahn-Teller vibronic interaction and monoclinic distortion. In the EuGa3(BO3)4 crystal, a new spectrum 2 was found, which also belongs to divalent copper but is observed at an excited state 31 cm-1 away from the ground state. Above 70 K, an isotropic EPR line with a width of 450 Gs, g = 2.1, appears and exists up to room temperature.

The Impact of Hydrogenation on Structural and Superconducting Properties of FeTe0.65Se0.35 Single Crystals.

Properties of FeTe0.65Se0.35 single crystals, with the onset of critical temperature (Tconset) at 15.5 K, were modified via hydrogenation performed for 10-90 h, at temperatures ranging from 20 to 250 °C. It was found that the tetragonal matrix became unstable and crystal symmetry lowered for the samples hydrogenated already at 200 °C. However, matrix symmetry was not changed and the crystal was not destroyed after hydrogenation at 250 °C. Bulk Tcbulk, determined at the middle of the superconducting transition, which is equal to 12-13 K for the as grown FeTe0.65Se0.35, rose by more than 1 K after hydrogenation. The critical current density studied in magnetic field up to 70 kOe increased 4-30 times as a consequence of hydrogenation at 200 °C for 10 h. Electron paramagnetic resonance measurements also showed higher values of Tcbulk for hydrogenated crystals. Thermal diffusion of hydrogen into the crystals causes significant structural changes, leads to degeneration of crystal quality, and significantly alters superconducting properties. After hydrogenation, a strong correlation was noticed between the structural changes and changes in the parameters characterizing the superconducting state.

Role of the paramagnetic donor-like defects in the high n-type conductivity of the hydrogenated ZnO microparticles.

The magnetic and electronic properties of the hydrogenated highly conductive zinc oxide (ZnO) microparticles were investigated by electron paramagnetic resonance (EPR) and contactless microwave (MW) conductivity techniques in the wide temperature range. The EPR spectra simulation allowed us to resolve four overlapping EPR signals in ZnO microparticles. The Lorentzian EPR line with isotropic g-factor 1.9623(5) was related to the singly ionized oxygen vacancy. Another Lorentzian line with g|| = 1.9581(5), g⊥ = 1.9562(5) was attributed to the zinc interstitial shallow donor center, while EPR signal with g|| = 1.9567(5), g⊥ = 1.9556(5) and Gaussian lineshape was assigned to the hydrogen interstitial shallow effective-mass-like donor. The EPR signal with g|| = 1.9538(5), g⊥ = 1.9556(5) and Lorentzian lineshape was tentatively attributed to the shallow donor center. The charge transport properties in ZnO microparticles have been investigated by the contactless MW conductivity technique at T = 5-296 K. Two conduction mechanisms, including ionization of electrons from the shallow donors to the conduction band and hopping conduction process, have been distinguished. The hopping conduction process follows Mott's variable-range hopping T-1/4 law at T = 10-100 K. The evaluated values of the average hopping distance (15.86 Å), and hopping energy (1.822 meV at 40 K) enable us to estimate the donor concentration in the investigated ZnO microparticles as ~ 1018 cm-3.

Nanoparticle core stability and surface functionalization drive the mTOR signaling pathway in hepatocellular cell lines.

Specifically designed and functionalized nanoparticles hold great promise for biomedical applications. Yet, the applicability of nanoparticles is critically predetermined by their surface functionalization and biodegradability. Here we demonstrate that amino-functionalized polystyrene nanoparticles (PS-NH2), but not amino- or hydroxyl-functionalized silica particles, trigger cell death in hepatocellular carcinoma Huh7 cells. Importantly, biodegradability of nanoparticles plays a crucial role in regulation of essential cellular processes. Thus, biodegradable silica nanoparticles having the same shape, size and surface functionalization showed opposite cellular effects in comparison with similar polystyrene nanoparticles. At the molecular level, PS-NH2 obstruct and amino-functionalized silica nanoparticles (Si-NH2) activate the mTOR signalling in Huh7 and HepG2 cells. PS-NH2 induced time-dependent lysosomal destabilization associated with damage of the mitochondrial membrane. Solely in PS-NH2-treated cells, permeabilization of lysosomes preceded cell death. Contrary, Si-NH2 nanoparticles enhanced proliferation of HuH7 and HepG2 cells. Our findings demonstrate complex cellular responses to functionalized nanoparticles and suggest that nanoparticles can be used to control activation of mTOR signaling with subsequent influence on proliferation and viability of HuH7 cells. The data provide fundamental knowledge which could help in developing safe and efficient nano-therapeutics.