In collaboration with the CRISMAT group from Caen in France we contributed a quantitative TEM analysis of inversion boundaries in their study of phonon scattering and electron doping by 2D structural defects in the ZnO–In2O3 system. ZnO(In) ceramics was synthesized using a simple solid-state process. Structural features and thermoelectric properties of Zn1-xInxO series with ultralow indium content (0 ? x ? 0.02) have been assessed. HAADF–STEM analyses indicate that indium has the ability to create multiple basal plane (b–IB) and pyramidal (p–IB) defects that produce domains with inverted polarity starting from dopant concentrations as low as 0.25 atom %. Interestingly, the formation of IBs causes increased phonon scattering while increasing the electrical conductivity, and thereby enhancing overall thermoelectric properties. This pure 2D effect is reported for the first time. Moreover, this study is a step forward to design of other thermoelectric compounds where dopant-induced planar defects in bulk transition metal compounds have the
COBISS.SI-ID: 31162407
Simple and chip low-temperature hydrothermal synthesis at 90oC enables preparation of ZnO films with high optical transparency and low resistivity. The formation of ZnO nucleation layer and an influence of its characteristics on growth and optical properties of the ZnO films were studied. Highly homogeneous and continuous nucleation layer of wellconnected ZnO grains with size from 30 to 100 nm, which enable hydrothermal growth of highly transparent ZnO film, were prepared.
COBISS.SI-ID: 25764903
Although the link between the inhalation of nanoparticles and cardiovascular disease is well established, the causal pathway between nanoparticle exposure and increased activity of blood coagulation factors remains unexplained. To initiate coagulation tissue factor bearing epithelial cell membranes should be exposed to blood, on the other side of the less than a micrometre thin air-blood barrier. For the inhaled nanoparticles to promote coagulation, they need to bind lung epithelial-cell membrane parts and relocate them into the blood. To assess this hypothesis, we use advanced microscopy and spectroscopy techniques to show that the nanoparticles wrap themselves with epithelial-cell membranes, leading to the membrane’s disruption. The membrane-wrapped nanoparticles are then observed to freely diffuse across the damaged epithelial cell layer relocating epithelial cell membrane parts over the epithelial layer. Proteomic analysis of the protein content in the nanoparticles wraps/corona finally reveals the presence of the coagulation-initiating factors, supporting the proposed causal link between the inhalation of nanoparticles and cardiovascular disease.
COBISS.SI-ID: 31607591
Coexistence of di?erent phases in chemically-homogeneous materials even at extremely low temperatures may result in complex properties like high Tc superconductivity, colossal magnetoresistance or giant electrostriction. Although it is clear that such phenomenon occur as a response of a frustrated system in order to remove a certain degeneracy, the details of the corresponding mechanism are usually blurred. It might be that similar physics implies also a self assembly of certain building blocks, for example, mesocrystals as the energetically most-favorite evolution at given conditions. In this work we characterized and explained the magnetism-induced inhomogeneity in the ?-NaMnO2 system. It was found that the coupling between the structural and magnetic degrees of freedom in a nearly-degenerate crystal structure lead to a novel phase of matter distinguished by an inhomogenous ground state.
COBISS.SI-ID: 27449895
The article explored the reasons for selectivity of the CuOx/SiO2CuOx/SiO2catalysts, modified with alkali and earth alkali elements, by methods of advanced electron microscopy techniques. In this work, CuOx/SiO2 catalysts were investigated in the propylene partial oxidation reaction. Ordered mesoporous silica (KIT-6) was used to deposit 1–10 wt. % copper and subsequently modified with Na, K and Ca. Operando XANES analysis revealed that a substantial fraction of Cu2? is transformed to Cu? during the propylene oxidation reaction. Additionally we found, that further oxidation of propylene oxide is, most likely, the main factor determining high selectivity for COx products. The alkali modification which increases the PO selectivity does not function via elimination of LAS, but exclusively through attenuation of nucleophilic character of oxygen species.
COBISS.SI-ID: 31445799
In collaboration with Department for Litospheric Research of Vienna University we contributed to their study of spinel (MgAl2O4) formation during replacement reaction between corundum (Al2O3) and periclase (MgO), involving reorganization of Al atoms in octahedral interstices, incorporation of Mg atoms into tetrahedral sites and a transition form the hexagonal close packed (hcp) to the cubic close packed (ccp) oxygen (O) sublattice. For the first time we show this type of transformation as a progressive diffusion controlled process at the atomic scale using quantitative HAADF–STEM. Spinel forms in a progressive zipper–like interface motion, in which MgAl2O4 adopts two crystallographic orientations related by the 180° rotation in the (111)SP || (0001)COR interface. Intergrowth of these domains generates a new type of coherent (111) twin boundaries in spinel that have previously not been reported and differ from growth twins of spinel, reported by Daneu et al. (2007). This is a case study of topotaxial replacement reactions involving hcp/ccp transition in general.
COBISS.SI-ID: 31592487
Using a grain-boundary diffusion process (GBDP) involving the electrophoretic deposition (EPD) of submicron TbF3 powder, we substantially increased the coercivity of sintered Nd-Fe-B permanent magnets. After experiencing optimized conditions at 875 °C for 10 h and subsequent annealing at 500 °C for 1 h, the coercivity was increased to 1536 kA/m (at 75 °C). This value is 1.94 times higher than that for a sintered magnet, without post-sintering heat treatment. By using field emission gun scanning electron microscopy (FEG-SEM) with an energy dispersive spectroscope (EDS), we confirmed the formation of various secondary intergranular phases and the core-shell-type microstructure, which increases the coercivity. The Tb content in the magnet, exposed to the EPD-based GBDP, was controlled by inductively coupled plasma optical electron spectroscopy (ICP-OES). The additional Tb detected in the magnet due to the described technology was only 0.12 wt%.
COBISS.SI-ID: 29734183
Composition evolution and structural properties of electrodeposited Fe-Co-Ni thin films have been studied by transmission electron microscopy along the growth direction. It was revealed for the first time that the evolution in the crystallite size is fully unrelated to the composition. It is thought that the reason of the independence of these phenomena is that their driving force is different. While the composition fluctuation is caused by the composition change in the solution, the stabilization of the crystal orientation and the start of the columnar growth are related to the stress in the deposit and the surface energy of the specific crystal planes. This is why the two trends (i.e., the composition fluctuation and the increase in grain size coupled with the appearance of the columnar ordering) appear as being superimposed onto each other.
COBISS.SI-ID: 31462951
The system of transition and noble metal i.e. Co–Pt, was chosen as an example to verify and explain the general formation mechanism for gas-filled hollow metallic spheres produced by PLA in the presence of an ambient nitrogen gas. The hollow spheres formation mechanism starts with the nitrogen bubble within the liquid nanosphere that was initially formed due to the abrupt drop of pressure and temperature. Due to the fast solidification and the formation of the solid rim the outward diffusion of nitrogen is heavily suppressed, resulting in a solid sphere that is characterized by a void filled with nitrogen gas. The obtained results support the idea that gas-filled hollow spheres could be fabricated in various complex metallic systems by applying PLA in the presence of a background gas, taking into consideration that in relation to the background gas high solubility differences between the melt and corresponding solids are achieved.
COBISS.SI-ID: 27217447
We have produced an innovative, theranostic material based on FePt/SiO2/Au hybrid nanoparticles (NPs) for both, photo-thermal therapy and magnetic resonance imaging (MRI). Furthermore, a new synthesis approach, i.e., Au double seeding, for the preparation of Au nanoshells around the FePt/SiO2 cores, is proposed. The photothermal and the MRI response were first demonstrated on an aqueous suspension of hybrid FePt/SiO2/Au NPs. The cytotoxicity together with the internalization mechanism and the intracellular fate of the hybrid NPs were evaluated in vitro on a normal (NPU) and a half-differentiated cancerous cell line (RT4). The control samples as well as the normal cell line incubated with the NPs showed no significant temperature increase during the in vitro photo-thermal treatment (?T ( 0.8 °C) and thus the cell viability remained high (~90%). In contrast, due to the high NP uptake by the cancerous RT4 cell line, significant heating of the sample was observed (?T = 4 °C) and, consequently, after laser irradiation the cell viability dropped significantly to ~60%. These results further confirm that the hybrid FePt/SiO2/Au NPs developed in the scope of this work were not only efficient but also highly selective photo-thermal agents. Furthermore, the improvement in the contrast and the easier distinction between the healthy and the cancerous tissues were clearly demonstrated with in vitroMRI experiments, proving that hybrid NPs have an excellent potential to be used as contrast agents.
COBISS.SI-ID: 30987559