Abstract: A series of BiVO4/3DOM TiO2 nanocomposites have been synthesized and their photocatalytic activity was investigated under visible light irradiation using the RhB dye as model pollutant molecule in an aqueous solution. The effect of the amount of BiVO4 as visible light sensitizer on the photocatalytic activity of BiVO4/3DOM TiO2 nanocomposites was highlighted. The heterostructured composite system leads to much higher photocatalytic efficiencies than bare 3DOM TiO2 and BiVO4 nanoparticles. As the proportion of BiVO4 in BiVO4/3DOM TiO2 nanocomposites increases from 0.04 to 0.6, the photocatalytic performance of the BiVO4/3DOM TiO2 nanocomposites increases and then decreases after reaching a maximum at 0.2. This improvement in photocatalytic perfomance is related to 1) the interfacial electron transfer efficiency between the coupled materials, 2) the 3DOM TiO2 inverse opal structure with interconnected pores providing an easy mass transfer of the reactant molecules and high accessibility to the active sites and large surface area and 3) the effect of light sensitizer of BiVO4. Intensive studies on structural, textural, optical and surface properties reveal that the electronic interactions between BiVO4 and TiO2 lead to an improved charge separation of the coupled BiVO4/TiO2 system. The photogenerated charge carrier densities increase with increasing the BiVO4 content, which acts as visible light sensitizer to the TiO2 and is responsible for the enhancement in the rate of photocatalytic degradation. However, the photocatalytic activity is reduced when the BiVO4 amount is much higher than that of 3DOM TiO2. Two reasons could account for this behavior. First, with increasing BiVO4 content, the photogenerated electron/hole pairs are accumulated at the surface of the BiVO4 nanoparticles and the recombination rate increases as shown by the PL results. Second, decreasing the amount of 3DOM TiO2 in the nanocomposite decreases the surface area as shown by the BET results. Moreover, the poor adsorptive properties of the BiVO4 photocatalyst also affect the photocatalytic performance, in particular at higher BiVO4 content. The present work demonstrates that BiVO4/3DOM TiO2 is a very promising heterojunction system for visible light photocatalytic applications.

Abstract: In vitro experiments provide a solid basis for understanding the interactions between particles and biological systems. An important confounding variable for these studies is the difference between the amount of particles administered and that which reaches the surface of cells. Here, we engineer a hydrogel-based nanoparticle system and combine in situ characterization techniques, 3D-printed cell cultures, and computational modeling to evaluate and study particle cell interactions of advanced particle systems. The framework presented demonstrates how sedimentation and diffusion can explain differences in particle cell association, and provides a means to account for these effects. Finally, using in silico modeling, we predict the proportion of particles that reaches the cell surface using common experimental conditions for a wide range of inorganic and organic micro- and nanoparticles. This work can assist in the understanding and control of sedimentation and diffusion when investigating cellular interactions of engineered particles.

Abstract: Towards the development of novel drug carriers for oral delivery of poorly soluble drugs mesoporous aerogel carbons (CAs), namely CA10 and CA20 with different pore sizes (10 and 20 nm, respectively), were evaluated. The non-steroidal anti-inflammatory lipophilic compound ibuprofen was incorporated via passive loading. The drug loaded carbon aerogels were systemically investigated by means of High-Resolution Transmission Electron Microscopy (HR-TEM), Nitrogen physisorption studies, X-ray diffraction (XRD), Differential Scanning Calorimetry (DSC), X-ray photon electron spectroscopy (XPS) and zeta-potential studies. In vitro release studies were performed in simulated intestinal fluids reflecting both fasted (FaSSIF) and fed (FeSSIF) state conditions. Cytotoxicity studies were conducted with human intestinal cells (Caco-2). Drug was in an amorphous state in the pores of the carbon carrier as shown from the physicochemical characterization studies. The results showed marked differences in the release profiles for ibuprofen from the two aerogels in the media tested whereas in vitro toxicity profiles appear to be compatible with potential therapeutic applications at low concentrations. (C) 2016 Elsevier B.V. All rights reserved.

Abstract: Objective. The aim was to evaluate the optical properties, mechanical properties and aging stability of yttria-stabilized zirconia with different compositions, highlighting the influence of the alumina addition, Y2O3 content and La2O3 doping on the translucency. Methods. Five different Y-TZP zirconia powders (3 commercially available and 2 experimentally modified) were sintered under the same conditions and characterized by X-ray diffraction with Rietveld analysis and scanning electron microscopy (SEM). Translucency (n = 6/group) was measured with a color meter, allowing to calculate the translucency parameter (TP) and the contrast ratio (CR). Mechanical properties were appraised with four-point bending strength (n = 10), single edge V-notched beam (SEVNB) fracture toughness (n = 8) and Vickers hardness (n = 10). The aging stability was evaluated by measuring the tetragonal to monoclinic transformation (n = 3) after accelerated hydrothermal aging in steam at 134 degrees C, and the transformation curves were fitted by the Mehl-Avrami-Johnson (MAJ) equation. Data were analyzed by one-way ANOVA, followed by Tukey's HSD test (alpha = 0.05). Results. Lowering the alumina content below 0.25 wt.% avoided the formation of alumina particles and therefore increased the translucency of 3Y-TZP ceramics, but the hydrothermal aging stability was reduced. A higher yttria content (5 mol%) introduced about 50% cubic zirconia phase and gave rise to the most translucent and aging-resistant Y-TZP ceramics, but the fracture toughness and strength were considerably sacrificed. 0.2 mol% La2O3 doping of 3Y-TZP tailored the grain boundary chemistry and significantly improved the aging resistance and translucency. Although the translucency improvement by La2O3 doping was less effective than for introducing a substantial amount of cubic zirconia, this strategy was able to maintain the mechanical properties of typical 3Y-TZP ceramics. Significance. Three different approaches were compared to improve the translucency of 3YTZP ceramics. (C) 2016 The Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Abstract: Chrome yellow refers to a group of synthetic inorganic pigments that became popular as an artists material from the second quarter of the 19th century. The color of the pigment, in which the chromate ion acts as a chromophore, is related to its chemical composition (PbCr1-xSxO4, with 0≤x≤0.8) and crystalline structure (monoclinic/orthorhombic). Their shades range from the yellow-orange to the paler yellow tones with increasing sulfate amount. These pigments show remarkable signs of degradation after limited time periods. Pure PbCrO4 (crocoite in its natural form) has a deep yellow color and is relatively stable, while the co-precipitate with lead sulfate (PbCr1-xSxO4) has a paler shade and seems to degrade faster. This degradation is assumed to be related to the reduction of Cr(VI) to Cr(III). We show that on increasing the sulfur(S)-content in chrome yellow, the band gap increases. Typically, when increasing the band gap, one might assume that a decrease in photo activity is the result. However, the photo activity relative to the Cr content, and thus Cr reduction, of sulfur-rich PbCr1-xSxO4 is found to be much higher compared to the sulfur-poor or non-doped lead chromates. This discrepancy can be explained by the evolution of the crystal and electronic structure as function of the sulfur content: first-principles density functional theory calculations show that both the absorption coefficient and reflection coefficients of the lead chromates change as a result of the sulfate doping in such a way that the generation of electron-hole pairs under illumination relative to the total Cr content increases. These changes in the material properties explain why paler shade yellow colors of this pigment are more prone to discoloration. The electronic structure calculations also demonstrate that lead chromate and its co-precipitates are p-type semiconductors, which explains the observed reduction reaction. As understanding this phenomenon is valuable in the field of cultural heritage, this study is the first joint action of photo-electrochemical measurements and first-principles calculations to approve the higher tendency of sulfur-rich lead chromates to darken.

Abstract: Self-propelled Janus particles, acting as microscopic vehicles, have the potential to perform complex tasks on a microscopic scale, suitable, e.g., for environmental applications, on-chip chemical information processing, or in vivo drug delivery. Development of these smart nanodevices requires a better understanding of how synthetic swimmers move in crowded and confined environments that mimic actual biosystems, e.g., network of blood vessels. Here, the dynamics of self-propelled Janus particles interacting with catalytically passive silica beads in a narrow channel is studied both experimentally and through numerical simulations. Upon varying the area density of the silica beads and the width of the channel, active transport reveals a number of intriguing properties, which range from distinct bulk and boundary-free diffusivity at low densities, to directional “locking” and channel “unclogging” at higher densities, whereby a Janus swimmer is capable of transporting large clusters of passive particles.

Abstract: Using Ginzburg-Landau formalism, we investigate the effect of confinement on the ground state of mesoscopic chiral p-wave superconductors in the absence of magnetic field. We reveal stable multichiral states with domain walls separating the regions with different chiralities, as well as monochiral states with spontaneous currents flowing along the edges. We show that multichiral states can exhibit identifying signatures in the spatial profile of the magnetic field if those are not screened by edge currents in the case of strong confinement. Such magnetic detection of domain walls in topological superconductors can serve as long-sought evidence of broken time-reversal symmetry. Furthermore, when applying electric current to mesoscopic p-wave samples, we found a hysteretic behavior in the current-voltage characteristic that distinguishes states with and without domain walls, thereby providing another useful hallmark for indirect confirmation of chiral p-wave superconductivity.

Abstract: Using the tight-binding model, we investigate the influence of vacancy disorder on electrical transport in graphene Hall bars in the presence of quantizing magnetic fields. Disorder, induced by a random distribution of monovacancies, breaks the graphene sublattice symmetry and creates states localized on the vacancies. These states are observable in the bend resistance, as well as in the total DOS. Their energy is proportional to the square root of the magnetic field, while their localization length is proportional to the cyclotron radius. At the energies of these localized states, the electron current flows around the monovacancies and, as we show, it can follow unexpected paths depending on the particular arrangement of vacancies. We study how these localized states change with the vacancy concentration, and what are the effects of including the next-nearest-neighbor hopping term. Our results are also compared with the situation when double vacancies are present in the system. Double vacancies also induce localized states, but their energy and magnetic field dependencies are different. Their localization energy scales linearly with the magnetic field, and their localization length appears not to depend on the field strength.

Abstract: Ultrathin superconductors of different materials are becoming a powerful platform to find mechanisms for enhancement of superconductivity, exploiting shape resonances in different superconducting properties. Here, we evaluate the superconducting gap and its spatial profile, the multiple gap components, and the chemical potential, of generic superconducting nanofilms, considering the pairing attraction and its energy scale as tunable parameters, from weak to strong coupling, at fixed electron density. Superconducting properties are evaluated at mean field level as a function of the thickness of the nanofilm, in order to characterize the shape resonances in the superconducting gap. We find that the most pronounced shape resonances are generated for weakly coupled superconductors, while approaching the strong coupling regime the shape resonances are rounded by a mixing of the subbands due to the large energy gaps extending over large energy scales. Finally, we find that the spatial profile, transverse to the nanofilm, of the superconducting gap acquires a flat behavior in the shape resonance region, indicating that a robust and uniform multigap superconducting state can arise at resonance.

Abstract: The effects of strain, induced by a Gaussian bump, on the magnetic field dependent transport properties of a graphene Hall bar are investigated. The numerical simulations are performed using both classical and quantum mechanical transport theory and we found that both approaches exhibit similar characteristic features. The effects of the Gaussian bump are manifested by a decrease of the bend resistance, RB, around zero-magnetic field and the occurrence of side-peaks in RB. These features are explained as a consequence of bump-assisted scattering of electrons towards different terminals of the Hall bar. Using these features we are able to give an estimate of the size of the bump. Additional oscillations in RB are found in the quantum description that are due to the population/depopulation of Landau levels. The bump has a minor influence on the Hall resistance even for very high values of the pseudo-magnetic field. When the bump is placed outside the center of the Hall bar valley polarized electrons can be collected in the leads.

Abstract: To investigate the impact of both the CoFe ferromagnetic layer thickness and the capping paramagnetic layer on the tunnel magnetoresistance (TMR), we performed first-principles simulations on epitaxial magnetic tunnel junctions contacted with either CoFe or Ta paramagnetic capping layers. We observed a strong oscillation of the TMR amplitude with respect to the thickness of the ferromagnetic layer. The TMR is found to be amplified whenever the MgO spin tunnel barrier is thickened. Quantization of the electronic structure of the ferromagnetic layers is found to be at the origin of this oscillatory behavior. Metals such as Ta contacting the magnetic layer are found to enhance the amplitude of the oscillations due to the occurrence of an interface dipole. The latter drives the band alignment and tunes the nature of the spin channels that are active during the tunneling process. Subsequently, the regular transmission spin channels are modulated in the magnetic tunnel junction stack and other complex ones are being activated.

Abstract: We present a method for area selective deposition of 2D WS2 nanoribbons with tunable thickness on a dielectric substrate. The process is based on a complete conversion of a prepatterned, H-terminated Si layer to metallic W by WF6, followed by in situ sulfidation by H2S. The reaction process, performed at 450 degrees C, yields nanoribbons with lateral dimension down to 20 nm and with random basal plane orientation. The thickness of the nanoribbons is accurately controlled by the thickness of the pre-deposited Si layer. Upon rapid thermal annealing at 900 degrees C under inert gas, the WS2 basal planes align parallel to the substrate.

Abstract: Dark field electron holography is a new TEM-based technique for measuring strain with nanometer scale resolution. Here we present the procedure to align a transmission electron microscope and obtain dark field holograms as well as the theoretical background necessary to reconstruct strain maps from holograms. A series of experimental parameters such as biprism voltage, sample thickness, exposure time, tilt angle and choice of diffracted beam are then investigated on a silicon-germanium layer epitaxially embedded in a silicon matrix in order to obtain optimal dark field holograms over a large field of view with good spatial resolution and strain sensitivity.

Abstract: The substitution of Cr3+ and Mn3+ for Fe3+ in the Bi4Fe6O13F oxyfluoride featuring the magnetically frustrated pentagonal Cairo lattice is reported. Bi4Fe4.1Cr0.9O13F and BiFe4.2Mn0.8O13F have been prepared using a solid state reaction in inert atmosphere. Their crystal structures were studied with transmission electron microscopy, powder X-ray diffraction and Fe-57 Mossbauer spectroscopy (S.G. P4(2)/mbc, a = 8.27836(2)angstrom, c = 18.00330(9) angstrom, R-F = 0.031 (Bi4Fe4.1Cr0.9O13F)), a= 8.29535(3)angstrom, c= 18.0060(1)angstrom, R-F = 0.027 (Bi4Fe4.1Cr0.9O13F)). The structures are formed by infinite rutile-like chains of the edge sharing BO6 octahedra (B transition metal cations) linked by the Fe2O7 groups of two corner-sharing tetrahedra. The"voids in thus formed framework are occupied by the Bi4F tetrahedra. The Fe-57 Mossbauer spectroscopy reveals that Cr3+ and Mn3+ replace Fe3+. exclusively at the octahedral positions. The Mn- and Cr-doped compounds demonstrate antiferromagnetic ordering below T-N =165 K and 120 K, respectively. (C) 2016 Elsevier Ltd. All rights reserved.