Abstract: Metal halide perovskites are one of the most investigated materials in optoelectronics, with their lead-based counterparts being renowned for their enhanced optoelectronic performance. The 3D CsPbX3 structure has set the standard with many studies currently attempting to substitute lead with other metals while retaining the properties of this material. This effort has led to the fabrication of metal halides with lower dimensionality, wherein particular 2D layered perovskite structures have captured attention as inspiration for the next generation of colloidal semiconductors. Here we report the synthesis of the Ruddlesden-Popper Cs2CdCl4:Sb3+ phase as colloidal nanoplatelets (NPs) using a facile hot injection approach under atmospheric conditions. Through strict adjustment of the synthesis parameters with emphasis on the ligand ratio, we obtained NPs with a relatively uniform size and good morphological control. The particles were characterized through transmission electron microscopy, synchrotron X-ray diffraction, and pair distribution function analysis. The spectroscopic characterization revealed most strikingly an intense cyan emission under UV excitation with a measured PLQY of similar to 20%. The emission was attributed to the Sb3+-doping within the structure.

Abstract: The Ni(1+)/Ni(2+) states of nickelates have the identical (3d(9)/3d(8)) electronic configuration as Cu(2+)/Cu(3+) in the high temperature superconducting cuprates, and are expected to show interesting properties. An intriguing question is whether mimicking the electronic and structural features of cuprates would also result in superconductivity in nickelates. Here we report experimental evidence for a bulklike magnetic transition in La(4)Ni(3)O(8) at 105 K. Density functional theory calculations relate the transition to a spin density wave nesting instability of the Fermi surface.

Abstract: High quality epitaxial c axis oriented La2NiO4+ä thin films have been prepared by the pulsed injection metal organic chemical vapor deposition technique on different substrates. High-resolution electron microscopy/transmission electron microscopy has been used to confirm the high crystalline quality of the deposited films. The c-parameter evolution has been studied by XRD as a function of time and gas atmosphere. The high temperature transport properties along the basal a−b plane of epitaxial La2NiO4+ä films have been measured, and the total conductivity of the layers has been found to increase as the thickness is reduced. Layers of 50 nm and thinner have shown a maximum conductivity larger than that measured for single-crystals, in particular, the 33 nm thick films with a conductivity of 475 S/cm in oxygen correspond to the highest value measured to date for this material.

Abstract: Whereas deformation twinning is known to be an important deformation mechanism for hexagonal materials like magnesium and pure titanium, so far almost no literature exists on the twinning behaviour of the Ti-6Al-4V alloy. In this work it was shown that the activation of twinning as a deformation mechanism could have a pronounced effect on the mechanical behaviour of the Ti-6Al-4V alloy. This effect is even more pronounced under dynamic loading conditions. Transmission electron microscopy showed that only the {1 0 1 2}{1 0 1 1} tensile twin system was activated under certain loading conditions. Light-optical microscopy and electron backscatter diffraction data were afterwards used to experimentally determine the twin fractions. The importance of twinning for the texture evolution was also studied. It was shown that even small twin fractions can lead to distinct texture features, especially due to the discrete reorientation of the c-axes. The experimental results were compared to simulated results that were obtained with a viscoplastic self-consistent crystal plasticity code, after experimental validation that twinning can be reliably modelled as a unidirectional slip system. Although good agreement was obtained for the experimental and simulated stress-strain curves, the simulated results concerning twinning correlated well only on a qualitative basis as the simulated twin fractions were systematically higher than the experimental fractions. This seems to strengthen the hypothesis made by other research groups that complete grains might reorient by twinning. (C) 2011 Elsevier B.V. All rights reserved.

Abstract: Mesoporous MIL-101(Cr) is used as host for a ship-in-a-bottle type adsorbent for selective U(VI) recovery from aqueous environments. The acid-resistant cage-type MOF is built in-situ around N,N-Diisobutyl-2-(octylphenylphosphoryl)acetamide (CMPO), a sterically demanding ligand with high U(VI) affinity. This one-step procedure yields an adsorbent which is an ideal compromise between homogeneous and heterogeneous systems, where the ligand can act freely within the pores of MIL-101, without leaching, while the adsorbent is easy separable and reusable. The adsorbent was characterized by XRD, FTIR spectroscopy, nitrogen adsorption, XRF, ADF-STEM and EDX, to confirm and quantify the successful encapsulation of the CMPO in MIL-101, and the preservation of the host. Adsorption experiments with a central focus on U(VI) recovery were performed. Very high selectivity for U(VI) was observed, while competitive metal adsorption (rare earths, transition metals...) was almost negligible. The adsorption capacity was calculated at 5.32 mg U/g (pH 3) and 27.99 mg U/g (pH 4), by fitting equilibrium data to the Langmuir model. Adsorption kinetics correlated to the pseudo-second-order model, where more than 95% of maximum uptake is achieved within 375 min. The adsorbed U(VI) is easily recovered by desorption in 0.1 M HNO3. Three adsorption/desorption cycles were performed. (C) 2017 Elsevier B.V. All rights reserved.

Abstract: ITEM specimens of a LaAlO3/SrTiO3 multilayer are prepared by FIB with internal lift out. Using a Ga+1 beam of 5 kV, a final cleaning step yielding top, top-angle, side, and bottom-angle cleaning is performed. Different cleaning procedures, which can be easily implemented in a dual beam FIB system, are described and compared; all cleaning types produce thin lamellae, useful for HRTEM and HAADF-STEM work up to atomic resolution. However, the top cleaned lamellae are strongly affected by the curtain effect. Top-angle cleaned specimens show an amorphous layer of around 5 nm at the specimen surfaces, due to damage and redeposition. Furthermore, it is observed that the LaAlO3 layers are preferentially destroyed and transformed into amorphous material, during the thinning process.

Abstract: The calculation of defect levels in semiconductors within a density functional theory approach suffers greatly from the band gap problem. We propose a band gap correction scheme that is based on the separation of energy differences in electron addition and relaxation energies. We show that it can predict defect levels with a reasonable accuracy, particularly in the case of defects with conduction band character, and yet is simple and computationally economical. We apply this method to ZnO doped with group III elements (Al, Ga, In). As expected from experiment, the results indicate that Zn substitutional doping is preferred over interstitial doping in Al, Ga, and In-doped ZnO, under both zinc-rich and oxygen-rich conditions. Further, all three dopants act as shallow donors, with the +1 charge state having the most advantageous formation energy. Also, doping effects on the electronic structure of ZnO are sufficiently mild so as to affect little the fundamental band gap and lowest conduction bands dispersion, which secures their n-type transparent conducting behavior. A comparison with the extrapolation method based on LDA+U calculations and with the HeydScuseriaErnzerhof hybrid functional (HSE) shows the reliability of the proposed scheme in predicting the thermodynamic transition levels in shallow donor systems.

Abstract: The instability of the Solid Electrolyte Interphase (SEI) at the surface of nano-silicon electrodes has been recognized as one of the key issues to explain the rapid capacity fading of theses electrodes. In this paper, two distinct Si-based systems are studied by using Electrochemical Impedance Spectroscopy (EIS). First, several EIS spectra are recorded along the second electrochemical cycle. Although the active material, the electrode formulation, and the experimental conditions are different for the two systems, the same phenomena are observed in both cases: (i) the SEI deposit around 50 kHz, (ii) the charge transfer (CT) with a characteristic frequency varying from 300 to 1 500 Hz, and (iii) an inductive loop at ∼1 Hz which appears only when the potential of the electrode is below 0.35 V vs Li. As the latter has never been reported for Si-based electrodes, the second step of the work consists in understanding this phenomenon. Thanks to the results obtained in a set of several complementary experiments, we finally attribute the inductive loop to the constant formation/deposition of SEI products, in competition with the CT process. In addition, we propose a mechanism for this specific phenomenon and the equivalent circuit to fit the recorded EIS spectra.

Abstract: We present the post-modification of a gallium based Metal Organic Framework, COMOC-4, with a Mo-complex. The resulting Mo@COMOC-4 was characterized by means of N2 sorption, XRPD, DRIFT, TGA, XRF, XPS and TEM analysis. The results demonstrate that even at high Mo-complex loadings on the framework, no aggregation or any Mo or Mo oxide species are formed. Moreover, the Mo@COMOC-4 was evaluated as a catalyst in the epoxidation of cyclohexene, cyclooctene and cyclododecene employing TBHP in decane as oxidant. The post-modified COMOC-4 exhibits a very high selectivity toward the epoxide (up to 100%). Regenerability and stability tests have been carried out demonstrating that the catalyst can be recycled without leaching of Mo or loss of crystallinity.