Two-Dimensional Transition Metal Dichalcogenides under Electron Irradiation: Defect Production and Doping

Using first-principles atomistic simulations, we study the response of atomically thin layers of transition metal dichalcogenides (TMDs)-a new class of two-dimensional inorganic materials with unique electronic properties-to electron irradiation. We calculate displacement threshold energies for atoms in 21 different compounds and estimate the corresponding electron energies required to produce defects. For a representative structure of MoS_{2}, we carry out high-resolution transmission electron microscopy experiments and validate our theoretical predictions via observations of vacancy formation under exposure to an 80?keV electron beam. We further show that TMDs can be doped by filling the vacancies created by the electron beam with impurity atoms. Thereby, our results not only shed light on the radiation response of a system with reduced dimensionality, but also suggest new ways for engineering the electronic structure of TMDs.     

The effect of temperature on elastic constants and bulk modulus

A model pseudopotential depending on an effective core radius is proposed to study the elastic constants C ₁₁, C ₁₂, C ₄₄ and bulk modulus B of Cu, Ag, Au, Ni, Pt and Rh at various temperatures (300–1500 K). The contribution of d-like electron is taken into account by introducing repulsive short-range Born-Mayer term. An excellent agreement between theoretical investigation and experimental findings has confirmed our formalism.     

Interrelating scattering characteristics to internal electric fields for Gaussian-random-sphere particles

We investigate the single-scattering interference mechanism related to the negative polarization branch (NPB) and intensity enhancement branch (IEB) near the backscattering direction for wavelength-scale Gaussian-random-sphere particles. Previously, we showed that for wavelength-scale spherical particles there is a two-part mechanism related to the longitudinal and the transverse components of the internal electric fields that are responsible for producing both the NPB and IEB near the backscattering direction. For comparison with the previous study, we have chosen the ensemble-averaged parameters of the Gaussian-random-sphere particles to be equivalent to those for spherical particles. We conclude that the same mechanism also can explain the NPB and IEB for non-spherical particles and that the mechanism seems to be stronger inside spherical particles, mainly because of stronger interference, and becomes weaker as the particle becomes more non-spherical.     

Mn(III) mixed‐ligand complexes with bis‐pyrazolones and ciprofloxacin drug: synthesis,characterization and antibacterial activities

The fluoroquinolone family member ciprofloxacin is well known for its drug design and coordinating ability towards metal ions. The coordination chemistry of this drug with metal ions of biological and pharmaceutical importance is of considerable interest. Novel Mn(III) mixed‐ligand complexes of ciprofloxacin with various bis‐pyrazolone‐based dinegative bidentate ligands were synthesized and characterized on the basis of their physical properties, magnetic susceptibility measurements, (FT‐IR and electronic) spectral studies. The FAB‐mass spectrum of [Mn(A⁹)(L)(H₂O)₂]·H₂O [where H₂A⁹ = 4,4′‐(p‐tolylmethylene)bis(3‐methyl‐1‐phenyl‐4,5‐dihydro‐1H‐pyrazol‐5‐ol) and HL = 1‐cyclopropyl‐6‐fluoro‐4‐oxo‐7‐(piperazin‐1‐yl)‐1,4‐dihydroquinoline‐3‐carboxylic acid] was determined. All the synthesized compounds were screened for their bioactivity. The mixed‐ligand complexes exhibited comparable activities against two Gram‐negative (Escherichia coli and Serratia marcescens) and two Gram‐positive (Staphylococcus aureus and Bacillus subtilis) microorganisms. Copyright © 2011 John Wiley & Sons, Ltd.     

Homeomorphisms of Bounded Variation

We show that the inverse of a planar homeomorphism of bounded variation is also of bounded variation. In higher dimensions we show that f ⁻¹ is of bounded variation provided that f ϵ W ^1,1(Ω; R ⁿ ) is a homeomorphism with |Df| in the Lorentz space L ^n-1,1(Ω). Dedicated to Tadeusz Iwaniec on his 60th birthday     

α-Aminophosphonates, -Phosphinates,and -Phosphine Oxides as Extraction and Precipitation Agents for Rare Earth Metals,Thorium, and Uranium: A Review

α-Aminophosphonates, -phosphinates, and -phosphine oxides are a group of organophosphorus compounds that were investigated as extraction agents for rare earth (RE) metals and actinoids for the first time in the 1960s. However, more systematic investigations of their extraction properties towards REs and actinoids were not started until the 2010s. Indeed, recent studies have shown that these α-amino-functionalized compounds can outperform the commercial organophosphorus extraction agents in RE separations. They have also proven to be very efficient extraction and precipitation agents for recovering Th and U from RE concentrates. These actinoids coexist with REs in some of the commercially important RE-containing minerals. The efficient separation and purification of REs is becoming more and more important every year as these elements have a pivotal role in many existing technologies. If one also considers the facile synthesis of α-amino-functionalized organophosphorus extractants and precipitation agents, it is expected that they will be increasingly utilized in the extraction chemistry of REs and actinoids in the future. This review collates α-aminophosphonates, -phosphinates, and -phosphine oxides that have been utilized in the separation chemistry of REs and actinoids, including their most relevant synthetic routes and molecular properties. Their extraction and precipitation properties towards REs and actinoids are also discussed.     

Theoretical simulation of photovoltaic response of graphene-on-semiconductors

Using the fundamental models for voltage and current, we report on the photovoltaic behavior of graphene-on-semiconductor-based devices. The graphene-n-Si and graphene-n-GaAs systems are studied for open-circuit voltage (V _OC) and short-circuit current density (J _SC) under low- and high-level injection conditions. The effects of semiconductor doping density and surface recombination velocity on the V _OC of both systems are investigated. The V _OC for graphene-n-Si under low- and high-level injection conditions are found to be 0.353 V and 0.451 V, respectively, whereas the V _OC for graphene-n-GaAs under low- and high-level injection conditions are 0.441 V and 0.471 V, respectively. The J _SC for graphene-n-Si under low- and high-level injection conditions are calculated as 3 mAcm^?2 and 4.78 mAcm^?2, respectively, whereas the J _SC for graphene-n-GaAs under low- and high-level injection conditions are 5.2 mAcm^?2 and 6.68 mAcm^?2, respectively. These results are in good agreement with the reported experimental work.