Near‐IR‐Triggered,Remote‐Controlled Release of Metal Ions: A Novel Strategy for Caged Ions

A ligand incorporating a dithioethenyl moiety is cleaved into fragments which have a lower metal‐ion affinity upon irradiation with low‐energy red/near‐IR light. The cleavage is a result of singlet oxygen generation which occurs on excitation of the photosensitizer modules. The method has many tunable factors that could make it a satisfactory caging strategy for metal ions.     

The soft Giant Monopole Resonance as a probe of the spin-orbit splitting

The isoscalar monopole response is studied in doubly magic ²⁰⁸Pb , ^{100, 132}Sn nuclei using the Skyrme HF+RPA model. A low-energy strength is predicted and corresponds to almost pure single-particle excitations. These pure single-particle excitations allow to analyse the splitting of the corresponding spin-orbit partners. A good agreement with the spin-orbit splitting data is found in the case of ²⁰⁸Pb . The experimental width of the giant monopole resonance may hinder the measurement of the soft monopole mode.     

ESR and TL studies of irradiated Anatolian laurel leaf (Laurus nobilis L.)

Laurel leaf (Laurus nobilis L.) samples that originated from Turkey were analyzed by electron spin resonance (ESR) and thermoluminescence (TL) techniques before and after γ-irradiation. Unirradiated (control) laurel leaf samples exhibit a weak ESR singlet centered at g=2.0020. Besides this central signal were two weak satellite signals situated about 3 mT left and right to it in radiation-induced spectra. The dose–response curve of the radiation-induced ESR signal at g=2.0187 (the left satellite signal) was found to be described well by a power function. Variation of the left satellite ESR signal intensity of irradiated samples at room temperature with time in a long term showed that cellulosic free radicals responsible for the ESR spectrum of laurel leaves were not stable but detectable even after 100 days. Annealing studies at four different temperatures were used to determine the kinetic behavior and activation energy of the radiation-induced cellulosic free radicals responsible from the left satellite signal (g=2.0187) in laurel leaves. TL measurements of the polymineral dust isolated from the laurel leaf samples allowed distinguishing between irradiated and unirradiated samples.     

The influence of the growth rate on the eutectic spacings,undercoolings and microhardness of directional solidified bismuth–lead eutectic alloy

Bi–Pb alloy at the eutectic composition was unidirectionally solidified upwards with five different growth rates (V = 7.05–113.09 μm/s) at constant temperature gradient (G = 2.18 K/mm) in a Bridgman type directional growth furnace in order to investigate dependency of eutectic spacing (λ), minimum undercooling (ΔT) and microhardness (HV) on the growth rates (V). The values of λ and HV were measured from the quenched samples and the minimum undercooling (ΔT) were determined from the Jackson–Hunt eutectic theory. The dependency of eutectic spacings, microhardness and undercooling on growth rate was investigated. According to these results it has been found that the value of λ decreases with increasing the value of V and that the values of HV and ΔT increase for a constant G. The values of λ²V, λΔT and ΔTV^?0.5 were determined by using the values of λ, ΔT and V. The results obtained in the present work have been compared with those predicted by the Jackson–Hunt eutectic theory and with similar experimental results.     

Investigation of Solvent Effects on Photophysical Properties of New Aminophthalimide Derivatives-Based on Methanesulfonate

Novel aminophthalimide derivatives were synthesized starting from (3aR,7aS)-2-(2-hydroxypropyl)-3a,4,7,7a–tetrahydro-1H-isoindole-1,3(2H)-dione (9) , and solvent effects on the photo-physical properties of these newly synthesized aminophthalimide derivatives (compounds 14 and 15) were investigated using UV-Vis absorption spectroscopy, steady-state and time-resolved fluorescence measurements. Both absorption and fluorescence spectra exhibited bathochromic shift with the increased polarity of the solvents for both molecules. Solute-solvent interactions were analyzed using the Lippert-Mataga and Bakhshiev polarity functions, and Kamlet-Taft and Catalan multiple linear regression approaches. The results revealed that these two molecules experienced specific interactions. Furthermore, photo-physical parameters were calculated for both molecules in all of the solvents, such as the fluorescence quantum yield, fluorescence lifetime, radiative (k_r) and non-radiative (k_nr) rate constant values. It was observed that the fluorescence quantum yield values decreased linearly with increasing solvent polarity. This study proved the new dyes including isopropyl methanesulfonate group displayed different behavior from previous studies of aminophthalimide derivatives in water. It was recommended that these new dyes having interesting properties by changing solvent can be used various applications such as environmentally sensitive fluorescent probes, labels in biology, laser industry.     

Intrinsic and Mn doped InAs quantum dots studied at the atomic scale by cross-sectional scanning tunneling microscopy

Cross-sectional Scanning Tunneling Microscopy (X-STM) is an ideal tool to study the structural properties of semiconductor nanostructures, such as InAs self-assembled quantum dots (QDs) and the properties of individual doping atoms at the atomic scale. The technique allows for a precise determination of the size, shape and composition of overgrown semiconductor nanostructures which can be part of a (complex) multilayer structure. In this paper we discuss our recent results on InAs QD structures that were capped by various methods in order to control their size and shape. We will show that the capping process does strongly affect the final QD structure and thus forms a very important step in the dot formation process. Recently people have started to investigate magnetically doped QDs. We have used our X-STM technique to study the incorporation of single Mn-impurities in InAs/GaAs QDs.     

Effects of the AlN nucleation layer thickness on the crystal structures of an AlN epilayer grown on the 6H-SiC substrate

The influence of the LT-AlN(NL) growth times on the mosaic structure parameters of the AlN layer grown on the LT-AlN(NL)/6H-SiC structures as well as the dislocation densities and the strain behaviours in the AlN epilayers has been investigated using XRD measurements. The growth times of the LT-AlN(NL) were changed to 0, 60, 120, 180, and 240?s. We observed that the mosaic structure parameters of the AlN epilayers were slightly affected by the LT-AlN(NL) growth times. However, the dislocation densities in the AlN layer are affected by the growth times of the LT-AlN(NL) layer. The highest edge dislocation density (5.48?×?10¹⁰?±?2.3?×?10⁹?cm^?2) was measured for the sample in which 120?s grown LT-AlN(NL) was used. On the other hand, highest screw type dislocation density (1.21?×?10¹⁰?±?1.7?×?10⁹?cm^?2) measured in the sample E that contains 240?s growth LT-AlN(NL). The strain calculation results show that the samples without LT-AlN(NL) suffered maximum compressive in-plane strain (?10.9?×?10^?3?±?1.8?×?10^?4), which can be suppressed by increasing the LT-AlN(NL) growth times. The out-of-plane strain also has a compressive character and its values increase with LT-AlN(NL) growth times between 60 and 180?s. Same out-of-plane strain values were measured for the LT-AlN(NL) growth times of 180 and 240?s. Furthermore, the form of the biaxial stress in the AlN epilayer changed from compressive to tensile when the LT-AlN(NL) growth times were greater than 120?s.     

Ab Initio Study on Hypothetical Silver Nitride

We perform the ab initio calculations based on norm-conserving pseudopotentials and density functional theory to investigate the structural, elastic, and thermodynamical properties for silver nitride （AgN） compound that is a member of the 4d transition metal group and has not been synthesized yet. The obtained results are compared with the other available theoretical data, and the agreement is, generally, quite good. We also present the pressure-dependent behaviour of some mechanical and thermodynamical properties for the same compounds.     

First-principles investigation of the structural,dynamical, electronic,and elastic properties of WGe2 and W5Ge3

ABSTRACT

We have investigated the structural, dynamical, elastic, and electronic properties of WGe₂ and W₅Ge₃ compounds in different phases. We have considered the C11_b (tetragonal, space group I4/mmm) and C23 (orthorhombic, space group Pnma) strukturbericht phases for WGe₂ compound and D8₁ (tetragonal, space group I4/mcm), D8_m (tetragonal space group I4/mcm) strukturbericht phases for W₅Ge₃ compound. The structural parameters, formation enthalpies, phonon dispersion curves, elastic constants, mechanical modulus, anisotropic factors, thermal conductivities, and electronic structures have been investigated using generalised gradient approximation within in the plane wave pseudopotential density functional theory. The calculated lattice constants are in a good agreement with the experimental data. The considered phases for WGe₂ and W₅Ge₃ compounds have a metallic character. The results indicated that all phases for compounds are both mechanically stable and dynamically stable except for W₅Ge₃-D8₁. The anisotropy in some mechanical modulus has been investigated using several elastic anisotropy indexes and directional dependence of compressibility, Young’s moduli, shear moduli, and Poisson’s ratio.