Spectral analysis on a phonon spectral function of a solid-state plasma in a doped semiconductor

We report an analysis on a phonon spectral function of a solid-state plasma formed in a doped semiconductor. Real and imaginary parts of phonon propagators are evaluated including carrier screening effects within a random phase approximation, and finite-temperature spectral behavior of the phonon spectral function is examined in terms of plasmon-phonon coupled modes and quasiparticle excitation mode of the plasma. The results are applied to the case of conduction electrons in a wurtzite GaN considering carrier-phonon coupling channel via polar optical phonons. We show that the dispersion relations of the plasmon-LO phonon coupled (‘upper’ and ‘lower’) modes and the character of the additional modes via single quasiparticle excitations are heavily associated with the nonlocal and dynamic behavior of the energy shift and collisional broadening of the dressed phonon propagator of the plasma.     

Electrode metal penetration of amorphous indium gallium zinc oxide semiconductor thin film transistors

Penetration effects of various electrode materials, namely Al, Au, and Cu, on the physical and electrical characteristics of amorphous oxide semiconductor thin film transistors (TFTs) were investigated. Amorphous indium gallium zinc oxide (a-IGZO) TFTs were fabricated with conventional staggered bottom gate structures on a p-type Si substrate. X-ray photoemission spectroscopy (XPS) analysis under the electrode deposition area revealed variations in the oxygen bonding states and material compositions of the a-IGZO layer. Field-emission scanning electron microscopy (FE-SEM) with the line scan of energy dispersive spectroscopy (EDS) showed lateral penetration by the electrode metal. To compare the electrical characteristics of the tested TFTs, the initial current–voltage (I–V) transfer characteristics were examined. In addition, the tested TFTs fabricated using various electrode materials were tested under bias stress to verify the correlations between variations in TFT characteristics and both the metal work function and penetration-induced oxygen vacancies in the channel around the contact area.     

Influence of interlayer coupling and intra-layer Coulomb interaction on electronic transport in bilayer graphene

Calculations of renormalized perpendicular conductivity within Kubo formula employing single particle temperature dependent Green's function formalism for bilayer graphene has been attempted. On the basis of numerical analysis, perpendicular conductivity as a function of temperature, interlayer coupling, onsite Coulomb interaction and carrier concentration per site has been analyzed for both AA- and AB-stacked bilayer graphene. It is found that perpendicular conductivity increases with interlayer coupling and also with temperature at low temperatures while at higher temperatures, there is saturation in perpendicular conductivity. Influences of onsite Coulomb interaction and carrier concentration per site on perpendicular conductivity is just opposite to each other while onsite Coulomb energy suppresses the rate of increase of σ_⊥/σ_⊥0 with temperature, on the other hand increase in carrier density per site enhance this rate significantly. Finally, theoretically obtained results on temperature dependent perpendicular conductivity are viewed in terms of electronic transport data as well as recent theoretical works available in bilayer graphene.     

Measurements of the spatially resolved electron temperature and plasma potential in ferrite-core side type Ar/He inductively-coupled plasmas

Spatial distributions of the effective electron temperature (T_eff) and plasma potential were studied from the measurement of an electron energy probability function in a side type ferrite-core inductively coupled plasma with an argon–helium mixture. As the helium gas was diluted at the fixed total gas pressure of 5 mTorr in an argon discharge, the distribution of the plasma density and plasma potential changed from a concave to a flat profile, and finally became a convex profile, while all spatial profiles of T_eff were hollow shapes with helium dilution in the argon discharge. This evolution of the plasma potential with helium gas could be explained by the increased energy relaxation length (λ_ε), indicating the transition of electron kinetics from local to non-local kinetics.     

Designing quantitative structure activity relationships to predict specific toxic endpoints for polybrominated diphenyl ethers in mammalian cells

Polybrominated diphenyl ethers (PBDEs) are known as effective flame retardants and have vast industrial application in products like plastics, building materials and textiles. They are found to be structurally similar to thyroid hormones that are responsible for regulating metabolism in the body. Structural similarity with the hormones poses a threat to human health because, once in the system, PBDEs have the potential to affect thyroid hormone transport and metabolism. This study was aimed at designing quantitative structure–activity relationship (QSAR) models for predicting toxic endpoints, namely cell viability and apoptosis, elicited by PBDEs in mammalian cells. Cell viability was evaluated quantitatively using a general cytotoxicity bioassay using Janus Green dye and apoptosis was evaluated using a caspase assay. This study has thus modelled the overall cytotoxic influence of PBDEs at an early and a late endpoint by the Genetic Function Approximation method. This research was a twofold process including running in vitro bioassays to collect data on the toxic endpoints and modeling the evaluated endpoints using QSARs. Cell viability and apoptosis responses for Hep G2 cells exposed to PBDEs were successfully modelled with an r² of 0.97 and 0.94, respectively.     

Removal of cationic methylene blue and malachite green dyes from aqueous solution by waste materials of Daucus carota

In present study adsorption capacity of waste materials of Daucus carota plant (carrot stem powder: CSP and carrot leaves powder: CLP) was explored for the removal of methylene blue (MB) malachite green (MG) dye from water. The morphology and functional groups present were investigated by scanning electron microscope (SEM) and Fourier transform infrared (FTIR) spectroscopy. The operating variables studied were pH, adsorbent dose, ionic strength, initial dye concentration, contact time and temperature. Equilibrium data were analysed using Langmuir and Freundlich isotherm models and monolayer adsorption capacity of adsorbents were calculated. Kinetic data were studied using pseudo-first and pseudo-second order kinetic models and the mechanism of adsorption was described by intraparticle diffusion model.Various thermodynamic parameters such as enthalpy of adsorption ΔH°, free energy change ΔG° and entropy ΔS° were estimated. Negative value of ΔH° and negative values of ΔG° showed that the adsorption process was exothermic and spontaneous. Negative value of entropy ΔS° showed the decreased randomness at the solid–liquid interface during the adsorption of MB and MG onto CSP and CLP.     

2,2,2‐Trifluoroacetophenone as an Organocatalyst for the Oxidation of Tertiary Amines and Azines to N‐Oxides

A cheap, mild and environmentally friendly oxidation of tertiary amines and azines to the corresponding N‐oxides is reported by using polyfluoroalkyl ketones as efficient organocatalysts. 2,2,2‐Trifluoroacetophenone was identified as the optimum catalyst for the oxidation of aliphatic tertiary amines and azines. This oxidation is chemoselective and proceeds in high‐to‐quantitative yields utilizing 10 mol % of the catalyst and H₂O₂ as the oxidant.     

Uncatalyzed Hydroamination of Electrophilic Organometallic Alkynes: Fundamental,Theoretical, and Applied Aspects

Simple reactions of the most used functional groups allowing two molecular fragments to link under mild, sustainable conditions are among the crucial tools of molecular chemistry with multiple applications in materials science, nanomedicine, and organic synthesis as already exemplified by peptide synthesis and “click” chemistry. We are concerned with redox organometallic compounds that can potentially be used as biosensors and redox catalysts and report an uncatalyzed reaction between primary and secondary amines with organometallic electrophilic alkynes that is free of side products and fully “green”. A strategy is first proposed to synthesize alkynyl organometallic precursors upon addition of electrophilic aromatic ligands of cationic complexes followed by endo hydride abstraction. Electrophilic alkynylated cyclopentadienyl or arene ligands of Fe, Ru, and Co complexes subsequently react with amines to yield trans‐enamines that are conjugated with the organometallic group. The difference in reactivities of the various complexes is rationalized from the two‐step reaction mechanism that was elucidated through DFT calculations. Applications are illustrated by the facile reaction of ethynylcobalticenium hexafluorophosphate with aminated silica nanoparticles. Spectroscopic, nonlinear‐optical and electrochemical data, as well as DFT and TDDFT calculations, indicate a strong push–pull conjugation in these cobalticenium– and Fe– and Ru–arene–enamine complexes due to planarity or near‐planarity between the organometallic and trans‐enamine groups involving fulvalene iminium and cyclohexadienylidene iminium mesomeric forms.     

铝合金表面电偶腐蚀与电子功函数的关系

铝合金中经常会引入一些第二相来改善其性能,第二相由于和铝基体的电位差不同,将会对铝合金的局部腐蚀产生重大的影响.为了揭示铝合金腐蚀的物理本质,本文利用基于密度泛函理论第一性原理的计算方法,详细计算了铝合金中一些主要第二相(Al_2Cu、Al_3Ti和Al_7Cu_2Fe)的多种晶面的电子功函数,分析了电子从各个晶面逸出的难易,求得了第二相与Al基体的本征电势差,我们发现不同的晶面暴露在合金最外层,会显著地影响本征电势差;即便是同一晶面,暴露在最外层的原子种类和构型不同,对腐蚀的影响也不一样.从电子的层面解释了电偶腐蚀发生的原因.