Biosynthesis of gold nanoparticles using diatoms—silica-gold and EPS-gold bionanocomposite formation

Novel synthesis of gold nanoparticles, EPS-gold, and silica-gold bionanocomposites by biologically driven processes employing two diatom strains (Navicula atomus, Diadesmis gallica) is described. Transmission electron microscopy (TEM) and electron diffraction analysis (SAED) revealed a presence of gold nanoparticles in the experimental solutions of the diatom culture mixed with tetrachloroaureate. Nature of the gold nanoparticles was confirmed by X-ray diffraction studies. Scanning electron microscopy (SEM) and TEM showed that the nanoparticles were associated with the diatom frustules and extracellular polysaccharides (EPS) excreted by the diatom cells. Due to its accessibility, simplicity, and effectiveness, this method of nanocomposites preparation has great importance for possible future applications.     

Numerical analysis of the effects of carrier dynamics on the switch-on and gain-switching of quantum dot lasers

A systematic analysis of the influence of the capture, inter-level relaxation and exciton dephasing time constants on the dynamic behavior of quantum dot Fabry-Perot semiconductor lasers is done taking into account the lasing from the ground and excited states. The simulation results show that the carrier time constants studied influence significantly the static characteristic of the laser, its switch-on response and the pulses generated by gain-switching.     

The Role of Diffusion-induced Misfit at Epitaxial Heterointerfaces

The diffusion-induced misfit at heterointerfaces and related defect-structure phenomena are derived analytically. On the basis of a simple diffusion model for epitaxial combinations the resulting distributions of misfit, stress, and misfit dislocation density along the diffusion direction can be quantified. Their diffusion-induced parameters can be expressed by relatively simple relations of material parameters (e.g. diffusion coefficients, Vegard's constants, elastic constants), which allow the quick estimation of their influence at epitaxial heterointerfaces.     

Temperature- and humidity-related degradation of conducting polyaniline films

The time dependence of dc conductivity of conducting polyaniline films was measured in relation to temperature and relative humidity of the environment. Optical and structural properties of the samples were checked using Fourier transform infrared (FTIR) spectroscopy.     

Synthesis of New Modified with Rhodamine B Peptides for Antiviral Protection of Textile Materials

Here we report on the synthesis and characterization of three new N-modified analogues of hemorphin-4 with rhodamine B. Modified with chloroacetyl, chloride cotton fabric has been dyed and color coordinates of the obtained textile materials were determined. Antiviral and virucidal activities of both the peptide-rhodamine B compounds and the dyed textile material were studied. Basic physicochemical properties (acid-base behavior, solvent influence, kinetics) related to the elucidation of structural activity of the new modified peptides based on their steric open/closed ring effect were studied. The obtained results lead to the conclusion that in protic solvent with change in pH of the environment, direct control over the dyeing of textiles can be achieved. Both the new hybrid peptide compounds and the modification of functionalized textile materials with these bioactive hemorphins showed virucidal activity against the human respiratory syncytial virus (HRSV-S2) and human adenovirus serotype 5 (HAdV-5) for different time intervals (30 and 60 min) and the most active compound was Rh-3.     

Co-Precipitated Ni-Mg-Al Hydrotalcite-Derived Catalyst Promoted with Vanadium for CO2 Methanation

Co-precipitated Ni-Mg-Al hydrotalcite-derived catalyst promoted with vanadium were synthesized with different V loadings (0–4 wt%) and studied in CO₂ methanation. The promotion with V significantly changes textural properties (specific surface area and mesoporosity) and improves the dispersion of nickel. Moreover, the vanadium promotion strongly influences the surface basicity by increasing the total number of basic sites. An optimal loading of 2 wt% leads to the highest activity in CO₂ methanation, which is directly correlated with specific surface area, as well as the basic properties of the studied catalysts.     

Die Herstellung von Reinstsiliciumscheiben: Mehr Chemie als man glaubt

Monocrystalline semiconductor wafers made of silicon represent the base material for microelectronic devices. The transfer of the precursor material quartz into a 300 mm wafer deposited with an epitaxial layer requires a multitude of process steps, part of which are determined by chemical reactions. This article has introduced into the manufacturing of semiconductor silicon and the processes etching, polishing, cleaning and epitaxy. This technology branch, though, is distinguished by extreme requirements regarding surface perfection and cleanliness, which may be expressed in atomic layers (surface roughness of the wafers) and ppt (contamination of chemicals)     

Charge transport in polyaniline doped with 3-nitro-1,2,4-triazol-5(4H)-one

Polyaniline (PANI) base was protonated in aqueous solutions of an organic acid, 3-nitro-1,2,4-triazol-5(4H)-one (NTO). The temperature dependence of DC conductivity of PANI-NTO seems to correspond to the theory of variable range hopping (VRH) in three dimensions. The frequency dependence of AC conductivity also reflects the hopping nature of mobile charges. The activation energy for the polymers with protonation degree above 0.12 remains constant with increasing dopant concentration and DC conductivity. The value of this constant may correspond to the energy needed for the ionization of dopant counterion. The fit of the electric relaxation function to the stretched exponential function ϕ(t) = exp[−(t/τ)^β] gives the stretch parameter β about 0.35, which shows that the distribution of relaxation times is broad and indicates a high inhomogeneity in the distribution of a dopant.     

Tris(benzophenoneimino)phosphane and Related Compounds

A new group of bases with benzophenoneiminyl (bpi) moiety has been synthesized and characterized in this work. The title compound tris(benzophenoneimino)phosphane (P(bpi)₃) 1 was prepared with a convenient one-pot approach: benzophenone imine was deprotonated using MeMgCl and reacted with PBr₃ in diglyme. The method could be considered as a method of choice for preparing other (amino)phosphanes in case lithio-intermediates and/or protonated phosphane is out of consideration. Phosphane 1 is further used to prepare a range of related phosphonium cations and phosphazenes. Phosphonium cations were deprotonated to assess the stability of the resulting phosphonium ylides. In some cases, the bulky substances were capable of forming P−N heterocycles. Experimental (MeCN) and computational (MeCN, THF, gas-phase) basicities of benzophenone imine, phosphane 1 , phosphonium ylides, and phosphazenes, as well as some representative XRD structures, are presented and discussed.     

A hybrid heuristic for the rectilinear picture compression problem

4OR - In the rectilinear picture compression problem we aim at selecting a minimum number of rectangular submatrices of a binary matrix $$M\in \{0,1\}^{m\times n}$$ , such that (a) every submatrix...