First-principles study of electron dynamics with explicit treatment of momentum dispersion on Si nanowires along different directions

ABSTRACT

In this research, ground-state electronic structure and optical properties along with photoinduced electron dynamics of Si nanowires oriented in various directions are reviewed. These nanowires are significant functional units of future nano-electronic devices. All observables are computed for a distribution of wave vectors at ambient temperature. Optical properties are computed under the approximation of momentum conservation. The total absorption is composed of partial contributions from fixed values of momentum. The on-the-fly non-adiabatic couplings obtained along the ab initio molecular dynamics nuclear trajectories are used as parameters for Redfield density matrix equation of motion. The main outcomes of this study are transition energies, light absorption spectra, electron and hole relaxation rates, and electron transport properties. The results of these calculations would contribute to the understanding of the mechanism of electron transfer process on the Si nanowires for optoelectronic applications.     

The influence of stereoisomerism on the biological behavior of 99mTc labeled penicillamine

The aim of this study is to investigate stereoisomeric behavior of penicillamine and the effect of temperature on labeling. In addition, it was explored how stereoisomerism affected biological behavior of them. In the present work, D- and L-enantiomers of penicillamine(D-PA, L-PA) were labeled with ^99mTc using SnCl₂ as reducing agent and their radiopharmaceutical potentials were investigated. Quality control procedures were carried out using thin layer radiochromatography (TLRC), electrophoresis and high performance liquid radiochromatography (HPLRC). HPRLC chromatograms showed two peaks for ^99mTc-D-PA, while a single peak was observed for ^99mTc-L-PA at room temperature. However, the single peak was observed at 90 °C for both isomers. Labeling yields of each isomer were found to be over 98%. Biological activity of these complexes was determined on male Albino Wistar rats by biodistribution studies. While the biodistribution result of ^99mTc-D-PA showed high uptake in the liver, maximum uptake of ^99mTc-L-PA was observed in the kidneys. Both two complexes were cleared rapidly from the blood, mainly by the renal system. Since the activity concentration of ^99mTc-D-PA at the 30th minute in the kidneys and the liver reached a maximum value and at the 120th minute, it was removed by renal and hepatobiliary excretion. As a result, it can be concluded that stereoisomerism affect not only the chemical behavior, but also differs their biological behavior of these compounds.     

Vibrational spectroscopic and thermal studies of some 3-phenylpropylamine complexes

Four new Hofmann–3-phenylpropylamine (3PPA) type complexes with chemical formulae M(3PPA)₂Ni(CN)₄ (M = Ni, Co, Cd, and Pd) have been prepared and their vibrational spectra are reported in the region of 4000–60 cm⁻¹. The vibrational bands arising from 3PPA ligand molecule, the polymeric sheet and metal–ligand bands of the compounds are assigned. The thermal behaviour of these complexes is also provided using the DTA and TGA along with the magnetic susceptibility data. The results indicate that the monodentate 3PPA ligand molecule bonds to the metal atom of |M–Ni(CN)₄|_∞ polymeric layers and hence the compounds are similar in structure to Hofmann-type complexes.     

Development and Validation of Selective Spectrophotometric Methods for the Determination of Pregabalin in Pharmaceutical Preparation

Three simple, quick and sensitive methods are described for the spectrophotometric determination of pregabalin (Pgb) in pharmaceutical preparations. Among them, the first two methods are based on the reaction of Pgb as n-electron donors with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) and 7,7,8,8-tetracyanoquinodimethane (TCNQ) as π-acceptors to give highly colored complex species. The colored products were quantitated spectrophotometrically at 494 and 841 nm for DDQ and TCNQ, respectively. Optimization of the different experimental conditions was conducted. Beer’s law was obeyed in the concentration ranges 2.0—30.0 and 1.5—10 µg•mL－1 for DDQ and TCNQ methods, respectively. The third method is based on the interaction of ninhydrin (NN) with primary amine present in the pregabaline. This reaction produces a blue coloured product in N,N-dimethylformamide (DMF) medium, which absorbs maximally at 573 nm. Beer’s law was found in the concentration range 40.0—180.0 μg•mL－1. The methods were applied successfully to the determination of this drug in pharmaceutical dosage forms.     

New type of tetrazine‐substituted metallophthalocyanines by microwave irradiation: Synthesis and characterization

5,6‐bis(4‐methylphenyl)‐2,3‐dihydro‐1,2,3,4‐tetrazine 2 was synthesized by the dimerization of ethyl p‐methylbenzoateformylhydrazone 1 in hydrazinehydrate solution. 2,3‐bis(4‐methylphenyl)‐6,7,14,15‐tetrahydro[1,2,3,4]tetrazino [2,3d][1,8, 4,5]benzodithia‐diazecine‐10,11‐dicarbonitrile 4 was sythesized by cyclization reaction of tetrazine monomer 2 onto 1,2‐bis‐(2‐iodoethylmercapto)‐4,5‐dicyanobenzene 3 . Co(II) and Cu(II) phthalocyanine complexes were prepared by reaction of the dinitrile compound ( 4 ) with the chlorides of Co(II), Cu(II), and DMAE at 175°C, 350 W in a microwave oven for 10 min. Zn(II)‐phthalocyanine complex was prepared by reaction of the dinitrile compound 4 with the acetate of Zn(II) and DMAE at 175°C, 350 W in a microwave oven for 10 min. The new compounds were characterized by a combination of IR, ¹H‐NMR, ¹³C NMR, UV‐vis, elemental analysis, and MS spectral data. © 2010 Wiley Periodicals, Inc. Heteroatom Chem 21:456–461, 2010; View this article online at wileyonlinelibrary.com . DOI 10.1002/hc.20623     

Syntheses and modifications of bisdiazonium salts of 3,8-benzo[c]cinnoline and 3,8-benzo[c]cinnoline 5-oxide onto glassy carbon electrode and the characterization of the modified surfaces

The goal of this study was to prepare novel glassy carbon electrode surfaces using two similar bis-diazonium salts, 3,8-benzo[c]cinnoline (3,8-BCC-BDAS) and 3,8-benzo[c]cinnoline 5-oxide (3,8-BCCNO-BDAS) at the glassy carbon (GC) surface. These diazonium salts were reduced electrochemically and covalently electrografted onto the glassy carbon electrode surface to form modified electrodes. Electrochemical reduction of 3,8-BCC-BDAS and 3,8-BCCNO-BDAS salts on the electrode surface yielded a compact and stable film. The existence of BCC moieties on the GC surface was characterized by X-ray photoelectron spectroscopy, reflectance-adsorption infrared spectroscopy, cyclic voltammetry, ellipsometry, and electrochemical impedance spectroscopy. The stability and working potential range of the novel modified electrodes were also studied. The possibility of analytical application of these novel surfaces for inorganic cations and especially selectivity to copper ions was investigated. 3,8-diaminobenzo[c]cinnoline (3,8-DABCC) and its 5-oxide derivative (3,8-DABCCNO) were synthesized from the reductive cyclization of 2,2′-dinitrobenzidine and prepared their bisdiazonium salts via the tetrazotization reactions of the diamines with NaNO₂. The structures of 3,8-DABCC and 3,8-DABCCNO and their corresponding bisdiazonium salts are confirmed by spectral analysis.     

Solution of soliton equations in terms of neutral fermion particles

In this paper we exploit the algebraic structure of the soliton equations and find solutions in terms of neutral free fermion particles. We show how pfaffians arise naturally in the fermionic approach to soliton equations. We write the τ-function for neutral free fermions in terms of pfaffians. Examples of how to get soliton, rational and dromion solutions from τ-functions for the various soliton equations are given.     

Characterizing killing vector fields of standard static space-times

We provide a global characterization of the Killing vector fields of a standard static space-time by a system of partial differential equations. By studying this system, we determine all the Killing vector fields in the same framework when the Riemannian part is compact. Furthermore, we deal with the characterization of Killing vector fields with zero curl on a standard static space-time.     

Synthesis and proton conductivity studies of azole functional organic electrolytes

As an attempt to produce azole functional proton conductors, organic electrolytes with triazole and tetrazole functional groups were synthesized via substitution reaction of 1,3,5-benzenetricarbonyl trichloride with aminotriazole and aminotetrazole. The samples were doped with triflic acid with molar ratios of 0.25 and 0.50. FTIR, nuclear magnetic resonance (NMR), and elemental analysis were used to characterize the resulting materials. Thermogravimetric analysis showed that the samples are thermally stable up to 150?°C. The effect of acid doping on proton conductivity was investigated with impedance spectrometer. Both pure samples and the doped ones revealed high proton conductivity. In anhydrous conditions (TMA)-TriTA_0.50 and TMA-TetTA_0.50 have proton conductivities of 1.8 and 19?mS/cm at 150?°C, respectively. Solid-state NMR studies revealed that there are three different types of hydrogen-bonded acidic proton in the systems. Moreover, these different types of acidic protons present at different ratio in triazole and tetrazole systems.     

Simultaneous determination of cation exchange capacity and surface area of acid activated bentonite powders by methylene blue sorption

To distinguish the ion exchanged and physically adsorbed methylene blue cations (MB⁺) on ionic surfaces, acid activated bentonite samples were used as porous adsorbents. A natural calcium bentonite (CaB) sample from Enez/Edirne, Turkey, was acid activated at 90 °C for 16 h with various HCl/CaB ratios. The irreversible exchange and physical adsorption of MB⁺ cations on the ionic solids have simultaneously occurred. The ion exchanged (m_ex) and physically adsorbed (m_ad) MB⁺ contents were obtained as the values of sorption capacity at c = 0 and the increase to a plateaus of adsorption isotherms, respectively. The m_ad value was taken to be monolayer adsorption capacity. Cation exchange capacity (CEC) and specific surface area (S_MB) for each sample were calculated from the m_ex and m_ad values, respectively. Also, the BET specific surface areas (S_BET) and pore size distribution were determined from low temperature nitrogen adsorption/desorption data. A linear correlation between the S_MB and S_BET values was found.