Sharif Digital Repository

Multi-component photocatalysts based on apatite-coated Ag/AgBr/TiO(2) were prepared by the deposition method. The effects of various kinds of apatites, with hydroxyl and fluoro substituents, on photocatalytic activity were investigated. The antibacterial processes in the dark, and under visible light, on two types of bacteria indicate that the multi-composites can inhibit the growth of bacteria by two different mechanisms. TEM images and optical microscopic data demonstrate that by attaching the nanosize catalyst to the outer membrane of the cell, the bacteria could not derive nourishment from surrounding media, i.e. this component acts as bacteria-static. The mechanism for deactivation of... 

Solute-solvent and solvent-solvent interactions were investigated for binary mixtures of an ionic liquid (IL) 2-hydroxy ethylammonium formate as with methanol, ethylene glycol and glycerol. The physicochemical properties of the solvent mixtures at 25 °C, over the whole range of mole fractions, were determined using solvatochromic probes. High normal polarity ( ENT ) in the alcohol-rich region confirms solute-solvent interactions in this medium. Dipolarity/polarizability (π ∗) show a different trend to ENT with a positive deviation from ideal behavior in IL-glycerol mixtures. However, these deviations for other solvent mixtures are insignificant. Contrary to what is observed for ENT and π ∗,... 

Zeolite-based Ag/AgBr and Ag/AgBr/TiO2 photocatalysts were prepared by sol–gel and deposition methods and were characterized. Their photocatalytic activities were evaluated by inactivation of Escherichia (E.) coli and the photodegradation of Acid Blue 92 and potassium permanganate. The composites containing Ag/AgBr showed the antibacterial activity in the dark by releasing Ag+ ions into the medium. The results for inactivation of E. coli indicated that Ag/AgBr/TiO2 modified photocatalyst had better antibacterial activity than Ag/AgBr/zeolite, while zeolite and TiO2/zeolite did not show any antibacterial activity under visible light and dark conditions. Photodecolarization rate was affected... 

Two types of nanosized photocatalyst, TiO 2 P-25 and ap/Ag/AgBr/TiO 2, were used for decolorization of Acid Blue 92 (AB92) in dark, visible light (V-L), and UV media. Under UV and V-L, the effect of three possible photodegradation processes of AB92 including photocatalytic degradation, self-photosensitization, and direct photolysis were studied. Results showed that in UV/photocatalysts, photocatalytic degradation is the major process for photodecolorization. However, in the presence of TiO 2, self-photosensitization has the major role under V-L. Because of the presence of AgBr as photoactive center in ap/Ag/AgBr/TiO 2, the main process is the photocatalytic degradation in V-L. By using... 

Various ionic liquids (ILs) and their mixtures were coated on the Pt/Al2O3 catalyst and the resulting IL-coated catalysts were used in the synchronous hydrogenation of cyclohexene and acetone. The rate constant (k) and selectivity (S) toward CO hydrogenation were determined for several catalysts in various solvents. The solvatochromic parameters (ETN, normalized polarity parameter; π*, dipolarity-polarizability; β, hydrogen-bond acceptor basicity; α, hydrogen-bond donor acidity) were determined for the used ILs and solvents and the obtained selectivities were modeled based on the solvatochromic parameters of the IL layer and bulk solvent while using the Multiparameter Linear Regression (MLR)... 

Solute-solvent and solvent-solvent interactions were investigated for binary mixtures of an ionic liquid (IL) 2-hydroxy ethylammonium formate as with methanol, ethylene glycol and glycerol. The physicochemical properties of the solvent mixtures at 25 °C, over the whole range of mole fractions, were determined using solvatochromic probes. High normal polarity (ETN) in the alcohol-rich region confirms solute-solvent interactions in this medium. Dipolarity/polarizability (π *) show a different trend to ETN with a positive deviation from ideal behavior in IL-glycerol mixtures. However, these deviations for other solvent mixtures are insignificant. Contrary to what is observed for E TN and π*,... 

A combined experimental and computational study was carried out on the gas phase pyrolysis reaction of diallylsulfoxide. Allylalcohol and Thioacrolein were detected as the major products during a unimolecular reaction. Experimental kinetic studies were carried out via a static system over the pressure of 21-55 torr and temperature of 435.2-475.1 K. Based on the experiments, the reaction is homogeneous and proceeds through a zwitterionic intermediate. Computational studies at the DFT (B3LYP) and QCISD(T) levels with 6-311++G(d,p) basis set indicated a two-step concerted pathway as the possible route. Comparison between the experimental and theoretical activation parameters for the most... 

Fe3O4 magnetic nanoparticles (MNPs) were prepared by co-precipitation method. The nanoparticles were silica coated using TEOS, and then modified by the polymeric layers of polypropylene glycol (PPG) and polyethylene glycol (PEG). Finally, the core-shell samples were decorated with Ag, Au, and Cu nanoparticles. The products were characterized by vibrating sample magnetometry (VSM), TGA, SEM, XRD, and FTIR methods. The antibacterial activity of the prepared samples was evaluated in inactivation of E. coli and S. aureus microorganisms, representing the Gram-negative and Gram-positive species, respectively. The effect of solid dosage, bacteria concentration and type of polymeric modifier on the... 

Multi-component photocatalysts based on apatite-coated Ag=AgBr=TiO 2 were prepared by the deposition method. The effects of various kinds of apatites, with hydroxyl and fluoro substituents, on photocatalytic activity were investigated. The antibacterial processes in the dark, and under visible light, on two types of bacteria indicate that the multi-composites can inhibit the growth of bacteria by two different mechanisms. TEM images and optical microscopic data demonstrate that by attaching the nanosize catalyst to the outer membrane of the cell, the bacteria could not derive nourishment from surrounding media, i.e. this component acts as bacteria-static. The mechanism for deactivation of... 

Apatite-coated Ag/AgBr/TiO2 was prepared by deposition of Ag as novel metal to generate electron-hole pairs by extending the excitation wavelength to the visible-light region, AgBr, and hydroxy apatite as photosensitive material and adsorption bioceramic, respectively. The energy dispersive X-ray spectrometry clearly showed the presence of Ti, Ag, Ca, and P elements on the surface of catalyst. The bactericidal experiments in dark media indicated that only the novel catalyst shows inhibiting growth of bacteria in this case. A transmission electron microscopy image illustrated that catalyst nanoparticles adhere to the outer membrane of the cell and act as an inhibitor to the nourishment of... 

Structural and intermolecular interactions of solvatochromic probes 4-nitroaniline, 4-nitroanisole, and Reichardt’s dye were investigated in the binary mixtures of 2-hydroxy ethylammonium formate as an ionic liquid with N,N-dimethyl formamide, dimethyl amine, and dimethyl sulfoxide. Solvatochromic parameters (ETN, normalized polarity parameter; π*, dipolarity/polarizability; β, hydrogen-bond acceptor basicity; α, hydrogen -bond donor acidity) were determined in ionic liquid mixtures at 25 °C using UV−vis spectroscopy. ETN parameters obtained from absorbance of Reichardt’s dye within various mixtures of ionic liquid were observed to be higher than predicted values from ideal additive... 

The reaction kinetics of 2-bromo-5-nitro thiophene with piperidine was studied in a solvent with a mixture of propan-2-ol with methanol and n-hexane at 25°C. The measured rate coefficients of the reaction demonstrated dramatic variations in propan-2-ol–n-hexane mixtures and mild variations in propan-2-ol–methanol system. The second-order rate coefficients of the reaction, kA, decreased sharply with n-hexane content. The multiparameter correlation of log kA versus molecular-microscopic solvent parameters shows interesting results in these solutions. Linear free energy relationship investigations confirm that polarity has a major effect on the reaction rate and hydrogen bond ability of the... 

Functionalized magnetic core–zeolitic shell nanocomposites were prepared via hydrothermal and precipitation methods. The products were characterized by vibrating sample magnetometer, X-ray powder diffraction, Fourier transform infrared spectroscopy, nitrogen adsorption–desorption isotherms, and transmission electron microscopy analysis. The growth of mordenite nanocrystals on the outer surface of silica-coated magnetic nanoparticles at the presence of organic templates was well approved. The removal performance and the selectivity of mixed metal ions (Pb2+ and Cd2+) in aqueous solution were investigated via the sorption process. The batch method was employed to study the sorption kinetic,... 

Ab initio, DFT, Monte Carlo statistical mechanics and atom in molecule methods have been applied to investigate the hydrogen bonding effect of protic solvents, apart from the bulk properties, on the reaction of cyclopentadiene and vinyl acetate. The results show that methanol accelerates the rate of the reaction more than water. DFT calculations demonstrate that the interaction of the carbonyl group oxygen atom with solvent molecules in transition state is stronger and more effective than the ether-type oxygen atom. Also, when the solvent molecule is near the oxygen of the carbonyl group the rate of reaction is larger than when it is near the ether-type oxygen. In addition, methanol... 

A joint theoretical and experimental study of the kinetic and mechanism of the rearrangement of allyl p-tolyl ether was performed in order to study the kinetic and mechanism of the reaction. Experimental studies were performed in gas phase over a temperature range of 493.15–533.15 K. The experimental Arrhenius parameters of this reaction were measured to be Ea = 36.08 kcal mol−1, ΔS# = −7.88 cal mol−1 K−1, and Log A = 11.74, experimentally. Using GC for the mixture of the reaction with and without cyclohexene demonstrated that the reaction is clean without any radical intermediates. The experimental results show that the studied reaction is unimolecular and proceeds through a concerted... 

Selective oxidations of alkenes were investigated using molecular oxygen in aqueous solution under mild conditions. Colloidal gold nanoparticles are particularly versatile catalysts for oxidation reaction with exceptionally high efficiency and significant selectivity. Gold nanorods (Au NRs) exhibited a slightly enhanced activity compare to gold nanospheres  

We demonstrate theoretically by density functional non-equilibrium Green's function method that a much simplest two-terminal wire can exhibit switching, and we present a realistic theory of its behavior. We consider a C20-bowl molecular wire sandwiched between an Au (1 0 0) substrate and a monatomic Au scanning tunneling microscope (STM) tip. Lateral motion of the tip over the pentagon ring causes it to change from one conformation class to the other and to switch between a strongly and a weakly conducting state. Thus, surprisingly, despite their apparent simplicity, these Au/C20/Au nanowires are shown to be a convenient switch, the simplest two-terminal molecular switches to date.... 

In this paper, we study the electrical transport and Negative Differential Resistance (NDR) in a single molecular conductor consisting of a cysteine sandwiched between two Au(111) electrodes via the Density Functional Theory-based Nonequilibrium Green's Function (DFT-NEGF) method. We show that (surprisingly, despite their apparent simplicity, these Au/cysteine/Au nanowires are shown to be a convenient NDR device) the smallest two-terminal molecular wire can exhibit NDR behavior to date. Experiments with a conventional or novel self-assembled monolayer (SAM) are proposed to test these predictions. The projected density of states (PDOSs) and transmission coefficients T(E) under various...