Journal of Physical and Theoretical Chemistry
Volume:6 Issue: 1, Spring 2009

Sn02 nanowires with diameters of 30 — 200 nm have been synthesized by using carbothermalprocess via a thick film of tin dioxide and carbon powder precursor. The nanowires werecharacterized by X-ray power diffraction (XRD), scanning electron microscopy (SEM),transmission electron microscopy (TEM) and Selected Area Electron Diffraction (SAED).The gas sensing characteristic of nanowires toward ethanol vapor was investigated. The gassensitivity experiments have demonstrated that the as-synthesized Sn02 materials exhibitgood sensitivity to ethanol vapors, which may offer potential applications in gas sensors. Thedetails of its sensing characteristics were observed and discussed.

High purity lead titanate nanopowders in tetragonal form have been successfully prepared bycitric acid gel method using lead nitrate and tetra-n-butyl titanate as Pb and Ti sourcesrespectively and citric acid as complexing reagent. The precursors were calcined at varioustemperatures ranging from 450 °C to 600 °C for 2 h. Fourier Transform InfraredSpectroscopy (FT-IR), X-ray diffraction (XRD) and Transmission Electron Microscopy(TEM) were used to characterize the crystallization process, particle size and morphology ofthe calcined powders. The results indicated that lead titanate nanoparticles with an averagesize ranging from 35-50 nm could be obtained after calcining of the dried gel at 550°C for2 h.

Serum Albumin is the most aboundant protein in blood plasma. Its two major roles aremaintaining osmotic pressure and depositing and transporting compounds. In this paper,Albumin-methanol solution simulation is carried out by three techniques including MonteCarlo (MC), Molecular Dynamic (MD) and Langevin Dynamic (LD) simulations. Byinvestigating energy changes by time and temperature (between 273 to 313K), it is found thatMC method is not suitable for macromolecule simulations. Also by comparing optimizedenergy in Albumin-water system and Albumin-methanol system,it is distinguished thatbecause of existing more hydrogen bondings Albumin-water system is more stable thanAlbumin-methanol.

We introduce a model for prediction the behavior of electrodes which modified withcarbon nanotubes in a polymer medium. These kinds of polymer composites aredeveloped in recent years, and experimental data for its percolation threshold isavailable. We construct a model based on percolation theory and fractal dimensionsand using experimental percolation threshold for calculating the moments of currentdistribution function.

Bimetallic Pt-V supported by Gamma-alumina is used to observe the changes of nheptanewhen passed over this catalyst. The Pt concentration was kept constant at0.1wt% while the concentration of the vanadium was 0.5wt%. The activity andselectivity of catalyst have been determined under conditions at 450-500 degreescentigrade and 15-30 attn. The experimental results show that the addition of secondmetal to the Pt catalyst results in a modification of the metal and acid functions. Theresults show that when vanadium is present, the catalyst has high selectivity foraromatization reaction.

This study concerns about quantum chemical modeling behavior of 02 on Cr (100)surface by using density functional theory (DFT) by LANL2DZ and 6 — 31G* basissets, we presented the results of our first principles electronic structure calculationson the 02 molecules and their interface with Cr (100) surface. The chromium metalhas the body-centered cubic structure, and chromium cluster has five Cr atoms thatused to form the perfect Cr (100) surface. Three possible adsorption site, top, bridgeand center site are considered in the calculations. The predicted results show that thebridge site are considerably stronger than at top and center site. So the bridge siteapproach is important for the chemisorptions processes, because the adsorptionenergy is lower than top site.

The complexation of Alkali metal cations by the water-soluble p-sulfonic acid calix(4)arenewas thermodynamically characterized using spectrophotometeric data which are consistentwith the formation of a 1:1 complex resulting from electrostatic interactions between thesulfonato groups and alkali metal cations. In this study, we determined the formationconstants (log K) of the complexes and have compared in deferent pH (1.0 and 1.5) at 25°C.

Chemical denaturation and thermal denaturation of13-lactoglobulin A (f3 — lgA) in the absenceand presence of various concentrations sugar osmolytes and polyols were measured bymonitoring changes in the absorption coefficients at pH 2.0. It has been observed that AGD°(H20), (Gibbs free energy change in absence of denaturant at 25 °C) of f3-1gA in the presenceof 10% (w/v) Trehalose, Sucrose, Sorbitol and Mannitol is increased. We report that thefunctional dependence of AGD°, (Gibbs free energy change at 25 °C) of protein in the absenceand the presence of sugar osmolytes on denaturant concentration is linear. Trehalose is foundto induce remarkable stability of 13-1gA against chemical denaturation. The values of Tm(midpoint of denaturation), AHm (enthalpy change at Tm), and ACp (constant-pressure heatcapacity change) under a given solvent condition were measured. It has been observed thateach sugar stabilizes the protein in terms of Tm and AGD°.

The pH dependence study reveals that the Cys 206 sulphydryl group of bovine carbonicanhydrase in the native form is not exposed. During the reaction of 2,2'-dithiobispyridine (2-DTP) with the enzyme, there was no absorbance change recorded. In the presence ofsurfactants, the pH dependence profiles of the apparent second order rate constants, kapp, forthe reaction of 2-DTP with bovine carbonic anhydrase assume simple profile forms, whichresemble the diprotic acid titration curve. These simple profiles were quantitatively analyseswith Eq. (1) in the text. Best-fit lines drawn with the parameters shown in Table 1 areobtained. The mean pKi value of 5.1 and the mean pK2 of 8.4 are assigned to His 167 andCys 206, respectively. The pH dependence of the apparent second-order rate constant, kapp, inthe higher concentrations of SDS is higher than that in the lower concentrations. It shows thatthe Cys 206 sulphydryl group of bovine carbonic anhydrase is more exposed in the higherconcentrations of SDS.

This paper deals with application of polyaniline coated on wood sawdust for removal ofmethylene blue (MB) dye from aqueous solutions. Polyaniline coated onto sawdust (termedas PAn/SD) was prepared via direct chemical polymerization onto sawdust which waspreviously soaked in the monomer (aniline) solution in acidic (HC1) media. Adsorptionexperiments were carried out using batch system. The effects of different system variablessuch adsorbent dose, initial dye concentration, pH, contact time were then studied. It wasfound that PAn/SD is efficient and cost effective adsorbents for removal of MB dye fromaqueous solutions.