Search

A study to show that the polycationic H-bonded chains of dabcoH[Br.sup.6] are transformed into a different structure of H-bonded cations and anions by modest pressure of about 0.4 Gpa was conducted. The low-pressure triggering of this transformation has suggested that it is a possible source of defects in the real structure at normal conditions, where they can be responsible for anomalous dielectric properties, including relaxor-like behavior of NH...N hydrogen-bonded compounds.

N-(2-Mercaptopropionyl)gycine (tiopronin)-coated silver nanoparticles (average diameter of metal core=5 nm) were prepared by a modified Brust method. It is found that increasing the particular layer contributes to florescence enhancement.

An experimental and computational document states that helices can influence the pK(sub a) of residues located at the N-terminus, but the real nature of this perturbation remains unclear. The origin of the effect of 3(sub10-) and alpha-polyalanine helices on the pKa of an N-terminal cysteine residue is examined in gas phase as well as in aqueous solution by means of density functional theory.

The adsorption of the N atom on the M(111) (M = Cu, Ag, Au) surfaces is investigated by means of quantum chemical calculations using both cluster and slab models. Optimized results indicate that the basis set of the N atom has a distinct effect on the adsorption energy but an indistinct one on the equilibrium distance.

The redox properties of the intermediate radicals derived from OH radical reactions of 5-substituted uracils 1c-h (R = F, Cl, Br, NO2, NH2, OH) was determined by using a redox titration method in the pulse radiolysis of N2O-saturated phosphate buffer solution. The product study showed that the yield of isobarbituric acid and isodialuric acid increased due to the one-electron reduction of 5-oxyl radical 5 by N,N,N',N'-tetramethyl-p-phenylenediamine and the one electron oxidation of 5-oxo radical by tetranitromethane respectively.

The reaction [[Ru[(N[H.sub.3]).sub.5]pz].sup.2+] + Co[([C.sub.2][O.sub.4]).sub.3.sup.3-] is analyzed in aqueous solutions of p-sulfonatocalix[n]arene (n = 4, 6, and 8) and the results are interpreted by using the pseudophase model. The results have shown that the rigidity and/or flexibility of the assembled rings have a significant impact on the thermodynamics of inclusion of the guest into the host and on the kinetics of the electron transfer processes that take place in these media.

The investigation of the reversible binding reaction of oxygen to N,N'-ethylene bis(salicylideneiminato) cobalt(II) (CoS) which is coordinated by a photoisomerizable stilbazole residue of copolymer is reported.

An unusually slow association of two polymerizable organic molecules, HOOC[(C[H.sub.2]).sub.3]CCCC[(C[H.sub.2]).sub.3]COOH and [(EtO).sub.3]Si[(C[H.sub.2]).sub.3]N[H.sub.2] in their common solvent is reported.

The studies about the photoinduced electron-transfer (ET) reaction between some coumarin derivatives and amines such as aniline (AN) and N,N-dimethylaniline (DMAN) at different water/sodium 1,4-bis(2-ethylhexyl)sulfosuccinate (AOT) values which could make the systems more conducive for the observation of the Marcus inverted region is reported.

A spectrophotometric analysis of the oxidation of hydroxylamine by [(Ir[Cl.sub.6]).sup.2-] in deoxygenated aqueous solutions in the range of pH4 tp 9 at 25 degree centigrade is described to test the electron-transfer (ET) and proton-coupled electron transfer (PCET) mechanism. A mechanism is suggested in which rate constant ([k.sub.1]) relates to concerted PCET and rate constant (k') corresponds to ET from N[H.sub.2][O.sup.-] and the large KIE for k' is attributed to the equilibrium isotope effect for p[K.sub.a] of N[H.sub.2]OH.

Four different density functional theory (DFT) studies are conducted to explain the structural and electronic properties of the four polymorphs of crystalline CL-20, a high energy density compound. The [epsilon]-CL-20 crystal is shown to be highly affected by the hydrostatic pressure.

A cheap and reproducible wet process, the seeded growth approach to fabricate Ag nanofilms on Si for electrochemical ATR-surface enhanced IR absorption spectroscopy (SEIRAS) application, is described. Conductive, adhesive and SEIRA-active Ag nanofilms were acquired with subsequent chemical plating in a modified Ag-mirror reaction and pyridine was found to bind via its N end to the Ag electrode.

Poly(N-isopropylacrylamide) (PNIPAM) gels with different sizes in the micrometer scale are synthesized to study swelling kinetics. It is shown that the characteristic swelling time scales with the inverse of the particle dimension squared.

The atomic and electronic structures of fluorinated BN nanotubes (BNNTs) were investigated by generalized gradient approximation (GGA) density functional theory (DFT). It was found that at low F coverages, F atom prefer to be attached at the B positions as far apart as possible and the adsorption energies at different F coverages are quite close, thus showing that the electronic properties of BNNTs can be engineered by fluorination.

Density functional theory (DFT) calculations are used to study the N-doping effects on the electronic and optical properties of Ti[O.sub.2] rutile crystal. The results have shown that substitutional N to Ti structure has a bandgap narrowing in the rutile crystal because N impurity introduces some energy states in the bottom of the conduction band.

An investigation on the adsorption of N-isopropylacrylamide (NIPAM) based thermoresponsive polymers at the air-water interface is conducted by using drop and bubble shape tensiometry. It was found that the rate of polymer adsorption increased as the molecular weight of the polymer decreased.

The chemical behavior of beta-cyclodextrin/nonionic surfactant mixed systems is investigated by using the basic hydrolysis of N-methyl-N-nitroso-p-toluenesulfonamide as a chemical probe. The variations in the hydrophobicity of the surfactant monomer have helped in determining the percentages of uncomplexed cyclodextrin in equilibrium with the micellar system that are in the range of 5-95%.

Microgels particles based on poly (N-isopropylacrylamide) is shown to display an initial swelling behavior. The thermodynamic reasons for the observed expansion and subsequent shrinkage of the particles are considered.

The observed result of N 1s binding energy (BE) at 401.3 eV corresponds to the oxidized nitrogen and indicates a possible Ti-N-O linkage on the surface of N-TiO2 nanoparticles. The possibility of significant atmospheric degradation of the N-TiO2 nanoparticle surface is likely, and the same is demonstrated from the O 1s results.

The strongly nonideal behavior of the N-methylpyrrolidone (NMP) + methanol binary solvent was studied over the wide ranges of pressure and temperature. From the measured and derived excess properties, strong H-bonding is correlated with several cubic EOS, yielding inaccurate results with the most common equation of state (EOS) and very good data fitting with the Sako-Wu-Prausnitz equation.

The computational and infrared studies of the reactions of nitrobenzene on a Si(100) surface which is a prototypical model reaction for understanding the behavior of bifunctional molecules on semiconductor surfaces is described. Computational exploration suggests that two stable structures could be formed and the initial reaction of nitrobenzene with the Si(100)-2*1 occurs through 1,3-dipolar cycloadditions of the nitro group to the silicon surface dimer.

Equilibrium geometry configuration of the 'CH'/N substituted Alq3 and Gaq3 derivatives are calculated by density functional theory. It is shown that the change of 'CH'/N substituted position on 8-hydroxyquinoline ligand is a powerful approach for the tuning of emitting color.

The first complete FTIR characterization of H2, N2 and C2H4 molecular complexes formed on the Cr(II) sites in the Phillips catalyst is discussed. A remarkable increase in the signal-to-noise ratio of the IR spectra of adsorbed species is obtained with the use of a silica aerogel support for Cr(II) sites.

Density functional theory (DFT) calculations were used for examining the adsorption of atomic oxygen and nitrogen on the beta-cristobalite (100) surface. A strong chemisorption on top Si and in a bridge is observed for a first Si layer with average adsorption energy of 5.89 eV (singlet state) or 4.87 eV (triplet state).

Thermal desorption mass spectrometry, thermogravimetric analysis and Fourier transform IR analyses were used for examining the hydrogen desorption mechanism in the reaction from LiH + LiNH2 to Li2NH + H2 by replacing LiD or LiND2 for LiH or LiNH2. The reaction of LiH and NH3 molecules result in the formation of LiNH4 molecule in the hydrogen desorption process.

A report on the synthesis, characterization, and electrochemical application of Ca(OH)2-, Co(OH)2- and Y(OH)3-coated Ni(OH)2 tubes with mesoscale dimensions is presented. These composite tubes are prepared through a two-step chemical precipitation within an anodic alumina membrane under ambient conditions.

The basic photoelectron properties and the visible light activity of nitrogen-doped titania in the mineralization of the pollutant 4-chlorophenol are reported. Nitrogen-doped titania photocatalysts were prepared from titanium tetraisopropoxide or titanium tetrachloride and thiourea where the yellow powders obtained after calcination at 400-600 degree Celsius photocatalyze the mineralization of 4-chlorophenol by visible light.

Mesostructured hollow spheres of graphitic N-doped carbon (CNx) materials may be noncast from solid core mesoporous silica SBA-15 spheres through a chemical vapor deposition (CVD) route. The hollow spheres are generated when the SBA-15 silica/carbon composite obtained after CVD is subjected to silica etching in hydrofluoric (HF) acid.

Structural and electrical transport properties of a family of pi-stacking soluble organic semiconductors, N,N'-dialkyl-3,4,9,10-perylene tetracarboxylic diimides is reported. Further, the structures of evaporated polycrystalline films are studied using X-ray diffraction and atomic force microscopy.

In the study conducted the application to determination of ionization constants of functional groups and to the investigation of the hydrolysis and sorption of copper on different types of sorbents are described. It is suggested that the developed method can be useful for the investigation of ion exchangers, and it has the potential to increase the interactions in other porous systems.

The full quartic six-mode force field for the NH, CO, and CN stretches of the peptide bonds of a cyclic dipeptide rigidly held by a bridge is computed at the ab initio level and used for the simulation of two-dimensional three-pulse femtosecond infrared measurements. The analysis of the complete set of one- and two-color signals generated at all four possible wavevectors shows distinct signatures of anharmonicities, mode couplings, Fermi resonance, and relative transition dipole orientations.

The efficiency of electron injection at two concentrations through fluorescence and transient absorption measurements is studied. From fluorescence measurements, it is confirmed that the aggregates (N3-Zn(super 2+)) of N3 dyes with Zn(super 2+) ions are formed in ZnO films and electron injection from (N3-Zn(super 2+)) to ZnO films is inefficient.