Volume 230, Issue 8

Photoelectron photoion coincidence (PEPICO) spectroscopy as an attractive new technique for combustion analysis was used in a fixed-photon-energy configuration to provide quantitative species profiles in laminar premixed flames. While such measurements are conventionally performed with molecular-beam mass spectrometry (MBMS) using electron ionization (EI) or vacuum ultraviolet (VUV) photoionization (PI) with synchrotron radiation, these techniques have some limitations. The possibility to record photoelectron spectra (PES) simultaneously with photoionization data, providing fingerprint information for reliable species identification, presents a significant advantage of PEPICO spectroscopy especially in complex reactive mixtures. The multiplex approach presented here, enhanced by the imaging capabilities of the electron and ion detection in the so-called double-imaging PEPICO scheme (i 2 PEPICO), provides, in different experimental situations, an unprecedentedly detailed combustion analysis regarding both species identification and quantification. Problems and perspectives of the present fixed-photon-energy PEPICO approach will be discussed.

Quantum mechanical lineshapes of collision-induced absorption (CIA) at room temperature are computed for gaseous molecular oxygen using theoretical values for induced dipole moments and new isotropic interatomic potential as input. Comparison with measured spectra of the rototranslational collision-induced absorption shows good agreement over the full range of frequencies. Empirical models of the dipole moment which reproduce the experimental spectra and the first two spectral moments more closely than the fundamental theory are also given. The quality of the present potential has been checked by comparing between calculated and experimental thermo-physical and transport properties over a wide temperature range, which are found to be in good agreement.

Three different surfactants based on fatty acids (octanoic, tridecanoic and oleic) and ethylenediamine were synthesized and their chemical structures were confirmed by FT-IR, 1 H-NMR and 13 C-NMR spectroscopy. The surface-active properties of the prepared surfactants were determined by using interfacial tension.The synthesized surfactants were evaluated as corrosion inhibitors for carbon steel in a solution of 0.50 M HCl at 40 ℃. Potentiodynamic polarization, linear polarization resistance corrosion rate and electrochemical impedance spectroscopy measurements were used for this study. Experimental results showed that, the inhibition efficiency increases with increasing the surfactant concentration, getting maximum inhibition efficiency ranged between 97.10 and 99.61% at 400 ppm. Potentiodynamic polarization curves showed that, the three compounds act as mixed type. The adsorption of investigated surfactants obeyed the Langmuir adsorption isotherm, and the thermodynamic parameters were calculated and discussed. Obvious correlation was found between the corrosion inhibition efficiency and the quantum chemical parameters. The obtained theoretical results have been adapted with the experimental data.

The kinetics of oxidation of a few aliphatic primary alcohols with 1-chlorobenzimidazole (CBI) was studied in aqueous acetic acid medium. The reactions were found to be first order each with respect to the concentrations of CBI and alcohol. The added HClO 4 increases the rate and the order in HClO 4 was found to be fractional. The reactions were catalyzed by NaCl and fractional order dependence was observed. The ionic strength had negligible influence on the rate. The reaction rates increase with decrease in dielectric constant of acetic acid. Addition of benzimidazole, one of the products does not affect the rate. Effect of temperature on the reaction rates was studied at different temperatures and the various activation and thermodynamic parameters were evaluated. The rate constants show good correlation with Taft–Pavelich Dual substituent parameter model (DSP). Product analysis shows the formation of aldehydes as major products of oxidation of aliphatic primary alcohols. CBIH + has been postulated as the reactive oxidizing species. A mechanism involving a proton transfer by water molecule has been proposed.

Using the inclusion complexation of methylene blue with p -sulfonatocalix[6]arene (Calix-S6) as a chemical indicator, the association constants of inclusion complexes of Calix-S6 with visible-spectroscopically inert 1-butyl-3-methylimidazolium salts (ionic liquids (IL): counter anions BF 4 – , PF 6 – , and Cl – ) were determined. It was found that the experimentally observed association constants of IL with Calix-S6 in a water-methanol mixture increased in the order of counter anion Cl –  < BF 4 –  < PF 6 – . The 19 F NMR signals of counter anions BF 4 – and PF 6 – shift upfield upon addition of Calix-S6. From the 19 F NMR chemical shifts, we suggested that Calix-S6 forms weak 1:1 complexes with the BF 4 – and PF 6 – anions. The binding constants and their thermodynamic parameters for the complexation of the BF 4 – and PF 6 – anions with Calix-S6 were evaluated in a water-methanol mixture (6:4 ( V / V )) at 298 K: K A  = 26.2 M – 1 for BF 4 – and 106 M – 1 for PF 6 – . Based on the results, the characteristics for the complexation of the counter anions with Calix-S6 were discussed and the inclusion constants of Calix-S6 with the cationic ring moiety of 1-butyl-3-methyl-imidazolium salts were determined.

Two new ionic liquids derived from natural product salicylate, 1-methyl-3-ethylimidazolium salicylate ([Emim][Sal]) and 1,2-dimethyl-3-ethylimidazolium salicylate ([Emmim][Sal]), were synthesized and characterized. The density, surface tension, viscosity, and electrical conductivity of two ionic liquids were determined from 288.15 to 343.15 K. The physico−chemical properties of the ionic liquids were estimated from the experimental data by empiric or semi-empiric methods, such as, coefficients of thermal expansion, molecular volume, standard molar entropy, lattice energy, enthalpy of vaporization, and so on. According to the interstice model of ionic liquids, the interstice parameters like coefficients of thermal expansion and interstice volume etc. were estimated, too. The experimental results and Density Functional Theory (DFT) calculation were employed to discuss the structure characteristics caused by differences of cations/anions for properties of two ionic liquids. And by the Vogel–Fulcher–Tamman (VFT) equation, the temperature dependences of the ILs viscosities and electric conductivities were graphically described. The structures, the energetics and COSMO volumes of all investigated ions are obtained by combining DFT calculations and the COSMO–RS methodology to describe intermolecular interactions of ionic liquids.

Nanocrystalline nickel oxide (NiO), chromium and cobalt doped NiO nanoparticles have been prepared successfully by chemical precipitation method. NiO, Cr and Co-doped NiO nanoparticles have been characterised using various analytical techniques such as X-ray diffraction, FESEM, HRTEM, UV absorption and M-H curves. The average grain size of NiO, Cr and Co-doped NiO nanoparticles are 10.33 nm, 9.54 nm and 8.70 nm respectively. The UV absorbance study shows a strong absorption edge at 314.96 nm, 308.64 nm and 305.37 nm respectively. The band gap values of NiO, Cr and Co-doped NiO nanoparticles are 3.936 eV, 4.017 eV and 4.060 eV. The incorporation of chromium and cobalt into NiO nanoparticles have strongly influenced the magnetic behaviour and the material got converted from super paramagnetic to ferromagnetic material.