Reference LPI-ARTICLE-1999-017View record in Web of Science Record created on 2006-02-21, modified on 2017-05-12

/pdf/metal-oxide-surfaces-and-their-interactions-with-aqueous-22jt31pax0.pdf

Metal Oxide Surfaces and Their Interactions with Aqueous Solutions and Microbial Organisms.

Nanocrystals of MgO and CaO have been prepared by a modified aerogel/hypercritical drying/dehydration method. For nanocrystalline MgO (AP-MgO) surface areas ranged from 250 to 500 m2/g, whereas for AP-CaO 100−160 m2/g. These materials have been compared with more conventional (CP) microcrystalline samples of lower surface area with regard to (1) morphology (AP-samples (autoclave preparation) are tiny polyhedral crystallites, while CP-samples (conventional preparation) are larger, hexagonal platelets and cubes); (2) residual surface OH (AP-samples have less acidic OH, which are more isolated from each other; (3) acid gas adsorption (AP-samples adsorb more SO2 and CO2 at low pressures and room temperature and prefer monodentate rather than bidentate adsorption modes, but at higher pressures CP-samples adsorb more SO2 and HCl apparently due to the formation of more well ordered multilayers); (4) destructive adsorption of organophosphorus compounds and chlorocarbons (AP-samples are superior due to higher surf...

Nanocrystals as Stoichiometric Reagents with Unique Surface Chemistry

Site Heterogeneous Catalysts: Strategies, Methods, Structures, and Activities Christophe Copeŕet,*,† Aleix Comas-Vives,† Matthew P. Conley,† Deven P. Estes,† Alexey Fedorov,† Victor Mougel,† Haruki Nagae,†,‡ Francisco Nuñ́ez-Zarur,† and Pavel A. Zhizhko†,§ †Department of Chemistry and Applied Biosciences, ETH Zürich, Vladimir Prelog Weg 1−5, CH-8093 Zürich, Switzerland ‡Department of Chemistry, Graduate School of Engineering Science, Osaka University, CREST, Toyonaka, Osaka 560-8531, Japan A. N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, Vavilov str. 28, 119991 Moscow, Russia

Surface Organometallic and Coordination Chemistry toward Single-Site Heterogeneous Catalysts: Strategies, Methods, Structures, and Activities

Nonradical-based advanced oxidation processes for pollutant removal have attracted much attention due to their inherent advantages. Herein we report that magnesium oxides (MgO) in CuOMgO/Fe3O4 not only enhanced the catalytic properties but also switched the free radical peroxymonosulfate (PMS)-activated process into the 1O2 based nonradical process. CuOMgO/Fe3O4 catalyst exhibited consistent performance in a wide pH range from 5.0 to 10.0, and the degradation kinetics were not inhibited by the common free radical scavengers, anions, or natural organic matter. Quantitative structure-activity relationships (QSARs) revealed the relationship between the degradation rate constant of 14 substituted phenols and their conventional descriptor variables (i.e., Hammett constants σ, σ-, σ+), half-wave oxidation potential (E1/2), and pKa values. QSARs together with the kinetic isotopic effect (KIE) recognized the electron transfer as the dominant oxidation process. Characterizations and DFT calculation indicated that the incorporated MgO alters the copper sites to highly oxidized metal centers, offering a more suitable platform for PMS to generate metastable copper intermediates. These highly oxidized metals centers of copper played the key role in producing O2•- after accepting an electron from another PMS molecule, and finally 1O2 as sole reactive species was generated from the direct oxidation of O2•- through thermodynamically feasible reactions.

/pdf/tuning-of-persulfate-activation-from-a-free-radical-to-a-3lm36sr5f1.pdf

Tuning of Persulfate Activation from a Free Radical to a Nonradical Pathway through the Incorporation of Non-Redox Magnesium Oxide

Resonant two‐photon ionization (R2PI) time‐of‐flight mass spectroscopy is used to record S0–S1 spectra of the neutral complexes C6H6–H2O, C6H6 –HDO, C6H6–D2O, C6H6–(H2O)2, and C6H6–(D2O)2. In C6H6–H2O, the lack of an S0–S1 origin transition and the presence of a splitting at 610 (which is absent in C6H6 –HDO) provide vibronic level evidence that the water molecule is on the sixfold axis undergoing internal rotation about that axis. Rotational band contour analysis of the 610 transitions of the isotopomers confirms this picture and also determines a ground state center‐of‐mass separation between C6H6 and D2O of 3.32±0.07 A, very close to that predicted by ab initio calculations. R2PI scans of the van der Waals structure in the isotopic series C6H6–H2O, C6H6 –HDO, and C6H6–D2O provide tentative assignments for three of the six van der Waals modes in the complex. In C6H6–(H2O)2, rotational band contour analysis of the origin transition provides a best‐fit structure in which the two water molecules reside on ...

Multiphoton ionization studies of clusters of immiscible liquids. I. C6H6–(H2O)n, n=1,2

Hydroxyl groups as IR active surface probes on MgO crystallites

Raman spectra of solutions of dimethyl sulphoxide (DMSO) in carbon tetrachloride (CCl 4 ) and water are reported for both parallel and perpendicular polarizations in the S=O stretching region. The various bands obtained were subjected to Gaussian band fittings. It was observed that the bands for solutions in CCl 4 may be fitted satisfactorily by considering four components and those for solutions in water may be fitted by considering five components. It is inferred that the band at ca 1070 cm -1 observed in the spectra of DMSO in CCl 4 belongs to the S=O stretching mode of free DMSO, whereas the two bands observed at ca 1058 cm -1 and ca 1040 cm -1 belong to out-of-phase and in-phase S=O stretchings of the cyclic dimer. The low-frequency band at ca 1025 cm -1 is assigned to linear dimer/higher polymers. Aqueous solutions of DMSO show an additional band at ca 1010 cm -1 due to DMSO hydrogen-bonded with water.

Self-association of dimethyl sulphoxide and its dipolar interactions with water: Raman spectral studies

Ab initio molecular orbital calculations on trimethyl phosphate (TMP) were done using 6-31G* and 6-31G** basis sets, both at RHF and MP2 levels of theory. We located three minima corresponding to C3, C1, and Cs symmetries, given in order of increasing energies. At the MP2/6-31G** level, the energy difference between the C3 and C1 conformers was 0.56 kcal/mol, while that between the C3 and Cs was 1.43 kcal/mol. Our observations are at variance with an earlier ab initio calculation, employing smaller basis sets, STO-3G* and 4-31G*, which had reported that the C1 conformer was the lowest in energy. Furthermore, the earlier calculation did not report the occurrence of a minimum corresponding to the Cs symmetry. Vibrational frequency calculations were done at the HF and MP2 levels. The computed frequencies were found to compare well with experimental vapor phase and matrix isolation data reported earlier, leading to a definitive assignment of the infrared features of TMP. The barrier for conformer interconvers...

Ab Initio Study of Trimethyl Phosphate: Conformational Analysis, Dipole Moments, Vibrational Frequencies, and Barriers for Conformer Interconversion

Infrared spectral studies on preferential solvation of lithium ions in binary mixtures of acetonitrile and dimethyl formamide

CNDO/Force calculations have been performed on a series of molecules, H2CO, F2CO, CF4, CHF3, CH2F2 and CH3F. The optimum geometries and force fields are reported. It is found that the method can successfully predict the geometries of polyatomic molecules. The bending force constants and interaction force constants are, in general, comparable with experimental values both with respect to sign and magnitude. The stretching force constants have higher values than the experimental force constants. However, the trend in stretching force constants of a series of molecules is comparable with that of the corresponding experimental values.

/pdf/calculation-of-optimum-geometries-and-force-fields-by-the-183zw1km8h.pdf

Surjit Singh

Papers

Hydroxyl groups as IR active surface probes on MgO crystallites

Self-association of dimethyl sulphoxide and its dipolar interactions with water: Raman spectral studies

Ab Initio Study of Trimethyl Phosphate: Conformational Analysis, Dipole Moments, Vibrational Frequencies, and Barriers for Conformer Interconversion

Infrared spectral studies on preferential solvation of lithium ions in binary mixtures of acetonitrile and dimethyl formamide

Calculation of optimum geometries and force fields by the CNDO/force method