The use of O_2^{\begin{array}{*{20}c}--\\\cdot \\ \end{array} } radical anions as spin probes for testing nanostructured materials based on zirconium oxide

The conditions of formation of $O_2^{\begin{array}{*{20}c}--\\\cdot \\ \end{array} } $ radical anions on the surface of zirconium oxide systems including nanostructured pillared clays, in interaction with hydrogen peroxide and an NO + O₂ mixture of gases were studied by the EPR method. The special features of the formation of these radicals depending on the phase composition, structure, and degree of hydroxylation of the surface are discussed.     

A theoretical study of the vibrational structure in the \documentclass{article}\pagestyle{empty}\begin{document}$\tilde{A}^{2}A_{1} - \tilde{X}^{2}B_{1}$\end{document} transition of PH2

The potential energy curves of the bending mode of PH₂ in the ground ²B₁ and the excited ²A₁ states have been calculated using ab initio SCF -MO wave-functions. The radical is found, in agreement with experiment, to be bent in the two states. The calculated results clarify the interpretations of the anomalous behaviour of observed vibrational intervals, and offer an explanation of the ‘quasilinearity’; of the radical in the ²A₁ state.     

Electrochemical Detection of ClO$\rm{ {_{3}^{-}}}$, BrO$\rm{ {_{3}^{-}}}$, and IO$\rm{ {_{3}^{-}}}$ at a Phosphomolybdic Acid Linked 3‐Aminopropyl‐Trimethoxysilane Modified Electrode

A composite film modified electrode containing a Keggin‐type heteropolyanion, H₃(PMo₁₂O₄₀)?H₂O, was fabricated with 3‐aminopropyltrimethoxysilane (APMS) attached on an electrochemically activated glassy carbon (GC) electrode through the formation of C? O? Si bond. PMo₁₂O was then complexed with APMS through the electrostatic interaction between the phosphate groups of PMo₁₂O and amine groups of APMS (PMo₁₂O ‐APMS). XPS and cyclic voltammetry were employed for characterization of the composite film. The PMo₁₂O ‐APMS modified electrode showed three reversible redox pairs with smaller peak‐separation and was stable in the larger pH range compared with that in a solution phase. The catalytic properties of the modified electrode for the reduction of ClO , BrO , and IO were studied and the modified electrode exhibited good electrocatalytic activities for the three anions. The experimental parameters, such as pH, temperature, and the applied potential were optimized. The detection limits were determined to be 7.0±0.35 μM, 4.0±0.17 μM, and 0.1±0.04 μM for ClO , BrO , and IO , respectively. The modified electrode was applied to natural water samples for the detection of ClO , BrO , and IO .     

Crystallographic report: Octameric sodium trimethylsilanolate hemihydrate hemi‐THF solvate, [$\hbox{NaOSiMe}_{3}{ \cdot} {1 \over 2} \hbox{H}_{2}\hbox{O}{\cdot} {1 \over 2}$THF]8

The title compound is composed of two Na₄O₄ heterocubanes which are connected via four µ‐OSiMe₃ groups. The oxygen atoms of the water molecules occupy two corners of an Na₄O₄ cube and additionally form hydrogen bonds to the µ‐OSiMe₃ groups with O·O distances in the range 2.649(4)–2.714(4) Å. Copyright © 2004 John Wiley & Sons, Ltd.     

Density functional theory study of the structures and stabilities of CuO\documentclass{article}\pagestyle{empty}\begin{document}$_{3}^{-}$\end{document} and CuO3

Hybrid density functional theory calculations on the structures, vibrational frequencies, electron binding and dissociation energies, and bonding properties of CuO$_{3}^{-}$ and CuO₃ species have been carried out. Stable isomers containing an O₃ subunit and composed of O₂ bound to CuO have been located on the potential energy hypersurfaces of CuO$_{3}^{-}$ and CuO₃. The isomers formed by O₂ bonded to CuO in side‐on and end‐on coordination are more stable than those containing an O₃ subunit. © 2001 John Wiley & Sons, Inc. Int J Quant Chem 81: 162–168, 2001     

Low-Lying Isomers of (TiO\begin{document}$_{2}$\end{document})\begin{document}$_{n}$\end{document} (\begin{document}${n}$\end{document}=2-8) Clusters

Although there are diverse bond features of Ti and O atoms, so far only several isomers have been reported for each (TiO\begin{document}$_2$\end{document})\begin{document}$_n$\end{document} cluster. Instead of the widely used global optimization, in this work, we search for the low-lying isomers of (TiO\begin{document}$_2$\end{document})\begin{document}$_n$\end{document} (\begin{document}$n$\end{document}=2\begin{document}$-$\end{document}8) clusters with up to 10000 random sampling initial structures. These structures were optimized by the PM6 method, followed by density functional theory calculations. With this strategy, we have located many more low-lying isomers than those reported previously. The number of isomers increases dramatically with the size of the cluster, and about 50 isomers were found for (TiO\begin{document}$_2$\end{document})\begin{document}$_7$\end{document} and (TiO\begin{document}$_2$\end{document})\begin{document}$_8$\end{document} with the energy within kcal/mol. Furthermore, new lowest isomers have been located for (TiO\begin{document}$_2$\end{document})\begin{document}$_5$\end{document} and (TiO\begin{document}$_2$\end{document})\begin{document}$_8$\end{document}, and isomers with three terminal oxygen atoms, five coordinated oxygen atoms as well as six coordinated titanium atoms have been located. Our work highlights the diverse structural features and a large number of isomers of small TiO\begin{document}$_2$\end{document} clusters.     

Calculation of 3-Center One-Electron Integrals \left\langle {AB|r_c^{ - 1} } \right\rangle and Coulomb Repulsion Matrix Elements \left\langle {AB|CC'} \right\rangle in an Exponential Type Spherical AO Basis

A new method for calculating 3-center one-electron integrals and matrix elements of electron interaction of $\left\langle {AB|CC'} \right\rangle $ type in MO LCAO theory, where A, B, and C are the centers of exponential type AO including Slater and hydrogen-like basis functions, has been developed. Integrals of this type are reduced to double integrals over the square with edge 1. This provides the grounds for effective calculation of quantum-chemical 3-center integrals in a basis of exponential type spherical functions.     

On the calculation of arbitrary multielectron molecular integrals over Slater‐type orbitals using recurrence relations for overlap integrals. III. Auxiliary functions \documentclass{article}\pagestyle{empty}\begin{document}$Q_{nn'}^{q}$\end{document} and \documentclass{article}\pagestyle{empty}\begin{document}$G_{-nn'}^{q}$\end{document}

The auxiliary functions $Q_{nn'}^{q}(p,pt)$ and $G_{-nn'}^{q}(p_{a},p,pt)$ which are used in our previous paper [Guseinov, I. I.; Mamedov, B. A. Int J Quantum Chem 2001, 81, 117] for the computation of multicenter electron‐repulsion integrals over Slater‐type orbitals (STOs) are discussed in detail, and the method is given for their numerical computation. The present method is suitable for all values of the parameters p_a, p, and pt. Three‐ and four‐center electron‐repulsion integrals are calculated for extremely large quantum numbers using relations for auxiliary functions obtained in this paper. © 2001 John Wiley & Sons, Inc. Int J Quantum Chem, 2001     

On the anomaly of the quasiclassical product distributions of the \hbox{OH} +\hbox{CO} \rightarrow\hbox{H} +\hbox{CO}_2 reaction

A grid empowered molecular simulator (GEMS) embodying in a single workflow the ab initio treatment of elementary chemical processes has been extended to four atom reactions. GEMS has been used to carry out a massive quasiclassical investigation for the $\hbox{OH} +\hbox{CO} \rightarrow\hbox{H} +\hbox{CO}_2$ reaction on the most recently proposed potential energy surface. The type of potential energy surface used and the possibility of running the simulations on the grid have allowed us to keep the error of the order of a few percent at all values of the collision energy and to estimate accurately the dependence of the reaction cross section on the collision energy. The accuracy of the calculations has allowed to unequivocally single out the fact that the calculated center-of-mass angular distribution is clearly isotropic and radically differs from the asymmetric forward?Cbackward structure obtained from the experiment. However, when the laboratory frame analogues are compared, the difference almost vanishes.     

Voltammetric Behavior of MoS$\rm{ {_{4}^{2-}}}$ and SbS$\rm{ {_{4}^{3-}}}$ as Possible Components of “Dissolved Sulfide” in Oxic Natural Waters

Nanomolar concentrations of dissolved sulfide have been observed in O₂‐ bearing natural waters. The sulfide consists of oxidation‐resistant, unknown chemical components that might include metal‐sulfide complexes, elemental sulfur in various forms or organic sulfur compounds. Here we show that thioanions are also plausible components. Tetrathiomolybdate and tetrathioantimonate ions deposit respectively 3 and 4 equivalents of HgS at mercury electrodes. In cathodic stripping voltammetry, a common method to quantify nanomolar sulfide in nature, MoS and SbS would therefore contribute to “total dissolved sulfide.” Limited evidence suggests that thioanions may be powerful complexing agents that would be capable of affecting trace metal speciation and bioavailability in natural waters.     

"Dry" NiCo\begin{document}$_\textbf{2}$\end{document}O\begin{document}$_\textbf{4}$\end{document} Nanorods for Electrochemical Non-enzymatic Glucose Sensing

A rod-like NiCo\begin{document}$_2$\end{document}O\begin{document}$_4$\end{document} modified glassy carbon electrode was fabricated and used for non-enzymatic glucose sensing. The NiCo\begin{document}$_2$\end{document}O\begin{document}$_4$\end{document} was prepared by a facile hydrothermal reaction and subsequently treated in a commercial microwave oven to eliminate the residual water introduced during the hydrothermal procedure. Structural analysis showed that there was no significant structural alteration before and after microwave treatment. The elimination of water residuals was confirmed by the stoichiometric ratio change by using element analysis. The microwave treated NiCo\begin{document}$_2$\end{document}O\begin{document}$_4$\end{document} (M-NiCo\begin{document}$_2$\end{document}O\begin{document}$_4$\end{document}) showed excellent performance as a glucose sensor (sensitivity 431.29 \begin{document}$\mu $\end{document}A\begin{document}$\cdot$\end{document}mmol/L\begin{document}$^{-1}$\end{document}\begin{document}$\cdot$\end{document}cm\begin{document}$^{-2}$\end{document}). The sensing performance decreases dramatically by soaking the M-NiCo\begin{document}$_2$\end{document}O\begin{document}$_4$\end{document} in water. This result indicates that the introduction of residual water during hydrothermal process strongly affects the electrochemical performance and microwave pre-treatment is crucial for better sensory performance.