Physical and chemical properties of Co n?m Cu m nanoclusters with n?=?2–6 atoms via ab-initio calculations

The aim of this work is to investigate the influence of the preparation method on the surface charge and electrokinetic properties of poly-??-caprolactone-based particles using poloxamer 188 as stabilizing agent. To target such objective, two processes (the nanoprecipitation and the emulsification-diffusion) are used to prepare well-defined nanospheres ranging in hydrodynamic diameters from 100 to 200?nm. The effect of the materials used on the particle zeta potential is systematically studied to compare the two preparation methods. The polarity of the organic solvent directly affects the zeta potential of particles prepared via the emulsification-diffusion method. The results obtained suggest that the aqueous phase used for preparing particles affects the possible re-arrangement of polymers during the emulsification step. As the aqueous phase is saturated with the organic solvent, the polar and the non-polar moieties of the polymer chains might be re-conformed following organic solvent diffusion from the particle core to the continuous phase. Regarding the nanoprecipitation process, the electrokinetic properties of the particles were found to be organic solvent independent, but principally affected by the pH and the salinity of the aqueous phase used during the particle preparation.     

Modeling the H5+ potential-energy surface: a first attempt

 Ab initio molecular electronic structure calculations are performed for H₅ ⁺ at the QCISD(T) level of theory, using a correlation-consistent quadruple-zeta basis set. Structures, vibrational frequencies and thermochemical properties are evaluated for ten stationary points of the H₅ ⁺ hypersurface and are compared with previous calculations. The features of the H₃ ⁺…H₂ interaction at intermediate and large intermolecular distances are also investigated. Furthermore, an analytical functional form for the potential-energy surface of H₅ ⁺ is derived using a first-order diatomics-in-molecule perturbation theory approach. Its topology is found to be qualitatively correct for the short-range interaction region. Received: 15 March 2001 / Accepted: 5 July 2001 / Published online: 11 October 2001     

Origins of the Reactivity in 1,3-Dipolar Cycloadditions of Acyl Isocyanide Ylides

1,3-Dipolar cycloadditions are the preferred method to generate five-membered heterocyclic rings. Surprisingly, cycloadditions based on acyl-isocyanide ylides have remained underexplored by the chemical community. Acyl-isocyanide ylides readily react with dipolarophiles, such as substituted alkenes, to yield Δ¹-pyrroline derivatives. As an explanation for the observed reactivity of this reaction is lacking, extensive density functional theory calculations were performed to scrutinize the mechanistic features of the transformation. Herein we explain the experimental outcome of the reaction using a variety of reactivity theories and predict opposed regioselectivity for electron-poor and electron-rich dipolarophiles. With the insights obtained, we hope to incentivize the design of new cycloaddition reactions based on the acyl-isocyanide ylides motif.     

Cyclic voltammetry of immobilized particles as an alternative pesticide screening method for Aedes aegypti mosquitoes

Journal of Solid State Electrochemistry - Today, pest control by chemical treatment is the main strategy against pest insects. This article proposes to show how cyclic voltammetry of immobilized...