Plasmon heating mediated Friedel-Crafts alkylation of anisole using supported AuNP@Nb2O5 catalysts

Two different hybrid materials composed of gold nanoparticles (AuNPs) supported on either commercial niobium oxide HY 340 or mesoporous niobium oxide catalyzed the Friedel-Crafts alkylation of anisole by benzyl chloride. Excitation of the surface plasmon of the supported AuNPs allowed the reaction to occur at lower temperatures by acting as an alternative heat source. The localized heating produced via plasmon excitation permitted the acid catalyzed reaction to occur - at the Lewis acid sites on the Nb₂O₅ support - at 80 °C while thermal-dark reactions using a conventional heat source, required temperatures of 120 °C or higher. The catalytic activity of the tested hybrid materials decreased with storage time. However, the deactivation showed to be reversible upon lyophilisation indicating that the nature of the deactivation could be due to water adsorption.     

Voltammetric studies of the interaction between lead metal ion and the methyl parathion pesticide

Journal of Solid State Electrochemistry - In this work, the interaction of the pesticide methyl parathion (MP) with the lead metal ion was evaluated using a carbon electrode reused from a zinc...     

Atrane complexes chemistry as a tool for obtaining trimodal UVM-7-like porous silica

Abstract

The use of atrane complexes as hydrolytic precursors enables the homogeneous incorporation of manganese (25 ≤ Si/Mn ≤ 48) throughout the porous walls of the nanoparticles of a surfactant-templated bimodal mesoporous silica (UVM-7). The subsequent leaching of the manganese nanodomains allows adding controlled microporosity to the host silica framework. The resulting final silica material presents three pore systems structured at different length scales: interparticle textural-type macroporosity (ca. 43.2 nm), ordered intraparticle mesoporosity (ca. 2.63 nm; after template removal), and well-dispersed microporosity (< 2 nm; as consequence of the lixiviation of the Mn-rich domains). The good dispersion of the guest element (Mn) in the silica intermediate provided by the atrane route is responsible for the disordered but regular microporosity achieved.     

Control of N‐Heterocyclic Carbene Catalyzed Reactions of Enals: Asymmetric Synthesis of Oxindole‐γ‐Amino Acid Derivatives

A strategy to control the switch between a non‐cycloaddition reaction and a cycloaddition reaction of enals, using N‐heterocyclic carbene (NHC) catalyisis, has been developed. The new scalable protocol leads to γ‐amino‐acid esters bearing a tetrasubstituted stereocenter in good yields and high stereoselectivities by homo‐Mannich reactions of enals and isatin‐derived ketimines. By simply changing the N‐ketimine substituent to an ortho‐hydroxy phenyl group, the corresponding spirocyclic oxindolo‐γ‐lactams are obtained.     

Taking Advantage of Hydrophobic Fluorine Interactions for Self‐Assembled Quantum Dots as a Delivery Platform for Enzymes

Self‐assembly of nanoparticles provides unique opportunities as nanoplatforms for controlled delivery. By exploiting the important role of noncovalent hydrophobic interactions in the engineering of stable assemblies, nanoassemblies were formed by the self‐assembly of fluorinated quantum dots in aqueous medium through fluorine–fluorine interactions. These nanoassemblies encapsulated different enzymes (laccase and α‐galactosidase) with encapsulation efficiencies of ≥74 %. Importantly, the encapsulated enzymes maintained their catalytic activity, following Michaelis–Menten kinetics. Under an acidic environment the nanoassemblies were slowly disassembled, thus allowing the release of encapsulated enzymes. The effective release of the assayed enzymes demonstrated the feasibility of this nanoplatform to be used in pH‐mediated enzyme delivery. In addition, the as‐synthesized nanoassemblies, having a diameter of about 50 nm, presented high colloidal stability and fluorescence emission, which make them a promising multifunctional nanoplatform.     

A general framework for the construction of piecewise-polynomial local interpolants of minimum degree

In this paper we consider the problem of designing piecewise polynomial local interpolants of non-uniformly spaced data. We provide a constructive approach that, for any assigned degree of polynomial reproduction, continuity order, and support width, allows for generating the fundamental spline functions of minimum degree having the desired properties. Finally, the proposed construction is extended to handle open sets of data and to the case of multiple knots.     

Dividends in finite time horizon

In this paper, we consider the classical risk model modified in two different ways by the inclusion of a dividend barrier. For Model I, we present numerical algorithms, which can be used to approximate or bound the expected discounted value of dividends up to a finite time horizon, t, or ruin if this occurs earlier. We extend this by requiring the shareholders to provide the initial capital and to pay the deficit at ruin each time it occurs so that the process then continues after ruin up to time t. For Model I, we assume the full premium income is paid as dividends whenever the surplus exceeds a set level. In our Model II, we assume dividends are paid at a rate less than the rate of premium income. Copyright © 2012 John Wiley & Sons, Ltd.     

Uniform convergence of basic Fourier–Bessel series on a q-linear grid

We study Fourier–Bessel series on a q-linear grid, defined as expansions in complete q-orthogonal systems constructed with the third Jackson q-Bessel function, and obtain sufficient conditions for uniform convergence. The convergence results are illustrated with specific examples of expansions in q-Fourier–Bessel series.