NADH oxidation on screen-printed electrode modified with a new phenothiazine diazonium salt

NADH oxidation catalysts are extremely important in the field of electrochemical biosensors and enzymatic biofuel cells. Based on the growing diazonium chemistry, we synthesized the diazonium salt of the well-known NADH mediator toluidine blue O. The electrochemical reduction of the diazonium moiety by cyclic voltammetry onto a screen-printed electrode leads to an electrocatalyst suitable for the oxidation of NADH. The amperometric response for its oxidation shows a maximal current of 1.2 μA ([NADH] = 100 μM). Based on electrochemical measurements, the surface coverage is found to be 3.78 × 10^? 11 mol cm^? 2 and the heterogeneous standard rate constant k_h is 1.21 ± 0.16 s^? 1. The sensitive layer for the oxidation of NADH is improved by electrografting the diazonium salt with a potentiostatic method. Both the surface coverage and the heterogeneous standard rate constant k_h are improved and found to be 6.08 ± 0.63 × 10^? 11 mol cm^? 2 and ~ 5.02 s^? 1, respectively. The amperometric response is also improved by an 8 fold factor, reaching 9.87 μA ([NADH] = 120 μM). These remarkably high values for screen-printed electrodes are comparable to glassy carbon electrodes making this method suitable for low-cost bioelectronical devices.     

Cyclodextrins as growth controlling agents for enhancing the catalytic activity of PVP-stabilized Ru(0) nanoparticles

Cyclodextrins act as growth controllers in the synthesis of PVP-stabilized Ru(0) nanoparticles, leading to enhancement of the catalytic activity in the hydrogenation of furfural.     

Supramolecular shuttle and protective agent: a multiple role of methylated cyclodextrins in the chemoselective hydrogenation of benzene derivatives with ruthenium nanoparticles

Efficient chemoselectivities have been obtained in the hydrogenation of benzene derivatives under biphasic liquid-liquid conditions using Ru(0) nanoparticles stabilized and controlled by the relevant choice of cavity and methylation degree of cyclodextrins.     

A lattice Boltzmann model for coupled diffusion

Diffusion coupling between different chemical components can have significant effects on the distribution of chemical species and can affect the physico-chemical properties of their supporting medium. The coupling can arise from local electric charge conservation for ions or from bound components forming compounds. We present a new lattice Boltzmann model to account for the diffusive coupling between different chemical species. In this model each coupling is added as an extra relaxation term in the collision operator. The model is tested on a simple diffusion problem with two coupled components and is in excellent agreement with the results obtained through a finite difference method. Our model is observed to be numerically very stable and unconditional stability is shown for a class of diffusion matrices. We further develop the model to account for advection and show an example of application to flow in porous media in two dimensions and an example of convection due to salinity differences. We show that our model with advection loses the unconditional stability, but offers a straight-forward approach to complicated two-dimensional advection and coupled diffusion problems.     

Investigating the effect of randomly methylated β-cyclodextrin/block copolymer molar ratio on the template-directed preparation of mesoporous alumina with tailored porosity

Supramolecular assemblies formed between cyclodextrins and block copolymers can be efficiently used as templates for the preparation of mesoporous materials with controlled porosity. In this work, we use dynamic light scattering (DLS) and viscosity measurements to follow the variations occurring in the size and morphology of the triblock copolymer poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide) (P123) micelles in the presence of various amounts of randomly methylated β-cyclodextrin (RAMEB). The results obtained with a series of solution compositions reveal that the cyclodextrin-to-copolymer (RAMEB/P123) molar ratio plays a crucial role in the growth rate of the micelles. At low RAMEB/P123 molar ratios (below ~7.5), a swelling effect of the cyclodextrin in the P123 micelles is noticed together with a modification of the micellar curvature from spherical to ellipsoidal. At high molar ratios (~7.5 and above), an abrupt transition toward large supramolecular assemblies, which no longer resemble micelles, occurs. When the RAMEB-swollen P123 micelles are used as templates to direct the self-assembly of colloidal boehmite nanoparticles, mesoporous γ-Al₂O₃ materials with high surface areas (360–400 m²/g), tunable pore sizes (10–20 nm), large pore volumes (1.3–2.0 cm³/g) and fiberlike morphologies are obtained under mild conditions. The composition of the mixed micellar solution, in particular the cyclodextrin-to-copolymer molar ratio, appears to be a key factor in controlling the porosity of alumina.     

Gallium‐Assisted Transfer Hydrogenation of Alkenes

We report a rare case of alkene transfer hydrogenation using a main‐group compound instead of a transition‐metal complex as catalyst. We disclosed that 1,4‐cyclohexadiene can be used as H₂ surrogate towards olefin reduction in the presence of [IPrGaCl₂][SbF₆]. Hydrogenative cyclizations have also been carried out because this cationic gallium complex is also a potent hydroarylation catalyst.     

Reactivity of cyclohexene epoxides toward intramolecular acid-catalyzed cyclizations for the synthesis of naturally occurring cage architectures

This account compiles our results on the reactivity of cyclohexene epoxides toward the synthesis of naturally occurring cage architectures, in particular, the one found in harringtonolide. Bicyclic and branched monocyclic functional triads (hydroxy-epoxy-esters) were synthesized with the aim of undertaking cascade processes toward the formation of lactone and/or cycloether bridges, through a central epoxide opening. This work successfully culminated in the cascade cyclization of the fully oxygenated bridge-structure of harringtonolide, by using a dual Brønsted-Lewis acid complex.     

Enantioenriched Methylene‐Bridged Benzazocanes Synthesis by Organocatalytic and Superacid Activations

Achieving in a straightforward way the synthesis of enantioenriched elaborated three‐dimensional molecules related to bioactive natural products remains a long‐standing quest in organic synthesis. Enantioselective organocatalysis potentially offers a unique opportunity to solve this problem, especially when combined with complementary modes of activation. Here, we report the sequential association of organocatalytic and superacid activations of simple linear achiral readily available precursors to promote the formation of unique highly elaborated chiral methylene‐bridged benzazocanes exhibiting three to five fully‐controlled stereocenters. This peculiar backbone, difficult to assemble by standard synthetic approaches, is closely related to bioactive natural and synthetic morphinans and benzomorphans. The formation of a highly reactive chiral 7‐membered ring N‐acyl iminium superelectrophilic ion, evidenced by low‐temperature in situ NMR experiments, triggers a challenging stereoselective Friedel–Crafts‐type cyclization.     

Lattice Boltzmann Solid Particles in a Lattice Boltzmann Fluid

We define a lattice Boltzmann model of solid, deformable suspensions immersed in a fluid itself described in terms of the lattice Boltzmann method. We discuss the rules governing the internal dynamics of the solid object as well as the rules specifying the interaction between solid and fluid particle. We perform a numerical drag experiment to validate the model. Finally we consider the case of a population of flexible chains in suspension in a shear stress flow and study the influence on the velocity profile.