Atomic contacts via electrochemistry in water/cyclodextrin media: a step toward protected atomic contacts

Atomic contacts are nanoscience devices proposed for applications such as single-atom switches in nanoelectronic circuits or one-molecule sensing devices. The conductance of such contacts varies in a stepwise fashion with a tendency to quantize near integer multiples of the conductance quantum (G0) but can also deviate significantly from integer values upon molecular adsorption. However, for sensing applications it is first necessary to coat the contact permanently to avoid nonspecific adsorption. Here, we show that marked differences are observed between atomic contacts generated in water, and in water/beta-CD. In this latter medium, atomic contacts with unusual properties can be generated. They have below 1 G0 conductance, low conductance fluctuation with time, and appear to be protected or partially protected from salicylate external molecular probes. Such contacts are not obtained in water, in water/glucose, or when beta-CD is added after 1 G0 contacts have been generated in water. These results indicate specific adsorption of beta-cyclodextrin on the atomic contacts and are compatible with the formation of encapsulated atomic contacts. However, direct independent structural evidence is still needed to confirm or infirm this interpretation.     

A rare pyridine to pyrrole conversion leading to a side product in epoxide ring opening

A minor side product in a manufacturing batch of the intermediate 4 was observed and separated. The minor side product 5 was purified by preparative HPLC and its structure was determined by the analysis of comprehensive NMR and MS data. The structure of 5 reveals that its mechanism of formation includes a rare conversion of a pyridine moiety to a pyrrole.     

Nonradiative deactivation of excited hemicyanines studied with submolecular spatial resolution by time-resolved surface second harmonic generation at liquid-liquid interfaces

The excited-state dynamics of aminostilbazolium dyes is known to be dominated by nonradiative deactivation through large-amplitude motion. In order to identify the coordinate(s) responsible for this process, the excited-state lifetimes of two dialkylaminostyryl-methylpyridinium iodides have been measured at liquid-liquid interfaces using time-resolved surface second harmonic generation. We found that the decay time of the excited-states of both compounds was increasing with the viscosity of the apolar phase, consisting of n-alkanes of varying length, but was unaffected by that of the polar phase, made of water/glycerol mixtures. This indicates that the nonradiative deactivation is associated with the twist of the dialkylaniline group, which is located in the apolar part of the molecule.     

On carboxylate as a leaving group at the active site of Mo nitrogenase: electrochemical reactions of some MO and W carboxylates, formation of mono-, di- and tri-hydrides and the detection of an MoH2(N2) intermediate

A carboxylate ligand can function as a leaving group at a reduced molybdenum dihydride centre and this exposes a site at which dinitrogen or other small molecules can bind ; dihydrogen loss occurs after substrate binding ; protic attack intercepts carboxylate loss affording a trihydride intermediate which can partake in a hydrogen evolution cycle : it is suggested that carboxylate loss from the reduced Mo centre of nitrogenase might similarly lead to substrate binding and thence obligatory evolution of H₂.     

Synthesis of functionalized alkoxyalkylidene gem-bisphosphonates

We report the synthesis of a series of new functionalized bisphosphonates and bisphosphonic acids with an alkoxy group fixed at the geminal carbon, which is proposed to increase their lipophilicity and so their bioavailability. Subsequently, the alkylation of these alkoxy bisphosphonates with allyl bromide is reported. The reactivity of the allyl group has been studied to give access to alkoxy bisphosphonates functionalized by diverse groups including alcohol, aldehyde, carboxylic acid, epoxide and amine.     

Nanocomposite PEO-based polymer electrolyte using a highly porous,super acid zirconia filler

In this work we report a new composite, PEO-based lithium polymer electrolyte containing a micro-sized, nanoporous zirconium–oxide–sulfate (Zr–O–SO4) filler synthesized by a surfactant templating sol–gel route. By thermal and transport studies, we show that the particular morphology of the filler enhances the properties of the material leading to a solvent-free electrolyte having unique features in terms of ionic conductivity, lithium ion transference number and thermal behaviour. Finally, the galvanostatic test of the lithium battery prepared using lithium iron phosphate, LiFePO4, as the cathode, lithium metal as the anode and the studied membrane as the electrolyte, shows enhanced performances also at the medium–low temperatures.     

Adhesive microarrays for multipurpose diagnostic tools

We are reporting here a new technology for the straightforward production of integrated microarrays. The approach is based on the use of adhesive supports enabling (i) the immobilization of biomolecules as microarrays (up to 2500 spots per cm(2)) and (ii) the easy assembly of these microarrays with complex 3D structures such as 96-well bottomless microplates or polymer and glass microfluidic networks. The analytical performances of the system were demonstrated for sandwich protein detection (C-reactive protein) and hybridization assays, both in classical 96-well microplate format and microfluidic environment.     

Shrinking Hydrogel‐DNA Spots Generates 3D Microdots Arrays

This report describes a straightforward approach for the achievement of sub‐100 micrometers size hydrogel dots supporting DNA immobilization. Hydrogel‐DNA spots are arrayed and UV‐crosslinked on PolyShrink, an innovative polymer material having the remarkable property of isotropically shrinking under high temperature. Curing the microarray enables then spot miniaturization, resulting in 6 µm thick and 60 µm wide hydrogel dots in which oligonucleotides are immobilized in a 3D hydrophilic environment. The probe immobilization within the hydrogel network and its capacity to detect targets specifically and quantitatively is demonstrated using chemiluminescent as well as colorimetric detection techniques. The hydrogel material improves probe accessibility within the spot, leading to an enhanced sensitivity.