ACTION DESIMINES SUR LES MONOCHLOROPHOSPHINES: NOUVELLE VOIE D'ACCES A DES CETONES β-PHOSPHORYLEES

Abstract

The reaction of imines 1 with monochlorophosphines leads to β-phosphorylketones obtained in the ketonic 2 or enolic forms 2′. The structure of all obtained products is confirmed by NMR and IR spectroscopy.     

Heterodyne detection for Fiber Bragg Grating sensors

In this paper, we present a Fiber-Bragg-Grating-based temperature sensor. The technique employs heterodyne detection using two Fiber Bragg Gratings. One of the gratings is used as a reference (local oscillator) and the second as a sensing arm. This sensor uses a Folded Mach-Zehnder interferometer. As the temperature changes, the Bragg wavelength of the FBG shifts. The heterodyne detection is used to detect the frequency difference between the reference and sensing signals that is caused by the temperature change. The dynamic range and sensitivity of the sensor were analyzed and presented.     

Physicochemical and rheological properties of thickeners produced from Tunisian clays

Modification of two samples of Tunisian clays of the type of natural smectites with organic derivatives of ammonium salts was studied. The physicochemical properties of the modified products and the possibility of their use as components of lubricating oils were analyzed. Published in Russian in Zhurnal Prikladnoi Khimii, 2006, Vol. 79, No. 3, pp. 387–392. This article was submitted by the authors in English.     

First Synthesis of γ,γ′-Diphosphonylketones and Their Reactivity in the Fischer Reaction

Two synthetic methods leading to the new n , n '-diphosphonylketones 2 and 2 ' are reported. The first method involves the base-catalyzed addition of diethylphosphite to diarylideneketones. The second one utilizes the reaction of triethylphosphite and ethoxydiphenylphosphine with g , g '-bis(dimethylamino)ketone hydrochlorides. On reaction with phenylhydrazine hydrochloride, compounds 2 and 2 ' give the corresponding 2-(phosphonoethyl)3-(phosphonomethyl)indoles 3 . The structure of all obtained products is confirmed by NMR ( 1 H, 31 P, 13 C) and IR spectroscopy.     

Action de 3-hydrazino-2-(N,N-dialkylaminométhyl)propanenitriles sur quelques iminoesters N-fonctionnalisés : synthèse de dérivés triazoliques

Reaction of 3-hydrazino-2-(N,N-dialkylaminomethyl)propanenitriles with a series of N-functionalized iminoesters: Synthesis of triazolic compounds. The reaction of 3-hydrazino-2-(N,N-dialkylaminomethyl)propanenitriles with a series of N-functionalized iminoesters leads to the formation of triazolones and triazoles. The latter, presenting two reactive sites in positions 1 and 6, undergo intramolecular cyclization, to form triazolopyrimidine in good yields.     

Decoration of discretely immobilized cowpea mosaic virus with luminescent quantum dots

This report describes two related methods for decorating cowpea mosaic virus (CPMV) with luminescent semiconductor nanocrystals (quantum dots, QDs). Variants of CPMV are immobilized on a substrate functionalized with NeutrAvidin using modifications of biotin-avidin binding chemistry in combination with metal affinity coordination. For example, using CPMV mutants expressing available 6-histidine sequences inserted at loops on the viral coat protein, we show that these virus particles can be specifically immobilized on NeutrAvidin functionalized substrates in a controlled fashion via metal-affinity coordination. To accomplish this, a hetero-bifunctional biotin-NTA moiety, activated with nickel, is used as the linker for surface immobilization of CPMV (bridging the CPMVs' histidines to the NeutrAvidin). Two linking chemistries are then employed to achieve CPMV decoration with hydrophilic CdSe-ZnS core-shell QDs; they target the histidine or lysine residues on the exterior virus surface and utilize biotin-avidin interactions. In the first scheme, QDs are immobilized on the surface-tethered CPMV via electrostatic attachment to avidin previously bound to the virus particle. In the second strategy, the lysine residues common to each viral surface asymmetric unit are chemically functionalized with biotin groups and the biotinylated CPMV is discretely immobilized onto the substrate via NeutrAvidin-biotin interactions. The biotin units on the upper exposed surface of the immobilized CPMV then serve as capture sites for QDs conjugated with a mixture of avidin and a second protein, maltose binding protein, which is also used for QD-protein conjugate purification. Characterization of the assembled CPMV and QD structures is presented, and the potential uses for protein-coated QDs functionalized onto this symmetrical virion nanoscaffold are discussed.     

A hybrid quantum dot-antibody fragment fluorescence resonance energy transfer-based TNT sensor

We demonstrate the use of luminescent QDs conjugated to antibody fragments to develop solution-phase nanoscale sensing assemblies, based on fluorescence resonance energy transfer (FRET) for the specific detection of the explosive 2,4,6-trinitrotoluene (TNT) in aqueous environments. The hybrid sensor consists of anti-TNT specific antibody fragments attached to a hydrophilic QD via metal-affinity coordination. A dye-labeled TNT analogue prebound in the antibody binding site quenches the QD photoluminescence via proximity-induced FRET. Analysis of the data collected at increasing dye-labeled analogue to QD ratios provided an insight into understanding how the antibody fragments self-assemble on the QD. Addition of soluble TNT displaces the dye-labeled analogue, eliminating FRET and resulting in a concentration-dependent recovery of QD photoluminescence. Sensor performance and specificity were evaluated.     

Theoretical study of the Ni growth on Pt stepped surfaces

We have investigated the growth of Ni on Pt stepped surfaces with (1 1 1) terraces by means of potentials derived from the second moment approximation in a tight-binding model. The activation energies associated to these processes are determined. The Schwoebel barriers of Ni atoms descending steps of Pt stepped surfaces are calculated for different kinds of straight steps (A and B steps) differing by the orientation of the ledge. In addition, we study the diffusion of Ni adatoms at fcc or hcp sites in the presence of small adislands on the terraces, in the vicinity of the A and B steps. We show that a good estimate of the potential wells and diffusion barriers could be given by introducing a lateral effective pair interaction model, the interactions extending up to the next nearest neighbors. Finally, we have carried out Kinetic Monte-Carlo simulations to investigate the Ni wire formation at Pt step edges and the influence of the exchange processes in the alloy formation.     

Growth of perfect and smooth Ag and Co monatomic wires on Pt vicinal surfaces: A kinetic Monte Carlo study

Growing perfect monatomic chains on surfaces is generally a hard task since it depends strongly on the experimental conditions and on the species used as templates or adsorbates. In the present study, the growth of Co and Ag monatomic wires on a Pt(9 9 7) vicinal surface is investigated over a large range of temperature. A semi-empirical potential is used to extract the main diffusion barriers responsible for the growth of Co and Ag wires on the Pt(9 9 7) vicinal surface. Kinetic Monte Carlo simulations are performed to investigate the wire formation at step-edges. We show that step decoration occurs at 150 K for Ag and at temperatures higher than 250 K for Co in agreement with growth experiments. If no interdiffusion is taken into account, Co and Ag behave similarly and perfect wires form between 150 and 500 K for Ag and between 300 and 500 K for Co. In the case of Co, an exchange mechanism leading to interlayer diffusion at step-edges is shown to strongly influence the temperature range for which the perfect wires are observed. An activation barrier of 0.65 eV for this mechanism is found to be adequate to reproduce the experimental features observed by Gambardella et al. [P. Gambardella, M. Blanc, L. Burgi, K. Kuhnke, K. Kern, Surf. Sci., 449 (2000) 93]. At higher temperatures, above 500 K, detachment from steps strongly hinders the wire formation at step feet. As a main conclusion, the exchange diffusion barrier can be extracted directly from the comparison between observation of step decoration and numerical simulations.