Search results for "Optica"

Electrochromic Performances of Poly(Azure A) Films from Digital Video-Electrochemistry (DVEC)

2020

Poly(Azure A) (PAA) films doped with sodium dodecyl sulfate (SDS) were grown on transparent indium tin oxide (ITO) glass substrates by cyclic voltammetry. The electrochromism of PAA was investigated by digital video-electrochemistry (DVEC). DVEC consists of the acquisition of sequential digital images during the electro-stimulated changes of PAA color. The evolution of red, green, and blue (R, G, B) colors intensity (I) of analyzed pixels provides enough sensitivity to detect changes of some nmol cm−2 of electroactive centers. Besides, the different time evolution of these color intensities can serve to discern among different electroactive centers activated in the polymer. For the first ti…

Fluorescence enhancement of amine-capped CdSe/ZnS quantum dots by thiol addition

2011

The present communication reports that while addition of alkyl thiols drastically reduces the fluorescence of CdSe core quantum dots, it actually enhances the emission properties of already highly fluorescent amine-capped CdSe/ZnS core-shell quantum dots.

Optical planar Bragg grating sensor for real-time detection of benzene, toluene and xylene in solvent vapour

2012

Abstract We report on an optical planar Bragg grating sensor functionalized by a comparatively simple method to detect substances such as benzene, toluene and xylene (BTX). The functionalization is performed by allyl substituted γ -cyclodextrin derivatives which are immobilized on the sensor surface by dip coating. Our results prove the capability of this functionalized sensor system to detect lowest concentrations of BTX in solvent vapour in real-time with a sensitivity of 3±0.4 pm/100 ppm for benzene, 8±1 pm/100 ppm for toluene and 32±1 pm/100 ppm for m-xylene. Taking into account the spectral resolution and repeatability of the interrogation system this corresponds to a minimum concentra…

Quantum dot/cyclodextrin supramolecular systems based on efficient molecular recognition and their use for sensing.

2011

A supramolecular system based on ketoprofen functionalised CdSe/ZnS nanoparticles and pyrene-modified β-CD was prepared and successfully used for molecular sensing of different analytes. In addition, a strategy for the individual recovery of all the components of the sensing assay is reported.

Deep Levels in Silicon Doped n-Indium Selenide

1992

1992

A structural investigation is described of poly(L-lactic acid) by best fitting of powder X-ray diffraction patterns. The examined sample shows the already known pseudo-orthorhombic α-form, and it was possible to determine the location of the two 103 polymeric helices in the unit cell and the size distribution of the crystallites. Furthermore, a study is reported of the crystallization kinetics of the above cited polymer by light depolarization measurements in an optical microscope. The crystallization kinetic constants in bulk were evaluated in a temperature range (70–165°C) wider than that previously resulting from measurements of radial growth of spherulites.

Free-standing smectic LC elastomer films

2001

ABSTRACTWe probe the mesophase transitions and layer structures in thin ordered smectic liquid crystalline elastomer films by means of x-ray diffraction and optical microscopy. Oriented elastomer films of submicrometer thickness are produced by crosslinking freely suspended smectic polymer films. After crosslinking, the mesomorphism is similar to that of the precursor polymer. Smectic layers align parallel to the film plane. The layer spacing increases with temperature in the SmC* phase while it decays above the SmC*-SmA transition.

Determination of the absolute configuration of (−)-abietic acidviaits (4R,5R,9R,10R)-7,13-abietadien-18-ylp-bromobenzoate derivative

2006

The absolute configuration of the title bromo derivative of abietic acid, C27H35BrO2, has been determined. The structural analysis confirms the absolute stereochemistry for (−)-abietic acid proposed by Bose & Struck [(1959). Chem. Ind. (London), pp. 1628–1630] on the basis of optical rotatory dispersion measurements. The mol­ecule exhibits a trans anti 6/6/6 tricyclic hydro­carbon skeleton, with the cyclo­hexane ring in the expected chair form and the two cyclo­hexene rings, the double bonds of which are conjugated, in half-chair conformations.

Polymer Selection and Cell Design for Electric-Vehicle Supercapacitors

2000

Supercapacitors are devices for applications requiring high operating power levels, such as secondary power sources in electric vehicles (EVs) to provide peak power for acceleration and hill climbing. While electronically conducting polymers yield different redox supercapacitor configurations, devices with the n-doped polymer as the negative electrode and the p-doped polymer as the positive one are the most promising for EV applications. Indeed, this type of supercapacitor has a high operating potential, is able to deliver all the doping charge and, when charged, has both electrodes in the conducting (p- and n-doped) states. This study reports selection criteria for polymer materials and ce…

Investigation of Polyol Adsorption on Ru, Pd, and Re Using vdW Density Functionals

2015

Biomass-based feedstocks are often oxygenated compounds characterized by large amounts of hydroxyls. As an example, polyols and sugar alcohols are largely employed as reactants for different chemical catalytic transformations such as oxidation, dehydration, and hydrodeoxigenation, which usually occur in aqueous medium. With the goal of gaining new insights into processes that could be industrially relevant, the adsorption of the OH groups on metal surfaces and in the presence of water has to be correctly reproduced and described, within a chosen theoretical framework. Toward this goal, several tests were performed on the catalytically relevant metal Ru, Pd, and Re, benchmarking their bulk a…