Search results for "Confined"

Self-Radiolysis of Tritiated Water Stored in Zeolites 4A: Production and Behavior of H 2 and O 2

2015

International audience; Radiolysis of confined water and self-radiolysis of tritiated water give rise to several unanswered questions. To take into account this double specificity, we studied systems of zeolites 4A containing tritiated water at different water loading ratios. Two tritiated waters were synthesized at the volumetric activities of 27 and 60 TBq L −1. For each one, five samples were prepared, differentiated by their water loading ratios, expressed in percentage, close to 4%, 7%, 11%, 14%, and 19%. The study of the radiolysis in those systems revealed a double role of zeolites 4A: first, they increase the decomposition of water. Then they enhance the recombination of the major s…

Electric field control of the optical properties in magnetic mixed-valence molecules

2014

We propose the use of an electric field stimulus to strongly affect the optical properties of ferromagnetic mixed-valence (MV) dimers. This proposal is based on the prediction of an anomalous Stark effect in the intervalence absorption bands of these multi-electron MV systems. As distinguished from the conventional Stark effect observed in one-electron dimers, a strong change of the intervalence bands accompanies the crossing of the different spin levels caused by the application of an electric field. This new effect can be referred to as giant spin-dependent Stark effect. In spintronics this opens up the possibility for optical detection of the spin state in these magnetic molecules.

Confined environments for the preparation of Luminescent nanophosphors

2018

Conformation of Polyethylene Glycol inside Confined Space: Simulation and Experimental Approaches

2021

The modification of the inner nanopore wall by polymers is currently used to change the specific properties of the nanosystem. Among them, the polyethylene glycol (PEG) is the most used to prevent the fouling and ensure the wettability. However, its properties depend mainly on the chain structure that is very difficult to estimate inside this confined space. Combining experimental and simulation approaches, we provide an insight to the consequence of the PEG presence inside the nanopore on the nanopore properties. We show, in particular, that the cation type in the electrolyte, together with the type of electrolyte (water or urea), is at the origin of the ion transport modification in the n…

Application of Nanoemulsions in the Synthesis of Nanoparticles

2018

Abstract Nanodroplets of a liquid in another immiscible liquid provide confined spaces in which chemical reactions can take place. If these reactions lead to the formation of nanoparticles, as it is the case for polymerization or precipitation reactions, nanodroplets can be used as templates for particle synthesis. The most common example of application of nanoemulsions for particle synthesis is the preparation of polymer nanoparticles by miniemulsion polymerization, but also inorganic materials can be produced in this way. Nanoemulsions are as well an excellent platform for preparing polymer/inorganic hybrid nanoparticles, either by using directly the templating effect of droplets during t…

Polymer chains confined into tubes with attractive walls: A Monte Carlo simulation

1994

A bead-spring off-lattice model of a polymer chain with repulsive interactions among repeating units confined into straight tubes of various cross sections, DT2, is studied by Monte Carlo simulation. We are also varying the chain length from N = 16 to 128 and the strength of a short-range attractive interaction between the repeating units and the walls of the tube. Longitudinal and perpendicular static linear dimensions of the chains are analyzed, as well as the density profile of repeating units across the tube. These data are interpreted in terms of scaling concepts describing the crossover between three-dimensional and quasi-one-dimensional chain conformations and the adsorption transiti…

Anomalous scaling of the critical temperature of unmixing with chain length for two-dimensional polymer blends

2003

The thermodynamics, structure and the chain configurations of symmetrical polymer mixtures confined into ultrathin films are studied by Monte Carlo simulations of the bond fluctuation model. It is shown that the Flory-Huggins–type scaling of the critical temperature (Tc ~ N) with chain length N in the bulk is replaced by a weaker increase, Tc ~ N1/2, in an ultrathin film, and this is interpreted in terms of geometric arguments. The pair-correlation function g(r) of monomers from different chains exhibits a pronounced correlation hole, and the density of intermolecular contacts zc decreases with N as zc ~ N−1/2.

Monte Carlo simulation studies of the interfaces between polymeric and other solids as models for fiber-matrix interactions in advanced composite mat…

1996

As a coarse-grained model for dense amorphous polymer systems interacting with solid walls (i.e., the fiber surface in a composite), the bond fluctuation model of flexible polymer chains confined between two repulsive surfaces is studied by extensive Monte Carlo simulations. Choosing a potential for the length of an effective bond that favors rather long bonds, the full temperature region from ordinary polymer melts down to the glass transition is accessible. It is shown that in the supercooled state near the glass transition an “interphase” forms near the walls, where the structure of the melt is influenced by the surface. This “interphase” already shows up in static properties, but also h…

Coherent Light Harvesting through Strong Coupling to Confined Light

2018

When photoactive molecules interact strongly with confined light modes, new hybrid light-matter states may form: the polaritons. These polaritons are coherent superpositions of excitations of the molecules and of the cavity photon. Recently, polaritons were shown to mediate energy transfer between chromophores at distances beyond the Förster limit. Here we explore the potential of strong coupling for light-harvesting applications by means of atomistic molecular dynamics simulations of mixtures of photoreactive and non-photo-reactive molecules strongly coupled to a single confined light mode. These molecules are spatially separated and present at different concentrations. Our simulations sug…

THE PHYSICAL ORIGIN OF PROTEIN DYNAMICAL TRANSITION: A LIQUID-LIQUID TRANSITION IN HYDRATION WATER?

2015

In this thesis I study, by means of neutron scattering, calorimetry, and dielectric spectroscopy, the physical origin of protein dynamical transition (PDT) which is usually observed at ~230 K in protein hydrated powders and is deemed necessary for protein function. Measurements reported in this thesis have been performed on hydrated powders of Myoglobin. The combined use of different experimental techniques gives a coherent description of the PDT and reveals a connection with a liquid-liquid crossover occurring in the protein hydration water at about the same temperature. In order to deepen our understanding of this connection and to obtain a direct experimental evidence of the existence of…