Search results for " interfaces"

Molecular Association of a Nonionic and an Ionic-Induced Surfactant:  Cryptand (221D) NaCl in Water

2003

The cryptand 5-decyl-4,7,13,16,21-pentaoxa-1,10-diazabicyclo-[8.8.5] tricosane [221D] strongly resembles a surfactant in its characteristics:  it contains a hydrophilic headgroup, the cryptand unit, and a hydrophobic unit, the decyl chain. It is insoluble in water, but in the presence of an appropriate amount of NaCl, as a consequence of the complex formation between 221D and Na+, it becomes soluble and forms aggregates. The aggregates, depending on the NaCl-221D molar ratio, can be considered as mixed ionic nonionic micelles or ionic micelles. The evolution of the aggregate dimensions and their shape has already been studied at two NaCl-221D molar ratios as a function of the 221D concentra…

Thermodynamics of Micellization of Sodium Alkyl Sulfates in Water at High Temperature and Pressure

2001

Apparent molar volumes VΦ,S were determined for sodium octyl, decyl, and dodecyl sulfates in water at 2 and 19 MPa from 25 to 130 °C. The shapes of VΦ,S vs the surfactant concentration curves depend on the surfactant alkyl chain, temperature and pressure. The standard partial molar volumes were calculated from data in the premicellar region whereas the partial molar volumes of the surfactant in the micellar phase were obtained from data in the postmicellar region. The partial molar expansibility and compressibility were evaluated from the dependence of the partial molar volume on temperature and pressure, respectively. Attention was focused to the expansibility and its pressure coefficient …

Emissions and spatial variability of N2O, N2 and nitrous oxide mole fraction at the field scale, revealed with 15N isotopic techniques.

2006

Abstract The accurate measurement of nitrous oxide (N 2 O) and dinitrogen (N 2 ) during the denitrification process in soils is a challenge which will help to estimate the contribution of soil N 2 O emissions to global warming. Oxygen concentration, nitrate concentration and carbon availability are generally the main factors that control soil denitrification rate and the amount of N 2 O or N 2 emitted. The aim of this paper is to present a database of the N 2 O mole fraction measured at the field scale, and to test hypotheses concerning its regulation. A 15 N-nitrate tracer solution was added to 36 undisturbed soil cores on a 20 m×20 m cultivated field plot. Fluxes of CO 2 , N 2 O and N 2 f…

Interaction of Nanometric Clay Platelets

2008

International audience; The free energy of interaction between two nanometric clay platelets immersed in an electrolyte solution has been calculated using Monte Carlo simulations as well as direct integration of the configurational integral. Each platelet has been modeled as a collection of charged spheres carrying a unit chargethe face of a platelet contains negative charges, and the edge, positive charges. The calculations predict that a configuration of “overlapping coins” is the global free energy minimum at intermediate salt concentrations (10−100 mM). A second weaker minimum, corresponding to the well-known “house of cards” configuration, also appears in this salt interval. At low sal…

Ion-ion correlation and charge reversal at titrating solid interfaces

2009

Confronting grand canonical titration Monte Carlo simulations (MC) with recently published titration and charge reversal (CR) experiments on silica surfaces by Dove et al. and van der Heyden it et al, we show that ion-ion correlations quantitatively explain why divalent counterions strongly promote surface charge which, in turn, eventually causes a charge reversal (CR). Titration and CR results from simulations and experiments are in excellent agreement without any fitting parameters. This is the first unambiguous evidence that ion-ion correlations are instrumental in the creation of highly charged surfaces and responsible for their CR. Finally, we show that charge correlations result in "a…

Mobile supported monolayers of ionic amphiphiles: variation of domain morphology via preadsorbed polyelectrolytes

1992

Possibilities of Elementary Musical Lessons for Children Communication Skills

2012

Object of the paper - explore the possibilities of musical lesson for the child for communication skills. The paper was used for theoretical metod - analysis of scientific literature and empirical research method – pedagogical observations of individual and group lessons. Theoretically and practically explored and described possibilities of music lessons for communication skills. The author main conclusions of the study: 1. By participating in the musical play, children are encouraged musical hearing, physical coordination, language development, emotional and social development, communication and independence skills, etc. 2. When creating classesmodels to integrate all the musical creativit…

Role of Ge nanoclusters in the performance of photodetectors compatible with Si technology

2013

In this work, we investigate the spectral response of metal-oxide- semiconductor photodetectors based on Ge nanoclusters (NCs) embedded in a silicon dioxide (SiO2) matrix. The role of Ge NC size and density on the spectral response was evaluated by comparing the performance of PDs based on either densely packed arrays of 2 nm-diameter NCs or a more sparse array of 8 nm-diameter Ge NCs. Our Ge NC photodetectors exhibit a high spectral responsivity in the 500-1000 nm range with internal quantum efficiency of ~ 700% at - 10 V, and with NC array parameters such as NC density and size playing a crucial role in the photoconductive gain and response time. We find that the configuration with a more…

Noble metal nanoparticles in organic matrix

2020

Abstract The purpose of this work is the synthesis and study of the properties of nanocomposite structures created by noble metal (silver) nanoparticles (NP's), an exciting class of materials with unique properties differ from both bulk and atomic behavior, which are self-organize in a thin organic film of copper phthalocyanine (CuPc). The structure and morphology of this material, depending on the amount of deposited silver, was studied in ultrahigh vacuum using transmission electron microscopy (TEM) and photoelectron spectroscopy (PES). Metallic atoms deposited on the surface of an organic substrate diffuse into the substrate, forming NPs with a narrow size distribution, which correlates …

Nanocomposites by Electrostatic Interactions:  1. Impact of Sublayer Quality on the Organization of Functionalized Nanoparticles on Charged Self-Asse…

2000

Bis-benzamidines were studied as linkers for the formation of gold nanoparticle assemblies on planar gold surfaces modified with ω-mercaptohexadecanoic acid. In situ ellipsometry, external reflecti...