Papers by Keyword: Neutron Reflectivity

Abstract: Lipids and proteins can influence each other in so many different ways. Lipids may affect the structure of membrane proteins by influencing their backbone conformation, the tilt, rotation angles of their transmembrane (TM) segments, and the orientation of their side chains. The membrane-spanning parts in integral membrane proteins are predominantly hydrophobic, and most often helical. At the lipid-protein interface, the TM part of the protein and the hydrocarbon chains of the lipid molecules have to coexist to maintain the integrity of the membrane. Lipids are important components of lipid membrane are used in various experiments reported in this thesis and can act as model lipid bilayers. Once they support on solid substrate like silicon wafers, their structural properties can investigate by X-ray and neutron reflectivity and by other useful techniques. Reflectivity technique can provide detailed information such as their thickness and interaction between lipids and peptides. The thesis reports a detailed investigation of these lipids and peptides by X-ray and neutron reflection techniques

Abstract: The aim of this work is to elaborate nanocomposite thin films sensitive to a magnetic field by incorporating magnetic nanoparticles in a symmetrical diblock copolymer matrix organized in lamellae on plane substrates. On the one hand, the symmetrical diblock copolymer P(n-BMA)-b-PS is synthesized by ATRP and characterized by several methods. On the other hand, nanoparticles made of maghemite -Fe2O3 are functionalized with PS using the “grafting from” technique in order to make them compatible with polystyrene and to insert them in PS lamellae. Composite films are elaborated by “spin coating” a solution containing both the -Fe2O3@PS core-shell nanoparticles and the copolymer onto a silicon substrate. After annealing, these films are characterized mainly by AFM and neutron reflectivity to investigate the lamellar order.

Abstract: The thermal annealing behavior of the SnO2 thin films elaborated by sol-gel method has been studied by the neutrons reflectivity technique. From the fit of the experimental data using Parratt32 software program developed at HMI, Berlin, scattering length density, thickness and roughness are extracted. The obtained results show that the film thickness increases with the increasing annealing temperature, and the roughness is higher at 500 °C. Whereas, approximately, the same scattering length density is obtained after each annealing temperature.

Abstract: Iron self-diffusion measurements in amorphous and nanocrystalline chemically homogenous multilayers (CHM) of FeZr/57FeZr, (with nm range periodicity) have been studied with neutron reflectivity technique. It has been found that both the activation energy for diffusion and the pre-factor were significantly smaller as compared with bulk alloys. Effect of compressive stress on self-diffusion reveals a significant dependence on the activation energy as a function of applied stress. On the basis of the obtained results the diffusion mechanism in amorphous and nanocrystalline CHM of FeZr/57FeZr is reviewed in this paper.