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Milan K. Sanyal

Surface Physics Division, Saha Institute of Nuclear Physics
1/AF Salt Lake, Kolkata 700064 INDIA

Chemically synthesized nanoparticles with a metal core surrounded by a dielectric ligand shell have received a lot of interest in recent years because of their unique electrical, magnetic and optical properties.Unusually low surface roughness of about 0.5nm of water-surface due to its anomalously high surface tension provide us perhaps the best method for formation of monolayer of nanoparticles on substrate. We shall discuss here results of a X-ray scattering study carried out to understand structure and morphology of monolayer of such nanoparticles having gold-core and thiol-shell directly on the water surface before the monolayer undergoes a continuous transition to a bilayer. Our results demonstrate buckling of the monolayer over a large surface pressure range (1 to 15mN/m). The buckled state exhibits reversibility on decompression and can be annealed with temperature.

Understanding chemical reactivity at the liquid-liquid interface is of fundamental importance in several important research areas including drug delivery and diffusion through biological membranes, as the effect of this inhomogeneous environment can alter the behavior of the reacting molecules. Microscopic measurements that provide direct information in nanometer length-scales are essential to obtain a proper understanding of the phenomena occurring at the interface, besides measurements of macroscopic properties that are generally employed. We shall also discuss here the results of a synchrotron X-ray scattering study of the formation of gold nanoparticles at the toluene-water interface through a reduction reaction.