Planar Synthesis of Anisotropic Nanoparticles
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Planar Synthesis of Anisotropic Nanoparticles Gennady B. Khomutov, Radmir V. Gaynutdinov1, Sergey P. Gubin2, Alexander Yu. Obydenov, Eugene S. Soldatov, Alla L. Tolstikhina1, Artem S. Trifonov Faculty of Physics, Moscow State University, Moscow 119899, Russia, [email protected] 1 Institute of Crystallography RAS, Moscow 119899, Russia 2 Institute of General and Inorganic Chemistry RAS, Moscow 119899, Russia ABSTRACT A novel method of two-dimensional (2-D) synthesis of anisotropic nanoparticles have been developed in which nanoparticle growth is an example of 2-D process where true 2-D diffusion of precursor molecules and active intermediates, metal atoms and its complexes, nucleus and growing nanoparticles, surfactants and additives occurs only in the plain of a monolayer at the gas/liquid interface. Nanoparticles were generated via ultraviolet decomposition of a volatile insoluble metal-organic precursor compound (iron pentacarbonyl) and by chemical reduction of palladium from Pd3(CH3COO)6 molecules in a mixed Langmuir monolayer with stearic acid, arachidic acid or octadecyl amine on the aqueous subphase surface. The properties of such surfactants to form Langmuir monolayer and to prevent aggregation of nanoparticles were here combined successfully. Atomic force microscopy, scanning tunneling microscopy and transmission electron microscopy techniques were used to study morphology of deposited nanoparticulate monolayers. The size and shape of nanoparticles were dependent substantially on the monolayer composition and state during the synthesis process. We demonstrate that planar synthesis in a monolayer at the gas/liquid interface allows to produce anisotropic extremely flat nanoparticles with very high surface to volume ratio and unique morphologies such as iron-containing magnetic nano-rings. INTRODUCTION Synthesis of nanosize metal-containing particles (metallic, oxidic and semiconductor) has recently drawn great attention because of their unique physicochemical properties and potentially wide applications in diverse devices and processes exploiting nanophase and nanostructured materials [1-3]. Anisotropic nanoparticles are of particular interest for basic and applied studies due to the anisotropy of size-dependent properties and substantial surface effects which can result in much more rich and enhanced physical and chemical properties compared to the conventional isotropic spherical particles. Therefore, development of novel methods for effective shape and size control of nanoparticles is of principal importance for nanoparticles research. The method of nanoparticles synthesis often influences the properties of the product, particularly the shape, size, crystal morphology and degree of crystallinity [4-11]. A novel approach to the synthesis of anisotropic nanoparticles was introduced recently in which nanoparticles were fabricated in a mixed Langmuir monolayer at the gas/liquid interface [12]. In the present study, nanoparticles were generated by the ultraviolet (UV) decomposition of Fe(CO)5, and by chemical redu
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