A Simple Method to Self-Assemble Two-dimensional and Three-dimensional Superlattices of Gold Nanoparticles
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1056-HH03-01
A Simple Method to Self-Assemble Two-dimensional and Three-dimensional Superlattices of Gold Nanoparticles Tao Fu, Hai-Yan Qin, Wen-Jiang Li, and Sailing He Department of Optical Engineering, Centre for Optical and Electromagnetic Research, Hangzhou, 310058, China, People's Republic of ABSTRACT Citrate-capped gold nanoparticles with narrow diameter distribution were prepared by the reduction of chloroauric acid with borohydride. After the gold nanoparticles were transferred to toluene solution through ligand conformation change, close-packed two-dimensional nanocrystal lattices were obtained on transmission electron microscopy (TEM) copper grids by evaporating approximately 10 µL of concentrated particle dispersion. The formation of the thiolate gold nanoparticles was investigated by UV-visible absorption spectroscopy and FTIR spectra. The 2D Fourier transform power spectra of the monolayer confirmed the supperlattices’ hexagonal symmetry. Furthermore, long-range-ordered bilayer superlattices, of which the nanoparticles in the top layer piled on the ones in the bottom layer, could also be observed by transmission electron microscopy.
INTRODUCTION Gold nanostructures play important roles in many aspects because of their extraordinary physical and chemical properties.[1] For instance, gold nanoparticles are the most stable metal nanoparticles, and they present fascinating properties, which explain their comprehensive application in biology and catalysis.[2] Thiolate-stabilized gold nanoparticles, in particular, have been a subject of intensive research due to their intriguing properties.[1d] Recently, many works have focused on the self-assembly of thiolate-stabilized gold nanoparticles into 2D, 3D superlattices,[3] which have attracted wide interest for theoretical and experimental investigations of the properties, such as size effect on color, size induced quantum effect, light absorption and many more. However, for most of these self-assembled systems, one significant challenge remains the ability to obtain uniform shape and size monodispersed gold nanoparticles which are dispersed in non-polar solution such as toluene. For only in the non-polar solution, the particle-particle and particles-substrate interactions could cause nanoparticles to self-assemble into superlattice structures upon drying from a colloidal suspension on a solid surface. The aerosol technique [3c] and the liquid-liquid two-phase technique[4] are the two methods which were most adopted on the overall field during the last decade. Compared with the aerosol technique, the liquid-liquid two-phase technique are more popular because the size of gold nanoparticles prepared using this method has a narrower distribution. And this method does not need special equipment. Our
approach is set apart from proceeding techniques such that the gold nanoparticles were first synthesized in the aqueous solution and then transferred to toluene in the presence of the dodecanethiol as phase transfer reagent instead of TOAB. Furthermore, size self-sel
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