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October 5, 2005


Dr. Francis Zamborini
Department of Chemistry
University of Louisville
"Synthesis of One-Dimensional Metal Nanostructures Directly on Surfaces"

Abstract.  This presentation describes the synthesis of metal nanorods and metal nanorod/single-wall carbon nanotube heterojunctions directly on surfaces by reducing a metal salt solution onto surface-attached 2-5 nm diameter gold nanoparticle "seeds" with ascorbic acid in the presence of cetyltrimethylammonium bromide (CTAB).  The surface-attached seeds act as a nucleation site for selective deposition of the metal and the CTAB promotes anisotropic growth into one-dimensional (1D) structures.  Seeds have been placed on glass and silicon surfaces, patterned on surfaces, and attached to single-wall carbon nanotubes (SWCNTs) to form metal/SWCNT 1D heterojunctions directly on surfaces.  For Au, the nanorod length (L) can be controlled between 200 nm and 1200 nm and aspect ratio (AR) between 6 and 22 by varying the metal salt (HAuCl4) concentration and time in "growth solution".  The yield is low (10%) and dispersity is high (25-35%), however.  We describe atomic force microscopy (AFM) experiments closely examining the growth process and the role of the seed and also discuss methods for improving yields and reducing size dispersity.  Nanorods were patterned by patterning gold nanoparticle "seeds" on surfaces prior to placement in growth solution.  Gold nanorods were mechanically manipulated between electrode gaps and connected electrochemically.  The electronic properties of gold nanorod/SWCNT heterojunctions are also a major focus of our group.  Finally, porous, tubular 1D Pd, Au, and Pt nanostructures were synthesized directly on surfaces by galvanic place-exchange with Ag nanorods/nanowires.  This work is important because improved methods for controlling the synthesis and assembly of 1D nanomaterials are needed in order to better study the relationship between structure and function (catalytic, fluorescence enhancement, Raman scattering, etc.) and compare experimental results with theory.  Assembly, patterning, and alignment of metal nanorods on surfaces are also important for their use in nanoelectronics, plasmonics, and electronic-based sensing applications.  

Vanderbilt University