The assembly and alignment of one-dimensional silver, platinum, palladium, gold, and gold/palladium core/shell structures directly on surfaces by chemical methods.

摘要

This thesis describes (1) the wet chemical synthesis and alignment of Au and Ag nanorods/nanowires (Au NRs and Ag NRs/NWs) directly on surfaces by seed-mediated growth, (2) formation of Pd and Pt nanowires directly on surfaces by combining seed-mediated growth and galvanic exchange with Pd and Pt metal salts, (3) the formation of core/shell Au/Pd nanostructures, by combining seed-mediated growth, silver overgrowth and galvanic replacement reaction, directly on a surface, and (4) the formation of silver nanoislands, core/shell Au/Ag nanostructures, and growth of Au nanostructures in PDMS channels. The motivation for this work is to chemically synthesize and surface-assemble one-dimensional (1D) nanostructures for future application in nanoelectronics, sensing, and catalysis.;We synthesized silver nanorods and nanowires (Ag NRs and NWs) from surface-attached Au nanoparticles (Au NPs) by seed-mediated growth, varying the synthesis conditions. The optimal condition for growth of Ag NRs/NWs was found to be at pH 10.6. Under our conditions Ag NRs/NWs grow with a ∼5 % yield, with the length ranging from 50 nm to >10 mum, and diameter of ∼ 35 nm. Of the 1D structures grown, approximately 40 % are NRs (AR ≤20) and 60 % are NWs (AR > 20). Aspect ratio (AR) is the ratio of the length to the width of a nanostructure.;We used a simple chemical amidation reaction to control alignment of the grown Ag NRs/NWs on the surface. This procedure led to alignment of ∼67% +/- 5% of Ag nanostructures on the surface within a range of 30°. Also, we greatly improved the yield of NRs/NWs from ∼5% to 36% +/- 13% by removing other existing shapes with adhesive tape.;Seed-mediated growth combined with galvanic exchange led to the formation of Pt and Pd 1D nanostructures. Also, combining the seed-mediated growth of Au with Ag overgrowth followed by galvanic exchange leads to interesting Au/Pd core/shell 1D structures grown directly on surfaces.;Forming metal nanostructures on the surface with controlled morphology and shape is a key component to SERS applications. We describe a simple chemical procedure for the formation of silver nanostructures deposited using a chemical layer-by-layer procedure on the surface. We also describe a simple chemical approach for creating gold/silver core/shell structures on surfaces.;One potential future application for metal one-dimensional nanostructures is their use as components in nanoelectronic devices. This requires controlled patterning and alignment of these strictures on surfaces. We describe the use of PDMS with molded microscale channels for growing 1D Au nanorods within the channels in order to control the orientation and placement of these 1D metals on a surface.