Synthesis, functionalization, and biological interactions of metallic and semi-conducting nanowires

Metallic and semi-conducting nanowires have been synthesized via templated deposition into nanoporous alumina membranes. The wires fabricated by this method are generally 300 nm in diameter and 5--25 mum in length. Metallic wires, such as nickel and gold, were synthesized by electrodeposition while semi-conducting ZnO nanowires could be fabricated by using either sol-gel methods or by electrodeposition. The templated deposition technique allows for the fabrication of nanowires composed of multiple segments of different materials. By taking advantage of the unique surface chemistry of different metals, nanowires with nickel and gold segments were selectively functionalized with different ligands on each segment.; Nickel-gold nanowires were functionalized with palmitic acid, a 16-carbon fatty acid, and (1-mercaptoundec-11-yl)-hexaethylene glycol, a long chain thiol terminated with hexa(ethylene glycol). When these "bifunctional" wires were combined with a fluorescent antibody, fluorescence was only observed on the nickel segments, while the gold segments exhibited little or no fluorescence. Thus, a multi-component nanoparticle can be created such that protein will selectively adhere to a specific region of the particle. The adsorption of protein to hydrophobic nickel wires was quantified by examining the Langmuir isotherm for myoglobin adsorption. A surface coverage of 6.5 x 10 -11 +/- 2.7 x 10-12 mol/cm 2 was calculated.; The interaction of nanowires with mammalian cells was also examined. Using a fluorescence quenching assay, the internalization of single component nickel nanowires was studied. The results of these experiments indicated that single component nickel nanowires are not immediately internalized when introduced to cells, but they become internalized within 24 hours. Bifunctional nanowires with a hydrophobic nickel segment and a hydrophilic, protein-resistant gold segment were also incubated with cells for varying amounts of time. Confocal microscopy experiments showed that these wires were completely internalized by cells after 24 hours. However, on shorter time scales, the partial internalization of two-part nanowires was observed, where the hydrophobic nickel segment was taken up by the cell while the protein resistant gold segment remained outside the cell.