Synthesis, characterization and applications for gold-silver alloy and nanoporous gold nanowires

Electrodeposition of gold-silver alloys from a solution containing potassium gold cyanide, potassium silver cyanide and sodium carbonate has been investigated. Cyclic voltammograms for deposition from Au(CN)₂− + Ag(CN)₂− + Na₂CO ₃ (pH 13) solution show characteristic deposition peaks for gold and silver with the separation of 550 mV. The composition of the deposited alloys is dependent on the deposition potential (or current) and solution chemistry.; Compositionally modulated Au_xAg_1−x/Au _yAg_1−y multilayers and multisegment nanowires were deposited from a single solution containing KAu(CN)₂ + KAg(CN) ₂ +Na₂CO₃ (pH 13). Multisegment nanowires were prepared by sequential deposition at −0.7 V and −1.2 V from Au(CN) ₂− + Ag(CN)₂− solution into porous Al₂O₃ templates. The different segments deposited at −0.7 V and −1.2 V are clearly distinguished by scanning electron microscopy and optical microscopy under blue light illumination.; A two-step process has been developed for the fabrication of a new class of nanoparticles: nanoporous nanowires. The fabrication process involves electrochemical deposition of a single-phase binary alloy into a nanoporous template, followed by subsequent etching of the less noble component. These nanoporous gold nanowires are characterized by diameters of 20 nm or larger, lengths up to tens of microns, and a porous structure with controlled pore dimensions. In contrast to conventional solid nanoparticles, nanoporous nanowires have a high surface area and well defined pore morphology. Furthermore, nanoporous segments can be incorporated into multisegment nanorods or nanowires. In this dissertation, it is demonstrated that nanoporous gold (NPG) nanowires and multisegment nanowires incorporating Au/NPG layers and Pt/NPG layers can be fabricated by dealloying [Au/Au _xAg_1−x]_n or [Pt/Au_xAg_1−x ]_n (0.18 < x < 0.32) alloy nanowires.; Application for nanowires in gene therapy has been explored. It has shown that DNA can be attached to the surface of gold nanowires using amine-terminated thiols [NH₂-(CH₂)_n-SH]. Preliminary experiments indicate that transfection can be achieved with functionalized nanowires. Multiple functionality can be introduced into individual nanowires by exploiting the ability of different ligands to bind to different materials.