Selective Functionalization of Two-Component Magnetic Nanowires

Gold, nickel, and two-segment nickel−gold nanowires have been synthesized by electrodeposition into alumina templates. The nanowires have ∼350-nm diameters and were typically 12−22 μm in length. The nanowires were removed from the templates and were functionalized with organic molecules. Adsorption isotherms were constructed for the binding of 8,13-bis(1-hydroxyethyl)-3,7,12,17-tetramethyl-21H,23H-porphine-2,18-dipropionic acid to nickel nanowires in ethanol solution at 298 K. Adduct formation constants of 9 ± 5 × 106 M-1 and limiting surface coverages of 8 × 10-10 mol/cm2 were abstracted from the isotherms. Surface functionalization conditions were identified where thiols bind selectively to gold and carboxylic acids bind to nickel. Nanowires with free amino or thiol functional groups were reacted with activated dyes to yield amide, thiourea, and thioether covalent linkages that were quantified by fluorescence microscopy. These reactions with two-segment nickel−gold nanowires produced materials that emitted light only on one segment of the nanowire or emitted light of different colors on each segment.