Surfactant mediated assembly of gold nanowires on surfaces

The potential of surfactant interactions to direct both the placement and orientation of gold nanowires onto surfaces from solution has been investigated. Gold nanowires were synthesized by template electrodeposition in porous aluminum oxide membranes. Their assembly onto surfaces was controlled by functionalizing the nanowires and surfaces with self-assembled monolayers of thiol based surfactants. Nanowires were assembled from solution onto patterned functional surfaces, and after excess solvent had evaporated the arrangement of nanowires on the surface was observed. A variety of assembly techniques, based upon wettability, electrostatic, or chemical interactions have been studied. Nanowire assembly onto surfaces with patterned wettability resulted in the placement of nanowires on hydrophilic regions with a specific orientation. Hydrogen bonding and carboxylate salt attachment of mercaptoundecanoic acid functionalized nanowires to reactive regions of patterned surfaces has been demonstrated, with unbound wires removed by washing. Similarly, electrostatic interactions between charged nanowires and surfaces have been demonstrated to preferentially assemble nanowires onto oppositely charged surface regions. Although selective attachment of nanowires to reactive surface regions was achieved by both chemical and electrostatic assembly techniques, these methods did not control the orientation of assembled nanowires.