Template synthesis of braided gold nanowires with gemini surfactant–HAuCl4 aggregates

Abstract

One-dimensional braided gold nanowires with 40–50 nm in width and several micrometers in length which were fabricated by using cationic gemini surfactant hexamethylene-1,6-bis (dodecyl dimethylammonium bromide) (C12C6C12Br2). Through simply regulating the mole ratio of C12C6C12Br2 to HAuCl4, the morphology of the gold products changed into nanoparticles and nanowires. The CryoTEM images indicated that the C12C6C12Br2/HAuCl4 mixture formed spherical or fibrillar aggregates depending on the mole ratio of C12C6C12Br2 to HAuCl4, which performed as the versatile templates for morphology-controlled synthesis of the multiple gold nanomaterials. The HRTEM and SAED results suggested the nanowires and braided nanowires were polycrystalline. The gold nanostructure displayed a time-dependent growth process, i.e., first the nanoparticles arranged in one dimension, and then assembled into nanowires. Therefore, a template-directed aggregation and fusion process of nanoparticles is proposed for the formation of the one-dimensional gold nanomaterials. The braided nanowires exhibited a higher catalytic activity in the reduction of p-nitroaniline than that of the nanowires. This gemini surfactant-based template provides a versatile strategy for the morphology-controlled synthesis of gold nanomaterials, and may be applied for the synthesis of other noble-metal nanomaterials.