Template synthesis of braided gold nanowires with gemini surfactant-HAuCl_4 aggregates

摘要

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) (C_(12)C _6C_(12)Br_2). Through simply regulating the mole ratio of C_(12)C_6C_(12)Br_2 to HAuCl _4, the morphology of the gold products changed into nanoparticles and nanowires. The CryoTEM images indicated that the C_(12)C _6C_(12)Br_2/HAuCl_4 mixture formed spherical or fibrillar aggregates depending on the mole ratio of C _(12)C_6C_(12)Br_2 to HAuCl_4, 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.