Formation of carboxylic acid nanorods on oleylamide-capped Au nanoparticles

This paper describes nanorod formation induced by nanoparticle seeds. Carboxylic acids self-assemble on graphite into an epitaxial pattern. However, this persistent pattern is changed into nanorods by nanoparticles. Two control parameters have been identified, including nucleus/substrate contact angle and seed-to-critical nucleus size ratio. Effective carboxylic chain length and nanoparticle size range are identified, which can be related to the seed size effect. Some nanorods are detached when methyl-terminated nanoparticles are used, and the percentage of detached nanorods increases with increasing carbon chain length. In contrast, the nanorods do not detach from carboxyl-terminated nanoparticles. This study offers direct experimental evidence to molecular simulation prediction that nuclei display a confined morphology on a highly curved seed surface due to the difficulty of maintaining an unstrained structure and they readily detach from the surface during heterogeneous crystal nucleation. This study contributes a solution-based method for the making of nanorods.