Size-tunable uniform gold octahedra: fast synthesis, characterization, and plasmonic properties

A modified polyol process was developed to synthesize uniform and high-purity gold (Au) octahedra in a refluxing 1,5-pentanediol (PD) solution by introducing the cationic surfactant poly(diallyldimethylammonium) chloride (PDDA). Well-defined octahedral Au nanocrystals (NCs) with sizes ranging from 30 to 110 nm could be facilely and precisely prepared in high yield by controlling the experimental parameters. Our study indicates that the surfactant PDDA with the preferential adsorption on the {111} planes of Au nuclei plays a crucial role for the controllable synthesis of uniform octahedral Au NCs. Moreover, the size-dependent optical properties of Au nanooctahedra were systematically investigated. The surface plasmon resonance (SPR) absorption peaks were red-shifted from 536 to 613 nm with the increasing sizes. It is promising that octahedral Au NCs with the size-dependent plasmonic properties are potential candidates for a broad range of applications related to optics, metamaterial, biomedicine, and catalysis.