Synthesis of Prolate-Shaped Au Nanoparticles and Au Nanoprisms and Study of Catalytic Reduction Reactions of 4-Nitrophenol.

The growth into anisotropic one or two dimensions is important in plasmonic gold nanomaterials because extinction occurs along multiple axes and sometimes the resonance extends to the near-infrared region. The surfactant mixture of cetyltrimethylammonium bromide (CTAB) and Pluronic triblock copolymers has been recently demonstrated to be efficient anisotropic soft templates for the growth of noble metal nanomaterials. Seed-mediated growth of two types of anisotropic Au nanoparticles is achieved in this study. One is one-dimensional prolate-shaped Au nanoparticles with the average aspect ratios of 2.29 and 2.59, and the other is two-dimensional gold nanoprisms with the average edge length of 50.4 nm. These anisotropic structures are believed to be produced by the tendency of Pluronic copolymers to be micellized anisotropically at the elevated temperatures and by the preference for being lamellar mesophases in the phase diagrams when the concentration is highest. When prepared in the surfactant mixture of CTAB and L-64 (17.9%), Au nanoparticles containing spherical particles (27.9 nm) as the major products show the best catalytic performances in the reduction reactions of 4-nitrophenol.