Wet chemical synthesis of high aspect ratio cylindrical gold nanorods

Gold nanorods with aspect ratios of 4.6 +/- 1.2, 13 +/- 2, and 18 +/- 2.5 t all with 16 +/- 3 nm short axis) are prepared by a seeding growth approach in the presence of an aqueous miceller template. Citrate-capped 3.5 nm diam eter gold particles, prepared by the reduction of HAuCl4 with borohydride, are used as the seed. The aspect ratio of the nanorods is controlled by var ying the ratio of seed to metal salt. The long rods are isolated from spher ical particles by centrifugation.