High-aspect-ratio gold nanorods synthesized in a surfactant gel phase

One-dimensional gold nanorods can grow spontaneously in a surfactant solution. In this study, a mixture of hexadecyltrimethylammonium bromide (HTAB) and octadecyltrimethylammonium bromide (OTAB) was used as a surfactant solution. When the solution gelled, high-aspect-ratio gold nanorods, with an average long-axis length of ∼1100 nm and an aspect-ratio of ∼50, were synthesized with a yield of ∼90%, whereas no high-aspect-ratio gold nanorods were synthesized when the solution did not gel. This phenomenon indicates that there is a close relation between the gelation of a surfactant solution and the elongation of gold nanorods.