Redispersion of dried gold nanorods in the presence of 6-amino-1- hexanethiol hydrochloride

Aggregates of phosphatidylcholine-passivated gold nanorods were prepared by the addition of hydrochloric acid in the presence of 6-amino-1-hexanethiol hydrochloride (AHT). The aggregates dried in vacuum formed a solid film showing a metallic gold color. In spite of the absence of the stable surface-wrapping agents, such as balky polymer or thiol-molecules that form stable self-organized films on a gold surface, the dried aggregates dispersed again in water. The redispersed gold nanorods in water did not form aggregates. If the dried nanorods were kept at room temperature for 24 h, they did not disperse in water again; however, at -30 °C, some of gold nanorods could be redispersed in water. At -80 °C, gold nanorods could be redispersed in water as colloidal nanoparticles even after 2 months. The phosphatidylcholine and AHT molecules on the nanorod surfaces contributed to the suppression of the contact of nanorods, which were in the metallic gold color films.