Seedless synthesis of gold nanorods with tunable plasmonic peaks beyond 1300 nm

Gold nanorods (AuNRs), as relatively common materials used in biomedical areas, have been synthesized by means of many methods. However, the conventional seed-mediated method is limited by complex operations and low yield. Besides, for further applications of AuNRs, well monodispersed AuNRs and tunable longitudinal surface plasmon resonance (LSPR) remain to be improved. Herein, we report a one-pot method for synthesizing AuNRs without seeding agents. In this method, we use phenols as reducing agents and hydrochloric acid and nitric acid are used to regulate the pH of the growth solution. AuNRs with the longest LSPR peak position reaching 1340 nm are prepared. Furthermore, by systematically optimizing concentrations of the reagents involved in the growth solution, different aspect ratios of AuNRs are synthesized. The facile synthesis, controllability aspect ratio, and long LSPR peak make our method promising for wider applications of AuNRs.