Vesicle-directed generation of gold nanoflowers by gemini amphiphiles and the spacer-controlled morphology and optical property.

In this article, we developed an effective approach to generate gold nanoflowers (AuNFs) by vesicles made from a series of gemini amphiphiles (G2-G10) with different spacer lengths. The gemini amphiphiles were found to form vesicles in aqueous solution. Upon mixing with vesicles in the presence of AgNO(3), HAuCl(4) could be reduced into gold nanoflowers by ascorbic acid. The vesicles directed the growth of the AuNFs, and the spacer length of the gemini amphiphiles showed obvious control of the morphology and optical properties of the formed AuNFs. At a lower HAuCl(4) concentration, the minimum-sized AuNFs were formed when vesicles from the amphiphile with a spacer length of 4 were applied. Upon increasing the spacer length, branched nanoflowers are predominantly produced. A seed-growth mechanism together with the conformational change of the spacer of the gemini amphiphiles was proposed according to the studies on reaction processes. In addition, the formed gold nanoflowers showed obvious surface-enhanced Raman scattering activity for R6G. The present method provided an efficient, controllable way to synthesize branched gold nanostructures.