Modulation of plasmonic chiral shell growth on gold nanorods via nonchiral surfactants.

Abstract

Recently, in combination with seed-mediated growth, thiolated chiral molecule-guided growth has shown great promise in obtaining chiral plasmonic nanostructures. Previously, with the assistance of chiral cysteines (Cys), we realized helical growth of plasmonic shells on gold nanorod (AuNR) seeds dispersed in cetyltrimethylammonium bromide (CTAB) solution. Herein, we further studied the roles of non-chiral cationic surfactants in tuning the helical growth. Both the counter anion and the hydrocarbon chain length of the surfactants were found to affect the formation of helical shells greatly. In particular, we exhibited surfactant-modulated conversion of the chiral shell deposition mode between layer growth and island growth. By optimizing growth conditions, an obvious plasmonic circular dichroism (PCD) response could be achieved for the island helical shell. Our findings demonstrated promising potential of nanochemical synthesis in fabricating chiral plasmonic nanostructures with small structural sizes.