Facile synthesis of two-dimensional highly branched gold nanostructures in aqueous solutions of cationic gemini surfactant

Abstract

Snowflake-like two-dimensional highly branched gold nanostructures (2DHBNs) have been constructed in the presence of hexamethylene-1,6-bis (dodecyl dimethylammonium bromide) (C12C6C12Br2) through the reduction of HAuCl4 by ascorbic acid. High resolution transmission electron microscopy results indicate that the 2DHBNs are uniform in crystallographic orientation, where the branched nanostructures grow along the <211> direction and present multiple twin planes stacked along the <111> direction. An ex situ kinetic study, followed by TEM observations, shows that the 2DHBNs are evolved from triangular nanoprisms through overgrowth along the <211> direction. The gemini surfactant C12C6C12Br2 is found to be the most essential factor for the formation of the 2DHBNs. C12C6C12Br2 may selectively absorb onto the (111) planes, which promotes the construction of 2D nanostructures. Moreover, C12C6C12Br2 can act as an excellent kinetic modifier to control the growth of the nanostructures, which also affects the generation of branched nanostructures. The as-prepared 2DHBNs exhibit an efficient surface-enhanced Raman scattering (SERS) property which has potential application in constructing sensitive SERS substrates.