Assembly Characteristics of Gold Nanoparticles and Nanorods in Ionic Surfactant Solutions

Abstract

Gold nanoparticles (NPs) and nanorods (NRs) were synthesized by chemical reduction in the aqueous micellar solution of ionic surfactants. Their surfaces were subsequently modified by cysteine. In the cationic cetyltrimethylammonium bromide (CTAB) solution, the linear cross‐assembly of gold NRs with NPs in alternate order was observed and could be related to the size‐dependent densities of their surface charges. The irregular aggregation of gold NRs (and NPs) appeared in the anionic sodium dodecyl sulfate (SDS) solution. Micellar electrokinetic capillary chromatography (MEKC) showed that cysteine‐binding gold NRs resulted in the decrease of their negative surface charge in the SDS solution. Experimental results indicated that the ionic surfactant which stabilized both gold NPs and NRs has the extraordinary effect on not only the location of the surface modification but also the interaction of the assembly for these NPs and NRs. Mechanism on the assembly of gold NPs and NRs in the ionic solutions will be discussed.