Polyelectrolyte-Coated Gold Nanorods:  Synthesis, Characterization and Immobilization

The versatile layer-by-layer (LbL) approach has been used for the synthesis of polyelectrolyte-coated gold nanorods. The simple process first involves the synthesis of gold nanorods by our previously published three-step seed-mediated protocol. The presence of a bilayer of the surfactant cetyltrimethylammonium bromide (CTAB) on the gold nanorod surface imparts a net positive charge to the nanorods. Alternate adsorption of anionic and cationic polyelectrolytes on these positively charged gold nanorods leads to the formation of polyelectrolyte multilayers around the nanorods. These coated gold nanorods have been characterized by UV−vis spectroscopy, zeta potential measurements, and transmission electron microscopy (TEM). Depending on the surface chemical functionality of the coated gold nanorods, they have been selectively immobilized onto either cationic or anionic surfaces. Scanning electron microscopy (SEM) has been used to visualize the immobilized nanorods and to determine the nanorod density on flat surfaces.