Colloidal dispersions of gold rods characterized by dynamic light scattering and electrophoresis

The colloidal stability of nearly monodisperse aqueous dispersions of rod-s haped gold particles is studied by dynamic light scattering and electrophor esis. The average length of the gold particles is adjusted between 39 and 7 30 nm, and the diameter is about 17 nm. The translational diffusion coeffic ients are consistent with calculations for single nonaggregated rods with a 10-15 nm thick poly(vinyl pyrrolidone) (PVP) adsorption layer. This suppor ts the colloidal stability observed. Electrophoresis measurements show that the PVP-stabilized gold rods are negatively charged with a zeta potential of about -47 mV, which according to interaction calculations is sufficient for double-layer stabilization. Gold-sphere dispersions are investigated fo r comparison. It turns out that PVP-stabilized gold spheres have a zeta pot ential similar to that of the colloidal rods.