Bovine Serum Albumin as an Effective Surface Regulating Biopolymer for Morphology Control of Gold Polyhedrons

Morphology control of gold nanocrystals was successfully carried out via a modified polyol process using bovine serum albumin (BSA) as a surface regulating biopolymer. By combining a small amount of AgNO3 as an additive, BSA yielded regular Au octahedrons, cubes, and higher polygons owing to the underpotential deposition of Ag species onto {100} facets. Unexpectedly, a uniform tetrahexahedral morphology that had high-index facets of {740} and {210} on the surface was formed at a relatively high concentration of AgNO 3 with BSA, and was due to the coordination power of BSA to a gold surface weaker than that of poly(vinyl pyrrolidone). The resulting gold polyhedrons were aggregated after the synthesis because of the partial denaturation of BSA, but the simple surface exchange with 11-mercaptoundecanoic acid enabled a stable dispersion in aqueous solution.