Elucidating the impact of nanoparticle size and shape on biological systems is of fundamental importance to nanotoxicology and biomedicine. Currently, the ability to determine this is limited by the lack of a model nanoparticle system having a narrow size and shape distribution over the relevant size range (2-200 nm). Hydroquinone can be used to produce 50-200 nm gold nanoparticles that are relatively monodispersed in size with nearly spherical shapes.