The color of colloidal gold

With the use of an electron microscope to measure the particle size and size distribution, the absorption spectra of monodisperse spherical gold colloids of varying particle size have been measured. The influence of particle shape, state of aggregaation, and chemical composition are also discussed. The absorption spectra of monodisperse, spherical sols are in close agreement with the theoretical predictions of Gustav Mie, and it is proposed that the optical constants of metals be derived from absorption spectra of metallic colloids by application of the Mie equations.