Abstract
Colloidal liquid of gold or silver nanoparticle exhibits red or yellow color, respectively, as well as the film containing them. This is because the surface plasmon in the nanoparticle co-oscillates in accordance with the incident light of a certain wave length, and absorbs the light. As a result, the complementary color of the absorbed light is observed. In this article, the mechanism of the light absorption by surface plasmon is briefly explained together with the factors which influence the wave length of the absorbed light. Next, the preparing method of gold and silver nanoparticles developed by the authors is shown. Finally, an example of application, where the gold nanoparticle was used as a coating colorant, and the characteristics of the plasmon coloring are exhibited.
