A plurality of gold nanoparticles disposed on a surface of a substrate includes nanoparticles having an average particle density greater than 1.8×1011 particles per squared centimeter of the surface. The gold nanoparticles include a monomodal diameter distribution and an average diameter capable of being arbitrarily controlled between about 5 nm to about 300 nm. The surface may be a three-dimensional surface or an internal surface.