Refractive Index Regulation of Gold Nanocrystal Superlattices by Varying the Nanocrystal Size

Micrometer-sized three-dimensional superlattices with different lattice constants were fabricated by assembling Au nanocrystals modified with mercaptosuccinic acid in aqueous suspensions. The refractive index of the superlattices was varied between 2.3 and 3.3 by altering the size of the component nanocrystals between 3.11 and 4.68 nm. As a result, the metal content of the superlattices varied between 23 and 36%. The correlation between nanocrystal size and the optical permittivity estimated from the refractive index was explained using the Maxwell-Garnett theory. (C) 2010 The Japan Society of Applied Physics