Efficient nonlinear optical properties of dyes confined in interlayer nanospaces of clay minerals.

Nonlinear optical (NLO) responses from organic dyes can be maximized when the dyes are aligned in appropriate manners in bulk materials. The use of restricted nanospaces provided by interlayer spacing of inorganic layered materials is a promising strategy for imposing suitable molecular alignments for NLO materials on dyes. The hybrid materials thus obtained exhibit salient NLO responses owing to the improved molecular orientation. In some cases, extension of the π-electron system as a consequence of improved molecular planarity, obtained by the intercalation of a dye into the 2-dimensional interlayer space of an inorganic layered material, is also observed as a factor that enhances NLO responses of chromophores at the molecular level. This review focuses on recent progress in the strategies for controlling the molecular orientation of NLO-phores by employing clay minerals, which are one of the typical inorganic layered materials. In addition, development of a means for fabricating composites that satisfy the properties of an optical material, such as a sufficient size and thickness, a flat surface, and low light-scattering characteristics is required to utilize the superior NLO properties observed for clay/dye hybrid materials for practical applications. A novel means for obtaining such a hybrid material is also outlined.