Smectite-type clay minerals as nanomaterials

Dilute aqueous smectite suspensions are well Suited to convert into functional nanofilms. The functionalization is performed by ion exchange of amphiphilic molecules carrying the desired functionality. A functionalized clay mineral nanofilm is obtained by the organization of the molecules at the clay surface and by the organization of the elementary clay platelets in the film. Two techniques are presented: self-assembling and Langmuir-Blodgett (LB). Self-assembling is a very simple experiment, but the organizational order of the clay mineral particles is low. Nevertheless, films with nonlinear optical properties which are able to generate frequency-doubled light have been produced. The drawback of disorder of the clay platelets in the film can be largely overcome with the LB technique. Well organized films are obtained. In the presence of amphiphilic ruthenium(II)-bipyridine complexes, nonlinear optical properties are measured. In the presence of two dyes, oxacarbocyanine and rhodamine 13, simultaneously adsorbed, efficient energy transfer between the donor (oxacarbocyanine) and the acceptor (rhodamine B) is measured. Fundamental research into the organization of molecules at clay mineral platelets is necessary to optimize the materials for specific applications.