Nanocomposite films derived from exfoliated functional aluminosilicate through electrostatic layer-by-layer assembly

Multilayered nanocomposite films were prepared from aluminosilicate platele ts with functional chromophores and polyelectrolytes through electrostatic layer-by-layer assembly. Fluorescent dye coumarin was intercalated into the layered aluminosilicate hectorite, and the resulting hectorite/coumarin in tercalation complex particles were broken down into individual platelets by means of extensive shaking and sonication of their water suspension. Atomi c force microscopy (AFM) and transmission electron microscopy data show tha t the exfoliated platelets have the form of lathes of approximately 10-40 n m width, 150-400 nm length, and 2-3 nm average thickness. This last value i s consistent with the overall thickness of a single aluminosilicate lamella sheathed with coumarin molecules on both sides. Given the strong negative surface charge of the aluminosilicate layers, films of nanocomposites could be formed by electrostatic layer-by-layer assembly using a cat;ionic polye lectrolyte. The AFM topography of such films revealed a homogeneous monolay er coverage of the underlying substrate. Linear buildup of the multilayer f ilms of up to 20 cycles was demonstrated and investigated using UV/vis abso rption spectroscopy. The resulting transparent films have exhibited strong characteristic blue-green fluorescence due to coumarin dye molecules adhere d to the exfoliated hectorite platelets.