Layer-by-Layer Assemblies Composed of Polycationic Electrolyte, Organic Dyes, and Layered Silicates

The formation of layer-by-layer (LBL) assemblies is a simple procedure, suitable for the construction of thin films with well-defined structures and compositions. LBL assemblies based on layered silicates, cationic organic dyes, and polycationic electrolyte were investigated by absorption and fluorescence spectroscopies. The formations of two simple films were investigated: one film bearing a laser dye, oxazine 1, and the second based on J-aggregates of pseudoisocyanine. A detailed study based on chemometric methods (principal component analysis, multivariate curve resolution-alternating least squares) confirmed the very complex nature of the LBL assembly formation. During the assembly deposition, the outer surface with the adsorbed dye often exhibited significant changes upon the formation of a new layer. These changes mainly included a partial desorption of the dye and structural rearrangement of the adsorbed dye species, including molecular aggregation. A complex film composed of alternating layers of the two dyes was made mainly for the purpose of investigating photophysical phenomena, such as fluorescence quenching and intermolecular resonance energy transfer. The results obtained can be useful for further studies leading to the development of functional materials based on photoactive dyes, inorganic layered carriers, and polyelectrolytes.