Layer-by-layer assembled thin films of nanocolloids

Scope and method of study. The goals of this study were (1) to understand the growth conditions for multilayers of various nanocolloids; (2) to prepare complex films and estimate the influence of their internal structure on their properties; and (3) to develop a methods of free-standing film preparation Successful fulfillment of these goals demonstrates the capabilities of the layer-by-layer (LBL) assembly method in thin film preparation and realizes its advantages for the preparation of the complex structures based on inorganic nanomaterials and the organic polyelectrolytes.; Finding and conclusions. It has been shown, that the growth of films of magnetic Fe3O4 and semiconductor CdTe nanoparticles occurs in sandwich-like mode, when surface of the substrate or previously' deposited layer completely covered with next adsorbed layer. On the other hand, yttrium iron garnet (YIG) nanoparticles (NP) films grow in a domain expansion mode. To switch the growth mechanism for YIG it was necessary to modify the nanoparticle surface with 3-aminopropyltrimetoxysilane to form a positively charged shell around each particle. The hydrocarbon chain attached to the NP resulted in the interaction of similar groups of the polymer while the surface charge prevented coagulation of the colloidal solution The possibility of preparation of graded film with asymmetric internal structure has been demonstrated on example of LBL deposition of CdTe nanoparticles of different sizes. Single wall carbon nanotubes (SWNT) can be also LBL assembled in thin films. They also can be aligned when deposition is performed in laminar flow cell. The preparation of free-standing LBL films is possible by breaking the bonding between substrate and first adsorbed layer. Free-standing films from different nanomaterials including magnetic and semiconductor nanoparticles, SWNT, and alumosilicate montmorillonite have been prepared. It was shown that the introduction of interlayers of clay or poly(acrylic) acid interlayers increases the mechanical stability of obtained LBL assembled free-standing films. The ultimate stress of SWNT based composite materials was found to be close to some industrial ultrahard ceramics and cermets.