Self-Assembled Multilayers of Titania Nanoparticles and Nanosheets with Polyelectrolytes

Self-assembled multilayer films of titania nanoparticles and composite films of nanoparticles/nanosheets have been fabricated on various substrates using appropriate polyelectrolytes as counterions. UV−vis spectroscopy and ellipsometric data for the multilayer buildup process of TiO 2 nanoparticles indicated that a nearly equivalent amount of nanoparticles can be deposited layer-by-layer with a polyanion such as poly(sodium 4-styrene sulfonate). The average thickness of the TiO 2 nanoparticle layer was determined to be about 6.3 nm, which is in good agreement with TEM and AFM data. TiO 2 nanoparticles and Ti 1 - δ O 2 nanosheets are assembled in various sequences with appropriate polyelectrolytes sandwiched between them, which yielded novel intergrown nanoparticle/nanosheet films. Polymers between the nanoparticle and/or nanosheet layers could be decomposed by UV irradiation to yield inorganic multilayer films, which is confirmed by IR and X-ray photoelectron spectroscopy combined with Ar + depth profiling. Small ions such as SO 4 2 - and NH 4 + were resulted from polymers as counterions for the nanoparticles and nanosheets.