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 TiO2 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 TiO2 nanoparticle layer was determined to be about 6.3 nm, which is in good agreement with TEM and AFM data. TiO2 nanoparticles and Ti1-deltaO2 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 SO42- and NH4+ were resulted from polymers as counterions for the nanoparticles and nanosheets.