Polyelectrolyte/nanoparticle hybrid films on anisometric colloids studied by electro-optics

In this study, electro-optics is applied for the first time for investigation of suspension stability and electrical properties of colloidal particles covered with hybrid multilayer film. The polyelectrolyte/nanoparticle hybrid film is prepared onto ellipsoidal β-FeOOH particles through a subsequent layer-by-layer adsorption of anionic poly(sodium 4-styrene sulfonate), cationic poly(diallyldimethylammonium chloride), and silica nanoparticles. The formation of each layer is done with fine control of the adsorption process in order to produce stable and well defined system. The adsorbed amounts of the highly charged PSS and PDADMAC have been measured by UV–vis spectroscopy, whereas the amount of the adsorbed silica nanoparticles was calculated from the thickness of the adsorbed layers. The comparison of the electrical polarizability of the PSS and PADMAC coated particles allowed us to calculate the charge balance in this bi-layer as positive. The relaxation frequency of the kilohertz electro-optical effect was found to depend on the charge density of each adsorbed component, which means that the polarization of the excess charge in the outermost layer dominate the behavior of the entire composite film.