Magnetic nanocomposites fabricated via the layer-by-layer approach.

In this study we describe the fabrication and characterization of nanocomposites consisting of layer-by-layer assembled polyaniline, sulfonated polystyrene, and maghemite nanoparticle layers. In order to assemble the starting components via electrostatic interaction, stable magnetic fluid containing maghemite nanoparticles (d approximately = 7 nm) with either positive or negative surface charges was used as source of nanoparticles for the layer-by-layer assembly. The structure, morphology, electrical and magnetic properties of such nanocomposite films were investigated by UV-Vis spectroscopy, atomic force microscopy, electrical, and magnetic measurements. The amount of PANI, PSS and maghemite nanoparticles within the nanocomposite films increased almost linearly with the number of deposited layers. Atomic force microscopy image of typical polyaniline/maghemite nanocomposites reveal nanoparticles adsorbed all over the film surface. The as-produced nanocomposite exhibits electrical conductivity and superparamagnetism behavior at room temperature, the latter confirmed by the absence of magnetic hysteresis.