Layer-by-Layer Assembly of Bifunctional Nanofilms: Surface-Functionalized Maghemite Hosted in Polyaniline

This study reports on the pioneering use of the layer-by-layer (LbL) technique to produce multilayered (1 to 50 bilayers) bifunctional nanocomposite films consisting of negatively charged citrate-coated maghemite nanoparticle (cit-MAG) hosted in positively charged conducting polyaniline (doped-PANI). The aim is to use the LbL. assembly to fabricate thin nanocomposite films displaying superparamagnetic and conductivity properties and with fine control of the end properties as a function of the preparation condition. Multilayered cit-MAG/PANI bifunctional nanocomposite films were systematically investigated in order to access information regarding the nanofilm structure, electrical conductivity, and magnetic properties. Using the isothermal adsorption of each individual electrolyte (cit-MAG dispersion and doped-PANI solution) onto solid substrates (silicon and glass) the average time for deposition of a single layer (cit-MAG or doped-PANI) was fixed in 3 min. Independent evaluation using UV-vis spectroscopy and tomic force microscopy indicated a linear correlation between the nominal number of adsorbed cit-MAG/PANI bilayers and the material content (film thickness), even for the smallest number of adsorbed bilayers. Values of electrical conductivity (film thickness) found for the 10-bilayered cit-MAG/PANI nanocomposite films were in the range of 10(-2)-10(-4) Scm(-1) (25-63 nm) for gamma-Fe2O3 concentration within the employed magnetic fluid suspension in the range of 10(-4)-10(-3) g L-1. Values of the blocking temperature obtained from ZFC/FC curves recorded for the nanofilm produced using the highest gamma-Fe2O3 concentrated Suspension (2 x 10 (3) g L-1) monotonically increase from 30 to 40 K as the number of cit-MAG/PANI bilayers increases from 5 to 50 bilayers. Therefore, we found that the end properties can be easily and precisely modulated by varying the concentration of the magnetic fluid used for film deposition and/or controlling the nominal number of cit-MAG/PANI bilayers in the nanocomposite.