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

摘要

This study reports on the pioneering use of the layer-bgmma-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 atomic 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 gmma-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 gmma-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.