Rapid one-step chemical synthesis of polyaniline-manganese ferrite nanocomposites without external initiator and mechanical agitation

Abstract

We describe a rapid one-step, room temperature method to chemically synthesize bulk quantities of nanocomposites comprising specifically of manganese ferrite (MnFe2O4) and polyaniline (conductive form). Typically a chemical agent, for example ammonium peroxydisulfate, is used to start the polymerization of aniline in the presence of ferrites, and stirring of the reaction system for several hours is also very common. Our approach allows for the nanocomposites to be formed in less than thirty minutes without adding an external polymerization initiator/surfactant and applying any form of mechanical agitation. This process affords the possibility to grow thin films of polyaniline-MnFe2O4 directly on device substrates. Structural, thermal, magnetic and electrical studies did reveal significant chemical interactions between MnFe2O4 and polyaniline matrix. The nanocomposites are magnetic semiconductors with long rod-shaped structures of average diameter in the nanometer scale range and optical properties resembling that of conductive polyaniline. They exhibit a positive magnetoresistance across all temperature ranges with a minimum at around 250 K, corresponding to the temperature for their uniform-to-irregular transition in dynamic stability behavior and likewise coinciding with a minimum in their profile of electrical conduction mechanism (one-dimensional variable range hopping below 250 K) – these complementarities are important for hybrid spintronic applications.