Role of Raman Imaging Microscopy in Explaining the Structural-Electrical Conductivity Property Shown by Polyaniline/MgFe2O4 Core-Shell Nanocomposite

Rasha      M. Khafagy

doi:10.2174/157341312800620188

Abstract

In this article, dispersive Raman imaging microscopy was used in characterizing the structures of: Polyaniline (PAni), MgFe2O4, and PAni/MgFe2O4 nanocomposite designed in the form of core-shell, and is used also in explaining their electrical conductivity properties. MgFe2O4 nanoparticles have been incorporated into the PAni polymer for capping and stabilizing the ferrite nanoparticles, and for tailoring the polymer's properties as well. Electrical conductivity results revealed that after an applied voltage of 0.98 V, equivalent to threshold electric field (E) of 5.5 V.cm-1, PAni/MgFe2O4 core-shell nanocomposite showed enhanced electrical conductivity (σ) of 4.39x10-1 S.cm-1, which is higher than the conductivity obtained from both parents materials at equivalent electric field values (σ = 3.9x10-1 and 5.81x10-10 S.cm-1 at E = 5.5 V.cm-1 for PAni and MgFe2O4 nanoparticles respectively). Moreover, at applied voltage of 1.3 volt, high conductivity values up to 8.7x10-1 S.cm-1 were obtained from the prepared PAni/MgFe2O4 core-shell nanocomposite after being stated in literature that it is difficult to simultaneously obtain high conductivity (>0.01 S.cm-1) for the PAni composites, and despite the insulating property of MgFe2O4, which was assumed to lower the net electrical conductivity of the synthesized core-shell nanocomposite. This value of relatively high conductivity is reached due to the core-shell design of the samples, and due to the changes that occurred in the PAni structure after coating MgFe2O4 nanoparticles. Dispersive Raman imaging spectroscopy operating in the microscopic mode assisted in understanding the electrical conductivity behavior showed by PAni/MgFe2O4 core-shell nanocomposite, as it revealed that shelling MgFe2O4 with PAni resulted in a weak interfacial interaction between the core and the shell materials, which might change the molecular conformation of PAni from being of compact coil structure to an expanded coil like structure, that resulted in better conductivity of the core-shell nanocomposite, while XRD Patterns proved that MgFe2O4 nano-filler reduced the crystallinity of PAni, and acted as an oxidizing agent that enhanced the intermolecular component of the bulk conductivity in PAni/MgFe2O4 core-shell nanocomposite. This combination between the Raman spectral data, and the electrical conductivity data is considered as an approach in using and getting usefulness from the Raman microscopy spectroscopic data, and in interpreting electrical conductivity results as well.

Keywords: Polymer-ferrite nanocomposites, Core-shell, Polyaniline, MgFe2O4, Raman imaging microscopy, structural-electrical property relationship, electrical conductivity

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