Nanocomposites and nanomaterials

EPR spectroscopy study of synthesized polyaniline (PANI)/TiO2 nanoparticles composites
Melnyk A.K.1, Zahornyi M.M.2 
1 Institute for Sorption and Endoecology Problems NAS of Ukraine, Generala Naumova str., 13, Kyiv-03164, Ukraine.
E-mail: mak106@ukr.net 
2 Institute for Problems of Materials Science NAS of Ukraine, Krzhyzhanivskogo str, 3, Kyiv-03142, Ukraine. 

In our current research TiO2 nanoparticles with a size of 5-100 nm were encapsulated by PANI via the “in situ” polymerization of aniline. PANI-modified TiO2 composites exhibit significantly higher photocatalytic activity than the initial PANI [1]. EPR spectroscopy experiments were performed to study the transition of electrons from PANI to TiO2, the evolution of paramagnetic centres concentration too. The non-linear nature of ΔH and PMC concentrations (spin/g) dependencies versus TiO2 content in the composites may be explained by the electronic interaction between the PANI and TiO2. Temperature experiments carried out in the range of 77–300 K revealed strong ΔH dependencies with maximum values in the “critical” region of 150–220 K. Such behaviour could be explained by the existence of two types of polarons, having different temperature dependence of activation energy and therefore in conductivity of samples [2]. EPR study of two composites involving TiO2 nanoparticles of different nature show, that for the composite based on anatase, broadening of linewidth is quite significant in comparison with PANI/P25 one. Such difference can be determined by both TiO2 nature, and on the other hand by the surface morphology and size of the oxide nanoparticles. These factors could affect the interaction between charge carriers with lattice optical phonons of the PANI chains and also on the dipole-dipole interactions between spins. The broader line can be produced by polarons involved in homogenous disordered media (1D or 3D) or inhomogeneous disorder.

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2.Karray F., Kassiba A. EPR investigations of silicon carbide nanoparticles functionalized by acid doped polyaniline // Physica B.-2012.-407.-P. 2119-2125.
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