Calorimetric, optical and catalytic activity studies of europium chloride-polyvinyl alcohol composite system

Polyvinyl alcohol (PVA) films doped with europium chloride (EuCl3) have been prepared by casting from their aqueous solutions. The phase transitions and thermal decomposition behavior of the prepared samples were investigated by thermal analysis and the interactions between the host PVA and Eu3+ were examined by FTIR spectroscopy. The optical absorption was recorded at room temperature in the range of 190-1000 nm. From the absorption edge studies, the values of the Urbach energy (E-e) were found to be 0.56 eV in case of the pure polymer: however, its value increased to be in the range of 1.21-1.75 eV. These energy values indicate that the model based on electronic transitions between localized states is not preferable and transitions are made between band tails. Optical parameters such as refractive index and complex dielectric constant have been determined. The dispersion of the refractive index is discussed in terms of the single-oscillator Wemple-DiDomenico model. Color properties of the prepared samples are discussed in the framework of CIE L*u*v* color space. The prepared samples have been used as catalysts in the photocatalytic degradation of p-nitrophenol (PNP) in aqueous solution under UV light irradiation using H2O2 as oxidizing agent. The catalytic activity of the Eu-polymer towards the photodegradation of PNP greatly increased after doping with Eu3+ ions. The highest catalytic activity was noticed at the optimum pH value of 5.5. (C) 2011 Elsevier Ltd. All rights reserved.