1. Department of Chemistry; St. Xavier's College (Autonomous), Tirunelveli; Tamil Nadu-627 002 India
2. Institut Européen des Membranes, IEM, UMR 5635; Université de Montpellier, CNRS, Montpellier; France
3. Materials Research Centre; College of Engineering; Swansea University, Swansea SA2 8PP; UK