1. Nanotechnology and Advanced Materials Research Institute, NAMRI, University of Ulster, Jordanstown campus, BT37 0QB UK, Institute of Analytical Chemistry, Peking University, Beijing, 100871 P.R. China, Department of Materials, University of Oxford, Parks Road, OX1 3PH UK, and Fire Safety Engineering Research and Technology Centre, University of Ulster, Jordanstown campus, BT37 0QB UK