1. Environmental Engineering Laboratory, Department of Civil Engineering, Faculty of Engineering, University of Malaya, 50603 Kuala Lumpur, Malaysia
2. Institut fuer Technische Chemie, Leibniz Universität Hannover, Callinstrasse 3, D-30167 Hannover, Germany
3. Nanotechnology & Catalysis Research Center (NANOCAT), University of Malaya, 50603 Kuala Lumpur, Malaysia