1. Department of Petrochemical Engineering, Faculty of Engineering and Green Technology, Universiti Tunku Abdul Rahman, Kampar 31900, Perak, Malaysia
2. School of Chemical Engineering, Universiti Sains Malaysia, Nibong Tebal 14300, Penang, Malaysia
3. Departament de Física, Facultat de Ciències, Universitat Autònoma de Barcelona, E-08193 Bellaterra, Spain
4. Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), C/dels Til.lers s/n, Campus UAB, E-08193 Bellaterra, Spain
5. Department of Physics, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, United States