1. Department
of Chemistry, National University of Singapore, Singapore 117543
2. Department
of Physics, Shahid Chamran University, Ahvaz, Iran 6135713749
3. Department
of Physics, Malayer University, Malayer, Iran 6571995863
4. Department
of Physics, National University of Singapore, Singapore 117542
5. Department
of Materials Science and Engineering, National University of Singapore, Singapore 117576