1. Department of Chemistry Bangladesh University of Engineering and Technology (BUET) Dhaka 1000 Bangladesh
2. Center of Research Excellence in Nanotechnology King Fahd University of Petroleum & Minerals KFUPM Box 5040 Dhahran 31261 Saudi Arabia
3. Physics Department King Fahd University of Petroleum & Minerals KFUPM Box 5047 Dhahran 31261 Saudi Arabia