1. Chemistry Department King Fahd University of Petroleum and Minerals Dhahran 31261 Saudi Arabia
2. Center of Research Excellence in Nanotechnology (CENT) King Fahd University of Petroleum and Minerals Dhahran 31261 Saudi Arabia
3. Physics Department King Fahd University of Petroleum & Minerals <orgDiv/KFUPM Box 5047 Dhahran 31261 Saudi Arabia