1. Department of Energy & Materials EngineeringDongguk University, Seoul 100-715 Republic of Korea
2. Center of Research Excellence in Nanotechnology (CENT)King Fahd University of Petroleum and Minerals, KFUPM Box-5040 Dhahran 31261 Saudi Arabia
3. Center of Research Excellence in Renewable EnergyKing Fahd University of Petroleum and Minerals Dhahran 31261 Saudi Arabia