1. Laboratory of Photonics and Interfaces, Institute of Chemical Sciences and Engineering, École Polytechnique Fédérale de Lausanne, Lausanne CH-1015, Switzerland
2. National Nanotechnology Research Centre, King Abdulaziz City for Science and Technology (KACST), P.O. Box 6086, Riyadh 11442, Saudi Arabia
3. National Center for Petrochemicals Technology, King Abdulaziz City for Science and Technology (KACST), P.O. Box 6086, 11442 Riyadh, Saudi Arabia