1. Materials Science and Nanotechnology Program, Faculty of Science, Khon Kaen University, Khon Kaen 40002, Thailand
2. Department of Physics, Faculty of Science, Khon Kaen University, Khon Kaen 40002, Thailand
3. Integrated Nanotechnology Research Center, Khon Kaen University, Khon Kaen 40002, Thailand
4. Nanotec-KKU Center of Excellence on Advanced Nanomaterials for Energy Production and Storage, Khon Kaen University, Khon Kaen 40002, Thailand