1. Department of Physics, Faculty of Science, Kasetsart University, Bangkok 10900, Thailand
2. National Nanotechnology Center (NANOTEC), National Science and Technology Development Agency (NSTDA), Pathum Thani 12120, Thailand
3. Nano Environmental and Health Safety Research Team, National Nanotechnology Center (NANOTEC), National Science and Technology Development Agency (NSTDA), Pathum Thani 12120, Thailand
4. Department of Physics, Faculty of Science, Mahidol University, Bangkok 10400, Thailand