1. Department of Engineering and System Science, National Tsing Hua University, 101, Section 2, Kuang-Fu, Hsinchu 30013, Taiwan
2. Nano Science and Technology Program, Taiwan International Graduate Program, Academia Sinica, Taipei 11529, Taiwan
3. Institute of Physics, Academia Sinica, Taipei 11529, Taiwan
4. Institute of Organic and Polymeric Materials, National Taipei University of Technology, Taipei, 10608, Taiwan
5. Department of Medical Research, MacKay Memorial Hospital, Tamsui, New Taipei City 25173, Taiwan
6. Discipline of Physics, School of Chemistry and Physics, College of Agriculture, Engineering and Science, University of KwaZulu-Natal, Durban, 4000, South Africa