1. Department of Applied Physics The Hong Kong Polytechnic University Kowloon Hong Kong 999077 China
2. Department of Biomedical Engineering The Hong Kong Polytechnic University Kowloon Hong Kong 999077 China
3. State Key Laboratory for Emerging Infectious Diseases Department of Microbiology LKS Faculty of Medicine The University of Hong Kong Pokfulam Hong Kong 999077 China
4. Research Centre for Nanoscience and Nanotechnology The Hong Kong Polytechnic University Kowloon Hong Kong 999077 China