1. HKBU Institute of Research and Continuing Education Shenzhen Guangdong 518057 China
2. Department of Physics Hong Kong Baptist University (HKBU) Kowloon Tong Hong Kong SAR China
3. Department of Physics The Chinese University of Hong Kong Sha Tin Hong Kong SAR China
4. Department of Chemistry Southern University of Science and Technology Shenzhen Guangdong 518055 China
5. Institute of Advanced Materials State Key Laboratory of Environmental and Biological Analysis Golden Meditech Centre for Neuro Regeneration Sciences HKBU Kowloon Tong Hong Kong SAR China