1. Department of Materials Science and Engineering City University of Hong Kong 83 Tat Chee Avenue Kowloon Hong Kong 999077 China
2. Department of Chemistry Engineering Research Center of Advanced Rare Earth Materials (Ministry of Education) Tsinghua University Beijing 100084 China
3. Department of Chemistry The Chinese University of Hong Kong Shatin, NT Hong Kong 999077 China
4. Department of Materials Science and Engineering Southern University of Science and Technology Shenzhen 518055 China
5. Department of Electrical Engineering City University of Hong Kong 83 Tat Chee Avenue Kowloon Hong Kong 999077 China