1. Department of Applied Biology and Chemical TechnologyThe Hong Kong Polytechnic University Hung Hom Kowloon Hong Kong SAR 999077 China
2. Key Laboratory of Organic SolidsInstitute of ChemistryChinese Academy of Sciences Beijing 100190 P. R. China
3. Key Laboratory of Nonferrous Metal Chemistry and Resources Utilization of Gansu ProvinceState Key Laboratory of Applied Organic Chemistry and College of Chemistry and Chemical EngineeringResearch Center of Biomedical NanotechnologyLanzhou University Lanzhou 730000 P. R. China