1. School of Marine Science and Technology Harbin Institute of Technology Weihai 264209 P. R. China
2. Department of Materials Science and Engineering National University of Singapore 117573 Singapore
3. School of Materials Science and Engineering Harbin Institute of Technology Weihai 264209 P. R. China
4. Key Laboratory of Functional Inorganic Material Chemistry Ministry of Education School of Chemistry and Materials Science Heilongjiang University Harbin 150080 P. R. China