1. College of Science Institute of Materials Physics and ChemistryNanjing Forestry University Nanjing 210037 P. R. China
2. School of Materials Science & EngineeringJiangsu University Zhenjiang 212013 P. R. China
3. School of Chemistry, Physics and Mechanical EngineeringQueensland University of Technology Brisbane QLD 4001 Australia
4. Key Laboratory for Photonic and Electronic Band Materials Ministry of EducationSchool of Physics and Electronic Engineering Harbin Normal University Harbin 150025 P. R. China