1. Center on Nanoenergy ResearchSchool of Physical Science and Technology Guangxi University Nanning Guangxi 530004 P. R. China
2. CAS Center for Excellence in NanoscienceBeijing Key Laboratory of Micro-nano Energy and SensorBeijing Institute of Nanoenergy and Nanosystems Chinese Academy of Sciences Beijing 100083 P. R. China
3. Department of Civil Engineering Monash University Clayton 3800 Australia
4. School of Nanoscience and Technology University of Chinese Academy of Sciences Beijing 100049 P. R. China