1 State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences Lanzhou 730000 China lpwang@licp.cas.cn gazhang@licp.cas.cn +86 931 4968163 +86 931 4968080.
2 University of Chinese Academy of Sciences Beijing 100039 China.
3 Key Laboratory of Marine Materials and Related Technologies, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences Ningbo 315201 China.