基金supported,in part,by the National Science Foundation(CHE-1012256 and DMR-0804049)by the ACS-Petroleum Research Fund(49137-ND10)+1 种基金J.Huang was supported,in part,by a research fellowship from the China Scholarship Councilperformed as a User Project at the National Center for Electron Microscopy,Lawrence Berkeley National Laboratory,which is supported by the US Department of Energy