1. Key Laboratory of Nano Chemistry, Key Laboratory of Oilfield Chemistry, CNPC, Research Institute of Petroleum Exploration & Development (RIPED), PetroChina, Beijing 100083, P. R. China
2. Key Laboratory of Nano Chemistry, CNPC, Beijing 100083, P. R. China
3. Department of Chemical Engineering, Waterloo Institute for Nanotechnology, University of Waterloo, 200 University Avenue, Waterloo, ON N2L 3G1, Canada