1. School of Chemistry and Chemical Engineering, Southwest Petroleum University, Chengdu 610500, Sichuan, P. R. China, State Key Laboratory of Oil & Gas Reservoir Geology and Exploitation, Southwest Petroleum University, Chengdu 610500, Sichuan, P. R. China, and Departamento de Química, Universidade de Coimbra, 3004-535 Coimbra, Portugal