1. New Energy Research Institute; School of Environment and Energy; South China University of Technology; Guangzhou Higher Education Mega Center; Guangzhou Guangdong 510006 P.R. China
2. Department of Physics and Siyuan Laboratory; Jinan University; Guangzhou Guangdong 510632 P.R.China
3. Department of Chemistry and Biochemistry; University of California; 1156 High Street Santa Cruz CA 95064 USA