1. Key Laboratory of Eco-Environments in Three Gorges Reservoir (Ministry of Education); School of Chemistry and Chemical Engineering; Southwest University; Chongqing 400715 P. R. China
2. Department of Materials; Imperial College London; Prince Consort Road London SW7 2AZ UK
3. School of Chemistry and Chemical Engineering; Chongqing University; Chongqing 400044 P. R. China