1. School of Environmental and Biological Engineering; Nanjing University of Science and Technology; Nanjing 210094 China
2. School of Chemical Engineering; Nanjing University of Science and Technology; Nanjing 210094 China
3. American Advanced Nanotechnology; Houston TX 77459 USA
4. Chemistry Department; College of Arts and Sciences; University of South Florida; Tampa FL 33620-4202 USA