1. Department of Electrical and Computer Engineering, University of Alberta, Edmonton, Alberta T6G 1H9, Canada
2. Nanotechnology Research Centre, National Research Council Canada, Edmonton, Alberta T6G 2M9, Canada
3. Department of Physics, University of Alberta, Edmonton, Alberta T6G 2E1, Canada
4. Department of Chemistry, University of Alberta, Edmonton, Alberta T6G 2G2, Canada
5. Department of Chemistry, Indian Institute of Technology Kharagpur, Kharagpur, West Bengal 721302, India