1. Centre for Molecular Nanometrology, WestCHEM, Department of Pure and Applied Chemistry, University of Strathclyde, 295 Cathedral Street, Glasgow, U.K., G1 1XL
2. Department of Biomedical Engineering, University of Strathclyde, 106 Rottenrow, Glasgow, U.K., G4 0NW
3. Centre for Microsystems and Photonics, Electronic and Electrical Engineering, University of Strathclyde, 204 George Street, Glasgow, U.K., G1 1XW
4. Centre for Biophotonics, Strathclyde Institute for Pharmacy and Biomedical Sciences, University of Strathclyde, 161 Cathedral Street, Glasgow, U.K., G4 0RE