1. School of Chemistry & Tyndall National Institute, University College Cork, Cork, T12 YN60, Ireland
2. AMBER Centre, Environmental Research Institute, University College Cork, Cork, T23 XE10, Ireland
3. School of Chemistry and CRANN & AMBER Centre, Trinity College Dublin, Dublin 2, Ireland
4. Department of Photonics, Tyndall National Institute, University College Cork, Cork, Ireland
5. Department of Physics, Bose Institute, 93/1, A.P.C Road, Kolkata, 700009, India
6. Université de Toulouse, UMR 5215 INSA, CNRS, UPS, Laboratoire de Physique et Chimie des Nano-Objets, 135 avenue de Rangueil, F-31077 Toulouse cedex 4, France
7. Department of Materials, Royal School of Mines, Imperial College London, UK
8. TEMUL, Department of Physics, Bernal Institute, University of Limerick, Limerick, V94 T9PX, Ireland