1. Department of Applied Physics; National Technical University of Athens; Heroon Politechniou 9 Zographou (Athens) 15780 Greece
2. Department of Physics and Mathematics; University of Hull; Cottingham road HU67RX Kingston upon Hull United Kingdom
3. Institute of Nanoscience and Nanotechnology; National Centre for Scientific Research Demokritos; Terma Patriarchou Grigoriou; Aghia Paraskevi 15310 Greece
4. European Bioenergy Research Institute; Aston University,; Aston Triangle, Birmingham B4 7ET United Kingdom
5. Chemical Engineering and Applied Chemistry; School of Engineering and Applied Sciences; Aston University; Aston Triangle, Birmingham B4 7ET UK