[1] Sheffield Hallam Univ, Sch Engn, Elect Res Grp, Phys Elect & Fibre Opt Res Labs, Sheffield S1 1WB, S Yorkshire, England
[2] Univ Sheffield, Dept Chem, Sheffield S1 4DU, S Yorkshire, England
[3] Univ Nottingham, Sch Mech Mfg Engn & Management, Nottingham NG7 2RD, England