[1] Tech Univ Darmstadt, Joint Res Lab Nanomat, Jovanka Bontschits Str 2, D-64287 Darmstadt, Germany
[2] Karlsruher Inst Technol, Inst Nanotechnol, Hermann von Helmholtz Pl 1, D-76344 Eggenstein Leopoldshafen, Germany
[3] Univ Birmingham, Sch Chem, Birmingham B15 2TT, W Midlands, England
[4] Rutherford Appleton Lab, ISIS Facil, Harwell Campus, Didcot OX11 0QX, Oxon, England