a
Materials Research Laboratory, University of California, Santa Barbara, USA
E-mail: hawker@mrl.ucsb.edu
b
Swedish Medical Nanoscience Center, Department of Neuroscience, Karolinska Institutet, Retzius väg 8, Stockholm SE-171 77, Sweden
c
Department of Fibre and Polymer Technology, KTH Royal Institute of Technology, School of Chemical Science and Engineering, Teknikringen 56-58, Stockholm SE-100 44, Sweden
d
Department of Chemistry and Biochemistry and Materials Department, University of California, Santa Barbara, USA