[1] Columbia Univ, Dept Biomed Engn, New York, NY 10027 USA
[2] NYU, Dept Chem, New York, NY 10003 USA
[3] Kings Coll London, Comprehens Canc Ctr, Sch Canc & Pharmaceut Sci, Imaging Therapies & Canc Grp, London SE1 1UL, England
[4] Imperial Coll London, Dept Chem, Mol Sci Res Hub, London W12 0BZ, England
[5] NASA, Planetary Syst Branch, Ames Res Ctr, Moffett Field, CA 94035 USA
[6] Columbia Univ, Dept Appl Phys & Appl Math, New York, NY 10027 USA