[1] Michigan State Univ, Dept Elect & Comp Engn, E Lansing, MI 48824 USA
[2] Rice Univ, Dept Chem, Houston, TX 77005 USA
[3] Rice Univ, Dept Mech Engn & Mat Sci, Houston, TX 77005 USA
[4] Rice Univ, Smalley Inst Nanoscale Sci & Technol, Houston, TX 77005 USA