[1] Univ Penn, Dept Chem, Philadelphia, PA 19104 USA
[2] Univ Penn, Dept Elect & Syst Engn, Philadelphia, PA 19104 USA
[3] Univ Penn, Dept Mat Sci & Engn, Philadelphia, PA 19104 USA
[4] Univ Hong Kong, Dept Elect & Elect Engn, Pokfulam Rd, Hong Kong, Peoples R China
[5] Ohio State Univ, Dept Elect & Comp Engn, Columbus, OH 43210 USA