1. Department of Chemical and Biomolecular Engineering, University of Maryland, College Park, Maryland 20742, US Army Research Laboratory, Sensors and Electron Devices Directorate, Adelphi, Maryland 20783, Department of Chemistry and Biochemistry, University of Maryland, College Park, Maryland 20742, Department of Materials Science and Engineering, University of Maryland, College Park, Maryland 20742, and Department of Physics, Yeshiva University, New York, New York 10016