1. Department of Physics and Optical Engineering, Rose-Hulman Institute of Technology, CM 192, 5500 Wabash Avenue, Terre Haute, IN 47803, USA
2. Office of the Chancellor and Center for Nanoscience, Departments of Chemistry & Biochemistry and Physics & Astronomy, University of Missouri–St. Louis, 401 Woods Hall, One University Boulevard, St. Louis, MO 63121, USA