1. Center for Nanotechnology and Molecular Materials Wake Forest University Winston‐Salem NC 27109 USA
2. Department of Physics Wake Forest University Winston‐Salem NC 27106 USA
3. State Key Laboratory for Modification of Chemical Fibers and Polymer Materials Shanghai 201620 P. R. China
4. College of Materials Science and Engineering Donghua University Shanghai 201620 P. R. China
5. Department of Chemistry Wake Forest University Winston‐Salem NC 27106 USA