1. Department of Chemistry and Biochemistry, North Dakota State University, Fargo, North Dakota 58108, United States
2. Engineering Research Center for Nanomaterials, Henan University, Kaifeng, Zhengzhou Province 475004, P. R. China
3. Materials and Nanotechnology Program, North Dakota State University, Fargo, North Dakota 58108, United States
4. Department of Physics, North Dakota State University, Fargo, North Dakota 58108, United States
5. Department of Coatings and Polymeric Materials, North Dakota State University, Fargo, North Dakota 58108, United States