1. Collaborative Innovation Center for Nanomaterials & DevicesCollege of PhysicsQingdao University Qingdao 266071 China
2. Center for Nanofibers & NanotechnologyNational University of Singapore Singapore 119077 Singapore
3. Department of Mechanical EngineeringColumbia University New York NY 10027 USA
4. Department of Physiology and PathophysiologySchool of Basic Medical SciencesQingdao University Qingdao 266071 China
5. Laboratory for Biological Effects of Nanomaterials & NanosafetyNational Center for Nanoscience & Technology Beijing 100190 China