1. School of Chemical Engineering and Australian Centre for NanoMedicine (ACN); University of New South Wales; Sydney NSW 2052 Australia
2. Department of Ultrasound; the First Affiliated Hospital of Chongqing Medical University; Chongqing 400010 China
3. Electron Microscope Unit; University of New South Wales; Sydney NSW 2052 Australia
4. School of Chemistry; ARC Centre of Excellence in Convergent Bio-Nano Science and Technology and Australian Centre for NanoMedicine (ACN); University of New South Wales; Sydney NSW 2052 Australia
5. State Key Laboratory of High Performance Ceramics and Superfine Microstructure; Shanghai Institute of Ceramics; Chinese Academy of Sciences; Shanghai 200050 China