1. Department of Biomedical Engineering University of Houston Houston TX 77204 USA
2. Electron Microscopy Core Houston Methodist Research Institute Houston TX 77030 USA
3. Department of Chemistry University of Houston Houston TX 77204 USA
4. Department of Physics and TcSUH University of Houston Houston TX 77204 USA
5. College of Materials and Energy South China Agricultural University Guangzhou 510642 China
6. Department of Materials Science and NanoEngineering Rice University TX 77005 USA