1. Departments of Materials Science and Engineering, Chemistry and Chemical Biology, and Physics, Cornell University, Ithaca, New York 14853, United States, Department of Radiology, Memorial Sloan-Kettering Cancer Center, 1275 York Avenue, New York, New York 10065, United States, and Cornell High Energy Synchrotron Source (CHESS), Cornell University, Ithaca, New York 14853, United States