A compound, a method of imaging a cell, and a method of detecting a cancer, an inflammatory disease, or a neoplastic disease are provided. The compound includes a nitroxide derivative of a fluorophore that is activatable upon exposure to free radicals. The method of imaging a cell includes contacting the cell with an activatable nitroxide derivative of a fluorophore. The method of detecting a cancer, an inflammatory disease, or a neoplastic disease includes administering an activatable nitroxide derivative of a fluorophore and then imaging one or more cells contacted with the compound.
