The present invention provides a novel class of pro-fluorescent probes for reactive oxygen species (ROS). One exemplary probe is mitochondria peroxy yellow 1 (MitoPY1), a new type of flurophore for imaging mitochondrial H2O2 in living cells with ROS and spatial specificity. The invention also provides methods of using pro-fluorescent probes to detect analytes. One exemplary method comprises using a pro-fluorescent probe of the invention to detect an explosive.