The accurate and sensitive detection of radical oxidants is a central problem in the field of chemical biology.[1] Radical oxidants can be detected in vitro with fluorescent leucodyes such as dihydroethidium (DHE),[2] dihydrorhodamine (DHR),[3] the hydrocyanines,[4] redoxfluor-1,[5a] and their organelle-specific analogues.[5b] Although these probes are widely used in cell culture, their accuracy is compromised by their high levels of ...