Fluorescence detection of hydroxyl radicals

The hydroxyl radical (OH), a product of water radiolysis, reacts to hydroxylate aromatic organic compounds. In some cases, these hydroxylated products are fluorescent. Examples include the benzoate, coumarin, and phenoxazinone systems. For representative members of these systems, we have determined both the rate constants for reaction with OH and the yields of the fluorescent products. The rate constants all fall in the range 2×109 to 2×1010 L mol−1 s−1, and the yields 5–11% per OH. These results suggest that it may prove feasible to construct a probe consisting of two groups both of which must react with OH to become fluorescent. The efficient process of fluorescence resonance energy transfer implies that such a probe might be able to detect OH clusters, which are generally assumed to be a characteristic feature of energy deposition by ionizing radiation.