Fluorescent Switch-on Probe for Carbon-Centered Radicals and Real-Time Assessment of Toluene Degradation Efficacy

Carbon-centered radicals derived from parent compounds are primary radical intermediates involved in the degradation of organic pollutants. This study presents a bifunctional probe with a fluorescent "switch-on" and radical capture functions for in situ trapping and specific detection of carbon-centered radicals. Carbon-centered radicals can be quickly trapped and they can notably turn on the 11-fold fluorescence, which enables the monitoring of unstable and short-lived carbon-centered radicals generated during toluene degradation. The proposed system was applied to assess the toluene degradation efficacy in real time. The fluorescence response was similar to that of the toluene degradation efficiency measured using high-performance liquid chromatog-raphy (HPLC). In addition, the benzyl radical was identified as the primary carbon-centered radical intermediate by high-resolution liquid chromatography-mass spectrometry (LC-MS), which provides direct evidence for the toluene degradation mechanism by thermally activated persulfate.