A rhodamine coumarin-derived fluorescence probe that selectively detects Fe3+and measures radiation dosesElectronic supplementary information (ESI) available: 1H NMR and LCMS spectra of REC. Schematic illustration of the mechanism and the fluorescence spectra of RECat different pHs. Fluorescence spectra and CIE 1931 of RECas a function of increasing Fe3+concentration. Change in I585/I405as a function of increasing Fe2+concentration. I585/I405of RECsolution responding to different metal ions. Schematic illustration of the mechanism of RECfor sensing X-ray doses. Reaction kinetics of RECprobe with 10 Gy irradiated Fe2+. Fluorescence spectra and CIE 1931 of RECprobe with different X-ray doses. See DOI: https://doi.org/10.1039/d3ay01875j

We synthesized a fluorescence ratiometric probe by combining coumarin and rhodamine B with ethylenediamine to sense Fe3+and measure ionizing radiation doses. The presence of Fe3+caused rhodamine to transition from a closed helical structure to an open-ring structure. Additionally, fluorescence resonance energy transfer (FRET) occurred between coumarin and rhodamine B. As a result, the fluorescence intensity at 405 nm (I405) due to coumarin was decreased, whereas that at 585 nm (I585) derived from open-ring structure rhodamine B was increased. The ratio of I585and I405(I585/I405) linearly increased as the Fe3+concentration increased. The probe sensed Fe3+in a 0–110 μM range, with a lower limit of detection (LOD) of 0.226 μM. Inspired by Fricke dosimeters, we extended the probe to measure X-ray doses using the fluorescence methodology. The probe measured X-ray doses in a 0–30 Gy range with a lower LOD of 0.5 Gy. Additionally, the dosing capability was independent of the dosing rates. Our probe showed potential for detecting Fe3+and measuring ionizing radiation doses.