A rhodamine coumarin-derived fluorescence probe that selectively detects Fe 3+ and measures radiation doses.

We synthesized a fluorescence ratiometric probe by combining coumarin and rhodamine B with ethylenediamine to sense Fe 3+ and measure ionizing radiation doses. The presence of Fe 3+ 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 ( I 405 ) due to coumarin was decreased, whereas that at 585 nm ( I 585 ) derived from open-ring structure rhodamine B was increased. The ratio of I 585 and I 405 ( I 585 / I 405 ) linearly increased as the Fe 3+ concentration increased. The probe sensed Fe 3+ 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 Fe 3+ and measuring ionizing radiation doses.