Highly Sensitive and Selective Fluorescent Probe for Detection of Fe³⁺ Based on Rhodamine Fluorophore

A simple rhodamine-based fluorescent probe L1, which exhibits good response to Fe³⁺ in CH₃CN/Tris-HCl buffer (v:v = 9:1, pH 7.00) solution. With the experimental conditions optimized, the probe L1 could be used as a fluorescent and colorimetric probe for Fe³⁺ with the detection limit as low as 0.29 μM. The binding constant (K_a) of Fe³⁺ binding to the probe L1 were calculated to be 1.4 × 10¹⁰ M^-2, respectively from a Benesi-Hildebrand plot. With the addition of Fe³⁺, the CH₃CN/Tris-HCl buffer (v:v = 9:1, pH 7.00) solution of the probe L1 exhibited a obviously color change from transparent to pink with distinctive changes. More importantly, the recognition process of the probe L1 for Fe³⁺ was chemically reversible on the addition AcO^-. Graphical Abstract.