A novel boronic acid-based fluorescent sensor for selectively recognizing Fe³⁺ ion in real time

Boronic acid provides faster fluorescence response to Fe³⁺ compared to other reported sensors, which is critical for continuous dynamic detection. Herein, we reported a novel boronic acid-based sensor 4 that could recognize Fe³⁺ ion in real time. After 10 equiv. of Fe³⁺ ion (1 mM) was added, the fluorescence of sensor 4 was immediately quenched by 96%. While other ions, including Ba²⁺, Ca²⁺, Cr²⁺, Cd²⁺, Co²⁺, Cs²⁺, Cu²⁺, Fe²⁺, K⁺, Li⁺, Mg²⁺, Mn²⁺, Na⁺, Ni²⁺ or Zn²⁺, respectively, did not change the fluorescence significantly. Further tests indicated that the high selectively sensing Fe³⁺ ion benefits from the two boronic acid functionalities in the structure. Moreover, interference experiments showed this sensor has an excellent anti-interference ability. In addition, we performed binding activity test in rabbit plasma and other real samples for practical applications, obtaining similar results. And the thin layer loading sensor 4 was also successfully applied to recognize Fe³⁺ ion among various ions. Therefore, 4 may serve as a potential sensor for continuous monitoring and detecting Fe³⁺ ion in real time.