Fluorenone-Based Fluorescent and Colorimetric Sensors for Selective Detection of I-Ions: Applications in HeLa Cell Imaging and Logic Gate

Abstract

Fluorenone-based fluorescent and colorimetric sensors 1 and 2 have been developed that displayed selective detection of iodide ions in the presence of interferences. Sensors displayed the fluorescence emission enhancement response toward I- with detection limits of 8.0 and 11.0 nM, respectively, which is accomplished through inhibition of intramolecular charge transfer and C=N isomerization. Excellent sensitivity and unique fluorescence enhancement response of sensors toward I- make them superior because most of the previously reported iodide sensors are based on the fluorescence quenching mechanism and are less sensitive. The sensing potential of sensors toward I- ions was investigated through 1H NMR titration, dynamic light scattering, Job's plots, and density functional theory analysis. Further, sensors displayed reversible behavior by the alternate addition of I- and Cu2+ ions that substantiate their role as recyclable sensors for the on-site detection of I- ions. Advantageously, fluorescence enhancement response of sensors was favorably used for fluorescence imaging of I- in live HeLa cells and the design of the logic gate. These sensors were successfully applied in diversified applications such as the preparation of sensors' coated paper strips and the determination of I- ions in blood serum, food, and real water samples.