Naphthoquinone-Based Colorimetric and Fluorometric Dual-Channel Chemosensor for the Detection of Fe2+ Ion and Its Application in Bio-Imaging of Live Cells and Zebrafish

A new naphthoquinone-based chemosensor 2-((3-hydroxyphenyl)­amino)-3-(phenylthio)­naphthalene-1,4-dione (2HPN) was successfully synthesized for the selective detection of Fe2+. The sensing property of the chemosensor 2HPN was evaluated in aqueous acetonitrile (CH3CN) medium by a fluorescence emission method. The metal-binding studies of the ligand 2HPN showed selective “turn-on” fluorescence responses for Fe2+ (K a = 1.0 × 106 M–1). The detection limit of the ligand 2HPN to Fe2+ was calculated to be 0.272 μM, which is lower than the World Health Organization recommendation (0.3 mg/L) in drinking water. The most significant feature of the obtained chemosensor 2HPN is its ability to sense Fe2+ via naked-eye detection over various metal ions. The chemosensor operated via the intramolecular charge transfer effect, which was supported by Fourier transform infrared analysis, NMR titrations, and quantum chemical calculations. The efficiency of the chemosensor 2HPN as a biomarker for Fe2+ was successfully proven by imaging in human cancer cells and zebrafish. Thus, the chemosensor 2HPN could be a useful biomarker for the precise sensing of Fe2+ in clinical diagnosis.