Simple Colorimetric and Fluorescence Chemosensing Probe for Selective Detection of Sn²⁺ Ions in an Aqueous Solution: Evaluation of the Novel Sensing Mechanism and Its Bioimaging Applications

Abstract

An easily accessible colorimetric and fluorescence probe 4-((3-chloro-1,4-dioxo-1,4-dihydronaphthalen-2-yl)amino)benzenesulfonamide (<b>4CBS</b>) was successfully developed for the selective and sensitive detection of Sn²⁺ in an aqueous solution. The sensing mechanism involves reduction of -C═O into -C-OH groups in <b>4CBS</b> upon the addition of Sn²⁺, which initiates the fluorescence turn-on mode. A better linear relationship was achieved between fluorescence intensity and Sn²⁺ concentration in the range of 0-62.5 μM, with a detection limit (LOD) of 0.115 μM. The binding mechanism of <b>4CBS</b> for Sn²⁺ was confirmed by Fourier transform infrared analysis, NMR titrations, and mass (electrospray ionization) spectral analysis. Likewise, the proposed sensing mechanism was supported by quantum chemical calculations. Moreover, bioimaging studies demonstrated that the chemosensing probe <b>4CBS</b> is an effective fluorescent marker for the detection of Sn²⁺ in living cells and zebrafish. Significantly, <b>4CBS</b> was able to discriminate between Sn²⁺ in human cancer cells and Sn²⁺ in normal live cells.