Design of multiple-target chemoprobe: “naked-eye” colorimetric recognition of Fe3+ and off–on fluorogenic detection for Hg2+ and its on-site applications

WOS:000739252600001A novel multiple-target chemoprobe (E)-N′-((9-pentyl-9H-carbazole-3-yl)methylene)thiophene-2-carbohydrazide (CTH) was designed, successfully synthesized and employed for the detection of Hg2+ and Fe3+ ions as off–on fluorometric and colorimetric responses, respectively, in H2O/DMF (10/90, v/v, Britton–Robinson buffer, pH 7) medium. The chemoprobe CTH demonstrated high sensitivity towards Hg2+ and Fe3+, among wide range of competitive cations with low recognition limits of 5.1 nM and 5.89 µM, respectively. The complexes of the chemoprobe CTH were synthesized and characterized by 1H-NMR titration, FT-IR and MALDI-TOF MS techniques, which confirmed the binding stoichiometries and the possible sensing mechanisms, were suggested based on the hydrolysis reaction of C=N group. The practical utility of the chemoprobe CTH was revealed in quantification of the trace amounts of Hg2+ and Fe3+ in water samples. Also, a silica-coated test paper was used for the fluorescent monitoring of Hg2+, providing a novel approach for the quantitative and on-site detection in real samples. More excitingly, a smartphone application was employed for the visual detection of Fe3+ by recognizing the RGB (red/green/blue) of the chemoprobe CTH solution. Graphical abstract: [Figure not available: see fulltext.]