A reaction based dual-modal probe for fluorescent and photoelectrochemical determination of thiophenol

The analytical method with dual-modal signals has the merits of each response mode and thus can achieve high accuracy, reliability, and adaptability. In this study, we report a dual-modal probe (DMP), which can realize both fluorescence (FL) and photoelectrochemical (PEC) detection of thiophenol (TP). The probe DMP was prepared by incorporating the recognition moiety (dinitrophenyl, DNP) for TP into a precursor molecule of coumarin dye. In aqueous solution, DMP can specifically react with TP to remove the DNP group and further undergoes intramolecular cyclization to generate a coumarin dye with strong fluorescence emission. After being covalently attached to the surface of TiO2 substrate, DMP can also display a similar structure response to TP, and the afforded product has an enhanced photoelectric effect. Thus DMP can realize both “OFF-ON” fluorescence and photocurrent signals in responding to TP. The dual-modal probe has high specificity and sensitivity to TP, and the detection limits were 11 nM and 32 nM for fluorescence and photoelectrochemical sensing modes, respectively. In addition, DMP can realize fluorescence imaging of TP in living cells and PEC detection of TP in real water samples. The proposed dual-modal probe based on the reactive small organic molecule provides a universal strategy for the development of efficient dual-mode assays for other important environmental and biological targets.