Dual-mode Ce-MOF-based sensors for the fluorescent/electrochemical detection of 4-nitrophenol

Abstract

4-Nitrophenol (4-NP) is a common material in industrial production and a toxic pollutant, which poses a threat to the environment and human health if not handled properly. Herein, we designed and synthesized two new metal–organic frameworks (MOFs), namely, Ce-MOF-1 and Ce-MOF-2, with both fluorescent and electrochemical activities, which exhibited a capability for the dual-mode sensing of 4-NP. The fluorescence emission spectra at 366 nm of both Ce-MOF-1 and Ce-MOF-2 displayed a significant turn-off signal affected by the competitive absorption and photoelectron transfer of 4-NP, with detection limits of 1.25 and 0.78 μM, respectively. Simultaneously, in electrochemical sensing, 4-NP was irreversibly reduced to 4-hydroxylamine phenol under the catalysis of Ce-MOF-1 and Ce-MOF-2 coated on electrodes, which exhibited a higher accuracy than fluorescence, with detection limits of 0.36 and 0.41 μM, respectively, for the quantitative sensing of 4-NP. Due to their complementary immunity to interference in electrochemical and fluorescence methods for 4-NP detection, the Ce-MOFs exhibited a more accurate 4-NP detection ability than other sensors. Finally, both Ce-MOFs demonstrated excellent stability, reproducibility, and selectivity in the dual-mode sensing of 4-NP in tap water, providing superior adaptability, reliability and accuracy compared to the traditional single-mode sensing method.