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

4-Nitrophenol (4-NP) is a common stuff involved in industrial production as well as a toxic pollutant which poses a threat to the environment and human health if not handled properly. Here, we have designed and synthesized two new metal-organic frameworks (MOFs), namely Ce-MOF-1 and Ce-MOF-2 with both fluorescent and electrochemical activities, which exhibite 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 the detection limits of 1.25 and 0.78 μM, respectively. Simutanously, in electrochemical sensing, 4-NP is irreversibly reduced to 4-hydroxylamine phenol under the catalysis of Ce-MOFs coating on electrode, which exhibit higher accuracy than fluorescence with detection limits of 0.36 and 0.41 μM, respectively, for the quantitatively sensing of 4-NP. Due to their complementary immunity to interference in electrochemical and fluorescence methods for 4-NP detection, Ce-MOFs exhibit more accurate 4-NP detection ability compared to other sensors. Finallly, both Ce-MOFs demonstrate excellent stability, reproducibility and selectivity in dual-mode sensing of 4-NP in tap water, that provides superior adaptability, reliability and accuracy compared to the traditional single-mode sensing method.