In this study, we used a simple and rapid colourimetric reaction for visual sensing of Fe2+ and Pb2+ ions in water by employing nano-MnO2 as a natural oxidase mimic to respectively catalyse ABTS and TMB in citrate-phosphate buffer solution (C-PBS) at
25°C and pH 3.8. It was found that nano-MnO2 possessed highly oxidase-mimicking activity with the K
m values of 0.030 and 0.027 toward ABTS and TMB, respectively, indicating TMB had a stronger affinity on nano-MnO2 than ABTS. Interestingly, the presence
of 0.01 mmol·L−1 Fe2+/Pb2+ ion was able to significantly down-regulate the activity of MnO2 nanozyme in nano-MnO2-mediated ABTS reaction processes (P < 0.01), which mainly due to the strong adsorption of metal ion
toward nano-MnO2 surface via the electrostatic attractions, thus leading to the passivation and inactivation of MnO2 nanozyme catalytic activity. Thereinto, Fe2+ reacted with multivalent manganese by oxidation-reduction, while Pb2+ was specifically
adsorbed onto the surface of MnO2 nanozyme and formed complexes. Notably, only Fe2+ ion inhibited the activity of MnO2 nanozyme-TMB with a detection limit as low as 1.0 μmol·L−1. In MnO2 nanozyme-ABTS sensing systems, Fe2+
and Pb2+ ions detection limit of 0.5 and 2.0 μmol·L−1 were, respectively, achieved with a linear response range of 0–0.02 and 0–0.8 mmol·L−1, implying the developed MnO2 nanozyme-ABTS sensor was potentially
applicable for the visual determination of Fe2+ and Pb2+ ions in water. In the real water samples, MnO2 nanozyme-ABTS achieved high accuracy (relative errors: 3.4‐10.5%) and recovery (96‐110%) for respective detection of Fe2+ and Pb2+
ions. The simple and rapid MnO2 nanozyme-ABTS sensing systems might provide a practical assay for visual detection of Fe2+ and Pb2+ ions in the environmental water samples.
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ABTS and TMB;
Fe2+ and Pb2+ ions;
Document Type: Research Article
Anhui Province Key Laboratory of Farmland Ecological Conservation and Pollution Prevention, School of Resources and Environment, Anhui Agricultural University, Hefei, China
College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing, China
Department of Crop and Soil Sciences, University of Georgia, Griffin, GA, USA
May 3, 2019
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