Highly sensitive colorimetric detection of atmospheric sulfate formation-involved substances using plasmonic molybdenum trioxide nanosheets

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© 2020 Elsevier B.V. The ongoing urban air pollution has resulted in an increased demand for detecting atmospheric sulfate formation-involved substances. Here, we present a series of colorimetric assays based on plasmonic MoO3-x nanosheets for visual colorimetric detection of atmospheric sulfate formation-involved substances, including hydrogen peroxide (H2O2), Fe2+/Fe3+, bisulfite (HSO3−), and sulfur dioxide (SO2). We show that the plasmonic MoO3-x nanosheets with blue color can be oxidized by hydroxyl radicals ([rad]OH) generated by the Fenton reaction between Fe2+/Fe3+ and H2O2 to produce colorless MoO3 nanosheets, resulting in a distinct absorbance change. However, when HSO3−/SO2 is introduced, the [rad]OH will react with them to yield sulfate, which inhibits the oxidation of MoO3-x nanosheets, leading to the color recovery. Using these detection systems, we determine H2O2, Fe2+, Fe3+, and HSO3− with detection limits of 60 nM, 50 nM, 400 nM, and 1 μM, respectively. Especially, SO2 is selectively assayed with an ultralow detection limit, down to 50 ppb level. In addition, the present colorimetric assay is further utilized to detect SO2 in real air with a good accuracy to demonstrate the practicality of the colorimetric method.

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Sensors and Actuators, B: Chemical