Facile, green and scalable synthesis of single-layer manganese dioxide nanosheets and its application for GSH and cTnI colorimetric detection.

Manganese dioxide (MnO) nanosheets possess unique physical and chemical properties, making them widely applicable in various fields, such as chemistry and biomedicine. Although MnO nanosheets are produced using bottom-up wet chemistry synthesis methods, their scale is below the gram level and requires a long processing time, restricting their effective scale-up from laboratory to market. We report a facile, green and scalable synthesis of MnO nanosheets by mixing Shiranui mandarin orange juice and KMnO for 30 minutes. We produced more than one gram (1.095) of MnO nanosheets with a 0.65 nm mean thickness and a 50 nm mean lateral size. Furthermore, we established a visual colorimetric biosensing strategy based on MnO nanosheets for the assay of glutathione (GSH) and cardiac troponin I (cTnI), offering high sensitivity and feasibility in clinical samples. For GSH, the limit of detection was 0.08 nM, and for cTnI, it was 0.70 pg mL. Meanwhile, the strategy can be used for real-time analysis by applying a smartphone-enabled biosensing strategy, which can provide point-of-care testing in remote areas.