“…MnO 2 nanosheet, a type of transition metal oxide, has low toxicity and good biocompatibility, rich redox chemistry, and excellent catalytic and oxidase-like activity. Owing to its superior chemical and physical properties, many researchers have combined MnO 2 nanosheets with chem/biosensing techniques for the determination of dopamine, 14 hydroquinone, 15 glutathione, 16 salmonella, 17 etc . More importantly, different from the reported peroxidase mimics for colorimetric sensing, MnO 2 nanosheets represent a label-free colorimetric probe that can oxidize the colorless 3,3′,5,5′-tetramethylbenzidine (TMB) into a blue product (oxTMB), which has a characteristic UV–vis spectrum absorbance at 652 nm, without the addition of H 2 O 2 .…”