CuMnO2 nanoflakes as pH-switchable catalysts with multiple enzyme-like activities for cysteine detection

As delafossite type of metal oxide materials, CuMnO 2 nanoflakes show great promise for optoelectronics applications due to their excellent optical, electric and multiferroic properties. Here, we for the first time demonstrate that CuMnO 2 nanoflakes possess intrinsic activity of mimicking enzymes of peroxidase, oxidase and catalase . Through modulating the pH value, CuMnO 2 nanoflakes can catalyze the reduction of oxygen (O 2 ) and hydrogen peroxide (H 2 O 2 ) at acidic environment, and the decomposition of H 2 O 2 to produce O 2 at alkaline pH. The mechanism of their peroxidase-like activity has been proposed as the generation of hydroxyl radical ( OH). Based on the colorimetric reaction of CuMnO 2 nanoflakes and the hindrance of the peroxidase-like activity in the presence of H 2 O 2 and l -cysteine, a simple platform for l -cysteine detection with low detection limit of 11.26 μM has been developed. Compared with other bimetallic oxides, CuMnO 2 nanoflakes exhibit higher sensitivity and lower detection limit towards l -cysteine. Surprisingly, the proposed method for l -cysteine estimation can also be used in milk samples. These findings pave the way for further investigation about the catalytic activity of CuMnO 2 nanoflakes and make them a promising candidate for biomedical applications.