Oxygen-Deficient Mn2O3 Nanosheets for Dual Colorimetric and Electrochemical Detection of Epinephrine

We report using the 2D oxygen-deficient mesoporous Mn2O3 nanosheets to act as laccase enzyme mimicked dual colorimetric and electrochemical nanosensors for highly sensitive detection of epinephrine. Scientists have been highly motivated to develop nanomaterial-based sensors for the practical detection of epinephrine (EP) in real samples. EP is a crucial biomarker for different mental disorders, including Parkinson's disease. Manganese oxides and their composites are extensively utilized as oxidase-mimicked catalysts, in which chromogenic compound is utilized for colorimetric sensing. For the first time, we utilized the 2D Mn2O3 nanosheets as laccase-mimicked nanosensors for both colorimetric and electrochemical detection without using any chromogenic compounds. The oxygen-deficient mesoporous structures of the 2D Mn2O3 nanosheets provide high surface areas and abundant reactive sites for activation and adsorption of the analytes. When the EP molecules are adsorbed onto the porous structures of the Mn2O3 nanosheets, electron transfer occurs and EP converts into adrenochrome, which is a colorful compound. The response of color change was measured in absorption intensity. The linear range of detection of the nanosensor was 1-100 mu M, and the limit of the detection (LOD) was 0.25 mu M. The Mn2O3 nanosheets were further utilized as an electrochemical sensor too for the detection of EP, and the LOD observed for the electrochemical nanosensor was 0.13 mu M with a linear range of 500 nM to 325 mu M. The nanosensor's performance was evaluated in blood serum and urine, yielding R-2 values of 0.9985 and 0.9948, respectively. This highlights the potential of the 2D Mn2O3 nanosheets for EP sensing. We believe that our laccase-mimicked 2D Mn2O3 nanosheets and their application as dual colorimetric and electrochemical nanosensors is a good platform that can be equally applied for biological and environmental applications.