A bimetallic core-shell Cu@MnO nanozyme with enhanced oxygen activation for efficient oxidase-like activity.

The construction of bimetallic catalysts with two catalytic sites is reported to be an innovative and effective approach to enhance catalytic activity. Accurate structural design is one of most important approaches in regulating the compatibility of the synergistic effects between the two catalysts of bimetallic nanozymes but remains an enormous challenge. In this study, the Cu@MnO bimetallic catalyst with a core-shell structure is designed and synthesized using CuO precursor as the sacrifice template. The bimetallic oxide Cu@MnO nanozyme exhibits excellent oxidase-mimicking activity to catalyze 3,3'5,5'-tetramethylbenzidine (TMB) within 1 min. Density functional theory calculations demonstrate that the enhanced absorption and activation of O near the bimetallic catalyst sites via the synergistic and augmenting effects between the Cu and Mn sites. Based on the efficient oxidase-like activity of the Cu@MnO nanozyme, we propose a colorimetric assay and exhibit the most excellent analytical performances reported so far in the colorimetric detection of uric acid (UA). The linear range is 0.1-1500 μM in solution buffer and 0.5-1000 μM in human blood serum, with the limit of detection of 0.036 μM and 0.16 μM, respectively. According to the Receiver Operating Characteristic (ROC) curve, the Cu@MnO nanozyme shows a high precision in quantifying real clinical blood samples with the sensitivity and specificity above 90 %. The proposed core-shell Cu@MnO bimetallic catalyst not only provides a simple method for UA detection but also sheds light on the construction of other nanozyme-based biosensing platforms.