Defect-rich and ultrathin nitrogen-doped carbon nanosheets with enhanced peroxidase-like activity for the detection of urease activity and fluoride ion

Although carbon nanozymes have attracted great interest due to their good biocompatibility, low cost, and high stability, designing high-active carbon nanozymes still faces great challenges. Herein, ultrathin nitrogen-doped carbon nanosheets with rich defects (d-NC) were prepared through a high-temperature annealing process, using potassium chloride and ammonium chloride as templates. Owing to the large specific surface area, rich defects and the high exposure of active sites, the proposed d-NC nanozymes exhibited excellent peroxidase-like activity. The d-NC nanozymes possess maximal reaction velocity and their specific activity is 9.4-fold higher than that of nitrogen-doped carbon nanozymes, indicating that the induced defects can boost the catalytic performance. Benefited from the good peroxidase-like activities of d-NC nanozymes, the colorimetric sensing platforms were constructed for the detection of urease activity and fluoride ion, exhibiting satisfactory stability and selectivity. This study not only offers a way to synthesize carbon nanozymes with improved enzyme-like activities but also broadens their applications in colorimetric biosensing. (C) 2021 Published by Elsevier B.V. on behalf of Chinese Chemical Society and Institute of Materia Medica, Chinese Academy of Medical Sciences.