Metal-free carbon-dots nanozyme with oxidase-like activity as photocatalysts for highly efficient detection/reduction of Cr(VI) and antibacterial application

Wastewater containing Cr(VI) and bacteria indicated significant challenges and threats to public health and ecological environments. Hence, it is necessary to construct novel method for detecting and treatment such wastewater. Non-metal-doped carbon dots nanozyme (TA-CDs) were effectively synthesized by one-pot hydrothermal method utilizing tartaric acid (TA) and L-tryptophan (L-trp) as ingredients. TA-CDs revealed excellent water solubility, optical stability, and biocompatibility. Particularly noteworthy, TA-CDs (150 μg/mL) exhibited outstanding light-responsive oxidase-like activity, efficiently generating ${\text{e}}^{\text{-}}$, ${\text{O}}_{\text{2}}^{\bullet -}$ and ${\text{CO}}_{\text{2}}^{\bullet \text{-}}$. Furthermore, TA-CDs illustrated an exceptional linear relationship with Cr(VI) in an extensive detection range and low detection limits (0.51 μM), as well as high selectivity and anti-interference properties. Simultaneously, TA-CDs also demonstrated significant photocatalytic activity, achieving approximately 70.26 % reduction in 40 mg/L Cr(VI) and realized excellent antimicrobial performance (inhibition rates of 97.18 % and 82.67 % against E. coli and S. aureus, respectively). In short, this research not only provided a multifunctional carbon-dots nanoenzyme for recognition, photoreduction of Cr(VI), and photodynamic antibacterial application, but also offered novel strategy and methodology for detection and treatment of water containing heavy metals and microorganisms.