MnCo2S4 nanozymes with dual enzyme-mimicking activities for catalytic degradation and optical monitoring of organic pollutants

초록

Nanozymes have attracted considerable attention as robust catalytic alternatives to natural enzymes for catalytic degradation and monitoring of environmental pollutants. Herein, we report manganese cobalt sulfide nanozymes (MnCo2S4 NZs) exhibiting dual peroxidase- and laccase-like activities. The coexistence of Mn and Co active sites enables both reactive oxygen species (ROS)-mediated and ROS-independent catalytic pathways, resulting in enhanced catalytic efficiency and excellent operational stability across a broad range of pH and temperature conditions. The peroxidase-like activity of MnCo2S4 NZs efficiently catalyzes the degradation of organic pollutants, including Neutral Red and Crystal Violet, achieving approximately 99% removal within 20 min through the generation of highly reactive hydroxyl radicals (center dot OH), as confirmed by radical scavenger experiments. In addition, their intrinsic laccase-mimicking oxidation activity enables the transformation of the hazardous aromatic compound o-phenylenediamine (OPD) into 2,3-diaminophenazine (DAP), which serves as both a chromophoric and fluorescent product. The formation of DAP allowed convenient optical monitoring of the catalytic transformation through absorbance and fluorescence signals over a broad concentration range. Furthermore, MnCo2S4 NZs maintained high catalytic activity in tap water and river water spiked with OPD, demonstrating their practical applicability in complex aqueous matrices. Owing to their high catalytic activity, stability, reusability, and optical monitoring capability, MnCo2S4 NZs represent promising multifunctional NZs for the catalytic degradation and analysis of organic pollutants.

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