Polymeric Nanocapsule Enhances the Peroxidase-like Activity of Fe₃O₄ Nanozyme for Removing Organic Dyes

Peroxidase-like nanozymes are nanoscale materials that can closely mimic the activity of natural peroxidase for a range of oxidation reactions. Surface coating with polymer nanogels has been considered to prevent the aggregation of nanozymes. For a long time, the understanding of polymer coating has been largely limited to its stabilization effect on the nanozyme in aqueous media, while little is known about how polymer coating plays a role in interaction with substrates and primary oxidants to dictate the catalytic process. This work reported a facile sequential modification of Fe3O4 nanoparticles to polyacrylamide coated nanozymes, and as low as 112 mg/L samples with only 5 mg/L Fe3O4 could nearly quantitatively (99%) remove a library of organic dyes with either H2O2 or Na2S2O8 as primary oxidants. The catalytic results and molecular simulation provide both experimental and computational evidence that the hydrogen bonding interaction between the reactant and nanozymes is key for the high local concentration hence catalytic efficiency. We envision that this work, for the first time, provides some insights into the role of polymer coating in enhancing the catalytic activity of nanozyme apart from the well-known water dispersity effect.