Protein-sized nanozymes «artificial peroxidase» based on template catalytic synthesis of Prussian Blue

We report on Prussian Blue based nanozymes, comparable in size with a natural enzyme peroxidase. Protein-sized nanoparticles have been synthesized in the course of reduction of ferric ion (Fe³⁺) and ferricyanide ([Fe(CN)₆]^3-) one-to-one mixture in reversed micelles (isooctane|AOT|water) used as templates. Aniline chosen as the best reductant for this aim has led to formation of composite (according to Raman spectroscopy) Prussian Blue - polyaniline nanoparticles. The protein-like size of the nanoparticles (∅ = 4 - 6 nm) has been confirmed by DLS and TEM imaging. Kinetic investigations of peroxidase-like activity in reversed micelles resulted in the catalytic rate constant belonging to the same size-dependence as regular bulk catalytically synthesized nanozymes (slope ≈ 2.6), allowing to denote the reported Prussian Blue nanoparticles synthesized in reversed micelles as nanozymes «artificial peroxidase». Hydrogen peroxide sensors made by dipping the suspension of the latter onto the electrode support, displayed two-fold higher sensitivity as compared to the Prussian Blue film-based ones. Protein-sized nanozymes «artificial peroxidase» would obviously provide an advantage over regular nanozymes in (bio)sensors and analytical kits.