HCP-to-FCC Phase Transformation of Ruthenium Nanocrystals Selectively Activate Hydrogen Peroxide for Boosting Peroxidase-like Activity

Due to the simultaneous activation of hydrogen peroxide (H₂O₂) and oxygen, Ru nanocrystals exhibit inherent peroxidase- and oxidase-like activities, thereby limiting their extensive application in biosensing. Phase engineering of Ru nanocrystals holds great promise for enhancing catalytic activity and selectivity but remains a challenge. Here, highly active Ru nanocrystals with a metastable face-centered cubic (fcc) structure were successfully synthesized via a facile wet-chemical method followed by an etching step, enabling selective activation of H₂O₂ and demonstrating promising peroxidase-like activity. Compared to the thermodynamically favored hexagonal close-packed Ru nanocrystals, the resultant fcc Ru shows an over 5-fold enhancement in the maximum reaction velocity of the peroxidase-like catalysis, while its oxidase-like performance exhibits a minor decline, indicating a transition from multienzyme activity to specificity. Theoretical calculations reveal that the phase transformation of Ru not only results in an upward shift of the d-band center to enhance H₂O₂ adsorption but also regulates the O-O bonding strength of H₂O₂ to achieve selective H₂O₂ activation. As a proof of concept, a colorimetric sensor based on fcc Ru nanocrystals was successfully constructed, achieving accurate and sensitive detection of organophosphorus pesticides. This work not only offers promising prospects for phase engineering of Ru nanocrystals but also highlights the significance of the Ru phase transition in hydrogen peroxide activation.