Correlations Between Colloidal Stability and Peroxidase Activity of Prussian Blue Nanozymes in Salt Solutions

Prussian blue (PB) nanozymes have emerged as durable enzyme-mimicking catalysts with broad applications across many fields. Practical uses often involve exposure to salinity that influences their colloidal and catalytic behaviors, yet the specific effects of ions on PB particles are underexplored. This study investigates how electrolyte type and concentration affect the colloidal stability and enzyme-like activity of PB nanozymes using monovalent (NaCl, KCl, CsCl) and multivalent ions (CaCl₂, LaCl₃). Electrophoresis and dynamic light scattering measurements revealed that both concentration and ion composition significantly affect stability with specific ion adsorption altering charge density and aggregation, consistent with the DLVO theory. Findings further indicate that higher ionic strengths compress the electric double layer, improving substrate accessibility and accelerating horseradish peroxidase (HRP)-like catalytic reactions. Remarkably, Cs⁺ ions substantially boost activity through their unique ability to disrupt water structure and integrate into PB's lattice. These findings highlight the importance of considering ion specificity when designing PB-containing dispersions for optimal stability and catalytic performance.