Multi-Scale Water Modulation for Regulating Water Reactivity and Suppressing Nanoscale Zero-Valent Iron (nZVI)...

Water is not a passive solvent but an actively tunable participant in aqueous-phase redox processes, whose reactivity can be regulated by modulating its molecular states and dynamics. Here, we introduce a multi-scale water modulation strategy using a hydrophilic polysaccharide network to reorganize the aqueous environment and suppress the corrosion of nanoscale zero-valent iron (nZVI). At the molecular scale, the polysaccharides tune free water (FW) into bound and intermediate water (BW/IW), which together account for ∼45% of total water. This water-state redistribution elevates the reaction barrier for H₂O-Fe(0) interactions from 8.2 eV (FW) to 10.5 eV (BW), and the observed reaction rate constant (k_obs) shows a strong linear dependence on the BW+IW fraction (R² ≈ 0.99). At the nanoscale, the network imposes hydrophilic confinement (mesh size ≈ 1.1 nm) that restricts water access to reactive Fe(0) sites, causing a rapid attenuation of early-stage reactions (<12 days). At the macroscale, the modulated water forms a viscoelastic matrix (G' > G″) that retains in situ-generated H₂ microdomains, creating interfacial shielding that suppresses prolonged reactions (>12 days). By linking water's molecular organization to macroscopic redox behavior, this work provides a framework for using the water modulation to stabilize corrosion-sensitive nanoparticles.