Architected Redox-Active Colloids for Tunable Charge Transport in Aqueous Systems

Colloids, a foundational class of soft matter, are increasingly explored as programmable frameworks for electrochemical function. Traditionally regarded as passive carriers, colloids can be architected to form internal pathways for ion and electron transport. Their dispersibility, processability, and compatibility with aqueous media make them promising candidates for safe and sustainable redox systems, yet aqueous electrolytes remain limited by narrow potential windows, poor stability of redox sites, and sluggish charge transport. Architected redox-active colloids (RACs) composed of polystyrene (PS) spheres embedded with ethyl viologen (EV) address these limitations. Fabricated through a swelling-mediated loading process, RACs allow independent control of particle size, redox-site density, and internal EV organization. This design enables direct control over redox capacity and reversibility, surpassing what is accessible in dissolved redox molecules or simple colloidal dispersions. Colloids with densely organized and spatially continuous EV domains exhibit enhanced charge transport and stability, demonstrating that internal architecture, rather than total redox content alone, governs electrochemical performance. These findings establish RACs as a robust and flow-compatible platform for aqueous electrochemical systems and provide a generalizable strategy for designing soft colloidal materials with integrated charge transport functionality.