Modulation of charged chemical transport by electrostatic forces in polyelectrolyte hydrogels

초록

Polyelectrolyte hydrogels are promising electrolytic media for interfacing soft biological systems with electronics. We investigated how fixed charges in 2-acrylamido-2-methyl-1-propane sulfonate (AMPS-) and (3-acrylamidopropyl)trimethylammonium (APTQ+) hydrogels affect steady-state currents (ISS) of ferricyanide (Fe (CN)63-) and hexaammineruthenium(III) (Ru(NH3)63+) measured at Au and carbon ultramicroelectrodes (UMEs) under varying ionic strengths. Ferricyanide showed significantly suppressed current in APTQ+ gels due to electrostatic attraction and partial immobilization, but remained mobile in AMPS-gels. UV-Vis spectra confirmed the distribution trends of Fe(CN)63-within the gels, supporting the electrochemical findings. In contrast, the positively charged Ru(NH3)63+ displayed reduced mobility in AMPS-gels and relatively free diffusion in APTQ+ gels. Adjusting NaCl concentration modulated electrostatic screening and thus probe transport. These results demonstrate that fixed charge interactions within hydrogels can critically influence ion diffusion and redox activity. This must be carefully considered in the design of hydrogel-based systems for sensing, energy storage, and bioelectronic applications.

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