Self-Healing Antifouling Hydrogel Sensors Enabling Long-Term Monitoring of Potassium Ions in Marine Environments

Precise monitoring of ions in marine environments is crucial for maintaining ecosystem stability and ensuring marine food safety. However, nonspecific adsorption induced by marine microorganisms severely compromises the long-term performance of electrochemical sensors, accelerating signal degradation and device failure. Here, we report a self-healing, antifouling potassium ion-selective electrode enabled by a peptide hydrogel-based antifouling layer incorporating Fmoc-FF dipeptides (ekF), which endows the system with intrinsic self-repair capability. The resulting sensor exhibits exceptional long-term stability and antifouling performance under marine conditions. The drift over a 24 h period is merely 0.2 mV h-1. The ekF layer effectively suppresses biofouling, yielding ultralow bacterial adhesion rates of 0.15% for Escherichia coli (E. coli) and 0.024% for Staphylococcus aureus (S. aureus), while also efficiently inhibiting the colonization of Chlorella. The incorporation of the terminal Fmoc-FF group markedly enhances the mechanical robustness of the hydrogel, achieving a high storage modulus (G') of approximately 105 Pa, together with rapid gelation within 2 s. Importantly, the dynamic supramolecular interactions introduced by Fmoc-FF enable self-healing of the antifouling layer after mechanical damage, thereby substantially extending sensor operational lifetime. Consequently, the lifetime of the sensor is prolonged from 6 to 10 days upon introduction of the antifouling layer and further extended to 18 days after integration of self-healing functionality. This work establishes a robust, self-healing antifouling electrochemical sensing platform for long-term ion monitoring in marine environments and provides a broadly applicable strategy to overcome biofouling-induced instability in marine sensing technologies.