Bifunctional antifouling strategy based on polypeptide hydrogels for enhancing long-term stability of potassium ion...

The detection of potassium ions (K⁺) is of critical importance in the fields of marine science and health monitoring. Although solid-contact ion-selective electrodes (SC-ISEs) offer advantages for on-site detection, they are susceptible to biofouling, which reduces their long-term stability. An antifouling potassium ion sensor was developed through the modification of a potassium ion-selective electrode with a polypeptide hydrogel incorporated with zinc oxide nanoparticles (ZnO NPs). The zwitterionic polypeptide hydrogel effectively inhibits the adhesion of biofoulants, while under ultraviolet irradiation, the ZnO NPs can generate reactive oxygen species that efficiently eliminate bacteria, such as E. coli and S. aureus, on the electrode surface, thereby establishing a bifunctional antifouling and antibacterial surface. Furthermore, the sensor also exhibits significant inhibitory effects on Chlorella adsorption. In complex systems such as seawater, sweat and urine, the antifouling potassium ion sensor demonstrated long-term stability in potential responses when continuously immersed in these complex media. More importantly, the sensor was capable of accurately determining potassium ions in various complex real samples as verified by the inductively coupled plasma mass spectrometry, demonstrating significant potential for long-term monitoring of potassium ion in complex environments. This work provides irrefutable evidence that a bifunctional coating integrating zwitterionic polypeptide hydrogel with ZnO NPs significantly enhances the antifouling and antibacterial properties of K⁺-ISE. The strategy offers an efficient way to develop practical environmental monitoring devices with robust performances.