Facile fabrication of anti-fouling polymeric membrane potentiometric ion sensors based on a biocide 4,5-dichloro-2-n-octyl-4-isothiazolin-3-one-containing self-adhesive waterborne polyurethane coating†

Polymeric membrane ion-selective electrodes (ISEs) are a powerful tool for ion sensing. However, their application in complicated environmental water samples is still a challenge owing to the occurrence of electrode biofouling. To address this issue, we propose a facile and effective method for enhancing the anti-biofouling properties of these sensors. A self-adhesive coating based on waterborne polyurethane and biocide 4,5-dichloro-2-n-octyl-4-isothiazolin-3-one is prepared. The anti-fouling potentiometric ion sensor can be obtained by simply drop-casting such a self-adhesive coating. The classical poly(vinyl chloride) membrane-based Ca²⁺-ISE is chosen as a model. Compared to the unmodified pristine Ca²⁺-ISE, the obtained anti-fouling sensor exhibits remarkable improved anti-fouling properties such as a much lower adhesion rate of bacteria (96.8% reduction after modification), higher anti-microbial rate and superior anti-algal properties. More importantly, the proposed potentiometric sensor displays excellent long-term response stability even when immersed in real seawater or a solution with high levels of algae for 30 days. It is anticipated that this simple and flexible approach could be extended to fabricate other anti-fouling electrochemical or optical membrane sensors. This work may lay an important foundation for development of anti-fouling chemical sensors for environmental water monitoring.