Improving the Environmental Compatibility of Marine Sensors by Surface Functionalization with Graphene Oxide

Improving the durability relating to biofouling resistance is still a major challenge for sensors applied in marine monitoring. Herein, a novel antifouling approach implementing biofouling resistance without compromising the sensor's performance is proposed. A polymeric membrane calcium ion-selective electrode (Ca²⁺-ISE) is chosen as a model sensor. An antifouling coating based on graphene oxide (GO) can be formed on the sensor's surface via the layer-by-layer technique in a simple and controllable manner. The GO coating works as a protection layer to impede the settlement of marine bacterial cells on the sensor surface due to its dual functionality of both antiadhesive and antimicrobial properties. The assembly of the GO coating does not influence the sensor's performance in terms of linear range and response slope. The biofouling resistance of the proposed sensor to marine bacterial cells is evaluated by using the colony-forming unit (CFU) counting method and confocal laser scanning microscopy analysis. An improved antimicrobial activity and a significant decrease in the adsorption of bacterial cells are observed for the GO-coated Ca²⁺-ISE. Moreover, negligible change is observed in the analysis performance of the GO-coated Ca²⁺-ISE after 7 day exposure to a rather high concentration marine bacterial suspension of ∼10⁹ CFU mL^-1. This work provides an efficient strategy of developing GO-based antifouling coatings to improve the environmental compatibility of marine sensors.