Integrated Capsaicin-Functionalized Superhydrophobic Photothermal Coating for Sustainable Antifouling Control at the...

Marine biofouling at the dynamic air-seawater interface is a critical challenge in the protection of marine equipment and poses a severe threat to offshore infrastructures. In response, herein, an integrated capsaicin-functionalized superhydrophobic photothermal coating was developed for sustainable antifouling application. This coating is constructed on a robust polythiourethane matrix, into which a covalently tethered capsaicin analog and fluorinated segments are molecularly engineered to confer persistent bioactivity and low surface energy. The incorporation of hydroxylated carbon nanotubes (CNT-OH) creates a hierarchical microstructure and enables efficient broadband solar-thermal conversion. The optimized coating exhibits exceptional superhydrophobicity (water contact angle >151°, contact angle hysteresis <5°), rapid photothermal response (reaching ∼79°C under 1-sun irradiation), and remarkable mechanical durability. Biological evaluations demonstrate outstanding antifouling performance against bacteria (E. coli), microalgae (Chlorella), and macrofoulers (mussels) under both dark and illuminated conditions, while showing negligible acute toxicity to Artemia nauplii. The superior performance stems from a synergistic dual-mode mechanism: the integrated effects of contact-active approach-avoidance and Cassie-state superhydrophobicity passively inhibit fouling adhesion, while the CNT-mediated photothermal action provides an additional active contribution to the detachment or inactivation of residual organisms under sunlight. This work provides a novel, eco-friendly, and energy-saving strategy for antifouling protection at the air-seawater interface.