Electrodeposition of capsaicin-induced ZnO/Zn nanopillar films for marine antifouling and antimicrobial corrosion

Zinc oxide with the morphology of nanopillar is promising marine antifouling materials as they can kill adhered bacteria and fungi. The zinc oxide with the morphology of nanopillar has shown super-antibacterial properties on galvanized steel, which makes ZnO/Zn nanopillar films promising in marine antifouling and antimicrobial corrosion. Thus, an efficient approach to coat ZnO/Zn nanopillar films on steel is of great significance. The electrodeposition method is a universal method for both ZnO crystals and galvanized coatings, and it can control the morphologies and structures of the resultant films. Therefore, in this study, capsaicin was added into an alkaline electrolyte to induce the formation of ZnO nanopillars. Due to capsaicin addition to the electrolyte, ZnO/Zn nanopillar films were obtained in a single cathodic electrodeposition. The added capsaicin in the electrolyte was absorbed on the electrodepositing surface by the functional –NH– groups in amide bond. The Zn(OH)42− diffusion was promoted by negatively shifted electrodepositing potential. The scanning electron microscopy (SEM) and X-ray diffraction (XRD) results illustrate that regular ZnO nanopillars were obtained when the capsaicin concentration was 0.6 g L−1 in the electrolyte. The resultant ZnO/Zn nanopillar films showed high antibacterial properties in Escherichia coli suspended solutions and relatively low living bacterial coverage, indicating promising application in marine antifouling. Electrochemical evaluation revealed that the obtained capsaicin-induced ZnO/Zn nanopillar films exhibited significantly enhanced corrosion resistance in a sulfate-reducing bacteria (SRB) medium. Moreover, the results illustrate that adding 0.6 g L−1 concentration of capsaicin in the electrolyte yielded the best films, which featured the lowest bacterial coverage and highest corrosion resistance.