Fabrication and testing of a multifunctional SiO₂@ZnO core–shell nanospheres incorporated polymer coating for sustainable marine transport

We report the development of a coating system relying on the incorporation of SiO₂@ZnO core–shell nanospheres in polyurethane media as a novel approach to achieve longevity and sustainability in marine transport. This polymeric coating showed significant improvement in surface abrasion resistance, the transition from a hydrophilic state to a hydrophobic state (~ 125.2° ± 2°), improved antifungal, antibacterial and antialgae effects which make the proposed coating ideal to protect steel surfaces against biofouling. To substantiate our claims, we performed X-ray diffraction, Transmission electron microscopy, Fourier transform infrared spectroscopy, scanning acoustic microscopy, Thermogravimetric analysis (TGA), contact angle measurements, antimicrobial (antialgal, antibacterial, antifungal) tests and Taber abrasion tests (ASTM D1044 and D4060) to highlight the mechanical and biological functionality as well as the bonding configuration of this coating. The wear analysis of the Taber abraded coating using SEM and optical microscopy showed significant improvement in the adhesion and shear resistance achieved by the SiO₂@ZnO core–shell nanospheres incorporated PU coating which was a contrasting feature compared to using PU alone. The overall investigations we performed led us to find out that the addition of 4% (wt.) SiO₂@ZnO core–shell nanoparticles to the PU media deposited on the low carbon steel surface demonstrated remarkable antimicrobial performance with almost no bacterial growth, significant reductions in growth for algae to about 90% and fungus to about 95%.