Preparation of a Nanosilica-Silane-Iopromide Superhydrophobic Coating for Physical-Based Antibacterial Activity

Abstract Microbial contamination causes severe biofouling in marine environments, whereas conventional biocide-based strategies are often limited by durability and environmental concerns. Herein, a fluorine-free superhydrophobic coating with physical-based antibacterial activity was developed using nanosilica (SiO2) as a micro−nano structural building unit, iopromide as an interfacial modifier, octadecyltrichlorosilane (OTS) and methyltrimethoxysilane (MTMS) as hydrophobic modifiers. The optimized SiO2@OTS&MTMS-I-4.5 coating exhibited excellent superhydrophobicity, with a water contact angle (WCA) of 154.47° ± 1.20°, a sliding angle (SA) of 2.05° ± 1.03°, and a surface energy of 12.49 mJ·m−2. FT-IR and XPS analyses confirmed the formation of a cross-linked Si−O−Si network and the stable incorporation of iopromide-related chemical groups. SEM-based image analysis further showed that the projected protruding-feature coverage increased to 96.45% for SiO2@OTS&MTMS-I-4.5, indicating more continuous microscale rough-feature coverage on the optimized coating. The coating retained superhydrophobicity during 6 h immersion in aqueous solutions with pH values ranging from 1 to 14 and exhibited self-cleaning behavior. Furthermore, the SiO2@OTS&MTMS-I-4.5 coating showed reductions in recovered viable bacteria of 59.57% for Escherichia coli and 54.66% for Staphylococcus aureus under the tested co-culture conditions, while CLSM analysis revealed surface bacterial coverage reductions of 98.93% and 65.89%, respectively. The physical antibacterial effect is mainly associated with the nanosilica-derived hierarchical roughness and the low-surface-energy silane network, which help stabilize a trapped air layer at the solid−liquid interface and reduce bacterial contact. Overall, this work provides a fluorine-free nanosilica-silane coating strategy for reducing bacterial surface accumulation through physical anti-adhesion.