Visible-light-responsive Fe2O3–TiO2–carbon dot nanocomposite coatings for enhanced biofouling mitigation in aquaculture cage nets

Abstract

A photocatalytic antifouling coating was designed for aquaculture cage nets, as biofouling is a persistent challenge in aquaculture that substantially reduces operational efficiency and compromises the economic performance of the systems. A nanostructured composite was developed using nano-titanium dioxide (TiO₂), iron(III) oxide (Fe₂O₃), and carbon dots (CDs). The antifouling efficacy of the composite was evaluated by applying it onto a (3-glycidyloxypropyl)trimethoxysilane (silane)-pretreated polyethylene substrate, followed by immersion in natural estuarine waters. This ternary photocatalytic composite, formed by the interaction between the CC bond of CDs and inorganic oxides, exhibited a reduced band gap from 4 eV to 1.7 eV by suppressing electron–hole recombination. The uniform distribution in the composite was evidenced by XRD, the characteristic peaks of TiO₂ and Fe₂O₃ suggested nanoscale crystallinity, and the 2θ = 21° peak suggested the presence of low-crystalline CDs in the matrix, which was confirmed by transmission electron microscopy. The nanocomposite uniformly coated over silane-pretreated polyethylene exhibited strong interfacial bonding between CD aromatic moieties and glycidyloxy C–O–C groups. Nets coated with a 0.05% FeTiCD nanocomposite exhibited excellent biofouling resistance in a six-month field trial. Fe(III) doping introduced mid-gap states, enabling efficient electron transfer to CDs and sustained reactive oxygen species (ROS) production, thereby disrupting the attachment of biofouling organisms. This nanocomposite offers a scalable, low-impact antifouling solution that supports more sustainable aquaculture operations.