Green-synthesized TiO2@Cu2O hybrid nanoparticles for mechanically reinforced, antibacterial, and antifouling poly(vinyl chloride–vinyl isobutyl ether) coatings

The development of multifunctional coatings with antimicrobial, self-cleaning, and protective performance has intensified interest in nanostructured additives. Rutile TiO₂ offers strong light scattering, UV resistance, stability, and low cost, whereas Cu₂O provides intrinsic antibacterial activity via copper ion release and reactive oxygen species generation. Constructing TiO₂@Cu₂O core–shell heterostructures enhances charge separation, broadens visible-light absorption, and promotes synergistic antibacterial effects. Herein, TiO₂@Cu₂O nanopowders were green-synthesized with L-ascorbic acid being used as a reductant, polyethylene glycol and Tween 80 as surfactants. XRD, TEM, SEM, and EDS analyses confirmed the formation of Cu₂O crystals (4.17 wt.%) on rutile TiO₂ nanorods without altering the host crystal structure. The hybrid nanostructures extended optical absorption from 450 to 800 nm. Incorporation of 2 wt.% TiO₂@Cu₂O into poly(vinyl chloride–vinyl isobutyl ether) (PVE) coatings enhanced impact resistance, relative hardness, adhesion, and abrasion resistance by 28.6%, 51.4%, 12.5%, and 22.9%, respectively. The modified coatings exhibited strong antibacterial activity against Pseudomonas stutzeri B27, improved UV–humidity aging resistance, and reduced photodegradation and gloss loss. Controlled Cu ion release (23 µg/L) in seawater contributed to biofilm suppression and antifouling performance, highlighting the potential of TiO₂@Cu₂O as a multifunctional additive for durable PVE-based protective coatings.