Multifunctional imidazole-functionalized polyaspartamide/TiO₂ composites for UV screening, heavy metal removal, and suppressed photocatalytic activity

With the acceleration of global warming, increased exposure to ultraviolet (UV) radiation resulting from ozone layer depletion has raised significant concerns about skin-related health risks. Inorganic sunscreens, particularly those based on titanium dioxide (TiO₂), are commonly used but face limitations such as visible white turbidity and skin oxidation caused by the photocatalytic activity of TiO₂. In this study, we synthesized TiO₂/polyaspartamide composites (T-PH and T-PA) functionalized with histamine and aminopropyl imidazole, respectively. These imidazole-bearing polymers were covalently grafted onto TiO₂ nanoparticles, enhancing their dispersion stability and enabling efficient heavy metal adsorption through metal–ligand coordination. Compared to unmodified TiO₂, the composites exhibited a substantial reduction in white turbidity (up to a 33 % decrease in whiteness index) and significantly suppressed photocatalytic degradation of methylene blue (from 100 % to 16–30 %). Furthermore, the composites demonstrated improved adsorption capacities for Cu²⁺ and Ni²⁺ ions. These multifunctional TiO₂–polymer hybrids hold strong potential for next-generation sunscreens by offering effective UV shielding, enhanced optical transparency, and environmental remediation capabilities.