Sunlight driven photo-treatment of polyhydroxybutyrate microplastics mediated by carbon nanodots-doped ZnO mesocrystals: Induced surface changes boost degradation in soil and biofilm formation

Plastics are widely used due to their versatility. However, theiraccumulation as microplastics and nanoplastics in the environment posesa significant threat for the ecosystems. Although biodegradablepolymers, like polyhydroxybutyrate (PHB), offer a sustainablealternative, their degradation could still lead to fragmentation and MPaccumulation, hence it is essential to enhance biodegradation rates inorder to mitigate environmental impacts. This study investigates theintegration of photocatalytic pretreatment with natural biodegradationto accelerate PHB biodegradation. Photoactive ZnO mesocrystals dopedwith biowaste-derived carbon nanodots, prepared via a wet-chemicalapproach, are proposed to improve the photocatalytic efficiency undersunlight. ZnO mesocrystals doped with 30 wt\% of carbon nanodotsexhibited superior photocatalytic properties, thus photodegrading PHBmicroplastics more efficiently than bare ZnO. Phototreated PHBmicroplastics exhibit an improved biodegradation in soil when exposedfor a controlled irradiation time. Additionally, PHB microplasticsphoto-treated in the presence of doped mesocrystals showed an enhancedmicrobial colonization indicating improved biofilm formation. Thesefindings highlight the potential of photocatalytic pretreatment inmodifying surface properties to boost degradation in soil, thus offeringa promising strategy for reducing microplastic accumulation.