Natural-based UV-shielding additives to protect photosensitive pesticides: Production of nanoparticles from the co-self-assembly of lignin and tannin

This work explores the development of a renewable, carbon-neutral, light-colored UV-shielding film to protect photosensitive pesticides from solar radiation, as these chemicals are easily degraded under UV light, substantially reducing their efficiency and causing soil and water pollution. The abundant benzene rings in lignin and phenolic hydroxyls in tannin boosted the co-self-assembly of lignin and tannin into composite nanospheres by the simultaneous π-π stacking and H-bonding interactions between these two biopolymers. These lignin-tannin (LT) composite nanoparticles were used as natural UV-shielding additives to coat a poly-vinyl-alcohol (PVA) film, endowing the PVA-LT film with an excellent UV-shielding ability (>95 % efficiency) due to the strong π-π stacking and concentrated phenolic hydroxyls. Typical photosensitive pesticides covered with the PVA-LT film significantly increased their remaining rate by 1.5 times compared to those under the uncoated film. Besides, intensive intermolecular hydrogen bonds were generated between PVA and the abundant phenolic hydroxyl groups exposed on the hydrophilic shell of the LT coating, enhancing the mechanical properties and water vapor retention of the composite film. Our biodegradable composite film derived from natural plant extracts not only protected photosensitive pesticides from UV irradiation but also allowed the transmission of visible light to guarantee the photosynthesis process of crops.