Exploiting the Reducing Properties of Lignin for the Development of an Effective Lignin@Cu2O Pesticide

Lignin is a natural polymer produced in huge amounts by the paper industry. Innovative applications of lignin, especially in agriculture, represent a valuable way to develop a more sustainable economy. Its antioxidant and antimicrobial properties, combined with its biodegradability, make it particularly attractive for the development of plant protection products. Copper is an element that has long been used as a pesticide in agriculture. Despite its recognized antimicrobial activity, the concerns derived from its negative environmental impact is forcing research to move toward the development of more effective and sustainable copper-based pesticides. Here a simple and sustainable way of synthesizing a new hybrid material composed of Cu2O nanocrystals embedded into lignin, named Lignin@Cu2O is presented. The formation of cuprite nanocrystals leaves the biopolymer intact, as evidenced by infrared spectroscopy, gel permeation chromatography, and Pyrolysis-GC analysis. The combined activity of lignin and cuprite make Lignin@Cu2O effective against Listeria monocytogenes and Rhizoctonia solani at low copper dosage, as evidenced by in vitro and in vivo tests conducted on tomato plants.