Natural phenolics-Cu2-xSe photothermal nanoparticles and their combination with near-infrared irradiation for control of Penicillium expansum in postharvest citrus fruits

Blue mold caused by Penicillium results in significant economic losses for the citrus industry. In contrast to chemical fungicides, nanomaterials with low drug-resistant problems but efficient fungicidal effect have attracted attention in postharvest fungal control. Here, we develop natural phenolics-Cu 2-x Se nanoparticles with photothermal conversion performance to effectively inhibit Penicillium expansum , which was successfully applied to prevent blue mold in citrus. Natural phenolic compounds (e.g., tannic acid, hesperidin and gallic acid) can serve as reducing agents. The obtained Cu 2-x Se nanoparticles show good photothermal conversion effects with a temperature increase of 23.3 °C under 1064 nm near-infrared (NIR) irradiation for 6 min. Compared to phenolics-Cu 2-x Se nanoparticles alone, combined them with NIR irradiation can significantly enhance the antifungal activity against Penicillium expansum in vitro antifungal tests. The antifungal activity is attributed to the structure disruption of fungal cell walls and membranes, as well as mitochondrial dysfunction. In vivo experiments, Cu 2-x Se nanoparticles with NIR irradiation delayed the decay of citrus fruits more effectively than the Cu 2-x Se nanoparticles alone, maintaining fruit quality including total soluble solid, titratable acid, ascorbic acid and total phenolics. Our study demonstrates the potential of photothermal conversion nanomaterials and their combination with NIR irradiation as a new strategy for fruit preservation. • Phenolics-Cu 2-x Se NPs were prepared with good photothermal conversion effects. • Phenolics-Cu 2-x Se NPs can inhibit P. expansum and delay citrus fruit decay. • Combination of Cu 2-x Se NPs and NIR irradiation can enhance the antifungal activity. • Phenolics-Cu 2-x Se NPs with NIR irradiation can better maintain fruit quality. • Cu 2-x Se NPs and NIR damaged fungal cell walls, membranes and mitochondria.