Three-Dimensional Dendritic Biosynthetic Copper Oxide Nanoparticles: A Novel Approach for Enhanced Leaf Deposition and Retention to Reduce Environmental Impact

Copper-based fungicides are commonly utilized as protective germicides; however, their susceptibility to rain-induced washing leads to a substantial copper exposure, resulting in significant environmental pollution and potential ecological risks. This study focuses on the biosynthesis of copper oxide nanoparticles (Bio-CuNPs) at room temperature, utilizing copper sulfate pentahydrate and tea seed cake extract as reactive raw materials. The obtained Bio-CuNPs exhibit a distinctive dendritic three-dimensional topology. Notably, these Bio-CuNPs demonstrate superior wettability and spreadability on tomato, rice, and wheat leaves compared to the commercial product Kocide. The retention amount of Bio-CuNPs on the surface of plant leaves after rain washing exhibited a 75.89% to 84.31% increase compared to that of Kocide, attributed to the structural chimerism of Bio-CuNPs and the micro-nano structure of leaves. Regarding antimicrobial activity against Magnaporthe oryzae and Clavibacter michiganense, Bio-CuNPs showed better residual activity and a longer persistent period than Kocide. Safety experiments reveal that Bio-CuNPs effectively mitigate toxicity in zebrafish, with a reduction exceeding fivefold when compared to Kocide. Consequently, the prepared Bio-CuNPs hold significant promise as an eco-friendly alternative to traditional copper-based fungicides.