Phytotoxicity assessment of PEI-modified mixed phase copper oxide (CuO/Cu2O) nanoparticles in agricultural plants

Copper oxide nanoparticles (CuO NPs) were utilised in various agricultural applications. Their advantageous and detrimental effects on plants depend on the concentration and duration of exposure. While CuO NPs offer numerous benefits in agriculture, their potential toxicity to agricultural plants has emerged as a serious concern. To reduce the toxic effects of copper oxide nanoparticles, they were modified with a cationic polymer, polyethyleneimine (PEI). A chemical reduction method was employed to prepare PEI-coated CuO/Cu2O NPs, and the change in structure was characterised via various techniques. The results of X-ray diffraction, transmission electron microscopy, and X-ray photoelectron spectroscopy confirmed the presence of PEI coating on copper oxide nanoparticles. The phytotoxic effects of bare CuO NPs and PEI-coated CuO NPs were examined by exposing different plant species (Brassica juncea and Zea mays). The selected plants were treated with different concentrations of the synthesised CuO/Cu2O NPs and PEI-CuO/Cu2O NPs. The PEI-coated CuO/Cu2O NPs showed less inhibitory effects on the seed germination factors (i.e., germination index and germination percentage) of Brassica juncea, while in Zea mays, the inhibitory effects were only seen at high concentrations.