An eco-friendly synthetic polyethylene glycol-coated copper nanoclusters for efficiently suppress Alternaria alternata in tobacco and safety evaluation

Overused agrochemicals threaten the environment and human health. Nanotechnology has shown great potential for maintaining or minimizing environmental issues in agriculture. Herein, a polyethylene glycol-coated copper nanoclusters (PEG@Cu NCs) has been developed for efficient utilization by tobacco. The NCs showed the superior antifungal activity against Alternaria alternata, achieving comparable activity using a dose almost 35-fold lower than that of 46% copper hydroxide water power (WP). More importantly, PEG@Cu NCs exhibited excellent therapeutic potential via xylem delivery. In the meantime, promising bioavailability of the NCs was achieved, which could be absorbed by tobacco seedlings via roots and foliar tissues (epidermal and mesophyll cells). In addition, the biosafety of PEG@Cu NCs was investigated in tobacco and earthworms. Both root exposure (1.27–3.17 mg L−1) and leaf exposure (1.27–6.33 mg L−1) to PEG@Cu NCs had no negative effects on tobacco growth. The acute toxicity of PEG@Cu NCs to earthworms was low, as determined by the 7 day-LC50 value of 46.253 mg kg−1 and 14 day-LC50 value of 30.187 mg kg−1. Overall, such NCs are expected to be a competitive alternative to Cu-based fungicides in sustainable agriculture due to their superior antifungal properties, excellent biocompatibility, and high efficiency bioavailability.