Synthesis and antifungal activity of copper nanoparticles against Fusarium oxysporum pathogen of plants

For many decades, Cu ^2+ ions have been used as fungicides in agriculture. However, the accumulation of Cu ^2+ ions in the soil ecosystem will be disadvantage for environment. Thus, the substitution of copper nanoparticles for Cu ^2+ ion is necessary to develop long-term efficient, eco-friendly, and cost-effective fungicides. In this study, the copper nanoparticles were synthesized by chemical reduction method of Cu ^2+ with reductive agent of NaHB _4 in chitosan stabilizer. Characterizations of copper nanoparticles were determined by UV–vis spectra, Fourier transform infrared spectroscopy, X ray diffraction patterns and Transmission Electron Microscopy images. The antifungal efficacy of CuNPs was evaluated by testing against Fusarium oxysporum fungi at various concentrations from 20–100 ppm. The results revealed that copper nanoparticles samples inhibited significantly the growth of Fusarium oxysporum and the smaller diameter is, the higher antifungal efficacy is. The copper nanoparticles with 26.5 nm expressed an antifungal efficacy is higher than copper nanoparticles with 29 nm. The complete inhibition was observed at concentrations ≥ 80 ppm after 1 day and even 7 days of incubation for 2.0 CuNPs (26.5 nm) sample while fungi still survive on PDA plates containing 1.5 CuNPs (29 nm).