Abstract: In this study, a nano-Cu/polysaccharide composite film was prepared by the solution casting method using gelatin and sodium alginate as film-forming substrates. Before casting, green synthesized nano-Cu was incorporated into the film-forming solution by co-blending method. Field emission scanning electron microscopy (FE-SEM), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TAG), diffuse reflectance spectroscopy (DRS), texture analysis (TA) and inductively coupled plasma-mass spectrometry (ICP-MS) were used to characterize the structure, light transmittance and physicochemical properties of nano-Cu and the composite film. The antifungal activity of the composite film was also evaluated and applied to the biological control of the black spot disease of winter jujube. Finally, the migration of Cu2+ in the composite film was measured. The results showed that the particle size of green synthetic nano-Cu was approximately 44 nm, and gelatin/sodium alginate could be used as an excellent carrier for nano-Cu. The composite film had good thermal stability, barrier properties and mechanical properties. In addition, the inhibition rates of the composite films with different concentrations of nano-Cu against Alternaria alternata, Fusarium and Botrytis cinerea were up to 87.80%, 77.73% and 81.96%, respectively, showing good and broad-spectrum antifungal properties. The half maximal inhibitory concentration (IC50) of nano-Cu against A. alternata biomass was 0.25 g/L. When stored for 10 days, the composite film with nano-Cu at 0.25 g/L reduced the lesion diameter by 52.53% and the incidence of black spot disease by 53.16% compared with the control group, and the migration of Cu2+ was 0.018 7 μg/mL. This study provides a new idea for the application of nano-Cu and a theoretical basis for the development of new antifungal materials.

Key words: nano-Cu; composite film; antifungal; winter jujube; biological control