Silver Nanoparticle-Based Paper Packaging to Combat Black Anther Disease in Orchid Flowers

Metal nanoparticles have been reported to have a high antimicrobial activity against fungi, bacteria, and yeasts. In this study, we aimed to synthesize silver nanoparticles (AgNPs) using a chemical reduction method at 90 °C. The obtained AgNPs were used as an antifungal coating on packaging paper, to control the growth of Colletotrichum gloeosporioides in cut orchid flowers during the shipping process. The AgNPs were characterized by a UV-Vis spectroscopy and atomic force microscope (AFM). The results indicated that their shape was spherical and homogenous, with an average size of 47 nm. An AgNPs concentration of 20 and 50 particles per million (ppm), mixed with starch, was prepared as the coating solution. The paper coated with a concentration of 50 ppm exhibited a significant antifungal activity against C. gloeosporioides compared to 20 ppm. The coated paper had a higher water resistance and better mechanical properties compared to the uncoated paper. Additionally, we observed a significant reduction in the number of orchid inflorescence anthers, infected by C. gloeosporioides, when stored in the coated boxes. The current study demonstrates that paper boxes, coated with AgNPs, can be used in controlling the C. gloeosporioides infection during storage of cut orchid flowers.