Green Synthesis of Silver and Ferric Oxide Nanoparticles Using Syzygium cumini leaf Extract and Their Antifungal Activity when Applied to Oak Wood and Paper Pulp from Imperata cylindrica Grass Biomass

In the present work, Syzygium cumini leaf aqueous extract (LAE) was used to biosynthesize silver nanoparticles (AgNPs) and ferric oxide nanoparticles (Fe₂O₃NPs). The chemical compounds, phenolics and flavonoids, were identified using an HPLC analysis. The produced NPs were characterized via transmission electron microscopy (TEM), energy dispersive X-ray (EDX), zeta potential, and FT-IR analysis. The antifungal activity of the synthesized NPs, when applied to Oak wood samples and Imperata cylindrica paper pulp, was assayed against the growth of Fusarium culmorum Fcu761, Aspergillus fumigatus Afu694, and Aspergillus niger Ani245. The paper pulp from I. cylindrica grass biomass was made by the Kraft pulping process under a range of cooking conditions, such as maximum temperature, cooking durations, concentrations of active alkali, and ratios of solid to liquor, which affect the mechanical and physical properties of the unbleached pulps. According to HPLC analysis of S. cumini LAE, benzoic acid, gallic acid, ellagic acid, and rutin were the most abundantly identified compounds. The synthesized AgNPs and Fe₂O₃NPs were spherical in shape with diameters ranging from 19.04 nm to 40.11 nm and 20.67 nm to 44.11 nm, respectively. By zeta potential, AgNPs and Fe₂O₃NPs have charged potentials of -22.3 and − 12.1, respectively. The hydroxyl functional group in alcohols and phenolic compounds is characterized by FTIR spectra. According to the bioassay tests, the AgNPs have more promising antifungal activity against F. culmorum, A. fumigatus, and A. niger when applied to the Oak wood and I. cylindrica paper pulp samples than Fe₂O₃NPs. It is concluded that the bioactive compounds from S. cumini LAE were well mediated to synthesize AgNPs and Fe₂O₃NPs, where AgNPs can be significantly used as an antifungal agent for protecting wood and paper materials from the fungal infestation.