Green Synthesis of AgNPs Using Medicinal Himalaya Fern (Thelypteris erubescens): Structural Characterization, Effect on Maize Seed Germination and Antimicrobial Function

The green synthesis of silver nanoparticles (AgNPs) is a promising aspect of nanotechnology due to its stable, non-toxic, and eco-friendly approach. In this study, the medicinal Himalayan fern Thelypteris erubescens was used for the green synthesis of AgNPs (TeAgNPs), and its effects on seed germination of maize and antimicrobial properties were investigated. TeAgNPs were synthesized by adding silver nitrate to the plant methanolic extract. The synthesis of AgNPs was confirmed by a change in color from light yellow to dark brown, representing the actual reduction of silver ions. Scanning electron microscopy (SEM) images showed that the nanoparticles were mainly spherical, ranging in size from 30-40 nm, with some observed aggregation. X-ray (XRD) diffraction analysis indicated that the AgNPs displayed a crystalline structure with a particle size of 32.6 nm. The TeAgNPs application (concentrations: 25, 50, and 75 mg/L) significantly enhanced maize germination, root, and shoot growth, which was better than the control treatment. Moreover, TeAgNP concentrations (10, 15, and 20 μg/mL) displayed antibacterial and antifungal activity via agar well diffusion. The most potent inhibition was against Klebsiella pneumonia and Aspergillus niger (18.33 and 13.3 mm), respectively, highlighting TeAgNPs’ potential anti-pathogenic use. TeAgNP application demonstrated superior antibacterial efficiency compared to the fern’s methanolic extracts. Phytochemical analysis of the T. erubescens methanolic extracts identified various bioactive compounds, including alkaloids, tannins, and flavonoids, which might play a role in the stabilization and biological efficiency of its AgNPs. Our eco-friendly and cost-effective AgNP synthesis approach exploits the fern Thelypteris erubescens potential against microbial strains and its positive effects on plant growth for promising applications in agriculture.