In Situ Green Synthesis of Metal Oxide Nanoparticles Using Onion Peel

The growing demand for sustainable nanomaterials has created a need for environmentally friendly methods for nanoparticle synthesis and the integration of nanoparticles into functional structures. Conventional CuO nanoparticle production methods generally require toxic chemicals and multi-step processing, limiting their environmental sustainability. Thus, finding sustainable synthesis methods continues to be a significant challenge.

In this study, a sustainable approach was developed for the in situ green synthesis of CuO nanoparticles within electrospun polyacrylonitrile (PAN) nanofibers, using onion (Allium cepa) peel as a natural reducing and stabilizing agent. Dried and ground onion peel powder was incorporated directly into a PAN solution, then electrospun. Subsequently, the nanofibers were immersed in CuSO₄·5H₂O solutions of varying concentrations, thereby reducing Cu²⁺ ions and forming CuO nanoparticles directly within the fibrous matrix without additional chemical reducing agents. UV–vis analysis confirmed the formation of CuO nanoparticles at 320 nm, and SEM images showed their homogeneous distribution throughout the PAN nanofiber matrix.

The findings indicate that agricultural waste-derived biomolecules can serve as both reducing and stabilizing agents, thereby enabling the fabrication of functional CuO/PAN nanocomposite nanofibers through a simple, environmentally benign process. The developed CuO-loaded nanofibers are promising candidates for advanced air and water filtration applications, where the combination of a nanofibrous architecture and uniformly distributed CuO nanoparticles may enhance contaminant capture, antimicrobial activity, and overall filtration performance. Furthermore, the proposed approach provides an effective route for converting onion peel waste into value-added functional materials for sustainable environmental technologies.