Green Synthesis and Characterization of Bismuth Oxide Nanoparticles for Optoelectronic Applications

Abstract

The green synthesis of bismuth oxide nanoparticles (Bi₂O₃) using peppermint (Mentha pulegium) extract offers an eco-friendly, cost-effective, and scalable alternative to conventional methods. In this study, Bi₂O₃ nanoparticles were successfully synthesized and characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), and ultraviolet-visible (UV-Vis) spectroscopy. XRD analysis confirmed a polycrystalline tetragonal structure (β-phase) with an average crystallite size of 58.06 nm, while SEM revealed uniformly distributed nanogranular-like morphologies. Optical studies demonstrated strong UV absorption (320–400 nm) and high visible-light transmittance, with a direct bandgap of 2.4 eV. Notably, the extinction coefficient (K) exhibited a pronounced peak (~1500 a.u.) at 400–450 nm, while the refractive index (n) displayed normal dispersion behavior, decreasing sharply in the visible range before stabilizing in the near-IR region. These optoelectronic properties, classified the material as a semiconductor, highlight the nanoparticles' potential for UV shielding, solar cells, photocatalysis, and optoelectronic devices. The study underscores the efficacy of plant-mediated synthesis for producing functional nanomaterials with reproducible and tunable properties, aligning with sustainable development goals.