Sonochemical Facile Synthesis of Bismuth Oxide Nanoparticles Using Citrus Lemon Extract and Its Catalytic Activity on Azo Dye Degradation

Abstract The synthesis of bismuth oxide nanoparticles through sono-cavitation using citrus lemon extract as a simple, eco-friendly and cost-efficient method was evaluated. The aqueous extract of citrus lemon acted as a bio-reducing and capping/stabilizing agent in the single-step biosynthesis of bismuth oxide nanoparticles. Different instrumental techniques have been used to characterize the biosynthesized bismuth oxide nanoparticles, including UV–vis spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray powder diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), Raman spectroscopy, X-ray photoelectron spectroscopy and energy-dispersive X-ray spectroscopy (EDS). UV–vis spectroscopy revealed the formation of stable bismuth oxide nanoparticles at λ max of 400 nm with a surface plasmon resonance (SPR) band. TEM revealed that the biosynthesized bismuth oxide nanoparticles were rod shaped with a particle size of 26 nm. A potential mechanism for the formation of bismuth oxide nanoparticles with the influence of sono-cavitation has been suggested based on the observed findings. These catalytic capabilities of the bio-synthesized bismuth oxide nanoparticles were then evaluated by degradation of toxic azo dyes under different laboratory conditions. The azo dye Congo red (CR) was effectively degraded to 86% within 30 min under optimum experimental conditions using 0.12 g/mL catalyst. Thus, the phytochemical citrus lemon offers a cheap and eco-friendly solution for the synthesis of catalytic nanoparticles to degrade highly toxic organic compounds such as azo dyes. Graphical Abstract