Comprehensive Study on Lemon Juice-Based Green Synthesis and Catalytic Activity of Bismuth Nanoparticles

Bismuth nanoparticles have gained considerable interest in catalysis because of their small size, large surface-to-volume ratio, and low toxicity. In spite of these advantages, the toxic reagents and solvents used in the synthetic process are significant limitations to their development and utilization. In this study, a green approach employing easily accessible lemon juice was applied for the synthesis of bismuth nanoparticles (BiNPs) as a green alternative to conventional chemical ones. This study clarified the formation and growing process of green-synthesized BiNPs using lemon juice as a reducing and capping agent. The reaction time and amounts of lemon juice significantly affect the growth, morphology, and stability of BiNPs, as confirmed from XRD, DLS, SEM, and TEM analyses. The synthesized BiNPs effectively catalyzed the reduction of 4-nitrophenol to 4-aminophenol in the presence of NaBH₄, and the reduction was significantly accelerated by sunlight and the removal of the fibrous coating layer around BiNPs. Moreover, the synthesized BiNPs also show excellent catalytic efficacy toward the reduction of organic dyes, namely, methyl orange, methylene blue, and rhodamine B. All catalytic reductions followed the pseudo-first-order kinetics, and the rate constants are in the order of k _MB > k _RhB > k _MO > k _4-NP. The stated biogenic synthetic route paves the way for the green industrial fabrication of BiNPs and their uses in catalysis for wastewater treatment.