Green synthesis of niobium (V) oxide nanoparticles using pecan nutshell (Carya illinoinensis) and evaluation of its antioxidant activity

Niobium is a metal that has been attracting great interest in producing high-technology materials, in which niobium oxide nanoparticles (Nb₂O₅-NPs) are inserted. In this context, the present study aims to develop and characterize structurally and morphologically niobium (V) oxide nanoparticles (Nb₂O₅-NPs) by the green synthesis method from pecan nutshell (C. illinoinensis) extract. Nb₂O₅-NPs were characterized by Attenuated Total Reflection Fourier Transform Infrared (ATR-FTIR), Scanning Electron Microscopy (SEM), X-ray diffraction (XRD) and N₂ porosimetry (BET/BJH method). The antioxidant potential of the pecan nutshell extract was determined for the quantification of phenolic compounds and flavonoids. The XRD diffractogram showed that the Nb₂O₅-NPs presented a semicrystalline structure with the presence of the pseudohexagonal phase of Nb₂O₅. The ATR-FTIR spectrum confirmed the presence of a band vibration of the Nb-O at 600 cm⁻¹. The Nb₂O₅-NPs presented spherical morphology according to the SEM micrography with a specific surface area of 1.72 m² g⁻¹ and 36.31 nm pore diameter (isotherm type III) by the N₂ porosimetry. The pecan nutshell extract showed the presence of polyphenols (336.8 mgAG mL⁻¹) and flavonoids (200.1 mgCt mL⁻¹), demonstrating the high potential to act as a bioreducing and stabilizing agent for the green synthesis of Nb₂O₅-NPs. Therefore, the green synthesis of Nb₂O₅-NPs is feasible with potential application in different fields.