Tailoring niobium pentoxide nanoparticles via distinct chemical routes: structural characterization and antibacterial evaluation

Niobium pentoxide (Nb₂O₅) nanoparticles (NPs) hold promise for biomedical applications owing to their tunable physicochemical properties. Here, Nb₂O₅NPs were synthesized via two chemical routes: (i) direct dissolution of Nb₂O₅in hydrofluoric acid (HF), and (ii) reaction of ammonium niobate (V) oxalate hydrate with hydrogen peroxide (H₂O₂). Characterization by x-ray diffraction, electron microscopy, and dynamic light scattering confirmed route-dependent differences in crystallinity, size, and dispersion. Antibacterial assays against<i>E. coli</i>revealed highest efficacy for H₂O₂-derived NPs (12 g l^-1), attributed to their ultra-small crystallites (∼4.5 nm), monodispersity (PDI = 0.118), and good colloidal stability. In the HF route, the 5 g l^-1sample also showed strong antibacterial activity, likely due to increased particle concentration despite larger size distribution. Mechanistic studies demonstrated that bactericidal effects correlated with enhanced reactive oxygen species (ROS) generation, particularly in H₂O₂-synthesized NPs with oxygen-defect structures. Inductively coupled plasma mass spectrometry confirmed low but detectable Nb ion release, indicating that ROS production, rather than ion leaching, was the dominant antibacterial mechanism. These findings highlight the importance of synthesis route and precursor concentration in tailoring the antibacterial performance of Nb₂O₅NPs, supporting their potential as effective nanomaterials for biomedical applications.