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

Niobium pentoxide (Nb₂O₅) nanoparticles hold promise for biomedical applications owing to their tunable physicochemical properties. Here, Nb₂O₅ nanoparticles were synthesized via two chemical routes: (i) direct dissolution of Nb₂O₅ in 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 Escherichia coli revealed highest efficacy for H₂O₂-derived nanoparticles (12 g/L), 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 sample 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 nanoparticles with oxygen-defect structures. ICP-MS 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 Nb₂O₅ nanoparticles, supporting their potential as effective nanomaterials for biomedical applications.