Flower-like assembly of single-phase V–TiO ₂ microneedles for sustainable water remediation

Abstract Designing efficient photocatalysts that operate under sunlight is critical for sustainable water remediation. This work presents the synthesis of flower-like assemblies of single-phase vanadium-doped titanium dioxide (V–TiO 2 ) microneedles via a simple sol-gel method. The engineered microneedle architecture offers enhanced surface area and light-scattering properties, while the substitutional doping of V 5+ ions into the TiO 2 structure results in significant bandgap narrowing (3.13 eV) and suppressed electron-hole recombination. Comprehensive structural and surface analyses were performed using X-ray diffraction, scanning electron microscopy, Fourier-transform infrared, and UV/vis spectroscopy. Photocatalytic studies under UV and sunlight conditions reveal that thermally annealed V–TiO 2 (ΔV-TiO 2 ) achieves 80 % degradation of methylene blue (MB), markedly outperforming undoped TiO 2 . The photocatalytic reaction follows pseudo-first-order kinetics with a rate constant of 1.7 × 10 −2 min −1 , approximately four times higher than that of annealed pristine TiO 2 (ΔTiO 2 ). The enhanced activity is attributed to improved charge separation and redox dynamics introduced by vanadium incorporation. These findings demonstrate the effectiveness of ΔV-TiO 2 microneedles as highly active, sunlight-driven photocatalysts for the degradation of organic contaminants in wastewater.