Structural, optical and photocatalytic properties of hydrothermally synthesized bismuth tungstate nanoparticles

We systematically synthesized bismuth tungstate (Bi₂WO₆) nanoparticles via a hydrothermal method, varying reaction time to study their structural, optical and photocatalytic properties. Characterization via X-ray diffraction, Raman and FTIR confirmed the formation of the orthorhombic Bi₂WO₆ phase, showing improved crystallinity and increased crystallite size (21–40 nm) with longer reaction times. FE-SEM analysis revealed a morphological evolution from irregular aggregates to distinct flower-like nanostructures as the reaction time increased. Optical studies showed a reduction in the band gap from 2.94 to 2.72 eV, thereby enhancing visible-light absorption. Photoluminescence (PL) studies showed reduced emission intensity in the BWO-20 sample, indicating reduced electron–hole recombination and improved charge-separation efficiency. BET analysis demonstrated mesoporous characteristics, with enhanced specific surface area and pore volume, for the Bi₂WO₆ nanoparticles synthesized at a 20 h hydrothermal reaction time. The sample exhibited optimal photocatalytic efficiency, degrading 73.2% of crystal violet (CV) and 85.6% of malachite green (MG) within 60 min under visible light. These results highlight the potential of hydrothermally synthesized Bi₂WO₆ nanoparticles as effective visible-light-driven photocatalysts for environmental remediation.