Surfactant-tuned Bi₂WO₆ nanostructures for degradation of organic pollutants

Hierarchical Bi₂WO₆ nanostructures were successfully synthesized via a surfactant-assisted hydrothermal method employing cetyltrimethylammonium bromide (CTAB), sodium dodecyl sulphate (SDS), polyethylene glycol (PEG), and polyvinylpyrrolidone (PVP) to modulate crystal growth, morphology, and functional efficiency. X-ray diffraction (XRD) verified the formation of pure orthorhombic Bi₂WO₆ with crystallite sizes ranging from 18 to 28 nm, depending on the surfactant used. Surface morphology analysis via scanning electron microscopy (SEM) revealed distinct structural variations, with PVP-assisted Bi₂WO₆ displaying a uniform flower-like architecture. The optimised hydrothermal conditions, particularly the use of polyvinylpyrrolidone (PVP) and cetyltrimethylammonium bromide (CTAB), played a crucial role in achieving the flower-like Bi₂WO₆ morphology. Elemental composition was verified using energy dispersive X-ray analysis (EDAX), while Raman spectroscopy confirmed the stability of the WO₆ octahedral framework. X-ray photoelectron spectroscopy (XPS) identified the oxidation states of Bi³⁺, W⁶⁺, and O²⁻, further validating the chemical structure. Optical characterisation by ultraviolet–visible (UV–vis) diffuse reflectance spectroscopy revealed visible-light responsiveness, with bandgap energies ranging from 2.60 to 2.78 eV. Among all variants, PVP-mediated Bi₂WO₆ demonstrated exceptional photocatalytic activity, achieving ~94% degradation of Rhodamine B (RhB) under visible light in 50 minutes. Furthermore, it demonstrated significant antibacterial activity, making it a promising candidate for environmental remediation. The enhanced performance is attributed to improved morphology, efficient charge separation, and a narrowed bandgap.