Abstract

Metal oxide nanocomposites continue to attract attention for their tunable optical, catalytic, and antimicrobial properties. This study presents the green synthesis of tungsten oxide–cerium oxide (WO3-CeO2) nanocomposites using ethaline-based deep eutectic solvents (DES) and DES-water mixtures, revealing how solvent structure directly governs material performance. FTIR confirmed the formation of WO3 and CeO2 through characteristic metal oxide bands, while XRD showed well-defined monoclinic W18O49, hexagonal Ce2O3 and Ce2WO6 phases. The SEM analysis revealed highly aggregated microspherical clusters with a broad particle size distribution. Also, the composites exhibited pronounced photochromic response, with the DES-water composite samples rapidly changing to light-blue colour within 10 s under UV irradiation, driven by hydrogen-assisted electron trapping and W5+/W6+ redox cycling, as the UV-Vis absorption showed broad charge-transfer bands consistent with visible-light activation. Moreover, under light-assisted catalysis, the composites efficiently degraded bromophenol blue, achieving significant decolorization within 60 min, while the electrochemical impedance spectroscopy confirmed enhanced charge mobility in DES-water samples, with a markedly lower Rct (≈229 Ω) compared to pure DES analogues. Furthermore, the antimicrobial assays demonstrated strong, concentration-dependent inhibition of S. aureus and E. coli, with DES-water composites showing the highest activity. In conclusion, there results established DES-templated tungsten oxide–cerium oxide composite as a versatile, high-performance functional materials for environmental, optical, and antimicrobial applications.

Key words: Deep eutectic solvent, Ethaline, Tungsten oxide, Cerium oxide, antimicrobial activity, Photochromic, Photocatalytic