Synthesis and characterization of RF sputtered WO3/TiO2 bilayers

• WO3/TiO2 bilayer heterostructures were prepared by RF magnetron sputtering.
• The TiO2 film contained an anatase–rutile phase mixture in an amorphous matrix.
• The ultra-thin WO3 layer coverage increased, until a continuous film was formed.
• The photocatalytic efficiency was further enhanced via narrowing of materials' band gap value.
• The bilayer structure exhibit extended photocatalytic activity following post-activation.

Ultra-thin WO3/TiO2 bilayer thin films with various amounts of WO3 materials were deposited on glass substrates using RF reactive magnetron sputtering in an attempt to enhance the photocatalytic activity and/or photoinduced hydrophilic conversion of titania-based materials. AFM images reveal changes in surface morphology on increasing WO3 film thickness. Core level and valence band XPS spectra suggest band gap narrowing with the increase of tungsten atomic concentration in the bilayer structure. Both hydrophilic conversion and the photocatalytic activity of the surface were quantified via contact angle measurements. The latter process involved monitoring the contact angle changes induced by the decomposition of an additional oleic acid overlayer, as an effect of UV light irradiation. All the investigated samples exhibit similar photocatalytic features and close values for the hydrophilic conversion rates.

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