TiO2-WO3-Eu2(WO4)3 film heterostructures: Synthesis, luminescent, optoelectronic and photocatalytic properties

Titanium-supported TiO2-WO3-Eu2(WO4)3 film heterostructures have been formed by combining two methods - plasma electrolytic oxidation (PEO) of titanium in acidic tungstate solution and extraction pyrolytic (EP) deposition of europium organic extract paste. As a result of annealing of the composites at 700 and 800 °C for 2 h, Eu2(WO4)3 and WO3 crystallize in their composition, while anatase from PEO coating transforms into rutile. WO3 microcrystals and elongated chains of molten formations attributed to Eu2(WO4)3 are visible on SEM images of the composite surfaces. XPS confirms the presence of Eu3+, W6+, W5+, and W4+ in the subsurface layers of the composites. The luminescence properties of the resulting composites were evaluated from the luminescence excitation spectra and luminescence spectra at 300 K. All composites exhibit luminescence in the red region with a maximum at λmax ≈ 620 nm (λex = 250 nm). All formed coatings exhibited photocatalytic activity in the reaction of degradation of indigo carmine (IC, 10 mg/L, pH 4.6) under UV irradiation. [Display omitted] •PEO and EP were used to obtain TiO2-WO3-Eu2(WO4)3 film heterostructures on Ti.•WO3 microcrystals and elongated Eu2(WO4)3 chains were found on their surface.•The resulting composites are red phosphors and photocatalysts under UV irradiation.•Luminescence intensity is due to Eu2(WO4)3 and increases with annealing temperature.•Photoactivity in IC degradation and optoelectronic properties are due to WO3.