The photocatalytic reaction of the thin film TiO₂-Sr ₄Al₁₄O₂₅ phosphors for benzene gas

Phosphorescent materials coated with titanium dioxide were fabricated and photocatalytic reactions between these materials and VOCs gases were examined. A thin film (approx. 100 nm) of nanosized TiO₂ was deposited on the Sr₄Al₁₄O₂₅: Eu²⁺, Dy ³⁺,Ag⁺ phosphor using low-pressure chemical vapor deposition (LPCVD). The characteristics of the photocatalytic reaction were examined in terms of the decomposition of benzene gas using a gas chromatography (GC) system under ultraviolet (λ = 365 nm) and visible light (λ > 420 nm) irradiation. TiO₂-coated Sr₄Al ₁₄O₂₅: Eu²⁺, Dy³⁺,Ag⁺ phosphor showed different photocatalytic behavior compared with pure TiO ₂. TiO₂-coated phosphorescent materials showed a much faster photocatalytic decomposition of benzene gas under visible irradiation compared to the pure TiO₂ for which the result was practically negligible. This suggests that the extension of the absorption wavelength to visible light occurred through energy band bending by a heterojunction at the interface of the Sr₄Al₁₄O₂₅-TiO₂ composite. Also, the Sr₄Al₁₄O₂₅-TiO₂ composite showed the photocatalytic decomposition of benzene in darkness due to the photon light emitted from the Sr₄Al₁₄O₂₅ phosphors.