Enhancement in the photocatalytic activity of Au@TiO ₂ nanocomposites by pretreatment of TiO ₂ with UV light

A novel, efficient and controlled protocol for the synthesis and enhanced photocatalytic activity of Au@TiO ₂ nanocomposite is developed. TiO ₂ (P25) was pretreated by employing UV light (λ = 254 nm) and the pretreated TiO ₂ was uniformly decorated by gold nanoparticles (AuNPs) in presence of sodium citrate and UV light. UV pretreatment makes the TiO ₂ activated, as electrons were accumulated within the TiO ₂ in the conduction band. These accumulated electrons facilitate the formation of AuNPs which were of very small size (2-5 nm), similar morphology and uniformly deposited at TiO ₂ surface. It leads to formation of stable and crystalline Au@TiO ₂ nanocomposites. The rapidity (13 hours), monodispersity, smaller nanocomposites and easy separation make this protocol highly significant in the area of nanocomposites syntheses. As-synthesized nanocomposites were characterized by TEM, HRTEM, TEM-EDX, SAED, XRD, UV-visible spectrophotometer and zeta potential. Dye degradation experiments of methyl orange show that type I (Au@TiO ₂ nanocomposites in which TiO ₂ was pretreated with UV light) has enhanced photocatalytic activity in comparison to type II (Au@TiO ₂ nanocomposites in which TiO ₂ was not pretreated with UV light) and TiO ₂ (P25). This shows that pretreatment of TiO ₂ provides type I a better catalytic activity.