Sol–gel synthesis of Au/TiO2 thin films for photocatalytic degradation of phenol in sunlight

Thin films of Au/TiO2 on glass substrates have been prepared by simple sol–gel dip coating method using a sol of colloidal gold doped titanium peroxide (Au/TiO2 sol). The sol of colloidal gold and titanium peroxide forms a viscous gel after 1–3 h depending on the concentration of both colloidal gold and titania. The sol of particular viscosity range (140–2800 cps) was used to deposit the Au/TiO2 thin films of uniform thickness on various substrates such as glass slides, glass helix and silica rashig rings. Films deposited on glass plates after drying were transparent, uniform in color as well as thickness. Optical characterization by UV–vis spectrophotometer showed a shift in optical absorption wavelength to visible region may be due to the incorporation of gold nanoparticles into titania structure. The optimum concentration of gold loading was found to be 1–2% (by weight) beyond this the gold particles disturb the gel network resulting the formation of gelatinous precipitate. Thin film photo-catalyst prepared was characterized by various techniques such as UV–vis, TG-DTA, XRD, ICP-OES and TEM. The photo-activity of the thin films was tested in sunlight using phenol as model pollutant. The kinetic study showed that the rate of decomposition of phenol using Au/TiO2 photo-catalyst was improved by 2–2.3 times than undoped TiO2.

The addition of colloidal Au in TiO2 shifts absorption edge of TiO2 films from 360 nm in UV to 430–440 nm in visible region. This increased absorption results in the 2–2.3 times enhancement in photo-catalytic activity of Au/TiO2 thin film catalyst than undoped TiO2 films. Figure optionsDownload as PowerPoint slide