Visible-light-responsive Al2O3 powder: Photocatalytic study

A visible-light-responsive hybrid material was prepared by surface-modification of gamma-Al2O3, an insulator with a bandgap of about 8.7 eV, with 5-aminosalicylic acid (5-ASA), leading to the formation of an interfacial charge transfer (ICT) complex. The microstructural characterization of pristine gamma-Al2O3 includes X-ray diffraction analysis, transmission electron microscopy, and nitrogen adsorption-desorption isotherms. The pristine gamma-Al2O3 powder consists of agglomerated rod-like nanoparticles ((2-3) x (15-20) nm, diameter x length) with the large specific surface area (similar to 420 m(2)/g). An enormous absorption red-shift is observed upon the formation of the ICT complex. The absorption onset of the inorganic-organic hybrid was found to be at 730 nm by diffuse reflection spectroscopy. The photocatalytic performance of prepared samples was thoroughly tested using the decolorization of the organic dye crystal violet (CV) under illumination in different spectral regions and different light intensities. Excitation with UV light leads to complete decolorization of CV, while the degradation kinetics are impeded when a visible light source is used. Also, the increase of UV light intensity induced significantly faster degradation kinetics of CV, while the degradation rates of CV are quite insensitive to the increase of visible light intensity.