Photooxidation of organic dye molecules on TiO2 and zinc-aluminum layered double hydroxide ultrathin multilayers

Multilayered self-assembling films from colloidal particles with constant or variable surface charge were prepared on the surface of glass plates using the “layer by layer” (LBL) technique. As particles with variable charge, TiO2 photocatalyst particles and silica sol particles were used for the preparation of multilayered, up to 20-layer films. The colloid particles with constant charge was a suspension of zinc-aluminum layer double hydroxide (ZnAl-LDH), 20 layers of which were deposited on the surface of glass plates using the LBL technique. Layer buildup was monitored by absorbance measurements at a wavelength of λ = 500 nm. The buildup of ZnAl-LDH layers was also followed by XRD measurements. Both TiO2 or TiO2/SiO2 multilayered films and ZnAl-LDH multilayered films were shown to disintegrate acridine orange (AO) dye via photooxidation. The photocatalytic efficiency of ZnAl layer double hydroxide, the new photocatalyst we introduce is close to that of the well-known P25 Degussa titanium dioxide.