Analysis of the photocatalytic activity of CdS+ZnTiO3 nanocomposite films prepared by sputtering process

ZnTiO3 and CdS + ZnTiO3 nanoparticulate composite films were deposited at room temperature onto glass substrates using the radio frequency sputtering process. The composite films were grown by employing a target prepared with commercial high purity CdS powder and ZnTiO3 nanopowder at CdS/ZnTiO3 ratio of 1/4. Subsequently, annealing of the as-deposited layers was performed at 300 °C and 500 °C in open atmosphere. The samples were characterized by X-ray diffraction, atomic force microscopy, transmission and scanning electron microscopy, and UV–Vis, Raman and photoluminescence spectroscopies. Results show that the zinc titanate nanoparticles in ZnTiO3 and CdS + ZnTiO3 films exhibit mainly cubic phase of ZnTiO3, where the hexagonal phase is also present in a minor proportion. The observed CdS quantum dots grow in hexagonal phase. The photocatalytic activity (PA) was tested by means of the degradation of methylene blue (MB) measurements. The bi-component CdS-ZnTiO3 nanocomposite film annealed at 300 °C exhibits superior MB degradation than CdS + ZnTiO3 annealed at 500 °C and pure ZnTiO3, which is due to an adequate coupling of the energy band gap of both materials. This coupling promotes an efficient separation of photo-generated electron-hole pairs between CdS + ZnTiO3. A discussion about the different PA in the composites studied is included.