Efficient photodecoloration catalysts, based on ZnO nanoparticles coated in two steps on glass substrates

ZnO, ZnO:Ag and ZnO:Cu thin coatings were prepared on glass substrates by an innovative dip-coating technique coupled with the addition of ZnO nanoparticles and their structural, morphological and optical properties were investigated. X-ray Diffraction (XRD) analysis revealed the coatinǵs hexagonal wurtzite phase with a preferred (002) plane orientation. The mean crystallite size calculated on the basis of the Debye-Scherrer model was 31 nm and a small dislocation density of 1.04×10-3 nm-2 was obtained, indicating the existence of few lattice defects and good crystallinity. The atomic force microscopy (AFM) observation showed the coatinǵs granular nature composed of spherical nanoparticles with almost homogeneous distribution. The average transmittance in the visible región is around 75-80% and optical bandgap, 3.25 eV, respectively were obtained for our coatings indicating their suitability in photocatalytic applications. UV-vis spectrometry reveals a methylene blue (MB) dye decoloration efficiency of 96% after 180 min using ZnO:Ag (3:3 layers) film.