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 coating´s 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 coating´s 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.