Photocatalytic activity of nanostructured ZnO films prepared by two different methods for the photoinitiated decolorization of malachite green

Patterned thin films ZnO are successfully prepared on glass substrates by the sol-gel method using both dip coating and spin coating. Two different procedures are applied for preparation of the films: (i) polymeric one (zinc acetate and ethylcellulose) and (ii) one with complexing agent monoethanolamine (zinc acetate and 2-methoxyethanol). The films of ZnO nanocrystallites with hexagonal crystal structure are characterized by means of scanning electron microscopy, X-ray photoelectron spectroscopy and X-ray diffraction. The films obtained by procedure (i) possess needle-like structure, while the films obtained by procedure (ii) have ganglia on the surface. The as-obtained ZnO films are studied with respect to the photoinitiated bleaching of malachite green (MG) under UV illumination in aqueous solutions. It turns out that the films obtained by procedure (ii) have a better photocatalytic activity than those deposited by procedure (i). It is proven that the films have also some activity in darkness, which is lower than the activities under UV light.