VISIBLE LIGHT PHOTOCATALYSIS BY TAILORING CRYSTAL DEFECTS IN ZINC OXIDE NANOSTRUCTURES

The photocatalytic activity of zinc oxide (ZnO) nanoparticles, films and nanowires as a potential visible light photocatalyst is presented in this work. ZnO nanoparticles were synthesized in different alcoholic solvents. Crystal defects were introduced either by doping the crystallites with manganese or by fast crystallization (using microwave irradiation during synthesis). ZnO, with a band gap of 3.37 eV, normally absorbs electromagnetic waves in the ultraviolet region, but introducing defects into its crystal lattice can shift the absorption more toward the visible light band from 400nm to 700nm by creating intermediate states which inhibit electron-hole recombination. The undoped ZnO nanoparticles synthesized using microwaves showed comparable photocatalytic activities to the doped samples using the conventional heating method. To increase the effective surface area of the photocatalyst, ZnO nanowires were grown by a solution-based technique. Methylene blue degradation was observed to be enhanced in the presence of the ZnO nanowires compared to the ZnO nanoparticles. Intentional defect creation in photocatalysts could be an attractive possibility to apply in the visible light photocatalytic degradation studies.