Defect mediated photocatalytic activity in shape-controlled ZnO nanostructures

Shape-controlled ZnO nanostructures were synthesized through a facile soft-chemical approach by varying the concentration of OH⁻ ions. X-ray diffraction and Raman spectra reveal the formation of highly crystalline single-phase hexagonal wurtzite nanostructure. It has been observed that the concentration of OH⁻ ions plays an important role in controlling the shape of ZnO nanostructures. TEM micrographs indicate that well-spherical particles of size about 8 nm were formed at lower concentration of OH⁻ ions whereas the higher concentration of OH⁻ ions favor the formation of nanorods of length 30-40 nm. The optical studies confirmed that the band gap and near band edge emission of ZnO nanostructures are strongly dependent on the shape of particles. Furthermore, the decrease in the intensity of green emission as shape of particles changes from sphere to rod indicates the suppressing of defect density, which in turn influences the photocatalytic activity and ferromagnetic-like behavior of ZnO nanostructures.