Microstructure, vibrational and visible emission properties of low frequency ultrasound (42 kHz) assisted ZnO nanostructures

Abstract

Size and shape tuneable ZnO nanostructures were prepared by a low frequency ultrasound (42 kHz) routeusing various organic solvents as the reaction media. The crystalline nature, lattice parameters andmicrostructural parameters such as microstrain, stress and energy density of the prepared ZnOnanostructures were revealed through X-ray diffraction (XRD) analysis. The organic solvents influencedthe size and morphology of the ZnO nanostructures, and interesting morphological changes involvinga spherical to triangular shaped transition were observed. The visible emission properties and latticevibrational characteristics of the nanostructures were drastically modified by the changes in size andshape. Raman spectral measurements revealed the presence of multiphonon processes in the ZnOnanostructures. The intensity of the visible emission band was found to vary with the size andmorphology of the structures. The strongest visible emission band corresponded to the structure withthe largest surface/volume ratio and could be attributed to surface oxygen vacancies. The control overthe size and morphology of ZnO nanostructures has been presented as a means of determining theintensity of the visible emission band.