Effect of the Diameter on the Band Gap of ZnO Nanorods

ZnO nanomaterials have different properties from the bulk. One interesting property is band gap. It is found that the band gap is dependent on the dimensions of the nanostructures. Many methods have been used by researchers [1-7] to produce ZnO nanostructures but amongst the soft chemistry methods, chelating agents are normally used [1,6,7]. In this work zinc oxide nanostructures have been synthesized using the sol-gel synthesis method. The effect of a synthesis with and without the use of gelling agent is investigated. One sample is done using a sol-gel synthesis route using tartaric acid and the other sample is synthesized without using a gelling agent at all. Results showed that the samples are pure, however the sample prepared without using the gelling agent are made up of rods with long aspect ratios while the one obtained using the gelling agent are made up of rods with lower aspect ratios. It is found that the band gap of the high aspect ratio ZnO is smaller than the one with low aspect ratio. This is attributable to the lattice expansion of the lower aspect ratio ZnO nanorods as obtained from quantitative X-Ray diffraction. Therefore, a characteristic of ZnO nanomaterials is dependent on their dimensions.