Abstract: Influence of polydispersity on UV absorption spectra of ZnO nanoparticles, which were prepared from zinc bromide and sodium hydroxide as well as zinc acetate and sodium hydroxide in 2-propanol, had been studied. The particle size was measured with UV absorption spectrometry in-situ and high resolution transmission electron microscope (HRTEM). The growth kinetics of ZnO nanoparticles was in agreement with LSW (Lifshitz-Slyozov-Wagner) model for coarsening where the particle volume was proportional to aging time. However, the particle size distribution was found to be inconsistent with the LSW model, which has been reported previously for other systems. Computer numerical calculation was used to determine the effect of the distribution function on the UV absorption spectra of ZnO suspension. It was found that absorption spectra bent near the UV absorption edge and shifted with the increase of standard deviation (SD) of normal distribution function, which can lead to an over-estimation of the particle size from UV spectra. For monodispersed ZnO suspensions (SD/γ<5%), the over-estimation of particle size is only about 2%. If SD/γ of the particle is 15%, the over-estimation can be as high as 15.1%.

Key words: ZnO, Nanoparticles, UV absorption, Absorption edge, Band gap, Numerical imitation