Structural, optical and photoelectric properties of indium-doped zinc oxide nanoparticles prepared in dimethyl sulphoxide

ZnO and In3+-doped ZnO nanoparticles were prepared by homogeneous nucleation in a dimethyl sulphoxide (DMSO). During the synthesis the concentration of the zinc acetate precursor (0.01-0.1 mol dm(-3)) and the In3+/Zn2+ molar ratio (0.01-0.1) were varied. The crystalline structure of the nanoparticles was investigated by X-ray diffraction. The thermal behaviour of the particles was determined by thermogravimetric (TG) and differential scanning calorimetric (DSC) measurements. The surface properties were examined by X-ray photoelectron spectroscopy (XPS) and streaming potential measurements. From the results of these experiments it was established that the In3+ ions built into the crystal lattice of the ZnO and the surface of the particles enriched in In3+ ions. The morphological properties and the particle size were studied by transmission electron microscopy (TEM) and dynamic light scattering (DLS). It was found the primary particle size decreased with the increasing In3+/Zn2+ molar ratio and with the increasing zinc precursor concentration and the primary particles formed aggregates. The size of the aggregates increased with the increasing Zn2+ ion concentration and with the increasing In3+ content of the particles. The optical properties were investigated by UV-vis absorbance and photoluminescence (PL) measurements. Due to the presence of the In3+ ions the optical properties of the nanocrystals also changed. Blue shift was found in the absorbance spectra of the nanoparticles compared to the spectrum of the pure ZnO, and a new broad emission band centered at 465 nm appeared in the emission spectra of the doped samples, which could be caused by the generation of more interstitial Zn defects in the crystal lattice. Photoelectric properties of the calcined ZnO and some of the doped samples were studied on the surface of interdigitated microelectrodes. (C) 2007 Elsevier B.V. All rights reserved.