Facile hydrothermal synthesis of Zn_1-xFe_xO nanoparticles

Even if ZnO NPs have been widely investigated, they are still relevant given their versatility in various fields of application. Hence there is a necessity to advance techniques and synthesize ZnO NPs in a highly controlled manner to enhance their properties.

It is well known that the properties of nanoparticles depend mostly on the size and the homogeneity of their crystalline structure. Hydrothermal synthesis is a promising technique, as it promotes the highly controlled synthesis of nanoparticles at low temperatures and short reaction times, without the need for expensive equipment and the production of polluting effluents.

This study achieved not only the synthesis of ZnO NPs but also the crystallization of Zn_1-xFe_xO solid solution NPs with the inclusion of Fe²⁺ ions in quantities from 1 to 10% in the zinc oxide wurtzite structure. These nanoparticles were synthesized through hydrothermal reactions, carried out on Teflon-lined stainless-steel autoclaves at a temperature of 160 °C and a reaction time of only 1 hour using Zn(NO₃)₂ 6H₂O as the zinc ion precursor, FeCl₂·4H₂O as iron atoms and NaOH solutions as hydrothermal media.

The synthesized nanoparticles were analyzed using XRD, which presented highly defined peaks proving the exclusive crystallization of ZnO NPs and their gradual shift to lower angles, matching with the expansion of the lattice of the unit cell, from 45 nm to 53 nm with 10% Fe²⁺ substitution. Also, the Zn_1-xFe_xO nanoparticles exhibited a notable change in colour and hue relative to the ZnO NPs. Finally, DLS indicated a size of about 60 nm and high homogeneity of the NPs. Meanwhile, UV-Vis spectroscopy indicated the formation of Zn_1-xFe_xO nanoparticles.