Nanoestruturas de Óxido de Zinco obtidas pelo Método Hidrotermal de Microondas Doméstico

Abstract

The motivation of this work was to obtain zinc oxide (ZnO), which is a semiconductor of large technological application, by a new chemical method, the Hydrothermal Method coupled to the use of a domestic microwave oven. Such method favors the obtainment of materials at lower temperature and short time period, besides favoring the formation of particles with controlled size and morphology, and also allowing a good control of the particle properties. The ZnO samples were synthesized at low temperature (100 °C) and at a short time period, using different reaction media: water, ethanol and water/ethanol (1:1); and alkalized with NaOH and NH4OH. X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Field Emission Gun (FEG), Infrared Spectroscopy (IR), Raman Spectroscopy, UV-vis Spectroscopy and Photoluminescence techniques were carried out to characterize the material. All the samples obtained crystallized in a hexagonal structure of the wurtzite type whose unit cell volumes do not significantly vary with the time. Moreover, the samples alkalized with NH4OH were more organized, both in the short and in the long ranges, than the samples alkalized with NaOH. This was due to the formation of two different ions with opposite charges, − 24 ) (OH Zn and + 24 3 Zn(NH ) , that are attracted to each other during the process and then lead to the material organization. Several structures, such as spherical nanoparticles, nanoarrays, nanorods and flower-like clusters were obtained according to the reaction medium, alkali and synthesis time. The size of these structures increases with the increase of the synthesis time and varies from 20 to 570 nm, when they are synthesized in a lower time and from 500 nm to 1,5 μm in a higher synthesis time, showing that the particle sizes can be controlled easily.