Efeito da radiação micro-ondas na interação da prata com nanocristais de hidroxiapatita

Abstract

The aim of this work was to evaluate the effect of microwave heating on the insertion of Ag+ ions in hydroxyapatite (HA) nanocrystals ion exchange. Assynthesized HA nanocrystals obtained by the precipitation method in aqueous medium were immersed in an Ag+-containing solution (0.1 mol L-1) and heated in a microwave oven at 100°C/15 min under a power of 800 W. The nanocrystals were also heated in an oil bath at 80°C/4 h. To isolate the effect of the heating sources from the Ag+ ions, the HA nanocrystals were also heated in aqueous solution without Ag+ ions. All the assays were characterized by wavelength dispersive X-ray fluorescence spectroscopy, X-ray diffraction with Rietveld refinement, transmission electron microscopy and Fourier transform infrared spectroscopy. Regardless of the heating source, Ag+ ions reacted with HA nanocrystals resulting in the formation of Ag3PO4 and Ag0 phases. Microwave heating was able to accelerate these reactions. In addition, both the microwave heating and Ag+ ions clearly affected the insertion of the HPO4 2- and CO3 2- ions into the PO4 3- and OH- sites of the HA structure. As a consequence of these occupations, the lattice parameters, unit cell volume, crystallite size, morphology and aspect ratio of the HA nanocrystals were affected. The observed results indicate that microwave heating was able to alter not only crystallographic aspects of the HA phase, but also the Ag+-doping rate of the HA nanocrystals in aqueous solution.