Functionalization of the hydroxyapatite surface with ZnO for alizarin immobilization

Abstract

The surface of hydroxyapatite (HAp) was functionalized by the deposition of ZnO using microwave-assisted co-precipitation and hydrothermal synthesis with sucrose as a template. X-ray diffraction indicated the formation of ZnO/Zn-HAps without a significant change in the crystallinity of HAp. X-ray photoelectron spectroscopy indicated the substitution of Ca2+ by Zn2+ in the HAp structure and the formation of ZnO/Zn-HAp-type compounds, corroborating the refinement data. The morphology of the prepared particles was investigated through field emission gun-scanning electron microscopy and transmission electron microscopy, which revealed that nanoflowers of ZnO were deposited on the HAp surface. ZnO/Zn-doped HAps was impregnated with alizarin (AZ) at pH 4 and 8.5, resulting in hybrid pigments with varying hues of red. Attenuated total reflectance-Fourier transform infrared spectroscopy, UV–vis spectroscopy, and X-ray photoelectron spectroscopy suggested that better solids@dye interactions occurred at pH 8.5, and as indicated by C1s spectra, the appearance of the peak at 286.5 eV (C = O) and an increase in the peak intensity at 284.6 eV (C–C/H) confirmed the adsorption of the dye on the surface. Photodegradation tests revealed that the prepared pigments were highly stable after exposure to light.