Sintesi e caratterizzazione di nanoidrossiapatiti funzionalizzate con rame

The present work focuses on the synthesis and characterization of hydroxyapatite (HA, Ca10(PO4)6(OH)2), a very versatile ceramic material, with a particular interest on its surface and interfacial properties. The HA belongs to the calcium phosphates group which are apatites. The structure is formed by tetrahedral PO4 groups, calcium atoms and hydroxyl units, resulting in a stoichiometric Ca/P ratio of 1.67. Hydroxyapatites are intrinsically present in nature being the main constituent of dental enamel and human bones, where they are present in a percentage of 50% in weight. They can be naturally extracted from biological sources or wastes or artificially produced in the form of nanoparticles. They are characterized by a surface hydrated layer which confers to them a great ionic mobility, ion exchange and adsorption capacities. Moreover, hydroxyapatite shows both acidic and basic properties due to the presence of both acid and basic sites. Thanks to the adsorption capacities, to the acid-base adjustability and to the many possible ionic substitution, the hydroxyapatite results to be a promising material in both biomedical and catalytic applications, as well as in the environmental remediation field. In the present work experimental research is proposed to tailor the surface properties of nanometric HA. A non-stoichiometric hydroxyapatite with the {010} facet rich in phosphorous terminations, labelled as P_rich HA, has been synthetised by a co-precipitation method to obtain nanometric size, low crystallinity degree and high specific surface area. The prepared sample has been functionalized with copper by an ion-exchange method, where the Ca2+ surface cations are substituted with Cu2+ cations. In order to verify the success of the synthesis in terms of crystalline phase composition and to study the surface properties of both functionalized and non-functionalized samples different techniques are employed. X-ray powder diffraction (XRPD) and transmission electron microscopy (TEM) are performed to have structural and morphological information, while UV-vis-NIR spectroscopy to assess the electronic properties. Low temperature N2 adsorption is performed to evaluate the specific surface area. Fourier Transform Infrared (FTIR) spectroscopic analysis of probe molecules are employed to investigate the surface sites. The obtained results are compared, in the course of this study, with both crystalline calcium-rich hydroxyapatite (Ca_rich HA) and amorphous calcium phosphate (ACP) samples.