Structural Imperfections of the Hydroxyapatite Surface Layer to Engineer Its Electrical Potential
Summary of the Doctoral Thesis
Anna Bystrova, Riga Technical University, Latvia
The Doctoral Thesis aims to identify the influence of hydroxyapatite (Hap) defects (such as OH-group, H-, O-vacancies, H-interstitials, and their combination) on the electrical potential of HAp’s surface which influences biocompatibility and control cell adhesion.
HAp contains various structural imperfections (defects) and has a non-stoichiometric composition. The structural imperfections induce the heterogeneity of the surface electrical potential. However, the role of the defects OH-group, H-, O-vacancies, H-interstitials, and their combination in the formation of HAp surface polarization and their influence on HAp surface charge, energy band structure and electron work function has not yet been investigated.
In this Thesis, for the first time the theoretical and experimental approaches were used to investigate the influence of structural imperfections (OH-, H-, O-vacancies, H-interstitials, and hydrogen atoms filling unsaturated hydrogen bonds) on HAp electrical properties.
The computer simulations of HAp structures analyse the properties of these effects. Semiempirical methods of molecular mechanics and quantum mechanics, as well as methods of density functional theory were employed.
The experimental studies of the HAp surface electrical properties were carried out by photoluminescence (PL) emission, synchrotron excitation spectroscopy, threshold photoelectron (PE) emission spectroscopy. The influence of annealing, hydrogenation, microwave, gamma irradiation and their combination on HAp defects was investigated experimentally for the first time. The obtained results are in accordance with computational data.
The achieved results will help to improve technologies to engineer the surface charge of Hap.
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