Study On Preparation Of Hydroxyapatite Nanoparticles With The Spherical Morphology

Hydroxyapatite has similar chemical composition and crystal structure with human hard tissues.Owing to its excellent bioactivity,biocompatibility,harmless and safe to transplant into the living body of human being,it can make a chemical bonding with collagen of bone,therefore,it was widely used in tissue engineering,bone repair or replacement and dental materials.In recent years,with the development of drug and gene carrier,researchers gradually developed many other novel application of HAP nanoparticles such as controlled release of protein,gene carrier,drugs and growth factor.At present,the preparation of hydroxyapatite nanoparticles with the regular morphology and different spatial structure has become a hot spot in biological materials.The purpose of this study is to synthesize hydroxyapatite nanoparticles with the spherical morphology and high dispersion.In this thesis,the surfactant cetyl trimethyl ammonium bromide(CTAB)was induced the nucleation and growth process of HAP under hydrothermal conditions,and studied the influence of different concentration of CTAB and reaction temperature on the particle size and morphology of products.X-ray diffraction(XRD),Fourier transform infrared spectrometer(FTIR),Scanning electron microscopy(SEM),Transmission electron microscopy(TEM),Energy dispersive X-ray spectrum(EDS)and nitrogen adsorption/desorption were employed to characterize the products.HAP nanoparticles with high crystallinity were synthesized under hydrothermal conditions,but the irregular morphology and agglomeration between particles occurred inevitably.In order to improve the morphology and dispersion,the carbon quantum dots(CQDs)used as the core were first introduced in the synthesis system and induced deposited of calcium orthophosphates on the surface of CQDs through homogeneous deposition to gain hydroxyapatite nanoparticles with the spherical morphology.We investigated the influence of reaction parameters,such as the concentration of CQDs,the amounts of CTAB and reactant,solution pH,reaction temperature,reaction time and the different of additives on the particle size and morphology of products in the synthesis process.The products were characterized by above mentioned measurements.Transmission electron microscopy result indicated that the introduction of CQDs favor the samples with the uniform spherical morphology of an average diameter of ca.5 nm,good dispersion.The carbon quantum dots were used as the core to adsorb surfactant CTAB molecular layers on the surface,then,PO43-adsorbed layers were formed on the surface of CQDs by electrostatic attraction.Subsequently,PO43-adsorbed layers react with Ca2+ to form calcium orthophosphates coatings.The HAP nanoparticles with regular morphology were synthesized by adjusting the reaction conditions so that calcium orthophosphates were coated on the surface of CQDs uniformly.The experimental results indicated that the optimal reaction conditions were as following: the system was reacted under the refluxed condition at 80 ? for 8 h,the molar ratio of CTAB: Na3PO4 was 1: 1,solution pH value was 10,cyclohexane was added to the system.The synthetic products were uniform with an average diameter of ca.60 nm,appropriate spherical morphology,good dispersion at the optimal reaction conditions.The molar ratio of Ca/P is 1.61 slightly lower than that of hydroxyapatite of the stoichiometric ratio is 1.67.Nitrogen adsorption/desorption experiment result showed that the specific surface areas,BJH adsorption pore volume and pore diameter of the synthetic products were 93.5 m2/g,25 nm and 0.5682 ml/g,respectively.Mesoporous comes from interparticle cavity.