The Research Of Hydrothermal Synthesis Of Nano-hydroxyapatite Regulated By Amino Acids

There are many biological minerals in nature which are composed of inorganic materials and organic matrix by highly ordered self-assembly.These biominerals have diverous morphology and complex structure,which exibitite unique and excellent performance.During the biomineralization(such as hydroxyapatite,HAp),organic matrix play vital role in providing the nucleation sites,and also regulate the growth of the HAp crystal orientation.The organic matrix mainly involved in collagen fibers,whose basic units are amino acids.Thus it is of great importance to investigate how these amino acids affect on the composition,crystal structure and crystal size of HAp.In this study,four kinds of amino acids(aspartic acid,glycine,serine and arginine)were studied to regulate the performance of hydroxyapatite during hydrothermal synthesis process.The nucleation and growth of HAp as well as its morphological structure and properties were systematically studied by tuning the kinds of amino acids,concentrations,reaction temperature and time,also the pH value of reaction.The composition and structure of HAp were characterized by XRD,FTIR,SEM,TEM,TG,BET,Zeta potential to analysis composition,morphology,physical and chemical properties regulated by all kinds of amino acids in different concentrations.The results showed that we synthesized HAp particles with different morphology(micro-flower and rod)and particle size distribution regulated by several kinds of amino acids in 150 ?,2 h hydrothermal conditions.X-ray analysis results showed that the crystallinity of products regulated these amino acids are weaker than control;FTIR and TG results proved these amino acid absorbed on the crystal surface of HAp,and the quantity of adsorption decreased in turn of Asp(6.21%)> Ser(1.89%)> Gly(1.81%).SEM results showed that when the concentration of Asp is 0.12 M,which meant the molar ratio of-COOH/Ca is 12,we can synthesized multilevel structure of micro-flower HAp particles successfully,whose diameter distributed in 2-3?m,and which had specific surface area of 142 ?/g.It was a very promising carrier.For neutral Gly and Ser,when the concentration of Gly is 0.045 M,and 0.03 M for Ser,the average length of rod HAp particles decreased from 130 to 65-70 nm compared with control group,which did not significantly reduce in diameter,Gly and Ser significantly inhibited the growth of crystal's c axis;Ser had stronger inhibition than Gly because the side chains.Ser had hydroxyl group,as a result it can interact with HAp crystal face.As for alkaline Arg owned positively charged guanidine groups,can bind to HAp(001)crystal plane as strong electrostatic attraction,which made average length of particle decrease from 130 to 75 nm.The effect of several kinds of amino acid on regulation of HAp was different.We discussed regulation of HAp particles by these amino acids in the hydrothermal conditions systematically,and came up with the corresponding theoretical model,which provides the theory instruction for synthesizing different morphology of materials.