Preparation of amine-incorporated hydroxyapatite through a single-step hydrothermal reaction

Abstract

We report on the preparation of an amine-incorporated hydroxyapatite (NH2-HAP) by applying o-phosphorylethanolamine (PEA) as a phosphate source. By changing the ratio of PEA to normal phosphate source, three samples of NH2-HAPs having different contents of amine are synthesized. The TEM analysis confirmed that NH2-HAP exhibits elongated rod shape which is similar to the hexagonal rod of pure hydroxyapatite (HAP). As the concentration of PEA increases, the average size of NH2-HAP along (001) direction decreases approximately from 55.4(±10.39) to 31.2(±8.3) nm. The XRD patterns of NH2-HAPs are well matched with typical HAP patterns. Line broadening of XRD peaks in NH2-HAP seems to originate from low crystallinity and smaller size compared to pure HAP. Primary amine group on the surface of NH2-HAP is confirmed by both surface elemental analysis (XPS) and the ninhydrin test. The nitrogen content of NH2-HAP surface is approximately 0.6 ∼ 1.1 at.% based on XPS experiment.