Surface Characterization of Hydroxyapatite and Related Calcium Phosphates by XPS and TOF-SIMS

摘要

The surfaces of six biologically interesting calcium phos-phate (CaP) phases (hydroxyapatite, dibasic calcium phosphate dihydrate, dibasic calcium phosphate, mono-basic calcium phosphate, /i-tribasic calcium phosphate, octacalcium phosphate) have been examined by X-ray photoelectron spectroscopy (XPS) and time-of4light sec. ondary ion mass spectrometry (TOP-SIMS). The intensity of an O(ls) shake-up satellite correlates with the phos-phate oxygen content. Together with the Ca/P and 0/Ca XPS peak ratios, this feature helps provide identification of the CaP phase(s) present in the surface of unknown samples and establish their mole fractions, as proven with a bone sample. Contributions from carbonate impurities can be quantified using its C(ls) peak at 279.9 eV and subtracted from the 0(ls) line shape to aid identification. Principal component analysis (PCA) has been applied successfully to analyze TOF-SIMS spectra of these six CaP phases. Multivariate analysis can help differentiate these CaP phases using the first two PCs, which are dominated by the relative intensities of only a few key ions: P03, 0, Cat, Ca0H~, P02-, and OH-.