An ex situ study of the adsorption of calcium phosphate from solution onto TiO2(110) and Al2O3(0001)

Ex situ atomic force microscopy and x-ray photoelectron spectroscopy are employed to characterise the adsorption of calcium phosphate from an aqueous solution of CaCl2.H2O and KH2PO4 onto rutile-TiO2(110) and α-Al2O3(0001). Prior to immersion, the substrates underwent wet chemical preparation to produce well-defined surfaces. Calcium phosphate adsorption is observed on both rutile-TiO2(110) and α-Al2O3(0001), with atomic force microscopy images indicating island-type growth. In contrast to other studies on less well-defined TiO2 and Al2O3 substrates, the induction period for calcium phosphate nucleation appears to be comparable on these two surfaces.