Biomimetic synthesis of carbonated hydroxyapatite thin films

Free-standing continuous carbonated hydroxyapatite (HA) films were synthesized at room temperature through a biomimetic pathway. A stearic acid monolayer was utilized as a template for inducing deposition from supersaturated calcium phosphate solutions. Crystalline films could be collected at the water-air interface after just 8 h at room temperature when the Ca/P molar ratio of the supersaturated solution is 1: 1, whereas the period of time necessary to obtain a crystalline film lengthens to 12 days when the Ca/P of the supersaturated solution is 9:1. The films obtained from this last solution display smoother surfaces, contain a greater amount of carbonate substituted to phosphate ions, and exhibit a greater Ca/P molar ratio, which slightly increases with time. Heat treatment up to 700 degrees C allows to obtain continuous films of HA crystals preferentially oriented almost orthogonal to the film surface. On the other hand, heat treatment of the films deposited from solution with a Ca/P ratio of 1:1 allows to get bi-phasic films constituted of smooth HA/p-tricalcium phosphate aggregates. degrees (c) 2005 Elsevier B.V. All rights reserved.