Synthesis of nanoporous calcium phosphate spheres using poly(acrylic acid) as a structuring unit

Abstract

Calcium phosphate (CaP) spheres with nanopores were synthesized using poly(acrylic acid) (PAA) as the structuring unit. In this method, colloidal droplets of the PAA/Ca2+ complex were prepared by adding a Ca(NO3)(2) solution to a PAA aqueous solution and then mixed with an (NH4)(2)HPO4 solution, which allowed the nucleation and growth of CaP nanocrystals in the PAA matrix. Thereafter, the as-synthesized PAA/CaP spheres were heat-treated at 550 degrees C for 3 h to remove the PAA phase, followed by treatment in ammonium nitrate solution to remove the CaO phase formed as an impurity. The prepared Cap spheres showed a narrow size distribution with an average diameter of 146 +/- 43 nm and nanopores formed via the removal of the CaO phase. (C) 2009 Elsevier B.V. All rights reserved.