Hydroxyapatite micro- and nanoparticles: Nucleation and growth mechanisms in the presence of citrate species

authors	Martins, MA; Santos, C; Almeida, MM; Costa, MEV
nationality	International
journal	JOURNAL OF COLLOID AND INTERFACE SCIENCE
author keywords	hydroxyapatite; nanoparticles; microparticles; stabilization; aggregation; self-organization
keywords	CALCIUM PHOSPHATES; CRYSTALLIZATION; 37-DEGREES-C; DEPENDENCE; PARTICLES; NANORODS; ACID
abstract	Hydroxyapatite (HAP) particles with different morphologies were precipitated from homogeneous calcium/citrate/phosphate solutions at physiological temperature. Small variations of the starting solution pH in the range 7.4 < pH < 8.5 made it possible to switch the precipitated particle morphology from a micrometric bundlelike to a nanometric needlelike shape. The role of the existing citrate species as calcium chelates is here discussed within the framework of particle nucleation and growth mechanisms. While temperature-dependent calcium citrate complex (Cacit) stability is here suggested to control the free calcium availability and thereby the nucleation rate, the adsorbed citrate species are proposed to control the nanoparticle stability. Moreover, an attempt to detail the role of citrate species in the ordered aggregation of HAP nuclei leading to the observed peanut and bundlelike microparticles morphology is also presented. (c) 2007 Elsevier Inc. All rights reserved.
publisher	ACADEMIC PRESS INC ELSEVIER SCIENCE
issn	0021-9797
year published	2008
volume	318
issue	2
beginning page	210
ending page	216
digital object identifier (doi)	10.1016/j.jcis.2007.10.008
web of science category	Chemistry, Physical
subject category	Chemistry
unique article identifier	WOS:000252482800010