Preparation and characterization of nanosized hydroxyapatite particles in AOT inverse microemulsion

Abstract

Nanosized particles of hydroxyapatite (HAP) were synthesized by reacting Ca (H₂ PO₄)₂· H₂ 0 solution complex with equimolar Ca(OH)₂ saturated solution in sodium bis (2-ethylhexyl) sulfosuccinate (AOT)/isooctane water-in-oil microemulsion. The formation of microemulsion strongly depended on water content w (w = [H₂O]/[AOT] molar ratio) and concentration of surfactant and cosurfactant (1-octanol). By the variety of conductivity with w and the partial ternary phase diagram derived from a series of demarcation points, we set the basic component of microemulsions: [AOT] = 0. 1 M(mol/ dm₃), [1-octanol] = 0.1 M and w = 3–9. Dynamic light scattering (DLS), UV-visible absorbance, TEM analysis and X-ray diffraction were used to characterize the microemulsion, formation of particles and resulting HAP particles. At low water content (w < 9), the water pool radius of the droplet in the Ca(H₂ PO₄)₂ · H₂O microemulsion lineally depended on w. The size of final HAP particles was strongly affected by water content w and reactant concentration. With increasing water content w from 3 to 9, the size of HAP particles increased from 10–20 nm to 40–50 nm at reactant concentration [Ca(H₂ PO₄) 2 · H₂ 0] = 12 × 10^-3 mol/ dm³. The resulting HAP particles were poorly crystallized and spherical in morphology.

Keywords

hydroxyapatite / microemulsion / nanoparticles

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