HIGH SURFACE AREA HYDROXYAPATITE NANOPARTICLES SYNTHESIZED VIA CALCIUM STEARATE ENCAPSULATION BY MIXED SURFACTANT-MEDIATED APPROACH

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Acidic aqueous solution of calcium phosphate was mixed with both or either of nonaethyleneglycol monododecylether (C₁₂EO₉) and polyoxyethylene (20) sorbitan monostearate (Tween60) and then treated with aqueous ammonium at 25°C. In contrast to both single surfactant systems, the TEM image of the resulting solid in the mixed surfactant showed an aggregate of lath-shaped particles 4-8 nm wide and above 100 nm in length,consisting of 2-3 nm wide core particles encapsulated with calcium-stearate (Ca-St) films. On calcination at 500°C, the Ca-St encapsulated solid was converted into HAp nanoarticles with a surface area of as high as 364 m²g^-1.