Sonochemical synthesis of nano-hydroxyapatite using natural rubber latex as a templating agent

Abstract Natural rubber latex was successfully used as a template in the synthesis of nano-hydroxyapatite (HAp) with the aid of a sonochemical process (20 kHz) at 25 °C. The hydroxyapatite precursor was obtained using ultrasonic irradiation for 0, 10, 20, 30, 40, 50 and 60 min, respectively. It was then dried at 70 °C and calcined at 600 °C for 2 h (3 °C/min). The effect of sonication time and Ca:P ratio (1.5 and 1.67) on the properties of the powder was investigated by means of thermogravimetric analysis (TGA), X-ray diffraction (XRD), FT-Raman spectroscopy, transmission electron microscopy (TEM) and surface area analysis (N 2 -BET method). A lower temperature of formation for synthesised nano-HAp occurred in the case of a (Ca:P) ratio of 1.5. The study clearly indicated that a smaller diameter (8 nm) of nano- rod-like morphology resulted from a 20 min dose of ultrasonic irradiation at a (Ca:P) ratio of 1.5. A possible mechanism of nano-rod formation is that the short polyisoprene chain may act efficiently as a structure-directing agent playing an important role in the formation of nano-structural hydroxyapatite.