Fabrication of platy apatite nanocrystals loaded with TiO 2 nanoparticles by two-step emulsion method and their photocatalytic activity

Abstract

Nanometer-sized TiO 2 island structure on the platy hydroxyapatite nanocrystals (HAp) has been accomplished by two-step emulsion process. At the first step, platy HAp nanocrystals, of which size was in the range of 70–200 nm after heat-treatment at 1078 K for 1 h, were prepared using the W/O emulsion system. Before the second step, HAp nanocrystals were immersed in NaH 2PO 4 solution for the formation of hydroxyl group on their surface. In the following, titanium tetraisopropoxide reacted with the hydroxyl group of HAp surface to form TiO 2 nanoparticles on the surface of HAp nanocrystals, which were dispersed in the micrometer-sized methanol droplets of polyethylene cetylether–cyclohexane mixture (methanol/oil emulsion). The resulting hydroxyapatite nanocrystals loaded with TiO 2 nanoparticles showed the high photocatalytic activity comparing to the commercial TiO 2 catalyst.