Nano-particles of hydroxyapatite formed by underwater laser ablation method

Hydroxyapatite (HAp) is a biocompatibility material. We have successfully obtained the nano-particles of hydroxyapatite by the underwater laser ablation. A sintered HAp ceramics target was made of commercially available HAp powder and it was placed in the purified water. The focused KrF excimer laser outputs were irradiated on the target surface at the fluence from 7 J/cm² to 23 J/cm² at the repetition rate of 100 Hz. We found that the amount of the particles increased in proportional to the laser fluence. However, the rate of content of sub-micron particles was became larger at the lower laser fluence. The particles made by 7J/cm² laser ablation were dispersing in the water for 12 hours after stopping the laser irradiation.