Synthesis and Optical limiting Characteristics of HAP@SiO2 core-shell Nanoparticles

Hydroxyapatite (HAP) nanoparticles were prepared by chemical precipitation method. The as prepared HAP particles were coated with silica via the hydrolysis of tetraethylorthosilicate for a coating time of 24 h, resulting in the formation of HAP@SiO2 core-shell structure. The shape, size and silica coating formation of the resultant particles were confirmed by Transmission Electron Microscopy (TEM), X-Ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR) and UV-Vis Diffuse Reflectance Spectroscopy (UV-DRS). The non linear optical limiting properties of HAP and HAP@SiO2 nanoparticles dispersed in ethylene glycol were studied at 532nm using 5ns Nd:YAG laser pulses. Our observation indicated that Three photon absorption was responsible for optical limiting characteristics in those nanoparticles and it was seen that the optical nonlinearity was enhanced in core-shell structures as compared with single counterparts.