Porous nanoparticles of Al and Ti generated by laser ablation in liquids

Abstract

Experimental results are presented on the generation of porous nanoparticles of either Al or Ti by laser ablation of solid targets in ethanol, water, and n-propanol saturated with hydrogen. The nanoparticles are characterized by high resolution transmission electron microscopy (HR TEM) and optical absorption spectroscopy. Saturation of the liquid with gaseous hydrogen leads to the formation of internal cavities in nanoparticles. In the case of short laser pulses (180fs, Ti:sapphire laser at 800nm wavelength), the nanoparticles are mostly spherical with the size of 30–50nm at concentration about 1015cm−3. The cavity occupies from 20 to 50% of the particle volume. Longer laser pulses (70ns, Nd:YAG laser at 1064nm wavelength) generate facetted nanoparticles with facetted cavities inside. The mechanism of formation of cavities is discussed on the basis of temperature-dependent solubility of hydrogen in metals.