Internal structure of nanoparticles of Al generated by laser ablation in liquid ethanol

Al NPs are synthesized by laser ablation of a bulk Al target immersed into liquid ethanol saturated with hydrogen at atmospheric pressure. The nanoparticles possess a well-distinguished core-shell structure. High Resolution Transmission Electron Microscopy shows several layers inside the Al nanoparticle: oxide layer, amorphous Al, single crystal Al, and a cavity in the center. Formation of the cavity is attributed to the sharp increase of hydrogen dissolution in Al upon its melting and its eventual release after the solidification.