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