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Herein we show how the unique temporal and thermal events occurring during the pulsed excimer laser ablation of an Al target in water result in hollow Al 2 O 3 micro/nanoparticles with smooth surfaces and an amorphous structure. We demonstrate that the hollow particles are formed on laser-induced bubbles from laser ionized/evaporated liquid during the ablation. The fabrication of hollow particles can be improved by the addition of ethanol to the water, and the particles contain crystalline Al. Our work and the associated mechanism represent a new paradigm to fabricate hollow particles directly from bulk material; that is, the excimer laser ablation produces nanoclusters from the target and bubbles from the liquid, and the bubble interfaces trap the nanoclusters, resulting in the formation of hollow particles.

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Micro/nanoparticles were fabricated by pulsed-excimer-laser ablation of a Pt target in water. Three kinds of hollow Pt particles (coalesced by micrograins, assembled by nanocrystals or with smooth shells) were observed together with solid particles using different laser fluences (2.3-6.8 J cm(-2)) and after 6000 laser shots. We propose that the hollow particles were formed on laser-produced bubbles which provided thermodynamically preferred nucleation sites and diffusion sinks for the laser-fabricated Pt clusters or particles. Although the hollow particles are a small proportion, the results have extended the scope of particles that pulsed-laser ablation in liquid can fabricate, and have enriched the mechanistic scenario of laser ablation and nanostructure formation in liquid.