Rutile microtubes assembly from nanostructures obtained by ultra-short laser ablation of titanium in liquid

Pulsed laser ablation of a titanium target in water was performed by an ultra-short laser source (Ti-sapphire, λ = 800 nm, 1 kHz, 100 fs). The obtained structures were characterized by atomic force microscopy, scanning electron microscopy, X-ray photoelectron spectroscopy, micro-Raman spectroscopy and X-ray diffraction, revealing the presence of non-stoichiometric titanium oxide nanoparticles with a certain amount of crystalline rutile phase. Upon remaining in water the ablated species, the formation of a lamellar phase has been observed. This lamellar phase rolls up to microtubes by remaining in water for a month, through a self-assembling process. The formed microtubes, with an inner diameter of about 2 μm and an outer diameter of 4 μm are characterized by a smooth interior surface and aggregation of nanoparticles on the outer surface.