Bismuth oxide is an important bismuth compound having applications in electronics, photo-catalysis and medicine. At the nanoscale, bismuth oxide experiences a variety of new physico-chemical properties because of its increased surface to volume ratio leading to potentially new applications. In this manuscript, we report for the very first time the synthesis of bismuth oxide (Bi₂O₃) nano-flakes by pulsed laser ablation in liquids without any external assistance (no acoustic, electric field, or magnetic field). The synthesis was performed by irradiating, pure bismuth needles immerged in de-ionized water, at very high fluence ∼160 J cm⁻² in order to be highly selective and only promote the growth of two-dimensional structures. The x- and y-dimensions of the flakes were around 1 μm in size while their thickness was 47.0 ± 12.7 nm as confirmed by AFM analysis. The flakes were confirmed to be α- and γ-Bi₂O₃ by SAED and Raman spectroscopy. By using this mixture of flakes, we demonstrated that the nanostructures can be used as antimicrobial agents, achieving a complete inhibition of Gram positive (MSRA) and Gram negative bacteria (MDR-EC) at low concentration, ∼50 ppm.

Vanadium pentoxide is the most important vanadium compound by being the precursor to most vanadium alloys. It also plays an essential role in the production of sulfuric acid as well as in metal-ion batteries and supercapacitors. In this paper, pulsed laser ablation in liquids is used to synthesize “naked” vanadium pentoxide nanostructures. The resulting particles take up “nearly-spherical” and “flower-like” morphologies, composed of α-V₂O₅ and β-V₂O₅ crystalline phases. Even “naked”, the nanostructures are stable in time with a zeta potential of −51 ± 7 mV. In order to maximize the production of vanadium pentoxide nanostructure, the optimal repetition rate was determined to be @ ∼6600 Hz when irradiating a pure vanadium target in DI-water. This corresponds to a cavitation bubble lifetime of around ∼0.15 ms. At that repetition rate, the production reached ∼10 ppm per minute of irradiation. Finally, from the characterization of the α-V₂O₅ and β-V₂O₅ nanostructures, the surface energy of each phase has been carefully determined at 0.308 and 1.483 J cm⁻², respectively. Consequently, the β-phase was found to display a surface energy very close to platinum. The exciton Bohr radius has been determined at 3.5 ± 0.7 nm and 2.0 ± 0.6 nm for α-V₂O₅ and β-V₂O₅ phases, respectively.