| 研究実績の概要 |
The project aimed at investigating the effect of high pressure on the properties and morphologies of nanoparticles (NPs) prepared via the laser ablation in liquid (LAL) technique. Thus far, no effect of environment pressure on product NPs was reported, though LAL is an increasingly used, green and convenient method to prepare nanomaterials at laboratory scale.
We mainly focused on investigating the effect of medium pressure on the ablation of Zn in water-ethanol and of Sn target in CO2. In the first system, photoluminescence (PL) was measured and thoroughly analyzed to reveal how different defects in ZnO NPs are governed by both medium chemistry and pressure. It was found that the defects inside the product NPs (and consequently- PL) are much more effected by the medium composition (water/ethanol ratio), while pressure mainly affected the size and morphology of the produced NPs.
Meanwhile, in the second system, in-situ shadowgraphy was used to study the behavior of the ablated zone over time, as it first emerged, then developed as a bubble-like structure (BLS), and finally collapsed. The BLS was found to follow 4 independent phases: formation, expansion, shrinkage and final collapse. The BLS lifetime was shown to be pressure-dependent, being the longest near the density fluctuation ridge of the medium, i.e., at 8.8 MPa at 40 degrees Celsius (in case of CO2).
The results obtained in this project clearly indicate that both medium composition and pressure can be used as additional tools to tune the morphology and properties of nanostructures produced via the LAL technique.
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