Laser-assisted preparation of complex colloidal nanostructures by nanosecond ablation in liquid

The paper presents results on nanosecond laser ablation of ZnO nanostructures immersed in a liquid. The nanostructured ZnO samples were prepared in two steps. In the first one, a thin catalyst Au layer was deposited on the glass substrate by standard on-axis pulsed laser deposition (PLD) technique. In the next step, using again the PLD method, ZnO was deposited on the Au layer and thus the nanostructured ZnO samples were produced. The as-prepared samples were then immersed in double distilled water and irradiated by nanosecond laser pulses delivered by a Nd: YAG laser system at λ = 532 nm. Two different configurations of irradiation – against the structure and through the glass substrate – were used in the ablation in liquid experiments. The influence of the laser fluence for each of the ablation configurations used on the size, shape and optical properties of the obtained colloidal nanostructures was investigated. It was established optimal processing conditions, allowing transfer of the ZnO nanostructures from the substrate into the liquid medium. The nanostructures shape and size distribution were evaluated by means of transmission electron microscopy. Selected area electron diffraction was employed for chemical phase identification of the produced nanostructures. The colloids obtained were investigated by optical transmission spectroscopy in the near UV and in the visible region.