Fabrication of gold and silver nanoparticles with pulsed laser ablation under pressurized CO2

Siti Machmudah, Wahyudiono, Noriharu Takada, Hideki Kanda, Koichi Sasaki and Motonobu Goto

Abstract

Pulsed laser ablation (PLA) has become a promising method for the synthesis of nanoclusters for photonics, electronics and medicine. In this work PLA in pressurized CO₂ has been applied for fabrication of gold and silver nanoparticles. Laser ablation was performed with an excitation wavelength of 532 nm under various pressures (0.1–20 MPa), temperatures (40–80 °C) of CO₂ medium and ablation times (1500–9000 s). On the basis of the experimental result, it follows that structures of gold (Au) and silver (Ag) nanoparticles were significantly affected by the changes in CO₂ density. The structures of gold and silver nanoparticles also changed with an increase of ablation time. From a field-emission scanning electron microscopy (FE-SEM) image of the fabricated gold nano-structured particles on silicon wafer, it was seen that a network structure of smaller gold particles was fabricated. A similar morphology of particles fabricated from silver plate was observed. Silver particles contain nanoparticles with large-varied diameter ranging from 5 nm to 1.2 μm. The mechanism of nanoparticles fabrication could be observed as follows. Bigger gold/silver particles melted during the ablation process and then ejected smaller spherical nanoparticles, which formed nanoclusters attached on the molten particles