Fabrication of gold and silver nanoparticles with pulsed laser ablation under pressurized CO ₂

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.

Nickel nanoparticles generated by pulsed laser ablation in liquid CO2

“…This shows that the aggregation of nickel particles connects to the aggregation of carbon particles. However, under liquid CO 2 , small particles attached in sphere-like agglomerates could not be observed with the specificity available to particles generated under supercritical CO 2 [33]. This may be due to the changed CO 2 density.…”

“…This may be due to the changed CO 2 density. The network structure of agglomerated particles may change the properties of the nickel nanoparticles [33]. The agglomeration phenomenon may occur due to the dense environment, which can hasten coagulation and quenching of the metal atoms.…”

“…The morphology, structure, elemental composition, and particle size distribution of the generated particles are discussed here. Previously, Machmudah et al [11,12,33] conducted pulse laser ablation under dense CO 2 to generate nanoparticles with gold and silver plates as the target. They reported that gold and silver nanoparticles have been produced with a laser wavelength of 532 nm.…”

Formation ofAu–carbon nanoparticles by laser ablation under pressurizedCO2

“…In the images, a network structure of smaller Au nanoclusters seems to surround larger Au nanoparticles. This arrangement may form due to the fast coagulation and quenching of the Au atoms in the dense CO 2 environment . Saitow et al performed nanosecond PLA with an excitation wavelength of 532 nm in supercritical CO 2 to produce Au nanoparticles.…”

“…Furthermore, employing CO 2 as the reaction medium has been shown to prevent contaminating the generated nanoparticles with impurities from the organic solvents usually used as a reaction medium . This paper presents further insight from the previously reported gold nanoparticles synthesis via PLA in pressurized or supercritical CO 2 since we conducted more comprehensive analysis. We demonstrate that the generated Au nanoparticles were not pristine Au nanoparticles as believed in earlier studies, but the composite of Au and C nanoparticles.…”