Gold nanoparticles fabricated by pulsed laser ablation in supercritical CO₂

Nanosecond pulsed laser ablation (PLA) of gold plate with an excitation wavelength of 532 nm was carried out in supercritical CO₂ (scCO ₂) to fabricate gold nanoparticles. Surface morphology of the gold plate after irradiation and the crater depth after PLA were observed by scanning electron microscopy and laser scanning microscopy, while extinction spectra of gold nanoparticles collected in the glass slide was measured by UV-Vis spectrophotometer. The gold plate was ablated at various scCO₂ densities and irradiation times at constant temperature of 40°C. The ablation was also conducted at atmospheric condition with air to evaluate the environmental dependence of ablation. Both surface morphology of the irradiated gold plate and crater depth formation were significantly affected by the changes in scCO₂ density, the surrounding environment, and irradiation time. As expected, the increasing scCO₂ density resulted in a deeper ablation crater, however, the deepest crater was obtained at a density of 0.63 g/cm³ or pressure of 10 MPa. Gold nanoparticles generated by PLA in scCO₂ have been confirmed at the spectra band near 530 nm.