Nano-structured particles production using pulsed laser ablation of gold plate in supercritical CO2

An advanced method for producing nano-structured materials has been developed by performing pulsed laser ablation of gold plate in supercritical CO2 (SCCO2). The method successfully generated gold nano-structured particles with allowing the selective generation of clusters. Laser ablation was performed with an excitation wavelength of 532 nm. Generated gold nano-structured particles collected in the silicon (Si) wafer and the ablated gold plate were analyzed by field emission gun scanning electron microscopy (FE-SEM), scanning electron microscopy (SEM), and 3D laser scanning microscopy. Absorption spectrum of generated gold nano-structured particles collected in the glass slide was also evaluated by UV-Vis spectrophotometer. Gold plate was ablated at various SCCO2 densities and irradiation time at constant temperature of 40 and 60 °C. Both surface of ablated gold plate and amount of gold nano-structured particles were significantly affected by the changes in SCCO2 density and the surrounding environment. Surface morphology of ablated gold plate was significantly affected by irradiation time. As increasing irradiation time, plume deposited in the crater vicinity of ablated gold plate was clearly observed. The depth of crater increased with increasing pressure or SCCO2 density and temperature due to heat transfer properties of CO2 change in the system. The deepest crater was observed at 10 MPa and 60 °C. The spectra of generated gold nano-structured particles in a glass slide contain bands near 530 nm. The peak near 530 nm has been known to correspond to the plasmon band of gold nanospheres with diameters <50 nm. In FE-SEM image of the generated gold nano-structured particles on the Si wafer, a network structure of smaller gold particles was fabricated. The network structure consisted of a chain of nanospheres with a mean diameter of 15 nm was observed at 10 MPa and 60 °C of PLA. Based on the results, this new method can also be used to obtain other nano-structured metals with various forms.