Formation of Metal-Composite Nanoparticles by Laser Ablation under Supercritical CO$_{\mathrm{2}}$

Gold (Au), silver (Ag), titanium (Ti) and iron (Fe) nanoparticles were produced by pulsed laser ablation (PLA) of a metal plate in supercritical CO$_{\mathrm{2}}$. Metal plate was placed in the center of high pressure chamber and ablated by using Nd: YAG laser with 532 nm and 1064 nm of wavelength. The experiments were performed at temperatures of 31$^{\mathrm{o}}$C-80$^{\mathrm{o}}$C and pressures of 5-15 MPa with irradiation time of 15 minutes. The generated particles were analyzed by using field emission scanning electron microscopy (FE-SEM), scanning transmission electron microscopy (STEM), transmission electron microscopy (TEM) system equipped with energy dispersive X-ray spectroscopy (EDS). The results showed that the generated particles are spherical in shape with average diameter 5-100 nm. Besides, based on EDS results, the generated particles consists of carbon, oxygen and metal which provide the evidence of reaction between metal target and solution (CO$_{\mathrm{2}})$. Moreover, the influence of CO$_{\mathrm{2}}$ by changing the temperatures and pressures were also studied and the possible mechanisms of particles formation are discussed. This provides useful insight for the synthesis of composite nanoparticles which can be applied in several fields, such as catalysis and photonics.