Metallic copper colloids by reductive laser ablation of nonmetallic copper precursor suspensions.

Pulsed laser ablation in liquids (PLAL) has developed to a convenient and efficient method for the synthesis of colloidal solutions. So far, in most cases, the laser pulse is focused on bulk targets like metal plates. An interesting alternative is the use of suspended μm-sized precursors. This leads to higher production rates and simpler setups. A thorough understanding of the mechanism is essential in order to gain control over the characteristics of the synthesized nanoparticles. Therefore, we investigated the formation of copper colloids by PLAL of CuO, Cu3N, Cu(N3)2, and Cu2C2 powders in organic liquids. Thus, we can compare copper precursors based on elements of the 4th, 5th, and 6th main group. The chemical composition of the resulting nanoparticles is revealed by electron energy loss spectroscopy (EELS). The presented investigations point to a reductive ablation process followed by laser-driven aggregation and coalescence steps instead of a simple fragmentation mechanism.