Laser-induced plasma spectroscopy in pulsed laser ablation synthesis of nanoparticles in liquid

Synthesizing nanoparticles (NPs) using pulsed laser ablation (PLA) in liquids involves performing laser ablation of a target immersed in water or an organic solvent. The type of liquid used significantly affects the composition of the synthesized NPs. This work aims to verify whether spectroscopy of laser induced plasma (LIP) can help to explain the differences in laser ablation processes occurring in various solvents. Three targets (copper, copper oxide, and tellurium) immersed in three different solvents (water, ethanol, and acetone) were used for the spectral characterization of LIP. The highest intensity of the oxygen emission line was detected in water and the lowest in acetone, which perfectly agrees with a degree of oxidation of copper and tellurium NPs. This was also confirmed by the presence of a CuO emission band at 615 nm in water, while in acetone, this band was absent - surprisingly even in the case of the copper oxide target. Laser desorption ionization mass spectrometry (LDI MS) of produced Cu NPs showed lower abundance of oxidation products in ethanol and acetone. In the case of the CuO target, the LDI MS spectra showed only oxidation products. In the case of tellurium, TeO emission bands at 434-440 nm and 412-414 nm were detected only in water, confirming that oxidized TeO₂ NPs form only in water and not in acetone or ethanol. The LDI MS analysis results confirmed that TeO₂ NPs were produced in water, while in the case of acetone pure metallic Te NPs were detected.