Direct observation of aluminium ions produced via pulsed laser ablation in liquid: a ‘turn-on’ fluorescence study

Abstract

An Al metal plate was ablated by a pulsed Nd–YAG laser to produce nano-structured Al and gamma-Al₂O₃ in deionized water without any surfactants or catalysts. In this study, direct evidence for the production of Al³⁺ ions from the plasma plume is presented for the first time by characterizing the absorption and emission spectra of their [Al(salophen)]⁺ complex. Very interestingly, a remarkable increase in the fluorescence intensity was observed when the Al³⁺ ions, produced via the pulsed laser ablation, complexed with the salophen ligand. This fluorescence ‘turn-on’ behaviour of [Al(salophen)]⁺ was investigated by DFT/TD-DFT calculations. Based on these results, mechanisms for the production of aluminium and alumina nanoparticles in the pulsed laser ablation in liquid (PLAL) process are proposed.