Investigating double pulse nanoparticle enhanced laser induced breakdown spectroscopy

Abstract

Several strategies have been effectively tested in the past to improve the Laser Induced Breakdown Spectroscopy (LIBS) signal, involving peculiar experimental configurations, such as Double Pulse LIBS (DP-LIBS). Recently, sample treatment has proven to be a viable and simple way to enhance the LIBS performances; in particular, the Nanoparticle-Enhanced LIBS (NELIBS) methodology uses a deposition of metal nanoparticles (NPs) on the sample to greatly increase the emission of the LIBS plasma.In this work, we investigate the possibility of combining, for the first time, DP-LIBS with NELIBS. The chosen set-up uses two parallel non-collinear laser pulses to ensure the activation of NPs during both pulses, while maintaining the low-pressure environment typical of DP-LIBS. The two laser beams are spatially separated so that the second beam is focused within the shock wave generated by the first one. This configuration allows the exploitation of the combined enhancement of both DP-LIBS and NELIBS.Several tests on copper targets have been performed to determine the best set-up for the maximum magnitude of the signal enhancement by adjusting different parameters such as pulse energies and offset distances. Commercially available silver NPs and NPs prepared by pulsed laser ablation in liquid have been tested and their performances compared with standard DP-LIBS.