Intensity enhancement of LIBS of glass by using Au thin films and nanoparticles

We investigate the features of Au nanoparticles (NPs) formation by laser irradiation of thin films and its application in Nanoparticle Enhancement Laser Induced Breakdown Spectroscopy (NELIBS). Ns laser pulsed irradiation of Au thin films previously deposited on glass, allowed simultaneously the modification of the surface morphology of the metal film and the enhancement of the LIBS signal of the glass. Our results demonstrate that the presence of Au either as thin film or NPs favors the formation of a plasma composed by Au and the elements of underlying substrate. Thus, it is possible observing the optical emission of the glass at much lower irradiance than in conventional LIBS. The effect of the thickness of the starting film, laser fluence and number of pulses on the nanostructuration of the surface and the enhancement of the emission signal were analyzed. Under the studied conditions, the first pulse produces the formation of Au NPs and a LIBS spectrum with dominant emission of Au lines over the lines from the substrate. The subsequent pulses modify the NPs morphology and decrease the amount of Au on the substrate, thus the emission of the glass elements dominates the spectrum. After a certain number of pulses, the NPs are removed leaving an apparently clean surface after the analysis.