Impact of Ag NPs on temporal evolution of plasma emission in nanoparticle-enhanced laser-induced breakdown spectroscopy

Abstract

Nanoparticle-enhanced laser-induced breakdown spectroscopy (NELIBS) has been applied in many disciplines with its capability of improving detection sensitivity due to the spectral enhancement effect. However, the mechanism of spectral enhancement still requires further investigation. In this work, spectral enhancement in NELIBS was investigated by evaluating the time-resolved and integrated emission of the plasma. Silver nanoparticles (Ag NPs) of different sizes and concentrations were deposited on an aluminum (Al) substrate and ablated with a Nd:YAG laser. The plasma emission on the Al substrate was measured using a monochromator equipped with a photomultiplier tube (PMT) and a fiber spectrometer. The NELIBS plasma exhibited longer lifetime and stronger signal intensity than normal LIBS plasma, which contributed to the spectral enhancement. The temporal emission profile also revealed higher emissions during the early plasma stage in NELIBS, suggesting the presence of more emitters in the plasma. This was further supported by the relative atomic concentration of NELIBS plasma to normal LIBS plasma, determined using the Boltzmann plot method. The varying enhancement effect of different sizes and concentrations of Ag NPs on the spectral enhancement might be attributed to their different abilities to promote the emitters. These findings offer valuable insights into the enhancement mechanisms of NELIBS with Ag NPs as the enhancer.