ABSTRACT
In this paper, Nanoparticle-Enhanced Laser Induced Breakdown Spectroscopy is applied to transparent samples and gemstones with the aim to overcome the laser induced damage on the sample. We propose to deposit a layer of AuNPs on the sample surface by drying a colloidal solution before ablating the sample with a 532â¯nm pulsed laser beam. This procedure ensures that the most significant fraction of the beam, being in resonance with the AuNP surface plasmon, is mainly absorbed by the NP layer, which in turn results the breakdown to be induced on NPs rather than on the sample itself. The fast explosion of the NPs and the plasma induction allow the ablation and the transfer in the plasma phase of the portion of sample surface where the NPs were placed. The employed AuNPs are prepared in milliQ water without the use of any chemical stabilizers by Pulsed Laser Ablation in Liquids (PLAL), in order to obtain a strict control of composition and impurities, and to limit possible spectral interferences (except from Au emission lines). Therefore with this technique it is possible to obtain, together with the emission signal of Au (coming from atomized NPs), the emission spectrum of the sample, by limiting or avoiding the direct interaction of the laser pulse with the sample itself. This approach is extremely useful for the elemental analysis by laser ablation of high refractive index samples, where the laser pulse on an untreated surface can otherwise penetrate inside the sample, generate breakdown events below the superficial layer, and consequently cause cracks and other damage. The results obtained with NELIBS on high refractive index samples like glasses, tourmaline, aquamarine and ruby are very promising, and demonstrate the potentiality of this approach for precious gemstones analysis.
ABSTRACT
In this article, an increase of 1-2 orders of magnitude in laser-induced breakdown spectroscopy (LIBS) signals was obtained by depositing silver nanoparticles on metal samples. Nanoparticle-enhanced LIBS (NELIBS) was found to be a robust and flexible tool for the chemical analysis of metals because the sample emission signal did not appear to be affected much by the size and concentration of deposited nanoparticles (NPs) within the ranges of 10 nm for diameter and 1 order of magnitude for concentration. On the other hand, preliminary NELIBS tests on insulators and semiconductors did not show any significant enhancement with respect to conventional LIBS. In this article, we present a detailed investigation of the fundamental features of NELIBS spectra, in addition to some examples of analytical applications to the quantitative analysis of metal alloys.
