Feasibility of nanoparticle-enhanced LIBS (NELIBS) for the analysis of archaeological metallic artifacts: a critical assessment

Nanoparticle-Enhanced Laser-Induced Breakdown Spectroscopy (NELIBS) is a LIBS variant that, in its original implementation, is based on intensifying the emission intensity of the sample under investigation by depositing nanoparticles on its surface. In this work, we evaluated the feasibility of this approach for the analysis of historical samples by carrying out NELIBS of a bronze archaeological object. Our purpose was exploiting the emission enhancement to perform single-shot analysis of ancient metallic samples and to improve the LOD (Limit Of Detection) of minor and trace elements while also reducing the sample damage. To this end, we carried out LIBS and NELIBS analysis of one bronze helmet fragment (VII century BCE), and we adopted two different analytical approaches i.e., calibration lines drawn with a set of copper-based standard alloys, and Calibration-Free (CF). When depositing NPs on the surface of the archaeological sample, some critical issues arose, which have the potential to limit the applicability of NELIBS to metallic samples with surfaces altered by corrosion and burial deposits, such as those of ancient artifacts. We discussed these issues and proposed experimental and analytical approaches to mitigate their detrimental effects on the analysis. Our results showed that the LOD decreased for all the elements analyzed in the standard alloys and in the archaeological sample, though not in the same extent, and confirmed that, while requiring some special care for experimental optimization and data analysis, NELIBS can be a powerful approach in heritage science studies.