Laser-induced breakdown spectroscopy applied to the evaluation of penetration depth of bactericidal treatments based on silver nanoparticles in limestones

Abstract

In this work, laser-induced breakdown spectroscopy (LIBS) was used to evaluate the depth penetration of nanoparticles employed as biocidal treatment in stones.The penetration of a biocidal treatment, based on silver nanoparticles, was studied on limestones from Utrera (Seville, Spain). This stone was commonly employed in historical buildings in south Spain. Silver nanoparticles provide an effective protection against bacterial development, but their assessment depends on the depth penetration of the particles. Therefore, LIBS depth profiles were used to localize the nanomaterials in the stone matrix to determine silver penetration with the aim of controlling the treatment process.The characteristic emission of Ag(I) at 338.289 nm was successfully identified in the LIBS spectra of the treated samples, demonstrating the capability of the LIBS technique to be used for the detection of silver nanoparticles in limestone. In addition, LIBS depth profiles were useful for characterizing the diffusion of this nanoparticle in the calcareous matrix of the limestone. The penetration of the silver bactericidal treatment in the Utrera limestone was estimated to be 130–230 μm by LIBS depth analyses. This proof of concept demonstrates the capability of LIBS for depth analysis of limestone treated with silver nanoparticles and provides a useful tool to characterize the effectiveness of this biocidal treatment.