Assessment by laser-induced breakdown spectroscopy of penetration depth in limestones of four nano-biocides based on silver/titanium nanoparticles

•Laser induced breakdown spectroscopy (LIBS) technique for the in-depth analysis of nanoparticles used in cultural heritage field.•Biocidal treatment based on silver/titanium nanoparticles applied to limestone employed in heritage buildings for protective purposes.•High sensitivity LIBS technique for detecting a small amount of nanoparticles treatment.