Nanolimes doped with quantum dots for stone consolidation assessment.

Abstract

Currently, the application of consolidation treatments based on nanolimes (Ca(OH)2 nanoparticles) has become a common practice during the restoration of historical buildings. However, recent studies have showed that their effectiveness on stone materials is lower than expected. This result is due to the accumulation of nanolimes near the surface, which decreases their penetration depth into stone matrix and, consequently, results in a low restoration effectiveness. This research is focused on a new nanocomposite based on Ca(OH)2 nanoparticles doped with ZnO quantum dots whose fluorescence shows the real penetration of the nanomaterial into the stone matrices and allows us to study the affinity between nanolimes and the solvent used in the application in order to improve the penetration of the treatment into stones. Different mixtures of solvents have been probed to improve the penetration depth by analysing their kinetic stabilities and using thin-layer chromatography to evaluate their capacity to transport the nanolimes. Furthermore, a new support for thin-layer chromatography based on mortar has been designed, which has the advantage of having the same chemical composition as the limestones. Moreover, the effectiveness of the treatments was studied on limestones from Puerto de Santa María and Espera (Spain), which have been widely used in historical and contemporary buildings in the southwest of Spain. Nanolimes doped with ZnO quantum dots allow one to choose the optimal solvents for each kind of stone based on their fluorescence from UV radiation. Additionally, the fluorescence of the quantum dots could be used as an indicator of the consolidated areas for cultural heritage applications.