Synergies of sugar-derived epoxy-silica hybrids and amino-functionalized silica NPs for advanced stone conservation

Abstract

Innovative approaches to stone conservation materials are essential for addressing the challenges of preserving cultural heritage while meeting environmental and sustainability standards. Based on this premise, this study delves into the synergy between sol-gel processes and nanotechnology to develop advanced epoxy-silica hybrid materials tailored for stone conservation. This investigation specifically targeted the use of amino-functionalized mesoporous silica nanoparticles (NH₂-SiO₂ NPs) as interactive carriers for natural phenolic biocidal compounds within advanced sugar-based hybrid, demonstrating significant potential in the field of stone conservation. The novel products exhibited improved multifunctional properties attributed to the surface-modified NPs, which facilitated their intimate incorporation into the hybrid network. This integration promoted the creation of homogeneous materials with adapted flexibility, particularly critical for thermal expansion effects, and ensuring mechanical integrity even in outdoor environments. Furthermore, the encapsulation of natural biocidal compounds such as carvacrol and curcumin addressed their intrinsic drawbacks of volatility and coloration effects, preserving their efficacy while minimizing also plasticizing adverse effect on base thermoset. Indeed, the inclusion of curcumin-loaded NH₂-SiO₂ as dual bactericidal system provided the most favorable compatibility in terms of thermo-mechanical behavior. This system exhibited thermal resistance up to 350 °C and featured inter-joined flexible crystalline domains, distinguished by glass-transition temperatures of 67 and 99 °C. Furthermore, it exhibited enhanced hydrophobic properties reaching contact angles of 105°, and showcased an optimal live/dead ratio response against bacteria. The laboratory scale testing demonstrated a balanced set of features with significant capabilities in both recovering and maintaining the integrity of the lithic substrate, against common degradation patterns induced by prolonged acid exposure.