# Recent Developments in Materials Science for the Conservation and Restoration of Historic Artifacts
## 2 Inorganic Nanomaterials in Cultural Heritage Conservation  
### Inorganic Nanomaterials--Potential Alternatives in Conservation Science  
Traditionally, conservation methods were based on a trial-and-error approach, which can be invasive and non-selective. For instance, early conservators used natural materials like saliva or bile for cleaning artifacts, which lacked precision and could lead to further damage [6]. Furthermore, conventional solvents used in cleaning processes are often toxic and environmentally harmful, posing risks not only to the artifacts but also to the conservators [9]. These methods frequently leave residues that require invasive rinsing steps, which may alter the artifact's original state [6].  
Recent developments in materials science have significantly enhanced the conservation and restoration of historic artifacts, addressing the numerous challenges faced in preserving these invaluable cultural treasures. Among the innovative materials, nanomaterials have emerged as a promising solution due to their unique properties and versatility.  
Nanomaterials offer a transformative approach to overcoming these limitations. For example, metal oxide nanoparticles like titanium dioxide (TiO\({}_{2}\)) have been successfully employed for their self-cleaning properties and ability to inhibit microbial growth on surfaces [10]. Nanomaterials also provide tailored solutions that can be specifically designed to meet the needs of different types of artifacts, for example in enhancing the mechanical properties of deteriorated materials while maintaining their aesthetic integrity [11].  
Generally speaking, the widespread use of nanomaterials in conservation procedures is due to their unique properties. Among these properties, of particular interest for heritage science applications are enhanced strength and durability. Nanomaterials, such as silica and titanium dioxide nanoparticles, significantly improve the mechanical strength of the treated materials. Their high surface area-to-volume ratio allows for better adhesion to substrates, leading to enhanced structural integrity. For example, studies have shown that silica nanoparticles can increase the compressive strength of stone when used in consolidation treatments [12]. On the other hand, nanoparticles can penetrate deeper into porous materials, providing better reinforcement against physical stresses and environmental degradation. Silica nanoparticles have been effective in consolidating degraded stone by filling voids and enhancing compressive strength [13].  
Figure 1: Graphical representation of the aspects presented in the following sections.  
At the same time, recent works explore the capitalization of nanomaterials' barrier properties (by creating protective coatings that shield artifacts from environmental factors such as moisture, UV radiation, and pollutants) [14] and their hydrophobicity. Many nanomaterials impart hydrophobic properties to surfaces, preventing water ingress, which can lead to deterioration. Coatings containing siloxane and TiO\({}_{2}\) have been effective in protecting porous stones from water damage [15].