Graphene-Enhanced Nanomaterials for Wall Painting Protection

Wall paintings as the highly valuable treasure have been facing severe damaging problems over the years. Ca(OH)(2) as a promising material to protect them has been studied for more than a decade. However, the synthesis methods are still costly, complex, and usually, involve an organic solvent. In addition, problems such as large particle size (>150 nm), slow and weak carbonation, and low consolidation strength for wall paintings remain unsolved. This study demonstrates an unprecedented concept of wall painting protection enabled by graphene-enhanced nanomaterials through strategically synthesizing Ca(OH)(2)/graphene quantum dot (GQD) nanohybrids using a facile and economic aqueous method. The nanohybrids are uniform and small (center distribution at about 80 nm) and show strong adhesivity to wall painting pigments. In addition, the anti-UV absorption ability of the nanohybrids is also a significant advantage. More importantly, the Ca(OH)(2) is fully carbonated into a stable CaCO3 crystal phase calcite because of the GQD, which is crucial in wall painting consolidation. As a result, the graphene-enhanced nanohybrids show superior conservation efficiency compared to as-synthesized Ca(OH)(2) and commercial Ca(OH)(2) materials. The result opens a new direction for protecting cultural heritage using the newly emerging 2D nanomaterials.