Nanocomposites composed of modified natural polymer and inorganic nanomaterial for safe, high-efficiency, multifunctional protection of paper-based relics

Paper-based relics as important carriers of human history and civilization have been facing severe damage problems, and their protection is a major project for cultural heritage restoration. So far, safe, high-efficiency, and multifunctional protection materials are still urgent to be developed. Herein, through screening a series of alkaline nano-oxides and cleverly combining the advantages of modified natural polymer (quaternized chitosan) and inorganic nanomaterials (ZnO), we successfully prepared their functional nanocomposites with multiple properties and pioneered their smart application for multifunctional protection of paper relics. By spraying loads, this kind of nanocomposites can effectively and safely inhibit the acid degradation of paper relics and long-term maintain a natural or weak basic state even under harsh accelerated aging conditions. Meanwhile, the coating of nanocomposites does not change the chromatic aberration but partially improves the hydrophobicity. Moreover, the mechanical properties of paper relics are reinforced up to more than one time for all-around tensile strength, folding endurance, and tearing strength. It is worth noting that the usage of nanocomposites can avoid the discoloration or fading of pH-sensitive pigments/dyes and prevent the blue/red inks from ink-spreading. By integrating the anti-microorganism effects of the two components, the nanocomposites have exhibited a broad antimicrobial capacity for both fungi (e.g., Plectosphaerella cucumerina and Aspergillus unguis ) and bacteria (e.g., Staphylococcus aureus ). The acquired knowledge not only represents an advanced step for designing functionalized inorganic/polymer nanocomposite but also sheds light on the multi-functional integrated protection of paper-based relics.