Efficient and Removable Photoprotection of Paper-based Cultural Relics via Highly Dispersible Carbon...

Paper-based cultural relics have high cultural value. However, they are vulnerable to irreversible ultraviolet (UV) damage, including photodegradation, oxidation, and acidification during preservation or display, which cause the papers to fade, change color, and lose original strength and lifespan. Given the high sensitivity and importance of paper-based cultural relics, this study proposes a practical and reversible UV protection strategy for papers based on carbon dots/hydroxyethyl cellulose (CDs/HEC) composites. CDs are embedded in biodegradable HEC to prevent aggregation, which endows the composites with film-forming and UV absorption properties. The UV shielding effect of CDs/HEC can be tuned by varying the concentration of CDs. In addition, CDs/HEC can be attached to clean surfaces such as glass and easily removed from surfaces. Artificial accelerated UV aging experiments show the deceleration of acidification, oxidation, and photodegradation in the protected bamboo paper, mulberry paper, Xuan paper, and machine-made paper. It is noteworthy that UV irradiation of papers resulted in photo-yellowing or photobleaching, which is related to lignin chromophore photodegradation and the change of fluorescent substance in the paper. The combined results demonstrate the potential use of CDs as an effective, practical, safe, and customizable advanced protective material against photodamage to papers and paper-based cultural relics.