Preventive conservation of paper-based relics with visible light high-transmittance ultraviolet blocking film based on carbon dots.

Paper-based relics is an important carrier for recording and preserving information, however, it faces irreversible UV-induced damage, including photocleavage, oxidation, acidification and discoloration, which seriously affects its value and lifespan. Carbon dots (CDs) possess excellent UV absorption and good chemical stability, making them suitable for UV protection. Herein, we propose a high-security and efficient method utilizing CDs films (CDFs) for preventive protection of paper against UV damage. The CDFs with high tunable UV absorbance and minimal absorbance in the visible light range, effectively shield paper from UV radiation while preserving its visual appeal. Moreover, the UV transmittance of the film can be fine-tuned to the content of CDs and can be easily removed from the paper without residue. Artificial accelerated UV aging experiments demonstrate the deceleration of acidification, oxidation, and photocleavage in the protected bamboo paper and Xuan paper. This research paces a new direction for the protection of paper and paper-based relics and artworks with emerging carbon materials, offering customizable protection effects tailored to specific preservation and exhibition requirements. This research pioneers a novel approach to preventive protection of paper and paper-based relics using emerging carbon dots materials, offering tailored protection for diverse preservation needs.

Carbon Quantum Dots for Long-Term Protection against UV Degradation and Acidification in Paper-Based Relics.

Paper-based cultural relics constitute a significant and invaluable part of human civilization and cultural heritage. However, they are highly vulnerable to environmental factors such as ultraviolet (UV) photodegradation and acidification degradation, posing substantial threats to their long-term preservation. Carbon quantum dots (CQDs), known for their outstanding optical properties, high water solubility, and good safety, offer a promising solution for slowing down UV damage and acidification of paper-based relics during storage and transportation. Herein, we propose a feasible strategy for the simple preparation of CQDs with high dispersion stability, excellent UV absorption, room-temperature phosphorescence, and photostability for the safety protection of paper. Accelerated aging experiments were conducted using UV and dry-heat aging methods on both CQD-protected paper and unprotected paper, respectively, to evaluate the effectiveness of CQD protection. The results demonstrate a slowdown in both the oxidation and acid degradation processes of the protected paper under both UV-aging and dry-heat aging conditions. Notably, CQDs with complex luminescence patterns of both fluorescence and room-temperature phosphorescence also endue them as enhanced optical anticounterfeiting materials for multifunctional paper protection. This research provides a new direction for the protection of paper-based relics with emerging carbon nanomaterials.

Regulating Phase Distribution of Dion-Jacobson Perovskite Colloidal Multiple Quantum Wells Toward Highly Stable Deep-Blue Emission.

Metal halide perovskite colloidal quantum wells (CQWs) hold great promise for modern photonics and optoelectronics. However, current studies focus on Ruddlesden-Popper (R-P) phase perovskite CQWs that contain bilayers of monovalent long-chain alkylamomoniums between the separated perovskite octahedra layers. The bilayers are packed back-to-back via weak van der Waals interaction, resulting in inferior charge carrier transport and easier decomposition of perovskite. This report first creates a new type of perovskite colloidal multiple QWs (CMQWs) in the form of Dion-Jacobson (D-J) structure by introducing an asymmetric diammonium cation. Furthermore, the phase distribution is optimized by the synergistic effect of valeric acid and zwitterionic lecithin, finally achieving pure deep-blue emission at 435 nm with narrow full width at half maximum. The diammonium layer in D-J perovskite CMQWs features extremely short width of only ≈0.6 nm, thereby contributing to more effective charge carrier transport and higher stability. Through the continuous photoluminescence (PL) measurement and corresponding theoretical calculation, the higher stability of D-J perovskite CMQWs than that of R-P structural CMQWs is confirmed. This work reveals the inherent superior stability of D-J structural CMQWs, which opens a new direction for fabricating stable perovskite optoelectronics.

Synergistic Effect of Halogen Ions and Shelling Temperature on Anion Exchange Induced Interfacial Restructuring for Highly Efficient Blue Emissive InP/ZnS Quantum Dots.

InP quantum dots (QDs) have attracted much attention owing to their nontoxic properties and shown great potential in optoelectronic applications. Due to the surface defects and lattice mismatch, the interfacial structure of InP/ZnS QDs plays a significant role in their performance. Herein, the formation of In-S and Sx -In-P1-x interlayers through anion exchange at the shell-growth stage is revealed. More importantly, it is proposed that the composition of interface is dependent on the synergistic effect of halogen ions and shelling temperature. High shelling temperature contributes to the optical performance improvement resulting from the formation of interlayers, besides the thicker ZnS shell. Moreover, the effect relates to the halogen ions where I- presents more obvious enhancement than Br- and Cl- , owing to their different ability to coordinate with In dangling bonds, which are inclined to form In-S and Sx -In-P1-x bonds. Further, the anion exchange under I- -rich environment causes a blue-shift of emission wavelength with shelling temperature increasing, unobserved in a Cl- - or Br- -rich environment. It contributes to the preparation of highly efficient blue emissive InP/ZnS QDs with emission wavelength of 473 nm, photoluminescence quantum yield of ≈50% and full width at half maximum of 47 nm.